Rare Earth-organic Framework Materials Based On 2,6-pyridinedicarboxylic Acid Preparation And White Light Fitting Study

Metal-Organic Frameworks（MOFs）are a kind of materials with a channel structure constructed by metal nodes（also sub-building units,or SBU）and organic bridge ligands.Their structures and functions are With tunability and designability,MOFs have become one of the hot spots in scientific research.Compared with inorganic materials,metal-organic frame luminescent materials have attracted more and more attention due to their advantages such as high specific surface area,convenient function and structure control,multiple emission sites,and a wide range of emission wavelengths.In view of the difference in energy levels between the triplet excited state(25,000 cm^-1)of 2,6-pyridinedicarboxylic acid（H₂PDA）and the Eu³⁺excitation level(17,200 cm^-1)and the Tb³⁺excitation level(20,400 cm^-1)of rare earth ions Small,can transmit energy to Eu³⁺and Tb³⁺more effectively under the antenna effect,and promote stronger red and green emission of Eu³⁺and Tb³⁺.Therefore,the blue and rare earth ions of organic ligand H₂PDA are proposed to be used in this paper based on the principle of three primary colors.Eu³⁺red light and Tb³⁺green light,through the introduction of Gd³⁺,Ca²⁺,Zn²⁺matrix to effectively reduce costs,together to achieve white light fitting,to provide design ideas and theoretical basis for the development of new white light fitting material.In this paper,2,6-pyridinedicarboxylic acid（H₂PDA）was used as organic ligand,Eu³⁺and Tb³⁺were rare earth ions,Gd³⁺,Ca²⁺and Zn²⁺were used as matrix.The cerium matrix Ln₂PDA₃(Gd³⁺,Eu³⁺,Tb³⁺)was prepared by hydrothermal method:(Gd³⁺,Eu³⁺,Tb³⁺Materials,calcium matrix MPDA:(Ca²⁺,Eu³⁺,Tb³⁺)materials and zinc matrix MPDA:(Zn²⁺,Eu³⁺,Tb³⁺)materials,combined with XRD phase analysis,SEM-EDS morphology and energy spectrum analysis,FT-IR infrared spectroscopy The composition was characterized by analysis,TG thermogravimetric analysis and PL fluorescence spectrum analysis.The composition,morphology,composition and functional groups of the composites were investigated with different hydrothermal temperatures,different solvents,and different rare earth doping ratios.The effect of luminescence,and then its luminescence mechanism was discussed.The results of the study are as follows:（1）Different hydrothermal temperatures（90°C,120°C,160°C）,different solvents（ethanol+distilled water,methanol+distilled water,DMF+distilled water）,and different rare earth doping ratios(Gd³⁺:Eu³⁺:Tb³⁺=45:4:1,Gd³⁺:Eu³⁺:Tb³⁺=44:5:1,Gd³⁺:Eu³⁺:Tb³⁺=43:6:1)characteristic diffraction peaks of the ruthenium matrix Ln₂PDA₃:(Gd³⁺,Eu³⁺,Tb³⁺)The homologous correspondences indicate that the crystal structures of the cerium matrix composites prepared under different conditions are the same.Compared with the organic ligand H₂PDA,the cerium composites prepared under different conditions all retain the benzene-nitrogen ring structure of H₂PDA.(Gd³⁺,Eu³⁺,Tb³⁺)replaced hydrogen in H₂PDA to form oxygen atom coordination;SEM-EDS results further showed that Gd³⁺,Eu³⁺,and Tb³⁺all entered the lattice of Ln₂PDA₃:(Gd³⁺,Eu³⁺,Tb³⁺)materials,and Gd³⁺content Far larger than Eu³⁺and Tb³⁺.At the hydrothermal temperature of 90°C,the solvent was DMF+distilled water and Gd³⁺:Eu³⁺:Tb³⁺=43:6:1,the CIE chromaticity coordinates（0.3331,0.3308）of the lanthanum matrix Ln₂PDA₃:(Gd³⁺,Eu³⁺,Tb³⁺)with high intensity white were synthesized.materials.The environment-friendly ethanol+distilled water was used as the solvent,and the hydrothermal temperature was 90°C.Under conditions of Gd³⁺:Eu³⁺:Tb³⁺=44:5:1,CIE chromaticity coordinates（0.3341,0.3316）were also synthesized with high intensity white light.The matrix Ln₂PDA₃:(Gd³⁺,Eu³⁺,Tb³⁺)materials,and the crystals are elliptical flakes with a major diameter of about 1μm to 1.7μm and a minor diameter of about 0.5μm to 1μm.（2）Preparation of different rare earth doping ratios(Ca²⁺:Eu³⁺:Tb³⁺=45:4:1,Ca²⁺:Eu³⁺:Tb³⁺=44:5:1,Ca²⁺:Eu³⁺:Tb³⁺=43:6:1)The calcium matrix MPDA:(Ca²⁺,Eu³⁺,Tb³⁺)materials all have a one-to-one corresponding peak,indicating that the calcium matrix composites prepared at different rare earth doping ratios are amorphous;compared with the organic ligand H₂PDA,different rare earths doped The calcium matrix composites prepared under the miscellaneous conditions all retained the nitrogen benzene ring structure of H₂PDA.The metal ions(Ca²⁺,Eu³⁺,Tb³⁺)replaced the hydrogen in the H₂PDA to form the oxygen atom coordination.SEM-EDS results further showed that Ca²⁺,Eu³⁺,and Tb³⁺enters the lattice of MPDA:(Ca²⁺,Eu³⁺,Tb³⁺)materials,and the Ca²⁺content is much greater than that of Eu³⁺and Tb³⁺.High-intensity white-light calcium matrix with CIE chromaticity coordinates（0.3314,0.3342）was synthesized under the conditions of hydrothermal temperature of90°C,solvent of ethanol+distilled water and Ca²⁺:Eu³⁺:Tb³⁺=43:6:1.MPDA:(Ca²⁺,Eu³⁺,Tb³⁺)material.（3）The characteristic diffraction peaks of the Zn²⁺:Eu³⁺:Tb³⁺=47:2:1,Zn²⁺:Eu³⁺:Tb³⁺=46:3:1,Zn²⁺:Eu³⁺:Tb³⁺=45:4:1 zinc matrix MPDA:(Zn²⁺,Eu³⁺,Tb³⁺)materials all corresponded to each other,indicating that the zinc matrix composites prepared at different rare earth doping ratios The crystal structure is the same.Compared with the organic ligand H₂PDA,the zinc matrix composites prepared at different rare earth doping ratios retain the benzene ring structure of H₂PDA.Metal ions(Zn²⁺,Eu³⁺,Tb³⁺)replace hydrogen in H₂PDA to form oxygen.Atom coordination;SEM-EDS results further show that:Zn²⁺,Eu³⁺,and Tb³⁺all enter the lattice of MPDA:(Zn²⁺,Eu³⁺,Tb³⁺)materials,and the Zn²⁺content is much larger than that of Eu³⁺and Tb³⁺.High-intensity white-light zinc matrix with CIE chromaticity coordinates（0.3311,0.3351）was synthesized at a hydrothermal temperature of 90°C,solvent of ethanol+distilled water and Zn²⁺:Eu³⁺:Tb³⁺=45:4:1.MPDA:(Ca²⁺,Eu³⁺,Tb³⁺)materials,and the crystals have a square sheet shape with a side length of about 4.2μm to 5.7μm.（4）At the hydrothermal temperature of 90°C and the solvent is DMF+distilled water,a white light emitting substrate Gd-3(Gd³⁺:Eu³⁺:Tb³⁺=43:6:1)was synthesized;at the same hydrothermal temperature,the solvent was green.In the case of environmentally friendly ethanol+distilled water,a white light-emitting neodymium matrix Gd-2(Gd³⁺:Eu³⁺:Tb³⁺=44:5:1)material and a calcium matrix Ca-3(Ca²⁺:Eu³⁺:Tb³⁺=43:6:1)were also synthesized.Material and zinc matrix Zn-3(Zn²⁺:Eu³⁺:Tb³⁺=45:4:1)material,in which the calcium matrix Ca-3(Ca²⁺:Eu³⁺:Tb³⁺=43:6:1)material is amorphous and its heat The stability is not as good as that of Gd-3(Gd³⁺:Eu³⁺:Tb³⁺=43:6:1)and zinc matrix Zn-3(Zn²⁺:Eu³⁺:Tb³⁺=45:4:1)materials.Compared with the traditional inorganic white light emitting materials,the white light emission intensity of the synthesized strontium matrix,calcium matrix,and zinc matrix metal-organic framework materials is higher;and the introduction of different substrates（especially the introduction of calcium matrix and zinc matrix）,greatly The synthesis cost of the metal-organic framework material is reduced.Compared with the commonly used DMF,the solvent is ethanol+distilled water to make the preparation process more green and environmentally friendly.Therefore,the prepared ruthenium matrix,calcium matrix and zinc matrix metal-organic framework material are expected to become new types.White light emitting materials are widely used.