Ester-Crosslinked Polymers of Intrinsic Microporosity Membranes with Enhanced Plasticization Resistance for Co2 Separation

•Ester-crosslinked PIM membranes were prepared through tailored carboxylation, esterification and thermal cross-linking processes.•Thermal treatment temperature and time play a critical role in the performance of crosslinked PIM membranes.•Crosslinked PIM have higher separation performance than PIM-1 and exceed the Robeson upper bounds.•Crosslinked PIM membranes exhibit enhanced CO2 plasticization resistance up to a CO2 pressure of 42 bar.