Unraveling the amine oxidative coupling activity of hierarchical porous Fe-N-4-O-1 single-atom catalysts: oxygen atom-mediated dual reaction pathway

Heteroatom doping is an efficacious strategy for electronic structure modulation and intrinsic activity adjustment, but the mechanisms accounting for activity enhancement remain controversial. Herein, a controllable self-assembly strategy is applied to manufacture atomically dispersed Fe-N-4-O-1 anchored N-doped porous carbon. The Fe-N-4-O-1 active sites possess a coordination number of 5, which exhibit splendid catalytic activity compared with Fe-N-4 sites. The oxygen atoms on Fe-N-4-O-1 sites can not only modulate the adsorption free energy of benzylamine molecules, but also directly oxidize the adsorbed benzylamine molecule to the corresponding imine, thereby promoting the oxidative coupling process of benzylamine. The Fe-N-4-O-1 coordination, high atomic Fe loading density and huge specific surface area are proven to be three decisive factors affecting the overall activity. Moreover, a possible reaction mechanism involving dual Fe-N-4-O-1 oxidative and Fe-N-4 reactive oxygen species pathways is proposed, which affords guidance for high-efficiency catalyst design toward oxidation-related reactions.