On the role of multifunctional ionic liquids for the oxidative carboxylation of olefins with carbon dioxide

Abstract

Ionic liquids (ILs) are catalysts with profound effects on the activity and selectivity for the transformation of CO2. In particular, highly functionalisable and immobilisable imidazolium based ILs (ImILs) activate CO2 molecules and have demonstrated activity towards CO2 cycloaddition reactions. The addition of hydroxyl groups has also been reported to enhance the cycloaddition reaction. An ideal system would combine both functionalities for superior performance. In addition, integrating the cycloaddition with the epoxidation of olefins employing multifunctional catalysts in one-pot would improve process efficiency, reduce waste and costs. However, the interaction between the cation-anion and the hydroxyl groups needs to be elucidated to realize these advantages. Herein, the viability of using ILs as bifunctional catalyst for one-pot reaction is evaluated by combining theoretical and experimental studies. Density functional theory (DFT) simulations of both reactions using halogenated and hydroxyl functionalized ImLs are presented. The position of the hydroxyl group close to the imidazolium unit primarily influences the opening of the epoxide and its activation for the cycloaddition reaction, thus facilitating the catalysis. In addition, experimentally the selectivity increases considerable with the catalyst immobilization. For the epoxidation reaction the DFT calculations and experimental results demonstrated favoring hydrolysis reaction.