Improved Interfacial Affinity and CO2 Separation Performance of Asymmetric Mixed Matrix Membranes by Incorporating Postmodified MIL-53(Al)

Asymmetric mixed matrix membranes(MMMs) with MOFs hold great application potential for energy-efficient gas separations. However, the particle aggregation and nonselective interfacial microvoids restrict the gas separation performance of asymmetric MMMs. Herein, nanoporous metal–organic framework (MOF) of MIL-53(Al) was modified with aminosilane after solvothermal synthesis. The postfunctionalization by grafting alkyl chains can form hydrogen bonds with polymer chains to enhance the affinity with polymer matrix and facilitate the preferential adsorption of CO₂ by dipole–quadrupole interaction with the functional group. Then the postmodified MIL-53(Al) was incorporated as filler into poly(ether imide) Ultem1000 to fabricate high-quality asymmetric MMMs with well dispersed particles in polymer matrix and good adhesion at the MOFs-polymer interface. The Ultem/S-MIL-53(Al) asymmetric MMMs exhibited remarkable combinations of gas permeance and ideal selectivity for CO₂/N₂ separation at 10 wt % filler loading. The CO₂ permeance achieved 24.1 GPU, an increase of 165% compared with pure Ultem membrane. Meanwhile, the ideal CO₂/N₂ selectivity also increased from 31.0 up to 41.1. The strategy of post covalent modification for MOFs provides an effective way to improve the interfacial affinity and gas separation performance.