Fluorine-decorated ionic liquid salts used for the efficient transformation of low concentration CO2

Abstract

As a C1 feedstock, CO₂ has the potential to be uniquely highly economical in both a chemical and a financial sense. Herein, through a precise design and controllable synthesis, a series of fluorine-modified ionic liquid salts composed of quaternary phosphonium cations or imidazolium cations with bromide anions were constructed. Their catalytic activity in the cycloaddition reaction of CO₂ with epoxides to form cyclic carbonates was comprehensively investigated to illustrate the promotion effect of the functional fluorine group in the ionic liquid based catalysts. Our experimental results show that the obtained fluorine-modified ionic liquids exhibit much higher catalytic activity than the original ionic liquids with similar structure due to the high affinity of fluorine with CO₂. The difference of catalytic activities was further amplified when the cycloaddition reactions were carried out under low CO₂ concentration conditions and the fluorine-containing ionic liquids F-IL-TCP possessed the highest catalytic activity with a conversion of 76.4% in 96 h, which is much higher than the fluorine free ionic liquid IL-TCP. It is believed that this work paved a way for the development of novel catalysts for the efficient elimination and transformation of CO₂.