Polyoxotungstate ([PW11O39]7−) immobilized on mesoporous polymer for selective liquid-phase oxidation of alcohols using H2O2

Abstract

Selective oxidation of alcohols is an attractive organic transformation and has received tremendous attention from the scientific community over the years. Herein, a mesoporous polymer (MP) was synthesized by a template-free solvothermal approach. The surface of the MP was functionalized with quaternary ammonium groups and polyoxotungstate anion (PW₁₁O₃₉⁷⁻) was subsequently supported on the MP as a counter anion to the ammonium cation by a simple ion-exchange procedure. The structure of PW₁₁ and PW₄ complexes was confirmed by ³¹P NMR and FTIR analysis. The surface properties of all the catalysts synthesized were explored by various characterization techniques such as nitrogen sorption, TGA, contact angle measurement, and ICP-OES analysis. The synthesized PW₁₁/MP catalysts were employed for selective oxidation of alcohols. Among the various PW₁₁ supported catalysts, PW₁₁/MP (80 : 20) demonstrated excellent catalytic activity for the oxidation of alcohols using aqueous H₂O₂. The PW₁₁/MP (80 : 20) catalyst showed good catalytic activity for oxidation of a wide range of alcohols including substituted, heterocyclic and secondary alcohols. The superior catalytic activity of PW₁₁/MP (80 : 20) is attributed to an optimum balance in the hydrophilicity/hydrophobicity in the mesoporous environment, better catalyst wettability, and enrichment of reactants in the catalytic active sites.