Palladium/polyoxometalate as a cooperative and reusable catalytic system for room temperature aerobic oxidation of alcohols to the corresponding carbonyl compounds in aqueous media

Abstract The design of cooperative catalytic systems modeled on nature is a significant development in organic synthesis. In this research, selective oxidation of the primary and secondary alcohols to the corresponding carbonyl compounds using oxygen as an environmentally friendly oxidant and in the presence of the heterogeneous cooperative catalytic system of palladium, sandwich type polyoxometalate [(OCe)₃ (PW₉O₃₄)₂]¹²⁻ and hydroquinone (HQ) were investigated. In the first method, palladium nanoparticles on siliceous mesocellular foam (MCF) and polyoxometalate (POM) on Nd-doped TiO₂ nanoparticles were immobilized. Then the aerobic oxidation of the alcohols to the corresponding carbonyl compounds in the presence of the Pd@MCF/POM@TiO₂/HQ catalytic system in THF solvent at 40 oC was investigated. In the second method, both palladium and polyoxometalate nanoparticles were immobilized on the same MCF. Then, POM-Pd@MCF/HQ as an efficient and reusable biomimetic catalytic system was used for the aerobic oxidation of the alcohols to the corresponding carbonyl compounds with good to excellent yields in water as solvent at room temperature. The Pd@MCF, POM@TiO₂ and POM-Pd@MCF compounds were identified and confirmed by various techniques.