Spin state-dependent in-situ photo-Fenton-like transformation from oxygen molecule towards singlet oxygen for selective water decontamination.

The development of O-dominanted selective decontamination for water purification was hampered by extra HO consumption and poor O generation. Herein, we proposed the reconstruction of Fe spin state using near-range N atom and long-range N vacancies to enable efficient generation of HO and sequential activation of HO into O after visible-light irradiation. Theoretical and experimental results revealed that medium-spin Fe(III) strengthened O adsorption, penetrated e electrons to antibonding p-orbital of oxygen, and lowered the free energy of O activation, enabling the oxygen protonation for HO generation. Thereafter, the electrons of HO could be extracted by low-spin Fe(III) and rapidly converted into O in a nonradical path. The developed O-dominated in-situ photo-Fenton-like system had an excellent pH universality and anti-interference to inorganic ions, dissolved organic matter, and even real water matrixes (e.g., tap water and secondary effluent). This work provided a novel insight for sustainable and efficient O generation which motivated the development of new-generation selective water treatment technology.