Methods of fabricating support layers using a cosolvent and PORE former

Abstract

Described herein are methods of fabricating a nanoporous polymer membranes. These methods can comprise forming a film of a casting solution comprising a gas permeable polymer, a solvent, a co-solvent, and a porogen; contacting the film with humid air to induce phase separation in the film; and contacting the film with an aqueous solution to induce phase separation in the film.

Description

[0001] METHODS OF FABRICATING SUPPORT LAYERS USING A

[0002] COSOLVENT AND PORE FORMER

[0003] CROSS-REFERENCE TO RELATED APPLICATIONS

[0004] This application claims benefit of U.S. Provisional Application No. 63 / 564,351, filed March 12, 2024, which is hereby incorporated herein by reference in its entirety.

[0005] STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0006] This invention was made with government support under grant / contract number DE- FE0031731 awarded by the Department of Energy, The government has certain rights in the invention.

[0007] BACKGROUND

[0008] There has been growing concern about global warming since the CO2concentration in the atmosphere has surpassed 400 ppm in the past decade. The combustion of fossil fuels is one of the major contributors to the large amount of CO2, emissions. A variety of strategies for addressing CO2emissions have been suggested. For example, membranes technologies have been suggested as a promising approach to capture CO2from large stationary sources. Once captured, the CO2could be compressed and geologically sequestered. However, improved membranes for the separation of CO2are needed to successfully implement these solutions.

[0009] SUMMARY

[0010] Disclosed herein are methods of fabricating a nanoporous polymer membranes as well as nanoporous polymer membranes prepared by these methods. These nanoporous polymer membranes can exhibit an interconnected, transmembrane network of pores that facilitates gas permeance across the membrane. As a result, these nanoporous polymer membranes are particularly well suited for uses as support layers in the fabrication of composite polymer membrane.

[0011] Methods of fabricating a nanoporous polymer membranes can comprise forming a film of a casting solution comprising a gas permeable polymer, a solvent, a co-solvent, and a porogen; contacting the film with humid air to induce phase separation in the film; and contacting the film with an aqueous solution to induce phase separation in the film.

[0012] In some embodiments, the method is performed as a continuous process. For example, in some examples, the method can be performed continuously in a roll-to-roll casting machine. In certain examples, the method is performed continuously in a roll-to-roll casting machine at a rate of at least I ft / min, such as a rate of from 1 ft / min to 10 ft / min, or a rate of from 1 ft / min to 5 ft / min.

[0013] In some embodiments, forming the film of the casting solution comprises knife casting (or doctor blading) the casting solution.

[0014] The film can be formed on a suitable support. In some embodiments, the film is formed on a fabric support (e.g., a non-woven fabric support or a woven fabric support). In some cases, a tension is applied to the fabric support to ensure flatness of the fabric support during film formation.

[0015] In some cases, the film is formed under inert atmosphere (e.g., under the exclusion of water vapor), so as to prevent premature phase separation of the casting solution. In some examples, the film is formed under nitrogen.

[0016] In some embodiments, contacting the film with humid air comprises passing the film through a humidity chamber.

[0017] In some embodiments, the film is contacted with the humid air for a period of time of from 5 seconds to 5 minutes, such as from 5 second to 2 minutes, from 5 seconds 1 minute, or from 5 seconds to 50 seconds.

[0018] In some embodiments, the humid air has a relative humidity of from 10% to 100%, such as from 20% to 95% or from 30% to 90%.

[0019] In some embodiments, contacting the film with the aqueous solution comprises immersing the film in a coagulation bath, such as passing the film through a coagulation path.

[0020] In some embodiments, the aqueous solution comprises water.

[0021] In some embodiments, the aqueous soluti on is maintained at a temperature of from 5°C to 70°C, such as from 5°C to 50°C, or from 5°C to 40°C.

[0022] The composition of the casting solution can be varied so as to provide nanoporous polymer membranes having the properties desired for a particular application. In some embodiments, the gas permeable polymer comprises a polymer chosen from polyamides, polyimides, polypyrrol ones, polyesters, sulfone-based polymers, nitrile-based polymers, polymeric organosilicones, fluorinated polymers, polyolefins, copolymers thereof, and blends thereof. In certain embodiments, the gas permeable polymer comprises polyethersulfone or polysulfone.

[0023] In some embodiments, the gas permeable polymer comprises from 5% by weight to 35% by weight of the casting solution (e.g., from 10% by weight to 20% by weight of the casting solution), based on the total weight of the casting solution.

[0024] In some embodiments, the solvent, comprises a polar solvent. In some embodiments, the solvent comprises a water miscible solvent. In certain embodiments, the solvent comprises JV-methyl-2-pyrroli done (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), dimethylacetamide (DMAc), and combinations thereof.

[0025] In some embodiments, the solvent, comprises from 30% by weight, to 65% by weight of the casting solution (e.g., from 35% by weight to 60% by weight of the casting solution), based on the total weight of the casting solution.

[0026] In some embodiments, the co-solvent comprises a C1-C8alcohol, a C1-C8diol, a C1-C8alkoxy alcohol, a C1-C8alkoxy diol, a phenyl alkoxy alcohol, or a combination thereof. In certain embodiments, the co-solvent comprises a C3-C8alcohol, a C3-C8diol, a C3-C8alkoxy alcohol, a C3-C8alkoxy diol, a phenyl alkoxy alcohol, or a combination thereof. In some embodiments, the co-solvent, comprises 3 -methoxy propanol.

[0027] In some embodiments, the co-solvent comprises from 20% by weight to 60% by weight of the casting solution (e.g., from 20% by weight, to 55% by weight of the casting solution, or from 25% by weight to 45% by weight of the casting solution), based on the total weight of the casting solution.

[0028] In some embodiments, the co-solvent and the solvent are present in the casting solution in weight ratio of from 0,25 : 1 to 1.5: 1.

[0029] In some embodiments, the porogen comprises from 0.1% by weight to 60% by weight of the casting solution (e.g., from 5% by weight to 60% by weight of the casting solution), based on the total weight, of the casting solution.

[0030] In some embodiments, the porogen comprises a salt, such as an alkali metal halide (e.g., LiCl), an alkaline earth metal halide, or an ammonium salt. In some embodiments, the co-solvent also functions as a porogen.

[0031] In some embodiments, the casting solution further comprises a viscosity enhancer. In some embodiments, the casting solution further comprises a hydrophilic additive, such as a hydrophilic polymer. In some embodiments, the hydrophilic additive comprises polyvinylalcohol, polyvinylacetate, polyethylene oxide, polyvinylpyrrolidone, polyacrylamine, a polyamine such as polyallylamine, polyvinyl amine, or polyethylenimine, polysiloxane, copolymers thereof, and blends thereof.

[0032] In some embodiments, the nanoporous polymer membrane has a thickness of less than 1 mm (e.g., less than 500 microns, less than 250 microns, less than 100 microns, or less than 50 microns).

[0033] In some embodiments, the nanoporous polymer membrane exhibits an average pore size of from 15 nm to 60 nm.

[0034] In some embodiments, the nanoporous polymer membrane exhibits a surface porosity of from 15% to 40%.

[0035] Also provided herein are nanoporous polymer membranes prepared by the methods described herein.

[0036] Further provided are composite polymer membranes comprising a support layer comprising a nanoporous polymer membrane prepared by the methods described herein; and a selective polymer layer disposed on the support layer.

[0037] DESCRIPTION OF DRAWINGS

[0038] Figure 1 , Schematic diagram of a pilot-scale continuous casting machine including a knife casting and a vapor- and nonsolvent-induced phase separation performed in sequential steps.

[0039] Figure 2A-2B. Micrographs showing the surface morphology of (Figure 2A) the PES substrate in Example 1 and (Figure 2B) the PES substrate prepared using NMP as the only solvent in Comparative Example 1 .

[0040] Figure 3. Micrograph showing the surface morphology of the PES substrate in Example 2.

[0041] Figure 4. Micrograph showing the surface morphology of the PES substrate in Example 3.

[0042] Figure 5. Micrograph showing the surface morphology of the PES substrate in Example 4. DETAILED DESCRIPTION

[0043] Definitions

[0044] As used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a pharmaceutical carrier” includes mixtures of two or more such carriers, and the like.

[0045] 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, 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. It is also understood that there are a number of values disclosed herein, and that each value is also herein disclosed as “about” that particular value in addition to the value itself. For example, if the value “10” is disclosed, then “about 10” is also disclosed. It is also understood that when a value is disclosed that “less than or equal to” the value, “greater than or equal to the value” and possible ranges between values are also disclosed, as appropriately understood by the skilled artisan. For example, if the value “10” is disclosed the “less than or equal to 10”as well as “greater than or equal to 10” is also disclosed. It is also understood that the throughout the application, data is provided in a number of different formats, and that this data, represents endpoints and starting points, and ranges for any combination of the data points. For example, if a particular data point “ 10” and a particular data point 15 are disclosed, it. is understood that greater than, greater than or equal to, less than, less than or equal to, and equal to 10 and 15 are considered disclosed as well as between 10 and 15. It is also understood that each unit between two particular units are also disclosed. For example, if 10 and 15 are disclosed, then 11, 12, 13, and 14 are also disclosed.

[0046] In this specification and in the claims which follow, reference will be made to a number of terms which shall be defined to have the following meanings:

[0047] “Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not. The term “n-membered” where n is an integer typically describes the number of ring-forming atoms in a moiety where the number of ring-forming atoms is n. For example, piperidinyl is an example of a 6-membered heterocycloalkyl ring, pyrazolyl is an example of a 5-membered heteroaryl ring, pyridyl is an example of a 6-membered heteroaryl ring, and 1,2,3,4-tetrahydro-naphthalene is an example of a 10-membered cycloalkyl group.

[0048] As used herein, the phrase “optionally substituted” means unsubstituted or substituted. As used herein, the term “substituted” means that a hydrogen atom is removed and replaced by a substituent. It is to be understood that substitution at a given atom is limited by valency.

[0049] Throughout the definitions, the term “Cn-m” indicates a range which includes the endpoints, wherein n and m are integers and indicate the number of carbons. Examples include C1-4, C1 -6, and the like.

[0050] As used herein, the term “Cn-malkyl”, employed alone or in combination with other terms, refers to a saturated hydrocarbon group that may be straight-chain or branched, having n to m carbons. Examples of alkyl moi eties include, but are not limited to, chemical groups such as methyl, ethyl, w-propyl, isopropyl, n-butyl, fer / -butyl, isobutyl, sec-butyl; higher homologs such as 2-m ethyl- 1 -butyl, w-pentyl, 3-pentyl, / / -hexyl, 1,2,2- tri methylpropyl, and the like. In some embodiments, the alkyl group contains from 1 to 6 carbon atoms, from 1 to 4 carbon atoms, from 1 to 3 carbon atoms, or 1 to 2 carbon atoms.

[0051] As used herein, “Cn-malkenyl” refers to an alkyl group having one or more double carbon-carbon bonds and having n to m carbons. Example alkenyl groups include, but are not limited to, ethenyl, w-propenyl, isopropenyl, w-butenyl, xec-butenyl, and the like. In some embodiments, the alkenyl moiety contains 2 to 6, 2 to 4, or 2 to 3 carbon atoms.

[0052] As used herein, “Cn-malkynyl” refers to an alkyl group having one or more triple carbon-carbon bonds and having n to m carbons. Example alkynyl groups include, but are not limited to, ethynyl, propyn-l-yl, propyn-2-yl, and the like. In some embodiments, the alkynyl moiety contains 2 to 6, 2 to 4, or 2 to 3 carbon atoms.

[0053] As used herein, the term “Cn-malkylene”, employed alone or in combination with other terms, refers to a divalent alkyl linking group having n to m carbons. Examples of alkylene groups include, but are not limited to, ethan-l,2-diyl, propan-1, 3-diyl, propan-1, 2- diyl, butan-l,4-diyl, butan-1, 3-diyl, butan-l,2-diyl, 2-methyl -propan- 1, 3-diyl, and the like. In some embodiments, the alkylene moiety contains 2 to 6, 2 to 4, 2 to 3, 1 to 6, 1 to 4, or 1 to 2 carbon atoms. As used herein, the term “Cn-malkoxy”, employed alone or in combination with other terms, refers to a group of formula -O-alkyl, wherein the alkyl group has n to m carbons. Example alkoxy groups include methoxy, ethoxy, propoxy (e.g., w-propoxy and isopropoxy), fert-butoxy, and the like. In some embodiments, the alkyl group has 1 to 6, 1 to 4, or 1 to 3 carbon atoms.

[0054] As used herein, the term “Cn-malkylamino” refers to a group of formula -NH(alkyl), wherein the alkyl group has n to m carbon atoms. In some embodiments, the alkyl group has 1 to 6, 1 to 4, or 1 to 3 carbon atoms.

[0055] As used herein, the term “Cn-malkoxycarbonyl” refers to a group of formula -C(O)O-alkyl, wherein the alkyl group has n to m carbon atoms. In some embodiments, the alkyl group has 1 to 6, 1 to 4, or 1 to 3 carbon atoms.

[0056] As used herein, the term “Cn-malkylcarbonyl” refers to a group of formula -C(O)~ alkyl, wherein the alkyl group has n to m carbon atoms. In some embodiments, the alkyl group has 1 to 6, 1 to 4, or 1 to 3 carbon atoms.

[0057] As used herein, the term “Cn-malkylcarbonylamino” refers to a group of formula -NHC(O)-alkyl, wherein the alkyl group has n to m carbon atoms. In some embodiments, the alkyl group has 1 to 6, 1 to 4, or 1 to 3 carbon atoms.

[0058] As used herein, the term “Cn-malkylsulfonylamino” refers to a group of formula -NHS(O)2-alkyl, wherein the alkyl group has n to m carbon atoms. In some embodiments, the alkyl group has I to 6, 1 to 4, or 1 to 3 carbon atoms.

[0059] As used herein, the term “aminosulfonyl” refers to a group of formula -S(O)2NH2.

[0060] As used herein, the term “Cn-malkylaminosulfonyl” refers to a group of formula -S(O)2NH(alkyl), wherein the alkyl group has n to m carbon atoms. In some embodiments, the alkyl group has 1 to 6, 1 to 4, or 1 to 3 carbon atoms.

[0061] As used herein, the term “di(Cn-malkyl)aminosulfonyl” refers to a group of formula -S(O)2N(alkyl)2, wherein each alkyl group independently has n to m carbon atoms. In some embodiments, each alkyl group has, independently, 1 to 6, 1 to 4, or 1 to 3 carbon atoms.

[0062] As used herein, the term “aminosulfonyl amino” refers to a group of formula - NHS(O)2NH2.

[0063] As used herein, the term “Cn-malkylaminosulfonylamino” refers to a group of formula -NHS(O)2NH(alkyd), wherein the alkyl group has n to m carbon atoms. In some embodiments, the alkyl group has I to 6, 1 to 4, or 1 to 3 carbon atoms. As used herein, the term “di(Cn-malkyl)aminosulfonylamino” refers to a group of formula -NHS(O)2N(alkyl X wherein each alkyl group independently has n to m carbon atoms. In some embodiments, each alkyl group has, independently, 1 to 6, 1 to 4, or 1 to 3 carbon atoms.

[0064] As used herein, the term “aminocarbonyl amino”, employed alone or in combination with other terms, refers to a group of formula -NHC(O)Nl Iz.

[0065] As used herein, the term “Cn-malkylaminocarbonylamino” refers to a group of formula -NHC(O)NH( alkyl), wherein the alkyl group has n to m carbon atoms. In some embodiments, the alkyl group has 1 to 6, 1 to 4, or I to 3 carbon atoms.

[0066] As used herein, the term “di(Cn-malkyl)aminocarbonylamino” refers to a group of formula -NHC(O)N(alkyl)2, wherein each alkyl group independently has n to m carbon atoms. In some embodiments, each alkyl group has, independently, 1 to 6, 1 to 4, or 1 to 3 carbon atoms.

[0067] As used herein, the term “Cn-malkylcarbamyl” refers to a group of formula -C(O)- NH(alkyl), wherein the alkyl group has n to m carbon atoms. In some embodiments, the alkyl group has 1 to 6, 1 to 4, or 1 to 3 carbon atoms.

[0068] As used herein, the term “thio” refers to a group of formula -SH.

[0069] .As used herein, the term “Cn-malkyl sulfinyl” refers to a group of formula -S(O)- alkyl, wherein the alkyl group has n to m carbon atoms. In some embodiments, the alkyl group has I to 6, 1 to 4, or 1 to 3 carbon atoms.

[0070] As used herein, the term “Cn-malkylsulfonyl” refers to a group of formula -S(O)2- alkyl, wherein the alkyl group has n to m carbon atoms. In some embodiments, the alkyl group has 1 to 6, 1 to 4, or 1 to 3 carbon atoms.

[0071] As used herein, the term “amino” refers to a group of formula -NH2.

[0072] As used herein, the term "aryl," employed alone or in combination with other terms, refers to an aromatic hydrocarbon group, which may be monocyclic or polycyclic (e.g., having 2, 3 or 4 fused rings). The term "Cn-maryl" refers to an aryl group having from n to m ring carbon atoms. Aryl groups include, e.g., phenyl, naphthyl, anthracenyl, phenanthrenyl, indanyl, indenyl, and the like. In some embodiments, aryl groups have from 6 to about 20 carbon atoms, from 6 to about 15 carbon atoms, or from 6 to about 10 carbon atoms. In some embodiments, the aryl group is a substituted or unsubstituted phenyl.

[0073] As used herein, the term “carbamyl” to a group of formula -C(O)NH2. As used herein, the term “carbonyl”, employed alone or in combination with other terms, refers to a -C(=O)- group, which may also be writen as C(O).

[0074] As used herein, the term “di(Cn-m-alkyl)amino” refers to a group of formula - N(alkyl ri, wherein the two alkyl groups each has, independently, n to m carbon atoms. In some embodiments, each alkyl group independently has 1 to 6, 1 to 4, or 1 to 3 carbon atoms.

[0075] As used herein, the term “di(Cn-m-alkjd)carbamyl” refers to a group of formula - C(O)N(alkyl)2, wherein the two alkyl groups each has, independently, n to m carbon atoms. In some embodiments, each alkyl group independently has 1 to 6, 1 to 4, or 1 to 3 carbon atoms.

[0076] As used herein, the term “halo” refers to F, Cl, Br, or I. In some embodiments, a halo is F, Cl, or Br. In some embodiments, a halo is F or Cl.

[0077] As used herein, “Cn-mhaloalkoxy” refers to a group of formula -O-haloalkyl having n to m carbon atoms. An example haloalkoxy group is OCF3. In some embodiments, the haloalkoxy group is fluorinated only. In some embodiments, the alkyl group has 1 to 6, 1 to 4, or 1 to 3 carbon atoms.

[0078] As used herein, the term “Cn-mhaloalkyl”, employed alone or in combination with other terms, refers to an alkyl group having from one halogen atom to 2s+l halogen atoms which may be the same or different, where “s” is the number of carbon atoms in the alkyl group, wherein the alkyl group has n to m carbon atoms. In some embodiments, the haloalkyl group is fluorinated only. In some embodiments, the alkyl group has 1 to 6, 1 to

[0079] 4, or 1 to 3 carbon atoms.

[0080] As used herein, “cycloalkyl” refers to non-aromatic cyclic hydrocarbons including cyclized alkyl and / or alkenyl groups. Cycloalkyl groups can include mono- or polycyclic (e.g., having 2, 3 or 4 fused rings) groups and spirocycles. Cycloalkyl groups can have 3, 4,

[0081] 5, 6, 7, 8, 9, or 10 ring-forming carbons (C3-10). Ring-forming carbon atoms of a cycloalkyl group can be optionally substituted by oxo or sulfido (e.g., C(O) or C(S)). Cycloalkyl groups also include cycloalkylidenes. Example cycloalkyl groups include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclopentenyl, cyclohexenyl, cyclohexadienyl, cycloheptatrienyl, norbomyl, norpinyl, norcarnyl, and the like. In some embodiments, cycloalkyl is cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cyclopentyl, or adamantyl. In some embodiments, the cycloalkyl has 6-10 ring-forming carbon atoms. In some embodiments, cycloalkyl is adamantyl. ,Also included in the definition of cycloalkyl are moi eties that have one or more aromatic rings fused (i.e., having a bond in common with) to the cycloalkyl ring, for example, benzo or thienyl derivatives of cyclopentane, cyclohexane, and the like. A cycloalkyl group containing a fused aromatic ring can be attached through any ring-forming atom including a ring-forming atom of the fused aromatic ring.

[0082] As used herein, “heteroaryl” refers to a monocyclic or polycyclic aromatic heterocycle having at least one heteroatom ring member selected from sulfur, oxygen, and nitrogen. In some embodiments, the heteroaryl ring has 1, 2, 3, or 4 heteroatom ring members independently selected from nitrogen, sulfur and oxygen. In some embodiments, any ring-forming N in a heteroaryl moiety can be an N-oxide. In some embodiments, the heteroaryl has 5-10 ring atoms and 1, 2, 3 or 4 heteroatom ring members independently selected from nitrogen, sulfur and oxygen. In some embodiments, the heteroaryl has 5-6 ring atoms and 1 or 2 heteroatom ring members independently selected from nitrogen, sulfur and oxygen. In some embodiments, the heteroaryl is a five-membered or sixmembered heteroaryl ring. A five-membered heteroaryl ring is a heteroaryl with a ring having five ring atoms wherein one or more (e.g., 1, 2, or 3) ring atoms are independently selected from N, O, and S. Exemplary? five-membered ring heteroaryls are thienyl, furyl, pyrrolyl, imidazolyl, thiazolyl, oxazolyl, pyrazolyl, isothiazolyl, isoxazolyl, 1,2,3-triazolyl, tetrazolyl, 1,2,3-thiadiazolyl, 1, 2, 3 -oxadiazol yl, 1,2,4-triazolyl, 1,2,4-thiadiazolyl, 1,2,4- oxadiazolyl, 1 ,3,4-triazolyl, 1,3,4-thiadiazolyl, and 1,3,4-oxadiazolyl. A six-membered heteroaryl ring is a heteroaryl with a ring having six ring atoms wherein one or more (e.g., 1, 2, or 3 ) ring atoms are independently selected from N, O, and S. Exemplary sixmembered ring heteroaryls are pyridyl, pyrazinyl, pyrimidinyl, triazinyl and pyridazinyl.

[0083] As used herein, “heterocycloalkyl” refers to non-aromatic monocyclic or polycyclic heterocycles having one or more ring-forming heteroatoms selected from O, N, or S. Included in heterocycloalkyl are monocyclic 4~, 5-, 6-, and 7-membered heterocycloalkyl groups. Heterocycloalkyl groups can also include spirocycles. Example heterocycloalkyl groups include pyrrolidin-2-one, l,3-isoxazolidin-2~one, pyranyl, tetrahydropuran, oxetanyl, azetidinyl, morpholino, thiomorpholino, piperazinyl, tetrahydrofuranyl, tetrahydrothienyl, piperidinyl, pyrrolidinyl, isoxazolidinyl, isothiazolidinyl, pyrazolidinyl, oxazolidinyl, thiazolidinyl, imidazolidinyl, azepanyl, benzazapene, and the like. Ring-forming carbon atoms and heteroatoms of a heterocycloalkyl group can be optionally substituted by oxo or sulfido (e.g., C(O), S(O), C(S), or S(O)2, etc.). The heterocycloalkyl group can be attached through a ring-forming carbon atom or a ring-forming heteroatom. In some embodiments, the heterocycloalkyl group contains 0 to 3 double bonds. In some embodiments, the heterocycloalkyl group contains 0 to 2 double bonds. Also included in the definition of heterocycloalkyl are moieties that have one or more aromatic rings fused (i.e., having a bond in common with) to the cycloalkyl ring, for example, benzo or thienyl derivatives of piperidine, morpholine, azepine, etc. A heterocycloalkyl group containing a fused aromatic ring can be attached through any ring-forming atom including a ring-forming atom of the fused aromatic ring. In some embodiments, the heterocycloalkyl has 4-10, 4-7 or 4-6 ring atoms with 1 or 2 heteroatoms independently selected from nitrogen, oxygen, or sulfur and having one or more oxidized ring members.

[0084] At certain places, the definitions or embodiments refer to specific rings (e.g., an azetidine ring, a pyridine ring, etc.). Unless otherwise indicated, these rings can be attached to any ring member provided that the valency of the atom is not exceeded. For example, an azetidine ring may be attached at any position of the ring, whereas a pyridin-3-yl ring is attached at the 3-position.

[0085] The term “compound” as used herein is meant to include all stereoisomers, geometric isomers, tautomers, and isotopes of the structures depicted. Compounds herein identified by name or structure as one particular tautomeric form are intended to include other tautomeric forms unless otherwise specified.

[0086] Compounds provided herein also include tautomeric forms. Tautomeric forms result from the swapping of a single bond with an adjacent double bond together with the concomitant migration of a proton. Tautomeric forms include prototropic tautomers which are isomeric protonation states having the same empirical formula and total charge. Example prototropic tautomers include ketone - enol pairs, amide - imidic acid pairs, lactam -- lactim pairs, enamine -- imine pairs, and annular forms where a proton can occupy two or more positions of a heterocyclic system, for example, 1H- and 3H-imidazole, 1H-, 2H- and 4H- 1,2,4-triazole, 1H- and 2H- isoindole, and 1H- and 2H-pyrazole. Tautomeric forms can be in equilibrium or sterically locked into one form by appropriate substitution.

[0087] In some embodiments, the compounds described herein can contain one or more asymmetric centers and thus occur as racemates and racemic mixtures, enantiomerically enriched mixtures, single enantiomers, individual diastereomers and diastereomeric mixtures (e.g., including (7<)~ and (5)-enantiomers, diastereomers, (D)-isomers, (Z)-isomers, (+) (dextrorotatory) forms, (-) (levorotatory) forms, the racemic mixtures thereof, and other mixtures thereof). Additional asymmetric carbon atoms can be present in a substituent, such as an alkyl group. All such isomeric forms, as well as mixtures thereof, of these compounds are expressly included in the present description. The compounds described herein can also or further contain linkages wherein bond rotation is restricted about that particular linkage, e.g., restriction resulting from the presence of a ring or double bond (e.g., carbon-carbon bonds, carb on-nitrogen bonds such as amide bonds). Accordingly, all cis / trans and E / Z isomers and rotational isomers are expressly included in the present description. Unless otherwise mentioned or indicated, the chemical designation of a compound encompasses the mixture of all possible stereochemically isomeric forms of that compound.

[0088] Optical isomers can be obtained in pure form by standard procedures known to those skilled in the art, and include, but are not limited to, diastereomeric salt formation, kinetic resolution, and asymmetric synthesis. See, for example, Jacques, et al., Enantiomers, Racemates and Resolutions (Wiley Interscience, New York, 1981); Wilen, S.H., et al.. Tetrahedron 33:2725 (1977); Eliel, E.L. Stereochemistry of Carbon Compounds ( McGraw'- Hill, NY, 1962); Wilen, S.H. Tables of Resol ving Agents and Optical Resolutions p. 268 (E.L. Eliel, Ed., Univ, of Notre Dame Press, Notre Dame, IN 1972), each of which is incorporated herein by reference in their entireties. It is also understood that, the compounds described herein include all possible regioisomers, and mixtures thereof, w'hich can be obtained in pure form by standard separation procedures known to those skilled in the art, and include, but are not limited to, column chromatography, thin-layer chromatography, and high-performance liquid chromatography.

[0089] Methods of Making Nanoporous Polymer Membranes

[0090] Disclosed herein are methods of fabricating nanoporous polymer membranes. These nanoporous polymer membranes can exhibit an interconnected, transmembrane network of pores that facilitates gas permeance across the membrane. As a result, these nanoporous polymer membranes are particularly well suited for uses as support layers in the fabrication of composite polymer membrane.

[0091] Methods of fabricating a nanoporous polymer membranes can comprise forming a film of a casting solution comprising a gas permeable polymer, a solvent, a co-solvent, and a porogen; contacting the film with humid air to induce phase separation in the film; and contacting the film with an aqueous solution to induce phase separation in the film. In some embodiments, the method is performed as a continuous process. For example, in some examples, the method can be performed continuously in a roll-to-roll casting machine. In certain examples, the method is performed continuously in a roll-to-roll casting machine at a rate of at least 1 ft / min, such as a rate of from 1 ft / min to 10 ft / min, or a rate of from 1 ft / min to 5 ft / min.

[0092] In some embodiments, forming the film of the casting solution comprises knife casting (or doctor blading) the casting solution.

[0093] The film can be formed on a suitable support. In some embodiments, the film is formed on a fabric support (e.g., a non-woven fabric support, or a woven fabric support). In some cases, a tension is applied to the fabric support to ensure flatness of the fabric support during film formation.

[0094] In some cases, the film is formed under inert atmosphere (e.g., under the exclusion of water vapor ), so as to prevent premature phase separation of the casting solution. In some examples, the film is formed under nitrogen.

[0095] In some embodiments, contacting the film with humid air comprises passing the film through a humidity chamber.

[0096] In some embodiments, the film is contacted with the humid air for a period of time of from 5 seconds to 5 minutes, such as from 5 second to 2 minutes, from 5 seconds 1 minute, or from 5 seconds to 50 seconds.

[0097] In some embodiments, the humid air has a relative humidity of from 10% to 100%, such as from 20% to 95% or from 30% to 90%.

[0098] In some embodiments, contacting the film with the aqueous solution comprises immersing the film in a coagulation bath, such as passing the film through a coagulation path .

[0099] In some embodiments, the aqueous solution comprises water.

[0100] In some embodiments, the aqueous solution is maintained at a temperature of from 5°C to 70°C, such as from 5°C to 50°C, or from 5°C to 40°C.

[0101] The composi tion of the casting solution can be varied so as to provide nanoporous polymer membranes having the properties desired for a particular application.

[0102] In some embodiments, the gas permeable polymer comprises a polymer chosen from polyamides, polyimides, polypyrrolones, polyesters, sulfone-based polymers, nitrile-based polymers, polymeric organosilicones, fluorinated polymers, polyolefins, copolymers thereof’ and blends thereof. In certain embodiments, the gas permeable polymer comprises polyethersulfone or polysulfone.

[0103] In some embodiments, the gas permeable polymer comprises from 5% by weight to 35% by weight of the casting solution (e.g., from 10% by weight to 20% by weight of the casting solution), based on the total weight of the casting solution.

[0104] In some embodiments, the solvent comprises a polar solvent. In some embodiments, the solvent comprises a water miscible solvent. In certain embodiments, the solvent comprises / V-methyl-2-pyrrolidone (NMP), dimethyl formamide (DMF), dimethyl sulfoxide (DMSO), dimethyl acetamide (DMAc), and combinations thereof.

[0105] In some embodiments, the solvent comprises from 30% by weight to 65% by weight of the casting solution (e.g., from 35% by weight to 60% by weight of the casting solution), based on the total weight of the casting solution.

[0106] The casting solution can further comprise a co-solvent. Examples of suitable co- solvents include compounds having a hydrophobic portion (alkyl or aryl chain), a hydrophilic portion (e.g., an alcohol), and optionally an alkoxy portion. Co-solvents as provided herein include alcohols (e.g., C1-C8alcohols, such as C3-C8alcohols, and C1-C8diols, such as C3-C8diols), alkoxy alcohols (e.g., C1-C8alkoxy alcohols, such as C3-C8alkoxy diols, C1-C8alkoxy diols, such as C3-C8alkoxy diols, and phenyl alkoxy alcohols), glycol ether, glycol and glycerol. The term "alcohol" is used according to its ordinary meaning and refers to an organic compound containing an -OH groups attached to a carbon atom. The term "diol" is used according to its ordinary' meaning and refers to an organic compound containing two -OH groups attached to two different, carbon atoms. The term "alkoxy alcohol" is used according to its ordinary’ meaning and refers to an organic compound containing an alkoxy linker attached to a -OH group.

[0107] Examples of co-solvents include alcohols, such as lower carbon chain alcohols such as isopropyl alcohol, ethanol, n-propyl alcohol, n-butyl alcohol, sec-butyl alcohol, n-amyl alcohol, sec-amyl alcohol, n-hexyl alcohol, sec-hexyl alcohol, 4-methyl-2-propanol, and the like; alkoxy alcohols such as 3-methoxy propanol; alcohol ethers, polyalkylene alcohol ethers, polyalkylene glycols, poly(oxyalkylene)glycols, poly(oxyalkylene)glycol ethers, ethoxylated phenol, or any combination of two or more co-solvents.

[0108] In some embodiments, the co-solvent, comprises a C1-C8alcohol, a C1-C8diol, a C1-C8alkoxy alcohol, a C1-C8alkoxy diol, a phenyl alkoxy alcohol, or a combination thereof. In certain embodiments, the co-solvent comprises a C3-C8alcohol, a C3-C8diol, a C3-C8 alkoxy alcohol, a C3-C8alkoxy diol, a phenyl alkoxy alcohol, or a combination thereof. In some embodiments, the co-solvent comprises 3 -methoxy propanol.

[0109] In some embodiments, the co-solvent comprises from 20% by weight to 60% by weight of the casting solution (e.g., from 20% by weight to 55% by weight of the casting solution, or from 25% by weight to 45% by weight of the casting solution), based on the total weight of the casting solution.

[0110] In some embodiments, the co-solvent and the solvent are present in the casting solution in weight ratio of from 0,25 : 1 to 1.5: 1.

[0111] In some embodiments, the porogen comprises from 0.1% by weight to 60% by weight of the casting solution (e.g., from 5% bv weight to 60% bv weight of the casting solution), based on the total weight of the casting solution.

[0112] In some embodiments, the porogen comprises a salt, such as an alkali metal halide (e.g., LiCl), an alkaline earth metal halide, or an ammonium salt. In some embodiments, the co-solvent also functions as a porogen.

[0113] In some embodiments, the casting solution further comprises a viscosity enhancer.

[0114] In some embodiments, the casting solution further comprises a hydrophilic additive, such as a hydrophilic polymer. In some embodiments, the hydrophilic additive comprises polyvinylalcohol, polyvinyl acetate, polyethylene oxide, polyvinylpyrrolidone, polyacrylamine, a polyamine such as polyallylamine, polyvinyl amine, or polyethylenimine, polysil oxane, copolymers thereof, and blends thereof.

[0115] In some embodiments, the nanoporous polymer membrane has a thickness of less than 1 mm (e.g., less than 500 microns, less than 250 microns, less than 100 microns, or less than 50 microns).

[0116] In some embodiments, the nanoporous polymer membrane exhibits an average pore size of from 15 nm to 60 nm.

[0117] In some embodiments, the nanoporous polymer membrane exhibits a surface porosity of from 15% to 40%.

[0118] Also provided herein are nanoporous polymer membranes prepared by the methods described herein.

[0119] Composite Polymer Membranes

[0120] Further provided are composite polymer membranes comprising a support layer comprising a nanoporous polymer membrane prepared by the methods described herein; and a selective polymer layer disposed (e.g., coated) on the support layer. The selective polymer layer can comprise a polymer matrix comprising a “fixed carrier,” a “mobile carrier,” or a combination thereof. In some cases, the polymer layer can comprise a polymer matrix comprising a polyguanidine polymer. Optionally, the polymer matrix can further comprise a hydrophilic polymer, an amine-containing polymer, or a combination thereof. In some embodiments, the selective polymer layer can further comprise a mobile carrier (e.g., a guanidine-based mobile carrier, an amine-based mobile carrier, or a combination thereof) dispersed within the polymer matrix. Optionally, the selective polymer later can further include a CO2-philic ether, a graphene oxide, carbon nanotubes, or a combination thereof, dispersed within the polymer matrix.

[0121] Support Layer

[0122] The support layer can comprise a nanoporous polymer membrane prepared by the methods described herein. In certain embodiments, the support layer can bedisposed on a base. The base can be in any configuration configured to facilitate formation of a membrane suitable for use in a particular application. For example, the base can be a flat disk, a tube, a spiral wound, or a hollow fiber base. The base can be formed from any suitable material. In some embodiments, the layer can include a fibrous material. The fibrous material in the base can be a mesh (e.g., a metal or polymer mesh), a woven or nonwoven fabric, a glass, fiberglass, a resin, a screen (e.g., a metal or polymer screen). In certain embodiments, the base can include a non-woven fabric (e.g., a non-woven fabric comprising fibers formed from a polyester).

[0123] Selective Polymer Layer

[0124] The selective polymer layer can comprise a polymer matrix comprising a “fixed carrier,” a “mobile carrier,” or a combination thereof. In some examples, the selective polymer layer can comprise a polymer matrix comprising a polyguanidine polymer. Optionally, the polymer matrix can further comprise a hydrophilic polymer, an amine- containing polymer, or a combination thereof. In some embodiments, the selective polymer layer can further comprise a mobile carrier (e.g., a guanidine-based mobile carrier, an amine-based mobile carrier, or a combination thereof) dispersed within the polymer matrix. Optionally, the selective polymer later can further include a COs-philic ether, a graphene oxide, carbon nanotubes, or a combination thereof, dispersed within the polymer matrix.

[0125] In some cases, the selective polymer layer can be a polymer matrix through which gas permeates via diffusion or facilitated diffusion. The selective polymer layer can comprise a polymer matrix having a CO2:N2selectivity of at least 10 at 57°C and 4 bar feed pressure. For example, the polymer matrix can have a CO2:N2 selectivity of at least 25 (e.g., at least 50, at least 75, at least 100, at least 125, at least 150, at least 175, at least 200, at least 225, at least 250, at least 275, at least 300, at least 325, at least 350, at least 375, at least 400, at least 425, at least 450, or at least 475) at 57°C and 4 bar feed pressure. In some embodiments, the polymer matrix can have a CO2.V selectivity of 500 or less (e.g., 475 or less, 450 or less, 425 or less, 400 or less, 375 or less, 350 or less, 325 or less, 300 or less, 275 or less, 250 or less, 225 or less, 200 or less, 175 or less, 150 or less, 125 or less, 100 or less, 75 or less, 50 or less, or 25 or less) at 57°C and 4 bar feed pressure.

[0126] In certain embodiments, the selective polymer layer can comprise a polymer matrix that has a CO2:N2selectivity ranging from any of the minimum values described above to any of the maximum values described above. For example, in certain embodiments, the selective polymer layer can comprise a polymer matrix that has a CO2:N2selectivity of from 10 to 500 at 57°C and 4 bar feed pressure (e.g., from 10 to 400 at 57°C and 4 bar feed pressure, from 75 to 400 at 57°C and 4 bar feed pressure, from 100 to 400 at 57°C and 4 bar feed pressure, from 10 to 350 at 57°C and 4 bar feed pressure, from 75 to 350 at 57°C and 4 bar feed pressure, from 100 to 350 at 57°C and 4 bar feed pressure, from 10 to 250 at 57°C and 4 bar feed pressure, from 75 to 250 at 57°C and 4 bar feed pressure, or from 100 to 250 at 57°C and 4 bar feed pressure). The CO2:N2selectivity of the selective polymer can be measured using standard methods for measuring gas permeance known in the art, such as those described in the examples below.

[0127] Polymer Matrix

[0128] In some embodiments, the polymer matrix can comprise a polyguanidine polymer. Optionally, the polymer matrix can further comprise a hydrophilic polymer, an amine- containing polymer, or a combination thereof.

[0129] In certain embodiments, the polymer matrix can include a polyguanidine polymer and a hydrophilic polymer. In certain embodiments, the polymer matrix can include a polyguanidine polymer and an amine-containing polymer. In certain embodiments, the polymer matrix can include a polyguanidine polymer, a hydrophilic polymer, and an amine- containing polymer.

[0130] The polyguanidine polymer can serve as a ‘‘fixed carrier” or a “fixed-site carrier.” The polyguanidine polymer can have any suitable molecular weight. For example, the polyguanidine polymer can have a weight average molecular weight of from 5,000 Da to 5, 000, 000 Da, or from 50,000 Da to 2,000,000 Da.

[0131] Examples of polyguanidine polymers include, but are not limited to, polyethylene guanidine, polytrimethylene guanidine, polytetramethylene guanidine, polypentamethylene guanidine, polyhexamethylene guanidine, polyheptamethylene guanidine, polyoctamethylene guanidine, polyethylene vV-methylguanidine, polytrimethylene A’~ methylguanidine, polytetramethylene JV-methylguanidine, polypentamethylene N- methyl guanidine, polyhexamethylene A-methylguanidine, polyheptamethylene N- methylguanidine, polyoctamethylene A-methylguanidine, polyethylene N,N'- dimethylguanidine, polytrimethylene AAV ’-dimethylguanidine, polytetram ethylene N,N’- dimethylguanidine, polypentamethylene A, N ’-dimethylguanidine, polyhexamethylene N,N’~ dimethylguanidine, polyheptamethylene N, N ’-dimethylguanidine, polyoctamethylene AyV’~ dimethylguanidine, poly(A-vinylguanidine), poly(A;-ally Iguani dine), poly(A- butylguanidine), poly(Ar-pentylguanidine), poly(Ar-hexylguanidine), poly(A- heptylguanidine), poly(A-octylguanidine), copolymers thereof, and blends thereof.

[0132] Polyethylene guanidine (PEG) can be synthesized from the polycondensation of guanidine hydrochloride (GH) and ethylene diamine (EDA) as follows:

[0133] The leaving product, ammonia (NH3), is removed from the polymer product.

[0134] Similarly, polytrimethylene guanidine and polytetramethylene guanidine can be synthesized from the polycondensation of guanidine hydrochloride with 1,3-propane diamine and 1,4-butane diamine, respectively, as shown in the following reactions, respectively: Polypentamethylene guanidine, polyhexamethylene guanidine, polyheptamethylene guanidine, and polyoctamethylene guanidine can also be synthesized from the polycondensation of guanidine hydrochloride with 1,5-pentane diamine, 1,6-hexane diamine, 1,7-heptane diamine, and 1,8-octane diamine, respectively. In a similar way, polyethylene N-methyl guanidine, polytrimethylene JV-methylguanidine, polyt etram ethylene A'-methylguanidine, polypentamethylene ; N-m ethyl guanidine, polyhexamethylene N- m ethylguanidine, polyheptamethylene A -methylguanidine, and poly octamethylene N- methyl guanidine can be prepared from the polycondensation of N-m ethyl guanidine hydrochloride with ethylene diamine, 1,3-propane diamine, 1,4-butane diamine, 1,5-pentane diamine, 1,6-hexane diamine, 1,7-heptane diamine, and 1,8-octane diamine, respectively. Similarly, polyethy 1 ene N, N ’-dimethylguanidine, polytrimethylene A', A '’-dimethylguanidine, polytetramethylene N, A' ’-dimethylguanidine, polypentamethylene N,N ’-dimethylguanidine, polyhexamethylene N,N ’ ’-dimethylguanidine, poly heptamethyl ene N,N ’-dimethylguanidine, and poly octamethylene AAV ’-dimethylguanidine can be prepared from the polycondensation of N,N ’-dimethyl guanidine hydrochloride with ethylene diamine, 1,3-propane diamine, 1,4- butane diamine, 1,5-pentane diamine, 1,6-hexane diamine, 1,7-heptane diamine, and 1,8- octane diamine, respectively.

[0135] The selective polymer layer can comprise any suitable amount of the polyguanidine polymer. For example, in some cases, the selective polymer layer can comprise from 10% to 90% by weight (e.g., from 10% to 70% by weight, from 10% to 50% by weight, from 20% to 50% by weight, or from 10% to 30% by weight) polyguanidine polymer, based on the total weight of the components used to form the selective polymer layer (the total dryweight of the selective polymer layer).

[0136] When present, the hydrophilic polymer can have any suitable molecular weight. For example, the hydrophilic polymer can have a weight average molecular weight of from 15,000 Da to 2,000,000 Da (e.g., from 50,000 Da to 200,000 Da). In some embodiments, the hydrophilic polymer can include polyvinylalcohol having a weight average molecular weight of from 50,000 Da to 150,000 Da. In other embodiments, the hydrophilic polymer can be a high molecular weight hydrophilic polymer. For example, the hydrophilic polymer can have a weight average molecular weight of at least 500,000 Da (e.g., at least 700,000 Da, or at least 1,000,000 Da).

[0137] The selective polymer layer can comprise any suitable amount of the hydrophilic polymer. For example, in some cases, the selective polymer layer can comprise from 10% to 90% by weight (e.g., from 10% to 50% by weight, or from 10% to 30% by weight) hydrophilic polymer, based on the total weight of the components used to form the selective polymer layer.

[0138] When present, the amine-containing polymer can include any suitable amine- containing polymer. Suitable examples of amine-containing polymers include, but are not limited to, polyvinylamine (PVAm), polyallylamine, polyethyleneimine, poly-A’- isopropylally famine, poly- N-tert-butyfallyf amine, poly- N-1,2-diniethylpropylallylamine, poiyvV-methylallylamine, poly-A'yV-dimethylallylamine, poly-2-vinylpiperidine, poly -4- vinylpiperidine, poly aminostyrene, chitosan, copolymers, and blends thereof. In some embodiments, the amine-containing polymer can comprise polyvinylamine (e.g., polyvinylamine having a weight average molecular weight of from 50,000 Da to 2,000,000 Da).

[0139] In some examples, the amine-containing polymer PVAm employed is purified from a commercial product named Polymin® VX from BASF (Vandalia, IL). The PVAm can have a high average molecular weight of 2,000 kDa. The amine-containing polymer can have a weight average molecular weight ranging from 300 to 3,000 kDa, but preferably to be higher than 1000 kDa.

[0140] The selective polymer layer can comprise any suitable amount of the amine- containing polymer. For example, in some cases, the selective polymer layer can comprise from 10% to 90% by weight (e.g., from 10% to 50% by weight, or from 10% to 30% by weight) amine-containing polymer, based on the total weight of the components used to form the selective polymer layer.

[0141] Mobile Carriers

[0142] In some embodiments, the selective polymer layer can further comprise a mobile carrier dispersed within the polymer matrix. The mobile carrier can comprise any molecule that, serves as a “mobile carrier” for CO2within the polymer matrix.

[0143] In some examples, the mobile carrier can comprise a guanidine-based mobile carrier, an amine-containing mobile carrier, or a combination thereof. In some embodiments, the mobile carrier can have a molecular weight of less than 1,000 Da (e.g., 800 Da or less, 500 or less, 300 Da or less, or 250 Da or less).

[0144] In some examples, the mobile carrier can be selected from 1, 1 ,3,3- tetram ethylguanidine, piperazine- 1 -carboximidamide, N-methylpiperazine- 1 - carb oxi midamide, V-ethylpiperazine-l-carboximidamide, A-propylpiperazine-1- carboximidamide, A-butylpiperazine- 1 -carboximidamide, A-pentylpiperazine- 1 - carboximidamide, A7-hexylpiperazine-l -carboximidamide, A-hepty 1 pi perazine- 1- carboximidamide, A-octylpiperazine-1 -carboximidamide, 2-(l-piperazinyl)ethylamine sarcosinate, 2-(l-piperazinyl)ethylamine glycinate, 2-(l-piperazinyl)ethylamine aminoisobutyrate, piperazine sarcosinate, piperazine glycinate, piperazine aminoisobutyrate, lithium sarcosinate, lithium glycinate, lithium aminoisobutyrate, potassium sarcosinate, potassium glycinate, potassium aminoisobutyrate, amidine with the structure Ri-(C=NH)-

[0145] Guanidine-Based Mobile Carriers

[0146] The guanidine-based mobile carrier can comprise any suitable compound comprising a guanidine moiety and having a molecular weight of less than 1 ,000 Da (e.g., 800 Da or less, 500 or less, 300 Da or less, or 250 Da or less). In some embodiments, the guanidine-based mobile carrier can be a water-soluble compound. In some embodiments, the guanidine-containing mobile carrier can be non-volatile at the temperatures at which the membrane will be stored or used.

[0147] In some embodiments, the guanidine-based mobile carrier can be a compound defined by Formula I below wherein

[0148] R1and R2are each independently selected from the group consisting of H, Ct-6 alkyl, C2-6alkenyl, C2-6alkynyl, C1-4haloalkyl, C3-10cycloalkyl, 6-10 membered and, 5-10 membered heteroaryl, and 4-10 membered heterocycloalkyl, wherein said C1 -6alkyl, C2-6alkenyl, C2-6alkynyl, C1-4haloalkyl, C3-10cycloalkyl, 6-10 membered aryl, 5-10 membered heteroaryl, and 4-10 membered heterocycloalkyl, are optionally substituted with 1, 2, 3, or 4 independently selected RAgroups, or R1and R2, together with the N atom to which they are attached, form a 4-9 membered heterocycloalkyl group or a 5-6 membered heteroaryl group, each optionally substituted with 1, 2, or 3 independently selected RAgroups; R3and R4are each independently selected from the group consisting of H, Cue alkyl, C2-6alkenyl, C2-6alkynyl, C1-4 haloalky], C3-10cycloalkyl, 6-10 membered aryl, 5-10 membered heteroaryl, and 4-10 membered heterocycloalkyl, wherein said Cue alkyl, C2-5alkenyl, C2-6alkynyl, C1-4haloalkyl, C3-10cycloalkyl, 6-10 membered aryl, 5-10 membered heteroaryl, and 4-10 membered heterocycloalkyl, are optionally substituted with 1, 2, 3, or 4 independently selected RAgroups, or R3and R4, together with the N atom to which they are attached, form a 4-9 membered heterocycloalkyl group or a 5-6 membered heteroaryl group, each optionally substituted with 1, 2, or 3 independently selected RAgroups,

[0149] R5is selected from the group consisting of H, C1 -6alkyl, C2-6alkenyl, C2-6alkynyl, C1-4haloalkyl, C3-10cycloalkyl, 6-10 membered aryl, 5-10 membered heteroaryl, and 4-10 membered heterocycloalkyl, wherein said Cue alkyl, C2-6alkenyl, C2-6alkynyl, C1-4haloalkyl, C3-10cycloalkyl, 6-10 membered aryl, 5-10 membered heteroaryl, and 4-10 membered heterocycloalkyl, are optionally substituted with 1, 2, 3, or 4 independently- selected RAgroups; and each RAis independently selected from OH, NO2, CN, halo, C1 -6alkyl, C2-6alkenyl, C2-6alkynyl, C1-4haloalkyl, Cue alkoxy, Cue haloalkoxy, cyano-C 1-3 alkyl, HO-C1-3 alkyl, amino, C1 -6alkylamino, di( C1 -6C a1l -k6yl)amino, thio, C1 -6alkylthio, C1 -6alkylsulfinyl, C1 -6alkyl sulfonyl, carbamyl, C1 -6alkylcarbamyl, di(C1 -6alkyl )carbamyl, carboxy, C1 -6alkylcarbonyl, C1 -6alkoxy carbonyl, C1 -6alkylcarbonylamino, C1 -6alkyl sulfonyl amino, aminosulfonyl, C1 -6alkylaminosulfonyl, di(C1 -6alkyllaminosulfonyl, aminosulfonylamino, C1 -6alkylaminosulfonylamino, di(C ue alkyl)aminosulfonylamino, aminocarbonylamino, Cue alkyl aminocarbonylamino, and di(C1 -6alkyl)aminocarbonylamino.

[0150] In some embodiments, R1, R2, R ’, and R4are all C1-4alkyl (e.g., methyl).

[0151] In some embodiments, R5is H. In other embodiments, R5can be Cue alkyl optionally substituted with 1, 2, 3, or 4 independently selected RAgroups. For example, R5can be a C1 -6alkyl group substituted with an OH group, or a Cue alkyl group substituted with an amino group.

[0152] In some examples, the guanidine-based mobile carrier can comprise one of the following

[0153] wherein n is an integer from 1 to 12, such as from 1 to 6. TMG is tetramethyguanidine, and PZC is piperazine- 1-carboximidamide.

[0154] Amine-Containing Mobile Carriers

[0155] Suitable amine-containing mobile carriers can include small molecules comprising one or more primary amine moieties and / or one or more secondary' amine moieties, such as an amino acid salt.

[0156] In some embodiments, the amine-containing mobile carrier can have a molecular weight of 1,000 Da or less (e.g., 800 Da or less, 500 or less, 300 Da or less, or 250 Da or less). In some embodiments, the amine-containing mobile carrier can be non-volatile at the temperatures at which the membrane will be stored or used. For example, amine-containing mobile carrier can comprise a salt of a primary' amine or a salt of a secondary amine.

[0157] In some cases, the amine-containing mobile carrier can include an aminoacid salt.

[0158] The amino acid salt can be a salt of any suitable amino acid. The amino acid salt may be derived, for instance, from glycine, arginine, lysine, histidine, 6-aminohexanoic acid, proline, sarcosine, methionine, or taurine. In some cases, the amino acid salt can comprise a salt of a compound defined by the formula below7

[0159] Wherein , independently for each occurrence in the amino acid, each of Ri, R?., Rs and R4 is selected from one of the following

[0160] or Ri and Rs, together with the atoms to which they are attached, form a five-membered heterocycle defined by the structure below when n is 1, or a six-membered heterocycle defined by the structure below when n is 2 Poly(amino-acids), for example, polyarginine, polylysine, polyonithine, or polyhistidine may also be used to prepare the amino acid salt.

[0161] In other embodiments, the amine-containing mobile carrier can be defined by a wherein are hydrogen or hydrocarbon groups having from 1 to 4 carbon atoms, n is an integer ranging from 0 to 4, ” is a. cation having a valence of 1 to .3 In some cases, the cation can be an amine cation having the formula: wherein R5and R6are hydrogen or hydrocarbon groups having from 1 to 4 carbon atoms, R7is hydrogen or hydrocarbon groups having from 1 to 4 carbon atoms or an alkyl amine of from 2 to 6 carbon atoms and I to 4 nitrogen atoms, y is an integer ranging from 1 to 4, and m is an integer equal to the valence of the cation. In some embodiments, Am+is a metal cation selected from Groups la, Ila, and Illa of the Periodic Table of Elements or a transition metal. For example, Am'rcan comprise lithium, aluminum, or iron.

[0162] Other suitable amine-containing mobile earners include aminoisobutyric acid- potassium salt, aminoisobutyric acid-lithium salt, aminoisobutyric acid-piperazine salt, glycine-potassium salt, glycine-lithium salt, gly cine-pi perazine salt, dimethylglycinepotassium salt, dimethylglycine-lithium salt, dimethylglycine-piperazine salt, piperadine-2- carboxlic acid- potassium salt, piperadine-2-carboxlic acid-lithium salt, piperadine-2- carboxlic acid-piperazine salt, piperadine-4-carboxlic acid- potassium salt, piperadine-4- carboxlic acid-lithium salt, piperadine-4-carboxlic acid-piperazine salt, piperadine-3- carboxlic acid- potassium salt, piperadine-3-carboxlic acid-lithium salt, piperadine-3- carboxlic acid-piperazine salt, and blends thereof.

[0163] CO2-Philic Ethers

[0164] Optionally, the selective polymeric layer can further include a one or more CO2- philic ethers dispersed within the polymer matrix. The CO2-philic ether can be a polymer, oligomer, or small molecule containing one or more ether linkages. Examples of CO2- philic ethers include alcohol ethers, polyalkylene alcohol ethers, polyalkylene glycols, poly(oxyalkylene)glycols, poly(oxyalkylene)glycol ethers, and ethoxylated phenol. In one embodiment, the CO2-philic ether can comprise alkyl ethoxylate (Cl-C6)-(EO)x, where x = 1 - 30 and the ethoxylate is linear or branched. In some embodiments, the CC)2-phiiic ether can comprise ethylene glycol butyl ether (EGBE), diethylene glycol monobutyl ether (DGBE), triethylene glycol monobutyl ether (TEGBE), ethylene glycol dibutyl ether (EGDE), polyethylene glycol monomethyl ether (mPEG), or any combination thereof. Graphene Oxide

[0165] Optionally, the selective polymer layer can further include graphene oxide dispersed within the polymer matrix.

[0166] The term “graphene” refers to a one-atom-thick planar sheet of sp2-bonded carbon atoms that are densely packed in a honeycomb crystal lattice. In one embodiment, it refers to a single-layer version of graphite.

[0167] The term “graphene oxide” herein refers to functionalized graphene sheets (FGS) — the oxidized compositions of graphite. These compositions are not defined by a single stoichiometry. Rather, upon oxidation of graphite, oxygen-containing functional groups (e.g., epoxide, carboxyl, and hydroxyl groups) are introduced onto the graphite. Complete oxidation is not needed. Functionalized graphene generally refers to graphene oxide, where the atomic carbon to oxygen ratio starts at approximately 2. This ratio can be increased by reaction with components in a medium, which can comprise a polymer, a polymer monomer resin, or a solvent, and / or by the application of radiant energy. As the carbon to oxygen ratio becomes very large (e.g., approaching 20 or above), the graphene oxide chemical composition approaches that of pure graphene.

[0168] The term “graphite oxide” includes “graphene oxide”, which is a morphological subset of graphite oxide in the form of planar sheets. “Graphene oxide” refers to a graphene oxide material compri sing either single-layer sheets or multiple-layer sheets of graphite oxide. Additionally, in one embodiment, a graphene oxide refers to a graphene oxide material that contains at least one single layer sheet in a portion thereof and at least one multiple layer sheet, in another portion thereof. Graphene oxide refers to a range of possible compositions and stoichiometries. The carbon to oxygen ratio in graphene oxide plays a role in determining the properties of the graphene oxide, as well as any composite polymers containing the graphene oxide.

[0169] The abbreviation “GO” is used herein to refer to graphene oxide, and the notation G0(m) refers to graphene oxide having a C:O ratio of approximately “m”, where m ranges from 3 to about 20, inclusive. For example, graphene oxide having a C:O ratio of between 3 and 20 is referred to as “GO(3) to GO(20)”, where m ranges from 3 to 20, e.g., m=3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20, including all decimal fractions of 0.1 increments in between, e.g., a range of values of 3-20 includes 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, and so on up to 20. Thus, as used herein, the term G0(m) describes all graphene oxide compositions having a C:O ratio of from 3 to about 20. For example, a GO with a C:O ratio of 6 is referred to as GO(6), and a GO with a C:O ratio of 8, is referred to as GO(8), and both fall within the definition of GO(m).

[0170] As used herein, “GO(L)” refers to low C:O ratio graphene oxides having a C:O ratio of approximately “L”, wherein L is less than 3, e.g., in the range of from about 1, including 1, up to 3, and not including 3, e.g., about 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2,7, 2.8, or about 2,9. In many embodiments, a GO(L) material has a C:O ratio of approximately 2. The designations for the materials in the GO(L) group is the same as that of the G0(m) materials described above, e.g., “00(2)” refers to graphene oxide with a C:O ratio of 2.

[0171] In some embodiments, the graphene oxide can be G0(m). In some embodiments, the graphene oxide can be GO(L). In some embodiments, the graphene oxide can be nanoporous.

[0172] Other Components

[0173] In some embodiments, the polymer matrix can further include a cross-linking agent. Cross-linking agents suitable for use in the polymer matrix can include, but are not limited to, formaldehyde, glutaraldehyde, maleic anhydride, glyoxal, divinyl sulfone, toluenediisocyanate, trimethylol melamine, terephthalatealdehyde, epichlorohydrin, vinyl acrylate, and combinations thereof. In some embodiments, the cross-linking agent can comprise formaldehyde, glutaraldehyde, or maleic anhydride. The polymer matrix can comprise any suitable amount of the cross-linking agent. For example, the polymer matrix can comprise 1 to 40 percent cross-linking agents by weight of the polymer matrix.

[0174] The polymer matrix can further include a base. The base can act as a catalyst to catalyze the cross-linking of the polymer matrix (e.g., cross-linking of a hydrophilic polymer with an ami tie-containing polymer). In some embodiments, the base can remain in the polymer matrix and constitute a part of the polymer matrix. Examples of suitable bases include potassium hydroxide, sodium hydroxide, lithium hydroxide, tri ethyl amine, 2 N. / V- dimethy I aminopyridine, hexamethyltriethylenetetraamine, potassium carbonate, sodium carbonate, lithium carbonate, and combinations thereof. In some embodiments, the base can include potassium hydroxide. The polymer matrix can comprise any suitable amount of the base. For example, the polymer matrix can comprise 1 to 40 percent base by weight of the polymer matrix.

[0175] The selective polymer layer further comprises carbon nanotubes dispersed within the polymer matrix. Any suitable carbon nanotubes (prepared by any suitable method or obtained from a commercial source) can be used. The carbon nanotubes can comprise single-walled carbon nanotubes, multiwalled carbon nanotubes, or a combination thereof.

[0176] In some cases, the carbon nanotubes can have an average diameter of at least 10 nm (e.g., at least 20 nm, at least 30 nm, or at least 40 nm). In some cases, the carbon nanotubes can have an average diameter of 50 nm or less (e.g., 40 nm or less, 30 nm or less, or 20 nm or less). In certain embodiments, the carbon nanotubes can have an average diameter ranging from any of the minimum values described above to any of the maximum values described above. For example, the carbon nanotubes can have an a verage diameter of from 10 nm to 50 nm (e.g., from 10 nm to 30 nm, or from 20 nm to 50 nm).

[0177] In some cases, the carbon nanotubes can have an average length of at least 50 nm (e.g., at least 100 nm, at least 200 nm, at least 300 nm, at least 400 nm, at least 500 nm, at least 600 nm, at least 700 nm, at least 800 nm, at least 900 nm, at least 1 gm, at least 5 gm, at least 10 pm, or at least 15 gm). In some cases, the carbon nanotubes can have an average length of 20 gm or less (e.g., 15 gm or less, 10 gm or less, 5 gm or less, 1 gm or less, 900 nm or less, 800 nm or less, 700 nm or less, 600 nm or less, 500 nm or less, 400 nm or less, 300 nm or less, 200 nm or less, or 100 nm or less).

[0178] In certain embodiments, the carbon nanotubes can have an average length ranging from any of the minimum values described above to any of the maximum values described above. For example, the carbon nanotubes can have an average length of from 50 nm to 20 gm (e.g., from 200 nm to 20 gm, or from 500 nm to 10 gm).

[0179] In some cases, the carbon nanotubes can comprise unfunctionalized carbon nanotubes. In other embodiments, the carbon nanotubes can comprise sidewall functionalized carbon nanotubes. Sidewall functionalized carbon nanotubes are well known in the art. Suitable sidewall functionalized carbon nanotubes can be prepared from unfunctionalized carbon nanotubes, for example, by creating defects on the sidewall by strong acid oxidation. The defects created by the oxidant can subsequently converted to more stable hydroxyl and carboxylic acid groups. The hydroxyl and carboxylic acid groups on the acid treated carbon nanotubes can then couple to reagents containing other functional groups (e.g., amine-containing reagents), thereby introducing pendant functional groups (e.g., amino groups) on the sidewalls of the carbon nanotubes. In some embodiments, the carbon nanotubes can comprise hydroxy-functionalized carbon nanotubes, carboxy- functionalized carbon nanotubes, amine-functionalized carbon nanotubes, or a combination thereof. In some embodiments, the selective polymer layer can comprise at least 0.5% (e.g., at least 1%, at least 1.5%, at least 2%, at least 2.5%, at least 3%, at least 3.5%, at least 4%, or at least 4.5%) by weight carbon nanotubes, based on the total dry weight of the selective polymer layer. In some embodiments, the selective polymer layer can comprise 5% or less (e.g., 4.5% or less, 4% or less, 3.5% or less, 3% or less, 2.5% or less, 2% or less, 1.5% or less, or 1% or less) by weight carbon nanotubes, based on the total dry weight of the selective polymer layer.

[0180] The selective polymer layer can comprise an amount of carbon nanotubes ranging from any of the minimum values described above to any of the maximum values described above. For example, the selective polymer layer can comprise from 0.5% to 5% (e.g., from 1% to 3%) by weight carbon nanotubes, based on the total dry' weight of the selective polymer layer.

[0181] If desired, the selective polymer layer can be surface modified by, for example, chemical grafting, blending, or coating to improve the performance of the selective polymer layer. For example, hydrophobic components may be added to the selective polymer layer to alter the properties of the selective polymer layer in a manner that facilitates greater fluid selectivity.

[0182] The total thickness of each layer in the membrane can be chosen such that the structure is mechanically robust, but not so thick as to impair permeability. In some embodiments, the selective polymer layer can have a thickness of from 50 nanometers to 5 microns (e.g., from 50 nm to 2 microns, or from 100 nanometers to 750 nanometers, or from 250 nanometers to 500 nanometers). In some embodiments, the support layer can have a thickness of from 1 micron to 500 microns (e.g., from 50 to 250 microns). In some cases, the membranes disclosed herein can have a thickness of from 5 microns to 500 microns.

[0183] Methods of Making

[0184] Methods of making these membranes are also disclosed herein. Methods of making membranes can include depositing (e.g., coating) a selective polymer layer on a support layer to form a selective layer disposed (e.g., coated) on the support layer.

[0185] Optionally, the support layer can be pretreated prior to deposition (e.g., coating) of the selective polymer layer, for example, to remove water or other adsorbed species using methods appropriate to the support and the adsorbate. Examples of absorbed species are, for example, water, alcohols, porogens, and surfactant templates.

[0186] The selective polymer layer can be prepared by first forming a coating solution including the components of the polymer ma trix (e.g., a polyguanidine polymer and one or more additional components, such as a hydrophilic polymer, an amine-containing polymer, a mobile carrier such as a guanidine-based mobile carrier or an amine-based mobile carrier, a CO2-philic ether, graphene oxide, carbon nanotubes, a crossdinking agent, a basic compound, or a combination thereof) in a suitable solvent. One example of a suitable solvent is water. In some embodiments, the amount of water employed will be in the range of from 50% to 99%, by weight of the coating solution. The coating solution can then be used in forming the selective polymer layer. For example, the coating solution can be coated onto a support later (e.g., a nanoporous gas permeable membrane) using any suitable technique, and the solvent may be evaporated such that a nonporous membrane is formed on the substrate. Examples of suitable coating techniques include, but are not limited to, “knife coating” or “dip coating”. Knife coating includes a process in which a knife is used to draw a polymer solution across a flat substrate to form a thin film of a polymer solution of uniform thickness after which the solvent of the polymer solution is evaporated, at ambient temperatures or temperatures up to about 100°C or higher, to yield a fabricated membrane. Dip coating includes a process in which a polymer solution is contacted with a porous support. Excess solution is permitted to drain from the support, and the solvent of the polymer solution is evaporated at ambient or elevated temperatures. The membranes disclosed can be shaped in the form of hollow fibers, tubes, films, sheets, etc. In certain embodiments, the membrane can be configured in a flat sheet, a spiral-wound, a hollow fiber, or a plate-and-frame configuration.

[0187] In some embodiments, membranes can be heated at a temperature and for a time sufficient for cross-linking to occur. In one example, cross-linking temperatures in the range from 80°C to 100°C can be employed. In another example, cross-linking can occur from 1 to 72 hours. The resulting solution can be coated onto the support layer and the solvent evaporated, as discussed above. In some embodiments, a higher degree of cross-linking for the polymer matrix after solvent removal takes place at about 100°C to about 180°C, and the cross-linking occurs in from about 1 to about 72 hours.

[0188] An additive may be included in the selective polymer layer before forming the selective polymer layer to increase the water retention ability of the membrane. Suitable additives include, but are not limited to, polystyrenesulfonic acid-potassium salt, polystyrenesulfonic acid-sodium salt, polystyrenesulfonic acid-lithium salt, sulfonated polyphenyleneoxides, alum, and combinations thereof. In one example, the additive comprises polystyrenesulfonic acid-potassium salt.

[0189] In some embodiments, the method of making these membranes can be scaled to industrial levels.

[0190] Methods of Use

[0191] The membranes disclosed herein can be used for separating gaseous mixtures. For example, provided are methods for separating a first gas from a feed gas comprising the first gas and one or more additional gases (e.g., at least a second gas). The method can include contacting any of the disclosed membranes (e.g., on the side comprising the selective polymer) with the feed gas under conditions effective to afford transmembrane permeation of the first gas. In some embodiments, the method can also include withdrawing from the reverse side of the membrane a permeate containing at least the first gas, wherein the first gas is selectively removed from the gaseous stream. The permeate can comprise at least the first gas in an increased concentration relative to the feed stream. The term “'permeate'’ refers to a portion of the feed stream which is withdrawn at the reverse or second side of the membrane, exclusive of other fluids such as a sweep gas or liquid which may be present at the second side of the membrane.

[0192] The membrane can be used to separate gases at any suitable temperature, including temperatures of 57°C or greater. For example, the membrane can be used at temperatures of from 57 C to 97 C. In some embodiments, a vacuum can be applied to the permeate face of the membrane to remove the first gas. In some embodiments, a sweep gas can be flowed across the permeate face of the membrane to remove the first gas. Any suitable sweep gas can be used. Examples of suitable sweep gases include, for example, air, steam, nitrogen, argon, helium, and combinations thereof.

[0193] The first gas can include an acid gas. For example, the first gas can be carbon dioxide, hydrogen sulfide, sulfur dioxide, sulfur tri oxi de, nitrogen oxide, or combinations thereof. In some embodiments, the membrane can be selective to carbon dioxide versus hydrogen, nitrogen, carbon monoxide, or combinations thereof In some embodiments, the membrane can be selective to hydrogen sulfide versus hydrogen, nitrogen, carbon monoxide, or combinations thereof. In certain embodiments, the first gas can comprise carbon dioxide and the second gas can comprise hydrogen. In certain embodiments, the first gas can comprise carbon dioxide and the second gas can comprise nitrogen.

[0194] The permeance of the first gas or the acid gas can be at least 50 GPU (e.g., 75 GPU or greater, 100 GPU or greater, 150 GPU or greater, 200 GPU or greater, 250 GPU or greater, 300 GPU or greater, 350 GPU or greater, 400 GPU or greater, 450 GPU or greater, 500 GPU or greater, 550 GPU or greater, 600 GPU or greater, 650 GPU or greater, 700 GPU or greater, 750 GPU or greater, 800 GPU or greater, 850 GPU or greater, 900 GPU or greater, 950 GPU or greater, 1000 GPU or greater, 1100 GPU or greater, 1200 GPU or greater, 1300 GPU or greater, 1400 GPU or greater, 1500 GPU or greater, 1600 GPU or greater, 1700 GPU or greater, 1800 GPU or greater, 1900 GPU or greater, 2000 GPU or greater, 2100 GPU or greater, 2200 GPU or greater, 2300 GPU or greater, or 2400 GPU or greater) at 57°C and 4 bar feed pressure.

[0195] The permeance of the first gas or the acid gas can be 2500 GPU or less at 57°C and 4 bar feed pressure (e.g., 2400 GPU or less, 2300 GPU or less, 2200 GPU or less, 2100 GPU or less, 2000 GPU or less, 1900 GPU or less, 1800 GPU or less, 1700 GPU or less, 1600 GPU or less, 1500 GPU or less, 1400 GPU or less, 1300 GPU or less, 1200 GPU or less, 1100 GPU or less, 1000 GPU or less, 950 GPU or less, 900 GPU or less, 850 GPU or less, 800 GPU or less, 750 GPU or less, 700 GPU or less, 650 GPU or less, 600 GPU or less, 550 GPU or less, 500 GPU or less, 450 GPU or less, 400 GPU or less, 350 GPU or less, 300 GPU or less, 250 GPU or less, 200 GPU or less, 150 GPU or less, 100 GPU or less, or 75 GPU or less).

[0196] The permeance of the first gas or the acid gas through the membrane can vary from any of the minimum values described above to any of the maximum values described above or even higher. For example, the permeance of the first gas or the acid gas can be from 50 GPU to 1500 GPU or even to 3000 GPU at 57°C and 4 bar feed pressure (e.g., from 300 GPU to 1500 GPU at 57°C, or from 500 GPU to 1500 GPU or even to 3000 GPU at 57°C and 4 bar feed pressure).

[0197] The membrane can exhibit a first gas / second gas selectivity of at least 10 at 57°C and 4 bar feed pressure. In some embodiments, the membrane can exhibit a first gas / second gas selectivity of up to 500 at 57°C and 4 bar feed pressure. For example, the membrane can exhibit a first gas / second gas selectivity of 10 or greater, 25 or greater, 50 or greater, 75 or greater, 100 or greater, 125 or greater, 150 or greater, 175 or greater, 200 or greater, 225 or greater, 250 or greater, 275 or greater, 300 or greater, 325 or greater, 350 or greater, 375 or greater, 400 or greater, 425 or greater, 450 or greater, or 475 or greater at 57°C and 4 bar feed pressure. In some embodiments, the permeance and selectivity of the membrane for the first gas or the acid gas can vary' at higher or lower temperatures.

[0198] By way of non-limiting illustration, examples of certain embodiments of the present disclosure are given below.

[0199] EXAMPLES

[0200] Fabrication of Polyethersulfone Substrates Using a Cosolvent, and Pore Former for Composite Membranes in Gas Separation.

[0201] Overview

[0202] Described herein are fabrication processes to produce high performance nanoporous polyethersulfone (PES) substrates by knife casting, and vapor- and nonsolvent-induced phase separations in sequential steps using a cosolvent and pore former, l-methoxy-2- propanol (MP). The resulting membranes can be used to prepare composite membranes for gas separation. By using this combination of components and steps, the fabricated PES substrates show a highly interconnected pore structure, presumably due to both the increased solvent hydrophobicity and the reduced casting solution thermodynamic stability by the cosolvent and pore former, MP, which induced the phase separation via spinodal decomposition mechanism. The highly interconnected pores in the PES substrates decreased mass transfer resistance and enhanced the gas permeance significantly. Moreover, by using the substrate with highly interconnected pores, the gas permeance of the prepared composite membrane was thus improved, presumably due to both the reduced lateral diffusion and substrate transport resistances.

[0203] Introduction

[0204] The composite membrane for gas separation can comprise a dense top layer responsible for the separation and a porous substrate layer to provide mechanical support. Although the major separation is achieved by the selective top layer, the pore structure of the substrate can have a significant effect on the gas transport performance of the composite membrane. Described herein are methods of fabricating polyethersulfone (PES) substrates with highly interconnected pores in pilot scale for composite membrane preparation that can be used for gas separation, such as CCb. separation from flue gas. The resultant PES substrates with highly interconnected pores are an effective support for the fabrication of composite membranes for gas separations including the removal and capture of CO2from Nb-containing streams, e.g., flue gas in coal- and / or natural gas-fired power plants.

[0205] The mass transfer resistance of a thin-film composite membrane is the sum of the resistance of each layer according to the resistance-in-series model. A more permeable substrate with higher porosity and smaller dense layer thickness will decrease the total mass transfer resistance of the composite membrane, thus increasing its gas (e.g., CO2) permeance. Moreover, the surface morphology of the substrate affects the gas (e.g., CO2) diffusion through the selective layer by introducing a lateral diffusion. A substrate with the higher surface porosity and pore density will decrease the lateral diffusion resistance and increase the gas (e.g., CO2) permeance of the composite membrane. Therefore, a substrate with well interconnected pores is desired to prepare a more permeable composite membrane.

[0206] A-methyl-2-pyrrolidone (NMP), dimethylfonnamide (DMF), and dimethylacetamide (DMAc) have been used to prepare the nanoporous substrates. However, these commonly used solvents are highly toxic. Compared to these solvents, 3- methoxy propanol (MP) shows much less toxicity along with a lower cost.

[0207] Described herein is a fabrication process that can produce PES substrates with highly interconnected pores by knife casting, and vapor- and nonsolvent-induced phase separations in sequential steps using a cosolvent and pore former, MP, for use in the preparation of composite membranes for gas separation. By using these methods, the fabricated PES substrates showed a highly interconnected pore structure. Compared with substrates prepared using only a conventional solvent (e.g., NMP), the mixed solvent system comprising the common solvent and MP is more hydrophobic and can decrease the thermodynamic stability of the casting solution significantly. As a result, the phase separation during the porous membrane formation process was induced via spinodal decomposition mechanism. Compared with the PES substrate prepared with the common solvent only, e.g., NMP, the PES substrate prepared with the mixed solvent system showed a much higher surface porosity and gas (e.g., CO2) permeance. Moreover, the advantage of using this improved substrate in composite membrane fabrication was demonstrated.

[0208] Also provided are fabrication processes for providing an efficient and effective method to fabricate PES substrates with highly interconnected pores that can be applied for the preparation of composite membranes in gas separation. It has thus demonstrated the fabrication process for the mass production of the PES substrates with highly interconnected pores through roll-to-roll fabrication.

[0209] Detailed Description

[0210] Casting Solution Preparation. The typical casting solution contains PES polymer, solvent, cosolvent, pore forming agent, viscosity enhancer and hydrophilic additive. In the casting solution, NMP was employed as the solvent, and MP functioned not only as a cosolvent as but also a pore forming agent, lithium chloride (LiCl) was applied not only as a viscosity enhancer but also as a pore forming agent, and polyvinylpyrrolidone (PVP) was used as a hydrophilic additive. The casting solution was prepared by dissolving PES, LiCl, and PVP in an appropriate amount of NMP / MP mixture at 60°C under magnetic / mechanical stirring. The homogeneous casting solution could be used for the subsequent casting. A typical PES content was 16 wt.% in the solution, while the LiCl concentration was 2 wt.%, the PVP concentration was 0.1 wt.%, and the weight ratio of MP to NMP was 1.

[0211] Pilot-scale Casting Process. The nanoporous PES substrates were fabricated by knife casting and vapor- and nonsolvent-induced phase separations in sequential steps. The PES substrate can be fabricated by employing a film applicator in lab scale or a casting knife in a continuous casting machine in pilot scale. As described in the following, the PES membrane was fabricated by a pilot-scale roll-to-roll casting machine, consisting of knife casting and vapor- and nonsolvent-induced phase separations in sequential steps, which is shown in Figure 1 .

[0212] The casting solution was continuously cast onto a non-woven fabric moving at a speed of 1 - 5 ft / min by a stationary stainless-steel knife (up to 21 -inch wide) with the predetermined gap setting. A tension of 3 - 6 Ibf was applied to ensure the flatness of the fabric. The trough holding the casting solution was purged with Nz at a sufficient flow rate (350 cc / min) to prevent the casting solution from phase separation. A humidity chamber was installed after the casting knife, and the rolling speed of the fabric could control the exposure time in the humidity chamber. Humid N2 was flowed into the humidity chamber to control the relative humidity. The relative humidity and the exposure time in the humidity chamber were 30% - 90% and 5 - 50 sec, respectively. Subsequently, the cast film was immersed into the water tank to form the PES substrate. The coagulation bath temperatures were controlled at 5 - 40°C.

[0213] Gas Transport Property Characterization. In order to measure the gas transport performance of the highly permeable substrate accurately, a permeation apparatus was assembled using pure CO2(10 L / min, 1.5 psig) as the feed gas. The active membrane area was 6.4 cm2. The temperature was controlled at 57°C, which is the typical temperature of flue gas in coal- and / or natural ga-fire power plants, via a temperature-controlled oven (Bemco Inc, Simi Valley, CA), Both the permeate flow rate and the pressure on the permeate side were measured by a mass flow meter (Alicat Scientific, Tucson, .AZ, USA).

[0214] Compared to the substrates, the composite membranes were much less permeable. Hence, the gas transport performances of composite membranes were characterized via a gas permeation testing apparatus equipped with a gas chromatograph (GC). The membrane was loaded into a rectangular stainless-steel cell with an effective area of 2.7 cm2, and a countercurrent flow configuration was used during the permeation measurement. A feed gas mixture of 20% CO2and 80% N2on a dry basis and a sweep gas of argon (Ar) were controlled by two mass flow controllers (Brooks instrument, Hatfield, PA), respectively. The feed and sweep gas flow rates were 98 and 30 cc / min, respectively. Moreover, the pressures were adjusted to be 1.5 psig and 1.1 psig for the feed and sweep sides, respectively. The temperature was controlled at 57°C via a temperature-controlled oven (Bemco Inc. Simi Valley, CA). The saturation water vapor content of 17.2% at 57°C were applied for both feed and sweep sides in all the transport experiments by humidifying the feed and sweep gases through stainless-steel humidifiers (Swagelok, Westerville, OH, U.S.A,) filled with Raschig glass ring packing. 100 ml water was pumped into the humidifier for both sides before the transport measurements. After the retentate and permeate gas streams were passed through their respective knockout vessels and dried by their respective dri erite tubes, they were sent to a GC for composition analysis. Then, the gas compositions were used to determine CO2permeance and CO2 / N2 selectivity.

[0215] Example 1

[0216] PES polymer (Ultrason*' E6020P, MW 75,000 Da, from BASF), LiCI, and PVP (MW 360,000 Da from Sigma-Aldrich) were employed for the PES substrate preparation. The detailed casting solution composition is summarized in Table 1. A MP / NMP weight ratio of 1 was used, corresponding to the NMP and MP concentrations each at 40.95 wt.% in the casting solution. The casting solution was prepared according to the aforementioned procedure, and the PES substrate was cast by the continuous casting machine shown in Figure 1. The relative humidity in the humidification chamber was 80%, and the exposure time was 5 s. The water bath temperature was 30°C. Table 1. Casting solution composition for the PES substrate in Example 1.

[0217] Figure 2A shows the scanning electron microscopy (SEM) for the surface morphology of the prepared PES substrate in Example 1. The average pore size and surface porosity were 36.6 ntn and 34.9%, respectively. For comparison, Figure 2B is the SEM of the PES substrate prepared using NMP as the only solvent in Comparative Example 1, indicating that the average pore size and surface porosity were 12.9 nm and 12,6%, respectively. In other words, the PES substrate prepared using the methods described herein had an approximately 1 .8-time increase on the surface porosity via the use of the MP / NMP mixed solvent.

[0218] Table 2 exhibits the substrate prepared using the methods described herein with a CO2permeance of 316,315 GPU (1 GPU = l()‘bcm3(STPl'cm^- s^'cmHg'1). For comparison, Table 3 shows a CO2permeance of 146,598 GPU for the PES substrate prepared using NMP as the only solvent in Comparative Example 1. Thus, the substrate prepared using the methods described herein had ~1.2 times more permeable than the PES substrate prepared using NMP as the only solvent (Comparative Example 1).

[0219] Table 2. Summary of the transport result and surface morphology of the PES substrate in Example 1.

[0220] Comparative Example 1. A PES substrate prepared using NMP as the only solvent was employed as a reference in Comparative Example 1. A PES concentration of 16 wt.%, a LiCl concentration of 2 wt.%, a PVP concentration of 0. 1%, and a NMP concentration of 81 .9 wt.% were employed. The same solution preparation procedure and casting process described in Example 1 were used. Table 3 shows the surface morphology and the CO2permeance of PES substrate prepared using NMP as the only solvent. As aforementioned, the SEM picture of the surface morphology for this PES substrate is shown in Figure 2B. Thi s substrate was used as a reference for showing the improvements of the PES substrate prepared using the MP / NMP mixed solvent

[0221] Table 3. Summary of the transport result and surface morphology of the PES substrate in Comparative Example I . Example 2. A PES substrate was prepared by the same procedure described in

[0222] Example 1 except that a lower MP / NMP ratio was employed. The detailed casting solution composition is summarized in Table 4. Figure 3 shows the surface morphology of the prepared PES substrate, and Table 5 summarizes the surface morphology and the CO2permeance of the PES substrate prepared using the methods described herein in Example 2. As shown, the average pore size and surface porosity were 17.1 nm and 20.7%, respectively. Compared to Comparative Examples 1, a more open morphology was obtained as the CO2permeance of Example 2 was 238,468 GPU

[0223] Table 4. Casting solution composition of the PES substrate in Example 2. Table 5. Summary of the transport results and surface morphology of the PES substrate in Example 2.

[0224] Example 3. ,A PES substrate was prepared by the same procedure described in Example 1 except that a higher PES concentration was employed. The detailed casting solution composition is summarized in Table 6. Figure 4 shows the surface morphology of the prepared PES substrate, and Table 7 summarizes the surface morphology and the CO2permeance of the improved PES substra te. As shown, the CO2permeance of the improved PES in Example 3 (247,913 GPU) was much higher than that of the PES substrate prepared using NMP as the only solvent (146,598 GPU in Comparative Example 1)

[0225] Table 6. Casting solution composition of the PES substrate in Example 3.

[0226] Table 7. Summary of the transport results and surface morphology of the PES substrate in Example 3.

[0227] Example 4. A PES substrate was prepared by the same procedure described in Example 1 except that a lower water bath temperature of 25°C was employed. Figure 5 shows the surface morphology of the prepared PES substrate, and Table 8 summarizes the surface morphology and the CO2permeance of the improved PES substrate. As shown, the CO2permeance of the improved PES in Example 4 (301,457 GPU) was much higher than that of the PES substrate prepared using NMP as the only solvent (146,598 GPU in

[0228] Comparative Example 1).

[0229] Table 8. Summary of the transport results and surface morphology of the PES substrate in Example 4.

[0230] Example 5. An amine-containing polymeric selective layer was coated on each substrate of Examples 1 and Comparative Example 1 described earlier to form the composite membranes. The selective layer consisted of polyvinylamine (PVAm) serving as the fixed-site carrier and 2-(l-piperaziny1)ethylamine sarcosinate (PZEA-Sar) as the mobile carrier. PVAm and PZEA-Sar were mixed with a weight ratio of 35 / 65. A suitable viscosity of the coating solution (> 1100 cp) was used to coat the selective layer on each of the aforementioned two substrates without defects. A selective layer thickness of - 170 nm was employed for all the composite membranes. The gas transport properties of the composite membranes were measured by the procedure described previously.

[0231] Table 9 lists the transport results of the prepared composite membranes by using the substrates fabricated from Examples 1 and Comparative Example 1, respectively. As shown, the composite membrane coated on the substrate in Example 1 yielded a CO2permeance of 1017 GPU, which was 441 GPU higher than that, of the composite membrane coated on the substrate in Comparative Example I . The CO2 / N2. selectivity of the composite membrane coated on the substrate in Example 1 was 163, which was slightly higher that of the composite membrane coated on the substrate in Comparative Example 1. The improved CO2permeance of the thin-film composite membrane was presumably attributed to both the reduced lateral diffusion and substrate transport resistances Table 9. Separation performances of the composite membranes with the substrates fabricated from Examples 1 and Comparative Example 1 ,

[0232] The compositions, systems, and methods of the appended claims are not limited in scope by the specific compositions, systems, and methods described herein, which are intended as illustrations of a few aspects of the claims. Any compositions, systems, and methods that are functionally equivalent are intended to fall within the scope of the claims. Various modifications of the compositions, systems, and methods in addition to those shown and described herein are intended to fall within the scope of the appended claims. Further, while only certain representative compositions, systems, and method steps disclosed herein are specifically described, other combinations of the compositions, systems, and method steps also are intended to fall within the scope of the appended claims, even if not specifically recited. Thus, a combination of steps, elements, components, or constituents may be explicitly mentioned herein or less, however, other combinations of steps, elements, components, and constituents are included, even though not explicitly stated.

[0233] The term “comprising” and variations thereof as used herein is used synonymously with the term “including” and variations thereof and are open, non-limiting terms. Although the terms “comprising” and “including” have been used herein to describe various embodiments, the terms “consisting essentially of’ and “consisting of’ can be used in place of “comprising” and “including” to provide for more specific embodiments of the invention and are also disclosed. Other than where noted, all numbers expressing geometries, dimensions, and so forth used in the specification and claims are to be understood at the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, to be consumed in light of the number of significant digits and ordinary' rounding approaches.

[0234] Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of skill in the art to which the disclosed invention belongs. Publications cited herein and the materials for which they are cited are specifically incorporated by reference.

Claims

WHAT IS CLAIMED IS:

1. A method of fabricating a nanoporous polymer membrane, the method comprising: forming a film of a casting solution comprising a gas permeable polymer, a solvent, a co-solvent, and a porogen; contacting the film with humid air to induce phase separation in the film, and contacting the film with an aqueous solution to induce phase separation in the film.

2. The method of claim 1, wherein the method is performed continuously in a roll-to- roll casting machine.

3. The method of any one of claims 1-2, wherein forming the film of the casting solution comprises knife casting the casting solution.

4. The method of any one of claims 1-3, wherein the film is formed on a fabric support.

5. The method of claim 4, wherein the fabric support comprises a non-woven fabric support.

6. The method any one of claims 4-5, wherein a tension is applied to the fabric support to ensure flatness of the fabric support during film formation.

7. The method of any one of claims 1-6, wherein the method is performed continuously in a roll-to-roll casting machine at a rate of at least 1 ft / min, such as a rate of from 1 ft / min to 10 ft / min, or a rate of from 1 ft / min to 5 ft / min.

8. The method of any one of claims 1-7, wherein the film is formed under inert atmosphere, such as under nitrogen.

9. The method of any one of claims 1-8, wherein contacting the film with humid air comprises passing the film through a humidity chamber.

10. The method of any one of claims 1-9, wherein the film is contacted with the humid air for a period of time of from 5 seconds to 5 minutes, such as from 5 second to 2 minutes, from 5 seconds 1 minute, or from 5 seconds to 50 seconds.

11. The method of any one of claims 1-10, wherein the humid air has a relative humidity of from 10% to 100%, such as from 20% to 95% or from 30% to 90%.

12. The method of any one of claims 1-11, wherein contacting the film with the aqueous solution comprises immersing the film in a coagulation bath, such as passing the film through a coagulation path.

13. The method of any one of claims 1-12, wherein the aqueous solution is maintained at a temperature of from 5°C to 70°C, such as from 5°C to 50°C, or from 5°C to 40°C.

14. The method of any one of claims 1-13, wherein the gas permeable polymer comprises a polymer chosen from polyamides, polyimides, polypyrrol ones, polyesters, sulfone-based polymers, nitrile-based polymers, polymeric organosilicones, fluorinated polymers, polyolefins, copolymers thereof, and blends thereof.

15. The method of claim 14, wherein the gas permeable polymer comprises polyethersulfone or polysulfone.

16. The method of any one of claims 1-15, wherein the solvent comprises a polar solvent.

17. The method of any one of claims 1-16, wherein the solvent comprises / V-methyl-2- pyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), dimethylacetamide (DMAc), and combinations thereof.

18. The method of any one of claims 1-17, wherein the co-solvent comprises a C1-C8alcohol, a C1-C8diol, a C1-C8alkoxy alcohol, a C1-C8alkoxy diol, a phenyl alkoxy alcohol, or a combination thereof.

19. The method of any one of claims 1-18, wherein the co-solvent comprises a C3-C8alcohol, a C3-C8diol, a C3-C8alkoxy alcohol, a (b-Cs alkoxy diol, a phenyl alkoxy alcohol, or a combination thereof.

20. The method of any one of claims 1-19, wherein the co-solvent comprises 3-methoxy propanol.

21. The method of any one of claims 1-20, wherein the solvent comprises from 30% by weight to 65% by weight of the casting solution (e.g., from 35% by weight to 60% by weight of the casting solution), based on the total weight of the casting solution.

22. The method of any one of claims 1-21, wherein the co-solvent comprises from 20% by weight to 60% by weight of the casting solution (e.g., from 20% by weight to 55% by weight of the casting solution, or from 25% by weight to 45% by weight of the casting solution), based on the total weight of the casting solution.

23. The method of any one of claims 1-22, wherein the co-solvent and the solvent are present in the casting solution in weight ratio of from 0.25: 1 to 1.5: 1.

24. The method of any one of claims 1-23, wherein the porogen comprises from 0.1% by weight to 60% bv weight of the casting solution (e.g., from 5% bv weight to 60% bv weight of the casting solution), based on the total weight of the casting solution.

25. The method of any one of claims 1-24, wherein the porogen comprises a salt, such as LiCl.

26. The method of any one of claims 1-25, wherein the co-solvent also functions as a porogen.

27. The method of any one of claims 1-26, wherein the casting solution further comprises a viscosity enhancer.

28. The method of any one of claims 1-27, wherein the casting solution further comprises a hydrophilic additive, such as a hydrophilic polymer.

29. The method of claim 28, wherein the hydrophilic additive comprises polyvinylalcohol, polyvinyl acetate, polyethylene oxide, polyvinylpyrrolidone, polyacrylamine, a polyamine such as polyallylamine, polyvinyl amine, or polyethylenimine, polysiloxane, copolymers thereof, and blends thereof.

30. The method of any one of claims 1-29, wherein the gas permeable polymer comprises from 5% by weight to 35% by weight of the casting solution (e.g., from 10% by wei ght to 20% by weight of the casting solution ), based on the total weight of the casting solution.

31. The method of any one of claims 1-30, wherein the nanoporous polymer membrane has a thickness of less than 1 mm (e.g., less than 500 microns, less than 250 microns, less than 100 microns, or less than 50 microns).

32. The method of any one of claims 1-31, wherein the nanoporous polymer membrane exhibits an average pore size of from 15 nm to 60 nm,33. The method of any one of claims 1-32, wherein the nanoporous polymer membrane exhibits a surface porosity of from 15% to 40%.

34. A nanoporous polymer membrane prepared by the method of any one of claims I -33 .

35. A composite polymer membrane comprising: a support, layer comprising a nanoporous polymer membrane prepared by the method of any one of claims 1-33; and a selective polymer layer disposed on the support layer.

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