A method for macro-scale preparation of three-dimensional hollow ZIF-L nanoframes

Abstract

The application discloses a method for macro-preparing three-dimensional hollow ZIF-L nanoframes. The method selects a ZIF synthesis solution with a surfactant regulation, and three-dimensional hollow ZIF-L nanoframes with uniform morphology can be prepared by dropping mother liquor to a hydrophobic film and naturally air-drying. The method is simple in process, and raw materials are cheap and easy to obtain. The ZIF-L nanoframes synthesized by the method are uniform in size, and the method can realize single-batch preparation of grams of the ZIF-L nanoframes, and is favorable for the large-scale production and application of the material.

Description

Technical Field

[0001] This invention relates to a method for the mass production of three-dimensional hollow ZIF-L nanoframeworks, belonging to the field of nanomaterial preparation technology. Background Technology

[0002] Metal-organic frameworks (MOFs) are porous, multifunctional materials composed of inorganic building blocks linked by organic linkers. Zeolite imidazole ester frameworks (ZIFs) are a subclass of the MOF family, consisting of planar tetrahedral metal ion nodes and imidazole ligands. ZIF-L, a member of the ZIF family, exhibits strong chemical stability, maintaining its structural integrity and functionality across a wide temperature and pH range, enabling stable operation in various environments. Furthermore, its structure is tunable, allowing for adjustments and modifications by selecting different metal and organic ligands to achieve diverse properties and functions. These unique properties have led to its widespread application in numerous fields such as gas separation, catalysis, and energy conversion.

[0003] However, traditional ZIF-L morphologies are two-dimensional nanosheets. Two-dimensional structures typically have small pore sizes and areas, limiting their capabilities in applications such as adsorption, separation, and storage. In contrast, three-dimensional structures generally possess richer pore structures and larger specific surface areas, capable of accommodating more molecules and ions. Furthermore, the hollow structure provides a large surface area for contacting the substances to be adsorbed, thereby increasing the efficiency and capacity of adsorption and separation. Therefore, the ability to prepare three-dimensional hollow ZIF-L and achieve large-scale production of three-dimensional hollow ZIF-L would have broader application prospects. Summary of the Invention

[0004] The purpose of this invention is to provide a method for the mass production of three-dimensional hollow ZIF-L nanoframeworks.

[0005] The technical solution for achieving the objective of this invention is as follows: A method for large-scale fabrication of three-dimensional hollow ZIF-L nanoframeworks, comprising:

[0006] Step 1: Dissolve the transition metal salt and surfactant in deionized water, add the above solution to the ligand solution, stir for a period of time to obtain a mixed solution of the three, and let it settle at room temperature;

[0007] Step 2: Remove the supernatant and drop the mother liquor onto the hydrophobic membrane;

[0008] Step 3: After the droplets have dried, scrape off the sample from the hydrophobic film and grind it to obtain ZIF-L nanoframework powder sample.

[0009] Furthermore, in step 1, the transition metal salt is one or both of zinc salt and cobalt salt, the surfactant is hexadecyltrimethylammonium bromide, and the ligand is 2-methylimidazole.

[0010] Further, in step 1, the molar ratio of surfactant to metal ion is (1:30) to (1:180); the molar ratio of transition metal salt to 2-methylimidazole is (1:30) to (1:70).

[0011] Furthermore, in step 1, the stirring time is 5 to 60 minutes.

[0012] Furthermore, in step 2, the amount of supernatant removed is 50% to 85% of the total volume; the amount of mother liquor added per square centimeter of hydrophobic membrane is 160 μL to 200 μL.

[0013] Furthermore, in step 2, the hydrophobic membrane is any one of polypropylene membrane, polyethylene terephthalate membrane, polyimide membrane, and polytetrafluoroethylene membrane.

[0014] Furthermore, in step 3, the drying time is 18h-24h.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] (1) This invention realizes the preparation of three-dimensional hollow ZIF-L nanoframeworks.

[0017] (2) This invention can prepare three-dimensional hollow ZIF-L nanoframeworks on a large scale, and can prepare gram-level ZIF-L nanoframeworks in one go.

[0018] (3) The process of the present invention is simple and the steps are easy to implement. Attached Figure Description

[0019] Figure 1 Scanning electron microscope image of the ZIF-L nanoframework prepared for Example 1.

[0020] Figure 2 Scanning electron microscope image of ZIF-67 nanocubes prepared for comparison Example 1.

[0021] Figure 3 This is a schematic diagram of the synthesis method.

[0022] Figure 4 Scanning electron microscope image of the ZIF-L two-dimensional nanosheets prepared for comparison Example 2.

[0023] Figure 5 Scanning electron microscope image of the ZIF-L two-dimensional nanosheets prepared for comparison Example 3.

[0024] Figure 6XRD patterns of samples prepared for Example 1 and Comparative Example 4.

[0025] Figure 7 Scanning electron microscope image of the sample prepared for comparison example 4.

[0026] Figure 8 Field preparation diagrams for implementation example 1 and comparative example 4. Detailed Implementation

[0027] To better understand the technical content of this invention, specific embodiments are described below.

[0028] Combination Figure 3 The method for mass-producing three-dimensional hollow ZIF-L nanoframeworks according to the present invention includes the following steps:

[0029] Step 1: Dissolve the transition metal nitrate and surfactant in deionized water, add the above solution to the ligand solution, stir for a period of time to obtain a mixed solution of the three, and let it settle at room temperature;

[0030] Step 2: Remove the supernatant and drop the mother liquor onto the hydrophobic membrane;

[0031] Step 3: After the droplets have dried, scrape off the sample from the hydrophobic film and grind it to obtain ZIF-L nanoframework powder sample.

[0032] Implementation Example 1

[0033] 1) Dissolve 10 mmol of cobalt nitrate hexahydrate and 0.06 mmol of hexadecyltrimethylammonium bromide in 100 mL of deionized water and stir well. Add 540 mmol of 2-methylimidazole to 700 mL of deionized water and stir well. Mix the two together and stir for 1 h, then let stand at room temperature for 24 h.

[0034] 2) Remove the supernatant and use a pipette to transfer 160 μL of the mother liquor onto a 1 square centimeter polypropylene hydrophobic membrane at room temperature.

[0035] 3) After the droplets have dried, scrape the sample off the polypropylene hydrophobic film and grind it to obtain a powder sample (e.g., Figure 8 The sample was weighed and found to be approximately 1.2g, confirming that gram-level production is achievable.

[0036] Figure 1 The image shown is a scanning electron microscope (SEM) image of the sample prepared in Example 1. Figure 1 The sample morphology can be seen to be a hollow framework composed of twelve interconnected edges. Each edge is composed of coordination compounds of metal ions and organic ligands, and the morphology is regular and evenly distributed.

[0037] Implementation Example 2

[0038] 1) Dissolve 10 mmol of cobalt nitrate hexahydrate and 0.06 mmol of hexadecyltrimethylammonium bromide in 100 mL of deionized water and stir well. Add 540 mmol of 2-methylimidazole to 700 mL of deionized water and stir well. Mix the two together and stir for 1 h, then let stand at room temperature for 24 h.

[0039] 2) Remove the supernatant and use a pipette to transfer 200 μL of the mother liquor at room temperature onto a 1 square centimeter polypropylene hydrophobic membrane each time.

[0040] 3) After the droplets dried, the sample on the polypropylene hydrophobic film was scraped off and ground. Scanning electron microscopy confirmed that the sample morphology was a hollow framework composed of twelve interconnected edges, indicating that a three-dimensional hollow nanoframework sample could still be obtained even with a larger droplet amount.

[0041] Implementation Example 3

[0042] 1) Dissolve 10 mmol of zinc nitrate hexahydrate and 0.06 mmol of cetyltrimethylammonium bromide in 100 mL of deionized water and stir well. Add 540 mmol of 2-methylimidazole to 700 mL of deionized water and stir well. Mix the two together and stir for 1 h, then let stand at room temperature for 24 h.

[0043] 2) Remove the supernatant and use a pipette to transfer 200 μL of the mother liquor onto a 1 square centimeter polyethylene terephthalate hydrophobic membrane at room temperature.

[0044] 3) After the droplets dried, the sample on the polyethylene terephthalate hydrophobic film was scraped off and ground. Scanning electron microscopy confirmed that the sample morphology was a hollow framework composed of twelve interconnected edges, indicating that even with a larger droplet amount, a three-dimensional hollow nanoframework sample could still be obtained by replacing the polyethylene terephthalate hydrophobic film.

[0045] Comparison Example 1

[0046] Dissolve 10 mmol of cobalt nitrate hexahydrate and 0.06 mmol of hexadecyltrimethylammonium bromide in 100 mL of deionized water and stir well. Add 540 mmol of 2-methylimidazole to 700 mL of deionized water and stir well. Mix the two solutions and stir for 1 h, then let stand at room temperature for 24 h.

[0047] Remove the supernatant, centrifuge the remaining mother liquor in a high-speed centrifuge, and wash it three times with anhydrous ethanol.

[0048] The centrifuged sample was dried in a vacuum drying oven at 60°C for 24 hours.

[0049] Figure 2To compare the scanning electron microscope image of the sample prepared in Example 1, from Figure 2 The results show that the sample morphology is a nanocube, indicating that the sample prepared by conventional methods cannot obtain a three-dimensional hollow nanoframework morphology but instead obtains a nanocube morphology.

[0050] Comparison Example 2

[0051] Dissolve 10 mmol of cobalt nitrate hexahydrate and 0.06 mmol of hexadecyltrimethylammonium bromide in 100 mL of deionized water and stir well. Add 80 mmol of 2-methylimidazole to 700 mL of deionized water and stir well. Mix the two solutions and stir for 1 h, then let stand at room temperature for 24 h.

[0052] Remove the supernatant, centrifuge the remaining mother liquor in a high-speed centrifuge, and wash it three times with anhydrous ethanol.

[0053] The centrifuged sample was dried in a vacuum drying oven at 60°C for 24 hours.

[0054] Figure 4 Scanning electron micrographs of the sample prepared for comparison example 2, from Figure 4 The sample morphology can be seen to be two-dimensional nanosheets, indicating that when the ratio of transition metal salt and ligand is not within the appropriate range, a three-dimensional hollow nanoframework morphology cannot be obtained, but a two-dimensional nanosheet morphology is obtained instead.

[0055] Comparison Example 3

[0056] 1) Dissolve 10 mmol of cobalt nitrate hexahydrate and 0.06 mmol of hexadecyltrimethylammonium bromide in 100 mL of deionized water and stir well. Add 80 mmol of 2-methylimidazole to 700 mL of deionized water and stir well. Mix the two together and stir for 1 h. Let stand at room temperature for 24 h.

[0057] 2) Remove the supernatant and use a pipette to transfer 160 μL of the mother liquor onto a 1 square centimeter polypropylene hydrophobic membrane at room temperature.

[0058] 3) After the droplets have dried, scrape off the sample from the polypropylene hydrophobic membrane and grind it to obtain two-dimensional leaf-shaped ZIF-L nanosheets.

[0059] Figure 5 To compare the scanning electron microscope (SEM) images of the sample prepared in Example 3, from... Figure 5 As can be seen, the sample morphology is still a two-dimensional nanosheet, indicating that when the ratio of cobalt nitrate hexahydrate and 2-methylimidazole ligand is not within the appropriate range, even if it is dropped onto a hydrophobic film, a three-dimensional hollow ZIF-L nanoframework cannot be obtained.

[0060] Comparison Example 4

[0061] 1) Dissolve 10 mmol of cobalt nitrate hexahydrate and 0.06 mmol of hexadecyltrimethylammonium bromide in 100 mL of deionized water and stir well. Add 540 mmol of 2-methylimidazole to 700 mL of deionized water and stir well. Mix the two together and stir for 1 h, then let stand at room temperature for 24 h.

[0062] 2) Remove the supernatant and use a pipette to transfer 10 μL of the mother liquor onto a 1 square centimeter silicon wafer at room temperature. Experiments showed that the silicon wafer surface could not withstand a larger amount of liquid added.

[0063] 3) After the droplets have dried, scrape the sample off the silicon wafer and grind it to obtain a small amount of three-dimensional hollow ZIF-L nanoframework powder sample (e.g. Figure 8 After weighing, the obtained three-dimensional hollow ZIF-L nanoframework was only in the milligram range.

[0064] Figure 6 To compare the XRD patterns of the samples prepared in Example 4 and Example 1, by Figure 6 It can be seen that the crystal structure of the sample did not change when dropped onto different substrates.

[0065] Figure 7 To compare the scanning electron microscope images of Example 4, by Figure 7 It can be seen that a three-dimensional hollow nanoframework structure can also be obtained by dropping it onto a silicon wafer.

[0066] Depend on Figure 8 It is known that mass production (gram-level) can be achieved by dropping the drop onto a hydrophobic film, but mass production cannot be achieved by dropping the drop onto a silicon wafer (hydrophilic substrate) instead of a hydrophobic film.

Claims

1. A method for macro-scale preparation of three-dimensional hollow ZIF-L nanoframes, characterized in that, The application relates to a method for preparing a ZIF-L nanoframe powder sample. The method comprises the following steps: Step 1, dissolving a transition metal salt and a surfactant in deionized water, adding the solution into a ligand solution, stirring for a period of time, and obtaining a mixed solution of the three, and then settling at room temperature; Step 2, removing supernatant, and dropping the mother liquor onto a hydrophobic film; Step 3, after the liquid drops are dried, scraping off the sample on the hydrophobic film and grinding to obtain a ZIF-L nanoframe powder sample; The molar ratio of the transition metal salt to 2-methylimidazole is (1:30)-(1:70); 2. The method of claim 1, wherein, The hydrophobic film is any one of a polypropylene film, a polyethylene terephthalate film, a polyimide film and a polytetrafluoroethylene film.

3. The method of claim 1, wherein, In step 1, the transition metal salt is one or both of a zinc salt and a cobalt salt, the surfactant is hexadecyl trimethyl ammonium bromide, and the ligand is 2-methylimidazole.

4. The method of claim 1, wherein, In step 1, the molar ratio of the surfactant to the metal ion is (1:30)-(1:180).

5. The method of claim 1, wherein, In step 1, the stirring time is 5-60 min.

6. The method of claim 1, wherein, In step 2, the amount of removed supernatant is 50%-85% of the total volume; and the amount of the mother liquor added per square centimeter of the hydrophobic film is 160 muL-200 muL.

7. The three-dimensional hollow ZIF-L nanoframework prepared according to the method of any one of claims 1-6. In step 3, the drying time is 18h-24h. The ZIF-L nanoframe powder sample has a three-dimensional hollow structure.

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