Photo-oxidative enhancement of polymericmolecular sieve membranes

摘要

High-performance membranes are attractive for molecular-level separations in industrialscalechemical, energy and environmental processes. The next-generation membranes forthese processes are based on molecular sieving materials to simultaneously achieve highthroughput and selectivity. Membranes made from polymeric molecular sieves such aspolymers of intrinsic microporosity (pore sizeo2 nm) are especially interesting in beingsolution processable and highly permeable but currently have modest selectivity. Here wereport photo-oxidative surface modification of membranes made of a polymer of intrinsicmicroporosity. The ultraviolet light field, localized to a near-surface domain, induces reactiveozone that collapses the microporous polymer framework. The rapid, near-surfacedensification results in asymmetric membranes with a superior selectivity in gas separationwhile maintaining an apparent permeability that is two orders of magnitude greater thancommercially available polymeric membranes. The oxidative chain scission inducedby ultraviolet irradiation also indicates the potential application of the polymer inphotolithography technology.