Enhanced Gas Separation Performance of Carbon Molecular Sieve Membranes Derived from Polyimide/Polyaniline Blend Precursors

Polyimide membranes are generally limited by the permeability–selectivity trade-off during gas separation, which significantly restricts their further development and practical applications. Carbon molecular sieve membranes derived from polyimide (PI) precursors via pyrolysis have attracted considerable attention due to their excellent molecular sieving capability. In this study, polyaniline (PANI) was introduced to modify the polyimide matrix, and a series of PI/PANI precursor membranes with different PANI loadings were fabricated, followed by pyrolysis to obtain the corresponding CMS/PANI membranes. The effects of PANI incorporation on the structural evolution and gas separation performance of the membranes were systematically investigated. The results demonstrated that PANI incorporation effectively increased the fractional free volume (FFV) of the precursor membranes and promoted the formation of microporous structures during pyrolysis, resulting in enhanced BET surface area and a more developed microporous network in CMS/PANI membranes. Compared with the pristine PI-derived CMS membrane, CMS/PANI membranes exhibited significantly improved gas permeability while maintaining comparable gas pair selectivity. Among the prepared membranes, CMS/PANI-20 achieved the optimal overall separation performance, with H2 and CO2 permeabilities of 2012 and 754 Barrer, respectively, and H2/CH4 and CO2/CH4 selectivities of 253 and 95, respectively, exceeding the corresponding Robeson upper bounds.