Synthesis And Sensing Properties Based On Flexible Tetracharboxylate MOFs

Metal-organic frameworks,or MOFs,are organic-inorganic hybrid materials with intramolecular pores formed by the self-assembly of organic ligands and metal ions or clusters through coordination bonds.Because of their easy structural design,high specific surface area and tunable porosity,their has attracted the wide attention of scientific research workers.Now,because of the complex composition of the target detection,a large number of constructed sensors have the disadvantages of high detection limit,low selectivity and sensitivity.Therefore,this thesis focuses on the design of sensors with low detection limit,high selectivity,and high sensitivity.They are applied to the detection of ions in water,antibiotics,nitro explosives,amino acids,and pesticides.The main research contents of this thesis are as follows:In this thesis,using H₄L（H₄L=5-（3,5-diccarboxybenzyl）interphthalic acid）with different nitrogen-containing auxiliary ligands,eleven new MOFs materials were synthesized by the hydrothermal method,namely{[Zn₂（L）（1,2,4,5-tpb）]（H₂O）}_n（1）,[Cd₂（L）（1,2,4,5-tpb）（H₂O）]_n（2）,[Zn₂（L）（1,2,4,5-tpb）（H₂O）₇]_n（3）,[Zn（H₂L）（4,4’-bpy）]_n（4）,[Cd₂（L）（4,4’-bpy）（H₂O）₄]_n（5）,[Cd₂（L）（dpe）（H₂O）₅]_n（6）,[Cd₂（L）（dpp）（H₂O）]_n（7）,[Cd（H₂L）（4,4’-bip）]_n（8）,[Cd₃（HL）₂（1,4-bibb）（H₂O）₆]_n（9）,[Zn（L）_0.5（1,2-bimb）]_n（10）,[Cd（L）_0.5（1,3-bimb）]_n（11）.H₄L=5-（3,5-diccarboxybenzyl）interphthalic acid,4,4’-bpy=4,4’-bipyridine,1,2,4,5-tpb=1,2,4,5-tetra（pyridin-4-yl）benzene,dpe=1,2-bis（2-pyrid yl）ethylene,dpp=4,4’-（1,3-propanediyl）bis-Pyridine 4,4’-（1,3-dipropyl）dipyridine,4,4’-bip=4,4’-di（1H-i Midazol-1-yl）-1,1’-biphenyl,1,4-bibb=1,4-double（pyrazole-1-methyl）biphenyl,1,2-bimb=（1,2）-ortho-imidazole,1,3-bimb=（1,3）-interposition imidazole.X-ray powder diffraction,infrared,elemental analysis,and thermogravimetric were also characterized.We using the luminescence properties of the complexes,the ions,antibiotics,nitro explosives,amino acids and pesticides were investigated.Then,the material studied fluorescence sensing performance,and finally explores its fluorescence sensing mechanism.The main research contents are described as follows:The MOFs materials 1-3 were synthesized by hydrothermal method using H₄L as an organic carboxylic acid ligand,1,2,4,5-tpb as a nitrogen-containing ligand,and Zn and Cd as central metal ions.Analysis of their structure:1-3 are all three-dimensional network structures.Experimental studies have shown that 1 for p-nitrophenol（4-NP）and fluoroamine（FLU）,2 enable p-nitrophenol（4-NP）,3 has high selectivity and sensitivity for p-nitrophenol（4-NP）and pyrimethamine（PTH）.Finally,the UV absorption spectrum of p-nitrophenol,pyrimethamine and fluoroamine and the fluorescence excitation spectrum of 1-3 were applied to explore the mechanism of fluorescence quenching.The cause of fluorescence quenching may be energy competition and absorption.MOFs 4-7 were synthesized by hydrothermal method using H₄L as organic carboxylate ligand,4,4’-bpy,dpe,dpp as nitrogen-containing ligand,and Zn and Cd as central metal ions 4-7.Analysis of the structure:4 and 7 are two-dimensional network structures,5 and 6 are three-dimensional network structures,as shown by experimental studies of fluorescence sensing,4 enable p-nitrophenol（4-NP）and fluoroidamine（FLU）,5 enable p-nitrophenol（4-NP）,6 enable 2,4,6-trinitrophenol（TNP）and fluorothioamine（FLU）,7 with high selectivity and sensitivity for p-nitrophenol（4-NP）and fluoroidamine（FLU）.The mechanism of fluorescence quenching was explored by UV with high selectivity and sensitivity for p-nitrophenol（4-NP）and fluoroidamine（FLU）.Finally,the application of UV absorption spectra of p-nitrophenol,2,4,6-trinitrophenol,fluoroamine and fluorescence excitation spectra of 4-7 to explore the mechanism of fluorescence quenching.The cause of fluorescence quenching may be energy competition and absorption.Using H₄L as the organic carboxylic acid ligand,1,3-bimb,1,2-bimb,1,4-bibb,4,4’-bip as nitrogen ligands and Zn and Cd as the central metal ions,MOFs materials8-11 were synthesized by hydrothermal method and analyzed their structures:8 and 10are two-dimensional reticular structures,9 and 11 are three-dimensional structures,and experimental fluorescence sensing studies show that 8 and 9 for 2,4,6-trinitrophenol（TNP）and fluorodixamine（FLU）,10 and 11 have high selectivity and high sensitivity for p-nitrophenol（4-NP）and fluorodixamine（FLU）.Finally,the application of UV absorption spectra of p-nitrophenol,2,4,6-trinitrophenol,fluoroamine and 8-11 explored the mechanism of fluorescence quenching.The cause of fluorescence quenching may be energy competition and absorption.