The synthesis and characterization of the 3-D framework of SO42− supported Keplerate-type polyoxometalate

We report a Keplerate-type polyoxometalate Na18K8[{Mo6O21(H2O)3(SO4)}12(Fe(H2O)2)30]·ca. 67 H2O (1), which is composed of 12 pentagonal {(Mo)Mo5} units and 30 [Fe(H2O)2]3+ linkers. This giant heterometal Keplerate-type cluster is supported by SO42− and display interesting topologies, which are connected by two kinds of Na+ cations (mononuclear and binuclear Na+ cations) to form three-dimensional (3-D) open-framework. The compound was characterized by the elemental analysis, thermogravimetry, spectroscopic methods (IR and UV/Vis), bond valence sum (BVS) calculations, X-ray photoelectron spectroscopy (XPS) and single crystal X-ray structure analysis. The photocatalytic property of compound 1 has been investigated, which shows a good photocatalyst for the degradation of RhB.

Graphical AbstractThe Keplerate cluster is composed of 12 slightly domed (virtual C5v symmetry), {(Mo)Mo5} pentagonal units connected by 30 [FeIII(H2O)2]3+ linker groups. The spherical shell encapsulates 12 heavily disordered tridentate sulfate groups. And the discrete polyanionic capsule contains 20 (Mo3Fe3O6) pores, the eight close association of the K+ ions and twelve Na+ ions to the twenty {Mo3Fe3O6} hexagonal pores reminiscent of K+-specific and Na+-specific crown ethers respectively, and other Na+ ions (mononuclear and binuclear Na+ ions) play the part of linking the discrete capsules to the three-dimensional (3-D) open-framework.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch Highlights► Supported by SO42–. ► Displays interesting 3-D topologies. ► A good photocatalyst for degradation of RhB.