Mixed-valence bimetallic Ce/Zr-NH2-UiO-66 modified with CdIn2S4 to form S-scheme heterojunction for boosting photocatalytic CO2 reduction

A bimetallic Ce/Zr-UiO-66-NH2/CdIn2S4 (Ce-NU66/CIS) heterojunction close interfacial contact has been designed by in-situ hydrothermal co-synthesis of Ce/Zr-NH2-UiO-66 and CdIn2S4. The one-pot-synthesized heterojunction was employed for CO2 reduction without any sacrificial agent. The Ce-NU66/CIS exhibits visible-light-active characteristics accompanied by improved excited charge separation, along with high surface area and well-dispersed heterojunction structure compared to the pristine MOF and CdIn2S4. Doping Ce ions can produce some oxygen vacancies (OVs) and enhance the electron density surrounding Zr4+ ions, which ultimately resulted in an increase in the photocatalytic effect. In the absence of any sacrificial reagents, the optimized 8 wt% Ce0.2NU66/CIS sample exhibited significantly improved photocatalytic CO2 reduction activity, with CO production rate of 6.01 μmol‧g−1‧h−1 and a high CO selectivity of 54.98 %, which were 3.72 and 1.96 times contrasting to the original CdIn2S4, and 17.83 and 2.47 times in comparison of NU66, respectively. Consequently, the bimetallic Ce/Zr-UiO-66-NH2/CdIn2S4 could have the potential to be used as a photocatalyst with improved properties for studying CO2 reduction. It may provide a rational design for constructing mixed-valent bimetallic for soler-driven CO2 conversion.