Atomic-Scale Aluminum Oxyfluoride-Confined Nanoporous Carbons for Exceptional Aging-Resistant Propylene/Propane Separation

Carbon molecular sieves (CMSs) offer a promising alternative to energy-intensive cryogenic distillation for gas separations such as C 3 H 6 /C 3 H 8 . However, they suffer from physical aging that reduces gas permeability and from a trade-off between size-sieving capability and mechanical stability. Herein, we address both challenges by engineering robust nanoporous carbons via an integrated low-temperature carbonization and vapor-phase infiltration (VPI) strategy. A 6FDA-DAM polyimide is carbonized at 500 °C to form mechanically resilient carbons and then subjected to VPI treatment to generate sub-nanometer aluminum oxyfluoride onto internal pore walls. The inorganic coating rigidifies carbon nanostructures, enhancing their resistance to physical aging, and narrows pore sizes, thereby increasing size-sieving ability. 6-Cycle VPI treatment of a CMS increases C 3 H 6 /C 3 H 8 selectivity from 16 to 43 with stable separation properties over 90 days, outperforming most leading CMSs and polymers. The VPI process enables atom-by-atom tuning of micropores and provides a scalable route to enhance membrane separation efficiency.