Environmentally friendly synthesis of metal organic frameworks for selected gas capture

Abstract

A method of making a gas capturing apparatus includes solubilizing at least two sorbent precursors in a solvent that includes at least one polyol to make a sorbent precursor solution, coating a porous substrate with the sorbent precursor solution to form a sorbent precursor coated substrate, and chemically reacting the at least two sorbent precursors on the sorbent precursor coated substrate to form a sorbent coated substrate.

Description

Attorney Docket No.: SP24-252ENVIRONMENTALLY FRIENDLY SYNTHESIS OF METAL ORGANIC FRAMEWORKS FOR SELECTED GAS CAPTUREFIELD OF THE DISCLOSURE

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application No. 63 / 696968 filed September 20, 2024, the content of which is incorporated herein by reference in its entirety.FIELD

[0002] The present disclosure relates generally to environmentally friendly synthesis of metal organic frameworks for selected gas capture, such as greenhouse gas capture.BACKGROUND

[0003] Efforts to address the effects of climate change include greenhouse gas, such as carbon dioxide, capture technology, which includes flowing a greenhouse gas containing fluid, such as ambient air, over or through a sorbent material capable of absorbing at least a portion of the greenhouse gas. This type of capture technology can be similarly utilized to capture any selected gas or gases from a fluid flow, such as for the removal of an undesirable component (e.g., a pollutant) from the fluid flow and / or the concentration or collection of a desired component from the fluid flow. The sorbent material can then be regenerated by increasing a temperature of the sorbent, such as by flowing a heated fluid (e.g., steam) thereover or therethrough, thereby removing captured carbon dioxide from the sorbent material. Suitable sorbent materials for this purpose can include metal organic frameworks (MOFs). MOFs include self-assembling porous structures formed from metal nodes with organic linkers, which can exhibit extremely high surface areas (e.g., greater than 7000 meters2 / gram). MOFs can be tuned for desired porosity and selectivity. In addition, MOFs’ tunable gas affinity gives them the unique ability to store and filter gasses at the same time. There is increased commercial interest for capturing selected gases in a more environmentally friendly manner.Attorney Docket No.: SP24-252SUMMARY

[0004] Embodiments disclosed herein include a method of making a gas capturing apparatus. The method includes solubilizing at least two sorbent precursors in a solvent comprising at least one polyol to make a sorbent precursor solution. The method also includes coating a porous substrate with the sorbent precursor solution to form a sorbent precursor coated substrate. In addition, the method includes chemically reacting the at least two sorbent precursors on the sorbent precursor coated substrate to form a sorbent coated substrate.

[0005] Additional features and advantages of the embodiments disclosed herein will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the disclosed embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings.

[0006] It is to be understood that both the foregoing general description and the following detailed description present embodiments intended to provide an overview or framework for understanding the nature and character of the claimed embodiments. The accompanying drawings are included to provide further understanding and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the disclosure, and together with the description serve to explain the principles and operations thereof.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG. 1 A is a schematic end view of an example porous substrate in accordance with embodiments disclosed herein;

[0008] FIG. IB is a schematic side cutaway view of the example porous substrate of FIG. 1A;

[0009] FIG. 2A is an exploded schematic end view of a portion of the example porous substrate of FIGS. 1A-1B;

[0010] FIG. 2B is an exploded schematic end view of a portion of the example porous substrate of FIGS. 1A-1B with a coating composition comprising a solid sorbent deposited thereon;Attorney Docket No.: SP24-252

[0011] FIG. 3 shows the chemical structure of 2,5-dioxidoterephthalate nickel(2+) dihydrate (NiMOF74);

[0012] FIGS. 4A-4C are schematic side views of an example method of making a gas capturing apparatus in accordance with embodiments disclosed herein;

[0013] FIG. 5 is a chart showing CO2 adsorption by NiMOF74 powders solubilized in comparative and exemplary solvent systems;

[0014] FIGS. 6A-6C are scanning electron microscope (SEM) images of a bare ceramic substrate and ceramic substrates grafted with NiMOF74 sorbents solubilized in comparative and exemplary solvent systems;

[0015] FIG. 7 is a chart showing CO2 adsorption by NiMOF74 sorbent grafted on a cellular ceramic substrate; and

[0016] FIG. 8A-8B are, respectively, SEM and transmission electron microscope (TEM) images of a glass substrate grafted with a NiMO74 sorbent solubilized in an exemplary solvent system.DETAILED DESCRIPTION

[0017] Reference will now be made in detail to the present preferred embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. However, this disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0018] Ranges can be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, for example by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0019] Directional terms as used herein - for example up, down, right, left, front, back, top, bottom - are made only with reference to the figures as drawn and are not intended to imply absolute orientation.Attorney Docket No.: SP24-252

[0020] Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order, nor that with any apparatus specific orientations be required. Accordingly, where a method claim does not actually recite an order to be followed by its steps, or that any apparatus claim does not actually recite an order or orientation to individual components, or it is not otherwise specifically stated in the claims or description that the steps are to be limited to a specific order, or that a specific order or orientation to components of an apparatus is not recited, it is in no way intended that an order or orientation be inferred, in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps, operational flow, order of components, or orientation of components; plain meaning derived from grammatical organization or punctuation, and; the number or type of embodiments described in the specification.

[0021] As used herein, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a” component includes aspects having two or more such components, unless the context clearly indicates otherwise.

[0022] As used herein, the term “essentially free” means a solution contains less than about 1% by volume of a stated constituent, including less than about 0.1% by volume of the stated constituent, and further including about 0% by volume of the stated constituent.

[0023] Embodiments disclosed herein relate to methods for attaching and forming metal organic framework (MOF) materials on and within porous inorganic substrates. This process utilizes a grafting during synthesis approach. With this approach, large MOF crystals can be grafted from within large macropores to the internal structure of microporous supports. In contrast, pre synthesized crystalline MOF materials may be unable to attach to surfaces and within macro pores without the addition of binding aides which add nonfunctioning mass, process steps and are too large to mechanically coat within micro pore substates.

[0024] Polymeric and cellulose binding agents have shown ability to aide in the attachment of MOF materials to substrate surfaces. This process adds nonfunctional mass, process steps and limits porous embedding. Grafting during synthesis, including without binders, allows for macro to micro porous substrate attachment and embedding, increasing MOF bindingAttorney Docket No.: SP24-252 potential within a high surface area support. In addition, physical removal and decreased degradation are improved by the MOF being trapped within the porous support structure.

[0025] FIGS. 1 A and IB show respective schematic end and side cutaway views of an example porous substrate 100 in accordance with embodiments disclosed herein. Porous substrate 100 includes a plurality of channels 102 extending therethrough. Specifically, porous substrate 100 comprises a honeycomb structure, wherein a M / N matrix of parallel channels 102 extend therethrough. And while FIGS. 1 A and IB show a porous substrate having a rectangular cross section with rectangular channels, embodiments disclosed herein include other geometries, such as porous substrates having other polygonal-shaped crosssections (e.g., triangular, pentagonal, hexagonal, etc.) or porous substrates having circular or elliptical cross-sections (e.g., cylindrical-shaped substrates), as well as any such substrates having channels with other polygonal-shaped cross-sections (e.g., triangular, pentagonal, hexagonal, etc.) or channels with circular or elliptical cross-sections (e.g., cylindrical-shaped channels).

[0026] In certain exemplary embodiments, porous substrate 100 comprises a ceramic substrate, a glass substrate, or a glass-ceramic substrate. For example, porous substrate 100 may comprise or consist essentially of at least one of cordierite, amorphous silica, fused silica, aluminum titanate, talc, clay, alumina, titania, or hollow glass microspheres

[0027] In certain exemplary embodiments, porous substrate 100 may have a porosity (i.e., total volume of pores in substrate relative to the total substrate volume) ranging from about 30% to about 70%, such as from about 35% to about 65%, and further such as from about 40% to about 60%. In certain exemplary embodiments, porous substrate 100 may have a median pore size (PoreD50) ranging from about 8 microns to about 30 microns, such as from about 10 microns to about 20 microns, and further such as from about 12 microns to about 18 microns.

[0028] In certain exemplary embodiments, such as when the porous substrate comprises hollow glass microspheres, the porous substrate may have a median pore size (D50) ranging from about 2 nanometers to about 40 nanometers, such as from about 3 nanometers to about 30 nanometers, and further such as from about 4 nanometers to about 20 nanometers, and yet further such as from about 5 nanometers to about 10 nanometers.Attorney Docket No.: SP24-252

[0029] In certain exemplary embodiments, porous substrate 100 may have a porosity ranging from about 30% to 45% and a PoreD50 ranging from about 8 microns to about 15 microns. In certain exemplary embodiments, porous substrate 100 may have a porosity ranging from about 45% to about 55% and a PoreD50 ranging from about 10 microns to about 20 microns. In certain exemplary embodiments, porous substrate 100 may have a porosity ranging from about 55% to about 70% and a PoreD50 ranging from about 15 microns to about 30 microns.

[0030] FIG. 2A shows an exploded schematic end view of a portion of the example porous substrate 100 of FIGS. 1 A-1B and FIG. 2B shows an exploded schematic end view of a portion of the example porous substrate 100 of FIGS. 1A-1B with a coating composition 104 comprising a sorbent material deposited thereon. Specifically, coating composition 104 comprising a sorbent material is deposited on channels 102 of porous substrate 100.

[0031] And while FIGS. 1 A-2B show a porous substrate 100 with a honeycomb structure, embodiments disclosed herein include porous substrates with other structures, such as hollow tubes, meshes, or flow through membranes.

[0032] Embodiments disclosed herein include those in which a sorbent material is synthesized from at least two sorbent precursors, which can be chemically reacted to form the sorbent material. For example, embodiments disclosed herein include those in which the sorbent material comprises 2,5-dioxidoterephthalate nickel(2+) dihydrate (NiMOF74), the chemical structure of which is shown in FIG. 3.

[0033] FIGS. 4A-4C show schematic side views of an example method of making a gas capturing apparatus, such as a carbon dioxide capturing apparatus, in accordance with embodiments disclosed herein. Specifically, FIG. 4A shows a schematic side view of a vessel 200 containing a solvent, wherein the solvent includes at least one polyol. The solvent is used to solubilize at least two sorbent precursors to make a sorbent precursor solution 110. The at least two sorbent precursors can be solubilized in the solvent using methods known to persons having ordinary skill in the art including, for example mechanical stirring and, as shown in FIG. 4A, sonication, wherein an ultrasonic transducer 202 emits ultrasonic waves into the sorbent precursor solution 110.

[0034] In certain exemplary embodiments, the solvent and the sorbent precursor solution 110 is essentially free of dimethylformamide (DMF). For example, in certain exemplary embodiments the solvent and the sorbent precursor solution 110 contains less than about 1%Attorney Docket No.: SP24-252 by volume of DMF, including less than about 0.1% by volume of DMF, and further including about 0% by volume of DMF.

[0035] In certain exemplary embodiments, the at least one polyol comprises a glycol, such as ethylene glycol. In certain exemplary embodiments, solvent comprises greater than about 50% polyol by volume, such as greater than about 60% polyol by volume, including from about 50% to about 90% polyol by volume, and further including from about 60% to about 80% polyol by volume. Such embodiments include those in which the solvent comprises polyol and water, wherein the ratio of polyol to water ranges from about 1.1 :1 to about 10: 1, such as from about 2: 1 to about 5: 1, and further such as from about 3 : 1 to about 4:1.

[0036] For example, embodiments disclosed herein include a solvent comprising greater than about 50% ethylene glycol by volume, such as greater than about 60% ethylene glycol by volume, including from about 50% to about 90% ethylene glycol by volume, and further including from about 60% to about 80% ethylene glycol by volume. Such embodiments include those in which the solvent comprises ethylene glycol and water, wherein the ratio of ethylene glycol to water ranges from about 1.1 : 1 to about 10: 1, such as from about 2: 1 to about 5:1, and further such as from about 3 : 1 to about 4: 1.

[0037] In certain exemplary embodiments, the solvent and the sorbent precursor solution comprises triethanolamine. For example, embodiments disclosed herein include those in which the solvent and sorbent precursor solution 110 comprises a glycol, such as ethylene glycol, and triethanolamine. Embodiments disclosed herein also include those in which the solvent and sorbent precursor solution 110 comprises ethylene glycol, triethanolamine, and water, wherein the ratio of ethylene glycol to water ranges from about 1.1 : 1 to about 10: 1, such as from about 2: 1 to about 5: 1, and further such as from about 3 : 1 to about 4:1.

[0038] In certain exemplary embodiments, the at least two sorbent precursors comprise nickel nitrate hexahydrate and dihydroxyterethphalic acid. Once the sorbent precursors have been solubilized in the solvent to make a sorbent precursor solution 110, the sorbent precursor solution 110 can be used to coat a porous substrate 100 in order to form a sorbent precursor coated substrate 100’. FIG. 4B shows a schematic side view of a vessel 200 in which a porous substrate 100 is immersed in the sorbent precursor solution 110 generated in FIG. 4A. By immersing the porous substrate 100 in the sorbent precursor solution 110, the porous substrate 100, including channels 102 (e.g., as shown in FIGS. 1 A-2B) is / are coatedAttorney Docket No.: SP24-252 with the sorbent precursor solution 110 in order to form a sorbent precursor coated substrate 100’. And while FIG. 4B shows coating the porous substrate 100 by immersing it in the sorbent precursor solution 110, embodiments disclosed herein include other methods of coating the porous substrate 100 with the sorbent precursor solution 110, such as, for example, piston coating processes as known to persons having ordinary skill in the art.

[0039] By coating the porous substrate 100 with the sorbent precursor solution 110, the at least two sorbent precursors are deposited on the sorbent precursor coated substrate 100’, including channels 102 (e.g., as shown in FIGS. 1 A-2B). The at least two sorbent precursors on the sorbent precursor coated substrate 100’ are then chemically reacted to form a sorbent coated substrate 100”. FIG. 4C shows a schematic side view in which heat is applied from a heat source 204 to vessel 200, which in turn heats the sorbent precursor coated substrate 100’ to facilitate chemical reaction between the at least two sorbent precursors and thereby form the sorbent coated substrate 100”. In certain exemplary examples, the at least two sorbent precursors comprise a metal hydrate and a phenolic acid and the sorbent comprises a metal organic framework comprising phenolic and carboxylic ligands. In certain exemplary embodiments, the at least two sorbent precursors comprise nickel nitrate hexahydrate and dihydroxyterethphalic acid and the sorbent comprises NiMOF74.

[0040] In certain exemplary embodiments, chemically reacting the at least two sorbent precursors on the sorbent precursor coated substrate 100’ comprises heating the sorbent precursor coated substrate 100’ to a temperature ranging from about 110°C to about 140°C. Such embodiments include those in which chemically reacting the at least two sorbent precursors on the sorbent precursor coated substrate comprises heating the sorbent precursor coated substrate for a time ranging from about 12 hours to about 72 hours.

[0041] Upon completion of chemical reaction, the sorbent coated substrate 100” is removed from vessel 200 and then optionally washed with an alcohol, such as methanol, to remove unattached surface materials. The sorbent coated substrate 100” may then be optionally washed with DMF to remove unreacted materials and then solvent exchanged with an alcohol, such as methanol, to replace the higher boiling point DMF. The sorbent coated substrate 100” may then be dried, such as vacuum dried, to remove solvent from pores and binding sites within the sorbent coated substrate 100”.

[0042] ExamplesAttorney Docket No.: SP24-252

[0043] Embodiments disclosed herein will be further described with reference to the following non-limiting examples.

[0044] Example 1 :

[0045] Comparative MOF powder NiMOF74 sorbent precursors comprising about 0.6 grams of Nickel nitrate hexahydrate (Aldrich) and about 0.12 grams of 2,5-Dihydroxyterethphalic acid (Aldrich) were solubilized in a reaction vessel with equal parts dimethylformamide (DMF), ethanol and deionized water, for a solution having a total volume of about 150 milliliters. The solution was then heated with optional sonication at a temperature of about 120-140°C for 12-72 hours. A color change of green to golden yellow visually indicated that the sorbent precursors were reacting to form NiMOF74. The reaction products were then filtered from the remaining solvent followed by methanol rinse, DMF washing, methanol solvent exchange, and vacuum drying at about 25 °C for about 72 hours.

[0046] Exemplary MOF powder NiMOF74 sorbent precursors comprising about 0.6 grams of Nickel nitrate hexahydrate (Aldrich) and about 0.12 grams of 2,5-Dihydroxyterethphalic acid (Aldrich) were solubilized in a reaction vessel with ethylene glycol, deionized water at a 75:25 volume ration with a 2X stoichiometric amount of triethanolamine, for a solution having a total volume of about 51 milliliters. The solution was then heated with optional sonication at a temperature of about 120-140°C for 12-72 hours. A color change of green to golden yellow visually indicated that the sorbent precursors were reacting to form NiMOF74. The reaction products were then filtered from the remaining solvent followed by methanol rinse, DMF washing, methanol solvent exchange, and vacuum drying at about 25°C for about 72 hours.

[0047] Samples of each of the comparative and exemplary MOF powders were placed on a VacPrep for heating to 175C under vacuum for 24 hours, removed, weighed, then placed on a Micromeritics 3-Flex adsorption analyzer for gas adsorption analysis. Sample files were then created using the sample weight after outgassing using a CO2 at 0°C analysis program in order to measure and report the amount of CO2 absorbed with the results shown in FIG. 5. As can be seen from FIG. 5, the more environmentally friendly ethylene glycol based solvent system yielded comparative CO2 adsorption as the DMF based systems.

[0048] Example 2:Attorney Docket No.: SP24-252

[0049] The NiMOF74 sorbent precursors used to make the comparative and exemplary MOF powders of example 1 were each solubilized in their respective solvent systems as set forth above. Following solubilization, a Corning® DuraTrap® GC gasoline particulate filter substrate having dimensions of about 6.5 millimeters x 6.5 millimeters x 50 millimeters and a median pore size of about 12 microns was placed in each reaction vessel. Each substrate was bare without any surface modifiers. The reaction vessels were then heated in the time and temperature ranges set forth above (in generating the comparative and exemplary MOF powders) in order to react the sorbent precursors and ultimately graft the resulting NiMOF74 sorbent onto the substrates. FIGS. 6A-6C show SEM images of substrates, wherein FIG. 6A shows a bare substrate, FIG. 6B shows a substrate grafted with DMF solubilized NiMOF74 precursors, and FIG. 6C shows a substrate grafted with ethylene glycol solubilized NiMOF74 precursors. As can be seen from FIGS. 6A-6C, both solvent systems show good attachment to the ceramic pore structure.

[0050] Gas adsorption of DMF synthesized NiMOF74 grafted on a ceramic substrate was analyzed under the same testing conditions as set forth above for MOF powders. A mass gain of about 18% due to MOF attachment was calculated. FIG. 7 shows absolute CO2 adsorption by the MOF grafted substrate material as well as CO2 adsorption by the MOF when accounting for its fraction of the total mass of the MOF grafted substrate. As can be seen from FIG. 7, CO2 adsorption by the NiMOF74 grafted onto the ceramic substrate is roughly equivalent CO2 adsorption by isolated powders of NiMOF74, demonstrating that grafting NiMOF74 onto the substrate does not negatively affect CO2 adsorption.

[0051] Example 3:

[0052] Corning Vycor® Glass with a porosity of between about 5 and 10 nanometers was used as a micro porous inorganic substrate to which NiMOF74 was grafted according to the synthesis method described above using the ethylene glycol based solvent system. During synthesis, solvents successfully transported the reactants into the micro pore structure for nucleation and formation of NiMOF74. FIGS. 8A and 8B show, respectively, SEM and TEM images demonstrating surface attachment of NiMOF74 crystals and formation away from the glass surface within the interconnected pores, wherein NiMOF74 crystals with greater than about a 400 nanometer diameter were randomly present within the support.Attorney Docket No.: SP24-252

[0053] Embodiments disclosed herein can enable a more environmentally friendly manufacture of greenhouse gas capturing apparatuses, including substantial elimination of use of environmentally hazardous DMF -based solvent systems in such manufacture.

[0054] While the above examples describe sonicating the solvent, other solubilizing methods known to persons having ordinary skill in the art, such as heating or agitating, may also be used.

[0055] It will be apparent to those skilled in the art that various modifications and variations can be made to embodiment of the present disclosure without departing from the spirit and scope of the disclosure. Thus, it is intended that the present disclosure cover such modifications and variations provided they come within the scope of the appended claims and their equivalents.

Claims

Attorney Docket No.: SP24-252CLAIMSWhat is claimed:

1. A method of making a gas capturing apparatus comprising: solubilizing at least two sorbent precursors in a solvent comprising at least one polyol to make a sorbent precursor solution; coating a porous substrate with the sorbent precursor solution to form a sorbent precursor coated substrate; and chemically reacting the at least two sorbent precursors on the sorbent precursor coated substrate to form a sorbent coated substrate.

2. The method of claim 1, wherein the solvent comprises less than about 0.1% by volume of dimethylformamide.

3. The method of claim 1, wherein the solvent is essentially free of dimethylformamide.

4. The method of any one of claims 1 to 3, wherein the at least one polyol comprises a glycol.

5. The method of claim 4, wherein the glycol comprises ethylene glycol.

6. The method of any one of claims 1 to 5, wherein the sorbent precursor solution comprises triethanolamine.

7. The method of any one of claims 1 to 6, wherein the solvent comprises greater than about 50% polyol by volume.

8. The method of any one of claims 1 to 7, wherein the sorbent comprises a metal organic framework.Attorney Docket No.: SP24-2529. The method of claim 8, wherein the metal organic framework comprises phenolic and carboxylic ligands.

10. The method of claim 9, wherein the sorbent comprises 2,5-dioxidoterephthalate nickel(2+) dihydrate (NiMOF74).

11. The method of claim 10, wherein the at least two sorbent precursors comprise nickel nitrate hexahydrate and dihydroxyterethphalic acid.

12. The method of any one of claims 1 to 11, wherein chemically reacting the at least two sorbent precursors on the sorbent precursor coated substrate comprises heating the sorbent precursor coated substrate to a temperature ranging from about 110°C to about 140°C.

13. The method of claim 12, wherein the chemically reacting the at least two sorbent precursors on the sorbent precursor coated substrate comprises heating the sorbent precursor coated substrate from about 12 hours to about 72 hours.

14. The method of any one of claims 1 to 13, wherein the porous substrate comprises a ceramic substrate, a glass substrate, or a glass-ceramic substrate.

15. The method of claim 14, wherein the porous substrate comprises at least one of cordierite, amorphous silica, fused silica, aluminum titanate, talc, clay, alumina, titania, or hollow glass microspheres.

16. The method of any one of claims 1 to 15, wherein the porous substrate comprises a median pore size (D50) ranging from about 8 micrometers to about 30 micrometers.

17. The method of any one of claims 1 to 16, wherein the porous substrate comprises a median pore size (D50) ranging from about 2 nanometers to about 40 nanometers.Attorney Docket No.: SP24-25218. The method of any one of claims 1 to 17, wherein the porous substrate comprises a plurality of channels extending therethrough.

19. The method of any one of claims to 1 to 18, wherein the solubilizing comprises sonicating, heating, or agitating the solvent.

20. The method of any one of claims 1 to 19, wherein the coating comprises immersing the porous substrate in the sorbent precursor solution.

21. The method of any one of claims 1 to 20, wherein the method further comprises applying an alcohol to the sorbent coated substrate.

22. The method of claim 21, wherein the alcohol comprises methanol.

23. The method of any one of claims 1 to 22, wherein the method further comprises drying the sorbent coated substrate.

24. The method of claim 23, wherein the drying comprises vacuum drying.

25. A sorbent coated substrate made by the method of any one of claims 1 to 24.

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