Developing Co-Ni Dual-Atom Catalysts with Synergistic Redox Capacity Via Coordination Self-Assembly and Nano-Confinement Effect

Combining CO2 reduction and toluene oxidation through photocatalysis is crucial for achieving carbon neutrality and producing high-value chemical products. Herein, a unique Co/Ni diatom-loaded ultrathin carbon nitride (CoSA-NiSA/UCN) has been meticulously synthesized using an innovative strategy of coordination self-assembly and nano-confinement effect. Molecular dynamics simulations (MD) and CO2 temperature-programmed desorption (CO2-TPD) techniques were employed to investigate CO2 with enhanced diffusion and mass transfer capabilities in real-world environments. Experimental and theoretical characterizations show that Co/Ni single atoms act as electron co-catalysts and hole co-catalysts, to effectively modulate the microenvironment on the two-dimensional CN surface and maintain the strongest redox capacity at the position of the conduction/valence band while achieving the effective separation of electron and hole pairs. When toluene was utilized as the sacrificial agent and reactant, the CoSA-NiSA/UCN photocatalytic reduction of CO2 to CO rate of 225.8 μmol g-1 h-1, and the oxidation of toluene to benzaldehyde rate of 486.9 μmol g-1 h-1 (selectivity 82.6%). Femtosecond transient absorption spectroscopy (fs-TA), Kelvin probe force microscopy (KPFM), and theoretical calculations reveal that the simultaneous presence of Co/Ni dual-atom reduces the free energy of *COOH production and enhances the ultrafast kinetic processes of proton coupling and electron-hole transfer. This study introduces a new approach to single-atom synthesis and logically advances the exploration of photogenerated carriers' potential in photocatalysts.