De‐carboxylation of cross‐linkable triptycene‐based polyimides for CO2 separation

Abstract Polymer‐based membrane technology holds immense promise for CO 2 separation. However, it faces persistent challenges, including the high CO 2 pressure‐induced plasticization and permeability‐selectivity trade‐offs, which significantly hinder the development of polymeric membranes. To tackle this issue, we synthesized a novel polyimide 6FDA‐DAT:DABA(6FDD) containing triptycene and carboxylic groups. Upon de‐carboxylation induced cross‐linking, the membrane demonstrated a simultaneous enhancement of gas permeability and selectivity. Specifically, compared to the uncross‐linked 6FDD, the 400°C‐24 h cross‐linked membrane exhibited a remarkable increase in CO 2 permeability by 177% (93.1 Barrer) and a significant rise in CO 2 /CH 4 selectivity by 47% (57.5), reaching the CO 2 /CH 4 upper bound. More importantly, the cross‐linked membrane displayed vastly improved CO 2 plasticization resistance, withstanding up to 42 bar of CO 2 feed pressure. The design of decarboxylated cross‐linked membranes in this work paves the way for creating high‐performing and plasticization‐resistant membranes with potential applications in high‐pressure CO 2 separations.