Click-based porous cationic polymers for enhanced carbon dioxide capture

Abstract

Imidazolium-based porous cationic polymers were synthesized using an innovative and facile approach, which takes advantage of the Debus–Radziszewski reaction to obtain meso-/microporous polymers following click-chemistry principles. In the obtained set of materials, click-based porous cationic polymers have the same cationic backbone, whereas they bear the commonly used anions of imidazolium poly(ionic liquid)s. These materials show hierarchical porosity and a good specific surface area. Furthermore, their chemical structure was extensively characterized using ATR-FTIR and SS-NMR spectroscopies, and HR-MS. These polymers show good performance towards carbon dioxide sorption, especially those possessing the acetate anion. This polymer has an uptake of 2 mmol g⁻¹ of CO₂ at 1 bar and 273 K, a value which is among the highest recorded for imidazolium poly(ionic liquid)s. These polymers were also modified in order to introduce N-heterocyclic carbenes along the backbone. Carbon dioxide loading in the carbene-containing polymer is in the same range as that of the non-modified versions, but the nature of the interaction is substantially different. The combined use of in situ FTIR spectroscopy and micro-calorimetry evidenced a chemisorption phenomenon that brings about the formation of an imidazolium carboxylate zwitterion.