The Synthesis,Structures And Properties Of Metal-organic Frameworks Based On Thiophene Dicarboxylic Ligand

Metal-organic frameworks?MOFs?,constructed by organic linkers and metal nodes,are a new class of crystalline porous materials.MOFs has high surface area,large porosity,adjustable pore size,ordered porous structure,adjustable physical and chemical properties and modification ability,which makes MOFs have a good application prospect in organic dye and metal ion adsorption,ion sensing and fluorescent probe.This paper used the alkaline earth dicarboxylate metal-organic frameworks and Zn-triazole-dicarboxylate metal-organic frameworks to study their properties in fluorescence detection and dye adsorption.The main contents are as follows:1.The recognition properties of metal cations were investigated by using three fluorescent alkaline earth thiophene-dicarboxylate metal-organic frameworks,namely[Mg?DMTDC??DMF?_1.5?H₂O?]·1.5DMF·H₂O?1?,[Ca?DMTDC??DMF?]?2?and[Sr?DMTDC??DMF?]?3??H₂DMTDC=3,4-dimethylthieno[2,3-b]thiophene-2,5-dicarboxylic acid?.The results indicate that 1-3 can recognize Fe³⁺ions through fluorescence quenching.Fluorescence titration analyses show that the quenching constants of compounds 1-3 were 8.1×10⁴,6.9×10⁴ and 2.9×10⁴ M^-1,respectively.Cycle experiments show 1-3 has good stability and favorable repeatability for sensing Fe³⁺.The recognition mechanism of Fe³⁺ions was studied by powder X-ray diffraction,infrared spectroscopy,ultraviolet spectroscopy and XPS spectroscopy.The results reveal that the recognition effect of 1-3 on Fe³⁺ion may be caused by the bonding between O/S atoms on the sulfur-containing dicarboxylate ligand and Fe³⁺ion,which leads to fluorescence quenching.2.A new porous three-dimensional metal-organic framework[?CH₃?₂NH₂][Zn₂?DMTDC?₂?3-mtz?]·4DMF·2.8H₂O?4?was synthesized by using3-methyl-3H-1,2,4-triazole?3-mtz?and the thiophene dicarboxylic acid ligand H₂DMTDC under solvothermal condition.The structure was characterized by single crystal X-ray diffraction,thermogravimetric analysis and infrared spectroscopy.Compound 4 exhibit effective pore cross-section of 11.9×6.3?²,and 61.0%of guset-accessible volumes,which is occupied by guset molecules and[?CH₃?₂NH₂]⁺cation.Ultraviolet spectroscopy studies indicate that compound 4 can selectively absorb cationic organic dyes over neutral and anionic dyes.Fluorescence analysis reveals that Tb³⁺-loading sample(Tb³⁺@4)can selectively recognize Fe³⁺ions by fluorescence quenching,proving that Tb³⁺@4 can be used as a probe for detecting Fe³⁺ions.3.A new three-dimensional porous MOF[?CH₃?₂NH₂][Zn₂?DMTDC?₂?tz?]·3DMF·5H₂O?5,tz=1,2,4-triazole?was synthesized by using 4-amino-4H-1,2,4-tria-zole?4-atz?and the thiophene dicarboxylic acid ligand H₂DMTDC under solvothermal condition.The structure of compound 5 was characterized by single crystal X-ray diffraction,thermogravimetric analysis and infrared spectroscopy.Compound 5 exhibit effective pore cross-section of 9.7×9.7?²,and 55.7%of guset-accessible volumes.Being similar with 4,compound 5 can also selectively adsorb cationic organic dyes over anionic and neutral dyes.