Three 3D silver-bis(triazole) metal–organic frameworks stabilized by high-connected Wells–Dawson polyoxometallates

Abstract

Three silver-bis(triazole) three-dimensional (3D) metal–organic frameworks (MOFs) with Wells–Dawson type polyoxometalates (POMs) as high-connected inorganic ligands have been isolated: [Ag₇(bte)₄(H₂O)(HP₂W^VI₁₆W^V₂O₆₂)]·2H₂O (1), [Ag₇(btp)₅(HP₂W^VI₁₆W^V₂O₆₂)]·H₂O (2) and [Ag₄(btb)_3.5(P₂W₁₈O₆₂)](H₂btb)·2H₂O (3) (bte = 1,2-bis(1,2,4-triazol-1-yl)ethane, btp = 1,3-bis(1,2,4-triazol-1-y1)propane, btb = 1,4-bis(1,2,4-triazol-1-y1)butane). Compound 1 contains a 3D metal–organic subunit, which is constructed from 1D Ag/bte chains and 2D layers based on hexanuclear [Ag₆(bte)₂]⁶⁺ circuits. The [P₂W₁₈O₆₂]⁸⁻ (P₂W₁₈) anions act as 10-dentate inorganic ligands incorporated into the channels of the 3D framework. In compound 2, the metal–organic subunits are a 2D layer constructed from the [Ag₅(btp)₂]⁵⁺ circuits and flexible Ag/btp helical chains. The P₂W₁₈ anions also act as 10-dentate inorganic ligands linking adjacent 2D layers to construct a 3D framework. Both 1 and 2 contain Ag–Ag bonds, which further stabilize the structures. Compared with 1 and 2, the metal–organic subunit of 3 is a 3D cage-like host architecture. Without the assistance of Ag–Ag bonds, two sets of these 3D MOFs interpenetrate each other to generate a 2-fold interpenetrating structure for stability, which are united by the 5-dentate P₂W₁₈ anions to construct an integrated 3D structure. The roles of coordination modes of silver centers and POMs, as well as the effects of organic ligand lengths on the metal–organic subunit and final structures, have been reported. In addition, the electrochemical properties, photochemical catalysis and antibacterial properties of title compounds have also been investigated.