Preparation,Structures And Fluorescence Sensing Of Metal-organic Frameworks Based On 4,4′-(benzo[c][1,2,5]-thiadiazole-4,7-diyl) Dibenzoic Acid

Metal-organic framework crystalline materials have been widely used in fluorescence sensing research due to their advantages of controllable structure,high sensitivity,fast response speed and low detection limit.As a branch of metal-organic framework materials,luminescent metal-organic frameworks have promising application prospects in the field of fluorescence sensing due to their porosity tunability and structural designability.In this thesis,4,4′-benzothiadiazole-4,7-dibenzoic acid（H₂BTDB）was selected as the ligand,and six novel rare earth metal-organic frameworks and three transition metal-organic frameworks were successfully constructed by solvothermal method.The structures and properties of the targeted metal-organic frameworks were characterized by X-ray single crystal diffraction,X-ray photoelectron spectroscopy,X-ray powder diffraction,ultraviolet-visible absorption spectroscopy,fluorescence spectroscopy and infrared spectroscopy.The chemical stability,biological cell sensing and fluorescence sensing properties of most of them have been studied in detail.The main research contents are as follows:1.Six rare-earth metal-organic frameworks with novel structures were synthesized from five rare-earth metal ions(Sm³⁺,Eu³⁺,Gd³⁺,Tb³⁺,and Dy³⁺)and H₂BTDB ligand,and their structures and properties were fully characterized.Fluorescence tests show that metal-organic framework 1 exhibits fluorescence quenching effect on Fe³⁺,and metal-organic framework 2exhibits fluorescence enhancement effect on Al³⁺and Ga³⁺.In addition,metal-organic framework 2 based film was successfully prepared,which can effectively detect Al³⁺and Ga³⁺in DMF solution,and represents the first rare earth metal-organic framework capable of identifying Ga³⁺.Interestingly,metal-organic framework 2 is hydrophilic and can also detect Al³⁺and Ga³⁺in living cells.Metal-organic framework 6 has a fluorescence enhancement effect on the acetylacetone and a fluorescence quenching effect on salicylaldehyde.2.Three novel transition metal-organic frameworks were constructed with two nitrogen-containing ligands and three transition metal ions,and their structures and properties were characterized in detail.Structural analysis shows that metal-organic frameworks 7-9 take a three-dimensional two-fold interpenetrated structure based on tetranuclear Cd²⁺clusters,a two-dimensional planar structure,and a three-dimensional six-fold interpenetrated structure,respectively.The fluorescence test results showed that histidine was detected by the metal-organic framework 7 through the fluorescence enhancement effect,and the metal-organic framework 7 had good selectivity,anti-interference and cycling performance.