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Interpenetrating frameworks are described as architectures which cannot be separated except if one of the individual motifs is broken. 1 In their complicated architectures, supramolecular connections (such as electrostatic interaction, hydrogen bond, πÀπ stacking, and cationÀπ interactions) among the individual motifs endow them with structural flexibility, which is important in the applications of gas storage, conductivity, biological chemistry, and so on. 2 Interpenetration is a subclass of entangled system studied extensively and developed rapidly nowadays. Individual motifs of the interpenetrating architectures are from two-dimensional (2D) nets to three-dimensional (3D) frameworks, and the number of interpenetrating units varies from 2 to 10. 3 Ongoing research in interpenetration focuses on the introduction of functional groups with available characters.Polyoxometalates (POMs) are early transition metal oxide clusters composed of Mo, W, V, Nb, and so on. POMs show a wide variety of interesting structural motifs with different sizes and topologies. Besides the classical Keggin, WellsÀDawson, Anderson, Waugh, Silverton, and Lindqvist types, many new structures have been found, such as closed cages, Wheels, dimeric anions, and transition-metal-centered heteropolyoxometalates. 4 POMs are in the nanosize scale and have abundant surface oxygen atoms, which make them excellent inorganic building blocks. In addition, POMs bear versatile properties in such fields as catalysis, photochemistry, magnetism, electrochemistry, and biochemistry. 5,6 Accordingly, POM-based interpenetrating compounds will not only show aesthetic architectures but also possess both properties of flexibility of interpenetration and versatile functions of POMs. 7 However, to obtain such compounds is difficult as the nanosized POMs with a big steric hindrance would inhibit the formation of interpenetration.Ag þ ion is a prominent metal linker in the POM-based metal organic frameworks (MOFs), for it not only possesses abundant coordination modes such as linear, T-type, "seesaw", "squarepyramidal", "trigonal-bipyramidal" and octahedral geometries 8 but also is useful in the areas of catalysis, biological chemistry, and so on. 9 In addition, the argentophilicity of Ag þ ions may conduce the formation of {Ag 2 } 2þ dimers, which may play a key role in the expansion of multiple dimensional structures. {Ag 2 } 2þ dimers acting as linkers can be classified into unsupported and supported ones according to their coordination modes; that is, two Ag þ ions in an unsupported {Ag 2 } 2þ dimer are fused only by Ag I 3 3 3 Ag I interaction, while those in a supported {Ag 2 } 2þ dimer are connected not only by Ag I 3 3 3 Ag I interaction but also by

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Five organic–inorganic hybrids containing mixed–valence multinuclear copper complexes and Keggin polyoxometalates, [CuI 5CuII 3(ptz)8(H2O)][HSiW12O40] (1), [CuI 10CuII 2(ptz)8(Cl)3][PW12O40] (2), [CuI 2CuII 4(ptz)6(OH)(H2O)2][PW12O40]·2H2O (3), CuI 2CuII 5(ptz)6(OH)2SiW12O40·6H2O (4), and [CuI 2CuII 5(ptz)6][PMoV 3MoVI 9O40]·8H2O (5) (ptz = 5-(2-pyridyl)-tetrazole), were hydrothermally synthesized and structurally characterized. Compound 1 exhibits a three-dimensional (3D) network that features unprecedented double chains consisting of tetranuclear Cu clusters. Compound 2 displays a 3D network that has unusual Cl-centered hexanuclear Cu clusters and Cl-bridged tetranuclear Cu units. Compound 3 shows a 3D supramolecular network extended by two-dimensional (2D) grid-like sheets which are composed of mixed-valence multinuclear copper chains and PW12 polyanions. Isostructural compounds 4 and 5 exhibit a 3D network consisting of 2D ladder-like copper–ptz layers and SiW12 (PMo12 in 5) polyanions. The roles of copper ions with different oxidation states and ptz ligands with different coordination modes in the construction of the copper–ptz frameworks are discussed. Their electrochemical properties were investigated as well.

By changing the polyoxoanions in the same metal-organic system (Ag/ptz), two novel inorganicorganic hybrids: [Ag 10 (ptz, are synthesized under hydrothermal conditions, and characterized by IR spectra, elemental analyses and single crystal X-ray diffraction. Compound 1 and 2 show 3D POMtemplated framework structures. In compound 1, a 2D layer is constructed by ''shield-like'' metalorganic circles templated by P 2 W 18 polyoxoanions, which is extended to a 3D structure by covalent bonds in an interdigital mode. In compound 2, a 3D network is constructed by 2D layers and a ''double bridge-pillar'', the Keggin polyoxoanion templates are enveloped in pairs in nanocages. The influences of polyoxoanion templates on the frameworks are discussed. The electrochemical behavior and luminescent properties for compound 1 and 2 are investigated.