Tuning free volume for enhanced gas separation by introducing fluorinated aryl ether diamine moiety in Tröger's-based membranes

Tröger's-based polymeric membranes have received tremendous attention for their inherent high free volume and excellent gas permeability. However, its selectivity was still unable to meet their industrial demand. In effort to achieve an optimization comprehensive performance, a set of homogeneous polymer chains was synthesized to fine-tune the free volume. These membranes were designed by copolymerization diamine moiety of 3, 3′-dimethylbiphenyl-4, 4′-diamine and 2, 2-bis [4-(4-aminophenoxy)phenyl] hexafluoropropane. Significant characterizations of their physical properties and chemical structures were carried out by FTIR, TGA, XRD, and mechanical strength. The effects of variation diamine content ratio were studied. An available simulation was carried out to elucidate the influence of introduced diamine. The permselectivity of membranes was evaluated by H2, CO2, O2, N2, and CH4. The objective performances of feed gas pressure, test temperature, and aging stability on membranes were further studied. The exciting results demonstrated that our membranes exhibit improved gas performance. Notably, for H2 separation, the H2/N2 and H2/CH4 selectivity was significantly enhanced by 125.7% (from 27.20 to 61.40) and 126.9% (from 30.41 to 69.02) with the addition of 30 mol% fluorinated diamine moiety while without much-compromising gas permeability was observed. These findings enlighten a facile and effective strategy in Tröger's-based polymer design towards high-purity gas separation.