LAUSR

Membranes have the potential to substantially reduce energy consumption of industrial chemical separations, but their implementation has been limited owing to a performance upper bound—the trade-off between permeability and selectivity. Although recent developments of highly permeable polymer membranes have advanced the upper bounds for various gas pairs, these polymers typically exhibit limited selectivity. We report a class of hydrocarbon ladder polymers that can achieve both high selectivity and high permeability in membrane separations for many industrially relevant gas mixtures. Additionally, their corresponding films exhibit desirable mechanical and thermal properties. Tuning of the ladder polymer backbone configuration was found to have a profound effect on separation performance and aging behavior. Description When aging is an asset Separations achieved using membrane processes offer the prospect of reducing the energy costs of industrial-scale chemical separations, but innovative membrane materials are required to achieve the combinations of flux and selectivity. Lai et al. developed a set of ladder polymers prepared using catalytic arene-norbornene annulation polymerization that incorporate fluorene and dihydrophenanthrene units (see the Perspective by Budd). Upon physical aging, these polymers contort in a way that enhances their size-sieving capabilities, as demonstrated for separation between methane and carbon dioxide mixes and hydrogen and methane. —MSL Aging of ladder polymer membranes can tune their structure, leading to enhanced separation of industrially important gas pairs.