Templated Synthesis of Mesoporous Co3O4 Nanostructures for the Liquid-Phase Aerobic Oxidation of Benzyl Alcohol to Benzaldehyde.

Mesoporous Co₃O₄ nanostructures, templated from different mesoporous silicas, SBA-3, SBA-5, and SBA-16, were used as catalysts for the liquid-phase selective oxidation of benzyl alcohol using molecular oxygen as the oxidant. The nanostructured Co₃O₄-16, templated from SBA-16, showed the best activity for the reaction, with 97.5% benzyl alcohol conversion and 100% benzaldehyde selectivity obtained after 3 h of reaction at 100°C. This could be attributed to its large number of oxygen vacancies and low surface Co³⁺/Co²⁺ ratio that were beneficial to O₂ activation, together with its three-dimensional nanostructure that facilitated the adsorption of benzyl alcohol, compared to Co₃O₄-3 and Co₃O₄-15. The material could be reused without losing activity if the organics adsorbed on the surface of the used sample were removed by calcination at 300°C for 1 h. A mechanism for the reaction was proposed, considering that the activation of molecular oxygen was the rate-determining step of the reaction. [ABSTRACT FROM AUTHOR]