Emerging organic pollutants (EOPs) present structural diversity and complex reactivity in advanced oxidation processes (AOPs), yet the intrinsic physicochemical determinants of their degradation remain unclear. Here, Fe-CN-X catalysts with tunable Fe spin states were constructed by modulating nitrogen coordination, enabling systematic evaluation of pollutant-catalyst interactions. Magnetic susceptibility and electron paramagnetic resonance analyses confirmed that Fe-CN-900 possesses the highest spin state (µeff = 2.38), which favors electron occupation in eg orbitals and increases Fe─O charge density. This electronic configuration markedly enhances PMS adsorption and elevates singlet oxygen (1O2) yield from 48% (Fe-CN-700) to 85% (Fe-CN-900). Kinetic studies of 7 representative pollutants revealed a strong correlation between ionization potential and degradation rates. High-spin Fe sites markedly promoted electron transfer from high-ionization-potential pollutants, while pollutant-specific degradation trends highlighted diminishing catalytic enhancement for readily degradable molecules (e.g., BPA) but substantial improvement for recalcitrant species (e.g., NB). Theoretical calculations further demonstrated that pyrrolic N coordination redistributes Fe valence electrons, facilitating 1O2-mediated electron transfer through vacant π* orbitals and lowering the electron escape barrier. This work establishes a direct mechanistic link between pollutant electronic properties and catalytic performance, providing theoretical guidance for rational spin-state engineering of catalysts toward efficient and selective degradation of chemically resistant EOPs.
Yang et al. (Tue,) studied this question.