Fabrication of Ce-doped UiO-66-NH2 for highly efficient and selective photocatalytic reduction of CO2 to CH4

Defect engineering by creating oxygen vacancies (OVs) and heterogeneous frustrated Lewis acid-base pairs (FLPs) emerged as an efficient strategy to enhance the selective conversion CO2 to CH4. Considering the intrinsic FLPs contained in UiO-66-NH2 (UNH for abbreviation), in this paper, the OVs was introduced therein by fabricating the Ce-doped UNH (denoted as UNH(Ce/Zr)) via one-step solvothermal route. The as-prepared UNH(Ce/Zr) catalyst exhibited the CH4 yield of 31.02 μmol·g−1·h−1 accompanied with the CH4 selectivity of 93 % and satisfying recycling stability. The XRD, SEM, FT-IR, XPS, TG, TPD and NH3 in situ DRIFTS and in situ FT-IR characterization results justified that the UNH(Ce/Zr) possess the obviously increased OVs sites and enhanced Lewis acidic and basic properties. Additionally, the photoelectrochemical characterization results showed that UNH(Ce/Zr)−0.014 efficiently improved photogenerated electron-hole separation efficiency and charge transfer rate. It could be concluded that it was the cooperative action of OVs and FLPs that led to the high CH4 selectivity and CH4 yield.