Rational Design,Synthesis And Properties Of Anthracyl Modified Metal-Organic Frameworks

Metal-organic frameworks(MOFs)are a new type of porous crystalline materials composed of organic ligands and inorganic metal nodes.They have been widely used in many fields,such as gas storage and separation,photocatalysis/electrocatalysis,proton conduction,drug delivery,chemical sensing and so on.Therefore,from the perspective of fluorescence sensing,this work explores the sensing performance of metal organic framework materials for toxic and harmful metals and organic small molecule pollutants.In this work,9,10-bis(N-benzimidazolyl)anthracene(L)was selected as main ligand,transition metal cadmium ions as inorganic nodes,and ten different organic polydentate carboxylic acid ligands as auxiliary ligands.Ten novel metal organic frameworks with luminescent properties were successfully synthesized by one pot method under solvothermal conditions.The crystal structures were determined by X-ray single crystal diffraction,and then the structure stability and thermal stability of the crystals were characterized by X-ray powder diffraction(PXRD)and thermogravimetric analysis(TGA).The fluorescence sensing properties of the crystals for anions/cations,antibiotics and other toxic and harmful pollutants were further studied by fluorescence titration experiments.Finally,the mechanism of fluorescence quenching in the detection process were discussed systematically by theoretical calculation(DFT),UV-vis absorption spectrum and fluorescence lifetime.The main contents are as follows:(1)Two two-dimensional coordination networks,CUST-531 and CUST-536,were synthesized by one pot method with cadmium ions as the metal centers.The experimental results show that CUST-531 has good fluorescence emission performance and high sensitivity and selectivity for TNP,which can be used for trace detection at ppb level.In addition,the selectivity of CUST-531 to TNP was not affected in the presence of other nitroaromatic compounds(NACs),which indicated that CUST-531had strong anti-interference ability.Cycle experiments also further prove that CUST-531 is a recyclable and sustainable fluorescent sensing material.(2)Six Cd-LMOFs:F1,F2,F3,F4,CUST-534 and CUST-535 were synthesized by solvothermal method with L ligand and six different bidentate rigid carboxylic acid ligands.It was characterized by X-ray single crystal diffraction,X-ray powder diffraction(PXRD),infrared spectroscopy(IR)and thermogravimetric analysis(TGA).Fluorescence titration experiments proved that F2,F3 and F4 showed high sensitivity,selectivity and reproducibility for the detection of TNP,ketone pesticides and Fe³⁺.In addition,the detection mechanisms were studied in detail by theoretical calculation(DFT)and UV-vis absorption spectrum analysis.F2,F3 and F4 are potential chemical sensors for the detection of trace pollutants,including nitroaromatic explosives,pesticides and ferric ions.(3)Two novel 3D Cd-MOFs,CUST-532 and CUST-533,were synthesized by solvothermal method.From the topological point of view,CUST-532 and CUST-533are two nodes,which can be expressed as(3,8)-connected three-dimensional network structure.The topological symbol is{4³}₂{4⁶·6¹⁸·8⁴}.As expected,both CUST-532and CUST-533 show excellent luminescent properties.Fluorescence sensing experiments show that CUST-532 and CUST-533 can be used as chemical sensors to rapidly and effectively detect antibiotic residues,Fe³⁺and Cr₂O₇^2-ions in the environment even in the low concentration range.In addition,the possible mechanisms of fluorescence quenching in the detection process were studied in detail.