Defect-free mixed-matrix membranes consisting of anion-pillared metal-organic frameworks and poly(ionic liquid)s for separation of acetylene from ethylene

Membrane separation is an effective strategy to reduce the energy consumption during conventional processes in the petrochemical industry. Currently, membrane separations of light hydrocarbons are still underdeveloped and the general problem of the poor compatibility between the polymer and inorganic particles in mixed-matrix membranes (MMMs) must be addressed. Herein, the separation of acetylene/ethylene mixture employing a defect-free mixed-matrix membrane consisting of anion-pillared metal-organic frameworks (MOFs, SIFSIX-2-Cu-i, SIFSIX = hexafluorosilicate, 2 = 4,4′-dipyridylacetylene, i = interpenetrated) and poly(ionic liquid)s (PILs) is for the first time reported. The strategy of enhancing compatibility by strong electrostatic interactions between ionic polymer and MOFs is realized and defect-free MMMs can be prepared readily without extra treatment. With optimized ion density, an acetylene/ethylene separation selectivity of 112.0 is achieved on SIFSIX-2-Cu-i/P[ATMA][BF4]-g-PEG500 ([ATMA][BF4] = 2-(acryloyloxy)ethyl-trimethylammonium tetrafluoroborate, PEG = poly(ethylene glycol)) mixed membrane, indicating that our strategy is effective to prepare highly selective defect-free membranes. The strategy of strengthening electrostatic interactions between ionic polymer and anion-pillared MOFs provides a general approach for the fabrication of defect-free MMMs which has promise in gas separation applications.