Large-Area Ultrathin Mixed Matrix Membranes Incorporating Small Rigid MOFs for Gas Separation

The integration of metal–organic frameworks into polymer matrices within mixed-matrix membranes (MMMs) presents a promising strategy for fabricating high-performance gas separation membranes. However, nanoparticle aggregation during the scale-up process reduces membrane permselectivity, limiting practical applications. This study presents a facile, solvent-induced vacuum sintering strategy for synthesizing small rigid ZIF-8 (SRZ) enriched with Zn2+ active sites. SRZ exhibited superior hydrophilicity and membrane-forming capability, enabling its homogeneous dispersion within polyvinylamine (PVAm) for the fabrication of large-area PVAm/SRZ/modified poly(ether sulfone) (MPSf) MMMs. These MMMs were uniform, dense, and defect-free, with an effective membrane area of up to 3100 cm2 and ultrathin selective layers of approximately 200 nm. Benefiting from abundant Zn2+ active sites and a rigid framework structure, the developed MMMs demonstrated high CH4 permeance (1933 GPU) and excellent CH4/N2 selectivity (3.5). To further demonstrate their potential, two PVAm/SRZ/MPSf MMMs were employed to construct spiral-wound membrane modules with a packing area of 6200 cm2. The SRZ-based membrane modules exhibited satisfactory CH4 permeance (1261 GPU) while maintaining acceptable CH4/N2 selectivity (3.35). This study presents a feasible approach to facilitate industrial applications of gas separation membranes.