High performance asymmetric polybenzimidazole-derived carbon molecular sieve hollow fiber membranes for elevated temperature H₂/CO₂ separation

Carbon molecular sieve membranes (CMSMs) show excellent H₂/CO₂ separation performance for hydrogen production from natural gas and solid hydrocarbons. However, fabricating scalable, mechanically robust defect-free asymmetric CMSMs with ultrathin selective layers (≤1 μm) in hollow fiber configuration remains challenging. This study presents a novel technique using precursor engineering and pyrolysis optimization to fabricate polybenzimidazole (PBI)-derived CMSM hollow fibers—the first having an ultrathin selective layer with a macrovoid-free porous interconnected sublayer. Among the PBI-CMS HFMs fabricated in this study, extensive variation in the gas separation performance was measured where H₂ permeance and ideal H₂/CO₂ selectivity varied three and two, respectively, orders of magnitude. The optimized PBI-CMSM, pyrolyzed at 700 °C with a 0.4 μm selective layer, achieved H₂ permeance of 100 GPU and H₂/CO₂ selectivity of 80. Long-term testing (∼850 h) under simulated syngas conditions demonstrated stable perm-selectivity, confirming resistance to physical aging and industrial viability.