Confined In Situ Synthesis of Uniformly Distributed Mixed Matrix Membranes via Solvent Evaporation for Efficient CO₂ Capture

The fabrication of polymers of intrinsic microporosity (PIMs)-based mixed matrix membranes (MMMs) is an effective strategy to combine the superior selectivity of porous nanofillers and the high gas permeability of PIMs, which is expected to be a new generation of membrane for efficient CO₂ capture. However, the aggregation and sedimentation of the nanofillers along with their insufficient interfacial compatibility with PIMs matrix often result in uncontrollable defects and non-selective voids among the polymer matrix, which seriously deteriorate the anticipated gas separation performance. For the first time, this work proposes a “solvent-evaporation-induced-confinement” strategy for in situ growth of zeolitic imidazole framework-90 (ZIF-90) nanofillers throughout amidoxime-functionalized PIM-1 (AOPIM-1) matrix. The defect-free microporous membrane exhibits a uniform distribution of highly loaded nanofillers with excellent PIMs-MOF interfacial compatibility. The optimized AOPIM-1/ZIF-90 (AO/ZIF) MMM exhibits an exceptional CO₂ separation performance with the CO₂/N₂ and CO₂/CH₄ selectivity of 42.08 and 71.25, respectively, and a CO₂ gas permeability of 1719.1 Barrer. In addition, in situ preparation of ZIF-8 and ZIF-67 nanofillers among the AOPIM-1 matrix further confirms the versatility of the proposed “solvent-evaporation-induced-confinement” strategy. The proposed strategy presents a versatile approach to achieve tunable growth of MOF nanofillers for the preparation of high-performance PIMs-based MMMs for carbon capture.