Porous structures constructed from [SiMo12O40] and [SiW12O40] Keggin units

Three compounds, K2(H2O)4H2SiMo12O40 · 7H2O (1), K2Na2(H2O)4SiW12O40 · 4H2O (2), and Na4(H2O)8SiMo12O40 · 6H2O (3) have been synthesized and structurally characterized by single-crystal X-ray analysis, IR, and thermogravimetry. Compounds 1 and 2 both show the high symmetry trigonal space group P3221 and a novel 3D network structure. The Keggin anions [SiM12O40]4−(M = Mo, W) are linked by potassium or sodium cations to generate hexagon-shaped channels along the c-axis, in which water molecules are accommodated. Compound 3 is tetragonal, space group P4/mnc constructed from [SiMo12O40]4− anions and Na ions.