Two porous three-dimensional (3D) metal–organic frameworks based on diverse metal clusters: selective sensing of Fe3+ and Cr2O72−†
Abstract
Two porous complexes, namely, {[H2N(Me)2]2[Zn5(L)2(OH)2]·3DMF·4H2O}n (1), and {[H2N(Me)2]4[Cu3(L)2(H2O)2]·4DMF·3H2O}n (2) were solvothermally constructed based on a symmetrical V-shaped rigid multicarboxylic acid ligand H5L (H5L = 3,5-di(2′,5′-dicarboxylphenyl)benzoic acid). Complexes 1 and 2 display 3D frameworks with various metal clusters. Complex 1 is a 3D porous framework with a (4,8)-connected topology featuring a 1D pore structure in the a-axis direction with a penta-nuclear cluster [Zn5(μ2-COO)6(μ1-COO)4(μ3-O)2]. By contrast, 2 displays a 3D (3,4)-connected net based on binuclear [Cu2(COO)4] paddlewheel SBUs. Complex 1 reveals solid-state luminescent properties at ambient temperature, and the maximum emission peak was observed at ∼443 nm (λex = 339 nm). Meanwhile, 1 shows high selectivity and sensitivity not only for Fe3+ cations but also for Cr2O72− anions via the luminescence quenching effect with a low detection limit, which thus could be a potential crystalline material for detecting these substances. The mechanisms of the quenching effect and sensing properties of 1 were discussed in detail.