Effect of ionic liquids clusters microenvironment on cycloaddition reaction of carbon dioxide

Abstract The mechanism for the cycloaddition of carbon dioxide and epoxides catalyzed by ionic liquids has been elucidated in lots of theoretical literature. It is well known that the calculated barrier height could not be compared with the activation energy. However, it is expected that the sequence of activity estimated by barrier height could be consistent with the experimental result. Actually, the calculated results are not accurate enough to be reliable. One of possible reasons is attributed to the improper treatment for the solvent effect. The solvent effect induced by ionic liquids is not carefully considered or neglected at all in most of previous theoretical studies. In this work, ionic liquids are really included in the catalytic system to consider the solvent effect by the ONIOM method along with the molecular dynamics simulations. When the solvent effect is considered, the theoretical reliability is greatly improved. More important, this model is suitable not only for non-protic ionic liquids but also for protic ones and not only for imidazolium ionic liquids but also for pyrazolium ionic liquids. The solvent effect aroused by epoxides is also considered by the same model.