Process for the preparation of mesoporous al-based mof materials with excellent benzene diffusion capacity

Abstract

The application provides a preparation method of a mesoporous aluminum-based MOF material with excellent benzene diffusion capacity. The method uses a trivalent aluminum salt as an aluminum source and 3,4',5-biphenyltricarboxylic acid as an organic ligand, the aluminum source and the organic ligand are dissolved in an organic solvent, then a regulator and water are added, the mixed reactants are fully stirred, and then are placed in an oven, the reaction temperature and time are set, and the reaction is carried out. After the reaction is completed, the mesoporous aluminum-based MOF material ZJU-621(Al) is obtained through centrifugal separation, washing of the material with a washing agent and vacuum drying. The structure of the MOF material is composed of aluminum clusters (Al8(OH) 15 (–COO)9) and 3,4',5-biphenyltricarboxylic acid through coordination bonds, and the MOF material has a specific surface area of 2344 m 2 / g and ordered mesoporous channels. The material has excellent benzene diffusion capacity, and the benzene diffusion coefficient of the material is 2.65*10 –5 cm 2 / s, which is much higher than that of other reported MOF materials, and is beneficial to the adsorption and desorption of adsorbates in the adsorption process. In summary, ZJU-621(Al) has potential practical application value in the field of benzene adsorption.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of adsorption material research and development, in particular to a preparation method of mesoporous aluminum-based MOF material with excellent benzene diffusion capacity. BACKGROUND

[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 reported aluminum-based MOFs materials are microporous materials, such as MOF-519 (Al), CAU-10 (Al) and Al-PMOF, which result in slow diffusion rate 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 benzene diffusion rate. SUMMARY

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

[0004] The present application adopts the following technical scheme: the preparation method of mesoporous aluminum-based MOF material with excellent benzene diffusion capacity is as follows:

[0005] Dissolve the trivalent aluminum salt and the 3,4',5-biphenyltricarboxylic acid ligand in a mixture of organic solvent, acid regulator and water according to a molar ratio of 1:1.5-2:1, and stir to mix uniformly. Then, the reaction is placed in a reaction kettle and reacted in an oven. After the reaction is completed, the product is separated. The product is washed with N,N-dimethylformamide, acetone / ethanol and other detergents in turn to remove the guest molecules in the pores of the MOF material, and then vacuum dried to obtain the 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 acid regulator is 15:1 to 20:1, and the volume ratio of the acid regulator to water is 1:3 to 3:1.

[0008] Furthermore, the acidity regulator is formic acid or acetic acid, with formic acid being more preferred.

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

[0010] Furthermore, the reaction temperature is 120℃~140℃.

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

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

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

[0014] (1) The novel aluminum-based MOF material prepared in this invention is named ZJU-621(Al). It consists of a 3,4',5-biphenyltricarboxylic acid ligand and the secondary building unit Al8(OH). 15 (–COO)9 is formed through coordinate bonds. ZJU-621(Al) has 2344m 2 Specific surface area per g and The ordered mesoporous channels are present. At P / P0 = 0.10 and 298 K, the diffusion coefficient of ZJU-621(Al) for benzene is as high as 2.65 × 10⁻⁶. -5 cm 2 / s is the highest reported benzene diffusion coefficient.

[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 this invention not only has a high benzene adsorption capacity of 9.99 mmol / g at P / P0 = 0.10, but also has the highest benzene diffusion coefficient of 2.65 × 10⁻⁶ compared with other MOFs. -5 cm 2 / s, which can be used for the adsorption and diffusion of benzene vapor. Attached Figure Description

[0017] Figure 1is a structural schematic diagram of the mesoporous aluminum-based MOF material prepared in Example 1 of the present application;

[0018] Figure 2 is the powder X-ray diffraction data of ZJU-621(Al) prepared in Example 1 of the present application, and the powder X-ray diffraction data thereof after standing in air for 7 days, and the theoretically calculated PXRD data diagram;

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

[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 application;

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

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

[0023] The present application will be further described below in combination with examples, comparative examples and the drawings.

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

[0025] 400 mg of aluminum nitrate nonahydrate and 400 mg of 3,4',5-biphenyltricarboxylic acid ligand (molar ratio of 1:1.32) were weighed and mixed into 15.00 mL of N,N-dimethylformamide, 3.00 mL of water, and 2.00 mL of formic acid. After the mixture was uniformly mixed by ultrasonic mixing, it was placed in a reaction kettle for reaction. The reaction temperature was 130°C, and the reaction time was 72 hours. After the reaction was completed, the white product, ZJU-621(Al), was obtained by centrifugal separation. The product was washed with N,N-dimethylformamide and acetone in sequence, and the washed product was stored in a vacuum drying box. The specific surface area of ZJU-621(Al) was 2344 m 2 / g and the ordered mesoporous channel size was The static adsorption amount of benzene vapor was determined by using a JW-ZQ100 vapor adsorption instrument, which was equipped with a vapor generation device and a heating device. The temperature of the vapor generation device was maintained at 313 K by using the heating device, so as to ensure the generation of stable benzene vapor. The adsorbent sample was preserved during the adsorption process, and the adsorption stability was stabilized by using a water bath heating method. Before the determination, ZJU-621(Al) was vacuum degassed at 378 K for 24 h to remove the guest molecules in the pore structure of the adsorbent, so as to activate the ZJU-621(Al) sample. At P / P0=0.10 and 298 K, the adsorption amount of benzene reached 9.99 mmol / g, which was higher than that of MOF-74(Mg) (6.02 mmol / g) and PAF-1 (7.83 mmol / g). In addition, the time sequence benzene vapor adsorption experiment of ZJU-621(Al) was carried out on a BSD-VVS multi-station gravimetric gas adsorption instrument. Taking ZJU-621(Al) as an example, the ZJU-621(Al) (57.65 mg) sample was heated at 120 ℃ for 12 hours to remove the guest molecules in the framework. Benzene vapor was introduced into the device cavity, 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 recorded continuously, and the benzene diffusion coefficient of ZJU-621(Al) reached 2.65×10 -5 cm 2 / s.

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

[0027] 400 mg of aluminum chloride hexahydrate and 400 mg of 3,4',5-biphenyltricarboxylic acid ligand (molar ratio of 1:1.18) were weighed and mixed into 15.00 mL of N,N-dimethylformamide, 3.00 mL of water, and 2.00 mL of formic acid. After the mixture was uniformly mixed by ultrasonic mixing, it was placed in a reaction kettle for reaction. The reaction temperature was 140 ℃, and the reaction time was 84 hours. After the reaction was completed, the white product, ZJU-621(Al), was obtained by centrifugal separation. The product was washed with N,N-dimethylformamide and acetone in sequence, and the washed product was stored in a vacuum drying box. The specific surface area of ZJU-621(Al) was 2134 m 2 / g, and the ordered mesoporous channel size was At P / P0=0.10 and 298 K, the adsorption amount of benzene reached 9.86 mmol / g, and the benzene diffusion coefficient was 2.45×10 -5 cm 2 / s.

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

[0029] 600 mg of aluminum nitrate nonahydrate (1.33 g) and 400 mg of 3,4',5-biphenyltricarboxylic acid ligand (molar ratio 1.14:1) were weighed and mixed into 15.00 mL of N,N-dimethylformamide, 3.00 mL of water, and 2.00 mL of formic acid. The mixture was ultrasonically mixed thoroughly and then placed in a reaction vessel for reaction. The reaction temperature was 130 °C, and the reaction time was 66 hours. After the reaction was completed, the product, ZJU-621(Al), was obtained by centrifugation. The product was washed successively with N,N-dimethylformamide and acetone, and then stored in a vacuum drying oven. The specific surface area of ​​ZJU-621(Al) was 2125 m² / g. 2 / g and ordered mesoporous channel size are At P / P0 = 0.10 and 298 K, its adsorption capacity for benzene reaches 9.72 mmol / g and the benzene diffusion coefficient is 2.42 × 10⁻⁶. -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 using a Brucker D8 Venture single-crystal X-ray diffractometer, ultimately yielding... Figure 1 The crystal structure shown corresponds to the theoretical powder X-ray diffraction (PXRD) data and the experimentally measured main PXRD peaks, indicating the accuracy of its crystal structure. (See attached image.) Figure 2 .

[0032] Example 5: Stability Analysis of the Mesoporous Aluminum-Based MOF Material Obtained in Example 1

[0033] After being exposed to air for 7 days, the PXRD data of the mesoporous aluminum-based MOF material showed consistent major diffraction peaks with those obtained immediately after the reaction, indicating its good chemical stability. (See [link to relevant documentation]). Figure 2 The thermogravimetric curve of this material did not change significantly before 150℃, indicating that it has good thermal stability. (See...) Figure 3 .

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

[0035] The N2 adsorption-desorption isotherms of ZJU-621(Al) after vacuum activation were measured at 77 K. (See figure...) Figure 4 The measured aperture is mainly concentrated in... See Figure 5 The spatial structure dimensions obtained from structural analysis are consistent with those obtained from structural analysis.Figure 1 , ).

[0036] Diffusion coefficient of benzene in mesoporous Al-based MOF material obtained in Example 1 at 25℃

[0037] The diffusion coefficient of benzene in ZJU-621(Al) after vacuum activation was measured at 298 K and relative pressure of 0.10, see Figure 6 . The diffusion coefficient of benzene in ZJU-621(Al) was as high as 2.65 x 10 –5 cm 2 / s, much higher than other materials, for example: ZJU-520(Al) was synthesized by using 3,5-di(4-carboxyphenyl)pyridine as organic ligand, which is a microporous material, and its diffusion coefficient was (2.72 x 10 –7 cm 2 / s) (Double-walled Al-based MOF with large microporous specific surface area for trace benzene adsorption); MOF-519(Al) was synthesized by using 1,3,5-tri(4-carboxyphenyl)benzene as organic ligand, which is a microporous material, and its diffusion coefficient was (6.49 x 10 –7 cm 2 / s) (High methane storage capacity in aluminum metal-organic frameworks). In summary, ZJU-621(Al) is a potential benzene diffusion material, which is beneficial to the adsorption of benzene under mild conditions.

[0038] Comparative Example 1

[0039] 400 mg of aluminum nitrate nonahydrate and 10 mg of 3,4',5-biphenyltricarboxylic acid ligand (molar ratio of 30:1) were weighed and mixed into 15.00 mL of N,N-dimethylformamide, 3.00 mL of water, and 2.00 mL of formic acid. After the mixture was uniformly mixed by ultrasonic, it was placed in a reaction kettle for reaction. The reaction temperature was 130℃, the reaction time was 72 hours, and after the reaction was completed, no product was obtained.

[0040] Comparative Example 2

[0041] Take 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, and 3.00 mL of water, and 12.00 mL of formic acid. After the mixture is uniformly mixed by ultrasonic, it is put into a reaction kettle for reaction. The reaction temperature is 130°C, the reaction time is 72 hours, and after the reaction is completed, no product is obtained.

[0042] Comparative Example 3

[0043] Take 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, and 3.00 mL of water, and 2.00 mL of formic acid. After the mixture is uniformly mixed by ultrasonic, it is put into a reaction kettle for reaction. The reaction temperature is 80°C, the reaction time is 72 hours, and after the reaction is completed, a white product is obtained by centrifugal separation. The product is washed with N,N-dimethylformamide and acetone in turn, and the washed product is stored in a vacuum drying box. The specific surface area of the product is 876 m 2 / g and the ordered mesoporous channel size is Its benzene diffusion coefficient is only 4.53 x 10 -6 cm 2 / s.

[0044] Comparative Example 4

[0045] Take 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, and 3.00 mL of water, and 2.00 mL of formic acid. After the mixture is uniformly mixed by ultrasonic, it is put into a reaction kettle for reaction. The reaction temperature is 130°C, the reaction time is 12 hours, and after the reaction is completed, a white product is obtained by centrifugal separation. The product is washed with N,N-dimethylformamide and acetone in turn, and the washed product is stored in a vacuum drying box. The specific surface area of the product is 1435 m 2 / g and the ordered mesoporous channel size is Its benzene diffusion coefficient is only 6.58 x 10 -6 cm 2 / s.

[0046] The mesoporous aluminum-based MOF material prepared in Example 1 has a periodic framework structure and is composed of 3,4',5-biphenyltricarboxylic acid and aluminum clusters, as shown in Figure 1 ZJU-621(Al) has good chemical stability, and its PXRD pattern does not change significantly after standing in air for 7 days, as shown in Figure 2In addition, the material also has good thermal stability, and the thermogravimetric analysis diagram does not have obvious loss before 150℃, 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, and the diffusion coefficient of benzene thereof is as high as 2.65×10 –5 cm 2 / s at a relative pressure of 0.10, which is much higher than that of other materials.

[0047] It can be seen from Comparative Example 1 and Comparative Example 1 that when the molar ratio of the aluminum source and the organic ligand is 30:1, which is not within the optimal ratio range, no product is obtained, and it can be seen that the amount and molar ratio of the aluminum source and the organic ligand are very important in the preparation of mesoporous ZJU-621(Al). It can be seen from Comparative Example 1 and Comparative Example 2 that when the volume ratio of the acid regulator and water is 4:1, which is not within the optimal ratio range, no product is obtained, and it can be seen that the amount of the acid regulator is also very important. It can be seen from Comparative Example 1 and Comparative Example 3 that when the reaction temperature is 80℃, which is not within the optimal reaction temperature range, 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, and the performance of the obtained product is decreased. It can be seen from Comparative Example 1 and Comparative Example 4 that when the reaction time is 12 hours, which is not within the optimal reaction time range, 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, and the performance of the obtained product is also decreased, so that the insufficient reaction temperature and reaction time lead to that the framework structure of the MOF is not perfect, the performance of the product is decreased, and it can be seen that the reaction temperature and the reaction time are very important for the preparation of ZJU-621(Al).

[0048] The embodiments shown in the present application are only preferred technical solutions, and should not be regarded as a limitation on the patent of the present application. In addition, any replacement and improvement made on the basis of the present application shall be within the protection scope of the present application.

Claims

1. A method for preparing a mesoporous aluminum-based MOF material having excellent benzene diffusion capacity, characterized by, The method comprises the following steps: The aluminum salt, 3,4',5-biphenyltricarboxylic acid, an acid regulator, water and an organic solvent are uniformly mixed; the uniformly mixed mixture is loaded into a reaction kettle inner container, and then is moved into an oven for reaction; after the reaction is completed, the product is separated by centrifugation, washed and vacuum dried to obtain the final mesoporous aluminum-based MOF material; the acid regulator is one or more of formic acid, acetic acid; the organic solvent is N,N dimethylformamide; the molar ratio of the aluminum salt and 3,4',5-biphenyltricarboxylic acid is 1:1.5~2:1; the volume ratio of the organic solvent and the acid regulator is 5:1~10:1; the volume ratio of water and the acid regulator is 1:1~2:1; the molar volume ratio of 3,4',5-biphenyltricarboxylic acid and water is 0.20 mmol / mL~0.80 mmol / mL; the reaction temperature is 120~140℃; the reaction time is 24~84 hours.

2. The production method according to claim 1, characterized by, The aluminum salt is a trivalent aluminum salt or a hydrate thereof.

3. The production method according to claim 1, characterized by, The flow of the washing product is: sequentially using N, N - dimethylformamide and washing the product with a washing agent, wherein the washing agent is a mixture of one or more of acetone, ethanol.

4. A mesoporous aluminum-based MOF material prepared by the method of any one of claims 1-3.

5. Application of the mesoporous aluminum-based MOF material of claim 4 as an adsorbent material in benzene adsorption.

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