Three 3D Metal-Organic Frameworks Constructed from Keggin Polyanions and Multi-nuclear AgI Clusters: Assembly, Structures and Properties

Three Keggin-based metal-organic frameworks (MOFs) containing multi-nuclear silver subunits, [Ag7(ptz)5(H2O)2][H2SiMo12O40] (1), [Ag8(ptz)5(H2O)2][AsW12O40] (2) and [Ag7(ptz)5(H2O)][HAsMo12O40] (3) (ptzH = 5-(4-pyridyl)-tetrazole), have been synthesized under hydrothermal conditions by changing the inorganic polyanions. The new compounds have been characterized by elemental analyses, TG analyses, IR spectroscopy, and single-crystal X-ray diffraction. In compound 1, the multi-nuclear Ag5(ptz)5 subunits are interconnected to form chains, which are further linked by AgI cations to construct a 3D MOF with large channels. Pairs of SiMo12O40 polyanions reside in the channels as penta-dentate inorganic ligands. In 2, six AgI cations link five ptz− anions to construct a hexa-nuclear subunit [Ag6(ptz)5], which is interconnected to form chains. These chains are further linked by AgI cations to construct a 3D MOF, where AsW12O40 polyanions reside as hexa-dentate ligands. Compound 3 exhibits a 3D MOF based on Ag5(ptz)5 subunits, in which the hexa-dentate AsMo12O40 polyanions are incorporated. The rigid tetrazole-based ligand ptz− plays an important role in the formation of the multi-nuclear subunits of the title compounds. The electrochemical properties of compound 1 and the photocatalytic properties of compounds 1 and 3 have been investigated.