Defective g-C3N4/covalent organic framework van der Waals heterojunction toward highly efficient S-scheme CO2 photoreduction

In this work, a novel van der Waals (vdW) heterojunction composite combining g-C₃N₄ with nitrogen vacancies and Tp-Tta COF manifests effective interface contact area and excellent photocatalytic CO₂ reduction performance. First-principles density functional theory calculation and experimental results suggest that the presence of nitrogen vacancies in g-C₃N₄ can widen the Fermi level gap between C₃N₄ (NH) and Tp-Tta COF, promoting the recombination of invalid photogenerated carriers through S-scheme pathway. Benefitted from the accelerated transfer of photogenerated charges at the vdW heterostructure interface, the deactivation of oxygen vacancies in C₃N₄ (NH)/COF is prevented and much higher photocatalytic activity and stability are obtained. The efficient electron transfer and the affinity of Tp-Tta for CO₂ are beneficial to the enhanced CO selectivity. This work provides insights for the design of S-scheme heterojunction photocatalyst for CO₂ reduction.