(514e) Carbon Molecular Sieve Membranes Derived from Cross-Linkable Copolyimide with Symmetrical and Non-Symmetrical Monomers for Gas Separations

Carbon molecular sieve (CMS) membranes with precise molecular discrimination ability and facile scalability are attractive for large-scale, energy-efficient gas separations. CMS membranes can be produced via controlled pyrolysis of polyimide precursors at high temperature, where entangled polyimide segments undergo aromatization and fragmentation into shorter rigid strands. Such strands organize into complex morphologies comprising distributed molecular sieve Langmuir domains within a disordered continuous phase. Manipulating the composition of polyimide precursor and pyrolysis temperatures allows tuning of separation performance of the CMS membranes. In this presentation, CMS membranes derived from a cross-linkable 6FDA-based copolyimide with symmetrical and non-symmetrical BPDA monomers are reported. The combination of precursors composition and pyrolysis protocols yield large difference in final CMS separation performance. Gas transport differences are interpreted in terms of a model reflecting both molecular sieving Langmuir domains and the less selective disordered continuous phase. Fundamental insights into structure evolution from the cross-linkable polyimide precursor to a final CMS membrane will be discussed. Our study offers a new strategy for tuning and understanding the CMS membrane structure and separation performance using tailor-designed carbon strands.