A Series of 3D Porous Lanthanide-Substituted Polyoxometalate Frameworks Based on Rare Hexadecahedral {Ln₆W₈O₂₈} Heterometallic Cage-Shaped Clusters

A series of 3D porous lanthanide-substituted polyoxometalate frameworks, Na₂[Ln₂(H₂O)₁₁]₂[Ln₃(H₂O)₃(α-SiW₁₁O₃₉)₂]₂·69H₂O (1-Ln, Ln = Sm, Eu, Gd, Tb, and Dy), are built from novel hexadecahedral {Ln₆W₈O₂₈} heterometallic cage-shaped clusters. Intriguingly, every tetrameric {[Ln₃(H₂O)₃(α-SiW₁₁O₃₉)₂]₂}^14– cage-cluster is linked with another eight tetrameric cage-clusters by Ln³⁺ cations, leading to a novel 3D inorganic porous framework, which exhibits good thermal and chemical stability, excellent water vapor adsorption capacity, and moderate proton conductive properties. Furthermore, the solid state luminescence spectra demonstrate that 1-Sm, 1-Eu, 1-Tb, and 1-Dy display the lanthanide characteristic emission bands. The temperature-dependent magnetic susceptibility indicates that there are antiferromagnetic interactions in 1-Tb and 1-Dy.