Divanadium-Substituted Phosphotungstate Supported on Magnetic Mesoporous Silica Nanoparticles as Effective and Recyclable Catalysts for the Selective Oxidation of Alcohols

A new magnetically recyclable catalyst (Fe3O4@mSiO(2)/NH-PV2W) was fabricated by immobilizing divanadium-substituted Keggin phosphotungstic acid H5PV2W10O40 on mesoporous-silica-coated Fe3O4 core-shell nanoparticles by a facile procedure. The magnetic core-shell nanoparticles were prepared by coating a thin mesoporous silica shell directly on pristine magnetic Fe3O4 and functionalized with amino radicals simultaneously. Then the active H5PV2W10O40 was immobilized on the mesoporous silica shell of the Fe3O4 core-shell nanoparticles. The obtained catalyst was characterized by using SEM, TEM, IR spectroscopy, XRD, N-2 sorption-desorption, and magnetometry. The catalytic properties were evaluated for a series of alcohols that were oxidized selectively to the corresponding aldehydes or ketones using hydrogen peroxide as the oxidant. The results show that H5PV2W10O40-loaded mesoporous silica-coated Fe3O4 catalyst presents high catalytic activities with 98% conversion of benzyl alcohol and 99% selectivity to benzaldehyde. After the reaction, the catalyst could be separated easily with an external magnetic field, and the recovered catalyst could be reused at least five times without any loss of catalytic activity.