CN110951083A

CN110951083A - Double-rare-earth metal organic framework material based on white light emission and preparation method thereof

Info

Publication number: CN110951083A
Application number: CN201811121076.4A
Authority: CN
Inventors: 王凤勤; 张奉孝; 蒲妍燕; 赵忠瑞; 宋艾琳; 李璟玉
Original assignee: Tianjin Polytechnic University
Current assignee: Tianjin Polytechnic University
Priority date: 2018-09-26
Filing date: 2018-09-26
Publication date: 2020-04-03

Abstract

The invention relates to a preparation method of white light-emitting organic-inorganic hybrid double rare earth metal organic framework and brief description of a preparation method thereof. Experimental research results show that the metal organic framework emitting white light is synthesized by using a blue-emitting 2, 5-thiophene dicarboxylic acid organic ligand and red-emitting and green-emitting rare earth metals of europium and terbium according to a three-primary-color principle. The method is to change the molar ratio of the rare earth metal europium to the terbium to search the MOFs emitted by white light under the same excitation wavelength, and then to search the MOFs emitting the white light by using different fluorescence excitation wavelengths under the rare earth metal europium and the terbium with the same ratio.

Description

Double-rare-earth metal organic framework material based on white light emission and preparation method thereof

Technical Field

The invention belongs to the field of material science and technology, and particularly relates to a preparation method for constructing a double rare earth metal organic framework with white light emission by using 2, 5-thiophenedicarboxylic acid (L) as an organic ligand and double rare earth metals of europium and terbium.

Background

Since the first recording of fluorescence by scientists at the end of the 16 th century, luminescent materials have been widely used in various fields of human life such as illumination, display, imaging, sensing, biomarkers, and medical diagnostics. The design and development of luminescent materials with good luminescent efficiency, long lifetime, low energy consumption and high stability have received a lot of attention from physical and chemical chemists. The white light LED becomes a new generation of energy-saving light source due to the advantages of energy conservation, environmental protection, low energy consumption, long service life, high color rendering property, high light energy concentration and the like. At present, the LED white light fluorescent powder is mainly formed by combining fluorescent powder with various colors, most of the fluorescent powder is made of inorganic luminescent materials, and besides some inorganic materials, organic compounds/polymers, metal compounds and the like are also available. However, the multi-color phosphors composed of a single inorganic light emitting material and a single organic light emitting material have disadvantages of low color rendering index, poor light stability, low light emitting efficiency, etc., thereby hindering the normal commercialization development thereof. Thus, scientists have conceived overcoming long-standing deficiencies in the performance of single phosphors or organic phosphors by hybridizing inorganic and organic components.

The rare earth luminescent metal-organic frameworks (LnMOFs) have potential exploration value in the aspect of white light materials due to the special structure, the unique energy transfer process and the excellent luminescent property of the rare earth luminescent metal-organic frameworks. In the single rare earth metal organic framework material, the rare earth ions can be used as a display emitting primary colors, and the organic ligand can be used as a cross-linking agent and a sensitizer or even a light emitter for the rare earth ions. However, the emission of the single rare earth luminescent MOFs can only cover a part of the visible spectrum, and in order to overcome the limitation factor, the characteristics of different monochromatic luminescence of different rare earth ions can be combined to obtain the dual-core rare earth MOFs material with more variable luminescent colors and better controllability. For double-rare-earth MOFs, the relative luminous intensity between rare-earth ions and ligands is determined by energy transfer, and different energy transfer efficiencies in the double-rare-earth MOFs can be caused by different chemical factors (rare-earth ion types and concentrations, ligand structures, coordination states and object types) and different physical parameters (excitation wavelength and temperature), so that the luminous color of the MOFs material is changed. The double rare earth MOFs has a plurality of luminescence advantages (1) luminescence sites are more abundant, and rare earth metal ions, organic ligands, guest molecules and the like can be used as the luminescence sites of the material; (2) the light-emitting range is wide, and all the wave bands from ultraviolet to near infrared (300-; (3) the energy transfer is more varied: there is Ligand-to-Metal charge transfer (Ligand-to-Metal charge transfer), Metal-to-Ligand energy transfer (Metal-to-Metal charge transfer) and rare earth Metal ion energy transfer (Metal-to-Metal charge transfer). The energy transfer process of Ln-MOFs is changed by changing the types of rare earth ions and organic ligands, and the regulation and control of the luminescent property of the complex can be realized. The double rare earth MOFs have abundant coordinated luminescence properties, so that the double rare earth MOFs have great application values in the aspects of white light materials and temperature sensing.

The invention selects organic ligand 2, 5-thiophene dicarboxylic acid (L) with blue light emission and Eu and Tb metal ions with red light and green light emission, successfully synthesizes double rare earth metal organic framework materials with white light emission according to the three primary colors principle, and the materials have characteristic fluorescence emission and can be used for White Light Emitting Diodes (WLEDS), fluorescent probes, molecular recognition, fluorescent sensing and the like.

Disclosure of Invention

The invention aims to provide a complex of double rare earth metals europium and terbium by taking 2, 5-thiophenedicarboxylic acid (L) as an organic ligand and a preparation method thereof. The metal organic complex has stable white light emission, and the complex has wide application prospect as a novel white light emission material.

The invention provides a preparation method of a double rare earth metal organic framework material with white light emission, which comprises the following steps:

the organic ligand and the metal ion of the invention are 2, 5-thiophenedicarboxylic acid (L) and rare earth metal ions of europium and terbium respectively, and Eu (NO) is added₃)₂·6H₂O(0.0012g，0.003mmol)、Tb(NO₃)₂·6H₂O (0.1800g, 0.397mmol), 2, 5-thiophenedicarboxylic acid (L) (0.0688g, 0.4mmol) and methanol (10ml) are mixed and then placed in a sealed stainless steel reaction kettle with a polytetrafluoroethylene lining, stirred to be uniform and then placed in a constant-temperature oven, heated for three days at 120 ℃, then cooled to room temperature, and filtered to obtain colorless transparent crystals. Wherein the ratio of europium to terbium is 1: 149 and the ratio of rare earth metal ions to 2, 5-thiophenedicarboxylic acid (L) ligand is 1: 1.

The method for synthesizing the double rare earth metal organic framework for white light emission comprises the following steps: based on the three primary colors principle of white light and the international pure white light CIE chromaticity coordinates (0.3333 ), we select an organic ligand 2, 5-thiophenedicarboxylic acid (L) with blue light emission and continuously adjust the molar ratio of rare earth metal ions Eu and Tb with red light and green light emission to synthesize MOFs, and make a CIE diagram corresponding to the MOFs, thereby obtaining the rare earth metal organic skeleton required by us for white light emission. The specific operation steps are as follows:

operation step 1 obtains a series of double rare earth MOFs (Eu) by controlling the molar ratio of rare earth metal ions Eu and Tb emitted by red light and green light_xTb_1-xL) molar ratio n (Eu: Tb) of the double rare earth metal ions europium and terbium, 1: 9, 2: 8, 3: 7, 4: 6, 5: 5, 1: 14, 1: 19, 1: 99, 1: 119, 1: 149, 1: 199 (not the simplest ratio) and choosing a fluorescence excitation wavelength of 320nm see fig. 1 to find a metal-organic framework closer to the CIE coordinates of white light (0.3333 ).

Operation step 2, different fluorescence excitation wavelengths are selected for the MOFs synthesized by the rare earth metal ions europium and terbium with the same molar ratio:

we select three proportions (Eu) in a series of double rare earth MOFs_xTb_1-xL) (where n (Eu: Tb) is 1: 119, 1: 149, 1: 199) was plotted on a CIE diagram with excitation wavelengths in the range of 320-380nm to find metal-organic frameworks which are closer to the CIE coordinates (0.3333 ) of white light.

The invention is not a metal organic framework which is obtained by combining simple rare earth metal and organic ligand and emits white light, but creatively adopts a novel idea, so that the invention has the advantages of high luminous intensity, pure white color, low energy excitation, high luminous efficiency, easy dissolution in organic solvent and the like.

The invention has the following remarkable advantages: (1) the synthetic materials are terbium nitrate hexahydrate, europium nitrate hexahydrate and 2, 5-thiophenedicarboxylic acid (L), and the materials are easy to obtain, and impurities are not generated in the reaction, and the impurities are completely converted into the metal organic framework which emits white light. (2) The organic solvent is a nontoxic, green and environment-friendly methanol solution. (3) The product obtained by the reaction is easy to clean, and pure crystals can be obtained by repeating the methanol solution for 2-3 times. (4) All property tests used solvents were selected to be non-toxic ethanol solutions.

Drawings

FIG. 1 is a CIE diagram of different proportions of MOFs at the same excitation wavelength.

FIG. 2 is a CIE diagram of MOFs at the same scale at different excitation wavelengths.

Detailed Description

Example 1, the method for synthesizing a double rare earth metal organic framework comprises the following steps:

eu (NO)₃)₂·6H₂O(0.0012g，0.003mmol)、Tb(NO₃)₂·6H₂O (0.1800g, 0.397mmol), 2, 5-thiophenedicarboxylic acid (L) (0.0688g, 0.4mmol) and methanol (10ml) are mixed and then placed in a sealed stainless steel reaction kettle with a polytetrafluoroethylene lining, stirred to be uniform and then placed in a constant-temperature oven, heated for three days at 120 ℃, then cooled to room temperature, and filtered to obtain colorless transparent crystals.

Example 2 a method of modulating white light emission from a dual rare earth metal organic framework comprises:

the crystals obtained in example 1 were ground to a powder and tested for fluorescence in a spectrofluorometer F-380 by selecting the MOFs with the same excitation wavelength and different molar ratios of the rare earth metal ions europium and terbium and calculating the corresponding CIE coordinates by CIE software. A series of double rare earth MOFs (Eu)_xTb_1-x-L) wherein n (Eu: Tb) ═ 1: 9, 5: 5, 1: 19, 1: 99, 1: 119, 1: 149, 1: 199-MOF have coordinates (0.6026, 0.3236), (0.5870, 0.3164), (0.5998, 0.3246), (0.5770, 0.3232), (0.5736, 0.3450), (0.5617, 0.3448), (0.5254, 0.3601), respectively, at a fluorescence excitation wavelength of 320nm, and its CIE chromatogram is shown in fig. 1. The selection of 1: 119-MOF, 1: 149-MOF and 1: 199-MOF resulted in the measurement of corresponding CIE data in the range of 320-380nm, which have CIE coordinates (0.3456, 0.2363), (0.3652, 0.3457), (0.2863, 0.3317), (0.3137, 0.2184), (0.3333, 0.3394), (0.2664, 0.3238), (0.2946, 0.2770), (0.3219, 0.3883), (0.2761, 0.3498) at different excitation wavelengths of 340nm, 350nm and 360nm, and the corresponding CIE diagram is shown in FIG. 2. The CIE coordinates of 1: 149-MOF at 350nm (0.3333, 0.3394) are obtained as closest to those of white light (0.3333 ), and it is considered that M which gives white light emission is soughtOFs, also provides reference for finding metal organic frameworks that emit white light.

Claims

1. A complex of 2, 5-thiophenedicarboxylic acid (L) as organic ligand and double rare-earth metals europium and terbium.

2. The process for the preparation of the complex of europium and terbium as a double rare earth metal according to claim 1, characterized in that it comprises the following steps: eu (NO)₃)₂·6H₂O(0.0012g，0.003mmol)、Tb(NO₃)₂·6H₂A mixture of O (0.1800g, 0.397mmol), 2, 5-thiophenedicarboxylic acid (L) (0.0688g, 0.4mmol) and methanol (10ml) was placed in a polytetrafluoroethylene liner, reacted at 120 ℃ for 72 hours at a constant temperature, then naturally cooled to room temperature, filtered, and the resulting product was washed with methanol and dried at room temperature to give transparent crystals.

3. The method for producing a complex of europium and terbium as defined in claim 2, wherein said mixed solution is placed in an autoclave and single crystals are grown by a solvothermal method.

4. The process for preparing a complex of europium and terbium as defined in claim 2, wherein the molar ratio of the rare earth metal ions is 1: 149, and the solution is 10mL in ethanol.

5. The process for the preparation of a double rare earth metal europium and terbium complex according to claim 2, wherein said ligands L and Eu (NO)₃)₂·6H₂O and Tb (NO)₃)₂·6H₂The molar ratio of the sum of the two is 1: 1.