Syntheses, structures and properties of 3D inorganic–organic hybrid frameworks constructed from lanthanide polymer and Keggin-type tungstosilicate

Inorganic–organic hybrid frameworks, namely [Ce(H2O)3(pdc)]4[SiW12O40]·6H2O 1, [M(H2O)4(pdc)]4[SiW12O40]·2H2O (M=Ce for 2a, La for 2b, Nd for 2c; H2pdc=pyridine-2,6-dicarboxylic acid) were assembled through incorporation of Keggin-type heteropolyanion [SiW12O40]4− within the voids of lanthanides-pdc network as pillars or guests under hydrothermal condition. Single-crystal X-ray analyses of these crystals reveal that compound 1 presents 3D pillar-layered framework with the [SiW12O40]4− anions located on the square voids of the two-dimensional Ce-pdc bilayer. Compounds 2a–c are isostructural and constructed from 3D Ln-pdc-based metal-organic framework (MOF) incorporating noncoordinating guests Keggin structure [SiW12O40]4−. Solid-state properties of compounds 1 and 2a–c such as thermal stability and photoluminescence have been further investigated.