Promoting CO ₂ Separation Performances in Copolymeric Membranes via Chemical Structure and Microstructure Rearrangement

Regulating the microstructure and gas transport pathways is one of the strategies to achieve efficient gas separation. In this work, copolymers were synthesized using dibenzofuran and dibenzo-18-crown-6 via the Friedel–Crafts reaction. The influence of the monomer ratio on the gas separation was first investigated. Subsequently, glycidyl trimethylammonium chloride was grafted onto the copolymer backbone. Afterward, non-solvent-induced microstructure rearrangement (MSR) was applied to the copolymer membrane. Results reveal that the MSR process significantly improved the gas separation performance of the membranes. Under optimized conditions, a CO2 permeability of 1222.8 Barrer and a CO2/N2 selectivity of 41.71 were achieved, showing an improvement of 3.1 and 3.9 times compared to the original membranes. In addition, the P(O–F0.5–C0.5)-GTA 2 wt % GlyK MSR membrane also exhibited excellent stability. This study demonstrates that both chemically regulating the polymer structure and physically inducing MSR can improve gas separation performance, providing insights into the molecular design of high-performance gas-separation membranes.