Efficient dimerization of perfluoroolefin catalyzed by strong nucleophilic bifunctional ionic liquids

Abstract

Following the principle of sustainable and green development, the environmentally friendly and highly efficient manufacturing of fluorine chemical products is becoming an unavoidable development trajectory. Ionic liquid catalysts have shown great potential to replace traditional metal salt catalysts, which cause environmental pollution, in the dimerization of perfluorinated olefins. In this study, a series of strong nucleophilic thiocyanate ionic liquids with various cationic structures were designed and synthesized. The catalytic activity of 4-dimethylaminopyridine (DMAP) ionic liquids exceeded that of reported catalysts, being 2.4 times higher than that of traditional metal salt catalysts, and 1.5 times higher than that of imidazole ionic liquids reported in the literature. Under the optimal reaction conditions, the high turnover frequency (TOF) value of the [C₆DMAP][SCN] catalyst performance reaches 325.04 h⁻¹. Based on the experimental results, density functional theory (DFT) and XPS analysis, the excellent catalytic performance of [C₆DMAP][SCN] can be attributed to the dual active sites of anions and cations, and a dual-activation reaction mechanism is further proposed. This study not only expands the application of ionic liquid in the hexafluoropropylene dimerization reaction but also helps establish a more efficient, green, and sustainable catalytic process for hexafluoropropylene dimerization.