Oxygen vacancy-engineered spin polarization overcoming spin-forbidden barriers for boosted visible-light molecular oxygen activation

As a green and abundant oxidant, the efficient activation and utilization of molecular oxygen (O₂) hold great promise for water decontamination. However, due to its spin-forbidden nature, the activation of O₂ remains kinetically limited without catalyst coupling or external energy input. Harnessing the daily solar radiation received by environmental water bodies to drive O₂ activation processes could simultaneously achieve water remediation and energy conservation. Herein, this study successfully constructs Fe₂O₃@TiO₂ hollow multi-shelled catalyst (FT-HoMS) with oxygen vacancies engineering to effectively activate O₂ for generating reactive oxygen species and subsequent removing levofloxacin under visible light illumination. Density functional theory calculations reveal that the spin polarization of FT-HoMS significantly eliminates the spin-forbidden of O₂, realizing electron transfer from the 3d orbital of Fe atom in FT-HoMS to π* orbital of O₂. Femtosecond transient absorption spectra and in-situ irradiation X-ray photoelectron spectroscopy further elucidate that efficient charge transport behavior on the interface of S-type heterojunction of FT-HoMS, confirming FT-HoMS can preserve the stronger redox capacity of electrons and holes. Notably, the FT-HoMS/O₂ system presents exceptional stability during 170 h continuous operation (∼100% levofloxacin removal) without common chemical oxidant input. And meanwhile, the FT-HoMS/O₂ system exhibits the outstanding application universality toward a wide array of organic pollutants and pathogenic bacteria. This study provides a novel catalyst design paradigm for eliminating the spin-forbidden of O₂, opening up a viable, additive-free, and environmental benign pathway for water decontamination.