Patent Application
20170173623
The invention relates generally to devices and methods for the synthesis of porous coordination polymer (PCP), and in particular to devices and methods for coating a surface of a material with a film of one or more porous coordination polymers.
An established method for synthesis of porous coordination polymer (PCP) coatings relies on the stepwise introduction of reagents with an intermediary wash step, often referred to as liquid phase epitaxy. This method requires considerable time and solvent to make a single film, which is undesirable.
The present invention provides devices and methods for producing films of porous coordination polymers (e.g., metal-organic frameworks) in the same size range as liquid phase epitaxy, but advantageously using a small fraction of the time and considerably less solvent.
According to an aspect, an apparatus is provided for coating a surface of a material with at least one film. The film comprises at least one porous coordination polymer. The apparatus comprises a body (e.g., a flow cell) having an interior space for holding the material to be coated. The body further includes at least one inlet and at least one outlet in communication with the interior space to permit fluid to flow in a downstream direction from the inlet, across the surface of the material in the interior space, and through the outlet. A plurality of flow channels are arranged to flow a plurality of different reagent solutions from respective supply sources to the at least one inlet. The flow channels merge into at least one mixing region, positioned upstream from the interior space, to mix the solutions prior to the mixture contacting the surface of the material in the interior space. The apparatus also includes fluid delivery means (e.g., at least one pressure source and valve system) arranged with the supply sources and the flow channels to select at least one combination of the reagent solutions to be mixed and to force the selected reagent solutions to flow from their respective supply sources, through the flow channels, and into the mixing region at independently controllable flow rates.
According to another aspect, a method is provided for coating a surface of a material with at least one film. The film comprises at least one porous coordination polymer. The method comprises the step of holding the material to be coated in the interior space of a body. The body includes at least one inlet and at least one outlet in communication with the interior space to permit fluid to flow in a downstream direction from the inlet, across the surface of the material in the interior space, and through the outlet. At least one pump and valve system is utilized to select at least one combination of reagent solutions from a plurality of different reagent solutions in respective supply sources. The selected reagent solutions are forced to flow from their respective supply sources, through a corresponding plurality of flow channels, and into at least one mixing region. The method also comprises the steps of mixing the selected reagent solutions in the mixing region prior to the mixture contacting the surface of the material in the interior space, and forcing the mixture to flow across the surface of the material.
According to another aspect, an apparatus is provided for coating a surface of a material with at least one film. The apparatus comprises a body having at least one inlet, at least one outlet, and an interior space for holding the material to be coated. The inlet and outlet are positioned with respect to the interior space to permit fluid to flow from the inlet, across the surface of the material, and through the outlet. A plurality of flow channels are arranged to flow at least one reagent solution and at least one other solution containing a catalyst from respective supply sources. The catalyst promotes growth of the film when mixed with other reagents. The flow channels are fluidicly connected to the at least one inlet, and the flow channels form at least one union for mixing the reagent and catalyst solutions prior to the mixture contacting the surface of the material in the interior space. The apparatus also comprises fluid delivery means (e.g., at least one pump and valve system) for forcing the reagent and catalyst solutions to flow from their respective supply sources, through the flow channels, and into the interior space at flow rates selected to control the respective concentrations of the reagents and catalyst in the mixture.
According to another aspect, a method is provided for coating a surface of a material with at least one film. The method comprises holding the material to be coated in the interior space of a body having at least one inlet and at least one outlet. The inlet and outlet are positioned with respect to the interior space to permit fluid to flow from the inlet, across the surface of the material, and through the outlet. The method also comprises forcing at least one reagent solution and at least one solution containing a catalyst to flow from respective supply sources through a corresponding plurality of flow channels to the at least one inlet. The catalyst promotes growth of the film. The reagent and catalyst solutions are mixed prior to the mixture contacting the surface of the material in the interior space, and the reagent and catalyst solutions are forced to flow from their respective supply sources and through the corresponding flow channels at flow rates selected to control the respective concentrations of the reagents and catalyst in the mixture. The mixture is forced to flow across the surface of the material to produce the film.
According to another aspect, an apparatus is provided for coating a surface of a material with at least one film. The film comprises at least one porous coordination polymer. The apparatus comprises a body having at least one inlet, at least one outlet, and an interior space for holding the material to be coated. The inlet and outlet are positioned with respect to the interior space to permit fluid to flow from the inlet, across the surface of the material, and through the outlet. At least one flow channel is arranged to flow reagents to the body. The flow channel is fluidicly connected to the inlet. The apparatus also comprises fluid delivery means (e.g., at least one pump and valve system) for forcing the reagents to flow from at least one supply source, through the flow channel, and into the interior space. At least one heat source is arranged to heat the reagents and/or the material in the interior space to a temperature sufficient to initiate growth of the film on the surface.
According to another aspect, a method is provided for coating a surface of a material with at least one film. The film comprises at least one porous coordination polymer. The method comprises holding the material to be coated in the interior space of a body having at least one inlet and at least one outlet. The inlet and outlet are positioned with respect to the interior space to permit fluid to flow from the inlet, across the surface of the material, and through the outlet. Reagents are forced to flow from at least one supply source and through the interior space of the body such that the reagents contact the surface of the material. The method also comprises the step of heating the material in the interior space and/or the reagents to a temperature sufficient to initiate growth of the film on the surface.
The foregoing aspects and advantages of the present invention will become better understood upon reading the following detailed description and upon reference to the drawings where:
In the following description, it is understood that all recited connections between structures can be direct operative connections or indirect operative connections through intermediary structures. A set of elements includes one or more elements. Any recitation of an element is understood to refer to at least one element. A plurality of elements includes at least two elements. Unless otherwise required, any described method steps need not be necessarily performed in a particular illustrated order. A first element (e.g. a signal or data) derived from a second element encompasses a first element equal to the second element, as well as a first element generated by processing the second element and optionally other data. Making a determination or decision according to a parameter encompasses making the determination or decision according to the parameter and optionally according to other data. Unless otherwise specified, an indicator of some quantity/data may be the quantity/data itself, or an indicator different from the quantity/data itself. Computer programs described in some embodiments of the present invention may be stand-alone software entities or sub-entities (e.g., subroutines, code objects) of other computer programs. Computer readable media encompass non-transitory media such as magnetic, optic, and semiconductor storage media (e.g. hard drives, optical disks, flash memory, DRAM), as well as communications links such as conductive cables and fiber optic links. According to some embodiments, the present invention provides, inter alia, computer systems comprising hardware (e.g. one or more processors and associated memory) programmed to perform the methods described herein, as well as computer-readable media encoding instructions to perform the methods described herein.
Suitable porous coordination polymers include porous crystalline materials such as a metal-organic frameworks (MOFs) or porous coordination frameworks. Preferred MOF subclasses include Zeolitic imidazolate framework (ZIF), IRMOF, and Multivariate MOF (MTV-MOF) made using a mix of organic linkers having the same geometry but varied chemical functionality. Suitable porous coordination polymers also include a covalent organic framework (COF) in which the framework includes covalent chemical bonds rather than metal coordination bonds. In rare embodiments, the porous coordination polymers comprise non-crystalline porous materials such as metal-organic polyhedron having discreet porous cages, porous metal-organic polymer, or metal-organic gel.
Metal-organic frameworks are an expanding class of porous crystalline materials that are built up from nodes of metal ions connected by organic linkers. These materials can typically be engineered to have pore apertures with a width or diameter in a range of less than 1 Angstrom to about 30 Angstroms (Yaghi, et. al., Nature 423, 705-714, Jun. 12, 2003). A class of exotic MOFs (“MOF-74”) with pore aperture diameters of 98 Angstroms have also been demonstrated (Deng, et. al., Science 336, 1018, 2012). MOFs with varying pore sizes can selectively adsorb molecules based on the size of the molecules. For example, engineered MOFs with pore sizes designed for carbon dioxide (CO2) adsorption can separate gases in industrial processes (Du, et. al., J. Am. Chem. Soc., 2013, 135 (2), pp 562-565). MOFs can also be used as receptor layers with a Quartz Crystal Microbalance (QCM) to act as a chemical sensor in controlled environments.
The pore size of the MOF (e.g., the average width, diameter or volume of the pore apertures) is preferably chosen to achieve a degree of selectivity of adsorbed molecules based on the size of the molecules. In some embodiments, the material (e.g., a substrate) that is coated with a film is a resonating member of a resonant sensor. Resonant sensors (e.g., cantilever, membrane and piezoelectric resonator-based sensors) use target molecules adsorbed in the sensing material (e.g., a film of PCP coated on the sensor) to change properties that are reflected in the resonance frequency. In some embodiments, an array of resonant sensors has MOFs of varying pore size on the resonating members of the sensors. The resonant sensors may be used as chemical sensors, where ambient molecular concentrations are monitored in real-time and the multiple sensors with varied pore sizes provide selectivity based on molecule size.
The apparatus 10 includes a body 16 (e.g., a flow cell) having at least one inlet 18, at least one outlet 20, and an interior space 22 for holding the substrate 12 to be coated. In some embodiments, the interior space 22 has a notch or other holding mechanism to align and hold the substrate 12 in a suitable orientation for reagent solutions to flow across at least one surface of the material to be coated. The inlet 18 and the outlet 20 are positioned with respect to the interior space 22 to permit fluid to flow in a downstream direction from the inlet 18, across at least one surface of the substrate 12 (flow direction indicated by arrow), and through the outlet 20 to a waste collector 24. In some embodiments, a mixture of reagent solutions is flowed continuously across the substrate 12, significantly reducing the time needed to coat the material with the film of porous coordination polymer.
A plurality of flow channels 26A, 26B, 26C (e.g., tubes or conduits) are arranged to flow reagent solutions from respective reagent supply sources 28A, 28B, 28C (e.g., containers). The flow channels 26A, 26B, 26C are fluidicly connected to the at least one inlet 18. The flow channels merge into at least one mixing region 30 that is positioned upstream of the interior space to mix the solutions prior to the mixture contacting the surface of the material in the interior space 22. In some embodiments, the mixing region 30 is positioned inside the body 16. In some embodiments, the mixing region is an intersection or union of the flow channels 26A, 26B, 26C positioned between the reagent supply sources 28A, 28B, 28C and the at least one inlet 18.
The mixing of the reagent solutions just prior to the mixture contacting the surface of the substrate 12 is effective in preventing premature nucleation of the polymer in solution, which is undesirable as it may lead to deposition of large particles and to reagent depletion. To prevent premature nucleation, the reagents are preferably separated into at least two non-reacting solutions that are stored in at least two different ones of the supply sources 28A, 28B, until they contact each other in the mixing region 30. For example, a MOF typically comprises at least one bidentate organic compound coordinated to at least one metal ion, and the metal ion is held in a separate solution from the solution containing the organic compound, until the separate solutions are mixed in the mixing region 30. Many recipes for metal-organic frameworks are known in the prior art. For example, MOFs are described in U.S. Pat. No. 5,648,508, U.S. Pat. No. 8,697,191, EP-A-0 790 253, M. O'Keeffe et al., J. Sol. State Chem., 152 (2000), pages 3 to 20, H. Li et al., Nature 402, (1999), page 276, M. Eddaoudi et al., Topics in Catalysis 9, (1999), pages 105 to 111, B. Chen et al., Science 291, (2001), pages 1021 to 1023, DE-A-101 11 230, DE-A 10 2005 053430, WO-A 2007/054581, WO-A 2005/049892 and WO-A 2007/023134.
The apparatus 10 also includes fluid delivery means for forcing selected ones of the reagent solutions to flow from their respective reagent supply sources 28A, 28B, 28C, through the flow channels 26A, 26B, 26C, and into the mixing region 30. The flow rates of the reagent solutions are selected to control the respective concentrations of the reagents in the mixture contacting the substrate 12. The fluid delivery means typically comprises at least one pump and valve system 32 arranged to force the reagent solutions to flow from their respective reagent supply sources 28A, 28B, 28C and through the flow channels 26A, 26B, 26C at independently controllable flow rates. In some embodiments, at least one controller 34 is programmed to control the pump and valve system 32 according to user-selectable parameters. The user-programmable control is preferably provided by LabVIEW (Laboratory Virtual Instrument Engineering Workbench) which is a system-design platform and development environment commercially available from National Instruments.
The controller 34 is preferably programmable to vary the combination of reagent solutions that are pumped from their respective reagent supply sources 28A, 28B, 28C and through the flow channels 26A, 26B, 26C. For example, in some embodiments the flow rates of the reagent solutions are varied over time in a substantially periodic (e.g., sinusoidal) pattern. An example of a suitable pump is a rotary piston pump with built-in flow control (e.g., valves) for directing fluid to move in different flow channels at independently controllable flow rates. In other embodiments, other types of pumps may be employed such as diaphragm, piston, plunger, and centrifugal pumps. In some embodiments, valves are separate from the at least one pump. The fact that one or more valves may be built into the pump system is just a specific embodiment and not limiting. In alternative embodiments, the fluid delivery means may comprise any source of differential pressure. For example, pressure may be supplied to the headspace of the reagent supply sources 28A, 28B, 28C to force fluid flow at desired flow rates.
An optional heat source 36 is arranged to heat the reagents and/or the substrate 12 in the interior space 22 to a temperature sufficient to initiate growth of the film of porous coordination polymer on the surface of the substrate 12. In some embodiments, the heat source 36 is arranged to heat the reagent solutions prior to the mixture of reagent solutions contacting the surface of the substrate 12 in the interior space 22. In other embodiments, the heat source 36 is arranged to heat the material in the interior space 22 (e.g., the substrate 12) while the mixture of reagents is forced to flow across the surface of the substrate 12. In some embodiments, both the reagents and substrate 12 are heated by the at least one heat source 36.
In any of these heating embodiments, the heating of the reagents and/or of the material to be coated in the interior space 22 to a temperature sufficient to initiate growth of the film of porous coordination polymer on the surface is effective in preventing early nucleation of the polymer in solution. Premature nucleation is undesirable as it may lead to deposition of large particles and to reagent depletion. When heat is used to initiate the growth of the film, one reagent supply source 28A may be connected to the body 16 by a flow channel 26A. The one reagent supply source 28A may contain all the necessary reagents for film growth when activated by heat. Alternatively, the apparatus 40 may comprise multiple flow channels 26A, 26B, 26C arranged to flow multiple reagent solutions from respective reagent supply sources 28A, 28B, 28C as in previous embodiments.
In some embodiments, the reagents are cooled to a temperature below room temperature prior to forcing the reagents to flow from one or more reagent supply sources 28A, 28B, 28C. Room temperature is typically about 22° C. The heat source 36 may be part of a more complete environmental control system that controls multiple environmental parameters (e.g., temperature and pressure) within the body 16 of the apparatus 40. In preferred embodiments, the heat source 36 heats the interior space 22 and/or the substrate 12 using convection, although many other suitable heat sources may be used in alternative embodiments.
The flow rates of the reagent solutions may vary. Flow rates are selected to control the respective concentrations of the reagents in the mixture contacting the surface to be coated. An easy way to adjust concentrations is to vary the relative flow rates of one reagent solution to another. The reaction of a reagent A with a reagent B removes A and B from solution at some rate as they meet in the mixing region 30. So the concentration is preferably maintained in a range where enough material is reacting (reagent A and B) to form a layer of film, but not at concentrations so high that we sediment out particles, which is undesirable for the layer of film being formed. The flow rate and temperature both contribute to the process. Flow rates are typically selected to maintain the concentration of each reagent in a desired range based on the rate at which reagents are removed from solution by undergoing reaction. The ideal concentration range is high enough that the reaction occurs sufficiently quickly, but not so high as to lead to rapid particle formation and sedimentation onto the substrate from solution.
Pumps and valves may be controlled for continuous flow or for more complex flow rate profiles, such as a ramp from zero to a high flow rate F, then to a lower flow rate f, and then back to zero again. Each reagent solution may have the same or different flow rate profiles. In some embodiments, these flow rate profiles are coordinated with different temperatures. For example, a recipe for creating a MOF film could include: Step 1 at temperature 20° C., flow Reagent Solution A at flow rate FA, and Reagent Solution B at flow rate FB for 20 minutes. Step 2 at temperature 20° C., Reagents Solutions A and B are off, turn on Wash C at flow rate FC for 5 minutes. Step 3 at temperature 200° C., flow Reagent Solution A at flow rate F3 and Reagent Solution B at flow rate F4 for 32 minutes. Step 4 at Temperature 30° C., 20 minutes, no reagents. These and many other recipes are possible where flow rate profiles are coordinated with different temperatures for different time periods.
For example, in some embodiments, the substrate 12 is a mass transducer. The film deposition process and thickness of the film 14 is monitored by running the transducer during film growth. A controller 34 is in communication with the fluid delivery means (e.g., pump and valve system 32) and the electrical circuit via readout electronics 64. In some embodiments, the controller 34 is programmed to stop flow of the reagent solutions in response to at least one electrical signal indicative of a desired thickness of the film 14 on the substrate 12. For example, the sensor data (e.g., electrical signals indicative of film growth) is fed into the pump controller 34, which stops the flow of the reagent solutions and initiates rinsing of the substrate 12 with solvent, once the desired film thickness is achieved.
Multiple reagent solutions are flowed through the apparatus at constant flow rates and at room temperature (e.g., 22° C.) for a fixed period of time. Reaction variables are selected according to a desired film thickness (e.g., in the range of 10 nm to 10 μm).
Referring to
Flow rates of the reagents are varied with time. A first reagent flows through the interior space 22 of the flow cell prior to the flow of other reagents to allow that first reagent to react with the surface in the absence of the other reagents.
Referring to
A first PCP film (seed layer) is grown using a first combination of reagents, after which a second combination of reagents is flowed, optionally followed by other combinations of reagents, resulting in a film with layers of different PCP materials.
Referring to
Flow rates of reagent solutions are varied over time in a periodic (e.g., sinusoidal) pattern to improve film quality by alternating which reagent is present in higher concentration in the mixture.
Referring to
Heating of the reagents and/or the material to be coated to initiate growth of the film on the surface.
Referring to
Reagents and at least one catalyst are mixed prior to contacting the surface to be coated.
Referring to
Grow a self-assembled monolayer (SAM) on a gold-coated substrate, and produce a MOF film over the SAM.
A substrate coated with gold is loaded into a flow cell. The substrate is rinsed by flowing water, acetone, and isopropanol through the cell sequentially. The substrate is cleaned by flowing either or both of a 5/1/1 mixture of water/30% solution of ammonium hydroxide/30% solution of hydrogen peroxide and a 5/1/1 mixture of water/40% solution of hydrochloric acid/30% solution of hydrogen peroxide through the cell. If both solutions are used, an ethanol rinse step is be performed between them to avoid mixing the acid and base. The substrate is rinsed by flowing ethanol through the cell. To grow the self-assembled monolayer (SAM), a solution of 0.2 mM 16-mercaptohexadecanoic acid (which forms the SAM) and 0.02 mM acetic acid (an additive to prevent multilayer SAM growth) in ethanol is flowed across the cell. The substrate is allowed to sit in the solution undisturbed for >12 hours.
The substrate is rinsed by flowing ethanol through the cell. To grow the MOF, three solutions are flowed through the cell in an ABCBABCB pattern (where B is a rinse step to remove the components of A and C that have not fully bound to the surface of the substrate). Solution A is a 1 mM solution of copper(II) acetate in ethanol. Solution B is ethanol. Solution C is a 0.2 mM solution of trimesic acid in ethanol. The substrate is rinsed by flowing ethanol through the cell. Air is pumped through the cell to remove liquid solvents. Solvent remaining in the pores of the MOF is removed by heating in air to 100 degrees C. (the temperature may vary depending on the MOF). The substrate is removed from the flow cell.
The description above illustrates embodiments of the invention by way of example and not necessarily by way of limitation. Many other embodiments and examples of the apparatus and method are possible. Accordingly, the scope of the invention should be determined by the following claims and their legal equivalents.
This application claims the benefit of U.S. provisional patent application 62/269,925 filed on Dec. 18, 2015, which application is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62269925 | Dec 2015 | US |
