Photo-thermal driven MOF (Metal Organic Framework) synthesis method and device

Abstract

The invention relates to a photo-thermal driven MOF (Metal Organic Framework) synthesis method and device, and the method comprises the following steps: pretreating a metal raw material and an organic ligand to form a mixed solution, and improving the reaction activity by utilizing a photo-thermal effect under the irradiation of 365 nm ultraviolet light, so that a solution system is rapidly heated in a local area and forms a high-energy reaction microenvironment; therefore, the reaction temperature and time required by traditional solvothermal synthesis are obviously reduced; according to the present invention, the synthesis of the MOF materials such as ZIF-8, Cu-BTC and the like is rapidly completed under the mild condition by using the green solvent such as water or ethanol as the medium, the method has characteristics of green environmental protection, low energy consumption and simple operation, and the obtained MOF material has characteristics of excellent specific surface area, high yield, complete crystal, rapid preparation and scale amplification potential; meanwhile, water is used as a reaction medium in the whole preparation process, organic polluting solvents such as N, N-dimethylformamide and acetonitrile are not used, efficient and green synthesis is achieved, and the method has the remarkable technical effects of being environmentally friendly, high in energy efficiency, high in yield and the like.

Description

Technical Field

[0001] This invention relates to the field of adsorption materials, and more specifically to a photothermal-driven method and apparatus for synthesizing MOFs. Background Technology

[0002] Metal-organic frameworks (MOFs) are a class of porous crystalline materials composed of metal ions / clusters and organic ligands. They possess characteristics such as high porosity, large specific surface area, and tunable structure, showing great application potential in adsorption separation, catalysis, and sensing. However, the progress towards industrial-scale manufacturing of MOFs remains slow. Core bottlenecks include high preparation costs, long reaction times in traditional methods, and a lack of green preparation processes. The synthesis of many MOFs generally suffers from problems such as high solvent consumption, low yield, and slow crystallization rate. In particular, organic solvents such as N,N-dimethylformamide and acetonitrile are often used, resulting in high costs and environmental pollution.

[0003] MOF materials have a wide range of applications due to their high specific surface area, excellent chemical stability, and regular microporous structure. They excel in gas adsorption and separation, catalysis, and drug delivery, and have also attracted much attention due to their low-cost raw materials and relatively mild preparation conditions. Traditional MOF preparation methods often employ room-temperature solvothermal or heating-solvothermal methods, which involve mixing metal salts and ligands in methanol, ethanol, or DMF, and completing the reaction through prolonged static incubation or heating. These methods still have significant drawbacks: firstly, the reaction time is long, ranging from tens of minutes to several hours; secondly, some methods are highly dependent on solvents, generating large amounts of organic waste liquid; and thirdly, the synthesis yield is relatively low. More importantly, traditional solvothermal methods consume a lot of energy during heating and holding processes, limiting the economic viability of large-scale preparation.

[0004] For example, in the prior art, CN118530471A discloses a method for preparing ZIF-8, in which zinc salt is dissolved in a solvent and 2-methylimidazole is dissolved in a solvent; the two are mixed and placed in a reaction vessel; the reaction vessel is placed in a microwave synthesis extractor, and after gradient heating, the reaction is carried out. After washing and drying, ZIF-8 is obtained. Compared with the traditional hydrothermal method, the ZIF-8 prepared by microwave synthesis has a higher yield, a higher BET specific surface area, and better dispersibility. Although microwave synthesis improves the reaction yield, the method still uses the solvent N,N-dimethylformamide, and organic waste liquid cannot be avoided.

[0005] In view of the above problems, this invention is proposed. Summary of the Invention

[0006] This invention overcomes the shortcomings of existing technologies and provides a photothermal-driven method and apparatus for synthesizing ZIF-8.

[0007] Specifically, it includes:

[0008] A photothermal driven MOF device specifically includes a protection unit and a reaction unit;

[0009] The protection unit includes a heat sink and a light shield, and the reaction unit includes an ultraviolet lamp and a reaction flask;

[0010] A photothermal-driven method for synthesizing MOFs, wherein the method employs a photothermal-driven MOF device for synthesis;

[0011] The specific preparation steps are as follows:

[0012] Step 1: Premix the metal salt and corresponding organic ligand of the synthesized MOF with the solvent, add a regulator during mixing, and mix thoroughly to prepare a mixed solution;

[0013] Step 2: Place the mixed solution in the photothermal synthesis apparatus;

[0014] Step 3: Turn on the photothermal synthesis equipment, irradiate for a certain period of time, then remove the reaction solution and cool it to room temperature;

[0015] Step 4: Filter, wash, and dry the reactants to obtain the MOF product.

[0016] Furthermore, the MOF is ZIF-8 or Cu-BTC; the metal nitrate is copper nitrate or zinc nitrate;

[0017] Furthermore, the organic ligand is 2-methylimidazolium or 1,3,5-benzenetricarboxylic acid;

[0018] Furthermore, when the MOF is ZIF-8, the solvent is water; when the MOF is Cu-BTC, the solvent is ethanol.

[0019] Furthermore, in step A, the mass ratio of the metal nitrate and organic ligand to the solvent in the raw material is 1:9-12.

[0020] Furthermore, the regulator is ammonia.

[0021] Furthermore, the photothermal effect uses a 365 nm ultraviolet light source; the irradiation time in step C is 5-35 min.

[0022] Technical Principles

[0023] High-performance MOF materials (such as ZIF-8 and Cu-BTC) are prepared using green solvents water and ethanol. By introducing a 365 nm ultraviolet light source into the reaction system, a photothermal effect is achieved to rapidly heat and activate the reactants, significantly shortening the crystallization process and thus significantly accelerating crystal nucleation and growth, improving energy efficiency, and reducing solvent consumption. The photothermal effect can increase the local reaction temperature and species diffusion rate in a very short time, resulting in more uniform nucleation and higher crystal quality in MOFs. While ensuring high crystallinity and specific surface area of ​​the product, the reaction time required under traditional heating conditions is significantly shortened, achieving rapid, efficient, and low-energy-consumption preparation of MOF materials.

[0024] Technical effect

[0025] This invention provides a photothermal-driven method for the synthesis of MOFs, which offers significant advantages such as being environmentally friendly, energy-efficient, and yield-efficient. This method utilizes the photothermal effect generated by 365 nm ultraviolet light to promote the rapid reaction between metal ions and ligands, causing the solution system to rapidly heat up in a localized region and form a high-energy reaction microenvironment. This significantly reduces the reaction temperature and time required for traditional solvothermal synthesis. The entire preparation process uses water as the reaction medium, avoiding the use of organic polluting solvents such as N,N-dimethylformamide and acetonitrile, thus achieving highly efficient and green synthesis.

[0026] Photothermal synthesis allows for rapid and uniform heating of the reaction system, making the nucleation and growth process of MOFs more controllable and enabling the production of high-quality MOF materials with consistent crystal structure, uniform particle size, and stable structure. The power and irradiation range of the light source can be independently adjusted, facilitating precise regulation of the crystal growth process and thereby increasing the specific surface area and crystallinity of the final material. Photothermal synthesis offers advantages such as ease of operation, high energy efficiency, short reaction time, and rapid crystallization, demonstrating great potential for the rapid preparation of MOF materials in the laboratory.

[0027] The photothermal synthesis method described in this invention is simple to operate and has an extremely short reaction time, typically requiring only a few minutes to complete the crystallization process of ZIF-8. Under optimized illumination conditions, the yield of a single batch reaction can reach over 75%. The resulting MOFs all exhibit excellent specific surface areas. Developing a suitable photothermal reaction device for laboratory use and its corresponding rapid and green preparation process is of great significance for promoting the large-scale application of MOF materials from the laboratory. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the photothermal-driven MOF synthesis apparatus of the present invention;

[0029] Note: UV lamp (1) Heat sink (2) Shielding plate (3) Reaction flask (4)

[0030] Figure 2The images show the PXRD patterns of the ZIF-8 material synthesized by photothermal drive and the ZIF-8 material synthesized by solvothermal drive according to embodiments of the present invention.

[0031] Figure 3 The images show the PXRD patterns of Cu-BTC materials synthesized by photothermal drive and Cu-BTC materials synthesized by solvothermal drive according to embodiments of the present invention.

[0032] Figure 4 The N2 adsorption isotherms (77 K) of the ZIF-8 material synthesized by photothermal drive and the ZIF-8 material synthesized by solvothermal drive are shown in the embodiments of the present invention.

[0033] Figure 5 The N2 adsorption isotherms (77 K) of Cu-BTC material synthesized by photothermal drive and Cu-BTC material synthesized by solvothermal drive are shown in the embodiments of the present invention. Detailed Implementation

[0034] The present invention will be further described below with reference to specific embodiments.

[0035] like Figure 1 As shown, a photothermal driven MOF synthesis device includes an ultraviolet lamp (1), a heat sink (2) placed above the device, and a light shield (3) around it. A reaction flask (4) is placed inside the device.

[0036] The photothermal-driven MOF synthesis method in this embodiment includes the following steps:

[0037] A. Prepare a solution by pre-mixing the metal raw materials, organic ligands, and solvents;

[0038] B. Place the prepared mixed solution into the reaction flask and place the reaction flask near the ultraviolet lamp so that it is within the ultraviolet lamp irradiation range;

[0039] C. Turn on the photothermal synthesis equipment. After irradiating the reaction flask with ultraviolet light for a certain period of time, remove the reaction solution and cool it to room temperature. Then wash and dry the sample. Throughout the reaction process, the light shield can prevent the influence of sunlight and / or fluorescent light on the reaction flask, and the heat sink can prevent the temperature of the reaction area from overheating, ensuring the safe conduct of the experiment.

[0040] Example 1

[0041] Zinc nitrate hexahydrate and the organic ligand 2-methylimidazolium were mixed with deionized water in a molar ratio of 1:2, with a solid-to-water mass ratio of 1:10 to prepare a solution. A certain amount of ammonia water was added, with the ammonia water concentration being 28% of the water mass. The mixture was then stirred for 3 minutes to ensure homogeneity. The reaction flask was placed inside a photothermal synthesis apparatus and irradiated for 5 minutes. The reaction solution was then removed and cooled to room temperature. The sample was then washed and dried. The synthesized sample is designated as sample C.

[0042] Example 2

[0043] Copper nitrate and the organic ligand 1,3,5-benzenetricarboxylic acid were prepared into a solution with ethanol. The molar ratio of copper nitrate to organic ligand was 2:1, and the mass ratio of solid to water was 1:10. The solution was stirred for 3 min to ensure uniform mixing. The reaction flask was placed inside a photothermal synthesis apparatus and irradiated for 30 min. The reaction solution was then removed and cooled to room temperature. The sample was then washed and dried. The synthesized sample was denoted as sample D.

[0044] Comparative Example 1

[0045] Zinc nitrate and the organic ligand 2-methylimidazole were added to a 20 mL reaction vessel in a molar ratio of 1:2. 15 mL of N,N-dimethylformamide was added, and the reaction was carried out at 140 °C for 24 h. The product was washed twice with water and twice with methanol. The synthesized sample was designated as sample A.

[0046] Comparative Example 2

[0047] Copper nitrate and the organic ligand 1,3,5-benzenetricarboxylic acid were added to a 20 mL reaction vessel in a molar ratio of 2:1, followed by the addition of 15 mL of ethanol. The reaction was carried out at 90 °C for 12 h, and the resulting product was washed twice with ethanol. The synthesized sample was designated as Sample B.

[0048] Performance testing experiment example

[0049] 1. The crystal structures of the samples prepared in comparative cases 1-2 and the samples prepared in implementation cases 1-2 of this invention were characterized using a Bruker D8 Advance X-ray diffractometer.

[0050] 2. The specific surface area of ​​the samples prepared in Comparative Cases 1-2 and the samples prepared in Implementation Cases 1-2 of this invention was measured using a Micromeritics® TriStar II Plus fully automated surface area and porosity analyzer.

[0051] like Figure 2 and Figure 3 As shown, the PXRD diffraction peak intensities of samples A and B are significantly lower than those of samples C and D, indicating that the nucleation and growth rates of crystals are slower under no illumination, resulting in relatively lower crystal integrity and order in the obtained materials. In contrast, samples C and D, prepared under 365 nm ultraviolet light irradiation, exhibit significantly enhanced diffraction peak intensities, demonstrating that the photothermal effect can effectively increase the local energy density of the solution, promote directional coordination and rapid nucleation between metal ions and ligands, thereby achieving rapid crystal growth and structural homogenization.

[0052] like Figure 4 and Figure 5 As shown, the N2 adsorption-desorption isotherm measured at 77 K further verifies the influence of illumination conditions on the pore structure of the material. Samples C and D exhibit significantly higher N2 adsorption capacities, indicating that the photothermal effect can form a more complete, regular, and interconnected pore structure, thereby significantly increasing the specific surface area. In contrast, samples A and B, prepared under non-illuminating conditions, have lower adsorption capacities. This trend is consistent with the PXRD results, further demonstrating that photothermal assistance can effectively improve the microstructure and internal pore structure of crystals.

[0053] The yields and specific surface areas of the synthesized samples also differed significantly. Photothermal synthesis yielded higher yields and significantly improved specific surface areas than hydrothermal synthesis. Both ZIF-8 and Cu-BTC achieved high yields through photothermal synthesis, with substantial improvements in specific surface area performance. The reaction time was also greatly shortened, eliminating the need for other organic solvents and significantly increasing synthesis efficiency.

[0054]

[0055] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A photothermally driven method for synthesizing MOFs, characterized in that, The specific preparation steps of the MOF synthesis method are as follows: Step 1: Premix the metal salt and corresponding organic ligand of the synthesized MOF with the solvent, add a regulator during mixing, and mix thoroughly to prepare a mixed solution; Step 2: Place the mixed solution in the photothermal synthesis apparatus; Step 3: Turn on the photothermal synthesis device, irradiate with ultraviolet light for a certain period of time, and then cool the mixed solution to room temperature; Step 4: Filter, wash, and dry the reactants to obtain the ZIF-8 product. The MOF is ZIF-8 or Cu-BTC; When the MOF is ZIF-8, the organic ligand is 2-methylimidazole and the metal nitrate is zinc nitrate; when the MOF is Cu-BTC, the organic ligand is 1,3,5-benzenetricarboxylic acid and the metal nitrate is copper nitrate.

2. The photothermally driven MOF synthesis method as described in claim 1, characterized in that, When the MOF is ZIF-8, the solvent is water; when the MOF is Cu-BTC, the solvent is ethanol.

3. The photothermally driven MOF synthesis method as described in claim 1, characterized in that, In step 1, the mass ratio of the metal nitrate and organic ligand of the raw material to the solvent is 1:9-12.

4. The photothermally driven MOF synthesis method as described in claim 1, characterized in that, The regulator is ammonia.

5. The photothermally driven MOF synthesis method as described in claim 1, characterized in that, The irradiation time in step 3 is 5-35 minutes.

6. The photothermally driven MOF synthesis method as described in claim 1, characterized in that, The photothermal effect is achieved using a 365 nm ultraviolet light source.

7. The method according to any one of claims 1-6 uses a photothermally driven MOF device for synthesis, characterized in that: Includes protection units and reaction units; The protection unit includes a heat sink and a light shield, and the reaction unit includes an ultraviolet lamp and a reaction bottle; the mixed solution from step 2 is placed in the reaction bottle.

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