A purely inorganic germanium–molybdenum–oxo cluster with ruthenium participation for visible-light-driven CO2 reduction†

Photocatalytic carbon dioxide reduction is considered an important strategy to solve environmental problems, such as greenhouse gases, but designing and synthesizing effective photocatalysts is a challenge. In recent years, photocatalytic carbon dioxide reduction by polyoxometalates (POMs) has attracted increasing research interest. Herein, the first purely inorganic ruthenium–germanium–molybdenum–oxygen cluster, Na₁₂Rb₂[Ru₂O₂(GeMo₁₀O₃₆)₂]·44H₂O (Ru₂Ge₂Mo₂₀), was synthesized by hydrothermal and volatilization methods and applied to photocatalytic carbon dioxide reduction. The yield of CH₄ reached 547.84 μmol g⁻¹ in the heterogeneous photocatalytic reaction system with an electron selectivity of 96.86% with respect to CO (71.08 μmol g⁻¹) after 6 h. The reaction mechanism was confirmed by UV-Vis diffuse reflection spectroscopy, ultraviolet photoelectron spectroscopy (UPS), electrochemical measurements, and steady-state fluorescence quenching experiments. This work provides a reference for the design of Ru-containing polyoxometalates for photocatalytic CO₂ reduction.