Dual-nodes bridged cobalt-modified Keggin-type polyoxometalate-based chains for highly efficient CO₂ photoconversion

The design of efficient catalysts for photocatalytic CO₂ conversion is of great importance for the sustainable development of society. Herein, three polyoxometalate (POM)-based crystalline materials were formulated prepared by substituting transition metals and adjusting solvent acidity with 2-(2-pyridyl) benzimidazole (pyim) as the light-trapping ligand, namely {[SiW₁₂O₄₀][Co(pyim)₂]₂}·2C₂H₅OH (SiW12Co2), {[SiW₁₂O₄₀][Ni(pyim)₂]₂}·2C₂H₅OH (SiW12Ni2), and {[SiW₁₂O₄₀][Mn(pyim)₂]₂}·2C₂H₅OH (SiW12Mn2). X-ray crystallography diffraction analysis indicates that the three complexes exhibit isostructural properties, and form a stable one-dimensional chain structure stabilized by two [M(pyim)₂]₂²⁺ (M = Co, Ni, and Mn) fragments serving as dual-nodes to the adjacent SiW₁₂ units. A comprehensive analysis of the structural characterization and photocatalytic CO₂ reduction properties is presented. Under light irradiation, SiW12Co2 exhibited a remarkable CO generation rate of 10 733 μmol g^-1 h^-1 with a turnover number of 328, outperforming most of the reported heterogeneous POM-based photocatalysts. Besides, cycling tests revealed that SiW12Co2 is an efficient and stable photocatalyst with great recyclability for at least four successive runs. This study proves that the successful incorporation of diverse transition metals into the POM anion could facilitate the development of highly efficient photocatalysts for the CO₂RR.