Robust bimetallic high-valent Co14Mn1-oxo active centers ultra-efficiently activate PMS for the removal of tetracycline

Second-sphere oxygen doping stabilizes high-valent Co(IV) = O active centers. • Co 14 Mn 1 -oxo achieves complete tetracycline removal within 20 s. • Non-radical oxidation pathway driven by Co(IV) = O and singlet oxygen ( 1 O 2 ). • Excellent stability and recyclability in complex water environments. • Provides a new coordination-sphere strategy for advanced oxidation catalysts. Tailoring the local coordination and electronic microenvironment of metal centers is crucial for achieving high efficiency catalysis and maintaining catalyst stability during peroxymonosulfate (PMS) activation. Conventional strategies often introduce a second metal to modulate the oxygen reduction potential, but this typically disrupts coordination symmetry and compromises structural stability. Here, we develop an oxygen-doping strategy within the second coordination sphere to construct structurally robust Co 14 Mn 1 -oxo active centers. Systematic characterization and Density functional theory (DFT) reveals that oxygen doping reduces the electron density of primary Co sites, thereby weakening bonding effects and suppressing structural distortion of Mn N during PMS activation. The optimized catalyst enables complete tetracycline (TC) degradation within 20 s and extends operational lifetime over 2000-fold. Meanwhile, the weakened coordination field decreased the energy level of the Co O σ* orbital, promoting nucleophilic attack by high-valent Co(IV) = O species on TC and increasing the degradation rate by fivefold. Electron paramagnetic resonance (EPR) and quenching experiments confirmed that the TC degradation was predominantly governed by non-radical pathways, mainly mediated by Co(IV) = O species and singlet oxygen ( 1 O 2 ). In addition, the dual-active-site architecture significantly reduced the energy barrier for O O bond cleavage in PMS to form Co(IV) = O. This work offers a feasible design strategy for stabilizing high-valent metal species via second-sphere engineering, offering a new perspective for designing highly efficient and stable environmental catalysts. This work develops an oxygen-doping strategy within the second coordination sphere to construct robust Co 14 Mn 1 -oxo active centers, establishing a non-radical oxidation pathway dominated by high-valent Co(IV) = O species. The optimized catalyst achieves complete tetracycline removal within 20 s, demonstrating an exceptional reaction rate of 0.2273 s −1 . Download: Download high-res image (189KB) Download: Download full-size image