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

Abstract

The development of ¹O₂-dominanted selective decontamination for water purification was hampered by extra H₂O₂ consumption and poor ¹O₂ 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 H₂O₂ and sequential activation of H₂O₂ into ¹O₂ after visible-light irradiation. Theoretical and experimental results revealed that medium-spin Fe(III) strengthened O₂ adsorption, penetrated e_g electrons to antibonding p-orbital of oxygen, and lowered the free energy of O₂ activation, enabling the oxygen protonation for H₂O₂ generation. Thereafter, the electrons of H₂O₂ could be extracted by low-spin Fe(III) and rapidly converted into ¹O₂ in a nonradical path. The developed ¹O₂-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 ¹O₂ generation_, which motivated the development of new-generation selective water treatment technology.

Keywords: In-situ H(2)O(2); Nonradical activation; Refractory organic contaminants; Singlet oxygen; Spin state.