Novel pyrrolidinium-based polymeric ionic liquids with cyano counter-anions: HIGH performance membrane materials for post-combustion CO₂ separation

Polymeric ionic liquids (PILs) are blossoming as a new generation of materials at the interface of many areas leading to a renaissance of the field of ionic polymers. Although PILs are interesting membranes materials for CO₂ separation, additional research is still required to realize their full potential. In this work, pyrrolidinium-based polymers containing different cyano-functionalized counter-anions were synthesized by straightforward anion exchange reactions and characterized. Their film forming ability blended with different amounts of free ionic liquid (IL) was evaluated and the CO₂ and N₂ permeation properties through the prepared composites were determined. The results show that increasing the IL content in the composites not only increased CO₂ permeability but also boosted the CO₂/N₂ permselectivity, leading to improved separation performances. The best performance was achieved for the C(CN)₃-based membrane containing 60wt% of IL, which overcomes the Robeson 2008 upper bound, with CO₂ permeability of 439.3Barrer and CO₂/N₂ permselectivity of 64.4. Therefore, the pyrrolidinium-based PIL combined with the [C(CN)₃]^- as counter-anion has potential for efficient post-combustion CO₂ separation, suggesting the preparation of high performance membranes for industrial applications.