Synthesis Of Luminescent Metal-organic Frameworks And The Application For Fe³⁺ And Al³⁺ Detection

As ubiquitous substances in the environment and human body,it is very important to detect metal ions accurately.Especially nowadays,with the development of technology,industrial pollution is increasingly aggravated.Heavy metals in wastewater and sewage pollute soil and water bodies particularly seriously.Food safety incidents caused by heavy metal pollution also occur frequently,which seriously threaten not only the safety of the public’s lives and properties,but also the orderly development of the national economy.As we all know,iron ions(Fe³⁺)are an essential nutrient for humans affecting the electron transfer,oxygen storage and transport process in the process of DNA and RNA synthesis.However,excess or deficiency of Fe³⁺may cause some diseases,such as endotoxemia and liver cirrhosis.Aluminum（Al）is a non-essential trace element for the human body,and the absorption level of Al³⁺directly affects human health.Too much Al³⁺can cause many diseases such as Alzheimer’s disease and Parkinson’s disease.Therefore,it is of great significance to develop a sensitive and specific method for the detection of metal ions.Fluorescence method is widely used in metal ions sensing because of its economical,convenient,high efficiency and suitable for real-time feedback.Metal-organic framework materials（MOFs）are characterized by new topological networks with high porosity,high surface area and tunable properties,and have a wide range of applications in the fields of catalysis,chemical sensing,gas storage/separation,drug release,and optics.Luminescent metal-organic framework materials（LMOFs）,as a typical MOFs,have excellent fluorescence properties and can effectively detect certain metal ions using the open coordination sites of ligands.In our work,fluorescent sensors based on LMOFs had been developed for fluorescence sensing of Fe³⁺and Al³⁺in aqueous solution.The main research results are as follows:1.The fabrication of Al-MOF fluorescence sensor and application of Fe³⁺detection.In this work,a simple solvothermal method was used to prepare an aluminum-based luminescent metal-organic framework material,and a fluorescent sensor platform was constructed based on the material to detect Fe³⁺in aqueous solution.The results showed that Al-MOF with excellent optical properties could achieve rapid and sensitive detection of Fe³⁺,and the limit of detection could reach 0.6μM,which was far below the maximum level allowed by the World Health Organization（5.36μM）.In addition,the sensor also showed application value for the detection of Fe³⁺in actual sample.2.The fabrication of UiO-（OH）₂@Rh B dual emission ratiometric fluorescence sensor and application of Al³⁺detection.Compared with traditional single-emission fluorescence detection methods,ratiometric fluorescence technique has attracted much attention because of its decreased environmental impact,easy identification of color and intensity changes.In this work,2,5-dihydroxyterephthalic acid,Zr OCl₂·8H₂O and Rhodamine B were used as raw materials to prepare a dual-emission metal-organic framework material UiO-（OH）₂@Rh B through a simple one-pot hydrothermal method for the proportional fluorescence sensing of Al³⁺in aqueous solution.The material was characterized by a series of characterization methods.The UiO-（OH）₂@Rh B fluorescence sensor exhibited two emission peaks at 500 nm and 583 nm when excited by a single wavelength（420 nm）.With the increase of Al³⁺content,the fluorescence color changed from orange to green under ultraviolet light.There was a good linear relationship between the fluorescence intensity ratio(I₅₀₀/I₅₈₃)and the concentration of Al³⁺in the range of 0-10 and 10-20μM,and the limit of detection was 10 n M.The spike test had been carried out in actual samples with a recovery of 89.08%-113.61%.The response mechanism suggested that-OH could capture Al³⁺in water through coordination and high electrostatic affinity and achieved turn-on ratiometric fluorescence through the suppression of excited-state intramolecular proton transfer process.