Research On Preparation And Fluorescence Sensing Properties Of Functionalized Metal Organic Framework

The development of metal organic frameworks?MOFs?has attracted extensive attention of researchers.MOFs have great application prospects in many fields such as gas storage,drug delivery,catalysis,and chemical sensing.Luminescent metal organic frameworks?LMOFs?are an important branch of MOFs.LMOFs are active in the field of chemical sensing because of its advantages such as excellent fluorescence performance,functionalized framework structure,high specific surface area,and so on.The luminescent UiO series with the advantages of high stability,easy functionalization,and unsaturated metal sites have become the representative materials of LMOFs.Up to now,fluorescent sensors based on the UiO series of MOFs have been used to detect ions,organic molecules,biomolecules,gases,pH and temperature.In order to make fluorescent probes exhibit high specificity and sensitivity,it is very important to introduce appropriate functionalized groups into MOFs without destroying the framework structure.Post-synthetic modification?PSM?provides a new method for this purpose,and expands the application of MOFs fluorescent materials.In this work,two kinds of modified MOFs based on UiO-66-NH₂ were successfully prepared as fluorescent sensors,which realized the sensitive detection of uric acid?UA?and creatinine?Cre?,respectively.The detailed studies are as follows:1.The fluorescent sensor UiO-PSM was successfully prepared for detecting UA based on the amidation reaction of UiO-66-NH₂ and 2-picolinic acid?PA?.There are suitable UA recognition sites and abundant?electrons in UiO-PSM.UA can effectively quench the fluorescence of probe through the coordination,hydrogen bond,and?-?interactions.The detection follows the static fluorescent quenching mechanism based on the calculation of Stern-Volmer equation and the experiment of fluorescent lifetime.A series of characterization and fluorescent experiments show that the probe has good structure,thermal,and fluorescence stability.The probe exhibits fast response time?1 min?,high sensitivity?DL=2.3 nM?,high selectivity,and good recoverability to UA.In addition,the probe has been successfully used in the detection of UA in human serum and urine samples.The recovery values are from 96.94%to 104.58%,and the relative standard deviation?RSD?values are less than 2.21%?n=3?.2.The fluorescent probe UiO-HQCA-Al was synthesized by PSM of UiO-66-NH₂ with 8-hydroxy-2-quinolinecarboxaldehyde?HQCA?and Al³⁺to detect Cre.In the sensing system,the fluorescence of UiO-HQCA is firstly quenched by Al³⁺through energy transfer and electron transfer interaction.After adding Cre,the interaction between Al³⁺and UiO-HQCA disappears,and then the fluorescence is restored due to the formation of Lewis acid-base complexes between Al³⁺and Cre.The probe has fast response time?1 min?,high sensitivity?DL=4.7 nM?and selectivity for Cre detection.When the sensor was used to detect Cre in human serum and urine samples,the recovery values are in the range of 97.0%?102.7%with RSD less than 1.9%?n=3?.