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

Graphical Animal magnetism : A magnetically recoverable catalyst is fabricated by immobilizing divanadium-substituted Keggin phosphotungstate on mesoporous-silica-coated Fe 3 O 4 core–shell nanoparticles by a facile procedure. This material presents a high catalytic activity for the selective oxidation of alcohols. A new magnetically recyclable catalyst (Fe 3 O 4 @mSiO 2 /NH-PV 2 W) was fabricated by immobilizing divanadium-substituted Keggin phosphotungstic acid H 5 PV 2 W 10 O 40 on mesoporous-silica-coated Fe 3 O 4 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 Fe 3 O 4 and functionalized with amino radicals simultaneously. Then the active H 5 PV 2 W 10 O 40 was immobilized on the mesoporous silica shell of the Fe 3 O 4 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 H 5 PV 2 W 10 O 40 -loaded mesoporous silica-coated Fe 3 O 4 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.