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

Abstract

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.

A Perspective on Heterogeneous Catalysts for the Selective Oxidation of Alcohols

“…Especially in the case of mixed oxides, the surface can be enriched by one or the other cation, [2a,58] as schematically shown in Figure 4, which can eventually define the nature and the electronic state of the adsorption sites on the surface. Mixed oxides are particularly interesting as they provide a means to adjust the band structure [59] and the oxidation degree of the cationic species on the surface and therefore tuning of the active sites [60] . Also depending on composition, one oxide phase can be atomically dispersed in the other one, essentially creating an efficient catalyst as reported for V and Fe antimonates for oxidation of ethanol to acetaldehyde [2a] .…”

Microwave-assisted oxidation reaction of primary alcohols with sensitive functional groups to aldehydes using ruthenium diphosphorus complexes

“…The solvent-free oxidation was carried out at three different temperatures (Table 1, entries [15][16][17], where the obtained yields were 95, 96 and 98 percent at 100, 120 and 140 °C, respectively. These results suggest that for substrates that are able to act as both the reagent and homogeneous medium, the solvent has minimal or no effect on the reactivity, which is highly desirable.…”

“…The oxidation reaction is one the most fundamental reactions in synthetic organic chemistry and has been the subject of numerous studies. [10][11][12][13][14][15][16][17] Ruthenium is a well stablished metal for the oxidation of alcohols. 11,18 Aldehydes, as a result of their increased electrophilic nature, are more reactive and suitable for a broader range of transformations than the precursor alcohols.…”

Dual Stimuli-Responsive Copper Nanoparticles Decorated SBA-15: A Highly Efficient Catalyst for the Oxidation of Alcohols in Water

“…Mesoporous silica material-supported catalysts have been proven to be the most ideal catalysts because of their high surface area, wall thickness, high porosity, and large and uniform channel size. To prevent the agglomeration of CuNPs, the use of a stabilizing agent is essential for the synthesis of CuNPs [ 15 , 16 , 17 ]. Although the wet impregnation method is an effective method for incorporating metals on a silica surface, that method usually results in non-uniform dispersion.…”