Design,preperation And Performance Of Heavy Metal Sensors Based On Luminescent Metal-organic Frameworks

In recent years,with the development of morden society,the environmental hazards and food safety problems caused by heavy metals have attracted widespread attention.Traditional treatment methods have some limitations and irrationality,which affected the accuracy of heavy metal detection results,and hindered reflection of the real situation of heavy metals in food and environment.Therefore,it is necessary to develop novel technology to detect heavy metals in the environment efficiently and accurately.In recent years,Luminscient metal-organic frameworks(LMOFs),as a type of representative nanomaterial,have been developed as ideal sensors in food analysis.Compared with the traditional detection technology,LMOFs can realize the specific recognition of target molecules by adopting different recognition groups.Such flexible adjustable feature makes LMOFs compatible with complex food environment,and realizes rapid detection of hazardous substances,which is of great significance for food safety control.In this study,based on the LMOFs,two kinds of multifunctional sensors were designed and and the detection performance and mechanism of the sensors were studied.The main contents and results of this paper are as follows:(1)Preparation of RhB@ZIF-8 and the performance for copper ion detection and removal.A simple and effective encapsulating strategy was adopted to introduce fluorescent dye(RhB)into the traditional MOFs material(ZIF-8)as a new intelligent sensor(RhB@ZIF-8).The results of SEM,FT-IR and XRD showed that the morphology of the composite has no obvious change,the average size of the particles is 50-100 nm,and the complete crystal characteristics of single MOFs component are maintained.TEM,UV-Vis and zeta potential proved the stable encapsulation of RhB.BET test results showed that the composite had large surface area,pore volume and uniform pore size.Particularly,ascribed to the favorable ions binding affinity of ZIF-8 and self-calibrating effect of RhB,the as-prepared smart adsorbent demonstrates a superior adsorption performance of 608 mg g^-1,broad response range(0.05-200 ppm,2.07×10^-7-8.29×10^-4 M),ultrahigh sensitivity(0.04 ppm,1.91×10^-7 M)toward Cu²⁺and strong anti-interference ability.Different from the traditional materials,the fluorescence response of the synthesized composite changes linearly with the copper ions concentration and has a certain correlation with the adsorption process.The energy matching between the removal and detection process is proved by DFT theoretical calculation,which provides a certain reference value for the development of effective bifunctional fluorescent sensor technology,proving a new idea for the construction of multifunctional nanoadsorbent materials.(2)Missing-linker Engineering of Lanthanide-Based Metal-Organic Framework for Regulation Detection of Cd²⁺.A modulator-assisted strategy was adopted to elaborately introduce missing-linker defects into a lanthanide-based metal-organic framework(Eu@UIO-MOFs-X)to achieve defective construction and tunable performance.SEM,TGA,¹H NMR,XRD and other characterization methods proved that different degrees of defects were successfully introduced into the framework,and the regulatory effect of the introduction of ligand defects on the detection performance was further studied.Importantly,the successful creation of missing-linker defects allows for improved properties including superior adsorption ability and efficient energy transfer,which are inherently weak in the parent MOFs.The resultant Eu@UIO-MOFs-2 sensor with 0.53 missing linkers per Zr-O cluster shows a remarkably enhanced response slope and realizes excellent trace detection under the range of 0-10 ppm with ultralow detection limit to 5.67×10^-7 M(114 ppb).The dual signal change and ratio detection based on two luminescence centers makes it have which provides a double insurance and reduce the error rate for Cd²⁺tracking detection.At the same time,the probe has been successfully applied to practical samples,which proves the feasibility of the synthesized probe Eu@UIO-MOFs for the accurate identification of Cd²⁺.Therefore,through the regulatory of defect engineering in the probe structure,the detection performance can be actively regulated,which provides a new way to explore innovative technologies for monitoring pollutants in water.