Cross-Linked Mixed-Matrix Membranes Incorporating PVDF, Ionic Liquid, and Augmented ZIF-L Embedded Fillers for Efficient CO₂/N₂ Separation

This study aimed to develop an effective CO2/N2 selective separation membrane for the capture of CO2 from air or flue gas. Polyvinylidene fluoride (PVDF) was chosen as the organic substrate for the preparation of mixed-matrix membranes (MMMs). To enhance the CO2 mass transfer rate, an ionic liquid (IL) with high CO2 solubility was introduced through direct material blending, while a leaf-like zeolitic imidazolate framework (ZIF-L) was functionalized with silane coupling agents as the inorganic filler. Subsequently, the prepared PVDF-IL@ZIF MMMs were tested for the CO2 separation performance and mechanical properties. The results revealed that IL loading could significantly enhance the separation performance of MMMs for CO2/N2 separation, and the AZL-incorporated IL loading MMM (PPAZL) exhibited the optimal gas separation performance, with 24.5% CO2/N2 selectivity at 2 bar transmembrane pressure. Notably, AZL also demonstrated superior interfacial compatibility with PVDF compared to both ZIF-8 and pristine ZIF-L, which facilitated the maximization of IL loading in the MMM, achieving more than 10% higher IL capacity than ZIF-8-filled counterparts while stabilizing IL immobilization within the membrane matrix.