Fabrication of Claisen thermally rearranged hollow fiber membranes derived from allyl functionalized copolyimide for CO2 removal from natural gas

Thermally rearranged (TR) polymers are well known for their exceptional gas permeability and have been considered as promising candidates for hollow fiber membranes in natural gas purification. However, the conventional TR process requires temperatures above 400 °C, which often compromises both gas transport performance and mechanical integrity. In this study, we developed Claisen thermal rearrangement (CTR) hollow fiber membranes derived from allyl-functionalized copolyimides under mild thermal conditions. By exploiting the [3,3]-sigmatropic rearrangement, the required rearrangement temperature was reduced to 160 °C. The resulting CTR membranes demonstrated a CO 2 permeance of 281.57 GPU with a CO 2 /CH 4 selectivity of 25.37 after thermal treatment at 200 °C. Notably, CTR fibers exhibited excellent resistance to CO 2 plasticization up to 2.0 MPa, markedly superior to their precursor membranes. Furthermore, the elastic modulus of CTR hollow fiber membranes increased by more than an order of magnitude, reaching 1.56 GPa. Overall, this work presents an energy-efficient strategy based on [3,3]-sigmatropic rearrangement for fabricating high-performance hollow fiber membranes, holding great potential for application in natural gas purification.