Surface-Dependent Role of Oxygen Vacancies in Dimethyl Carbonate Synthesis from CO 2 and Methanol over CeO 2 Catalysts

The conversion of CO 2 into value-added commodity chemicals, such as dimethyl carbonate (DMC), represents an environmentally friendly approach to CO 2 utilization. This study exhaustively investigates the influence of oxygen vacancies (O v ) on CeO 2 catalysts and, in particular, the role of surface structure. By integrating density functional theory calculations with experimental synthesis, we analyze the complex reaction mechanisms involved in DMC synthesis over both oxidized (Sto-(111), Sto-(110), and Sto-(100)) and nonoxidized (O v sub -(111), O v sur -(110), and O v sur -(100)) CeO 2 catalysts. Our findings indicate that O v on the (111) surface inhibits DMC formation, whereas O v on the (110) and (100) surfaces promotes it. This differential behavior is primarily attributed to O v ’s modulation of the microscopic coordination environment on distinct surfaces, which impacts the rate-limiting step of C–O bond formation: CO 2 + OCH 3 → CH 3 OCOO (monodentate methyl carbonate, MMC) and CH 3 OCO + OCH 3 → DMC. Additionally, analysis of the highly active Sto-(111) and O v sur -(110) catalysts shows that their unique surface coordination microenvironments mitigate steric hindrance and facilitate an optimal arrangement of Lewis acid sites in proximity to Lewis base sites, thereby enhancing the DMC activity. This work underscores the pivotal role of surface structure in determining the effects of O v, paving the way for the rational design of CeO 2 -based catalysts for the direct synthesis of DMC from CO 2 and methanol.