A two-dimensional Cu-MOF nanosheet and its continuous synthesis method and application

Abstract

The present invention discloses a two-dimensional Cu-MOF nanosheet and its continuous synthesis method and application. The continuous synthesis method includes: assembling a microfluidic pneumatic continuous reaction device, mixing the metal copper salt solution in syringe A and the organic ligand solution in syringe B in a mixer to obtain a reaction solution, the reaction solution continuously flows in a reaction tube, and the oxygen in syringe C is used to cut the continuously flowing reaction solution into slugs of uniform size, which are reaction micro-sites; the slugs in the reaction tube flow through a heating device with a set temperature, and the product is collected by a collecting device. The above-mentioned continuous synthesis method of the present invention has simple steps, does not require a complex peeling step, and can directly obtain a two-dimensional nanosheet with relatively uniform thickness, numerous wrinkles, and can maximize the exposure of catalytic active sites, and has good electrocatalytic CO2 reduction activity.

Description

Technical Field

[0001] The present invention relates to the technical field of nano-electrocatalytic materials, and in particular to a two-dimensional Cu-MOF nanosheet and a continuous synthesis method and application thereof. Background Art

[0002] The information disclosed in the background of the invention is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Metal-organic frameworks (MOFs) are crystalline porous materials with periodic network structures formed by the self-assembly of metal ions and organic ligands. Different metal coordination and organic ligand designs give MOFs a regular porous structure, large surface area, and tunable functionality. These properties of MOFs have many potential applications, especially by leveraging the unique two-dimensional morphology of MOFs to achieve specific functions.

[0004] However, like other two-dimensional materials, two-dimensional MOFs tend to stack tightly vertically due to π-π interactions, van der Waals forces, or hydrogen bonds. This layered stacking structure prevents sufficient exposure of reactive sites and slows the diffusion of substrates, limiting their performance. Compared to bulk 2D MOFs, 2D MOF nanosheets with layer thicknesses below 10 nm can expose more active sites on their surfaces, promising excellent performance in separation and catalytic reactions. These unique properties and broad application prospects highlight the urgent need to synthesize 2D MOF nanosheets.

[0005] Traditionally, two-dimensional MOF nanosheets are obtained by exfoliating two-dimensional bulk MOFs from top to bottom, including physical exfoliation, chemical exfoliation, and liquid phase exfoliation. However, this method often results in the MOF nanosheets having the disadvantages of uneven thickness and size. In addition, due to the strong interlayer interaction, these exfoliated MOF nanosheets are easily re-stacking into bulk MOFs. To solve this problem, researchers began to use a bottom-up synthesis method to directly prepare two-dimensional MOF nanosheets (Adv. Mater., 2016, 28, 4149-4155; Small Methods, 2017, 1, 1600030), which is similar to interfacial induced synthesis and surfactant / small molecule assisted synthesis, which helps to selectively control the growth direction of MOF crystals. Although the bottom-up method can directly grow two-dimensional MOF nanosheets and control the thickness of the nanosheets, the auxiliary substances used will inevitably lead to insufficient utilization of surface active sites, thereby reducing the performance of the two-dimensional MOF nanosheets. In summary, at present, the direct synthesis of two-dimensional MOF nanosheets with uniform size still has certain technical difficulties. Summary of the Invention

[0006] In view of this, the present invention provides a two-dimensional Cu-MOF nanosheet and its continuous synthesis method and application, which solves the problem of difficult peeling and uneven thickness in the top-down method in the prior art, and the problem of easy coverage of reaction sites in the bottom-up method.

[0007] In a first aspect, the present invention provides a continuous synthesis method of two-dimensional Cu-MOF nanosheets, comprising the following steps:

[0008] Assembling a microfluidic pneumatic continuous reaction device, the microfluidic pneumatic continuous reaction device comprising syringe A, syringe B, syringe C, a reaction tube, a mixer, a heating device, and a collecting device, syringe A being pre-filled with a metal copper salt solution, syringe B being pre-filled with an organic ligand solution, and syringe C being pre-filled with oxygen;

[0009] The metal copper salt solution in syringe A and the organic ligand solution in syringe B are mixed in a mixer to obtain a reaction liquid. The reaction liquid flows continuously in the reaction tube. The oxygen in syringe C is used to cut the continuously flowing reaction liquid into slugs of uniform size. The slugs are the reaction micro-locations. The slugs in the reaction tube flow through a heating device with a set temperature, and the products are collected by a collecting device.

[0010] Preferably, in the microfluidic pneumatic continuous reaction device, syringe A and syringe B are respectively connected to the mixer, the mixer and the collection device are connected through a reaction tube, a heating device is provided between the mixer and the collection device, and the reaction tube passes through the heating device; syringe C is connected to the reaction tube, and the connection between syringe C and the reaction tube is located between the mixer and the heating device.

[0011] Further preferably, the microfluidic pneumatic continuous reaction device further comprises a tee, and the C syringe is connected to the reaction tube via the tee.

[0012] Preferably, the reaction tube is a transparent polytetrafluoroethylene hose; further preferably, the reaction tube has an inner diameter of 1-3 mm, an outer diameter of 2-4 mm, and a difference between the outer diameter and the inner diameter of 0.5 mm or more.

[0013] Preferably, the metal copper salt is selected from any one of copper nitrate, copper acetate, copper chloride, copper sulfate and copper carbonate.

[0014] Preferably, the solvent of the metal copper salt solution is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, acetone, formic acid, methanol, ethanol, and water.

[0015] Preferably, the concentration of the metal copper salt solution is 0.02-1 mol / L.

[0016] Preferably, the organic ligand is selected from any one of fumaric acid, benzoic acid, terephthalic acid, trimesic acid and 2,5-dihydroxyterephthalic acid.

[0017] Preferably, the solvent of the organic ligand solution is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, acetone, formic acid, methanol, ethanol and water.

[0018] Preferably, the concentration of the organic ligand solution is 0.02-1 mol / L.

[0019] Preferably, the ratio of the fluid flow rates in syringe A, syringe B, and syringe C is 1:1:(5-20).

[0020] More preferably, the fluid flow rate in syringe A is 40-200 μL / min, the fluid flow rate in syringe B is 40-200 μL / min, and the fluid flow rate in syringe C is 290-1200 μL / min.

[0021] Preferably, the heating temperature of the heating device is 80-120°C.

[0022] Preferably, the purity of the oxygen is above 99.999%.

[0023] Preferably, the method further comprises a step of post-processing the collected product, wherein the post-processing comprises centrifugation or filtration, washing and drying.

[0024] In a second aspect, the present invention provides two-dimensional Cu-MOF nanosheets prepared by the above-mentioned continuous synthesis method, wherein the thickness of the two-dimensional Cu-MOF nanosheets is 3-5 nm.

[0025] In a third aspect, the present invention provides the application of the above-mentioned two-dimensional Cu-MOF nanosheets in the electrocatalytic reduction of CO2.

[0026] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0027] (1) The continuous synthesis method of two-dimensional Cu-MOF nanosheets provided by the present invention has simple steps, does not require complex peeling steps, can directly obtain two-dimensional nanosheets, and can achieve continuous production with high efficiency. At the same time, it uses oxygen as the driving force of the reaction and participates in the reaction, which is green and environmentally friendly and has the potential for industrial application.

[0028] (2) The two-dimensional Cu-MOF nanosheets prepared by the continuous synthesis method of the present invention have a uniform thickness between 3 and 5 nm, which solves the problem of uneven thickness and easy stacking of nanosheets in the existing top-down synthesis of two-dimensional nanosheets. It also solves the disadvantage of the existing bottom-up synthesis of two-dimensional nanosheets that the additional auxiliary substances cover the catalytic active sites.

[0029] (3) The two-dimensional Cu-MOF nanosheets prepared in the present invention have numerous wrinkles, which can maximize the exposure of catalytic active sites. They have good electrocatalytic CO2 reduction activity, a Faradaic efficiency higher than 90%, and a CO selectivity higher than 55%. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute undue limitations thereon. It is obvious that one of ordinary skill in the art could derive other drawings based on these drawings without inventive effort.

[0031] Figure 1 Schematic diagram of a microfluidic pneumatic continuous reaction device according to Example 1 of the present invention;

[0032] Figure 2 This is a physical picture of the reaction solution in the reaction tube of Example 2 of the present invention before and after the reaction;

[0033] Figure 3 is an X-ray diffraction (XRD) spectrum of the two-dimensional Cu-MOF nanosheet prepared in Example 2 of the present invention;

[0034] Figure 4 is a scanning electron microscope (SEM) image of the two-dimensional Cu-MOF nanosheet prepared in Example 2 of the present invention;

[0035] Figure 5 This is an atomic force microscope (AFM) image of the two-dimensional Cu-MOF nanosheet prepared in Example 2 of the present invention;

[0036] Figure 6 is the X-ray diffraction (XRD) spectrum of the Cu-MOF material prepared in Comparative Example 1 of the present invention;

[0037] Figure 7 This is a scanning electron microscope (SEM) image of the Cu-MOF material prepared in Comparative Example 1 of the present invention;

[0038] Figure 8 This is a scanning electron microscope (SEM) image of the Cu-MOF material prepared in Comparative Example 2 of the present invention;

[0039] Figure 9 This is a scanning electron microscope (SEM) image of the Cu-MOF material prepared in Comparative Example 3 of the present invention;

[0040] Figure 10 This is a scanning electron microscope (SEM) image of the Cu-MOF material prepared in Comparative Example 4 of the present invention;

[0041] In the figure, 1. Syringe A; 2. Syringe B; 3. Syringe C; 4. First injection tube; 5. Second injection tube; 6. Mixer; 7. Tee; 8. Third injection tube; 9. Oven; 10. Reaction tube; 11. Collection bottle. DETAILED DESCRIPTION

[0042] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0043] The technical solution of the present invention is further described below with reference to specific embodiments.

[0044] Example 1

[0045] This embodiment provides the assembly of a microfluidic pneumatic continuous reaction device, such as Figure 1 shown.

[0046] The microfluidic pneumatic continuous reaction apparatus includes syringe A 1, syringe B 2, syringe C 3, a first injection tube 4, a second injection tube 5, a mixer 6, a tee 7, a third injection tube 8, an oven 9, a reaction tube 10, and a collection flask 11. The first injection tube 4, the second injection tube 5, the third injection tube 8, and the reaction tube 10 are all transparent polytetrafluoroethylene hoses with an inner diameter of 2 mm and an outer diameter of 3 mm.

[0047] Syringe A 1 is connected to mixer 6 via a first injection tube 4. Syringe B 2 is connected to mixer 6 via a second injection tube 5. Mixer 6 and collection flask 11 are connected via reaction tube 10. An oven 9 is located between mixer 6 and collection flask 11, and reaction tube 10 passes through oven 9. Oven 9 is an electrically heated constant-temperature forced-air drying oven used to heat reaction tube 10. Syringe C 3 is connected to a third injection tube 8, which is connected to reaction tube 10 via a tee 7 located between mixer 6 and heating device 9.

[0048] Example 2

[0049] This embodiment provides a continuous synthesis method of two-dimensional Cu-MOF nanosheets, using the microfluidic pneumatic continuous reaction device provided in Example 1, and the specific steps are as follows:

[0050] Dissolve copper nitrate trihydrate in a mixed solution of N,N-dimethylformamide (27 mL) and methanol (3 mL) to a concentration of 0.1 mol / L, and add the solution to syringe A. Dissolve 2,5-dihydroxyterephthalic acid in a mixed solution of N,N-dimethylformamide (27 mL) and methanol (3 mL) to a concentration of 0.05 mol / L, and add the solution to syringe B. Add high-purity oxygen (purity greater than 99.999%) to syringe C. Heat the oven to 100°C.

[0051] The flow rates of syringe A, syringe B, and syringe C were set at 98.17 μL / min, 98.17 μL / min, and 589.1 μL / min, with the flow rates of syringes A, B, and C in a ratio of approximately 1:1:6. First, the copper salt solution and organic ligand solution in syringes A and B were mixed in a mixer to produce a reaction solution. Oxygen in syringe C was used to cut the continuously flowing reaction solution into uniformly sized plugs, which became the reaction microsites. The plugs were then dried in a 100°C oven. The resulting solution was collected in a collection flask, centrifuged, washed with deionized water, and isolated. The product was then freeze-dried for 12 hours to obtain the two-dimensional Cu-MOF nanosheets.

[0052] Actual pictures of the reaction liquid in the reaction tube before and after the reaction Figure 2 shown.

[0053] The X-ray diffraction (XRD) spectrum of the two-dimensional Cu-MOF nanosheets prepared in this example is as follows: Figure 3 As shown in Figure 3, the two-dimensional Cu-MOF is completely consistent with the main peak of the simulation peak, indicating that the Cu-MOF was successfully synthesized.

[0054] The scanning electron microscope (SEM) images of the two-dimensional Cu-MOF nanosheets prepared in this example are shown in FIG. Figure 4 As shown by Figure 4 It can be seen that the obtained Cu-MOFs are all in the morphology of two-dimensional nanosheets, without any stacking phenomenon, and the surface of the two-dimensional nanosheets has many wrinkles, which can expose the catalytic active sites to the greatest extent and facilitate the shuttling of reaction substrate molecules.

[0055] The atomic force microscope (AFM) images of the two-dimensional Cu-MOF nanosheets prepared in this example are shown in FIG. Figure 5 As shown by Figure 5 It can be seen that the thickness of the two-dimensional Cu-MOF nanosheet is 3-5 nm, which is an ultra-thin two-dimensional nanosheet.

[0056] Example 3

[0057] This embodiment provides a continuous synthesis method of two-dimensional Cu-MOF nanosheets, using the microfluidic pneumatic continuous reaction device provided in Example 1, and the specific steps are as follows:

[0058] Dissolve copper nitrate trihydrate in a mixed solution of N,N-dimethylformamide (27 mL) and methanol (3 mL) to prepare a solution with a concentration of 0.2 mol / L, and add it to syringe A. Dissolve 2,5-dihydroxyterephthalic acid in a mixed solution of N,N-dimethylformamide (27 mL) and methanol (3 mL) to prepare a solution with a concentration of 0.1 mol / L, and add it to syringe B. Add high-purity oxygen to syringe C, and heat the oven to 100°C.

[0059] The flow rates of syringes A, B, and C were set at 98.17 μL / min, 98.17 μL / min, and 589.1 μL / min, with the ratio of these rates being approximately 1:1:6. First, the copper salt solution and organic ligand solution in syringes A and B were mixed in a mixer to create a reaction solution. Oxygen in syringe C then cut the continuously flowing reaction solution into uniformly sized plugs, which served as reaction microsites. The plugs were then dried in a 100°C oven, and the resulting solution was collected in a collection flask. The product was then isolated by centrifugation, washed with deionized water, and freeze-dried for 12 hours to yield two-dimensional Cu-MOF nanosheets.

[0060] Example 4

[0061] This embodiment provides a continuous synthesis method of two-dimensional Cu-MOF nanosheets, using the microfluidic pneumatic continuous reaction device provided in Example 1, and the specific steps are as follows:

[0062] Dissolve copper nitrate trihydrate in a mixed solution of N,N-dimethylformamide (27 mL) and methanol (3 mL) to prepare a solution with a concentration of 0.1 mol / L, and add it to syringe A. Dissolve 2,5-dihydroxyterephthalic acid in a mixed solution of N,N-dimethylformamide (27 mL) and methanol (3 mL) to prepare a solution with a concentration of 0.05 mol / L, and add it to syringe B. Add high-purity oxygen to syringe C, and heat the oven to 100°C.

[0063] The flow rates of syringes A, B, and C were set at 49.1 μL / min, 49.1 μL / min, and 589.1 μL / min, with the ratio of these rates being approximately 1:1:12. First, the copper salt solution and organic ligand solution in syringes A and B were mixed in a mixer to create a reaction solution. Oxygen in syringe C then cut the continuously flowing reaction solution into uniformly sized plugs, which served as reaction microsites. The plugs were then dried in a 100°C oven, and the resulting solution was collected in a collection flask. The product was then isolated by centrifugation, washed with deionized water, and freeze-dried for 12 hours to yield two-dimensional Cu-MOF nanosheets.

[0064] Example 5

[0065] This embodiment provides a continuous synthesis method of two-dimensional Cu-MOF nanosheets, using the microfluidic pneumatic continuous reaction device provided in Example 1, and the specific steps are as follows:

[0066] Dissolve copper chloride in a mixed solution of N,N-dimethylformamide (27 mL) and methanol (3 mL) to a concentration of 0.1 mol / L, and add it to syringe A. Dissolve 2,5-dihydroxyterephthalic acid in a mixed solution of N,N-dimethylformamide (27 mL) and methanol (3 mL) to a concentration of 0.05 mol / L, and add it to syringe B. Add high-purity oxygen to syringe C, and heat the oven to 100°C.

[0067] The flow rates of syringes A, B, and C were set at 98.17 μL / min, 98.17 μL / min, and 589.1 μL / min, with the ratio of these rates being approximately 1:1:6. First, the copper salt solution and organic ligand solution in syringes A and B were mixed in a mixer to create a reaction solution. Oxygen in syringe C then cut the continuously flowing reaction solution into uniformly sized plugs, which served as reaction microsites. The plugs were then dried in a 100°C oven, and the resulting solution was collected in a collection flask. The product was then isolated by centrifugation, washed with deionized water, and freeze-dried for 12 hours to yield two-dimensional Cu-MOF nanosheets.

[0068] Example 6

[0069] This embodiment provides a continuous synthesis method of two-dimensional Cu-MOF nanosheets, using the microfluidic pneumatic continuous reaction device provided in Example 1, and the specific steps are as follows:

[0070] Dissolve copper nitrate trihydrate in a mixed solution of N,N-dimethylformamide (27 mL) and ethanol (3 mL) to a concentration of 0.1 mol / L, and add it to syringe A. Dissolve 2,5-dihydroxyterephthalic acid in a mixed solution of N,N-dimethylformamide (27 mL) and ethanol (3 mL) to a concentration of 0.05 mol / L, and add it to syringe B. Add high-purity oxygen to syringe C, and heat the oven to 100°C.

[0071] The flow rates of syringes A, B, and C were set at 98.17 μL / min, 98.17 μL / min, and 589.1 μL / min, with the ratio of these rates being approximately 1:1:6. First, the copper salt solution and organic ligand solution in syringes A and B were mixed in a mixer to create a reaction mixture. Oxygen in syringe C was used to cut the continuously flowing reaction solution into uniformly sized plugs, which served as reaction microsites. The plugs were then oven-dried at 100°C. The resulting solution was collected in a collection flask, centrifuged, washed with deionized water, and freeze-dried for 12 hours to yield two-dimensional Cu-MOF nanosheets.

[0072] Example 7

[0073] The difference from Example 1 is that the organic ligand is different. In this example, fumaric acid is used instead of 2,5-dihydroxyterephthalic acid.

[0074] Example 8

[0075] The difference from Example 1 is that the organic ligand is different. In this example, benzoic acid is used instead of 2,5-dihydroxyterephthalic acid.

[0076] Example 9

[0077] The difference from Example 1 is that the organic ligand is different. In this example, terephthalic acid is used instead of 2,5-dihydroxyterephthalic acid.

[0078] Example 10

[0079] The difference from Example 1 is that the organic ligand is different. In this example, trimesic acid is used instead of 2,5-dihydroxyterephthalic acid.

[0080] Example 11

[0081] The difference from Example 1 is that the metallic copper salt is different. In this example, copper acetate monohydrate is used instead of copper nitrate trihydrate.

[0082] Example 12

[0083] The difference from Example 1 is that the metallic copper salt is different. In this example, anhydrous copper sulfate is used instead of copper nitrate trihydrate.

[0084] Example 13

[0085] The difference from Example 1 is that the metallic copper salt is different. In this example, copper carbonate is used instead of copper nitrate trihydrate.

[0086] Comparative Example 1

[0087] The difference from Example 1 is that the type of gas in syringe C is different. In this comparative example, high-purity nitrogen is used instead of high-purity oxygen, and Cu-MOF material is finally obtained.

[0088] The X-ray diffraction (XRD) spectrum of the Cu-MOF material prepared in this comparative example is as follows: Figure 6 As shown in Figure 2, it can be seen that the main peak of the Cu-MOF material is completely consistent with the simulation peak, indicating that the Cu-MOF material was successfully synthesized.

[0089] The scanning electron microscope (SEM) images of the Cu-MOF material prepared in this comparative example are as follows: Figure 7 As shown by Figure 7 It can be seen that the obtained Cu-MOF materials all have a three-dimensional nanorod morphology, indicating that after changing the reaction atmosphere to nitrogen, no Cu-MOF material with a two-dimensional nanosheet morphology can be obtained.

[0090] Comparative Example 2

[0091] The difference from Example 1 is that the type of gas in the C syringe is different. In this comparative example, high-purity hydrogen is used instead of high-purity oxygen, and finally a Cu-MOF material is obtained.

[0092] The scanning electron microscope (SEM) images of the Cu-MOF material prepared in this comparative example are as follows: Figure 8 As shown by Figure 8 It can be seen that the obtained Cu-MOF materials all have a three-dimensional nanorod morphology, indicating that after the reaction atmosphere is replaced with hydrogen, no Cu-MOF material with a two-dimensional nanosheet morphology can be obtained.

[0093] Comparative Example 3

[0094] The difference from Example 1 is that the type of gas in syringe C is different. In this comparative example, high-purity carbon dioxide is used instead of high-purity oxygen, and Cu-MOF material is finally obtained.

[0095] The scanning electron microscope (SEM) images of the Cu-MOF material prepared in this comparative example are as follows: Figure 9 As shown by Figure 9It can be seen that the obtained Cu-MOF materials all have a three-dimensional nanorod morphology, indicating that after the reaction atmosphere is replaced with carbon dioxide, no Cu-MOF material with a two-dimensional nanosheet morphology can be obtained.

[0096] Comparative Example 4

[0097] The difference from Example 1 is that the type of gas in syringe C is different. In this comparative example, high-purity air is used instead of high-purity oxygen to finally obtain Cu-MOF material.

[0098] The scanning electron microscope (SEM) images of the Cu-MOF material prepared in this comparative example are as follows: Figure 10 As shown by Figure 10 It can be seen that the obtained Cu-MOF material has a special morphology of two-dimensional nanosheets grown on three-dimensional nanorods, which means that after replacing the reaction atmosphere with air, no pure Cu-MOF material with two-dimensional nanosheet morphology can be obtained.

[0099] Application Examples

[0100] The Cu-MOF materials prepared in Examples 2-6 and Comparative Examples 1-4 were used for a CO2 electrocatalytic reduction reaction, comprising the following steps:

[0101] Step 1: 5 mg of catalyst and 50 μL of Nafion (5 wt.%) were dispersed in 150 μL of water and 300 μL of ethanol, and ultrasonicated for 30 min to form a homogeneous slurry. The slurry was then sprayed onto carbon paper and dried at room temperature to serve as the working electrode.

[0102] In step 2, the reaction was carried out in a flow cell with a 1M KOH solution as the electrolyte, which was added to the cathode and anode chambers using a peristaltic pump. The product gas composition was analyzed using an online gas chromatograph (GC) from Shimadzu Instruments Co., Ltd., Japan. Qualitative and quantitative analysis of the product gases was performed using a flame ionization detector (FID) and a thermal conductivity detector (TCD). The results are shown in Table 1.

[0103] Table 1 CO2 electrocatalytic reduction reaction performance of Cu-MOF materials of Example and Comparative Example

[0104]

[0105] Comparison of the hydrogenation reduction results above demonstrates that the Cu-MOF material with a two-dimensional nanosheet structure prepared in the present invention exhibits strong reactivity, far exceeding the reactivity of the catalyst used in the comparative example. The rich wrinkled structure of the two-dimensional Cu-MOF nanosheets prepared in the present invention facilitates the exposure of catalytically active sites, promotes the diffusion of reactant molecules within the material, and accelerates the adsorption and activation of reactant molecules at the catalytically active sites, thereby enhancing the catalytic activity of the catalyst.

[0106] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A continuous synthesis method of two-dimensional Cu-MOF nanosheets, characterized in that: The steps include: Assembling a microfluidic pneumatic continuous reaction device, the microfluidic pneumatic continuous reaction device comprising syringe A, syringe B, syringe C, a reaction tube, a mixer, a heating device, and a collecting device, syringe A being pre-filled with a metal copper salt solution, syringe B being pre-filled with an organic ligand solution, and syringe C being pre-filled with oxygen; the purity of the oxygen being above 99.999%; The copper salt solution in syringe A and the organic ligand solution in syringe B are mixed in a mixer to obtain a reaction solution. The reaction solution flows continuously in a reaction tube. The oxygen in syringe C is used to cut the continuously flowing reaction solution into slugs of uniform size. The slugs are the reaction micro-locations. The slugs in the reaction tube flow through a heating device with a set temperature, and the product is collected by a collecting device. The ratio of the fluid flow rates in syringes A, B, and C is 1:1:(12-20); The thickness of the two-dimensional Cu-MOF nanosheet is 3-5 nm.

2. The continuous synthesis method according to claim 1, wherein In the microfluidic pneumatic continuous reaction device, syringe A and syringe B are respectively connected to a mixer, the mixer and the collection device are connected through a reaction tube, a heating device is provided between the mixer and the collection device, and the reaction tube passes through the heating device; syringe C is connected to the reaction tube, and the connection between syringe C and the reaction tube is located between the mixer and the heating device; further, the microfluidic pneumatic continuous reaction device also includes a tee, and syringe C is connected to the reaction tube through the tee.

3. The continuous synthesis method according to claim 2, wherein The reaction tube is a transparent polytetrafluoroethylene hose.

4. The continuous synthesis method according to claim 2, wherein The reaction tube has an inner diameter of 1-3 mm and an outer diameter of 2-4 mm, and the difference between the outer diameter and the inner diameter is greater than 0.5 mm.

5. The continuous synthesis method according to claim 1, wherein The metal copper salt is selected from any one of copper nitrate, copper acetate, copper chloride, copper sulfate and copper carbonate; and the organic ligand is selected from any one of fumaric acid, benzoic acid, terephthalic acid, trimesic acid and 2,5-dihydroxyterephthalic acid.

6. The continuous synthesis method according to claim 1, wherein The solvent of the metal copper salt solution is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, acetone, formic acid, methanol, ethanol, and water; the solvent of the organic ligand solution is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, acetone, formic acid, methanol, ethanol, and water.

7. The continuous synthesis method according to claim 6, wherein The concentration of the metal copper salt solution is 0.02-1 mol / L; the concentration of the organic ligand solution is 0.02-1 mol / L.

8. The continuous synthesis method according to claim 1, wherein The fluid flow rate in syringe A was 40-200 μL / min, the fluid flow rate in syringe B was 40-200 μL / min, and the fluid flow rate in syringe C was 290-1200 μL / min.

9. The continuous synthesis method according to claim 1, wherein include: The heating temperature of the heating device is 80-120°C.

Images