Mixed Matrix Membranes Based on Benzimidazole-Modulated MOFs for Enhanced CO ₂ Capture and H ₂ Separation

Mixed matrix membranes (MMMs) integrate the benefits of organic polymer membranes with porous inorganic fillers, leading to an enhancement in both gas permeability and separation selectivity. As a commonly used filler, ZIF-8 exhibits promise in enhancing the gas separation performance of MMMs. However, further improving the gas selectivity of ZIF-8-based MMMs remains a challenge. To improve the gas selectivity of ZIFs, we synthesized ZIF-BI via the “mixed linker method” using a bulky benzimidazole ligand, which restricts imidazole ring twisting and enhances gas selectivity. At a 40 wt % ZIF-BI loading, the ZIF-BI/6FBDA MMM exhibited CO2 and H2 permeabilities of 25.7 and 49.6 Barrer, respectively. Additionally, the CO2/CH4 and H2/N2 selectivities reached 151.4 and 261.1, both transcending the 2008 Robeson upper bounds. This work provides an innovative way to make ZIF materials and high-performance gas separation membranes, offering solutions for CO2 capture and H2 separation.