A novel rare earth metal organic framework material, preparation method and application

Abstract

The application belongs to the technical field of new materials, and discloses a novel rare earth metal organic framework material, a preparation method and application. 10 The basic building unit of the novel rare earth metal organic framework material has a chemical formula of C5H5O 3+ Ln, denoted as Ln-MOFs, takes formic acid HCOOH as a unique organic ligand. The preparation method of the Ln-MOFs is to utilize the chemical reaction that formamide gradually generates ammonia and formic acid by reacting with water when heated; in a heating and self-generated pressure environment, the deprotonated formic acid and rare earth Ln 3+ ions self-assemble to generate the Ln-MOFs with a novel structure. The application effectively reduces the generation of by-products and improves the purity of the Ln-MOFs material by optimizing the reaction conditions, adjusting the precursor ratio and adopting multiple washing and other post-processing steps, and can further prepare room temperature phosphor materials, which are applied to the fields of fluorescent / afterglow dual-mode optical anti-counterfeiting and information security storage.

Description

Technical Field

[0001] The present invention relates to the technical field of new materials, and in particular to a novel rare earth metal organic framework material, a preparation method and an application thereof. Background Art

[0002] Metal-organic frameworks (MOFs) are materials constructed from metal ions or metal clusters and organic ligands. Due to their unique inorganic-organic hybrid network, extremely high specific surface area, controllable pore size, and excellent thermal and chemical stability, they have broad applications in sensing, catalysis, drug delivery, gas adsorption and separation. By designing and selecting different ligands and metal ions, MOFs with diverse structures can be obtained, with their internal pore sizes and channels modified to suit diverse application needs. Lanthanide metal organic frameworks (Ln-MOFs) are a key branch of the MOF family. Due to the larger ionic radius of rare earth ions, they offer more complex and versatile structures, enabling them to meet a wider range of requirements. Furthermore, designed Ln-MOFs can absorb external energy through their ligands and transfer it to the rare earth ions, resulting in the emission of the characteristic luminescence of the rare earth ions with a long lifetime, sharp emission peak, and high quantum yield. These MOFs are widely used in optical applications such as light-emitting diodes, optical information storage, and optical anti-counterfeiting.

[0003] However, there are still many technical difficulties in the design and industrial production of MOFs products for specific uses and performance. The current synthesis method of MOFs is mainly the solvent thermal method, which usually involves directly mixing the screened ligands and metal salts in a solution, and then conducting a long reaction in a high-temperature and high-pressure reactor. The reaction conditions are relatively harsh and require a high-temperature and high-pressure environment. The synthesis process is complex, risky, and requires high equipment, which greatly limits the industrial application of MOFs materials. The existing ultrasonic synthesis method is to ultrasonically treat a mixture of metal salts and organic ligands in a solvent, and use the cavitation effect generated by ultrasound to promote the reaction. The reaction conditions are mild, the operation is simple, and small-sized MOFs crystals can be prepared, but there is a problem of low purity of the synthesized MOFs material.

[0004] Therefore, it is necessary to explore reliable targeted MOFs product design methods and safe, simple, and high-purity MOFs material synthesis methods. Summary of the Invention

[0005] The present invention addresses the deficiencies in the prior art regarding existing methods for synthesizing rare earth metal organic framework materials. The purpose of the present invention is to provide novel rare earth metal organic framework materials, preparation methods, and applications. By simultaneously improving targeted MOFs product design methods and material synthesis methods, optimizing reaction conditions, adjusting precursor ratios, and employing post-processing steps such as multiple washings, the generation of by-products is effectively reduced and the purity of Ln-MOFs materials is improved, thereby achieving the goal of obtaining high-purity MOFs materials under safe and simple reaction conditions to meet the needs of industrial production.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A new type of rare earth metal organic framework material, the chemical formula of its basic building block is C5H5O 10 Ln, denoted as Ln-MOFs, uses formic acid (HCOOH) as the only organic ligand.

[0008] This new rare earth metal organic framework material belongs to the orthorhombic system with a space group of C2221. The asymmetric unit of Ln-MOFs contains a crystallographically independent Ln 3+ ion, three coordinated bridged HCOO - ligand and a free formic acid molecule; each rare earth (Ln 3+ ) ion is coordinated with eight oxygen atoms, all of which belong to the deprotonated formic acid molecule; Ln 3+ Ions and HCOO - Ligands bridge to form a three-dimensional framework structure; along the crystal axis a, the Ln-MOFs framework presents one-dimensional open channels; in the original sample, uncoordinated HCOOH molecules occupy these channels; the framework is simplified to an 8-connected single-node network, with the dot symbol 3 6 .4 15 .5 7 , which belongs to the ecu topology type.

[0009] A method for preparing the novel rare earth metal organic framework material is characterized in that it comprises the following steps:

[0010] (1) Weigh a set amount of rare earth salt and add it to a glass bottle. Then, add formamide and deionized water in a set ratio. Place the glass bottle in an ultrasonic oscillator and perform ultrasonic treatment at a temperature of 20 to 30 °C for 25 minutes. The ultrasonic frequency is set to 40 kHz until the solution in the bottle becomes clear and transparent, forming a uniform first dispersion.

[0011] (2) The glass bottle containing the first dispersion in step (1) is sealed and placed in an oven. The reaction is carried out at 95°C for 10 to 24 hours. The mixture is cooled to room temperature and the resulting block crystals are collected by filtration. The block crystals are washed three times with formamide and anhydrous ethanol respectively. The block crystals are dried in a vacuum drying oven for 6 hours at a temperature of 70 to 80°C to obtain high-purity Ln-MOFs material.

[0012] The rare earth salt in step (1) is one of rare earth nitrate and rare earth chloride. 3+ 、La 3 + 、Ce 3+ 、Pr 3+ 、Nd 3+ 、Sm 3+ 、Eu 3+ 、Gd 3+ , Tb 3+ 、Dy 3+ 、Ho 3+ 、Er 3+ 、Tm 3+ 、Yb 3+ 、Lu 3+ One, two or more of.

[0013] In step (1), the amount of formamide is 5 to 10 mL, and the amount of deionized water is 0.05 to 0.1 mL relative to 0.8 to 1.2 mmol of rare earth salt.

[0014] The synthesis method in step (2) utilizes a formamide hydrolysis reaction, specifically, formamide reacts with water under heating conditions to generate ammonia (NH3) and formic acid, respectively.

[0015] One application of the aforementioned new rare earth metal organic framework material is to use Ln-MOFs to encapsulate the dye 4,4'-bipyridine (4,4'-bipyridine) to prepare a room temperature phosphorescent material, labeled Ln-MOFs-biby.

[0016] A method for preparing the dye-encapsulated Ln-MOFs-biby phosphorescent material is synthesized using a "one-pot method" and comprises the following steps:

[0017] S1. Weigh a predetermined amount of rare earth salt and dye 4,4'-bipyridine and add them to a glass bottle. Then, add formamide and deionized water in a predetermined ratio. Place the glass bottle in an ultrasonic oscillator and perform sonication at a temperature of 20-30°C for 25 minutes at a frequency of 40 kHz until the solution in the bottle becomes clear and transparent, forming a uniform second dispersion.

[0018] S2. Seal the glass bottle containing the first dispersion in step S1, place it in an oven, react at 95°C for 10 to 24 hours, cool it to room temperature, and collect the resulting block crystals by filtration; wash them with formamide and anhydrous ethanol, respectively; and dry them in a vacuum drying oven for 6 hours at a temperature of 70 to 80°C to obtain the dye-encapsulated Ln-MOFs-biby phosphorescent material.

[0019] In step (3), relative to 0.8 to 1.2 mmol of the rare earth salt, the amount of the dye 4,4'-bipyridine is 0.8 to 1.6 mmol, the amount of formamide is 5 to 10 mL, and the amount of deionized water is 0.05 to 0.1 mL.

[0020] In the step (4), the obtained crystals are washed with formamide and anhydrous ethanol respectively until the filtrate emits no blue light under ultraviolet light (365 nm ultraviolet light irradiates the dye 4,4'-bipyridine, which will emit blue light).

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The novel rare earth metal organic framework material, preparation method and application provided by the present invention, through the simultaneous improvement of targeted MOFs product design method and material synthesis method, optimizes reaction conditions, adjusts precursor ratio and adopts the effective combination of post-processing steps such as multiple washing, effectively reduces the formation of by-products and improves the purity of Ln-MOFs material, realizes the acquisition of high-purity MOFs material under safe and simple reaction conditions, and meets the needs of industrial production.

[0023] 2. The novel rare earth metal organic framework material provided by the present invention is composed of formamide and Ln 3+ The MOFs were synthesized by a solvothermal reaction. Due to the extremely strong volatility and hygroscopicity of formic acid, there have been no reports of MOFs formed with formic acid as the sole ligand with rare earth ions. Our method cleverly and effectively utilizes the chemical reaction of formamide gradually reacting with water to produce ammonia and formic acid during heating. Under the conditions of heating and autogenous pressure, the deprotonated formic acid and Ln 3+ The ions self-assembled to form Ln-MOFs, and the bulk crystals successfully collected from the bottom of the reaction vessel were named Ln-MOFs. This strategy of the invention provides a new method for the synthesis of rare earth metal organic frameworks, and the synthesized MOFs material is high in purity.

[0024] 3. The novel rare earth metal organic framework material and preparation method provided by the present invention are self-assembled and synthesized in a glass bottle under low-temperature solvent thermal conditions. The method has simple steps, convenient operation, easy control of reaction conditions, low cost, high repeatability of the obtained product, no pollution to the environment, and is easy to industrialize.

[0025] 4. The novel rare earth metal organic framework material provided by the present invention has high purity, good repeatability, environmental friendliness, stable structure and performance, and has abundant and stable pores. It is suitable as a carrier for gases, quantum dots, nanoparticles, organic small molecule drugs or dyes, etc., and has broad application prospects in many fields such as catalysis, adsorption separation, optics, electricity, and magnetism.

[0026] 5. The dye-encapsulated Ln-MOFs phosphorescent material and preparation method provided by the present invention are synthesized in a "one-pot" method under low-temperature solvent thermal conditions. The process is simple, the conditions are relatively loose, the cost is low, the repeatability is good, it is environmentally friendly, and it can be produced in large quantities.

[0027] 6. The dye-encapsulated Ln-MOFs-biby phosphorescent material provided by the present invention has good reproducibility, is environmentally friendly, and has stable structure and performance. Ln-MOFs are particularly well-suited for encapsulating the dye 4,4'-bipyridine, improving the dye's stability and reducing its non-radiative relaxation, resulting in a long-lasting room-temperature phosphorescent material. Lu-MOFs-bipy, the resulting material after encapsulating 4,4'-bipyridine in a lutetium (Lu) metal-organic framework, emits visible blue light under UV light at room temperature and continues to emit green phosphorescent light even after the UV light is turned off. This material has broad applications in fluorescence / afterglow dual-mode optical anti-counterfeiting, information security, and storage.

[0028] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The three-dimensional framework structure and topological structure of the Lu-MOFs material obtained in Example 1 of the present invention;

[0030] Figure 2 The powder X-ray diffraction pattern of the Lu-MOFs material obtained in Example 1 of the present invention and the diffraction pattern simulated based on single crystal data;

[0031] Figure 3 1 is a fluorescence spectrum of Lu-MOFs and Lu-MOFs-bipy materials obtained in Examples 1 and 2 of the present invention respectively under 365 nm light source excitation;

[0032] Figure 4This is a phosphorescence spectrum of the Lu-MOFs-bipy material obtained in Example 2 of the present invention under 365 nm light source excitation;

[0033] Figure 5 This is a fluorescence spectrum of the Lu-25%Eu-MOFs material obtained in Example 7 of the present invention under excitation of a 365 nm light source. DETAILED DESCRIPTION

[0034] Basic Example

[0035] A new type of rare earth metal organic framework material, the chemical formula of its basic building block is C5H5O 10 Ln, denoted as Ln-MOFs, uses formic acid HCOOH as the only organic ligand. The framework of this material is an 8-connected single-node network with a dot symbol of 3 6 .4 15 .5 7 , belonging to the ecu topology; the material belongs to the orthorhombic system with a space group of C2221; the asymmetric unit of Ln-MOFs contains a crystallographically independent rare earth Ln 3+ ion, three coordinated bridged HCOO - ligand and a free formic acid molecule; each Ln 3+ The ion is coordinated with eight oxygen atoms, all of which belong to the deprotonated formic acid molecule; Ln 3+ Ions and HCOO - The ligands bridge to form a three-dimensional framework structure; along the a crystal axis, the Ln-MOFs framework presents one-dimensional open channels, and the uncoordinated HCOOH molecules occupy the multiple one-dimensional open channels.

[0036] The preparation method of the novel rare earth metal organic framework material comprises the following steps:

[0037] (1) Weigh a set amount of rare earth salt and add it to a glass bottle. Then, add formamide and deionized water in a set ratio. Place the glass bottle in an ultrasonic oscillator and perform ultrasonic treatment (ultrasonic treatment conditions are: temperature 20-30°C, time 25 minutes, and ultrasonic frequency set to 40 kHz) until the solution in the bottle becomes clear and transparent, forming a uniform first dispersion.

[0038] The rare earth salt is one of rare earth nitrate and rare earth chloride;

[0039] The rare earth ion is Y 3+ 、La 3+ 、Ce 3+ 、Pr 3+ 、Nd 3+ 、Sm 3+ 、Eu 3+ 、Gd3+ , Tb 3+ 、Dy 3+ 、Ho 3+ 、Er 3+ 、Tm 3+ 、Yb 3+ 、Lu 3+ One, two or more of the following;

[0040] For each 0.8 to 1.2 mmol of rare earth salt, the amount of formamide used is 5 to 10 mL, and the amount of deionized water used is 0.05 to 0.1 mL.

[0041] (2) The glass bottle containing the first dispersion is sealed and placed in an oven. The glass bottle is allowed to react at 95°C for 10 to 24 hours. The hydrolysis reaction of formamide is used to react formamide with water under heating conditions to generate ammonia and formic acid to synthesize block crystals. The block crystals are then cooled to room temperature and collected by filtration. The block crystals are washed three times with formamide and anhydrous ethanol respectively. Finally, the block crystals are dried in a vacuum drying oven for 6 hours at a temperature of 70 to 80°C to obtain high-purity Ln-MOFs materials.

[0042] The application of the novel rare earth metal organic framework material is to use Ln-MOFs to encapsulate the dye 4,4'-bipyridine (4,4'-bipyridine) to prepare a room temperature phosphorescent material, labeled Ln-MOFs-biby. Specifically, the "one-pot method" is used to synthesize the encapsulated dye Ln-MOFs-biby phosphorescent material, including the following steps:

[0043] S1: Weigh a predetermined amount of rare earth salt and dye 4,4'-bipyridine into a glass bottle. Then, add formamide and deionized water in the predetermined ratio. Place the glass bottle in an ultrasonic oscillator and sonicate at a temperature of 20-30°C for 25 minutes at a frequency of 40 kHz until the solution in the bottle becomes clear and transparent, forming a uniform second dispersion.

[0044] The amount of dye 4,4'-bipyridine is 0.8 to 1.6 mmol, the amount of formamide is 5 to 10 mL, and the amount of deionized water is 0.05 to 0.1 mL relative to 0.8 to 1.2 mmol of the rare earth salt.

[0045] S2: Seal the glass bottle containing the second dispersion, place it in an oven, react at 95°C for 10 to 24 hours, cool to room temperature, and filter to collect the resulting block crystals; wash the block crystals with formamide and anhydrous ethanol respectively until the filtrate emits no blue light under ultraviolet light; place it in a vacuum drying oven and dry it for 6 hours at 70 to 80°C to obtain the dye-encapsulated Ln-MOFs-biby phosphorescent material.

[0046] The following describes the embodiments of the present invention in detail. Unless otherwise specified, the equipment and materials used are commercially available.

[0047] Example 1

[0048] A novel rare earth metal organic framework material, preparation method and application are specific refinements of the basic embodiment.

[0049] See attached Figure 1-Figure 3 The novel rare earth metal organic framework material provided in this embodiment is specifically Lu-MOFs material.

[0050] The Lu-MOFs material provided in this embodiment has a basic building block of chemical formula C5H5O 10 Lu, denoted as Lu-MOFs, uses formic acid (HCOOH) as the only organic ligand.

[0051] The new Lu-MOFs material belongs to the orthorhombic crystal system with a space group of C2221. The asymmetric unit of Lu-MOFs contains a crystallographically independent Lu 3+ ion, three coordinated bridged HCOO - ligand and a free formic acid molecule; each Lu 3+ The ion is coordinated with eight oxygen atoms, all of which belong to the deprotonated formic acid molecule; Lu 3+ Ions and HCOO - Ligands bridge to form a three-dimensional framework structure; along the crystal axis a, the Lu-MOFs framework presents one-dimensional open channels; in the original sample, uncoordinated HCOOH molecules occupy these channels; the framework is simplified to an 8-connected single-node network, with the dot symbol 3 6 .4 15 .5 7 , which belongs to the ecu topology type (see Figure 1).

[0052] The preparation method of the novel rare earth metal organic framework material Lu-MOFs provided in this embodiment comprises the following steps:

[0053] (1) Weigh 0.8 mmol of LuCl3×6H2O and add it to a glass bottle. Then, add 10 mL of formamide and 0.1 mL of deionized water in the set ratio. Place the glass bottle in an ultrasonic oscillator for ultrasonic treatment. During the ultrasonic treatment, the temperature is controlled at 25°C, the ultrasonic time is 25 minutes, and the ultrasonic frequency is 40 kHz until the solution in the bottle becomes clear and transparent, forming a uniform first dispersion.

[0054] (2) The glass bottle containing the first dispersion in step (1) was sealed and placed in an oven. The reaction was carried out at 95°C for 12 hours. The reaction was cooled to room temperature. The resulting block crystals were collected by filtration. The resulting crystals were washed three times with formamide and anhydrous ethanol respectively. The crystals were placed in a vacuum drying oven and dried for 6 hours at 75°C to obtain Lu-MOFs material.

[0055] During their research, the inventors discovered that due to the extremely high volatility and hygroscopicity of formic acid, there had been no previous reports of MOFs using formic acid as the sole ligand with rare earth ions. Our method cleverly utilizes the chemical reaction of formamide gradually reacting with water during heating to produce ammonia (NH3) and formic acid. Under heating and autogenous pressure, the deprotonated formic acid and Ln 3+ The ions self-assembled to form Lu-MOFs. We named the bulk crystals successfully collected from the bottom of the reaction vessel Lu-MOFs, with formic acid serving as the sole organic ligand. This example effectively reduced byproduct formation and increased the purity of the Ln-MOFs material by optimizing reaction conditions, adjusting the precursor ratio, and employing post-processing steps such as multiple washings. This strategy provides a new approach for the synthesis of high-purity rare earth metal-organic frameworks.

[0056] like Figure 1 As shown in the figure, (a) is the three-dimensional structure diagram of Lu-MOFs crystal, and (b) is the topological structure diagram of Lu-MOFs. The figure shows that Lu-MOFs has abundant pores and spatial effects. It can be used as a carrier of gas molecules, quantum dots, nanoparticles, organic small molecule drugs or dyes, and has broad application prospects in many fields such as catalysis, adsorption separation, optics, electricity, and magnetism.

[0057] like Figure 2 As shown in the figure, the powder X-ray diffraction pattern of the Lu-MOFs material matches very well with the diffraction pattern simulated based on the single crystal data, proving that by effectively combining the optimization of reaction conditions, adjustment of the precursor ratio, and multiple washing and other post-processing steps, the formation of by-products is effectively reduced and the purity of the Ln-MOFs material is improved. The Lu-MOFs material has higher phase purity and high-quality crystals.

[0058] Example 2

[0059] This embodiment, based on the basic embodiment, specifically provides the application of a new rare earth metal organic framework material, using Lu-MOFs to encapsulate the dye 4,4'-bipyridine (4,4'-bipyridine) to prepare a room temperature phosphorescent material, labeled Lu-MOFs-biby.

[0060] The preparation method of the dye-encapsulated Lu-MOFs-biby phosphorescent material provided in this embodiment adopts a "one-pot" synthesis method comprising the following steps:

[0061] S1. Weigh 0.8 mmol of LuCl3×6H2O and 1.2 mmol of the dye 4,4'-bipyridine and add them to a glass bottle. Then, add 10 mL of formamide and 0.1 mL of deionized water in a predetermined ratio. Place the glass bottle in an ultrasonic oscillator and sonicate at a temperature of 25°C, a duration of 25 minutes, and a frequency of 40 kHz until the solution in the bottle becomes clear and transparent, forming a uniform first dispersion.

[0062] S2. Seal the glass bottle containing the first dispersion in step S2, place it in an oven, react at 95°C for 12 hours, cool to room temperature, filter and collect the resulting block crystals, wash the resulting crystals with formamide and anhydrous ethanol, respectively, until the filtrate emits no blue light under ultraviolet lamp (365 nm) irradiation (365 nm ultraviolet lamp irradiates the dye 4,4'-bipyridine, which will emit blue light), then place it in a vacuum drying oven and dry it for 6 hours at 75°C to obtain the dye-encapsulated Lu-MOFs phosphorescent material, named Lu-MOFs-biby.

[0063] like Figure 3 As shown in the figure, under ultraviolet light (365 nm), Lu-MOFs are non-fluorescent, but Lu-MOFs-biby encapsulated with the dye 4,4'-bipyridine exhibits blue light emission with the highest emission intensity at 435 nm.

[0064] like Figure 4 As shown in Figure 3, by collecting the delayed spectrum (0.1 millisecond) of 365 nm excitation, Lu-MOFs-biby encapsulated with the dye 4,4'-bipyridine exhibits green light emission with the highest emission intensity at 545 nm.

[0065] Therefore, the dye-encapsulated Lu-MOFs-biby phosphorescent material can be used as a dual-mode optical filler to prepare solid or liquid products for fluorescence / afterglow dual-mode optical anti-counterfeiting, which can be specifically used in the manufacture of printed anti-counterfeiting inks, special anti-counterfeiting paper, etc.

[0066] In Example 1-2 of the present invention, the chemical reaction of formamide gradually reacting with water to generate ammonia and formic acid during heating is cleverly utilized, and the deprotonated formic acid is used as the only ligand and Ln 3+ Ionic self-assembly forms Ln-MOFs with a new structure. The new Ln-MOFs material shows a rich and stable pore structure with a spatial effect. It can be used as a carrier for gas molecules, quantum dots, nanoparticles, organic small molecule drugs or dyes, and has broad application prospects in many fields such as catalysis, adsorption separation, and light, electricity, and magnetism. The present invention demonstrates the excellent effect of Ln-MOFs on the encapsulation of the dye 4,4'-bipyridine. Among them, Lu-MOFs-bipy can emit blue light under room temperature and under the irradiation of ultraviolet light, and still has green phosphorescence emission visible to the naked eye after the ultraviolet light is turned off. It can be used in fluorescence / afterglow dual-mode optical anti-counterfeiting and information security, storage and other fields. The preparation method provided by the present invention has the advantages of simple steps, easy control, and high repeatability.

[0067] Example 3

[0068] The novel rare earth metal organic framework material, preparation method and application thereof provided in this embodiment are substantially the same as those in Example 1, except that the novel rare earth metal organic framework material is specifically a Y-MOFs material.

[0069] The Y-MOFs material provided in this embodiment has a basic building block with the chemical formula of C5H5O 10 Y, denoted as Y-MOFs, in which formic acid serves as the only organic ligand.

[0070] The preparation method of the Y-MOFs material provided in this embodiment comprises the following steps:

[0071] (1) Weigh 0.8 mmol of YCl3×6H2O and add it to a glass bottle. Then, add 10 mL of formamide and 0.1 mL of deionized water in the set ratio. Place the glass bottle in an ultrasonic oscillator for ultrasonic treatment. During the ultrasonic treatment, the temperature is controlled at 25°C, the ultrasonic time is 25 minutes, and the ultrasonic frequency is 40 kHz until the solution in the bottle becomes clear and transparent, forming a uniform first dispersion.

[0072] (2) The glass bottle containing the first dispersion in step (1) was sealed and placed in an oven. The reaction was carried out at 95 °C for 12 hours. The mixture was cooled to room temperature. The resulting block crystals were collected by filtration. The resulting crystals were washed three times with formamide and anhydrous ethanol respectively. The crystals were placed in a vacuum drying oven and dried for 6 hours at 75 °C to obtain the Y-MOFs material.

[0073] Example 4

[0074] The novel rare earth metal organic framework material, preparation method and application thereof provided in this embodiment are substantially the same as those in Example 1, except that the novel rare earth metal organic framework material is specifically Eu-MOFs material.

[0075] The Eu-MOFs material provided in this embodiment has a basic building block with the chemical formula of C5H5O 10 Eu, denoted as Eu-MOFs, in which formic acid serves as the only organic ligand.

[0076] The preparation method of the Eu-MOFs material provided in this embodiment comprises the following steps:

[0077] (1) Weigh 0.8 mmol of EuCl3×6H2O and add it to a glass bottle. Then, add 10 mL of formamide and 0.1 mL of deionized water in the set ratio. Place the glass bottle in an ultrasonic oscillator for ultrasonic treatment. The temperature during ultrasonic treatment is controlled at 25°C, the ultrasonic time is 25 minutes, and the ultrasonic frequency is 40 kHz until the solution in the bottle becomes clear and transparent, forming a uniform first dispersion.

[0078] (2) The glass bottle containing the first dispersion in step (1) was sealed and placed in an oven for reaction at 95°C for 12 hours. The mixture was cooled to room temperature and the resulting block crystals were collected by filtration. The resulting crystals were washed three times with formamide and anhydrous ethanol respectively and dried in a vacuum drying oven for 6 hours at 75°C to obtain Eu-MOFs material.

[0079] Example 5

[0080] The novel rare earth metal organic framework material, preparation method and application thereof provided in this embodiment are substantially the same as those in Example 1, except that the novel rare earth metal organic framework material is specifically a Tb-MOFs material.

[0081] The Tb-MOFs material provided in this embodiment has a basic building block with the chemical formula of C5H5O 10 Tb, denoted as Tb-MOFs, in which formic acid serves as the only organic ligand.

[0082] The preparation method of the Tb-MOFs material provided in this embodiment comprises the following steps:

[0083] (1) Weigh 0.8 mmol of TbCl3×6H2O and add it to a glass bottle. Then, add 10 mL of formamide and 0.1 mL of deionized water in the set ratio. Place the glass bottle in an ultrasonic oscillator for ultrasonic treatment. During the ultrasonic treatment, the temperature is controlled at 25°C, the ultrasonic time is 25 minutes, and the ultrasonic frequency is 40 kHz until the solution in the bottle becomes clear and transparent, forming a uniform first dispersion.

[0084] (2) The glass bottle containing the first dispersion in step (1) was sealed and placed in an oven. The reaction was carried out at 95°C for 12 hours. The mixture was cooled to room temperature. The resulting block crystals were collected by filtration. The resulting crystals were washed three times with formamide and anhydrous ethanol respectively. The crystals were placed in a vacuum drying oven and dried for 6 hours at 75°C to obtain Tb-MOFs material.

[0085] Example 6

[0086] The novel rare earth metal organic framework material, preparation method and application thereof provided in this embodiment are substantially the same as those in Example 1, except that the novel rare earth metal organic framework material is specifically a Yb-MOFs material.

[0087] The Yb-MOFs material provided in this embodiment has a basic building block with the chemical formula of C5H5O 10 Yb, denoted as Yb-MOFs, in which formic acid serves as the only organic ligand.

[0088] The preparation method of the Yb-MOFs material provided in this embodiment comprises the following steps:

[0089] (1) Weigh 0.8 mmol of YbCl3×6H2O and add it to a glass bottle. Then, add 10 mL of formamide and 0.1 mL of deionized water in the set ratio. Place the glass bottle in an ultrasonic oscillator for ultrasonic treatment. During the ultrasonic treatment, the temperature is controlled at 25°C, the ultrasonic time is 25 minutes, and the ultrasonic frequency is 40 kHz until the solution in the bottle becomes clear and transparent, forming a uniform first dispersion.

[0090] (2) The glass bottle containing the first dispersion in step (1) was sealed and placed in an oven. The mixture was reacted at 95°C for 12 hours, cooled to room temperature, and the resulting block crystals were collected by filtration. The resulting crystals were washed three times with formamide and anhydrous ethanol, respectively, and dried in a vacuum drying oven at 75°C for 6 hours to obtain the Yb-MOFs material.

[0091] Example 7

[0092] The novel rare earth metal organic framework material, preparation method and application thereof provided in this embodiment are substantially the same as those in Example 1, except that the novel rare earth metal organic framework material is specifically a Lu-25%Eu-MOFs material.

[0093] The Lu-25%Eu-MOFs material provided in this embodiment has a basic building block chemical formula of C5H5O 10 Lu 0.75 Eu 0.25, denoted as Lu-25%Eu-MOFs, in which formic acid is the only organic ligand.

[0094] The preparation method of the Lu-25%Eu-MOFs material provided in this embodiment includes the following steps:

[0095] (1) Weigh 0.6 mmol of LuCl3×6H2O and 0.2 mmol of EuCl3×6H2O, add them to a glass bottle, add 10 mL of formamide and 0.1 mL of deionized water in the set ratio, and place the glass bottle in an ultrasonic oscillator for ultrasonic treatment. During the ultrasonic treatment, the temperature is controlled at 25°C, the ultrasonic time is 25 minutes, and the ultrasonic frequency is 40 kHz until the solution in the bottle becomes clear and transparent, forming a uniform first dispersion.

[0096] (2) The glass bottle containing the first dispersion in step (1) was sealed and placed in an oven. The reaction was carried out at 95°C for 12 hours. The mixture was cooled to room temperature and the resulting block crystals were collected by filtration. The resulting crystals were washed three times with formamide and anhydrous ethanol respectively. The crystals were placed in a vacuum drying oven and dried for 6 hours at 75°C to obtain Lu-25%Eu-MOFs material.

[0097] like Figure 5 As shown in Figure 3, under UV light (365 nm), Lu25%Eu-MOFs exhibit red light emission.

[0098] The novel rare earth metal organic framework materials, preparation methods and applications disclosed in the above embodiments of the present invention focus on the design of a new simple method for preparing high-purity rare earth metal organic frameworks. The preparation method of the rare earth metal organic framework (Ln-MOFs) cleverly utilizes the chemical reaction of formamide with water to gradually generate ammonia and formic acid when heated. In a heated and self-generated pressure environment, the deprotonated formic acid reacts with the rare earth Ln to form ammonia and formic acid. 3+ Ionic self-assembly generates high-purity Ln-MOFs with novel structures.

[0099] The above-described embodiments of the present invention effectively reduce byproduct formation and improve the purity of Ln-MOFs materials by optimizing reaction conditions, adjusting precursor ratios, and employing post-processing steps such as multiple washings. The Ln-MOFs materials provided by the present invention possess a rich and stable pore structure, making them suitable as carriers for gases, quantum dots, nanoparticles, organic small molecule drugs, or dyes, and have broad application prospects in catalysis, adsorption separation, and numerous fields such as optics, electricity, and magnetism. The present invention demonstrates the outstanding performance of Ln-MOFs in encapsulating the dye 4,4'-bipyridine, preparing a room-temperature phosphorescent material (Ln-MOFs-bipy). The Lu-MOFs-bipy, obtained by encapsulating 4,4'-bipyridine in a lutetium (Lu) metal-organic framework, emits blue fluorescence at room temperature when exposed to ultraviolet light and continues to emit visible green phosphorescence after the UV light is extinguished. This material is suitable for applications in fluorescence / afterglow dual-mode optical anti-counterfeiting and information security storage. The preparation method provided by the present invention has the advantages of simple steps, easy operation, mild conditions, good repeatability, etc.

[0100] It should be noted that the present invention is not limited to the above-mentioned embodiments. Within the scope of the present invention, other novel rare earth metal organic framework materials, preparation methods and applications obtained by adopting other components, proportions and preparation process conditions can achieve the technical effects described in the present invention. Therefore, the present application document will no longer list them one by one.

[0101] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Any person skilled in the art can, without departing from the scope of the present invention, utilize the methods and technical contents disclosed above to make many possible variations or modifications to the present invention's technical solutions into equivalent embodiments with equivalent variations. Therefore, any equivalent modifications made based on the structure, construction, and principles of the present invention that do not depart from the content of the present invention should be included within the scope of protection of the present invention.

Claims

1. A rare earth metal organic framework material, characterized in that: The chemical formula of its basic building block is C5H5O 10 Ln, denoted as Ln-MOFs, uses formic acid HCOOH as the only organic ligand; the framework of this material is an 8-connected single-node network, with the dot symbol 3 6 .4 15 .5 7 , belonging to the ecu topology; the material belongs to the orthorhombic system with a space group of C2221; the asymmetric unit of Ln-MOFs contains a crystallographically independent rare earth Ln 3+ ion, three coordinated bridged HCOO - ligand and a free formic acid molecule; each Ln 3+ The ion is coordinated with eight oxygen atoms, all of which belong to the deprotonated formic acid molecule; Ln 3+ Ions and HCOO - The ligands bridge to form a three-dimensional framework structure; along the a crystal axis, the Ln-MOFs framework presents one-dimensional open channels, and the uncoordinated HCOOH molecules occupy the multiple one-dimensional open channels.

2. A method for preparing the rare earth metal organic framework material according to claim 1, characterized in that: It includes the following steps: (1) Weigh a set amount of rare earth salt and add it to a glass bottle. Then, add formamide and deionized water in a set ratio. Place the glass bottle in an ultrasonic oscillator and ultrasonicate until the solution in the bottle becomes clear and transparent, forming a uniform first dispersion. (2) The glass bottle containing the first dispersion is sealed, placed in an oven, and allowed to stand at 95°C. The formamide hydrolysis reaction is used to react with water under heating conditions to generate ammonia and formic acid to synthesize block crystals; then the formamide is cooled to room temperature and the generated block crystals are collected by filtration; the block crystals are washed with formamide and anhydrous ethanol respectively; finally, the block crystals are dried in a vacuum drying oven to obtain high-purity Ln-MOFs materials.

3. The method for preparing a rare earth metal organic framework material according to claim 2, wherein: The rare earth salt in step (1) is one of rare earth nitrate and rare earth chloride; The rare earth ions in the rare earth salt are La 3+ 、Ce 3+ 、Pr 3+ 、Nd 3+ 、Sm 3+ 、Eu 3+ 、Gd 3+ , Tb 3+ 、Dy 3+ 、Ho 3+ 、Er 3+ 、Tm 3+ 、Yb 3+ 、Lu 3+ One, two or more of the following; Ultrasonic treatment conditions were as follows: temperature of 20–30 °C, time of 25 min, and ultrasonic frequency of 40 KHz.

4. The method for preparing a rare earth metal organic framework material according to claim 2, wherein: In step (1), the amount of formamide used is 5 to 10 mL, and the amount of deionized water used is 0.05 to 0.1 mL, relative to 0.8 to 1.2 mmol of rare earth salt.

5. The method for preparing a rare earth metal organic framework material according to claim 2, wherein: In the step (2), the reaction is carried out in an oven at 95°C for 10 to 24 hours to synthesize bulk crystals, and then cooled to room temperature and filtered to collect the resulting bulk crystals; the bulk crystals are washed three times with formamide and anhydrous ethanol respectively; and dried in a vacuum drying oven for 6 hours at a temperature controlled at 70 to 80°C to obtain Ln-MOFs material.

6. An application of the rare earth metal organic framework material according to claim 1, characterized in that: Ln-MOFs were used to encapsulate the dye 4,4'-bipyridine to prepare a room-temperature phosphorescent material labeled Ln-MOFs-biby.

7. The use of the rare earth metal organic framework material according to claim 6, characterized in that: Specifically, a one-pot method is used to synthesize the dye-encapsulated Ln-MOFs-biby phosphorescent material, including the following steps: S1: Weigh a predetermined amount of rare earth salt and dye 4,4'-bipyridine into a glass bottle. Then, add formamide and deionized water in the predetermined ratio. Place the glass bottle in an ultrasonic oscillator and sonicate at a temperature of 20-30°C for 25 minutes at a frequency of 40 kHz until the solution in the bottle becomes clear and transparent, forming a uniform second dispersion. S2: Seal the glass bottle containing the second dispersion and place it in an oven for reaction at 95°C for 10 to 24 hours. Cool it to room temperature and collect the resulting block crystals by filtration. Wash the block crystals with formamide and anhydrous ethanol, respectively. Dry them in a vacuum drying oven for 6 hours at 70 to 80°C to obtain the dye-encapsulated Ln-MOFs-biby phosphorescent material.

8. The use of the rare earth metal organic framework material according to claim 7, characterized in that: In step S1, relative to 0.8 to 1.2 mmol of the rare earth salt, the amount of the dye 4,4'-bipyridine is 0.8 to 1.6 mmol, the amount of formamide is 5 to 10 mL, and the amount of deionized water is 0.05 to 0.1 mL.

9. The use of the rare earth metal organic framework material according to claim 7, characterized in that: In step S2, the obtained block crystals are washed with formamide and anhydrous ethanol respectively until the filtrate emits no blue light under ultraviolet light.

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