Schottky Junction and D-A₁-A₂ System Dual Regulation of Covalent Triazine Frameworks for Highly Efficient CO₂ Photoreduction

Covalent triazine frameworks (CTFs) are emerging as a promising molecular platform for photocatalysis. Nevertheless, the construction of highly effective charge transfer pathways in CTFs for oriented delivery of photoexcited electrons to enhance photocatalytic performance remains highly challenging. Herein, a molecular engineering strategy is presented to achieve highly efficient charge separation and transport in both the lateral and vertical directions for solar-to-formate conversion. Specifically, a large pi-delocalized and pi-stacked Schottky junction (Ru-Th-CTF/RGO) that synergistically knits a rebuilt extended pi-delocalized network of the D-A(1)-A(2) system (multiple donor or acceptor units, Ru-Th-CTF) with reduced graphene oxide (RGO) is developed. It is verified that the single-site Ru units in Ru-Th-CTF/RGO act as effective secondary electron acceptors in the lateral direction for multistage charge separation/transport. Simultaneously, the pi-stacked and covalently bonded graphene is regarded as a hole extraction layer, accelerating the separation/transport of the photogenerated charges in the vertical direction over the Ru-Th-CTF/RGO Schottky junction with full use of photogenerated electrons for the reduction reaction. Thus, the obtained photocatalyst has an excellent CO2-to-formate conversion rate (approximate to 11050 mu mol g(-1) h(-1)) and selectivity (approximate to 99%), producing a state-of-the-art catalyst for the heterogeneous conversion of CO(2 )to formate without an extra photosensitizer.