Catalytic selectivity in hexafluoropropylene trimerization using tailored nucleophilic ionic liquids

Abstract

Perfluoro olefins, as one of the most promising types of fluorinated coolants, support the application of immersion liquid cooling technology. Ionic liquid catalysts exhibit significant potential in olefin oligomerization reactions. In this paper, a variety of thiocyanate ionic liquids with strong nucleophilicity were designed and synthesized for hexafluoropropylene trimerization. DABCO-based ionic liquids exhibited a selectivity 24% higher and a turnover frequency (TOF) 9 times greater than those of conventional catalysts. Under optimal reaction conditions, [C₈DABCO][SCN] achieved up to 86.6% selectivity and 151.6 h⁻¹ TOF. As demonstrated by the experimental results and density functional theory (DFT) calculations, the enhanced catalytic efficacy of [C₈DABCO][SCN] can be ascribed to the nucleophilic anion, in conjunction with the cation endowed with a cyclic structure and nitrogen atom lone pair of electrons. The trimerization reaction pathway was further proposed based on the product distribution.