Patent Application
20240317785
The present application is in the field of metal-organic frameworks. More specifically, the present application relates to process for their preparation and uses thereof.
Porous solids, depending on their components, topology, and stability, can have applications ranging from separations and catalysis to sensing and delivery vessels, to name a few general categories. With the evolution of new classes of porous solids-such as metal-organic frameworks (MOFs), covalent organic frameworks (COFs), polymers of intrinsic microporosity (PIMs), porous aromatic frameworks (PAFs), and porous molecular cages—the ability to tune the chemistry and engineering of porous materials has increased significantly. With any porous solid, there are challenges to its formation and utilization. From surface enthalpic considerations, a void in a solid is always unfavorable, molecular surfaces exposed to nothing (vacuum) will be stabilized by any interaction with another molecular surface. As such, the bonds and interactions sustaining a pore pay the energetic penalty for forming a void. On the basis of this criterion, strong bonding and interactions are highly desirable. A second desired feature is order. Order in a porous material translates to regular pore size and geometry and hence more predictable performance in terms of adsorption, as well as the ability to develop structure-property relationships. In some cases, lower degree of order may be desirable, for example in the transport of solids. As such, materials having a tunable degree of order are desirable.
Specifically, MOFs are a class of material where metal clusters are linked together by organic linkers in intricate structures through coordination bonds. MOFs are typically noted for balancing porosity and crystallinity while offering systematic structural variation. Interestingly, the IUPAC definition of a MOF is a coordination network requiring potential porosity and does not demand crystallinity. That said, the majority of interest in MOFs stems from their porosity, which can be finely tuned for an ever increasing range of applications. While single crystallinity facilitates structure determination and consequently dissemination, for most practical targets, crystallinity is not needed. However, for most applications, a MOF needs to maintain framework integrity upon exposure to water. For this reason, there is a need for MOFs having higher chemical, thermal and hydrolytic stability.
Compared to traditional carboxylate MOFs counterparts, metal phosphonate MOFs are more stable, from thermal, chemical, and hydrolytic perspectives. This is due to their robust coordination bonds between metal and oxygen of phosphonate groups. This is often accompanied by the formation of dense and amorphous products owing to the rapid formation of bonds in multiple dimensions.
As a corollary, the stronger phosphonate-metal bond often means lack of reversibility in assembly, giving less ordered materials. While monovalent and divalent metal phosphonates can display sufficient kinetic reversibility to yield materials with, if not single crystallinity, at least some structural coherence, higher valency metal phosphonates tend to precipitate rapidly as amorphous solids.
There is need to provide MOFs having higher chemical, thermal and hydrolytic stability. Alternative synthetic methods are also needed, especially for the tri- and tetra-valence metals.
It has been surprisingly shown herein that chromium(III) phosphonate MOFs of the present application provide highly stable and porous MOFs, with tunable degrees of coherence. The processes of the present application provide for the preparation of such chromium(III) phosphonate MOFs. Specifically, chromium(III) phosphonate MOFs obtained from hydrogen-bonded metal-organic frameworks (HMOFs) provide ordered and stable porous materials. Comparable materials and processes did not display the same properties, highlighting the surprising results obtained with the materials and processes of the application.
Accordingly, the present application includes a process for preparing a chromium(III) phosphonate metal-organic framework (MOF) comprising:
The present application further includes a process for preparing a chromium(III) phosphonate metal-organic framework (MOF) comprising:
Also provided is chromium(III) phosphonate MOFs prepared using the process of the present application.
The present application also includes a method to uptake at least one substance comprising contacting a source comprising the at least one substance with the MOFs of the present application under conditions for uptake of the at least one substance into the MOFs.
Also included is a MOF or HMOF prepared using a process of the present application further comprising at least one substance or at least one gas.
Further provided is a proton conducting solid comprising a MOF prepared using a process of the present application.
Also provided is an ion conducting solid comprising a MOF prepared using a process of the present application.
Provided is a battery comprising the ion conducting solid of the present application.
Other features and advantages of the present application will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating embodiments of the application, are given by way of illustration only and the scope of the claims should not be limited by these embodiments, but should be given the broadest interpretation consistent with the description as a whole.
The embodiments of the application will now be described in greater detail with reference to the attached drawings in which:
Unless otherwise indicated, the definitions and embodiments described in this and other sections are intended to be applicable to all embodiments and aspects of the present application herein described for which they are suitable as would be understood by a person skilled in the art.
The term “and/or” as used herein means that the listed items are present, or used, individually or in combination. In effect, this term means that “at least one of” or “one or more” of the listed items is used or present.
As used in the present application, the singular forms “a”, “an” and “the” include plural references unless the content clearly dictates otherwise.
In embodiments comprising an “additional” or “second” component, such as an additional or second compound, the second component as used herein is chemically different from the other components or first component. A “third” component is different from the other, first, and second components, and further enumerated or “additional” components are similarly different.
As used in this application and claim(s), the words “comprising” (and any form of comprising, such as “comprise” and “comprises”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “include” and “includes”) or “containing” (and any form of containing, such as “contain” and “contains”), are inclusive or open-ended and do not exclude additional, unrecited elements or process steps.
The term “consisting” and its derivatives as used herein are intended to be closed terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, and also exclude the presence of other unstated features, elements, components, groups, integers and/or steps.
The term “consisting essentially of”, as used herein, is intended to specify the presence of the stated features, elements, components, groups, integers, and/or steps as well as those that do not materially affect the basic and novel characteristic(s) of these features, elements, components, groups, integers, and/or steps.
The term “suitable” as used herein means that the selection of the particular composition or conditions would depend on the specific steps to be performed, the identity of the components to be transformed and/or the specific use for the compositions, but the selection would be well within the skill of a person trained in the art.
The present description refers to a number of chemical terms and abbreviations used by those skilled in the art. Nevertheless, definitions of selected terms are provided for clarity and consistency.
The terms “about”, “substantially” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. These terms of degree should be construed as including a deviation of at least ±5% of the modified term if this deviation would not negate the meaning of the word it modifies or unless the context suggests otherwise to a person skilled in the art.
The term “aq.” as used herein refers to aqueous.
The term “alkyl” as used herein, whether it is used alone or as part of another group, means a straight or branched chain, saturated, unsubstituted or substituted alkyl group. The number of carbon atoms that are possible in the referenced alkyl group are indicated by the prefix “Cn1-n2”. For example, the term C1-4 alkyl means an alkyl group having 1, 2, 3 or 4 carbon atoms.
The term “aryl” as used herein, whether it is used alone or as part of another group, refers to carbocyclic groups containing at least one aromatic ring. Aryl groups are either unsubstituted or substituted.
The term “heteroaryl” as used herein, whether it is used alone or as part of another group, refers to cyclic groups containing at least one heteroaromatic ring in which one or more of the atoms are a heteroatom selected from O, S and N and the remaining atoms are C. Heteroaryl groups are either unsubstituted or substituted.
The term “alkylene”, whether it is used alone or as part of another group, means a straight or branched chain, saturated, unsubstituted or substituted alkylene group, that is, a saturated carbon chain that contain substituents on two or more of its ends. The number of carbon atoms that are possible in the referenced alkylene group are indicated by the prefix “Cn1-n2”. For example, the term C1-6alkylene means an alkylene group having 1, 2, 3, 4, 5 or 6, carbon atoms.
The term “alkenylene”, whether it is used alone or as part of another group, means a straight or branched chain, unsaturated, unsubstituted or substituted alkylene group, that is, an unsaturated carbon chain that contains substituents on two or more of its ends and at least one double bond. The number of carbon atoms that are possible in the referenced alkenylene group are indicated by the prefix “Cn1-n2”. For example, the term C2-6alkylene means an alkylene group having 2, 3, 4, 5 or 6, carbon atoms.
The term “alkynylene”, whether it is used alone or as part of another group, means a straight or branched chain, unsaturated, unsubstituted or substituted alkylene group, that is, an unsaturated carbon chain that contains substituents on two or more of its ends and at least one triple bond. The number of carbon atoms that are possible in the referenced alkynylene group are indicated by the prefix “Cn1-n2”. For example, the term C2-6alkynylene means an alkylene group having 2, 3, 4, 5 or 6, carbon atoms.
The term “cycloalkylene”, whether it is used alone or as part of another group, means an unsubstituted or substituted cycloalkylene group, that is, a saturated carbocycle that contains substituents on two or more of its ends. The number of carbon atoms that are possible in the referenced cycloalkylene group are indicated by the prefix “Cn1-n2”. The cycloalkylene group is either monocyclic or polycyclic, with polycyclic rings being either bridged, fused, spirocyclic or linked by a bond.
The term “arylene”, whether it is used alone or as part of another group, means an unsubstituted or substituted arylene group, that is, an unsaturated carbocycle that contains at least one aromatic ring and substituents on two or more of its ends. The arylene group is either monocyclic or polycyclic, with polycyclic rings being either bridged, fused, spirocyclic or linked by a bond.
The term “heteroarylene”, whether it is used alone or as part of another group, means an unsubstituted or substituted heteroarylene group, that is, a cyclic group containing at least one heteroaromatic ring in which one or more of the atoms are a heteroatom selected from O, S and N and the remaining atoms are C, and substituents on two or more of its ends. The heteroarylene group is either monocyclic or polycyclic, with polycyclic rings being either bridged, fused, spirocyclic or linked by a bond.
The term “aryl-based” in reference to a polyphosphonic acid or a salt thereof means that the phosphonic acid groups are substituents on one or more aryl rings which, in the case of two or more aryl rings, are either fused or linked together by a linker group.
The term “heteroaryl-based” in reference to a polyphosphonic acid or a salt thereof means that the phosphonic acid groups are substituents on one or more heteroaryl rings which, in the case of two or more aryl rings are either fused or linked together by a linker group.
The term, “aryl- and heteroaryl-based” in reference to a polyphosphonic acid or a salt thereof means that the phosphonic acid groups are substituents on a ring structure that comprises at least one aryl and at least one heteroaryl ring, which are either fused or linked together by a linker group.
The term “substituted” as used herein means that one or more available hydrogen atoms in a referenced group are replaced with a substituent.
The term “available”, as in “available hydrogen atoms”, refers to hydrogen atoms that would be known to a person skilled in the art to be capable of replacement by another atom or group.
The term “linker group” as used herein refers to a functional group that links two other groups together.
A first ring being “fused” with a second ring means the first ring and the second ring share two adjacent atoms there between.
A first ring being “bridged” with a second ring means the first ring and the second ring share two non-adjacent atoms there between.
A first ring being “spirofused” with a second ring means the first ring and the second ring share one atom there between.
The terms “metal-organic framework” or “MOF” as used herein refer to a class of compounds comprising metal ions or clusters coordinated to organic ligands to form one-, two-, or three-dimensional structures containing potential voids (pores).
The terms “hydrogen-bonded metal-organic framework” or “HMOF” as used herein refer to a class of porous materials which are constructed from organic moieties and at least one metal species via hydrogen bonding.
The terms “porous” or “porosity” as used herein refer to the void (i.e. “empty”) spaces in a material.
The term “guest molecule or “template molecule” as used herein refers to molecules filling the void spaces (pores) in porous materials.
The term “polyphosphonate” as used herein refers to a molecule comprising at least two phosphonate groups.
The term “phosphonate group” as used here refers to a salt of phosphonic acid having the formula —P(O)(O−)2 or —P(O)(OH)(O−) each of which is charge balanced by a suitable cation.
The term “polyphosphonic acid” as used herein refers to a molecule comprising at least two phosphonic acid groups.
The term “phosphonic acid group” as used herein refers to a group having the formula —P(O)(OH)2.
It has been surprisingly shown herein that chromium(III) phosphonate MOFs of the present application provide highly stable and porous MOFs, with a high degree of coherence. The processes of the present application provide such chromium(III) phosphonate MOFs. Specifically, chromium(III) phosphonate MOFs obtained from hydrogen-bonded metal-organic frameworks (HMOFs) provide ordered and stable porous materials.
Forming trivalent metal phosphonate MOFs has proved challenging. In some embodiments, the present application provides porous hydrogen-bonded metal-organic frameworks based on hexaaquachromium(III) phosphonates. Rather than direct metal-ligand coordination, [Cr(H2O)6]3+ units form highly complementary hydrogen bonds to organophosphonates, yielding single crystalline solids. While not wishing to be limited by theory, the inertness of the d3 octahedral Cr(III) complex is believed to sustain the coordinated water molecules and hence the hydrogen bonds and network stability.
These crystalline solids (HMOFs) can, upon heating and loss of coordinated water, convert to highly robust, primary sphere chromium phosphonate MOFs. Notably, the porosity and order designed into HMOF is translated to the MOF. This supramolecular approach of the present application offers a general route to a new family of robust MOFs.
Typically, in metal phosphonate chemistry, linear diphosphonate linkers will not form porous frameworks because the anchor points of the pendant groups to the layers are at a separation amenable to efficient packing. Using the hexaaqua complex separates the organic pillars and enables porosity akin to using a guanidinium cation in guanidinium sulfonates or other second sphere complex sulfonates. With the intent of using the HMOF structures as intermediates for MOFs, linkers are selected to favor a more porous structure.
Rather than forming a chromium(III) phosphonate MOF directly, HMOFs can be dehydrated to induce primary sphere metal coordination. In this way, the order in the HMOFs can be translated to the MOFs. The advantage of chromium phosphonate MOFs is thermal and chemical stability. Thus, the formation of robust and porous chromium(III) phosphonate MOFs may be achieved through the process of the present application. In some embodiments, these MOFs have a high degree of structural coherence or order as confirmed by PXRD and pore size analysis. This degree of order originates from their formation from porous hydrogen-bonded complexes of [Cr(H2O)6]3+ with the polyphosphonate linkers. Being supramolecular, weakly bonded solids, the aqua complexes readily order via highly complementary H-bonds with numerous phosphonates. Alternatively, in some embodiments, the degree of structural coherence or order is tuned, for example, using rate of heating. In some embodiments, disorder in structure is desirable and is increased with increasing heating rate. In some embodiments, the MOFs have tunable properties based on their structural coherence or order. For example, in some embodiments an increase in disorder in the structure provides higher ion conduction.
Accordingly, the present application includes a process for preparing a chromium(III) phosphonate metal-organic framework (MOF) comprising: a) dehydrating a hydrogen-bonded metal-organic framework (HMOF) comprising chromium (III) hydrogen bonded to one or more organic polyphosphonate molecules by heating the HMOF at a controlled rate, and b) cooling the dehydrated HMOF from a) to provide the MOF.
In some embodiments, the controlled rate for heating is about 0.01 K/min to about 500 K/min. In some embodiments, the controlled rate for heating is about 0.2 K/min to about 50 K/min. For example, the controlled rate is 0.2 K/min, 2 K/min, 5 K/min, 10 K/min, 25 K/min, or 50 K/min. Selection of a different heating rate will affect the structure of the resultant MOF. As such, in some embodiments, the controlled heating rate is selected to generate a specific porous structure of MOF. In some embodiments, a smaller rate (i.e. a slower dehydration) results in a higher ordered MOF, and in some embodiments, a higher rate (i.e. a rapid dehydration) results in a higher pore dispersity.
In some embodiments, the controlled rate of heating comprises contacting the HMOF with a heating source that has been pre-heated to a temperature desired for dehydrating. In this embodiment, the controlled rate is dependent on the rate at which the HMOF itself heats to the dehydrating temperature.
In some embodiments, the HMOF is heated to a dehydrating temperature of about 25° C. to about 500° C. In some embodiments, the HMOF is heated to a dehydrating temperature of about 50° C. to about 500° C. In some embodiments, the cooling is at a controlled rate of about 1 K/min to about 300 K/min. In some embodiments, the controlled rate for cooling is about 10 K/min to 100 K/min. In some embodiments, the controlled rate for cooling is about 40 K/min.
In some embodiments, the controlled rate of cooling comprises contacting the HMOF with a cooling source that has been pre-cooled to a temperature desired for forming the MOF. In this embodiment, the controlled rate is dependent on the rate at which the MOF itself cools to the desired temperature. In some embodiments, the cooling comprises stopping or removing the heating source and letting the material cool to ambient or room temperature.
In some embodiments, the dehydration is conducted by heating the HMOF under gas pressure. In some embodiments, by heating under gas pressure, the resulting MOF forms pores that will selectively entrap or capture the gas. In some embodiments, the gas is hydrogen, methane, oxygen, carbon dioxide or nitrogen, or a mixture thereof. In some embodiments, the gas is CO2.
In some embodiments, the dehydration is conducted by heating the HMOF in a solvent. In some embodiments, the solvent is a guest molecule or template molecule as described herein.
In some embodiments, the dehydration is conducted by heating the HMOF under vacuum. In some embodiments, the dehydration is conducted by placing the HMOF under vacuum, without heating.
Porous H-bonded frameworks that are supported by [Cr(H2O)6]3+ units and organic polyphosphonic acids and/or polyphosphonates have been prepared.
In some embodiments, the HMOF is prepared by adding a solution comprising one or more organic polyphosphonic acid molecules and/or salts thereof to a solution comprising a chromium(III) salt to form a mixture; adding a guest molecule or template molecule to the mixture under conditions to provide the HMOF.
A person skilled in the art would appreciate that any suitable organic polyphosphonic acid molecule and/or salt thereof can be used to prepare the HMOFs and MOFs of the present application.
In some embodiments, the one or more organic polyphosphonic acid molecules or salts thereof is an aryl-based polyphosphonic acid or a heteroaryl-based polyphosphonic acid or is an aryl and heteroaryl-based polyphosphonic acid, or a salt of any of these. In some embodiments, the arylpolyphosphonic acid is an aryl-based diphosphonic acid, an aryl-based triphosphonic acid, an aryl-based tetraphosphonic acid, or an aryl-based hexaphosphonic acid, or a salt of any of these. In some embodiments, the heteroaryl-based polyphosphonic acid is a heteroaryl-based diphosphonic acid, a heteroaryl-based triphosphonic acid, a heteroaryl-based tetraphosphonic acid, or a heteroaryl-based hexaphosphonic acid, or a salt of any of these. In some embodiments, aryl is phenyl, naphthalene, anthracene or fluorene, or a combination thereof. In some embodiments, heteroaryl is pyrrole. In some embodiments, the aryl is unsubstituted or substituted. In some embodiments, the heteroaryl is unsubstituted or substituted.
In some embodiments, substituted refers to the substitution of one or more available H atoms with a substituent selected from halo, C1-4alkyl, —NH2, —NO2, —OH, —SH, —SO3H, —COOH, —COOR, —CHO, —NHR, —PO3H2, —PO3HR, —O(CH2CH2O)nH, and O(CH2CH2O)nR, wherein R is C1-6alkyl and n is 1-10. In some embodiments, the substituents are selected from F, Cl, methyl, ethyl, propyl, isopropyl and —NH2.
In some embodiments, the aryl-based polyphosphonic acids, heteroaryl-based polyphosphonic acids or aryl- and heteroaryl-based polyphosphonic acids, or salts of any of these, comprise fused aryl and/or heteroaryl groups.
In some embodiments, the aryl-based polyphosphonic acids, heteroaryl-based polyphosphonic acids or aryl- and heteroaryl-based polyphosphonic acids, or salts of any of these, comprise aryl and/or heteroaryl groups that are linked together by a linker group.
In some embodiments, the linker group is selected from C1-10alkylene, C2-10alkenylene, C2-10alkynylene, C3-20cycloalkylene and analogs thereof in which one or more carbon atoms are replaced with a heteroatom selected from O, S, P, Si and N. In some embodiments, the linker group is selected from arylene and heteroarylene.
In some embodiments, the linker group is a glycol chain of the formula:
wherein m is an integer from 1 to 10 and represents the point of attachment to the aryl-based polyphosphonic acids, heteroaryl-based polyphosphonic acids or aryl- and heteroaryl-based polyphosphonic acids.
In some embodiments, the aryl-based polyphosphonic acids, heteroaryl-based polyphosphonic acids or aryl- and heteroaryl-based polyphosphonic acids, or salts of any of these, are linked together by two or more polypropylene glycol or polyethylene glycol chains to form a crown ether structure. In some embodiments, the crown ether structure formed is a 14C4, 15C5 or a 18C6 crown ether structure.
A person skilled in the art would appreciate that any suitable organic polyphosphonic acid molecule, and/or a salt thereof, can be used to prepare the HMOFs and MOFs of the present application. Examples of such molecules are known in the art, including for example, those described in Yücesan, G. et al. Coordination Chemistry Reviews, 2018, 369:105-122. In some embodiments, the one or more organic polyphosphonic acid molecules, and/or salts thereof, are selected from the group consisting of:
or a salt thereof.
In some embodiments, the one or more organic polyphosphonic acid molecules and/or salts thereof are selected to obtain a specific structure of HMOF. In some embodiments, an organic polyphosphonic acid molecule, and/or a salt thereof, has different conformations, and each conformation is selected to obtain a specific structure of HMOF.
In some embodiments, the organic polyphosphonic acid molecule and/or a salt thereof is H4L1, wherein L1 is 4,4′-biphenyldiphosphonate and the HMOF comprises repeating units of [Cr(H2O)6][HL1]·(C3H6O)2 thus forming a continuous network. In some embodiments, network solids of different stoichiometries, i.e. of variable number of repeating units, are provided depending on various conditions such as varying the pH of the HMOF preparation.
In some embodiments, the organic polyphosphonic acid molecule and/or a salt thereof is H6L2, wherein L2 is 1,3,5-tris(4-phosphonophenyl)2,4,6-trimethylbenzene and the HMOF comprises repeating units of [Cr(H2O)6][H4.5L2]2·(C8H10)1.5, thus forming a continuous network. In some embodiments, network solids of different stoichiometries, i.e. of variable number of repeating units, are provided depending on various conditions such as varying the pH of the HMOF preparation.
In some embodiments, the organic polyphosphonic acid molecule and/or a salt thereof is H8L3, wherein L3 is durenetetraphosphonic acid (DTP) and the HMOF is [Cr(H2O)6]2[H2L3](H2O)2.
In some embodiments, the chromium(III) salt is a nitrate, halide (fluoride, chloride, bromide or iodide), tetrafluoroborate, sulfate, perchlorate, acetate, hexafluorophosphate, organosulfonate, organocarboxylate, carbonate, bicarbonate, bisulfate, hydrogenophosphate, or nitrite salt. In some embodiments, the chromium (III) salt is a nitrate salt.
In some embodiments, the guest molecule or template molecule is selected from acetone, acetonitrile, methanol, ethanol, isopropanol, acetic acid, ethylene glycol, ethyl acetate, nitrobenzene, nitromethane, toluene, ammonium compound, CO2, CO, methane, ethylene, propane, propene, acetylene, H3PO4, H2SO4, HCl, HBr, formic acid, H2CO3, HNO3, ortho-xylene, meta-xylene and para-xylene, or any salts thereof. In some embodiments, the guest molecule or template molecule is supercritical CO2. In some embodiments, the guest molecule or template molecule is a lithium salt, such as, but not limited to lithium nitrate and/or lithium perchlorate. Because the HMOF is held together only by weaker bonds (H-bonds), the structure can reorganize, and order and adapt to different guest molecules present to fill pores. As such, in some embodiments, the guest molecule or template molecule is selected to achieve specific structure and porosity. In some embodiments, the addition of acid is exothermic and hence provide a means of heating. Without being bound to theory, the addition of acid could be a means of heating to affect the HMOF to MOF transition but also leave the acid in the pores to enhance proton conduction. In some embodiments, the guest molecule is interchangeable. In some embodiments, the guest molecule is neutral. In some embodiments, the guest molecule is charged. In some embodiments, the guest molecule or template molecule is
In some embodiments, the counterion for the charged guest molecule is selected from a halide anion, NO3− or any suitable anion.
In some embodiments, the solvent for the solution comprising one or more organic polyphosphonic acid molecules, and/or salts thereof, is acetone, acetonitrile, methanol, ethanol, isopropanol, acetic acid, ethylene glycol, water, or mixture thereof. In some embodiments, the solvent for the solution comprising a chromium(III) salt is methanol, water, or mixture thereof.
In some embodiments, the process for preparing an HMOF further comprises collecting and drying the HMOF.
The present application also includes a process for preparing a chromium(III) phosphonate metal-organic framework (MOF) comprising: a) dehydrating a hydrogen-bonded metal-organic framework (HMOF) comprising chromium (III) hydrogen bonded to one or more organic polyphosphonate molecules by heating the HMOF at a controlled rate; wherein the HMOF is prepared by adding a solution comprising one or more organic polyphosphonic acid molecules or salts thereof to a solution comprising a chromium(III) salt to form a mixture; adding a guest molecule or template molecule in the mixture under conditions to provide the HMOF, and b) cooling the dehydrated HMOF from a) to provide the MOF. In some embodiments, the cooling in b) is at a controlled rate.
The present application also includes MOFs as described in any aspect or embodiment herein. In some embodiments, the MOF is as prepared according to any process of any previous aspect and embodiment herein. In embodiments, the MOF is as characterized according to any one of the figures.
The processes of the application produce highly stable, ordered and porous chromium(III) phosphonate MOFs. The MOFs of the present application have a wide range of applications.
In some embodiments, the present application includes a method to uptake at least one substance comprising contacting a source comprising the at least one substance with a MOF of the present application under conditions for the uptake of the at least one substance into the MOF. Also included in the present application is a use of an MOF of the present application for update of at least one substance.
In some embodiments the at least one substance is selected from one or more of hydrogen gas, methane, ethane, ethylene, acetylene, propane, propene, oxygen gas, carbon dioxide and nitrogen gas, water, xylene isomers.
In some embodiments, the uptake of at the least one substance is for the purposes of its storage, separation, controlled release, chemical reaction or as support. Such uses are described, for example in U.S. Pat. No. 8,648,002 and references cited therein.
In some embodiments, the present application includes a method of capturing and/or storing at least one gas in a MOF comprising contacting a source comprising the at least one gas with a MOF of the present application under conditions for binding of the at least one gas to the MOF. In some embodiments, the binding is in a plurality of pores present in the MOF, for example, using van der Waals forces. Also included in the present application is a use of an MOF of the present application for capturing and/or storing at least one gas. In some embodiments, the gas is hydrogen, methane, oxygen, carbon dioxide or nitrogen, or a mixture thereof. In some embodiments, the MOF is configured to capture and/or store methane or hydrogen for fueling vehicles. In some embodiments, the MOF is configured to capture and/or store carbon dioxide to reduce carbon dioxide emissions into the atmosphere.
In some embodiments, the present application includes a method of capturing at least one ion in a MOF comprising contacting a source comprising the at least one ion with a MOF of the present application under conditions for binding of the at least one ion to the MOF. In some embodiments, the binding is in a plurality of pores present in the MOF, for example, using van der Waals forces. Also included in the present application is a use of an MOF of the present application for capturing at least one ion. In some embodiments, the ion is lithium, or a mixture thereof. In some embodiments, the MOF is configured to selectively capture lithium.
Despite being weakly bonded, even the HMOFs of the present application demonstrate reversible gas sorption. Although the HMOFs may not be sufficiently robust for applications requiring permanent porosity, HMOFs may be used in reversible gas sorption applications, based on highly complementary and cooperative self-assembly.
The present application also includes a MOF or HMOF of the present application further comprising at least one substance or at least one gas.
In some embodiments, the present application also includes a use of an MOF of the present application as a proton conductor. For example, the MOFs of the present application are used as proton conducting solids, such as proton conducting membranes or components of proton conducting membranes.
Accordingly, the present application also includes a proton conducting solid comprising a MOF of the present application. In some embodiments, the proton conducting solid is for use in proton exchange membrane fuel cells (PEMFCs). Accordingly, the present application also includes a proton exchange solid comprising a MOF of the present application. The present application also includes a proton conducting membrane comprising a MOF of the present application. In some embodiments, the proton conducting membrane is for use in proton exchange membrane fuel cells (PEMFCs). Accordingly, the present application also includes a proton exchange membrane comprising a MOF of the present application. In some embodiments, the MOFs of the present application are stable enough to perform proton conduction at elevated temperatures, for example above 100° C.
In some embodiments, the present application also includes a use of an MOF of the present application as an ion conductor. For example, the MOFs of the present application are used as ion conducting solids, such as ion conducting membranes or components of ions conducting membranes. Accordingly, the present application also includes an ion conducting solid comprising a MOF of the present application. In some embodiments, the ion conducting solid is for use in with lithium electrolyte in batteries. Accordingly, the present application also includes an ion exchange solid comprising a MOF of the present application. The present application also includes an ion conducting membrane comprising a MOF of the present application. In some embodiments, the ion conducting membrane is for use in with lithium electrolyte in batteries. Accordingly, the present application also includes an ion exchange membrane comprising a MOF of the present application. In some embodiments, the MOFs of the present application are stable enough to perform ion conduction at elevated temperatures, for example above 100° C. In some embodiments, the ion is lithium, or any other suitable ion. In some embodiments, the present application includes a battery comprising an ion conducting solid comprising a MOF of the present application. In some embodiments, the present application includes a battery comprising an ion conducting membrane comprising a MOF of the present application.
The following non-limiting examples are illustrative of the present application.
All starting materials were purchased from commercial suppliers (Alfa Aesar and Sigma Aldrich) and were used without any further purification. Tetraethyl 1,4-benzenediphosphonate and 1,4-benzenediphosphonic acid were synthesized according to literature procedures.
Single crystal X-ray diffraction (PXRD) patterns were obtained using a Nonius Kappa APEX2 CCD equipped with a molybdenum X-ray source, 4-circle Kappa-geometry goniometer, and APEX2 1k CCD X-ray detector.
Powder X-ray diffraction (PXRD) patterns were obtained using a Rigaku X-ray MiniFlex II Diffractometer equipped with a cooper X-ray source and a scintillation counter detector and the data was collected between 3 to 50° (28) on a 0.02° step wise with a speed of 1°/min.
Variable temperature powder X-ray diffraction (VTPXRD) patterns were obtained using a Bruker D8 Advance (ECO) powder X-ray diffractometer with highly sensitive Lynxeye XE energy dispersive 1 D X-ray detector, a copper X-ray source and Twin-Twin optic system. The data was collected between 3 and 50° (28) with an increment of 25° and 65 min per step.
Elemental analysis was performed by a PerkinElmer 2400 Series II CHN elemental analyzer.
FT-IR analysis and spectra acquisition and manipulation were preformed using a Thermo-Nicolet Nexus 470 spectrophotometer in ATR mode. Spectra were obtained in the range of 4000-400 cm−1.
FT-Raman spectrum was obtained using a Bruker RAM II FT-Raman module within the region between 50 and 3600 cm−1.
NMR experiments were performed on a 400 MHz Bruker Advance 400 instrument. Samples were digested in proper deuterated solution and filtered before measured by Bruker Advance.
Thermogravimetric analysis (TGA) experiments were performed on a Netzsch STA 409 PC Luxx interfaced with a PC using Netzsch Instruments software. In a typical measurement, 5-10 mg sample was placed in an alumina pan and heated at a rate of 2° C./min from 25 to 1100° C. under a nitrogen atmosphere.
Hexaaquachromium(III) phenylphosphonate (1): Single crystal growth was performed by slow diffusion of acetone or isopropanol. In a 20 mL vial, chromium nitrate nonahydrate (88 mg, 0.22 mmol) was added to water (10 mL) and stirred, leaving a transparent purple solution. In a separate vial, phenyl phosphonic acid (100 mg, 0.63 mmol) was dissolved in water (5 mL) resulting in a clear colorless solution. The phosphonic acid solution was then poured into the chromium solution, resulting with a transparent purple solution with a pH≈3. From this solution ˜ 2 mL aliquot were placed in 4 mL vials placed inside a 20 mL vial with acetone as the diffusing solvent. Pale purple needle shaped crystals formed. These were examined by single x-ray diffraction, and were determined to have a formula of Cr(H2O)6(C6H5PO3)(C6H5PO3H).
Bulk synthesis was achieved by a modification of the single crystal procedure. Phenyl-phosphonic acid (105 mg, 0.664 mmol) was mixed in water (5 mL) and stirred to make a transparent colorless solution. This was added to a 250 mL Erlenmeyer flask containing water (25 mL) and chromium(III) nitrate nonahydrate (127 mg, 0.317 mmol) to make a clear purple solution. Using a dropping funnel, acetone (150 mL) was added while stirring over −5 min. Purple grey powder precipitated during acetone addition. After full acetone addition the powder was recovered by vacuum filtration and washed with methanol and acetone, resulting in a fine light grey-purple powder of 1 (42 mg, 0.089 mmol, 28.1%). Elemental analysis calculated (%) for 1 C12CrH25O18P2: C 30.46, H 4.90. Found C 30.40, H 4.86. PXRD patterns of the bulk powder matched with the simulated patterns from the single crystal. The synthesis can also be performed using methanol as a solvent in place of water and seems to result in approximately double the yield, with no change in the powder x-ray diffraction (PXRD) pattern.
Hexaaquachromium(III) 1,4-benzenediphosphonate (2): Single crystals of 2·ace and 2·MeCN were grown analogously to 1. Chromium(III) nitrate nonahydrate (167.8 mg, 0.42 mmol) was mixed into a 20 mL vial with 10 mL of water leaving a transparent purple solution. Separately, 1,4-benzenedisphosphonic acid (100 mg, 0.42 mmol) was dissolved in 5 mL of water to make a clear colorless solution. The phosphonic acid solution was added to the chromium one, resulting in a transparent purple solution. Aliquots of this solution were placed in 4 mL vials, which were then placed in a 20 mL vial for slow vapor diffusion with acetone or acetonitrile, resulting in plate-like purple crystals after 1 day. These were examined by single crystal x-ray diffraction, and were determined to have a formula of Cr(H2O)6(O3P—C6H4—PO3H)·(C3H6O) for 2·ace and Cr(H2O)6(O3P—C6H4—PO3H)·(C2H3N) for 2·MeCN.
Bulk synthesis was achieved by a modification of the single crystal procedure. 1,4-benzenediphosphonic acid (2.003 g, 8.413 mmol) was dissolved in water (200 mL) to make a transparent clear solution. This was added to a 1 L Erlenmeyer flask containing chromium (III) nitrate nonahydrate (2.869 g, 7.170 mmol) dissolved in water (150 mL) to make a clear purple solution. Using a dropping funnel, acetone (150 mL) was slowly added dropwise over 2 hours while stirring causing a fine precipitate to form. After full acetone addition the precipitate was filtered and washed with methanol and acetone, then dried to obtain 2.763 g of grey-blue 2·ace powder (6.10 mmol, 85.0%). Elemental analysis calculated (%) for 2·ace, Cr(H2O)6(O3P—C6H4—PO3H)·(C3H6O): C 23.85, H 5.11. Found: C 22.21, H 4.74. Discrepancies are likely due to facile acetone loss before measurement, with Cr(H2O)6(O3P—C6H4—PO3H)·(C3H6O)0.7 giving calculated values of C: 22.32, H: 4.90. PXRD patterns of bulk 2·ace matched with the simulated pattern obtained from the single crystal structure. The synthesis can also be performed by replacing the acetone with acetonitrile, ethanol or glacial acetic acid, all resulting in powders with PXRD patterns that match the simulated pattern of 2-ace.
Full removal of acetone could be achieved by applying vacuum at room temperature, resulting in 2a, Cr(H2O)6(O3P—C6H4—PO3H). Elemental analysis calculated (%) for 2a: C 18.24, H 4.34. Found C 18.26, H 4.15. Powders of 2 for synchrotron PXRD analysis were prepared by this method.
Submersion of 2a in water would result in an irreversible phase change to isomeric 2b, Cr(H2O)6(O3P—C6H4—PO3H). Elemental analysis calculated (%) for 2b: C 18.24, H 4.34. Found C 17.87, H 3.89. Powders of 2b for synchrotron PXRD analysis were prepared by this method.
To try and demonstrate a shape memory effect, samples of 2a (500 mg) were placed in ethanol (50 mL) in a glass pressure vessel and sealed. This was then placed in sand and heated in an oven at 75° C. for 8 days. Following treatment, the samples were vacuum filtered, washed with fresh ethanol and left to dry on the filter paper.
Single Crystal Synthesis of [Cr(H2O)6][OPAP2] Ortho-Xylene
Single crystal growth was done within a vial. In a 150 mL Erlenmeyer, Cr(H2O)63+ (0.02641 g, 0.001M) was dissolved in 66 mL of HNO3 (0.002M) which created an extremely light blue solution. In a separate 150 mL Erlenmeyer OPAP 2 (0.0416 g, 0.001M) was weighed then a solution of 22 mL HNO3 (0.002M) and 44 mL of methanol was added. This solution was sonicated. After sonication was completed, a filter syringe was used to remove any undissolved particles from the OPAP 2 solution then both solutions were refrigerated for 5 hours. The cooled solutions were then taken out of the fridge and 5 mL of the OPAP 2 was added to eleven 20 mL vial, followed by 1 mL of Ortho-xylene and finally 5 mL of the Cr(H2O)63+, which was then placed in a larger jar and methanol as an antisolvent was placed in the larger jar as a vapor diffusion. The jar was then capped and refrigerated for two weeks. After two weeks, thin clear needle like crystals were formed. Examined by single x-ray diffraction the formula was determined to be C87 H118 Cr O31 P6 with cell lengths of a 32.486(7) Å b 41.140(8) Å c 8.1430(16) Å and cell angles of α 90 β 90 γ 90.
Bulk Powder of [Cr(H2O)6][OPAP2] Ortho-Xylene
Bulk powder synthesis was based on the single crystal procedure scaled up. In a 150 mL Erlenmeyer, Cr(H2O)63+ (0.02641 g, 0.001M) was dissolved in 66 mL of DI water which created an extremely light blue solution. In a separate 150 mL Erlenmeyer OPAP 2 (0.0416 g, 0.001M) was weighed, then a solution of 22 mL DI water and 44 mL of methanol was added. This solution was sonicated. After sonication was completed a filter syringe was used to remove any undissolved particles from the OPAP 2 solution, then both solutions were refrigerated for 2 hours. The cooled solutions were then taken out of the fridge and the OPAP 2 was added to a 250 mL Erlenmeyer, followed by 8.0 mL of ortho-xylene and finally both solutions were well mixed. The Cr(H2O)63+ was added to the Erlenmeyer with the OPAP 2/xylene solution which formed a white precipitate, then capped and left out for 5 minutes followed by refrigerating for 2 weeks. The precipitate was recovered via vacuum filtration and as a white/grey color when dried. Elemental analysis (%) for [Cr(H2O)6][OPAP2]: C 55.87, H 6.04. found C 55.65, H 6.01. This was dehydrated via a quick dehydration by putting the product into an oven at 150° C. for 12 hours and cooled for 6 hours. Elemental analysis (%) for [Cr(H2O)6][OPAP2] after dehydrated: C 61.42, H 4.92. found C 60.38, H 5.48.
Single Crystal Synthesis of [Cr(H2O)6][OPAP2] Para-Xylene
Single crystal growth was done within a vial. In a 150 mL Erlenmeyer, Cr(H2O)63+ (0.02641 g, 0.001M) was dissolved in 66 mL of HNO3 (0.002M) which created an extremely light blue solution. In a separate 150 mL Erlenmeyer OPAP 2 (0.0416 g, 0.001M) was weighed then a solution of 22 mL HNO3 (0.002M) and 44 mL of methanol was added. This solution was sonicated. After sonication was completed, a filter syringe was used to remove any undissolved particles from the OPAP 2 solution, then both solutions were refrigerated for 5 hours. The cooled solutions were then taken out of the fridge and 1.5 mL of the OPAP 2 was added to a 5 mL vial, followed by 0.1 mL of para-xylene and finally 0.5 mL of the Cr(H2O)63+ then capped and refrigerated for two weeks. After two weeks, thin clear needle like crystals were formed. Examined by single x-ray diffraction, the formula was determined to be H6 Cr0.5 O3, C30 H31.5 O9 P3 with cell lengths of a 33.9386(12) b 17.2386(7) c 16.7083(6) and cell angles of α 90 β 90 γ 90.
Bulk Powder of [Cr(H2O)6][OPAP2] Para-Xylene
Bulk powder synthesis was based on the single crystal procedure scaled up. In a 150 mL Erlenmeyer, Cr(H2O)63+ (0.02641 g, 0.001M) was dissolved in 66 mL of DI water which created an extremely light blue solution. In a separate 150 mL Erlenmeyer OPAP 2 (0.0416 g, 0.001M) was weighed then a solution of 22 mL DI water and 44 mL of methanol was added. This solution was sonicated. After sonication was completed, a filter syringe was used to remove any undissolved particles from the OPAP 2 solution, then both solutions were refrigerated for 2 hours. The cooled solutions were then taken out of the fridge and the OPAP 2 was added to a 250 mL Erlenmeyer, followed by 8.0 mL of para-xylene and finally both solutions were well mixed. The Cr(H2O)63+ was added to the Erlenmeyer with the OPAP 2/xylene solution which formed a white precipitate, then capped and left out for 5 minutes followed by refrigerating for 2 weeks. The precipitate was recovered via vacuum filtration as a white/grey color when dried. Elemental analysis (%) for [Cr(H2O)6][OPAP2]: C 54.80, H 6.07. found C 55.08, H 6.10. This was dehydrated via a quick dehydration by putting the product into an oven at 150° C. for 12 hours and cooled for 6 hours. Elemental analysis (%) for [Cr(H2O)6][OPAP2] after dehydrated: C 60.60, H 4.58. found C 60.38, H 4.91.
Durenetetraphosphonic acid (H8L3) was synthesized followed the literature procedure reported by Norman Wong et al1 without modifications, as shown below.
H-PCMOF-50: 80.0 mg of Cr(NO3)3·9H2O was dissolved in 3.00 mL of RO water while 90.8 mg of H8L3 was dissolved in 5.00 mL of RO water with the help of heating. A clear, dark purple solution was gained after mixing these two solutions together. Slowly diffuse acetone to the previous mixture, a purple, block-type of crystal was grown within 36 h and collected by filtration after several washing with acetone.
Elemental analysis: [Cr(H2O)6]2[H2L3]·(H2O)2, theoretical results: C %: 14.86; H %: 5.49. Experimental results: C %: 14.81; H %: 5.02.
H-CALF-55 (Example 1) and H-CALF-50 (Example 2) were dehydrated to induce primary sphere metal coordination. In this way, the order in the HMOFs can be translated to the MOFs. The HMOFs were dehydrated by heating at 100° C. and 150° C., yielding MOFs CALF-55 ({CrHL1·H2O}) and CALF-50 ({Cr(H4.5L2)2·C8H10}) respectively
H-PCMOF-50 (Example 3), was treated for thermal dehydration by heating up to 200° C. with variable speed, holding for 10 minutes before cooling down to room temperature with a speed of 40 K/min. Specifically, the dehydration speed applied was 0.2, 2, 10, and 50 K/min, whereas the ‘#’ in the product name represents the dehydration speed. The purple color crystals became pale green after treatment. Elemental analysis was carried out for all samples (pre and after dehydration) and it was found that most water, both lattice and coordination waters, was removed. The formed MOF, PCMOF-50-#, has given the following elemental analysis results.
PCMOF-50-0.2, pre-impedance, [Cr2H2L3]·(H2O)2.5, theoretical results: C %: 20.11; H %: 2.87. Experimental results: C %: 20.33; H %: 2.75. Post-impedance, [Cr2H2L3]·(H2O)6, theoretical results: C %: 18.19; H %: 3.66. Experimental results: C %: 18.09; H %: 3.91.
PCMOF-50-2, pre-impedance, [Cr2H2L3]·(H2O)2.5, theoretical results: C %: 20.11; H %: 2.87. Experimental results: C %: 19.89; H %: 2.86. Post-impedance, [Cr2H2L]·(H2O)6, theoretical results: C %: 18.19; H %: 3.66. Experimental results: C %: 18.05; H %: 3.92.
PCMOF-50-10, pre-impedance, [Cr2H2L3]·(H2O)2.5, theoretical results: C %: 20.11; H %: 2.87. Experimental results: C %: 20.62; H %: 2.90. Post-impedance, [Cr2H2L]·(H2O)9, theoretical results: C %: 16.82; H %: 4.23. Experimental results: C %: 16.81; H %: 3.53.
PCMOF-50-50, pre-impedance, [Cr2H2L3]·(H2O)2.5, theoretical results: C %: 20.11; H %: 2.87. Experimental results: C %: 19.97; H %: 3.07. Post-impedance, [Cr2H2L]·(H2O)6, theoretical results: C %: 18.19; H %: 3.66. Experimental results: C %: 18.14; H %: 3.80.
Porous H-bonded frameworks that are supported by [Cr(H2O)6]3+ units and polyphosphonic acids: 4,4′-diphenyldiphosphonic acid (H4L1) and 1,3,5-tris(4-phosphonophenyl)2,4,6-trimethylbenzene, H6L2 have been prepared. The single crystal structures of the hydrogen-bonded metal-organic frameworks (HMOFs), {[Cr(H2O)6][HL1]·(C3H6O)2}, H-CALF-55 (C3H6O)2, and {[Cr(H2O)6][H4.5L2]2 (C8H10)1.5}, H-CALF-50, (Hydrogen bonded CALgary Framework) are presented along with their porosity analysis.
Purple crystals of the HMOF, {[Cr(H2O)6][HL1]·(C3H6O)2}, H-CALF-55 (C3H6O)2, where L1=4,4′-biphenyldiphosphonate, were grown by combining acetone solutions of H4L1 and chromium(III) nitrate, as defined above. The acetone allows for the formation of voids in the HMOF. The structure of H-CALF-55 (C3H6O)2 (
The powder X-ray diffraction (PXRD) pattern of H-CALF-55 (C3H6O)2 showed a phase change upon loss of the acetone molecules (
The linker molecule, H6L2, was prepared and also complexed with [Cr(H2O)6]3+, as noted above. This linker offers not only a trigonally divergent core but orthogonalized peripheral aryl rings to disfavor efficient pi-stacking of ligands. Dissolving Cr(NO3)3·9H2O, H6L2 and para-xylene in methanol yielded purple crystals of the hexaaquachromium(III) HMOF H-CALF-50. Single crystal x-ray diffraction found the chemical formula {[Cr(H2O)6][H4.5L2]2·(C8H10)1.5}, a formula supported by EA and TGA on the bulk powder. 1-D chains of hexaaquachromium(III) complexes run along the c-axis and each chain hydrogen bonds to the phosphonate ligands, forming 1-D rhombohedral channels of 12.86 Å×9.16 Å (
The hydrogen bonded networks, H-CALF-55 and H-CALF-50, were activated under mild conditions (30° C. under vacuum) to preserve the hexaaquachromium(III) centers.
Although the PXRD patterns suggest that H-CALF-55 is a contracted form of H-CALF-55·(C3H6O)2, the structure still exhibits porosity. This is possibly due to the difficulty of the longer biphenyl linkers to tilt uniformly throughout the interlayer. Random tilting of the pillars would retain uniform d-spacings between layers but prevent efficient packing. H-CALF-50 exhibits low surface area due to the presence of the o-xylene molecules filling the pore space. Conditions that effectively removed the o-xylene inevitably also caused loss of aqua ligands on chromium. Nonetheless, the porosity observed demonstrates the stability of these HMOFs and the retention of the hexaaqua coordination.
Although crystalline, the HMOFs are not exceptionally stable or porous. To remedy this, the hydrogen bonded networks are used as intermediates to making crystalline and porous chromium(III) phosphonate MOFs. There are reported cases of heterometallic CrIII/MnIII, CrIII/LnIII and CrIII/CoII clusters and frameworks. However, homonuclear chromium(III) phosphonate MOFs are rare. This is likely due to challenges in crystallizing such complexes. The multiple coordination modes provided by phosphonates result in ready formation of amorphous materials when coupled with high valency metals.
Rather than forming a chromium(III) phosphonate MOF directly, H-CALF-55 and H-CALF-50 were dehydrated to induce primary sphere metal coordination. In this way, the order in the HMOFs can be translated to the MOFs, as explained above yielding MOFs CALF-55 ({CrHL1·H2O}) and CALF-50 ({Cr(H4.5L2)2·C8H10}) respectively. This transformation occurs with a color change from purple to green, and TGA confirmed no coordinated water remained. Several peaks were observed in the PXRD patterns, indicating the MOFs possess a degree of order (
Variable temperature PXRD (VT-PXRD) (
A crystalline chromium phosphonate MOF was obtained and optimized by taking advantage of the pre-formed hydrogen bonded framework intermediate, H-PCMOF-50 (proton conducting metal-organic framework), which was supported by [Cr(H2O)6]3+ clusters and polyphosphonic acid, durenetetraphosphonic acid (DTP, H8L3).
The crystal structure formed initially was determined with M:L ratio of 2:1, which exhibited excellent hydrolytic stability, and moderate thermal stability. The unlocalized hydrogen bonded network feature and two acidic protons left per ligand revealed its ability as proton conductors. It was worth mentioning that the water stable phosphonate MOFs formed via thermal dehydration at 200° C., PCMOF-50, could optimize its proton conductivity from 1.61×10-5 S/cm to 1.61×10-3 S/cm at 85° C. and 95% relative humidity (RH), as high as two orders of magnitude, via thermal dehydration with variable rates. The high proton conductivity was attributed to the low activation energy of the proton pathways altered by water percolate process when the MOF was formed. Notably, PCMOF-50 can survive over a month under 95% RH with elevated temperature, even after soaking in an acid solution. Such a robust phosphonate MOF, with ordered microcrystalline structure, converted from hydrogen bonded frameworks serving as proton conductors with extraordinary performance may thus be obtained.
As provided above, the purple color hydrogen bond network crystals of H-PCMOF-50 could be obtained by slowly diffusing acetone to the mixture of chromium (III) nitrate nonahydrate, DTP, and RO water at ambient temperature. It crystallized in the monoclinic space group C2/m with a formula of [Cr(H2O)6]2[H2L3](H2O)2, where half of [Cr(H2O)6]3+ cation, a quarter of (H2L3)6− ligand and half water molecule in one asymmetric unit. The hexaaquachromium(III) cations aligned along a axis in octahedron with two of their C4 axes in the bc plane where the third one perpendicular to bc plane. As shown in
[a]R1 = Σ∥Fo| − |Fc∥/Σ|Fo|.
[b]wR2 = [Σw(Fo2 − Fc2)2/Σw(Fo2)2] 1/2.
Given hydrogen bonded in H-PCMOF-50 with a Dn-H—Ac distance longer than 2.5 Å that would has a bond energy less than 10 kcal/mol, which falls into the category of medium strength, the stability, for both thermal and hydrolytic, were tested. As shown in
Powdered samples of PCMOF-50 (3 to 5 mg each) were placed in a glass cell and were compressed between 2 solid titanium electrodes (0.3175 cm diameter). The sample length was measured by the difference between the empty cell and the filled cell and was typically to 1 to 2 mm in length. The sample cells were placed inside a humidity and temperature-controlled chamber (ESPEC BTL-433) and connected to a Princeton Applied Research VersaSTAT 3 impedance analyzer using a 2-probe setup. AC impedance data was collected by cycling between 106 and 1 Hz with 200 mV of applied potential using VersaStudio software by a manner of 10 points per decade. Samples were equilibrated at 25° C. and 95% relative humidity for a week before any further measurement.
Proton conductivity of all samples was measured under 95% relative humidity condition at various temperatures. The temperature was varied from 25° C. to 85° C. with a 10° C. increment for minimum of two heating and cooling cycles with 24 h for sample equilibration between each step. Following the heating and cooling cycles, the temperature was held at 25° C. and the humidity was decreased from 95% to the minimum of 35% to measure the relative humidity dependent proton conductivity of the samples. The temperature and humidity the conditions were within the operating capacities of the oven.
To characterize proton conductivity, alternating current (AC) impedance spectroscopy of a pelletized powder sample with controlled relative humidity and temperature was applied. The Nyquist plots of PCMOF-50-10, obtained from the cooling cycle, to ensure humidity equilibration, was illustrated in
The FT-IR spectra, elemental analysis results, and the reproducible impedance data, of these ordered crystalline chromium phosphonate proton conducting MOFs under 95% RH for 33 days at elevated temperature suggested that their integrity were greatly retained albeit with lower levels of crystallinity. The hydrolytic stability test was carried out by soaking PCMOF-50 in pH=1 solution for 24 hours and the 1H NMR spectra of the supernatant indicated zero PCMOF-50 digested during this process. Rehydration test was carried out on all samples with zero sign of color change that indicated that dehydrated MOFs were not rehydrated, which further confirmed by the elemental analysis (EA) results.
Cr(NO3)3·9H2O (20.1 mg, 0.0502 mmol) and oxalic acid (11.7 mg, 0.130 mmol) were combined in a 20 mL vial and dissolved in 10 mL of methanol. In a separate 20 mL vial, 1,3,5-tris(4-phosphonophenyl)benzene—structure shown below (20.7 mg, 0.0381 mmol) was dissolved in 5 mL of methanol, and 0.5 mL of a 0.021M NaOH solution in methanol was added. Both solutions were filtered through a syringe filter and combined in a separate vial. The solution immediately became cloudy and white, and upon settling for 18 hours, a mixture of white powder and purple single crystals of {[Cr(H2O)6][C24H21P3O9]·(CH3OH)5} was formed.
The bulk synthesis was achieved by dissolving Cr(NO3)3·9H2O (80.3 mg, 0.201 mmol) and oxalic acid (39.7 mg, 0.441 mmol) in 40 mL of methanol in a 100 mL round bottom flask. After filtering through a syringe filter, seeds of previously synthesized crystals of {[Cr(H2O)6][C24H21P3O9]·(CH3OH)5} were added to the solution. In a separate flask, 1,3,5-tris(4-phosphonophenyl)benzene (74.8 mg, 0.138 mmol) was dissolved in 24 mL of methanol and 4 mL of 0.021M NaOH solution in methanol was added. After filtering, the solution was combined with the chromium and oxalic acid solution, resulting in a slightly cloudy mixture. Letting the mixture settle for 18 hours yielded a pure phase of {[Cr(H2O)6][C24H21P3O9]·(CH30H)5}. The purple crystals were then solvent-exchanged with fresh methanol 4 times over a course of 24 hours.
A vial containing purple crystals of {[Cr(H2O)6][C24H21P3O9]·(CH30H)5}(˜50 mg) were:
12.54 g of 4-bromophenol, 4.06 g of KOH, and 5.46 mL of 1,2-bis(2-chloroethoxy)-ethane are dissolved in 35 mL of n-butanol and are refluxed at 120° C. for 24 h. This was poured into 150 mL of water and was extracted with 150 mL dichloromethane. The organic layer is washed three times with 40 mL of 1M sodium hydroxide followed by 40 mL of brine solution. The organic layer was dried over sodium sulfate and evaporated to give 1,1′-[1,2-ethanediylbis(oxy-2,1-ethanediyloxy)]bis-4,4′bromobenzene as a fine white solid. (MW: 460.16 C18H20O4Br2 Yield: 13.32 g, 83%) EA: Calculated; % C=46.96% H=4.39 Found; % C 46.80% H=4.32
18.5 g of 1,1′-[1,2-ethanediylbis(oxy-2,1-ethanediyloxy)]bis-4,4′bromobenzene was dissolved in 100 mL dry diisopropylbenzene at 80° C. under an inert atmosphere. To this, 0.84 g of anhydrous nickel (II) bromide was added and the temperature increased to 180° C. 20 mL of triethylphosphite was added dropwise over 4 hours. After 24 hours, another 0.67 g of anhydrous nickel (II) bromide was added and another 20 mL of triethylphosphite is added dropwise over 4 hours. After 24 more hours, this was allowed to cool and vacuum distillation was used to remove the diisopropylbenzene and unreacted triethylphosphite and starting material. The resulting black sludge was stirred in 50 mL of a 0.5M EDTA solution for 1 hour followed by the addition of 50 mL of chloroform. The organic layer was separated, dried over magnesium carbonate, and evaporated. 125 mL of hexanes was added to the resulting yellow oil and the solvent once again removed by evaporation. Upon standing, 1,1′-[1,2-ethanediylbis(oxy-2,1-ethanediyloxy)]bis-benzene-4,4′-bis-phosphonic diethyl ester precipitated as a fine white powder. (MW: 574.54 C26H40O10P2 Yield: 16.81 g, 73%) EA: Calculated; % C=54.32% H=7.03 Found; % C 54.40% H=7.49
10 g of 1,1′-[1,2-ethanediylbis(oxy-2,1-ethanediyloxy)]bis-benzene-4,4′-bis-phosphonic diethyl ester was dissolved in 200 mL of dry dichloromethane. To this, 6 equivalents (14 mL) of bromotrimethylsilane was added and the reaction stirred at room temperature for 24 hours under an inert atmosphere. Then, 200 mL of methanol was added and the solution was allowed to stir for an additional 24 hours. The mixture was evaporated and the resulting yellow oil was mixed with 100 mL of 6M HCl and left in the freezer to precipitate as a white powder. This was filtered and washed with water before allowing to dry. 1,1′-[1,2-ethanediylbis(oxy-2,1-ethanediyloxy)]bis-benzene-4,4′-bis-phosphonic acid·H2O (MW: 480.35 C18H24O10P2 Yield: 7.67 g, 95%) EA: Calculated; % C=44.98% H=5.46 Found; % C 44.85% H=5.40
The ligand (Pod-1) was dissolved in water with 2 equivalents of alkali metal hydroxide (Li/Na/K) to make a 0.01M solution of the salt (M2Pod-1). 1 equivalent of Cr(NO3)3 in water was added to this solution. The solution was left standing 5 minutes, then 2 equivalents of alkali metal hydroxide dissolved in water (0.1M solution) was added dropwise. This resulted in rapid precipitation of the HMOF as a blue-purple powder.
After letting stand for 15 minutes to complete precipitation and agglomeration, it was vacuum filtered, and the phase confirmed by pXRD.
Once dried, the blue-purple powder was placed in a saturated solution of lithium nitrate in acetone. After 18 h, the solution was quickly vacuum filtered to ensure no lithium nitrate salt remains. Lack of lithium nitrate salt and phase change were confirmed by pXRD.
Once dried, the blue-purple powder was placed in acetone. After 18 h, the solution was vacuum filtered. The phase was confirmed by pXRD.
0.647 g of chromium (III) nitrate nonahydrate dissolved in 160 mL of water was added to 0.747 g of Pod-1 and 0.181 g potassium hydroxide dissolved in 80 mL of water and 80 mL EtOH. To this, an additional 0.181 g of potassium hydroxide dissolved in 32 mL of water is added dropwise, precipitating the blue hydrogen-bonded network. The presence of a primary aqua shell around the chromium was confirmed through thermogravimetric analysis.
Li(A) templated-CrPod-1 MOF—A is Anion
The blue hydrogen-bonded network was soaked in 10 mL of a saturated solution of the lithium salt in acetone over a period of two weeks. Over this time, the colour transformed from blue to turquoise. The phase transformation of the hydrogen bonded framework was monitored by pXRD. After no further changes in the pXRD pattern were apparent, the material was filtered and placed in an oven for 24 hours at 100° C. in air to dehydrate and form the lithium templated chromium-phosphonate MOF. Schematic for templating CrPOD-1 with lithium is shown in
The blue hydrogen-bonded network was soaked in 10 mL of acetone over a period of three weeks. No phase or colour change was observed. After three weeks, the material was filtered and placed in an oven for 24 hours at 100° C. in air to dehydrate and form the non-templated chromium-phosphonate MOF.
Quantitative 7Li NMR was run using a Bruker CFI 600 MHz spectrometer using a zg30 pulse program with four scans. The relaxation delay (d1) was set to 15 s, over ten times the experimentally determined t1 to ensure full relaxation of the sample before each pulse. An acquisition time of 1.88 s was determined to maximize signal to noise. The receiver gain was consistently set to 2050.
Sample preparation involved pipetting 0.5 mL of the solution of interest into a 5 mm NMR tube. To this solution, 0.05 mL of a deuterated solvent that matched that of the solution was added. Each sample was prepared in triplicate to ensure accuracy between the results.
A calibration curve of the lithium salts in acetone was generated using stock solutions at 0.01M, 0.025M, 0.05M, 0.075M and 0.1M for each salt. These sample were run as per the experimental procedure described above. The single peak was set to 0 ppm, and integration was performed using Bruker TopSpin 3.6.1. From these integrations, a curve of peak intensity against concentration was generated. (
Lithium extraction experiments were performed on three CrPOD-1 MOF samples: One templated with lithium perchlorate, one templated with lithium nitrate, and one without a template. For each sample, the MOF was first soaked in water to remove the templating lithium salt. After 24 hours, the characteristic perchlorate/nitrate peaks in the IR spectra disappeared, indicating complete desorption of the lithium salt from the MOFs. As expected, no change was observed for the non-templated MOF.
These samples were filtered and 50 mg of each MOF was exposed to 3 mL of a 0.1M solution of lithium nitrate in acetone and another 50 mg exposed to 3 mL of a 0.1M solution of lithium perchlorate in acetone. After 24 hours, 0.5 mL of the solutions were pipetted into the NMR tube as described in the above experimental procedure and the 7Li NMR recorded. Again, the peak was set to 0 ppm, and integration was performed using Bruker TopSpin 3.6.1.
The remaining concentration of lithium in the solution was calculated from the calibration curve to determine the total amount of lithium extracted by the MOF. From the remaining concentration, the lithium extraction capacity of the MOF was determined using the following equation:
Where the capacity is in mmol/g, Ci and Cf are the initial and final concentrations in molarity, V is the volume of the solution in milliliters, and m is the sample mass in milligrams.
The results of these experiments are shown in
Lithium adsorption shows that the non-templated material had no affinity for lithium while the two templated versions did. Furthermore, the size of the counter ion greatly affects the uptake. Without being bound to theory, it is submitted that when the materials was templated with perchlorate (r=240 pm) it can adsorb more lithium than that templated with nitrate (r=179) due to additional templated space.
Acetone templated CrBPDP H-MOF was prepared as a slurry. Excess solvent was removed under gentle vacuum filtration. The H-MOF was allowed to remain slightly moist to prevent dehydration. The H-MOF powder (˜100 mg) was then transferred to a 75 mL glass reactor liner and placed inside a Parr 4740 high pressure vessel with gage block assembly. The vessel was sealed and pressurized to 10 Bar with 99.99% CO2. The CO2 was then cyclically released and repressurized five times to remove atmospheric gasses from the pressure vessel.
The vessel was then pressurized to 30 Bar and the gas inlet left open. The vessel was gently cooled to −15° C. resulting in the formation of liquid CO2. The desired maximum pressure was controlled by limiting the amount of time the inlet valve was left open and thus the quantity of liquid CO2 formed. Once pressurization was complete, the vessel was removed from the cold bath and allowed to warm over 6 hours.
The vessel was wrapped in heating tape and placed in a sand bath. The vessel was rapidly heated to achieve the critical conditions of 31° C. and 73.8 Bar, the temperature was then further raised to 120° C. over 1 hour. After 24 hours the reactor was allowed to cool and then depressurized. The MOF powder was collected and the porosity confirmed by gas adsorption.
The above procedure has been completed with several different H-MOFs, including ATP. Results are shown in
The above experiments confirmed that supercritical CO2 can be used as a H-MOF template to produce unique MOFs. It is submitted that optimal pressure, temperature, heating rate, and additives may be determined.
While the applicant's teachings described herein are in conjunction with various embodiments for illustrative purposes, it is not intended that the applicant's teachings be limited to such embodiments as the embodiments described herein are intended to be examples. On the contrary, the applicant's teachings described and illustrated herein encompass various alternatives, modifications, and equivalents, without departing from the embodiments described herein, the general scope of which is defined in the appended claims.
The present application claims priority to U.S. Provisional Patent Application No. 63/141,660, which was filed Jan. 26, 2021, the contents of which are incorporated herein by reference in their entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CA2022/050106 | 1/26/2022 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63141660 | Jan 2021 | US |
