Two polyoxometalate-directed 3D metal–organic frameworks with multinuclear silver–ptz cycle/belts as subunits

Abstract

Two new polyoxometalate (POM)-based metal–organic frameworks (MOFs) constructed from multinuclear silver–ptz cycle/belts, namely [Ag₇(ptz)₄(NO₃)(H₂O)][H₄P₂W₁₈O₆₂]·5H₂O (1) and [Ag₆(ptz)₄(H₂O)₂][HPMo₁₂O₄₀]·3H₂O (2) (ptzH = 5-(3-pyridyl)-1H-tetrazole), have been successfully synthesized under hydrothermal conditions via changing the polyoxoanions and adjusting the pH. Compound 1 exhibits a 3D framework constructed from the Wells–Dawson [P₂W₁₈O₆₂]⁶⁻ anion and a 2D layer based on two types of multinuclear Ag–ptz cycles. In compound 2, the 1D infinite multinuclear Ag–ptz belts consisting of repeated tetranuclear subunits [(Ag1)₂(Ag2)₂(ptz)₄] are connected by Ag3 ions to form a 2D layer. The adjacent 2D layers are further linked by tetra-dentate Keggin [PMo₁₂O₄₀]³⁻ anions to construct a 3D framework. The structural analyses reveal that the different polyoxoanions have a great influence on the Ag^I–ptz multinuclear cycle/belts and the whole structures. The influences of the pH and molar ratio of initial reactants in the hydrothermal process were also discussed. The electrochemical and photocatalytic properties of the title compounds have been studied in detail.