Research progress and challenges in polyimide and polyimide-derived gas separation membranes: A review

Polyimide (PI) has been widely regarded as an ideal material for high-performance gas separation membranes due to its exceptional mechanical strength, thermal and chemical stability, excellent film-forming properties, and versatile structural tunability. However, practical applications of PI membranes have been limited by challenges such as free volume collapse, physical aging, and high gas transport resistance. These issues are considered to be addressable through the precise regulation of polymer structures via both physical and chemical modification strategies. In this review, the influence of conventional monomer structures on the gas separation performance of PI membranes is examined. Recent advances in modification techniques such as copolymerization, covalent crosslinking, thermal treatment, polymer blending, multilayer composite fabrication, and photo-induced processing are systematically discussed. The structure-property relationships resulting from these modifications are analyzed, with emphasis placed on gas transport mechanisms, as well as the advantages and limitations of each approach. Furthermore, the application potential of PI-derived membranes is highlighted in key areas such as CO₂ capture, H₂ purification, He enrichment, and light hydrocarbon separation. Through the summarization of current design strategies and performance optimization methods, this review is intended to offer new insights and guidance for the development of next-generation PI-based gas separation membranes.