Enhanced Carbon Dioxide Capture from Landfill Gas Using Bifunctionalized Benzimidazole-Linked Polymers

Tuning the binding affinity of small gases and their selective uptake by porous adsorbents are vital for effective CO₂ removal from gas mixtures for environmental protection and fuel upgrading. In this study, an amine-functionalized benzimidazole-linked polymer (BILP-6-NH₂) was synthesized by a combination of pre- and postsynthetic modification techniques in two steps. Presynthetic incorporation of nitro groups resulted in stoichiometric functionalization (1 nitro/phenyl) in addition to noninvasive functionalization, where more than 80% of the surface area maintained compared to BILP-6. Experimental studies presented enhanced CO₂ uptake and CO₂/CH₄ selectivity in BILP-6-NH₂ compared to BILP-6, which are governed by the synergetic effect of benzimidazole and amine moieties. DFT calculations were used to understand the interaction modes of CO₂ with BILP-6-NH₂ and confirmed the efficacy of amine groups. Encouraged by the enhanced uptake and selectivity in BILP-6-NH₂, we have evaluated its performance in landfill gas separation under vacuum swing adsorption (VSA) settings, which resulted in very promising working capacity and sorbent selection parameters outperforming most of the best solid adsorbent in the literature.