Preparation method and application of in-situ grown dual MOF Janus fractal network material

Abstract

The present invention relates to a preparation method and application of an in-situ grown dual-MOF Janus fractal network material. The specific steps include: removing the mesophyll of a leaf using an alkaline solution to obtain a vein structure; sensitizing and activating the veins before electroplating them with copper; and sequentially growing two MOFs, CuTCNQ (TCNQ = 7,7,8,8-tetracyanoquinodimethane) and CuBTC (BTC = 1,3,5-benzenetricarboxylic acid), in situ on the front and back of the copper-plated veins, forming a Janus fractal metal network with an asymmetric microstructure and differential wettability. The front of the veins is covered with hydrophobic CuTCNQ nanoneedles, while the back is covered with hydrophilic rod-shaped CuBTC. Compared to traditional bare vein structures for fog water collection, the dual-MOF Janus fractal network material prepared by the present invention can significantly improve fog water collection efficiency. The preparation process has a short cycle and can prepare a super-hydrophobic structure in one step without the need for additional low-surface-energy materials for modification. More importantly, the entire process is fluorine-free, achieving true green environmental protection.

Description

Technical Field

[0001] The present invention relates to the technical field of controllable wettability of material surfaces and interfaces, and in particular to a preparation method and application of an in-situ grown dual-MOF Janus fractal network material. Background Art

[0002] Nature has endowed humans with a variety of optimized and efficient fractal network structures, such as blood vessels, rivers, tree branches, and leaf veins. These complex fractal networks exhibit perfect self-similarity. Among them, the fractal network structure inspired by leaf veins has become one of the most classic and successful biomimetic prototypes, with enormous application potential in a wide range of fields. Leaf veins, known as the "blood vessels" and "skeleton" of plant leaves, are responsible for efficiently capturing sunlight and transporting water with minimal energy consumption. Many researchers have mimicked the structure of leaf veins for mist water collection, but most rely on 3D printing to mimic the macroscopic appearance of leaf veins rather than using the actual leaf vein structure. While the fractal network structure of leaf veins facilitates the directional transport of droplets, when collected droplets spread into a water film on the leaf veins, they cannot be transported away in a timely manner, failing to generate a fresh surface, significantly reducing the efficiency of mist water collection. Summary of the Invention

[0003] The present invention provides a preparation method and application of a Janus fractal network material with in-situ growth of dual MOFs. A Janus fractal metal network with an asymmetric microstructure and a wettability gradient is obtained by in-situ growing two different MOFs (hydrophobic CuTCNQ and hydrophilic CuBTC) on opposite sides (front and back) of a metallized leaf vein. The CuTCNQ nanoneedles are in the shape of cactus thorns. Once the mist water nucleates and grows on the top of the CuTCNQ microneedles, the condensed tiny droplets will penetrate from the hydrophobic side of the leaf vein network to the hydrophilic side under the action of the Laplace pressure difference and capillary force, and at the same time refresh the dry hydrophobic surface to carry out a new round of mist collection. Compared with the traditional bare leaf vein structure for mist water collection, this solves the problem that when the collected droplets spread into a water film on the leaf vein, the droplets cannot be transported in time and a fresh surface cannot be generated, thereby greatly reducing the collection efficiency. The method provided by the present invention further shortens the process flow, prepares the super-hydrophobic structure in one step, does not require additional low-surface-energy materials for modification, achieves fluorine-free treatment, and provides design ideas for the development of efficient and green fog water collectors.

[0004] The present invention solves the above technical problems as follows: A method for preparing an in-situ grown dual-MOF Janus fractal network material comprises the following steps:

[0005] 1) remove the mesophyll of the leaves and wash them to obtain the leaf veins;

[0006] The specific procedure is as follows: After cleaning the leaves, soak them in a mixed aqueous solution of sodium hydroxide and sodium carbonate, heat and boil for 15-20 minutes, and gently brush the mesophyll with a soft brush, leaving the veins intact. The veins are then ultrasonically removed from the leaves in deionized water to remove any remaining mesophyll. The leaves are then bleached in a 10% aqueous solution of H₂O₂ for 20-30 minutes, and rinsed with deionized water to remove the veins. The leaves are preferably Magnolia alba leaves.

[0007] 2) Place the leaf veins in a 2+ Soak in sensitizing solution for 5 to 10 minutes, rinse with deionized water, and then place in Ag-containing + After soaking in activation solution for 5 to 10 minutes and in formaldehyde solution for 5 to 10 seconds, the leaf veins with Ag nanoparticles deposited on the surface were obtained after washing with deionized water;

[0008] 3) immersing the leaf veins with Ag nanoparticles deposited on the surface in an electrolyte solution containing copper sulfate for electroplating, washing with deionized water, and then drying to obtain copper-plated leaf veins;

[0009] 4) placing the copper-plated leaf vein above the vapor formed by heating the 7,7,8,8-tetracyanoquinodimethane / acetonitrile solution, so that the 7,7,8,8-tetracyanoquinodimethane is deposited on one side of the copper-plated leaf vein to form a superhydrophobic CuTCNQ film;

[0010] The specific steps are as follows: Use high-temperature tape to secure the copper-plated leaf vein to the top of a glass culture dish. Then, place an appropriate amount of TCNQ / acetonitrile solution at the bottom of the glass culture dish. The glass culture dish is then placed on a heating plate to heat it. The instantaneous heating produces a large amount of TCNQ vapor, which reacts with the Cu on top of the glass culture dish to form CuTCNQ. Finally, a dark purple film is deposited on the front side of the copper-plated leaf vein (the back side of the copper-plated leaf vein is tightly attached to the glass culture dish, while the front side of the copper-plated leaf vein faces downward to react with the TCNQ vapor), indicating that CuTCNQ nanoneedles have successfully grown on the copper-plated leaf vein surface.

[0011] 5) The other side of the copper-plated leaf vein is then floated on a hydrophilic solution. After the reaction is completed, a hydrophilic CuBTC film is formed on the other side of the copper-plated leaf vein. After washing and drying, a Janus fractal network water-collecting material is obtained.

[0012] The purpose of this application is to process the leaves into veins and place them in the sensitizing solution to make the vein surface full of Sn. 2+ ions, after activation by the activation solution, Ag + ions are reduced to Ag nanoparticles and deposited on the surface of leaf veins, while Sn 2+ ions are oxidized to Sn 4+ The reaction during the activation process is shown below:

[0013] 2Ag+ +Sn 2+ =2Ag+Sn 4+

[0014] After copper coating leaf veins, hydrophobic / hydrophilic MOFs can be grown in situ on their surfaces, leveraging the vein's structural characteristics to achieve directional droplet transport. One side (front) of the copper-coated vein reacts with hot TCNQ vapor to form superhydrophobic CuTCNQ nanoneedles, while the other side (back) remains suspended in the target solution and reacts to form hydrophilic CuBTC, forming a Janus fractal metal network with an asymmetric microstructure and differential wettability. The CuTCNQ nanoneedles are morphologically similar to the cone-shaped spikes of cacti used for fog water collection. This thorny structure intercepts micron-sized water droplets in fog and transports them to the other side—CuBTC—via a Laplace pressure difference. CuBTC is considered an ideal adsorbent for water collection in a variety of environments, from arid to humid to foggy. Its rod-like structure has been widely used in atmospheric water harvesting. As a hydrophilic MOF, CuBTC not only rapidly collects micron-sized droplets but also accelerates the transport of these droplets.

[0015] Preferably, the step 2) contains Sn 2+ Sn in sensitizing solution 2+ The concentration is 0.12~0.14mol / L.

[0016] The Sn-containing 2+ The preparation steps of the sensitizing solution are as follows: 4 ml of 98% concentrated sulfuric acid, 3 g of stannous chloride dihydrate, and 30-40 mg of tin particles are added to 100 ml of deionized water to obtain the sensitizing solution.

[0017] Preferably, in step 2), Ag is contained + Ag in activation solution + The concentration is 0.01~0.03mol / L.

[0018] The activation solution is prepared by adding 0.3-0.5 g of silver nitrate to 100 ml of deionized water, and then adding ammonia water dropwise until the solution becomes clear to obtain the activation solution.

[0019] Preferably, in step 3), Cu 2+ The concentration is 0.03~0.05mol / L.

[0020] The electrolyte solution is prepared by adding 5g of copper sulfate pentahydrate, 20g of potassium sodium tartrate, 10g of disodium ethylenediaminetetraacetic acid, 2g of nickel chloride, and 4g of sodium hydroxide to 500ml of deionized water. The electrolysis steps are as follows: connect a leaf vein to the negative pole of a power supply and a graphite sheet to the positive pole of a power supply. Electroplate the leaf vein in the copper-containing electrolyte solution for 20-30 minutes, then remove the leaf vein and rinse with deionized water.

[0021] Preferably, in step 4), the concentration of the 7,7,8,8-tetracyanobenzoquinodimethane / acetonitrile solution is 1 mol / L.

[0022] Preferably, in step 4), the heating temperature is 170-220° C. and the heating time is 40-80 min.

[0023] Preferably, in step 5), the hydrophilic solution is a mixed water / ethanol solution of copper nitrate and trimesic acid.

[0024] Preferably, in the hydrophilic solution, the concentration of trimesic acid is 2.1 g / L, the concentration of copper nitrate is 3.4 g / L; and the volume ratio of ethanol to water is 1:7.

[0025] The mixed solution with this concentration ratio can keep the leaf veins floating on the surface of the solution and does not come into contact with or react with the CuTCNQ superhydrophobic film on the front of the leaf veins.

[0026] Preferably, in step 5), the reaction time is 90 to 120 minutes.

[0027] The application of an in-situ grown dual-MOF Janus fractal network material prepared by the method described above in the preparation of a fog water collector.

[0028] The beneficial effects of the present invention are:

[0029] 1. The process provided by the present invention is simple, the raw materials are readily available, the cost is low, and it is non-toxic and harmless;

[0030] 2. The prepared dual-MOF Janus fractal network material has significant wettability differences. The contact angle on the CuTCNQ side can reach 156.5°, the sliding angle is less than 2°, and the contact angle on the CuBTC side can reach 67.5°.

[0031] 3. The prepared dual-MOF Janus fractal network material has a high fog water collection efficiency, and its fog water collection efficiency value reaches 1.23g / cm 2 / h, compared to 0.42g / cm of the original bare veins 2 / h, the fog water collection efficiency increased by 292.9%.

[0032] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and to implement it according to the contents of the description, the following preferred embodiments of the present invention are described in detail with reference to the accompanying drawings. The specific implementation methods of the present invention are given in detail by the following embodiments and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0034] Figure 1 Flow chart for the preparation of Janus fractal network water-harvesting materials;

[0035] Figure 2 Scanning electron microscope images, contact angles, and EDS spectra of the Janus fractal network water-collecting material and its intermediates prepared in Example 1:

[0036] (a) is a scanning electron microscope image of the copper-plated leaf vein surface and its static water contact angle after step 1;

[0037] (b) is a scanning electron micrograph of the superhydrophobic CuTCNQ leaf vein surface and its static water contact angle after completing step 2;

[0038] (c) is a scanning electron micrograph of the hydrophilic CuBTC leaf vein surface and its static water contact angle after step 3;

[0039] (d) SEM image of the longitudinal section of the Janus fractal network water-collecting material and its static contact angle;

[0040] (e) EDS spectra of Cu, C, and N elements on the surface of CuTCNQ leaf veins with superhydrophobic MOF;

[0041] (f) EDS spectra of Cu, C, and O elements on the surface of CuBTC veins with hydrophilic MOF;

[0042] (g) Rolling contact angle of CuTCNQ leaf vein surface with superhydrophobic MOF;

[0043] (h) Photograph of the hydrophilic side of a water droplet falling on the prepared Janus quasi-fractal network of the dual MOF;

[0044] Figure 3 Infrared, UV-Vis, Raman, XPS, XRD spectra and TEM images of the dual-MOF Janus fractal network water-collecting material prepared in Example 1:

[0045] (a) FTIR spectra of CuTCNQ and CuBTC on the Janus fractal network surface of the dual MOF.

[0046] (b) UV absorption spectra of CuTCNQ and CuBTC on the Janus fractal network surface of the dual MOF;

[0047] (c) Raman spectra of CuTCNQ and CuBTC on the Janus fractal network surface of the dual MOF;

[0048] (d) Fine spectra of Cu 2p of CuTCNQ and CuBTC on the Janus fractal network surface of the dual MOF;

[0049] (e) XRD spectra of CuTCNQ and CuBTC on the Janus fractal network surface of the dual MOF;

[0050] (f) TEM image of CuTCNQ on the Janus fractal network surface of the dual MOF.

[0051] Figure 4 These are optical photographs corresponding to samples at different stages of the preparation process of Example 1 of the present invention: a is the exposed leaf vein after removing the mesophyll; b is the copper-plated leaf vein; c is the CuTCNQ leaf vein with superhydrophobic MOF.

[0052] Figure 5 Figure a is a diagram of the fog water collection experimental device; b is the fog water collection efficiency corresponding to the original bare leaf vein (LV) in Example 1 of the present invention, the CuTCNQ leaf vein (CT-LV) in Example 1, the CuBTC leaf vein (CB-LV) in Comparative Example 1, and the Janus leaf vein with dual MOF (J-LV) in Example 1; c is a photograph of the droplet behavior changing with time on the surface of the original bare leaf vein (LV) in Example 1 of the present invention, the CuTCNQ leaf vein (CT-LV) in Example 1, the CuBTC leaf vein (CB-LV) in Comparative Example 1, and the Janus leaf vein with dual MOF (J-LV) in Example 1 during the fog water collection process. DETAILED DESCRIPTION

[0053] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0054] Example 1

[0055] like Figure 1 As shown, this embodiment provides a method for preparing a Janus fractal network water-collecting material, and the steps are as follows:

[0056] 1) Remove the mesophyll from the leaves

[0057] This example uses natural magnolia leaves, selected for their thick main veins, high vein density, attractive shape, and appropriate size. The selected magnolia leaves are cleaned and soaked in 300ml of deionized water containing 10.5g of sodium hydroxide and 6g of sodium carbonate, heated and boiled for 15-20 minutes. Remove and rinse thoroughly, then use a soft brush to gently brush away the mesophyll, leaving the veins intact. The leaf veins are then placed in deionized water and ultrasonically removed. The leaf veins are then bleached in a 10% H₂O₂ aqueous solution for 20-30 minutes, followed by a thorough rinse with deionized water.

[0058] 2) Preparation of leaf veins with surface-deposited Ag nanoparticles

[0059] a. Put 4ml of 98% concentrated sulfuric acid, 3g of stannous chloride dihydrate, and 30-40mg of tin particles (two particles) into 100ml of deionized water to prepare Sn-containing 2+ Sensitization solution. Soak the leaf veins in the sensitization solution for 5 to 10 minutes, then rinse with deionized water. In this step, the purpose of sensitization is to fill the leaf vein surface with Sn. 2+ ions, paving the way for the next step of activation.

[0060] b. Add 0.4g silver nitrate to 100ml deionized water and add ammonia water until the solution becomes clear to obtain Ag-containing + Activation solution. Soak the leaf veins treated in the previous step in the activation solution for 5 to 10 minutes. Then soak them in 10% formaldehyde solution for 5 to 10 seconds, and finally rinse them with deionized water. In this step, Ag + ions are reduced to Ag nanoparticles and deposited on the surface of leaf veins, while Sn 2+ ions are oxidized to Sn 4+ Ag nanoparticles are the core of electroless copper plating on leaf veins. The reaction during the activation process is shown in the following formula:

[0061] 2Ag + +Sn 2+ =2Ag+Sn 4+

[0062] 3) Electroplating leaf veins

[0063] Connect the leaf vein to the negative terminal of a power supply and the graphite sheet to the positive terminal. Add 5g of copper sulfate pentahydrate, 20g of potassium sodium tartrate, 10g of disodium ethylenediaminetetraacetic acid, 2g of nickel chloride, and 4g of sodium hydroxide to 500ml of deionized water to create an electrolyte solution. To improve the conductivity of the leaf veins during electroplating, wrap a layer of conductive copper paste around the petiole. Furthermore, to ensure a uniform and dense copper coating on the leaf veins, set the current to 0.1A. Electroplate the leaf veins in the copper plating solution for 20-30 minutes. Remove the leaf veins and rinse with deionized water.

[0064] 4) In situ growth of superhydrophobic MOF—CuTCNQ—on copper-plated leaf veins

[0065] The copper-plated leaf veins were cleaned with hydrochloric acid, deionized water, acetone, and ethanol in sequence, and then dried with nitrogen. (The cleaned and dried leaf veins should react immediately to minimize their oxidation time, otherwise a layer of CuO will form on the surface of the copper-plated leaf veins, affecting the next reaction.) The copper-plated leaf veins were taped to the top of the inner surface of a glass culture dish with high-temperature tape, and 5 to 10 ml of a 1M TCNQ / acetonitrile solution was placed at the bottom of the glass culture dish. Finally, the dish was heated at 220°C for 40 minutes to deposit TCNQ on the upper surface of the copper-plated leaf veins (the back of the copper-plated leaf veins was tightly attached to the glass culture dish, and the front of the copper-plated leaf veins faced downward to react with the TCNQ vapor), forming a CuTCNQ film. This yielded a CuTCNQ leaf vein with a superhydrophobic MOF.

[0066] 5) In situ growth of a hydrophilic MOF, CuBTC, on copper-plated leaf veins

[0067] Solution A was prepared by dissolving 0.168g of BTC in 10ml of anhydrous ethanol, and Solution B was prepared by dissolving 0.35g of copper nitrate trihydrate in 70ml of deionized water. Solutions A and B were then mixed to form Solution C. The CuTCNQ leaf vein from the previous step was floated on Solution C and reacted at room temperature for 120 minutes. While placing the CuTCNQ leaf vein on Solution C, the vein was gently pressed with tweezers to ensure that the underside of the vein was fully exposed to the reaction, while the front side was fully exposed to air. After the reaction was complete, the underside of the leaf vein was exposed to deionized water and floated in deionized water. The vein was gently shaken with tweezers to remove any unreacted surface material, and then dried in a 60°C oven for 5-10 minutes. This resulted in a dual-MOF Janus fractal network water-harvesting material with an asymmetric microstructure and differential wettability.

[0068] Comparative Example 1

[0069] This comparative example provides a CuBTC leaf vein with a super-hydrophilic MOF on its surface. The preparation steps are exactly the same as steps 1-3 of Example 1, except that after the leaf vein is copper-plated, the copper-plated leaf vein is directly immersed in the mixed solution C described in step 5 of Example 1 and reacted at room temperature for 4 hours to obtain a leaf vein with a hydrophilic CuBTC film.

[0070] The morphology of Example 1 and its intermediate product was analyzed, and the results were as follows: Figure 2 As shown. It can be found that after the copper-plated leaf veins react with TCNQ / acetonitrile solution, a fluffy needle-like structure will grow on the surface ( Figure 2b). The enlarged image shows that this structure is composed of disordered nanoneedles, resulting in increased surface roughness, which leads to a static contact angle of 156.5°. At this point, the leaf veins can stably float on the water surface. By adjusting the ratio of anhydrous ethanol and deionized water in solution C, the CuTCNQ leaf veins can be floated on solution C, causing the back of the leaf veins to react with BTC to form hydrophilic CuBTC. The static contact angle of the hydrophilic surface reaches 67.5° ( Figure 2 c). The front of the leaf vein exposed to air does not react with solution C and still maintains the superhydrophobicity of CuTCNQ. Finally, a Janus quasi-fractal metal network of dual MOFs with asymmetric microstructure and different wettability is obtained. Figure 2 Figure d shows that the upper surface of the leaf vein is superhydrophobic, while the lower surface is hydrophilic. Figure h shows the difference in wettability of the Janus quasi-fractal network of the dual-MOF prepared in Example 1. When a water droplet lands on the hydrophilic surface and then uses it as the lower surface, placed parallel to the ground, the droplet remains trapped under gravity. In this case, the upper surface is superhydrophobic, preventing the droplet from lingering and rolling down. Figure 2 e and f are the EDS spectra of the corresponding elements of CuTCNQ and CuBTC, respectively, which demonstrate the successful in situ growth of CuTCNQ and CuBTC.

[0071] like Figure 3 As shown, infrared, UV-Vis, Raman, XPS, XRD characterization tests and TEM images further proved that CuTCNQ and CuBTC were successfully grown on the leaf vein surface.

[0072] like Figure 4 As shown, Figures ac are optical photographs of leaf veins corresponding to different operation steps in Example 1, namely bare leaf veins, copper-plated leaf veins and CuTCNQ leaf veins.

[0073] like Figure 5 As shown, in a closed space, the relative humidity was controlled at approximately 90%, and the mist flow velocity was set to 0.4-0.5 m / s. Figure c shows the nucleation, accumulation, and directional transport of droplets on the surfaces of the original leaf veins in Example 1, the CuTCNQ leaf veins in Example 1, the CuBTC leaf veins in Comparative Example 1, and the Janus leaf veins with dual MOFs in Example 1. After a mist collection test with three cycles every 15 minutes, the mist collection efficiency of the Janus leaf veins with dual MOFs reached 1.23 g / cm 2 / h, compared to 0.42g / cm of the original bare veins 2 / h, the fog water collection efficiency increased by 292.9%.

[0074] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any ordinary technician in this industry can smoothly implement the present invention as shown in the drawings and described above. However, any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the scope of the technical solution of the present invention using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing an in-situ grown dual-MOF Janus fractal network material, characterized in that: The following steps are involved: 1) removing the mesophyll of Magnolia grandiflora leaves and washing them to obtain the leaf veins; 2) Place the leaf veins in a 2+ Soak in sensitizing solution, rinse with deionized water, and then place in Ag-containing + After soaking in activation solution and formaldehyde solution and washing with deionized water, leaf veins with Ag nanoparticles deposited on the surface were obtained; 3) immersing the leaf veins with Ag nanoparticles deposited on the surface in an electrolyte solution containing copper sulfate for electroplating, washing with deionized water and then drying to obtain copper-plated leaf veins; 4) placing the copper-plated leaf vein above the vapor formed by heating the 7,7,8,8-tetracyanoquinodimethane / acetonitrile solution, so that the 7,7,8,8-tetracyanoquinodimethane is deposited on one side of the copper-plated leaf vein to form a superhydrophobic CuTCNQ film; 5) The other side of the copper-plated leaf vein is then floated on a mixed water / ethanol solution of trimesic acid / copper nitrate. After the reaction is completed, a hydrophilic CuBTC film is formed on the other side of the copper-plated leaf vein. After washing and drying, a Janus fractal network water-collecting material is obtained.

2. The method for preparing an in-situ grown dual-MOF Janus fractal network material according to claim 1, characterized in that: In the step 2), Sn 2+ Sn in sensitizing solution 2+ The concentration is 0.12~0.14mol / L.

3. The method for preparing an in-situ grown dual-MOF Janus fractal network material according to claim 1, characterized in that: In the step 2), Ag + Ag in activation solution + The concentration is 0.01~0.03mol / L.

4. The method for preparing an in-situ grown dual-MOF Janus fractal network material according to claim 1, characterized in that: In the step 3), Cu in the electrolyte solution 2+ The concentration is 0.03~0.05mol / L.

5. The method for preparing an in-situ grown dual-MOF Janus fractal network material according to claim 1, characterized in that: In the step 4), the concentration of the 7,7,8,8-tetracyanobenzoquinodimethane / acetonitrile solution is 1 mol / L.

6. The method for preparing an in-situ grown dual-MOF Janus fractal network material according to claim 1, characterized in that: In the step 4), the heating temperature of the 7,7,8,8-tetracyanobenzoquinodimethane / acetonitrile solution is 170-220° C. and the heating time is 40-80 minutes.

7. The method for preparing an in-situ grown dual-MOF Janus fractal network material according to claim 1, characterized in that: In the step 5), the concentration of trimesic acid is 2.1 g / L, the concentration of copper nitrate is 3.4 g / L; and the volume ratio of ethanol to water is 1:

7.

8. The method for preparing an in-situ grown dual-MOF Janus fractal network material according to claim 1, characterized in that: In the step 5), the reaction time is 90 to 120 minutes.

9. Use of the Janus fractal network material prepared by the method according to claims 1-8 in fog water collection.

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