Highly Selective Oxidation of Benzene to Phenol Mediated by KHCO3 in the Bimetallic Mo-Cu/NC-H2O2 System.

Although selective oxidation of benzene to phenol (SOBP) by H2O2 is an important chemical process, overoxidation of benzene by the produced nonselective •OH during the activation of H2O2 inevitably reduces the oxidation selectivity. We, therefore, attempt to mediate the oxidation selectively by using electrophilic KHCO3 in the oxidation system. In this study, Mo-Cu/NC has been successfully synthesized via ball-milling bimetallic Mo-Cu and N-doped carbon, which exhibits high reactivity in SOBP by H2O2 and KHCO3 with a desirable phenol yield of 25.1% and selectivity of 100%. A series of characterizations and DFT calculations reveal that the reaction between H2O2 and KHCO3 produces HCO4-, which is then moderately activated on Mo1Cu2/NC via the nonradical pathway with the formation of Mo-(η2-O2) peroxo. Meanwhile, Ov at Mo1Cu2/NC facilitates the adsorption of benzene, which is then selectively oxidized by Mo-(η2-O2) peroxo to phenol via the oxygen atom transfer pathway. This study provides new insights on the importance of Mo-(η2-O2) peroxo mediated by H2O2-KHCO3 in selective oxidation of aromatic C-H bond via the nonradical pathway.