Cross-linked, porous imidazolium-based poly(ionic liquid)s for CO2 capture and utilisation

Abstract

CO₂ is the most influential greenhouse gas with drastic effects all over the world. Meanwhile, global warming is considered a hot topic to different groups of scientists dealing with the global warming phenomenon. As an alternative to the typically-used scrubbing agent that is heavily used in post-combustion capture technology, namely, monoethanolamine, with its well-known drawbacks, the ionic liquids (ILs) and their corresponding polymers, viz., poly(ionic liquid)s (PILs) have been exploited. In this study, we constructed new imidazolium-based PILs with high surface area fabricated from a 3-(3-(phthalimide)propyl)-1-vinylimidazolium bromide IL-precursor with N-allylphthalimide building blocks, in the presence of divinylbenzene serving as a cross-linker, through a free-radical polymerisation process, and provide their ability for the dual purposes of CO₂ capture and utilisation. In this context, the chemical structure of the monomers was fully characterised using elemental analysis, nuclear magnetic resonance and attenuated total reflectance-infrared spectroscopy. The polymeric materials were further examined by thermogravimetric analysis, the Brunauer–Emmett–Teller model and scanning electron microscopy. The sorption characteristics of the amine functionalised PILs were measured volumetrically with CO₂ uptake values up to 0.59 mmol CO₂ per g sorbent under RTP conditions (25 °C and 1 bar). For CO₂ utilisation purposes, the molar ratio of the ionic residues within the polymeric scaffold was increased ranging from one- and two- up to four-fold (×1, ×2, ×4), respectively. Remarkably, the polymeric materials showed excellent catalytic activity for the cycloaddition of CO₂ with epoxides to synthesise cyclic carbonates with almost quantitative conversion at 10 bar CO₂ and 110 °C.