Multiphase low-energy co2 capture mediated by proton-coupled organic redox

Abstract

The invention provides systems and methods of use for multiphase amine based CO2 capture mediated by proton-coupled redox active species.

Description

[0001] PATENT

[0002] ATTORNEY DOCKET NO: 51198-064WO2

[0003] MULTIPHASE LOW-ENERGY CO2CAPTURE MEDIATED BY PROTON-COUPLED ORGANIC REDOX

[0004] BACKGROUND OF THE INVENTION

[0005] Carbon dioxide (CO2) constitutes the principal contributor to anthropogenic greenhouse forcing. Amines — including primary, secondary, and tertiary amines and their blends — have been adopted at industrial scale as CO2 absorbents in aqueous and non-aqueous systems. Despite their efficacy, regeneration of C02-loaded amines is conventionally achieved by thermal desorption at elevated temperatures (typically >100 °C). Such thermal cycles accelerate amine oxidative and thermal degradation, promote amine volatilization and solvent loss, increase maintenance and corrosion issues, and impose substantial energy penalties. The resulting parasitic energy consumption can erode the overall carbon benefit by increasing indirect emissions from the energy supply.

[0006] To mitigate associated climate impacts, there is a need for CO2 capture and release processes that are both operationally robust and economically efficient. Accordingly, there is a need for new methods and systems for amine based CO2 capture utilizing PCET.

[0007] SUMMARY OF THE INVENTION

[0008] The invention features systems for multiphase amine based CO2 capture mediated by proton- coupled redox active species. These systems can assist in capturing and releasing CO2 from gas streams containing O2 while protecting oxygen sensitive proton-coupled redox active species.

[0009] In one aspect, the invention provides a system including an electrochemical cell including a first region including at least one electrode, a first electrolyte; a second region including at least one electrode, a second aqueous electrolyte including a proton-coupled redox active species, an inlet and an outlet; and a membrane disposed between the first region and a second region; a mixing region including a first inlet, a second inlet, and an agitating element; a settling region, in fluidic communication with the mixing region, including a first outlet and a second outlet; and a capture tank including a first inlet, a first outlet, and a non-aqueous capture solution, wherein the non-aqueous capture solution includes a non-aqueous solvent immiscible with the second aqueous electrolyte and an amine; wherein the outlet of the second region is in fluidic communication with the first inlet of the mixing region; the first outlet of the capture tank is in fluidic communication with the second inlet of the mixing region; the first outlet of the settling region is in fluidic communication with the inlet of the second region; and the second outlet of the settling region is in fluidic communication with the first inlet of the capture tank.

[0010] In some embodiments, the first electrolyte of the system is a solid electrolyte. In some embodiments, the first electrolyte of the system is a first aqueous electrolyte, and the first region of the electrochemical cell further includes an inlet and an outlet. In some embodiments, the settling region includes a gas outlet. In some embodiments, the system further includes a container including an inlet and an outlet, and filled with the first aqueous electrolyte, wherein the outlet of the container is in fluidic communication with the inlet of the first region, and the inlet of the container is in fluidic communication with the outlet of the first region. PATENT

[0011] ATTORNEY DOCKET NO: 51198-064WO2

[0012] In another aspect, the invention provides a system including, an electrochemical cell including, a first region including at least one electrode, a first aqueous electrolyte, an inlet and an outlet, a second region including at least one electrode, the first aqueous electrolyte, an inlet and an outlet; and a membrane disposed between the first region and a second region; and a first mixing region including a first inlet, a second inlet, and a mixer; a first settling region, in fluidic communication with the first mixing region, including a first outlet and a second outlet; a second mixing region including a first inlet, a second inlet, and an agitating element; a second settling region, in fluidic communication with the second mixing region, including a first outlet and a second outlet; and a capture tank including a first inlet, a first outlet, and a non-aqueous capture solution, wherein the first electrolyte and the second electrolyte are the same and includes a proton-coupled redox active species; wherein the non-aqueous capture solution includes a non-aqueous solvent immiscible with the first aqueous electrolyte and an amine; wherein the outlet of the second region is in fluidic communication with the first inlet of the first mixing region; the first outlet of the first settling region is in fluidic communication with the inlet of the first region; the second outlet of the first settling region is in fluidic communication with the first inlet of the capture tank; the outlet of the first region is in fluidic communication with the first inlet of the second mixing region; the first outlet of the capture tank is in fluidic communication with the second inlet of the second mixing region; the first outlet of the second settling region is in fluidic communication with the inlet of the second region; and the second outlet of the second settling region is in fluidic communication with the second inlet of the first mixing region.

[0013] In some embodiments, the first and / or the second settling region includes a gas outlet.

[0014] In some embodiments, the membrane, of the systems disclosed herein, is a cation exchange membrane (CEM), an anion exchange membrane (AEM), a bipolar membrane (BPM), or a size-selective membrane.

[0015] In some embodiments, the systems disclosed herein further include a power supply attached to the at least one electrode of the first region and to the at least one electrode of the second region.

[0016] In some embodiments, the capture tank further includes a second inlet and a second outlet. In some embodiments, the capture tank further includes a bubbler to introduce a gas to the non-aqueous capture solution.

[0017] In some embodiments, the non-aqueous solvent is selected from an aromatic solvent, a chain alcohol, an alkyl phosphite, and an alkyl carbonate. In some embodiments, the non-aqueous solvent is n- pentanol. In some embodiments, the non-aqueous solvent is n-butanol.

[0018] In some embodiments, the amine has the formula N(R)sor an ion thereof, wherein each R is independently H; optionally substituted C1-6 alkyl; optionally substituted C3-10 carbocyclyl; optionally substituted C1-9 heterocyclyl having one to four heteroatoms independently selected from O, N, and S; optionally substituted C6-20 aryl; optionally substituted C1-9 heteroaryl having one to four heteroatoms independently selected from O, N, and S. In some embodiments, the amine is phenethylamine. In some embodiments, the amine is 1 -hexaneamine.

[0019] In some embodiments, the proton-coupled redox active species is selected from a water-soluble anthraquinone, viologen, naphthoquinone, phenazine, fluorenone, alloxazine, vanadium complex, chromium complex, or a derivative thereof. In some embodiments, the proton-coupled redox active PATENT

[0020] ATTORNEY DOCKET NO: 51198-064WO2

[0021] In some embodiments, the system further includes an oxygen scrubber disposed to remove dissolved oxygen from the non-aqueous capture solution.

[0022] In a related aspect, the invention provides a method for the capture and release of CO2 including, providing a gas source including CO2 to a non-aqueous capture solution including a non-aqueous solvent and an amine, wherein the amine reacts with the CO2, forming amine-CC>2 adducts; providing an aqueous electrolyte including a proton-coupled redox active species to an electrochemical cell and electrochemically oxidizing the proton-coupled redox active species, wherein the oxidation of the proton- coupled redox active species releases one or more protons and lowers the pH of the aqueous electrolyte; contacting the non-aqueous capture solution and the aqueous electrolyte in a mixing region, wherein the non-aqueous capture solution and the aqueous electrolyte are immiscible, wherein the amine-CC>2 adducts at a phase interface are cleaved, releasing CO2 and an ammonium; separating the non-aqueous capture solution and the aqueous electrolyte; transporting the aqueous electrolyte to an electrochemical cell and electrochemically reducing the proton-coupled redox active species, wherein the reduction of the proton-coupled redox active species takes up one or more protons and increases the pH of the aqueous electrolyte; and contacting the aqueous electrolyte with the non-aqueous capture solution, wherein the ammonium is deprotonated to form an amine in the non-aqueous capture solution.

[0023] In some embodiments, the method is carried out in a system disclosed herein.

[0024] In some embodiments, the proton-coupled redox active species has the structure embodiments, the proton-coupled redox active species has a solubility that is less than 0.0001 mol / L (e.g., about 0.0001 mol / L, about 0.00001 mol / L, or about 0.000001 mol / L) in the non-aqueous capture solution.

[0025] In some embodiments, the CO2 is introduced to the non-aqueous capture solution by a bubbler in contact with the non-aqueous capture solution.

[0026] In some embodiments, the amine-CC>2 adducts are carbamates or carbamic acids of the amine. PATENT

[0027] ATTORNEY DOCKET NO: 51198-064WO2

[0028] In some embodiments, the non-aqueous capture solution and the aqueous electrolyte are separated by gravity-driven separation, centrifugal separation, or filtration.

[0029] In some embodiments, the pH of the aqueous electrolyte increases to at least pH 11 (e.g., about pH 11 , about pH 12, about pH 13, or about pH 14).

[0030] In some embodiments, the ammonium generated is partially or fully soluble in the aqueous electrolyte.

[0031] In some embodiments, the ammonium in the aqueous electrolyte deprotonates to form an amine and partitions into the non-aqueous capture solution.

[0032] In some embodiments, the process of providing a gas source to a non-aqueous capture solution including an amine and forming an amine-CC>2 adduct, providing an aqueous electrolyte including a proton-couple redox active species to an electrochemical cell and electrochemically oxidizing the proton- coupled redox active species, lowering the pH, contacting the non-aqueous capture solution and the aqueous electrolyte to cause the amine-CC>2 adducts to cleave at the phase interface, releasing CO2 and ammonium, separating the non-aqueous capture solution and the aqueous electrolyte, transporting the aqueous electrolyte to an electrochemical cell and electrochemically reducing the proton-coupled redox active species to increase the pH of the aqueous electrolyte, and contacting the aqueous electrolyte with the non-aqueous capture solution to deprotonate the ammonium to form an anime in the non-aqueous capture solution is repeated at least 1 (e.g., at least 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13, 14, 15, 16, 17,

[0033] 18, 19, 20, 21 , 22, 23, 24, 25, 26, 27, 28, 29, 30, 31 , 32, 33, 34, 35, 36, 37, 38, 39, 40, 41 , 42, 43, 44, 45,

[0034] 46, 47, 48, 49, 50, 51 , 52, 53, 54, 55, 56, 57, 58, 59, 60, 61 , 62, 63, 64, 65, 66, 67, 68, 69, 70, 71 , 72, 73,

[0035] 74, 75, 76, 77, 78, 79, 80, 81 , 82, 83, 84, 85, 86, 87, 88, 89, 90, 91 , 92, 93, 94, 95, 96, 97, 98, 99, or 100) times.

[0036] In some embodiments, the process of providing a gas source to a non-aqueous capture solution including an amine and forming an amine-CC>2 adduct, providing an aqueous electrolyte including a proton-couple redox active species to an electrochemical cell and electrochemically oxidizing the proton- coupled redox active species, lowering the pH, contacting the non-aqueous capture solution and the aqueous electrolyte to cause the amine-CC>2 adducts to cleave at the phase interface, releasing CO2 and ammonium, separating the non-aqueous capture solution and the aqueous electrolyte, transporting the aqueous electrolyte to an electrochemical cell and electrochemically reducing the proton-coupled redox active species to increase the pH of the aqueous electrolyte, and contacting the aqueous electrolyte with the non-aqueous capture solution to deprotonate the ammonium to form an anime in the non-aqueous capture solution is performed in a continuous flow reactor.

[0037] DEFINITIONS

[0038] By “about” is meant a value that is ± 10% of a recited value.

[0039] By “amide” is meant -R(C=O)NR2, wherein each R is H or alkyl, provided R is alkyl, as defined herein.

[0040] By “amino” is meant - NH2. PATENT

[0041] ATTORNEY DOCKET NO: 51198-064WO2

[0042] By “alkoxy” is meant a group of formula -OR, where R is an alkyl group, as defined herein.

[0043] By “alkyl” is meant straight chain or branched saturated groups from 1 to 6 carbons. Alkyl groups are exemplified by methyl, ethyl, n- and iso-propyl, n-, sec-, iso- and tert-butyl, neopentyl, and the like, and may be optionally substituted with one or more substituents.

[0044] By “alkyl ester” is meant -COOR, where R is an alkyl group, as defined herein.

[0045] By “alkyl thiol” is meant -S-R, where R is an alkyl group, as defined herein.

[0046] By “aryl” is meant an aromatic cyclic group in which the ring atoms are all carbon and having from 6 to 14 ring atoms. Aryl groups may be monocyclic or multicyclic. Exemplary aryl groups include phenyl, naphthyl, and anthracenyl. Aryl groups may be optionally substituted with one or more substituents.

[0047] By “carbamates” is meant a R2NCOOR’, wherein each R is independently H, optionally substituted C1-6 alkyl, optionally substituted C3-10 carbocyclyl, optionally substituted C1-9 heterocyclyl having one to four heteroatoms independently selected from O, N, and S, optionally substituted C6-20 aryl, optionally substituted C1-9 heteroaryl having one to four heteroatoms independently selected from O, N, and S and R’ is optionally substituted C1-6 alkyl, optionally substituted C3-10 carbocyclyl, optionally substituted C1-9 heterocyclyl having one to four heteroatoms independently selected from O, N, and S, optionally substituted C6-20 aryl, optionally substituted C1-9 heteroaryl having one to four heteroatoms independently selected from O, N, and S.

[0048] By “carbamic acid” is meant R2NCOOH, wherein each R is independently H, optionally substituted C1-6 alkyl, optionally substituted C3-10 carbocyclyl, optionally substituted C1-9 heterocyclyl having one to four heteroatoms independently selected from O, N, and S, optionally substituted C6-20 aryl, or optionally substituted C1-9 heteroaryl having one to four heteroatoms independently selected from O, N, and S.

[0049] By “carbocyclyl” is meant a non-aromatic cyclic group in which the ring atoms are all carbon. Exemplary carbocyclyl groups include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. Carbocyclyl groups may be optionally substituted with one or more substituents.

[0050] By “carboxyl” is meant -COOH. An exemplary ion of carboxyl is -COO-.

[0051] By “halo” is meant fluoro, chloro, bromo, or iodo.

[0052] By “heteroaryl” is meant an aromatic cyclic group in which the ring atoms include at least one carbon and at least one O, N, or S atom, and having from 5 to 14 ring atoms. Heteroaryl groups may include 1 to 4 O, N, or S ring atoms in a single ring. Heteroaryl groups may be monocyclic or multicyclic, and, when multicyclic, one or more rings may include all carbon ring atoms. Exemplary heteroaryl groups include oxazolyl, isoxazolyl, tetrazolyl, pyridyl, thienyl, furyl, pyrrolyl, imidazolyl, pyrimidinyl, thiazolyl, indolyl, quinolinyl, isoquinolinyl, benzofuryl, benzothienyl, pyrazolyl, pyrazinyl, pyridazinyl, isothiazolyl, benzimidazolyl, benzothiazolyl, benzoxazolyl, oxadiazolyl, thiadiazolyl, and triazolyl. Heteroaryl groups may be optionally substituted with one or more substituents. PATENT

[0053] ATTORNEY DOCKET NO: 51198-064WO2

[0054] By “heterocyclyl” is meant a non-aromatic cyclic group in which the ring atoms include at least one carbon and at least one O, N, or S atom, provided that at least three ring atoms are present. Exemplary heterocyclyl groups include epoxide, thiiranyl, aziridinyl, azetidinyl, thietanyl, dioxetanyl, morpholinyl, thiomorpholinyl, piperazinyl, piperidinyl, pyrrolidinyl, tetrahydropyranyl, tetrahydrofuranyl, dihydrofuranyl, tetrahydrothienyl, dihydrothienyl, dihydroindolyl, tetrahydroquinolyl, tetrahydroisoquinolyl, pyranyl, pyrazolinyl, pyrazolidinyl, dihydropyranyl, tetrahydroquinolyl, imidazolinyl, imidazolidinyl, pyrrolinyl, oxazolidinyl, isoxazolidinyl, thiazolidinyl, isothiazolidinyl, dithiazolyl, and 1 ,3-dioxanyl. Heterocyclyl groups may be optionally substituted with one or more substituents.

[0055] By “hydroxyl” is meant -OH. An exemplary ion of hydroxyl is -O-.

[0056] By “immiscible” is meant that in the absence of agitation, the components separate, forming distinct and identifiable layers.

[0057] By “in fluidic communication with” or “in fluidic communication,” is meant a connection between at least two physical elements, e.g., a channel, reservoir, inlet, outlet, etc., that allows for fluid to move between such device elements with or without passing through one or more intervening device elements. Fluid movement may be intermittently halted by one or more valves.

[0058] By “nitro” is meant -NO2.

[0059] By “nitrogen protecting group” is meant those groups intended to protect an amino group against undesirable reactions during synthetic procedures. Commonly used nitrogen protecting groups are disclosed in Greene, “Protective Groups in Organic Synthesis,” 3rdEdition (John Wiley & Sons, New York, 1999), which is incorporated herein by reference. Nitrogen protecting groups include acyl, aryloyl, or carbamyl groups such as formyl, acetyl, propionyl, pivaloyl, t-butylacetyl, 2-chloroacetyl, 2-bromoacetyl, trifluoroacetyl, trichloroacetyl, phthalyl, o-nitrophenoxyacetyl, a-chlorobutyryl, benzoyl, 4-chlorobenzoyl, 4-bromobenzoyl, 4-nitrobenzoyl, and amino acids such as alanine, leucine, and phenylalanine; sulfonyl- containing groups such as benzenesulfonyl, and p-toluenesulfonyl; carbamate forming groups such as benzyloxycarbonyl, p-chlorobenzyloxycarbonyl, p-methoxybenzyloxycarbonyl, p-nitrobenzyloxycarbonyl, 2-nitrobenzyloxycarbonyl, p-bromobenzyloxycarbonyl, 3,4-dimethoxybenzyloxycarbonyl, 3,5-dimethoxybenzyloxycarbonyl, 2,4-dimethoxybenzyloxycarbonyl, 4-methoxybenzyloxycarbonyl, 2-nitro-4,5-dimethoxybenzyloxycarbonyl, 3,4,5-trimethoxybenzyloxycarbonyl, 1 -(p-biph e ny ly I)- 1 - methylethoxycarbonyl, a,a-dimethyl-3,5-dimethoxybenzyloxycarbonyl, benzhydryloxy carbonyl, t-butyloxycarbonyl, diisopropylmethoxycarbonyl, isopropyloxycarbonyl, ethoxycarbonyl, methoxycarbonyl, allyloxycarbonyl, 2, 2, 2, -trichloroethoxycarbonyl, phenoxycarbonyl, 4-nitrophenoxy carbonyl, fluorenyl-9- methoxycarbonyl, cyclopentyloxycarbonyl, adamantyloxycarbonyl, cyclohexyloxycarbonyl, and phenylthiocarbonyl, alkaryl groups such as benzyl, triphenylmethyl, and benzyloxymethyl, and silyl groups, such as trimethylsilyl. Preferred nitrogen protecting groups are alloc, formyl, acetyl, benzoyl, pivaloyl, t-butylacetyl, alanyl, phenylsulfonyl, benzyl, t-butyloxycarbonyl (Boc), and benzyloxycarbonyl (Cbz).

[0060] By “nitrile” is meant -CEN. PATENT

[0061] ATTORNEY DOCKET NO: 51198-064WO2

[0062] By “oxo” is meant =O.

[0063] By “oxygen protecting group” is meant those groups intended to protect an oxygen containing (e.g., phenol, hydroxyl, or carbonyl) group against undesirable reactions during synthetic procedures. Commonly used oxygen protecting groups are disclosed in Greene, “Protective Groups in Organic Synthesis,” 3rd Edition (John Wiley & Sons, New York, 1999), which is incorporated herein by reference. Exemplary oxygen protecting groups include acyl, aryloyl, or carbamyl groups, such as formyl, acetyl, propionyl, pivaloyl, t-butylacetyl, 2-chloroacetyl, 2-bromoacetyl, trifluoroacetyl, trichloroacetyl, phthalyl, o- nitrophenoxyacetyl, a-chlorobutyryl, benzoyl, 4-chlorobenzoyl, 4-bromobenzoyl, t-butyldimethylsilyl, tri- iso-propylsilyloxymethyl, 4,4'-dimethoxytrityl, isobutyryl, phenoxyacetyl, 4-isopropylpehenoxyacetyl, dimethylformamidino, and 4-nitrobenzoyl; alkylcarbonyl groups, such as acyl, acetyl, propionyl, and pivaloyl; optionally substituted arylcarbonyl groups, such as benzoyl; silyl groups, such as trimethylsilyl (TMS), tert-butyldimethylsilyl (TBDMS), tri-iso-propylsilyloxymethyl (TOM), and triisopropylsilyl (TIPS); ether-forming groups with the hydroxyl, such methyl, methoxymethyl, tetrahydropyranyl, benzyl, p- methoxybenzyl, and trityl; alkoxycarbonyls, such as methoxycarbonyl, ethoxycarbonyl, isopropoxycarbonyl, n-isopropoxycarbonyl, n-butyloxycarbonyl, isobutyloxycarbonyl, secbutyloxycarbonyl, t-butyloxycarbonyl, 2-ethylhexyloxycarbonyl, cyclohexyloxycarbonyl, and methyloxycarbonyl; alkoxyalkoxycarbonyl groups, such as methoxymethoxycarbonyl, ethoxymethoxycarbonyl, 2-methoxyethoxycarbonyl, 2-ethoxyethoxycarbonyl, 2-butoxyethoxycarbonyl, 2- methoxyethoxymethoxycarbonyl, allyloxycarbonyl, propargyloxycarbonyl, 2-butenoxycarbonyl, and 3- methyl-2-butenoxycarbonyl; haloalkoxycarbonyls, such as 2-chloroethoxycarbonyl, 2- chloroethoxycarbonyl, and 2,2,2-trichloroethoxycarbonyl; optionally substituted arylalkoxycarbonyl groups, such as benzyloxycarbonyl, p-methylbenzyloxycarbonyl, p-methoxybenzyloxycarbonyl, p- nitrobenzyloxycarbonyl, 2,4-dinitrobenzyloxycarbonyl, 3,5-dimethylbenzyloxycarbonyl, p- chlorobenzyloxycarbonyl, p-bromobenzyloxy-carbonyl, and fluorenylmethyloxycarbonyl; and optionally substituted aryloxycarbonyl groups, such as phenoxycarbonyl, p-nitrophenoxycarbonyl, o- nitrophenoxycarbonyl, 2,4-dinitrophenoxycarbonyl, p-methyl-phenoxycarbonyl, m- methylphenoxycarbonyl, o-bromophenoxycarbonyl, 3,5-dimethylphenoxycarbonyl, p- chlorophenoxycarbonyl, and 2-chloro-4-nitrophenoxy-carbonyl); substituted alkyl, aryl, and alkaryl ethers (e.g., trityl; methylthiomethyl; methoxymethyl; benzyloxymethyl; siloxymethyl; 2,2,2,- trichloroethoxymethyl; tetrahydropyranyl; tetrahydrofuranyl; ethoxyethyl; 1-[2-(trimethylsilyl)ethoxy]ethyl; 2-trimethylsilylethyl; t-butyl ether; p-chlorophenyl, p-methoxyphenyl, p-nitrophenyl, benzyl, p- methoxybenzyl, and nitrobenzyl); silyl ethers (e.g., trimethylsilyl; triethylsilyl; triisopropylsilyl; dimethylisopropylsilyl; t-butyldimethylsilyl; t-butyld iphenylsilyl; tribenzylsilyl; triphenylsilyl; and diphenymethylsilyl); carbonates (e.g., methyl, methoxymethyl, 9-fluorenylmethyl; ethyl; 2,2,2- trichloroethyl; 2-(trimethylsilyl)ethyl; vinyl, allyl, nitrophenyl; benzyl; methoxybenzyl; 3,4-dimethoxybenzyl; and nitrobenzyl); carbonyl-protecting groups (e.g., acetal and ketal groups, such as dimethyl acetal, and 1 ,3-dioxolane; acylal groups; and dithiane groups, such as 1 ,3-dithianes, and 1 ,3-dithiolane); carboxylic acid-protecting groups (e.g., ester groups, such as methyl ester, benzyl ester, t-butyl ester, and orthoesters; and oxazoline groups. PATENT

[0064] ATTORNEY DOCKET NO: 51198-064WO2

[0065] By “phosphoryl” is meant -PO3H2. Exemplary ions of phosphoryl are -POsHT and -POs2-.

[0066] By “phosphonyl” is meant -PO3R2, wherein each R is H or alkyl, provided at least one R is alkyl, as defined herein. An exemplary ion of phosphonyl is -POsR-.

[0067] As used herein, a species is “soluble” if it dissolves in the solvent with a solubility of at least 0.0001 mol / L. For examples, a species has low solubility if it dissolves in the solvent of interest with a solubility of less than 0.0001 mol / L.

[0068] By “sulfonyl” is meant - SO2R, where R is hydroxyl, alkyl, aryl, or heteroaryl.

[0069] By “thiol” is meant -SH.

[0070] As noted, substituents may be optionally substituted with halo, optionally substituted C3-10 carbocyclyl; optionally substituted C1-9 heterocyclyl having one to four heteroatoms independently selected from O, N, and S; optionally substituted C6-20 aryl; optionally substituted C1-9 heteroaryl having one to four heteroatoms independently selected from O, N, and S; -CN; -NO2; -ORa; -N(Ra)2; -C(=O)Ra; - C(=O)ORa; -S(=O)2Ra; -S(=O)2ORa; -P(=O)Ra2; -O-P(=O)(ORa)2, or -P(=0)(ORa)2, or an ion thereof; wherein each Rais independently H, C1-6 alkyl; optionally substituted C3-10 carbocyclyl; optionally substituted C1-9 heterocyclyl having one to four heteroatoms independently selected from O, N, and S; optionally substituted C6-20 aryl; optionally substituted C1-9 heteroaryl having one to four heteroatoms independently selected from O, N, and S; an oxygen protecting group; or a nitrogen protecting group. Cyclic substituents may also be substituted with C1-6 alkyl. In specific embodiments of alloxazines, substituents may include optionally substituted with halo, optionally substituted C3-10 carbocyclyl; optionally substituted C1-9 heterocyclyl having one to four heteroatoms independently selected from O, N, and S; optionally substituted C6-20 aryl; optionally substituted C1-9 heteroaryl having one to four heteroatoms independently selected from O, N, and S; -NO2; -ORa; -N(Ra)2; -C(=O)Ra; -C(=O)ORa; - S(=O)2Ra; -S(=O)2ORa; -P(=O)Ra2; -O-P(=O)(ORa)2, or -P(=O)(ORa)2, or an ion thereof; wherein each Rais independently H, C1-6 alkyl; optionally substituted C3-10 carbocyclyl; optionally substituted C1-9 heterocyclyl having one to four heteroatoms independently selected from O, N, and S; optionally substituted C6-20 aryl; optionally substituted C1-9 heteroaryl having one to four heteroatoms independently selected from O, N, and S; an oxygen protecting group; or a nitrogen protecting group, and cyclic substituents may also be substituted with C1-6 alkyl. In specific embodiments of quinones, alkyl groups may be optionally substituted with one, two, three, or, in the case of alkyl groups of two carbons or more, four substituents independently selected from the group consisting of halo, hydroxyl, C1-6 alkoxy, SO3H, amino, nitro, carboxyl, phosphoryl, phosphonyl, thiol, C1-6 alkyl ester, optionally substituted C1-6 alkyl thiol, and oxo, or an ion thereof.

[0071] BRIEF DESCRIPTION OF THE DRAWINGS

[0072] FIG. 1 is a graph demonstrating the change in the readout of the CO2 partial pressure for a setup utilizing non-PCET pH modulated capture and release of CO2. PATENT

[0073] ATTORNEY DOCKET NO: 51198-064WO2

[0074] FIG. 2A is a graph demonstrating the pH change in the system during PCET modulated reduction, ammonium deprotonation, PCET modulated oxidation, and CO2 release.

[0075] FIG. 2B is a graph demonstrating the change in the readout of the CO2 partial pressure for a setup utilizing PCET pH modulation for capture and release of CO2.

[0076] FIG. 3 is a scheme of a system of the present invention, depicting the electrochemical cell, mixing region, settling region, and capture tank, as well as their various components.

[0077] FIG. 4 is a scheme of a system of the present invention, depicting the electrochemical cell including a solid electrolyte, mixing region, settling region, and capture tank, as well as their various components.

[0078] FIG. 5 is a scheme of a continuous flow system of the present invention, depicting the electrochemical cell, first mixing region, first settling region, second mixing region, second settling region, and capture tank, as well as their various components.

[0079] DETAILED DESCRIPTION

[0080] The present disclosure provides, inter alia, a system and a method of use of the system, e.g., for CO2 capture and release. The replacement of thermochemical regeneration with electrochemical processes reduces energy demand and avoids extreme operating conditions. Electrochemical pH-swing CO2 capture may replace thermochemical regeneration. In such systems, proton-coupled electron transfer (PCET) molecules generate controlled alkaline or acidic environments in aqueous solution to reversibly capture and release CO2. However, the limited oxygen stability of reduced PCET molecules limits implementation.

[0081] The invention employes an electrochemically mediated biphasic system for C02 capture and release from oxygen containing gas streams, employing PCET mediated pH swings in an aqueous phase, and an amine mediated CO2 capture and release process in a non-aqueous phase. The process leverages efficient PCET molecules (e.g., anthraquinones) to create a tunable pH swing in the aqueous phase, shifting between neutral-alkaline and neutral-acidic conditions. These controlled environments drive the reversible utilization of amine sorbents. Specifically, ammonium species are deprotonated to free amines under alkaline conditions, enabling CO2 absorption. Subsequent PCET-driven acidification protonates the amines back to ammonium form, triggering CO2 release.

[0082] Phase separation during gas contact ensures that oxygen does not directly interact with the PCET molecules, thereby resolving prior cycling stability issues. The system can be implemented in a continuous flow configuration, allowing repeated CO2 capture and release cycles with high efficiency.

[0083] It is further appreciated that certain features of the present disclosure, which are, for clarity, described in the context of separate embodiments, can also be provided in combination in a single embodiment. Conversely, various features of the present disclosure which are, for brevity, described in the context of a single embodiment, can also be provided separately or in any suitable subcombination. PATENT

[0084] ATTORNEY DOCKET NO: 51198-064WO2

[0085] Systems

[0086] Systems of the present invention (e.g., 1000) may include an electrochemical cell (e.g., 1100) including a first region (e.g.,1110) including at least one electrode (e.g., 1111), a first electrolyte (e.g., 1112), an inlet (e.g., 1113), and an outlet (e.g., 1114), a second region (e.g., 1120), including at least one electrode (e.g., 1121), a second aqueous electrolyte (e.g., 1122), an inlet (e.g., 1123), and an outlet (e.g., 1124), a membrane (e.g., 1130) disposed between the first region (e.g., 1110) and the second region (e.g. ,1120), and a container (e.g., 1140) including an inlet (e.g., 1141) and an outlet (e.g., 1142) and including the first aqueous electrolyte (e.g., 1112). The system further includes a mixing region (e.g., 1200) including a first inlet (e.g., 1201) and a second inlet (e.g., 1202) in fluidic communication with the settling region (e.g., 1300) including a first outlet (e.g., 1301) and a second outlet (e.g., 1302). The mixing region may also include an agitating element (e.g., 1203). Furthermore, the system includes a capture tank (e.g., 1400) including a first inlet (e.g., 1401), a first outlet (e.g., 1402), and a non-aqueous capture solution (e.g., 1403). In some embodiments, the system of the present invention further comprises a power supply (e.g., 1150) connected to at least one electrode of the first region (e.g., 1111) and to at least one electrode of the second region (e.g., 1121). An embodiment of the system of the present invention is shown in FIG. 3

[0087] In some embodiments, systems of the present invention (e.g., 2000) include an electrochemical cell (e.g., 2100) including a first region (e.g., 2110) including at least one electrode (e.g., 2111), and a first electrolyte (e.g., 2112), a second region (e.g., 2120), including at least one electrode (e.g., 2121), a second electrolyte (e.g., 2122), an inlet (e.g., 2123), and an outlet (e.g., 2124), and a membrane (e.g., 2130) disposed between the first region (e.g., 2110) and the second region (e.g., 2120). The system further includes a mixing region (e.g., 2200) including a first inlet (e.g., 2201) and a second inlet (e.g., 2202) in fluidic communication with the settling region (e.g., 2300) including a first outlet (e.g., 2301) and a second outlet (e.g., 2302). The mixing region may also include an agitating element (e.g., 2203). Furthermore, the system includes a capture tank (e.g., 2400) including a first inlet (e.g., 2401), a first outlet (e.g., 2402), and a non-aqueous capture solution (e.g., 2403). In some embodiments, the first electrolyte (e.g., 2112) is a solid electrolyte. In some embodiments, the second electrolyte (e.g., 2122) is an aqueous electrolyte (e.g., second aqueous electrolyte). In some embodiments, the system of the present invention further comprises a power supply (e.g., 2150) connected to at least one electrode of the first region (e.g., 2111) and to at least one electrode of the second region (e.g., 2121). An embodiment of the system of the present invention is shown in FIG. 4.

[0088] In some embodiments, the capture tank (e.g., 1400 or 2400) of the system (e.g., 1000 or 2000) includes a second inlet (e.g., 1404 or 2404) and a second outlet (e.g., 1405 or 2405). In some embodiments, the outlet (e.g., 1124 or 2124) of the second region (e.g., 1120 or 2120) of the electrochemical cell (e.g., 1100 or 2100) is in fluidic communication with the first inlet (e.g., 1201 or 2201) of the mixing region (e.g., 1200 or 2200). In some embodiments, the first outlet (e.g., 1402 or 2402) of the capture tank (e.g., 1400 or 2400) is in fluidic communication with the second inlet (e.g., 1202 or 2202) of the mixing region (e.g., 1200 or 2200). In some embodiments, the first outlet (e.g., 1301 or 2301) of the settling region (e.g., 1300 or 2300) is in fluidic communication with the inlet (e.g., 1123 or 2123) of the PATENT

[0089] ATTORNEY DOCKET NO: 51198-064WO2 second region (e.g., 1120 or 2120) of the electrochemical cell (e.g., 1100 or 2100). In some embodiments, the second outlet (e.g., 1302 or 2302) of the settling region (e.g., 1300 or 2300) is in fluidic communication with the first inlet (e.g., 1401 or 2401) of the capture tank (e.g., 1400 or 2400). In some embodiments, the first outlet (e.g., 1301 or 2301) of the settling region (e.g., 1300 or 2300) is located higher than the second outlet (e.g., 1302 or 2302) of the settling region. In some embodiments, the second outlet (e.g., 1302 or 2302) of the settling region (e.g., 1300 or 2300) is located higher than the first outlet (e.g., 1301 or 2301) of the settling region. In some embodiments, the inlet (e.g., 1141 or 2141) of the container (e.g., 1141 or 2141) of the electrochemical cell is in fluidic communication with the outlet (e.g., 1114 or 2114) of the first region (e.g., 1110 or 2110) and the outlet (e.g., 1142 or 2142) of the container is in fluidic communication with the inlet (e.g., 1113 or 2113) of the first region (e.g., 1110 or 2110).

[0090] In some embodiments, systems of the present invention (e.g., 3000) are configured to run continuously and may include an electrochemical cell (e.g., 3100) including a first region (e.g., 3110) including at least one electrode (e.g., 3111), an aqueous electrolyte (e.g., 3112), an inlet (e.g., 3113), and an outlet (e.g., 3114), a second region (e.g., 3120) including at least one electrode (e.g., 3121), the aqueous electrolyte (e.g., 3112), an inlet (e.g., 3123), and an outlet (e.g., 3124), and a membrane (e.g., 3130) disposed between the first region (e.g., 3110) and the second region (e.g., 3120). The system further includes a first mixing region (e.g., 3200) including a first inlet (e.g., 3201) and a second inlet (e.g., 3202) in fluidic communication with a first settling region (e.g., 3300) including a first outlet (e.g., 3301) and a second outlet (e.g., 3302). The system further includes a second mixing region (e.g., 3500) including a first inlet (e.g., 3501) and a second inlet (e.g., 3502) in fluidic communication with a second settling region (e.g., 3600) including a first outlet (e.g., 3601) and a second outlet (e.g., 3602). The first and / or second mixing region may also include an agitating element (e.g., 3203 or 3503). Furthermore, the system includes a capture tank (e.g., 3400) including a first inlet (e.g., 3401), a first outlet (e.g., 3402), and a non-aqueous capture solution (e.g., 3403). In some embodiments, redox active species in the aqueous electrolyte (e.g., 3112) are in different redox states in different regions of the system. In some embodiments, the system of the present invention further comprises a power supply (e.g., 3150) connected to at least one electrode of the first region (e.g., 3111) and to at least one electrode of the second region (e.g., 3121). An embodiment of the system of the present invention is shown in FIG. 5.

[0091] In some embodiments, the capture tank (e.g., 3400) of the system (e.g., 3000) includes a second inlet (e.g., 3404) and a second outlet (e.g., 3405). In some embodiments, the outlet (e.g., 3124) of the second region (e.g., 3120) of the electrochemical cell (e.g., 3100) is in fluidic communication with the first inlet (e.g., 3201) of the first mixing region (e.g., 3200). In some embodiments, the first outlet (e.g., 3301) of the first settling region (e.g., 3300) is in fluidic communication with the inlet (e.g., 3113) of the first region (e.g., 3110) of the electrochemical cell (e.g., 3100). In some embodiments, the outlet (e.g., 3114) of the first region (e.g., 3110) of the electrochemical cell (e.g., 3100) is in fluidic communication with the first inlet (e.g., 3501) of the second mixing region (e.g., 3500). In some embodiments, the first outlet (e.g., 3601) of the second settling region (e.g., 3600) is in fluidic communication with the inlet (e.g., 3123) of the second region (e.g., 3120) of the electrochemical cell (e.g., 3100). In some embodiments, the second outlet (e.g., 3602) of the second settling region (e.g., 3600) is in fluidic communication with the second PATENT

[0092] ATTORNEY DOCKET NO: 51198-064WO2 inlet (e.g., 3202) of the first mixing region (e.g., 3200). In some embodiments, the second outlet (e.g., 3302) of the first settling region (e.g., 3300) is in fluidic communication with the first inlet (e.g., 3401) of the capture tank (e.g., 3400). In some embodiments, the first outlet (e.g., 3402) of the capture tank (e.g., 3400) is in fluidic communication with the second inlet (e.g., 3502) of the second mixing region (e.g., 3500). In some embodiments, the first outlet (e.g., 3301) of the first settling region (e.g., 3300) is located higher than the second outlet (e.g., 3302) of the first settling region. In some embodiments, the second outlet (e.g., 3302) of the first settling region (e.g., 3300) is located higher than the first outlet (e.g., 3301) of the settling region. In some embodiments, the first outlet (e.g., 3601) of the second settling region (e.g., 3600) is located higher than the second outlet (e.g., 3602) of the second settling region. In some embodiments, the second outlet (e.g., 3602) of the second settling region (e.g., 3600) is located higher than the first outlet (e.g., 3301) of the second settling region.

[0093] In some embodiments, the first aqueous electrolyte (e.g., 1112 or 3112) and / or the second aqueous electrolyte (e.g., 1122 or 2122) of the system (e.g., 1000, 2000, or 3000) includes a proton- coupled redox active species. In some embodiments, the proton-coupled redox active species is present in aqueous solution from about 1 mM to about 10M, (e.g., from 1 mM to 10 M, 2 mM to 10 M, 3 mM to 10 M, 4 mM to 10 M, 5 mM to 10 M, 10 mM to 10 M, 15 mM to 10 M, 20 mM to 10 M, 30 mM to 10 M, 40 mM to 10 M, 50 mM to 10 M, 100 mM to 10 M, 150 mM to 10 M, 200 mM to 10 M, 300 mM to 10 M, 400 mM to 10 M, 500 mM to 10 M, 1 M to 10 M, 1.5 M to 10 M, 2 M to 10 M, 3 M to 10 M, 4 M to 10 M, 5 M to 10 M, 1 mM to 5 M, 2 mM to 4 M, 3 mM to 3 M, 4 mM to 2 M, 5 mM to 1 .5 M, 10 mM to 1 M, 15 mM to 500 mM, 20 mM to 400 mM, 30 mM to 300 mM, 40 mM to 200 mM, or 50 mM to 150 mM, e.g., about 1 mM, about 2 mM, about 3 mM, about 4 mM, about 5 mM, about 10 mM, about 15 mM, about 20 mM, about 30 mM, about 40 mM, about 50 mM, about 100 mM, about 150 mM, about 200 mM, about 300 mM, about 400 mM, about 500 mM, about 1 M, about 1 .5 M, about 2 M, about 3 M, about 4 M, about 5 M, or about 10 M).

[0094] In some embodiments, the capture tank is open to ambient air. In some embodiments, the capture tank (e.g., 1400, 2400, or 3400) includes one or more (e.g., one, two, three, etc.) gas inlets (e.g., 1404, 2404, or 3404) and one or more (e.g., one, two, three, etc.) gas outlets (e.g., 1405, 2405, or 3405). In some embodiments, the one or more gas inlets (e.g., 1404, 2404, or 3404) of the capture tank (e.g., 1400, 2400, or 3400) are connected to a source of gas including CO2 (e.g., atmospheric air or flue gas). In some embodiments, the one or more gas outlets (e.g., 1405, 2405, or 3405) are connected to a storage container to store released CO2.

[0095] In some embodiments, the first and / or second settling region (e.g., 1300, 2300, 3300, or 3500) may include a gas outlet (e.g., 1303, 2303, or 3503) configured to release CO2 from the system. In some embodiments, the gas outlet of the settling region is connected to a storage container to store released CO2.

[0096] In some embodiments, the non-aqueous capture solution is immiscible with the second aqueous electrolyte. In some embodiments, the non-aqueous capture solution includes aromatic solvents, chain alcohols, alkyl phosphites, and alkyl carbonates. In some embodiments, the solvent of the non-aqueous PATENT

[0097] ATTORNEY DOCKET NO: 51198-064WO2 capture solution is n-pentanol. In some embodiments, the solvent of the non-aqueous capture solution is n-butanol.

[0098] In some embodiments, the non-aqueous capture solution includes an amine having the formula N(R)3, wherein each R is independently H, optionally substituted C1-6 alkyl, optionally substituted C3-10 carbocyclyl, optionally substituted C1-9 heterocyclyl having one to four heteroatoms independently selected from O, N, and S, optionally substituted C6-20 aryl, or optionally substituted C1-9 heteroaryl having one to four heteroatoms independently selected from O, N, and S. In some embodiments, at least one (e.g., 1 or 2) R is H. In some embodiments, the amine is a mono-, di-, or tri- C1-6 alkyl amine. In some embodiments, the amine is a mono-, di-, or tri- C6-20 aryl substituted C1-6 alkyl amine In some embodiments, the non-aqueous capture solution includes a phenethylamine. In some embodiments, the non-aqueous capture solution includes 1 -hexaneamine. In some embodiments, the amine is present in the non-aqueous capture solution from about 1 mM to about 10M, (e.g., from 1 mM to 10 M, 2 mM to 10 M, 3 mM to 10 M, 4 mM to 10 M, 5 mM to 10 M, 10 mM to 10 M, 15 mM to 10 M, 20 mM to 10 M, 30 mM to 10 M, 40 mM to 10 M, 50 mM to 10 M, 100 mM to 10 M, 150 mM to 10 M, 200 mM to 10 M, 300 mM to 10 M, 400 mM to 10 M, 500 mM to 10 M, 1 M to 10 M, 1.5 M to 10 M, 2 M to 10 M, 3 M to 10 M, 4 M to 10 M, 5 M to 10 M, 1 mM to 5 M, 2 mM to 4 M, 3 mM to 3 M, 4 mM to 2 M, 5 mM to 1 .5 M, 10 mM to 1 M, 15 mM to 500 mM, 20 mM to 400 mM, 30 mM to 300 mM, 40 mM to 200 mM, or 50 mM to 150 mM, e.g., about 1 mM, about 2 mM, about 3 mM, about 4 mM, about 5 mM, about 10 mM, about 15 mM, about 20 mM, about 30 mM, about 40 mM, about 50 mM, about 100 mM, about 150 mM, about 200 mM, about 300 mM, about 400 mM, about 500 mM, about 1 M, about 1 .5 M, about 2 M, about 3 M, about 4 M, about 5 M, or about 10 M). Mixtures of amines may also be employed.

[0099] In some embodiments, the mixing region includes an agitating element that agitates the second aqueous electrolyte with the non-aqueous capture solution. Agitating elements include shakers, sonicators, stirrers, and mixers. In some embodiments, the agitating element is a mixer (e.g., 1203, 2203, 3203, or 3503).

[0100] In some embodiments, the second aqueous electrolyte and the non-aqueous capture solution separate in the settling region to form distinct layers. In some embodiments, the non-aqueous capture solution is the higher positioned, lower-density layer. In some embodiments, the non-aqueous solution is the lower positioned, higher-density layer.

[0101] In some embodiments, the mixing region and the settling region are the same. In some embodiments, the mixing region transitions into the settling region by removing agitation (e.g., turning off) from the mixing region.

[0102] In some embodiments, the system includes an oxygen scrubber to remove dissolved oxygen from the non-aqueous capture solution. In some embodiments, the system (e.g., 1000, 2000, or 3000) includes an oxygen scrubber at the first outlet (e.g., 1402, 2402, or 3402) of the capture tank (e.g., 1400, 2400, or 3400), configured to remove dissolved oxygen in the non-aqueous capture solution (e.g., 1403, 2403, or 3403). In some embodiments, the system (e.g., 1000, 2000, or 3000) includes an oxygen scrubber at the second inlet (e.g., 1202, 2202, or 3502) of the mixing region (e.g., 1300, 2300, or 3500), configured to remove dissolved oxygen in the non-aqueous capture solution (e.g., 1403, 2403, or 3403). In some PATENT

[0103] ATTORNEY DOCKET NO: 51198-064WO2 embodiments, the system (e.g., 1000, 2000, or 3000) includes an oxygen scrubber located between the first outlet (e.g., 1402, 2402, or 3402) of the capture tank (e.g., 1400, 2400, or 3400) and the second inlet (e.g., 1202, 2202, or 3502) of the mixing region (e.g., 1300, 2300, or 3500).

[0104] In some embodiments, the membrane of the system may be a cation exchange membrane (CEM), an anion exchange membrane (AEM), a bipolar membrane (BPM, e.g., including a CEM and an AEM), or a size-selective membrane. Standard CEM, AEM, BPM, and size-selective membranes are known in the art.

[0105] The systems of the invention may further include one or more pumps, connected to the inlet of the capture tank, to disperse the gas throughout the non-aqueous capture solution. Suitable pumps are known in the art. The systems may also contain dispersive elements, such as a bubbler or frit, connected to the inlet of the capture tank, to disperse the gas into solution. The systems may also include a storage container connected to the outlet of the capture tank, to store released CO2. The systems of the invention may also include components to assist in transporting the liquids and gases, e.g., pumps, magnetic stirrers, mixers, etc. Suitable pumps and stirrers are known in the art.

[0106] Redox Active Species

[0107] The present invention includes proton-coupled redox active species to mediate the capture and release of CO2. Exemplary proton-coupled redox active species for use in the invention are water-soluble quinones, anthraquinones, viologens, naphthoquinones, phenazines, fluorenones, alloxazines, isoalloxazines, polyoxometalates, vanadium complexes, chromium complexes, and their reduced counterparts, or derivatives thereof. The ability of phenazines, quinones, and anthraquinones to both accept and release at least one proton at modest electrical potentials makes them ideal candidates for creating pH “swings” in an aqueous solution. The pH-dependence of the redox potentials of the species can be used with the Nernst equation to estimate the amount of electrical energy, e.g., work, required to drive the redox of amine containing compounds to drive the CO2 capture and release cycles. In certain embodiments, the proton-coupled redox active species has a pKaof at least 7, at least 8, at least 9, at least 10, at least 11 , at least 12, at least 13 or at least 14.

[0108] The proton-coupled redox active species may be reduced in an electrochemical cell. Suitable proton-coupled redox active species include organic redox active species (e.g., anthraquinones, phenazines, phenoxazines, diquaternized bipyridines, naphthoquinones, fluorenones, and redox states thereof (e.g., one or two electron reduced states)), inorganic redox active species such as chromium, ruthenium, zinc, manganese, iron (e.g., ferrocene), or vanadium, e.g., V2+, V3+, and metalorganic redox active species such as CrPDTA (chromium 1 ,3-propylenediaminetetraacetate). Derivatives of suitable redox active species may include substitution groups to increase or decrease water solubility. Redox cores include, but are not limited to, para or ortho benzoquinone, naphthoquinone, anthraquinone, phenanthrenequinone, fluorenone, benzophenone, anthrone, xanthone, thioxanthone, acridone, phenazine, viologen, alloxazine, isoalloxazine, azobenzene, phthalimide, phenothiazine, naphthalimide, pyromellitic diimide, 1 ,4,5,8-naphthalenetetracarbodiimide, or benzo(c)cinnoline. PATENT

[0109] ATTORNEY DOCKET NO: 51198-064WO2

[0110] In some embodiments, suitable proton-coupled redox active species include an anthraquinone or a redox state thereof (e.g., a single or two electron reduced state). In some embodiments, the redox state of the anthraquinone is of formula (la). (la), or a salt or tautomer thereof. In some embodiments, the redox state of the anthraquinone is an anthrahydroquinone, e.g., an anthrahydroquinone of formula (lb) tautomer thereof. In some embodiments, both X are H. In some embodiments, both X are absent (i.e., both O are negatively charged). In some embodiments, one X is H, and one X is absent. In some embodiments, the redox state of the anthraquinone is an anthrahydroquinone, e.g., an anthrahydroquinone of formula (Ic) wherein X is H or absent or a salt or tautomer thereof.

[0111] In some embodiments, a suitable redox active species is the reduced form of an anthraquinone, a hydroquinone, e.g., a hydroquinone of formula (Id) PATENT

[0112] ATTORNEY DOCKET NO: 51198-064WO2 salt, deprotonated form, or tautomer thereof.

[0113] In any of formulas (la), (lb), (Ic), or (Id) each of R1, R2, R3, R4, R5, R6, R7and R8is independently selected from H; halo; optionally substituted C1-6 alkyl; oxo; optionally substituted C3-10 carbocyclyl; optionally substituted C1-9 heterocyclyl having one to four heteroatoms independently selected from O, N, and S; optionally substituted C6-20 aryl; optionally substituted C1-9 heteroaryl having one to four heteroatoms independently selected from O, N, and S; -CN; -NO2; -ORa(e.g., hydroxyl or Ci-6 alkoxy); - SRa(e.g., thiol or Ci-6 alkyl thiol); -N(Ra)2 (e.g., amino); -C(=O)Ra; -C(=O)ORa(e.g., carboxyl); -S(=O)2Ra; -S(=O)2ORa(e.g., SO3H); -P(=O)Ra2; and -P(=O)(ORa)2 (e.g., phosphonyl or phosphoryl); or any two adjacent groups selected from R1, R2, R3, and R4are joined to form an optionally substituted 3-6 membered ring, or an ion thereof, where each Rais independently H; optionally substituted C1-6 alkyl; optionally substituted C3-10 carbocyclyl; optionally substituted C1-9 heterocyclyl having one to four heteroatoms independently selected from O, N, and S; optionally substituted C6-20 aryl; optionally substituted C1-9 heteroaryl having one to four heteroatoms independently selected from O, N, and S; an oxygen protecting group; or a nitrogen protecting group. In some embodiments, the anthraquinone is water soluble.

[0114] In some embodiments, each of R1, R2, R3, R4, R5, R6, R7and R8is independently selected from halo, hydroxyl, carboxyl, sulfonate / sulfonic acid, alkylsulfonate / alkylsulfonic acid, phosphonyl, phosphoryl, alkylphosphonate / alkylphosphonic acid, amino, quaternary ammonium (e.g., trialkylamino), alkyl, heteroalkyl, alkoxy, glycoxy, polyalkyleneglycoxy, imino, polyimino, alkenyl, alkynyl, aryl, heteroaryl, heterocyclyl, nitro, nitrile, thiyl, and / or carbonyl groups, any of which is optionally substituted, or, any two adjacent groups of R1-R8can be joined together to form an optionally-substituted ring.

[0115] In some embodiments, each of R1, R2, R3, R4, R5, R6, R7and R8is independently selected from H, optionally substituted C1-6 alkyl, halo, hydroxyl, optionally substituted C1-6 alkoxy, SO3H, amino, nitro, carboxyl, phosphoryl, phosphonyl, and oxo, or an ion thereof. In particular embodiments, each of R1, R2, R3, R4, R5, R6, R7, and R8is independently selected from H, hydroxyl, optionally substituted C1-4 alkyl, carboxyl, and SO3H, such as each of R1, R2, R3, R4, R5, R6, R7and R8being independently selected from H, hydroxyl, optionally substituted C1-4 alkyl (e.g., methyl), and oxo. In some embodiments, at least one, e.g., at least two, of R1, R2, R3, R4, R5, R6, R7, and R8is not H.

[0116] In other embodiments, the anthraquinone, such as a 9,10-anthraquinone, is substituted with at least one hydroxyl group and optionally further substituted with a C1-4 alkyl, such as methyl. Exemplary anthraquinones include 2,6-bis(3-phosphonopropyl-1-oxy)anthraquinone (DPPEAQ), PATENT

[0117] ATTORNEY DOCKET NO: 51198-064WO2

[0118] 2,6-dihydroxy-9,10-anthraquinone (2,6-DHAQ), 1 ,5-dimethyl-2,6-dihydroxy-9,10-anthraquinone, 2,3,6,7-tetrahydroxy-9,10-anthraquinone, 1 ,3,5,7-tetrahydroxy-2,4,6,8-tetramethyl-9,10-anthraquinone, and 2,7-dihydroxy-1 ,8-dimethyl-9,10-anthraquinone. Ions and reduced species thereof are also contemplated.

[0119] In some embodiments, the proton-coupled redox active species is 1 ,5-bis[3- (trimethylammonio)propyl]anthraquinone (1 ,5-BTMAPAQ) and the redox state of the 1 ,5-BTMAPAQ is of formula (Ila). (Ila), or a salt or tautomer thereof.

[0120] In some embodiments, a suitable proton-coupled redox active species is the reduced form of the

[0121] 1 ,5-BTMAPAQ, a hydroquinone, e.g., a hydroquinone of formula (lib) (lib), or a salt, deprotonated form, or tautomer thereof.

[0122] Other proton-coupled redox active species are known in the art, e.g., WO 2019 / 136374, WO 2019 / 157437, WO 2023 / 023303, WO 2023 / 028041 , WO 2023 / 147421 , and WO 2025 / 019426, the redox active species of which are hereby incorporated by reference.

[0123] Any of the redox active species (e.g., proton-coupled redox active species) described herein may include one or more water-soluble substitution groups to increase solubility in one solution of interest (e.g., aqueous solution, e.g., aqueous electrolyte) and / or decrease solubility in a second solution of interest (e.g., non-aqueous solution, e.g., non-aqueous capture solution). For example, a redox active species may include two water-soluble substitution groups (e.g., two phosphate groups) to increase solubility in a first solution (e.g., aqueous electrolyte) that is aqueous and to decrease solubility in a second solution that is non-aqueous (e.g., non-aqueous capture solution). In some embodiments, the redox active species is water soluble. In some embodiments, the redox active species has a solubility that is less than about 0.01 mol / L (e.g., less than about 0.01 mol / L, less than about 0.001 mol / L, less than about 0.0001 mol / L, less than about 0.00001 mol / L, or less than about 0.000001 mol / L) in the second solution. In some embodiments, the redox active species is an anthraquinone, a viologen, a naphthoquinone, a phenazine, a phenoxazine, a phenothiazine, a fluorenone, an alloxazine, a vanadium ion or compound, a chromium ion or compound, a ruthenium compound, a zinc compound, a manganese compound, an iron compound, or water-soluble derivatives thereof. In some embodiments, the redox active species includes one or more alkoxy, amide, amino, carboxyl, heteroalkyl, heteroaryl, hydroxyl, PATENT

[0124] ATTORNEY DOCKET NO: 51198-064WO2 nitrile, nitro, phosphonyl, phosphoryl, sulfonyl and / or other water-soluble substitution groups. In some embodiments, the redox active species is a substituted anthraquinone including of one or more alkoxy, amide, amino, carboxyl, heteroalkyl, heteroaryl, hydroxyl, nitrile, nitro, phosphonyl, phosphoryl, sulfonyl and / or other water-soluble substitution groups.

[0125] In some embodiments, the proton-coupled redox active species are only slightly soluble in nonaqueous solvents (e.g., less than about 0.01 mol / L). In some embodiments, the solubility of the proton- coupled redox active species is less than about 0.01 mol / L (e.g., less than about 0.01 mol / L, less than about 0.001 mol / L, less than about 0.0001 mol / L, less than about 0.00001 mol / L, or less than about 0.000001 mol / L) in the non-aqueous solvent.

[0126] In some embodiments, the electrochemical cells described herein are symmetrical, i.e., including an aqueous electrolyte including one or more of the redox active species described herein on each side of the electrochemical cell. In some embodiments, the redox active species includes a water-soluble ferrocene derivative. Water-soluble ferrocene species are known in the art, e.g., WO 2018 / 032003, which are hereby incorporated by reference. In some embodiments, the electrolyte of the electrochemical cell includes a solid or gas electrolyte. Solid and gas electrolyte species are known in the art.

[0127] Methods of CO2 Capture and Release

[0128] The disclosure provides methods for capture and release of CO2 by combining amine modulated capture of CO2 with PCET derived pH swing driven release of CO2 and recovery of the amine. The methods of the invention further utilize immiscible aqueous and non-aqueous solvents (e.g., n-pentanol or n-butanol), to protect the PCET molecules (e.g., anthraquinones) from oxygen exposure. In the nonaqueous capture solution, the amine (e.g., phenethylamine or 1 -hexaneamine) is exposed to a gas including CO2, forming amine-CC>2 adducts (e.g., carbamates and / or carbamic acids). Concurrently or subsequently, an aqueous electrolyte (e.g., first and / or second aqueous electrolyte) including a proton- coupled redox active specie (e.g., anthraquinone, e.g., 1 ,5-BTMPAQ) is oxidized in an electrochemical cell, causing the proton-coupled redox active species to release one or more protons, causing the pH of the aqueous electrolyte of the system to decrease (e.g., about pH 1 , about pH 2, about pH 3, about pH 4, about pH 5, about pH 6, or about pH 7).

[0129] The oxidized second aqueous electrolyte and the amine-CC>2 adduct containing non-aqueous capture solution are contacted in the mixing region, resulting in the acid promoted release of CO2 and production of an ammonium (e.g., phenylethylammonium) at the phase interface of the two immiscible solutions. In some embodiments, the resulting ammonium partially partitions into the aqueous electrolyte. In some embodiments, the resulting ammonium fully partitions into the aqueous electrolyte. In some embodiments, the mixing region further includes an agitating element (e.g., mixer, e.g., 1203, 2203, 3203, or 3503) to agitate the immiscible solution to increase the interface between the two immiscible solutions. In some embodiments, the acid promoted release of CO2, generation of the ammonium, and / or the at least partial partitioning of the ammonium into the aqueous electrolyte causes the pH of the electrolyte to increase (e.g., about pH 6, about pH 7, about pH 8). PATENT

[0130] ATTORNEY DOCKET NO: 51198-064WO2

[0131] After mixing, the immiscible non-aqueous capture solution and the second aqueous electrolyte are moved to a settling region. In some embodiments, the settling region and the mixing regions are the same. In some embodiments, the mixing region transitions into the settling region with the removal (e.g., turning off) of the agitation. Once in the settling region, the two immiscible solutions separate. In some embodiments, the separation process of the second aqueous electrolyte and the non-aqueous capture solution is gravity driven. In some embodiments, the separation process of the second aqueous electrolyte and the non-aqueous capture solution is accomplished by centrifugal separation. In some embodiments, the separation process of the second aqueous electrolyte and the non-aqueous capture solution is accomplished by filtration. In some embodiments, during separation of the second aqueous electrolyte and the non-aqueous capture solution, the second aqueous electrolyte forms the higher layer. In some embodiments, during separation of the second aqueous electrolyte and the non-aqueous capture solution, the second aqueous electrolyte forms the lower layer.

[0132] Once separated, the second aqueous electrolyte is removed to the electrochemical cell. The second aqueous electrolyte is then reduced within the electrochemical cell, resulting in the reduction of the proton-coupled redox active species, resulting in the uptake of one or more protons, and an increase in the pH (e.g., about pH 9, about pH 10, about pH 11 , about pH 12, about pH 13, about pH 14) of the aqueous electrolyte. The reduced second aqueous electrolyte is then moved to the mixing region, where it contacts the non-aqueous capture solution. In some embodiments, the increased pH of the second aqueous electrolyte causes the ammonium to be deprotonated into an amine. In some embodiments, the ammonium is partially or fully soluble in the second aqueous electrolyte, and the ammonium is deprotonated into an amine in the second aqueous electrolyte. In some embodiments, the ammonium is partially soluble in the second aqueous electrolyte, and the deprotonation of the ammonium into an amine occurs in the interface between the second aqueous electrolyte and the non-aqueous capture solution. In some embodiments, the ammonium is not soluble in the second aqueous electrolyte, and the deprotonation of the ammonium into an amine occurs at the interface between the second aqueous electrolyte and the non-aqueous capture solution. The resulting amine is insoluble in the second aqueous electrolyte and partitions into the non-aqueous capture solution, resulting in the regeneration of the nonaqueous capture solution. In some embodiments, the deprotonation of the ammonium into the amine occurs prior to the introduction of the second aqueous electrolyte into the mixing region.

[0133] The regenerated non-aqueous capture solution and the second aqueous electrolyte are then transferred into the settling region, separating the immiscible solutions. The separated non-aqueous capture solution is then transferred to the capture tank and may be used for subsequent CO2 capture and release.

[0134] In some embodiments, the steps of CO2 capture, PCET oxidation of the second aqueous electrolyte, acid promoted CO2 release and ammonium production, PCET reduction of second the aqueous electrolyte, and deprotonation of the ammonium into an amine to restore the non-aqueous capture solution are repeated. In some embodiments, the method is repeated 1 to 10,000 times, e.g., at least 10, 50, 100, 150, 200, 500, 1000, or 5000 times without needing to replace the redox active species. PATENT

[0135] ATTORNEY DOCKET NO: 51198-064WO2

[0136] In some embodiments, the methods described herein are completed in a continuous flow system (e.g., continuous flow reactor, FIG. 5). In some embodiments, the step of acid promoted CO2 release and ammonium production and deprotonation of the ammonium into an amine are completed in separate mixing regions (e.g., 3200 and 3500 of FIG. 5). In some embodiments, the step of proton-coupled oxidation and reduction are completed in separate regions (e.g., 3110 or 3120 of FIG. 5) of the electrochemical cell.

[0137] In some embodiments, the gas including CO2 is flue gas. In some embodiments, the gas including CO2 is atmospheric air. In some embodiments, the gas including CO2 contains at least 0.04% (e.g. at least 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1 %, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1 %, 2%, 3%, 3.8%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 60%, 70%, 80%, or 90%) CO2. In some embodiments, the gas including CO2 contains at least 1 % (e.g., 1 %, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 21 %, 25%, 30%, 35%, 40%, 45%, 50%, 60%, 70%, 80%, or 90%) O2.

[0138] It should be appreciated that during the methods for CO2 capture and release described herein, neither proton-coupled redox active species included in the first aqueous electrolyte, nor the second aqueous electrolyte come in contact with a source of oxygen (e.g., gas containing CO2).

[0139] EXAMPLES

[0140] The invention will be further described by the following non-limiting examples.

[0141] Example 1 : Non-PCET Mediated Amine CO2 Capture and Release

[0142] To demonstrate the ability to mediate the CO2 capture and release utilizing a biphasic system, a biphasic system of an aqueous solution of 1 .0 M KCI (pH 13) and n-pentanol were prepared, with the n- pentanol forming the top layer. The inlet of the system was then exposed to a stream containing roughly 10% CO2, 20% O2, and the balance N2, and the readout of the CO2 partial pressure was monitored at the outlet of the system.

[0143] To this biphasic system, 0.10 M 2-phenylethylammonium chloride, which is highly water soluble, was added, which dissolved into the aqueous phase. The basic conditions of the aqueous phase quickly converted the 2-phenylethylammonium to 2-phenylethylamine, which then partitioned into the n-pentanol layer, where it was exposed to the atmosphere containing CO2, causing the formation of amine-CO2 adducts, resulting in the drop of the CO2 partial pressure at the outlet (FIG. 1).

[0144] Once the partial pressure of the CO2 at the outlet had equilibrated, indicating near complete consumption of the amine to form amine-CO2 adducts, the solution was acidified with an acid, causing the release of CO2, as shown by the spike in the partial pressure of CO2 in FIG. 1 and recovery of the 2- phenylethylammonium. PATENT

[0145] ATTORNEY DOCKET NO: 51198-064WO2

[0146] Example 2: PCET Mediated Amine CO2 Capture and Release

[0147] To demonstrate the ability to utilize PCET based pH modulation with the system of Example 1 , the aqueous layer utilized in Example 1 was modified to include 0.10 M of 1 ,5-BTMPAQ, as the proton- coupled redox active species.

[0148] The 1 ,5-BTMPAQ was reduced to increase the pH of the solution (~pH 13, FIG. 2A), which lead to the deprotonation of the 2-phenylethylammonium to its amine state, which partitioned into the nonaqueous phase. The biphasic solution was then exposed to the same CO2 containing gas stream as in Example 1 (20% O2, 10% CO2, and 70% N2). The results show a decline in the partial pressure of CO2 within the gas stream at the outlet of the system (FIG. 2B). As with Example 1 , the partial pressure of CO2 was allowed to equilibrate, indicating near total use of the amine to form the amine-CO2 adducts.

[0149] Subsequently, the 1 ,5-BTMPAQ was oxidized, leading to the release of protons, and a decrease in the pH (~ pH 1 .0, FIG 2A). The now acidic aqueous phase interacted with the amine-CO2 adducts at the phase interface, resulting in the release of CO2, as shown by the peak in FIG. 2B, and production of the 2-phenylethylammonium, which then partitioned into the aqueous phase, bringing the pH of the aqueous phase to near neutral (FIG. 2A). This resulting system, with the ammonium partitioned into the 1 ,5-BTMPAQ can then be reduced again, to initiate CO2 capture, and oxidized to initiate CO2 release, demonstrating the reusability of this biphasic system.

[0150] Furthermore, multiple experiments with this biphasic system resulted in a faradaic efficiency between 85% and 94%. Demonstrating that through the use of a biphasic system, PCET modulated pH swings may be used for CO2 capture from gas streams containing O2, which up to this point, has been problematic, as the limited oxygen stability of reduced PCET molecules is well known.

[0151] Example 3: PCET Mediated Amine CO2 Capture and Release in a Continuous Flow-Cell

[0152] PCET mediated amine CO2 capture and release in a continuous flow-cell is demonstrated using the system outlined in FIG. 5. The aqueous electrolyte of the electrochemical cell is first loaded with 0.10 M of 11 ,5-BTMPAQ, as the proton-coupled redox active species. To this aqueous electrolyte, an appropriate amount of 2-phenylethylammonium chloride is added to yield a 0.1 M solution of 2- phenylethylamonium. The capture tank is loaded with n-pentanol, as the non-aqueous solvent. Once the system is prepared, a power source provides current to the electrode on each side of the electrochemical cell, oxidizing the aqueous electrolyte at the anode, and reducing the aqueous electrolyte at the cathode. The reduction of the aqueous electrolyte at the cathode causes the PCET redox molecules to take up protons, increasing the local pH of the aqueous electrolyte (e.g., pH 13). This increase in the pH then causes the 2-phenylethylammonium to deprotonate and produce 2-phenylethylamine. The reduced aqueous electrolyte is transported to the first mixing region, where it encounters the n-pentanol. The 2- phenylethylammonium then partitions into the n-pentanol. The two immiscible phases are then allowed to settle in the first settling region.

[0153] The now settled aqueous and non-aqueous phases are then transported out of the first settling region. The non-aqueous capture solution is moved to the capture tank, where it is exposed to a gas PATENT

[0154] ATTORNEY DOCKET NO: 51198-064WO2 source containing CO2. During this exposure, the 2-phenylethylamine reacts with the CO2 to form amine- CO2 adducts. While the non-aqueous capture solution is being exposed to CO2, the aqueous electrolyte from the first settling region is transported to the anode side of the electrochemical cell, where it is oxidized. The oxidation of the aqueous electrolyte causes the PCET redox molecules to release protons, lowering the pH of the aqueous electrolyte (e.g., pH 1). The now acidic aqueous electrolyte is moved to the second mixing region and is mixed with capture solution containing amine-CC>2 adducts.

[0155] The acidic conditions of the aqueous electrolyte cause the amine-CC>2 adducts to cleave at the phase interface, releasing gaseous CO2 and forming an ammonium, which partitions into the aqueous electrolyte. The two phases are then allowed to separate in the second settling region, and the aqueous electrolyte is transferred back to the electrochemical cell. Simultaneously, the non-aqueous capture solution is transferred to the first mixing region.

Claims

PATENTATTORNEY DOCKET NO: 51198-064WO2CLAIMS1 . A system comprising: i) an electrochemical cell comprising: a) a first region comprising at least one electrode, a first electrolyte; b) a second region comprising at least one electrode, a second aqueous electrolyte comprising a proton-coupled redox active species, an inlet and an outlet; and c) a membrane disposed between the first region and a second region; ii) a mixing region comprising a first inlet, a second inlet, and an agitating element; iii) a settling region, in fluidic communication with the mixing region, comprising a first outlet and a second outlet; and iv) a capture tank comprising a first inlet, a first outlet, and a non-aqueous capture solution, wherein the non-aqueous capture solution comprises a non-aqueous solvent immiscible with the second aqueous electrolyte and an amine; wherein the outlet of the second region is in fluidic communication with the first inlet of the mixing region; the first outlet of the capture tank is in fluidic communication with the second inlet of the mixing region; the first outlet of the settling region is in fluidic communication with the inlet of the second region; and the second outlet of the settling region is in fluidic communication with the first inlet of the capture tank.

2. The system of claim 1 , wherein the first electrolyte is a solid electrolyte.

3. The system of claim 1 , wherein the first electrolyte is a first aqueous electrolyte, and the first region of the electrochemical cell further comprises an inlet and an outlet.

4. The system of any one of claims 1-3, wherein the settling region comprises a gas outlet.

5. A system comprising: i) an electrochemical cell comprising: a) a first region comprising at least one electrode, a first aqueous electrolyte, an inlet and an outlet; b) a second region comprising at least one electrode, the first aqueous electrolyte, an inlet and an outlet; and c) a membrane disposed between the first region and a second region; and ii) a first mixing region comprising a first inlet, a second inlet, and a mixer; iii) a first settling region, in fluidic communication with the first mixing region, comprising a first outlet and a second outlet; iv) a second mixing region comprising a first inlet, a second inlet, and an agitating element; v) a second settling region, in fluidic communication with the second mixing region, comprising a first outlet and a second outlet; and iv) a capture tank comprising a first inlet, a first outlet, and a non-aqueous capture solution, wherein the first electrolyte and the second electrolyte are the same and comprise a proton-coupledPATENTATTORNEY DOCKET NO: 51198-064WO2 redox active species; wherein the non-aqueous capture solution comprises a non-aqueous solvent immiscible with the first aqueous electrolyte and an amine; wherein the outlet of the second region is in fluidic communication with the first inlet of the first mixing region; the first outlet of the first settling region is in fluidic communication with the inlet of the first region; the second outlet of the first settling region is in fluidic communication with the first inlet of the capture tank; the outlet of the first region is in fluidic communication with the first inlet of the second mixing region; the first outlet of the capture tank is in fluidic communication with the second inlet of the second mixing region; the first outlet of the second settling region is in fluidic communication with the inlet of the second region; and the second outlet of the second settling region is in fluidic communication with the second inlet of the first mixing region.

6. The system of claim 5, wherein the first and / or the second settling region comprises a gas outlet.

7. The system of any one of claims 1 -6, wherein the membrane is a cation exchange membrane (CEM), an anion exchange membrane (AEM), a bipolar membrane (BPM), or a size-selective membrane.

8. The system of any one of claims 1 -7, wherein the system further comprises a power supply attached to the at least one electrode of the first region and to the at least one electrode of the second region.

9. The system of any one of claim 1-8, wherein the capture tank further comprises a second inlet and a second outlet.

10. The system of any one of claims 1 -9, wherein the capture tank further comprises a bubbler to introduce a gas to the non-aqueous capture solution.

11. The system of any one of claims 1 -10, wherein the non-aqueous solvent is selected from an aromatic solvent, a chain alcohol, an alkyl phosphite, and an alkyl carbonate.

12. The system of claim 11 , wherein the non-aqueous solvent is n-pentanol.

13. The system of claim 11 , wherein the non-aqueous solvent is n-butanol.

14. The system of any one of claims 1-13, wherein the amine has the formula N(R)3 or an ion thereof, wherein each R is independently H; optionally substituted C1-6 alkyl; optionally substituted C3-10 carbocyclyl; optionally substituted C1-9 heterocyclyl having one to four heteroatoms independently selected from O, N, and S; optionally substituted C6-20 aryl; or optionally substituted C1-9 heteroaryl having one to four heteroatoms independently selected from O, N, and S.

15. The system of claim 14, wherein the amine is phenethylamine.PATENTATTORNEY DOCKET NO: 51198-064WO216. The system of claim 14, wherein the amine is 1 -hexaneamine.

17. The system of any one of claims 1-16, wherein the proton-coupled redox active species is selected from a water-soluble anthraquinone, viologen, naphthoquinone, phenazine, fluorenone, alloxazine, vanadium complex, chromium complex, or a derivative thereof.

18. The system of claim 17, wherein the proton-coupled redox active species has the structure of19. The system of any one of claims 1-18, wherein the system further comprises an oxygen scrubber disposed to remove dissolved oxygen from the non-aqueous capture solution.

20. A method for the capture and release of CO2 comprising: a) providing a gas source comprising CO2 to a non-aqueous capture solution comprising a nonaqueous solvent and an amine, wherein the amine reacts with the CO2, forming amine-CC>2 adducts; b) providing an aqueous electrolyte comprising a proton-coupled redox active species to an electrochemical cell and electrochemically oxidizing the proton-coupled redox active species, wherein the oxidation of the proton-coupled redox active species releases one or more protons and lowers the pH of the aqueous electrolyte; c) contacting the non-aqueous capture solution and the aqueous electrolyte in a mixing region, wherein the non-aqueous capture solution and the aqueous electrolyte are immiscible, wherein the amine-CC>2 adducts at a phase interface are cleaved, releasing CO2 and an ammonium; d) separating the non-aqueous capture solution and the aqueous electrolyte; e) transporting the aqueous electrolyte to an electrochemical cell and electrochemically reducing the proton-coupled redox active species, wherein the reduction of the proton-coupled redox active species takes up one or more protons and increases the pH of the aqueous electrolyte; and f) contacting the aqueous electrolyte with the non-aqueous capture solution, wherein the ammonium is deprotonated to form an amine in the non-aqueous capture solution.21 . The method of claim 20, wherein the method is carried out in the system of any one of claims 1 -19.PATENTATTORNEY DOCKET NO: 51198-064WO222. The method of claim 20 or 21 , wherein the proton-coupled redox active species has the structure23. The method of any one of claims 20-22, wherein the proton-coupled redox active species has a solubility that is less than 0.0001 mol / L in the non-aqueous capture solution.

24. The method of any one of claims 20-23, wherein during step a), the CO2 is introduced to the nonaqueous capture solution by a bubbler in contact with the non-aqueous capture solution.

25. The method of any one of claims 20-24, wherein during step a), the amine-CC>2 adducts are carbamates or carbamic acids of the amine.

26. The method of any one of claims 20-25, wherein during step d), the non-aqueous capture solution and the aqueous electrolyte are separated by gravity-driven separation, centrifugal separation, or filtration.

27. The method of any one of claims 20-26, wherein during step e), the pH of the aqueous electrolyte increases to at least pH 1 1 .

28. The method of any one of claims 20-27, wherein the ammonium generated during step c) is partially or fully soluble in the aqueous electrolyte.

29. The method of claim 28, wherein after step e) the ammonium in the aqueous electrolyte deprotonates to form an amine and partitions into the non-aqueous capture solution during step f).

30. The method any one of claims 20-29, wherein the steps of a) - f) are repeated at least once.31 . The method of any one of claims 20-29, wherein the steps of a) - f) are performed in a continuous flow reactor.

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