Syntheses, Crystal Structures and Characterization of Two Zeotype Crystals of K4[Cr3O(H2O)3 (OOCH)6]2[P2W18O62] · 9.5H2O and K4[Cr3O(H2O)3(OOCH)6] · [H3P2W17Co(H2O)O61] · 20H2O*

Two novel zeotype crystals, K4[Cr3O(H2O)3(OOCH)6]2 [P2W18O62] · 9.5H2O(1) and K4[Cr3O(H2 O)3 · (OOCH)6] [H3P2W17 Co(H2O) O61] · 20H2O (2), were synthesized and their structures were determined using X-ray single crystal diffraction. Crystal data: C12H43O103.5 K4Cr6P2W18(1), hexagonal P6 (3)/m, a = 1.5895 (2) nm, b = 1.5895(2) nm, c = 2.1620 (4) nm, α = 90°, β = 90°, γ = 120°, V = 4.7305 (13) nm3, Z = 2, R1 = 0.0726, wR2 = 0.1542; C6H57O98 K4Cr3CoP2W17 (2), hexagonal P6(3)/mmc, a = 1.61328(3) nm, b = 1.61328(3) nm, c = 2.06613(9) nm, α = 90°, β = 90°, γ = 120°, V = 4.6570(2) nm3, Z = 2, R1 = 0.0377, wR2 = 0.1070. These crystals were characterized using elemental analysis, IR, TG-DTA, and XRD. It was found that the polyoxometalate anions maintained Wells-Dawson structure for crystal 1 and lacunary Wells-Dawson structure for crystal 2. Thermal analysis showed that crystal 1 lost the water of crystallization at 132 °C, whereas crystal 2 lost the water of crystallization at 100 °C. Crystal 1 could reversibly desorb and adsorb water molecules and its crystal structure could be restored after re-adsorbing the water molecules. It was also found from the XRD patterns that the void size of crystal 2 is smaller compared with that of crystal 1, which is attributed to the higher anion charges.