Diphenyl carbonate synthesis from CO2 over a ZnCeZrOX ternary solid solution: synergistic catalysis using oxygen vacancies and Lewis acid sites

Abstract

The direct synthesis of diphenyl carbonate (DPC) from CO₂ and phenol has attracted much attention as it can realize CO₂ utilization and can avoid phosgene usage in the traditional production process. Nevertheless, the achievement of high DPC yields is hindered by the difficult activation of CO₂. Herein, a dual metal incorporated ZnCeZrO_X catalyst was synthesized, and the synergistic catalysis mechanism between oxygen vacancies and Lewis acid sites was systematically demonstrated. Raman and EPR analyses revealed that the simultaneous introduction of Zn and Ce effectively promoted the formation of abundant oxygen vacancies, thereby enhancing the adsorption and activation of CO₂. NH₃-TPD and Py-IR characterizations demonstrated that dual doping of Zn and Ce modulated Lewis acidity, benefiting the adsorption of phenol and intermediates. Compared with ZnZrO_X and CeZrO_X, the ZnCeZrO_X catalyst demonstrated superior catalytic performance, achieving a phenol conversion of 47.6% and a DPC selectivity of 82.5%. DFT and in situ FTIR analyses indicated that oxygen vacancies activated CO₂ to form b-CO₃²⁻ species, while Lewis acid sites adsorbed phenol to facilitate the dissociation of the O_phenol–H bond, synergistically generating DPC. This study demonstrates synergistic catalysis using oxygen vacancies and Lewis acid sites, opening a novel avenue for DPC synthesis.