A flexible carbonized TiO2@Co-MOF@foam nickel-based photothermal composite material, a preparation method and application thereof

Abstract

The application discloses a flexible carbonized TiO2@Co-MOF@foam nickel-based photothermal composite material and a preparation method and application thereof. The preparation method comprises the following steps: immersing foam nickel into a mixed solution of a 2-methyl imidazole solution and a cobalt nitrate hexahydrate solution, and growing in situ to obtain a flexible base photothermal composite material with Co-MOF grown on the surface; repeatedly reacting TiCl4 vapor and water vapor with the flexible base photothermal composite material with Co-MOF grown on the surface to obtain a Co-MOF@foam nickel flexible base photothermal composite material with TiO2 deposited on the surface; and performing programmed temperature heat treatment on the Co-MOF@foam nickel flexible base photothermal composite material with TiO2 deposited on the surface to obtain the flexible carbonized TiO2@Co-MOF@foam nickel-based photothermal composite material. The material has good superhydrophilic performance, light absorption capacity, water evaporation rate and power generation performance, and has great application potential.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photothermal materials, and relates to a flexible carbonized TiO2@Co-MOF@foam nickel-based photothermal composite material and a preparation method and application thereof. BACKGROUND

[0002] With the increasing speed of urbanization and industrialization, the demand for fresh water resources by human beings is increasing. Considering that 97% of the water resources on the earth's surface are concentrated in the oceans, for this reason, human beings have obtained clean fresh water from seawater in various ways. However, the traditional seawater desalination technologies, including reverse osmosis, low-temperature multi-effect distillation, and solar energy collection driven by heliostats, parabolic troughs and Fresnel lenses to obtain fresh water by evaporation of seawater, have the disadvantages of consuming non-renewable energy, occupying a large amount of land, and being expensive to build, which greatly limits the application in the global range. In recent years, the interface solar desalination by water evaporation (SDIWE) technology has been studied more and more, which benefits from the fact that SDIWE uses clean and sustainable solar energy as an energy source, and has the characteristics of environmental protection, lightness, high evaporation efficiency and small heat loss. The light absorption and heat conversion capacity of the photothermal material as a key component of SDIWE directly determines the seawater evaporation rate and the ability to obtain clean fresh water.

[0003] Considering the existing photothermal conversion materials such as carbon-based materials, plasmonic metal nanoparticles, biomass materials, and semiconductor materials, although they have certain photothermal conversion performance, the materials themselves still have deficiencies, for example, the plasmonic metal nanoparticles have high preparation cost, the semiconductor materials have a complex preparation process, the biomass materials have inherent brittleness after high-temperature carbonization, and most of the photothermal materials have single function, which limits their large-scale practical application. SUMMARY

[0004] In view of the problems in the prior art, the application provides a flexible carbonized TiO2@Co-MOF@foam nickel-based photothermal composite material and a preparation method and application thereof, so as to solve the technical problems of brittleness, single function and poor evaporation performance of the photothermal material in the prior art.

[0005] The application is realized by the following technical scheme:

[0006] The application provides a preparation method of a flexible carbonized TiO2@Co-MOF@foam nickel-based photothermal composite material, which comprises the following steps:

[0007] S1: immersing the foam nickel in a mixed solution of 2-methylimidazole solution and cobalt nitrate hexahydrate, and growing in situ to obtain a flexible base photothermal composite material with Co-MOF grown on the surface;

[0008] S2: reacting TiCl4 vapor and water vapor repeatedly with the flexible-based photothermal composite material with Co-MOF grown on the surface to obtain a Co-MOF@foam nickel flexible-based photothermal composite material with TiO2 deposited on the surface;

[0009] S3: performing programmed temperature heat treatment on the Co-MOF@foam nickel flexible-based photothermal composite material with TiO2 deposited on the surface to obtain the flexible carbonized TiO2@Co-MOF@foam nickel-based photothermal composite material.

[0010] Preferably, before the foam nickel is immersed in the mixed solution of 2-methyl imidazole solution and cobalt nitrate hexahydrate in step S1, the foam nickel is pretreated, and the pretreatment specifically comprises ultrasonicating in acetone, deionized water and anhydrous ethanol in sequence for 20-30 min.

[0011] Preferably, after the pretreated foam nickel is dried at room temperature for 12 h, the foam nickel is immersed in the mixed solution of 2-methyl imidazole solution and cobalt nitrate hexahydrate for in-situ surface growth.

[0012] Preferably, in step S1, the immersion time is 4-6 h, and during the immersion, ultrasonicating is first performed for 1-2 min, and then natural immersion is performed.

[0013] Preferably, step S2 specifically comprises:

[0014] S201: placing the flexible-based photothermal composite material with Co-MOF grown on the surface in a sealed chamber, controlling the pressure in the sealed chamber to be 70-90 Pa and the temperature to be 90℃, and purging the reactor with nitrogen;

[0015] S202: introducing TiCl4 vapor into the reactor purged with nitrogen for 0.05-0.1 s, keeping the TiCl4 vapor in the reactor for 20-30 s, and then purging the reactor with nitrogen;

[0016] S203: introducing water vapor into the reactor after step S202 is completed for 0.05-0.1 s, reacting the TiCl4 vapor and the water vapor with the flexible-based photothermal composite material with Co-MOF grown on the surface for 20-30 s, and after the reaction is completed, purging the product after the reaction with nitrogen;

[0017] S204: repeating steps S202-S203 to obtain the Co-MOF@foam nickel flexible-based photothermal composite material with TiO2 deposited on the surface.

[0018] Preferably, the number of times of repeating steps S202-S203 is 60-250.

[0019] Preferably, in step S3, the programmed temperature rising process is specifically: rising from 50 DEG C to 200-250 DEG C, holding for 2-3 hours, then rising to 400-500 DEG C, holding for 2-3 hours, then lowering to 150-200 DEG C, and finally naturally cooling to room temperature, wherein the rising rate is 2-3 DEG C / min, and the lowering rate is 4-6 DEG C / min.

[0020] A flexible carbonized TiO2@Co-MOF@foam nickel-based photothermal composite material is prepared by the above method.

[0021] Preferably, the flexible carbonized TiO2@Co-MOF@foam nickel-based photothermal composite material has an evaporation rate of 2.10-2.50 kg·m -2 ·h -1 under 1 solar light intensity for 3.5wt% sea salt water, and a light absorption efficiency of 93-95% in the spectral range of 200-2500 nm.

[0022] The flexible carbonized TiO2@Co-MOF@foam nickel-based photothermal composite material is applied to the fields of interface solar water evaporation for obtaining clean water and evaporation-induced power generation.

[0023] Compared with the prior art, the present application has the following beneficial technical effects:

[0024] A method for preparing a flexible TiO2@Co-MOF@nickel foam-based photothermal composite material is disclosed. Co-MOF is grown in situ on nickel foam to form a framework with a nanoplate array, significantly increasing the surface area of ​​the nickel foam. TiO2 is then deposited on the Co-MOF surface. This TiO2 layer not only effectively protects the Co-MOF nanoplate array, preventing collapse and damage during carbonization, but also leverages the excellent light absorption capacity of TiO2 in the ultraviolet region. Simultaneously, the porous carbon formed after Co-MOF carbonization exhibits good light absorption in the ultraviolet-visible-near-infrared range. Therefore, the synergistic effect of these two methods achieves efficient light absorption across the entire solar spectrum. Furthermore, compared to the relatively smooth surface of nickel foam (NF), the abundant nanoplate array and pore size formed after TiO2@Co-MOF@nickel foam (CTCNF) not only generate capillary action, promoting sufficient water supply during evaporation, but also provide abundant evaporation sites due to the large pore size and specific surface area. Leveraging the superhydrophilic properties generated by capillary forces, high-concentration brine reflux and diffusion can be achieved simultaneously with rapid water supply, improving the salt resistance and long-term performance stability of TiO2@Co-MOF@nickel foam photothermal materials in seawater desalination applications. By controlling the material preparation process, a flexible TiO2@Co-MOF@nickel foam photothermal material was obtained, enhancing its structural stability and inter-regional transport capabilities. Beyond seawater evaporation desalination, the excellent hydrophilicity and rapid water supply capability of the flexible TiO2@Co-MOF@nickel foam-based photothermal composite material enable evaporation-induced power generation based on the ionic potential generated by interfacial solar water evaporation, thus offering significant advantages for all-weather power generation. This material possesses excellent superhydrophilic properties, light absorption capacity, water evaporation rate, and power generation performance, demonstrating enormous application potential.

[0025] Furthermore, pretreating the nickel foam before immersing it in a mixed solution of 2-methylimidazole and cobalt nitrate hexahydrate can clean the surface of the nickel foam and provide abundant reaction sites for in-situ growth of Co-MOF.

[0026] Furthermore, the pretreated nickel foam was dried at room temperature for 12 hours, and then immersed in a mixed solution of 2-methylimidazole solution and cobalt nitrate hexahydrate for in-situ surface growth. The purpose of drying at room temperature is to leave a small amount of ethanol inside the nickel foam, which will facilitate the entry of the 2-methylimidazole solution and cobalt nitrate hexahydrate into the pores of the nickel foam when it is immersed in the mixed solution of 2-methylimidazole solution and cobalt nitrate hexahydrate, thus forming a uniform Co-MOF in the pores of the nickel foam.

[0027] Furthermore, in step S1, the soaking time is 4 to 6 hours, and during the soaking process, the mixture is first sonicated for 1 to 2 minutes, and then naturally soaked. The purpose of sonication is to promote the entry of 2-methylimidazole solution and cobalt nitrate hexahydrate into the pores of the nickel foam, so that the Co-MOF formed on the surface of the nickel foam is more uniform.

[0028] Furthermore, a flexible photothermal composite material with Co-MOF grown on its surface is placed in a sealed chamber. The pressure in the sealed chamber is controlled at 70-90 Pa and the temperature at 90 °C. The pressure control ensures that the reaction chamber is under low vacuum (near vacuum conditions). The low vacuum and temperature control can remove residual or attached water on the pores of the porous material, activate the material, and ensure that the subsequently introduced chemical substances come into contact with the material as completely as possible and react.

[0029] Furthermore, during the programmed temperature rise process, the temperature is first increased from 50℃ to 200-250℃ and held for 2-3 hours to prevent structural fracture caused by uneven heating, thus avoiding loss of material flexibility. Then, the temperature is increased to 400-500℃ and held for 2-3 hours to achieve the conversion of Co-MOF into porous carbon, while increasing the bonding force between TiO2 and the composite material. Finally, the temperature is decreased to 150-200℃ to prevent uneven heating caused by rapid cooling, thus avoiding damage to the material structure. This controlled programmed temperature rise condition ensures that the material possesses good flexibility.

[0030] A flexible carbonized TiO2@Co-MOF@foamed nickel-based photothermal composite material is provided. The thickness of the TiO2 layer is 6-14 nm. On the one hand, it can effectively protect Co-MOF, and on the other hand, it can ensure that the porous structure of Co-MOF is not filled and blocked by the TiO2 layer. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic flowchart of a method for preparing a flexible TiO2@Co-MOF@foamed nickel-based photothermal composite material according to the present invention;

[0033] Figure 2 The mass change curve and evaporation rate change of the CTCNF sample and the original NF sample prepared in Example 2 of the present invention were respectively placed in 3.5wt% sea salt water and evaporated water under one light intensity.

[0034] Figure 3 The images shown are SEM images of the CTCNF sample and the original NF obtained in Example 2 of this invention; where (a) and (c) are SEM images of the original nickel foam, and (b) and (d) are SEM images of the CTCNF sample. In addition, (a) and (b) are magnified by 1000x, (c) and (d) are magnified by 10000x, and the inset in (d) is magnified by 60000x.

[0035] Figure 4 The contact angle test diagrams are of the CTCNF sample prepared in Example 2 of this invention and the original NF.

[0036] Figure 5 The flexibility test of the CTCNF sample prepared in Example 2 of the present invention;

[0037] Figure 6 The light absorption capacity test curves of the CTCNF and the original NF sample prepared in Example 2 of this invention are shown.

[0038] Figure 7 The surface temperature change curves of the CTCNF and the original NF sample (dry state) prepared in Example 2 of the present invention during the switching on and off of a sun lamp under one day.

[0039] Figure 8 The evaporation-induced power generation curves of the CTCNF sample prepared in Example 2 of this invention under darkness and one sun are shown. Detailed Implementation

[0040] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0041] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0042] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0043] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0044] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0045] like Figure 1 As shown, this invention provides a method for preparing a flexible TiO2@Co-MOF@nickel foam photothermal composite material, comprising:

[0046] S1: Nickel foam is immersed in a mixed solution of 2-methylimidazole and cobalt nitrate hexahydrate, and in situ growth is carried out to obtain a flexible photothermal composite material with Co-MOF growing on the surface.

[0047] Before immersing the nickel foam in a mixed solution of 2-methylimidazole and cobalt nitrate hexahydrate, it undergoes pretreatment. Specifically, the pretreatment involves ultrasonic cleaning in acetone, deionized water, and anhydrous ethanol for 20–30 minutes, repeated three times. The ultrasonic cleaning frequency is 30–50 kHz. The foam is then dried in a disposable petri dish at room temperature for 12 hours to obtain a clean, flexible nickel foam substrate. The purpose of drying at room temperature is to leave a small amount of ethanol inside the nickel foam, which facilitates the penetration of the 2-methylimidazole and cobalt nitrate hexahydrate solutions into the pores of the nickel foam during immersion, thus forming a uniform Co-MOF within the pores. The experiment revealed that after drying in a vacuum drying oven, the ethanol inside the pores was completely evaporated. When the nickel foam was immersed in a mixed solution of 2-methylimidazole and cobalt nitrate hexahydrate, it floated in the mixed solution. The 2-methylimidazole and cobalt nitrate hexahydrate could not penetrate into the interior of the nickel foam, resulting in the inability to grow Co-MOF uniformly in situ inside the nickel foam, which led to a decrease in the material's performance.

[0048] The molar ratio of 2-methylimidazole to cobalt nitrate hexahydrate was (7-9):1. Clean nickel foam was immersed in a mixed solution of 2-methylimidazole and cobalt nitrate hexahydrate and reacted at room temperature to obtain nickel foam with a Co-MOF nanoplate array grown on its surface. The immersion reaction time was 4-6 hours, and during the immersion process, it was first sonicated for 1-2 minutes, followed by natural immersion.

[0049] S2: TiO2 deposited on Co-MOF@nickel foam surface

[0050] TiCl4 vapor and water vapor are repeatedly reacted with the flexible photothermal composite material on which Co-MOF is grown on the surface to obtain a Co-MOF@foam nickel flexible photothermal composite material with TiO2 deposited on the surface.

[0051] Co-MOF@nickel foam was dried in a 60℃ oven for 1–2 hours. The dried Co-MOF@nickel foam was then placed in the atomic layer deposition instrument chamber. The pressure and temperature of the reaction chamber were controlled at 70–90 Pa and 90℃, respectively. Nitrogen gas was then introduced at a flow rate of 50 sccm. Each cycle of TiO2 deposition began with a TiCl4 vapor pulse and ended with a water vapor pulse. Specifically, TiCl4 vapor was introduced into the reaction chamber in a 0.05–0.1 s pulse, followed by exposure for 20–30 s, and then the reaction system was allowed to stand for 20–30 s. TiCl4 can fully penetrate into the porous material. Finally, nitrogen is used to purge for 60 seconds, followed by a 0.05-0.1 second pulse of water vapor into the reaction chamber for 20-30 seconds, allowing TiCl4 to fully react with the water vapor, thereby achieving TiO2 deposition. Finally, nitrogen is used to purge for another 60 seconds to complete one cycle of TiO2 deposition. The TiO2 deposition cycle is 60-250 times to obtain a Co-MOF@foam nickel flexible photothermal composite material with TiO2 deposited on the surface, namely TiO2@Co-MOF@foam nickel composite material.

[0052] (4) Carbide TiO2@Co-MOF@Nickel Foam Composite Material

[0053] The flexible TiO2@Co-MOF@nickel foam flexible photothermal composite material with TiO2 deposited on its surface was subjected to programmed temperature rise heat treatment to obtain the flexible TiO2@Co-MOF@nickel foam flexible photothermal composite material.

[0054] Specifically, TiO2@Co-MOF@nickel foam is placed in a tube furnace, and vacuuming and argon filling are performed sequentially, repeated 3 to 5 times. The carbonization temperature parameters are set, from 50℃ to 200-250℃, held for 2 to 3 hours, then increased to 400-500℃, held for 2 to 3 hours, then cooled to 150-200℃, and finally allowed to cool naturally to room temperature. The heating rate is 2-3℃ / min and the cooling rate is 4-6℃ / min, thus obtaining the carbonized TiO2@Co-MOF@nickel foam composite material.

[0055] The experimental procedure for the solar steam experiment in this invention is as follows:

[0056] A 3.5 wt% seawater solution was prepared to simulate seawater concentration, and a xenon lamp (CEL-S500, AM1.5 filter) was used to simulate solar light. The evaporation process was monitored using an electronic balance (AR224CN) with an accuracy of 0.0001 g, and the data was transmitted and recorded to a personal computer via SPDC data acquisition software V2.01. A simulated solar evaporation experimental platform was constructed. Analysis and calculations revealed the simulated seawater evaporation rate and the photothermal conversion efficiency of the flexible carbonized TiO2@Co-MOF@foam nickel-based photothermal composite material under experimental conditions, and the photothermal performance was studied.

[0057] The specific experimental procedure was as follows: A beaker was placed inside a protective sleeve made of polyvinyl chloride (PVC) foam to minimize the impact of ambient temperature changes during the experiment. Then, the flexible TiO2@Co-MOF@foam nickel-based photothermal composite material was placed on PVC foam wrapped in a superhydrophilic cleanroom cloth, ensuring stable floating in 3.5 wt% simulated seawater. All evaporation devices were placed on a precision electronic balance to monitor the mass change caused by water evaporation in real time. The experiment was conducted under one sun (1 kW·m²). -2 The flexible TiO2@Co-MOF@foamed nickel-based photothermal composite material prepared in this invention has a TiO2 layer thickness of 6–14 nm. Under one solar irradiance, the evaporation rate of 3.5 wt% seawater is 2.10–2.50 kg·m³. -2 ·h -1 The light absorption efficiency is 93%–95% in the spectral range of 200–2500 nm.

[0058] The technical solution of this invention can produce a flexible photothermal composite material with excellent light absorption, rapid photothermal response, superhydrophilicity, good flexibility, high evaporation rate, and all-day power generation capability. This is because atomically deposited TiO2 can cover the surface of the nanoplate array, avoiding structural damage during carbonization. Simultaneously, the TiO2-coated carbon nanoarray and abundant pores greatly improve light capture and water transport capabilities. Furthermore, leveraging the conductivity of the nickel foam substrate and utilizing the ionic potential generated during the evaporation process, the power generation function is achieved.

[0059] This invention provides a method for preparing a flexible carbonized TiO2@Co-MOF@foamed nickel-based photothermal composite material and its application in interfacial solar seawater evaporation. Utilizing an abundant array of carbon nanoplatelets encapsulating TiO2, the composite material exhibits excellent light absorption and photothermal conversion capabilities. Simultaneously, the capillary forces generated by the formed pores endow the composite photothermal material with excellent superhydrophilicity, resulting in an ultra-high evaporation rate and good evaporation-induced power generation capability. Furthermore, the foamed nickel maintains a certain degree of flexibility after controlling the carbonization temperature, greatly improving the stability and portability of the material structure. In summary, this invention provides a novel photothermal conversion material for solar-driven seawater desalination technology.

[0060] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0061] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0062] Example 1

[0063] A method for preparing a flexible TiO2@Co-MOF@nickel foam photothermal composite material includes the following steps:

[0064] ① Clean the substrate

[0065] In a CNC ultrasonic cleaning instrument with a frequency of 30-50kHz, deionized water, acetone, and anhydrous ethanol were used to clean nickel foam (2×3cm) for 20min in sequence, and this process was repeated 3 times. The foam was then placed in a disposable petri dish and dried at room temperature for 12h.

[0066] ② In-situ growth of Co-MOF yields flexible Co-MOF@nickel foam composite materials

[0067] 1.3138 g of 2-methylimidazole and 0.5821 g of cobalt nitrate hexahydrate were weighed using an electronic balance and dissolved separately in 40 mL of deionized water. After complete dissolution, the 2-methylimidazole aqueous solution was rapidly mixed with the cobalt nitrate hexahydrate aqueous solution to obtain a purple mixed solution. Dry nickel foam was then immediately immersed in the mixed solution, sealed with plastic wrap, and allowed to react at room temperature for 5 hours.

[0068] After the reaction was completed, the nickel foam with Co-MOF grown on the surface was washed three times with deionized water and anhydrous ethanol, and then dried in a disposable petri dish at room temperature for 12 hours.

[0069] ③ Co-MOF@Ni foam surface atomic layer deposition of TiO2

[0070] Before placing Co-MOF@nickel foam into the atomic layer deposition instrument chamber, it was dried in a 60°C oven for 2 hours. The dried Co-MOF@nickel foam was then placed into the atomic layer deposition instrument chamber. After controlling the pressure and temperature of the reaction chamber at 70–90 Pa and 90°C respectively, nitrogen gas was introduced at a flow rate of 50 sccm. Each cycle of TiO2 deposition started with TiCl4 vapor and ended with water vapor. TiCl4 was pulsed into the reaction chamber for 0.05 s, then exposed for 25 s, and finally purged with nitrogen gas for 60 s. Water vapor was then pulsed into the reaction chamber for 0.05 s, exposed for 25 s, and purged with nitrogen gas for 60 s, completing one cycle of TiO2 deposition. The TiO2 deposition cycle was repeated 60 times to obtain the TiO2@Co-MOF@nickel foam composite material.

[0071] ④ TiO2@Co-MOF@Nickel Foam Composite Material

[0072] TiO2@Co-MOF@nickel foam was placed in a tube furnace, and vacuuming and argon filling were performed sequentially 3-5 times. The carbonization temperature parameters were set, and the temperature was raised from room temperature to 200℃ and held for 2 hours. Then, the temperature was raised from 200℃ to 450℃ and held for 2 hours. Immediately afterwards, the temperature was lowered from 450℃ to 200℃, and finally, the temperature was lowered to room temperature under argon protection. During the carbonization process, the temperature change rate was 2℃ / min during both the heating and cooling stages, resulting in carbonized TiO2@Co-MOF@nickel foam composite material.

[0073] Example 2

[0074] A method for preparing a flexible TiO2@Co-MOF@nickel foam photothermal composite material includes the following steps:

[0075] ① Clean the substrate

[0076] In a CNC ultrasonic cleaning instrument with a frequency of 30–50 kHz, deionized water, acetone, and anhydrous ethanol were used to clean nickel foam (2×3 cm) for 20 min in sequence, and this process was repeated 3 times. The foam was then placed in a disposable petri dish and dried at room temperature for 12 h.

[0077] ② In-situ growth of Co-MOF yields Co-MOF@nickel foam flexible matrix composites

[0078] 1.3138 g of 2-methylimidazole and 0.5821 g of cobalt nitrate hexahydrate were weighed using an electronic balance and dissolved separately in 40 mL of deionized water. After complete dissolution, the 2-methylimidazole aqueous solution was rapidly mixed with the cobalt nitrate hexahydrate aqueous solution to obtain a purple mixed solution. Dry nickel foam was then immediately immersed in the mixed solution, sealed with plastic wrap, and allowed to react at room temperature for 5 hours.

[0079] After the reaction was complete, the nickel foam with Co-MOF grown on its surface was washed three times with deionized water and anhydrous ethanol, and then dried at room temperature for 12 hours in a disposable petri dish. After drying, a second Co-MOF growth was performed on the surface of the nickel foam.

[0080] ③ Co-MOF@Ni foam surface atomic layer deposition of TiO2

[0081] Before placing Co-MOF@nickel foam into the atomic layer deposition instrument chamber, it was dried in a 60°C oven for 2 hours. The dried Co-MOF@nickel foam was then placed into the atomic layer deposition instrument chamber. After controlling the pressure and temperature of the reaction chamber at 70–90 Pa and 90°C respectively, nitrogen gas was introduced at a flow rate of 50 sccm. Each cycle of TiO2 deposition started with TiCl4 vapor and ended with water vapor. TiCl4 vapor was pulsed into the reaction chamber for 0.05 s, then exposed for 25 s, and finally purged with nitrogen gas for 60 s. Deionized water was then pulsed into the reaction chamber for 0.05 s, exposed for 25 s, and purged with nitrogen gas for 60 s, completing one cycle of TiO2 deposition. The TiO2 deposition cycle was repeated 100 times to obtain the TiO2@Co-MOF@nickel foam composite material.

[0082] ④ TiO2@Co-MOF@Nickel Foam Composite Material

[0083] TiO2@Co-MOF@nickel foam was placed in a tube furnace, and the process of evacuating and purging with argon was repeated 3-5 times. The carbonization temperature parameters were set, with the temperature increased from room temperature to 200℃ and held for 2 hours, then increased to 450℃ and held for 2 hours, followed by a decrease from 450℃ to 200℃, and finally cooled to room temperature under argon protection. During the carbonization process, the temperature change rate was 2℃ / min during both the heating and cooling stages, resulting in carbonized TiO2@Co-MOF@nickel foam composite material. The obtained product is denoted as CTCNF.

[0084] Example 3

[0085] A method for preparing a flexible TiO2@Co-MOF@nickel foam photothermal composite material includes the following steps:

[0086] ① Clean the substrate

[0087] In a CNC ultrasonic cleaning instrument with a frequency of 30–50 kHz, deionized water, acetone, and anhydrous ethanol were used to clean nickel foam (2×3 cm) for 20 min in sequence, and this process was repeated 3 times. The foam was then placed in a disposable petri dish and dried at room temperature for 12 h.

[0088] ② In-situ growth of Co-MOF yields Co-MOF@nickel foam flexible matrix composites

[0089] 1.3138 g of 2-methylimidazole and 0.5821 g of cobalt nitrate hexahydrate were weighed using an electronic balance and dissolved separately in 40 mL of deionized water. After complete dissolution, the 2-methylimidazole aqueous solution was rapidly mixed with the cobalt nitrate hexahydrate aqueous solution to obtain a purple mixed solution. Dry nickel foam was then immediately immersed in the mixed solution, sealed with plastic wrap, and allowed to react at room temperature for 5 hours.

[0090] After the reaction was complete, the nickel foam with Co-MOF grown on its surface was washed three times with deionized water and anhydrous ethanol, and then dried at room temperature for 12 hours in a disposable petri dish. After drying, a third Co-MOF growth was performed on the surface of the nickel foam.

[0091] ③ Co-MOF@Ni foam surface atomic layer deposition of TiO2

[0092] Before placing Co-MOF@nickel foam into the atomic layer deposition instrument chamber, it was dried in a 60℃ oven for 2 hours. The dried Co-MOF@nickel foam was then placed into the atomic layer deposition instrument chamber. After controlling the pressure and temperature of the reaction chamber at 70–90 Pa and 90℃ respectively, nitrogen gas was introduced at a flow rate of 50 sccm. Each cycle of TiO2 vapor deposition started with TiCl4 and ended with water vapor. TiCl4 vapor was pulsed into the reaction chamber for 0.05 s, then exposed for 25 s, and finally purged with nitrogen gas for 60 s. Water vapor was then pulsed into the reaction chamber for 0.05 s, exposed for 25 s, and purged with nitrogen gas for 60 s, completing one cycle of TiO2 deposition. The TiO2 deposition cycle was repeated 140 times to obtain the TiO2@Co-MOF@nickel foam composite material.

[0093] ④ TiO2@Co-MOF@Nickel Foam Composite Material

[0094] TiO2@Co-MOF@nickel foam was placed in a tube furnace, and the process of evacuating and purging with argon was repeated 3-5 times. The carbonization temperature parameters were set, and the temperature was raised from room temperature to 200℃ and held for 2 hours. Then, the temperature was raised from 200℃ to 450℃ and held for 2 hours. Immediately afterwards, the temperature was lowered from 450℃ to 200℃, and finally, the temperature was lowered to room temperature under argon protection. During the carbonization process, the temperature change rate during both the heating and cooling stages was 2℃ / min, resulting in the carbonized TiO2@Co-MOF@nickel foam composite material.

[0095] Example 4

[0096] This invention discloses a method for preparing a flexible TiO2@Co-MOF@nickel foam photothermal composite material, comprising the following steps:

[0097] ① Clean the substrate

[0098] In a CNC ultrasonic cleaning instrument with a frequency of 30–50 kHz, deionized water, acetone, and anhydrous ethanol were used to clean nickel foam (2×3 cm) for 20 min in sequence, and this process was repeated 3 times. The foam was then placed in a disposable petri dish and dried at room temperature for 12 h.

[0099] ② In-situ growth of Co-MOF yields Co-MOF@nickel foam flexible matrix composites

[0100] 1.3138 g of 2-methylimidazole and 0.5821 g of cobalt nitrate hexahydrate were weighed using an electronic balance and dissolved separately in 40 mL of deionized water. After complete dissolution, the 2-methylimidazole aqueous solution was rapidly mixed with the cobalt nitrate hexahydrate aqueous solution to obtain a purple mixed solution. Dry nickel foam was then immediately immersed in the mixed solution, sealed with plastic wrap, and allowed to react at room temperature for 5 hours.

[0101] After the reaction was complete, the nickel foam with Co-MOF grown on its surface was washed three times with deionized water and anhydrous ethanol, and then dried at room temperature for 12 hours in a disposable petri dish. After drying, a fourth Co-MOF growth was performed on the surface of the nickel foam.

[0102] ③ Co-MOF@Ni foam surface atomic layer deposition of TiO2

[0103] Before placing the Co-MOF@nickel foam into the atomic layer deposition instrument chamber, it was dried in a 60°C oven for 2 hours. The dried Co-MOF@nickel foam was then placed into the atomic layer deposition instrument chamber. After controlling the pressure and temperature of the reaction chamber at 70–90 Pa and 90°C respectively, nitrogen gas was introduced at a flow rate of 50 sccm. Each cycle of TiO2 deposition started with TiCl4 vapor and ended with water vapor. TiCl4 vapor was pulsed into the reaction chamber for 0.05 s, then exposed for 25 s, and finally purged with nitrogen gas for 60 s. Water vapor was then pulsed into the reaction chamber for 0.05 s, exposed for 25 s, and purged with nitrogen gas for 60 s, completing one cycle of TiO2 deposition. The TiO2 deposition cycle was repeated 250 times to obtain the TiO2@Co-MOF@nickel foam composite material.

[0104] ④ TiO2@Co-MOF@Nickel Foam Composite Material

[0105] TiO2@Co-MOF@nickel foam was placed in a tube furnace, and the process of evacuating and purging with argon was repeated 3-5 times. The carbonization temperature parameters were set, and the temperature was raised from room temperature to 200℃ and held for 2 hours. Then, the temperature was raised from 200℃ to 450℃ and held for 2 hours. Immediately afterwards, the temperature was lowered from 450℃ to 200℃, and finally, the temperature was lowered to room temperature under argon protection. During the carbonization process, the temperature change rate during both the heating and cooling stages was 2℃ / min, resulting in the carbonized TiO2@Co-MOF@nickel foam composite material.

[0106] The technical solution of the invention will be further explained below using the CTCNF sample obtained in Example 2 as an example, in conjunction with the accompanying drawings.

[0107] I. Solar Steam Experiment

[0108] The evaporation performance of CTCNF is determined quantitatively through evaporation experiments:

[0109] The evaporation experiments were conducted using an experimental setup simulating sunlight. All data was read via an electronic balance using the mass difference of the brine and then transmitted to a computer for recording. All evaporation experiments were performed under a single solar radiation intensity.

[0110] like Figure 2As shown, evaporation experiments revealed that the mass of the simulated seawater evaporated continuously increased over time as evaporation proceeded, and the mass change tended to stabilize. Furthermore, compared to the original nickel foam, the CTCNF prepared in Example 2 had a mass of 2.30 kg·m³. -2 ·h -1 The evaporation rate of nickel foam (NF) is much higher than that of pure nickel foam (NF), which is only 1.02 kg·m³. -2 ·h -1 Clearly, in-situ growth of Co-MOF on NF substrate, followed by TiO2 deposition and carbonization on the surface atomic layer, as a photothermal material, greatly improves the efficiency of solar-driven interfacial water evaporation.

[0111] II. SEM Image Testing

[0112] like Figure 3 As shown, the CTCNF surface prepared in Example 2 has a rich array of nanoplates, which increases the capture and absorption of incident sunlight while providing abundant evaporation sites. In addition, the capillary action generated by the tiny pores between the arrays ensures rapid water supply.

[0113] III. Contact Angle Test

[0114] like Figure 4 As shown, the CTCNF prepared in Example 2 of the present invention has superhydrophilic properties. The water droplet completely wets the surface within 240ms. In contrast, the original NF still maintains a large contact angle for the water droplet at 48100ms.

[0115] The power generation performance comes from the concentration difference formed on the surface of the material during the evaporation process. At the same time, the device must be at a certain angle to the material, such as 45°, during the power generation process. Therefore, the hydrophilicity of the material is crucial. Good hydrophilicity can enable the material to have good water supply capacity and realize the reflux and diffusion of high concentration salt water, so as to maintain a certain ion concentration difference in the evaporation system and enable it to have stable power generation capacity.

[0116] IV. Flexibility Test

[0117] like Figure 5 As shown, the CTCNF prepared in Embodiment 2 of the present invention exhibits excellent flexibility. After bending, it can still return to its original shape and maintain its bent shape during the bending process. This flexibility effectively improves the ease of use and service life of the material, which is crucial for its practical application.

[0118] V. Full Solar Spectrum Light Absorption Capacity Test

[0119] like Figure 6As shown, the CTCNF prepared in Example 2 of the present invention has excellent light absorption capability. Compared with the original NF having a light absorption of 66.62% in the 200-2500nm spectral range, the CTCNF has a light absorption of 93.53%.

[0120] VI. Photothermal Response Speed ​​Test

[0121] like Figure 7 As shown, the CTCNF prepared in Example 2 of this invention has excellent photothermal response capability. It can reach a stable temperature of 78°C within 180 seconds under one sun. Under no light conditions, the surface temperature drops rapidly to room temperature, while the original NF can only rise to 40°C under the same conditions.

[0122] VII. Evaporation-Induced Power Generation Test

[0123] like Figure 8 As shown, the CTCNF prepared in Example 2 of this invention can generate electricity not only under one sun (stable output voltage: 180mV), but also under no-light conditions (stable output voltage: 140mV), thanks to the excellent superhydrophilic properties of the material.

[0124] Example 5

[0125] A method for preparing a flexible TiO2@Co-MOF@nickel foam photothermal composite material, comprising:

[0126] S1: The nickel foam was ultrasonically treated in acetone, deionized water and anhydrous ethanol for 20 min in sequence, and repeated 3 times. Then it was dried at room temperature for 12 h. The dried nickel foam was then immersed in a mixed solution of 2-methylimidazole solution and cobalt nitrate hexahydrate with a molar ratio of 7:1 to obtain a flexible photothermal composite material with Co-MOF grown on the surface. The immersion reaction time was 6 h. During the immersion process, the foam was ultrasonicated for 1 min first and then naturally immersed.

[0127] S2: TiO2 deposited on Co-MOF@nickel foam surface

[0128] Co-MOF@nickel foam was dried in a 60℃ oven for 2 hours. The dried Co-MOF@nickel foam was then placed in the atomic layer deposition instrument chamber, and the pressure and temperature of the reaction chamber were controlled at 90 Pa and 90℃, respectively. Nitrogen gas was then introduced at a flow rate of 50 sccm. Each cycle of TiO2 deposition started with a TiCl4 vapor pulse and ended with a water vapor pulse. Specifically, a TiCl4 vapor pulse was introduced into the reaction chamber for 0.05 s, followed by exposure for 20 s, and finally purging with nitrogen gas for 60 s. Then, a water vapor pulse was introduced into the reaction chamber for 0.05 s, followed by exposure for 30 s, and purging with nitrogen gas for 60 s to complete one cycle of TiO2 deposition. The TiO2 deposition cycle was repeated 60 times to obtain a Co-MOF@nickel foam flexible photothermal composite material with TiO2 deposited on its surface.

[0129] S3: TiO2 carbide@Co-MOF@nickel foam composite material

[0130] TiO2@Co-MOF@nickel foam was placed in a tube furnace and subjected to heat treatment. Specifically, the temperature was raised from 50°C to 200°C and held for 3 hours, then raised to 400°C and held for 3 hours. The temperature was then lowered to 150°C and finally allowed to cool naturally to room temperature. The heating rate was 2°C / min and the cooling rate was 4°C / min, resulting in a TiO2@Co-MOF@nickel foam composite material.

[0131] The flexible TiO2@Co-MOF@foamed nickel-based photothermal composite material prepared in this embodiment has a TiO2 layer thickness of 6 nm. Under one solar irradiance, its evaporation rate for 3.5 wt% seawater is 2.10 kg·m³. -2 ·h -1 The light absorption efficiency is 93% in the spectral range of 200–2500 nm.

[0132] Example 6

[0133] A method for preparing a flexible TiO2@Co-MOF@nickel foam photothermal composite material, comprising:

[0134] S1: The nickel foam was ultrasonically treated in acetone, deionized water and anhydrous ethanol for 25 min in sequence, and repeated 3 times. Then it was dried at room temperature for 12 h. The dried nickel foam was then immersed in a mixed solution of 2-methylimidazole solution and cobalt nitrate hexahydrate with a molar ratio of 8:1 to obtain a flexible photothermal composite material with Co-MOF grown on the surface in situ. The immersion reaction time was 5 h. During the immersion process, the foam was ultrasonicated for 1.5 min first, and then naturally immersed.

[0135] S2: TiO2 deposited on Co-MOF@nickel foam surface

[0136] Co-MOF@nickel foam was dried in a 60℃ oven for 1.8h. The dried Co-MOF@nickel foam was then placed in the atomic layer deposition instrument chamber, and the pressure and temperature of the reaction chamber were controlled at 85Pa and 90℃, respectively. Nitrogen gas was then introduced at a flow rate of 50sccm. Each cycle of TiO2 deposition started with a TiCl4 vapor pulse and ended with a water vapor pulse. Specifically, a TiCl4 vapor pulse was introduced into the reaction chamber for 0.08s, followed by exposure for 26s, and finally purged with nitrogen gas for 60s. Then, a water vapor pulse was introduced into the reaction chamber for 0.06s, followed by exposure for 26s, and purged with nitrogen gas for 60s to complete one cycle of TiO2 deposition. The TiO2 deposition cycle was repeated 100 times to obtain a Co-MOF@nickel foam flexible photothermal composite material with TiO2 deposited on its surface.

[0137] S3: TiO2 carbide@Co-MOF@nickel foam composite material

[0138] TiO2@Co-MOF@nickel foam was placed in a tube furnace and heat-treated by heating from 50°C to 230°C and holding for 2.5 hours, then heating to 440°C and holding for 2.5 hours; then cooling to 170°C and finally naturally cooling to room temperature. The heating rate was 2.5°C / min and the cooling rate was 4.5°C / min, thus obtaining the TiO2@Co-MOF@nickel foam composite material.

[0139] The flexible TiO2@Co-MOF@foamed nickel-based photothermal composite material prepared in this embodiment has a TiO2 layer thickness of 10 nm. Under one solar irradiance, its evaporation rate for 3.5 wt% seawater is 2.30 kg·m³. -2 ·h -1 The light absorption efficiency in the 200–2500 nm spectral range is 93.53%.

[0140] Example 7

[0141] A method for preparing a flexible TiO2@Co-MOF@nickel foam photothermal composite material, comprising:

[0142] S1: The nickel foam was ultrasonically treated in acetone, deionized water and anhydrous ethanol for 30 min in sequence, and repeated 3 times. Then it was dried at room temperature for 12 h. The dried nickel foam was then immersed in a mixed solution of 2-methylimidazole solution and cobalt nitrate hexahydrate with a molar ratio of 9:1 to obtain a flexible photothermal composite material with Co-MOF grown on the surface in situ. The immersion reaction time was 6 h. During the immersion process, the foam was ultrasonically treated for 2 min first, and then naturally immersed.

[0143] S2: TiO2 deposited on Co-MOF@nickel foam surface

[0144] Co-MOF@nickel foam was dried in a 60℃ oven for 2 hours. The dried Co-MOF@nickel foam was then placed in the chamber of an atomic layer deposition instrument. The pressure and temperature of the reaction chamber were controlled at 90 Pa and 90℃, respectively. Nitrogen gas was then introduced at a flow rate of 50 sccm. Each cycle of TiO2 deposition started with a TiCl4 vapor pulse and ended with a water vapor pulse. Specifically, a TiCl4 vapor pulse was introduced into the reaction chamber for 0.1 s, followed by exposure for 30 s, and finally purged with nitrogen for 60 s. Then, a water vapor pulse was introduced into the reaction chamber for 0.1 s, followed by exposure for 30 s, and purged with nitrogen for 60 s, thus completing one cycle of TiO2 deposition. The TiO2 deposition cycle was repeated 250 times to obtain a Co-MOF@nickel foam flexible photothermal composite material with TiO2 deposited on its surface.

[0145] S3: TiO2 carbide@Co-MOF@nickel foam composite material

[0146] TiO2@Co-MOF@nickel foam was placed in a tube furnace and subjected to heat treatment. Specifically, the temperature was raised from 50°C to 250°C and held for 2 hours, then raised to 500°C and held for 2 hours. The temperature was then lowered to 200°C and finally allowed to cool naturally to room temperature. The heating rate was 3°C / min and the cooling rate was 4°C / min, resulting in a TiO2@Co-MOF@nickel foam composite material.

[0147] The flexible TiO2@Co-MOF@foamed nickel-based photothermal composite material prepared in this embodiment has a TiO2 layer thickness of 14 nm. Under one solar irradiance, its evaporation rate for 3.5 wt% seawater is 2.20 kg·m³. -2 ·h -1 The light absorption efficiency is 93.5% in the spectral range of 200–2500 nm.

[0148] Example 8

[0149] A method for preparing a flexible TiO2@Co-MOF@nickel foam photothermal composite material, comprising:

[0150] S1: The nickel foam was ultrasonically treated in acetone, deionized water and anhydrous ethanol for 20 min in sequence, and repeated 3 times. Then it was dried at room temperature for 12 h. The dried nickel foam was then immersed in a mixed solution of 2-methylimidazole solution and cobalt nitrate hexahydrate with a molar ratio of 7:1 to obtain a flexible photothermal composite material with Co-MOF grown on the surface. The immersion reaction time was 4 h. During the immersion process, the foam was ultrasonicated for 1 min first and then naturally immersed.

[0151] S2: TiO2 deposited on Co-MOF@nickel foam surface

[0152] Co-MOF@nickel foam was dried in a 60℃ oven for 1 hour. The dried Co-MOF@nickel foam was then placed in the chamber of an atomic layer deposition instrument. The pressure and temperature of the reaction chamber were controlled at 75 Pa and 90℃, respectively. Nitrogen gas was then introduced at a flow rate of 50 sccm. Each cycle of TiO2 deposition started with a TiCl4 vapor pulse and ended with a water vapor pulse. Specifically, a TiCl4 vapor pulse was introduced into the reaction chamber for 0.1 s, followed by exposure for 30 s, and finally purging with nitrogen for 60 s. Then, a water vapor pulse was introduced into the reaction chamber for 0.1 s, followed by exposure for 30 s, and purging with nitrogen for 60 s to complete one cycle of TiO2 deposition. The TiO2 deposition cycle was repeated 250 times to obtain a Co-MOF@nickel foam flexible photothermal composite material with TiO2 deposited on its surface.

[0153] S3: TiO2 carbide@Co-MOF@nickel foam composite material

[0154] TiO2@Co-MOF@nickel foam was placed in a tube furnace and subjected to heat treatment, specifically by raising the temperature from 50°C to 230°C and holding it for 2 hours, then raising it to 480°C and holding it for 2 hours; then cooling it down to 170°C and finally allowing it to cool naturally to room temperature. The heating rate was 3°C / min and the cooling rate was 4°C / min, thus obtaining the TiO2@Co-MOF@nickel foam composite material.

[0155] The flexible TiO2@Co-MOF@foamed nickel-based photothermal composite material prepared in this embodiment has a TiO2 layer thickness of 13 nm. Under one solar irradiance, its evaporation rate for 3.5 wt% seawater is 2.30 kg·m³. -2 ·h -1 The light absorption efficiency is 94% in the spectral range of 200–2500 nm.

[0156] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

[0157] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a flexible TiO2@Co-MOF@nickel foam photothermal composite material, characterized in that, Includes the following steps: S1: Nickel foam is immersed in a mixed solution of 2-methylimidazole and cobalt nitrate hexahydrate, and in situ growth is carried out to obtain a flexible photothermal composite material with Co-MOF growing on the surface. S2: Repeatedly react TiCl4 vapor and water vapor with the flexible photothermal composite material on which Co-MOF is grown on the surface to obtain a Co-MOF@foam nickel flexible photothermal composite material with TiO2 deposited on the surface. S3: Perform programmed temperature rise heat treatment on the Co-MOF@foam nickel flexible photothermal composite material with TiO2 deposited on the surface to obtain the flexible carbide TiO2@Co-MOF@foam nickel flexible photothermal composite material.

2. The preparation method of a flexible TiO2@Co-MOF@nickel foam photothermal composite material according to claim 1, characterized in that, In step S1, before immersing the nickel foam in a mixed solution of 2-methylimidazole and cobalt nitrate hexahydrate, it is pretreated by sonicating it in acetone, deionized water and anhydrous ethanol for 20-30 minutes in sequence.

3. The preparation method of a flexible TiO2@Co-MOF@nickel foam photothermal composite material according to claim 2, characterized in that, In step S1, the pretreated nickel foam is dried at room temperature for 12 hours, and then immersed in a mixed solution of 2-methylimidazole solution and cobalt nitrate hexahydrate for in-situ surface growth.

4. The preparation method of a flexible TiO2@Co-MOF@nickel foam photothermal composite material according to claim 1, characterized in that, In step S1, the soaking time is 4 to 6 hours, and during the soaking process, the patient is first sonicated for 1 to 2 minutes, and then naturally soaked.

5. The preparation method of a flexible TiO2@Co-MOF@nickel foam photothermal composite material according to claim 1, characterized in that, Step S2 is as follows: S201: The flexible photothermal composite material with Co-MOF grown on its surface is placed in a sealed chamber, the pressure in the sealed chamber is controlled at 70-90 Pa and the temperature at 90 °C, and nitrogen is used to purge the reactor. S202: Introduce TiCl4 vapor into the reactor after nitrogen purging for 0.05 to 0.1 s, keep the TiCl4 vapor in the reactor for 20 to 30 s, and then purge the reactor with nitrogen. S203: Water vapor is introduced into the reactor after step S202 for 0.05 to 0.1 s, so that TiCl4 vapor and water vapor react with the flexible photothermal composite material with Co-MOF grown on the surface for 20 to 30 s. After the reaction is completed, nitrogen gas is introduced into the reactor to purge the product after the reaction. S204: Repeat steps S202 to S203 to obtain the Co-MOF@foam nickel flexible photothermal composite material with TiO2 deposited on the surface.

6. The method for preparing a flexible TiO2@Co-MOF@nickel foam photothermal composite material according to claim 5, characterized in that, Repeat steps S202 to S203 60 to 250 times.

7. The preparation method of a flexible TiO2@Co-MOF@nickel foam photothermal composite material according to claim 1, characterized in that, In step S3, the programmed heating process is as follows: heating from 50°C to 200-250°C and holding for 2-3 hours, then heating to 400-500°C and holding for 2-3 hours; then cooling down to 150-200°C and finally naturally cooling to room temperature. The heating rate is 2-3°C / min and the cooling rate is 4-6°C / min.

8. A flexible TiO2@Co-MOF@nickel foam photothermal composite material, characterized in that, It is prepared by the method described in any one of claims 1 to 7.

9. The flexible TiO2@Co-MOF@nickel foam photothermal composite material according to claim 8, characterized in that, The flexible TiO2@Co-MOF@nickel foam photothermal composite material exhibits an evaporation rate of 2.10–2.50 kg·m³ for 3.5 wt% seawater under one solar irradiance. -2 ·h -1 The light absorption efficiency is 93%–95% in the spectral range of 200–2500 nm.

10. The application of the flexible carbonized TiO2@Co-MOF@foamed nickel-based photothermal composite material according to any one of claims 8 to 9 in the fields of obtaining clean water through interfacial solar water evaporation and evaporation-induced power generation.

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