Co-O-Ce sites on defect-engineered Co0.05Ce0.95O2-δ solid solutions drive the direct conversion of CO2 to dimethyl carbonate

Co-doped CeO 2 creates synergistic Co-O-Ce interfaces and oxygen vacancies. • Distinct CH 3 OH and CO 2 activation sites alleviate competitive adsorption. • Achieves high DMC yield of 16.5 mmol·g −1 ·h −1 under 2 MPa CO 2 and 140 °C. • Excellent stability demonstrated over five consecutive reaction cycles. • In situ IR confirms cooperative mechanism at Co-O-Ce active centers and O V . The direct conversion of carbon dioxide (CO 2 ) and methanol (CH 3 OH) into dimethyl carbonate (DMC) represents a highly attractive route for sustainable chemical synthesis and carbon utilization. However, when operating without dehydrating agents (typically used to shift the thermodynamic equilibrium), the process faces a fundamental challenge on conventional CeO 2 -based catalysts: the competitive adsorption of CO 2 and CH 3 OH for similar active sites, which ultimately limits reaction efficiency. To address this challenge, an innovative strategy was developed through the design of defect-engineered Co 0.05 Ce 0.95 O 2-δ solid solutions. Comprehensive characterization using Raman spectroscopy, XPS, XANES and EXAFS spectra, and AC-TEM confirmed the successful incorporation of Co into the CeO 2 lattice. The incorporation of Co generated abundant oxygen vacancies (O V ) and unique Co-associated interfacial sites (Co-O-Ce). These sites collectively enhanced the catalyst's acidity and basicity and helped alleviate competitive adsorption. Specifically, Co-O-Ce sites are proposed to favor CH 3 OH adsorption and activation, while O V and adjacent Ce ions facilitate CO 2 adsorption and polarization. This cooperative interaction substantially enhances the reaction efficiency, enabling the catalyst to achieve a high DMC formation rate of 16.5 mmol·g −1 ·h −1 under mild conditions (140 °C, 2 MPa), which surpasses that of most reported CeO 2 -based catalysts under comparable conditions. Moreover, the catalyst exhibited outstanding stability over five consecutive cycles. The reaction mechanism, involving the synergistic function of the Co-O-Ce interface sites, was further validated by in situ infrared spectroscopy. Beyond providing a highly efficient and stable catalyst, this work offers fundamental insights into active site engineering for promoting cooperative activation in CO 2 conversion reactions. Download: Download high-res image (339KB) Download: Download full-size image