Preparation method of MOF microcrystal monodisperse film
MOF microcrystalline monodisperse films were prepared by hydrothermal reaction and ultrasound-assisted self-assembly technology, solving the synthesis problem and realizing efficient and pure film preparation and functional applications.
Patent Information
- Application Number
- CN202511117210.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-11
- Publication Date
- 2025-10-28
AI Technical Summary
Existing technologies struggle to synthesize monodisperse MOF microcrystalline films and lack effective assembly techniques.
MOF nanoparticles were prepared by hydrothermal reaction and then self-assembled at the gas-liquid interface with ultrasound assistance to form a thin film. The ionic environment was adjusted by sodium hydroxide and the surface tension was changed by ethanol to prepare a monodisperse MOF microcrystal film.
This technology enables large-scale production with simple and easily scalable processes, yielding surface-pure MOF microcrystalline monodisperse films suitable for functional applications.
Smart Images
Figure CN120842633A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for preparing MOF thin films, specifically a method for preparing MOF microcrystalline monodisperse thin films, belonging to the field of MOF thin film preparation technology. Background Technology
[0002] Metal-organic frameworks (MOFs) are a new type of crystalline material assembled from metal ions or metal clusters and organic linkers. MOFs possess large-area permanent microporous structures, regular and tunable-sized cavities, and customizable chemical properties, thus showing broad application prospects in gas storage, molecular separation, heterogeneous catalysis, chemical sensing, and drug delivery.
[0003] Over the past few years, scientists have made significant efforts to control the size and shape of MOF crystals, parameters that can significantly influence certain properties of the material (e.g., gas absorption) and are indeed crucial for biological applications. Small-sized MOF crystals can be easily fabricated into films using dip-coating or spin-coating. Furthermore, with the aid of the Langmuir-Blodgett (LB) technique, oriented MOF thin films can also be prepared from regularly shaped MOF crystals. MOF crystals with uniform size and regular shape not only allow for control of the thickness of oriented films but also enable the formation of two-dimensional or three-dimensional ordered structures through bottom-up self-assembly. However, this work is still in its early stages, with only three-dimensional self-assembly of MOF microcrystals currently achieved. The challenges in this emerging field lie in synthesizing monodisperse MOF microcrystal thin films and exploring suitable assembly techniques. Summary of the Invention
[0004] The purpose of this invention is to provide a simple process for obtaining MOF microcrystalline monodisperse thin films with pure surfaces.
[0005] To achieve the above objectives, the present invention adopts the following technical solution:
[0006] A method for preparing MOF microcrystalline monodisperse thin films includes the following steps:
[0007] (1) MOF nanoparticles were prepared by hydrothermal reaction using aminoterephthalic acid as the MOF structural molecule.
[0008] (2) The MOF nanoparticles were ultrasonically dispersed in deionized water, and sodium hydroxide solution was added to adjust the ion environment. The concentration of MOF nanoparticles was 0.25 mg / mL, the concentration of sodium hydroxide solution was 1 M, and the amount added was 1‰ of the MOF nanoparticle solution, so as to obtain MOF nanoparticle dispersion.
[0009] (3) Add ethanol to the MOF nanoparticle dispersion to change the surface tension of the solution. The amount of ethanol added is 30% of the MOF nanoparticle dispersion. Ultrasonic assistance is used to self-assemble MOF nanoparticles at the gas-liquid interface to form a thin film.
[0010] Preferably, in step (1), the MOF nanoparticles include: copper MOF nanoparticles, iron MOF nanoparticles, and zinc MOF nanoparticles; more preferably, the MOF nanoparticles are copper MOF nanoparticles, and the preparation method is as follows: aminoterephthalic acid and copper nitrate trihydrate are dissolved in N,N-dimethylformamide, and the ratio of aminoterephthalic acid, copper nitrate trihydrate, and N,N-dimethylformamide is 34g:49g:1000mL. Then, the mixture is transferred to a high-pressure reactor with a Teflon liner, heated at 150°C for 3h, cooled, washed twice with deionized water, then washed twice with ethanol, and dried to obtain copper MOF nanoparticles.
[0011] Preferably, in step (3), the ultrasonic parameters are: 50Hz, 3min.
[0012] The advantages of this invention are:
[0013] (1) MOF microcrystalline monodisperse films can be obtained with simple ultrasonic assistance. The process is simple, easy to promote, and suitable for large-scale production.
[0014] (2) During the preparation of MOF microcrystalline monodisperse films, since the MOF nanoparticles have not undergone any surface modification, the surface of the prepared MOF microcrystalline monodisperse films is very pure.
[0015] (3) The prepared MOF microcrystalline monodisperse film can be easily transferred to other solid substrates for functional use by methods such as Langmuir-Blodgett (LB) technology and self-supporting film transfer method. Attached Figure Description
[0016] Figure 1 This is a photograph of the thin film prepared in Example 1;
[0017] Figure 2 This is a SEM image of the thin film prepared in Example 1;
[0018] Figure 3 This is a photograph of the thin film prepared in Comparative Example 1;
[0019] Figure 4 The image shows the SEM image of the thin film prepared in Comparative Example 1.
[0020] Figure 5 This is a photograph of the solution prepared in Comparative Example 2;
[0021] Figure 6 This is a SEM image of the solution prepared in Comparative Example 2;
[0022] Figure 7 This is a photograph of the thin film prepared in Comparative Example 3;
[0023] Figure 8 This is a SEM image of the thin film prepared in Comparative Example 3;
[0024] Figure 9 This is a physical image of the thin film prepared in Comparative Example 4;
[0025] Figure 10 This is a SEM image of the thin film prepared in Comparative Example 4;
[0026] Figure 11 This is a photograph of the solution prepared in Comparative Example 5;
[0027] Figure 12 This is a SEM image of the solution prepared in Comparative Example 5;
[0028] Figure 13 This is a photograph of the solution prepared in Comparative Example 6;
[0029] Figure 14 This is a SEM image of the solution prepared in Comparative Example 6;
[0030] Figure 15 This is a photograph of the film prepared in Example 1 transferred onto a piece of paper. Detailed Implementation
[0031] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.
[0032] Example 1
[0033] 1. Preparation of MOF nanoparticles
[0034] MOF nanoparticles, such as copper MOF nanoparticles, iron MOF nanoparticles, and zinc MOF nanoparticles, are prepared by hydrothermal reaction.
[0035] In this specific embodiment, copper MOF nanoparticles were prepared by hydrothermal reaction. The specific preparation method is as follows:
[0036] 0.34 g of aminoterephthalic acid (MOF structural molecule) and 0.49 g of copper nitrate trihydrate were dissolved in 10 mL of N,N-dimethylformamide, and then transferred to a Teflon-lined high-pressure reactor. The mixture was heated at 150 °C for 3 h. After cooling, the mixture was washed twice with deionized water and then twice with ethanol. After drying, copper MOF nanoparticles were obtained.
[0037] 2. Dispersing MOF nanoparticles and adjusting the ionic environment of the solution
[0038] 5 mg of the previously prepared copper MOF nanoparticles were ultrasonically dispersed in 20 mL of deionized water. The concentration of the copper MOF nanoparticles was 0.25 mg / mL. After ultrasonic dispersion, 20 μL of 1 M sodium hydroxide solution (to adjust the ion environment) was added. The amount of sodium hydroxide solution added was 1‰ (v / v) of the copper MOF nanoparticle solution. The mixture was shaken until homogeneous to obtain a copper MOF nanoparticle dispersion.
[0039] 3. Ultrasonic-assisted self-assembly of MOF nanoparticles to form thin films
[0040] Add 6 mL of ethanol (to change the surface tension of the solution) to the 20 mL copper MOF nanoparticle dispersion prepared above. The amount of ethanol added is 30% (v / v) of the copper MOF nanoparticle dispersion. Use ultrasound (50 Hz, 3 min) to assist the copper MOF nanoparticles in self-assembling at the gas-liquid interface to form a thin film.
[0041] The thin film prepared in this way is shown in the figure. Figure 1 .
[0042] Scanning electron microscopy (SEM) revealed that the copper MOF nanoparticles had transformed into monodisperse copper MOF nanowires. Figure 2 ).
[0043] Comparative Example 1
[0044] The preparation method is basically the same as that in Example 1, except that when preparing the copper MOF nanoparticle dispersion, the amount of 1M sodium hydroxide solution added is 10μL, that is, the amount of sodium hydroxide solution added is 0.5‰ (v / v) of the copper MOF nanoparticle solution.
[0045] The thin film prepared in this way is shown in the figure. Figure 3 .
[0046] SEM observation of the film revealed that the copper MOF nanoparticles were aggregated in clusters. Figure 4 ).
[0047] Comparative Example 2
[0048] The preparation method is basically the same as that in Example 1, except that when preparing the copper MOF nanoparticle dispersion, the amount of 1M sodium hydroxide solution added is 2μL, that is, the amount of sodium hydroxide solution added is 0.1‰ (v / v) of the copper MOF nanoparticle solution.
[0049] Therefore, a thin film could not be prepared; only a solution was obtained. Figure 5 ).
[0050] SEM observation of the solution revealed that the copper MOF nanoparticles still existed in their original nanoparticle morphology. Figure 6 ).
[0051] Comparative Example 3
[0052] The preparation method is basically the same as that in Example 1, except that when preparing the copper MOF nanoparticle dispersion, the amount of 1M sodium hydroxide solution added is 30μL, that is, the amount of sodium hydroxide solution added is 1.5‰ (v / v) of the copper MOF nanoparticle solution.
[0053] The thin film prepared in this way is shown in the figure. Figure 7 .
[0054] SEM observation of the film revealed that the copper MOF nanoparticles aggregated into a bulk structure. Figure 8 ).
[0055] Comparative Example 4
[0056] The preparation method is basically the same as that in Example 1, except that when preparing the copper MOF nanoparticle dispersion, the amount of 1M sodium hydroxide solution added is 40μL, that is, the amount of sodium hydroxide solution added is 2‰ (v / v) of the copper MOF nanoparticle solution.
[0057] The thin film prepared in this way is shown in the figure. Figure 9 .
[0058] SEM observation of the film revealed that the copper MOF nanoparticles existed essentially in their original nanoparticle morphology. Figure 10 ).
[0059] Comparative Example 5
[0060] The preparation method is basically the same as that in Example 1, except that terephthalic acid was used as the MOF structural molecule in the preparation of copper MOF nanoparticles, and the amount used was 0.3156g.
[0061] Therefore, a thin film could not be prepared; only a solution was obtained. Figure 11 ).
[0062] SEM observation of the solution revealed that the copper MOF nanoparticles were in an irregular blocky shape. Figure 12 ).
[0063] Comparative Example 6
[0064] The preparation method is basically the same as that in Example 1, except that when preparing copper MOF nanoparticles, the MOF structural molecule used is pyromellitic acid, and the amount used is 0.4g.
[0065] Therefore, a thin film could not be prepared; only a solution was obtained. Figure 13 ).
[0066] SEM observation of the solution revealed that the copper MOF nanoparticles exhibited an octahedral morphology. Figure 14 ).
[0067] The principle of MOF nanoparticles self-assembling to form thin films at the gas-liquid interface: Sodium hydroxide is used to adjust the ionic environment of the MOF nanoparticle dispersion, causing the MOF nanoparticles to be converted into one-dimensional MOF nanowires. At the same time, due to the change in the ionic environment, the amino groups of aminoterephthalic acid (MOF structural molecule) become positively charged and the carboxyl groups become negatively charged. At this time, the one-dimensional MOF nanowires carry both positive and negative charges. The one-dimensional MOF nanowires begin to attract each other. Then, ethanol is added to change the surface tension of the solution, enabling the one-dimensional MOF nanowires to self-assemble at the gas-liquid interface and form a tightly structured thin film.
[0068] The amount of sodium hydroxide added is crucial to whether MOF nanoparticles can successfully self-assemble into a thin film at the gas-liquid interface, as can be seen from Example 1 and Comparative Examples 1 to 4:
[0069] (1) When the amount of sodium hydroxide solution (concentration of 1M) added is 2‰ (v / v) of the copper MOF nanoparticle solution (concentration of 0.25mg / mL), the copper MOF nanoparticles can be converted into monodisperse copper MOF nanowires. The copper MOF nanowires can successfully self-assemble at the gas-liquid interface to form a stable and relatively complete monodisperse film (Example 1).
[0070] (2) When the amount of sodium hydroxide solution added is insufficient (<1‰), because the surface charge of copper MOF nanoparticles is not balanced, copper MOF nanoparticles aggregate into clusters or still exist in the original form of nanoparticles. Therefore, it is impossible to form a stable and relatively complete film at the gas-liquid interface (Comparative Example 1), or even impossible to form a film at the gas-liquid interface (Comparative Example 2).
[0071] (3) When the amount of sodium hydroxide solution added is excessive (>1‰), the ionic environment is destroyed, which leads to the disruption of the surface charge balance of copper nanoparticles. Therefore, the copper MOF nanoparticles exist in the solution in their original form and cannot form a stable film at the gas-liquid interface (Comparative Example 3, Comparative Example 4).
[0072] Furthermore, the choice of MOF structural molecules is also crucial for the successful self-assembly of MOF nanoparticles into thin films at the gas-liquid interface, as can be seen from Comparative Examples 5 and 6:
[0073] The formation of the thin film is related to the simultaneous presence of amino and carboxyl groups. This is because only when amino and carboxyl groups are present can charge balance be achieved by regulating the ionic environment, thereby enabling the effective self-assembly of MOF nanoparticles at the gas-liquid interface and forming a stable thin film.
[0074] After the thin film is prepared, it can be transferred to a solid substrate (e.g., paper, organic film, silicon wafer) for functional use using methods such as Langmuir-Blodgett (LB) technology and self-supporting film transfer method. The transfer method is very easy.
[0075] The thin film prepared in Example 1 was transferred onto a 0.5cm × 0.5cm paper disc using a self-supporting film transfer method, and after standing and drying, the final product was obtained. Figure 15 The product shown.
[0076] It should be noted that the above embodiments are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is impossible to exhaustively list all possible implementations here. All obvious variations or modifications derived from the technical solutions of this invention are still within the scope of protection of this invention.
Claims
1. A method for preparing a MOF microcrystalline monodisperse thin film, characterized in that, Includes the following steps: (1) MOF nanoparticles were prepared by hydrothermal reaction using aminoterephthalic acid as the MOF structural molecule. (2) The MOF nanoparticles were ultrasonically dispersed in deionized water, and sodium hydroxide solution was added to adjust the ion environment. The concentration of MOF nanoparticles was 0.25 mg / mL, the concentration of sodium hydroxide solution was 1 M, and the amount added was 1‰ of the MOF nanoparticle solution, so as to obtain MOF nanoparticle dispersion. (3) Add ethanol to the MOF nanoparticle dispersion to change the surface tension of the solution. The amount of ethanol added is 30% of the MOF nanoparticle dispersion. Ultrasonic assistance is used to self-assemble MOF nanoparticles at the gas-liquid interface to form a thin film.
2. The method for preparing MOF microcrystalline monodisperse thin films according to claim 1, characterized in that, In step (1), the MOF nanoparticles include: copper MOF nanoparticles, iron MOF nanoparticles and zinc MOF nanoparticles.
3. The method for preparing MOF microcrystalline monodisperse thin films according to claim 2, characterized in that, The MOF nanoparticles are copper MOF nanoparticles, and the preparation method is as follows: Aminoterephthalic acid and copper nitrate trihydrate were dissolved in N,N-dimethylformamide and then transferred to a Teflon-lined high-pressure reactor. The mixture was heated at 150°C for 3 hours. After cooling, the mixture was washed twice with deionized water and then twice with ethanol. After drying, copper MOF nanoparticles were obtained.
4. The method for preparing MOF microcrystalline monodisperse thin films according to claim 3, characterized in that, The ratio of aminoterephthalic acid, copper nitrate trihydrate, and N,N-dimethylformamide is 34g:49g:1000mL.
5. The method for preparing MOF microcrystalline monodisperse thin films according to claim 1, characterized in that, In step (3), the ultrasonic parameters are: 50Hz, 3min.