A method for preparing a copper-based MOF molding material

Abstract

This invention discloses a method for preparing copper-based MOF molding materials, belonging to the field of functional material preparation. The method uses copper powder as the metal source, dispersing it thoroughly in methanol. Then, under stirring, the organic ligand BTC and the nitrogen-containing ligand 2-methylimidazole (2-MI) are added sequentially. After thorough stirring at room temperature, functionalized Cu-BTC is obtained. The methanol is then completely removed by centrifugation, and the undried Cu-BTC is transferred to a polytetrafluoroethylene (PTFE) reactor, where DMA is added. The mixture is then dried in an oven at 80 °C to obtain the Cu-BTC molding material. This invention is the first to synthesize copper-based MOF molding materials using elemental copper as a raw material. The synthesized MOF molding material has a large specific surface area, and the preparation method is simple, low-cost, and highly repeatable, making it suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of functional material preparation, specifically to a method for preparing a copper-based MOF molding material by directly preparing Cu-BTC using copper powder and organic ligand BTC and nitrogen-containing ligand 2-methylimidazole. Background Technology

[0002] Metal-organic frameworks (MOFs) are porous materials with periodic network structures formed through the self-assembly of inorganic metal ions or clusters and organic ligands. Extensively studied in the 21st century, MOFs are considered among the most effective catalysts due to their structural diversity, high porosity, and abundant unsaturated metal active sites. Numerous studies have utilized MOFs as mediators to achieve desired outcomes. As a promising and unique material, MOFs can be applied in various fields, including gas storage, drug delivery, photoelectrocatalysis, and pollutant degradation.

[0003] In addition to the inherent advantages of MOFs, such as extremely high specific surface area, adjustable structure and pore structure, and high porosity, MOF molded materials also possess superior mass transfer performance, ease of large-scale production, functional integration, reduced powdering issues, and improved recyclability. Through specific processing techniques, MOF molded materials not only retain the inherent high specific surface area, adjustable pore structure, and chemical diversity of MOFs, but also enhance their operability and stability in practical applications, thereby broadening the application range of MOF materials.

[0004] Cu-BTC is the most commonly used Cu-based MOF in the field of catalysis, possessing advantages such as large specific surface area, good thermal stability, and the ability to be synthesized on a large scale at room temperature. It is also one of the few MOFs that has achieved industrial-scale sales and production. However, traditional Cu-BTC synthesis mainly uses copper salts as raw materials via a hydrothermal method, which involves a long reaction cycle, high costs, high-temperature conditions, and demanding equipment. Directly using copper powder as the metal source not only eliminates the complex process conditions required for copper salt preparation but also reduces costs. It allows for the one-step synthesis of Cu-BTC materials under mild conditions and further construction of Cu-BTC MOF molding materials, possessing significant industrial value. Summary of the Invention

[0005] The purpose of this invention is to synthesize Cu-BTC MOFs molding materials from elemental copper and to provide a rapid and simple synthesis method. The aim is to replace copper salts with elemental copper, rapidly compounding Cu-BTC with the organic ligand BTC and the nitrogen-containing ligand 2-methylimidazole at room temperature, and then finally obtaining Cu-BTC MOFs molding materials under hydrothermal conditions. The method provided by this invention is simple and environmentally friendly, and can easily synthesize a functionalized Cu-BTC MOFs molding material.

[0006] To achieve the above objectives, the present invention provides the following solution: This invention provides a method for directly synthesizing functionalized Cu-BTC MOFs molding materials from elemental copper, comprising the following steps: The specific process is as follows: 1) Copper powder was dispersed in methanol, and organic ligand pyromellitic acid (BTC) and nitrogen-containing ligand 2-MI were added under stirring. The reaction was carried out completely at room temperature, and a blue precipitate was obtained by centrifugation and filtration. 2) Transfer the precipitate to the reactor and compact it until it fills the entire space below the surface of the reactor to fix the final molding state. Add N,N-dimethylacetamide and react in an oven at 80-120 ℃ to finally obtain the functionalized Cu-BTC MOFs molding material.

[0007] The preferred method involves dispersing copper powder in methanol, then sequentially adding the organic ligand BTC and the nitrogen-containing ligand 2-MI under continuous stirring. The mixture is stirred at room temperature for a certain period of time to ensure complete reaction. After standing, the mixture is centrifuged, and as much methanol as possible is poured out. The reaction product is then transferred to a polytetrafluoroethylene reactor, N,N-dimethylacetamide is added, and the mixture is dried in an oven at 80°C to obtain the functionalized Cu-BTC MOFs molding material.

[0008] In step 1): The copper powder has a particle size range of 1-100 μm, preferably 1-50 μm, and more preferably 1-30 μm; The mass ratio of copper powder, BTC, and 2-MI in the raw materials is 1:(1-10):(1-10), preferably 1:(1-5):(1-3), and more preferably 1:4:2; Based on 0.2 g of copper powder, the volume of methanol solvent used is 100-500 mL, preferably 100-300 mL, and more preferably 100-200 mL; The reaction time is 5-20 h, preferably 5-10 h, and more preferably 6-8 h.

[0009] In step 2): Based on 0.2 g of copper powder, the volume of N,N-dimethylacetamide (DMA) used is 100-150 μL; the reaction time is 2000-5000 min, preferably 3000-5000 min, more preferably 3000-4000 min; and the temperature range is 80-120 ℃, preferably 80-100 ℃, more preferably 80-90 ℃.

[0010] The Cu-BTC MOF molding material obtained by the method is a block molding material.

[0011] Furthermore, the mass ratio of copper powder, BTC, and 2-methylimidazole is 1:4:2, the solvent volume is 100 mL, the N,N-dimethylacetamide volume is 20 μL, and the reaction time is 7 h.

[0012] Furthermore, in the gram-scale reaction, the mass ratio of copper powder, BTC, and 2-MI is 1:4:2, the solvent volume is 500 mL, the volume of N,N-dimethylacetamide is 100-200 μL, and the reaction time is 7 h.

[0013] As a preferred embodiment of the present invention, Cu-BTC MOFs molding materials were successfully synthesized according to the above steps, and the resulting material had a specific surface area as high as 1915 m². 2 g -1 The yield is significantly higher than that of Cu-BTC materials synthesized by the traditional hydrothermal method (1092 m). 2 g -1 ).

[0014] The present invention also provides an application of the above-mentioned Cu-BTC MOFs molding material in gas separation.

[0015] As a preferred embodiment of the present invention, the operating method is as follows: The pre-activated sample is tightly packed into a stainless steel adsorption column (inner diameter 0.40 cm, column length 20 cm); the adsorption column is then activated under vacuum and a specified temperature, followed by helium purging to remove impurities until the detector shows no impurity signal, after which the analyte gas mixture is introduced. The breakthrough point is determined using a gas chromatograph. During the cycle test interval, the sample can be regenerated under a high vacuum of 393 K for 30 min. The feed gas pressure is controlled at 1 bar. The C2H6 / C2H4 and C3H8 / C3H6 mixed gases used in the experiment are provided by premixed standard gas cylinders.

[0016] The present invention discloses the following technical effects: This invention utilizes copper powder as the metal source and obtains functionalized Cu-BTC MOFs molding materials through the regulation of trimesic acid (BTC) and the nitrogen-containing ligand 2-methylimidazole (2-MI). In this invention, copper powder, BTC, and the nitrogen-containing ligand 2-MI are thoroughly stirred at room temperature. After centrifugation and filtration, the resulting precipitate is added to N,N-dimethylacetamide and dried at high temperature in a polytetrafluoroethylene autoclave to finally obtain the functionalized Cu-BTC MOFs molding material.

[0017] The preparation method provided by this invention has the potential for large-scale industrial production. It can scale up copper powder to the gram level and completely convert copper powder to obtain functionalized Cu-BTC MOFs molding materials.

[0018] This invention uses copper powder as the metal source. Since BTC alone is difficult to combine with copper powder at room temperature, 2-MI is selected as the second ligand. Through effective competitive coordination and deprotonation, the nucleation and growth of MOF crystals are balanced with the carboxyl groups in BTC. The Cu-BTC MOFs molded material prepared by this invention has an extremely high specific surface area. By selecting and adjusting the 2-methylimidazole ligand, its physicochemical properties are optimized. The preparation cost is low, and it has commercial potential. This method is simple to operate, time-saving, low-cost, and the reaction conditions are green and mild, enabling the stable production of Cu-BTC crystals, making it suitable for industrial production.

[0019] The Cu-BTC MOFs molded material obtained by this invention exhibits excellent separation performance of C2 and C3 hydrocarbons. It provides a versatile and easily scalable technical route for the direct preparation of molded adsorbents, therefore the Cu-BTC MOFs molded material of this invention can be used in multiple fields such as gas adsorption, pollutant degradation, and gas storage. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 (a) Molding images, SEM images and XRD patterns of Cu-BTC MOFs materials synthesized with copper nitrate as the metal source and organic ligand BTC.

[0022] Figure 2 (a) Images, SEM images and XRD patterns of the molded material of Cu-BTC MOFs synthesized with copper powder as the metal source and organic ligand BTC and nitrogen-containing ligand IMI.

[0023] Figure 3 Images, SEM images, and XRD patterns of Cu-BTC MOFs synthesized using copper powder as the metal source and organic ligand BTC and nitrogen-containing ligand 2-MI: (a) DMA: 0 μL; (b) DMA: 50 μL; (c) DMA: 100 μL; (d) DMA: 150 μL; (e) DMA: 200 μL; (f) DMA: 500 μL.

[0024] Figure 4 Images of Cu-BTC MOFs molded materials of different shapes synthesized using different containers with DMA addition of 150 μL.

[0025] Figure 5 Figure showing the mechanical strength test results of Cu-BTC molding material under a compression rate of 5 mm / min.

[0026] Figure 6 Gas adsorption isotherms of powdered and molded Cu-BTC MOFs: (a) N2 adsorption-desorption isotherm at 77 K (inset: corresponding pore size distribution); (b) CO2 adsorption isotherm at 195 K; (c, d) single-component adsorption isotherms of powdered and molded monomers for C2 hydrocarbons at 298 K; (e, f) adsorption isotherms for C3 hydrocarbons.

[0027] Figure 7 Breakthrough curves of Cu-BTC MOFs molding materials: (a) C2H4 / C2H6 (0.5 / 0.5, v / v, 1 mLmin) -1 ); (b) C2H4 / C2H6 (0.67 / 0.34, v / v, 1 mL min -1 ); (c) C2H4 / C2H6 (0.8 / 0.2, v / v, 1 mLmin -1 (d) Breakthrough curves of five cycles at 298 K.

[0028] Figure 8 Breakthrough curves of Cu-BTC MOFs molding materials: (a) C3H6 / C3H8 (0.2 / 0.8, v / v, 1 mLmin) -1 ); (b) C3H6 / C3H8 (0.5 / 0.5, v / v, 1 mL min -1 ); (c) C3H6 / C3H8 (0.67 / 0.33, v / v, 1 mLmin -1 (d) Experimental breakthrough curves for five cycles at 298 K.

[0029] Figure 9 Flowchart of Cu-BTC molding material preparation. Detailed Implementation

[0030] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0031] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, regarding numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and every other stated value or intermediate value within said range, is also included within the scope of this invention. The upper and lower limits of the range can be included or excluded independently.

[0032] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. 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.

[0033] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0034] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0035] Comparative Example 1 1. Cu-BTC (Cu 2+ Preparation of molding materials Weigh 5.63 g of Cu(NO3)2·3H2O into a 250 mL beaker, add 100 mL of ethanol, and stir until completely dissolved; this is called solution A. Weigh 4.832 g of trimesic acid (BTC) into a 250 mL beaker, add 100 mL of ethanol, and stir until completely dissolved; this is called solution B. Add solution A to solution B and stir at room temperature for 7 h. Centrifuge and filter, pouring out as much ethanol as possible, and transfer the solid to a 50 mL polytetrafluoroethylene (PTFE) reactor. Manually press the solid until it is level, ensuring it completely fills all spaces below the surface of the reactor. Then add 100 μL of N,N-dimethylacetamide (DMA), seal the reactor completely, and react in an 80 °C oven for 3500 min. After the reaction is complete, if the solid in the reactor is not dry, continue drying in a 60 °C oven to obtain the final product, which is a powder with a very small amount of lumps (e.g., Figure 1(As shown).

[0036] Comparative Example 2 Preparation of Cu-BTC (BTC+IMI) molding material The same experimental procedure was performed in five beakers, specifically as follows: 0.2 g of copper powder (particle size range 1-30 μm) was weighed into a 100 mL beaker, 100 mL of methanol was added, and the mixture was stirred at room temperature to ensure complete dispersion. 0.8 g of trimesic acid (BTC) was weighed and added to the above solution. After the trimesic acid was completely dissolved, 0.4 g of imidazole (IMI) was added, and the mixture was allowed to react completely at room temperature for 7 h.

[0037] Repeat the same steps (process and conditions as above) in 5 beakers. After the reaction is complete, centrifuge and filter the reaction products in the 5 beakers, pouring out as much methanol as possible. Transfer all the solid to a 50 mL polytetrafluoroethylene (PTFE) reactor, manually press it to level, ensuring the solid fills the entire reaction space below the surface. Add 100 μL of N,N-dimethylacetamide (DMA), then seal the reactor tightly and react in an 80 °C oven for 3500 min. If the solid is not dry after the reaction, continue drying in a 60 °C oven to obtain the final dried product. The obtained product is mostly in powder form, with only a small amount of lumps forming (e.g., Figure 2 (As shown).

[0038] Example 1 Preparation of Cu-BTC (BTC+2-MI) molding material The same experimental procedure was performed in five beakers, specifically as follows: 0.2 g of copper powder (particle size range 1-30 μm) was weighed into a 100 mL beaker, 100 mL of methanol was added, and the mixture was stirred at room temperature to ensure complete dispersion. 0.8 g of trimesic acid (BTC) was weighed and added to the above solution. After the trimesic acid was completely dissolved, 0.4 g of 2-methylimidazole (2-MI) was added, and the mixture was allowed to react completely at room temperature for 7 h.

[0039] Repeat the same steps (process and conditions as above) in 5 beakers. After the reaction is complete, centrifuge and filter the reaction products in the 5 beakers, pouring out as much methanol as possible, and transfer all the solid to a 50 mL polytetrafluoroethylene (PTFE) reactor. Manually press the solid until it is level, ensuring it fills the entire space below the surface of the reactor. Add 100 μL of N,N-dimethylacetamide (DMA), then seal the reactor tightly and react in an oven at 80 °C for 3500 min. If the solid is not dry after the reaction is complete, continue drying in an oven at 60 °C to obtain the final dried block product (e.g., ...). Figure 3As shown in c), the pressure obtained from the mechanical strength test of Cu-BTC molding material at a compression rate of 5 mm / min is 0.06 MPa.

[0040] Example 2 like Figure 3 As shown, the conditions were the same as in Example 1, except that the amount of N,N-dimethylacetamide (DMA) added was different. The amount of N,N-dimethylacetamide (DMA) was adjusted within the range of 0-500 μL (e.g., 0 μL, 50 μL, 150 μL, 200 μL, 500 μL, etc.) before synthesizing Cu-BTC molding material. In the final material, Cu-BTC molding material could be successfully synthesized when the amount of DMA added was 100-150 μL. The mechanical strength test of Cu-BTC molding material under a compression rate of 5 mm / min yielded a pressure of 0.06 MPa. The experiment showed that only when 100-150 μL of N,N-dimethylacetamide was added was the product completely blocky. When the amount of N,N-dimethylacetamide added was 0 μL, 50 μL, 200 μL, and 500 μL, powder was generated. Comparative Example 2 also showed some powder generation.

[0041] Application examples The powder and molded Cu-BTC MOFs material obtained in Comparative Example 1 and Example 1 were tested for their application in gas adsorption. The N2 adsorption-desorption isotherms of both materials were tested at 77 K, and the adsorption capacity of the Cu-BTC molded material for N2 was significantly increased (…). Figure 6 (a)), while the adsorption of CO2 at 195 K is significantly reduced ( Figure 6 (b) indicates that the molding material has a large specific surface area and relatively large pore size. It was applied to C2 (…) at 298 K. Figure 6 (cd)) and C3 ( Figure 6 (ef)) Adsorption of hydrocarbon gases revealed that, under the same conditions, both materials showed higher selectivity for olefins than for alkanes, and the Cu-BTC molding material exhibited higher adsorption capacity for both C2 and C3 gases. The Cu-BTC molding material was then used to separate C2H4 / C2H6 gases at different volume ratios. Figure 7 ) and C3H6 / C3H8 ( Figure 8 All three exhibited excellent and stable separation performance. The separation of C3H6 / C3H8 was significantly enhanced, which is consistent with... Figure 5 The results shown are consistent.

[0042] In summary, by comparing the powder and molded Cu-BTC MOF obtained in Comparative Example 1 and Example 1, it can be concluded that the Cu-BTC molding material obtained by the present invention can better achieve efficient separation of olefins / alkanes.

[0043] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a copper-based MOF molding material, characterized in that: The specific process is as follows: 1) Copper powder organic ligand pyromellitic acid (BTC) and nitrogen-containing ligand 2-methylimidazole (2-MI) are mixed and reacted in methanol, and the solid precipitate is collected by solid-liquid separation; 2) The solid precipitate obtained in step 1) is mixed and reacted with N,N-dimethylacetamide (DMA) to finally obtain functionalized Cu-BTC MOFs molding material.

2. The preparation method according to claim 1, characterized in that: In step 1): The copper powder has a particle size range of 1-100 μm, preferably 1-50 μm, and more preferably 1-30 μm; The mass ratio of copper powder, BTC, and 2-MI in the raw materials is 1:(1-10):(1-10), preferably 1:(1-5):(1-3), and more preferably 1:4:2; Based on 0.2 g of copper powder, the volume of methanol solvent used is 100-500 mL, preferably 100-300 mL, and more preferably 100-200 mL; The reaction time is 5-20 h, preferably 5-10 h, and more preferably 6-8 h.

3. The preparation method according to claim 1, characterized in that: In step 2): Based on 0.2 g of copper powder, the volume of N,N-dimethylacetamide (DMA) used is 100-150 μL; the reaction time is 2000-5000 min, preferably 3000-5000 min, more preferably 3000-4000 min; and the temperature range is 80-120 ℃, preferably 80-100 ℃, more preferably 80-90 ℃.

4. A Cu-BTC MOF molding material prepared by any one of claims 1-3.

5. The molding material according to claim 1, characterized in that: The molding material is a block molding material.

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