Turning the coordination environment of atomic Fe-N4 center by peripheral nitrogen species for boosted catalytic performance

Atomically dispersed metal-nitrogen-carbon (M-N-C) catalysts show great potential for heterogeneous catalysis. However, recognizing and engineering the microenvironment of M-N-x sites to achieve satisfactory catalytic performance remains challenging. Herein, we propose a facile g-C3N4-assisted template strategy to anchor atomic Fe-N-4 sites on highly nitrogen-doped carbon nanosheets. Through regulating the ratio and type of peripheral nitrogen species by carbonization temperature, the optimal Fe-N-C-800 catalyst showed significantly boosted catalytic activities (overall turnover frequency of 13.43 min(-1) and activation energy of 19.44 kJ mol(-1)) for nitroarene reduction with extremely low reductant dosage, exceeding most reported metal catalysts. Experimental and theoretical results reveal appropriate graphitic- and pyrrolic-N dopants surrounding the Fe-N-4 center can tailor the local electronic structure and contribute to obvious upshift of the d-band center, which dramatically promotes the adsorption and conversion of reactant substrates, eventually delivering the unprecedented catalytic performance. This work provides a guide for rational coordination environment regulation of single-atom catalysts for efficient chemical transformations.