Method for preparing high-defect metal organic framework material from green, non-corrosive, low-equivalent and multi-site modulating agent and application of high-defect metal organic framework material

Abstract

The invention belongs to the field of inorganic and organic material design and catalysts, and discloses a method for preparing a high-defect metal organic framework material from a green, non-corrosive, low-equivalent and multi-site modulating agent and application of the high-defect metal organic framework material. The invention provides a novel strategy of using a multi-site modulator, breaks through the traditional regulation dimension, and can realize effective competitive coordination with an original ligand under low equivalent weight by regulating the number and relative positions of coordination sites on the modulator, thereby realizing high-density defect introduction. The strategy breaks through a regulation and control mode that traditional modulation only depends on parameters such as the dosage and acidity of the modulation agent, and a brand new regulation and control dimension is provided for design of the modulation agent. Strong acid or high temperature conditions are not needed, the process is simple and convenient to operate, green, economical and easy to scale up, the synthesized high-defect metal organic framework material shows excellent performance in the fields of acid catalysis and the like due to the fact that a large number of open metal sites are exposed, and the practical application value of the high-defect metal organic framework material is remarkably expanded.

Description

[0001] The application belongs to the field of inorganic-organic material design and catalysts, and particularly relates to a method for green and non-corrosive preparation of high-defect metal-organic framework materials using a low-equivalent multi-site modulator, and application of the materials in acid catalysis. BACKGROUND

[0002] Metal-organic frameworks (MOFs) are a class of crystalline porous materials formed by metal nodes and organic ligands through coordination bonds, and have unique advantages such as high specific surface area, precisely controllable pore structure and functional diversity. In recent years, defect engineering has developed into a key strategy for performance regulation of MOFs materials, and the core is to introduce structural defects including ligand defects and cluster defects to precisely regulate the physicochemical properties of MOFs. Such artificially constructed defects can effectively expose more active sites, optimize the transport characteristics of the channels and improve the chemical reaction activity of the materials, thereby significantly expanding the application potential of MOFs in the fields of catalysis, gas separation, sensing and the like.

[0003] Among various defect engineering strategies of metal-organic frameworks, the modulation synthesis method is one of the most widely used methods at present, and the core is to introduce monocarboxylic acid substances as modulators in the synthesis process of metal-organic frameworks. Such modulators can compete with organic ligands for coordination sites of metal nodes, thereby slowing down the assembly rate of metal-ligand and realizing the improvement of crystallinity of the material. This method was initially used to regulate the grain size and morphology of metal-organic frameworks, and subsequent studies have shown that when the modulator forms a stable coordination with the metal node and cannot be replaced by the organic ligand, it will occupy the coordination site of the metal node, thereby constructing defects in the framework structure in a directional manner. Common modulators include monocarboxylic acid substances such as formic acid, acetic acid, difluoroacetic acid, trifluoroacetic acid, benzoic acid, citric acid and proline. There are two key factors affecting the formation of defects, namely the equivalent of the modulator and the ionization constant (pK a ), and it is confirmed that the greater the amount of modulator and the stronger the acidity, the more conducive to improving the defect introduction efficiency of the material.

[0004] The present application proposes a new modulation method, the core of which is to use a modulation agent with a higher number of coordination sites than the original ligand to promote defect formation. This strategy breaks the traditional modulation mode which only relies on the dosage and acidity of the modulation agent, providing a new control dimension for the design of modulation agents. Studies on Zr-MOFs as a model system show that a small amount of multi-site modulation agent can introduce a high density of defects without the need for large amounts of excess single-site modulation agents or highly corrosive acids required in traditional methods. The introduction of defects is also significantly affected by the spatial orientation of the carboxyl group and the number of carboxylic acid sites: the defect induction efficiency of ortho-substituted organic acids is higher than that of meta- or para-substituted products, and the more carboxylic acid sites the modulation agent has, the easier it is to induce defects. The results of Brønsted acid catalytic reaction tests show that the defect concentration has a significant impact on the catalytic activity: a moderate defect concentration can improve the catalytic performance by exposing open metal sites, while an excess of defects will cause the framework to collapse and reduce the accessibility of active sites, resulting in a decrease in catalytic activity. SUMMARY

[0005] One of the purposes of the present application is to provide a method for preparing high-defect metal organic framework materials through a low-equivalent multi-site modulation agent modulation strategy, which is green, economical and efficient in the preparation process.

[0006] The second purpose of the present application is to provide a catalytic application of a defective metal organic framework material.

[0007] Technical solutions of the present application:

[0008] A green and non-corrosive method for preparing high-defect metal organic framework materials based on low-equivalent multi-site modulation agents, which can also control the amount of defects to optimize performance. Multi-site modulation agents such as phthalic acid (2O), isophthalic acid (2M), trimesic acid (3O), trimesic acid (3M), benzene-1,3,5-tetracarboxylic acid (4OM), 1,2,3,4-butanetetracarboxylic acid, 3,5-pyrazole dicarboxylic acid, 3,3',5,5'-biphenyl tetracarboxylic acid, 2,4,5-thiazole tricarboxylic acid, and 1,2,4,5-cyclohexane tetracarboxylic acid and various substances with multiple coordination sites are used. The sample is named Zr-MOF-X-Y, where X is the name of the modulation agent and Y is the dosage (relative to the dosage of terephthalic acid).

[0009] A green and non-corrosive method for preparing high-defect metal organic framework materials based on low-equivalent multi-site modulation agents, which can also control the amount of defects to optimize performance. Multi-site modulation agents such as phthalic acid (2O), isophthalic acid (2M), trimesic acid (3O), trimesic acid (3M), benzene-1,3,5-tetracarboxylic acid (4OM), 1,2,3,4-butanetetracarboxylic acid, 3,5-pyrazole dicarboxylic acid, 3,3',5,5'-biphenyl tetracarboxylic acid, 2,4,5-thiazole tricarboxylic acid, and 1,2,4,5-cyclohexane tetracarboxylic acid and various substances with multiple coordination sites are used. The sample is named Zr-MOF-X-Y, where X is the name of the modulation agent and Y is the dosage (relative to the dosage of terephthalic acid).

[0010] The metal source and carboxylic acid ligand are mixed and added to a synthesis solvent, followed by the addition of a modulation agent to obtain solution I. Solution I is heated at a temperature of 25-220°C to synthesize MOFs. The obtained MOFs are filtered out and then washed with solvent I and solvent II in sequence, and then activated under vacuum to obtain high-defect metal organic framework materials.

[0011] Further, the synthetic solvent is one or more than two combinations of inorganic solvents such as N,N dimethylformamide, N,N dimethylacetamide, tetrahydrofuran, ethylene glycol, methanol, water, and acetone.

[0012] Further, the metal source is one or more than two combinations of metal salts of metals such as zirconium, titanium, copper, iron, magnesium, zinc, aluminum, cerium, cobalt, nickel, indium, and hafnium that can synthesize common MOFs.

[0013] Further, the carboxylic acid ligand is an organic ligand such as terephthalic acid used to synthesize common MOFs.

[0014] Further, the modulating agent is orthophthalic acid (2O), isophthalic acid (2M), trimesic acid (3O), trimesic acid (3M), pyromellitic acid (4OM), 1,2,3,4-butanetetracarboxylic acid, 1,2,4,5-cyclohexanetetracarboxylic acid, 3,5-pyrazole dicarboxylic acid, 3,3',5,5'-biphenyltetracarboxylic acid, 2,4,5-thiazole tricarboxylic acid, tetra-carboxyphenyl porphyrin, 2,6-di(pyridin-4-yl)naphthalene, or tri-(4-imidazolylphenyl)amine, and various ligands with multiple coordination sites; the modulating agent with a number of coordination sites higher than the original ligand breaks through the traditional modulation mode of relying only on the amount, acidity, and other parameters of the modulating agent, providing a new control dimension for the design of the modulating agent. A small amount of multi-site modulating agent can introduce a high density of defects, without the large amount of excess modulating agent or high corrosive acid required in traditional methods.

[0015] The molar ratio of the modulating agent to the metal ions in the metal source is 0.1:1-0.5:1.

[0016] Further, the washing condition is washing for 6-24h using solvent I and washing for 6-24h using solvent II.

[0017] The solvent I is N,N dimethylformamide or / and N,N dimethylacetamide.

[0018] The solvent II is methanol or / and ethanol.

[0019] Further, the vacuum activation condition is an oil bath at 80-150℃ and vacuum for 8-12h.

[0020] The application of the high-defect metal organic framework material obtained by the above method, the steps are as follows:

[0021] Mix the high-defect metal organic framework material, solvent, internal standard, and substrate, and ultrasonically mix them until they are uniformly mixed; heat and stir under an oil bath at 50-150℃ to perform the reaction.

[0022] The beneficial effects of the present application are:

[0023] 1、The present application adopts low equivalent multi-site modulator modulation strategy to prepare high defect metal organic framework material, and the synthesis process does not need to use a large amount of excess modulator and high corrosive acid, so as to effectively reduce the preparation cost and environmental pollution.

[0024] 2、The present application realizes efficient and controllable synthesis of defects: by selecting a multi-site modulator, and by means of its coordination characteristics, the non-stoichiometric coordination of metal clusters and organic ligands is induced in the synthesis process, so that a large amount of defects can be introduced under low modulator equivalent.

[0025] The high-defect metal organic framework material synthesized by the present application has excellent target application performance: the high-defect structure exposes a large number of open metal sites, significantly improves the chemical reaction activity of the material, and especially shows excellent catalytic performance in the field of catalysis (such as various Bronsted acid catalytic reactions), thereby expanding the practical application scenarios of metal organic framework materials. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is an XRD spectrum of Zr-MOF modulated by o-phthalic acid (2O);

[0027] Figure 2 is an XRD spectrum of Zr-MOF modulated by m-phthalic acid (2M);

[0028] Figure 3 is an XRD spectrum of Zr-MOF modulated by o-phthalic acid (3O);

[0029] Figure 4 is an XRD spectrum of Zr-MOF modulated by trimesic acid (3M);

[0030] Figure 5 is an XRD spectrum of Zr-MOF modulated by pyromellitic acid (4OM);

[0031] Figure 6 is a TGA spectrum of Zr-MOF modulated by o-phthalic acid (2O);

[0032] Figure 7 is a TGA spectrum of Zr-MOF modulated by m-phthalic acid (2M);

[0033] Figure 8 is a TGA spectrum of Zr-MOF modulated by o-phthalic acid (3O);

[0034] Figure 9 is a TGA spectrum of Zr-MOF modulated by trimesic acid (3M);

[0035] Figure 10 is a TGA spectrum of Zr-MOF modulated by pyromellitic acid (4OM);

[0036] Figure 11 is a SEM image of standard Zr-MOF;

[0037] Figure 12 SEM image comparison of Zr-MOFs modulated with phthalic acid (2O), where (a) is Zr-MOF-2O-0.10, (b) is Zr-MOF-2O-0.11;

[0038] Figure 13 SEM image comparison of Zr-MOFs modulated with isophthalic acid (2M), where (a) is Zr-MOF-2M-0.10, (b) is Zr-MOF-2M-0.20, (c) is Zr-MOF-2M-0.35;

[0039] Figure 14 SEM image comparison of Zr-MOFs modulated with trisbenzoic acid (3O), where (a) is Zr-MOF-3O-0.10, (b) is Zr-MOF-3O-0.15, (c) is Zr-MOF-3O-0.17;

[0040] Figure 15 SEM image comparison of Zr-MOFs modulated with trimesic acid (3M), where (a) is Zr-MOF-3M-0.10, (b) is Zr-MOF-3M-0.15;

[0041] Figure 16 SEM image comparison of Zr-MOFs modulated with pyromellitic acid (4OM), where (a) is Zr-MOF-4OM-0.10, (b) is Zr-MOF-4OM-0.15, (c) is Zr-MOF-4OM-0.17;

[0042] Figure 17 Nitrogen adsorption isotherms of Zr-MOFs modulated with phthalic acid (2O);

[0043] Figure 18 Nitrogen adsorption isotherms of Zr-MOFs modulated with isophthalic acid (2M);

[0044] Figure 19 Nitrogen adsorption isotherms of Zr-MOFs modulated with trisbenzoic acid (3O);

[0045] Figure 20 Nitrogen adsorption isotherms of Zr-MOFs modulated with trimesic acid (3M);

[0046] Figure 21 Nitrogen adsorption isotherms of Zr-MOFs modulated with pyromellitic acid (4OM);

[0047] Figure 22is the pore size distribution curve of Zr-MOF modulated using phthalic acid (2O);

[0048] Figure 23 is the pore size distribution curve of Zr-MOF modulated using isophthalic acid (2M);

[0049] Figure 24 is the pore size distribution curve of Zr-MOF modulated using trimesic acid (3O);

[0050] Figure 25 is the pore size distribution curve of Zr-MOF modulated using trimesic acid (3M);

[0051] Figure 26 is the pore size distribution curve of Zr-MOF modulated using pyromellitic acid (4OM);

[0052] Figure 27 is the conversion spectrum of Zr-MOF modulated using phthalic acid (2O);

[0053] Figure 28 is the conversion spectrum of Zr-MOF modulated using isophthalic acid (2M);

[0054] Figure 29 is the conversion spectrum of Zr-MOF modulated using trimesic acid (3O);

[0055] Figure 30 is the conversion spectrum of Zr-MOF modulated using trimesic acid (3M);

[0056] Figure 31 is the conversion spectrum of Zr-MOF modulated using pyromellitic acid (4OM). DETAILED DESCRIPTION

[0057] The specific embodiments of the present application are further illustrated in conjunction with the accompanying drawings and technical solutions.

[0058] Example 1

[0059] Specific steps for preparing Zr-MOF-2M sequence by low equivalent multi-site modulator modulation strategy:

[0060] (1) Measure 26 ml (340 mmol) of N, N-dimethylformamide (DMF) solvent and inject into a 30 ml glass bottle.

[0061] (2) First, weigh 53 mg (227 μmol) of zirconium tetrachloride (ZrCl4) and 37.7 mg (227 μmol) of terephthalic acid (BDC) into the solvent, and then add isophthalic acid (2M). The amount and ratio of isophthalic acid (2M) are shown in the following table:

[0062]

[0063] Subsequently, the solution was stirred to dissolve the solid.

[0064] (3) The solution was placed in an oven at 120°C for 48 hours for solvothermal synthesis of defective Zr-MOF;

[0065] (4) The obtained white powder was washed with DMF for 24 h, and then washed with methanol for 24 h, to obtain Zr-MOF-2M-0.10, Zr-MOF-2M-0.20, Zr-MOF-2M-0.30 and Zr-MOF-2M-0.35, respectively.

[0066] Example 2

[0067] Specific steps for preparing Zr-MOF-2O sequence by low equivalent multi-site modulator modulation strategy:

[0068] On the basis of Example 1, isophthalic acid (2M) was replaced by phthalic acid (2O), and the amount and ratio of phthalic acid (2O) were as follows:

[0069]

[0070] Other treatments were the same, to obtain Zr-MOF-2O-0.10 and Zr-MOF-2O-0.11.

[0071] Example 3

[0072] Specific steps for preparing Zr-MOF-3O sequence by low equivalent multi-site modulator modulation strategy:

[0073] On the basis of Example 1, isophthalic acid (2M) was replaced by phthalic acid (2O), and the amount and ratio of phthalic acid (2O) were as follows:

[0074]

[0075] Other treatments were the same, to obtain Zr-MOF-3O-0.10, Zr-MOF-3O-0.15 and Zr-MOF-3O-0.17.

[0076] Example 4

[0077] Specific steps for preparing Zr-MOF-3M sequence by low equivalent multi-site modulator modulation strategy:

[0078] On the basis of Example 1, isophthalic acid (2M) was replaced by phthalic acid (2O), and the amount and ratio of phthalic acid (2O) were as follows:

[0079]

[0080] Other treatments are the same, Zr-MOF-3M-0.10 and Zr-MOF-3M-0.15 are obtained.

[0081] Example 5

[0082] Specific steps for preparing Zr-MOF-4OM sequence by low equivalent multi-site modulator modulation strategy:

[0083] On the basis of Example 1, isophthalic acid (2M) is replaced by pyromellitic acid (4OM), and the amount and ratio of pyromellitic acid (4OM) are as follows:

[0084]

[0085] Other treatments are the same, Zr-MOF-4OM-0.10, Zr-MOF-4OM-0.15 and Zr-MOF-4OM-0.17 are obtained.

[0086] Comparative Example 1

[0087] Specific steps for preparing standard Zr-MOF:

[0088] On the basis of Example 1, remove "add isophthalic acid (2M)" in step (2), and other treatments are the same, to obtain standard Zr-MOF.

[0089] Comparative Example 2

[0090] Specific steps for preparing defect Zr-MOF with excess modulator:

[0091] On the basis of Example 1, isophthalic acid (2M) in step (2) is replaced by orthophthalic acid (2M), isophthalic acid (2M), trimesic acid (3M), benzene-1,3,5-tricarboxylic acid (3O) and pyromellitic acid (4OM), and the amount and ratio are as follows:

[0092]

[0093] Zr-MOF-2O-0.12, Zr-MOF-2M-0.37, Zr-MOF-3O-0.20, Zr-MOF-3M-0.17 and Zr-MOF-4OM-0.20 are obtained.

[0094] The materials obtained in Examples 1, 2, 3, 4, 5 and Comparative Examples 1 and 2 are characterized by X-ray powder diffraction as follows: Figures 1-5As shown, all of the Example 1, 2, 3, 4, 5 and Comparative Example 1 have the XRD characteristic peaks of Zr-Zr-MOF, and the modulated samples all show poor peak shape (representing poor crystallinity) compared with the standard Zr-MOF. The longitudinal comparison of each sample sequence shows that the crystallinity of the sample decreases with the increase of the amount of multi-site modulator; the characteristic peaks of Zr-MOF of Comparative Example 2 almost disappear, indicating that excessive multi-site modulator leads to too many defects, which can cause the collapse of the MOF structure. Figures 6-10 is the thermogravimetric analysis diagram of Example 1, 2, 3, 4, 5 and Comparative Example 1, 2, and the calculation of the number of defects shows that the number of defects of the defective Zr-Zr-MOF increases with the increase of the amount of modulator. Figure 11 is the scanning electron microscope (SEM) photo of the standard Zr-MOF, Figures 12-16 are the scanning electron microscope photos of the Zr-MOF-2O, Zr-MOF-2M, Zr-MOF-3O, Zr-MOF-3M and Zr-MOF-4OM sequence samples, respectively. The photos show that the crystal size of the Zr-MOF modulated by the multi-site modulator is significantly reduced compared with the standard Zr-MOF. Figures 17-21 is the nitrogen adsorption diagram of the five sequence samples, which proves that the specific surface area of all the sequence samples has a downward trend with the increase of the amount of multi-site modulator. Figures 22-26 is the pore size distribution curve of the five sequence samples, and no mesopore appears except Zr-MOF-3M-0.10, which is consistent with the characteristics of ligand defects. The above characterization can prove the successful synthesis of the defective Zr-MOF, and the number of defects has a positive correlation with the amount of multi-site modulator.

[0095] Example 6

[0096] Multi-site modulator modulated Zr-MOF for styrene epoxide ring-opening reaction

[0097] The Zr-MOF modulated by the desired organic acid has a gradient increase in the number of defects with the increase of the amount of modulator, and is applied to the styrene epoxide ring-opening reaction.

[0098] The steps are as follows: 1000 μL of isopropyl alcohol, 90 μL of n-dodecane and 46 μL of styrene oxide are added to a small glass bottle, in which isopropyl alcohol is used as a substrate and a solvent, and n-dodecane is used as an internal standard. The three reagents are mixed uniformly by ultrasonic, and then the mixed solution is injected into the reactor pre-activated and containing 8 mg of defective Zr-MOF, and the process is kept in vacuum, and then stirred in a 55°C oil bath. After 24 h of reaction, the sample is taken and the conversion rate of the reaction is obtained by calculating the peak area using the internal standard method by gas chromatograph.

[0099] The conversion rates 27-31 of the five sequence samples are shown, and it is found by analysis that all the sequence samples present a volcano trend, proving that the medium defect concentration can improve the catalytic performance by exposing the open metal sites, while the excess of defects will cause the framework to collapse and the accessibility of the active sites to decrease, resulting in the decrease of the catalytic activity. At the same time, the defect Zr-MOF obtained by using the modulator with a meta-carboxylic acid has higher reaction activity.

[0100] The above merely describes the preferred embodiments of the present application, and is not intended to limit the scope of the present application. It should be noted that, for those skilled in the art, some improvements and adjustments can be made without departing from the principles of the present application, and these improvements and adjustments should be considered as the protection scope of the present application.

Claims

1. A method for preparing high-defect metal-organic framework materials using a green, non-corrosive, low-equivalent multi-site modulator, characterized in that, The steps are as follows: The metal source and carboxylic acid ligand were mixed and added to the synthesis solvent, followed by the addition of a modifier to obtain solution I. Solution I was heated at 25-220℃ to synthesize MOFs. The obtained MOFs were filtered out and washed with solvent I and solvent II in sequence by stirring. After vacuum activation, high-defect metal-organic framework materials were obtained.

2. The method according to claim 1, characterized in that, The synthesis solvent is one or a combination of two or more of N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, ethylene glycol, methanol, water, and acetone.

3. The method according to claim 1, characterized in that, The metal source is one or more of zirconium, titanium, copper, iron, magnesium, zinc, aluminum, cerium, cobalt, nickel, indium, and hafnium.

4. The method according to claim 1, characterized in that, The carboxylic acid ligand is terephthalic acid; The modifiers are phthalic acid, isophthalic acid, triphenylcarboxylic acid, pyromellitic acid, pyromellitic tetracarboxylic acid, 1,2,3,4-butanetetracarboxylic acid, 1,2,4,5-cyclohexanetetracarboxylic acid, 3,5-pyrazoledicarboxylic acid, 3,3′,5,5′-biphenyltetracarboxylic acid, 2,4,5-thiazolyltricarboxylic acid, tetracarboxyphenylporphyrin, 2,6-bis(pyridin-4-yl)naphthalene, or tris-(4-imidazolylphenyl)amine.

5. The method according to claim 1, characterized in that, The molar ratio of the modulator to the metal ions in the metal source is 0.1:1 to 0.5:

1.

6. The method according to claim 1, characterized in that, The washing conditions are: washing with solvent I for 6-24 hours and washing with solvent II for 6-24 hours. Solvent I is N,N-dimethylformamide or / and N,N-dimethylacetamide; Solvent II is methanol and / or ethanol.

7. The method according to claim 1, characterized in that, The vacuum activation conditions are an oil bath at 80-150℃ with vacuuming for 8-12 hours.

8. An application of a high-defect metal-organic framework material obtained by any one of claims 1-6, characterized in that, The steps are as follows: The high-defect metal-organic framework material, solvent, internal standard, and substrate are mixed and ultrasonicated to ensure homogeneity; the reaction is carried out by heating and stirring in an oil bath at 50-150°C.

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