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

Polymer-based membrane technology holds immense promise for CO₂ separation. However, it faces persistent challenges, including the high CO₂ 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 CO₂ permeability by 177% (93.1 Barrer) and a significant rise in CO₂/CH₄ selectivity by 47% (57.5), reaching the CO₂/CH₄ upper bound. More importantly, the cross-linked membrane displayed vastly improved CO₂ plasticization resistance, withstanding up to 42 bar of CO₂ 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 CO₂ separations.