Syntheses,Structures And Properties Of Metal-Organic Frameworks Based On Fluorene Dicarboxylic Acid And Tetracarboxylic Acid Ligands

In the past two decades,metal-organic Frameworks(MOFs)have become one of the hot areas of research by scientists all over the world.It is supramolecular organic-inorganic hybrid crystalline materials formed by the coordination self-assembly of metal ions and organic ligands.The porous structure and abundant functional groups of MOFs contribute to their special physical and chemical properties,such as large specific surface area and high fluorescence intensity.Nowadays,MOFs are widely applied in numerous areas,including gas adsorption/separation,catalysis,magnetism,fluorescence sensing,electrochemistry,etc.In this text,four coordination polymers were synthesized by solvothermal self-assembly of 2,7-dicarboxylic acid-9,9-diethylfluorene(H₂L1),[1,1':4',1'-trip Henyl]-2',4,4',5'-tetracarboxylic acid(H₄L2)and pyrimidine-2-methylamine oxime(Hpmad),four different organic coordination polymer materials were obtained by solvothermal coordination assembly with transition metal ions.We have characterized crystal structures and basic properties of coordination polymers by single crystal X-ray diffraction,powder X-ray diffraction,elemental analysis,thermogravimetric analysis,infrared spectroscopy and fluorescence spectroscopy,and explored their sensing properties.The main research results of this thesis are summarized as follows:1.Based on 2,7-dicarboxylic acid-9,9-diethylfluorene(H₂L1)and Ca²⁺ion,[Ca L1(H₂O)₂]·3H₂O(1)and[Ca(L1)(CH₃OH)(DMA)(H₂O)₂]·2CH₃OH(2)have been synthesized by the sol vothermal method under high temperature and pressure conditions,four Ca₃(COO)₆ metal cl usters in complex 1 are connected by four L1^2-bridges to form a two-dimensional planar st ructure.Several two-dimensional structures are interconnected by coordination bonds to form a highly symmetric three-dimensional cubic skeleton.The complex 2 consists of a twisted parallelogram frame structure as a secondary building unit,which forms three-dimensional st acking structure through interconnection.Powder diffraction pattern shows that two complex es have high phase purity.Fluorescence spectra show that both complexes emit blue light.2.A highly symmetrical 3D MOF[Cd L1(H₂O)₂]·H₂O(3)was synthesized by solvothermal reaction of 2,7-dicarboxylic acid-9,9-diethylfluorene(H₂L1)with transition metal ion Cd²⁺at high temperature and high pressure condition.In the crystal structure,L1^2-ligand is coordinated by four oxygen atoms of carboxylic acid and four different Cd²⁺ions.Cd²⁺forms a one-dimensional Cd-O-C chain structure along a axis,and the two chains are bridged by L1^2-to form a 2D coordination network.The 2D coordination network is bridged by a one-dimensional Cd-O-C chain to form a three-dimensional rhombic channel structure on the bc crystal plane.Fluorescence test show that.the complex 3 emits blue light.The results of powder diffraction show that the complex 3 has a good match with the simulated chromatogram,and the framework had good phase purity.The fluorescence test showed that the complex 3 has a strong fluorescence quenching response to Fe³⁺in water deionized water.with the K_sv value calculated to be 46000 M^-1.3 also offers excellent anti-interference.Finally,we investigate the sensing mechanism of the complex 3 for Fe³⁺ions.3.A two-dimensional layered coordination polymer was prepared by solvothermal reaction of[1,1':4',1"-trip Henyl]-2',4,4",5'-tetraparboxylic acid(H₄L2),pyrimidine-2-methylamine oxime(Hpmad)with transition metal ions Cd²⁺under high temperature and high pressure.In the structure of[Cd₂L2(Hpmad)₂(H₂O)₂]·3H₂O(4),each Cd²⁺ion is hexagonal with two nitrogen atoms of the chelated Hpmad ligand,three different oxygen atoms of carboxylic acid of the L^4-ligand and one coordinated water molecule.The slightly distorted octahedral coordination geometry is formed by the hexagonal coordination of three carboxylic oxygen atoms in the L^4-ligand and one coordinated oxygen atom in the water molecule.4 show good solvent stability in different organic solvents.The results of metal ion selectivity experiments show that the fluorescence quenching response of Fe³⁺ions in 4 suspension was obvious,with the K_sv value calculated to be 1.283×10⁴ M^-1(R²=0.9807)in the concentration range of 0?50?M.The detection limit for Fe³⁺is 3.25?M.In addition,the compound 4 shows remarkable turn-on fluorescence response for selective detection of Mn O₄^-in aqueous solutions,with the K_sv value calculated to be 1.734×10⁴ M^-1(R²=0.9738)in the concentration range of 0?20?M.The detection limit for Mn O₄^-is 2.56?M.The results show that the complex 4 is a potential bifunctional fluorescence sensor for Fe³⁺and Mn O₄^-.The sensor also has good anti-interference and stability.Finally,we also investigate the detection mechanism of the coordination polymer for Fe³⁺and Mn O₄^-.