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]·2H ₂O (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(H ₂O)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 [XMo₁₂O ₄₀]^4- counterions. Moreover, these compounds display strong photoluimnescent properties in the solid state at room temperature.