Facile and Direct Hydroxylation of Benzene to Phenol over Graphene-Based Catalysts: Integrated Utilization of Greenhouse Nitrous Oxide

Graphene catalysis has recently emerged as a focus and herein a novel and highly efficient process is computationally designed using graphene-based catalysts that integrates the utilization of greenhouse nitrous oxide (N2O) as oxidant. The ground-state pristine graphene is not catalytically active for benzene hydroxylation, and doping and photocatalysis through excitations are employed to improve the catalyst systems, while both strategies exhibit limited effects. A combination of Be-doping and photocatalysis through excitations results in encouraging changes, where all energy barriers are moderate, so that the whole catalytic processes proceed facilely at mild conditions. Graphene materials, especially Be- and O-doped ones, are good photocatalysts due to the low excitation energies. Mechanistic studies indicate that the active sites of the excited-state graphene, whether pristine or doped, are oxygen anion radical (O center dot-) and distinct from the epoxide species for the ground state; in addition, Be-doping pronouncedly reduces the excitation energies and enhances the interactions with the active-site O species, which further show strong stabilization effects to transition states and reduce substantially the energy barriers.