Hydrophobic modification method of Al-based metal organic framework material

Abstract

The invention discloses a hydrophobic modification method of an Al-based metal organic framework material. According to the hydrophobic modification method of the Al-based metal organic framework material provided by the invention, the Al-based metal organic framework material and polydimethylsiloxane (PDMS) are placed in a high-temperature and closed environment to react for 20-120 minutes, so that the polydimethylsiloxane can coat the surface of the Al-based metal organic framework material with small molecular silane in a vapor deposition manner. On one hand, the method is short in time consumption, simple to operate and easy to control, hydrophobic modification of the Al-based metal organic framework material can be achieved within a short time, and good repeatability is achieved; on the other hand, the hydrophobicity of the Al-based metal organic framework material can be remarkably improved on the basis that the original pore structure of the Al-based metal organic framework material is reserved to the maximum extent, and then the adsorption selectivity of the Al-based metal organic framework material to VOC is greatly improved.

Description

TECHNICAL FIELD

[0001] The technology belongs to the technical field of metal-organic framework materials, and particularly relates to a hydrophobic modification method of an Al-based metal-organic framework material. BACKGROUND

[0002] Metal-organic frameworks (MOFs) are a class of highly ordered crystalline porous materials formed by metal ions and organic ligands through coordination bonds. Compared with other porous materials, MOFs have a wide application prospect due to their high specific surface area, developed pores and adjustable structure. However, the high cost of MOFs limits its application.

[0003] Aluminum is the third most abundant element in the earth's crust, and its source is widespread and inexpensive, so aluminum-based MOFs naturally have the advantage of low cost. In addition, aluminum-based MOFs also have a large specific surface area, so they have more advantages in promoting the industrial application of MOFs. The use of azobenzene-4,4'-dicarboxylic acid as a linker (organic ligand) to construct aluminum-based metal-organic framework (Al-AZB) was first realized in 2022 (Refilwe Mogale, Kovo G. Akpomie, Jeanet Conradie, Ernst H. G. Langner, Journal of Environmental Management 304 (2022) 114166; Refilwe Mogale, Kovo G. Akpomie, Jeanet Conradie, Ernst H. G. Langner, Journal of Molecular Structure 1268 (2022) 133648).

[0004] However, compared with adsorbing other guest molecules, the affinity of Al atoms to water molecules is stronger, so aluminum-based MOFs have problems such as instability in water and preferential adsorption of water molecules on active sites, which seriously limits the application of aluminum-based MOFs in the adsorption field. Hydrophobic modification can improve the selectivity of aluminum-based MOFs to adsorbates in humid air. Common hydrophobic modification methods include pre-synthesis modification and post-synthesis modification, etc. These methods all have problems such as long time consumption, complicated operation and poor repeatability. SUMMARY

[0005] The purpose of the present application is to solve the problems of long time consumption, complicated operation and poor repeatability in the related art when hydrophobic modification is performed on aluminum-based MOFs, and to provide a hydrophobic modification method of an Al-based metal-organic framework material.

[0006] To achieve the above object, the present application adopts the technical scheme of:

[0007] In the first aspect, the present application provides a method for hydrophobic modification of Al-based metal organic framework material, comprising the following steps:

[0008] Taking the Al-based metal organic framework material and polydimethylsiloxane, reacting under the condition of 200-300℃ for 20-120 minutes.

[0009] In an alternative embodiment, the weight ratio of the Al-based metal organic framework material to the polydimethylsiloxane is (0.01-20):(10-200).

[0010] In an alternative embodiment, the Al-based metal organic framework material is Al-AZB material, and the preparation process comprises:

[0011] Taking the aluminum salt dispersion and azobenzene-4,4'-dicarboxylic acid dispersion, mixing under the condition of vigorous stirring, reacting to obtain a reaction product;

[0012] Separating the solid in the reaction product, washing, and activating to obtain the Al-AZB material.

[0013] In an alternative embodiment, the weight ratio of the aluminum salt to azobenzene-4,4'-dicarboxylic acid is (1.02-6.72):(0.63-2.31).

[0014] And / or, the aluminum salt comprises at least one of aluminum chloride hexahydrate, anhydrous aluminum chloride, aluminum nitrate hydrate, aluminum sulfate, or aluminum acetylacetonate.

[0015] In an alternative embodiment, the preparation process of the aluminum salt dispersion comprises:

[0016] Taking the aluminum salt and adding it into an organic solvent, ultrasonicating for 15-45 minutes to obtain the aluminum salt dispersion;

[0017] Optionally, the usage amount of the organic solvent is 15-60 mL relative to 1.02-6.72 g of the aluminum salt. Within this usage range, the organic solvent can effectively dissolve the aluminum salt to form a stable and uniform solution, which is more conducive to the full contact between the reactants.

[0018] In an alternative embodiment, the preparation process of the azobenzene-4,4'-dicarboxylic acid dispersion comprises:

[0019] Taking the azobenzene-4,4'-dicarboxylic acid and adding it into an organic solvent, ultrasonicating for 15-45 minutes to obtain the azobenzene-4,4'-dicarboxylic acid dispersion;

[0020] Optionally, the amount of the organic solvent used is 15-60 mL relative to 0.63-2.31 g of azobenzene-4,4'-dicarboxylic acid. Within this amount range, the organic solvent can effectively disperse the azobenzene-4,4'-dicarboxylic acid to form a uniform suspension, and can significantly improve the reaction rate.

[0021] In an alternative embodiment, the organic solvent comprises at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, N,N-diethylacetamide and methanol.

[0022] In an alternative embodiment, the reaction conditions comprise a reaction temperature of 105-160℃ and a reaction time of 8-72 h.

[0023] In an alternative embodiment, the washing process comprises:

[0024] Sequentially using anhydrous methanol and N,N-dimethylformamide for washing, then centrifuging the solid and vacuum drying for 6-36 h;

[0025] And / or, the activation process comprises:

[0026] Vacuum activation at 50-180℃ for 12-60 h.

[0027] In a second aspect, the application provides a hydrophobic Al-based metal organic framework composite material, which is prepared by the above-mentioned hydrophobic modification method.

[0028] Compared with the prior art, the technical scheme of the application has at least the following beneficial effects:

[0029] The hydrophobic modification method of the Al-based metal organic framework material provided by the application can make the polydimethylsiloxane (PDMS) coat the small molecule silane on the surface of the Al-based metal organic framework material by gas phase deposition by placing the Al-based metal organic framework material and the polydimethylsiloxane (PDMS) in a high-temperature, closed environment for 20-120 minutes. On the one hand, this method is time-saving, simple to operate and easy to control, can realize the hydrophobic modification of the Al-based metal organic framework material in a short time, and has good repeatability; on the other hand, this method can significantly improve the hydrophobicity of the Al-based metal organic framework material on the basis of retaining the original pore structure of the Al-based metal organic framework material to a maximum extent, thereby greatly improving the adsorption selectivity of the Al-based metal organic framework material to VOC.

[0030] PDMS is a block-shaped organosilicon polymer, which has the advantages of convenient access and easy control of reaction conditions. It is cracked into small molecule silane at about 235℃ and polymerizes on the surface of Al-based metal organic framework material to form a dense organosilicon coating without affecting the crystal structure and pore structure of the Al-based metal organic framework material. The organosilicon coating can make the aluminum-based MOF have excellent hydrophobic properties, so that the adsorption amount of water of the aluminum-based MOF is greatly reduced in a humid atmosphere, and the adsorption performance of VOC (such as toluene) is significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0032] Figure 1 is the XRD test result graph of the four kinds of Al-AZB materials in the experimental examples of the present application;

[0033] Figure 2 is the FT-IR test result graph of the four kinds of Al-AZB materials in the experimental examples of the present application;

[0034] Figure 3 is the contact angle test result graph of the four kinds of Al-AZB materials in the experimental examples of the present application;

[0035] Figure 4 is the N2 isothermal adsorption test result graph of the Al-AZB and Al-AZB@PDMS-3 materials in the experimental examples of the present application;

[0036] Figure 5 is the water vapor isothermal adsorption test result graph of the Al-AZB and Al-AZB@PDMS-3 materials in the experimental examples of the present application;

[0037] Figure 6 is the toluene isothermal adsorption test result graph of the Al-AZB and Al-AZB@PDMS-3 materials in the experimental examples of the present application;

[0038] Figure 7 is the toluene breakthrough curve of the Al-AZB and Al-AZB@PDMS-3 materials in the experimental examples of the present application under 50% RH humidity. DETAILED DESCRIPTION

[0039] The following examples are provided to better enable those skilled in the art to further understand and practice the application, and are not intended to limit the scope of the application in any way. The application is measured by the claims and not by the examples, which provide further guidance to the practitioner on how to make and use the present application. Any product, process, or method that is equivalent in function or structure to a product, process, or method specifically described herein is within the scope of the present application.

[0040] Unless otherwise indicated, conventional methods of chemistry and biochemistry, molecular biology, and immunology were used in the examples. Unless otherwise indicated, reagents and materials were obtained from commercial suppliers and used without further purification.

[0041] The application is further described in detail by reference to specific examples. These examples are not to be construed as limiting the scope of the application in any manner.

[0042] Example 1

[0043] The hydrophobic Al-AZB composite material was prepared according to the following method:

[0044] (1) 1.02 g of aluminum chloride hexahydrate and 15 mL of N,N-dimethylformamide were mixed uniformly by ultrasonic for 25 min to obtain an aluminum salt dispersion liquid;

[0045] (2) 0.63 g of azobenzene-4,4'-dicarboxylic acid and 15 mL of N,N-dimethylformamide were mixed uniformly by ultrasonic for 25 min to obtain an azobenzene-4,4'-dicarboxylic acid dispersion liquid;

[0046] (3) The aluminum salt dispersion liquid and the azobenzene-4,4'-dicarboxylic acid dispersion liquid were mixed under vigorous stirring, and the reaction was carried out at 150°C for 8 hours to obtain a reaction product;

[0047] (4) The reaction product obtained in step (3) was centrifuged, and the solid was washed with anhydrous methanol and N,N-dimethylformamide for 5 times, respectively, and then the solid was centrifuged and vacuum dried for 12 h, and then vacuum activated at 150°C for 48 h to obtain an Al-AZB material;

[0048] (5) 0.1 g of the Al-AZB material obtained in step (4) and 1 g of PDMS were reacted at 235°C for 20 min to obtain a super-hydrophobic Al-AZB composite material.

[0049] Example 2

[0050] The hydrophobic Al-AZB composite material was prepared according to the following method:

[0051] (1) 2.31 g of aluminum chloride hexahydrate and 20 mL of N,N-dimethylformamide were mixed uniformly by ultrasonic for 15 min to obtain an aluminum salt dispersion liquid;

[0052] (2) Take 1.06 g of azobenzene-4,4'-dicarboxylic acid and 20 mL of N,N- dimethylformamide, mix uniformly under ultrasonic for 15 min to obtain azobenzene-4,4'- dicarboxylic acid dispersion liquid;

[0053] (3) Mix the aluminum salt dispersion liquid with the azobenzene-4,4'-dicarboxylic acid dispersion liquid under vigorous stirring, and react at 150°C for 8 hours to obtain a reaction product;

[0054] (4) Take the reaction product obtained in step (3), centrifugal separation, take the solid, wash with anhydrous methanol and N,N-dimethylformamide for 3 times in turn, then centrifugal separation the solid and vacuum drying for 36h, and vacuum activation at 150°C for 60h to obtain the Al-AZB material;

[0055] (5) Take 0.5 g of the Al-AZB material obtained in step (4) and 5 g of PDMS, and react at 235°C for 60 minutes to obtain the super-hydrophobic Al-AZB composite material.

[0056] Example 3

[0057] The hydrophobic Al-AZB composite material is prepared according to the following method:

[0058] (1) Take 6.72 g of aluminum chloride hexahydrate and 60 mL of N,N-dimethylformamide, mix uniformly under ultrasonic for 45 min to obtain an aluminum salt dispersion liquid;

[0059] (2) Take 2.31 g of azobenzene-4,4'-dicarboxylic acid and 60 mL of N,N-dimethylformamide, mix uniformly under ultrasonic for 45 min to obtain azobenzene-4,4'-dicarboxylic acid dispersion liquid;

[0060] (3) Mix the aluminum salt dispersion liquid with the azobenzene-4,4'-dicarboxylic acid dispersion liquid under vigorous stirring, and react at 150°C for 72 hours to obtain a reaction product;

[0061] (4) Take the reaction product obtained in step (3), centrifugal separation, take the solid, wash with anhydrous methanol and N,N-dimethylformamide for 5 times in turn, then centrifugal separation the solid and vacuum drying for 12h, and vacuum activation at 150°C for 36h to obtain the Al-AZB material;

[0062] (5) Take 2 g of the Al-AZB material obtained in step (4) and 20 g of PDMS, and react at 235°C for 120 minutes to obtain the super-hydrophobic Al-AZB composite material.

[0063] Comparative Example 1

[0064] The Al-AZB material is prepared according to the following method:

[0065] (1) Take 6.72 g of aluminum chloride hexahydrate and 60 mL of N,N- dimethylformamide, and mix them uniformly under ultrasonic for 45 min to obtain an aluminum salt dispersion liquid;

[0066] (2) Take 2.31 g of azobenzene-4,4'-dicarboxylic acid and 60 mL of N,N- dimethylformamide, and mix them uniformly under ultrasonic for 45 min to obtain an azobenzene-4,4'-dicarboxylic acid dispersion liquid;

[0067] (3) Mix the aluminum salt dispersion liquid and the azobenzene-4,4'- dicarboxylic acid dispersion liquid under vigorous stirring, and react them at 150°C for 72 h to obtain a reaction product;

[0068] (4) Take the reaction product obtained in step (3), centrifugalize, take the solid, wash it with anhydrous methanol and N,N-dimethylformamide for 5 times in turn, then centrifugalize the solid and vacuum dry it for 12 h, and vacuum activate it at 150°C for 36 h to obtain an Al-AZB material;

[0069] (5) Take 2 g of the Al-AZB material obtained in step (4), and react it at 235°C for 135 min in a closed state, and take it out for standby.

[0070] Comparative Example 2

[0071] The hydrophobic Al-AZB material is prepared according to the method of Example 3, except that the hydrophobic modification time in step (5) of the comparative example is 150 min, and specifically, step (5) of the comparative example is:

[0072] Take 2 g of the Al-AZB material obtained in step (4) and 20 g of PDMS, and react them at 235°C for 150 min in a closed state to obtain a super-hydrophobic Al-AZB composite material.

[0073] Comparative Example 3

[0074] The hydrophobic Al-AZB material is prepared according to the method of Example 3, except that the hydrophobic modification time in step (5) of the comparative example is 180 min, and specifically, step (5) of the comparative example is:

[0075] Take 2 g of the Al-AZB material obtained in step (4) and 20 g of PDMS, and react them at 235°C for 180 min in a closed state to obtain a super-hydrophobic Al-AZB composite material.

[0076] Comparative Example 4

[0077] The hydrophobic Al-AZB material is prepared according to the method of Example 3, except that the hydrophobic modification time in step (5) of the comparative example is 200 min, and specifically, step (5) of the comparative example is:

[0078] Take 2 g of Al-AZB material obtained in step (4) and 20 g of PDMS, and react at 235℃ for 200 minutes to obtain a super-hydrophobic Al-AZB composite material.

[0079] Comparative Example 5

[0080] The hydrophobic Al-AZB material was prepared according to the method of Example 3, except that the hydrophobic modification time in step (5) of the comparative example was 240 minutes. Specifically, step (5) of the comparative example was:

[0081] Take 2 g of Al-AZB material obtained in step (4) and 20 g of PDMS, and react at 235℃ for 240 minutes to obtain a super-hydrophobic Al-AZB composite material.

[0082] Experimental Example

[0083] The Al-AZB composite materials of Examples 1-3 were labeled as Al-AZB@PDMS-1, Al-AZB@PDMS-2, and Al-AZB@PDMS-3, respectively. The material of Comparative Example 1 was labeled as Al-AZB, and the Al-AZB composite materials of Comparative Examples 2-5 were labeled as Al-AZB@PDMS-D1, Al-AZB@PDMS-D2, Al-AZB@PDMS-D3, and Al-AZB@PDMS-D4, respectively. Then, structural characterization and performance testing were carried out, as follows:

[0084] (1) XRD analysis

[0085] XRD tests were performed on Al-AZB, Al-AZB@PDMS-1, Al-AZB@PDMS-2, and Al-AZB@PDMS-3, respectively, and the test results are shown in Figure 1

[0086] As can be seen from Figure 1 , Al-AZB, Al-AZB@PDMS-1, Al-AZB@PDMS-2, and Al-AZB@PDMS-3 all exhibit strong crystallinity, and the peak positions of each peak are consistent with the characteristic peaks of the simulated Al-AZB. This indicates that the crystals obtained are all Al-AZB crystals, and the crystallinity is not changed after PDMS deposition on the Al-AZB material, and the original structure of the Al-AZB material is preserved.

[0087] (2) FT-IR analysis

[0088] FT-IR tests were performed on Al-AZB, Al-AZB@PDMS-1, Al-AZB@PDMS-2, and Al-AZB@PDMS-3, respectively, and the test results are shown in Figure 2 ​as shown.

[0089] By Figure 2 It can be seen that, compared with Al-AZB, the hydrophobic modified Al-AZB@PDMS composite material has a slight vibration peak at 1095 cm -1 , which belongs to the expansion vibration peak of silicon-oxygen bond, while the methyl expansion vibration peak appears at 2933 cm -1 , which further indicates that the PDMS molecules have been successfully loaded onto the Al-AZB material. In addition, there is a characteristic peak of oxygen-aluminum bond at about 1000 cm -1 , and the wave number of the characteristic peak of the oxygen-aluminum bond on the modified material is shifted compared with the raw material, which also indicates that the PDMS has been loaded onto the Al-AZB material.

[0090] (3) Contact angle test

[0091] The contact angle tests were carried out on Al-AZB, Al-AZB@PDMS-1, Al-AZB@PDMS-2, and Al-AZB@PDMS-3 respectively, and the test results are shown in Figure 3 .

[0092] By Figure 3 It can be seen that the hydrophobicity of the material has been significantly improved. After the Al-AZB is modified by PDMS thermal deposition for 20 min, 60 min, and 120 min, the contact angle of the material increases from 45.4° to 138°, 153°, and 156° respectively, which indicates that the PDMS thin layer can indeed make the Al-AZB surface achieve super-hydrophobic effect.

[0093] (4) N2 isothermal adsorption test

[0094] N2 adsorption tests were carried out on Al-AZB and Al-AZB@PDMS-3 at 77K respectively, and the test results are shown in Figure 4 .

[0095] By Figure 4 It can be seen that the isotherm rises sharply and the N2 adsorption amount increases sharply at a very low relative pressure of N2, which indicates that there are many micropores in the material. After reaching the plateau in the second stage, the N2 adsorption amount grows relatively slowly, which indicates that the material contains mesopores. According to the trend of the isotherm, it can be judged that the adsorption isotherm is type IV isotherm. The N2 adsorption isotherm of the PDMS modified Al-AZB material is highly similar to that of the Al-AZB raw material, but the adsorption amount shows a downward trend, and the downward trend becomes significant as the modification time is prolonged, but it still maintains a relatively high adsorption amount, which indicates that the PDMS hydrophobic modification has limited effect on the N2 adsorption capacity of the Al-AZB material.

[0096] (5) Pore volume analysis test

[0097] The pore volume and porosity analysis tests were respectively performed on Al-AZB, Al-AZB@PDMS-(1-3) and Al-AZB@PDMS-(D1-D4), and the test results are shown in Table 1.

[0098] Table 1: Pore volume and porosity analysis test results of eight Al-AZB materials

[0099]

[0100] As shown in Table 1, after hydrophobic modification by PDMS, the specific surface area (BET), average pore size and average pore volume of the Al-AZB material are slightly lower than those of the Al-AZB raw material. The BET specific surface area of Al-AZB is 2316 m 2 / g, the pore volume and pore size are 1.5554 cm 3 / g and 2.6863 nm, while the maximum BET of the modified Al-AZB material is 2277 m 2 / g, and the maximum average pore volume and the maximum average pore size are 1.4131 cm 3 / g and 2.4824 nm, respectively. It can be inferred that the PDMS molecules are indeed loaded on the Al-AZB material, and combined with other pore parameters, it can be concluded that the PDMS molecules mainly cover the surface of the Al-AZB material, and fewer enter the pores of the Al-AZB material.

[0101] (6) Water vapor adsorption isotherm test

[0102] Water vapor isotherm adsorption tests were respectively performed on Al-AZB and Al-AZB@PDMS-3, and the test results are shown in Table 2. Figure 5

[0103] As shown in Table 2, at different temperatures, the maximum water adsorption capacity of the modified material Al-AZB@PDMS-3 is lower than that of the raw material Al-AZB. In particular, at room temperature (25℃), the maximum water adsorption capacity of the modified material Al-AZB@PDMS-3 (b, 11.47 mmol / g) is significantly lower than that of the raw material Al-AZB (a, 20.43 mmol / g), which indicates that the hydrophobic performance of the material after PDMS hydrophobic modification is indeed significantly improved. Figure 5 Figure 5 Figure 5

[0104] (7) Toluene adsorption isotherm test

[0105] Toluene isotherm adsorption tests were respectively performed on Al-AZB and Al-AZB@PDMS-3, and the test results are shown in Table 3. Figure 6 ​​​​​

[0106] Depend on Figure 6 It can be seen that the equilibrium adsorption capacities of toluene for Al-AZB and Al-AZB@PDMS-3 are similar. The equilibrium adsorption capacity of toluene for Al-AZB is 12.01 mmol / g, which is approximately 1 mmol / g higher than the 11.05 mmol / g for Al-AZB@PDMS-3. However, the adsorption ratio of toluene to water for Al-AZB@PDMS-3 is 0.9634, significantly higher than the 0.5879 adsorption ratio for toluene to water for Al-AZB. This indicates that the selectivity of the PDMS-modified Al-AZB@PDMS-3 material for toluene is significantly enhanced.

[0107] (8) Dynamic toluene column penetration test at 50% RH

[0108] Dynamic toluene column penetration experiments were conducted on Al-AZB and Al-AZB@PDMS-3 at 50% RH. The test temperature was 25°C, the toluene concentration was 50%, and the same penetration column was used for the test. The parameters such as sample mass and column length were kept consistent. The total airflow rate was 15 sccm. The test results are shown in the figure. Figure 7 shown.

[0109] Depend on Figure 7 It can be seen that the retention time of toluene in the penetration column per gram of Al-AZB is 659 minutes, and the retention time in the penetration column per gram of Al-AZB@PDMS-3 is 1186 minutes, which indicates that the AZB@PDMS-3 material can maintain a high toluene capture ability under high humidity.

[0110] The above description is merely a preferred embodiment of the present application; however, the scope of protection of the present application is not limited thereto. Any person skilled in the art who, within the technical scope disclosed in the present application, makes equivalent substitutions or modifications based on the technical solutions and improved concepts of the present application shall be covered by the scope of protection of the present application.

Claims

1. A method for hydrophobic modification of an Al-based metal-organic framework material, characterized in that, The method comprises the following steps: The Al-based metal organic framework material and the polydimethylsiloxane are reacted under a sealed condition at 200-300 ℃ for 20-120 minutes.

2. The hydrophobic modification method according to claim 1, characterized by, The weight ratio of the Al-based metal organic framework material to the polydimethylsiloxane is (0.01-20):(10-200).

3. The hydrophobic modification method according to claim 1, wherein, The Al-based metal organic framework material is an Al-AZB material, and the preparation process comprises: The aluminum salt dispersion liquid and the azobenzene-4,4'-dicarboxylic acid dispersion liquid are mixed under vigorous stirring to obtain a reaction product; The solid in the reaction product is separated, washed, and activated to obtain the Al-AZB material.

4. The hydrophobic modification method according to claim 3, wherein, The weight ratio of the aluminum salt to the azobenzene-4,4'-dicarboxylic acid is (1.02-6.72):(0.63-2.31). The aluminum salt comprises at least one of aluminum chloride hexahydrate, anhydrous aluminum chloride, aluminum nitrate hydrate, aluminum sulfate, or aluminum acetylacetonate.

5. The hydrophobic modification method according to claim 3, wherein, The preparation process of the aluminum salt dispersion liquid comprises: The aluminum salt is added into an organic solvent and ultrasonically treated for 15-45 minutes to obtain the aluminum salt dispersion liquid. Optionally, the amount of the organic solvent used is 15-60 mL relative to 1.02-6.72 g of the aluminum salt.

6. The hydrophobic modification method according to claim 3, wherein, The preparation process of the azobenzene-4,4'-dicarboxylic acid dispersion liquid comprises: The azobenzene-4,4'-dicarboxylic acid is added into an organic solvent and ultrasonically treated for 15-45 minutes to obtain the azobenzene-4,4'-dicarboxylic acid dispersion liquid. Optionally, the amount of the organic solvent used is 15-60 mL relative to 0.63-2.31 g of the azobenzene-4,4'-dicarboxylic acid.

7. The hydrophobic modification method according to claim 5 or 6, characterized by, The organic solvent comprises at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, N,N-diethylacetamide, and methanol.

8. The hydrophobic modification method according to claim 3, wherein, The reaction conditions comprise a reaction temperature of 105-160 ℃ and a reaction time of 8-72 hours.

9. The hydrophobic modification method of claim 3, wherein, The washing process comprises: The solid is sequentially washed with anhydrous methanol and N,N-dimethylformamide, then centrifuged and vacuum dried for 6-36 hours; The activation process comprises: The Al-based metal organic framework composite material is prepared by the hydrophobic modification method according to any one of claims 1-9.

10. A hydrophobic Al-based metal-organic framework composite, characterized in that, ​

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