Catalysis

Natural gas

Engineering

Polymer chemistry

Permeability (electromagnetism)

Materials science

Air separation

Biochemistry

Chemical engineering

Gas separation

Polymer

Microporous material

Thermodynamics

Physics

Organic chemistry

Membrane

Oxygen

Copolymer

Substituent

Composite material

Chemistry

Selectivity

Permeation

Volume (thermodynamics)

Proceedings of the National Academy of Sciences

Significance Gas separation membranes are an emerging energy-efficient alternative toward conventional, energy-intensive separation technologies such as cryogenic distillation. Ladder polymers with intrinsic microporosity show exceptional promise toward redefining state-of-the-art gas separation membranes due to their high permeability (throughput) and selectivity (separation efficiency). However, they are typically inhibited by major reductions in permeability over time due to collapsing membrane free volume (open space between polymer chains), forfeiting their greatest asset. This work explores a route toward enhanced aging resistance and overall separation performance by incorporating pentiptycene (an H-shaped scaffold containing five fused arene rings) into ladder-like polymers to incorporate natural, more permanent “micropores” that aren’t susceptible to densification of polymer chains that occurs over time in traditional microporous polymers.

Pentiptycene-based ladder polymers with configurational free volume for enhanced gas separation performance and physical aging resistance