Amorphous Engineering Driving d-Orbital High Spin Configuration for Almost 100% ¹O₂-Mediated Fenton-Like Reactions

The inherent atomic disorder in amorphous materials leads to unsaturated atomic sites or dangling bonds, effectively modulating the material's electronic states and rendering it an ideal platform for the growth of single atoms. Herein, the electronic structure of isolated cobalt atoms anchored on amorphous carbon nitride (Co-ACN) is modulated through a substrate amorphization engineering, enabling the thorough removal of pazufloxacin (PZF) in 1 min with a high reaction rate constant (k₁) of 3.504 min^-1 by peroxymonosulfate (PMS) activation. Experiments and theoretical calculations reveal that Co-ACN exhibited a higher coordination environment (Co-N₃) compared to crystalline Co-CCN (Co-N₂). Meanwhile, the t_2g energy level enhancement of Co 3d orbital promotes electron transition from t_2g to e_g, inducing more unpaired electrons and thereby driving the transition from a low-spin state (LS, t_2g ⁶e_g ¹) to a high-spin state (HS, t_2g ⁵e_g ²). The HS Co-ACN optimized the d-band center, boosted the electronic transfer, and weakened the interaction between Co 3d and O 2p orbitals of HSO₅ ^-, thereby enabling nearly 100% selective singlet oxygen (¹O₂) generation, whereas Co-CCN yielded coexisting reactive oxygen species (ROS). This work opens up a new paradigm for regulating the electronic structure of single-atom catalysts at the atomic scale.