Mixed Matrix Membranes Based on Benzimidazole-Modulated MOFs for Enhanced CO2 Capture and H2 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.