Transesterification of dimethyl carbonate and diethyl carbonate over [DBU+][IM−]@UiO-66: synergistic catalysis of acid-base active sites

Ethyl methyl carbonate (EMC) serves as a vital raw material in the production of electrolytes for lithium-ion batteries. In recent years, there has been increasing focus on the development of economically efficient methods to prepare EMC through the transesterification occurring between dimethyl carbonate (DMC) and diethyl carbonate (DEC). Nevertheless, the acidic or alkaline catalysts commonly used at present are not suitable for this system. Herein, the acid-base double active site catalyst, known as [DBU + ][IM − ]@UiO-66, is designed and prepared to enable its application in the synthesis of EMC. The synthesis of [DBU + ][IM − ]@UiO-66 involves the incorporation of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and imidazole (IM) molecules within the porous framework of UiO-66. The integration of these components creates an active catalyst with acid sites provided by the defect of UiO-66 and base sites derived from [DBU + ][IM − ] ionic liquid. The porous structure of UiO-66 offers an extensive surface area, ensuring sufficient exposure of the active sites for catalytic reactions. This catalyst combines the mutually reinforcing effects of acid and base sites, enhancing its catalytic performance and selectivity in the desired reaction. In the targeted synthesis of EMC, the [DBU + ][IM − ]@UiO-66 catalyst demonstrates remarkable efficiency. An EMC yield of 62% and an EMC selectivity of 99.5% were achieved, which demonstrated the effectiveness of the reaction system. The acid sites facilitate the activation of the reactants, while the base sites contribute to the formation of intermediate species. This dual functionality enhances the reaction kinetics and promotes the desired conversion of starting materials into EMC. • A new acid-base bifunctional catalyst, [DBU + ][IM − ]@UiO-66, has been designed and prepared. • The catalyst combines the synergistic effects of acidic and basic sites, enhancing its catalytic performance. • The mechanism of acid-base synergistic catalysis was elaborated. • [DBU + ][IM − ]@UiO-66 shows great structure stability and recyclability.