Manipulating d-orbital of Cu single atom site by coordination engineering for selective oxidation of benzene

Single-atom catalysts (SACs) enable atomic-level control over active sites, but orbital-level manipulation to steer catalytic behavior remains challenging. Here, we address this issue through d-orbital engineering of Cu SACs, achieving simultaneous control over coordination geometry (Cu-N₃) and high metal loading (33.2 wt%) for direct benzene-to-phenol oxidation with H₂O₂. The tri-coordinated Cu SAC (Cu-N₃-33.2) exhibits the highest performance with 85.8% benzene conversion and a turnover frequency of 680.3 h^-1 at 60 ^oC, ranking it among the best metal-based catalysts. In-situ ATR-IR spectroscopy and DFT calculations reveal that dynamically formed Cu-O intermediates, driven by p-d orbital hybridization between Cu (d orbitals) and O (p orbitals), lower the H₂O₂ activation barrier by 0.98 eV compared to Cu-N₄ sites. High-density atomic Cu sites prevent over-oxidation by consuming singlet oxygen (¹O₂). This work establishes a dual-parameter optimization paradigm, including orbital configuration and site density, redefining design principles for selective oxidation SACs.