Fine pore engineering in a series of isoreticular metal-organic frameworks for efficient C(2)H(2)/CO(2) separation

The separation of C(2)H(2)/CO(2) is not only industrially important for acetylene purification but also scientifically challenging owing to their high similarities in physical properties and molecular sizes. Ultramicroporous metal-organic frameworks (MOFs) can exhibit a pore confinement effect to differentiate gas molecules of similar size. Herein, we report the fine-tuning of pore sizes in sub-nanometer scale on a series of isoreticular MOFs that can realize highly efficient C(2)H(2)/CO(2) separation. The subtle structural differences lead to remarkable adsorption performances enhancement. Among four MOF analogs, by integrating appropriate pore size and specific binding sites, [Cu(dps)(2)(SiF(6))] (SIFSIX-dps-Cu, SIFSIX = SiF(6)(2-), dps = 4.4’-dipyridylsulfide, also termed as NCU-100) exhibits the highest C(2)H(2) uptake capacity and C(2)H(2)/CO(2) selectivity. At room temperature, the pore space of SIFSIX-dps-Cu significantly inhibits CO(2) molecules but takes up a large amount of C(2)H(2) (4.57 mmol g(−1)), resulting in a high IAST selectivity of 1787 for C(2)H(2)/CO(2) separation. The multiple host-guest interactions for C(2)H(2) in both inter- and intralayer cavities are further revealed by dispersion-corrected density functional theory and grand canonical Monte Carlo simulations. Dynamic breakthrough experiments show a clean C(2)H(2)/CO(2) separation with a high C(2)H(2) working capacity of 2.48 mmol g(−1).