Steering Oxygen Activation Pathways via Redox Dual‐Defects in 2D Hydrated WO ₃ for High‐Yield Singlet Oxygen Evolution

ABSTRACT The selective photocatalytic generation of singlet oxygen ( 1 O 2 ) offers a promising route for degrading persistent organic pollutants, yet its efficiency remains constrained by competing reactive oxygen species evolution pathways. Here, we demonstrate a rational defect‐engineering strategy to break this limitation by constructing redox dual‐sites in 2D hydrated WO 3 (WO 3 ·0.5H 2 O), while such architecturally tailored semiconductor materials remain a seldom‐achieved configuration for O 2 photoactivation. Through the coordinated introduction of Cs‐substitution defects and O vacancies (WO‐CO), a unique local electronic structure is created that not only enhances charge separation and O 2 adsorption but, more importantly, directs the transformation of superoxide radicals (•O 2 − ) selectively toward 1 O 2 . The dual‐defects establish a Yeager‐type (“side‐on”) O 2 adsorption geometry and a built‐in electric field that collectively raise the energy barrier of the conventional reduction pathway (Pathway I) while enabling simultaneous electron and hole transfer for oxidative 1 O 2 formation (Pathway II). Consequently, WO‐CO achieves a steady‐state 1 O 2 production rate 8.6–15.8 times higher than single‐defect or pristine catalysts, together with superior mineralization performance for various refractory aromatics, excellent cycling stability, and broad environmental adaptability. This work provides a mechanistic foundation for pathway‐specific O 2 activation and opens a new avenue in the design of high‐selectivity photocatalysts for advanced oxidation technologies.