Natural gas sweetening using polymeric membranes has emerged as a promising alternative for the removal of acid gases such as H₂S and CO₂ [1]. Nevertheless, these membranes often encounter limitations, including plasticization and swelling under high-pressure operating conditions, which result in significant downfall in performance [2,3]. To address these challenges, recent research has focused on developing materials capable of withstanding harsh separation environments while maintaining a favorable balance between permeability and selectivity. Polybenzimidazoles (PBIs) have gained attention as potential candidates for gas separation membranes due to their exceptional thermo-mechanical stability and suitability for extreme conditions. However, a key drawback of PBIs lies in their low processability, attributed to their high chain packing density, which negatively affects gas permeability.

In this study, we present a series of novel PBIs synthesized from various aromatic tetramines and terphenyl diacid moieties, using Eaton’s reagent with different proportions of triflic acid (TfOH). The objective is to develop PBIs with increased free volume and improved processability, making them more effective for gas separation membrane applications.

The authors are grateful for funding from PAPIIT (IG100323) and CONACyT CF-2023-G-220. The authors also thank G. Cedillo Valverde, A. Tejeda Cruz, and E. R-Morales (IIM-UNAM) for the NMR, XRD, and thermo-mechanical analyses. M. Rojas Rodriguez gratefully acknowledges CONAHCyT for Ph.D. fellowship.