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The complex 1 [Zn(BTC)2/3 ] ⋅ [HCON(CH3)2] ⋅ [C2H5OH]}n(1) was prepared from 1,3,5-benzenetricarboxylic acid (H3 BTC) and Zn(H) cation via a solvothermal technique. The complex 1 was characterized by single crystal X-ray diffraction (SXRD), Fourier transform-infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD) and fluorescence spectroscopy. Single crystal X-ray diffraction analysis indicates that complex 1 belongs to space group P21/n of the monoclinic system. In complex 1, the Zn(II) ion is coordinated with BTC3- anion through the oxygen atom on the carboxyl group, forming a three-dimensional Zn(II) metal-organic framework (MOF) structure with channels. And through intermolecular hydrogen bond interaction, ethanol and N, N'-dimethylformamide (DMF) molecules are encapsulated into parallelogram channels. Fluorescence spectrum analysis at room temperature shows that when the excitation wavelength is 297 nm, complex 1 has the strongest emission peak at 601 nm. [ABSTRACT FROM AUTHOR]

Three anionic metal-organic frameworks (MOFs) {[Zn 3 (BTEC) 2 (H 2 O)(4-BCBPY)]·(H 2 O)} n (1-3) (BTEC 4- = 1,2,4,5-benzenetetracarboxylic acid anion, 4-BCBPY 2+ = 1,1'-bis(4-cyanobenzyl)-4,4'-bipyridinium dication) were synthesized in the reaction of 1,2,4,5-benzenetetracarboxylic acid with different metal salts such as ZnNO 3 , ZnCl 2 , and ZnSO 4 , under solvothermal conditions in the presence of 1,1'-bis(4-cyanobenzyl)-4,4'-bipyridinium chloride. Single crystal X-ray diffraction analysis shows that compounds 1, 2 and 3 have MOF structures based on binuclear metal building units, which are connected by two protonated BTEC 4- ligands and three zinc ions, and the viologen cation 4-BCBPY 2+ is located in the channel to achieve charge balance. Compounds 1, 2 and 3 have good photosensitivity, respond to sunlight, UV light and blue ray, and turn blue. The D-A distance and π-π stacking distance of the discolored samples (1P, 2P and 3P) changed. In addition, the three compounds showed visible color changes to ammonia vapor, rapidly changing from white to blue. At the same time, the three compounds exhibited fluorescence quenching to ammonia vapor and Cr 2 O 7 2- . It is further proved that compounds 1, 2 and 3 are fluorescent sensors with a low detection limit (for Cr 2 O 7 2- : 10 -5 M) and high sensitivity for ammonia vapor and Cr 2 O 7 2- . It was found that photochromic behavior, ammonia sensing properties can be tuned by the nature of metal salts., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)