Copper foam surface coating as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of composite coatings, and particularly relates to a copper foam surface coating and a preparation method and application thereof. The preparation method comprises the steps that pretreated copper foam is soaked in a mixed solution composed of deionized water, sodium hydroxide and ammonium persulfate to be activated, and activated copper foam is obtained; the activated copper foam is immersed in a trimesic acid solution, and a light blue Cu-coated Cu3 (BTC) 2 functional layer is obtained on the surface of the copper foam; and immersing the copper foam of which the surface is covered with the Cu-coated Cu3 (BTC) 2 functional layer into a silane solution to finish the construction of the copper foam surface coating. A Cu-coated Cu3 (BTC) 2 heterostructure is constructed on the surface of a copper foam framework through bionic design to provide hydrophilic sites, then silane selective modification is adopted to achieve surface wettability gradient regulation and control to provide a hydrophobic area to more efficiently collect water, and therefore hydrophilic adsorption and hydrophobic transportation are coordinated to improve the water collection efficiency.

Description

Technical Field

[0001] This invention belongs to the field of composite coating technology, specifically relating to a copper foam surface coating, its preparation method, and its application. Background Technology

[0002] Freshwater scarcity has become a major challenge hindering global sustainable development, particularly in arid and semi-arid regions. Atmospheric water harvesting technology, as a novel method of water acquisition, has attracted significant attention due to its low energy consumption and environmentally friendly characteristics. In nature, many organisms with unique characteristics have evolved optimized structures to extract freshwater from the atmosphere.

[0003] In recent years, significant progress has been made in the research of mist collection materials based on biomimetic principles. Among them, copper foam materials are considered ideal water collection substrate materials due to their unique three-dimensional porous structure, high specific surface area, and good mechanical properties. However, existing copper foam-based water collection technologies still face the following problems:

[0004] Traditional copper foam water-collecting materials often employ a single hydrophilic or hydrophobic modification strategy, making it difficult to achieve synergistic optimization of droplet capture and water desorption. The functional coatings prepared by existing modification methods are mostly physically adsorbed or weakly chemically bonded to the copper foam substrate, which are prone to detachment, peeling, or wear under long-term use or mechanical friction, leading to a sharp decline in water-collecting performance. Some modified materials are susceptible to aging, degradation, or wettability changes under environmental factors such as ultraviolet radiation and temperature and humidity variations, resulting in unstable water-collecting performance. Furthermore, the interfacial bonding strength between some functional materials and the substrate is insufficient, making them prone to swelling or interfacial failure in humid environments, further exacerbating durability issues.

[0005] Therefore, developing a new copper foam surface coating is of great significance. Summary of the Invention

[0006] The technical problem to be solved by this invention is to provide a novel atmospheric water harvesting material that is efficient, stable, and suitable for arid regions, addressing the shortcomings of existing technologies. Through biomimetic design, a Cu@Cu3(BTC)2 heterostructure is constructed on the surface of a copper foam framework to provide hydrophilic sites. Subsequently, selective modification with silane is used to achieve surface wettability gradient regulation, providing hydrophobic regions for more efficient water harvesting. This synergistic effect of hydrophilic adsorption and hydrophobic transport enhances water collection efficiency.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] The first aspect of the present invention provides a copper foam surface coating, wherein the copper foam surface coating is a silane-modified Cu@Cu3(BTC)2 heterostructure.

[0009] The Cu@Cu3(BTC)2 heterostructure provides hydrophilic sites, and the silane modification provides hydrophobic regions, thereby realizing a Cu@Cu3(BTC)2@silane coating with a superhydrophobic-hydrophilic gradient structure.

[0010] The second aspect of the present invention provides a method for preparing a copper foam surface coating, comprising the following steps: activating a pretreated copper foam by immersing it in a mixed solution of deionized water, sodium hydroxide, and ammonium persulfate to obtain an activated copper foam; immersing the activated copper foam in a trimesic acid solution to obtain a light blue Cu@Cu3(BTC)2 functional layer on the surface of the copper foam; and immersing the copper foam with the Cu@Cu3(BTC)2 functional layer on its surface in a silane solution to complete the construction of the copper foam surface coating.

[0011] In some embodiments of the present invention, the pretreated copper foam is obtained by ultrasonically cleaning the cut copper foam with deionized water and ethanol in sequence to remove surface dust, and then drying the cleaned copper foam in a vacuum oven at 60°C for 12 h.

[0012] The concentration of sodium hydroxide in the mixed solution is 0.2 g / mL, and the concentration of ammonium persulfate is 0.855 g / mL; the molar ratio of sodium hydroxide to ammonium persulfate is 4:3.

[0013] The pretreated copper foam is immersed in the mixed solution for 20 minutes.

[0014] The concentration of the pyromellitic acid solution is 0.0102 g / mL; the solvent of the pyromellitic acid solution is anhydrous ethanol.

[0015] The activated copper foam is immersed in pyromellitic acid solution for 30 minutes.

[0016] The silane solution is a hexadecyltrimethylsilane solution; the concentration of the hexadecyltrimethylsilane solution is 20.2 wt%.

[0017] In some embodiments of the present invention, the solvent for the hexadecyltrimethylsilane solution is anhydrous ethanol.

[0018] The copper foam with a Cu@Cu3(BTC)2 functional layer on its surface is immersed in silane solution for 0.5 to 1 hour.

[0019] In some embodiments of the present invention, the copper foam with a Cu@Cu3(BTC)2 functional layer on its surface is immersed in a silane solution for 0.5 h.

[0020] A third aspect of the present invention provides an application of a copper foam surface coating in the collection of mist.

[0021] In some embodiments of the present invention, a Cu@Cu3(BTC)2@silane coating was successfully constructed on the surface of copper foam using the above preparation method. Through mist collection performance test experiments, it was shown that the coating has the best mist collection capability, demonstrating the application prospects of copper foam surface coating in mist collection.

[0022] The fourth aspect of this invention provides the application of a copper foam surface coating in the preparation of atmospheric water collection materials.

[0023] In some embodiments of the present invention, a Cu@Cu3(BTC)2@silane coating was successfully constructed on the surface of copper foam using the above preparation method. Through fog collection performance test combined with friction mechanical property verification test of the coating, it was shown that the Cu@Cu3(BTC)2@silane coating has excellent mechanical toughness and environmental adaptability, and can meet the requirements for long-term stable operation in harsh environments with frequent sandstorms, thus proving the application of copper foam surface coating in the preparation of atmospheric water collection materials.

[0024] Beneficial effects:

[0025] Compared to existing technologies, the Cu@Cu3(BTC)2@silane coating prepared in this invention successfully constructs a robust hydrophilic-hydrophobic gradient structure by in-situ growth of a Cu3(BTC)2 metal-organic framework on the surface of a copper foam followed by silanization modification. This structure utilizes the hydrophilic Cu3(BTC)2 layer to efficiently capture fog droplets and leverages the hydrophobic silane layer to achieve rapid water aggregation and desorption, thereby synergistically improving water collection efficiency. Simultaneously, the strong bond between the MOF and the substrate endows the coating with excellent mechanical durability, overcoming the problem of easy detachment of traditional coatings. The entire preparation process is simple and the conditions are mild, making this coating of great practical application value in addressing water shortages in arid regions. Attached Figure Description

[0026] The present invention will be further described in detail below with reference to the accompanying drawings, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0027] Figure 1 This is a flowchart illustrating the preparation process of the copper foam surface coating in this embodiment of the invention.

[0028] Figure 2 The Fourier transform infrared spectra of Cu, Cu(OH)2, Cu@Cu3(BTC)2 and Cu@Cu3(BTC)2@silane during the preparation process in the embodiments of the present invention are shown.

[0029] Figure 3 The images show the XRD patterns of Cu, Cu@sliane, Cu@Cu3(BTC)2 and Cu@Cu3(BTC)2@silane prepared in the embodiments of the present invention.

[0030] Figure 4 The images shown are SEM images and elemental mapping diagrams of Cu, Cu@Cu3(BTC)2, and Cu@Cu3(BTC)2@silane in the embodiments of the present invention.

[0031] Figure 5 The XPS spectra, Cu2p XPS spectra, O1s XPS spectra, and Si2p XPS spectra of Cu@Cu3(BTC)2 and Cu@Cu3(BTC)2@silane in the embodiments of the present invention are shown.

[0032] Figure 6 This is a comparison diagram of the surface superhydrophobic properties of Cu@Cu3(BTC)2 and Cu@Cu3(BTC)2@silane in the embodiments of the present invention.

[0033] Figure 7 This is a schematic diagram of the apparatus used for testing the mist collection performance in an embodiment of the present invention.

[0034] Figure 8 This is a macroscopic surface image of the Cu@Cu3(BTC)2 functional layer and the Cu@Cu3(BTC)2@silane coating during the absorption of mist vapor experiment in an embodiment of the present invention.

[0035] Figure 9 The diagram shows the mist collection efficiency of Cu, Cu@sliane coating, Cu@Cu3(BTC)2 functional layer and Cu@Cu3(BTC)2@silane coating in the embodiments of the present invention.

[0036] Figure 10 The results show the mist collection performance of the Cu@Cu3(BTC)2@silane coating at different spacings in the embodiments of the present invention.

[0037] Figure 11 The fog collection efficiency of the Cu@Cu3(BTC)2@silane coating at different temperatures in the embodiments of the present invention is shown.

[0038] Figure 12 The figures shown are experimental diagrams of tape peeling test and sand impact test of Cu@Cu3(BTC)2@silane coating in the embodiments of the present invention, and surface contact angle test diagram. Detailed Implementation

[0039] The present invention will be further described in detail below with reference to specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0040] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials described are commercially available unless otherwise specified.

[0041] Example 1:

[0042] This embodiment provides a method for preparing a coating on the surface of copper foam. Figure 1 The process flow diagram for preparing the coating on the surface of copper foam is shown, which includes the following steps:

[0043] (1) Surface activation of copper foam: Cut copper foam (Cu) into 2 cm × 2 cm pieces, and use deionized water and ethanol in sequence for ultrasonic cleaning to remove surface dust. Place the cleaned copper foam in a vacuum oven and dry it at 60 °C for 12 h. Soak the dried copper foam in a mixed solution of 40 ml deionized water, 8 g sodium hydroxide and 34.2 g ammonium persulfate for 20 min. Then clean the surface with deionized water to complete the surface activation of copper foam and obtain Cu@Cu(OH)2.

[0044] (2) In-situ growth and hydrophobic modification of the functional layer: The surface-activated copper foam was immersed in a solution of 50 ml anhydrous ethanol and 0.51 g trimesic acid for 8 min. After being taken out, it was dried at 60~80 ℃ for 30 min. A light blue Cu@Cu3(BTC)2 functional layer was obtained on the surface of the copper foam. The copper foam with the Cu@Cu3(BTC)2 functional layer was immersed in a 20.2 wt% hexadecyltrimethylsilane anhydrous ethanol solution for 30 min. Finally, a Cu@Cu3(BTC)2@silane coating with a wettability gradient structure was obtained on the surface of the copper foam.

[0045] Example 2:

[0046] This embodiment provides a method for preparing a coating on a copper foam surface, including the following steps:

[0047] The copper foam was cut into 2 cm × 2 cm pieces and ultrasonically cleaned with deionized water and ethanol in sequence to remove surface dust. The cleaned copper foam was then placed in a vacuum oven and dried at 60 °C for 12 h. The dried copper foam was then immersed in a hexadecyltrimethylsilane solution for 30 min to obtain a Cu@sliane coating on the surface of the copper foam.

[0048] Performance verification:

[0049] 1. The Cu, Cu@Cu(OH)2, Cu@Cu3(BTC)2 functional layers and Cu@Cu3(BTC)2@silane coating prepared in Example 1 were characterized using Fourier transform infrared spectroscopy. Figure 2 The Fourier transform infrared spectra of Cu, Cu@Cu(OH)2, Cu@Cu3(BTC)2, and Cu@Cu3(BTC)2@silane obtained during the preparation process in Example 1 are shown below. Figure 2 It can be seen that Cu@Cu3(BTC)2 at 728 cm⁻¹ -1 The presence of a characteristic absorption band at 1083 cm⁻¹ corresponds to the Cu-O stretching vibration of Cu₂(COO)₄, indicating that the BTC ligand is fully coordinated with the Cu center. -1 The absorption peaks that appeared changed their signal characteristics after silane modification, further demonstrating the successful recombination of silane.

[0050] 2. The Cu, Cu@sliane coating, Cu@Cu3(BTC)2 functional layer, and Cu@Cu3(BTC)2@silane coating in Examples 1 and 2 were characterized using X-ray diffraction. Figure 3 The XRD patterns of Cu, Cu@sliane, Cu@Cu3(BTC)2, and Cu@Cu3(BTC)2@silane prepared in Examples 1 and 2 are shown below. Figure 3 It can be seen that Cu3(BTC)2 crystals were successfully grown on the Cu surface. Furthermore, the attachment of silane did not change the crystal structure of Cu and Cu@Cu3(BTC)2.

[0051] 3. The Cu, Cu@Cu3(BTC)2 functional layer, and Cu@Cu3(BTC)2@silane coating in Example 1 were characterized by scanning electron microscopy. Figure 4 SEM images and elemental mappings of Cu, Cu@Cu3(BTC)2, and Cu@Cu3(BTC)2@silane are shown below. Figure 4 In the diagram, a and b are SEM images of Cu, c and d are SEM images of Cu@Cu3(BTC)2, e and f are SEM images of Cu@Cu3(BTC)2@silane, and g~i are elemental mapping images of Cu@Cu3(BTC)2@silane. Figure 4It can be seen that the Cu surface exhibits a relatively smooth network / skeleton structure, and the Cu@Cu3(BTC)2 surface is completely covered by a large amount of dense, irregular blocky or granular material. These materials exhibit a typical octahedral crystal morphology, indicating that Cu@Cu3(BTC)2 has been successfully grown on the Cu surface. The elemental mapping diagram shows that the spatial distribution of Cu, O and Si in the Cu@Cu3(BTC)2@silane sample is basically consistent, indicating that the components are well mixed and no macroscopic phase separation has occurred.

[0052] 4. The Cu@Cu3(BTC)2 functional layer and Cu@Cu3(BTC)2@silane coating in Example 1 were characterized by X-ray photoelectron spectroscopy. Figure 5 XPS spectra, Cu2p XPS spectra, O1s XPS spectra, and Si2p XPS spectra of Cu@Cu3(BTC)2 and Cu@Cu3(BTC)2@silane, where, Figure 5 In the diagram, 'a' represents the XPS full spectrum of Cu@Cu3(BTC)2 and Cu@Cu3(BTC)2@silane, 'b' represents the Cu2p XPS spectrum, 'c' represents the O1s XPS spectrum, and 'd' represents the Si2p XPS spectrum. The full spectrum (…) Figure 5 a) It can be seen that Cu2p, O1s, and Si2p signals coexist and there are no impurities. High-resolution Cu 2p spectrum ( Figure 5 In b), the Cu@Cu3(BTC)2@silane sample retained Cu 2+ Characteristic peaks (Cu 2p) 3 / 2 The peaks are located at 934.5 eV, with satellite peaks at 943.7 and 963.1 eV, indicating that the coordination environment of copper remained unchanged after modification. (O 1s spectrum) Figure 5 In (c), the binding energy of the main peak shifted slightly after silane modification (from 531.85 eV to 531.91 eV), and the Cu 2p spectrum showed that the chemical state of Cu remained unchanged. Overall, the introduction of silane did not significantly alter the coordination environment of the metal center in the MOF framework. Furthermore, a new Si 2p peak appeared at 103 eV in the Si 2p spectrum (…). Figure 5 d) Further confirmation that the silane layer has been successfully introduced.

[0053] 5. The hydrophilicity and hydrophobicity of the materials were characterized by dropping liquid droplets onto the surfaces of the Cu@Cu3(BTC)2 functional layer and the Cu@Cu3(BTC)2@silane coating in Example 1 and using a contact angle tester. Figure 6 A comparison graph showing the surface superhydrophobic properties of Cu@Cu3(BTC)2 and Cu@Cu3(BTC)2@silane, from... Figure 6It can be seen that the surface of Cu@Cu3(BTC)2 absorbs water molecules the instant it comes into contact with the droplet, thus demonstrating its hydrophilic properties. The surface of Cu@Cu3(BTC)2@silane, on the other hand, exhibits superhydrophobic properties.

[0054] 6. High-speed optical imaging technology was used to monitor the dynamic behavior of droplets on the surface of the Cu@Cu3(BTC)2 functional layer and Cu@Cu3(BTC)2@silane coating in Example 1 during the fog collection performance test experiment.

[0055] Figure 7 The diagram shows the apparatus for testing the fog collection performance. The specific experimental steps are as follows: A pre-cut sample (2 cm × 2 cm) is placed in a controlled environment chamber, positioned directly opposite the fog source outlet, with a spacing d set to 12.5 cm. The fog source is supplied with a constant current (60 ± 5.0 mL / h). -1 An ultrasonic humidifier was used, and the ambient temperature and relative humidity were stabilized at 23±2.0 ℃ and 70±3.0%, respectively. The collected moisture mass was measured using an analytical balance with an accuracy of 0.1 mg. The experimental period was 3 hours, with data read every 30 minutes, and three independent parallel experiments were repeated to ensure data reliability. The water collection rate (WCR) was calculated according to Formula 1.

[0056]

[0057] Where m t m0 and m0 represent the total mass and the initial mass of the beaker, respectively. S represents the sample surface area, and t represents the cumulative collection time.

[0058] Figure 8 Macroscopic surface images of Cu@Cu3(BTC)2 functional layer and Cu@Cu3(BTC)2@silane coating during fog absorption experiments, in which... Figure 8 In the diagram, 'a' represents the surface pattern of Cu@Cu3(BTC)2, and 'b' represents the surface pattern of Cu@Cu3(BTC)2@silane. Figure 8It is observed that on the superhydrophilic Cu@Cu3(BTC)2 surface, droplets rapidly spread and merge upon contact, forming a continuous water film covering the entire surface. This film-like condensation phenomenon blocks surface active sites, inhibiting the direct capture of subsequent droplets; simultaneously, the upward capillary force induced by uniform hydrophilicity hinders the desorption of condensed water, resulting in limited water collection efficiency. Conversely, on the Cu@Cu3(BTC)2@silane coating surface with a superhydrophobic-hydrophilic gradient structure, droplet behavior is significantly different. Droplets preferentially nucleate and grow into isolated microdroplets in the hydrophilic region, and then, driven by the surface energy gradient, migrate directionally to adjacent superhydrophobic regions and merge. This mechanism effectively avoids surface blockage, promotes continuous water capture and rapid desorption, thereby significantly improving the water collection rate.

[0059] 7. The mist collection efficiency of Cu, Cu@sliane coating, Cu@Cu3(BTC)2 functional layer and Cu@Cu3(BTC)2@silane coating in Examples 1 and 2 was characterized by mist collection performance test experiments. Figure 9 The diagram shows the mist collection efficiency of Cu, Cu@sliane coating, Cu@Cu3(BTC)2 functional layer, and Cu@Cu3(BTC)2@silane coating. Figure 9 In the graph, 'a' represents the water volume collected by mist per 30 minutes for the four samples, and 'b' is the collection efficiency per unit area. Figure 9 It can be seen that the Cu@Cu3(BTC)2@silane coating exhibits the best mist collection capability, with a collection rate of 442.5 mg / cm³ at a distance of 12.5 cm from the mist source. -2 h -1 This superior performance stems from the synergistic effect of the micro / nanostructured MOF layer and the silane coating. The MOF framework provides abundant adsorption sites to promote water vapor condensation, while the silane modification not only enhances surface hydrophobicity and accelerates droplet aggregation and expulsion, but also acts as a protective barrier to significantly improve the long-term structural stability of the MOF film in humid environments.

[0060] Example 3:

[0061] The mist collection performance of Cu@Cu3(BTC)2@silane coating under different conditions was further characterized.

[0062] 1. The distance d between the Cu@Cu3(BTC)2@silane coating and the fog source outlet was controlled to be 5 cm, 7.5 cm, 10 cm and 12.5 cm respectively, while other conditions remained unchanged, and fog collection performance test experiments were carried out. Figure 10 The results show the mist collection performance of Cu@Cu3(BTC)2@silane coatings with different spacings. Figure 10In the diagram, 'a' represents the mist collection volume at different spacings, 'b' represents the collection efficiency per unit area at different spacings, and 'c' represents the water circulation diagram when the optimal sample length 'd' = 5 cm. Figure 10 It can be seen that the water collection volume and collection rate of the Cu@Cu3(BTC)2@silane coating both show a monotonically decreasing trend with increasing collection distance. This is mainly due to the combined effect of air resistance and diffusion loss encountered by the droplets during transport. As the collection distance increases, the droplet suspension time prolongs, causing some fine droplets to evaporate or diffuse before reaching the collection surface; at the same time, the increased airflow resistance weakens the droplet kinetic energy and reduces its effective adhesion probability. Quantitative data show that the water collection volume reaches a peak of approximately 8320 mg at a distance of 5 cm, decreasing to approximately 5310 mg at 12.5 cm, a decrease of 36%; the corresponding collection rate decreases from 693 mg / cm. -2 h -1 Decreased to 442.5 mg cm -2 h -1 This indicates that fog collection performance is highly sensitive to system geometry, requiring optimization of spatial layout or the introduction of flow-guiding structures to suppress fog diffusion and thus improve collection efficiency. Furthermore, such as Figure 10 As shown in Figure c, four independent cyclic experiments were conducted under the optimal sample length d=5cm, with each cycle lasting approximately 3 hours. The four curves represent four cycles with different starting times, and their growth trends and final water collection volumes are highly consistent, indicating that the water collection performance is stable and repeatable under these conditions. The material exhibits excellent stability in multiple fog capture-regeneration cycles, with the collection rate consistently maintained above 95%.

[0063] 2. The mist collection performance of the Cu@Cu3(BTC)2@silane coating was tested by controlling the experimental temperature at 13~23 ℃. Figure 11 To determine the mist collection efficiency of the Cu@Cu3(BTC)2@silane coating at different temperatures, the following methods were used: Figure 11 It can be seen that the mass of fog collected on the surface increases significantly as the temperature rises from 13 ℃ to 23 ℃, indicating that heating is beneficial to improving the fog droplet capture efficiency.

[0064] 3. The abrasion resistance of the Cu@Cu3(BTC)2@silane coating was verified by tape peeling test and sand impact test. Figure 12 Experimental diagrams for tape peeling and sand impact tests, and surface contact angle tests, showing the Cu@Cu3(BTC)2@silane coating. Figure 12 In the diagram, 'a' represents the experimental image of the tape peel test, 'b' represents the experimental image of the sand impact test, 'c' represents the surface contact angle data of the tape peel test, and 'd' represents the surface contact angle data of the sand impact test. Figure 11As can be seen, the material maintains stable superhydrophobic properties after 100 tape peel cycles, indicating that its heterogeneous coating structure has excellent anti-adhesion and peel resistance. Further sand impact testing shows that even at 50 ms... -1 After undergoing 70 cycles of high-speed impact, the material maintained its superhydrophobic state and fog collection efficiency, with no significant performance degradation observed. These results indicate that the Cu@Cu3(BTC)2@silane coating possesses excellent mechanical toughness and environmental adaptability, meeting the requirements for long-term stable operation in harsh environments with frequent sandstorms.

[0065] This invention provides a copper foam surface coating, its preparation method, and its application. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A copper foam surface coating, characterized in that, The copper foam surface coating is a silane-modified Cu@Cu3(BTC)2 heterostructure.

2. The method for preparing the copper foam surface coating according to claim 1, characterized in that, The process includes the following steps: activating pretreated copper foam by immersing it in a mixed solution of deionized water, sodium hydroxide, and ammonium persulfate to obtain activated copper foam; immersing the activated copper foam in a trimesic acid solution to obtain a light blue Cu@Cu3(BTC)2 functional layer on the surface of the copper foam; and immersing the copper foam with the Cu@Cu3(BTC)2 functional layer on its surface in a silane solution to complete the construction of the copper foam surface coating.

3. The preparation method according to claim 2, characterized in that, The concentration of sodium hydroxide in the mixed solution is 0.2 g / mL, and the concentration of ammonium persulfate is 0.855 g / mL; the molar ratio of sodium hydroxide to ammonium persulfate is 4:

3.

4. The preparation method according to claim 3, characterized in that, The pretreated copper foam was immersed in the mixed solution for 20 minutes.

5. The preparation method according to claim 2, characterized in that, The concentration of the pyromellitic acid solution is 0.0102 g / mL; the solvent of the pyromellitic acid solution is anhydrous ethanol.

6. The preparation method according to claim 5, characterized in that, The activated copper foam was immersed in pyromellitic acid solution for 30 minutes.

7. The preparation method according to claim 2, characterized in that, The silane solution is a hexadecyltrimethylsilane solution; the concentration of the hexadecyltrimethylsilane solution is 20.2 wt%.

8. The preparation method according to claim 7, characterized in that, The copper foam with a Cu@Cu3(BTC)2 functional layer on its surface was immersed in silane solution for 0.5 to 1 hour.

9. The application of the copper foam surface coating of claim 1 in the collection of mist.

10. The application of the copper foam surface coating of claim 1 in the preparation of atmospheric water harvesting materials.

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