Enhanced Generation of Fe(IV)-Oxo Species via Chlorite Activation in Nanoconfined Covalent Organic Frameworks for Hypersaline Wastewater Decontamination

Heterogeneous radical-dominated advanced oxidation processes (AOPs) remain severely restricted in hypersaline wastewater matrices due to the interference of coexisting ions and natural organic matter (NOM). Herein, we propose a nonradical high-valent metal-oxo (HVM)-driven oxidation during chlorite activation for decontamination. By constructing a series of transition metal (Fe, Co and Mn) atomic sites into a bipyridine-based covalent organic framework (Bpy-COF), the experiments and theoretical calculations unravel the intensified mechanism that this design confers an enhanced confined effect toward accelerating chlorite diffusion (1.64 × 10-11 m2 s-1) and mass transfer into spatial nanopore channels (22-36 Å), further inducing a stronger molecular chlorite adsorption (Eads = -2.29 eV) upon Fe sites with a higher d-band center to facilitate Fe(IV)═O generation. This atomic-level nanoconfinement simultaneously integrates a size-sieving effect to block large molecular NOMs in nanoreactors, synergistically causing anti-inference against high concentrations of Cl- and organic matrices. Consequently, Fe-Bpy-COF nanoreactors achieve efficient selective degradation of electron-enriched pollutants, especially kobs of sulfamethoxazole (SMX) degradation at 0.1442 min-1, exhibiting a robust resilience to hypersaline and realistic water conditions. This study highlights the pivotal role of the nanoscale COF reactor design and provides novel insights into HVM-mediated decontamination with anti-interference in practical hypersaline wastewater.