Elucidating the Microenvironment Structure‐Activity Relationship of Cu Single‐Site Catalysts via Unsaturated N,O‐Coordination for Singlet Oxygen Production

Abstract Understanding the microenvironment structure‐activity relationship of singlet‐atom catalysts (SACs) is imperative for the development of high‐performance photocatalytic devices. However, the challenge remains to finely regulate the coordination microenvironment of SACs. Herein, single‐atom N_x─Cu─O_4‐x (x = 1–4) photocatalysts with different coordination environments are successfully prepared based on pre‐design reticular supramolecular covalent organic frameworks (COFs) for direct photocatalytic ¹O₂ production from O₂. The results show that the high activity of Cu SACs is closely related to the N,O‐coordination microenvironment, which is primarily ascribed to the different electrophilicity of the N, O atom. The electron configuration of N_3‐Cu‐O₁ endows photocatalyst enhanced charge transfer capability and the nearest D‐band center to the Fermi level. The “end‐on” type adsorption configuration of O₂ at the N₃─Cu─O₁ active site can promote the breaking of Cu─O bonds rather than O─O bonds. As a result, the N₃‐Cu‐O₁@COF photocatalyst exhibits the most optimal formation and desorption energies for intermediates •OOH, which provides an advantageous reaction pathway with fewer steps and a lower barrier for ¹O₂ production. This work highlights the structure‐activity relationship of SACs for long‐term applications.