Two-dimensional CuBDC nanosheet and preparation method thereof

Abstract

The application discloses a two-dimensional CuBDC nanosheet material and a preparation method thereof. The two-dimensional CuBDC nanosheet material has a length of 1-8 microns, a thickness of 15-25 nanometers and an aspect ratio of 40-533, preferably 100-300. The preparation method of the two-dimensional CuBDC nanosheet material comprises the following steps: (1) uniformly mixing inorganic copper salt, a complexing agent, N,N-dimethylformamide and acetonitrile to prepare a metal precursor solution; uniformly mixing terephthalic acid, N,N-dimethylformamide and acetonitrile to prepare a ligand solution; (2) mixing the metal precursor solution and the ligand solution, and reacting the obtained mixture under microwave heating; and (3) performing solid-liquid separation, washing and drying on the reacted mixture to obtain the two-dimensional CuBDC nanosheet material. The CuBDC nanosheet prepared by the application has a high aspect ratio, and the aspect ratio of the nanosheet can be flexibly controlled by adjusting the proportion of reaction raw materials and the temperature; the preparation method is simple, the material is cheap and easy to obtain, the cost is low, and the material is easy to be prepared in large quantities.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials, specifically relating to a metal-organic framework material CuBDC nanosheets and its preparation method. Background Technology

[0002] Metal-organic frameworks (MOFs) are organic-inorganic hybrid porous crystalline materials composed of metal ion centers and organic ligands. Two-dimensional (2D) MOF nanosheets are anisotropic MOFs with a two-dimensional layered structure, possessing ultrathin sheet thickness, good solubility and dispersibility, excellent photoelectric properties, and easily functionalizable pore surfaces. Compared with traditional isotropic MOFs, they not only retain their porosity and tunable pore size but also possess the long-range order and anisotropy of crystalline materials, high porosity, large specific surface area, and tunable pore size, making them widely applicable in energy storage, catalysis, sensing, and adsorption separation. 2D-MOFs are a class of novel materials with great potential.

[0003] Copper terephthalate (CuBDC) is a typical 2D MOF with a regular layered structure, and it has been reported in a considerable number of publications.

[0004] CN106252663B discloses a method for preparing CuBDC nanosheets: First, solid copper nitrate and solid terephthalic acid are weighed and mixed with the organic solvents acetonitrile and N,N-dimethylformamide; second, the mixture obtained in step one is heated and stirred in a water bath; third, the solution obtained in step two is dried in an oven to obtain CuBDC nanosheets, a metal-organic framework material. This method directly dissolves Cu salts in the solvent, resulting in rapid initial crystal nucleus formation. However, the morphology of the crystal nuclei is difficult to control, leading to severe agglomeration of the obtained CuBDC nanosheets, poor morphological regularity, large size, and low aspect ratio. Furthermore, this method uses conventional heating methods such as water baths, resulting in a long crystal growth process and low preparation efficiency.

[0005] CN114288879A discloses a method for preparing two-dimensional CuBDC-NH2: First, anhydrous copper acetate is dissolved in a mixed solution A to obtain anhydrous copper acetate solution; second, 2-aminoterephthalic acid is dissolved in a mixed solution B to obtain a 2-aminoterephthalic acid solution; third, the anhydrous copper acetate solution is sprayed into the 2-aminoterephthalic acid solution using an ultrasonic spray device, allowed to stand, and a solid is obtained. The solid is then washed and filtered to obtain a two-dimensional CuBDC-NH2 solid. The ultrasonic spray device used in this invention still involves macroscopic droplet feeding, which has limited control over the metal precursor. The crystal nucleation process and product structure remain difficult to control. The resulting CuBDC nanosheets exhibit severe agglomeration, large sheet thickness, easy stacking, large size, and low aspect ratio. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a two-dimensional CuBDC nanosheet material and its preparation method. The CuBDC nanosheets prepared by this invention have a high aspect ratio, and the aspect ratio of the nanosheets can be flexibly controlled by adjusting the ratio of reaction raw materials and temperature. The preparation method is simple, the materials are inexpensive and readily available, the cost is low, and it is easy to prepare in large quantities.

[0007] The two-dimensional CuBDC nanosheet material of the present invention has a length of 1-8 μm, a thickness of 15-25 nm, an aspect ratio of 40-533, preferably 100-300, and a BET specific surface area of ​​300-750 m². 2 / g; wherein the aspect ratio is the ratio of the length to the thickness of the nanosheet.

[0008] The preparation method of the two-dimensional CuBDC nanosheet material of the present invention includes the following: (1) Mix inorganic copper salt, complexing agent, N,N-dimethylformamide and acetonitrile evenly to prepare metal precursor solution; mix terephthalic acid, N,N-dimethylformamide and acetonitrile evenly to prepare ligand solution; (2) Mix the metal precursor solution with the ligand solution and react the resulting mixture under microwave heating conditions; (3) The mixture after reaction is separated into solid and liquid, washed and dried to obtain two-dimensional CuBDC nanosheet material.

[0009] In the method of the present invention, the inorganic copper salt in step (1) is one or more of copper nitrate, copper chloride, copper sulfate, copper acetate or basic copper carbonate, preferably copper nitrate.

[0010] In the method of the present invention, the complexing agent in step (1) is one or more of ethylenediaminetetraacetic acid, citric acid, humic acid, epigallocatechin gallate or Schiff base.

[0011] In the method of the present invention, the material composition of the metal precursor solution in step (1) by mass is: 1% to 2% inorganic copper salt, 0.7% to 1% complexing agent, 31% to 35% N,N-dimethylformamide, and 62% to 67% acetonitrile.

[0012] In the method of the present invention, the composition of the ligand solution in step (1) by mass is: 1% to 2% terephthalic acid, 55% to 70% N,N-dimethylformamide, and 27% to 35% acetonitrile.

[0013] In the method of the present invention, in step (1), the mass ratio of the metal precursor solution to the ligand solution is 0.8 to 1.2.

[0014] In the method of the present invention, the mixing method described in step (2) can be any method that is conducive to uniform mixing of materials, such as mechanical stirring, magnetic stirring, shaking table or ultrasonic vibration.

[0015] In the method of the present invention, the microwave heating conditions in step (2) are: frequency 2000-5000MHz, power 500-1000W, time 60-90min, and temperature 60-80℃.

[0016] In the method of this invention, the solid-liquid separation in step (3) is performed by centrifugation. The washing conditions are as follows: the washing solvent is N,N-dimethylformamide and methanol, and the purpose of washing is to remove unreacted excess solute and residual solvent.

[0017] In the method of the present invention, the drying conditions in step (3) are: vacuum drying or air atmosphere drying, 60-80℃, 18-24h.

[0018] The two-dimensional CuBDC nanosheet material of the present invention can be applied in the fields of gas storage, adsorption separation, heterogeneous catalysis, electrochemistry and analysis.

[0019] Compared with existing technologies, this invention has the following advantages: This invention reacts inorganic copper salts with a complexing agent to form Cu complexes that participate in the reaction. This allows for the control and retardation of the binding rate between metal ions and ligands, thereby controlling the nucleation process in the initial stage of the reaction. Simultaneously, microwave heating enhances the nucleus growth rate through its internal heating effect, maximizing the control of the crystal's two-dimensional morphology. Furthermore, the uniform temperature of the reaction system facilitates the production of 2D MOF nanosheet nuclei with uniform morphology and controllable length and aspect ratio. Using this invention, ultrathin 2D MOF nanosheets can be obtained, exposing more of the outer surface and resulting in a higher specific surface area. The materials used in this invention are inexpensive and readily available, the method is simple, the cost is low, the reaction time is short, and it is easy to prepare in large quantities. Attached Figure Description

[0020] Figure 1 (a) is a scanning electron microscope image of the length of CuBDC nanosheets prepared in Example 1 of the present invention.

[0021] Figure 1 (b) is a scanning electron microscope image of the thickness of the CuBDC nanosheets prepared in Example 1 of the present invention.

[0022] Figure 2 This is the XRD pattern of the CuBDC nanosheets prepared in Example 1 of this invention. Detailed Implementation

[0023] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the content of the present invention is not limited to the following embodiments. Unless otherwise specified, the reagents used in this embodiment are commonly used or commercially available products in the industry. The dimensions of the present invention are measured using scanning electron microscopy images, and the aspect ratio mentioned in the present invention is the ratio of the length to the thickness of the nanosheet. The BET specific surface area is tested using the low-temperature liquid nitrogen adsorption method.

[0024] Example 1 A metal precursor solution was prepared by adding 1 g of copper nitrate and 0.7 g of ethylenediaminetetraacetic acid complex to a mixed solvent of 20 mL N,N-dimethylformamide and 60 mL acetonitrile. A ligand solution was prepared by adding 1 g of terephthalic acid to a mixed solvent of 60 mL N,N-dimethylformamide and 20 mL acetonitrile. Under stirring, the metal precursor solution was slowly added dropwise to the ligand solution. The resulting mixture was then heated at 60 °C for 60 min using a microwave oven at 2500 MHz and 500 W. The reacted solution was centrifuged to separate the solid and liquid phases, then washed three times with N,N-dimethylformamide and three times with methanol. After vacuum drying at 80 °C for 18 h, the CuBDC nanosheets of this invention were obtained. SEM characterization showed that the nanosheets were uniform in size, with a length of 2-3 μm, a thickness of approximately 20 nm, an aspect ratio of 100-150, and a BET specific surface area of ​​450 m². 2 / g.

[0025] Example 2 A metal precursor solution was prepared by adding 1 g of copper sulfate and 1.6 g of epigallocatechin gallate complex to a mixed solvent of 20 mL N,N-dimethylformamide and 60 mL acetonitrile. A ligand solution was prepared by adding 1 g of H₂BDC to a mixed solvent of 60 mL N,N-dimethylformamide and 20 mL acetonitrile. The metal precursor solution was slowly added dropwise to the ligand solution under stirring. The resulting mixture was heated at 80 °C for 60 min using a microwave oven at 2000 MHz and 500 W. The reacted solution was centrifuged to separate the solid and liquid phases, then washed three times with N,N-dimethylformamide and three times with methanol. After vacuum drying at 80 °C for 24 h, CuBDC nanosheets of the present invention were obtained. SEM characterization showed that the nanosheets were uniform in size, with a length of 3-4 μm, a thickness of approximately 25 nm, an aspect ratio of 120-160, and a BET specific surface area of ​​530 m². 2 / g.

[0026] Example 3 A metal precursor solution was prepared by adding 1 g of basic copper carbonate and 0.7 g of ethylenediaminetetraacetic acid complex to a mixed solvent of 20 mL N,N-dimethylformamide and 60 mL acetonitrile. A ligand solution was prepared by adding 1 g of terephthalic acid to a mixed solvent of 60 mL N,N-dimethylformamide and 20 mL acetonitrile. The metal precursor solution was slowly added dropwise to the ligand solution under stirring. The resulting mixture was heated at 60 °C for 90 min using a microwave oven at 3000 MHz and 1000 W. The reacted solution was centrifuged to separate the solid and liquid phases, then washed three times with N,N-dimethylformamide and three times with methanol. After vacuum drying at 80 °C for 24 h, the CuBDC nanosheets of this invention were obtained. SEM characterization showed that the nanosheets were uniform in size, with a length of 6-7 μm, a thickness of 25 nm, an aspect ratio of 240-280, and a BET specific surface area of ​​640 m². 2 / g.

[0027] Example 4 A metal precursor solution was prepared by adding 1 g of copper nitrate and 0.44 g of a citric acid complex to a mixed solvent of 20 mL N,N-dimethylformamide and 60 mL acetonitrile. A ligand solution was prepared by adding 1 g of terephthalic acid to a mixed solvent of 60 mL N,N-dimethylformamide and 20 mL acetonitrile. Under stirring, the metal precursor solution was slowly added dropwise to the ligand solution. The resulting mixture was heated at 60 °C for 60 min using a microwave at 2500 MHz and 1000 W. The reacted solution was centrifuged to separate the solid and liquid phases, then washed three times with N,N-dimethylformamide and three times with methanol. After drying in air at 80 °C for 24 h, the CuBDC nanosheets of this invention were obtained. SEM characterization showed that the nanosheets were uniform in size, with a length of 4-5 μm, a thickness of 20 nm, an aspect ratio of 200-250, and a BET specific surface area of ​​470 m². 2 / g.

[0028] Comparative Example 1 Samples were prepared according to the method in Example 1 of CN106252663B. 0.3 g of copper nitrate solid and 1.313 g of terephthalic acid solid were weighed and dissolved in 20 mL of acetonitrile and 40 mL of N,N-dimethylformamide solution. The solution obtained in step 1 was heated and stirred in a water bath at 60 °C for 6 h. The solution obtained in step 2 was dried in an oven at 80 °C for 24 h. SEM characterization showed that the nanosheets had a length of 1 μm, a thickness of 60-80 nm, an aspect ratio of 10-20, and a BET specific surface area of ​​530-550 m². 2 / g.

Claims

1. A two-dimensional CuBDC nanosheet material, characterized in that: The nanosheets have a length of 1-8 μm, a thickness of 15-25 nm, and an aspect ratio of 40-533; where the aspect ratio is the ratio of the length to the thickness of the nanosheets; and a BET specific surface area of ​​300-750 m². 2 / g.

2. The two-dimensional CuBDC nanosheet material according to claim 1, characterized in that: The aspect ratio is 100-300.

3. A method for preparing the two-dimensional CuBDC nanosheet material according to claim 1 or 2, characterized in that... The following are included: (1) Inorganic copper salt, complexing agent, N,N-dimethylformamide and acetonitrile are mixed evenly to prepare a metal precursor solution; terephthalic acid, N,N-dimethylformamide and acetonitrile are mixed evenly to prepare a ligand solution; (2) The metal precursor solution and the ligand solution are mixed and the resulting mixture is reacted under microwave heating conditions; (3) The mixture after reaction is separated into solid and liquid, washed and dried to obtain two-dimensional CuBDC nanosheet material.

4. The method according to claim 3, characterized in that: The inorganic copper salt mentioned in step (1) is one or more of copper nitrate, copper chloride, copper sulfate, copper acetate, or basic copper carbonate.

5. The method according to claim 3, characterized in that: The complexing agent mentioned in step (1) is one or more of ethylenediaminetetraacetic acid, citric acid, humic acid, epigallocatechin gallate or Schiff base.

6. The method according to claim 3, characterized in that: The composition of the metal precursor solution in step (1) by mass is as follows: 1%–2% inorganic copper salt, 0.7%–1% complexing agent, 31%–35% N,N-dimethylformamide, and 62%–67% acetonitrile.

7. The method according to claim 3, characterized in that: The composition of the ligand solution in step (1) by mass is: 1%–2% terephthalic acid, 55%–70% N,N-dimethylformamide, and 27%–35% acetonitrile.

8. The method according to claim 3, characterized in that: In step (1), the mass ratio of the metal precursor solution to the ligand solution is 0.8 to 1.

2.

9. The method according to claim 3, characterized in that: The microwave heating conditions described in step (2) are: frequency 2000-5000MHz, power 500-1000W, time 60-90min, and temperature 60-80℃.

10. The method according to claim 3, characterized in that: The washing conditions in step (3) are as follows: the washing solvent is N,N-dimethylformamide and methanol to remove unreacted excess solute and residual solvent.

11. The method according to claim 3, characterized in that: The drying conditions for step (3) are: drying temperature of 60-80℃ and drying time of 18-24 hours.

12. The application of the two-dimensional CuBDC nanosheet material according to claim 1 or 2 in the field of adsorption separation.

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