Ferrate‐Crosslinked Polybenzimidazole‐Derived Carbon Molecular Sieve Membranes for Enhanced H ₂ /CO ₂ Separation

ABSTRACT 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 H 2 /CO 2 discrimination, posing substantial challenges to industrial scalability and cost‐effectiveness. In this study, an oxidative crosslinking strategy employing potassium ferrate (K 2 FeO 4 ) 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 FeO 4 2− ‐PBI‐12 h CMS@650°C membrane demonstrated remarkable gas transport performance, elevating H 2 permeability from 3.4 Barrer to 66 Barrer and H 2 /CO 2 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 H 2 /CO 2 separation. This work establishes an energy‐efficient pathway for producing high‐performance CMS membranes, offering a promising pathway toward more economically viable hydrogen purification.