Turn Off–On Fluorescent CO(2) Gas Detection Based on Amine-Functionalized Imidazole-Based Poly(ionic liquid)

[Image: see text] Poly(ionic liquids) (PILs) have been widely used for CO(2) capture because their characteristics resemble those of an ionic liquid, yet they have properties typically associated with polymers. We studied the application of the amine-functionalized poly(vinylimidazole)-based PIL (PVIm-NH(2)) as a chemosensor. The PVIm-NH(2) was successfully prepared by a facile and low-cost method and was characterized by several analytical techniques: proton nuclear magnetic resonance ((1)H NMR), Fourier transform infrared (FT-IR) spectroscopy, gel permeation chromatography (GPC), and spectrofluorometry. The ability of PVIm-NH(2) to detect CO(2) gas was evaluated in the presence of triethylamine (TEA). Under optimized conditions, the detection limit was calculated to be 2.86 × 10(–3) M with R(2) = 0.9906. Moreover, theoretical and experimental studies suggested a plausible mechanism whereby PVIm-NH(2) generates N-heterocyclic carbenes (NHCs) in the presence of TEA, which further reacts with CO(2) gas in aqueous media to form a carboxylic acid. Analysis of PVIm-NH(2) before and after the addition of TEA using the (1)H NMR technique showed the disappearance of the proton peak, thus suggesting a successful generation of NHC. Further analysis via (13)C NMR revealed the reaction of CO(2) and NHC to form a carboxylic acid group. Finally, we demonstrated that PIL is a promising candidate as a chemosensor through diverse structural modifications.