MOF-derived CeO2 catalysts with Pr doping: engineering oxygen vacancies for improved CO2 conversion to dimethyl carbonate

https://pubs.rsc.org/en/content/articlelanding/2024/ta/d4ta05554c

Abstract

Producing dimethyl carbonate (DMC) from CO₂ and methanol offers significant potential for carbon utilization. Ceria (CeO₂) is a key catalyst due to its abundant oxygen vacancies essential for CO₂ activation, but enhancing its catalytic performance for practical applications remains challenging. While doping with REMs (rare earth metals) has been recognized as a potential strategy for modulating defect sites of ceria, incorporating praseodymium (Pr) into defect-rich nanostructured ceria to optimize DMC synthesis is still unexplored. Herein, we systematically synthesized a series of CeO₂ catalysts using Ce containing metal–organic framework (MOF) templates, including Ce-MOF-808 and Ce-BTC, and further doped them with various rare earth metals (REMs) to evaluate their effectiveness in DMC conversion. Among them, Pr-doped CeO₂ derived from Ce-BTC templates exhibited the highest reactivity for DMC formation in a gas-phase flow reaction system. High-resolution imaging (HAADF and ABF-STEM) and spectroscopic analyses (Raman, XANES and XPS) revealed that Pr-doped CeO₂ from BTC exhibited significantly higher oxygen defect concentrations. Temperature-programmed desorption (TPD) of CO₂ and NH₃ showed that Pr-doped CeO₂ possesses enhanced acidic and basic properties, attributable to higher oxygen vacancies. These facilitated the formation of key reaction intermediates, such as bicarbonates and methoxy species, observed in in situ DRIFTS, leading to improved DMC yields in gas-phase reactions. Density Functional Theory (DFT) calculations corroborated these experimental findings, highlighting the pivotal role of defect sites in the activation of CO₂ and methanol, crucial for efficient DMC formation.