Construction of one Ru2W12-cluster and six lacunary Keggin tungstoarsenate leading to the larger Ru-containing polyoxometalate photocatalyst

Construction of two RuⅢ cations and six lacunary Keggin fragments resulted in a novel Ru2W12-cluster {(RuO6)2(WO3)12(H2O)12} bridged polyoxometalate, NaH11[(RuO6)(AsW9O33)3{(W6O3)(H2O)6}]2 53H2O (NaH11·1·53H2O), which represent the largest cluster in all the Ru-containing polyoxometalates. The most interesting characteristic is that the symmetry-related Ru2W12-cluster-based hexamers contain two windmill-shaped [(RuO6)(AsW9O33)3{(W6O3)(H2O)6}] trimers or the Ru2W12 cluster was tightly wrapped by six segments of B-β-AsW9O33. The other remarkable feature is that there have one intriguing cubane structure: which is composed of the Ru(1, 2) and W(1, 28, 50, 51, 52, 53) atoms. The oxygenation reactions of anilines to azoxybenzenes was evaluated when NaH11·1·53H2O served as effective catalyst by probing various reaction. The inherent redox property of oxygen-rich polyoxometalate surfaces and high photocatalytic activity of the Ru-containing metal cluster imbedded in NaH11·1·53H2O provide sufficient driving force for the photocatalytic transformation from anilines to azoxybenzenes. The oxidation of anilines can be realized with higher selectivity to afford various azoxybenzene compounds. The durability test shows that Ru-doping catalyst displays excellent chemical stability during the photocatalytic process.