(353e) Gas Chemisorption Blocks Its Diffusion in the Membrane

Membranes offer great potential to handle industrial gas separations in an energy-saving way, and highly permeable and selective membranes are desirable. However, leading polymeric membranes suffer an intrinsic permeability-selectivity trade-off that limits them under a performance upper bound. Here, we report a new rational design that introduces functional groups with strong chemisorption towards specific gas molecule in the membrane, thus detaining its diffusion and achieving high selectivity against it, as demonstrated by polyamine membranes for H₂/CO₂ separation. Amine groups can strongly absorb CO₂ molecules and cause high energy barriers for their desorption, leading to extremely poor CO₂ transport through the membrane even at high temperatures up to 90 ℃. As such, the polyamine-based thin-film composite (TFC) membrane exhibits an unprecedented ideal H₂/CO₂ selectivity of 1100 at 70 ℃, a new record on polymer-based membranes. Moreover, the TFC membrane shows stable and superior H₂/CO₂ separation performance, far surpassing the upper bound and state-of-the-art membranes, indicating great potential to be scaling-up. This study presents a new direction on designing highly selective membranes for a variety of separations and other applications.