Multistage MOFs heterostructure material based on crystal face modification strategy auxiliary growth and preparation method and application thereof

Abstract

The invention provides a multi-stage MOFs heterostructure material based on crystal face modification strategy assisted growth and a preparation method and application of the multi-stage MOFs heterostructure material. The method comprises the following steps: fully mixing a metal salt solution, an organic ligand solution and an organic solvent, and carrying out solvothermal reaction, centrifugation, washing and drying to obtain a seed crystal; the preparation method comprises the following steps: fully dispersing a metal salt solution, an organic ligand solution, a regulator solution and a seed crystal dispersion liquid in a solvent, and carrying out solvothermal reaction to obtain the MOFs heterostructure material; or continuing to take the MOFs heterostructure material as the seed crystal, and repeating the steps to obtain the multistage MOFs heterostructure material with the 2D module as the core-shell structure. According to the invention, the specific nucleation barrier of the crystal face is selectively regulated and controlled, and the 2D modules are spatially arranged on different crystal faces of the 1D template, so that the multilevel heterostructure is effectively constructed. The prepared multilevel MOFs heterostructure material has a good application prospect in the fields of optical communication, information encryption or high-end anti-counterfeiting.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of multi-level MOFs heterostructure materials based on crystal face modification strategy assisted growth and its preparation method and application, belong to optical anti-counterfeiting device material technical field. BACKGROUND

[0002] With the rapid development of high-end manufacturing and informationization, the authenticity verification of product and data has become a key technical requirement to protect supply chain security and anti-counterfeiting traceability. Photonic barcodes based on micro-nano structures have shown important application potential and strategic value in the field of anti-counterfeiting due to their unique optical coding characteristics and difficult-to-replicate structural advantages. Epitaxial heterostructures have multi-color emission and spatial resolution characteristics, which are the key foundation for building high-performance micro-nano photonic barcodes. Metal-organic frameworks (MOFs) have both the stability of inorganic materials and the designability of organic components, providing an ideal platform for precise construction of epitaxial heterostructures. However, the existing heterostructures have the same dimensionality as the seed template, which limits the structural diversity and functional expansion of information security functions.

[0003] Multi-level MOFs heterostructures have asymmetric configurations and heterogeneous surface chemistry through the anisotropic integration of different structural units. The synergistic effect of components of different dimensions significantly enhances the optical control capability, making them exhibit superior performance in high-security anti-counterfeiting and optoelectronics. Therefore, the rational design and precise synthesis of multi-level heterostructures are crucial for performance improvement.

[0004] However, there are still fundamental challenges in realizing the precise construction of this structure: the structural incompatibility of components of different dimensions causes lattice mismatch, hindering the formation of ordered interfaces. Although certain lattice matching epitaxy has made some progress, achieving spatial precision and topologically controllable growth of epitaxial parts remains a key challenge that needs to be addressed.

[0005] Therefore, the present application is proposed. SUMMARY

[0006] To overcome the shortcomings of the prior art, the present application provides a kind of multi-level MOFs heterostructure materials based on crystal face modification strategy assisted growth and its preparation method and application. The present application selectively controls the nucleation barrier of specific crystal face through crystal face modification strategy, spatially arranges two-dimensional (2D) modules on different crystal faces of one-dimensional (1D) templates, and effectively constructs multi-level heterostructures. The prepared multi-level MOFs heterostructure materials have good application prospects in the fields of optical communication, information encryption or high-end anti-counterfeiting.

[0007] The technical scheme of the present application is as follows: A preparation method of a multi-level MOFs heterostructure material based on crystal face modification strategy assisted growth, comprising the following steps: (1) fully mix a metal salt solution, an organic ligand solution and an organic solvent, and obtain a crystal seed through a solvothermal reaction, centrifugation, washing and drying; the metal salt is one or a combination of the other of terbium nitrate hexahydrate or europium nitrate hexahydrate; the organic ligand is 1,3,5-benzene tricarboxylic acid (BTC); (2) fully disperse a metal salt solution, an organic ligand solution, an adjusting agent solution and a crystal seed dispersion liquid in a solvent to obtain a mixed liquid, and obtain a MOFs heterogeneous structure material through a solvothermal reaction, centrifugation, washing and drying; the metal salt is one or a combination of the other of terbium nitrate hexahydrate or europium nitrate hexahydrate; the organic ligand is 1,3,5-benzene tricarboxylic acid; and the adjusting agent is 1,3,5-tris (4-carboxyphenyl) benzene; Alternatively, the MOFs heterogeneous structure material is continuously used as a crystal seed, and step (2) is repeated to obtain a multi-level MOFs heterogeneous structure material with a 2D module as a core-shell structure.

[0008] According to the application, preferably, in step (1), the solvent used for the metal salt solution is N,N-dimethylformamide (DMF), and the concentration is 6-8 mmol / L, preferably 7.5 mmol / L.

[0009] According to the application, preferably, in step (1), the solvent used for the organic ligand solution is N,N-dimethylformamide (DMF), and the concentration is 24-26 mmol / L, preferably 25 mmol / L.

[0010] According to the application, preferably, in step (1), when the metal salt is a combination of europium nitrate hexahydrate and terbium nitrate hexahydrate, the molar amount of the europium nitrate hexahydrate is 2-3% of the molar amount of the terbium nitrate hexahydrate.

[0011] According to the application, preferably, in step (1), the molar ratio of the metal salt to the organic ligand is 2-4:9-11, preferably 3:10.

[0012] According to the application, preferably, in step (1), the organic solvent is a mixed solvent of N,N-dimethylformamide (DMF), water and ethanol, wherein the volume ratio of N,N-dimethylformamide (DMF), water and ethanol is 4-6:2:2, preferably 4:2:2; and the molar amount of the metal salt to the volume of the organic solvent is 0.5-1.0 mmol / L, preferably 0.94 mmol / L.

[0013] According to the application, preferably, in step (1), the solvothermal reaction temperature is 70-90℃, and the solvothermal reaction time is 2-4h.

[0014] According to the application, preferably, in step (2), the solvent used for the metal salt solution is N,N-dimethylformamide (DMF), and the concentration is 6-8 mmol / L, preferably 7.5 mmol / L.

[0015] According to the application, preferably, in step (2), the solvent used for the organic ligand solution is N,N-dimethylformamide (DMF), and the concentration is 24-55 mmol / L, preferably 25-50 mmol / L.

[0016] According to the application, preferably, in step (2), when the metal salt is a combination of europium nitrate hexahydrate and terbium nitrate hexahydrate, the molar amount of europium nitrate hexahydrate is 2-3% of the molar amount of terbium nitrate hexahydrate.

[0017] According to the application, preferably, in step (2), the solvent used for the adjusting agent solution is N,N-dimethylformamide (DMF), and the concentration is 11-30 mmol / L, preferably 12.5-25 mmol / L.

[0018] According to the application, preferably, in step (2), the seed crystal dispersion solution is obtained by fully dispersing seed crystals in N,N-dimethylformamide (DMF); the mass of the seed crystals and the volume of N,N-dimethylformamide are in a ratio of 0.03-0.05 g / mL, preferably 0.04 g / mL. The volume ratio of the metal salt solution and the seed crystal dispersion solution is 1:0.2-0.5.

[0019] According to the application, preferably, in step (2), a surfactant can also be added to the mixed solution; the surfactant is ethanol; the volume ratio of the surfactant and the solvent is 0.5-2:7-10, preferably 0.5-1:7-9.5.

[0020] According to the application, preferably, in step (2), the molar ratio of the metal salt, the organic ligand, and the adjusting agent is 1-4:10:2-3, preferably 1.5-3:10:2.5.

[0021] According to the application, preferably, in step (2), the solvent is a mixed solvent of N,N-dimethylformamide (DMF) and water, wherein the volume ratio of N,N-dimethylformamide (DMF) to water is 6:2-6, preferably 6:3-6; the molar amount of the metal salt and the volume of the solvent are in a ratio of 0.5-10 mmol / L, preferably 0.75-1 mmol / L.

[0022] According to the application, preferably, in step (2), the solvothermal reaction temperature is 70-90℃, and the solvothermal reaction time is 2-4 h.

[0023] According to the application, in step (2), the number of times of repeating step (2) is determined according to actual needs.

[0024] A multi-level MOFs heterostructure material based on a crystal face modification strategy assisted growth is prepared by the above method.

[0025] According to the application, the micro-morphology of the multi-level MOFs heterostructure material is: a multi-level MOFs heterostructure composed of 1D microrod crystals and 2D sheet crystals.

[0026] According to the application, the multi-level MOFs heterostructure material is monochromatic or polychromatic under ultraviolet excitation.

[0027] The multi-level MOFs heterostructure material based on the crystal face modification strategy for assisted growth has the application in optical communication, information encryption, security labels or high-end anti-counterfeiting devices.

[0028] The technical features and beneficial effects of the application are as follows: 1. The application provides a method for synthesizing a multi-level MOFs heterostructure material based on a crystal face modification strategy for assisted growth.

[0029] 2. The application realizes the preparation of a multi-level MOFs heterostructure material by selectively controlling the crystal face nucleation barrier through a crystal face modification strategy, arranging 2D modules on different crystal faces of 1D template seeds in space, thereby realizing the preparation of a multi-level MOFs heterostructure material. The application first mixes an organic ligand solution, a metal salt solution and a solvent, and then promotes the formation of MOF microrod structures in a sealed reaction kettle under high temperature and high pressure, as template seeds for the second step of crystal growth. The formed microrod seeds are mixed with the metal salt solution, the organic ligand solution, the adjusting agent solution and the solvent required for the second step of reaction, and the reaction is continued under high temperature and high pressure. 1,3,5-tris (4-carboxyphenyl) benzene (BTB) is introduced as an adjusting agent into the precursor solution, and the adjusting agent produces steric hindrance in the MOF pores, interrupting the inherent 1D preferential growth of the Ln-BTC MOF, thereby forming a 2D regular microporous plate. The inherent high surface energy of the tip of the 1D template drives the preferential nucleation and selective epitaxial growth of the 2D module on the lattice-matched tip surface in the second step, thereby forming a dumbbell-shaped heterostructure with obvious optical contrast without a surfactant. In addition, by adding a surfactant to reasonably control the nucleation barrier driven by surface energy, the reactivity of the surface of the 1D template crystal is further improved, selective nucleation and crystal growth are realized, and by adjusting the surface energy of the crystal face, the number of 2D modules is accurately adjusted, thereby producing a diversified library of customized size heterostructures.

[0030] 1,3,5-tris(4-carboxyphenyl)benzene (BTB) is a molecule with triple symmetry, which partially embeds into the pore channel, with one arm anchoring in the host framework and the other two arms extending to the crystal growth interface. Due to steric hindrance, it effectively interferes with the original one-dimensional growth trend of the Ln-BTC MOF, limiting its axial extension, and thus promoting the lateral expansion of the crystal, ultimately compressing the original 1D rod structure into a two-dimensional plate crystal with a regular microporous array.

[0031] Ethanol acts as a surface modifier in the system, and its alkyl chain can preferentially adsorb on the microrod side surface rich in aromatic rings through CH-pi interaction, with its hydroxyl group oriented and exposed towards the solution interface. This orientation provides specific surface sites for subsequent epitaxial processes. Subsequently, unsaturated metal-oxygen clusters in the solution are more likely to coordinate with these exposed hydroxyl groups, thereby inducing the heterogeneous nucleation and expansion growth of two-dimensional modules on the microrod side wall.

[0032] 3、The present application selects specific types of metal salts, organic ligands, solvents, surfactants and modifiers to prepare multi-level MOFs heterogeneous structure materials. If the types or proportions of raw materials are not appropriate, the multi-level MOFs structure morphology obtained is not good, and even the preparation of the morphology structure material of the present application cannot be realized. The present application selects specific types of metal salts to ensure lattice matching and meet the conditions for epitaxial growth; the present application selects specific surfactants to selectively adjust the nucleation barrier of different crystal faces of 1D seeds, so as to regulate the number of 2D modules. The preparation method of the present application as a whole, the steps and conditions jointly act to achieve the excellent effect of the present application.

[0033] 4、The multi-level MOFs heterogeneous structure material prepared by the method of the present application exhibits monochromatic or polychromatic structure. The method of the present application can realize the construction of multi-level MOFs heterogeneous structure with programmable architecture and dimension; through surface modification, multi-level MOFs heterogeneous structure with controllable number of 2D modules is obtained; by adjusting the co-doping ratio of metal salt ions, precise control of polychromatic luminescence can be realized, providing a general platform for generating wide-spectrum adjustable output. The present application widens the dimension of the heterogeneous structure by connecting multiple 2D modules in series along the 1D axial rod, and by reasonably modulating each building block with specific color and morphological characteristics, the characteristic emission spectrum of different modules is embodied, so that the light spectrum can be edited into a photon barcode according to different characteristics. Such a device has excellent performance and low cost, and can be well applied in the fields of optical communication, information encryption or high-end anti-counterfeiting. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 Image of the multi-level MOFs heterogeneous structure prepared in Example 1 under ultraviolet excitation.

[0035] Figure 2SEM images of the multi-level MOFs heterostructure prepared for Example 1.

[0036] Figure 3 Images of the multi-level MOFs heterostructure prepared for Example 2 under UV excitation.

[0037] Figure 4 Images of the multi-level MOFs heterostructure prepared for Example 3 under UV excitation.

[0038] Figure 5 Images of the multi-level MOFs heterostructure prepared for Example 4 under UV excitation.

[0039] Figure 6 Images of the multi-level MOFs heterostructure prepared for Example 5 under UV excitation.

[0040] Figure 7 Images of the 1D core-shell heterostructure prepared for Example 6 under UV excitation.

[0041] Figure 8 Images of the multi-level MOFs heterostructure prepared for Example 7 under UV excitation Figure 9 Schematic diagram of the multi-level MOFs heterostructure prepared for Example 7 and schematic diagram of the photonic bar code encoding strategy based on the multi-level MOFs heterostructure prepared for Example 7.

[0042] Figure 10 Spectral feature map obtained from excitation region 1 of the multi-level MOFs heterostructure prepared for Example 7.

[0043] Figure 11 Images of the material prepared for Comparative Example 1 under UV excitation.

[0044] Figure 12 Images of the material prepared for Comparative Example 2 under UV excitation. DETAILED DESCRIPTION

[0045] The application is further described below through specific examples, but is not limited thereto.

[0046] The raw materials used in the examples are conventional raw materials and are commercially available unless otherwise specified; the methods used in the examples are prior art unless otherwise specified.

[0047] Example 1 A preparation method of a multi-level MOFs heterostructure material based on a crystal face modification strategy assisted growth, comprising the steps of: (1) Add 1 mL of 0.0075 mol / L N,N-dimethylformamide (DMF) solution of terbium nitrate hexahydrate (Tb(NO3)3·6H2O) and 1 mL of 0.025 mol / L N,N-dimethylformamide (DMF) solution of 1,3,5-benzenetricarboxylic acid to a mixed solution of 4 mL N,N-dimethylformamide (DMF), 2 mL water and 2 mL ethanol. Mix thoroughly and react at 80 °C for 3 hours. After the reaction is complete, centrifuge to collect the precipitate. Centrifuge the precipitate three times with DMF and dry to obtain 1D MOF seed material. Disperse 20 mg of seed material thoroughly in 0.5 mL N,N-dimethylformamide (DMF) solution to obtain 1D MOF seed dispersion.

[0048] (2) 1 mL of N,N-dimethylformamide (DMF) solution of europium nitrate hexahydrate (Eu(NO3)3·6H2O) with a concentration of 0.0075 mol / L, 1 mL of N,N-dimethylformamide (DMF) solution of 1,3,5-benzenetricarboxylic acid (BTC) with a concentration of 0.025 mol / L, 0.5 mL of N,N-dimethylformamide (DMF) solution of 1,3,5-tris(4-carboxyphenyl)benzene (BTB) with a concentration of 0.0125 mol / L, and 0.5 mL of seed dispersion were mixed and added to a solvent containing 6 mL of N,N-dimethylformamide (DMF) and 4 mL of water. The mixture was thoroughly mixed and subjected to a solvothermal reaction at 80 °C for 3 hours. After the reaction was completed, the precipitate was collected by centrifugation. The precipitate was centrifuged three times with DMF and dried to obtain dumbbell-shaped heterostructure material.

[0049] like Figure 1 The image shows the multi-level MOF heterostructure prepared in step (2) under a microscope after ultraviolet excitation. It is a dumbbell-shaped multicolor structure material with red 2D modules and green 1D microrods, exhibiting significant optical contrast. The scale bar is 10 μm.

[0050] like Figure 2 The image shows a SEM image of the multi-level MOF heterostructure material prepared in step (2). The microrods have regular shapes and smooth surfaces. The scale bar is 5 μm.

[0051] Example 2 A preparation method of a multi-level MOFs heterostructure material based on a crystal face modification strategy assisted growth, as described in Embodiment 1, except that in step (2), 1 mL of a DMF solution of terbium nitrate hexahydrate (Tb (NO3) 3·6H2O) (C = 0.0075 mol / L) is used to replace 1 mL of a DMF solution of europium nitrate hexahydrate (Eu (NO3) 3·6H2O) (C = 0.0075 mol / L), and other steps and conditions are consistent with Embodiment 1. Finally, a dumbbell-shaped single-color structure material is obtained, in which the 2D module is green and the 1D microrod is also green.

[0052] As Figure 3 The multi-level MOFs heterostructure material prepared in this embodiment is imaged under a microscope by ultraviolet excitation, and the obtained material is a dumbbell type, in which the 2D module is green and the 1D microrod is also green. The scale bar is 10 μm.

[0053] Embodiment 3 A preparation method of a multi-level MOFs heterostructure material based on a crystal face modification strategy assisted growth, as described in Embodiment 1, except that in step (2), 1 mL of a DMF solution of terbium nitrate hexahydrate (Tb (NO3) 3·6H2O) and europium nitrate hexahydrate (Eu (NO3) 3·6H2O) is used to replace 1 mL of a DMF solution of europium nitrate hexahydrate (Eu (NO3) 3·6H2O), the total molar concentration of metal salts is 0.0075 mol / L, and the molar amount of europium nitrate hexahydrate is 2% of that of terbium nitrate hexahydrate, and other steps and conditions are consistent with Embodiment 1. Finally, a dumbbell-shaped heterostructure material is obtained, in which the 2D module is yellow and the 1D microrod is green.

[0054] As Figure 4 The multi-level MOFs heterostructure material prepared in this embodiment is imaged under a microscope by ultraviolet excitation, and the obtained material is a dumbbell type, in which the 2D module is yellow and the 1D microrod is green. The scale bar is 10 μm.

[0055] Embodiment 4 A preparation method of a multi-level MOFs heterostructure material based on a crystal face modification strategy assisted growth, as described in Embodiment 1, except that in step (2), a surfactant ethanol is also added, as follows: A mixture of 1 mL of a 0.0075 mol / L solution of europium nitrate hexahydrate (Eu(NO3)3·6H2O) in N,N-dimethylformamide (DMF), 1 mL of a 0.025 mol / L solution of 1,3,5-benzenetricarboxylic acid (BTC) in N,N-dimethylformamide (DMF), 0.5 mL of a 0.0125 mol / L solution of 1,3,5-tris(4-carboxyphenyl)benzene (BTB) in N,N-dimethylformamide (DMF), and 0.5 mL of seed dispersion was added to a mixture of 6 mL of N,N-dimethylformamide (DMF), 3.5 mL of water, and 0.5 mL of ethanol. The mixture was thoroughly mixed and subjected to a solvothermal reaction at 80 °C for 3 hours. After the reaction was complete, the precipitate was collected by centrifugation. The precipitate was centrifuged three times with DMF and dried to obtain a multi-level heterostructure material with 3 2D red modules and green 1D microrods.

[0056] The other steps and conditions are the same as in Example 1.

[0057] like Figure 5 The image shows the multi-level MOF heterostructure material prepared in this embodiment, obtained under a microscope by ultraviolet excitation. The material has 3 2D modules. The scale bar is 10 μm.

[0058] Example 5 A method for preparing multi-level MOF heterostructure materials based on crystal plane modification strategy-assisted growth, as described in Example 1, except that: in step (2), the surfactant ethanol is added, as follows: A mixture of 1 mL of a 0.0075 mol / L solution of europium nitrate hexahydrate (Eu(NO3)3·6H2O) in N,N-dimethylformamide (DMF), 1 mL of a 0.025 mol / L solution of 1,3,5-benzenetricarboxylic acid (BTC) in N,N-dimethylformamide (DMF), 0.5 mL of a 0.0125 mol / L solution of 1,3,5-tris(4-carboxyphenyl)benzene (BTB) in N,N-dimethylformamide (DMF), and 0.5 mL of seed dispersion was added to a mixture of 6 mL of N,N-dimethylformamide (DMF), 3 mL of water, and 1 mL of ethanol. The mixture was thoroughly mixed and subjected to a solvothermal reaction at 80 °C for 3 hours. After the reaction was complete, the precipitate was collected by centrifugation. The precipitate was centrifuged three times with DMF and dried to obtain a multi-level heterostructure material with 5 2D red modules and green 1D microrods.

[0059] The other steps and conditions are the same as in Example 1.

[0060] like Figure 6The multi-level MOFs heterostructure material prepared in this example was imaged under a microscope by ultraviolet excitation. The number of 2D modules of the material was 5. The scale bar is 10 μm.

[0061] Example 6 A method for preparing a multi-level MOFs heterostructure material based on a crystal face modification strategy assisted growth, as described in Example 1, except that in step (2), a surfactant ethanol was also added, as follows: A 1 mL solution of europium nitrate hexahydrate (Eu(NO3)3·6H2O) with a concentration of 0.0075 mol / L in N,N-dimethylformamide (DMF), 1 mL of 1,3,5-benzenetricarboxylic acid (BTC) with a concentration of 0.025 mol / L in N,N-dimethylformamide (DMF), 0.5 mL of 1,3,5-tris (4-carboxyphenyl) benzene (BTB) with a concentration of 0.0125 mol / L in N,N-dimethylformamide (DMF), and 0.5 mL of a seed dispersion were mixed and then added to 6 mL of a mixed solution of N,N-dimethylformamide (DMF), 1.5 mL of water, and 2.5 mL of ethanol. The mixture was mixed thoroughly and then subjected to a solvent thermal reaction at 80°C for 3 hours. After the reaction, the precipitate was separated by centrifugation, and the precipitate was centrifuged three times with DMF. After drying, a completely covered 1D core-shell heterostructure material was obtained.

[0062] The other steps and conditions were consistent with Example 1.

[0063] As Figure 7 The 1D core-shell heterostructure material prepared in this example was imaged under a microscope by ultraviolet excitation. The scale bar is 10 μm.

[0064] Example 7 A method for preparing a multi-level MOFs heterostructure material based on a crystal face modification strategy assisted growth, comprising the steps of: The three-stage series multi-stage heterostructure material obtained in Example 4 was used as a seed crystal. 1 mL of a N,N-dimethylformamide (DMF) solution of terbium nitrate hexahydrate (Tb (NO3) 3·6H2O) with a concentration of 0.0075 mol / L, 1 mL of a N,N-dimethylformamide (DMF) solution of 1,3,5-benzenetricarboxylic acid (BTC) with a concentration of 0.05 mol / L, and 0.5 mL of a N,N-dimethylformamide (DMF) solution of 1,3,5-tris (4-carboxyphenyl) benzene (BTB) with a concentration of 0.025 mol / L were mixed with 0.5 mL of a seed crystal dispersion (20 mg of the seed crystal material was fully dispersed in 0.5 mL of a N,N-dimethylformamide (DMF) solution) and added to 3.5 mL of a mixed solution of N,N-dimethylformamide (DMF) and water and 0.5 mL of ethanol, which were fully mixed. The solution was subjected to a solvothermal reaction at 80°C for 3 hours. After the reaction, the precipitate was separated by centrifugation. The precipitate was centrifuged three times with DMF and dried to obtain a 1D microstick connected integrated 2D core-shell heterostructure.

[0065] As shown in Figure 8 The 1D microstick connected integrated 2D core-shell heterostructure material prepared in this example was imaged under a microscope by ultraviolet excitation. The obtained material was a 2D module with a core-shell heterostructure. The scale bar is 10 μm.

[0066] Figure 9 is a schematic diagram of the heterostructure prepared in this example and a schematic diagram of a photon barcode encoding strategy based on the heterostructure prepared in this example. Figure 10 is Figure 9 The spectral characteristics obtained by exciting region 1 (375 nm wavelength light excitation) and encoding according to the position and intensity information of the peaks; the different regions (top, middle region, and bottom) of the 2D module were excited to obtain spectra with unique characteristic information, and the position and intensity information of the peaks were encoded to obtain Figure 9 the barcode.

[0067] Comparative Example 1 A method for preparing a heterostructure material was used as described in Example 1, except that in step (2), no N,N-dimethylformamide (DMF) solution of 1,3,5-tris (4-carboxyphenyl) benzene (BTB) was added. The other steps and conditions were consistent with those of Example 1.

[0068] As shown in Figure 11 The heterostructure material prepared in this comparative example was imaged under a microscope by ultraviolet excitation. The obtained crystal did not have a multi-stage heterostructure characteristic. The scale bar is 10 μm.

[0069] Comparative Example 2 A preparation method of a heterostructure material, as described in Example 4, except that ethanol is replaced by acetone in step (2), and other steps and conditions are consistent with Example 4.

[0070] As Figure 12 The heterostructure material prepared for the present comparative example has images obtained by ultraviolet excitation under a microscope, and the obtained crystals do not achieve effective regulation of the number of 2D modules in the multi-level heterostructure, and still have dumbbell structure characteristics. The scale is 10 μm.

Claims

1. A method for preparing multi-level MOF heterostructure materials based on crystal plane modification strategy-assisted growth, comprising the following steps: (1) The metal salt solution, organic ligand solution and organic solvent are thoroughly mixed, and seed crystals are obtained by solvothermal reaction, centrifugation, washing and drying; the metal salt is one or a combination of terbium nitrate hexahydrate or europium nitrate hexahydrate; the organic ligand is 1,3,5-benzenetricarboxylic acid (BTC). (2) The metal salt solution, organic ligand solution, regulator solution, and seed crystal dispersion are fully dispersed in a solvent to obtain a mixed solution. After solvothermal reaction, centrifugation, washing, and drying, MOFs heterostructure material is obtained. The metal salt is one or a combination of europium nitrate hexahydrate or terbium nitrate hexahydrate. The organic ligand is 1,3,5-benzenetricarboxylic acid. The regulator is 1,3,5-tris(4-carboxyphenyl)benzene. Alternatively, using MOFs heterostructure materials as seed crystals, step (2) can be repeated to obtain multi-level MOFs heterostructure materials with 2D modules as core-shell structures.

2. The method for preparing multi-level MOF heterostructure materials based on crystal plane modification strategy assisted growth according to claim 1, characterized in that, Step (1) includes one or more of the following conditions: i. The solvent used for the metal salt solution is N,N-dimethylformamide (DMF) with a concentration of 6-8 mmol / L, preferably 7.5 mmol / L; ii. The solvent used for the organic ligand solution is N,N-dimethylformamide (DMF) with a concentration of 24-26 mmol / L, preferably 25 mmol / L; iii. When the metal salt is a combination of europium nitrate hexahydrate and terbium nitrate hexahydrate, the molar amount of europium nitrate hexahydrate is 2-3% of the molar amount of terbium nitrate hexahydrate; iv. The molar ratio of metal salt to organic ligand is 2-4:9-11, preferably 3:10; v. The organic solvent is a mixture of N,N-dimethylformamide (DMF), water and ethanol, wherein the volume ratio of N,N-dimethylformamide (DMF), water and ethanol is 4-6:2:2, preferably 4:2:2; the molar amount of the metal salt and the volume ratio of the organic solvent are 0.5-1.0 mmol / L, preferably 0.94 mmol / L; vi. The solvothermal reaction temperature is 70-90℃, and the solvothermal reaction time is 2-4h.

3. The method for preparing multi-level MOF heterostructure materials based on crystal plane modification strategy assisted growth according to claim 1, characterized in that, Step (2) includes one or more of the following conditions: i. The solvent used for the metal salt solution is N,N-dimethylformamide (DMF) with a concentration of 6-8 mmol / L, preferably 7.5 mmol / L; ii. The solvent used for the organic ligand solution is N,N-dimethylformamide (DMF) with a concentration of 24-55 mmol / L, preferably 25-50 mmol / L; iii. When the metal salt is a combination of europium nitrate hexahydrate and terbium nitrate hexahydrate, the molar amount of europium nitrate hexahydrate is 2-3% of the molar amount of terbium nitrate hexahydrate; iv. The solvent used for the conditioning solution is N,N-dimethylformamide (DMF) with a concentration of 11-30 mmol / L, preferably 12.5-25 mmol / L.

4. The method for preparing multi-level MOF heterostructure materials based on crystal plane modification strategy assisted growth according to claim 1, characterized in that, In step (2), the seed dispersion is obtained by fully dispersing the seed crystals in N,N-dimethylformamide (DMF); the ratio of the mass of the seed crystals to the volume of N,N-dimethylformamide is 0.03-0.05 g / mL, preferably 0.04 g / mL; the volume ratio of the metal salt solution to the seed dispersion is 1:0.2-0.

5.

5. The method for preparing multi-level MOF heterostructure materials based on crystal plane modification strategy assisted growth according to claim 1, characterized in that, In step (2), a surfactant may also be added to the mixture; the surfactant is ethanol; the volume ratio of surfactant to solvent is 0.5-2:7-10, preferably 0.5-1:7-9.

5.

6. The method for preparing multi-level MOF heterostructure materials based on crystal plane modification strategy assisted growth according to claim 1, characterized in that, In step (2), the molar ratio of metal salt, organic ligand and regulator is 1-4:10:2-3, preferably 1.5-3:10:2.

5.

7. The method for preparing multi-level MOF heterostructure materials based on crystal plane modification strategy assisted growth according to claim 1, characterized in that, Step (2) includes one or more of the following conditions: i. The solvent is a mixture of N,N-dimethylformamide (DMF) and water, wherein the volume ratio of N,N-dimethylformamide (DMF) to water is 6:2-6, preferably 6:3-6; the molar amount of the metal salt and the volume ratio of the solvent are 0.5-10 mmol / L, preferably 0.75-1 mmol / L; ii. The solvothermal reaction temperature is 70-90℃, and the solvothermal reaction time is 2-4h.

8. A multi-level MOF heterostructure material based on a crystal plane modification strategy for assisted growth, prepared by the method described in any one of claims 1-7.

9. The multi-level MOF heterostructure material grown with the crystal plane modification strategy according to claim 8, characterized in that, The microstructure of the multilevel MOFs heterostructure material is: a multilevel MOFs heterostructure composed of 1D microrod crystals and 2D sheet crystals; preferably, the multilevel MOFs heterostructure material is a monochromatic or multicolor heterostructure under ultraviolet excitation.

10. The application of the multi-level MOF heterostructure material grown with the crystal plane modification strategy as described in claim 8 in optical communication, information encryption, security tags or high-end anti-counterfeiting devices.

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