A cerium-based metal-organic framework material emitting white light and a preparation method and application thereof

Abstract

The present application belongs to the technical field of luminescent materials, and relates to a cerium metal-organic framework for white light emission and a preparation method and application thereof, to solve the problems that traditional white light LED needs to utilize multiple metal composites or multiple matrix composites and be sintered at high temperature to obtain multi-color fluorescent powder, and needs to be matched with corresponding LED chips to emit white light, and the corresponding preparation conditions are complex and the cost is high. 4,4'-(1H-pyrazole-1,3-diyl)dibenzoic acid is added into N,N-dimethylformamide; cerium salt is added into water; then the above two solutions are mixed and nitric acid is added, and hydrothermal reaction is carried out to obtain the cerium metal-organic framework material for white light emission. The preparation method disclosed by the present application is simple and has a high yield (>=82%). The prepared cerium metal-organic framework material can realize full-spectrum white light emission of a single matrix and a single metal ion, and the luminescent color coordinate value is close to the white light emission region (0.33, 0.33).

Description

Technical Field

[0001] This invention belongs to the field of luminescent materials technology, and relates to a method for preparing and applying a cerium-based metal-organic framework that emits white light. Background Technology

[0002] White-light-emitting diodes (WLEDs) possess numerous advantages such as long lifespan, high efficiency, and small size, making them one of the most ideal light-emitting elements currently available. There are two main methods for fabricating white LEDs: one is to combine LED chips of different emitting colors to obtain white light. This method requires multiple colors of phosphors and chips, and the power of different chips varies, making the circuit design more complex and costly. The other method is to combine blue or ultraviolet LED chips with corresponding phosphors. For example, using ultraviolet LED chips with phosphors emitting blue, green, and red light can produce white LEDs; or using blue LED chips with yellow phosphors can also produce white LEDs. White LEDs fabricated using this method have higher efficiency. For instance, Feng et al. synthesized YAG:Ce using a high-temperature solid-state method. 3+ Yellow fluorescent material was studied using orthogonal analysis to investigate the effects of calcination time, calcination temperature, and Ce. 3+ The effect of Ce concentration on the luminescence intensity of phosphor. At a calcination temperature of 1600 ℃, Ce... 3+ The phosphor exhibited the best luminescence performance under the conditions of a concentration of 0.12 mol and a calcination time of 4 h. When boric acid was used as a flux, a concentration of 1.2 wt% increased the luminescence intensity of the phosphor by approximately 40%. (YAG:Ce) 3+ The phosphor exhibits a bimodal excitation peak, with the maximum excitation peak at 467 nm and the maximum emission peak at 529 nm. Therefore, YAG:Ce 3+ Yellow phosphors can be matched with blue GaN chips to prepare dual-color LEDs. However, different colored phosphors are still required, and traditional phosphor preparation methods all require high-temperature sintering, resulting in complex preparation conditions (Feng Ying, Tong Yiping, Xie Fang, et al., YAG:Ce for white LEDs). 3+ Synthesis and Luminescent Properties of Phosphors [J]. Guangzhou Chemical Industry, 2019, 47(10):69-71+84. Therefore, the preparation of full-spectrum white light emitting phosphors using a simple method is of great research significance. Summary of the Invention

[0003] To address the technical problems of existing white LED technologies, which require multi-metal or multi-matrix composites and high-temperature sintering to produce multi-color phosphors, and which necessitate matching with corresponding LEDs to emit white light, as well as the complex preparation conditions and high costs associated with these processes, this invention proposes a method for preparing and applying a cerium-based metal-organic framework for white light emission. The cerium-based metal-organic framework material of this invention is synthesized in one step via a hydrothermal method, which is simple, yields high output, and can achieve full-spectrum white light emission from a single matrix and a single metal ion.

[0004] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0005] A method for preparing a cerium-based metal-organic framework material that emits white light, comprising the following steps:

[0006] (1) Add 4,4'-(1H-pyrazole-1,3-diyl)dibenzoic acid to N,N-dimethylformamide to form a 4,4'-(1H-pyrazole-1,3-diyl)dibenzoic acid solution;

[0007] (2) Add cerium salt to water to form a cerium salt solution;

[0008] (3) After mixing the 4,4'-(1H-pyrazole-1,3-dimethyl)dibenzoic acid solution obtained in step (1) and the cerium salt solution obtained in step (2), nitric acid is added and hydrothermal reaction is carried out to obtain a cerium-based metal-organic framework material that emits white light.

[0009] The concentration of the 4,4'-(1H-pyrazole-1,3-dimethyl)dibenzoic acid solution in step (1) is 13.3~40 mg / mL.

[0010] In step (2), the cerium salt is any one of cerium chloride, cerium acetate, or cerium nitrate. The cerium chloride is cerium chloride hexahydrate, and the cerium nitrate is cerium nitrate hexahydrate.

[0011] The concentration of the cerium salt solution in step (2) is 1.5~2.7 mg / mL.

[0012] In step (3), the mass ratio of 4,4'-(1H-pyrazole-1,3-diyl)dibenzoic acid to cerium salt is 1:(0.95~1.3).

[0013] In step (3), the volume ratio of 4,4'-(1H-pyrazole-1,3-dimethyl)dibenzoic acid solution, cerium salt solution and nitric acid is (0.5~1.5):(10~12):(0.1~0.15), wherein the mass fraction of nitric acid is 68%.

[0014] The temperature of the hydrothermal reaction in step (3) is 150~180 ℃.

[0015] The hydrothermal reaction in step (3) takes 72 to 96 hours. The hydrothermal reaction is carried out in a reactor that has the function of setting the temperature and time.

[0016] The white-light-emitting cerium-based metal-organic framework material prepared by the above method is a colorless prismatic crystal with an ordered crystal structure. It belongs to the monoclinic crystal system, space group P21 / c, and has the following cell parameters: a = 17.4278(5) / Å, b = 12.1359(3) / Å, c = 7.4214(2) / Å, α = 90°, β = 92.644°, γ = 90°, and V = 1567.97(7) / Å. 3 Z=4.

[0017] The application of the white light-emitting cerium-based metal-organic framework material in white light-emitting diodes.

[0018] The present invention has the following beneficial effects:

[0019] 1. Metal-organic frameworks (MOFs) are novel organic-inorganic hybrid materials with abundant functional sites, and they have wide applications in many fields. Among them, rare earth elements (Ce) are used in this invention. 3+ Organic framework materials combine the framework structure of MOFs with the luminescent properties of rare earth ions, exhibiting unique advantages in white light emission, specifically:

[0020] (1) The metal-organic framework (MOF) materials prepared by this invention have abundant luminescent sites. Both organic ligands used to construct the framework materials and rare earth ions can be used as luminescent units.

[0021] (2) Rare earth ions (Ce 3+ It possesses a rich energy level structure, with organic ligands (4,4'-(1H-pyrazole-1,3-dimethyl)dibenzoic acid) and rare earth ions (Ce). 3+ Effective energy transfer can occur between cerium and ligands, enabling rare-earth-organic framework materials to exhibit excellent luminescence properties (characteristic emission spectra and high luminescence efficiency). Specifically, in this invention, the characteristic emission of cerium is around 400 nm, belonging to the 5d-4f transition. The white light emission of MOFs synthesized with this ligand (4,4'-(1H-pyrazole-1,3-diyl)benzoic acid) is due to the high energy level matching between the two, enabling effective energy transfer. Therefore, the synthesized cerium-based metal-organic framework material can achieve full-spectrum white light emission; not every cerium and every ligand can emit white light. Furthermore, traditional white LEDs require multi-color phosphors, thus requiring multiple matrices and metal ions, while the cerium-based metal-organic framework material of this invention only requires one metal ion (Ce). 3+By combining it with an organic ligand (4,4'-(1H-pyrazole-1,3-dimethyl)dibenzoic acid), white light emission from a single matrix and a single metal ion can be achieved.

[0022] (3) In this invention, cerium is the most abundant rare earth metal among the lanthanides, which greatly reduces the cost of using cerium-based metal-organic framework materials for white LEDs.

[0023] 2. In this invention, the cerium-based metal-organic framework material prepared can achieve white light emission under ultraviolet light excitation (320nm excitation), with its color coordinates close to white light (0.33, 0.33) and a uniform spectral distribution. Furthermore, during the experiment, only minor adjustments to the experimental conditions (changing the amount of solvent, reaction temperature, and time) are needed to adjust the white light emission (the emission color coordinates can be adjusted from (0.33, 0.36) to (0.32, 0.32), (0.31, 0.32), or (0.31, 0.31)).

[0024] 3. The cerium-based metal-organic framework material of this invention is synthesized in one step via a hydrothermal method, which is simple, has a high yield (≥82%), and high reproducibility. It solves the technical problem that traditional white LEDs require multi-metal composites or multi-matrix composites and high-temperature sintering to produce multi-color phosphors (complex preparation conditions and high costs), and require corresponding LED chips to emit white light. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 The image shows the XRD pattern of the cerium-based metal-organic framework material synthesized in Example 1 of this invention.

[0027] Figure 2 The fluorescence spectrum of the cerium-based metal-organic framework material synthesized in Example 1 of this invention is shown.

[0028] Figure 3 This is the color coordinate diagram of the cerium-based metal-organic framework material synthesized in Example 1 of the present invention.

[0029] Figure 4 The image shows the XRD pattern of the cerium-based metal-organic framework material synthesized in Example 2 of this invention.

[0030] Figure 5The fluorescence spectrum of the cerium-based metal-organic framework material synthesized in Example 2 of this invention is shown.

[0031] Figure 6 This is the color coordinate diagram of the cerium-based metal-organic framework material synthesized in Example 2 of the present invention.

[0032] Figure 7 The fluorescence spectrum of the cerium-based metal-organic framework material synthesized in Example 3 of this invention is shown.

[0033] Figure 8 This is the color coordinate diagram of the cerium-based metal-organic framework material synthesized in Example 3 of the present invention.

[0034] Figure 9 The fluorescence spectrum of the cerium-based metal-organic framework material synthesized in Example 4 of this invention is shown.

[0035] Figure 10 This is the color coordinate diagram of the cerium-based metal-organic framework material synthesized in Example 4 of the present invention. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] The 4,4'-(1H-pyrazole-1,3-diyl)benzoic acid used in this invention was purchased from Jinan Henghua Technology Co., Ltd., product number 160112MA-3E. All other raw materials were commercially available products, and the nitric acid used had a mass fraction of 68%. The cerium acetate used in this invention has the CAS number 537-00-8; the cerium nitrate is cerium nitrate hexahydrate, with the CAS number 10294-41-4; and the cerium chloride is cerium chloride hexahydrate, with the CAS number 16651-27-7.

[0038] Example 1

[0039] A method for preparing a cerium-based metal-organic framework material that emits white light includes the following steps:

[0040] 20 mg of 4,4'-(1H-pyrazole-1,3-dimethyl)benzoic acid was added to 0.5 mL of N,N-dimethylformamide, and 26 mg of cerium nitrate hexahydrate was added to 10 mL of H2O. The two solutions were then mixed, and 100 μL of nitric acid was added. The mixture was then transferred to a reaction vessel and reacted at 180 °C for 72 h to obtain colorless rhombic crystals with a yield of 82%.

[0041] The cerium-based metal-organic framework material prepared in this embodiment is monoclinic with space group P21 / c and cell parameters a = 17.4278(5) / Å, b = 12.1359(3) / Å, c = 7.4214(2) / Å, α = 90°, β = 92.644°, γ = 90°, and V = 1567.97(7) / Å. 3 Z=4.

[0042] Figure 1 The image shows the XRD pattern of the cerium-based metal-organic framework material prepared in Example 1 of this invention. As can be seen from the image, the diffraction peaks of the synthesized sample are consistent with the results simulated by single-crystal diffraction data, which proves that the synthesized sample has high phase purity.

[0043] Figure 2 The fluorescence spectrum of the cerium-based metal-organic framework material synthesized in Example 1 of this invention is shown. Under 320 nm excitation, the emission spectrum of this material is in the range of 350-700 nm, with the main peaks at 390 nm and 560 nm, both of which are attributed to the emission of cerium ions.

[0044] Figure 3 The color coordinate diagram of the cerium-based metal-organic framework material synthesized in Example 1 of this invention is shown. Its emission color coordinates are (0.33, 0.36), indicating that the emission of the sample is located in the white light region.

[0045] Example 2

[0046] A method for preparing a cerium-based metal-organic framework material that emits white light includes the following steps:

[0047] 20 mg of 4,4'-(1H-pyrazole-1,3-dimethyl)benzoic acid was added to 1 mL of N,N-dimethylformamide, and 19 mg of cerium acetate was added to 12 mL of H2O. The two solutions were then mixed, followed by the addition of 150 μL of nitric acid. The mixture was then transferred to a reaction vessel and reacted at 150 °C for 96 h to obtain colorless rhombic crystals with a yield of 82%.

[0048] Figure 4 The image shows the XRD pattern of the cerium-based metal-organic framework material prepared in Example 2 of this invention. As can be seen from the image, the diffraction peaks of the synthesized sample are consistent with the results simulated by single-crystal diffraction data, which proves that the synthesized sample has high phase purity.

[0049] Figure 5The fluorescence spectrum of the cerium-based metal-organic framework material prepared in Example 2 of this invention is shown. Under 320 nm excitation, the emission spectrum of this material is in the range of 350-700 nm, with the main peaks at 390 nm and 560 nm, both of which are attributed to the emission of cerium ions.

[0050] Figure 6 The color coordinate diagram of the cerium-based metal-organic framework material prepared in Example 2 of the present invention is shown. Its emission color coordinates are (0.32, 0.32), indicating that the emission of the sample is located in the white light region.

[0051] Example 3

[0052] A method for preparing a white light-emitting cerium-based metal-organic framework material includes the following steps:

[0053] 20 mg of 4,4'-(1H-pyrazole-1,3-dimethyl)benzoic acid was added to 1.5 mL of N,N-dimethylformamide, and 21 mg of cerium chloride hexahydrate was added to 12 mL of H2O. The two solutions were then mixed, followed by the addition of 150 μL of nitric acid. The mixture was then transferred to a reaction vessel and reacted at 160 °C for 96 h to obtain colorless rhombic crystals with a yield of 85%.

[0054] Figure 7 The fluorescence spectrum of the cerium-based metal-organic framework material synthesized in Example 3 of this invention is shown. Under 320 nm excitation, the emission spectrum of this material is in the range of 350-700 nm, with the main peaks at 390 nm and 560 nm, both of which are attributed to the emission of cerium ions.

[0055] Figure 8 The color coordinate diagram of the cerium-based metal-organic framework material synthesized in Example 3 of the present invention is shown. Its emission color coordinates are (0.31, 0.32), indicating that the emission of the sample is located in the white light region.

[0056] Example 4

[0057] A method for preparing a white light-emitting cerium-based metal-organic framework material includes the following steps:

[0058] 20 mg of 4,4'-(1H-pyrazole-1,3-dimethyl)benzoic acid was added to 1 mL of N,N-dimethylformamide, and 20 mg of cerium chloride hexahydrate was added to 10 mL of H2O. The two solutions were then mixed, followed by the addition of 100 μL of nitric acid. The mixture was then transferred to a reaction vessel and reacted at 180 °C for 96 h to obtain colorless rhombic crystals with a yield of 86%.

[0059] Figure 9The fluorescence spectrum of the cerium-based metal-organic framework material synthesized in Example 4 of this invention is shown. Under 320 nm excitation, the emission spectrum of this material is in the range of 350-700 nm, with the main peaks at 390 nm and 560 nm, both of which are attributed to the emission of cerium ions.

[0060] Figure 10 The color coordinate diagram of the cerium-based metal-organic framework material synthesized in Example 4 of this invention is shown. Its emission color coordinates are (0.31, 0.31), indicating that the emission of the sample is located in the white light region.

[0061] Example 5

[0062] A method for preparing a cerium-based metal-organic framework material that emits white light includes the following steps:

[0063] 20 mg of 4,4'-(1H-pyrazole-1,3-dimethyl)benzoic acid was added to 0.9 mL of N,N-dimethylformamide, and 25 mg of cerium nitrate hexahydrate was added to 11 mL of H2O. The two solutions were then mixed and 120 μL of nitric acid was added. The mixture was then transferred to a reaction vessel and reacted at 170 °C for 84 h to obtain colorless rhombic crystals with a yield of 86%.

[0064] Through the above Examples 1-5, it was verified that the energy levels of cerium and organic ligands of the present invention are highly matched, enabling effective energy transfer. Therefore, the synthesized cerium-based metal-organic framework material can achieve full-spectrum white light emission. Traditional white LEDs require multi-color phosphors, thus requiring multiple matrices and metal ions. However, the cerium-based metal-organic framework material of the present invention only requires the selection of one metal ion and a rare earth salt to achieve white light emission from a single matrix and a single metal ion.

[0065] The cerium-based metal-organic framework material of the present invention can achieve white light emission under ultraviolet light excitation, with emission color coordinates close to (0.33, 0.33) and uniform spectral distribution.

[0066] The cerium-based metal-organic framework material of the present invention is synthesized in one step by hydrothermal method, which is simple, has a high yield, and is highly reproducible.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a cerium-based metal-organic framework material that emits white light, characterized in that, The steps are as follows: (1) Add 4,4'-(1H-pyrazole-1,3-diyl)benzoic acid to N,N-dimethylformamide to form a 4,4'-(1H-pyrazole-1,3-diyl)benzoic acid solution; the concentration of the 4,4'-(1H-pyrazole-1,3-diyl)benzoic acid solution is 13.3~40 mg / mL; (2) Add cerium salt to water to form a cerium salt solution; the concentration of the cerium salt solution is 1.5~2.7 mg / mL; (3) After mixing the 4,4'-(1H-pyrazole-1,3-dimethyl)dibenzoic acid solution obtained in step (1) and the cerium salt solution obtained in step (2), nitric acid is added and hydrothermal reaction is carried out to obtain cerium-based metal-organic framework material with white light emission; the hydrothermal reaction temperature is 150~180 ℃; the hydrothermal reaction time is 72~96 h.

2. The method for preparing the white light-emitting cerium-based metal-organic framework material according to claim 1, characterized in that: In step (2), the cerium salt is any one of cerium chloride, cerium acetate, or cerium nitrate.

3. The method for preparing the white light-emitting cerium-based metal-organic framework material according to claim 1, characterized in that: In step (3), the mass ratio of 4,4'-(1H-pyrazole-1,3-dimethyl)dibenzoic acid to cerium salt is 1:(0.95~1.3).

4. The method for preparing the white light-emitting cerium-based metal-organic framework material according to claim 3, characterized in that: In step (3), the volume ratio of 4,4'-(1H-pyrazole-1,3-dimethyl)dibenzoic acid solution, cerium salt solution and nitric acid is (0.5~1.5):(10~12):(0.1~0.15), wherein the mass fraction of nitric acid is 68%.

5. A cerium-based metal-organic framework material emitting white light, prepared by the method according to any one of claims 1-4, characterized in that: The white-light-emitting cerium-based metal-organic framework material has an ordered crystal structure, belonging to the monoclinic crystal system, with space group P21 / c, and cell parameters a=17.4278(5) / Å, b=12.1359(3) / Å, c=7.4214(2) / Å; α=90°, β=92.644°, γ=90°; V=1567.97(7) / Å 3 Z=4.

6. The application of the cerium-based metal-organic framework material emitting white light as described in claim 5 in white light-emitting diodes.

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