Controllable synthesis of mesoporous cobalt oxide for peroxide free catalytic epoxidation of alkenes under aerobic conditions

We report the synthesis of mesoporous Co3O4 by an inverse micelle template self-assembly method and its catalytic activity towards selective oxidation of alkenes to epoxides. The chemical and structural properties of the materials were characterized by powder X-ray diffraction, nitrogen sorption studies, electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis. The morphology of the material exhibits flower like nanoparticle aggregates. Nanoparticles are packed closely in a random manner to form the mesoporous network via connected interparticle voids. Particle size expansion could be observed with heat treatment (250 degrees C-450 degrees C), which strongly correlates with surface area of the material. Co-250, which has the highest surface area along with highest oxygen vacancies, gave the best performance in alkene epoxidation. The catalyst was found to be efficient in selective oxidation of alkenes to epoxides with a broad substrate scope and achieved > 99% conversion with high selectivity (93%). Liquid phase batch mode reactions were carried out under atmospheric pressure and aerobic conditions, in the absence of any additives. Moreover the catalyst could be recycled several times without losing its activity, which makes this catalyst economical and environmentally benign.