Preparation,Structures And Optoelectronic Properties Of Metal-Organic Frameworks Based On Benzothiadiazole Functionalized Ligands

In recent years,metal-organic frameworks（MOFs）,with the advantages of tunable structures,large surface area and adjustable pores,have been rapidly developed in the fields of fluorescence sensing,proton conduction and catalysis.Luminescent MOFs sensors have attracted a lot of attention due to their adjustable structural composition and good recyclability.In this thesis,the N-containing ligand 4,7-bis（1H-imidazol-1-yl）-2,1,3-benzothiadiazole（BIBT）and the O-containing ligand 4’,4’’’-（benzo[c][1,2,5]thiadiazole-4,7-diyl）bis（（[1,1’-biphenyl]-4-carboxylic acid））（H₂BTBC）were selected to synthesize 13 different MOFs.The structures,stabilities and fluorescence sensing properties were also analyzed by a series of characterization methods.The main contents are as follows:1.Eight transition metal-based MOFs were constructed by introducing different aromatic carboxylate ligands,the divalent transition metal centres including Cd²⁺,Zn²⁺and Co²⁺and the BIBT linker.MOF 1 could sense the toxic metal ion Hg²⁺in aqueous solution by fluorescence quenching effect.MOF 6 could achieve dual response sensing of H₂PO₄^-and CO₃^2-in ethanol solution by fluorescence enhancement and red-shift effect.While,the aerosol inkjet printing test paper,fluorescent film and light-emitting diode prepared based on 6 could better identify H₂PO₄^-and CO₃^2-.MOF 7 could selectively identify dopamine in biological fluids through fluorescence enhancement and blue-shift effects in DMF dispersions.In addition,a visual and portable assay platform has been developed with the help of a smartphone software"Colour Picker".Interestingly,MOF 7 is also capable of detecting dopamine in living cells and can be used as a potential biosensor;MOFs 2 and 8 exhibit the conductivity up to 9.9×10^–3 and 3.8×10^–3 S·cm^–1 at 98%RH and 60°C,both of which conduct protons via a transport mechanism（E_a>0.4 e V）.2.Five rare earth metal-based MOFs were constructed by introducing Sm³⁺,Eu³⁺,Gd³⁺,Tb³⁺and Dy³⁺and H₂BTBC linker.As a result,the fluorescence intensity of the H₂BTBC ligand was found to decrease gradually with increasing temperature.In addition,the H₂BTBC ligand was able to sense Fe³⁺ions in DMF solution with a fluorescence quenching effect and to sense straight-chain amines by a fluorescence enhancement effect.MOF 12 exhibits good chemical,acid–base and thermal stability,and is able to selectively identify ascorbic acid in biological fluids by fluorescence enhancement in DMF dispersion,providing a new idea for in vitro detection of ascorbic acid.