Amorphization Strategy to Circumvent the Oxo Wall for Generating Active Co(IV)═O Species in Fenton-Like Reactions

High-valent Co(IV)═O species have garnered significant attention as a promising non-radical reactive species. However, their selective generation encounters substantial challenges due to the oxo wall rule that emphasizes intrinsic instability of the terminal metal-oxygen (M─O) bond. Here, we propose an amorphization strategy for TiO₂ support to circumvent the limitation of oxo wall, favoring the formation of high-valent Co(IV)═O species. The advantages of Co(IV)═O species in terms of oxidative activity, durability, and environmental tolerance were investigated by Fenton-like catalysis. Mechanistic studies revealed that amorphous TiO₂ endowed Co single atoms with a Co-O₄ tetrahedral structure and a high-spin state of 3d electron, leading to strong Co 3d-O 2p interactions that promote peroxymonosulfate (PMS) activation. Notably, the produced Co(IV)═O species adopted a trigonal-bipyramidal-like configuration, which mitigated the electron occupation in the antibonding orbitals of terminal M─O bond, thus bypassing the oxo wall. This work enhances the understanding of the mechanism underlying heterogeneous Co(IV)═O formation and broadens strategies for preparing efficient catalysts for critical oxidation reactions.