Europium-based Metal Organic Frameworks For The Detection Of Radioactive And Heavy Metal Ions

Metal-Organic Frameworks?MOFs?,a new style of porous materials,are synthesized by self-assembly of metal ions/metal clusters and organic ligands.Owing to their structural diversity and tunability,MOFs have attracted extensive attention in the past 20 years,and have widely application prospects in many fields such as luminescence detection,gas adsorption and separation,catalysis,biomedicine,nonlinear optics,and magnetism materials.With the development of nuclear power,a large number of radioactive products,including actinide elements and their fission products,as well as the radioactive gases produced during the nuclear fuel cycle,which have aroused great concern.Industrial production process of chemical,electronic,mechanical manufacturing,instrumentation,etc.,will produce wastewater containing heavy metal ions?cadmium,chromium,copper,mercury,nickel,etc.?.The wastewater will enter the natural water through various approaches.If they are not monitored and removed in time,they will be enriched in the human body through the food chain,posing a great threat to human health.Therefore,the construction of luminescence MOFs materials with sensitivity to various cations to the detection of radioactive and heavy metal ions is of great significance.In this study,two europium metal organic framework materials with luminescence properties were self-assembled synthesized through solvothermal method by selecting suitable ligands.The single crystal structure of the complex was measured by single crystal X-ray diffractometer.The purity and stability of the complex were confirmed by X-ray powder diffraction measurment.The infrared spectrum,thermogravimetry analyses,luminescence spectra,and absorption spectrum were measured in order to further explore their mechanism of luminescence detection.The specific work as follows:?1?Under solvothermal conditions,an europium metal organic framework material[Eu₂?FDC?₃?DMA?₂]·4H₂O?complex 1?with luminescence property was synthesized using Eu?CH₃COO?₃ and 2,5-furandicarboxylic acid ligand.The crystal structure of the complex 1indicates it has a three-dimensional network structure.The material features the excellent pH stability ranging from 2 to 12,and selective luminescence quenching for Th⁴⁺which can be applied to the detection of Th⁴⁺.The detection mechanism of complex 1 is further proved by the uptake kinetics of Th⁴⁺,EDS elemental analysis,absorption spectroscopy,luminescence spectroscopy and Th⁴⁺competing adsorption.?2?A two-dimensional layered europium metal organic framework material[Eu₂?MTBC??OH?₂?DMF?₃?H₂O?₄]·2DMF·7H₂O?complex 2?was synthesized by using 4,4?,4??,4???-methanetetrayltetrakis-[1,1?-biphenyl]-4-carboxylicacid?H₄MTBC?ligand and Eu?CH₃COO?₃ under solvothermal conditions.Interestingly,it exhibits luminescence quenching phenomenon towards heavy metal Cu²⁺and radioactive UO₂²⁺.To explore its potential applications as Cu²⁺and UO₂²⁺probes,we systematically investigated the selectivity,concentration-dependent luminescence spectra,and detection limits of complex 2.The detection limits for Cu²⁺and UO₂²⁺were calculated to be 17.2?g/L and 309.2?g/L,respectively.The detection capacity of complex 2 for Cu²⁺is much lower than the US Environmental Protection Agency's standard for Cu²⁺in drinking water.However,complex 2 has a lower detection capacity for UO₂²⁺,which can be applied to heavily contaminated sites such as uranium mines and processing equipment.The evolution of concentration-dependent luminescence intensity can be fully understood by studying uptake kinetics and isotherms.In addition,we also studied the detection mechanism of complex 2 by combining UV-visible absorption spectroscopy,luminescence spectroscopy and luminescence lifetime.