Mesostructured nanocomposites (SBA-15:CeO₂), synthesized via two different methods, are analyzed to highlight their structural and morphological differences. The samples are tested for CO₂ adsorption/desorption at 25, 35, 50, and 70 °C, with enhanced adsorption capacity attributed to increased oxygen vacancies induced by the direct synthesis method.

This study investigates the role of oxygen vacancies in the CO₂ adsorption and desorption dynamics of SBA-15:CeO₂ nanocomposites synthesized by direct (DS) and postsynthesis (PS) methods. Physicochemical analyses reveal that the DS method increases the concentration of oxygen vacancies and structural defects within the CeO₂ framework, which significantly boosts CO₂ adsorption capacity and strengthens the gas-surface interactions. Among the materials, S_Ce4.a demonstrates the highest adsorption capacity, reaching 29.4 mg g^{− 1} at 25 °C and 10.7 mg g⁻¹ at 70 °C. These results indicate a physisorption mechanism governed by both thermal conditions and oxygen vacancies. Furthermore, S_Ce4.a and S_Ce10.a. exhibit remarkable stability over 20 adsorption–desorption cycles. The findings suggest that a lower cerium oxide content provides more accessible adsorption sites, making these materials promising candidates for high-performance. Overall, this work highlights synergistic interplay between oxygen vacancies and mesoporous structures, paving the way for the rational design of advanced materials for CO₂ capture technologies.