Thermally rearranged polyimide membranes incorporating triptycenes for improved CO2 capture and hydrogen separation

Thermally rearranged (TR) polymers are increasingly pivotal in gas separation membranes, with a pressing need for advancements in mechanical strength and separation performance. In this work, a novel variety of TR polymers were synthesized by polymerizing an amine-functionalized triptycene structure with thermally rearrangeable ortho-hydroxy groups. The TR membranes demonstrate enhanced gas permeability in H2/CH4 and CO2/CH4 tests and increased polymer chain spacing. Additionally, incorporating triptycene enhanced the mechanical properties of TR polymers, primarily attributed to the it-it stacking interactions of the triptycene units. Notably, the 6FDA-BAP:DAT (2:1) membrane thermally rearranged at 400 degrees C exhibited a H2 permeability of 225.3 Barrer and a H2/CH4 selectivity of 146.3, representing increases of 320 % and 154 %, respectively, compared to the precursor, and surpassing the H2/CH4 upper bound. This work presents a robust design strategy for preparing mechanically durable TR membranes with enhanced gas separation performance.