Turn Off-On Fluorescent CO2 Gas Detection Based on Amine-Functionalized Imidazole-Based Poly(ionic liquid).

Poly(ionic liquids) (PILs) have been widely used for CO2 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-NH2) as a chemosensor. The PVIm-NH2 was successfully prepared by a facile and low-cost method and was characterized by several analytical techniques: proton nuclear magnetic resonance (1H NMR), Fourier transform infrared (FT-IR) spectroscopy, gel permeation chromatography (GPC), and spectrofluorometry. The ability of PVIm-NH2 to detect CO2 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-NH2 generates N-heterocyclic carbenes (NHCs) in the presence of TEA, which further reacts with CO2 gas in aqueous media to form a carboxylic acid. Analysis of PVIm-NH2 before and after the addition of TEA using the 1H NMR technique showed the disappearance of the proton peak, thus suggesting a successful generation of NHC. Further analysis via 13C NMR revealed the reaction of CO2 and NHC to form a carboxylic acid group. Finally, we demonstrated that PIL is a promising candidate as a chemosensor through diverse structural modifications.