Method for in-situ preparation of HKUST-1 film based on gas-phase-assisted conversion

Abstract

The invention relates to the field of nano-films, and mainly relates to a method for in-situ preparation of an HKUST-1 film based on gas-phase-assisted conversion. The invention relates to a method for in-situ preparation of an HKUST-1 film based on gas-phase-assisted conversion. The method comprises the following steps: preparing a precursor solution by using copper salt, trimesic acid, a mixed solvent and an acidic regulator or a surfactant; the precursor solution is arranged on a substrate and reacts with a steam source solvent for 4-24 h under the conditions of sealing and 40-80 DEG C; after the reaction is finished, the HKUST-1 thin film is obtained. The invention provides a gas-phase-assisted conversion method which is simple and convenient to operate and high in universality and is used for directly synthesizing a compact and high-crystallinity HKUST-1 film on various substrates.

Description

Technical Field

[0001] This application relates to the field of nanofilms, and mainly to a method for in-situ preparation of HKUST-1 thin films based on gas-phase assisted conversion. Background Technology

[0002] Metal-organic frameworks (MOFs) are a class of materials composed of metal ions (usually transition metal ions, such as Cu). 2+ Zn 2+ Fe 2+ MOFs (Metal-Organic Filaments) are crystalline porous materials formed by the self-assembly of metal ions and organic ligands (mostly organic molecules containing carboxyl, amino, pyridyl, or other groups with strong coordination ability) through coordination bonds. Due to their unique assembly method, these materials not only possess the orderliness of a crystal structure but also contain a large number of regular and interconnected pores. This gives them significant characteristics such as high specific surface area, tunable porosity, and structural diversity. High specific surface area refers to the fact that some MOF materials can reach thousands of square meters per gram, far exceeding traditional porous materials such as activated carbon, providing ample active sites for adsorption and catalytic reactions. Tunable porosity allows for precise control of the size, shape, and even surface chemical properties of the pores by changing the type and valence state of metal ions or adjusting the molecular length and functional group structure of organic ligands, thus adapting to target molecules of different sizes and properties. Structural diversity stems from the rich combinations of metal ions and organic ligands, which can form one-dimensional chain structures, two-dimensional layered structures, and even three-dimensional frameworks, greatly expanding their application possibilities in various fields.

[0003] Among numerous MOF materials, HKUST-1 is a highly representative classic variety, also known by its chemical formula Cu3(BTC)2. Here, BTC represents the pyromellitic acid ligand, and this material is composed of Cu... 2+ It is assembled with pyromellitic acid through coordination, and the three carboxyl groups in the pyromellitic acid molecule are respectively bonded to different Cu. 2+ Stable coordination bonds are formed, ultimately constructing a three-dimensional mesh structure with face-centered cubic symmetry. This fixed and uniform pore size characteristic enables the selective separation of different molecules in a mixture based on differences in molecular size, thus possessing the function of molecular sieving. For example, it can be used in the field of gas separation to screen small molecule gases, or in liquid systems to purify organic molecules of specific sizes.

[0004] Currently, methods for preparing HKUST-1 thin films include liquid phase epitaxy, electrochemical deposition, and solvothermal methods. However, these methods suffer from problems such as complex processes, high equipment requirements, and difficulty in large-scale preparation. For example, liquid phase epitaxy requires multiple immersion cycles, making the process cumbersome; electrochemical deposition requires a conductive substrate, limiting its application; and the traditional solvothermal method easily leads to bulk nucleation, making it difficult to form uniform and continuous thin films.

[0005] Vapor-phase assisted conversion (VPC), as an emerging MOF thin film preparation technology, enables in-situ growth of MOF thin films under mild conditions by inducing precursor transformation through solvent vapor. However, reports on the preparation of HKUST-1 thin films using VPC are currently scarce. Therefore, further improvement and development are needed. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this application is to provide a method for in-situ preparation of HKUST-1 thin films based on gas-phase assisted conversion, which aims to provide a simple and universal gas-phase assisted conversion method for directly synthesizing dense, highly crystalline HKUST-1 thin films on various substrates.

[0007] The technical solution of this application is as follows: A method for in-situ preparation of HKUST-1 thin films based on gas-phase assisted conversion includes the following steps: Precursor solutions are prepared using copper salts, pyromellitic acid, mixed solvents, and acid modifiers or surfactants. The precursor solution is placed on the substrate and reacted with the vapor source solvent under sealed conditions at 40-80°C for 4-24 hours. After the reaction was completed, the HKUST-1 film was obtained.

[0008] The method described in this application achieves in-situ growth of HKUST-1 thin films through vapor-assisted conversion. Its core lies in the vapor-induced Cu in the precursor solution. 2+ Nucleation occurs through coordination with trimesic acid. The closed-system, mild reaction conditions of 40-80℃ avoid the high-temperature, high-pressure requirements of traditional solvothermal methods, reducing energy consumption. A reaction time window of 4-24 hours allows for dynamic equilibrium of film growth from the substrate surface to the epitaxial layer by controlling the vapor permeation rate and precursor concentration gradient. The introduction of acidic regulators or surfactants can modulate the solution pH and interfacial tension, inhibiting bulk nucleation while promoting heterogeneous nucleation on the substrate, significantly improving film crystallinity.

[0009] This process is compatible with a variety of substrates (such as silicon wafers, glass, and metal mesh). Its universality stems from the synergistic effect of the gas-liquid phase. The vapor not only provides the water molecules or organic solvents required for coordination, but also promotes the uniform spreading of the precursor on the substrate surface through the condensation-evaporation cycle, ultimately forming a continuous thin film without macroscopic defects. This solves the technical bottlenecks of uneven film formation and easy cracking in traditional methods.

[0010] Furthermore, the vapor source solvent is located below the substrate, and the precursor solution is disposed on the surface of the substrate.

[0011] The design, with the vapor source solvent located beneath the substrate, enables directional vapor transport through gravity and capillary action. This spatial arrangement allows vapor molecules to diffuse upwards from the bottom of the substrate, forming an adverse concentration gradient with the precursor solution on the substrate surface. When the vapor condenses on the substrate surface, localized supersaturation increases, triggering nucleation, while the upwardly diffusing vapor continuously replenishes the solvent molecules and ligands required for the coordination reaction. This bottom-up vapor transport path synergizes with the top-down precursor spreading, avoiding the bulk nucleation problem caused by uniform vapor distribution in traditional methods. Simultaneously, the vapor source beneath the substrate reduces the solution evaporation rate, maintaining a stable precursor concentration and ensuring continuous film growth. This design is particularly suitable for uniform film formation on large-area substrates, solving the thickness unevenness problem caused by multiple immersions in liquid phase epitaxy.

[0012] Furthermore, the preparation of the precursor solution involves dissolving the copper salt and the trimesic acid in the mixed solvent, then adding the acidity regulator or the surfactant, and ultrasonically treating the solution to dissolve it, thereby forming the precursor solution.

[0013] The cavitation effect generated by high-frequency vibration can accelerate the dissolution of copper salt and trimesic acid in a mixed solvent, breaking down local concentration differences and forming a homogeneous precursor solution. This homogeneity directly affects the subsequent film formation quality—if undissolved particles exist in the precursor solution, they are prone to becoming nucleation centers during the reaction, leading to macroscopic defects in the film. Ultrasonic treatment can also promote the dispersion of acid regulators or surfactants, ensuring their uniform distribution in the solution, thereby more effectively controlling the nucleation process. Furthermore, the microjets generated by ultrasound can enhance the wettability of the solution and substrate, promoting the uniform spreading of the precursor on the substrate surface. Synergistically with the vapor-induced effect in gas-phase assisted conversion, this enhances the crystallinity and continuity of the film.

[0014] Furthermore, the acidity regulator includes one or more of acetic acid and salicylic acid; The surfactant includes hexadecyltrimethylammonium bromide; The vapor source solvent is one or more of water and organic solvent B.

[0015] The weakly acidic environment of the acid regulator can promote the deprotonation of the carboxyl group of pyromellitic acid and enhance its affinity for Cu. 2+ The coordination activity of Cu is enhanced, while inhibiting Cu 2+ Hydrolysis side reactions ensure that the coordination reaction proceeds along the standard growth path of HKUST-1 crystals; at this time, the vapor source solvent (such as water) provides the water molecule environment required for coordination, and synergistically maintains the chemical equilibrium of the reaction system, avoiding nucleation disorder caused by local pH fluctuations.

[0016] Surfactants such as CTAB, with their cationic properties, can reduce the interfacial energy of the substrate and form an ordered monolayer on the substrate surface through electrostatic adsorption, guiding the crystal nuclei to grow along specific crystal plane orientations and inhibiting disordered nucleation. At this time, the vapor source solvent (such as methanol) controls the condensation-evaporation cycle of vapor on the substrate surface by adjusting the diffusion rate, thus avoiding bulk nucleation caused by the reduction of interfacial energy.

[0017] The use of acid regulators or surfactants can achieve precise control of nucleation sites. Together with the synergistic effect of the vapor source solvent, they form a three-dimensional control network of "reaction environment - nucleation path - crystal growth". Ultimately, while simplifying the process, it achieves the technical goal of high crystallinity, continuous uniformity and no macroscopic defects in the thin film, breaking through the technical bottleneck of disordered nucleation and chaotic crystal orientation in traditional methods.

[0018] Furthermore, the mixed solvent is a mixture of water and organic solvent A, wherein the volume ratio of water to organic solvent A is 1:(0.5-1.5). n(pyromellitic acid, mol): v(mixed solvent, L) = 1: (5-10); The molar ratio of the copper salt to the pyromellitic acid is 1.5:1 to 3:1.

[0019] Furthermore, according to the molar ratio, n(pyromellitic acid):n(copper salt):n(acid regulator) = 1:(1.5-3):(0.001-0.01). According to the molar ratio, n(pyromellitic acid):n(copper salt):n(surfactant) = 1:(1.5-3):(0.01-0.05).

[0020] Furthermore, the organic solvent A includes one or a mixture of two or more of ethanol, N,N-dimethylformamide or n-propanol; The copper salt is copper acetate, copper nitrate, or copper sulfate.

[0021] Furthermore, the substrate may include metal, metal oxide, glass, or polymer.

[0022] This application also provides an HKUST-1 film.

[0023] Furthermore, the thickness of the HKUST-1 film is 250-350 nm.

[0024] Compared with the prior art, this application has the following beneficial effects: 1. High versatility: By adjusting the synthesis parameters, HKUST-1 thin films with good crystallinity can be successfully grown on a variety of substrates.

[0025] 2. Good crystallinity: The obtained film has high crystallinity, uniform and continuous surface, and no macroscopic defects.

[0026] 3. Energy saving and environmental protection: The gas-phase assisted conversion process is carried out in a closed system, with less solvent consumption and low energy consumption. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the gas-phase assisted conversion device of this application.

[0028] Figure 2 This is an optical microscope image of the HKUST-1 thin film obtained in Example 1.

[0029] Figure 3 The image shows the XRD pattern of the HKUST-1 thin film obtained in Example 1.

[0030] Figure 4 This is an optical microscope image of the HKUST-1 thin film obtained in Comparative Example 1.

[0031] Figure 5 The image shows the XRD pattern of the HKUST-1 thin film obtained in Comparative Example 1.

[0032] Figure 6 Optical microscope images of the HKUST-1 thin films obtained in Example 3 and Comparative Example 2; Figure 6 In the image above, the image is an optical microscope image of the HKUST-1 thin film obtained in Example 3, and the image below, the image is an optical microscope image of the HKUST-1 thin film obtained in Comparative Example 2. Detailed Implementation

[0033] This application provides a method for in-situ preparation of HKUST-1 thin films based on gas-phase assisted conversion. To make the objectives, technical solutions, and effects of this application clearer and more explicit, the following provides a more detailed description. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0034] This application provides a method for in-situ preparation of HKUST-1 thin films based on gas-phase assisted conversion, comprising the following steps: Step 1: Substrate preparation: Provide a clean substrate, including but not limited to metals, metal oxides, glass, or polymers. Gold or quartz substrates are preferred.

[0035] Step 2: Preparation of precursor solution: Copper salt and pyromellitic acid are dissolved in a mixed solvent at a molar ratio of 1.5:1 to 3:1. Then, an acid regulator (such as acetic acid or salicylic acid) or surfactant is added, and the mixture is sonicated to dissolve it, forming a precursor solution.

[0036] The mixed solvent is a mixture of water and organic solvent A, with a volume ratio of water to organic solvent A of 1:(0.5-1.5).

[0037] Organic solvent A is ethanol, N,N-dimethylformamide, or n-propanol.

[0038] The copper salts are copper acetate, copper nitrate, or copper sulfate.

[0039] Acid regulators and surfactants are used to inhibit homogeneous nucleation and promote heterogeneous nucleation.

[0040] n(pyromellitic acid, mol): v(mixed solvent, L) = 1: (5-10).

[0041] The surfactant is preferably hexadecyltrimethylammonium bromide (CTAB).

[0042] The molar ratios are: n(triphenyl benzoic acid):n(copper salt):n(acid regulator) = 1:2:0.006; n(triphenyl benzoic acid):n(copper salt):n(surfactant) = 1:2:0.02.

[0043] Step 3: Gas-phase assisted conversion reaction: Place the vapor source solvent at the bottom of the reaction vessel.

[0044] The vapor source solvent is water, organic solvent B, or a mixture thereof. The volume ratio of water to organic solvent B is 1:(0.5-1.5).

[0045] Organic solvent B is ethanol, N,N-dimethylformamide, or n-propanol.

[0046] The substrate is placed inside the reaction vessel, above the solvent.

[0047] The precursor solution is dropped onto the matrix surface, the reaction vessel is sealed, and the reaction is carried out at 40-80℃ for 4-24 hours.

[0048] Step 4: Post-processing: After the reaction was completed, the substrate was cooled, removed and cleaned, and then air-dried to obtain the HKUST-1 film.

[0049] In this application, a blue, continuous and highly crystalline HKUST-1 film is also provided.

[0050] The thickness of the HKUST-1 film is 250-350 nm.

[0051] Schematic diagram of gas-phase assisted conversion device (see reference) Figure 1 .

[0052] The present application will be further described below through specific embodiments.

[0053] Example 1 1. Substrate preparation: Cut the gold-plated glass slide into 1.2cm × 1.0cm pieces, and ultrasonically clean it sequentially with acetone, isopropanol, deionized water, and isopropanol for 10 minutes each, then dry it with nitrogen. The gold substrate is then obtained.

[0054] 2. Preparation of precursor solution: Weigh 0.5 mmol (105 mg) of trimesic acid and 1.0 mmol (181 mg) of copper acetate into a small vial, add 4 mL of a mixed solvent of water and n-propanol (1:1 v / v), and add 30 μL of 0.1 mol / L acetic acid. Sonicate to dissolve, then filter. The precursor solution is obtained.

[0055] 3. Gas-phase assisted conversion reaction: A glass Raschig ring was placed at the bottom of a 70×35mm glass weighing bottle as a lifting platform. Water and n-propanol were mixed at a 1:1 v / v ratio to obtain a vapor source solvent, and 5 mL of the vapor source solvent was added to the glass weighing bottle. The gold substrate was placed on the lifting platform, and 100 μL of the precursor solution was dropped onto the surface of the gold substrate. The weighing bottle was sealed with sealing film and placed in a 60℃ oven for 12 hours.

[0056] 4. Post-treatment: After the reaction was completed, the substrate was cooled, removed, rinsed with anhydrous acetone, and air-dried. A blue, continuous, and highly crystalline HKUST-1 film with a thickness of approximately 300 nm was obtained.

[0057] Optical microscope image of HKUST-1 thin film (see reference) Figure 2 XRD pattern reference Figure 3 .

[0058] like Figure 2 and Figure 3 As shown, a continuous, defect-free, and highly crystalline HKUST-1 thin film was prepared by a gas-phase assisted conversion method. This method is a one-step, in-situ synthesis technique with mild conditions, simple equipment requirements, and no need for complex interface engineering or multi-step cyclic operations.

[0059] Example 2 1. Substrate preparation: Cut quartz sheets into 1.5cm × 1.5cm pieces, and ultrasonically clean them sequentially with 2 vol% Hellmanex III aqueous solution for 10 min, deionized water for 10 min, and ethanol for 5 min, then dry them with nitrogen. The resulting quartz substrate is obtained.

[0060] Subsequent steps, such as precursor solution preparation, gas-phase assisted conversion reaction, and post-treatment, were carried out according to the method in Example 1, and will not be described in detail here.

[0061] Example 3 1. Substrate preparation: Cut quartz sheets into 1.5cm × 1.5cm pieces, and ultrasonically clean them sequentially with 2 vol% Hellmanex III aqueous solution for 10 min, deionized water for 10 min, and ethanol for 5 min, then dry them with nitrogen. The resulting quartz substrate is obtained.

[0062] 2. Preparation of precursor solution: Weigh 0.5 mmol (105 mg) of trimesic acid and 1.0 mmol (181 mg) of copper acetate into a small vial, add 4 mL of a mixed solvent of water and n-propanol (1:1 v / v), and add 50 μL of 0.2 mol / L hexadecyltrimethylammonium bromide (CTAB) aqueous solution. Sonicate to dissolve, then filter. The precursor solution is obtained.

[0063] The gas-phase assisted conversion reaction and post-processing steps were carried out according to the method in Example 1.

[0064] Comparative Example 1 The same reactant ratio and solvent were used, but instead of gas-phase assisted conversion, a conventional solvothermal reaction was carried out at the same temperature.

[0065] That is, the substrate preparation and precursor solution preparation were carried out as described in Example 1. Then, 100 μL of the precursor solution was added dropwise to the substrate, the weighing bottle was sealed with sealing film, and the mixture was placed in a 60°C oven for 12 hours.

[0066] Then, post-processing is performed as described in Example 1.

[0067] The resulting product is a discontinuous HKUST-1 deposit with uneven grain size, which cannot form a uniform film.

[0068] Optical microscope image of the obtained product (see reference) Figure 4 XRD pattern reference Figure 5 .

[0069] like Figure 4 and Figure 5As shown, the HKUST-1 films prepared by the traditional solvothermal method are non-uniform, making it difficult to form continuous, dense, and defect-free films. Moreover, the crystallinity is worse than that of films prepared by the gas-phase assisted conversion method. At the same time, the reaction requires a large amount of solvent and precursor, resulting in low raw material utilization, high cost, and the generation of a lot of waste liquid.

[0070] Comparative Example 2 HKUST-1 thin films were synthesized according to the preparation method of Example 3 without the addition of CTAB.

[0071] An optical microscope image of the HKUST-1 thin film obtained in Example 3 is shown below. Figure 6 The optical microscope image of the HKUST-1 thin film obtained in Comparative Example 2, shown above, is as follows. Figure 6 As shown below.

[0072] like Figure 6 As shown, when CTAB is added (Example 3), the HKUST-1 film prepared has a uniform and continuous morphology; while when CTAB is not added (Comparative Example 2), the HKUST-1 film prepared has an uneven and discontinuous morphology.

[0073] This is mainly because CTAB can lower the interfacial energy barrier, create high-concentration microregions, and achieve selective heterogeneous nucleation, thereby preparing continuous and uniform MOF films.

[0074] It should be understood that the application of this application is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of this application.

Claims

1. A method for in-situ preparation of HKUST-1 thin film based on vapor phase assisted conversion, characterized in that, The method comprises the following steps: a precursor solution is prepared by using a copper salt, trimesic acid, a mixed solvent, an acid regulator or a surfactant; the precursor solution is arranged on a substrate, and a vapor source solvent is used to react with the precursor solution under a condition of sealing and 40-80 ℃ for 4-24 h; after the reaction, the HKUST-1 film is obtained.

2. The method for the gas phase-assisted conversion in-situ preparation of HKUST-1 thin film according to claim 1, characterized in that, The vapor source solvent is located below the substrate, and the precursor solution is arranged on the surface of the substrate.

3. The method for the gas phase assisted conversion in situ preparation of HKUST-1 thin film according to claim 1, characterized in that, The precursor solution is prepared by dissolving the copper salt and the trimesic acid in the mixed solvent, then adding the acid regulator or the surfactant, and ultrasonic treatment to make the acid regulator or the surfactant dissolve to form the precursor solution.

4. The method for the gas phase-assisted conversion in-situ preparation of HKUST-1 thin film according to claim 1, characterized in that, The acid regulator comprises one or more than two of acetic acid and salicylic acid; The surfactant comprises cetyltrimethylammonium bromide; The vapor source solvent is one or more than two of water and an organic solvent B.

5. The method for the gas phase-assisted conversion in situ preparation of HKUST-1 thin film according to claim 1, characterized in that, The mixed solvent is a mixture of water and an organic solvent A, and the volume ratio of the water to the organic solvent A is 1:(0.5-1.5); n(trimesic acid, mol):v(mixed solvent, L)=1:(5-10); The molar ratio of the copper salt to the trimesic acid is 1.5:1 to 3:

1.

6. The method for the gas phase-assisted conversion in situ preparation of HKUST-1 thin film according to claim 1, characterized in that, According to the molar ratio, n(trimesic acid):n(copper salt):n(acid regulator)=1:(1.5-3):(0.001-0.01); According to the molar ratio, n(trimesic acid):n(copper salt):n(surfactant)=1:(1.5-3):(0.01-0.05).

7. The method for in-situ preparation of HKUST-1 thin film based on vapor phase assisted conversion according to claim 5, characterized in that, The organic solvent A comprises one or more than two of ethanol, N,N-dimethylformamide and n-propanol; The copper salt is copper acetate, copper nitrate or copper sulfate.

8. The method for in-situ preparation of HKUST-1 thin film based on vapor phase assisted conversion according to claim 1, characterized in that, The substrate comprises metal, metal oxide, glass or polymer. 9.A HKUST-1 film prepared based on the method for preparing a HKUST-1 film in situ by vapor phase assisted conversion according to any one of claims 1-8.

10. The HKUST-1 film of claim 9, wherein, The thickness of the HKUST-1 film is 250-350 nm.

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