Polymeric ionic liquids for CO2 capture and separation: potential, progress and challenges

The increasing level of carbon dioxide (CO2) in the atmosphere is a big threat to the environment and plays a key role towards global warming and climate change. In this context to combat such issues, polymeric ionic liquids (PILs) serve as potential substitutes that offer an extremely versatile and tunable platform to fabricate a wide variety of sorbents for CO2 capture, in particular, for flue gas separation (CO2/N-2) and natural gas purification (CO2/CH4). Formerly, there have been several reports on exploitation of ionic liquids for CO2 sorption with promising results. However, just a few have focused on polymeric ionic liquids which significantly over-performed the sorption efficiency of the molecular ionic liquids. This review is first ever of its kind which showcases the potential of PILs as a new member of the CO2 adsorbent family. The most dynamic aspect of PILs research at present is the curiosity to explore their potential as solid sorbents for CO2 capture and separation. This review not only highlights the recent advances in the area of PILs as sorbents for CO2 uptake but also portrays the forthcoming challenges in improving their efficiency. The effect of various cations, anions, polymer backbones, alkyl substituents, porosity, cross-linking, molecular weight and moisture on the CO2 sorption capacity and separating efficiency is scrutinized in detail. Moreover, future strategies to increase the CO2 capture performance of PILs are also discussed.