Fabrication of p - n Heterostructured Photocatalysts with Triazine-Based Covalent Organic Framework and CuInS 2 for High-Efficiency CO 2 Reduction.

The application of covalent organic frameworks (COFs) for the photocatalytic reduction of CO 2 is mostly limited by severe charge recombination and low sunlight utilization. Herein, a triazine-based COF with an electron-rich and large π-conjugated system (TCOF) was employed as a building block and integrated with CuInS 2 (CIS) to construct a noble-metal-free and high-efficiency photocatalyst for CO 2 reduction. The in situ growth of CIS nanosheets on TCOF creates a p - n heterojunction, named CIS@TCOF. Compared with TCOF, the CIS@TCOF heterostructure exhibits a dramatically boosted photocatalytic performance in the reduction of CO 2 . The produced HCOOH yield over 10 wt % CIS@TCOF can be up to 171.2 μmol g -1 h -1 under visible light irradiation with good reproducibility, which is about 3 times as high as that over TCOF. Further in-depth studies indicate that the introduction of CIS not only enhances the visible light utilization but also restrains the recombination of photogenerated electron-hole pairs efficiently and facilitates the photoinduced charge transfer via the p - n heterojunction system due to the unique structural and compositional features. This research shows the great potential of COFs as efficient photocatalytic carbon fixation materials and provides a versatile route to construct semiconductor-COF heterostructures for photocatalysis.