Ultra‐Tuning of the Aperture Size in Stiffened ZIF‐8_Cm Frameworks with Mixed‐Linker Strategy for Enhanced CO 2 /CH 4 Separation

ZIF‐8 membrane has the potential for CO 2 /CH 4 separation based on size exclusion. But if traditionally prepared by solvothermal methods, it shows only negligible selectivity due to the linker mobility. Here, ≈500 nm‐thin hybrid ZIF‐7 x ‐8 membranes with suppressed linker mobility and narrowed window aperture are prepared by a fast current‐driven synthesis (FCDS) within 20 min. The in situ electric field during FCDS allows the formation of stiffened ZIF‐8_Cm as parent skeleton and the mixed‐linker strategy is applied to narrow the aperture size simultaneously. The ZIF‐7 22 ‐8 membrane shows significantly sharpened molecular sieving for CO 2 /CH 4 with a separation factor above 25, which soared tenfold compared with other unmodified ZIF‐8 membranes. Additionally, the membrane shows exceptional separation performance for H 2 /CH 4 and CO 2 /N 2 , with separation factors of 71 and 20, respectively. After 180 h temperature swing operation, it still maintains the excellent separation performance.