Atomically dispersed and electron-enriched Cu-O₄ active sites on BiOCl atomic layers for high selectivity methanol...

High selectivity photosynthesis of CH₃OH via photocatalytic CO₂ reduction has been severely challenged by retarded charge carrier dynamics and sluggish multi-electron reaction kinetics. Herein, single Cu atoms (Cu_SA) were introduced on BiOCl atomic layers (BOCAL) by a facile two-step method of electrostatic self-assembly and pyrolysis for efficient photocatalytic CO₂ reduction, with CH₃OH selectively produced at an evolution rate of 103.98 µmol g^-1 h^-1 and a selectivity of 99.14%. This excellent photocatalytic activity should benefit from the atomically dispersed Cu-O₄ coordination structure on BOCAL, which could accelerate the separation and migration of photogenerated charge carriers by creating the impurity energy level (IEL) in the forbidden band of BiOCl with a lowered work function. In situ spectral investigations and density functional theory (DFT) calculations unveil that the Cu-O₄ coordination structures with electron density increased by photogenerated oxygen vacancies (V_O) could act as the active sites to deliver electrons to CO₂ molecules for efficient activation, as well as promote CH₃OH generation by inhibiting *CO intermediate desorption and reducing the energy barrier of the rate-determining *COH + H → *CHOH step. This work provides a facile approach to the design of electronic structure-tuned single-atom active sites on two-dimensional (2D) nanostructures towards high selectivity CH₃OH photosynthesis, and also deepens the understanding of the single-atom and vacancy interaction between active sites and semiconducting supports for efficient CO₂ photoreduction.