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, {[Cd-5(L)(2)(H2O)(16)].4H(2)O}n (1), {[Pb-5(L)(2)(H2O)(2)].6H(2)O}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(mu(1)-COO)(5)(mu(2)-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.