Mechanistic insights into visible light-induced direct hydroxylation of benzene to phenol with air and water over pt-modified WO3 photocatalyst

Abstract

Activation of C(sp2)-H in aromatic molecules such as benzene is one of the challenging reactions. The tungsten trioxide supported Pt nanoparticles (Pt-WO3) exhibited hydroxylation of benzene in the presence of air and H2 O under visible-light (420 < λ < 540 nm) irradiation. The photocatalytic activities (yields and selectivity of phenol) were studied under several experimental conditions. Furthermore, investigations of mechanistic insight into hydroxylation of benzene have been carried out by analyses with apparent quantum yields (AQY), an H218 O isotope-labeling experiment, kinetic isotope effects (KIE), electrochemical measurements and density functional theory (DFT) calculations. It was proposed that dissociation of the O–H bond in H2 O is the rate-determining step. Furthermore, the substitution of the OH derived from H2 O with H abstracted from benzene by photo-formed H2 O2 indicated a mechanism involving a push-pull process for the hydroxylation of benzene into phenol.