Preparation,Luminescence Properties And Application Studies Of Multicomponent Ln-MOFs

Lanthanide metal-organic frameworks（Ln-MOFs）,self-assembled by lanthanide metal ions(Ln³⁺)and organic ligands,are a novel organic-inorganic hybrid luminescence material.As luminescence center,Ln³⁺ions endow MOFs excellent luminescence properties,such as characteristic emission,long luminescence lifetime and Stokes shift,high color purity of Ln³⁺ions.It is more important that the"Antenna effect"in MOFs overcomes the low luminous efficiency caused by the f-f transition barrier of Ln³⁺ions.It is more importantly that various luminescent sites and energy transfer processes can realize the tuning of luminescent colors and even white light emission in Ln-MOFs.Therefore,Ln-MOFs are considered as one of the most promising high-quality luminescent materials in WLED（white light emitting diode）applications.In this thesis,the 5-（4-carboxyphe-noxy）-isophthalic acid was selected as the first ligand,phen was used as the second ligand to synthesize two kinds of red-emitting Ln-MOFs:the binary Eu（cpioa）MOFs and the ternary Eu（cpioa）phen MOFs.In addition,to further prove the application potential of Ln-MOFs in WLED,a series of isostructural Ln-MOFs:Ln（cpioa）,Tb（cpioa）:x Eu³⁺and La_1-y-xTb_yEu_x（cpioa）（Ln=La,Eu,Tb）,are synthesized by the spontaneous self-assembly of Ln³⁺ions with H₃cpioa ligands.The structure,performance and application of Ln-MOFs are studied in detail by XRD,XPS,EDS,FT-IR,PL,QY,LT and CIE.The main research contents and conclusions are as follows:（1）A novel ternary Eu（III）metal–organic framework Eu（cpioa）phen（H₃cpioa:5-（4-carboxy-lphenoxy）-isophthalic,phen:1,10-phenanthroline monohydrate）was synthesized by a facile hydrothermal method.Structural and optical properties of the binary and ternary Eu（III）MOFs were studied in detail.Results show that,compared with the binary Eu（cpioa）MOF,the photoluminescence intensity of the ternary Eu（cpioa）phen MOFs is increased by 13.04 times,the quantum efficiency is increased by 67.2%,and the corresponding LED also have stronger red-light emission.The major possible reason for the highly improved photoluminescence properties might be due to the antenna effect induced by the addition of phen.Also,the highly improved crystallinity may also contribute to the greatly increased photoluminescence intensity and quantum efficiency.（2）The isostructural lanthanide metal-organic frameworks（MOFs）are synthesized by the spontaneous self-assembly of lanthanide ions(Ln=La³⁺,Tb³⁺and Eu³⁺)with H₃cpioa（5-（4-carboxy-lphenoxy）-isophthalic）ligands.Based on the detailed study on the structural properties,it’s found that different Ln³⁺ions have identical coordination environment in Ln-MOFs.By adjustment of the molar ratio of Ln³⁺ions,the chromaticity of Ln（cpioa）MOFs can be easily modulated.La_0.9Tb_0.093Eu_0.007（cpioa）（CIE coordinate:（0.319,0.331））shows a white emission very close to pure white-light（0.333,0.333）with a high quantum yields of 54.74%.Furthermore,corresponding white LED devices were fabricated,which indicates Ln（cpioa）MOFs might be a promising candidate phosphor for the WLED applications.In summary,Ln-MOFs,prepared by hydrothermal method,obtained a red phosphor with highly improved luminescence performance by introducing the second ligand.In addition,the chromaticity of Ln-MOFs（Ln=La,Tb,Eu）can be easily modulated and white light emitting materials can be easily achieved by the molar ratio of different Ln³⁺ions.