Dynamic evolution of nitrogen and oxygen dual-coordinated single atomic copper catalyst during partial oxidation of benzene to phenol

Single atom catalysts (SACs) with metal(1)-N-x sites have shown promising activity and selectivity in direct catalytic oxidation of benzene to phenol. The reaction pathway is considered to be involving two steps, including a H2O2 molecule dissociated on the metal single site to form the (metal(1)-N-x)=O active site, and followed by the dissociation of another H2O2 on the other side of metal atom to form O=(metal(1)-N-x)=O intermediate center, which is active for the adsorption of benzene molecule via the formation of a C-O bond to form phenol. In this manuscript, we report a Cu SAC with nitrogen and oxygen dual-coordination (Cu-1-N3O1 moiety) that doesn't need the first H2O2 activation process, as verified by both experimental and density function theory (DFT) calculations results. Compared with the counterpart nitrogen-coordinated Cu SAC (denoted as Cu-1/NC), Cu SAC with nitrogen and oxygen dual-coordination (denoted as Cu-1/NOC) exhibits 2.5 times higher turnover frequency (TOF) and 1.6 times higher utilization efficiency of H2O2. Particularly, the coordination number (CN) of Cu atom in Cu-1/NOC maintains four even after H2O2 treatment and reaction. Combining DFT calculations, the dynamic evolution of single atomic Cu with nitrogen and oxygen dual-coordination in hydroxylation of benzene is proposed. These findings provide an efficient route to improve the catalytic performance through regulating the coordination environments of SACs and demonstrate a new reaction mechanism in hydroxylation of benzene to phenol reaction.