The Design,Synthesis And Sensing Properties Of Functionalized Fluorescent Metal-Organic Framework Materials

As a kind of multi-functional inorganic-organic hybrid crystal materials,metal-organic frameworks（MOFs）had been widely studied by scientists and applied in various fields.In particular,the application of luminescent metal-organic frameworks（LMOFs）in chemical sensing has the advantages of convenient operation,high sensitivity,strong selectivity and fast response speed.Among them,UiO-66 has been considered as one of the most promising MOF materials due to its excellent chemical,water,thermal and mechanical stability.However,UiO-66 optical performance is not outstanding.The functional modification provides a new way to introduce specific functional groups to obtain the desired fluorescence sensing materials.Therefore,in this work,UiO-66 was used as the parent framework,and a fluorescence sensing material with both the chemical stability of UiO-66 and the luminescence characteristics of rare earth ions(Eu³⁺)was prepared through two-step functional modification,realizing the detection of Fe³⁺and Cr₂O₇^2-ions.The specific research is divided into the following two parts:1.UiO-66 was prepared by solvothermal method using terephthalic acid and zirconium tetrachloride as raw materials and benzoic acid as regulator.Subsequently,Eu³⁺@UiO-66-CA,a fluorescence sensing material with Eu³⁺ion characteristic emission,was obtained by using CA and Eu³⁺ion two-step functionalization modification.A series of characterization and fluorescence property studies showed that the prepared material has excellent structure,water and fluorescence stability,and the material has high selectivity to Fe³⁺and Cr₂O₇^2-ions,good anti-interference ability and fast response time.Mechanism studies have shown that the luminescence quenching of Eu³⁺@UiO-66-CA on Fe³⁺ion is caused by energy competitive absorption and weak coordination,and the luminescence quenching of Eu³⁺@UiO-66-CA on Cr₂O₇^2-ion is mainly caused by energy competitive absorption.In addition,the prepared Eu³⁺@UiO-66-CA has successfully realized the rapid detection of Fe³⁺and Cr₂O₇^2-ions in tap water and Yellow River water.The recoveries of 100.22～102.68%and the relative standard deviation（RSD,n=3）0.82～3.36%were obtained.2.UiO-66 with good chemical stability was synthesized by solvothermal method using terephthalic acid and zirconium tetrachloride as raw materials and formic acid as regulator.Then,Eu³⁺@UiO-66-EDTA,a fluorescence sensing material with characteristic emission of Eu³⁺ions,was obtained by using EDTA and Eu³⁺to functionalize UiO-66.Through a series of characterization and fluorescence property studies,it is proved that the material has excellent structure,water and fluorescence stability.Fluorescence sensing experiments have shown that the prepared Eu³⁺@UiO-66-EDTA has high selectivity,sensitivity and fast response time to Fe³⁺and Cr₂O₇^2-ions,and the process is not interfered by other metal cations and anions.Next,the luminescence quenching mechanism of Eu³⁺@UiO-66-EDTA on Fe³⁺and Cr₂O₇^2-ions was investigated.It has been shown that the luminescence quenching caused by Fe³⁺ion is due to energy competitive absorption and coordination,while the luminescence quenching caused by Cr₂O₇^2-ion is mainly due to energy competitive absorption.The recoveries of99.15～100.98%and the RSD（n=3）0.66～2.08%when Eu³⁺@UIO-66-EDTA was used for the detection of Fe³⁺and Cr₂O₇^2-ions in water samples.