Carbon nitride-based single-molecular Van der Waals heterojunction for selective photocatalytic CO₂ reduction to CO

Single-molecular heterojunctions have demonstrated significant application potential in the fields of photocatalysis due to prominent photoelectric properties, while the charge transfer behavior still need to be further discussed. In this work, a fresh single-molecular Van der Waals heterojunction is fabricated through self-assembly of dibromo(1,10-phenanthroline-κN1,κN10)nickel (NiphenBr) molecules on the surface PCN nanosheets, which dramatically boosts the performance of selective photocatalytic CO₂ reduction to CO. This unique assembled architecture effectively regulates electronic band structure and promotes the interfacial transfer and separation of photogenerated carriers owing to the π-π coupling effect between NiphenBr and PCN. Meanwhile, the single-molecular dispersed NiphenBr molecules also prevent their aggregation on PCN under the strong π-π interaction, and further provide abundant single-atom active sites for CO₂ reduction reaction. Therefore, the average rate of photocatalytic reduction of CO₂ to CO for the optimal NiphenBr/PCN-1 sample reaches 5.46 and 2.73 times that of PCN and NiphenBr, respectively. This work opens a new avenue for the single-molecular heterojunction in the application of photocatalytic reactions.