Universal preparation method of single-layer metal organic framework material

Abstract

The invention provides a general preparation method of a single-layer metal organic framework material. MonoMOF is synthesized based on coordination capability control of a regulator. By optimizing a regulator adapted to a ligand in the growth process of MOFs and systematically regulating and controlling the coordination effect between the regulator and the ligand, precise synthesis and functional regulation and control of functionalized monoMOFs with different pore diameters are realized, the problems of low synthesis success rate and limited application range of an existing method are solved, and the method is suitable for industrial production. A brand new thought and a technical basis are provided for large-scale preparation of the monoMOF material and application of the monoMOF material in the fields of catalysis, energy, biological medicine and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of single-layer metal organic framework (monoMOF) material synthesis, and particularly relates to a general preparation method for efficiently synthesizing monoMOF materials. Background Art

[0002] Metal-organic frameworks (MOFs) are a class of highly ordered crystalline porous materials formed by self-assembly of metal ions or metal clusters and organic ligands. Due to their large specific surface area, adjustable pore size, open metal sites, and excellent structural and functional tunability, they have shown important research value and broad application prospects in the fields of chemistry, materials, energy, life sciences, and environmental governance.

[0003] Monolayer metal-organic frameworks (monoMOFs), an emerging branch of the MOF field, are a novel type of two-dimensional molecular material (see Nature 2022, 602, 606; Science 2014, 346, 1356). Their monolayer structure endows monoMOFs with a higher surface area and more exposed active sites, significantly improving their mass transfer efficiency and facilitating functional modification. These properties enable monoMOFs to overcome the limitations of three-dimensional MOFs in areas such as catalysis of macromolecular substrates and assembly of functional components, demonstrating enormous potential for application in catalysis, energy, and biomedicine.

[0004] However, the single-layer structure of monoMOFs also presents significant challenges for precise synthesis. Compared to the over 100,000 reported three-dimensional MOFs, research on monoMOFs is still in its infancy and exploratory phase, with only a handful of reports to date. These synthetic methods often rely on trial-and-error and exfoliation methods. The former relies on researchers to continuously adjust reaction conditions (such as temperature, solvent, and ligand ratio) to find a suitable synthesis path. However, the lack of in-depth understanding of the relationships between these key variables leads to low synthetic success rates and significant consumption of experimental resources. Exfoliation methods, which mechanically or chemically remove single-layer structures from layered MOFs, have limited applicability, complex preparation processes, and low yields. Furthermore, the quality and uniformity of the resulting single-layer materials are difficult to guarantee, limiting their practical applications.

[0005] Therefore, the existing technology for the synthesis of single-layer metal-organic frameworks (monoMOFs) lacks systematicity and universality, making it difficult to prepare monoMOF materials on a large scale, and also limiting their application in catalysis, energy, biomedicine and other fields. Therefore, there is an urgent need to provide a universal method for the preparation of single-layer metal-organic framework materials to meet the material requirements of different pore sizes and functional requirements. Summary of the Invention

[0006] To address these issues, the present invention proposes a universal and universal method for synthesizing monoMOFs based on the control of modulator coordination capacity. By optimizing the modulator's compatibility with the ligand during MOF growth and systematically regulating the coordination interaction between the modulator and the ligand, this method achieves the precise synthesis and functionalization of monoMOFs with varying pore sizes and functionalizations. This overcomes the low synthesis success rate, limited applicability, and insufficient theoretical guidance inherent in existing methods, providing a new approach and technical foundation for the large-scale preparation of monoMOF materials and their applications in catalysis, energy, and biomedicine, thus completing the present invention.

[0007] The object of the present invention is to provide a method for preparing a single-layer metal organic framework material, comprising the following steps: (1) Prepare metal salt solution I, (2) Add metal salt solution I to the regulator to form a mixed solution, (3) Prepare ligand solution II, (4) Add ligand solution II to the mixed solution and heat to react. (5) After the reaction, post-treatment is performed to obtain monoMOF.

[0008] In step (1), a metal salt is added to a solvent, preferably with ultrasonic stirring, to obtain a metal salt solution I. The metal salt is an alkaline earth metal salt, a Group III metal salt, or a transition metal salt, preferably one of transition metal salts such as Zr, Hf, Y, and Eu.

[0009] The solvent is an amide solvent, preferably N,N-dimethylformamide or N,N-dimethylacetamide.

[0010] The temperature of the ultrasonic treatment is 1°C-50°C, preferably 10°C-40°C, and the time is 1-30 minutes, preferably 5-10 minutes.

[0011] In step (2), the regulator is an organic acid, preferably one of formic acid, acetic acid, trifluoroacetic acid, pentafluoropropionic acid, benzoic acid, etc., and the molar ratio of the metal salt to the regulator is 1:(10-400).

[0012] In step (3), the ligand is mixed with a solvent, preferably stirred, to form a ligand solution II, wherein the ligand is a dicarboxylic acid, preferably a linear dicarboxylic acid, such as terephthalic acid, biphenyldicarboxylic acid, terphenyldicarboxylic acid, etc., and the molar ratio of the metal salt to the ligand is 1:(0.1-2). The solvent is an amide solvent, preferably N,N-dimethylformamide or N,N-dimethylacetamide, and more preferably the same solvent as used in preparing solution I in step (1).

[0013] In step (4), ligand solution II is added to the mixed solution obtained in step (2), stirred, sealed, and heated to react. Preferably, the metal ions are hydrolyzed to form secondary building units (SBUs), and the ligands are connected to the SBUs to achieve the growth and extension of the MOFs. The modulator causes the ligands to extend only in the lateral direction, achieving the growth of a two-dimensional monoMOF.

[0014] According to a preferred embodiment of the present invention, the reaction temperature is 50°C-150°C, preferably 80°C-120°C, and the reaction time is 0.5-144h, preferably 2-72h.

[0015] In step (5), the post-treatment includes cooling, separation and washing, preferably naturally cooling to room temperature, centrifuging the obtained solid, and then washing with a solvent.

[0016] The present invention also provides a monoMOF solid material, which is prepared according to the above method and preferably has the following structural units: M x O y (OH) y' L z B p , in, M is a metal, preferably an alkaline earth metal, a third main group metal, or a transition metal; L is a dicarboxylic acid, preferably a dicarboxylic acid modified with functional groups of different lengths, types, and numbers; B is a monocarboxylic acid, preferably a monofatty acid or a monoaromatic acid; On this basis, the overall structural composition of the single-layer metal organic framework material is shown in the following general formula: [M x O y (OH) y' ] n L zn B pn . BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 2 is the XRD pattern of monoMOF synthesized in Example 1.

[0018] Figure 2 TEM image of monoMOF synthesized in Example 1.

[0019] Figure 3 This is a theoretical simulation image of the monoMOF synthesized in Example 1.

[0020] Figure 4 This is the STEM image of the monoMOF synthesized in Example 1.

[0021] Figure 5 This is the XRD pattern of the monoMOF synthesized in Example 2.

[0022] Figure 6 TEM image of monoMOF synthesized in Example 2.

[0023] Figure 7 This is the XRD pattern of monoMOF synthesized in Example 3.

[0024] Figure 8 TEM image of monoMOF synthesized in Example 3.

[0025] Figure 9 This is the XRD pattern of MOFs synthesized in Comparative Example 1.

[0026] Figure 10 TEM image of MOFs synthesized in Comparative Example 1.

[0027] Figure 11 This is the theoretical simulation image of the MOF synthesized in Comparative Example 1.

[0028] Figure 12 This is the STEM image of the MOF synthesized in Comparative Example 1.

[0029] Figure 13 This is the TEM image of the amorphous product synthesized in Comparative Example 2.

[0030] Figure 14 TEM image of the amorphous product synthesized in Comparative Example 3. DETAILED DESCRIPTION

[0031] The following detailed description of the present invention will make the features and advantages of the present invention more clear and explicit.

[0032] The present invention is described in detail below.

[0033] After extensive research and experimentation, the inventors discovered that the growth process of monoMOFs involves a complex synergistic interaction of multiple variables, including the electronic effects, spatial configuration, and coordination capacity of the regulator and ligand. However, a systematic theoretical model has yet to be established to fully understand these mechanisms, resulting in related research remaining in a "black box" exploration phase, making it difficult to achieve precise synthesis and functional control of monoMOFs.

[0034] The present invention constructs a growth model of monoMOF, systematically analyzes its reaction mechanism, and realizes the precise synthesis of monoMOF based on the control of the coordination ability of the regulator.

[0035] Therefore, according to the first aspect of the present invention, a general preparation method for a single-layer metal-organic framework material is provided. By regulating the coordination effect between the regulator and the ligand, the precise synthesis and functionalization regulation of monoMOF are achieved, thereby successfully preparing monoMOF based on the coordination ability of the regulator.

[0036] The preparation method of the present invention comprises the following steps: (1) Prepare metal salt solution I.

[0037] In the present invention, a metal salt is added to a solvent to form a metal salt solution I, and preferably ultrasonic stirring is performed to accelerate dissolution, thereby obtaining solution I.

[0038] The metal salt is an alkaline earth metal salt, a Group III metal salt, or a transition metal salt, preferably one of transition metal salts such as Zr, Hf, Y, and Eu.

[0039] The solvent is an amide solvent, preferably N,N-dimethylformamide or N,N-dimethylacetamide.

[0040] The temperature of ultrasonic treatment is 1°C-50°C, preferably 10°C-40°C, and the time is 1-30 minutes, preferably 5-10 minutes.

[0041] (2) Add metal salt solution I to the regulator to form a mixed solution.

[0042] In the present invention, the regulator is an organic acid, preferably a monocarboxylic acid, such as formic acid, acetic acid, trifluoroacetic acid, propionic acid, pentafluoropropionic acid, butyric acid, heptafluorobutyric acid, benzoic acid, phenylacetic acid, etc., preferably one of formic acid, acetic acid, trifluoroacetic acid, pentafluoropropionic acid, benzoic acid, etc.

[0043] According to the present invention, the molar ratio of the metal salt to the regulator is 1:(2-500), preferably 1:(10-400).

[0044] According to a preferred embodiment of the present invention, solution I is added to the regulator while maintaining stirring, preferably ultrasonic stirring.

[0045] (3) Prepare ligand solution II.

[0046] In the present invention, the ligand is mixed with a solvent to form a ligand solution II, and preferably stirred, such as ultrasonic stirring, to promote dissolution.

[0047] The ligand is a dicarboxylic acid, preferably a dicarboxylic acid modified with functional groups of different lengths, types, and numbers, more preferably a linear dicarboxylic acid, such as terephthalic acid, biphenyl dicarboxylic acid, terphenyl dicarboxylic acid, and the like.

[0048] According to the present invention, the molar ratio of the metal salt to the ligand is 1:(0.5-5), preferably 1:(0.1-2).

[0049] According to a preferred embodiment of the present invention, while maintaining stirring, preferably ultrasonic stirring The solvent is an amide solvent, preferably N,N-dimethylformamide or N,N-dimethylacetamide, and more preferably the same solvent as that used in preparing solution I in step (1).

[0050] (4) Add ligand solution II to the mixed solution and heat to react.

[0051] In the present invention, the ligand solution II is added to the mixed solution obtained in step (2), the mixture is stirred, sealed, and then heated to react.

[0052] The inventors have found through research that: On the one hand, metal ions can form secondary building units (SBUs) through hydrolysis. Subsequently, the ligands in the system connect with the SBUs to achieve the growth and extension of MOFs. On the other hand, during the growth of MOFs, the introduction of a regulator allows the ligand to extend only in the lateral direction (XY plane), and growth in the Z direction is prohibited, thereby achieving the growth of two-dimensional monoMOF.

[0053] Further research found that fine control can be achieved through regulators. Specifically, for different ligands, specific regulators can be selected, such as a series of monocarboxylic acid derivatives, which act as regulators in the growth process and can adapt to different ligands to achieve the synthesis of monoMOF.

[0054] In the present invention, this step is to heat the reaction in a solvent, commonly known as a "hydrothermal" reaction, which can also be called a "solvothermal" reaction. The reaction temperature is 50°C-150°C, preferably 80°C-120°C, and the reaction time is 0.5-144h, preferably 2-72h.

[0055] (5) After the reaction, post-treatment is performed to obtain monoMOF.

[0056] According to the present invention, the post-treatment includes cooling, separation and washing, preferably naturally cooling to room temperature, centrifuging the obtained solid, and then washing with a solvent.

[0057] According to a preferred embodiment, the washing solvent is an amide, alcohol, nitrile, ether or cyclic ether, aromatic hydrocarbon or ester solvent, preferably one of N,N-dimethylformamide, N,N-dimethylacetamide, methanol, ethanol, acetonitrile, tetrahydrofuran, benzene and ethyl acetate.

[0058] The monoMOF structured solid material obtained by the present invention is measured by XRD spectrum. The image signal proves that the product has a good crystallization state. The crystal plane index corresponding to all diffraction peaks ( hkl ) are satisfied l = 0, proof xy The direction is crystal and does not exist z The periodic structure in the direction confirms its single-layer structure; Furthermore, TEM detection proved that the product was a thin-sheet crystal; while STEM detection showed that a cluster metal structure could be formed, and the clusters were connected by dicarboxylic acids.

[0059] In summary, the monoMOF solid material obtained by the method of the present invention has the following structural units: M x O y (OH) y' L z B p , Preferably, the monoMOF structured solid material structure is a cluster, which appears as a single-layer structure on a macroscopic scale and has the following general structural formula as a whole: [M x O y (OH) y' ] n L zn B pn , In the above two formulas, M is a metal, preferably an alkaline earth metal, a third main group metal, or a transition metal; L is a dicarboxylic acid, preferably a dicarboxylic acid modified with functional groups of different lengths, types, and numbers; B is a monocarboxylic acid, preferably a monofatty acid or a monoaromatic acid; The parameters x, y, y', z, and p represent the ratios or distribution coefficients of M, O, OH, L, and B, respectively, and preferably satisfy the following relationship: The molar ratio of the ligand is M x :L=1:z, z=1-8; The molar ratio of ligand to modulator is L z :B=1:p, p=1-8; The values of y and y' make the monoMOF material electrically neutral; n represents the cluster size to a certain extent, that is, a single-layer MOF structure solid material composed of several structural units. Its value depends on the activity of the raw materials and reagents under the reaction conditions, as well as the reaction scale and reaction time. It usually ranges from 1 to tens of thousands, for example, 5-5000, preferably 1000-10000.

[0060] The second aspect of the present invention provides a monoMOF material prepared by the above method.

[0061] The general preparation method of a single-layer metal-organic framework material provided by the present invention and the single-layer metal-organic framework material obtained thereby have the following beneficial effects: Precisely controlling the growth of monoMOF solves the problem of existing methods that are difficult to control the single-layer structure; It provides a highly versatile synthetic method suitable for the growth of different functional ligands; Through fine-tuning of regulators, precise design of monoMOF pore size and functionalization is achieved, broadening its application range.

[0062] Example 1 Add 0.5 mL of N,N-dimethylformamide and 1 mg (about 3.12 μmol) of hafnium chloride to a beaker and stir ultrasonically to accelerate dissolution to obtain Solution I. Add 30 mg (about 214 μmol) of p-fluorobenzoic acid (B1) to a 5 mL glass bottle, and transfer solution I to the 5 mL glass bottle while maintaining ultrasonic stirring.

[0063] Add 0.5 mL of N,N-dimethylformamide and 0.6 mg (about 1.886 μmol) of terphenyldicarboxylic acid (L1) into a beaker and stir to dissolve to obtain Solution II.

[0064] Add solution II to the glass bottle while stirring, seal it, and place it in an oven for hydrothermal reaction at 100°C for 48 hours; The glass bottle after the reaction was taken out and naturally cooled to room temperature. The obtained liquid was centrifuged to obtain a colloidal solid, which was centrifuged and washed with N,N-dimethylformamide to obtain 0.48 mg of monoMOF material. Its XRD pattern is as follows Figure 1 As shown, the spectrum signal proves that the product is in a good crystallization state, and the crystal plane indices corresponding to all diffraction peaks ( hkl ) are satisfied l = 0, proof xy The direction is crystal and does not exist z The periodic structure in the direction confirms its single-layer structure; its TEM image is as follows Figure 2 As shown, it is proved that the product is a thin plate crystal; The structural image of its theoretical simulation is as follows Figure 3 As shown, Hf 12 O8(OH) 14 Metal Oxide Clusters ( Figure 3The blue polyhedron) is the basic building block, and 12 terphenyl dicarboxylic acid ligands (L1, gray connecting rods) bridge adjacent cluster units in the lateral dimension to form a three-dimensional extended network structure (average per Hf 12 Cluster coordinated with 6 L1); at the same time, 6 B1 are used to cap the cluster unit in the longitudinal dimension to achieve spatial confinement, and the final chemical composition is (Hf 12 O8(OH) 14 )(L1)6(B1)6 stable monolayer structure; Figure 4 STEM microscopy clearly reveals that Hf 12 The periodic arrangement characteristics of the clusters and their geometric parameters are highly consistent with the theoretical model, confirming the feasibility of the structural design.

[0065] Example 2 Add 0.5 mL of N,N-dimethylformamide and 1 mg (about 3.12 μmol) of hafnium chloride to a beaker and stir ultrasonically to accelerate dissolution to obtain Solution I. Add 20 mg (about 142 μmol) of p-fluorobenzoic acid (B1) to a 5 mL glass bottle, and transfer solution I to the 5 mL glass bottle while maintaining ultrasonic stirring.

[0066] Add 0.5 mL of N,N-dimethylformamide and 0.6 mg (about 2.478 μmol) of diphenyldicarboxylic acid (L2) into a beaker and stir to dissolve to obtain solution II'.

[0067] Add solution II' into the glass bottle while stirring, seal it and place it in an oven for hydrothermal reaction at 100℃ for 48h; The glass bottle after the reaction was taken out and cooled naturally to room temperature. The obtained liquid was centrifuged to obtain a colloidal solid, which was centrifuged and washed with N,N-dimethylformamide to obtain 0.42 mg of monoMOF material. Its XRD pattern is shown as follows: Figure 5 As shown, the spectrum signal proves that the product is in a good crystallization state, and the crystal plane indices corresponding to all diffraction peaks ( hkl ) are satisfied l = 0, prove xy The direction is crystal and does not exist z The periodic structure in the direction confirms its single-layer structure; its TEM image is as follows Figure 6 As shown, it is proved that the product is a thin-sheet crystal. After analysis, its unit structure is (Hf 12 O8(OH) 14 )(L2)6(B1)6, indicating that the obtained product is different from the product of Example 1 in the ligand.

[0068] Example 3 Add 0.5 mL of N,N-dimethylformamide and 1 mg (about 3.12 μmol) of hafnium chloride to a beaker and stir ultrasonically to accelerate dissolution to obtain Solution I. Add 20 mg (about 104 μmol) of 3,5-dichlorobenzoic acid (B3) to a 5 mL glass bottle and transfer solution I to the 5 mL glass bottle while maintaining ultrasonic stirring.

[0069] Add 0.5 mL of N,N-dimethylformamide and 0.8 mg (about 1.822 μmol) of 2''-nitro-[1,1':4',1'':4'',1'''-quaterphenyl]-4,4'''-dicarboxylic acid (L3) into a beaker and stir to dissolve to obtain solution II'.

[0070] Add solution II' into the glass bottle while stirring, seal it and place it in an oven for hydrothermal reaction at 100℃ for 48h; The glass bottle after the reaction was taken out and cooled naturally to room temperature. The obtained liquid was centrifuged to obtain a colloidal solid, which was centrifuged and washed with N,N-dimethylformamide to obtain 0.55 mg of monoMOF material. Its XRD pattern is shown as follows: Figure 7 As shown, the spectrum signal proves that the product is in a good crystallization state, and the crystal plane indices corresponding to all diffraction peaks ( hkl ) are satisfied l = 0, proof xy The direction is crystal and does not exist z The periodic structure in the direction confirms its single-layer structure; its TEM image is as follows Figure 8 As shown, it is proved that the product is a thin crystal. After analysis and detection, its unit structure is determined to be (Hf 12 O8(OH) 14 )(L3)6(B3)6.

[0071] Comparative Example 1 Add 0.5 mL of N,N-dimethylformamide and 1 mg (about 3.12 μmol) of hafnium chloride to a beaker and stir ultrasonically to accelerate dissolution to obtain Solution I. Add 60 mg (about 440.7 μmol) of p-toluic acid (B4) to a 5 mL glass bottle, and transfer solution I to the 5 mL glass bottle while maintaining ultrasonic stirring.

[0072] Add 0.5 mL of N,N-dimethylformamide and 0.6 mg (about 1.886 μmol) of terphenyldicarboxylic acid (L1) into a beaker and stir to dissolve to obtain Solution II.

[0073] Add solution II to the glass bottle while stirring, seal it, and place it in an oven for hydrothermal reaction at 100°C for 48 hours; The glass bottle after the reaction was taken out and cooled naturally to room temperature. The obtained liquid was centrifuged and washed with N,N-dimethylformamide to obtain 0.62 mg of MOF material. Its XRD pattern is shown as follows: Figure 9 As shown, the spectrum signal proves that the product is in a good crystal state, which is consistent with Figure 1 Compared with the previous results, the increased diffraction peaks correspond to the crystal plane indices ( hkl ) is not satisfied l = 0, proof xy The direction is crystalline and there is z The periodic structure in the direction confirms its multilayer MOF structure; its TEM image is as follows Figure 10 As shown, it is proved that the product is a three-dimensional crystal; the structural image of its theoretical simulation is shown in Figure 11 As shown, Hf 12 O8(OH) 14 Metal oxide clusters are the core building blocks ( Figure 11 In the lateral dimension, 12 terphenyl dicarboxylate ligands (L1, gray rods) serve as bridging groups to connect adjacent Hf 12 Cluster; in the longitudinal dimension, 6 L1 ligands serve as axial connection units to form a spatially extended network (each Hf 12 The cluster is coordinated with 9 L1 on average); its STEM image is as follows Figure 12 As shown, the authenticity of the theoretical simulation structure is proved. After analysis and detection, it is determined that its unit structure is roughly (Hf 12 O8(OH) 14 )(L1)9.

[0074] Comparative Example 2 Add 0.5 mL of N,N-dimethylformamide and 1 mg (about 3.12 μmol) of hafnium chloride to a beaker and stir ultrasonically to accelerate dissolution to obtain Solution I. While maintaining ultrasonic stirring, solution I was transferred to a 5 mL glass bottle.

[0075] Add 0.5 mL of N,N-dimethylformamide and 0.6 mg (about 1.886 μmol) of terphenyldicarboxylic acid (L1) into a beaker and stir to dissolve to obtain Solution II.

[0076] Add solution II to the glass bottle while stirring, seal it, and place it in an oven for hydrothermal reaction at 100°C for 48 hours; The glass bottle after the reaction was taken out and cooled naturally to room temperature. The obtained liquid was centrifuged to obtain about 0.80 mg of colloidal solid. The non-crystallized product was obtained by centrifugation and washing with N,N-dimethylformamide. The TEM image of the product is shown below. Figure 13 shown.

[0077] Comparative Example 3 Add 0.5 mL of N,N-dimethylformamide and 1 mg (about 3.12 μmol) of hafnium chloride to a beaker and stir ultrasonically to accelerate dissolution to obtain Solution I. Add 30 mg (about 214 μmol) of p-fluorobenzoic acid (B1) to a 5 mL glass bottle, and transfer solution I to the 5 mL glass bottle while maintaining ultrasonic stirring.

[0078] Add 0.5 mL of N,N-dimethylformamide and 0.6 mg (about 1.96 μmol) of 4,4'-dithiodibenzoic acid (L4) into a beaker and stir to dissolve to obtain Solution II.

[0079] Add solution II to the glass bottle while stirring, seal it, and place it in an oven for hydrothermal reaction at 100°C for 48 hours; The glass bottle after the reaction was taken out and cooled naturally to room temperature. After centrifugation of the obtained liquid, about 0.78 mg of colloidal solid was obtained. The non-crystallized product was obtained by centrifugation and washing with N,N-dimethylformamide. The TEM image of the product is shown below. Figure 14 shown.

[0080] The present invention has been described in detail above with reference to specific embodiments and exemplary examples. However, these descriptions should not be construed as limiting the present invention. Those skilled in the art will appreciate that various equivalent substitutions, modifications, or improvements may be made to the technical solutions and implementations of the present invention without departing from the spirit and scope of the present invention, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for preparing a single-layer metal organic framework material, characterized in that: The method comprises the following steps: (1) Prepare metal salt solution I, (2) Add metal salt solution I to the regulator to form a mixed solution. (3) Prepare ligand solution II, (4) Add ligand solution II to the mixed solution and heat to react. (5) After the reaction, post-treatment is performed to obtain monoMOF.

2. The preparation method according to claim 1, characterized in that In step (1), a metal salt is added to a solvent, preferably with ultrasonic stirring, to obtain a metal salt solution I. The metal salt is an alkaline earth metal salt, a Group III metal salt, or a transition metal salt, preferably one of transition metal salts such as Zr, Hf, Y, and Eu. The solvent is an amide solvent, preferably N,N-dimethylformamide or N,N-dimethylacetamide.

3. The preparation method according to claim 2, characterized in that In step (1), the temperature of ultrasonic treatment is 1°C-50°C, preferably 10°C-40°C, and the time is 1-30 minutes, preferably 5-10 minutes.

4. The preparation method according to any one of claims 1 to 3, characterized in that In step (2), the regulator is an organic acid, preferably one of formic acid, acetic acid, trifluoroacetic acid, pentafluoropropionic acid, benzoic acid, etc. The molar ratio of the metal salt to the regulator is 1:(2-500), preferably 1:(10-400).

5. The preparation method according to any one of claims 1 to 4, characterized in that In step (3), the ligand and the solvent are mixed, preferably stirred, to form a ligand solution II. The ligand is a dicarboxylic acid, preferably a linear dicarboxylic acid, such as terephthalic acid, biphenyl dicarboxylic acid, terphenyl dicarboxylic acid, etc. The molar ratio of the metal salt to the ligand is 1:(0.5-5), preferably 1:(0.1-2).

6. The preparation method according to claim 5, characterized in that In step (3), the solvent is an amide solvent, preferably N,N-dimethylformamide or N,N-dimethylacetamide, and more preferably the same solvent as that used in preparing solution I in step (1).

7. The preparation method according to any one of claims 1 to 6, characterized in that In step (4), ligand solution II is added to the mixed solution obtained in step (2), the mixture is stirred, sealed, and heated to react.

8. The preparation method according to claim 1 or 7, characterized in that In step (4), the reaction temperature is 50°C-150°C, preferably 80°C-120°C, and the reaction time is 0.5-144h, preferably 2-72h.

9. The preparation method according to any one of claims 1 to 8, characterized in that: In step (5), the post-treatment includes cooling, separation and washing, preferably naturally cooling to room temperature, centrifuging the obtained solid, and then washing with a solvent.

10. A monoMOF solid material prepared according to the method according to any one of claims 1 to 9.

Images