Effect of Electronic Structure over Late Transition-Metal M₁-N₄ Single-Atom Sites on Hydroxyl Radical-Induced Oxidations

Hydroxyl radical (^•OH)-induced oxidations are of great importance in chemical transformations. Carbon-supported late transition-metal single-atom catalysts (SACs) with bioinspired M₁-N₄ single-atom sites can effectively activate the peroxide group to produce ^•OH. Nevertheless, little is known about how electronic structures of M₁-N₄ sites affect ^•OH generation. Herein, dependent on the theoretical design and experimental realization of uniform M₁-N₄/C (M: Fe, Co, Ni, and Cu) SACs, a positive correlation relationship between ^•OH-induced oxidation activity and d-band center over the M₁-N₄ site has been revealed. In detail, by changing the M atoms with different numbers of d electrons, the d-band center of the M₁-N₄ could be turned. Moreover, the enhancement of d-band center heightens the interaction strength between the ^•OH intermediate and the M₁-N₄ site, which results in a higher oxidation activity. In this case, the efficient M₁-N₄ catalyst for the oxidation reaction can be screened by tuning the doped M atom. Moreover, notably, Fe₁-N₄ with the highest d-band center value has the lowest free energy change of the rate-determining step (0.06 eV) for ^•OH generation. Taking advantage of this, in both Fenton-like reaction and ^•OH-induced C-H bond activation reaction, the Fe₁-N₄ site displays at least 1 order of magnitude higher activity than the most of the supported late transition-metal catalysts and comparable activity to reported noble metal catalysts. This work is expected to provide guidance for designing high-efficiency heterogeneous catalysts in ^•OH-induced oxidations and bridge heterogeneous and enzymatic catalysis by using M₁/C SAC as a platform.