“…4 The thermodynamic limitation can be overcome by reacting CO 2 with high-energy substrates, such as epoxides, hydrogen or amines, while the kinetics of CO 2 conversion can be improved by utilising appropriate catalysts. 5,6 Particularly, the reaction of CO 2 and epoxides to yield cyclic carbonates is a promising route in the context of green chemistry as it has a theoretical 100% atom efficiency, it can be generally carried out under solvent-free conditions at relatively mild temperature and CO 2 pressure, and the obtained cyclic carbonates typically have low toxicity, high boiling point and high polarity, leading to a wide range of applications as green solvents, components for electrolyte solutions for lithium-based batteries, monomers for the preparation of polymers, and reactants for organic synthesis. 7,8 The simplest and most affordable catalysts for the cycloaddition of CO 2 to epoxides are halide salts, among which the ones that show the best catalytic performance are organic halides such as imidazolium salts, quaternary ammonium salts and phosphonium salts.…”