Co3O4 of regular cubic shape as high-efficiency catalyst for the preparation of lactones through the Baeyer–Villiger oxidation of cyclic ketones with dioxygen

The Co 3 O 4 catalysts with regular cubes in shape were prepared by direct hydrothermal synthesis with the assistance of a triblock copolymer (P123). The synthesized materials were characterized by powder X-ray diffraction, scanning electron microscopy, and nitrogen adsorption–desorption techniques. It was found that the Co 3 O 4 catalysts showed high catalytic activity and selectivity for the Baeyer–Villiger oxidation of cyclic ketones in the presence of 1,2-dichloroethane and dioxygen. The effects of reaction conditions (catalyst amount, reaction temperature, reaction time, and different solvents) on the catalytic performance of Co 3 O 4 were investigated. It was observed that under optimal reaction conditions, cyclohexanone conversion and ε-caprolactone selectivity could reach 98 and 100 %, respectively. In addition, the process has advantages such as mild reaction conditions, simple operation, and high product yield. Furthermore, the catalyst can be reused for several times without obvious loss of activity and selectivity.