Three Cd(II)-based luminescent metal-organic frameworks constructed from the mixed-ligand strategy for highly selective detection of nitrobenzene

Three new Cd(II) luminescent metal-organic frameworks (LMOFs), namely { [Cd(bib) (bdc)]center dot DMF center dot H2O}(n) (1), [Cd(bib)(ndc)(H2O)]center dot DMF}(n) (2) and { [Cd-2(bib)(2)(bpdc)(2)]center dot 1.5H(2)O) - (3) (bib = 1,3-bis(1-imidazolyl)benzene, H(2)bdc = 1,4-benzenedicarboxylic acid, H(2)ndc = 1,4-naphthalenedicarboxylic acid, H(2)bpdc = biphenyl-4,4'-dicarboxylic acid and DMF = N,N-dimethylformamide), have been synthesized by combining the V-shaped bib ligand and different dicarboxylate ligands under solvothermal conditions. Complex 1 displays a 4-fold interpenetrated 3D framework with sra topology. Complex 2 presents a 2D (4,4) layer structure derived from bib and ndc(2-) mixed spacers. Complex 3 is a 2-fold interpenetrated array based on 2D (4,4) wave-like coordinated layers. The structural diversity among these complexes can be realized by the abduction of linear dicarboxylate ligands. The results demonstrate that the length of dicarboxylate ligands makes an impact on the structural diversity. Moreover, the complexes 1-3 can be well dispersed in different solvents, which exhibit highly selective and sensitive detection for nitrobenzene (NB) over other solvents by means of fluorescence quenching effect. The work illuminates fine-tuning of structure and in turn sensing properties towards LMOFs based on the reasonable selection of organic ligands.