Dynamic evolution of nitrogen and oxygen dual-coordinated single atomic copper catalyst during partial oxidation of benzene to phenol
Weiming Chen, Hongqiang Jin, Feng He, Peixin Cui, Changyan Cao, Weiguo Song
Abstract
Single atom catalysts (SACs) with metal1-Nx 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 (metal1-Nx)=O active site, and followed by the dissociation of another H2O2 on the other side of metal atom to form O=(metal1-Nx)=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 (Cu1-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 Cu1/NC), Cu SAC with nitrogen and oxygen dual-coordination (denoted as Cu1/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 Cu1/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.