Synthesis,Characterization And Application Of Multifunctional Luminescent MOFs Materials

As a new type of porous organic-inorganic hybrid materials,metal-organic framework materials?MOFs?have huge applications in many fields.Due to its excellent characteristics,it has huge application prospects in many fields such as luminescence,selective adsorption separation,drug delivery,gas storage,and catalysis,and thus has become one of the widely concerned objects of current research.Fluorescent MOFs have a variety of light-emitting properties due to their different construction modes and different light-emitting sites,not only shows great potential in the two fields of display and lighting,but also shows outstanding performance in fluorescence detection and biological imaging.However,there are still many factors that limit their development,and their luminescence mechanism is not clear,which also makes it impossible to fundamentally optimize the material.In this paper,we mainly focus on two kinds of fluorescent metal organic framework LMOFs with different luminescence mechanisms.They are lanthanide fluorescent MOFs?Tb/Eu-DMBDC?whose luminescence source is metal ion and fluorescent metal organic framework M-MOF-74 whose luminescence source is ligand.On the basis of systematically discussing their luminescence mechanism,their potential applications have been studied.In this work,we synthesized lanthanide fluorescent MOF,based on the mixed metal Ln-MOF of Tb³⁺and Eu³⁺?Tb/Eu-MOF?.The characteristics of the porous structure and modifiability of the pore surface of MOFs and MOFs are highly versatile MOF materials,which have the advantages of high fluorescence intensity and good monochromaticity.We studied the time-resolved spectrum of its energy transfer?ENT?process and the ENT process from Ln-MOF to methylene blue?MB⁺?.The results show that Tb/Eu-MOF not only exhibits an extended emission spectrum relative to single metal Ln-MOF,but also shows a tunable fluorescence lifetime by changing the atomic ratio of Tb³⁺and Eu³⁺,which can be attributed to Tb³⁺Energy transfer to Eu³⁺.In addition,in the presence of MB⁺,energy transfer from Tb³⁺to MB⁺occurs in the hybrid node Ln-MOF,while Eu³⁺does not occur.This provides a feasible way to adjust the ENT rate and efficiency by changing the atomic ratio of Tb³⁺and Eu³⁺.In other words,Ln-MOF has internal and external energy transfer,and can control the ratio of metal ions to adjust the rate and efficiency of fluorescence intensity and energy transfer.In addition,based on the study of the energy transfer kinetics of bimetallic lanthanide MOFs,we systematically designed experiments and improved experiments to explore the temperature dependence of the fluorescence intensity of bimetallic lanthanide MOFs,making it potentially applicable to luminescence thermometers.In addition,in this paper,the luminescent metal organic framework M-MOF-74 was also synthesized by hydrothermal method,in which zinc-nitrate hexahydrate,copper nitrate,cobalt nitrate hexahydrate,nickel nitrate hexahydrate were used as metal salts and2,5-dihydroxyterephthalic acid was used as ligand.Compared with the ligand,the absorption spectrum of M-MOF-74 is red-shifted,which may be caused by the coordination of metal ions to the ligand.The ligand has strong fluorescence,after the synthesis of M-MOF-74,the fluorescence intensity decreases and the fluorescence lifetime decreases.Among M-MOF-74?M=Zn,Co,Cu,Ni?,Zn-MOF-74 has the highest fluorescence intensity and the shortest fluorescence lifetime.M-MOF-74 not only has special optical characteristics,but also has a wide range of applications.The toluene adsorption capacity of Zn-MOF-74 can reach 308 mg·g^-1,which indicated that this material is very useful in removing toluene in industrial applications.Application prospects.In addition,Zn-MOF-74 also exhibited excellent adsorption performance for carbon dioxide,and exhibited outstanding proton conductivity after acid modification of Zn-MOF-74.