Carbon Molecular Sieve Membranes Derived From Dual‐Cross–linked Polybenzimidazole for Enhanced H2/CO2 Separation

Abstract The need for efficient CO 2 separation during hydrogen production from fossil fuels drives the development of advanced, energy‐efficient solutions. Membrane technology offers a promising approach for separating CO 2 from H 2 , which, however, faces the challenge of low H 2 /CO 2 selectivity. To address this challenge, a novel strategy to cross–link polybenzimidazole (PBI) using potassium persulfate (K 2 S 2 O 8 ) is proposed, followed by pyrolysis to fabricate highly selective carbon molecular sieve (CMS) membranes. The cross–linked PBI‐derived CMS membranes exhibit significantly enhanced permeability and H 2 /CO 2 selectivity compared to neat PBI‐CMS membranes. For instance, the CMS membrane prepared from PBI cross–linked for 24 h and pyrolyzed at 900 °C (denoted as KPBI 24 CMS@900) demonstrates outstanding molecular sieving capability. This membrane achieves an H 2 permeability of 55 Barrer with an H 2 /CO 2 selectivity of 48 tested at 100 °C, significantly surpassing its non‐cross–linked counterparts and the 2008 Robeson upper bound. The design principles of this study provide a robust technical foundation for persulfate‐cross–linked PBI and offer an innovative approach for preparing high‐performance CMS membranes.