Metal organic framework film and preparation method and application thereof

Abstract

The invention relates to a metal organic framework film and a preparation method and application thereof. The preparation method comprises the following steps: pretreating a conductive substrate; preparing a precursor solution: respectively dissolving a metal salt and an organic ligand in methanol according to a molar ratio of 1: (1-3), and performing ultrasonic mixing to form a uniform ZIF series precursor solution; electrochemical deposition is conducted, specifically, the pretreated FTO conductive glass serves as a working electrode, electrochemical deposition is conducted for 10-60 minutes under the voltage of 4-8 V, and a ZIF-8 or ZIF-67 thin film is synchronously generated on the surface of the FTO conductive glass; performing post-treatment: performing vacuum drying to obtain a finished product of the metal organic framework film. Compared with the prior art, the invention aims to solve the problems of high temperature, high pressure, high cost, low efficiency and environmental protection of a solvothermal method and a hydrothermal method, and provides a more convenient, environment-friendly and efficient preparation way to meet the requirements of the ZIF material in high-precision devices such as photoelectric devices, catalytic devices and sensing devices.

Description

Technical Field

[0001] The present invention relates to the technical fields of material chemistry and electrochemistry, and particularly to a metal-organic framework thin film, a preparation method thereof, and an application thereof. Background Art

[0002] The ZIF (zeolitic imidazolate framework) series belongs to a kind of metal-organic framework (MOF) materials. It has received extensive attention due to its zeolite-like topological structure, excellent porosity, specific surface area, and chemical stability. ZIF-8 and ZIF-67 are the most representative materials in the ZIF series, with zinc (Zn) and cobalt (Co) as metal nodes respectively, and the ligand is usually imidazole or its derivative. These materials exhibit excellent properties in the fields of gas separation, gas storage, catalysis, and energy storage, and thus have great application potential in the industrial and scientific research fields. The current preparation methods of ZIF materials mainly include the solvothermal method and the hydrothermal method. Although these traditional methods can prepare high-quality ZIF materials, they have the following limitations: The solvothermal method and the hydrothermal method usually need to be carried out under high temperature and high pressure conditions. The reaction temperature is usually above 100°C, and a long heating and cooling process is required (for example, the secondary solvothermal method described in CN 107349805A needs to carry out seed generation and growth step by step, with a complex process and high energy consumption). Since the reaction process depends on the temperature and solvent environment, the growth of crystals is often difficult to control, and the obtained material morphology and size distribution are uneven. This unstable structure has an adverse effect on applications such as gas adsorption and catalysis, and it is difficult to meet the application requirements that require high consistency and specific structures, resulting in higher equipment and energy costs and being unfavorable for large-scale industrial production. The reaction time of traditional methods often needs several hours to several days to obtain an ideal material morphology and crystallinity, and the preparation cycle is relatively long. This is inefficient for industrial applications and difficult to meet the high-yield demand.

[0003] Traditional methods are difficult to precisely control the thickness and uniformity in the preparation of thin films, resulting in instability of ZIF materials in applications with high material quality requirements such as optoelectronics and gas sensing. In addition, the ZIF materials prepared by conventional methods are usually in powder form and are difficult to be directly applied to many high-end devices that require a thin film structure. Most solvothermal methods and hydrothermal methods need to use organic solvents, which pose a potential environmental pollution risk, are unfavorable for green preparation, and are difficult and costly to recycle solvents in the post-treatment process.

[0004] Therefore, it is urgent to solve the problems of high temperature and high pressure, high cost, low efficiency, and environmental protection of the solvothermal method and the hydrothermal method, and provide a more convenient, environmentally friendly, and efficient preparation route. Summary of the Invention

[0005] The object of the present invention is to overcome the defects existing in the above-mentioned prior art and provide a metal-organic framework thin film, a preparation method and an application thereof, aiming to provide a method for preparing ZIF-8 and ZIF-67 based on electrochemistry, aiming to solve the problems of high temperature and pressure, high cost, low efficiency and environmental protection of the solvothermal method and the hydrothermal method, and provide a more convenient, environmentally friendly and efficient preparation method to meet the needs of ZIF materials in high-precision devices such as optoelectronics, catalysis and sensing.

[0006] The object of the present invention can be achieved by the following technical solutions:

[0007] In the first aspect of the present invention, a method for electrochemically preparing a metal-organic framework thin film is provided, including the following steps:

[0008] S1: Pretreat the conductive substrate: Place the FTO conductive glass in a detergent aqueous solution, ethanol, and isopropanol in sequence for ultrasonic cleaning, and then blow dry with argon and perform ultraviolet ozone treatment;

[0009] S2: Prepare the precursor solution: Dissolve the metal salt and the organic ligand in methanol according to a molar ratio of 1:1 to 3, and ultrasonically mix to form a uniform ZIF series precursor solution;

[0010] S3: Electrochemical deposition: Use the pretreated FTO conductive glass as the working electrode, perform electrochemical deposition at a voltage of 4-8V for 10-60 minutes, and simultaneously generate ZIF-8 or ZIF-67 thin film on the surface of the FTO conductive glass;

[0011] S4: Post-treatment: Vacuum dry to obtain the finished product of the metal-organic framework thin film.

[0012] Further, in S1, the process of ultraviolet ozone treatment is: Place the FTO conductive glass in an ultraviolet disinfection cabinet capable of releasing ozone for treatment for 5-15 minutes;

[0013] In S4, the process of vacuum drying is: Vacuum dry the deposited thin film at 60°C for 2-4 hours.

[0014] Further, in S1, the ultraviolet ozone treatment time is 15 minutes;

[0015] The surface area of the FTO conductive glass is 2-6 cm 2 .

[0016] Further, in S2, the metal salt is selected from zinc acetate hexahydrate or cobalt nitrate hexahydrate;

[0017] The organic ligand is 2-methylimidazole;

[0018] The molar ratio of the metal salt to the organic ligand is 1:2 to 2:1.

[0019] Further preferably, in S2, the molar ratio of the metal salt to the organic ligand is 1:2 to 1:1.

[0020] Most preferably, in S2, the molar ratio of the metal salt to the organic ligand is 1:1.

[0021] Further, in S3, the electrochemical deposition adopts a two-electrode system, and the current density is controlled to be 0.5 - 2 A / cm 2 .

[0022] Further, in S3, the deposition voltage for generating the ZIF-8 thin film is 8 V, and the deposition time is 60 minutes;

[0023] The deposition voltage for generating the ZIF-67 thin film is 8 V, and the deposition time is 120 minutes.

[0024] The second aspect of this aspect provides a metal-organic framework thin film prepared by the above method. In S3, as Figure 3 and Figure 4 shown, the thickness of the thin film is 1 - 8 μm.

[0025] Further, the metal-organic framework thin film exhibits stable electrochemically grown characteristics within the voltage range of 4 - 8 V.

[0026] The third aspect of the present invention provides an application of the above metal-organic framework thin film, which is used for a gas separation membrane, an electrochemical sensor, or a catalytic electrode.

[0027] The electrochemical method for preparing the metal-organic framework thin film according to the embodiments of the present invention has at least the following beneficial effects:

[0028] (1) High-efficiency preparation and controllability: The electrochemical deposition technology has good controllability. By adjusting the electrochemical parameters, the growth rate, thickness, and morphology of the MOF thin film surface can be precisely controlled, thus ensuring uniformity and denseness. Compared with the traditional liquid-phase method or vapor deposition method, the method of the present invention is more simple and efficient, and is suitable for large-scale preparation.

[0029] (2) Precise control of thickness and structure: The electrochemical method can precisely control the thickness and structure of the MOF thin film by adjusting parameters such as current, voltage, and reaction time. This high controllability enables parameters such as the pore size and specific surface area of the thin film to be adjusted as needed, meeting the specific requirements of different applications, and is suitable for application fields such as gas separation and catalysis that require high porosity and specific pore size distributions.

[0030] (3) High material structure uniformity and consistency: The MOF thin films deposited by the electrochemical method have high uniformity and consistency. Compared with the MOF powder materials prepared by traditional methods, the thin films obtained by electrochemical deposition are more uniform in terms of thickness distribution, pore structure, etc., which can reduce the material inhomogeneity and improve the stability and performance of the device.

[0031] (4) Shorten the reaction time and improve the preparation efficiency: The electrochemical method has a fast reaction rate and can complete the preparation of MOF thin films in a short time, thus improving the preparation efficiency and shortening the process cycle. Compared with the solvothermal method and the hydrothermal method that require reaction times of several hours or even several days, the electrochemical preparation can be completed in a few minutes to a few hours, which is suitable for industrial production and rapid R & D applications. Description of the Drawings

[0032] Figure 1 is a schematic diagram of the principle of preparing metal-organic frameworks by the two-step electrochemical method in Example 1 of the present invention;

[0033] Figure 2 is the XRD pattern of the metal-organic framework material prepared by the two-step electrochemical method in Example 1 of the present invention;

[0034] Figure 3 is the SEM image of the metal-organic framework material prepared by the two-step electrochemical method in Example 1 of the present invention;

[0035] Figure 4 is the SEM image of the metal-organic framework material prepared by the two-step electrochemical method in Example 1 of the present invention. Detailed Embodiments

[0036] The present invention specifically relates to a method for efficiently preparing ZIF series metal-organic frameworks (Metal-Organic Frameworks, abbreviated as MOF) materials by an electrochemical method, especially applicable to the preparation of ZIF (Zeolitic Imidazolate Frameworks) materials based on zinc and cobalt metal nodes such as ZIF-8 and ZIF-67, and is mainly applied to functional material fields such as catalysis, gas separation, gas storage, sensors, and energy storage.

[0037] The present invention uses an electrochemical deposition technique to synchronously prepare ZIF-8 and ZIF-67 thin films on a conductive glass substrate, significantly simplifying the preparation process. The prepared ZIF-8 and ZIF-67 thin films both exhibit good crystal structures and pore characteristics. The test results show that ZIF-8 and ZIF-67 exhibit relatively stable thin film growth during the electrochemical synthesis process at different voltages. Especially at higher voltages, the film thickness increases significantly and the structural stability is good, making it suitable for electrochemical applications that require a larger thickness and high stability. The electrochemical method provided by the present invention can achieve precise control of the thickness and uniformity of ZIF series thin films, and has the characteristics of environmental friendliness, energy conservation and low consumption, providing a new solution for the application of ZIF materials in multifunctional devices.

[0038] During the process of electrochemically preparing ZIF-8 and ZIF-67 materials, the present invention realizes the precise assembly and uniform coverage of MOF thin films. For this reason, in the first aspect of the present invention, an electrochemical method for efficiently preparing metal-organic framework thin films is proposed. This method can control the thickness and structure of the thin film and can also significantly enhance... In the second aspect of the present invention, a general preparation method is also provided, which can be applied to the electrodeposition of large-area thin films. The present invention has the advantages of simple process, controllable time, good uniformity and easy scale-up production.

[0039] In specific implementation, the MOF material prepared by electrochemistry is the ZIF series, such as ZIF-8 and ZIF-67.

[0040] In specific implementation, the metal-organic frameworks prepared by electrochemistry are ZIF-8 and ZIF-67. The prepared metal-organic framework thin films have good structures and properties.

[0041] In specific implementation, the area of the FTO treated with ultraviolet light is 2 cm 2 ~6 cm 2 .

[0042] In specific implementation, the FTO treated with ultraviolet light is prepared through the following steps:

[0043] 1) Using FTO glass as the substrate, ultrasonically clean it in a mixture of dishwashing liquid and water, ethanol, and isopropanol for 10 minutes respectively, then dry it with argon and store it in a glove box for later use.

[0044] 2) Place the dried FTO conductive glass in UV-O3 and perform ultraviolet treatment for 15 minutes.

[0045] In specific implementation, the FTO treated with ultraviolet light is ultrasonically cleaned in a mixture of dishwashing liquid and water, ethanol, and isopropanol for 5 to 15 minutes in sequence.

[0046] In specific implementation, the ultraviolet-treated FTO is placed in UV-O3 for ultraviolet treatment for 5 to 15 minutes.

[0047] In specific implementation, the metal-organic framework thin film prepared by the electrochemical method is obtained through the following steps:

[0048] 3) Dissolve zinc acetate dihydrate (0.41 g, 2.0 mmol) in 30 ml of methanol, and dissolve 2-methylimidazole (0.55 g, 2.0 mmol) in 20 ml of methanol. After ultrasonic treatment for 10 min respectively, mix them and continue ultrasonic treatment for 10 min to obtain a ZIF-8 precursor solution.

[0049] 4) Perform electrodeposition in the ZIF-8 solution with two electrodes. According to some embodiments of the present invention, the voltage of the electrochemical reaction is 4V - 8V.

[0050] In specific implementation, the time of the electrochemical reaction is 10 min - 60 min.

[0051] In specific implementation, the molar ratio of zinc acetate dihydrate to 2-methylimidazole is 1:(1 - 3).

[0052] In specific implementation, after the electrochemical reaction, a step of vacuum drying is also included.

[0053] In specific implementation, the temperature of the vacuum drying is 60 °C.

[0054] In specific implementation, the time of the vacuum drying is 2 h - 4 h.

[0055] The present invention can be applied to the electrodeposition of large-area thin films. This technology has the advantages of simple process, controllable time, good uniformity, and easy scale-up production.

[0056] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Features such as preparation means, materials, structures, or composition ratios that are not clearly described in this technical solution are regarded as common technical features disclosed in the prior art. The reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the technical field, unless otherwise specified.

[0057] Example 1

[0058] Example 1 provides a method for preparing a metal-organic framework thin film by the electrochemical method, including ultraviolet-treated FTO conductive glass and ZIF-8 electrodeposited on the FTO. The preparation method of the ZIF-8 thin film electrodeposited on the ultraviolet-treated FTO conductive glass is as follows:

[0059] S1. Using a 1 cm × 2 cm FTO glass as the substrate, ultrasonically clean it in a mixture of dishwashing liquid and water, ethanol, and isopropanol for 10 minutes respectively, then dry it with argon and store it in a drying oven for later use.

[0060] S2. Place the dried FTO conductive glass in UV - O3 and perform ultraviolet treatment for 15 minutes.

[0061] In specific implementation, the ultraviolet - treated FTO is ultrasonically cleaned in a mixture of dishwashing liquid and deionized water, absolute ethanol, and isopropanol for 15 minutes in sequence.

[0062] In specific implementation, the ultraviolet - treated FTO is placed in UV - O3 and subjected to ultraviolet treatment for 15 minutes.

[0063] In specific implementation, the ZIF - 8 prepared by the electrochemical method is obtained through the following steps:

[0064] S3. Dissolve zinc acetate hexahydrate (0.41 g, 2.0 mmol) in 30 ml of methanol solution, and dissolve 2 - methylimidazole (0.55 g, 2.0 mmol) in 20 ml of methanol solution. After ultrasonic treatment for 10 min respectively, mix them and continue ultrasonic treatment for 10 min to obtain a ZIF - 8 solution.

[0065] S4. Use a two - electrode to grow a thin film on the ultraviolet - treated FTO conductive glass in the ZIF - 8 solution. The reaction voltage is 8 V, the current is 1 A, and the electrodeposition time is 1 h.

[0066] S5. Place the ZIF - 8 thin film prepared electrochemically in a vacuum oven and dry it at 60 °C for 2 h - 4 h to obtain the product.

[0067] The flow schematic diagram of the electrochemical method for preparing metal - organic framework thin films is as Figure 1 shown, intuitively showing the advantages of simplicity and easy control of this method. Then, perform XRD testing on the ZIF - 8 thin film prepared by the electrochemical method in Example 1. The results are as Figure 2 shown (a is the XRD pattern of ZIF - 8, b is the XRD pattern of ZIF - 67). The results show that ZIF - 8 is successfully synthesized on the FTO conductive glass. The SEM cross - sectional schematic diagram of the ZIF - 8 thin film prepared by the electrochemical method is as Figure 3 shown ( Figure 3 , a is the SEM image of the morphology and cross - sectional thickness of the ZIF - 8 thin film under the condition of a voltage of 8 V. b is the SEM image of the morphology and cross - sectional thickness of the ZIF - 8 thin film under the condition of a voltage of 10 V. c is the SEM image of the morphology and cross - sectional thickness of the ZIF - 8 thin film under the condition of a voltage of 12 V), which intuitively shows the morphology of the ZIF - 8 thin film deposited on the substrate by the electrochemical method.

[0068] Example 2

[0069] Example 2 provides a two-step electrochemical method for preparing a metal-organic framework thin film, including an FTO conductive glass treated with ultraviolet light and ZIF-67 electrodeposited on the FTO. The preparation method of the ZIF-67 thin film electrodeposited on the FTO conductive glass treated with ultraviolet light is as follows:

[0070] S1. Using a 1 cm × 2 cm FTO glass as the substrate, ultrasonically clean it in a mixture of dishwashing liquid and water, ethanol, and isopropanol for 10 minutes respectively, then dry it with argon and store it in a drying oven for later use.

[0071] S2. Place the dried FTO conductive glass in UV-O3 and perform ultraviolet treatment for 15 minutes.

[0072] Specifically, the FTO treated with ultraviolet light is ultrasonically cleaned in a mixture of dishwashing liquid and deionized water, absolute ethanol, and isopropanol for 15 minutes in sequence.

[0073] Specifically, the FTO treated with ultraviolet light is placed in UV-O3 and subjected to ultraviolet treatment for 15 minutes.

[0074] According to some embodiments of the present invention, the ZIF-67 prepared by the electrochemical method is obtained through the following steps:

[0075] S3. Dissolve cobalt nitrate hexahydrate (0.291 g, 1.0 mmol) in 30 ml of methanol, dissolve 2-methylimidazole (0.164 g, 2.0 mmol) in 30 ml of methanol, ultrasonically mix them for 10 minutes respectively, and then continue to ultrasonically mix for 10 minutes to obtain a ZIF-67 solution.

[0076] S4. Use a two-electrode to grow a thin film on the FTO conductive glass that has been ultraviolet-treated in the ZIF-67 solution. The reaction voltage is 8 V, the current is 1 A, and the electrodeposition time is 2 h.

[0077] S5. Place the ZIF-8 thin film prepared electrochemically in a vacuum oven and dry it at 60 °C for 2 h - 4 h to obtain it.

[0078] The flow schematic diagram of the electrochemical method for preparing the metal-organic framework thin film is as Figure 1 shown. After that, the ZIF-67 thin film prepared by the electrochemical method in Example 1 is subjected to XRD testing, and the results are as Figure 2 shown. The results show that ZIF-67 is successfully synthesized on the FTO conductive glass. The SEM cross-sectional schematic diagram of the ZIF-67 thin film prepared by the electrochemical method is as Figure 4 shown( Figure 4, a is the SEM image of the morphology and cross-sectional thickness of the ZIF-67 thin film under the condition of a voltage of 8V. b is the SEM image of the morphology and cross-sectional thickness of the ZIF-67 thin film under the condition of a voltage of 10V. c is the SEM image of the morphology and cross-sectional thickness of the ZIF-67 thin film under the condition of a voltage of 12V), which intuitively shows the morphology of the ZIF-67 thin film deposited on the substrate by the electrochemical method.

[0079] In Examples 1 and 2, the efficient preparation of ZIF series thin films in metal-organic frameworks (MOFs) was achieved by the electrochemical method, showing several significant advantages. First of all, the electrochemical deposition method can be operated at normal temperature and pressure, which not only reduces the requirements for equipment but also greatly reduces energy consumption, being more energy-saving and environmentally friendly than traditional high-temperature and high-pressure processes. In addition, by precisely controlling parameters such as current density, potential, and deposition time, fine adjustment of the film thickness and uniformity can be realized, thus ensuring the quality and consistency of the material. This controllability is particularly important in the preparation of ZIF series materials because it directly affects the pore structure and specific surface area of the thin film, and then affects the catalytic activity, gas adsorption, and separation effect. The ZIF series thin films prepared by this electrochemical method exhibit excellent pore structure and chemical stability. They not only have good antioxidant and moisture resistance in various environments but also have a uniform pore size distribution and a high specific surface area, which significantly improves the performance of the material in applications such as gas separation, storage, and catalyst carriers. Compared with the ZIF series materials in powder form, the thin film form is more convenient for direct application in devices, reducing the subsequent processing steps and providing greater convenience for practical applications. More importantly, the process flow of the embodiments of the present invention is simple, highly repeatable, suitable for large-scale industrial production, and reduces the production cost. This efficient and low-consumption preparation method broadens the application prospects of ZIF series materials, provides new material solutions for fields with high-performance requirements such as catalysis, gas sensing, and energy storage, and shows broad commercial potential.

[0080] The above description of the embodiments is to facilitate the understanding and use of the invention by those of ordinary skill in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative labor. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A method for electrochemically preparing a metal-organic framework thin film, characterized in that, It includes the following steps: S1: Pretreat the conductive substrate: sequentially place the FTO conductive glass in a dishwashing liquid aqueous solution, ethanol, and isopropanol for ultrasonic cleaning, then blow dry with argon and perform ultraviolet ozone treatment; S2: Prepare the precursor solution: dissolve the metal salt and the organic ligand in methanol according to a molar ratio of 1:1 to 3, and ultrasonically mix to form a uniform ZIF series precursor solution; S3: Electrochemical deposition: use the pretreated FTO conductive glass as the working electrode, perform electrochemical deposition at a voltage of 4 - 8V for 10 - 60 minutes, and simultaneously generate a ZIF-8 or ZIF-67 thin film on the surface of the FTO conductive glass; S4: Post-treatment: vacuum dry the ZIF-8 or ZIF-67 thin film to obtain the finished product of the metal-organic framework thin film.

2. The method for electrochemically preparing a metal-organic framework thin film according to claim 1, wherein, In S1, the process of ultraviolet ozone treatment is: place the FTO conductive glass in an ultraviolet disinfection cabinet capable of releasing ozone and treat for 5 - 15 minutes; In S4, the process of vacuum drying is: vacuum dry the deposited thin film at 60°C for 2 - 4 hours.

3. The method for electrochemically preparing a metal-organic framework thin film according to claim 2, wherein In S1, the ultraviolet ozone treatment time is 15 minutes; The surface area of the FTO conductive glass is 2-6 cm 2 .

4. The method for electrochemically preparing a metal-organic framework thin film according to claim 1, characterized in that, In S2, the metal salt is selected from zinc acetate hexahydrate or cobalt nitrate hexahydrate; The organic ligand is dimethylimidazole; The molar ratio of the metal salt to the organic ligand is 1:2 to 2:

1.

5. The method for electrochemically preparing a metal-organic framework thin film according to claim 4, wherein, In S2, the molar ratio of the metal salt to the organic ligand is 1:

1.

6. The method for electrochemically preparing a metal-organic framework thin film according to claim 1, wherein, In S3, the electrochemical deposition adopts a two-electrode system, and the current density is controlled to be 0.5-2 A / cm 2 .

7. A method for electrochemically preparing a metal-organic framework thin film according to claim 1, characterized in that, In S3, when generating the ZIF-8 thin film, the deposition voltage is 8V and the deposition time is 60 minutes; The deposition voltage for generating the ZIF-67 thin film is 8V and the deposition time is 120 minutes.

8. A metal-organic framework thin film prepared by the method according to any one of claims 1 to 7, characterized in that, In S3, the thickness of the thin film is 0.5 - 5μm and it has a uniform microporous structure.

9. The metal-organic framework thin film according to claim 8, wherein The metal-organic framework thin film exhibits stable electrochemically grown characteristics within a voltage range of 4 - 8V.

10. Use of the metal-organic framework thin film as described in claim 8, characterized in that, It is used for gas separation membranes, electrochemical sensors, or catalytic electrodes.

Images