CuBDC nanosheet, and preparation method and application thereof

Abstract

This invention discloses a CuBDC nanosheet, its preparation method, and its applications. The CuBDC nanosheet is a single-layer two-dimensional CuBDC nanosheet material; the aspect ratio of the CuBDC nanosheet is 80–400. The CuBDC nanosheet is single-layered, possessing a high aspect ratio and a large specific surface area. The preparation method is simple, the material is inexpensive and readily available, resulting in low cost and ease of mass production. The CuBDC nanosheet is suitable for gas storage, adsorption separation, heterogeneous catalysis, electrochemistry, and analytical applications.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials, specifically relating to a CuBDC nanosheet, its preparation method, and its application. 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 porous surfaces. Compared with traditional isotropic MOFs, they not only retain their porosity and tunable pore size but also possess the advantages of long-range order and anisotropy of crystalline materials, high porosity, and large specific surface area, 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 numerous publications. Although it has excellent morphology and properties, the synthesis steps are difficult to control and reproducible. Only by precisely controlling the solution concentration of metal ions and ligands and the reaction rate can two-dimensional nanosheets with excellent morphology be obtained. Currently, most of the CuBDC nanosheets synthesized in the literature are not monolayers and require secondary processing, or have a low aspect ratio.

[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. In this method, Cu salt is directly dissolved in the solvent, resulting in rapid initial crystal nucleus formation, but the morphology of the nuclei is difficult to control. The resulting CuBDC nanosheets are stacked, difficult to peel, and have poor morphological regularity. This method uses conventional heating methods such as water baths, resulting in a long crystal growth process, low efficiency, and low yield.

[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, resulting in severe aggregation of the obtained CuBDC nanosheets, large sheet thickness, easy stacking, and a low aspect ratio.

[0006] In current preparation methods, there is no effective way to control the contact reaction rate between the metal solution and the ligand solution. The resulting CuBDC nanosheets are relatively thick with a low aspect ratio, and the reaction is difficult to complete, resulting in a low yield. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides CuBDC nanosheets, their preparation method, and applications. The CuBDC nanosheets are monolayered, possessing a high aspect ratio and a large specific surface area. The preparation method is simple, using readily available and inexpensive materials, resulting in low cost and ease of mass production. The CuBDC nanosheets are suitable for gas storage, adsorption separation, heterogeneous catalysis, electrochemistry, and analytical applications.

[0008] The first aspect of this invention provides a CuBDC nanosheet. The CuBDC nanosheet is a single-layer two-dimensional CuBDC nanosheet material; the aspect ratio of the CuBDC nanosheet is 80 to 400, preferably 100 to 300; wherein the aspect ratio is the ratio of the length to the thickness of the nanosheet.

[0009] According to the present invention, the specific surface area of ​​the CuBDC nanosheets is 580–630 m². 2 / g.

[0010] According to the present invention, the length of the CuBDC nanosheet is 2-6 μm, preferably 4-5 μm, and the thickness is 15-25 nm, preferably 18-22 nm.

[0011] A second aspect of this invention provides a method for preparing CuBDC nanosheets. The method includes:

[0012] (1) The method uses a thin-film reactor; a thin-film component is provided in the thin-film reactor, which divides the reactor into an upper region and a lower region; the thin-film component is provided with holes;

[0013] (2) Place the copper ion solution in the upper region of the thin film reactor; place the ligand solution in the lower region of the thin film reactor; the copper ion solution is dripped into the ligand solution through the pores of the thin film component, and the reaction occurs in the lower region of the reactor. After separation, the CuBDC nanosheets are obtained.

[0014] According to the present invention, in step (1), the lower region of the thin-film reactor can accommodate the reaction solution including copper ion solution and ligand solution, so that the reaction can occur. Preferably, the volume ratio of the upper region to the lower region is 1:1 to 1:2.

[0015] According to the present invention, in step (1), the thin-film reactor is provided with a liquid inlet and outlet. The liquid inlet and outlet are used for injecting or discharging the solution.

[0016] According to the present invention, in step (1), the pore diameter of the holes on the thin film component is 3 to 5 μm; the porosity is 80% to 90%. More preferably, the pore thickness is 30 to 60 μm.

[0017] According to the present invention, in step (1), the material of the thin film component is at least one of polytetrafluoroethylene film, polyvinylidene fluoride film, polyvinylidene fluoride, and nylon. The thin film component is immersed in a mixed solution with a volume ratio of N,N-dimethylformamide:acetonitrile = 1:2 to 2:1.

[0018] According to the present invention, in step (2), the copper ion solution comprises an inorganic copper salt, N,N-dimethylformamide, and acetonitrile. Further, based on the mass of the copper ion solution, the copper ion solution comprises: 0.8%–1.5% inorganic copper salt, 22%–27% N,N-dimethylformamide, and 72%–77% acetonitrile. The inorganic copper salt comprises one or more of copper nitrate, copper chloride, copper sulfate, copper acetate, or basic copper carbonate. The solution is prepared using conventional methods.

[0019] According to the present invention, in step (2), the ligand solution comprises terephthalic acid, N,N-dimethylformamide, and acetonitrile. Further, based on the mass of the ligand solution, the ligand solution comprises: 0.8%–1.5% terephthalic acid, 72%–77% N,N-dimethylformamide, and 22%–27% acetonitrile. The solution is prepared using conventional methods.

[0020] According to the present invention, in step (2), the mass ratio of copper ion solution to ligand solution is 0.8 to 1.2.

[0021] According to the present invention, in step (2), the copper ion solution is added over a period of 100 to 120 minutes.

[0022] According to the present invention, in step (2), the reaction is carried out under microwave heating. The microwave heating temperature is 40–55°C, and the time is 3–6 hours. The microwave heating frequency is 2000–5000 MHz, and the power is 500–1000 W. A blue suspended solid is obtained after the reaction.

[0023] According to the present invention, in step (2), the separation can be performed using conventional solid-liquid separation methods, preferably centrifugation. After separation, washing and / or drying can be performed. The washing solvent is N,N-dimethylformamide and / or chloroform. The purpose of washing is to remove unreacted excess solute and residual solvent. The drying conditions are: temperature 60–80°C, time 18–24 h. The drying can be vacuum drying or air drying.

[0024] The third aspect of this invention provides the application of the CuBDC nanosheets or CuBDC nanosheets prepared by the preparation method in the fields of gas storage, adsorption separation, heterogeneous catalysis, electrochemistry, and analysis.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] 1. The CuBDC nanosheets of the present invention are single-layer two-dimensional CuBDC nanosheet materials; the aspect ratio of the CuBDC nanosheets is 80-400. The CuBDC has a high aspect ratio and a large specific surface area, making it suitable for gas storage, adsorption separation, heterogeneous catalysis, electrochemistry, and analytical fields.

[0027] 2. In the preparation method of CuBDC nanosheets of the present invention, the method employs a thin-film reactor; a thin-film component is provided in the thin-film reactor, which divides the reactor into an upper region and a lower region; pores are provided on the thin-film component; in the reactor, a copper ion solution is dripped into the ligand solution through the pores, and a reaction occurs in the lower region of the reactor, and the CuBDC nanosheets are obtained after separation.

[0028] This invention employs an interface-controlled reactor with a microporous membrane as its core. By controlling the pore size of the microporous membrane, the binding rate of metal ions and ligands is controlled and delayed, thereby controlling the nucleation process in the initial stage of the reaction and regulating the two-dimensional morphology of the crystal. This is beneficial for obtaining monolayer 2D MOF nanosheet nuclei with uniform morphology and controllable length and aspect ratio. Furthermore, due to the long-term existence of the reaction interface, the reaction can continue until completion, resulting in a high yield. This invention can produce ultrathin monolayer 2D MOF nanosheets with more exposed outer surface area and 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 yield is high, and it is easy to prepare in large quantities. The CuBDC has a high aspect ratio and a large specific surface area, making it suitable for gas storage, adsorption separation, heterogeneous catalysis, electrochemistry, and analytical fields.

[0029] 3. The CuBDC nanosheets of the present invention are applicable to gas storage, adsorption separation, heterogeneous catalysis, electrochemistry and analysis. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the thin-film reactor in this invention.

[0031] Wherein, 1-thin film reactor, 2-inlet, 3-outlet, 4-upper zone, 5-thin film component, 6-lower zone, 7-contact reaction zone, 8-hole on the thin film component.

[0032] Figure 2 , 4 Figures 5 and 6 are scanning electron microscope images of the length of CuBDC nanosheets prepared in Example 1 of this invention.

[0033] Figure 3 This is a scanning electron microscope image of the thickness of the CuBDC nanosheets prepared in Example 1 of this invention. Detailed Implementation

[0034] 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 this industry.

[0035] The dimensions of the CuBDC nanosheets of this invention are measured using scanning electron microscopy images. The aspect ratio described in this invention is the ratio of the length to the thickness of the nanosheet.

[0036] In this invention, the BET specific surface area was measured using a Micrometrics ASAP 2460N2 adsorption instrument, employing a cryogenic liquid nitrogen adsorption method at a temperature of 77K.

[0037] In this invention, a Zeiss Gemini Ultra-55 scanning electron microscope was used for testing, with an irradiation energy of 5 keV.

[0038] In this invention, each example employs the following... Figure 1 The thin-film reactor 1 is shown. A thin-film component 5 is installed in the reactor, dividing it into an upper region 4 and a lower region 6. The thin-film component has holes 8. An inlet 2 and an outlet 3 are provided on the thin-film component for liquid entry and exit. During the preparation of nanosheets, a copper ion solution is placed in the upper region 4, and a ligand solution is placed in the lower region 6. The copper ion solution is dripped into the ligand solution in the lower region through the holes 8 of the thin-film component, where a reaction occurs in the contact reaction zone 7 of the lower region of the reactor. After separation, the CuBDC nanosheets are obtained.

[0039] In this embodiment of the invention, the volume ratio of the upper region to the lower region of the membrane reactor is 1:1.5. The membrane component is made of polytetrafluoroethylene. Before use, the membrane component is immersed in a mixed solution of N,N-dimethylformamide and acetonitrile in a 1:1 ratio.

[0040] In this invention, CO2 permeability is referred to as gas permeability (P), which is the amount of gas that permeates through a unit area per unit time under a unit pressure difference. The calculation formula is as follows:

[0041]

[0042] Among them, P i It is gas permeability, measured in Barrers (1 Barrer = 10⁻⁶). -10 cm 3 (STP)·cm·cm -2 ·sec -1 ·cmHg -1 V is the downstream volume, in cm³. 3 R is the gas constant, 8.314 J·mol⁻¹. -1 ·K -1 T is temperature, in Kelvin (K), and S is the effective permeable area of ​​the membrane, in cm². 2 dP i / dt represents the rate of increase of downstream gas pressure over time, l is the membrane thickness in cm, and ΔP i It is the pressure difference, and the unit is bar.

[0043] In this invention, the CO2 / CH4 selectivity refers to the ratio of the CO2 to the CH4 gas permeability, calculated using the following formula:

[0044]

[0045] Example 1

[0046] In this example, the pores on the thin film reactor membrane component have a thickness of 30 μm, a pore diameter of 5 μm, and a porosity of 88%.

[0047] A copper ion solution was prepared by adding 0.5 g of copper nitrate to a mixed solvent of 15 g of N,N-dimethylformamide and 45 g of acetonitrile.

[0048] A ligand solution was prepared by adding 0.5 g of terephthalic acid to a mixture of 45 g of N,N-dimethylformamide and 15 g of acetonitrile.

[0049] The copper ion solution and ligand solution were injected into the upper and lower regions of the thin-film reactor at a mass ratio of 1:1. The copper ion solution was dripped into the ligand solution through the pores of the thin-film component, and the reaction occurred in the lower region of the reactor. The dripping time of the copper ion solution was 120 min. The reactor was placed in a microwave heating device with a frequency of 2500 MHz and a power of 500 W. The heating temperature was 55 °C for 6 h. In the middle membrane-controlled reaction zone, the solution interface of the two solutions was controlled to have slow contact, and the reaction occurred, generating a blue suspended solid.

[0050] The reacted solution was centrifuged to separate the solid and liquid phases, then washed three times with N,N-dimethylformamide and three times with chloroform. After vacuum drying at 80°C for 18 h, CuBDC nanosheets were obtained with a yield of 78 wt%.

[0051] SEM characterization revealed that the monolayer nanosheets were uniform in size, with a length of 2–6 μm, a thickness of approximately 20 nm, an aspect ratio of 100–300, and a BET specific surface area of ​​580 m². 2 / g.

[0052] Example 2

[0053] In this example, the pores on the thin film reactor membrane component have a thickness of 35 μm, a pore diameter of 5 μm, and a porosity of 88%.

[0054] A copper ion solution was prepared by adding 0.72 g of copper sulfate to a mixed solvent of 12 g of N,N-dimethylformamide and 36 g of acetonitrile.

[0055] A ligand solution was prepared by adding 0.9 g of terephthalic acid to a mixture of 45 g of N,N-dimethylformamide and 15 g of acetonitrile.

[0056] The copper ion solution and ligand solution were injected into the upper and lower regions of the thin-film reactor, respectively, at a mass ratio of 4:5. The copper ion solution was dripped into the ligand solution through the pores of the thin-film component, and the reaction occurred in the lower region of the reactor. The copper ion solution was added over a period of 110 minutes. The reactor was placed in a microwave heating device with a frequency of 2000 MHz and a power of 500 W, and heated to 55°C for 3 hours. In the middle membrane-controlled reaction zone, the solution interface of the two solutions was controlled for slow contact, resulting in a reaction that produced a blue suspended solid.

[0057] The reacted solution was centrifuged to separate the solid and liquid phases, then washed three times with N,N-dimethylformamide and three times with chloroform. After vacuum drying at 80°C for 18 hours, the CuBDC nanosheets of the present invention were obtained with a yield of 70%.

[0058] SEM characterization revealed that the monolayer nanosheets were uniform in size, with a length of 3–4 μm, a thickness of approximately 20 nm, an aspect ratio of 150–200, and a BET specific surface area of ​​585 m². 2 / g.

[0059] Example 3

[0060] In this example, the pores on the thin film reactor membrane component have a thickness of 45 μm, a pore diameter of 4 μm, and a porosity of 88%.

[0061] A copper ion solution was prepared by adding 0.96 g of basic copper carbonate to a mixed solvent of 18 g of N,N-dimethylformamide and 54 g of acetonitrile.

[0062] A ligand solution was prepared by adding 0.8 g of terephthalic acid to a mixture of 45 g of N,N-dimethylformamide and 15 g of acetonitrile.

[0063] The copper ion solution and ligand solution were injected into the upper and lower regions of the thin-film reactor at a mass ratio of 6:5. The copper ion solution was dripped into the ligand solution through the pores of the thin-film component, and the reaction occurred in the lower region of the reactor. The copper ion solution was added over a period of 100 min. The reactor was placed in a microwave heating device with a frequency of 3000 MHz and a power of 1000 W, and the heating temperature was 40 °C for 6 h. In the middle membrane-controlled reaction zone, the solution interface of the two solutions was controlled for slow contact, and the reaction occurred, generating a blue suspended solid.

[0064] The reacted solution was centrifuged to separate the solid and liquid phases, then washed three times with N,N-dimethylformamide and three times with chloroform. After vacuum drying at 80°C for 24 hours, CuBDC nanosheets were obtained with a yield of 76%.

[0065] SEM characterization revealed that the monolayer nanosheets were uniform in size, with a length of 4–6 μm, a thickness of approximately 25 nm, an aspect ratio of 160–240, and a BET specific surface area of ​​596 m². 2 / g.

[0066] Example 4

[0067] In this example, the pores on the thin-film reactor membrane component have a thickness of 60 μm, a pore diameter of 3 μm, and a porosity of 88%.

[0068] A copper ion solution was prepared by adding 0.6 g of copper nitrate to a mixed solvent of 15 g of N,N-dimethylformamide and 45 g of acetonitrile.

[0069] A ligand solution was prepared by adding 0.6 g of terephthalic acid to a mixture of 45 g of N,N-dimethylformamide and 15 g of acetonitrile.

[0070] The copper ion solution and ligand solution were injected into the upper and lower regions of the thin-film reactor at a mass ratio of 1:1. The copper ion solution was dripped into the ligand solution through the pores of the thin-film component, and the reaction occurred in the lower region of the reactor. The dripping time of the copper ion solution was 110 min. The reactor was placed in a microwave heating device with a frequency of 2500 MHz and a power of 1000 W, and the heating temperature was 40 °C for 6 h. In the middle membrane-controlled reaction zone, the solution interface of the two solutions was controlled to have slow contact, and the reaction occurred, generating a blue suspended solid.

[0071] The reacted solution was centrifuged to separate the solid and liquid phases, then washed three times with N,N-dimethylformamide and three times with chloroform. After drying in air at 80°C for 24 hours, CuBDC nanosheets were obtained with a yield of 75%.

[0072] SEM characterization revealed that the monolayer nanosheets were uniform in size, with a length of 4–6 μm, a thickness of approximately 15 nm, an aspect ratio of 266–400, and a BET specific surface area of ​​630 m². 2 / g.

[0073] Comparative Example 1

[0074] A copper ion solution was prepared by adding 0.5 g of copper nitrate to a mixed solvent of 15 g of N,N-dimethylformamide and 45 g of acetonitrile.

[0075] A ligand solution was prepared by adding 0.5 g of terephthalic acid to a mixture of 45 g of N,N-dimethylformamide and 15 g of acetonitrile.

[0076] The copper ion solution and ligand solution were mixed evenly at a mass ratio of 1:1. The reaction solution was then placed in a microwave heating device with a frequency of 2500MHz and a power of 500W, heated to 55℃ for 6 hours, and a blue suspended solid was generated.

[0077] The reacted solution was centrifuged to separate the solid and liquid phases, then washed three times with N,N-dimethylformamide and three times with chloroform. After vacuum drying at 80°C for 18 h, CuBDC nanosheets were obtained with a yield of 47 wt%.

[0078] Nanosheets are multilayered, stacked two-dimensional nanosheet materials. The nanosheets are 1 μm long, approximately 60–80 nm thick, with an aspect ratio of 12–17 and a BET specific surface area of ​​490 m². 2 / g.

[0079] Comparing Comparative Example 1 with Example 1, it can be seen that the present invention can obtain two-dimensional nanosheets with higher aspect ratio and larger specific surface area using a thin-film controlled reactor, and the yield of CuBDC is also improved.

[0080] Application examples

[0081] The materials prepared in the above examples were assembled into batteries for constant current charge-discharge testing. The test conditions were: current density 5000 mA / g, 100 cycles, and the test results are shown in Table 1.

[0082] Gas separation membrane materials prepared by doping the materials in the above examples with polyimide polymers (referred to as Comparative Example 2) were tested for gas separation. The test conditions were: separation of a mixed gas with a CO2:CH4 volume ratio of 1:1, pressure of 4 bar, temperature of 35 °C, and CuBDC nanosheet loading of 10 wt%. The test results are shown in Table 2.

[0083] Table 1 Results of the 100-cycle test

[0084]

[0085]

[0086] Table 2 Separation test results

[0087] <![CDATA[CO2 / CH4 selectivity]]> <![CDATA[CO2 Permeability (unit: Barrer)]]> Example 1 25.8 120 Example 2 25.4 124 Example 3 26.7 118 Example 4 26.1 119 Comparative Example 1 17.9 101 Comparative Example 2 20.2 100

Claims

1. A CuBDC nanosheet, which is a single-layer two-dimensional CuBDC nanosheet material; the aspect ratio of the CuBDC nanosheet is 100~400; the specific surface area of ​​the CuBDC nanosheet is 580~630 m². 2 / g; the length of the CuBDC nanosheets is 2~6μm; the thickness is 15~25nm.

2. The CuBDC nanosheets according to claim 1, characterized in that, The CuBDC nanosheets have a length of 4-5 μm and a thickness of 18-22 nm.

3. A method for preparing CuBDC nanosheets according to any one of claims 1 to 2, comprising: (1) The method uses a thin-film reactor; the thin-film reactor is equipped with a thin-film component, which divides the reactor into an upper region and a lower region; The thin film component has holes; (2) Place the copper ion solution in the upper region of the thin-film reactor; The ligand solution is placed in the lower region of the thin-film reactor; copper ion solution is dripped into the ligand solution through the pores of the thin-film component, and the reaction occurs in the lower region of the reactor. After separation, the CuBDC nanosheets are obtained. In step (1), the pore diameter of the thin film component is 3~5μm; the porosity is 80~90%; and the pore thickness is 30~60μm. In step (2), the reaction is carried out under microwave heating; the temperature of microwave heating is 40~55℃ and the time is 3~6h.

4. The preparation method according to claim 3, characterized in that, In step (2), the copper ion solution includes inorganic copper salt, N,N-dimethylformamide and acetonitrile.

5. The preparation method according to claim 4, characterized in that, In step (2), based on the mass of the copper ion solution, the copper ion solution includes: 0.8% to 1.5% inorganic copper salt, 22% to 27% N,N-dimethylformamide, and 72% to 77% acetonitrile.

6. The preparation method according to claim 3, characterized in that, In step (2), the ligand solution includes phthalic acid, N,N-dimethylformamide and acetonitrile.

7. The preparation method according to claim 6, characterized in that, In step (2), the ligand solution comprises, based on the mass of the ligand solution, 0.8% to 1.5% terephthalic acid, 72% to 77% N,N-dimethylformamide, and 22% to 27% acetonitrile.

8. The preparation method according to claim 3, characterized in that, In step (2), the mass ratio of copper ion solution to ligand solution is 0.8 to 1.

2.

9. The preparation method according to claim 3, characterized in that, In step (2), the copper ion solution is added over a period of 100-120 minutes.

10. The application of CuBDC nanosheets according to any one of claims 1 to 2 or CuBDC nanosheets prepared by the preparation method according to any one of claims 3 to 9 in the fields of gas storage, adsorption separation, heterogeneous catalysis, electrochemistry or analysis.

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