Significant enhancement of CO₂/N₂ separation in PEBA membranes via molecular-level incorporation of 2-aminobenzimidazole

In the field of membrane-based CO₂ capture, improving membrane selectivity and optimizing the membrane fabrication process are crucial goals. This study proposed an innovative strategy involving the molecular-level incorporation of 2-aminobenzimidazole (2-ABI) into the membrane matrix. This approach leverages both the CO₂-facilitating effect of 2-ABI and its ability to enhance intermolecular interactions among the polymer chains, enabling highly efficient CO₂/N₂ separation. The process of incorporating poly(ether-block-amide) (PEBA, Pebax2533) with amino group-containing small molecule compounds was realized by introducing 2-ABI. The amino hydrogen of 2-ABI forms strong hydrogen-bonding interactions with the carbonyl oxygen of the amide group (-NHC(=O)-) in PEBA. This inclusion decreases the available free volume within the polymer matrix and supplies numerous amino groups. Consequently, it forms new pathways for CO₂ transport and heightens the CO₂ selectivity through synergistic effects. Compared to the original Pebax2533 membrane, which had a CO₂ permeance of 174.2 GPU and a CO₂/N₂ selectivity of 18.0 at room temperature and a pressure of 1.11 bar, the performance of the hybrid membranes was significantly improved. Specifically, the 2-ABI/PEBA-3 membrane demonstrated a CO₂ permeance of 229.0 GPU, marking a 31.4 % increase from the original membrane, along with a CO₂/N₂ selectivity of 49.4, which is a remarkable 175.0 % improvement. This straightforward approach, which involves directly adding 2-ABI, presents new opportunities for improving the CO₂ separation characteristics of polymeric membranes.