Preparation method of mesoporous aluminum-based MOF (Metal Organic Framework) material with excellent benzene diffusivity

Abstract

The invention provides a preparation method of a mesoporous aluminum-based MOF (Metal Organic Framework) material with excellent benzene diffusivity. The method comprises the following steps: by taking positive trivalent aluminum salt as an aluminum source and 3, 4 ', 5-biphenyl tricarboxylic acid as an organic ligand, dissolving the aluminum source and the organic ligand in an organic solvent, then adding a regulator and water, fully stirring and mixing reactants, putting the mixture into a drying oven, and setting reaction temperature and reaction time for reaction. And after the reaction is finished, carrying out centrifugal separation, washing the material with a detergent, and carrying out vacuum drying to obtain the mesoporous aluminum-based MOF material ZJU-621 (Al). The structure of the MOF material is formed by an aluminum cluster (Al8 (OH) 15 (-COO) 9) and 3, 4 ', 5-biphenyl tricarboxylic acid through a coordinate bond, and the MOF material has a specific surface area of 2344 m < 2 > / g and a # imgabs0 # ordered mesoporous channel. The material has excellent benzene diffusion capacity, the benzene diffusion coefficient is 2.65 * 10 <-5 > cm < 2 > / s and is far higher than that of other reported MOFs materials, and adsorption and desorption of adsorbate in the adsorption process are facilitated. In conclusion, ZJU-621 (Al) has potential practical application value in the field of benzene adsorption.

Description

Technical Field

[0001] The invention relates to the field of research and development of adsorption materials, and in particular to a method for preparing a mesoporous aluminum-based MOF material with excellent benzene diffusion capacity. Background Art

[0002] Aluminum-based metal-organic frameworks (MOFs), as an important branch of the MOFs family, have the advantages of low toxicity, low cost and abundance in nature (Double-walled Al-based MOF with large microporous specific surface area for trace benzene adsorption. Nat. Commun. 2024, 15, 3204-3212), and have excellent adsorption potential for harmful gases such as benzene. However, most of the aluminum-based MOFs materials reported are microporous materials, such as MOF-519 (Al), CAU-10 (Al) and Al-PMOF, which lead to slow diffusion rates of small molecules, limiting their application in adsorption mass transfer diffusion (High methane storage capacity in aluminum metal-organic frameworks. J. Am. Chem. Soc. 2014, 136, 5271-5280). Therefore, it is urgent to develop mesoporous aluminum-based MOFs materials to significantly improve their performance, such as the diffusion rate of benzene. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing a mesoporous aluminum-based MOF material with excellent benzene diffusion ability. The present invention provides a mesoporous aluminum-based MOF material with excellent benzene diffusion ability in the field of adsorption and diffusion of aluminum-based MOFs materials.

[0004] The present invention adopts the following technical solution: The preparation method of the mesoporous aluminum-based MOF material with excellent benzene diffusion ability is:

[0005] The trivalent aluminum salt and 3,4',5-biphenyltricarboxylic acid ligand are dissolved in a mixture of an organic solvent, an acidic regulator and water at a molar ratio of 1:1.5 to 2:1, and stirred to mix evenly. Then, the reactants are placed in a reactor and placed in an oven for reaction. After the reaction is completed, the product is separated. The product is washed with detergents such as N,N-dimethylformamide and acetone / ethanol in turn to remove the guest molecules in the pores of the MOF material, and then vacuum dried to obtain a mesoporous aluminum-based MOF material.

[0006] Furthermore, the trivalent aluminum salt is Al(NO3)3·9H2O or AlCl3·6H2O, preferably Al(NO3)3·9H2O.

[0007] Furthermore, the organic solvent is N,N-dimethylformamide, the volume ratio of the organic solvent to the acidic regulator is 15:1 to 20:1, and the volume ratio of the acidic regulator to water is 1:3 to 3:1.

[0008] Furthermore, the acidity regulator is formic acid or acetic acid, more preferably formic acid.

[0009] Furthermore, the detergent is one or both of acetone and ethanol, preferably acetone.

[0010] Furthermore, the reaction temperature is 120°C to 140°C.

[0011] Furthermore, the reaction time is 24 hours to 84 hours.

[0012] Furthermore, the preparation method of the mesoporous aluminum-based MOF material is applied in the adsorption of benzene.

[0013] The present invention has the following beneficial effects:

[0014] (1) The novel aluminum-based MOF material prepared by the present invention is named ZJU-621(Al). It is composed of 3,4',5-biphenyltricarboxylic acid ligand and secondary building block Al8(OH) 15 (–COO)9 is formed by coordination bonds. ZJU-621(Al) has 2344m 2 The specific surface area and The diffusion coefficient of ZJU-621(Al) for benzene is as high as 2.65×10 -5 cm 2 / s, which is the maximum benzene diffusion coefficient reported so far.

[0015] (2) The ZJU-621(Al) prepared by the present invention has good chemical stability and thermal stability.

[0016] (3) The ZJU-621(Al) prepared in the present invention not only has a high benzene adsorption capacity of 9.99 mmol / g when P / P0=0.10, but also has the highest benzene diffusion coefficient of 2.65×10 -5 cm 2 / s, can be used for the adsorption and diffusion of benzene vapor. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1Schematic diagram of the structure of the mesoporous aluminum-based MOF material prepared in Example 1 of the present invention;

[0018] Figure 2 The powder X-ray diffraction data of ZJU-621(Al) prepared in Example 1 of the present invention, and the powder X-ray diffraction data after standing in air for 7 days, as well as the PXRD data diagram obtained by theoretical calculation;

[0019] Figure 3 is a thermogravimetric curve of the mesoporous aluminum-based MOF material prepared in Example 1 of the present invention;

[0020] Figure 4 is a 77K nitrogen adsorption-desorption isotherm diagram of the mesoporous aluminum-based MOF material prepared in Example 1 of the present invention;

[0021] Figure 5 is a pore size distribution diagram of the mesoporous aluminum-based MOF material prepared in Example 1 of the present invention;

[0022] Figure 6 It is the benzene diffusion coefficient of the mesoporous aluminum-based MOF material ZJU-621 (Al) prepared in Example 1 of the present invention and other MOFs materials. DETAILED DESCRIPTION

[0023] The present invention is further described below in conjunction with embodiments, comparative examples and accompanying drawings.

[0024] Example 1 Preparation method for mesoporous aluminum-based MOF material with excellent benzene diffusion ability

[0025] Weigh 400 mg of aluminum nitrate nonahydrate and 400 mg of 3,4',5-biphenyltricarboxylic acid ligand (molar ratio of 1:1.32), mix into 15.00 mL of N,N-dimethylformamide, 3.00 mL of water, and 2.00 mL of formic acid. After the mixture is ultrasonically mixed, it is placed in a reactor for reaction. The reaction temperature is 130 ° C, the reaction time is 72 hours, and after the reaction is completed, centrifugal separation is performed to obtain a white product, namely ZJU-621 (Al). The product is washed with N,N-dimethylformamide and acetone in turn, and the washed product is stored in a vacuum drying oven. The specific surface area of ​​ZJU-621 (Al) is 2344m 2 / g and the ordered mesoporous channel size is The static adsorption amount of benzene vapor was determined by using a JW-ZQ100 vapor adsorption instrument, which was equipped with a steam generator and a heating device. The temperature of the steam generator was maintained at 313K by the heating device to ensure the generation of stable benzene vapor. The adsorbent sample was preserved during the adsorption process and stabilized by water bath heating. Before the measurement, ZJU-621(Al) was vacuum degassed at 378K for 24h to remove the guest molecules in the pore structure of the adsorbent and to achieve the purpose of activating the ZJU-621(Al) sample. At P / P0=0.10 and 298K, the adsorption amount of benzene reached 9.99mmol / g, which was higher than MOF-74(Mg) (6.02mmol / g) and PAF-1 (7.83mmol / g). In addition, a time series of benzene vapor adsorption experiments on ZJU-621(Al) were carried out on a BSD-VVS multi-station gravimetric gas phase adsorption instrument. Taking ZJU-621(Al) as an example, a sample of ZJU-621(Al) (57.65 mg) was heated at 120°C for 12 hours to remove the guest molecules in the skeleton. Benzene vapor was introduced into the chamber of the device, and the relative pressure and adsorption temperature were controlled at 0.10 and 298 K. The mass of ZJU-621(Al) and the combustion chamber pressure were continuously recorded, and the benzene diffusion coefficient of ZJU-621(Al) was obtained to be as high as 2.65×10 -5 cm 2 / s.

[0026] Example 2 Preparation method for mesoporous aluminum-based MOF material with excellent benzene diffusion ability

[0027] Weigh 400 mg of aluminum chloride hexahydrate and 400 mg of 3,4',5-biphenyltricarboxylic acid ligand (molar ratio of 1:1.18), mix into 15.00 mL of N,N-dimethylformamide, 3.00 mL of water, and 2.00 mL of formic acid. After the mixture is ultrasonically mixed, it is placed in a reactor for reaction. The reaction temperature is 140°C and the reaction time is 84 hours. After the reaction is completed, centrifugal separation is performed to obtain a white product, namely ZJU-621 (Al). The product is washed with N,N-dimethylformamide and acetone in turn, and the washed product is stored in a vacuum drying oven. The specific surface area of ​​ZJU-621 (Al) is 2134 m 2 / g and the ordered mesoporous channel size is At P / P0=0.10 and 298K, the adsorption capacity of benzene reaches 9.86mmol / g and the benzene diffusion coefficient is 2.45×10 -5 cm 2 / s.

[0028] Example 3 Preparation method of mesoporous aluminum-based MOF material with excellent benzene diffusion ability

[0029] Weigh 600 mg of aluminum nitrate nonahydrate (1.33) and 400 mg of 3,4',5-biphenyltricarboxylic acid ligand (molar ratio of 1.14:1), mix into 15.00 mL of N,N-dimethylformamide, 3.00 mL of water, and 2.00 mL of formic acid. After the mixture is ultrasonically mixed, it is placed in a reactor for reaction. The reaction temperature is 130 ° C, the reaction time is 66 hours, and after the reaction is completed, centrifugal separation is performed to obtain a white product, namely ZJU-621 (Al). The product is washed with N,N-dimethylformamide and acetone in turn, and the washed product is stored in a vacuum drying oven. The specific surface area of ​​ZJU-621 (Al) is 2125m 2 / g and the ordered mesoporous channel size is At P / P0=0.10 and 298K, the adsorption capacity of benzene reaches 9.72mmol / g and the benzene diffusion coefficient is 2.42×10 -5 cm 2 / s.

[0030] Example 4 Structure of the mesoporous aluminum-based MOF material obtained in Example 1

[0031] The structure of mesoporous aluminum-based MOF materials was analyzed by Brucker D8 Venture single crystal X-ray diffractometer, and finally the Figure 1 The crystal structure shown in FIG. 1 corresponds to the theoretical powder X-ray diffraction (PXRD) data of the structure and the main diffraction peaks of the experimentally measured PXRD, indicating that the crystal structure is accurate. Figure 2 .

[0032] Example 5 Stability analysis of the mesoporous aluminum-based MOF material obtained in Example 1

[0033] After the mesoporous aluminum-based MOF material was placed in the air for 7 days, its PXRD data were consistent with the main PXRD diffraction peaks obtained by the reaction, indicating that it has good chemical stability. Figure 2 The thermogravimetric curve of the material did not change significantly before 150°C, indicating that it has good thermal stability. Figure 3 .

[0034] Example 6 N2 adsorption-desorption isotherms of the mesoporous aluminum-based MOF material obtained in Example 1 at 77K

[0035] At 77K, the N2 adsorption-desorption isotherms of ZJU-621(Al) after vacuum activation were measured. Figure 4 . It can be measured that the pore size is mainly concentrated See Figure 5 , which is consistent with the spatial structure size obtained by structural analysis ( Figure 1 , ).

[0036] Example 7 Diffusion coefficient of the mesoporous aluminum-based MOF material obtained in Example 1 for benzene at 25°C

[0037] At a relative pressure of 0.10 and 298K, the benzene diffusion coefficient of ZJU-621(Al) after vacuum activation and the materials reported in the literature were determined. Figure 6 The diffusion coefficient of ZJU-621(Al) for benzene is as high as 2.65×10 –5 cm 2 / s, which is much higher than other materials. For example, ZJU-520 (Al) is made of 3,5-di(4-carboxyphenyl)pyridine as an organic ligand. This material is a microporous material with a diffusion coefficient of (2.72×10 –7 cm 2 / s)(Double-walled Al-based MOF with large microporous specific surface area for trace benzene adsorption); MOF-519(Al) is made of 1,3,5-tri(4-carboxyphenyl)benzene as an organic ligand. This material is a microporous material with a diffusion coefficient of (6.49×10 –7 cm 2 / s)(High methane storage capacity in aluminum metal-organicframeworks). In summary, ZJU-621(Al) is a potential benzene diffusion material, which is conducive to the adsorption of benzene under mild conditions.

[0038] Comparative Example 1

[0039] Weigh 400 mg of aluminum nitrate nonahydrate and 10 mg of 3,4',5-biphenyltricarboxylic acid ligand (molar ratio of 30:1), mix into 15.00 mL of N,N-dimethylformamide, 3.00 mL of water, and 2.00 mL of formic acid. After the mixture is ultrasonically mixed, it is placed in a reactor for reaction. The reaction temperature is 130°C and the reaction time is 72 hours. After the reaction is completed, there is no product.

[0040] Comparative Example 2

[0041] Weigh 400 mg of aluminum nitrate nonahydrate and 400 mg of 3,4',5-biphenyltricarboxylic acid ligand (molar ratio of 1:1.32), mix into 15.00 mL of N,N-dimethylformamide, 3.00 mL of water, and 12.00 mL of formic acid. After the mixture is ultrasonically mixed, it is placed in a reactor for reaction. The reaction temperature is 130°C and the reaction time is 72 hours. After the reaction is completed, no product is produced.

[0042] Comparative Example 3

[0043] Weigh 400 mg of aluminum nitrate nonahydrate and 400 mg of 3,4',5-biphenyltricarboxylic acid ligand (molar ratio of 1:1.32), mix into 15.00 mL of N,N-dimethylformamide, 3.00 mL of water, and 2.00 mL of formic acid. After the mixture is ultrasonically mixed, it is placed in a reactor for reaction. The reaction temperature is 80 ° C, the reaction time is 72 hours, and after the reaction is completed, centrifugal separation is performed to obtain a white product. The product is washed with N,N-dimethylformamide and acetone in turn, and the washed product is stored in a vacuum drying oven. The specific surface area of ​​the product is 876m 2 / g and the ordered mesoporous channel size is The diffusion coefficient of benzene is only 4.53×10 -6 cm 2 / s.

[0044] Comparative Example 4

[0045] Weigh 400 mg of aluminum nitrate nonahydrate and 400 mg of 3,4',5-biphenyltricarboxylic acid ligand (molar ratio of 1:1.32), mix into 15.00 mL of N,N-dimethylformamide, 3.00 mL of water, and 2.00 mL of formic acid. After the mixture is ultrasonically mixed, it is placed in a reactor for reaction. The reaction temperature is 130 ° C, the reaction time is 12 hours, and after the reaction is completed, centrifugal separation is performed to obtain a white product. The product is washed with N,N-dimethylformamide and acetone in turn, and the washed product is stored in a vacuum drying oven, and its specific surface area is 1435m 2 / g and the ordered mesoporous channel size is The diffusion coefficient of benzene is only 6.58×10 -6 cm 2 / s.

[0046] The mesoporous aluminum-based MOF material prepared in Example 1 has a periodic skeleton structure and is composed of 3,4',5-biphenyltricarboxylic acid and aluminum clusters. Figure 1 ZJU-621(Al) has good chemical stability. After being placed in air for 7 days, its PXRD pattern did not change significantly. Figure 2In addition, the material also has good thermal stability, and its thermogravimetric analysis chart does not show obvious loss before 150°C, see Figure 3 The specific surface area of ​​ZJU-621(Al) is 2344m 2 / g(see Figure 4 ) and ordered mesoporous channels (See Figure 5 ZJU-621(Al) has excellent benzene diffusion capacity. When the relative pressure is 0.10, its diffusion coefficient for benzene is as high as 2.65×10 –5 cm 2 / s, much higher than other materials.

[0047] Comparing Example 1 with Comparative Example 1, it can be seen that when the molar ratio of the aluminum source and the organic ligand is 30:1, it is not within the optimal ratio range, resulting in no product. It can be seen that the amount and molar ratio of the aluminum source and the organic ligand are very important in the preparation process of mesoporous ZJU-621 (Al). Comparing Example 1 with Comparative Example 2, it can be seen that when the volume ratio of the acidic regulator and water is 4:1, it is not within the optimal ratio range, and there is no product. It can be seen that the amount of the acidic regulator is also very important. Comparing Example 1 with Comparative Example 3, it can be seen that when the reaction temperature is 80°C, it is not within the optimal reaction temperature range, and the specific surface area of ​​the obtained product is only 876m 2 / g, the diffusion coefficient of benzene is only 4.53×10 -6 cm 2 / s, the performance of the obtained product is reduced. Comparison of Example 1 and Comparative Example 4 shows that when the reaction time is 12 hours, it is not within the optimal reaction time range, and the specific surface area of ​​the obtained product is only 1435m 2 / g, the diffusion coefficient of benzene is only 6.58×10 -6 cm 2 / s, the performance of the obtained product also decreased. Therefore, the insufficient reaction temperature and reaction time resulted in the imperfect framework structure of MOF, which made the performance of the product deteriorate. It can be seen that reaction temperature and reaction time are crucial for the preparation of ZJU-621(Al).

[0048] The embodiments shown in the present invention are only preferred technical solutions and should not be regarded as limitations on the patent of the present invention. In addition, all replacements and improvements based on the present invention belong to the protection scope of the present invention.

Claims

1. A method for preparing a mesoporous aluminum-based MOF material with excellent benzene diffusion capacity, characterized in that: The method comprises the following steps: Aluminum salt, 3,4',5-biphenyltricarboxylic acid, acidic regulator, water and organic solvent are mixed evenly; the evenly mixed mixture is loaded into the inner tank of a reactor, and then moved into an oven for reaction. After the reaction is completed, the final mesoporous aluminum-based MOF material is obtained by centrifugal separation, product washing and vacuum drying.

2. The preparation method according to claim 1, characterized in that: The aluminum salt is trivalent aluminum salt or its hydrate.

3. The preparation method according to claim 1, characterized in that: The acidic regulator is one or more of formic acid and acetic acid; and the organic solvent is N,N-dimethylformamide.

4. The preparation method according to claim 1, characterized in that: The molar ratio of the aluminum salt to 3,4',5-biphenyltricarboxylic acid is 1:1.5-2:1; the volume ratio of the organic solvent to the acidic regulator is 5:1-10:1; the volume ratio of water to the acidic regulator is 1:1-2:1; and the molar volume ratio of 3,4',5-biphenyltricarboxylic acid to water is 0.20 mmol / mL-0.80 mmol / mL.

5. The preparation method according to claim 1, characterized in that: The reaction temperature is 120° C. to 140° C.; the reaction time is 24 hours to 84 hours.

6. The preparation method according to claim 1, characterized in that: The process of washing the product is: using N,N-dimethylformamide and a detergent to wash the product in sequence, wherein the detergent is one or a mixture of acetone and ethanol.

7. A mesoporous aluminum-based MOF material prepared by the method according to any one of claims 1 to 6.

8. Use of the mesoporous aluminum-based MOF material according to claim 7 as an adsorption material in benzene adsorption.

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