Outstanding CO₂ Photoreduction in Single-Atom Thulium Modified Carbon Nitride

CO₂ reduction photocatalysts are favorable for obtaining renewable energy. Enriched active sites and effective photogenerated-carriers separation are keys for improving CO₂ photo-reduction. A thulium (Tm) single atom tailoring strategy introducing carbon vacancies in porous tubular graphitic carbon nitride (g-C₃N₄) surpassing the ever-reported g-C₃N₄ based photocatalysts, with 199.47 µmol g^-1 h^-1 CO yield, 96.8% CO selectivity, 0.84% apparent quantum efficiency and excellent photocatalytic stability, is implemented in this work. Results revealed that in-plane Tm sites and interlayer-bridged Tm-N charge transfer channels significantly enhanced the aggregation/transfer of photogenerated electrons thus promoting CO₂ adsorption/activation and contributing to *COOH intermediates formation. Meanwhile, Tm atoms and carbon vacancies both benefit for rich active sites and enhanced photogenerated-charge separation, thus optimizing reaction pathway and leading to excellent CO₂ photo-reduction. This work not only provides guidelines for CO₂ photo-reduction catalysts design but also offers mechanistic insights into single-atom based photocatalysts for solar fuel production.