Patent Application
20240336636
The present invention relates to metal-organic frameworks, MOFs.
Metal-organic frameworks, MOFs, are crystalline and porous materials composed of metal-based nodes and organic linkers. They demonstrate extensive structural diversity and tunability due to the plethora of available choices for and arrangements of these building blocks. Many key MOF structural families arise from systematically expandable topologies that are defined by the chemistry and geometry of the interaction between a single node and a single linker. These topologies generate the structures for applications that depend on the pore geometries and dimensionalities, arising from the number, nature and connectivity of windows, channels and cages in the materials.
However, there remains a need to improve MOFs.
It is one aim of the present invention, amongst others, to provide a metal-organic framework, MOF, which at least partially obviates or mitigates at least some of the disadvantages of the prior art, whether identified herein or elsewhere.
A first aspect provides a three-dimensional metal-organic framework, MOF, comprising a plurality of crystallographically-ordered heterolinkers, including a first linker and a second linker, respectively periodically arranged between metal nodes, defining cages having a plurality of mutually different window types, including a first window type and a second window type, therebetween, wherein the respective window types correspondingly comprise mutually different heterolinker arrangements.
A second aspect provides a single-step method of synthesising a MOF according the first aspect, the method comprising:
According to the present invention there is provided a MOF, as set forth in the appended claims. Also provided is a method. Other features of the invention will be apparent from the dependent claims, and the description that follows.
The first aspect provides a three-dimensional, 3D, metal-organic framework, MOF, comprising a plurality of crystallographically-ordered heterolinkers, including a first linker and a second linker, respectively periodically arranged between metal nodes, defining cages having a plurality of mutually different window types, including a first window type and a second window type, therebetween, wherein the respective window types correspondingly comprise mutually different heterolinker arrangements. The MOF is synthesized via a single-step method, as described with respect to the second aspect. By synthesizing via the single-step method, the structure and/or composition of the MOF and/is not constrained by the respective structure(s) and/or composition(s) of precursor(s) thereof and/or intermediary(ies), in contrast with a multi-step method.
In this way, the structure of the MOF may be precisely controlled and/or the functional properties finely tuned, thereby controlling global properties of the MOF, for example porous properties, surface area and pore volume, as well as the local properties, for example the size and/or the shape of cages and/or windows therebetween.
Conventionally, the vast majority of MOFs are binary frameworks, combining one node and one linker, and the ability to precisely control the structure and finely tune the functional properties is limited. MOFs with multiple building blocks were first reported in 2008 and offer increased structural and chemical diversity in the resulting porous frameworks, but their expansion as a distinct class of materials has been slow. Typical exploratory synthesis approaches applied in binary MOFs have not been proven so successful in the synthesis of multicomponent MOFs. The addition of one more component does not only add one more variable to the system but it also restricts the range of compositions and conditions that allow the formation of the new compound due to the different solubilities, stabilities and reactivities of the components. The positionally ordered introduction of multiple linkers into the network topologies of these key families offers a distinct mechanism for precise control of the guest-accessible space. The associated requirement for extra linker components can be expected to complicate full exploration of the resulting larger chemical space.
Hence, the inventors have applied a more systematic and detailed study of complex chemical spaces for the synthesis of multicomponent MOFs. Automated high-throughput (HT) methods for materials synthesis and analysis are powerful tools for the systematic exploration of multiparameter chemical systems. They enable the screening of larger numbers of reactions than purely manual methods, accelerating the detailed investigation of complex chemical spaces. The large numbers of variables associated with MOF synthesis and in particular with multiple linker MOFs renders HT synthesis an appropriate approach for the discovery of new phases.
Zirconium carboxylate MOFs built from the [Zr6O4(OH)4]12+ cluster unit have received considerable attention not only for their high chemical stability but also for their three-dimensional porosity, structural diversity and ability to incorporate many chemical functionalities. The 12-connected, 12-c, framework of UiO-66 (
By way of an example, the inventors have synthesised a new 12-c Zr MOF with equal content of ordered terephthalate and fumarate linkers. This MOF has been prepared in single step synthesis and was synthesised by high-throughput exploration of the broad chemical space ZrOCl2/Terephthalic acid/Fumaric acid/Formic acid in DMF. The new MOF is based on the underlying fcu topology where the [Zr6O4(OH)4]12+ clusters are connected by six terephthalate and six fumarate linkers. The two linkers are arranged orderly within the crystal structure and they form a combination of porous features, called cages, that has never been observed before, a distorted tetrahedron and a distorted octahedron. These cages share two kinds of windows, which are the narrowest parts of the porous framework and determine the diffusion properties of this material. The arrangement of linkers produces trigonally distorted tetrahedral and octahedral cages which share two types of windows that are differentiated by the linkers that describe them. This is the first fcu Zr MOF with two types of windows and reflects the opportunity to control three-dimensional MOF porosity precisely through multiple linker chemistry. Thus, the control of adsorption, separation and catalysis of gas and liquid molecules is achieved in the MOF according to the first aspect. The advantage of the MOF according to the first aspect, compared with similar families of materials, is that the inventors precisely tune not only the size but also the shape of these porous features, cages and their windows, creating different kinds of these porous features, cages and their windows within the same material. The cages and their windows are ordered in the structure of, for example, Zr6(BDC)3(Fum)3 and form two distinct diffusion pathways for gaseous and liquid molecules increasing the probability to achieve efficient separations. Moreover, the approach present herein can be expanded to other combinations of dicarboxylate molecules, organic linkers, and produce a series of MOFs where the size and shape of windows can be tuned to match requirements for specific applications. The synthesis of chemically robust metal organic frameworks with porous properties that can precisely tuned in terms of size and shape are of great importance for industrial applications such gas storage and gas separations. The invention enables the possibility to carry out industrial separations of great importance such as o-Xylene/m-Xylene, paraffin/olefin (e.g. ethane/ethylene) and linear/branched alkanes (e.g. n-butane/iso-butane).
Generally, MOFs are known, being a subclass of coordination polymers, and are crystalline, porous materials composed of secondary building units (SBUs): metal-based nodes (ions or clusters) and organic linkers. Particularly, a MOF is a coordination network with organic ligands (also known as linkers or struts) containing potential voids (also known as pores or cavities). Hence, the MOF according to the first aspect is a coordination network with organic ligands containing potential voids, with repeating coordination entities extending in three dimensions. It should be understood that the MOF according to the first aspect hence defines a unit cell that repeats in three dimensions.
In one example, the MOF is based on and/or derived from a MOF included in http://rcsr.anu.edu.au/. In one example, the MOF is based on and/or derived from UiO-66, MIL-53, MIL-68, MIL-100 or MIL-101.
The MOF comprises the plurality of crystallographically-ordered heterolinkers, including the first linker and the second linker, respectively periodically arranged between the metal nodes. It should be understood that the first linker and the second linker are mutually different (i.e. heterolinker, also known as mixed-linker). It should be understood that the heterolinkers are crystallographically-ordered, respectively periodically arranged between the metal nodes. In other words, the unit cell of the MOF repeats in three dimensions, notwithstanding unavoidable defects. That is, respective positions of the heterolinkers are precisely located in the MOF, such that crystallographically-equivalent nodes are connected to the heterolinkers identically i.e. the coordination of the nodes is identical, chemically and structurally. That is, the heterolinkers are not crystallographically-disordered, such as randomly arranged. In this way, crystallographic analytical techniques such as X-ray crystallography or transmission electron microscopy provide characteristic crystallographic diffraction patterns.
Generally, the heterolinkers may be any organic linker molecule or molecule combination capable of binding to at least two metal nodes and comprising an organic moiety (i.e. a C based group comprising at least one C—H bond and optionally one or more heteroatoms such as N, O, S, B, P, Si). In one example, the organic moiety includes 1 to 50 C atoms i.e. C1 to C50.
In one example, the first linker and/or the second linker comprises and/or is an aliphatic linker, including 1 to 50 C atoms (i.e. C1 to C50), such as a single chain, branched or cyclic aliphatic linker, or a salt thereof. In one example, the aliphatic linker comprises a linear or a branched C1 to C20 alkyl group or a C3 to C12 cycloalkyl group. The term alkyl includes linear and branched alkyl groups such as all isomers of propyl, butyl, pentyl and hexyl. In one example, the alkyl group is linear. In one example, the cycloalkyl group is cyclopentyl or cyclohexyl. In one example, the aliphatic linker is a carboxylate aliphatic linker, for example a ditopic carboxylate aliphatic linker. Examples of suitable aliphatic linkers include ethanedioic acid (also known as oxalic acid), fumaric acid, acetylenedicarboxylic acid, propanedioic acid, acetylene dicarboxylic acid (ADC) and muconic acid. Other suitable aliphatic linkers are known.
In one example, the first linker and/or the second linker comprises and/or is an aromatic linker (i.e. comprising an aromatic moiety) or a salt thereof. In one example, the aromatic moiety comprises one or more aromatic rings, for example two, three, four or five rings, with the rings present mutually separately and/or at least two rings present in condensed form. In one example, the aromatic moiety comprises one, two or three rings, preferably one or two rings, most preferably only one ring. In one example, a ring, for example one ring or each ring, comprises at least one heteroatom such as N, O, S, B, P, Si, preferably N, O and/or S. In one example, the aromatic linker is a carboxylate aromatic linker, for example a ditopic carboxylate aromatic linker Examples of suitable aromatic linkers include benzene-1,4-dicarboxylic acid (also known as terephthalic acid or BDC), benzene-1,3-dicarboxylic acid, benzene-1,2-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, 1,1′-biphenyl 4,4′-dicarboxylic acid, benzene-1,3,5-tricarboxylic acid (BTB), R-BDC, TTDC, NDC, BPDC, HPDC, PDC, TPDC, DCPB, benzene tribiphenylcarboxylic acid (BBC), 5,15-bis (4-carboxyphenyl) zinc (II) porphyrin (BCPP), 1,4-benzene dicarboxylic acid (BDC), 2-amino-1,4-benzene dicarboxylic acid (R3-BDC or H2N BDC), 1,1′-azo-diphenyl 4,4′-dicarboxylic acid, cyclobutyl-1,4-benzene dicarboxylic acid (R6-BDC), benzene tricarboxylic acid, 2,6-naphthalene dicarboxylic acid (NDC), 1,1′-biphenyl 4,4′-dicarboxylic acid (BPDC), 2,2′-bipyridyl-5,5′-dicarboxylic acid, adamantane tetracaboxylic acid (ATC), adamantane dibenzoic acid (ADB), adamantane teracarboxylic acid (ATC), dihydroxyterephthalic acid (DHBDC), biphenyltetracarboxylic acid (BPTC), tetxahydropyrene 2,7-dicarboxylic acid (HPDC), hihydroxyterephthalic acid (DHBC), pyrene 2,7-dicarboxylic acid (PDC), pyrazine dicarboxylic acid, camphor dicarboxylic acid, benzene tetracarboxylic acid, 1,4-bis(4-carboxyphenyl)butadiyne, nicotinic acid and terphenyl dicarboxylic acid (TPDC).
In one example, the first linker comprises and/or is an aliphatic linker, as described previously, and the second linker comprises and/or is an aromatic linker, as described previously, or vice versa. In one example, the first linker is fumaric acid and the second linker is benzene-1,4-dicarboxylic acid.
In one example, the first linker and the second linker have mutually different lengths. In this way, the different window types have different shapes, for example relatively distorted compared with a homolinker analogue MOF including only the first linker or the second linker. Conventionally, by replacing the linker in a homolinker MOF with a linker that is topologically similar or identical but of increased length, pore size (i.e. cage size and window size) is scaled uniformly, thereby providing isoreticular MOFs (i.e. MOFs having same structural topology). In contrast, by having first and second linkers of mutually different lengths, relative lengthening or shortening of the respective lengths thereby scales pore size (i.e. cage size and window size) non-uniformly, thereby providing isoreticular MOFs (i.e. MOFs having same structural topology) or anisoreticular MOFs (i.e. MOFs having different structural topologies, derived therefrom). It should be understood that the respective lengths of the first linker and the second linker are their respective lengths in the MOF, for example as measured and/or calculated crystallographically. For example, a triangular window provided by an arrangement of three first linkers or three second linkers, respectively periodically arranged between the metal nodes, is an equilateral triangular window. In contrast, a triangular window provided by an arrangement of two first linkers and one second linker or one first linker and two second linkers, respectively periodically arranged between the metal nodes, wherein the first linker and the second linker have mutually different lengths, is an isosceles triangular window. In this way, a size of the window (also known as aperture size) may be controlled, thereby controlling diffusion through the MOF, separation by the MOF and/storage in the MOF. In one example, a difference in length between the first linker and the second linker is in a range from 1% to 25%, preferably in a range from 5% to 15%, by length of the first linker and/or the second linker. The inventors have determined that such differences in length may be accommodated by distortion. In one example, a difference in length between the first linker and the second linker corresponds with and/or is at most 1 C—C (single, double or triple) bond, at most 2 C—C (single, double or triple) bonds, at most 3 C—C (single, double or triple) bonds or at most 4 C—C (single, double or triple) bonds.
In one example, the first linker and the second linker have mutually different shapes. In this way, a size and/or a shape of the window may be controlled, thereby controlling diffusion through the MOF, separation by the MOF and/storage in the MOF, due at least in part to steric effects of the first linker and/or the second linker. For example, a linear linker (for example 1,4-benzene dicarboxylic acid or 1,1′-biphenyl 4,4′-dicarboxylic acid) and a zigzag linker (for example fumaric acid or 2,6-naphthalene dicarboxylic acid (NDC)) form different window in size and shape compare to a linear linker and a bent linker (1,3-benzene dicarboxylic acid or 2,5-thiophene dicarboxylic acid). In one example, the first linker comprises and/or is a linear linker, for example as described above, and the second linker comprises and/or is a bent linker or a zigzag linker.
In one example, the first linker and the second linker have mutually different side groups. In this way, a size of the window may be controlled, thereby controlling diffusion through the MOF, separation by the MOF and/storage in the MOF, due at least in part to steric effects of the first linker and/or the second linker. Additionally and/or alternatively, the side groups may functionalise the MOF i.e. wherein one or more of the backbone atoms of the linkers carries a pendant functional group or itself forms a functional group. Functional groups are typically groups capable of reacting with compounds entering the MOF or acting as catalytic sites for reaction of compounds entering the MOF. Suitable functional groups include amino, nitro, thiol, oxyacid, halo (e.g. chloro, bromo, fluoro) and cyano groups or heterocyclic groups (e.g. pyridine), each optionally linked by a linker group, such as carbonyl. The functional group may also be a phosphorus-or sulfur-containing acid. If the first linker and the second linker have mutually different side functional groups, multivariate MOFs are provided. Linkers having specific functionalities may be used to target applications such as CO2 capture and storage and/or to enhance interaction with target molecules. For example, amine functionalized MOFs can be used to achieve a higher total adsorption energy of CO2 molecules. For example, amide functional groups, such as urea, thiourea and squaramide, may be used for hydrogen bonding catalysis.
In one example, the first linker is planarly arranged, for example only planarly arranged such as in a first plane, between the metal nodes. That is, the first linker connects the metal nodes in two mutually orthogonal dimensions (i.e. a first dimension and a second dimension, wherein the first dimension and the second dimension are mutually orthogonal), thereby providing mutually parallel planes of metal nodes having the first linker, for example only the first linker, arranged between these metal nodes. It should be understood that the first linker and/or the second linker are not necessarily oriented in the first dimension and/or the second dimension. In one example, the first linker is planarly arranged between the metal nodes (i.e. in planes) and the second linker is arranged therebetween (i.e. bridging between the planes). In one example, the first linker and/or the second linker are planarly arranged between the metal nodes (i.e. in planes) and the first linker and/or the second linker is arranged therebetween (i.e. bridging between the planes).
In one example, a molar ratio of the first linker to the second linker is P: Q, wherein P and Q are each natural numbers in a range from 1 to 17. In one example, the metal nodes are N-connected, wherein N is a natural number in a range from 3 to 18, for example 4-connected (4-c), 6-connected (6-c), 8-connected (8-c), 10-connected (10-c) or 12-connected (12-c) with respect to the heterolinkers. In one example, the metal nodes are N-connected, wherein N is a natural number in a range from 3 to 18, and wherein a molar ratio of the first linker to the second linker is P: Q, wherein P and Q are each natural numbers and P+Q=N. In one example, the metal nodes are 4-connected and a molar ratio of the first linker to the second linker is 1:3, 2:2 or 3:1. In one example, the metal nodes are 6-connected and a molar ratio of the first linker to the second linker is 1:5, 2:4 (i.e. 1:2), 3:3 (i.e. 1:1), 4:2 (i.e. 2:1) or 5:1. In one example, the metal nodes are 8-connected and a molar ratio of the first linker to the second linker is 1:7, 2:6 (i.e. 1:3), 3:5, 4:4 (i.e. 1:1), 5:3, 6:2 (i.e. 3:1) or 7:1. In one example, the metal nodes are 10-connected and a molar ratio of the first linker to the second linker is 1:9, 2:8 (i.e. 1:4), 3:7, 4:6 (i.e. 2:3), 5:5 (i.e. 1:1), 6:4 (i.e. 3:2), 7:3, 8:2 (i.e. 4:1) or 9:1, preferably 2:8 (i.e. 1:4), 4:6 (i.e. 2:3), 5:5 (i.e. 1:1), 6:4 (i.e. 3:2) or 8:2 (i.e. 4:1) (for example, Zr6(BDC)(NDC)4). In one example, the metal nodes are 12-connected and a molar ratio of the first linker to the second linker is 1:11, 2:10 (i.e. 1:5), 3:9 (i.e. 1:3), 4:8 (i.e. 1:2), 5:7, 6:6 (i.e. 3:3 or 1:1), 7:5, 8:4 (i.e. 2:1), 9:3 (i.e. 3:1), 10:2 (i.e. 5:1) or 11:1, preferably 3:9 (i.e. 1:3), 4:8 (i.e. 1:2), 6:6 (i.e. 3:3 or 1:1) (for example, Zr6(BDC)3(Fum)3), 8:4 (i.e. 2:1) (for example, Zr6(BDC)4(TDC)2) or 9:3 (i.e. 3:1).
In one example, the first linker and/or the second linker is a ditopic linker, for example a ditopic carboxylate linker. Examples of suitable ditopic linkers, as described above, include oxalic acid, fumaric acid, acetylenedicarboxylic acid, terephthalic acid (also known as BDC), 2,6-naphthalene dicarboxylic acid, 1,1′-biphenyl 4,4′-dicarboxylic acid, muconic acid, as described above. In one example, the first linker and/or the second linker is a tritopic linker, for example a tritopic carboxylate linker. In one example, the first linker and/or the second linker is a tetratopic linker, a hexatopic linker or octatopic linker, for example a tetratopic carboxylate linker, a hexatopic carboxylate linker or carboxylate octatopic linker, respectively.
In one example, the first linker and/or the second linker comprises and/or is a carboxylic acid containing linker (i.e. a carboxylate linker), a nitrogen containing linker (e.g. containing pyridyl, pyrazole, imidazole, etc), a cyano linker, a phosphonic acid linker, a linker based on mixed functional groups a sulfonyl linker and/or a metal-bearing linker. Other acids besides carboxylic acids, e.g. boronic acids and/or phosphonic acids may be used. In one example, the first linker and/or the second linker is a ditopic linker, including two such linkers.
In one example, the plurality of crystallographically-ordered heterolinkers includes a third linker, respectively periodically arranged between the metal nodes. The third linker may be as described with respect to the first linker and/or the second linker, mutatis mutandis.
Without wishing to be bound by any theory, the plurality of heterolinkers may be selected according to the following rules, which are given in priority order:
The MOF comprises the plurality of crystallographically-ordered heterolinkers respectively periodically arranged between the metal nodes (also known as vertices or cornerstones).
In one example, the metal is: a transition metal, for example a Period 4 transition metal such as selected from Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, a Period 5 transition metal such as selected from a group consisting of Y, Zr, Nb and Mo, a Period 6 transition metal such as selected from a group consisting of Lu, Hf, Ta and W; a rare earth metal selected from a group consisting of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu; or a mixture thereof.
In one example, the metal is selected from Zr, Hf, Ti, a rare earth metal selected from a group consisting of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu; or a mixture thereof.
In one example, the MOF is a Zr-based MOF, wherein the nodes are Zr-based inorganic groups or clusters, for example Zr ions connected by bridging oxygen and/or hydroxide groups. It should be understood that these inorganic groups are further coordinated to at least one of the heterolinkers. In one example, the inorganic groups are additionally connected to non-bridging modulator species, complexing reagents and/or ligands (for example sulfates or carboxylates such as formate, benzoate or acetate) and/or solvent molecules. Typically, a Zr oxide cluster is based on an idealized octahedron of Zr-ions which are us-bridged by inorganic bridging ligands such as O2− and/or OH− ions via faces of the octahedron and further saturated by coordinating moieties containing O-atoms such as carboxylate groups. Other inorganic bridging ligands include SH−, NH2, N3−, CO, Cl−, CN− and PPh2
In one example, the metal nodes have 8 to 36 coordination sites for the heterolinkers, preferably 24 coordination sites for the heterolinkers. In this way, at least 4, preferably 6, 8, 10 or 12 bidentate ligand groups of the heterolinkers may bind to each metal node. In one example, the metal nodes have a coordination number of 12 (i.e. 12-connected or 12-c, also known as 12-coordinated) (for example, Zr6(BDC)3(Fum)3, Zr6(BDC)4(TDC)2), 10 (for example, Zr6(BDC)(NDC)4), 8, 6 or 4. It should be understood that the coordination of the metal nodes is with respect to the heterolinkers.
Without wishing to be bound by any theory, the metal nodes may be selected according to the following rules:
The plurality of crystallographically-ordered heterolinkers are respectively periodically arranged between the metal nodes, defining the cages. It should be understood that the cages define polyhedral pores (also known as voids) between the coordination network of metal nodes and heterolinkers. Typically, the pores are micropores, having a diameter of 2 nm or less, or mesopores, having a diameter in a range from 2 to 50 nm. It should be understood that the diameter of the pore is that of the largest sphere that may be received entirely in the pore.
If the first linker and the second linker have mutually different lengths, a shape of the cages is distorted compared with a homolinker MOF. For example, a tetrahedral cage may be distorted to a trigonal pyramidal cage by including relatively shorter or longer second linker(s) therein. For example, an octahedral cage may be distorted to a trigonal antiprism cage by including relatively shorter or longer second linker(s) therein.
In one example, the MOF defines a plurality of mutually different cage types, including a first cage type and a second cage type, having the plurality of mutually different window types therebetween. It should be understood that the different cages may be defined by the respective metal nodes and/or the heterolinkers thereof and may be thus mutually distinguished by shape and/or size as well as chemistry (i.e. of the respective metal nodes and/or the heterolinkers).
The cages have the plurality of mutually different window types, including the first window type and the second window type, therebetween. The respective window types correspondingly comprise mutually different heterolinker arrangements. It should be understood that windows of the plurality of mutually different window types define polygonal apertures between the polyhedral pores defined by the cages. In other words, a window is a side of a cage such that edges of the cage provide the window. Hence, the windows may limit a maximum size of a molecule that may move, for example diffuse and/or be transported, through the MOF. It should be understood that the different windows may be defined by the respective metal nodes and/or the heterolinkers thereof and may be thus mutually distinguished by shape and/or size as well as chemistry (i.e. of the respective metal nodes and/or the heterolinkers). In one example, the first window type and/or the second window type is polygonal, for example a convex polygon having three, four, five, six, seven, eight or more edges (i.e. triangular, quadrilateral, pentagonal, hexagonal, heptagonal or octagonal, respectively). In one example, the first window type is a regular convex polygon, for example an equilateral triangle, and the second window type is an irregular convex polygon, for example an isosceles triangle.
In one example, the respective window types have mutually different ratios of the first linker to the second linker. In one example, the first window type has E edges, wherein E is a natural number greater than or equal to 3, wherein a ratio of the first linker to the second linker is in a range from (E-e):E to E:(E-e), wherein e is a natural number in a range from 0 to E.
In one example, the first window type comprises only the first linker and/or the second window type comprises the first linker and the second linker.
In one example, the MOF has an underlying net, for example selected from a group consisting of: fcu (cuboctahedron); ftw (square and cuboctahedron); shp (hexagonal prism); ith (isosahedron); bcu and reo (cube); csq, scu and sqc (square and cube); flu (tetrahedron and cube); the (triangle and cube); stp (square and trigonal prism); spn (triangle and trigonal antiprism); pcu (octahedron); gar (tetrahedron and octahedron); hxg (hexagon and hexagon); she (square and hexagon); kgd (triangle and hexagon, 2D net); lvt (square); and sql (square, 2D net). In one example, the MOF has a fcu topology (for example, Zr6(BDC)3(Fum)3, Zr6(BDC)4(TDC)2) or a bct topology (for example, Zr6(BDC)(NDC)4).
The second aspect provides a single-step method of synthesising a MOF according the first aspect, the method comprising:
preparing a solution comprising the metal and/or a precursor thereof and the plurality of heterolinkers, including the first linker and the second linker, and/or precursors thereof and optionally a modulator, dissolved in a solvent;
heating the solution at a temperature in a range from 100° C. to 140° C., preferably in a range from 110° C. to 130° C. for example 120° C., for a time period in a range from 12 hours to 96 hours, preferably in a range from 24 hours to 72 hours, for example 48 hours; and collecting the synthesised MOF, optionally comprising cooling, washing and/or drying the synthesised MOF.
By synthesizing via the single-step method, the structure and/or composition of the MOF and/is not constrained by the respective structure(s) and/or composition(s) of precursor(s) thereof and/or intermediary(ies), in contrast with a multi-step method. For example, a multi-step method of synthesizing a conventional MOF comprising a plurality of crystallographically-ordered heterolinkers, including a first linker and a second linker, respectively periodically arranged between metal nodes, comprises synthesizing an intermediary network using only the first linker (i.e. a single linker and hence the intermediary network comprises crystallographically-ordered homolinkers) and then subsequently including the second linker in the intermediary network, to form the conventional MOF comprising the plurality of crystallographically-ordered heterolinkers, including the first linker and the second linker, respectively periodically arranged between metal nodes. However, in contrast to the MOF according to the first aspect, the plurality of crystallographically-ordered heterolinkers, including the first linker and the second linker, of the conventional MOF instead define cages having only a single window type, rather than a plurality of mutually different window types, including the first window type and the second window type, therebetween, wherein the respective window types correspondingly comprise mutually different heterolinker arrangements, as defined for the MOF according to the first aspect.
The method may comprise any of the steps described with respect to the first aspect.
The metal, the precursor thereof, the plurality of heterolinkers, the first linker, the second linker and/or the precursors thereof may be as described with respect to the first aspect.
In one example, the solvent comprises and/or is dimethylformamide (DMF), diethylformamide (DEF), dimethylacetamide (DMA), ethanol, acetonitrile, water or a mixture thereof.
In one example, the modulator comprises and/or is a monocarboxylic acid (for example formic acid, acetic acid, benzoic acid, trifluoroacetic acid), a mineral acid (for example hydrochloric acid, hydrofluoric acid) or a mixture thereof.
Throughout this specification, the term “comprising” or “comprises” means including the component(s) specified but not to the exclusion of the presence of other components. The term “consisting essentially of” or “consists essentially of” means including the components specified but excluding other components except for materials present as impurities, unavoidable materials present as a result of processes used to provide the components, and components added for a purpose other than achieving the technical effect of the invention, such as colourants, and the like.
The term “consisting of” or “consists of” means including the components specified but excluding other components.
Whenever appropriate, depending upon the context, the use of the term “comprises” or “comprising” may also be taken to include the meaning “consists essentially of” or “consisting essentially of”, and also may also be taken to include the meaning “consists of” or “consisting of”.
The optional features set out herein may be used either individually or in combination with each other where appropriate and particularly in the combinations as set out in the accompanying claims. The optional features for each aspect or exemplary embodiment of the invention, as set out herein are also applicable to all other aspects or exemplary embodiments of the invention, where appropriate. In other words, the skilled person reading this specification should consider the optional features for each aspect or exemplary embodiment of the invention as interchangeable and combinable between different aspects and exemplary embodiments.
For a better understanding of the invention, and to show how exemplary embodiments of the same may be brought into effect, reference will be made, by way of example only, to the accompanying diagrammatic Figures, in which:
1H NMR spectrum of the cubic phase material with composition Zr:T:F=0.25:0.19:0.56 and FA:Zr=167, synthesised in the first batch synthesis, after digestion in a mixture of NaOD (60 μL) and D2O (640 μL). From the relative integrations of the peaks corresponding to terephthalate and fumarate, the molar ratio in which the two linkers are present in the material was calculated to be T:F=1:1.84. This is further evidenced by the PXRD pattern of the material (
1H NMR spectrum of the cubic phase material with composition Zr:T:F=0.5:0.25:0.25 and FA:Zr=167, synthesised in the first batch synthesis, after digestion in a mixture of NaOD (60 μL) and D2O (640 μL). The nominal composition of the material from the reaction composition has a T:F molar ratio of T:F=1:1, however from the relative integrations of the peaks corresponding to terephthalate and fumarate, the molar ratio in which the two linkers are present in the material was calculated to be T:F=1:0.64. This therefore suggests that under these reaction conditions, the system shows a preference for terephthalate over fumarate.
1H NMR spectrum of the crude product Zr6(BDC)3(Fum)3, after washing with DMF and digestion in a mixture of NaOD (60 μL) and D2O (640 μL). From the relative integrations of the terephthalate and fumarate peaks in the spectrum, the linkers are found to be present with a T:F ratio of T:F=1:0.84. The observed fumarate deficiency from the nominal composition, T:F=1:1, and lack of other species being present means that it is likely that some of the formate present is bound to the [Zr6O4(OH)4]12+ cluster at vacant binding sites, acting as a charge balancing species. However, the proportion of formate which can be attributed formate is bound to the cluster cannot be determined from this data, due to the presence of DMF in the pores and on the surface of the material. Under the conditions used for the digestion of the material, any DMF present is decomposed to dimethylamine and formate, giving rise to the two large peaks observed in the spectrum.
1H NMR spectrum of the sample of Zr6(BDC)3(Fum)3, after solvent exchange with methanol. The material was dried under ambient conditions to allow most of the methanol on the surface of the material to evaporate prior to digestion in the NMR solvent mixture, NaOD (60 μL) and D2O (640 μL). From the relative integrations of the terephthalate, fumarate, MeO-/MeOH and formate peaks in the spectrum, the molar ratio in which these species are present was calculated as T:F:MeOH:FA=1:0.92:3.4:0.2. The solvent exchange process successfully replaced the DMF in the pores of the material, as indicated by the lack of a dimethylamine peak in the NMR and the presence of a peak corresponding to methanol, which is present as methoxide under the conditions in which the 1H NMR was run. The deviation in the equimolar ratio between the two linkers in the T:F:MeOH:FA molar ratio calculated from the spectrum, T:F:MeOH:FA=1:0.92:3.4:0.2, indicates that there are missing linker defects in the structure, which results in vacant binding sites at the [Zr6O4(OH)4]12+ cluster. These vacant binding sites are occupied charge balancing species. One of these charge balancing species is formate, a small amount of which is still present in the 1H NMR spectrum of the methanol exchanged sample, despite there being no dimethylamine. Therefore, this remaining formate is likely to be bound to the [Zr6O4(OH)4]12+ clusters of the material, occupying missing linker defect sites. Some of these missing linker defect sites may also be occupied by methoxide, which can also fulfil the role of charge balancing. However, due to the presence of methanol in the pores and on the surface of the material, which by 1H NMR cannot be distinguished from methoxide bound to the [Zr6O4(OH)4]12+ cluster, the number of missing linker defects and therefore exact composition of the material, cannot be accurately determined from the methanol exchanged sample.
1H NMR spectrum of Zr6(BDC)3(Fum)3 obtained after solvent exchange with methanol, and activation under dynamic vacuum at 60° C. for 24 hours. From the relative integrations of the terephthalate, fumarate, MeO/MeOH and formate peaks in the spectrum, the molar ratio in which these species are present was calculated as T:F:MeOH:FA=1:0.92:0.6:0.2. The process of activation under vacuum at elevated temperature removes all of the methanol from the pores and surface of the material, therefore meaning that all species observed in the 1H NMR after activation are chemically bound to the structure and not simply guest species. This therefore means that the formate and methoxide present in the sample after activation can be attributed charge balancing species, bound to the [Zr6O4(OH)4]12+ cluster at vacant binding sites where the material exhibits defects, thus enabling the exact composition of the framework to be accurately calculated. The absence of a single linker leaves 4 binding sites vacant at the [Zr6O4(OH)4]12+ cluster, which can be occupied by formate and/or pairs of MeO/MeOH. From the molar ratio in which terephthalate, fumarate, MeO/MeOH and formate are present in the sample, T:F:MeOH:FA=1:0.92:0.6:0.2, and the theoretical formula of the material in which the sum of the linkers equates to 6, the formula of the activated material was calculated to be Zr6O4(OH)4(BDC)2.77(Fum)2.55(MeO)0.83(MeOH)0.83(Formate)0.55. This therefore means that, out of the theoretical 6 linkers, 0.68 (11.3%) are missing and these defect sites are occupied by formate and MeO/MeOH. This linker occupancy with 11.3% of missing linkers is in line with the values reported for single crystals of UiO-66, which contain 10% of missing linkers, and powders of UiO-66 which contain up to 20% and 33% of missing linkers when prepared with a formic acid or trifluoroacetic acid modulators respectively. The formula calculated by 1H NMR was consistent with the mass losses observed by TGA for the sample (
1H NMR spectrum of the product Zr6(BDC)4(TDC)2, after one hour of washing with MeOH and digestion in a mixture of NaOD (60 μL) and D2O (640 μL). From the relative integrations of the terephthalate and thiophene dicarboxylate peaks in the spectrum, the linkers are found to be present with a T:S ratio of T:S=1.5:1. The observed terephthalate deficiency from the nominal composition, T:S=2:1, and lack of other species being present means that it is likely that some of the formate present is bound to the [Zr6O4(OH)4]12+ cluster at vacant binding sites, acting as a charge balancing species. However, the proportion of formate which can be attributed formate is bound to the cluster cannot be determined from this data, due to the presence of DMF in the pores and on the surface of the material. Under the conditions used for the digestion of the material, any DMF present is decomposed to dimethylamine and formate, giving rise to the two large peaks observed in the spectrum.
1H NMR spectrum of the sample of Zr6(BDC)4(TDC)2, after overnight exchange with MeOH. The material was dried under ambient conditions to allow most of the methanol on the surface of the material to evaporate prior to digestion in the NMR solvent mixture, NaOD (60 μL) and D2O (640 μL). The solvent exchange process successfully replaced the DMF in the pores of the material, as indicated by the decrease in intensity of fumarate and dimethylamine peaks compared to the NMR of
1H NMR spectrum of the sample of Zr6(BDC)(NDC)4, after overnight exchange with acetone. The material was dried under ambient conditions to allow most of the methanol on the surface of the material to evaporate prior to digestion in the NMR solvent mixture, NaOD (60 μL) and D2O (640 μL).
General Experimental Details: All reagents were purchased from commercial suppliers and used without modification. Zirconyl chloride octahydrate (ZrOCl2·8H2O, purity 98%), zirconium chloride (ZrCl4, anhydrous, purity 99.99%), fumaric acid (purity ≥99%), terephthalic acid (purity ≥98%), sodium hydroxide-d (40 wt. % in D2O) and deuterium oxide (99.9 atom % D) were obtained from Sigma-Aldrich Co. N,N-Dimethylformamide (DMF) and methanol were obtained from Fisher Scientific. Formic acid (purity 97%) was obtained from Alfa Aesar. Automated liquid dispensation was performed with an Eppendorf epMotion 5075t liquid-handling platform. 20 mL headspace screw neck glass vials with metal screw caps were purchased from VWR International.
MOF synthesis with liquid-handling robots: Mixed-linker Zr-based MOFs with terephthalate and fumarate linkers, were prepared in batches and the components of each reaction mixture were transferred to the reaction vessel, a 20 mL headspace screw neck glass vial, by automated dispensation of their solution in DMF, with the exception of formic acid, which was dispensed neat. In a typical batch synthesis, ZrOCl2·8H2O was dissolved in DMF to prepare a stock solution of concentration 0.0225 M. The concentration of this solution was fixed, and chosen to be as high as possible, whilst remaining below the solubility limit of ZrOCl2·8H2O in DMF at room temperature to ensure that the solution remained as a stable homogeneous mixture for the entire duration of the automated sample preparation, which, for the second batch of syntheses in which 54 samples were prepared, required 2 hours to complete. The volume of 0.0225 M ZrOCl2·8H2O stock solution dispensed into each reaction mixture, and therefore the quantity of ZrOCl2·8H2O used in each 10 mL scale reaction was also fixed at 38 mg, 0.12 mmol. The linker stock solutions were prepared by dissolving terephthalic acid and fumaric acid in DMF at a total linker, (T+F), concentration of 0.15 M, with different T:F molar ratios (Table S1 and Table S3). The different reaction mixtures were prepared using the Eppendorf epMotion 5075t liquid handling platform, with dispensation directly into the reaction vessel. In each batch of syntheses, the individual reaction mixtures were prepared in parallel and the components were added to the mixture in the same order (formic acid —ZrOCl2·8H2O stock—T:F linker stock—DMF). DMF was dispensed into each vial to ensure every reaction had the same fill factor, with a total reaction solution volume of 10 mL. The vials were then sealed with metal screw caps, before being heated at 120° C. for 48 hours. Powder products were collected by centrifugation and washed with DMF and methanol. In the specific examples below, batch 1 refers to samples from the first iteration and batch 2 to samples in the second iteration.
Batch 1 Experimental: A stock solution of the metal source was prepared by dissolving ZrOCl2·8H2O (5.63 mmol, 1.81 g) in DMF (250 mL). Linker stock solutions with five different T:F molar ratios, T:F=1:0, 0.75:0.25, 0.5:0.5, 0.25:0.75 and 0:1, were prepared at a total linker (T+F) concentration of 0.15 M in DMF (25 mL). The quantities of terephthalic acid and fumaric acid used in each solution are summarised in Table S1.
The order in which the reaction components were added, formic acid —ZrOCl2·8H2O stock—T:F linker stock—DMF, was the same for each of the 45 individual reaction mixtures in the batch, with the process of automated dispensation lasting 1.5 hours. The vials were sealed with metal screw caps before being heated at 120° C. for 48 hours. Powder products were collected by centrifugation and washed twice with DMF (5 mL) followed by methanol (5 ml).
Batch 2 Experimental: A stock solution of the metal source was prepared by dissolving ZrOCl2·8H2O (6.75 mmol, 2.18 g) in DMF (300 mL). Linker stock solutions with three different T:F molar ratios, T:F=0.375:0.625. 0.5:0.5 and 0.625:0.375, were prepared at a total linker (T+F) concentration of 0.15 M in DMF (250 mL). The quantities of terephthalic acid and fumaric acid used in each solution are summarised in Table S3.
Synthesis with ZrOCl2
Briefly, ZrOCl2·8H2O (2.18 g, 6.75 mmol) was dissolved in DMF (300 mL) to prepare a solution with concentration 0.0225 M. An equimolar solution of terephthalate and fumarate was prepared at a total molar concentration of 0.15 M, by dissolving terephthalic acid (3.12 g, 18.75 mmol) and fumaric acid (2.18 g, 18.75 mmol) in DMF (250 mL). Formic acid (1.69 mL) was mixed with the ZrOCl2 solution (5.29 mL), terephthalate-fumarate solution (0.79 mL) and DMF (2.23 mL) in a 20 mL screw capped glass vial. The vial was sealed with a metal screw cap and the mixture heated at 120° C. for 48 hours. After cooling to 25° C., the resulting white solid was collected by centrifugation and washed with DMF (5 mL) and methanol (5 mL) and dried under ambient conditions.
Synthesis with ZrCl4
Briefly, in a 20 mL screw capped glass vial, ZrCl4 (0.0277 mg, 0.12 mmol) was dissolved in a mixture of DMF (7.5 mL) and formic acid (1.5 mL). The vial was sealed with a metal screw cap and the mixture was sonicated at 50° C. for 45 minutes. An equimolar solution of terephthalate and fumarate, with a total concentration of 0.16 M, was prepared by dissolving terephthalic acid (0.3294 g, 2 mmol) and fumaric acid (0.2301 g, 2 mmol) in DMF (25 mL). 1 mL of this terephthalate-fumarate solution was added to the vial containing the ZrCl4/DMF/formic acid mixture upon completion of the sonication. The vial was sealed with a metal screw cap and the mixture heated at 120° C. for 48 hours. After cooling to 25° C., the resulting white solid was collected by centrifugation and washed with DMF (5 mL) and methanol (5 mL) and dried under ambient conditions.
Synthesis of Zr6(BDC)3(Fum)3 with ZrCl4: In order to produce larger amounts of sample required for the detailed characterisation of Zr6(BDC)3(Fum)3 following structure solution, a point in the second batch of syntheses, with composition Zr:T:F=0.4286:0.2857:0.2857 and FA:Zr=334:1 was identified which yielded the Zr6(BDC)3(Fum)3 phase with high purity and with good yield. A set of 12 identical reactions mixtures with this composition were prepared using ZrCl4 as the metal source, in order to ensure the Zr6(BDC)3(Fum)3 phase maximise the phase purity of the sample for detailed characterisation. ZrCl4 (0.12 mmol, 0.0277 g) was weighed into each vial before DMF (7.5 mL) and formic acid (1.5 mL) was added. The vials were sealed with metal screw caps and the reaction mixtures sonicated at 50°° C. for 45 minutes. During this time, a linker stock solution, with the T:F molar ratio T:F=0.5:0.5, was prepared at a total linker (T+F) concentration of 0.16 M by dissolving terephthalic acid (2 mmol, 0.3294 g) and fumaric acid (2 mmol, 0.2301 g) in DMF (25 mL). After sonication, 1 mL of the T:F linker stock solution was added to each of the reaction mixtures, and the vials resealed with metal screw caps, before being heated at 120° C. for 48 hours. After the completion of the reaction, the purity of the solid product formed was determined by PXRD of the powder in the supernatant.
Solvent Exchange and Activation: Reaction mixtures from the scale-out syntheses described above with ZrCl4, which yielded the Zr6(BDC)3(Fum)3 phase with high purity were combined and the material collected by centrifugation. The supernatant was decanted, replaced with DMF (25 mL) and the mixture shaken for 1 hour. This process of washing with DMF was repeated three times. The DMF was then decanted after centrifugation, and the material stirred in methanol (20 mL) for a total of 9 days, during which time the methanol was replaced 4 times. Each time the methanol was replaced, the material was collected by centrifugation, solvent decanted and the material allowed to dry under atmospheric conditions to the point that it can be handled as a powder. At this point of each exchange, a 1H NMR was obtained after digestion of a small amount of the material in NaOD (60 μL) and D2O (640 μL). The methanol exchanged material, which exhibited no phase change by PXRD after the solvent exchange, giving the Zr6(BDC)3(Fum)3 purely, and which did not show evidence for the presence of DMF decomposition products by NMR, was activated under high-vacuum (10−5 bar) at 60° C. for 24 hours to remove all guest species. The activated material was transferred to the sample tube for porosity measurement under an Ar atmosphere.
Nuclear Magnetic Resonance (NMR) spectroscopy. All CH NMR spectra were recorded in solution using a Bruker ADVANCE-400 MHZ NMR spectrometer. All spectra were recorded in a solvent mixture of D2O (640 μL) and NaOD (60 μL), with the residual solvent peak of D2O (4.79 ppm for 1H).
Thermal analysis. Thermal Gravimetric Analysis (TGA) was performed under air atmosphere on a TA Instruments Q600 between 25 and 1000° C., with a scan rate of 10° C. min−1 and gas flow of 100 mL min−1.
Gas sorption analysis. Nitrogen adsorption-desorption isotherm was collected at 77 K using a Micrometrics Tristar II PLUS Surface Area and Porosity Analyzer. Guest species were removed from the pores of the material under dynamic vacuum as detailed in the experimental section, before being degassed on the analysis port for 2 hours at 77 K prior to measurement. BET area was calculated using the pressure range 0.008<P/P0<0.05, which was selected using the consistency criteria.
Laboratory PXRD. Laboratory based powder X-ray data were collected at room temperature on Bruker D8 Advance diffractometers with a monochromated Cu radiation source (Kα1, λ=1.5406 Å).
Synchrotron PXRD. Synchrotron powder X-ray diffraction data were collected at the I11 beam line at Diamond Light Source with λ=0.826596(10) Å. Data were collected at room temperature using the Position Sensitive Detector (PSD, Mythen-2), with the samples sealed in borosilicate capillaries.
Comparison of the PXRD pattern of Zr6(BDC)3(Fum)3 with those of UiO-66 and MOF-801 suggests that the new material adopts a different symmetry. As a consequence, an independent indexing procedure was performed. A standard peak search followed by profile fitting was used to estimate the low-to-medium-angle peak maximum positions, providing approximate unit cell parameters through the Singular Value Decomposition algorithm as implemented in TOPAS-Academic V5. The space group was assigned based on the observed systematic absences which were consistent with R
Calculation of T:F Ratio by 1H NMR: The incorporation of both the terephthalate and fumarate linkers in the materials was determined by 1H NMR of the digested samples in a mixture of NaOD (60 μL) and D2O (640 μL). The relative quantities in which the two linkers present in the samples was determined from the relative integrations of the corresponding peaks for each of these species. In each spectrum the relative integration of terephthalate, which has 4 protons, was taken to be equal to 1. Therefore, as each molecule of fumarate contains only 2 protons, half that of terephthalate, in order to calculate the quantity of formate present and the T:F ratio of each sample, the relative integration of the fumarate peak in the spectra was doubled, an equivalent operation to dividing the value of the integration by the number of protons of fumarate, 2, and multiplying by the number of protons of terephthalate, 4, which the integrations were calculated relative to.
Calculation of the Volume of Chemical Space Explored: The region of the chemical space explored in the first iteration of the synthesis (
From the calculated volumes of the polygons which represent the regions of chemical space explored in batches 1 and 2, 65.80 and 4.49 respectively, the volume of the region defined by the points of batch 2 was calculated to be 14.7 times smaller than that which is defined by the points of batch 1.
In calculating the T:F:MeOH:FA molar ratios of the methanol exchanged material (
The experimental values for the BET surface area and pore volume of MOF-801 and UiO-66 MOFs were taken from Furukawa et al., while the values for our material were obtained following the protocols described in section Methods. The calculated values were obtained using Zeo++ for a spherical probe of 3.64 Å in diameter (the kinetic diameter of a dinitrogen molecule) for reported CIF files of the three MOFs. To standardise the description of the [Zr6O4(OH)4]12+ cluster in all three structures, all μ3-O(H) bridges were treated as equivalent to each other and represented by a single oxygen atom located at the average position of the two oxygen atoms. The calculated values in Table S10 were obtained using the calculated density of an ideal defect-free structure. All calculated values are very much in line with the experimental observations.
The ditopic linkers terephthalate and fumarate were selected for the exploration of mixed-linker Zr MOF synthesis as they both form 12-c fcu topology MOFs, UiO-66 and MOF-801 (
The synthesis of UiO-66 and MOF-801 has been achieved over a broad range of overall concentrations and compositions of the starting materials in various solvent systems. We chose ZrOCl2·8H2O as the metal source because it forms the stable solutions essential for automated dispensing. We then selected the reaction conditions to be explored for the robotic high-throughput synthesis of Zr-based MOF with mixed terephthalate (T) and fumarate (F) linkers by evaluating reported conditions from the literature where ZrOCl2·8H2O was used (summarised in
We adopted a grid search and used automated dispensing of reaction mixtures by liquid-handling robots to accelerate the exploration of the space. The chemical space was sub-divided to span a broad range of compositions, covered by a set of 45 points (Table S2), in the first, broad iteration of the exploration of new phases. The two linkers were introduced in mixtures of five different compositions, T:F=1:0, 0.75:0.25, 0.5:0.5, 0.25:0.75 and 0:1, at each of three molar ratios between ZrOCl2 and total amount of linker Zr:(T+F)=0.25:0.75, 0.5:0.5, and 0.66:0.33 (
After the completion of the reactions, the samples were classified by visual inspection. Only 11 out of 45 (light grey in
The PXRD pattern from the sample with composition Zr:T:F=0.5:0.25:0.25 and FA:Zr=334, marked as the circled blue point in
The second iteration of reactions was focused in a region of the chemical space (
As observed in the first batch, in the second batch there were distinct regions where the reactions yielded no solid product, which were the mixtures with low linker and high modulator content, and regions where solid product was formed. PXRD patterns of the solid products (
Zr6(BDC)3(Fum)3 is a 12-c framework of [Zr6O4(OH)4]12+ clusters connected by six terephthalates and six fumarates in the fcu topology (
The lower rhombohedral symmetry of Zr6(BDC)3(Fum)3 (
Zr clusters and fumarates thus form close-packed hexagonal layers, describing the ab plane of the rhombohedral structure, which are connected by the terephthalates (
The two windows in Zr6(BDC)3(Fum)3 define two types of possible diffusion pathways for guest molecules. In the path parallel to the Zr fumarate layers, the guest passes through the 2T1F window only (blue arrow in
The organic components of Zr6(BDC)3(Fum)3 were analysed by 1H NMR after digestion of the sample in NaOD/D2O. The MeOH-exchanged sample displays molar ratios T:F:MeOH:FA=1:0.92:3.4:0.2 (
The experimental BET surface area and pore volume of Zr6(BDC)3(Fum)3 lie between the respective values of MOF-801 (690 m2g−1/0.27 cm3g−1) and UiO-66 (1290 m2g−1/0.49 cm3g−1). The ordered arrangement of two ditopic linkers in the fcu net controls the global porous properties, surface area and pore volume, as well as the local ones, the size and the shape of the individual cages and windows. This approach offers additional tuning capabilities for the porous properties of a high symmetry net through the precise locally-and long-range ordered definition of intermediate surface areas created from distinct pore shapes. The well-established isoreticular expansion or contraction of a single linker MOF offer large changes in surface area and pore size that preserve the shape and number of cages and windows, while solid solution mixed-linker MOFs generate intermediate surface areas in locally heterogeneous pore systems arising from long-range multiple linker disorder.
General Experimental Details: All reagents were purchased from commercial suppliers and used without modification. Zirconyl chloride octahydrate (ZrOCl2·8H2O, purity 98%), zirconium chloride (ZrCl4, anhydrous, purity 99.99%), thiophene dicarboxylic acid (purity≥99%), terephthalic acid (purity≥98%), sodium hydroxide-d (40 wt. % in D2O) and deuterium oxide (99.9 atom % D) were obtained from Sigma-Aldrich Co. N,N-Dimethylformamide (DMF) and methanol were obtained from Fisher Scientific. Formic acid (purity 97%) was obtained from Alfa Aesar. Automated liquid dispensation was performed with an Eppendorf epMotion 5075t liquid-handling platform. 20 mL headspace screw neck glass vials with metal screw caps were purchased from VWR International.
MOF synthesis with liquid-handling robots: Mixed-linkerZr-based MOFs with terephthalate and thiophene dicarboxylate linkers, were prepared in batches and the components of each reaction mixture were transferred to the reaction vessel, a 20 mL headspace screw neck glass vial, by automated dispensation of their solution in DMF, with the exception of formic acid, which was dispensed neat. In a typical batch synthesis, ZrOCl2·8H2O was dissolved in DMF to prepare a stock solution of concentration 0.0225 M. The concentration of this solution was fixed, and chosen to be as high as possible, whilst remaining below the solubility limit of ZrOCl2·8H2O in DMF at room temperature to ensure that the solution remained as a stable homogeneous mixture for the entire duration of the automated sample preparation. The volume of 0.0225 M ZrOCl2·8H2O stock solution dispensed into each reaction mixture, and therefore the quantity of ZrOCl2·8H2O used in each 10 mL scale reaction was also fixed at 38 mg, 0.12 mmol. The linker stock solutions were prepared by dissolving terephthalic acid and 2,5-thiophenedicarboxylic acid in DMF at a total linker, (T+S), concentration of 0.15 M, with different T:S molar ratios (Table 1). The different reaction mixtures were prepared using the Eppendorf epMotion 5075t liquid handling platform, with dispensation directly into the reaction vessel. In each batch of syntheses, the individual reaction mixtures were prepared in parallel and the components were added to the mixture in the same order (formic acid —ZrOCl2·8H2O stock—T:S linker stock—DMF). DMF was dispensed into each vial to ensure every reaction had the same fill factor, with a total reaction solution volume of 10 mL. The vials were then sealed with metal screw caps, before being heated at 120° C. for 48 hours. Powder products were collected by centrifugation and washed with DMF and methanol.
Batch synthesis Experimental: A stock solution of the metal source was prepared by dissolving ZrOCl2·8H2O (7.882 mmol, 2.54 g) in DMF (300 mL). Linker stock solutions with five different T: S molar ratios, T:S=0.75:0.25, 0.67:0.33, 0.5:0.5, 0.33:0.67 and 0.25:0.75, were prepared at a total linker (T+S) concentration of 0.15 M in DMF (25 mL). The quantities of terephthalic acid and 2,5-thiophenedicarboxylic acid used in each solution are summarised in Table 1.
The order in which the reaction components were added, formic acid —ZrOCl2·8H2O stock—T:S linker stock—DMF, was the same for each of the 60 individual reaction mixtures in the batch, with the process of automated dispensation lasting 2 hours. The vials were sealed with metal screw caps before being heated at 120° C. for 48 hours. Selected powder products were collected by centrifugation and washed three times each with DMF (25 mL) followed by methanol (25 mL).
Products that were identified from batch synthesis as phase pure, were scaled-out to obtain more material. Synthesis of selected compositions (formic acid —ZrOCl2·8H2O stock—T:S linker stock-DMF) were repeated up to 15 times within separate 20 mL screw-capped vials, following the same conditions as described for MOF synthesis with liquid-handling robots. The powder products in separate vials were checked for phase purity with Powder X-Ray Diffraction patterns, then combined for washing and use for further analysis.
Solvent Exchange and Activation: Reaction mixtures from the scale-out syntheses described above, which yielded the Zr6(BDC)4(TDC)2 phase with high purity were combined and the material collected by centrifugation. The supernatant was decanted, replaced with DMF (25 mL) and the mixture stirred for 1 hour. This process of washing with DMF was repeated three times. The DMF was then decanted after centrifugation, and the material was stirred in methanol (25 mL) and the mixture stirred for 1 hour, this was repeated. Then fresh methanol was added and the mixture was stirred overnight, and the methanol was replaced afterwards. Each time the methanol was replaced, the material was collected by centrifugation, solvent decanted and the material allowed to dry under atmospheric conditions to the point that it can be handled as a powder.
Before and after the overnight stirring in methanol, 1H NMR was obtained after digestion of a small amount of the material in NaOD (60 μL) and D2O (640 μL). Only very low intensity peaks for the presence of DMF decomposition products were observed by NMR after the overnight washing. The methanol exchanged material, which exhibited no phase change by PXRD after the solvent exchange, giving the Zr6(BDC)4(TDC)2 purely, was activated under high-vacuum (10-5 bar) at 150° C. for 24 hours to remove all guest species. The activated material was transferred to the sample tube for porosity measurement under an Ar atmosphere.
Nuclear Magnetic Resonance (NMR) spectroscopy. All 1H NMR spectra were recorded in solution using a Bruker ADVANCE-400 MHZ NMR spectrometer. All spectra were recorded in a solvent mixture of D2O (640 μL) and NaOD (60 μL), with the residual solvent peak of D2O (4.79 ppm for 1H).
Thermal analysis. Thermal Gravimetric Analysis (TGA) was performed under air atmosphere on a TA Instruments Q600 between 25 and 1000° C., with a scan rate of 10° C. min−1 and gas flow of 100 mL min−1.
Gas sorption analysis. Nitrogen adsorption-desorption isotherm was collected at 77 K using a Micrometrics Tristar II PLUS Surface Area and Porosity Analyzer. Guest species were removed from the pores of the material under dynamic vacuum as detailed in the experimental section, before being degassed on the analysis port for 2 hours at 77 K prior to measurement. BET area was calculated using the pressure range 0.008<P/P0<0.05, which was selected using the consistency criteria.
Laboratory PXRD. Laboratory based powder X-ray data were collected at room temperature on Bruker D8 Advance diffractometers with a monochromated Cu radiation source (Kα1, Å=1.5406 Å).
Synchrotron PXRD. Synchrotron powder X-ray diffraction data were collected at the 111 beam line at Diamond Light Source with λ=0.826596(10) Å. Data were collected at room temperature using the Position Sensitive Detector (PSD, Mythen-2), with the samples sealed in borosilicate capillaries.
Comparison of the PXRD pattern of Zr6(BDC)4(TDC)2 with those of UiO-66 and DUT-67 suggests that the new material adopts a different symmetry. As a consequence, an independent indexing procedure was performed. A standard peak search followed by profile fitting was used to estimate the low-to-medium-angle peak maximum positions, providing approximate tetragonal unit cell parameters (a=20.0053 Å, c=42.1233 Å) through the Singular Value Decomposition algorithm as implemented in TOPAS-Academic V5. The space group was assigned based on the observed systematic absences which were consistent with I41/acd. The structure model was built based on the comparison of the unit cell with that of UiO-66, slightly smaller a and b axes and c axis of double length. The crystallographically independent portion of the Zr6O8 cluster and of the terephthalate and thiophene dicarboxylate linkers were modelled by rigid bodies through the z-matrix formalism. The structure refinement was then carried out with the Rietveld method, as implemented in TOPAS-Academic V5.
Calculation of T:S Ratio by 1H NMR: The incorporation of both the terephthalate and fumarate linkers in the materials was determined by 1H NMR of the digested samples in a mixture of NaOD (60 μL) and D2O (640 μL). The relative quantities in which the two linkers present in the samples was determined from the relative integrations of the corresponding peaks for each of these species. In each spectrum the relative integration of terephthalate, which has 4 protons, was taken to be equal to 1. Therefore, as each molecule of thiophene dicarboxylate contains only 2 protons, half that of terephthalate, in order to calculate the T:S ratio of each sample, the relative integration of the thiophene dicarboxylate peak in the spectra was doubled.
The ditopic linkers terephthalate (BDC or T) and thiophene dicarboxylate (TDC or S) were selected for the exploration of mixed-linker Zr MOF synthesis as they both form MOFs, UiO-66 and DUT-67 respectively, and they differ in length (the distance between carboxylate carbons is 6.0 and 5.3 Å respectively) and shape (linear versus bent,
The synthesis of UiO-66 and DUT-67 has been achieved over a broad range of overall concentrations and compositions of the starting materials in various solvent systems. We chose ZrOCl2·8H2O as the metal source because it forms the stable solutions essential for automated dispensing. We then selected the reaction conditions to be explored for the robotic high-throughput synthesis of Zr-based MOF with mixed terephthalate (T) and thiophene dicarboxylate(S) linkers by evaluating reported conditions from the literature where ZrOCl2·8H2O was used in Zr MOF synthesis. The solvent, DMF, and modulator, formic acid, were chosen to be the same for all reactions as they have been used extensively in synthesis of both UiO-66 and DUT-67. The time and temperature of reaction were fixed at 48 hours and 120° C. respectively, to provide sufficient duration and high enough temperature to favour formation of a new phase without encountering problems due to DMF volatility. In order to exploit the liquid-handling robot used to prepare reaction mixtures, we selected conditions that enabled the use of stock solutions of the reaction components. The implicit necessity for these solutions to be stable at room temperature throughout the duration of the automated sample preparation, which required up to 2 hours to complete, imposed a limit on the concentration of the ZrOCl2·8H2O stock solution used of 0.0225 M, because of its solubility in DMF. The volume of this stock solution added to each reaction mixture was also fixed, giving each 10 mL-scale reaction mixture the same ZrOCl2·8H2O concentration of 38 mg/10 mL. The combinatorial parameters explored in the high-throughput syntheses were thus limited to the ratio between the two linkers, (T:S), and their total amount relative to the quantity of Zr, Zr:(T+S), as well as the amount of formic acid (FA:Zr). These three parameters were expected to have the largest influence on the chemistry and potential formation of a new phase.
We adopted a grid search and used automated dispensing of reaction mixtures by liquid-handling robots to accelerate the exploration of the space. The chemical space was sub-divided to span a broad range of compositions, covered by a set of 60 points (Table 2), in the first, broad iteration of the exploration of new phases. The two linkers were introduced in mixtures of five different compositions, T:S=0.75:0.25, 0.67:0.33, 0.5:0.5, 0.33:0.67 and 0.25:0.75, at each of four molar ratios between ZrOCl2 and total amount of linker Zr:(T+S)=0.33:0.67,0.4:0.6 0.5:0.5, and 0.67:0.33 (
After the completion of the reactions, the samples were classified by visual inspection. Only 5 out of 60 (brown in
The sample with composition Zr:T:S=0.5:0.25:0.25 and FA:Zr=310 exhibits the pure form of the new phase. Zr6(BDC)4(TDC)2 crystallizes in I41/acd (space group no. 142), a=b=19.9887(7) Å, c=42.0560(4) Å, V=16803.23(8) Å3. The space group assignment was based on the observed systematic absences. The structure model was built based on the comparison of the unit cell with that of UiO-66, slightly smaller a and b axes and c axis of double length. The structure refinement was performed by Rietveld method with TOPAS-Academic V5 (see Characterisation Techniques and
Zr6(BDC)4(TDC)2 is a 12-c framework of [Zr6O4(OH)4]12+ clusters connected by eight terephthalates and four thiophene dicarboxylates in the fcu topology (
The lower tetragonal symmetry of Zr6(BDC)4(TDC)2 compared to the cubic Fm
This regular arrangement of two linkers with different lengths on the fcu net (
The organic components of Zr6(BDC)4(TDC)2 were analysed by 1H NMR after digestion of the sample in NaOD/D2O. The MeOH-exchanged samples (
Zr6(BDC)4(TDC)2 exhibits a type I N2 adsorption desorption isotherm (
General Experimental Details: All reagents were purchased from commercial suppliers and used without modification. Zirconyl chloride octahydrate (ZrOCl2·8H2O, purity 98%), zirconium chloride (ZrCl4, anhydrous, purity 99.99%), fumaric acid (purity ≥99%), terephthalic acid (purity ≥98%), sodium hydroxide-d (40 wt. % in D2O) and deuterium oxide (99.9 atom % D) were obtained from Sigma-Aldrich Co. N,N-Dimethylformamide (DMF) and methanol were obtained from Fisher Scientific. Formic acid (purity 97%) was obtained from Alfa Aesar. Automated liquid dispensation was performed with an Eppendorf epMotion 5075t liquid-handling platform. 20 mL headspace screw neck glass vials with metal screw caps were purchased from VWR International.
Zr(BDC)(2,6NDC) MOF synthesis with liquid-handling robots: Mixed-linker Zr-based MOFs with terephthalate (BDC) and 2,6-naphthalenedicarboxylate (NDC) linkers, were prepared in batches and the components of each reaction mixture were transferred to the reaction vessel, a 20 mL headspace screw neck glass vial, by automated dispensation of their solution in DMF, with the exception of acetic acid (AA), which was dispensed neat. In a typical batch synthesis, ZrOCl2·8H2O (1.81 g, 5.63 mmol) was dissolved in DMF (250 mL) to prepare a stock solution of concentration 0.02 M. Terephthalic acid (8.31 g, 50 mmol) was dissolved in DMF (250 mL) to produce a stock solution with a concentration of 0.2 M. Similarly, a stock solution of 2,6-NDC was prepared by dissolving 2,6-NDC (2.70 g, 12.5 mmol) in DMF (250 mL). All stock solutions were sonicated for 10 minutes after the addition of solvent to aid dissolution. The different reaction mixtures were prepared using the Eppendorf epMotion 5075t liquid handling platform, with dispensation directly into the reaction vessel. In each batch of syntheses, the individual reaction mixtures, the compositions of which varied by Zr:L, T:N and AA:Zr ratios, were prepared in parallel and the components were added to the mixture in the same order (acetic acid—ZrOCl2·8H2O stock—2,6-NDC and terephthalate linker stocks—DMF). DMF was dispensed into each vial to ensure every reaction had the same fill factor, with a total reaction solution volume of 15 mL. The vials were then sealed with metal screw caps, before being heated at 120° C. for 72 hours. Powder products were collected by centrifugation and washed with DMF (10 mL) and acetone (20 mL). In the first iteration of the synthesis, referred to as batch 1, 45 different reaction mixtures were prepared. The subsequent two iterations, referred to as batch 2 and batch 3, consisted of 24 and 36 samples respectively. The specific compositions of the samples prepared in each of the three iterations of the synthesis performed are detailed in Tables 3 to 5.
Nuclear Magnetic Resonance (NMR) spectroscopy. All cH NMR spectra were recorded in solution using a Bruker ADVANCE-400 MHz NMR spectrometer. All spectra were recorded in a solvent mixture of D2O (640 μL) and NaOD (60 μL), with the residual solvent peak of D2O (4.79 ppm for 1H).
Laboratory PXRD. Laboratory based powder X-ray data were collected at room temperature on Bruker D8 Advance diffractometers with a monochromated Cu radiation source (Kα1, λ=1.5406 Å).
Comparison of the PXRD pattern of Zr6(BDC)(NDC)4 with those of UiO-66, DUT-52, DUT-53 and DUT-84 suggests that the new material adopts a different symmetry. As a consequence, an independent indexing procedure was performed. A standard peak search followed by profile fitting was used to estimate the low-to-medium-angle peak maximum positions, providing approximate orthogonal unit cell parameters (a=14.7101 Å, b=16.9534 c=25.2602 Å) through the Singular Value Decomposition algorithm as implemented in TOPAS-Academic V5. The space group was assigned based on the observed systematic absences which were consistent with Immm. The structure model was built based on the comparison of the unit cell with that of DUT-53, slightly smaller a and b axes and longer c axis. The crystallographically independent portion of the Zr6O8 cluster and of the terephthalate and naphthalene dicarboxylate linkers were modelled by rigid bodies through the z-matrix formalism. The structure refinement was then carried out with the Rietveld method, as implemented in TOPAS-Academic V5.
Calculation of T:N Ratio by 1H NMR: The incorporation of both the terephthalate and naphthalene dicarboxylate linkers in the materials was determined by 1H NMR of the digested samples in a mixture of NaOD (60 μL) and D2O (640 μL). The relative quantities in which the two linkers present in the samples was determined from the relative integrations of the corresponding peaks for each of these species. In each spectrum the relative integration of terephthalate, which has 4 protons, was taken to be equal to 1. Therefore, as each molecule of naphthalene dicarboxylate contains 6 protons, three times that of terephthalate, in order to calculate the T:N ratio of each sample, the relative integration of the naphthalene dicarboxylate peak in the spectra was divided by 1.5
The ditopic linkers terephthalate (BDC or T) and 2,6-naphthalene dicarboxylic acid (NDC or N) were selected for the exploration of mixed-linker Zr MOF synthesis as they both form 12-c fcu topology MOFs, UiO-66 and DUT-52 respectively, and they differ in length (the distance between carboxylate carbons is 6.0 and 8.0 Å respectively) and shape (linear versus zig-zag,
The synthesis of UiO-66 and DUT-52 has been achieved over a broad range of overall concentrations and compositions of the starting materials in various solvent systems. We chose ZrOCl2·8H2O as the metal source because it forms the stable solutions essential for automated dispensing. We then selected the reaction conditions to be explored for the robotic high-throughput synthesis of Zr-based MOF with mixed terephthalate (T) and naphthalene dicarboxylate (N). The solvent, DMF, and modulator, acetic acid, were chosen to be the same for all reactions as they have been used in synthesis of both UiO-66 and DUT-52. The time and temperature of reaction were fixed at 72 hours and 120° C. respectively, to provide sufficient duration and high enough temperature to favour formation of a new phase without encountering problems due to DMF volatility. In order to exploit the liquid-handling robot used to prepare reaction mixtures, we selected conditions that enabled the use of stock solutions of the reaction components.
We adopted a grid search and used automated dispensing of reaction mixtures by liquid-handling robots to accelerate the exploration of the space. The chemical space was sub-divided to span a broad range of compositions, covered by a set of 45 points (Table 3), in the first, broad iteration of the exploration of new phases. The two linkers were mixed in five different compositions, T:N=0.75:0.25, 0.66:0.34, 0.5:0.5, 0.34:0.66, and 0.25:0.75, at each of three molar ratios between ZrOCl2 and total amount of linker Zr:(T+N)=0.25:0.75, 0.5:0.5, and 0.66:0.34 (
After the completion of the reactions, the samples were classified by visual inspection. Only 6 out of 45 (grey in
The second batch of reactions was focused in a region of the chemical space around the hit of the first batch (B1 Hit in
PXRD patterns of the solid products showed that the known mixed cubic phase and 6-c DUT-84 are formed in the samples of this batch. Exception is the sample with composition AA:Zr=400, Zr:(T+N)=0.25:0.75 and T:N=0.25:0.75 (B2 Hit in
The third batch of reactions, marked with blue points in
The new phase Zr6(BDC)(NDC)4 crystallizes in Immm (space group no. 71), a=14.9651(9) Å, b=16.901(1) Å, c=25.1785(8) Å, V=6253.38(8) Å3. The structure model was built based on the comparison of the unit cell with that of DUT-53, slightly smaller a and b axes and longer c axis. The structure refinement was performed by Rietveld method with TOPAS-Academic V5 (see Characterisation Techniques and
Zr6(BDC)(NDC)4 is a 10-c framework of [Zr6O4(OH)4]12+ clusters connected by two terephthalates and eight napthalate dicarboxylates in the bet topology (
The lower orthorhombic symmetry of Zr6(BDC)(NDC)4 compared to the tetragonal I4/mmm structure of the 8-c DUT-53 is associated with the arrangement of the terephthalate linker that connects Zr6 clusters along a axis (
The organic components of Zr6(BDC)(NDC)4 were analysed by 1H NMR after digestion of the sample in NaOD/D2O (
The inventors have identified three-dimensional metal-organic framework, MOF, comprising a plurality of crystallographically-ordered heterolinkers, including a first linker and a second linker, respectively periodically arranged between metal nodes, defining cages having a plurality of mutually different window types, including a first window type and a second window type, therebetween, wherein the respective window types correspondingly comprise mutually different heterolinker arrangements. In this way, the structure of the MOF may be precisely controlled and/or the functional properties finely tuned, thereby controlling global properties of the MOF, for example porous properties, surface area and pore volume, as well as the local properties, for example the size and/or the shape of cages and/or windows therebetween.
The inventors have synthesised and characterised three example MOFs: Zr6(BDC)3(Fum)3, Zr6(BDC)4(TDC)2 and Zr6(BDC)(NDC)4.
The two-linker ordered MOF, Zr6(BDC)3(Fum)3, was discovered by high-throughput experimental exploration of the chemical space defined by ZrOCl2, terephthalic acid, fumaric acid and formic acid. The material is only formed in a narrow region of this space, in contrast to the linker-disordered cubic material formed by the same two linkers. The identification of the linker-ordered system by single-step self-assembly then required the screening at fine compositional resolution that is enabled by the high-throughput approach. Although each linker individually affords an important, well-studied member of the key fcu net Zr-based MOF family, both with one pore window and a single guest diffusion path, Zr6(BDC)3(Fum)3 is not a simple intermediate between these structures. Rather, its structure is generated by ordered linker decoration of the fcu net that breaks the symmetry to introduce anisotropy into the three-dimensional porosity, which is now characterised by two distinct diffusion paths. The ordering of terephthalate and fumarate binding to the [Zr6O4(OH)4]12+ cluster creates two windows of different shape that describe the distorted octahedral and tetrahedral cages defining these paths. This ordering precisely defines the porosity locally to each cage and is distinct from the locally heterogeneous tuning offered by disordered multiple linker MOF average structures. The resulting simultaneous tuning of pore size and shape, which affords interval pore volume between the parents, differs from isoreticular expansion in that it tunes within a defined range of extra-framework space. Multiple linker ordered decoration of canonical single linker MOF topologies can harness the resulting combinatorial and chemical diversity of linker sets to generate new porous materials families where the size and shape of the internal space can be precisely modified for optimal guest interaction.
Zr6(BDC)4(TDC)2 crystallizes in I41/acd (space group no. 142), a=b=19.9887 (7) Å, c=42.0560 (4) Å, V=16803.23(8) Å3. Zr6(BDC)4(TDC)2 is a 12-c framework of [Zr6O4(OH)4]12+ clusters connected by eight terephthalates and four thiophene dicarboxylates in the fcu topology. The Zr6 core of the cluster adopts tetragonal bipyramidal geometry, where the four equatorial edges are occupied in an ordered manner only by the thiophene dicarboxylate linkers, which connect with four other clusters. The remaining eight edges of the cluster are occupied by terephthalates that connect to eight other clusters.
The new phase Zr6(BDC)(NDC)4 crystallizes in Immm (space group no. 71), a=14.9651 (9) Å, b=16.901(1) Å, c=25.1785(8) Å, V=6253.38(8) Å3. Zr6(BDC)(NDC)4 is a 10-c framework of [Zr6O4(OH)4]12+ clusters connected by two terephthalates and eight napthalate dicarboxylates in the bct topology. The Zr6 core of the cluster adopts tetragonal bipyramidal geometry, where two of the four equatorial edges are occupied in an ordered manner only by the terephthalate linkers, which connect with two other clusters, and the other two are occupied by terminal acetate ligands. The remaining eight edges of the cluster are occupied by naphthalene dicarboxylates that connect to eight other clusters.
Although a preferred embodiment has been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims and as described above.
Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.
All of the features disclosed in this specification (including any accompanying claims and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at most some of such features and/or steps are mutually exclusive.
Each feature disclosed in this specification (including any accompanying claims, and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.
The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2110269.4 | Jul 2021 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2022/051836 | 7/15/2022 | WO |
