Lanthanide−Organic Cation Frameworks with Zeolite Gismondine Topology and Large Cavities from Intersected Channels Templated by Polyoxometalate Counterions

A family of organic−inorganic hybrid frameworks, {[Ln(H2O)4(pdc)]4} [XMo12O40]·2H2O (Ln = La, Ce, and Nd; X = Si and Ge; H2pdc = pyridine-2,6-dicarboxylate), have been prepared under hydrothermal conditions and characterized by single crystal X-ray diffraction analyses, elemental analyses, IR, and thermal gravimetric analyses. Single crystal X-ray diffraction reveals that all six compounds are isostructural, and each consists of a zeolite-like four-connected three-dimensional cationic framework {[Ln(H2O)4(pdc)]4}4+ and ball-shaped Keggin type [XMo12O40]4− as templates. Interesting channels exist in the cationic framework with the gismondine topology, and these channels intersect each other to form large cavities, which array in a zigzag fashion and are occupied by nanosized [XMo12O40]4− counterions. Moreover, these compounds display strong photoluminescent properties in the solid state at room temperature.