Porous ceria materials for efficient direct conversion of carbon dioxide and methanol to dimethyl carbonate

Abstract

Ceria (CeO₂) is widely considered as a superior catalytic material for the direct conversion of carbon dioxide (CO₂) and methanol into dimethyl carbonate (DMC). Developing porous structures is a versatile way to increase the surface area, to create defects, and to improve the mass transfer of the resulting materials, consequently enhancing their catalytic performance. However, most of the reported preparation methods of porous CeO₂ involve complex hydrothermal (100–120 °C) or refluxing (95–140 °C) processes followed by calcination at temperatures of 500–650 °C. In this work, we report a simple and low temperature approach to prepare porous CeO₂, which involves mixing the raw materials at room temperature, followed by drying and then calcining at 450 °C. A DMC formation rate of 14.8 mmol g⁻¹ h⁻¹ is achieved for one of the obtained porous CeO₂, which is much higher than those of the most reported CeO₂ (0.51–11 mmol g⁻¹ h⁻¹). Further studies show that the DMC formation rate has a positive link to the parameters following the order: the CO₂ uptake amount at 25 °C, the amount of weak acidity, the Ce³⁺ concentration, the amount of weak basicity, and the BET surface area of the CeO₂ catalysts in this study. In addition, there seems to be an optimum oxygen vacancy concentration of the CeO₂ samples for the DMC formation rate. This study provides a simple strategy for the preparation of a porous CeO₂ material as a highly efficient catalyst for the catalytic conversion of CO₂, which can not only mitigate the greenhouse gas CO₂, but also turn it into value-added and versatile chemical DMC.