Hot solution strategy to prepare Zr-MOF/polyimide mixed matrix membranes for high-performance helium separation

Polymer membranes demonstrate strong potential for helium recovery applications but typically encounter permeability-selectivity trade-off in He/CH₄ and He/N₂ separations. Mixed-matrix membranes (MMMs) incorporating metal-organic frameworks (MOFs), renowned for their exceptional permeability-selectivity combinations, offer a viable strategy to address this limitation. In this study, we introduced a hot solution strategy for MOF/6FAB MMMs (6FAB: 6FDA-mPDA/HAB (6:4); MOF: UiO-66-NH₂) that achieved helium separation performance transcending the 2016 upper bound. By implementing 80 °C rather than conventional room temperature fabrication, the thermally processed MMMs exhibited strengthened interfacial compatibility through enhanced O–H⋯N hydrogen bonding between 6FAB's hydroxyl groups and UiO-66-NH₂'s amine functionalities. The optimized compatibility facilitated unprecedented 40 wt% MOF loadings, yielding remarkable He/CH₄ selectivity (257.2) and He permeability (516 Barrer). These values represented 824 % and 116 % enhancement over the pristine 6FAB polyimide membrane, while maintaining operational stability. These results validated the efficacy of thermal processing in engineering defect-free, high-performance membranes for advanced gas separations.