Facet-dependent activity of TiO2/covalent organic framework S-scheme heterostructures for CO2 photoreduction

Covalent organic framework (COF) has shown great potential in constructing S-Scheme junctions with both spatial separation and strong redox ability of photogenerated charge carriers. Engineering the interfacial structure between COF and semiconductor photocatalysts is of vital importance to realize the high-efficiency CO2 photoreduction. Herein, the contribution of material facets to the S-scheme photocatalysis of TiO2/COF heterojunctions is studied. The internal electric field between TiO2 and COF benefits the S-scheme transfer of photoexcited charge carriers, which is highly dependent on the exposed facets of TiO2. 101-TiO2 with electron-rich surface and lower conduction band is proved to be a promising oxidation photocatalyst for the construction of S-scheme junctions. Nanoarchitecture of T-101/COF can effectively convert CO2 into valuable CO fuels, with a reduction rate of 11.6 μmol h−1, which is 14.5 and 4.6 times higher than that of pristine 101-TiO2 and T-001/COF, respectively. This work reveals that facet engineering can provide a versatile approach to improve the efficiency of S-scheme heterostructures for artificial photosynthesis.