Diamine-Crosslinked and Blended Polyimide Membranes: An Emerging Strategy in Enhancing H₂/CO₂ Separation

The increasing demand for high-purity hydrogen (H₂) as renewable energy sources is driving advancements in membrane technology, which is essential for achieving efficient gas separation. Polyimide (PI) membranes have become an emerging option for H₂/CO₂ separation due to its excellent thermal stability and stability under harsh conditions. However, the neat PI membrane suffers performance loss due to CO₂ plasticization effect and an encountered trade-off limit between permeability and selectivity. Therefore, membrane modification by crosslinking and blending emerged as a recent strategy to enhance the membrane's performance and properties. This paper provides: (1) An overview of the possible method to do the modification in PI membranes, including the advantages and challenges of the membrane modification types; (2) As blending and crosslinking is the most popular modification for the PI membrane, their roles in enhancing membrane properties for improved H₂/CO₂ separation are discussed; (3) The critical parameters of the blending and crosslinking processes are also clarified for the optimal purification process; (4) The future outlook for H₂/CO₂ separation using membrane technology is discussed, aiming to provide commercialization strategy for optimal H₂/CO₂ separation. Thus, this review could provide guidelines for the readers to implement changes that significantly enhance the membrane's features for high-purity H₂ production.