Design And Synthesis Of MOFs And Their Detection Of Iron Ion And Fluoride Ion

Metal-organic framework material is a complex of network structure formed by metal ions or metal clusters and organic ligands through coordination bonds,also known as porous coordination polymers.Due to their diverse compositions,large surface area,tunable topology,and excellent designability of pore size and pore surface,MOFs have received increasing attention in recent years due to their strong structural advantages.Among them,luminescent metal organic framework materials are an important sub-category of MOF materials.Compared with traditional luminescent materials,LMOFs have many advantages such as color change detectable by naked eye,low detection limit,and simple sample preparation process,the luminescence-responsive behavior to target analytes can be achieved through rational design of the framework,modulation of energy transfer and electron transfer processes.Therefore,suitable functional sites can be added to the LMOF to achieve specificity and selectivity for the analyte molecule.The research content of this paper is divided into the following two parts:1.Fluorescence detection of Fe³⁺in water by Zn-TCPP nanosheets.In this part,a common luminescent organic ligand linker tetrakis(4-carboxyphenyl)porphyrin(TCPP)and d¹⁰ metal Zn(II)were used as metal nodes to synthesize a facile bottom-up method.Zn-TCPP nanosheets,and structural characterization of the material.Nitrogen in porphyrins can bind to the metal ions to be tested,which may result in a decrease in fluorescence intensity when exposed to target ions;Zn(II)metal cations belong to the category of"green"metal ions,which meet the increasing sustainability requirements in the biological environment,and the use of Zn(II)ions guarantees ecological compatibility and low cost.We explored the fluorescence properties of ligands and materials and found that organic ligands were the source of their fluorescence;the influence of solvation effect on material luminescence is discussed;To discuss its application in the field of fluorescence detection,it has high sensitivity to Fe³⁺(K_SV reaches 0.172×10~5 L·mol^-1)and low detection limit(LOD value is 8.72×10^-6 mol·L^-1);subsequent use of fluorescence emission spectroscopy,Fourier transform infrared(FT-IR)spectroscopy,ultraviolet-visible(UV-vis)absorption spectroscopy,and the detection study found that the mechanism of fluorescence quenching of Fe³⁺detected by Zn-TCPP nanosheets is because the coordination binding of Zn-TCPP nanosheets and Fe³⁺occurs,which affects the electron transfer efficiency,and thus the fluorescence quenching occurs.2.Fluorescence detection of F^-in water by NH₂-MIL-101(Fe).In this part,NH₂-MIL-101(Fe)was synthesized by a solvothermal method,and structural characterization.Its organic ligand is 2-aminoterephthalic acid,and the?-conjugated aromatic ring itself can provide strong fluorescence emission,at the same time,amine functional groups can participate in various chemical reactions and can be used as functional sites to identify the target molecule.The fluorescence properties of ligands and materials were explored,and organic ligands were found to be the source of fluorescence;the influence of solvation effect on the luminescence of materials was discussed;its application in the field of fluorescence detection was discussed,and its high sensitivity to F^-(K_SV reached 0.53×10~5 L·mol^-1)and low detection limit(LOD value of 4.58×10^-5 mol·L^-1),this value is far lower than the maximum limit stipulated in the national drinking water hygiene standard(GB5749-2006),and it shows an obvious fluorescence enhancement response;Subsequent detection studies using fluorescence emission spectroscopy,Fourier transform infrared(FT-IR)spectroscopy,and ultraviolet-visible(UV-vis)absorption spectroscopy found that the detection mechanism of NH₂-MIL-101(Fe)for F^-is as follows:the functional recognition group NH₂-in NH₂-MIL-101(Fe)is coordinated with the analyte F^-to form a new complex,or other sensitization,which enhances the electrical density around the2-amino-terephthalic acid organic ligand,thereby enhancing the electron transfer efficiency,so that LMCT and inner filter effects are suppressed.Finally,the fluorescence intensity of NH₂-MIL-101(Fe)showed an enhanced effect.