Triple-ligand zeolitic imidazolate frameworks for highly CO2 selective mixed matrix membranes

•A series of triple ligand-coordinated ZIF-8s (TAZIF-8s) were successfully prepared.•The TAZIF-8s enhanced chemical interaction and molecular sieving ability toward CO2.•A high dispersibility of TAZIF-8s enabled high TAZIF-8 loading (40 wt%) mixed matrix membranes (MMMs).•TAZIF-8 MMMs effectively suppressed both the physical aging and CO2-induced plasticization.•High CO2 separation performance of TAZIF-8 MMMs was retained even after water vapor exposure.