Ferrate-Crosslinked Polybenzimidazole-Derived Carbon Molecular Sieve Membranes for Enhanced H₂/CO₂ Separation

The fabrication of carbon molecular sieve (CMS) membranes via pyrolysis of crosslinked polymeric precursors has proven highly effective for hydrogen purification, offering unparalleled molecular sieving capabilities. However, conventional approaches typically require pyrolysis temperatures above 800°C to achieve precise H₂/CO₂ discrimination, posing substantial challenges to industrial scalability and cost-effectiveness. In this study, an oxidative crosslinking strategy employing potassium ferrate (K₂FeO₄) is introduced to synergistically integrate proton transfer, hydrogen bonding, and covalent crosslinking, enabling the formation of a highly selective CMS membrane at a significantly reduced pyrolysis temperature of 650°C. The optimized FeO₄ ^2--PBI-12 h CMS@650°C membrane demonstrated remarkable gas transport performance, elevating H₂ permeability from 3.4 Barrer to 66 Barrer and H₂/CO₂ selectivity from 14.4 to 75.3 under industrially relevant conditions (11 atm, 100°C), compared to its polymer precursor. These metrics transcend the 2008 Robeson upper bound and rank among the highest reported for H₂/CO₂ separation. This work establishes an energy-efficient pathway for producing high-performance CMS membranes, offering a promising pathway toward more economically viable hydrogen purification.