Mixed-Ligand Zn-MOFs for Highly Luminescent Sensing of Nitro Compounds

Three ZnII metal‐organic frameworks (Zn‐MOFs), [Zn2(tib)(HL1)(H2L1)0.5]⋅2H2O (1), [Zn2(tib)(L2)]⋅H2O (2) and [Zn3(tib)(L3)2(H2O)6]⋅2 H2O (3), have been prepared by reactions of 1,3,5‐tris(1‐imidazolyl)benzene (tib), and biphenyl‐3,3′,4,4′‐tetracarboxylic acid (H4L1), 4,4′‐oxydiphthalic acid (H4L2), or benzene‐1,3,5‐tricarboxylic acid (H3L3) with corresponding ZnII salts, respectively. Single crystal structure analyses reveal that 1 and 2 are constructed by Zn‐centered polyhedra, tib and multidentate tetracarboxylate ligands to form 3‐dimensional frameworks. In contrast, when the tetracarboxylate ligands were replaced by tricarboxylate ligand, layered structure of 3 is produced. These compounds are further characterized by powder X‐ray diffraction, element analyses, thermogravimetric analyses and photoluminescent spectroscopy. The luminescent properties of three Zn‐MOFs dispersed in different solvents have been investigated systematically, demonstrating high sensitivity for the detection of nitro compounds via a fluorescence quenching mechanism. Don't lose trace: Three ZnII metal–organic frameworks (Zn‐MOFs) based on mixed ligands have been synthesized by a hydrothermal method. Compounds 1 and 2 are 3‐dimensional frameworks, and 3 is a layered structure. Changes in the luminescence of the three Zn‐MOFs dispersed in different solvents allow for the detection of trace amounts of nitro compounds through a fluorescence quenching mechanism.