Facilely Cross-Linking Polybenzimidazole with Polycarboxylic Acids to Improve H2/CO2 Separation Performance

Polybenzimidazole (PBI) with a strong size-sieving ability exhibits attractive H-2/CO2 separation properties for blue H-2 production and CO2 capture. Herein, we report that PBI can be facilely cross-linked with polycarboxylic acids, oxalic acid (OA), and trans-aconitic acid (TaA) to improve its separation performance. The acids react with the amines on the PBI chains, decreasing free volume and increasing size-sieving ability. The acid doping increases H-2/CO2 selectivity from 12 to as high as 45 at 35 degrees C. The acid-doped samples demonstrate stable H-2/CO2 separation performance when challenged with simulated syngas containing water vapor at 150 degrees C, which surpasses state-of-the-art polymers and Robeson's upper bound for H-2/CO2 separation.