In-situ crystallization of porous nanoparticles in confined space for mixed-matrix membrane fabrication

Mixed-matrix membranes (MMMs), which combine the flexible processability of polymers with the high mass-transfer capabilities of porous fillers such as metal-organic frameworks (MOFs), are widely regarded as next-generation, high-performance materials for CO 2 capture. However, challenges such as MOF aggregation and poor interfacial compatibility between MOFs and polymers often result in membrane defects, ultimately reducing CO 2 /N 2 selectivity. To address this issue, we propose an in situ MOF crystallization strategy within confined spaces to construct defect-free MMMs for CO 2 separation. In this method, prepolymers and MOF precursors are molecularly dissolved in a solvent. Following UV-induced crosslinking of the prepolymers, a gel membrane is formed, providing a confined environment for in situ MOF crystallization. The high degree of crosslinking ensures a uniform distribution of MOF nanoparticles and limits their size. This uniformity enhances interfacial interactions and effectively suppresses the formation of interfacial defects. The optimized membrane exhibited a simultaneous increase in both CO 2 permeability and CO 2 /N 2 selectivity, a 17.5-fold and 26% enhancement, respectively, compared with the pristine polymer membrane. Furthermore, due to its strong interfacial structure, the membrane demonstrated excellent mechanical stability under applied pressure and maintained consistent performance over 200 h of continuous operation. This method offers a novel and effective approach for fabricating uniform, defect-free MMMs for advanced CO 2 separation applications.