Preparation of porous organic cages/polyimide mixed matrix membranes and their gas separation performance

Mixed matrix membranes (MMMs) have garnered significant attention in the field of gas separation due to their excellent comprehensive properties. However, the interface structure defects caused by insufficient compatibility between materials limit their wide application. Porous organic cages with high specific surface area, high porosity, soluble processing and structural stability are considered to be ideal fillers for the preparation of mixed matrix membranes in gas separation. MMMs with porous organic cage as filler and polyimide as matrix were prepared by solution blending method. The morphology and structure of the material were characterized by infrared spectroscopy, wide angle X-ray and scanning electron microscopy. The results show that MMMs are successfully prepared without obvious structural defects. And the performance tests results show that MMMs have good thermal properties (glass transition temperature > 280℃, 10% weight loss temperature > 510℃) and mechanical properties (tensile strength > 55 MPa). The addition of porous structure CC3 greatly improv the gas separation performance of the membrane. The permeability of He and CO₂ of MMMs reach the best when the addition amount of CC3 is 8wt%, which is 88% and 90% higher than the pure PI membrane. At 6wt%, MMMs have the best gas selectivity. The ideal selectivity coefficient of He/N₂ and CO₂/N₂ are 46.9 and 30.3, respectively, which is 37% and 40% higher than the pure PI membrane, respectively, which achieves a synergistic enhancement of both permeability and selectivity.