Thermally Tailored Amidoxime-Functionalized PIM-1 Membranes with CO2-Imprinted UiO-66-NH2 for CO2/N2 Separation

Polymers of intrinsic microporosity (PIMs) are promising membrane materials for CO2 separation due to their high permeability; however, their limited CO2/N2 selectivity restricts practical application. Herein, mixed-matrix membranes (MMMs) were fabricated by incorporating a CO2-molecularly imprinted UiO-66-NH2 filler (MIP@U) into amidoxime-functionalized PIM-1 (AOPIM-1), followed by thermal treatment at 160 or 250 °C under vacuum to regulate the membrane microstructure. Spectroscopic and porosity analyses (FTIR, XRD, and N2 physisorption) show that thermal treatment at 160 °C promoted oxadiazole-ring formation, leading to enhanced subnanometer microporosity and improved CO2/N2 selectivity. In contrast, treatment at 250 °C partially regenerates nitrile groups and generates larger micropores, resulting in higher CO2 permeability but reduced selectivity. The MIP@U filler introduces CO2-recognition cavities and improves interfacial compatibility, enabling synergistic control of polymer microporosity and interfacial transport pathways. The optimized 3 wt % MIP@U/AOPIM-1-TR160 membrane achieves a CO2 permeability of ∼1600 Barrer and a CO2/N2 selectivity of 50.8. The membrane also demonstrates stable performance under pressures up to 12 bar and during 30 h of continuous operation at 2 bar. This study highlights a dual-approach strategy combining thermally tailored PIM chemistry with molecularly imprinted MOF fillers for designing high-performance MMMs for CO2 capture.