Exploitation of Pore\nStructure for Increased CO<sub>2</sub> Selectivity in Type 3 Porous\nLiquids

CO<sub>2</sub> capture requires materials with high adsorption\nselectivity and an industrial ease of implementation. To address these\nneeds, a new class of porous materials was recently developed that\ncombines the fluidity of solvents with the porosity of solids. Type\n3 porous liquids (PLs) composed of solvents and metal–organic\nframeworks (MOFs) offer a promising alternative to current liquid\ncarbon capture methods due to the inherent tunability of the nanoporous\nMOFs. However, the effects of MOF structural features and solvent\nproperties on CO<sub>2</sub>–MOF interactions within PLs are\nnot well understood. Herein experimental and computational data of\nCO<sub>2</sub> gas adsorption isotherms were used to elucidate both\nsolvent and pore structure influences on ZIF-based PLs. The roles\nof the pore structure including solvent size exclusion, structural\nenvironment, and MOF porosity on PL CO<sub>2</sub> uptake were examined.\nA comparison of the pore structure and pore aperture was performed\nusing ZIF-8, ZIF-L, and amorphous-ZIF-8. Adsorption experiments here\nhave verified our previously proposed solvent size design principle\nfor ZIF-based PLs (1.8× ZIF pore aperture). Furthermore, the\nCO<sub>2</sub> adsorption isotherms of the ZIF-based PLs indicated\nthat judicious selection of the pore environment allows for an increase\nin CO<sub>2</sub> selectivity greater than expected from the individual\nPL components or their combination. This nonlinear increase in the\nCO<sub>2</sub> selectivity is an emergent behavior resulting from\nthe complex mixture of components specific to the ZIF-L + 2′-hydroxy­acetophenone-based\nPL.