Method of preparing porous co 2 adsorbent material & uses thereof

Abstract

The invention relates to a method for the preparation of a CO2 adsorbent material, in particular in particular material MOF-based CO2 adsorbent material and new CO2 adsorbent material useful for CO2 capture.

Description

[0001] METHOD OF PREPARING POROUS CO2ADSORBENT MATERIAL & USES THEREOF

[0002] Field of the Invention

[0003] The present invention pertains generally to the field of CO2 capture and new adsorbent materials useful in CO2 adsorption.

[0004] Background of the Invention

[0005] Atmospheric CO2 levels are rising at an alarming rate primarily due to the continued combustion of fossil fuels that are used in electricity generation (The Intergovernmental Panel on Climate Change: Global Warming of 1.5°C. https : / / www. ipcc. ch / sr!5 / ; Hulme et al., 2016, Nat. Clim. Change, 6 (3), 222-224). Although the most appropriate strategy to overcome this entails an energy transition to renewables, fossil fuels still supply some 80 % of the world’s energy (Rahman et al., 2017, Renew. Sust. Energ. Rev., 71, 112-126; Trancoso et al. , 2017, Geophys. Res. Lett., 44 (5), 2310-2318).

[0006] Unfortunately, the energy demand also continues to rise faster than renewables Renewable Electricity; International Energy Agency (IEA): Paris, 2022). Given this, and that energy transitions are historically slow, it is projected that fossil fuels will be used for many years to come. Thus, to meet the target NetZero by 2050, the rapid implementation of efficient processes that can selectively capture large quantities of CO2 from large points sources, such as fixed coal- or gas- fired power plants, as well as air is a necessity IPCC, Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. Masson-Delmotte, V.; Zhai, P.; Pirani, A.; Connors, S. L.; Pean, C.; Berger, S.; Caud, N.; Chen, Y.; Goldfarb, L.; Gomis, M. I.; Huang, M.; Leitzell, K; Lonnoy, E.; Matthews, J. B. R.; Maycock, T. K; Waterfield, T.; Yelekqi, O.; Yu, R.; Zhou, B. Cambridge University Press: Cambridge, United Kingdom and New York, NY, USA, 2021; Vol. In Press; IPCC, Climate Change 2022: Mitigation of Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. Shukla, P. R. ; Skea, J.; Slade, R; Al Khourdajie, A.; van Diemen, R.; McCollum, D.; Pathak, M.; Some, S.; Vyas, P.; Fradera, R.; Belkacemi, M.; Hasija, A.; Lisboa, G.; Luz, S.; Malley, J. Cambridge University Press: Cambridge, UK and New York, NY, USA, 2022; Vol. In Press).

[0007] The most mature technology for post-combustion carbon capture (PCC) consists of aqueous alkanolamine solutions, also known as amine scrubbers (Rochelle et al., 2009, Science, 325, 1652- 1654). Despite their high selectivity towards CO2 in typical PCC streams (12-16 % CO2, 73-77 % N2, 5-7 % H2O, 3-4 % O2 and traces of SOX, NOXand H2S at 1 bar and 313 K or higher), they suffer from some important limitations such high CO2 adsorption enthalpies (>-100 kJ / mol) (Rochelle et al., 2009, Science, 325, 1652-1654) and high heat capacities (3-4 J / K g) (Sumida et al, 2012, Chem. Rev., 112 (2), 724-781; Weiland et al., 1997, J. Chem. Eng. Data , 42 (5), 1004-1006) which leads to large energy penalties that can significantly reduce power plant efficiency by as much as 30-50 % (Goto et al, 2013, Appl. Energy , 111, 710-720; Raganati et al, 2021 Energy Fuels, 35, 16, 12845- -12868). Moreover, liquid amines are often highly corrosive (Zhao et al, 2011, Energy Procedia, 4, 93-100) and suffer from poor thermal stability under the temperatures necessary for the subsequent release of the CO2 (393-473°C) (Voice et al, 2011, Energy Procedia, 4, 171-178). As an alternative, many consider porous solid adsorbents as promising owed to lower heat capacities, which could cut the parasitic energy loss by a factor of 2 (Herzog et al, 2009, Clean Air Task Force, Doris Duke Foundation).

[0008] Of several classes of solid adsorbents, Metal-Organic Frameworks (MOFs) Furukawa et al., 2013, Science, 341, 974-987) offer advantageous solutions owed to record surface areas and pore volumes (Honicke et al, 2018, Angew. Chem. Int. Ed., 57 (42), 13780-13783) and highly tunable porous structures Sun et al, 2018, J. Am. Chem. Soc., 140, 16697-16703). Over the years, various postsynthetic modification strategies in MOFs have been assessed with the aim at improving their CO2 capacity (Ding et al., 2019, Chem. Soc. Rev., 48 (10), 2783-2828) including the coordination of alkylamines to open metal sites (OMS) (Kim et al., 2020, Science, 369 (6502), 392-396; Pirzadeh et al., 2020, Ind. Eng. Chem. Res., 59 (1), 366-378; Li et al, 2019, J. Mater. Chem. A, 7 (13), 7867- 7874; Siegelman et al., 2017, J. Am. Chem. Soc. 2017, 139 (30), 10526-10538) or the wet impregnation of amine-containing molecules (Martinez et al., 2016, Chem. Eng. Sci., 142, 55-61; Zhong et al, 2018, ACS Sustainable Chem. Eng. 6 (12), 16493-16502) or polymers (Lin et al., 2013, Sci. Rep., 3 (1), 1859; Gaikwad et al, 2021, Journal of Environmental Chemical Engineering, 9 (4), 105523; Kang et al, 2019, Microporous Mesoporous Mater., 281, 84-91; Gaikwad et al. 2019, Microporous Mesoporous Mater., 277, 253-260; Darunte et al, 2016, ACS Sustainable Chem. Eng., 4 (10), 5761-5768).

[0009] The reason behind this effort is that amine functional groups can chemisorb CO2 via a nucleophilic attack on the carbon of the CO2 molecule to form either a carbamate or a bicarbonate species (Sumida et al., 2012, Chem. Rev., 112 (2), 724-781; da Silva et al., 2007, International Journal of Greenhouse Gas Control, 1 (2), 151-157). Despite their large CO2 adsorption capacity even at high temperatures, many amine-infused materials quickly lose their performance upon adsorption / desorption cycling (Darunte et al., 2016, supra). This is atributed to several phenomena including amine degradation (through the formation of urea species) (Choi et al., 2016, Nat. Commun., 7 (1), 12640; Drage et al., 2008, Microporous Me sopor ous Mater., 116 (1), 504-512; Drage et al, 2009, Energy Procedia, 1 (1), 875-880; Sayari et al., 2012, J. Am. Chem. Soc., 134 (33), 13834-13842) or amine leaching from the MOF pores. The latter could stem from weak van der Waals interactions between the impregnated amines and the MOF (Lin et al, 2013, supra; Darunte et al., 2016, supra) or the displacement of the amines from the framework surface due to more favorable interactions with water (Milner et al, 2018, Chem. Sci., 9 (1), 160-174).

[0010] Some of the most prominent work was done by Long et al. where amines were appended to open metal sites in a family of MOFs that have honeycomb like 1-D channels, namely MOF-74 or CPO- 27 (M2(dobdc) where M = Zn, Mg, Mn, Fe Ni, Co and dobdc = 2,5-dioxido-l,4- benzenedicarboxylate) and the extended ligand analogues (M2(dobpdc where dobpdc= 4,4'- dioxidobiphenyl-3,3'-dicarboxylate)(A cZ>o«a / t / et al., 2012, J. Am. Chem. Soc., 134 (16), 7056- 7065 ; Siegelman et al., 2017, J. Am. Chem. Soc., 139 (30), 10526-10538; Milner etal., 2018, supra, 9 (1), 160-174; Forse et al., 2018, J. Am. Chem. Soc., 140, 18016-18031; Siegelman, et al, 2019, J. Am. Chem. Soc., 141 (33), 13171-13186). In one of the first studies, incorporation of the diamine N,N'-dimethylethylenediamine (mmen) was achieved by appendage to the OMS of Mg2-dobpdc, which was further tested towards air and flue gas CO2 capture and exhibited remarkable performance under dry conditions (2.0 mmol / g at 0.39 mbar and 298 K, for direct air capture, and 3.14 mmol / g at 0.15 bar and 313 K, for flue gas capture). The group recently found that by modifying the dimensions of the appended alkylamines to longer tetraamines, they can be bridged between neighboring OMS giving rise to long-term cyclability even in humid conditions Kim et al., 2020, Science, 369, 392-396).

[0011] As a another example, Jones and co-workers studied the amine (tris(2-amino ethyl)amine) and polyamine (polyethyleneimine or PEI, MW 800) impregnation in a chromium MOF, namely Cr- BDC (also known as MIL-lOl-(Cr)) for direct air capture applications (Darunte et al, 2016, supra).

[0012] Despite a high CO2 capacity for the alkylamine-loaded MOF, the materials offered poor cyclability, which was attributed it to the high volatility of the low molecular weight amine. As such, the use of higher molecular PEI (polyethyleneimine) was tested upon screening of increasing loading amounts. It was found that sample loaded with 1.06 mmol PEI / g Cr-BDC offered the best compromise between amine efficiency and capacity (3.3 mmol CO2 / g at 1 bar and 2.5 mmol CO2 / g at 0.15 bar at 298 K). Notably, only a slight drop in performance after 3 cycles using 400 ppm CO2 in dry helium was reported for the PEI impregnated Cr-BDC. To reduce amine degradation, researchers have focused on reducing the number of highly reactive primary amines via chemical capping agents, for instance, such as epoxides. As an example, Wood et al. used a polymer consisting of high-molecular weight PEI crosslinked with a branched epoxide (trimethylolpropane triglycidyl ether) for direct air capture (DAC) (Xu et al., 2019, ACS Appl. Mater. Interfaces, 11 (30), 26770-26780; Xu et al., 2020, Chem. Commun., 56 (52), 7151-7154). The best-performing polymer, tested under DAC conditions and steam regeneration at 393 K using a breakthrough setup, offered a CO2 uptake of 52.4 mg / g, which could be retained over 10 cycles (Xu et al., 2020, supra). Although the authors confirmed the formation of the polymers via FT-IR, the surface area and pore volumes of the materials were not assessed. Given that such polymers are unlikely to offer high accessible porosity for CO2 to enter and exit, impregnating already porous templates with such polymers becomes an attractive strategy to increase the accessibility surface area of the polymers in hopes to boost CO2 capacity. As an example, Choi et al. synthesized a PEI capped with 1,2-epoxybutane (EB) through the use of mono epoxides, and subsequently impregnated silica beads with the EB-capped PEI using methanol. The resulting material offered a CO2 capacity of 2.2 mmol / g, which was well retained after 50 consecutive temperature swing cycles in a simulated flue gas mixture (15% CO2, 3% H2O, 2% Ar in N2 balance at 313 K for adsorption and 100% CO2 at 393 K for desorption) (Choi et al., 2016, supra; Min et al., 2018, Nat. Commun., 9 (1), 726).

[0013] Therefore, given that the global energy demand is growing faster than renewables, capturing CO2 from large point sources is becoming increasingly urgent. While the implementation of solid adsorbents for CO2 capture from flue gas mixtures is a viable solution, the development of highly efficient capture materials having long-term cyclability is still needed.

[0014] Summary of the Invention

[0015] A general object of this invention is to provide porous CO2 adsorbent material and a cost-effective process for the preparation of the same.

[0016] It has been unexpectedly found that reacting amines containing at least 2 amino groups with a crosslinking agent containing at least two epoxy groups within a porous substrate leads to the formation of porous CO2 adsorbent material with enhanced CO2 capture performance and cycling performance.

[0017] One of the specific objects of this invention is to provide a method for the preparation of porous- support based CO2 adsorbent material, in particular MOF -based CO2 adsorbent material, which are useful in CO2 separations from gas mixtures. It is advantageous to provide a facile and scalable method for the preparation of CO2 adsorbent material.

[0018] It is advantageous to provide a method for the preparation of CO2 adsorbent material which lasts for less than half a day, typically less than 12 hours.

[0019] It is advantageous to provide a single-step method for the preparation of CO2 adsorbent material which does not need to isolate or dry any intermediate product.

[0020] It is advantageous to provide a method for the preparation of MOF -based CO2 adsorbent material with high cycling performance.

[0021] It is advantageous to provide a method for the preparation of CO2 adsorbent material with a high amine density entrapped in the pores of said material.

[0022] It is advantageous to provide a method for the preparation of CO2 adsorbent material adapted to different porous supports.

[0023] An object of this invention is to provide a CO2 adsorbent material based on a porous material, useful for CO2 capture.

[0024] It is advantageous to provide CO2 adsorbent material with high CO2 capacity (typically higher than 1.0 mmol / g at 0.15 bar and 313 K).

[0025] It is advantageous to provide CO2 adsorbent material with high CO2 / N2 selectivity (typically IAST CO2 / N2 selectivity at 313 K higher than 50, in particular higher than 150 or 200).

[0026] It is advantageous to provide CO2 adsorbent material with CO2 / N2 separation performance under extreme conditions (i.e. both dry and highly humid conditions).

[0027] It is advantageous to provide CO2 adsorbent material with efficient CO2 / N2 separation time in highly humid CO2 / N2 mixtures (typically higher than 110 min / g in CO2 / N2 mixtures (15 / 85) containing 80% RH at 313 K and 2 mL / min flow rate).

[0028] It is advantageous to provide CO2 adsorbent material with a high isosteric heat of CO2 adsorption (typically higher than 50 kJ / mol).

[0029] It is advantageous to provide CO2 adsorbent material presenting strong resistance to adsorption / desorption cycling under variable temperature conditions, in particular a cyclability over the course of repeated temperature swing adsorption (TSA) cycles (e.g. 313 K adsorption and 393 K desorption). Objects of this invention have been achieved by providing a method of preparation according to claim 1, a CO2 adsorbent material according to claim 12 and uses thereof according to claim 15.

[0030] Disclosed herein is a method for the preparation of a CO2 adsorbent material, said method comprising the steps of: a) Providing a porous material either in dry form or dispersed in a solvent; b) Adding an amine-containing solution to the said porous material, wherein said amine- containing solution comprises an amine compound with at least 2 amino groups; c) Adding an epoxide compound to the amine treated porous material at least 30 seconds after the amine-containing solution addition, wherein said epoxide compound comprises at least 2 epoxy groups; d) Leaving the mixture under mixing until the cross-linking of the amines and epoxides occurs; e) Recovering the material comprising cross-linked amines and epoxides inside the said porous material, by isolating the porous material from the mixture.

[0031] Also disclosed herein is CO2 adsorbent material obtainable by a process according to the invention.

[0032] Also disclosed herein is a CO2 adsorbent material, wherein said material comprises a porous substrate containing in situ cross-linked polymers between amines containing at least 2 amino groups and a cross-linking agent containing at least two epoxy groups through epoxide ring opening reaction obtainable from a method according to the invention. Also disclosed herein is the use of a CO2 adsorbent material for CO2 removal from a gas mixture.

[0033] Other features and advantages of the invention will be apparent from the claims, detailed description, and figures.

[0034] Brief Description of the drawings

[0035] Figure 1 is a schematic representation of an illustration of the method of the invention wherein amines with at least 2 amino groups are reacted with a cross-linking agent containing at least two epoxy groups within a porous substrate called “ship-in-a-bottle” polymerization wherein the polymerization of the amines occurs within the porous structure of the substrate. (1) Porous material (e.g. a MOF material) is provided either in dry form or dispersed in a solvent (e,g, dispersed in methanol), (2) an amine-containing solution is added to the said porous material, wherein said amine-containing solution comprises an amine compound with at least 2 amino groups, (3) an epoxide compound (e.g. in solution in methanol) is added to the amine treated porous material at least 30 seconds after the amine-containing solution addition, wherein said epoxide compound comprises at least 2 epoxy groups and the cross-linking reaction mixture is let under mixing until the cross-linking of the amines and epoxides occurs (e.g. for about 3h) to obtain (4) the material comprising cross-linked amines and epoxides inside the said porous material.

[0036] Figure 2 shows CO2 adsorption efficiency of materials of the invention as described in Example 3. a) CO2 (solid symbols) and N2 (empty symbols) adsorption isotherms at 313 K; b) isosteric heat of CO2 adsorption of the bare Cr-BDC and materials of the invention; Cr-BDC (diamonds), Cr- BDC-TAEA-TMPTE (circles), Cr-BDC-TEPA-BDE (triangles pointing up), Cr-BDC-TAEA- BDE (squares) and Cr-BDC-TEPA-TMPTE (triangles pointing down). The synthesis of these materials was done at larger scales (550 mg).

[0037] Figure 3 represents breakthrough plots under dry ( CCE 85: 15) (N2 as dash-dot lines and CO2 as dotted lines) and humid conditions ( CCE 85:15 with 80% RH) (N2 as solid lines and CO2 as dashed lines) of a) the bare Cr-BDC and the amine-epoxide composites b) Cr-BDC-TAEA-TMPTE (2), c) Cr-BDC-TAEA-BDE (1), d) Cr-BDC-TEPA-BDE (3) and e) Cr-BDC-TEPA-TMPTE (4) as described under Example 3.

[0038] Figure 4 presents the long-term cyclability of materials of the invention after 100 TSA cycles under 313 K adsorption and 393 K desorption of pure CO2 as described in Example 3. a) TAEA-based materials including Cr-BDC-TAEA-TMPTE (dotted line), Cr-BDC-TAEA-BDE (dashed line), Cr- BDC-TAEA in cyclohexane (solid) and Cr-BDC-TAEA in methanol (dash-dot line); b) TEPA- based materials; Cr-BDC-TEPA-BDE (solid), Cr-BDC-TEPA-TMPTE (dashed), Cr-BDC-TEPA in cyclohexane (dotted) and Cr-BDC-TEPA in methanol (dash-dot line).

[0039] Figure 5 represents CO2 adsorption isotherms at 313 K for bare CDMC (diamonds) and crosslinked CDMC-TAEA-BDE synthesized using different TAEA volumes, while keeping the same BDE ratio; 405 uL TAEA (circles), 338 uL TAEA (squares) and 270 uL TAEA (triangles) as described in Example 4.

[0040] Figure 6 represents CO2 adsorption isotherms at 313 K for bare MOF-derived carbon (diamonds) and crosslinked MOF-derived carbons with TEPA-BDE (circles), TAEA-BDE (squares) and DETA-BDE (triangles) as described in Example 4.

[0041] Detailed description of embodiments of the invention

[0042] The term “amines comprising at least 2 amino groups” refers to branched and linear amines. Examples of linear alkyamines comprise ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), pentaethylenehexamine (PEHA), Linear Polyethylenimine (PEI) or Dipropylene triamine (DPA). Examples of branched alkyamines comprise tris(2-aminoethyl)amine (TAEA), Tris(2- aminopropyl)amine (TAP A), branched Polyethylenimine (PEI), Polypropylenimine tetramine dendrimer (DAB-Am-4).

[0043] The term “epoxide comprises at least 2 epoxy groups” refers to di-, tri-and multi-epoxides.

[0044] Examples of epoxides suitable in method according to the invention comprise butadiene diepoxide (BDE), diglycidyl ether (DGE), ethyleneglycol diglycidyl ether (EGDE), neopentyl glycol diglycidyl ether (NPGDE), bisphenol A diglycidyl ether (BPA-DE) and trimethylolpropane triglycidyl ether (TMPTE).

[0045] Suitable “porous material” a material having a BET surface area typically around from about 50 m2 / g and greater (e.g. from about 100 to about 4’000 m2 / g, preferably from 500 to about 4’500 m2 / g) and a pore volume value from about 0.1 cm3 / g and greater (e.g. from about 0.2 to about 5 cm3 / g preferably from 0.5 to 4 cm3 / g).

[0046] According to a particular embodiment, porous materials according to the invention are MOFs having a BET surface area from about 500 to about 4’000 m2 / g (e.g. from about 800 to about 3’500 m2 / g) and a pore volume value from about 0.2 to about 4 cm3 / g (e.g. from about 1 to about 3 cm3 / g).

[0047] The surface area and pore volume can be obtained by measuring N2 isotherms at 77K and subsequently fit the BET model as described in Brunauer et al., J. Am. Chem. Soc., 1938, 60, 2, 309 319 and Osterrieth et al., Adv. Mater., 2022, 34, 2201502 to extract the surface area. The surface area of porous materials can be also assessed by measuring Ar isotherms at 87K as described in Datar et al., Langmuir 2022, 38, 38, 11631 11640, which should give similar results as per N2 isotherms at 77K. However, some porous materials exhibit pores smaller than the kinetic diameter of N2 and N2 isotherms at 77K could exhibit lack of porosity. In these cases, CO2 isotherms at 195K can be used to test the porosity of the materials, thanks to the smaller diameter of CO2, using in this case the Langmuir model to obtain the surface area. Adsorbents modified with amines could also present lower surface areas than expected due to the repulsion between N2 gas used in the measurement and the amine groups present in the pores. As such, surface areas of these materials could be also assessed using CO2 isotherms at 195K (Kim et al, Microporous and Mesoporous Materials, 2016, 224, 294-301).

[0048] Examples of suitable porous materials according to the invention are MOFs, in particular MIL- 101(Cr) (alternatively called Cr-BDC = Cr3O(X)(H2O)2(BDC)3 where BDC is 1,4- benzenedicarboxylic acid and X = OH' or F' depending on the synthetic route). According to another embodiment, MOFs materials are Zr-based MOFs such as Zr-BDC and Zr- BDC-NH2.

[0049] Other examples of porous substrates include porous carbons, chitosan-derived carbon (e.g. as described in Peng et al., 2019, Chemical Engineering Journal, Volume 359, Pages 1159-1165) and MOF derived carbons (e.g. as described in Gadipelli etal., 2015, Adv. Mater., 27: 4903-4909; Ding et al., 2016, Chem. Commun., 52, 9757-9760).

[0050] The term “polymer” refers to the product of the cross-linking reaction between the amines and epoxide groups.

[0051] The expression “CO2 removal” refers to any gas separation where CO2is the target, such as natural gas sweetening, Direct Air Capture (DAC), Post-Combustion Capture (PCC), and the removal of CO2 from gas mixtures produced during incineration or cement / steel production.

[0052] Referring to the figures, in particular first to Figure 1, is provided an illustration of a method for the preparation of a CO2 adsorbent material.

[0053] More specifically, the steps of the embodiment illustrated in Figure 1 comprise: a) Providing a porous material either in dry form or dispersed in a solvent; b) Adding an amine-containing solution to the said porous material, wherein said amine- containing solution comprises an amine compound with at least 2 amino groups; c) Adding an epoxide compound to the amine treated porous material at least 30 seconds after the amine-containing solution addition, wherein said epoxide compound comprises at least 2 epoxy groups; d) Mixing the mixture under cross-linking reaction conditions; e) Recovering the material comprising cross-linked amines and epoxides inside the said porous material by isolating the porous material from the mixture.

[0054] According to a particular embodiment, the porous material is provided in dry form.

[0055] According to another particular embodiment, the porous material is provided dispersed in a polar solvent such as a polar alcohol, such as methanol, ethanol.

[0056] According to another particular embodiment, the porous material is provided dispersed in an apolar solvent (e.g. acetone, ether or cyclohexane).

[0057] According to another particular embodiment, the porous material is provided in the form of a MOF, in particular Cr-BDC. According to another particular embodiment, the porous material is provided in the form of a mesoporous chitosan-derived carbon.

[0058] According to another particular embodiment, the porous material is provided in the form of a MOF derived carbon such as carbonized MOF-5 (Zn-BDC).

[0059] According to another particular embodiment, the epoxide compound is added to the amine treated porous material after 5 min or less after the amine-containing solution addition.

[0060] According to a particular embodiment, the amine and epoxide are provided at an amine:epoxide molar ratio from about 1 : 10 to about 10: 1, for example from about 1 :4 to about 4: 1 (e.g. amine:epoxide ratio of 1 :2 to 3: 1).

[0061] According to a particular embodiment, the alkylamines have a molecular weight from about 60 g / mol to about 10’000 g / mol, preferably from about 100 to about 2’000 g / mol (e.g. from about 120 to 1’000 g / mol).

[0062] According to a particular embodiment, the alkylamines have a molecular weight from about 60 g / mol to about 1’200 g / mol.

[0063] According to a particular embodiment, the amine is a linear alkylamine.

[0064] According to a particular embodiment, the linear alkylamine is TEPA.

[0065] According to a particular embodiment, the amine is a branched alkylamine.

[0066] According to a particular embodiment, the branched alkylamine has at least two primary amines.

[0067] According to a particular embodiment, the branched alkylamine is TAEA.

[0068] According to a particular embodiment, the epoxide is a linear epoxide.

[0069] According to a particular embodiment, the epoxide is a linear epoxide with a MW from about 80 to about 350 g / mol for di and tri-epoxides.

[0070] According to a particular embodiment, the linear epoxide is BDE.

[0071] According to a particular embodiment, the branched epoxide is TMPTE.

[0072] According to a particular embodiment, the amine is a branched alkylamine and the epoxide is a linear epoxide.

[0073] According to another particular embodiment, the amine is a branched alkylamine and the epoxide is a branched epoxide. According to a particular embodiment, the amine is TAEA and the epoxide is BDE (e.g. a molar ratio 2: 1 for TAEA-BDE).

[0074] According to a particular embodiment, the amine was TAEA and the epoxide was TMPTE e.g. a molar ratio 3: 1 for TAEA- TMPTE).

[0075] According to a particular embodiment, the amine was TEPA and the epoxide was TMPTE e.g. a molar ratio 3 : 1 for TEPA- TMPTE).

[0076] According to a particular embodiment, the mixing under cross-linking reaction conditions is carried out for 30 s or longer, for example from about 5 min to about 24 h.

[0077] According to a particular embodiment, the method of the invention allows the conversion of small alkylamines (e.g. MW from 100 to 1000 g / mol) for example from 140 to 200 g / mol) into larger polymeric units (e.g. from about 250 to 50’000 g / mol), for example from about 700 to about 850 g / mol) directly inside of the pores of the host porous substrate, according to the epoxide ring opening reaction.

[0078] According to a particular embodiment, the recovering of the material from the solution is carried out via centrifugation or filtration.

[0079] Typically, the porous material is isolated from the solution by centrifugation or filtration to remove the excess of amines and / or epoxides.

[0080] According to a further particular embodiment, the porous material is isolated from the solution by centrifugation or filtration at room temperature.

[0081] According to a further particular embodiment, the residual solvent is removed from the isolated material under inert condition.

[0082] According to another further particular aspect, the method further comprises a step of subjecting the recovered material to a drying step under inert conditions (e.g. vacuum or nitrogen) after the centrifugation or filtration step.

[0083] According to a further particular aspect, the recovered material is dried either under atmospheric conditions at temperatures not higher than 50°C (e.g. 25-40°C) or under vacuum or under an inert gas flow to lead to a CO2 adsorbent material according to the invention.

[0084] According to a further particular aspect, the drying step is conducted under atmospheric conditions at temperatures not higher than 50°C (e.g. 25-40°C). According to another further particular aspect, the drying step is conducted under vacuum or under an inert gas flow at a temperature from about 25°C to 150°C (e.g. about 120°C) for 3h to about 24 h (e.g. from about 6 to about 12h).

[0085] According to a particular embodiment, is provided a CO2 adsorbent material obtainable by a process according to the invention.

[0086] According to another particular embodiment, is provided a CO2 adsorbent material, wherein said material comprises a porous substrate, containing in situ cross-linked polymers from amines containing at least 2 amino groups and a cross-linking agent containing at least two epoxy groups through epoxide ring opening reaction.

[0087] According to another particular embodiment, is provided a CO2 adsorbent material, wherein said material comprises a porous substrate presenting a BET surface area from about 50 to about 4’500 m2 / g, from about 50 to about 4’000 m2 / g, preferably 500 to 4’500 m2 / g (e.g. from about 800 to about 3’500 m2 / g for example from 850-1200 m2 / g or from 850-3500 m2 / g).

[0088] According to another particular embodiment, the BET of the CO2 adsorbent material according to the invention is lower than the initial BET of the starting porous material since the polymer resulting from the cross-linking is occupying the pores but cross-linked polymer is still accessible for CO2 capture.

[0089] According to a further particular embodiment, is provided a CO2 adsorbent material according to the invention having a CO2 capacity higher than 1 mmol / g at 0.15 bar and 313 K, for example from 1.5 to about 5 mmol / g.

[0090] According to further particular embodiment, is provided a CO2 adsorbent material according to the invention having a IAST CO2 / N2 selectivity at 313 K higher than 50, in particular higher than 150 or 200 (e.g. from about 170 to about 450).

[0091] According to another further particular embodiment, is provided a CO2 adsorbent material according to the invention having a cyclability over the course of repeated temperature swing adsorption (TSA) cycles (e.g. 313 K adsorption and 393 K desorption) up to 100 cycles with less than 2% weight loss with 100% CO2.

[0092] According to another further particular embodiment, is provided a CO2 adsorbent material according to the invention which is subjected to a drying treatment before use under atmospheric conditions at temperatures not higher than 50°C (e.g. 25-40°C). According to another further particular embodiment, is provided a CO2 adsorbent material according to the invention which is subjected to vacuum before use (e.g. at a temperature from about 25°C to about 150°C (e.g. about 120°C) for 3 to about 24 h (e.g. from about 6 to about 12h).

[0093] According to another further particular embodiment, is provided a CO2 adsorbent material according to the invention which is subjected before use to temperatures from about 25°C to about 150°C (e.g. about 120°C) in absence of oxidative environment, e.g. under a flow of an inert gas for 3 to about 24 h (e.g. from about 6 to about 12h).

[0094] According to another particular embodiment, the dried recovered material as a powder can be shaped into other structures, pellets, beads, or extrudates for use in CO2 capture as described in Yang et al., J. Am. Chem. Soc. 2020, 142, 31, 13415 13425 and Yeskendir et al., Mater. Adv., 2021,2, 7139-7186.

[0095] According to another particular embodiment, the dried recovered material is activated before use for CO2 capture, for example by applying a step as described herein.

[0096] According to another particular embodiment, is provided the use of the CO2 adsorbent material according to the invention for CO2 capture.

[0097] The invention having been described, the following examples are presented by way of illustration, and not limitation.

[0098] EXAMPLES

[0099] The method of the invention has been exemplified as follows with comparative examples shown below.

[0100] All chemicals were obtained from commercial sources and used as received without further purification. Cr(NO3)3 9H2O (99 %, 1000 g) was purchased from Acros Organics, 1,4- benzenedicarboxylic acid (BDC) (99+ %, 500 g) from Acros Organics, HNO3 (69 %, 1 L) from Roth, tris(2-aminoethyl)amine (TAEA) (97 %, 100 g) from Alfa Aesar, trimethylolpropane triglycidyl ether (TMPTE) (technical grade, 250 mL) from Sigma Aldrich, tetraethylene pentamine (TEPA) (technical grade, 500 g) from Sigma Aldrich, 1,3-butadiene diepoxide (BDE) (97 %, 25 mL) from Sigma Aldrich, methanol (MeOH) (8 L) from Reactolab, N,N-dimethylformamide (DMF) (99 %, 2.5L) from Fisher Chemical, ethanol (EtOH) (8 L) from Reactolab and anhydrous cyclohexane (99.5 %, 1 L) from Sigma Aldrich.

[0101] Example 1: Method of preparation of MOE based CO2 adsorbent material according to the invention The method of the invention was applied to a porous MOF substrate. Cr-BDC was selected as the porous substrate given its high stability and large surface area (3450 m2 / g), pore volume (1.66 cm3 / g), and cage sizes (2.9 nm and 3.4 nm diameter accessible through two micropore windows of 1.2 and 1.6 nm) (Zhao et al., 2015, Dalton Trans., 44 (38), 16791-16801).

[0102] Synthesis of Cr-BDC (porous material)

[0103] The synthetic procedure was adapted from the above reference where Cr(NO3)3 OELO and BDC were dispersed in deionized water, and 1 eq. of HNO3 (69 %) was added to the mixture that was heated in an autoclave at 200°C for 16 h.

[0104] In a 1 L Teflon jar, 52.8 g Cr(NOs)3 9H2O (0.132 mol) was dispersed in 18.0 g BDC (0.108 mol) in 660 mL deionized H2O and add 8.56 mL HNO3 69% (0.132 mol, 1 eq. respect chromium nitrate). The mixture was stirred for 30 min, bring the autoclave to a preheated oven at 473 K and let react for 16 h and let cool down naturally in the oven for 12 h. The supernatant was decanted and the solid collected in six 50 mL falcon tubes by centrifugation for 10 min at 7’800 rpm. The supernatant was discarded and the product was washed once with 35 mL DMF / falcon tube shaking them for 10 min. The solid was transferred to a 500 mL glass jar where 200 mL of fresh DMF was added and the mixture stirred at 700 rpm for 6 h. The solids were centrifuged and the supernatant discarded and this process was repeated 3 more times to ensure proper removal of unreacted species. In a similar manner, it was proceeded with ethanol, adding 200 mL of fresh solvent and stirring for 6 h, repeating this process 3 times. After that, the solid was dried in a vacuum oven at room temperature for 24 h. The material was heated up to 150°C during 2 h and kept at this temperature for 12 h under vacuum prior to N2 adsorption isotherm measurement at 77 K for BET surface area calculation.

[0105] The powder X-ray diffraction (PXRD) pattern of the resulting MOF matched the simulated one and the BET surface area (SBET), 3’309 m2 / g and pore volume (Vp), 1.65 cm3 / g were calculated from the N2 adsorption isotherms collected at 77 K. These values are in agreement with those previously reported (3’450 m2 / g and 1.6 cm3 / g). Further, Field-Emission Scanning Electron Microscopy (FE- SEM) images reveal octahedral crystals having an average size of 1.32 ± 0.25 pm (statistics were calculated using 100 particles of the same sample).

[0106] Synthesis of Cr-BDC-amine-epoxide composites (CO 2 adsorbent material according to the invention)

[0107] The method of the invention was applied as follows: a) Providing the MOF obtained above as dispersed in a polar solvent (e.g. methanol)

[0108] Small scale: 55 mg of as-synthesized Cr-BDC was dispersed in 2 mL MeOH. 10-times scale: the original reactions were performed at 10 times larger scales. 550 mg of as- synthesized Cr-BDC was dispersed in 20 mL MeOH. b) Adding an amine to the mixture, wherein said amine comprises at least 2 amino groups under stirring

[0109] Small scale: the desired amount of amine (see below) was added directly to this suspension. 10-times scale: the desired amount of amine (see below) was added directly to this suspension using a 100 mL round bottom flask. c) Adding an epoxide solution in a polar solvent (e.g. methanol) to the mixture not more than 5 min after the amine addition, wherein said epoxide comprises at least 2 epoxy groups

[0110] Small scale: The selected amount of epoxide (see below) was dissolved in 2 mL MeOH, which was added to the mixture.

[0111] 10-times scale: the selected amount of epoxide (see below) was dissolved in 20 mL MeOH, which was added to the original mixture. d) Leaving the cross-linking reaction mixture under stirring for about 3h

[0112] The suspension was stirred at 25°C for 3 h (or the desired temperature and time during optimization experiments). e) Recovering the material comprising cross-linked amines and epoxides inside the said porous material, by isolating the porous material from the mixture at room temperature and removing the residual solvent preferably in absence of oxygen

[0113] Finally, the mixture is centrifuged for 5 min at 7800 rpm and the supernatant is discarded. The resulting solid is vacuum dried at room temperature for 24 h.

[0114] Various conditions used:

[0115] Amine-epoxide ratios employed for the 10-times scale-up reactions:

[0116] Cr-BDC- 101-TAEA-TMPTE (3:1) (2)

[0117] 4.05 mL TAEA (36 equivalents) were employed as amine source and 2.56 mL TMPTE (12 equivalents) as epoxide source.

[0118] Cr-BDC-101-TEPA-BDE (3:1) (3)

[0119] 5.25 mL TEPA (36 equivalents) were employed as amine source and 0.71 mL BDE (12 equivalents) as epoxide source.

[0120] Cr-BDC-101-TAEA-BDE (2:1) (1) 4.05 mL TAEA (36 equivalents) were employed as amine source and 1.07 mL BDE (18 equivalents) as epoxide source.

[0121] Cr-BDC-TEPA-TMPTE (3:1) (4)

[0122] 5.25 mL TEPA (36 equivalents) were employed as amine source and 2.56 mL TMPTE (12 equivalents) as epoxide source.

[0123] Cr-BDC-TAEA-TMPTE 100-times scale: the original Cr-BDC-TAEA-TMPTE reaction was performed at 100 times larger scale. 5.5 g of as-synthesized Cr-BDC was dispersed in 200 mL MeOH and 40.5 mL TAEA was added directly to this suspension using a 1 L round bottom flask. Next, 25.6 mL od TMPTE was dissolved in 200 mL MeOH, which was added to the original mixture. The suspension was stirred at 298 K for 3 h. Finally, the mixture is centrifuged for 5 min at 7800 rpm and the supernatant is discarded. The resulting solid is vacuum dried at room temperature for 24 h. The material was activated by heating up to 393 K during 1 h and kept at this temperature for 12 h under vacuum prior to CO2 and N2 adsorption isotherm measurements.

[0124] Comparative examples (not from the invention)

[0125] Synthesis of bare polymers

[0126] The synthesis of the bare polymers was performed using the same amine-epoxide ratios, solvent amount, temperature and time as per the composites, but without porous substrate (no MOF added). In short, a certain amount of amine (see below) was dissolved in 20 mL MeOH in a 100 mL round bottom flask, to which a selected amount of epoxide (see below) dissolved in 20 mL MeOH was added. The solution was stirred at 298 K for 3 h. Next, the mixture is vacuum dried at room temperature for 24 h to obtain a honey -like polymer. Finally, the gel was activated at 393 K under vacuum for 12 h in order to complete the crosslinking and obtain a hard, solid polymer.

[0127] TAEA-TMPTE (3:1)

[0128] 4.05 mL TAEA (36 equivalents) were employed as amine source and 2.56 mL TMPTE (12 equivalents) as epoxide source.

[0129] TEPA-BDE (3:1)

[0130] 5.25 mL TEPA (36 equivalents) were employed as amine source and 0.71 mL BDE (12 equivalents) as epoxide source.

[0131] TAEA-BDE (2:1)

[0132] 4.05 mL TAEA (36 equivalents) were employed as amine source and 1.07 mL BDE (18 equivalents) as epoxide source.

[0133] TEPA-TMPTE (3:1) 5.25 mL TEPA (36 equivalents) were employed as amine source and 2.56 mL TMPTE (12 equivalents) as epoxide source.

[0134] Synthesis of Cr-BDC amine impregnated in cyclohexane (no epoxide)

[0135] The synthesis of these materials was done as a control to compare the effect of the epoxide crosslinking with the amines inside the MOF pores. This protocol was adapted from Li et al., 2019, supra. Cr-BDC was previously activated in a Schlenk line at 150°C for 12 h under vacuum. Next, working in the glovebox, 405 pL TAEA in 4 mL of anhydrous cyclohexane were added to 55 mg of activated Cr-BDC (Cr-BDC-TAEA in cyclohexane) or 525 pL TEPA in 4 mL of anhydrous cyclohexane were added to 55 mg of activated Cr-BDC (Cr-BDC-TEPA in cyclohexane). In both cases, the amine solution was stirred for only 5 min with the MOF powder and was subsequently centrifuged and washed 3 times with 15 mL cyclohexane outside the glovebox. Finally, the samples were dried in a vacuum oven at room temperature for 24 h. The material was activated by heating up to 393 K during 1 h and kept at this temperature for 12 h under vacuum prior to CO2 adsorption isotherm measurements and TSA cycles.

[0136] Synthesis of Cr-BDC amine impregnated in methanol (no epoxide)

[0137] The synthesis of these materials was done as a control to compare the effect of the epoxide crosslinking with the amines inside the MOF pores. The reaction conditions were the same as per the amine-epoxide composites of the invention, but in this case, no epoxide was added during the synthesis. In short, 55 mg of Cr-BDC was dispersed in 2 mL MeOH and the desired amount of amine (405 pL TAEA for the MIL-101 -TAEA or 525 pL TEPA for the Cr-BDC-TEPA), which was also dissolved in 2 mL MeOH, was added to this suspension. The suspension was stirred at 25°C for 3 h. Finally, the mixture is centrifuged for 5 min at 7’800 rpm and the supernatant is discarded. The resulting solid is vacuum dried at room temperature for 24 h. The material was activated by heating up to 393 K during 1 h and kept at this temperature for 12 h under vacuum prior to CO2 adsorption isotherm measurements and TSA cycles.

[0138] Example 2: Characterization of the MOF based CO2 adsorbent material according to the invention

[0139] The BET surface area, SBET, of the four composites, calculated from the measured N2 isotherms at 77 K, shows an expected drop ranging from 63-74 % (1’234-866 m2 / g) after the polymer modification when compared to the parent Cr-BDC (3’309 m2 / g). Surprisingly, the composites containing the linear amine, TEPA, (Cr-BDC-TEPA-TMPTE (4) and Cr-BDC-TEPA-BDE (3)) have a lower SBET when compared to those of the branched amine, TAEA, (Cr-BDC-TAEA- TMPTE (2) and Cr-BDC-TAEA-BDE (1)); however, they all retain their crystallinity post- functionalization. Given the decrease in the composite surface areas and shift in the pore size distribution to lower values, it is expected that the amine and epoxide species have reacted inside the MOF pores and are likely filling the largest pores first. The pore volume of the parent Cr-BDC (1.65 cm3 / g) decreases after the cross-linking by 65-75 % (0.41-0.57 cm3 / g).

[0140] To assess whether the polymer was found coating the external surface of the MOF crystals or well adsorbed in their pores, FE-SEM images were also obtained for all four composites and these images indicated that the MOF crystals retain sharp edges, further confirming that significant amounts of polymeric species do not accumulate on the external surface of the crystals. Further, there is also no evidence of polymeric aggregates independent from the MOF crystals. This was further supported by Transmission Electron Microscopy - Energy Dispersive X-rays (TEM-EDX) analysis of MOF crystals that were placed in an epoxy resin and serially sliced. The amine- containing polymer was found throughout the internal surface of the crystals, as indicated by a significant increase in the nitrogen signal throughout the composites.

[0141] Thermogravimetric analysis (TGA) data collected from RT up to 1073 K under air, shows a drop in the residual weight percentage for all four tested composites of the invention, when compared to the bare MOF; this is attributed to amine-epoxide crosslinked and hence, organics present in the framework pores. The organic content was estimated to be between 39 to 43 % for the four composites. Further, the elemental analysis (EA) results also showed a higher C % and N % content, which comes from the adsorbed organics in the pores.

[0142] To understand the nature of the polymerized species formed during the crosslinking reaction, a control experiment was carried out to form the bulk polymers using the same procedures as before, but without the MOF. During the reaction, the liquid became highly viscous, like honey. Interestingly, after heating the bulk polymers under vacuum (393 K for 12 h), to mimic the activation process of the MOF -polymer composites, there was a hardening of the material forming a rocky solid; this confirms that such a curing step is likely key to prevent the leaching of low- molecular weight oligomers inside the MOF pores. After curing, the four control polymers were dissolved in D2O and analyzed viaJH NMR spectroscopy. Notably, the peaks associated with the protons of the epoxide rings (2.90-3.15 ppm in BDE and 2.75-3.00 ppm in TMPTE) disappeared after being mixed with the amines due to the polymerization. In addition, the peaks related to the pendant ethyl group of TMPTE epoxide (0.88 and 1.38 ppm, for -CH3 and -CH2-, respectively) as well as the other proton signals of TMPTE between 3.30 and 4.10 ppm, become significantly broadened after the reaction with both TEPA and TAEA amines, indicating that the original molecule loses its symmetry. In the case of the reaction of TAEA with either BDE and TMPTE, there are several signs of the amine-epoxide reaction. First, the main signals of TAEA centered at 2.56 and 2.72 ppm (related to -CH2-CH2-) indicate a broadening and hence again a loss of symmetry. Moreover, there is a new signal centered at 2.62 ppm that arises from the crosslinking; this is attributed to new -CH2- groups that are formed when the epoxide rings open. Next, the bulk polymers, made without the MOF, were dissolved in the NaOD / EEO mixture (60 pL NaOD 40% in D2O in 500 pL D2O), which are the required conditions to digest Cr-BDC and the respective composites, to assess whether the basic conditions impact the polymer structure. However, all proton signals only shift slightly upfield, thus confirming that the polymer structure was retained under the digestion conditions. Next, the four activated Cr-BDC composites were digested using the same NaOD / D2O mixture (60 pL NaOD 40% in D2O in 500 pL D2O) as the bulk polymers, and the samples were sonicated for 30 min to ensure full dissolution of the Cr3+clusters. The resulting 'H NMR spectra prove the polymeric species formed within the MOF have similar chemical environments as the bulk polymers. In the case of the digested composites, the signal-to-noise ratio was lower than in the spectra of the bulk polymer due to lower concentration of polymer in the MOF pores. Also, the signal of the BDC ligand was found in all the digested composite samples at 7.70 ppm.

[0143] Considering that the polymers formed with and without the MOF look similar according to 'H NMR, the molecular weight of the polymers was also assessed. For this, electrospray Ionization- Mass Spectrometry (ESI-MS) data was collected on the bulk polymers synthesized without the MOF (dissolved in MeOH) and the polymer liberated from the MOF pore using a NaOH / methanol mixture (100 pL NaOH 10M in 500 pL methanol). Surprisingly, the ESI-MS spectra of the four bulk polymers, shown in, indicate low-MW oligomers, in addition to a signal originating from unreacted amine m / z signal (147.2 for TAEA and 190.2 for TEPA). For instance, for the branched- branched bulk polymer, TAEA-TMPTE, species ranging from trimeric oligomers (TAEA-TMTPE- TAEA, m / z = 594.5) to hexameric oligomers (4(TAEA)-2(TMPTE), m / z = 1188.96) could be identified. For the branched-linear structure, TAEA-BDE, oligomers of up to eleven units (6(TAEA)-5(BDE), m / z = 1307.1) were observed, and for the linear-linear reaction, TEPA-BDE, there were species reaching up to seven units (4(TEPA)-3(BDE)), m / z = 1014.9) with a purely linear structure. Last, the linear-branched polymer, TEPA-TMPTE, had oligomer sizes up to five units (3(TEPA)-2(TMPTE), m / z = 1201.9). When further comparing these ESI-MS spectra with those of the polymers liberated from the composites, there is a shift towards even lower MW oligomeric species indicating that the MOF pores may restrict the propagation of the polymeric chains. For instance, the branched-branched Cr-BDC-TAEA-TMPTE (2) composite presented dimeric to tetrameric structures with Na+generating adducts due to its presence in the digestion mixture (TAEA-TMPTE + Na+, m / z = 471.31, 2(TAEA)-TMPTE + 2Na+, m / z = 640.5, 3(TAEA)- TMPTE + 2Na+, m / z = 786.5). The branched-linear Cr-BDC-TAEA-BDE (1) revealed trimeric (TAEA-BDE-TAEA + Na+, m / z = 401.33) and tetrameric species (2(TAEA)-2(BDE), m / z 465.38). In the case of linear-linear, Cr-BDC-TEPA-BDE (3) higher MW structures were observed; there were trimeric 2(TEPA)-BDE + 2Na+(m / z = 510.4) and hexameric oligomers 3(TEPA)-3(BDE) + Na+(m / z = 850.7) observed. Notably, the longer chains obtained from the purely linear reactants (amine: TEPA) and epoxide (BDE) could be due to easier diffusion of TEPA and BDE in the pores of Cr-BDC over the branched reactants. Last, the linear-branched Cr-BDC-TEPA-TMPTE (4) composite also exhibited small species crosslinked in the pores such as dimeric TEPA-TMPTE + 3Na+(m / z = 560.4) and trimeric 2(TEPA)-TMPTE (m / z = 705.6) species.

[0144] Example 3: CO2 capture performance of the material of the invention

[0145] The CO2 material was activated by heating up to 393 K during 1 h and kept at this temperature for 12 h under vacuum prior to CO2 and N2 adsorption isotherm measurements and TSA cycles.

[0146] Each MOF-polymer composite of the invention was assessed for the PCC application. Flue gas is composed mainly of N2 (73-75 %) and CO2 (~15 %), and small quantities of other species such as O2, NOX, water vapor, etc. As such, the CO2 / N2 (15 / 85) selectivity of these composites was assessed via CO2 and N2 adsorption isotherms measured at 313 K (Figure 2a) using the IAST method (Simon et al., 2016, Comput. Phys. Commun., 200, 364-380).

[0147] While the bare MOF has a selectivity value of 11, the amine-epoxide composites offer CO2 / N2 (15 / 85) selectivity ranging from 202 to 416, which is 20 to 40 times higher than the bare Cr-BDC (Table 1 Summarizing the CO2 and N2 capacity at 313 K, and the calculated selectivity and enthalpy of adsorption of all the composites synthesized at larger scales and the bare Cr-BDC).

[0148] Table 1

[0149] Such performance highlights the benefits of the method of the invention, which not only favors an enhancement in CO2 capacity, but also a significant decrease in the N2. Notably, the adsorption capacity for N2 gas at 850 mbar and 313 K was reduced by at least a factor of 2, from 0.10 mmol / g for the parent Cr-BDC to 0.02-0.05 mmol / g for the composites (Table 1). Therefore, it is expected that such materials will present a minimal loss of CO2 capacity when exposed to post-combustion streams, where N2 is the predominant component (85 %). The observed trend in selectivity follows Cr-BDC-TEPA-BDE (3) > Cr-BDC-TAEA-BDE (1) > Cr-BDC-TAEA-TMPTE (2) ~ Cr-BDC- TEPA-TMPTE (4) » Cr-BDC.

[0150] The isosteric heat of CO2 adsorption (Qsi) of all four composites was then assessed. For this, isotherms, measured at variable temperatures (313, 333 and 353 K) were fit with a dual-site Langmuir model following Equation 1 : btPfb2P q ~qsat’1l + b P+ qsat’21 + b2P where q is the adsorbed amount in mmol / g, qsat,i is the adsorption capacity for site 1, bi is the Langmuir parameter for site 1 (qsat,2 and A 2 are the equivalent for site 2) and P is the pressure in Pa.

[0151] Next, the Clausius-Clapeyron equation (Equation 2 below) was subsequently used to calculate the isosteric enthalpy of adsorption, Qst, for CO2.

[0152] The Qst plots of the four composites expectedly indicate a chemisorption process with values ranging from -98 to -124 kJ / mol (Table 1), which stems from a nucleophilic attack of the amine on the carbon of the CO2, forming carbamate species in dry conditions and carbamate / bicarbonate species in humid environments. Notably, the branched-branched composite (Cr-BDC-TAEA- TMPTE) (2) had the highest Qstvalue -124 kJ / mol, while the linear-linear composite (Cr-BDC- TEPA-BDE) (3) showed the lowest value -98 kJ / mol. The lower Qstlikely stems from a higher ratio of accessible secondary amines over primary amines, the former being naturally weaker nucleophiles. For instance, TEPA already has a lower number of primary amines when compared to TAEA. Moreover, the reactivity of BDE as the crosslinking agent is higher than TMPTE and thus BDE could further reduce more primary amines to secondary amines during the reaction. The remaining two composites, containing either a branched amine with linear epoxide (Cr-BDC- TAEA-BDE) (1) or the linear amine with branched epoxide (Cr-BDC-TEPA-TMPTE) (2) have similar Qstvalues, which are -110 and -111 kJ / mol, respectively, despite a significant difference in the CO2 adsorption capacity at 0.15 bar (Table 1). As a reference, the isotherms of the bare Cr- BDC, were fitted to a single-site Langmuir model; as expected, the Qstvalue is in a similar range as other physisorbent materials, -30 kJ / mol. Thus, the isosteric heat of adsorption follows the trend: Cr-BDC-TAEA-TMPTE (2) > Cr-BDC-TEPA-TMPTE (4) ~ Cr-BDC-TAEA-BDE (1) > Cr-BDC- TEPA-BDE (3) » Cr-BDC.

[0153] While thermodynamic parameters are an important part of assessing a material’s potential in PCC applications, the materials will ultimately need to function under continuous flow, thus assessment of their kinetic performance in gas mixtures is pertinent. For that, breakthrough experiments were carried out in a custom-built apparatus where approximately 300 mg of previously activated sample were mixed with 300 mg of glass beads (108 pm diameter) to minimize the pressure drop throughout the bed. Next, the sample in the bed was purged with He at 313 K and a dry mixture of N2 and CO2 (85:15) was flowed through the bed (2 mL / min) held at a temperature of 313 K. The composition of the outlet stream was monitored using a mass spectrometer, as the parent MOF and all four composites were studied. Under dry conditions, the N2 / CO2 kinetic separation between was up to 12 times higher (103 min / g) for the best-performing composite (Cr-BDC-TAEA-BDE (1), branched-linear) when compared to the parent material, Cr-BDC (8 min / g) (Figure 3a and 3d). Whilst the linear-branched Cr-BDC-TEPA-TMPTE (4) composite presented the lowest breakthrough separation time (51 min / g) (Figure 3e), both Cr-BDC-TAEA-TMPTE (branched- branched) (2) and Cr-BDC-TEPA-BDE (linear-linear) (3) offered intermediate separation times of 87 and 89 min / g, respectively (Figures 3b and 3c).

[0154] Next, each sample was also tested under humid conditions by flowing the CCE mixture (85:15) with an 80 % relative humidity (RH). In this case, the bed was pre-saturated with 80 % RH under He flow for 2 h prior to flowing the gas mixture. Remarkably, under humid conditions the kinetic separation time between N2 and CO2 was increased for all the composites by 25 to 39 %. This behavior can be easily explained. In the dry state there is the primary formation of carbamate species, which have two amines involved in the chemisorption per CO2. However, humid conditions promote the formation of bicarbonate species, where only one protonated amine participates in the adsorption process of CO2 as presented below CO2 adsorption a proposed mechanism using amines in dry or humid conditions (Scheme 1) (D'Alessandro et al., 2010, Angew. Chem. Int. Ed., 49 (35), 6058-6082).

[0155] Scheme 1 a) b) This decrease in the amine:CO2 ratio increases capacity. On the contrary, the breakthrough separation time of the parent Cr-BDC reduced by 38 %, due to the competitive nature of water for CO2 adsorption sites (Figure 3a). The observed trend in the humid breakthrough experiments is as follows: Cr-BDC-TAEA-BDE (1) > Cr-BDC-TEPA-BDE (3) ~ Cr-BDC-TAEA-TMPTE (2) > Cr- BDC-TEPA-TMPTE (4) » Cr-BDC, and, within error of the experiment, follows the same trend as observed under the dry conditions (Table 2).

[0156] Table 2 It can therefore be deduced that the use of branched amine (TAEA) is favored in breakthrough experiments when compared to the linear ones (TEPA), likely due to the larger number of accessible primary amines. Further, the use of a linear epoxide (BDE) compared to the branched one (TMPTE) is best; this likely stems from the lower molecular weight, which boosts capacity (Table 2). Further, the linearity of the BDE could help ease access to amines.

[0157] While breakthrough time and thermodynamic parameters are important part of the assessment process for PCC applications, long-term cyclability is equally important. So, motivated by the nice performance of the composites presented here, cyclability of each of the four materials was assessed under temperature swing adsorption (TSA) conditions, with 5-minute adsorption (313 K) and desorption (393 K) cycles. For a comparison, Cr-BDC was also impregnated with only the two amines, TAEA and TEPA, excluding the crosslinking agents. For this, traditional wet impregnation approaches were used in either anhydrous cyclohexane or MeOH (McDonald et al., 2012, supra).

[0158] The anhydrous cyclohexane can create a chemical potential difference due to the non-polar nature of the solvent, promoting more amine impregnation into the Cr-MOF after activation, particularly appendage to the open Cr3+sites. For the four materials produced using traditional wet impregnation approaches, the CO2 adsorption isotherms were collected at 313 K. The measurements expectedly revealed a higher capacity (0.15 bar) for the materials impregnated using cyclohexane (4.10 mmol / g for Cr-BDC-TAEA and 2.40 mmol / g for Cr-BDC-TEPA) when compared to the two materials impregnated with the amines in methanol (2.09 mmol / g for Cr-BDC- TAEA and 1.81 mmol / g for Cr-BDC-TEPA). Also, as expected, the branched amine in all cases gave rise to higher capacities. Next, the four MOF-polymer composites and four materials obtained via traditional wet impregnation were assessed over the course of -100 TSA cycles. For this, the samples were loaded in a TGA instrument and pure CO2 was employed as gas while the temperature was programmed to switch from 313 K (adsorption) to 393 K (desorption) (Figure 4). From these experiments, the importance of the epoxide crosslinking on the long-term performance can be seen. For instance, in the case of the TAEA-containing materials (Figure 4a), both the Cr-BDC-TAEA impregnated in cyclohexane and in methanol present a remarkable loss of capacity during the first 10 cycles (Figure 4). Even though they had higher capacities in the CO2 adsorption isotherms than that of the Cr-BTC-TAEA-epoxide composites, their capacity is significantly lower after only a few adsorption / desorption cycles. Notably, the baseline shown in the TGA plots drop dramatically with cycling owed to amine loss, which decreases the overall mass of the composite after each cycle. On the contrary, the Cr-BDC-TAEA-TMPTE (2) and Cr-BDC-TAEA-BDE (1) composites have flat baselines in the TGA plots, which indicates that amine loss is eliminated. Both amine- epoxide composites present significantly higher capacities after 100 cycles when compared to Cr- BDC impregnated with the TAEA using traditional approaches. Notably, the final capacity of Cr- BDC-TAEA is only 0.77 mmol / g and 0.46 mmol / g in cyclohexane and methanol, respectively.

[0159] In the case of Cr-BDC-TEPA (Figure 4b) and the two epoxide-amine composites, Cr-BDC-TEPA- BDE (3) and Cr-BTC-TEPA-TMPTE (4), a similar trend is observed; while Cr-BDC-TEPA prepared in cyclohexane or methanol presented higher capacities in the CO2 adsorption isotherms, they quickly lose their capacity during the first few cycles in the TSA cycling experiments (Figure 4b). Moreover, they again reveal a plummeting baseline. On the contrary, Cr-BDC-TEPA-BDE (3) and Cr-BDC-TEPA-TMPTE (4) composites present a flat baseline, and their cycling capacities are more well-maintained over 100 adsorption / desorption cycles (from 1.71 and 1.69 mmol / g to 1.16 and 0.87 mmol / g, respectively) (Figure 4b). It is noted that by cycle 100, most of the material’s cyclable capacity has plateaued, with the exception of Cr-BDC-TEPA in cyclohexane, which is still continuing to decrease significantly.

[0160] Last, given that flue gas is highly humid, we selected one of the best performing materials according to the aforementioned cycling experiments (Figure 4a), namely Cr-BDC-TAEA-TMPTE, and subsequently cycled it more than 350 times in a CO2 / N2 (~15% / 85%) mixture containing 80% relative humidity. As expected, the measurements again present a flat baseline, indicating limited to no amine loss during cycling. Further, the cyclable capacity remains effectively the same over the cycle period. Unfortunately, there are also peaks and troughs observed in the TGA data as well, which reveal ~2 weight % fluctuations in the quantity of CO2 and H2O adsorbed. Given this, the temperature of the room that houses the TGA was measured during a second set of cycling experiments. The temperature profile matches the thermal fluctuations observed in the room. Such temperature changes directly impact the humidity level in the gas mixture overtime and subsequently give rise to the observed fluctuations in the TGA plots. The latter makes it impossible to elucidate the actual quantity of CO2 present in the sample at a given time. To overcome this issue, it is envisioned that such TGA cycling experiments should be carried out inside of a temperature and humidity-controlled environment in the future. Nevertheless, beyond the temperature control issues, the humid cycling experiments indicate minimal loss of overall capacity in the materials and hence minimal to no amine degradation after extensive cycling. This consistent performance over time makes these new composite materials of strong interest.

[0161] With the aim to demonstrate that this synthetic approach was reproducible, three different reactions for each amine-epoxide combination were synthesized; indeed, the isotherms showed similar CO2 capacity for all repeated reactions. Noteworthy, the powder X-ray diffraction (PXRD) patterns of each Cr-BDC-amine-epoxide composite match well with the expected PXRD pattern of Cr-BDC, confirming the stability of the MOF in the presence of an excess of amines.

[0162] The CO2 adsorption isotherm obtained from the resulting composite is comparable to that of the reaction done on the 10-time scale.

[0163] Example 4: Method of preparation of porous carbon-based CO2 adsorbent material according to the invention

[0164] The method of the invention is also suitable to various types of porous materials. The method of the invention was used with Chitosan-Derived Mesoporous Carbon (CDMC) and MOF- derived carbons as porous substrates.

[0165] Chitosan-Derived Mesoporous Carbon (CDMC) and MOF-derived carbons were prepared as described in the literature. The Powder X-ray diffraction (PXRD) pattern showed that the synthesized CDMC is amorphous and the thermal gravimetric analysis (TGA) showed no residual inorganic content in the CDMC, meaning that the silica beads template was successfully removed by the HF treatment.

[0166] The textural properties of the as-synthesized CDMC are presented under Table 3:

[0167] Table 3

[0168] 9 3 3 3

[0169] Sample SBET (m / g) Vp (cm / g) V micro (cm / g) V meso (cm / g)

[0170] CDMC 847 259 046 E17

[0171] Crosslinking CDMC with Amines and Epoxides

[0172] The as-synthesized CDMC dispersed in methanol and then two amines were used separately in the method of the invention: TAEA (branched amine with 4 amine groups) and TEPA (linear amine with 5 amine groups). They were crosslinked separately with two epoxides, namely BDE (linear with 2 epoxide groups) and TMPTE (branched with 3 epoxide groups).

[0173] The pore size distributions of the impregnated carbons, derived from the isotherms, show that the pores of the carbons are filled by the polymer molecules. The total pore volume is 6 to 20 times smaller than for the bare CDMC. The micropores in particular (< 2 nm) are almost completely filled, the few remaining pores are mostly mesopores (< 50 nm). The diffusion of the amines and epoxides into the pores being successful, the CO2 uptake of these impregnated carbons was assessed by measuring CO2 adsorption isotherms at 313 K, the relevant postcombustion capture temperature. In all the cases the CO2 capacity at 0.15 bar and 313 K was remarkably higher than that of the bare CDMC support (0.3 mmol / g). CO2 capacities as high as 2.18 mmol / g at 0.15 bar and 313 K were obtained for the CDMC-TAEA-BDE composite (5) (2: 1 TAEA:BDE molar ratio) which is 7 times higher than the bare CDMC porous support (Figure 5).

[0174] Crosslinking MOF-derived carbons with Amines and Epoxides

[0175] MOF-derived carbons from MOF-5 (Zn-BDC) and IRMOF-3 (Zn-NH2-BDC) were synthesized and then cross-link the amines inside of the porous structure to make a solid sorbent for CO2 capture, according to a method of the invention. These MOFs are synthesized using inexpensive and readily available materials, and their synthesis is well-documented (Gadipelli et al., 2015, supra; Ding et al., 2016, supra).

[0176] MOFS (Zn-BDC) synthesis

[0177] 2.2 g (10.0 mmol) of Zn(AcO)2 2(H2O) (zinc acetate) are put inside a round-bottom flask and 75 mL of N,N-dimethylformamide (DMF) are added. The mix is stirred at room temperature until the zinc acetate is dissolved. In a separate glass vial, 660 mg (4.0 mmol) of terephthalic acid (BDC) are added to 75 mL of DMF to make the linker solution. The mix is sonicated at room temperature until the linker is dissolved. The linker solution is slowly added (dropwise) to the Zn solution. A precipitate is formed. The mix is left in the flask, at room temperature, under stirring, for 24h. It is then collected into 3x50 mL centrifuge tubes for washing: 1 wash with 40 mL DMF and 3 washes with 40 mL tetrahydrofuran (THF). A white paste is collected.

[0178] IRMOF-3 (Zn-NH2-BDC) synthesis

[0179] The procedure is the exact same as for the MOF-5, with the BDC linker being replaced with 720 mg (4.0 mmol) NH2-BDC (2-amino terephthalic acid).

[0180] Carbonization of the MOF

[0181] The paste-like MOF suspension in THF is put inside a quartz tube furnace under Ar or N2 flow (both yielded the same results). Heating program: from room temperature to l’000°C at 5°C / min, then l’000°C for 6h. A black powder is collected.

[0182] The CO2 capacity for the bare MOF-derived carbons was assessed by measuring adsorption isotherms at 313 K and low capacities between 0.4-0.7 mmol / g were obtained for all the carbonized MOFs.

[0183] Amine-epoxide crosslinking in MOF-derived carbons

[0184] The method of the invention was used with butadiene diepoxide (BDE) as cross-linking agent and MOF-5 (Zn-BDC)-derived carbons as porous substrate, with a selection of 3 low-molecular weight amines: tris(2-aminoethyl)amine (TAEA), diethylenetriamine (DETA) and tetraethylenepentamine (TEPA). The highest CO2 adsorption capacity is observed for TEPA-BDE composite (6), followed by TAEA-BDE composite (7), and then by DETA-BDE (8).

[0185] Impregnation with low molecular weight amines 60 mg of carbonized MOF was put into a glass vial with 2 mL methanol (MeOH). 2.7 mmol of the corresponding amine were added under stirring at room temperature: 405 pL of tris(2-aminoethyl)amine (TAEA), 292 pL of diethylenetriamine (DETA) and 513 pL of tetraethylenepentamine (TEPA) respectively. 107 pL (1.38mmol) of 1,3- butadiene diepoxide (BDE) was mixed separately to 2mL MeOH, then added to the vial in order to crosslink the amines. After 3h under stirring at room temperature, the mix is centrifuged, the supernatant is discarded and the leftover solid is dried overnight under a vacuum.

[0186] CO2 capacities as high as 2.58 mmol / g were obtained for the MOF-5-DC-TEPA-BDE composite (6), which is 5 times larger than the parent MOF-5-derived carbon (Figure 6).

[0187] Herein, altogether, those data support that the method of the invention is simple and scalable and allows to crosslink amines and epoxides in the pores of a porous substrate leading to a high performing adsorbent for post combustion CO2 capture. The method allows to provide materials with high CO2 / N2 selectivity (e.g. 301), intermediate isosteric heat of CO2 adsorption (e.g. -110 kJ / mol), high CO2 capacity (from higher than 1.8 mmol / g such as for 2.2 mmol / g), and remarkable CO2 / N2 separation times (e.g. up to 142 min / g). Moreover, the obtained materials have a good cycling capacity which is well retained, even after 100 cycles, in both dry and humid conditions in a temperature swing process (313K adsorption and 393K desorption) carried out inside of a TGA very suitable for CO2 capture from flue gases.

Claims

Claims1. A method for the preparation of a CO2 adsorbent material comprising the steps of: a) Providing a porous material either in dry form or dispersed in a solvent; b) Adding an amine-containing solution to the said porous material, wherein said amine- containing solution comprises an amine compound with at least 2 amino groups; c) Adding an epoxide compound to the amine treated porous material at least 30 seconds after the amine-containing solution addition, wherein said epoxide compound comprises at least 2 epoxy groups; d) Mixing the mixture under cross-linking reaction conditions; e) Recovering the material comprising cross-linked amines and epoxides inside the said porous material by isolating the porous material from the mixture and preferably removing the residual solvent from the isolated material under inert condition.

2. A method according to claim 1, wherein the porous material has a porosity presents a BET surface area from about 500 to 4’500 m2 / g (e.g. from 850-3’500 m2 / g).

3. A method according to claim 1, wherein the porous material has a pore volume value 0.5 to 4 cm3 / g.

4. A method according any one of the preceding claims, wherein the amine and epoxide are provided at an amine:epoxide molar ratio from 1 : 10 to about 10: 1 (e.g. amine:epoxide ratio of 1 :2 to 3: 1).

5. A method according to any one of the preceding claims, wherein the porous material is provided in the form of a MOF, in particular Cr-BDC.

6. A method according to any one of claims 1 to 4, wherein the porous material is provided in the form of a mesoporous chitosan-derived carbon or a MOF-derived carbon.

7. A method according to any one of the preceding claims, wherein the alkylamine has a molecular weight from about 60 g / mol to about l’200g / mol).

8. A method according to any one of the preceding claims, wherein the alkylamine is a linear alkylamine.

9. A method according to any one of the preceding claims, wherein the alkylamine is TEPA.

10. A method according to any one of claims 1 to 7, wherein the amine is a branched alkylamine.

11. A method according to claim 10, wherein the branched alkylamine is TAEA.

12. A method according to any one of the preceding claims, wherein the epoxide is a linear epoxide.

13. A method according to claim 12, wherein the linear epoxide is BDE.

14. A method according to any one of claims 1 to 11, wherein the epoxide is TMPTE.

15. A method according to any one of the preceding claims, wherein the recovering of the material from the solution is carried out via centrifugation or filtration.

16. A method according to any one of the preceding claims, further comprises a step of subjecting the recovered material to a drying step in absence of oxidative environment at a temperature from about 25°C to 150°C.

17. A CO2 adsorbent material obtainable by a process according to anyone of claims 1 to 16.

18. A CO2 adsorbent material, wherein said material comprises a porous substrate containing in situ cross-linked polymers from amines containing at least 2 amino groups and a cross-linking agent containing at least two epoxy groups through epoxide ring opening reaction, wherein the porous material has a porosity presents a BET surface area from about 500 to 4’500 m2 / g (e.g. from 850-3’500 m2 / g).

19. A CO2 adsorbent material according to claims 17 or 18 having a CO2 capacity higher than 1 mmol / g at 0.15 bar and 313 K.

20. A CO2 adsorbent material according to anyone of claims 16 to 19 having a IAST CO2 / N2 selectivity at 313 K higher than 50, in particular higher than 150 or 200.

21. Use of a CO2 adsorbent material according to any one of claims 16 to 20 for CO2 removal from a gas mixture.

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