Luminescent metal-organic frameworks constructed by a V-shaped pentacarboxylic acid ligand as bifunctional chemosensors for Fe3+ and Cr2O72-

In this paper, two unique 3D MOFs, namely, {[Cd5(L)2(H2O)16]·4H2O}n (1), {[Pb5(L)2(H2O)2]·6H2O}n (2) were obtained by taking advantage of 2,4-di(3′,5′-dicarboxylphenyl)benzoic acid (H5L) and Cd(Ⅱ), Pb(Ⅱ) metal ions under solvothermal conditions. The coordination diversity of the H5L ligand gives rise to two distinct coordination modes in 1–2, which contributes to the MOFs with multifarious structures. Complex 1 exhibits a 3D 5-connected topology, and Cd(Ⅱ) metal ions of 1 show three different coordination geometries. 2 displays a 3D (2,3,4,7)-connected net on the basis of penta-nuclear [Pb5(μ1-COO)5(μ2-COO)5] clusters, as well the structure of complex 2 contains specific 1D Pb–O–Pb chains. A room temperature, 1–2 shows eminent solid-state luminescence properties and the maximum emission peaks are ∼416 ​nm & ∼429 ​nm respectively. At the same time, due to the luminescence quenching effect of complex 1, it reveals excellent selectivity and sensitivity for Fe3+ cations and Cr2O72− anions with low detection limit. The fluorescence quenching mechanisms of complex 1 were also lucubrated.