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

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 Nx & horbar;Cu & horbar;O4-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 N3-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 & horbar;Cu & horbar;O1 active site can promote the breaking of Cu & horbar;O bonds rather than O & horbar;O bonds. As a result, the N3-Cu-O1@COF photocatalyst exhibits the most optimal formation and desorption energies for intermediates center dot 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. Single-atom Nx-Cu & horbar;O4-x@COF (x = 1-4) photocatalysts with different coordination environments are prepared based on pre-design reticular supramolecular COFs for direct photocatalytic 1O2 production from O2. The results indicate that the N3 & horbar;Cu & horbar;O1@COF photocatalyst exhibits superior photoelectric properties and 1O2 generation ability. This work reveals the microenvironment structure-activity relationship of single-atom catalysts via finely unsaturated N,O-coordination. image