Universal Ligand-Assisted Supermolecular Strategy to Synthesize Single-Atom Catalysts for Solar-to-Ethanol Conversion

Abstract Single-atom catalysts (SACs) have attracted significant attention; however, their catalytic properties are not satisfactory due to the sparse and inhomogeneity of the single-atom sites. Herein, we report a novel ligand-assisted supermolecular (LASM) strategy for the preparation of carbon nitride (CN)-supported SACs (M1-CNs) with controllable and high active metal loadings. The ligands in the metal chelates can immobilise the metal and control their type and content, while the formed hydrogen-bonded supermolecules can inhibit the fusion of the CN precursor. Therefore, M1-CN SACs (M: Cr, Mn, Fe, Co, Ni, Cu, Zn, Pd, Ag, and Cd) and multiple-metals SACs (Mα 1/Mβ 1-CNs: Fe/Cu and Cu/Zn/Ag) were successfully prepared. The as-synthesizd Cu1-CN have a record-high loading of 9.75 at.%. Notably, Cu1-CNs with high loadings achieved highly selective solar-driven photoreduction of CO2 to ethanol, a breakthrough result in the field of 100% C2+ product construction using SACs, which stands among the best solar-to-ethanol single-atom photocatalysts up to date. Combining experimental evidence including X-ray absorption analysis and theoretical calculations, revealed that the Cu1-CN with high loading promoted the C–C coupling of *CO intermediate products. This work provides a novel strategy for the controllable preparation of M1-CNs and for the design of SACs with high selectivity and efficiency for the photoreduction of CO2 to C2+ products.