Optimizing Sieving Effect for CO₂ Capture from Humid Air Using an Adaptive Ultramicroporous Framework

Abstract

Excessive CO2 in the air can not only lead to serious climate problems but also cause serious damage to humans in confined spaces. Here, a novel metal–organic framework (FJI‐H38) with adaptive ultramicropores and multiple active sites is prepared. It can sieve CO2 from air with the very high adsorption capacity/selectivity but the lowest adsorption enthalpy among the reported physical adsorbents. Such excellent adsorption performances can be retained even at high humidity. Mechanistic studies show that the polar ultramicropore is very suitable for molecular sieving of CO2 from N2, and the distinguishable adsorption sites for H2O and CO2 enable them to be co‐adsorbed. Notably, the adsorbed‐CO2‐driven pore shrinkage can further promote CO2 capture while the adsorbed‐H2O‐induced phase transitions in turn inhibit H2O adsorption. Moreover, FJI‐H38 has excellent stability and recyclability and can be synthesized on a large scale, making it a practical trace CO2 adsorbent. This will provide a new strategy for developing practical adsorbents for CO2 capture from the air.

Pore engineering of metal–organic frameworks for boosting low-pressure CO2 capture

“…Very recently, an adaptive UM-MOF, FJI-H38, assembled from 3,5-di(4 H -1,2,4-triazol-4-yl) benzoic acid and Co(BF 4 ) 2 was reported by Song and co-workers. 57 Interestingly, the pore size of FJI-H38 reduced from 4.2 to 3.4 Å after CO 2 capture, indicative of the adsorbed-CO 2 -induced pore shrinkage. Such characteristics endow FJI-H38 with good superiority in sieving of CO 2 from air (2.33 mmol g −1 at 0.01 bar).…”

“…, have also been demonstrated as ligands to give UM-MOFs. 54–57,79,80 Nandi et al synthesized a nickel-based UM-MOF, Ni-4PyC, based on the solvothermal reaction of Ni 2+ with isonicotinic acid. 54 Grand canonical Monte Carlo (GCMC) simulations suggest that the CO 2 adsorption amount of Ni-4PyC can reach up to 8.2 mmol g −1 at 10 bar and 298 K with a remarkably high CO 2 /H 2 selectivity of 285 for H 2 /CO 2 mixtures (20 : 80) at 40 °C and 10 bar.…”

Water-stable metal–organic frameworks (MOFs): rational construction and carbon dioxide capture

“…26d ). 190 Like N and O atoms, the more electronegative fluorine atoms can also adsorb CO 2 effectively. As confirmed by Eddaoudi's group, the CO 2 adsorbed in the pores of NbOFFIVE-1-Ni can be efficiently stabilized by four different (NbOF 5 ) 2− with a C⋯F distance of 3.050(8) Å, lower than the sum of the van der Waals radii of C and F atoms ( Fig.…”

“…39a ). 190 Due to the stable CoN 4 O nodes, FJI-H38 could retain its framework in aqueous solutions with a pH of 2–12. It could capture trace CO 2 from air with the high adsorption capacity (0.57 mmol g −1 at 0.5 mbar and 2.33 mmol g −1 at 0.01 bar) and the very high adsorption selectivity (6469 at 0.5 mbar) but a relatively low adsorption enthalpy (27 kJ mol −1 ) ( Fig.…”

Physicochemical properties, equilibrium adsorption performance, manufacturability, and stability of TIFSIX-3-Ni for direct air capture

“…Their small pore sizes and chemical nature allow for high CO2 adsorption capacity at the relevant low pressures (> 1.0 mmol g -1 at 0.4 mbar CO2 and 25 °C) and limited N2 adsorption, as well as lower CO2 heat of adsorption than many amine-functionalized chemisorbents. Notable ultramicroporous MOFs reported for DAC include NbOFFIVE-1-Ni, SIFSIX-3-Cu, SIFSIX-18-Ni-β, TIFSIX-3-Ni, TIFSIX-3-Co, GeFSIX-3-Ni, WO2F4-1-Ni, and FJI-H38 [9][10][11][12][13][14][15][16]. We direct the reader to Zhang et al [17] and Bose et al [18] for a comprehensive overview of these, and other MOF adsorbents for DAC.…”