Metal-organic Framework Luminescent Materials Based On Carboxylic Acid Ligands And Their Sensing Properties

Luminescent Metal-organic frameworks(LMOFs)are porous framework materials with light-emitting characteristics bridged by inorganic metal centers(metal ions or metal clusters)and organic linkers with various types of functional groups,making MOFs rich in structure and applied widely,especially the MOFs constructed from carboxylic acid ligands.They have great application value in fluorescence sensing,gas separation,gas storage,etc.Due to the rich coordination mode of carboxyl groups,the design is based on The LMOFs materials constructed by carboxylic acid ligands,whose unique luminescence characteristics and large specific surface area can be used to detect heavy metal ions,water molecules,small organic molecules and other counter substances through optical performance changes,which is an excellent optical sensor.Environmental issues has always been an urgent problem in social development,especially heavy metal ions and organic solutions flowing out of industrial production,which will have a great impact on human life.And the water content in organic solvents will also have a great impact on industrial production.Therefore,this paper designed a series of fluorescent sensors based on LMOFs constructed by carboxylic acid ligands to detect heavy metals Fe³⁺,water in organic solvents,and nitrobenzene.1.By adding thiophene-2,5-dicarboxylic acid(H₂TDC)to the reaction system,a series of new hollow spherical terbium metal-organic framework materials(Tb-MOFs)were synthesized only by solvothermal method.The results of single crystal analysis confirm that H₂TDC is just used as a reaction aid.Comparing the morphology of Tb-MOFs without H₂TDC and without H₂TDC in reaction system,it is found that H₂TDC is the key reagent for the formation of hollow sphere structure of it.Further studies have found that Tb-MOFs can be used.For Fe³⁺sensing,the detection limit and quenching constant of Tb-MOFs for Fe³⁺in water are 2.05?M and 0.058?M^-1,respectively.2.The reaction system remains the same,and a series of new hollow spherical lanthanide metal-organic framework materials(Ln-MOFs)have been synthesized by the solvent method.Different Tb³⁺and Eu³⁺ratios can realize the adjustment of luminous color as green-yellow-orange-red.By monitoring the lifetimes of the excited states ⁵D₄(Tb³⁺)and ⁵D₀(Eu³⁺)of Ln-MOFs,the energy transfer between Tb³⁺and Eu³⁺is confirmed,and the energy conversion efficiency is high,indicating that the ligand 1,3,5-tricarboxylic acid(H₃BTC)has a good antenna effect.Ln-MOFs can be used as fluorescent probes to specifically recognize water molecules and nitrobenzene(NB)in organic solvents.3.Use 5-aminoisophthalic acid(H₂AIP)as organic linker,2-methylimidazole(2-MI)as reaction aid and Tb³⁺to synthesize hollow network Tb-MOFs-1 material,through single crystal X-ray Diffraction(XRD),scanning electron microscopy(SEM),etc.The crystal structure,morphology,and luminescence characteristics of Tb-MOFs-1 are explored.And the Tb-MOFs-1 can achieve the detection of trace amounts of water in different organic solvents by switching the color changes.This work provides a simple method for designing and synthesizing multifunctional hollow spherical MOFs,providing ideas for exploring the fluorescent sensors of the detecting targets(Fe³⁺,NB,Water).