A Rigid and Planar Aza-Based Ternary Anhydride for the Preparation of Cross-Linked Polyimide Membrane Displaying High CO2/CH4 Separation Performance

In this study, based on the preparation of hexaazatriphenylene-ternary-anhydride (HAT-T), polyimide membranes were prepared by reaction of 4,4 '-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 4,4 '-diaminodiphenyl sulfide (SDA), 2,2 '-bis (trifluoromethyl)diaminobiphenyl (TFDB) and 5-amino-2-(4-aminophenyl) benzimidazole (PABZ). Polyimide films with a hexazobenzo structure have good film-forming properties, high molecular weight (M-n = 0.79-11.79 x 10(6), M-w = 1.03-16.60 x 10(6)) and narrow molecular weight distribution (polymer dispersity index = 1.17-1.54). With the introduction of rigid HAT-T, the tensile strength and elongation at break of polyimide films are 195.63-510.37 MPa and 4.00-9.70%, respectively, with excellent mechanical properties. The gas separation performance test shows that hexaazatriphenylene-containing polyimide films have good gas selectivity for CO2/CH4. In particular, the separation performance of PIc-t (6FDA/PABZ/HAT-T) surpasses the "2008 Robeson Upper Bound". The selectivity of 188.43 for CO2/CH4 gas reveals its potential value in the separation and purification of methane gas.