Mesoporous Silica-Supported CuCo₂O₄ Mixed-Metal Oxides for the Aerobic Oxidation of Alcohols

Mesoporous silica-supported spinel phase CuCo2O4 mixed-metal oxide nanoparticles were synthesized as a catalyst for the selective oxidation of substituted benzyl alcohols to aromatic aldehydes, in which oxygen gas was used as an oxidant. It possessed high catalytic activity, achieving nearly 100% conversion in 8 h, which was much higher than mesoporous silica-supported CuO nanoparticles, Co3O4 nanoparticles, and their mixtures, demonstrating the advantage of mixed metal oxide due to its unique electronic states. The enhanced catalytic activity of CuCo2O4 may come from the presence of Cu3+ in the octahedral sites of the spinel phase crystal structure. A self-supported mesoporous CuCo2O4 replica material with same crystal phase was also synthesized. However, it was found that the self-supported replica material gave much lower reactivity in this reaction, which may be because the surface copper ions were preferentially etched by NaOH during the template removal process.