A zif-8-based super-hydrophobic mof, and a preparation method and application thereof

Abstract

The application relates to the technical field of metal organic framework functional materials, and discloses a ZIF-8-based super-hydrophobic MOF as well as a preparation method and application thereof. The ZIF-8-based super-hydrophobic MOF is prepared by the following method: 2-methyl imidazole and fluorine-containing ligand FL are used as mixed ligands to perform a coordination reaction with Zn ions to obtain ZIF-8-FL material; the ZIF-8-FL material is grafted and modified with a modifying agent under the action of an acid-binding agent, and the ZIF-8-based super-hydrophobic MOF is obtained; wherein the modifying agent is alkyl acid chloride or fluorine-containing anhydride. The ZIF-8-based super-hydrophobic MOF is prepared by introducing mixed ligands and grafting and modifying, and has the advantages of simple process, low cost and suitability for large-scale production. The ZIF-8-based super-hydrophobic MOF prepared by the application has high chemical stability and excellent hydrophobic performance in an acidic environment, avoids the defect that conventional MOFs are prone to degradation, has excellent separation efficiency and selectivity in an oil-water separation process, can effectively separate oil-water mixtures in various complex systems, and has wide market application prospect and economic benefits.

Description

Technical Field

[0001] This application relates to the field of metal-organic framework functional materials technology, specifically to a ZIF-8-based superhydrophobic MOF, its preparation method, and its application. Background Technology

[0002] Oil-water separation technology is of great significance in environmental protection and industrial production, especially in the treatment of complex systems such as industrial wastewater, oilfield wastewater and marine oil spills, where rapid and efficient oil-water separation technology is particularly important.

[0003] Currently, commonly used oil-water separation materials include membrane materials, adsorbent materials, and superhydrophobic materials. However, traditional oil-water separation materials exhibit poor stability under acidic conditions and are susceptible to corrosion or degradation, leading to decreased separation efficiency. Furthermore, the complex and costly preparation processes of some oil-water separation materials limit their widespread application in practice.

[0004] Metal-organic frameworks (MOFs) have attracted widespread attention in recent years due to their high specific surface area, tunable pore size, and good chemical stability. Among them, ZIF-8, a zinc-based MOF, possesses a unique zeolite-like topology and high structural stability, showing potential for application in oil-water separation. However, the stability of existing ZIF-8 materials in acidic environments still needs improvement, and its hydrophobic properties also need further enhancement to adapt to more complex oil-water separation conditions.

[0005] Therefore, it is particularly necessary to develop a ZIF-8-based metal-organic framework material with excellent stability and hydrophobic properties under acidic conditions. Summary of the Invention

[0006] This application provides a ZIF-8-based superhydrophobic MOF, its preparation method, and its application, aiming to solve the problems of low stability and poor hydrophobic properties of existing ZIF-8 materials in acidic environments.

[0007] To achieve the above objectives, the present application adopts the following technical solution.

[0008] A first aspect of this application provides a ZIF-8-based superhydrophobic MOF, prepared by the following method:

[0009] Using 2-methylimidazolium and fluorine-containing ligand FL as mixed ligands, a coordination reaction was carried out with Zn ions to obtain ZIF-8-FL material;

[0010] The ZIF-8-FL material is grafted with a modifier under the action of an acid-binding agent to obtain the desired product.

[0011] The modifier is an alkyl acyl chloride or a fluorinated anhydride.

[0012] Preferably, the chemical structure of the fluorinated ligand FL is shown in formula (1):

[0013]

[0014] Where R1 is R2 is

[0015] n is an integer from 0 to 10.

[0016] Preferably, the chemical structure of the alkyl acyl chloride is shown in formula (2):

[0017]

[0018] Where x is an integer from 7 to 18;

[0019] The chemical structure of the fluorinated anhydride is shown in formula (3):

[0020]

[0021] Where y is an integer from 0 to 4.

[0022] Preferably, the acid-binding agent is triethylamine or pyridine.

[0023] Preferably, the molar percentage of the fluorinated ligand FL in the mixed ligand is 5-20%.

[0024] A second aspect of this application provides a method for preparing the aforementioned ZIF-8-based superhydrophobic MOF, comprising:

[0025] S1, zinc nitrate hexahydrate, 2-methylimidazole and fluorine-containing ligand FL were dispersed in a first organic solvent to carry out a coordination reaction. The solid product was collected, washed and dried to obtain ZIF-8-aFL material.

[0026] S2, ZIF-8-FL material is dispersed in a second organic solvent, and then an acid-binding agent and a modifier are added for grafting reaction under an inert atmosphere to obtain ZIF-8-based superhydrophobic MOF.

[0027] Preferably, the first organic solvent is at least one of methanol or N,N-dimethylformamide;

[0028] And / or,

[0029] The second solvent is at least one of dichloromethane, trichloromethane, or tetrahydrofuran.

[0030] Preferably, the molar ratio of zinc nitrate hexahydrate to 2-methylimidazole is 1:(5-7);

[0031] And / or,

[0032] The mass ratio of the ZIF-8-FL material to the modifier is 1:(1-36);

[0033] And / or,

[0034] The molar ratio of the acid-binding agent to the modifier is (1:1) to (1000:1).

[0035] Preferably, the temperature of the coordination reaction is 20–70°C; the temperature of the grafting reaction is 20–40°C.

[0036] A third aspect of this application provides the application of the above-described ZIF-8-based superhydrophobic MOF or the ZIF-8-based superhydrophobic MOF prepared by the above-described preparation method in oil-water separation materials.

[0037] Compared with the prior art, the beneficial effects of this application are as follows:

[0038] This application prepares ZIF-8-based superhydrophobic MOFs by introducing mixed ligands and grafting modification. The process is simple, low-cost, and suitable for large-scale production.

[0039] The ZIF-8-based superhydrophobic MOF prepared in this application exhibits high chemical stability and excellent hydrophobic properties in acidic environments, avoiding the defects of conventional MOF materials that are easily degraded. It also has excellent separation efficiency and selectivity in oil-water separation processes, and can effectively separate oil-water mixtures in a variety of complex systems, showing broad market application prospects and economic benefits. Attached Figure Description

[0040] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 XRD patterns of the MOF material and ZIF-8 prepared in Example 1;

[0042] Figure 2 The image shows the SEM image of the ZIF-8-based superhydrophobic MOF prepared in Example 1.

[0043] Figure 3 The image shows the contact angle test results of the ZIF-8-based superhydrophobic MOF prepared in Example 1.

[0044] Figure 4The XRD pattern of the ZIF-8-based superhydrophobic MOF prepared in Example 1 after soaking in hydrochloric acid for 1 week;

[0045] Figure 5 The XRD pattern of the ZIF-8-based superhydrophobic MOF prepared in Example 2;

[0046] Figure 6 The image shows the SEM image of the ZIF-8-based superhydrophobic MOF prepared in Example 2.

[0047] Figure 7 The image shows the contact angle test results of the ZIF-8-based superhydrophobic MOF prepared in Example 2.

[0048] Figure 8 The XRD pattern of the ZIF-8-based superhydrophobic MOF prepared in Example 2 after soaking in hydrochloric acid for 1 week;

[0049] Figure 9 The XRD pattern of the ZIF-8-based superhydrophobic MOF prepared in Example 3;

[0050] Figure 10 The image shows the SEM image of the ZIF-8-based superhydrophobic MOF prepared in Example 3.

[0051] Figure 11 The contact angle test diagram of the ZIF-8-based superhydrophobic MOF prepared in Example 3;

[0052] Figure 12 The XRD pattern of the ZIF-8-based superhydrophobic MOF prepared in Example 3 after soaking in hydrochloric acid for 1 week. Detailed Implementation

[0053] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0054] In the following description of this embodiment, the terms "including", "comprising", "having", and "containing" are all open-ended terms, meaning that they include but are not limited to.

[0055] In the following description of this embodiment, the term "and / or" is used to describe the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, B existing alone, and A and B existing simultaneously. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0056] In the following description of this embodiment, the term "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0057] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms "a" and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0058] Those skilled in the art should understand that, in the following description of the embodiments of this application, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0059] Those skilled in the art will understand that the numerical ranges in the embodiments of this application should be understood as each intermediate value between the upper and lower limits of the specifically disclosed range. Each smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this application. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0060] Unless otherwise stated, the technical / scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. While this application describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this application. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0061] In a first aspect, this application provides a ZIF-8-based superhydrophobic MOF, which is prepared by the following method:

[0062] Using 2-methylimidazolium and fluorine-containing ligand FL as mixed ligands, a coordination reaction was carried out with Zn ions to obtain ZIF-8-FL material;

[0063] ZIF-8-FL material was grafted with a modifier under the action of an acid-binding agent to obtain a ZIF-8-based superhydrophobic MOF. The modifier was an alkyl acyl chloride or a fluoro anhydride.

[0064] In this application, the chemical structure of the fluorinated ligand FL is shown in formula (1):

[0065]

[0066] Where R1 is R2 is

[0067] n is an integer from 0 to 10.

[0068] In this application, the preferred molar percentage of the fluorinated ligand FL in the mixed ligands is 5-20%.

[0069] In this application, alkyl acyl chlorides or fluoro anhydrides are used as modifiers to graft ZIF-8-FL materials, ultimately yielding ZIF-8-based superhydrophobic MOFs. The chemical structure of the alkyl acyl chloride is shown in formula (2):

[0070]

[0071] Where x is an integer from 7 to 18;

[0072] The chemical structure of the fluorinated anhydride is shown in (3):

[0073]

[0074] Where y is an integer from 0 to 4.

[0075] In this application, an acid-binding agent is used to promote the grafting reaction between alkyl acyl chlorides or fluoro anhydrides and ZIF-8-FL material. The acid-binding agent can be triethylamine or pyridine, with triethylamine being preferred.

[0076] This application utilizes a hybrid bonding strategy combined with functionalization modification techniques to prepare a novel ZIF-8 material with superhydrophobic properties, namely, a ZIF-8-based superhydrophobic MOF. The ZIF-8-based superhydrophobic MOF exhibits high chemical stability and excellent hydrophobic properties in acidic environments, avoiding the degradation defects of conventional MOFs. Furthermore, it demonstrates superior separation efficiency and selectivity in oil-water separation processes, effectively separating oil-water mixtures from various complex systems.

[0077] Secondly, this application provides a method for preparing the aforementioned ZIF-8-based superhydrophobic MOF, comprising:

[0078] S1, zinc nitrate hexahydrate, 2-methylimidazole and fluorine-containing ligand FL are dispersed in a first organic solvent to carry out a coordination reaction. The solid product is collected, washed and dried to obtain ZIF-8-FL material.

[0079] In this application, the first solvent may be methanol or N,N-dimethylformamide, or a mixture of methanol and N,N-dimethylformamide. Zinc nitrate hexahydrate, 2-methylimidazole, and the fluorinated ligand FL undergo a coordination reaction in the first solvent at 20–70 °C. The reaction product is collected by centrifugation, and the solid phase product is washed repeatedly with methanol. Then, it is dried at 100–110 °C for 12–24 h to obtain the product ZIF-8-FL material.

[0080] Specifically, to indicate the molar percentage of FL ligands in the ZIF-8-FL material, the ZIF-8-FL material is referred to as ZIF-8-(a)FL, where a represents the molar percentage of FL in the total ligands.

[0081] In this application, the preferred molar ratio of zinc nitrate hexahydrate to 2-methylimidazole is 1:(5-7), and the preferred molar number of fluorinated ligand FL accounts for 5-20% of the total molar number of fluorinated ligand FL and 2-methylimidazole.

[0082] S2, ZIF-8-FL material is dispersed in a second organic solvent, and then an acid-binding agent and a modifier are added for grafting reaction under an inert atmosphere to obtain ZIF-8-based superhydrophobic MOF.

[0083] In this application, the second solvent may be at least one of dichloromethane, trichloromethane, or tetrahydrofuran. Under a nitrogen atmosphere and with the aid of an acid-binding agent, the ZIF-8-FL material and the modifier undergo a grafting reaction in the second organic solvent at 20–40 °C. The reaction product is collected as a solid phase by high-speed centrifugation. The solid phase is washed multiple times with methanol and then dried at 100–110 °C for 12–24 h to obtain a ZIF-8-based superhydrophobic MOF, denoted as ZIF-8-aFL-b, where b represents different types of modifiers.

[0084] Preferably, the mass ratio of ZIF-8-FL material to the modifier is 1:(1-36), more preferably 1:(25-36); and preferably the molar ratio of the acid-binding agent to the modifier is (1:1) to (1000:1). Under these conditions, superhydrophobic and superoleophilic ZIF-8-based MOFs can be prepared.

[0085] This application prepares ZIF-8-based superhydrophobic MOFs by introducing mixed ligands and grafting modification. The process is simple, low-cost, and suitable for large-scale production.

[0086] The ZIF-8-based superhydrophobic MOF prepared in this application exhibits high chemical stability and excellent hydrophobic properties in acidic environments. It demonstrates excellent separation efficiency and selectivity in oil-water separation processes, and can be used as an oil-water separation material, or for the preparation of oil-water separation materials. It can effectively separate oil-water mixtures in various complex systems and has broad application prospects.

[0087] The present application will be further illustrated by the following examples.

[0088] Comparative preparation of ZIF-8

[0089] 3.9 mmol of zinc nitrate hexahydrate and 27.6 mmol of 2-methylimidazole were added to a mixed solution of 40 mL methanol and 40 mL N,N-dimethylformamide. The mixture was reacted at 30 °C for 2 h. The resulting mixture was then centrifuged at 6000 rpm, and the precipitate was collected. The precipitate was washed three times with methanol and dried at 100 °C for 12 h to obtain ZIF-8 material.

[0090] Example 1

[0091] This embodiment provides a method for preparing ZIF-8-based superhydrophobic MOFs, including:

[0092] Preparation of 4-(2-(trifluoromethyl)-1H-imidazol-5-yl)phenol: 20 mmol of 2-(4-hydroxyphenyl)-2-oxoacetaldehyde, 20 mmol of 2,2,2-trifluoroacetaldehyde, 42 mmol of ammonia water, and 200 mL of ethanol were mixed and stirred at 60 °C for 20 hours. After cooling to room temperature, the reaction mixture was concentrated under vacuum to remove ethanol. 50 mL of water was added to the concentrate, and the mixture was extracted with ethyl acetate (3 × 20 mL). The extract was then dried over anhydrous magnesium sulfate, filtered, and concentrated under vacuum. The residue was sublimated to give a solid. The chemical structure of 4-(2-(trifluoromethyl)-1H-imidazol-5-yl)phenol is shown below:

[0093]

[0094] S1, 3.9 mmol of zinc nitrate hexahydrate, 22.08 mmol of 2-methylimidazole, and 5.52 mmol of 4-(2-(trifluoromethyl)-1H-imidazol-5-yl)phenol were added to a mixed solution of 40 mL of methanol and 40 mL of N,N-dimethylformamide, respectively, wherein the molar percentage of 4-(2-(trifluoromethyl)-1H-imidazol-5-yl)phenol in the mixed ligands was 20%. The mixed solution was reacted at 30 °C for 2 h, and the resulting mixture was centrifuged at 6000 rpm to collect the precipitate. The precipitate was washed three times with methanol and dried at 100 °C for 12 h to obtain ZIF-8-FL material, denoted as ZIF-8-20%FL.

[0095] S2, 0.03 g of ZIF-8-20%FL was ultrasonically dispersed in 15 mL of chloroform. Under a nitrogen atmosphere, 348 μl of triethylamine and 612 μl of heptafluorobutyric anhydride were added, and the mixture was stirred at 30 °C for 24 h. The resulting mixture was then centrifuged at 6000 rpm, and the precipitate was collected. The precipitate was washed three times with methanol and dried at 100 °C for 12 h to obtain a ZIF-8-based superhydrophobic MOF, designated ZIF-8-20%FL-7F.

[0096] The MOF materials prepared in Example 1 and the ZIF-8 materials of the comparative example were characterized. The XRD patterns of ZIF-8-20%FL and ZIF-8-20%FL-7F prepared in Example 1, and ZIF-8 prepared in the comparative example, are shown below. Figure 1 As shown. By Figure 1 It can be seen that ZIF-8-20%FL, ZIF-8-20%FL-7F and ZIF-8 exhibit the same peak at the corresponding positions, that is, the complex ZIF-8-20%FL and the ZIF-8-based superhydrophobic MOF ZIF-8-20%FL-7F prepared in this application all retain the framework structure and crystallinity of ZIF-8 structure.

[0097] The ZIF-8-based superhydrophobic MOF prepared in Example 1, namely ZIF-8-20%FL-7F, was characterized by morphological testing, and its SEM image is shown below. Figure 2 As shown. From Figure 2 It can be seen that the ZIF-8-20%FL-7F sample exhibits a typical rhombic dodecahedral morphology. Compared with the particle size of ZIF-8 nanocrystals (approximately 50 nm), the average particle size of ZIF-8-20%FL-7F crystals has increased by 10 times, reaching 500 nm.

[0098] Hydrophobicity tests were performed on ZIF-8-20%FL-7F prepared in Example 1, and the contact angle test results are as follows: Figure 3 As shown. From Figure 3 It can be seen that the contact angle between ZIF-8-20%FL-7F and water is 151.9°, indicating that ZIF-8-20%FL has excellent superhydrophobicity.

[0099] The stability of ZIF-8-20%FL-7F prepared in Example 1 was tested, and the specific method was as follows:

[0100] It was soaked in hydrochloric acid solution with pH=2 for 1 week, and then its XRD pattern was tested. The test results are as follows. Figure 4 As shown. From Figure 4 It can be seen that after soaking in hydrochloric acid solution with pH=2 for 1 week, ZIF-8-20%FL-7F still maintains the typical ZIF-8 diffraction structure. Its framework structure remains relatively intact under acidic conditions and has high stability.

[0101] Example 2

[0102] This embodiment provides a method for preparing ZIF-8-based superhydrophobic MOFs, including:

[0103] Preparation of 4-(5-(trifluoromethyl)-1H-1,2,4-triazol-3-yl)phenol: 20 mmol of ethyl trifluoroacetate, 26 mmol of 85% hydrazine hydrate, and 200 mL of ethanol were mixed and stirred at 67 °C for 2 hours. After cooling to room temperature, 16 mmol of 4-hydroxybenzoamide hydrochloride and 16 mmol of potassium hydroxide were added, and the mixture was refluxed and stirred for another 20 hours. After cooling to room temperature, the reaction mixture was concentrated under vacuum to remove ethanol. 50 mL of water was added to the concentrate, and the mixture was extracted with ethyl acetate (3 × 20 mL), dried over anhydrous magnesium sulfate, filtered, and concentrated under vacuum. The residue was sublimated to give a solid. The chemical structure of 4-(5-(trifluoromethyl)-1H-1,2,4-triazol-3-yl)phenol is shown below:

[0104]

[0105] S1, 3.9 mmol of zinc nitrate hexahydrate, 22.63 mmol of 2-methylimidazole, and 4.97 mmol of 4-(5-(trifluoromethyl)-1H-1,2,4-triazol-3-yl)phenol were added to a mixed solution of 40 mL of methanol and 40 mL of N,N-dimethylformamide, respectively, wherein the molar percentage of 4-(2-(trifluoromethyl)-1H-imidazole-5-yl)phenol in the mixed ligands was 18%. The mixed solution was reacted at 30 °C for 2 h, and the resulting mixture was centrifuged at 6000 rpm to collect the precipitate. The precipitate was washed three times with methanol and dried at 100 °C for 12 h to obtain ZIF-8-FL material, denoted as ZIF-8-18%FL.

[0106] S2, 0.03 g of ZIF-8-18%FL was ultrasonically dispersed in 15 mL of chloroform. Under a nitrogen atmosphere, 348 μl of triethylamine and 0.76 g of octadecyl chloride were added, and the mixture was stirred at 30 °C for 24 h. The resulting mixture was then centrifuged at 6000 rpm, and the precipitate was collected. The precipitate was washed three times with methanol and dried at 100 °C for 12 h to obtain a ZIF-8-based superhydrophobic MOF, denoted as ZIF-8-18%FL-C18.

[0107] The XRD pattern of ZIF-8-18%FL-C18 prepared in Example 2 is as follows: Figure 5 As shown. By Figure 5 It can be seen that, compared with IF-8, ZIF-8-18%FL-C18 also exhibits the same peak at the corresponding position, which retains the framework structure and crystallinity of ZIF-8.

[0108] The ZIF-8-18%FL-C18 prepared in Example 2 was subjected to morphological characterization tests, and its SEM images are shown below. Figure 6 As shown. From Figure 6 It can be seen that the ZIF-8-18%FL-C18 sample exhibits a typical rhombic dodecahedral morphology, but compared with the particle size of ZIF-8 nanocrystals (approximately 50 nm), the average particle size of ZIF-8-18%FL-C18 crystals has increased by 8 times, reaching 400 nm.

[0109] The hydrophobicity of ZIF-8-18%FL-C18 prepared in Example 2 was tested, and the contact angle test results are as follows: Figure 7 As shown. From Figure 7 It can be seen that the contact angle between ZIF-8-18%FL-C18 and water is 152.1°, indicating that ZIF-8-18%FL-C18 has excellent superhydrophobicity.

[0110] The stability of ZIF-8-18%FL-C18 prepared in Example 2 was tested. Specifically, it was immersed in hydrochloric acid solution at pH 2 for one week, and then its XRD pattern was measured. The test results are as follows: Figure 8 As shown. From Figure 8 It can be seen that after soaking in hydrochloric acid solution with pH=2 for 1 week, ZIF-8-18%FL-C18 still maintains the typical ZIF-8 diffraction structure. Its framework structure remains relatively intact under acidic conditions and has high stability.

[0111] Example 3

[0112] This embodiment provides a method for preparing ZIF-8-based superhydrophobic MOFs, including:

[0113] Preparation of 4-(5-(trifluoromethyl)-1H-1,2,4-triazol-3-yl)but-1-ol: 20 mmol of ethyl trifluoroacetate, 26 mmol of 85% hydrazine hydrate, and 200 mL of ethanol were mixed and stirred at 67 °C for 2 hours. After cooling to room temperature, 16 mmol of 5-hydroxypentanoimide hydrochloride and 16 mmol of potassium hydroxide were added, and the mixture was refluxed and stirred for another 20 hours. After cooling to room temperature, the reaction mixture was concentrated under vacuum to remove ethanol. 50 mL of water was added to the concentrate, and the mixture was extracted with ethyl acetate (3 × 20 mL), dried over anhydrous magnesium sulfate, filtered, and concentrated under vacuum. The residue was sublimated to give a solid. The chemical structure of 4-(5-(trifluoromethyl)-1H-1,2,4-triazol-3-yl)but-1-ol is shown below:

[0114]

[0115] S1, 3.9 mmol of zinc nitrate hexahydrate, 23.46 mmol of 2-methylimidazole, and 4.14 mmol of 4-(5-(trifluoromethyl)-1H-1,2,4-triazol-3-yl)but-1-ol were added to a mixed solution of 40 mL of methanol and 40 mL of N,N-dimethylformamide, respectively, wherein the molar percentage of 4-(2-(trifluoromethyl)-1H-imidazole-5-yl)phenol in the mixed ligands was 15%. The mixed solution was reacted at 30 °C for 2 h, and the resulting mixture was centrifuged at 6000 rpm to collect the precipitate. The precipitate was washed three times with methanol and dried at 100 °C for 12 h to obtain ZIF-8-FL material, denoted as ZIF-8-15%FL.

[0116] S2, 0.03 g of ZIF-8-15%FL was ultrasonically dispersed in 15 mL of chloroform. Under a nitrogen atmosphere, 348 μl of triethylamine and 493 μl of pentafluoropropionic anhydride were added, and the mixture was stirred at 30 °C for 24 h. The resulting mixture was then centrifuged at 6000 rpm, and the precipitate was collected. The precipitate was washed three times with methanol and dried at 100 °C for 12 h to obtain a ZIF-8-based superhydrophobic MOF, designated ZIF-8-15%FL-5F.

[0117] The XRD pattern of ZIF-8-15%FL-5F prepared in Example 3 is as follows: Figure 9 As shown. By Figure 9 It can be seen that, compared with ZIF-8, ZIF-8-15%FL-5F also exhibits the same peak at the corresponding position, which retains the framework structure and crystallinity of ZIF-8.

[0118] The ZIF-8-15%FL-5F prepared in Example 3 was subjected to morphological characterization tests, and its SEM images are shown below. Figure 10As shown. From Figure 10 It can be seen that the ZIF-8-15%FL-5F sample exhibits a typical rhombic dodecahedral morphology. Compared with the particle size of ZIF-8 nanocrystals (approximately 50 nm), the average particle size of ZIF-8-15%FL-5F crystals has increased by 4 times, reaching 200 nm.

[0119] Hydrophobicity tests were performed on ZIF-8-15%FL-5F prepared in Example 3, and the contact angle test results are as follows: Figure 11 As shown. From Figure 11 It can be seen that the contact angle between ZIF-8-15%FL-5F and water is 155.7°, indicating that ZIF-8-15%FL-5F has excellent superhydrophobicity.

[0120] The stability of ZIF-8-15%FL-5F prepared in Example 3 was tested. Specifically, it was immersed in hydrochloric acid solution at pH 2 for one week, and then its XRD pattern was measured. The test results are as follows: Figure 12 As shown. From Figure 12 It can be seen that after soaking in hydrochloric acid solution with pH=2 for 1 week, ZIF-8-15%FL-5F still maintains the typical ZIF-8 diffraction structure. Its framework structure remains relatively intact under acidic conditions and has high stability.

[0121] ZIF-8-based superhydrophobic MOFs prepared in Examples 1-3 were used to prepare ZIF-8-based superhydrophobic MOF@PP composite membranes. Oil-water separation experiments were conducted to test their oil-water separation performance. The methods are as follows:

[0122] 20 mg of ZIF-8-based superhydrophobic MOF and 2 mg of polyvinylidene fluoride were dispersed in N-methyl-2-pyrrolidone. After stirring the slurry for 1 hour, it was coated onto one side of PP with a scraper and then vacuum dried at 60 °C for 12 hours to prepare ZIF-8-20%FL-7F@PP composite film, ZIF-8-18%FL-C18@PP composite film and ZIF-8-15%FL-5F@PP composite film.

[0123] 100g toluene, 0.1g sodium dodecyl sulfate, and 10g hydrochloric acid (pH=2) were mixed thoroughly and stirred at 700rpm for 24 hours to prepare a water-in-oil emulsion. A vacuum filtration system was assembled using a filter and a vacuum filtration flask. The three composite membranes were cut into circular pieces with a diameter of approximately 4cm and used as filter membranes to separate oil and water from the emulsified oil wastewater.

[0124] To quantitatively assess separation accuracy, separation efficiency is calculated by testing the rejection rate (Rj):

[0125] Rj=(1-C p / C f)×100%

[0126] Cp and Cf represent the water concentrations in the permeate and feed solution, respectively.

[0127] Testing revealed that the composite membranes incorporating the ZIF-8-based superhydrophobic MOF prepared in this application exhibit excellent separation performance for oil-water mixtures. Specifically, the ZIF-8-20%FL-7F@PP composite membrane achieved a separation efficiency of 98.4% for a toluene-hydrochloric acid mixture at pH 2. The ZIF-8-18%FL-C18@PP composite membrane achieved a separation efficiency of 98.7% for the same pH 2 solution. The ZIF-8-15%FL-5F@PP composite membrane achieved a separation efficiency of 99.3% for the same pH 2 solution.

[0128] Although this application has been described in detail in this specification with general descriptions and specific embodiments, some modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, such modifications or improvements made without departing from the spirit of this application are all within the scope of protection claimed in this application.

Claims

1. A ZIF-8-based superhydrophobic MOF, characterized in that, Prepared by the following method: ZIF-8-FL material was obtained by using 2-methylimidazole and fluorine-containing ligand FL as mixed ligands to coordinate with Zn ions. ZIF-8-FL material was grafted with a modifier under the action of an acid-binding agent to obtain ZIF-8-based superhydrophobic MOF. The modifier is an alkyl acyl chloride or a fluorinated anhydride; The chemical structure of the fluorine-containing ligand FL is shown in formula (1): (1) Where R1 is , or R2 is or n is an integer from 0 to 10; The acid-binding agent is triethylamine or pyridine.

2. The ZIF-8-based superhydrophobic MOF according to claim 1, characterized in that, The chemical structure of the alkyl acyl chloride is shown in formula (2): (2) Where x is an integer from 7 to 18; The chemical structure of the fluorinated anhydride is shown in formula (3): (3) Where y is an integer from 0 to 4.

3. The ZIF-8-based superhydrophobic MOF according to claim 1, characterized in that, The molar percentage of the fluorinated ligand FL in the mixed ligand is 5-20%.

4. The method for preparing the ZIF-8-based superhydrophobic MOF according to claim 1, characterized in that, include: S1, zinc nitrate hexahydrate, 2-methylimidazole and fluorine-containing ligand FL are dispersed in a first organic solvent to carry out a coordination reaction. The solid product is collected, washed and dried to obtain ZIF-8-FL material. S2, ZIF-8-FL material is dispersed in a second organic solvent, and then an acid-binding agent and a modifier are added for grafting reaction under an inert atmosphere to obtain ZIF-8-based superhydrophobic MOF.

5. The preparation method according to claim 4, characterized in that, The first organic solvent is at least one of methanol or N,N-dimethylformamide; and / or, The second solvent is at least one of dichloromethane, trichloromethane, or tetrahydrofuran.

6. The preparation method according to claim 4, characterized in that, The molar ratio of zinc nitrate hexahydrate to 2-methylimidazole is 1:(5~7); And / or, The mass ratio of the ZIF-8-FL material to the modifier is 1:(1~36); And / or, The molar ratio of the acid-binding agent to the modifier is (1:1) to (1000:1).

7. The preparation method according to claim 4, characterized in that, The temperature for the coordination reaction is 20~70℃; The grafting reaction is carried out at a temperature of 20~40℃.

8. The application of the ZIF-8 based superhydrophobic MOF according to any one of claims 1-3 or the ZIF-8 based superhydrophobic MOF prepared by the preparation method according to any one of claims 4-7 in oil-water separation materials.

Images