Highly Permeable Mixed Matrix Membranes for Gas Separation via Dual Defect‐Engineered Zeolitic Imidazolate Framework‐8

Defect engineering of metal–organic frameworks (MOFs) is a promising strategy for tailoring the interfacial characteristics between MOFs and polymers, aiming to create high‐performance mixed matrix membranes (MMMs). This study introduces a new approach using dual defective alkylamine (AA)‐modulated zeolitic imidazolate framework‐8 (DAZIF‐8), to develop high‐flux MMMs. Tributylamine (TBA) and triethylamine (TEA) monodentate ligands coordinate with zinc ions in varying compositions. A mixture of Zn(CH3COO)2·2H2O:2‐methylimidazole (Mim):AA in a 1:1.75:5 molar ratio facilitates high‐yield coordination between Zn and multiple organic ligands, including Zn‐Mim, Zn‐TEA, and Zn‐TBA (>80%). Remarkably, DAZIF‐8 containing 3 mol% TBA and 2 mol% TEA exhibits exceptional characteristics, such as a Brunauer–Emmett–Teller surface area of 1745 m2 g−1 and enhanced framework rigidity. Furthermore, dual Zn‐AA coordination sites on the framework's outer surface enhance compatibility with the polyimide (PI) matrix through electron donor–acceptor interactions, enabling the fabrication of high‐loading MMMs with excellent mechanical durability. Importantly, the PI/DAZIF‐8 (60/40 w/w) MMM demonstrates an unprecedented 759% enhancement in ethylene (C2H4) permeability (281 Barrer) with a moderate ethylene/ethane (C2H4/C2H6) selectivity of 2.95 compared to the PI, surpassing the polymeric upper limit for C2H4/C2H6 separation. Various defective zeolitic imidazolate framework‐8 (ZIF‐8) derivatives are synthesized. Dual‐defective ZIF‐8 (DAZIF‐8) is produced using both tributylamine and triethylamine. DAZIF‐8 exhibits unexpectedly higher Brunauer–Emmett–Teller surface area and pore volume than single‐defective ZIF‐8. The polyimide/DAZIF‐8 membrane boosts C2H4 permeability by 759%, retaining C2H4/C2H6 selectivity and resisting C2H4 plasticization up to 32 atm.