Unprecedented gas separation performance of a difluoro-functionalized triptycene-based ladder PIM membrane at low temperature

Advanced membrane materials are playing increasingly important roles in solving global energy intensive separation problems. Herein, we introduce a high-performance intrinsically microporous Troger's base-derived ladder polymer (DFTTB) as an advanced membrane material for low-temperature gas separation applications. DFTTB was obtained by design of a 2,3-difluoro-functionalized triptycene (DFTrip) building block. The resulting ladder polymer exhibited high microporosity (SBET = 918 m2 g−1), good thermal and mechanical properties, and excellent gas separation performance at or above the latest 2015 permeability/selectivity trade-off curves for H2/N2, H2/CH4 and O2/N2 with H2 and O2 permeabilities of 5468 and 650 barrer coupled with H2/N2, H2/CH4 and O2/N2 selectivities of 50, 38 and 6.0, respectively. Furthermore, DFTTB displayed unprecedented performance at sub-ambient temperatures with an O2/N2 selectivity of 10.1 and O2 permeability of 137 barrer at −30 °C. This high selectivity coupled with up to ∼100-fold higher O2 and H2 permeability than commercial glassy polymer membrane materials, provides new opportunities for low temperature air separation and hydrogen recovery from petrochemical process streams.