Harnessing Metal-Substituted CeO₂ Catalysts for Chemical Fixation of CO₂ into Glycerol Carbonate: A Dual Approach.

Reducing anthropogenic CO₂ emissions is crucial, and converting CO₂ into value-added chemicals offers a sustainable solution. In this work, a series of metal-substituted CeO₂ catalysts were synthesized for the cascade synthesis of glycerol carbonate via cycloaddition and transesterification reactions using CO₂, propylene oxide, and glycerol. XRD and FE-SEM analyses confirmed the formation of core-hollow nanospheres architecture, while complementary physicochemical characterizations verified their structural and surface properties. Among the catalysts, the Mg-substituted CeO₂ (CHNS-Mg/CeO₂) exhibited the highest catalytic activity under solvent and additive-free conditions, achieving a 96% glycerol carbonate yield at 160 °C and 20 bar CO₂ after 8 h, along with moderate yields of propylene carbonate and propylene glycol. Systematic studies revealed that the incorporation of Mg into the CeO₂ lattice enhanced Lewis basic sites and oxygen vacancies, as evidenced by XPS analysis, thereby improving the levels of CO₂ activation and reactants adsorption. The CHNS-Mg/CeO₂ catalyst demonstrated excellent recyclability, maintaining both structural integrity and activity over 10 cycles. Comparative evaluations with other monometallic and bimetallic oxide/hydroxide catalysts confirmed its superior performance. A plausible multistep mechanism, supported by experimental data and DFT calculations, highlights the synergistic role of Ce and O lattice sites as Lewis's acid and base centers in activating CO₂, glycerol, and propylene oxide. Overall, this study establishes a robust and scalable catalytic system for efficient CO₂ utilization and glycerol valorization, combining experimental evidence and theoretical validation to advance sustainable carbon conversion technologies.