Orbital Fine-Tuning of d/p-Band Centers Enables Highly Preferential Single-Electron Oxygen Activation

The single-electron photocatalytic reduction of molecular oxygen to superoxide radicals (O₂ ^•-) represents the rate-determining step in environmental photochemistry, yet achieving high selectivity toward this pathway remains a formidable challenge. Here, we introduce a conceptually driven orbital-hybridization strategy to precisely regulate the d/p orbitals of polymeric phenylethynylcopper (PECu) through chlorine doping. Rather than acting as a conventional heteroatom dopant, Cl^- serves as an "orbital fine-tuner", enhancing the coordination polarization of C≡C─Cu units and shortening the Cu─Cu ladder spacing to construct an efficient metal-metal charge-transfer (MMCT) channel. This interfacial electronic engineering markedly improved d/p-band center proximity (Δε_d-p), thereby optimizing the adsorption and activation of O₂ intermediates at alkyne active sites. The optimized PCC photocatalyst exhibits exceptional selectivity for the O₂ → O₂ ^•- single-electron reduction pathway, achieving a superoxide yield of 471.38 µmol/L and significantly enhanced water decontamination performance. This work extends conventional band-center engineering from activity optimization to highly preferential single-electron oxygen activation by identifying d/p-band-center proximity as a key electronic descriptor governing selective single-electron O₂ reduction.