Photo-thermal material based on RE-MOF, photo-thermal interface evaporator and preparation method and application of photo-thermal material

Abstract

The invention provides a photo-thermal material based on RE-MOF, a photo-thermal interface evaporator and a preparation method and application of the photo-thermal material. The photo-thermal material based on the RE-MOF comprises a two-dimensional nanosheet-shaped rare earth MOF material and a polydopamine coating layer on the surface of the rare earth MOF material. According to the photo-thermal material based on RE-MOF, the rare earth MOF material is coated with polydopamine, so that the photo-thermal material has high light absorption capacity and hydrothermal stability, the evaporation efficiency and photo-thermal conversion capacity of a photo-thermal interface evaporator can be effectively improved, the photo-thermal conversion capacity of the photo-thermal interface evaporator can be effectively improved when the photo-thermal material is applied to the photo-thermal interface evaporator, and the photo-thermal efficiency of the photo-thermal interface evaporator is improved. The photo-thermal interface evaporator which is high in sunlight absorption capacity, stable in performance structure, high in photo-thermal conversion efficiency and good in salt tolerance can be obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of solar-driven seawater desalination, and relates to a RE-MOF-based photothermal material, a photothermal interface evaporator, and a preparation method and application thereof. Background Art

[0002] The shortage of fresh water resources is a problem that cannot be ignored by human beings at this stage. Extracting fresh water resources from seawater is a feasible solution. At present, traditional seawater desalination technologies mainly include multi-stage flash evaporation, reverse osmosis, electrodialysis and membrane distillation, but these solutions have more or less some problems, such as high energy consumption, high cost, environmental pollution and other defects.

[0003] Solar energy is an inexhaustible green and clean energy. If the abundant solar energy is used in the production of fresh water resources, it will be of great significance. However, the efficiency of directly using solar energy to evaporate seawater is very low. Therefore, photothermal interface evaporation technology came into being. Solar photothermal interface evaporation technology can effectively reduce the energy transfer process and improve energy utilization and evaporation efficiency by selectively heating the thin layer of water at the interface.

[0004] At present, the materials used in the field of photothermal interface evaporation are materials with high solar energy absorption rates, such as semiconductor materials, carbon-based materials, metal nanoparticles and organic polymers. However, the solar energy absorption bandwidth of most semiconductor materials is insufficient, which limits their solar energy photothermal conversion efficiency; traditional carbon-based materials have broadband solar energy absorption rates, but are easily affected by pollutants in seawater; metal nanoparticles have good photothermal conversion performance, but the high preparation cost restricts their large-scale application. Therefore, the high cost, narrow light absorption range, poor stability and low production efficiency restrict the practical application of these materials.

[0005] MOF has a large specific surface area and high porosity, making it an ideal choice for water treatment applications, and has attracted the interest of researchers in the field of photothermal interfacial evaporation. By customizing the MOF structure or combining it with other photothermal agents, its light absorption and photothermal conversion capabilities can be effectively improved. RE-MOF is a special subset of MOF that has many applications in the field of photothermal tumor treatment and is a very promising photothermal conversion material. However, there is little research in the field of photothermal interfacial evaporation, and the technology development is relatively blank.

[0006] Based on the above research, it is necessary to provide a RE-MOF-based photothermal material with stable performance, strong sunlight absorption capacity, high photothermal conversion efficiency and good resistance to salt deposition. Summary of the invention

[0007] The purpose of the present invention is to provide a RE-MOF-based photothermal material, a photothermal interface evaporator, and a preparation method and application thereof. The RE-MOF-based photothermal material adopts polydopamine to coat the rare earth MOF material, so that the photothermal material has higher light absorption capacity and hydrothermal stability, which can effectively improve the evaporation efficiency and photothermal conversion capacity of the photothermal interface evaporator.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a RE-MOF-based photothermal material, wherein the RE-MOF-based photothermal material comprises a two-dimensional nanosheet-shaped rare earth MOF material and a polydopamine coating layer on the surface of the rare earth MOF material.

[0010] The present invention adopts a two-dimensional nanosheet rare earth MOF with a surface coated with polydopamine as a photothermal material, wherein the rare earth MOF material itself has excellent photothermal conversion ability. After the surface is coated with a polydopamine coating layer, not only can the stability of the rare earth MOF material in water be improved, so that it can be stable in the evaporator, but also the light absorption capacity of the photothermal material is improved; therefore, the photothermal material of the present invention has the characteristics of large specific surface area, small particles, strong sunlight absorption capacity and high water stability, thereby effectively improving the evaporation efficiency and photothermal conversion capacity of the evaporator.

[0011] Preferably, the mass ratio of the rare earth MOF material to the polydopamine coating layer is 1:(0.1-10), for example, 1:0.1, 1:1, 1:5 or 1:10, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0012] The mass ratio of the rare earth MOF material and the polydopamine coating layer described in the present invention will affect the performance of the photothermal material. If the polydopamine coating layer is too much relative to the rare earth MOF material, the photothermal conversion capacity of the MOF will be reduced; if the polydopamine coating layer is too little relative to the rare earth MOF material, the stability of the rare earth MOF in water will be affected.

[0013] Preferably, the rare earth atoms in the rare earth MOF material include any one of cerium, neodymium, erbium or ytterbium, or a combination of at least two of them, preferably ytterbium.

[0014] Preferably, the organic ligand in the rare earth MOF material includes porphyrin and / or porphyrin derivatives, preferably 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin.

[0015] In a second aspect, the present invention provides a method for preparing a photothermal material based on RE-MOF as described in the first aspect, the preparation method comprising the following steps:

[0016] The rare earth MOF material, dopamine and the first solvent are mixed, and then the pH of the system is adjusted to polymerize dopamine on the surface of the rare earth MOF material, and then solid-liquid separation, washing and drying are performed to obtain the RE-MOF-based photothermal material.

[0017] The polydopamine coating layer of the present invention is directly obtained by in-situ polymerization.

[0018] Preferably, the mass ratio of the rare earth MOF material to dopamine is 1:(0.1-10), for example, 1:0.1, 1:1, 1:5 or 1:10, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0019] Preferably, the pH of the regulating system is 8-13, for example, 8, 10, 12 or 13, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0020] Preferably, the mixing time is 8-24 hours, for example, 8 hours, 10 hours, 15 hours, 20 hours or 24 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0021] Preferably, the mixing includes dispersing the rare earth MOF material in deionized water to form a rare earth MOF dispersion, adding dopamine to a mixed solution including Tris-HCL buffer, deionized water and ethanol to form a dopamine solution, and then mixing the rare earth MOF dispersion and the dopamine solution.

[0022] Preferably, the concentration of the rare earth MOF dispersion is 0-10 mg / mL, but does not include 0 mg / mL. For example, it can be 2 mg / mL, 5 mg / mL, 8 mg / mL or 10 mg / mL, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable.

[0023] Preferably, the dopamine solution is prepared by adding 0-100 mg (excluding 0 mg) of dopamine hydrochloride, for example 10 mg, 30 mg, 50 mg, 70 mg, 90 mg or 100 mg, to 1 mL of 1 mol / L Tris-HCL buffer, 6 mL of deionized water and 3 mL of ethanol.

[0024] Preferably, the method for preparing the rare earth MOF material comprises the following steps:

[0025] The organic ligand, the rare earth salt and the second solvent are mixed to obtain a reaction precursor solution, and then the reaction precursor solution is heated, and then solid-liquid separation and washing are performed to obtain the rare earth MOF material.

[0026] Preferably, the heating method includes microwave heating.

[0027] Preferably, the specific steps of microwave heating include: transferring the reaction precursor solution into a glass vial, and placing the vial in a microwave oven for heating at a certain power for a certain time.

[0028] Preferably, the volume of the reaction precursor solution is 1-10 mL, for example, 1 mL, 5 mL or 10 mL, the volume of the glass vial is 10-50 mL, for example, 10 mL, 30 mL or 50 mL, the power of the microwave heating is 100-700 W, for example, 100 W, 300 W, 500 W, or 700 W, and the time of the microwave heating is 5-30 min, for example, 5 min, 10 min, 20 min or 30 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] Further preferably, the volume of the reaction precursor solution is 1-2 mL, for example, 1 mL, 1.5 mL or 2 mL, the volume of the glass vial is 10-20 mL, for example, 10 mL, 15 mL or 20 mL, the power of the microwave heating is 200-300 W, for example, 200 W, 250 W or 300 W, and the time of the microwave heating is 10-20 min, for example, 10 min, 15 min or 20 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are equally applicable.

[0030] Preferably, the mass ratio of the organic ligand, the rare earth salt and the second solvent is (1-10):(1-10):(1000-2000), for example, it can be 1:1:1000, 5:5:1500 or 10:10:2000, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] Preferably, the rare earth salt includes any one of cerium nitrate hexahydrate, neodymium nitrate hexahydrate, erbium nitrate pentahydrate or ytterbium nitrate pentahydrate, or a combination of at least two thereof, preferably ytterbium nitrate pentahydrate.

[0032] Preferably, in the reaction precursor solution, the content of rare earth salt is 0.005-0.1wt%, for example, 0.005wt%, 0.01wt%, 0.05wt% or 0.1wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0033] Preferably, in the reaction precursor solution, the content of the organic ligand is 0.005-0.1wt%, for example, 0.005wt%, 0.01wt%, 0.05wt% or 0.1wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0034] Preferably, the organic ligand comprises porphyrin and / or porphyrin derivatives, preferably 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin.

[0035] Preferably, the second solvent comprises any one of N,N-dimethylformamide, N,N-dimethylacetamide or deionized water, or a combination of at least two thereof, preferably N,N-dimethylformamide.

[0036] In a third aspect, the present invention provides a RE-MOF-based photothermal interface evaporator, wherein the RE-MOF-based photothermal interface evaporator comprises a hydrogel and the RE-MOF-based photothermal material as described in the first aspect, and the photothermal interface evaporator has a pore structure.

[0037] The present invention adopts hydrogel as the evaporator substrate, and adds a RE-MOF-based photothermal material therein. The photothermal interface evaporator has a pore structure to form a high-strength double-network hydrogel photothermal interface evaporator. The channel formed by the pore structure can not only effectively transmit water, but also continuously dissolve and transport the salt ions generated on the surface of the evaporator into the bulk water, thereby preventing salt from depositing on the surface of the evaporator and improving the cycle stability of the interface evaporator.

[0038] Preferably, the photothermal interface evaporator has a vertically arranged pore structure.

[0039] The vertically arranged pore structure of the present invention enables the evaporator to have vertically oriented channels, which can transport water in a directional manner and prevent salt from being deposited on the surface of the evaporator.

[0040] Preferably, in the photothermal interface evaporator, the content of the photothermal material is 0.01-1wt%, for example, it can be 0.01wt%, 0.05wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt% or 1wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0041] In the photothermal interface evaporator described in the present invention, if there is too little photothermal material, the evaporation rate and photothermal conversion efficiency of the photothermal interface evaporator will be reduced. If there is too much photothermal material, the internal pores of the hydrogel will be blocked, affecting its water transmission performance, and further reducing the evaporation rate and photothermal conversion efficiency of the entire evaporator.

[0042] In a fourth aspect, the present invention provides a method for preparing a photothermal interface evaporator based on RE-MOF as described in the third aspect, the preparation method comprising the following steps:

[0043] (1) mixing a water-soluble polymer material, the photothermal material as described in the first aspect, a cross-linking agent and a third solvent to obtain a mixed solution;

[0044] (2) transferring the mixed solution into a mold for directional freezing, wherein the mold has a temperature gradient in a vertical and horizontal direction during the directional freezing, and thawing after the directional freezing;

[0045] (3) The directional freezing and thawing process of step (2) is repeated, and the product of the directional freezing obtained last time is freeze-dried to obtain the RE-MOF-based photothermal interface evaporator.

[0046] The present invention uses a water-soluble polymer material to form a hydrogel material under the action of a cross-linking agent. At the same time, a photothermal material is added in the process of forming the hydrogel material, and a directional freezing method is used to assist the mold to have a temperature gradient in the vertical and horizontal directions, so that the mixed liquid can be frozen in a certain direction in the mold to form directionally growing ice crystals. For example, the temperature at the bottom of the mold is low, and the temperature gradually increases upwards, so that the hydrogel ice crystals can grow vertically and directional. Finally, after the solvent is removed by freeze-drying, a directional channel (such as a vertically arranged channel) can be formed.

[0047] The present invention cycles the directional freezing and thawing process of step (2) to exert physical cross-linking to form a hydrogel; that is, the present invention uses chemical cross-linking of a cross-linking agent and physical cross-linking of cyclic freezing and thawing to form a hydrogel.

[0048] Preferably, the mixing in step (1) comprises: adding a water-soluble polymer material into water and heating and dissolving it to obtain a hydrogel precursor solution; mixing the photothermal material with deionized water to obtain a photothermal material dispersion, and adding the photothermal material dispersion and a cross-linking agent into the hydrogel precursor solution and heating and stirring;

[0049] Preferably, the concentration of the photothermal material dispersion is 0-10 mg / mL, but does not include 0 mg / mL. For example, it can be 1 mg / mL, 3 mg / mL, 5 mg / mL, 7 mg / mL, 9 mg / mL or 10 mg / mL, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 6-10 mg / mL.

[0050] The present invention can change the content of the photothermal material in the evaporator by changing the concentration of the photothermal material dispersion, thereby ensuring the evaporation efficiency and photothermal conversion capacity of the evaporator.

[0051] Preferably, in the hydrogel precursor solution, the content of the water-soluble polymer material is 1-10wt%, for example, it can be 1wt%, 3wt%, 5wt%, 7wt%, 9wt% or 10wt%, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 3-7wt%.

[0052] Preferably, the temperature for heating and dissolving the water-soluble polymer material is 90-120°C (preferably 100-105°C), for example, 90°C, 100°C, 110°C or 120°C, and the time is 0.5-4h (preferably 1-2h), for example, 0.5h, 1.5h, 2.5h, 3.5h or 4h, but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0053] Preferably, the temperature of the heating and stirring is 90-120°C (preferably 100-105°C), for example, 90°C, 100°C, 110°C or 120°C, and the time is 10-30min (preferably 15min), for example, 10min, 20min or 30min, but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0054] Preferably, the water-soluble polymer material includes any one of polyvinyl alcohol, agar, sodium alginate or chitosan, or a combination of at least two thereof, preferably polyvinyl alcohol and agar.

[0055] Preferably, the mass ratio of polyvinyl alcohol to agar is (1-9):(1-9), for example, 9:1, 7:3, 5:5 or 3:7, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0056] Preferably, the cross-linking agent includes KH560 silane coupling agent or a hydrochloric acid-glutaraldehyde mixed solution.

[0057] Preferably, the bottom of the mold in step (2) is made of metal and the side walls are made of plastic.

[0058] Preferably, the bottom of the mold in step (2) is a brass plate, and the side is a polytetrafluoroethylene material.

[0059] Preferably, the mold in step (2) is a cylindrical mold with an inner diameter of 2-4 cm, for example, 2 cm, 3 cm or 4 cm, and a height of 2-4 cm, for example, 2 cm, 3 cm or 4 cm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0060] Preferably, the freezing source for the directional freezing in step (2) is located at the bottom of the mold, and the mold has a temperature gradient that gradually decreases from top to bottom in the vertical and horizontal directions, so that the solution inside the mold is directionally frozen from bottom to top.

[0061] Preferably, the directional freezing method includes placing the bottom of the mold in liquid nitrogen to allow the hydrogel ice crystals in the mixed liquid to grow vertically upward.

[0062] The specific steps of directional freezing of the present invention include: placing the mold in an insulating container (such as a foam box), adding a certain volume of liquid nitrogen to the bottom of the foam box, the liquid nitrogen can completely cover the bottom of the mold, so that the mold has a temperature gradient in the vertical direction, and the mixed liquid in the mold will be directionally frozen from bottom to top, and the directional freezing can be completed by waiting for the mixed liquid inside the mold to be completely frozen; pay attention to keeping the freezing process of the mixed liquid stable, so that the ice crystals grow vertically and evenly upward to form an anisotropic ice crystal template.

[0063] The multiple directional freezing and thawing cycles of the present invention refer to that the frozen gel is placed at room temperature and thawed again, and the freezing and thawing process is repeated multiple times. Preferably, the freezing and thawing cycle is 2-4 times, preferably 3 times.

[0064] Preferably, the vacuum degree of the freeze-drying in step (3) is 5-30 Pa, for example, it can be 5 Pa, 10 Pa, 15 Pa, 20 Pa, 25 Pa or 30 Pa, the temperature is -80 to -40 ° C, for example, it can be -40 ° C, -50 ° C, -60 ° C, -70 ° C or -80 ° C, and the time is 12-48 h, for example, it can be 12 h, 20 h, 30 h, 40 h or 48 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0065] In a fifth aspect, the present invention provides an application of the RE-MOF-based photothermal interface evaporator as described in the third aspect, wherein the application includes use for seawater desalination.

[0066] When the photothermal interface evaporator of the present invention is used, it can be directly placed above the water body to be desalinated.

[0067] Compared with the prior art, the present invention has the following beneficial effects:

[0068] (1) The photothermal material of the present invention is a polydopamine-coated RE-MOF material, which can not only improve the stability of RE-MOF in water, but also improve the light absorption capacity of the composite material, thereby effectively improving the evaporation efficiency and photothermal conversion capacity of the evaporator;

[0069] (2) The present invention uses hydrogel as the evaporator substrate, and adds RE-MOF-based photothermal materials to the hydrogel precursor, assisted by directional freezing technology to form a high-strength double-network hydrogel interface evaporator with vertically oriented channels. The oriented channels can not only effectively transport water, but also continuously dissolve and transport the salt ions generated on the surface of the evaporator into the bulk water, thereby preventing salt from depositing on the surface of the evaporator and improving the cycle stability of the interface evaporator. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 XRD patterns of RE-MOF and RE-MOF@PDA prepared in Example 1 of the present invention.

[0071] Figure 2 This is a scanning electron microscope image of the photothermal interface evaporator prepared in Example 1 of the present invention at a scale of 100 μm.

[0072] Figure 3 This is a scanning electron microscope image of the photothermal interface evaporator prepared in Example 1 of the present invention at a scale of 1 μm.

[0073] Figure 4 This is the heating and cooling curve of the RE-MOF dispersion described in Example 1 of the present invention under 532nm laser irradiation.

[0074] Figure 5 This is the heating and cooling curve of the RE-MOF@PDA dispersion described in Example 1 of the present invention under 532nm laser irradiation.

[0075] Figure 6 This is a physical schematic diagram of the photothermal interface evaporator described in the present invention simulating a solar evaporation system.

[0076] Figure 7 This is a schematic diagram of the application of the photothermal interface evaporator of the present invention.

[0077] Figure 8 This is an infrared temperature diagram of the photothermal interface evaporator described in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 of the present invention during the evaporation process.

[0078] Fig. 9 The figure shows the changes in surface salt accumulation of the photothermal interface evaporator described in Example 2 of the present invention under the irradiation of high-concentration salt water (15%).

[0079] Fig.10This is a schematic diagram of the salt dissolution process on the surface of the photothermal interface evaporator described in Example 2 of the present invention.

[0080] Among them, 1-solar simulator, 2-photothermal interface evaporator, 3-electronic balance, 4-polyethylene foam, 5-beaker. DETAILED DESCRIPTION

[0081] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0082] Example 1

[0083] This embodiment provides a photothermal material based on RE-MOF, wherein the photothermal material based on RE-MOF includes a two-dimensional nanosheet rare earth MOF material and a polydopamine coating layer on the surface of the rare earth MOF material, wherein the mass ratio of the rare earth MOF material to the polydopamine coating layer is 1:2;

[0084] The preparation method of the RE-MOF-based photothermal material comprises the following steps:

[0085] (1) 23.7 mg of ligand TCPP (5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin) and 40.5 mg of ytterbium nitrate hexahydrate were dissolved in 90 mL of DMF, with the mass ratio of TCPP, ytterbium nitrate hexahydrate and DMF being about 3:5:1125, and ultrasonic-assisted dissolution was performed to obtain a reaction precursor solution;

[0086] (2) 2 mL of the above reaction precursor solution was transferred to a glass vial, which was placed in a microwave oven and heated at a power of 270 W for 10 min. After centrifugal washing and drying, the nanosheet RE-MOF material was obtained, which was then dissolved in deionized water to form a RE-MOF dispersion with a concentration of 10 mg / mL.

[0087] (3) Take 3 mL of the above RE-MOF dispersion and add 10 mL of a 6 mg / mL dopamine hydrochloride solution thereto, wherein the dopamine hydrochloride solution is prepared by adding 60 mg of dopamine hydrochloride to 1 mL of a 1 mol / LTris-HCl buffer solution, 6 mL of deionized water, and 3 mL of an ethanol mixed solution;

[0088] The above solution was stirred at room temperature for 8 h to allow dopamine to oxidatively polymerize on the surface of RE-MOF. Finally, the RE-MOF@PDA photothermal material, i.e., polydopamine-coated RE-MOF, was obtained by filtration, washing and drying.

[0089] This embodiment also provides a RE-MOF-based photothermal interface evaporator, wherein the RE-MOF-based photothermal interface evaporator comprises a hydrogel and a RE-MOF-based photothermal material as described in this embodiment, wherein the content of the photothermal material is 0.15 wt %;

[0090] The preparation method of the photothermal interface evaporator comprises the following steps:

[0091] (I) dispersing the photothermal material obtained in Example 1 in deionized water to form a RE-MOF@PDA photothermal material dispersion;

[0092] 0.5 g of polyvinyl alcohol and 0.5 g of agar were added to 15 mL of deionized water, and dissolved by heating in an oil bath at 105° C. and 300 rpm to obtain a hydrogel precursor solution;

[0093] (II) 3 mL of RE-MOF@PDA photothermal material dispersion with a concentration of 10 mg / mL was added to the hydrogel precursor solution and stirred evenly, and then 0.2 g of KH560 crosslinker was added and stirred for 5 min. Then, the solution was transferred while hot to a mold with a brass bottom and a polytetrafluoroethylene sidewall. The inner diameter of the mold was 2 cm and the height was 4 cm.

[0094] (III) Using liquid nitrogen to assist in directional freezing of hydrogel: placing the mold in a foam box, adding liquid nitrogen to the bottom of the foam box, the liquid nitrogen covers the bottom of the mold, forming a vertically arranged temperature gradient in the mold, waiting for the solution in the mold to be completely frozen, and then transferring the mold to deionized water for dissolution, repeating freeze-thaw three times, and finally placing the frozen hydrogel in a freeze dryer and freeze-drying it at -55°C for 24 hours to obtain the photothermal interface evaporator.

[0095] The XRD spectra of RE-MOF and RE-MOF@PDA prepared in this example are as follows: Figure 1 As shown by Figure 1 It can be seen that the MOF synthesized by microwave method has obvious crystallization peak, indicating that the sample has good crystallinity, the structure of MOF after polydopamine coating has basically not changed, and the spectrum matches well.

[0096] The scanning electron microscope image of the photothermal interface evaporator prepared in Example 1 of the present invention at a scale of 100 μm is as follows: Figure 2 The SEM image at 1 μm is shown in Figure 3 As shown by Figure 2 and Figure 3 It can be seen that it presents a vertically arranged pore structure, and the photothermal material is relatively evenly dispersed on the hydrogel substrate.

[0097] Example 2

[0098] This embodiment provides a photothermal material based on RE-MOF, wherein the photothermal material based on RE-MOF includes a two-dimensional nanosheet rare earth MOF material and a polydopamine coating layer on the surface of the rare earth MOF material, wherein the mass ratio of the rare earth MOF material to the polydopamine coating layer is 1:0.1;

[0099] The preparation method of the RE-MOF-based photothermal material comprises the following steps:

[0100] (1) 23.7 mg of ligand TCPP (5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin) and 40.5 mg of ytterbium nitrate hexahydrate were dissolved in 90 mL of DMF, with the mass ratio of TCPP, ytterbium nitrate hexahydrate and DMF being about 3:5:1125, and a reaction precursor solution was obtained by ultrasonic-assisted dissolution;

[0101] (2) 2 mL of the above reaction precursor solution was transferred to a glass vial, which was placed in a microwave oven and heated at a power of 700 W for 5 min. After centrifugal washing and drying, the nanosheet RE-MOF material was obtained, which was then dissolved in deionized water to form a RE-MOF dispersion with a concentration of 10 mg / mL;

[0102] (3) taking 3 mL of the above RE-MOF dispersion, adding 10 mL of a 0.3 mg / mL dopamine hydrochloride solution thereto, wherein the dopamine hydrochloride solution is prepared by adding a certain amount of dopamine hydrochloride to a mixed solution of 1 mL of 1 mol / LTris-HCl buffer, 6 mL of deionized water, and 3 mL of ethanol;

[0103] The above solution was stirred at room temperature for 24 hours to allow dopamine to oxidatively polymerize on the surface of RE-MOF. Finally, the RE-MOF@PDA photothermal material, i.e., polydopamine-coated RE-MOF, was obtained by filtration, washing and drying.

[0104] This embodiment also provides a RE-MOF-based photothermal interface evaporator, wherein the RE-MOF-based photothermal interface evaporator comprises a hydrogel and a RE-MOF-based photothermal material as described in this embodiment, wherein the content of the photothermal material is 0.15 wt %;

[0105] The preparation method of the photothermal interface evaporator comprises the following steps:

[0106] (I) dispersing the photothermal material obtained in Example 2 in deionized water to form a RE-MOF@PDA photothermal material dispersion;

[0107] 0.5 g of polyvinyl alcohol and 0.5 g of agar were added to 15 mL of deionized water, and dissolved by heating in an oil bath at 120° C. and 300 rpm to obtain a hydrogel precursor solution;

[0108] (II) 3 mL of RE-MOF@PDA photothermal material dispersion with a concentration of 10 mg / mL was added to the hydrogel precursor solution and stirred evenly, and then 0.2 g of KH560 crosslinker was added and stirred for 5 min. Then, the solution was transferred while hot to a mold with a brass bottom and a polytetrafluoroethylene sidewall. The inner diameter of the mold was 2 cm and the height was 4 cm.

[0109] (III) Using liquid nitrogen to assist in directional freezing of hydrogel: placing the mold in a foam box, adding liquid nitrogen to the bottom of the foam box, the liquid nitrogen covers the bottom of the mold, forming a vertically arranged temperature gradient in the mold, waiting for the solution in the mold to be completely frozen, and then transferring the mold to deionized water for dissolution. Repeat freezing and thawing three times, and for the last time placing the frozen hydrogel in a freeze dryer and freeze-drying it at -40°C for 48 hours to obtain the photothermal interface evaporator.

[0110] Example 3

[0111] This embodiment provides a photothermal material based on RE-MOF, wherein the photothermal material based on RE-MOF includes a two-dimensional nanosheet rare earth MOF material and a polydopamine coating layer on the surface of the rare earth MOF material, wherein the mass ratio of the rare earth MOF material to the polydopamine coating layer is 1:10;

[0112] The preparation method of the RE-MOF-based photothermal material comprises the following steps:

[0113] (1) 23.7 mg of ligand TCPP and 40.5 mg of ytterbium nitrate hexahydrate were dissolved in 90 mL of DMF, with the mass ratio of TCPP, ytterbium nitrate hexahydrate and DMF being about 3:5:1125, and ultrasonic-assisted dissolution was performed to obtain a reaction precursor solution;

[0114] (2) 2 mL of the above reaction precursor solution was transferred to a glass vial, which was placed in a microwave oven and heated at a power of 100 W for 30 min. After centrifugal washing and drying, the nanosheet RE-MOF material was obtained, which was then dissolved in deionized water to form a RE-MOF dispersion with a concentration of 10 mg / mL.

[0115] (3) Take 3 mL of the above RE-MOF dispersion and add 10 mL of a 30 mg / mL dopamine hydrochloride solution thereto, wherein the dopamine hydrochloride solution is prepared by adding a certain amount of dopamine hydrochloride to a mixed solution of 1 mL of 1 mol / LTris-HCl buffer, 6 mL of deionized water, and 3 mL of ethanol;

[0116] The above solution was stirred at room temperature for 8 h to allow dopamine to oxidatively polymerize on the surface of RE-MOF. Finally, the RE-MOF@PDA photothermal material, i.e., polydopamine-coated RE-MOF, was obtained by filtration, washing and drying.

[0117] This embodiment also provides a RE-MOF-based photothermal interface evaporator, wherein the RE-MOF-based photothermal interface evaporator comprises a hydrogel and a RE-MOF-based photothermal material as described in this embodiment, wherein the content of the photothermal material is 0.15 wt %;

[0118] The preparation method of the photothermal interface evaporator comprises the following steps:

[0119] (I) dispersing the photothermal material obtained in Example 3 in deionized water to form a RE-MOF@PDA photothermal material dispersion;

[0120] 0.5 g of polyvinyl alcohol and 0.5 g of agar were added to 15 mL of deionized water, and dissolved by heating in an oil bath at 90° C. and 300 rpm to obtain a hydrogel precursor solution;

[0121] (II) 3 mL of RE-MOF@PDA photothermal material dispersion with a concentration of 10 mg / mL was added to the hydrogel precursor solution and stirred evenly, and then 0.2 g of KH560 crosslinker was added and stirred for 5 min. Then, the solution was transferred while hot to a mold with a brass bottom and a polytetrafluoroethylene sidewall. The inner diameter of the mold was 2 cm and the height was 4 cm.

[0122] (III) Using liquid nitrogen to assist in directional freezing of hydrogel: placing the mold in a foam box, adding liquid nitrogen to the bottom of the foam box, the liquid nitrogen covers the bottom of the mold, forming a vertically arranged temperature gradient in the mold, waiting for the solution in the mold to be completely frozen, and then transferring the mold to deionized water for dissolution. Repeat freezing and thawing three times, and for the last time placing the frozen hydrogel in a freeze dryer and freeze-drying it at -80°C for 12 hours to obtain the photothermal interface evaporator.

[0123] Example 4

[0124] This embodiment provides a RE-MOF-based photothermal material, and the RE-MOF-based photothermal material and the preparation method of the RE-MOF-based photothermal material are the same as those in Embodiment 1.

[0125] This embodiment also provides a photothermal interface evaporator based on RE-MOF. The preparation method of the photothermal interface evaporator is the same as that of Example 1, except that the concentration of the RE-MOF@PDA photothermal material dispersion in step (II) is 8 mg / mL, so that the content of the photothermal material in the photothermal interface evaporator becomes 0.12 wt%.

[0126] Example 5

[0127] This embodiment provides a RE-MOF-based photothermal material, and the RE-MOF-based photothermal material and the preparation method of the RE-MOF-based photothermal material are the same as those in Embodiment 1.

[0128] This embodiment also provides a photothermal interface evaporator based on RE-MOF. The preparation method of the photothermal interface evaporator is the same as that of Example 1, except that the concentration of the RE-MOF@PDA photothermal material dispersion in step (II) is 6 mg / mL, so that the content of the photothermal material in the photothermal interface evaporator becomes 0.09 wt%.

[0129] Example 6

[0130] This embodiment provides a RE-MOF-based photothermal material, and the RE-MOF-based photothermal material and the preparation method of the RE-MOF-based photothermal material are the same as those in Embodiment 1.

[0131] This embodiment also provides a photothermal interface evaporator based on RE-MOF. The preparation method of the photothermal interface evaporator is the same as that of Example 1, except that the concentration of the RE-MOF@PDA photothermal material dispersion in step (II) is 4 mg / mL, so that the content of the photothermal material in the photothermal interface evaporator becomes 0.06 wt%.

[0132] Example 7

[0133] This embodiment provides a RE-MOF-based photothermal material, and the RE-MOF-based photothermal material and the preparation method of the RE-MOF-based photothermal material are the same as those in Embodiment 1.

[0134] This embodiment also provides a photothermal interface evaporator based on RE-MOF. The preparation method of the photothermal interface evaporator is the same as that of Example 1, except that the concentration of the RE-MOF@PDA photothermal material dispersion in step (II) is 2 mg / mL, so that the content of the photothermal material in the photothermal interface evaporator becomes 0.03 wt%.

[0135] Example 8

[0136] The present embodiment provides a photothermal material based on RE-MOF, which is the same as that in Example 1 except that the mass ratio of the rare earth MOF material and the polydopamine coating layer is 1:0.1; the preparation method of the photothermal material is also the same as that in Example 1 except that the formula quantity is adaptively changed.

[0137] This embodiment further provides a photothermal interface evaporator based on RE-MOF. Except for using the photothermal material described in this embodiment, the rest of the photothermal interface evaporator is the same as that of Embodiment 1.

[0138] Example 9

[0139] The present embodiment provides a photothermal material based on RE-MOF, which is the same as that in Example 1 except that the mass ratio of the rare earth MOF material to the polydopamine coating layer is 1:10; the preparation method of the photothermal material is also the same as that in Example 1 except that the formula amount is adaptively changed.

[0140] This embodiment further provides a photothermal interface evaporator based on RE-MOF. Except for using the photothermal material described in this embodiment, the rest of the photothermal interface evaporator is the same as that of Embodiment 1.

[0141] Example 10

[0142] This embodiment provides a RE-MOF-based photothermal material, and the RE-MOF-based photothermal material and the preparation method of the RE-MOF-based photothermal material are the same as those in Embodiment 1.

[0143] This embodiment also provides a photothermal interface evaporator based on RE-MOF. The preparation method of the photothermal interface evaporator is the same as that of Example 1, except that in step (III), the mold is placed in a refrigerator for freezing instead of directional freezing, so that the obtained photothermal interface evaporator changes its adaptability.

[0144] Comparative Example 1

[0145] This comparative example provides a photothermal material, which is the same as Example 1 except that it does not contain a polydopamine coating layer; the preparation method of the photothermal material is the same as Example 1 except that the polydopamine coating step is not performed.

[0146] This comparative example further provides a photothermal interface evaporator, which is the same as Example 1 except that the photothermal material of this comparative example is not coated with polydopamine.

[0147] Comparative Example 2

[0148] This comparative example provides a photothermal material, which is the same as Example 1 except that the photothermal material is a pure polydopamine material; the preparation method of the photothermal material is the same as Example 1 except that the rare earth MOF preparation step is not performed.

[0149] This comparative example also provides a photothermal interface evaporator, which is the same as Example 1 except that the polydopamine material of this comparative example is used as the photothermal material.

[0150] Comparative Example 3

[0151] This comparative example provides a photothermal interface evaporator, which is the same as Example 1 except that it does not contain photothermal material.

[0152] The preparation method of the photothermal interface evaporator described in this comparative example is the same as that of Example 1 except that no photothermal material is added during the preparation.

[0153] Performance Test:

[0154] A 532 nm laser was used to irradiate the photothermal material dispersion, and an infrared thermal imager was used to record the temperature change of the dispersion. The photothermal conversion efficiency of the photothermal material obtained in the above embodiment was tested through the temperature rise and fall curve of the solution. The temperature rise and fall curve of the RE-MOF dispersion in Example 1 of the present invention under 532 nm laser irradiation is as follows: Figure 4 As shown, the temperature rise and fall curve of the RE-MOF@PDA dispersion under 532nm laser irradiation is as follows Figure 5 As shown, the laser thermal conversion efficiencies of the two under 532nm laser irradiation are calculated to be 33.1% and 42.5% respectively through the cooling curve. It can be seen that the polydopamine coating effectively improves the photothermal conversion efficiency.

[0155] The photothermal interface evaporators prepared in the above-mentioned embodiments and comparative examples were subjected to a solar energy simulation evaporation test to test their evaporation rate and photothermal conversion efficiency under pure water conditions.

[0156] The specific test steps are as follows:

[0157] (1) Evaporation rate

[0158] The evaporation performance of the RE-MOF-based interface device was tested using a simulated sunlight interface evaporation system. The actual picture of the entire evaporation system is as follows: Figure 6 As shown, the schematic diagram of the photothermal interface evaporator placed in the beaker is shown in Figure 7 As shown, the simulated sunlight interface evaporation system includes a xenon lamp solar simulator 1, a beaker 5, an electronic balance 3, polyethylene foam 4, and a photothermal interface evaporator 2. By adjusting the current of the xenon lamp and the distance between the light source surface and the hydrogel surface, the light intensity received by the photothermal interface evaporator surface is set to 1 standard sunlight intensity of 1 kW / m 2During the test, the mass change of water in the beaker is recorded by an electronic balance, and the change of the surface temperature of the evaporator is recorded by a thermal imager. The whole test is carried out at 25℃ and 50% humidity. When the evaporation process is stable, the evaporation mass of simulated seawater is recorded within a certain period of time, and the test is repeated 3 times to take the average value.

[0159] The evaporation rate is calculated using Equation 1, which is:

[0160]

[0161] Among them, Δm is the mass change of the whole system, A is the area of ​​the photothermal interface evaporator surface receiving light, and T is the evaporation time.

[0162] (2) Photothermal conversion efficiency:

[0163] The hydrogel evaporator and the blank evaporator with the same evaporation surface area were placed in a dark room under the same conditions, and the mass changes of the two were recorded over a period of time. First, the latent heat H of the bulk water was calculated by Equation 2 LV , and then the equivalent evaporation enthalpy of water in the hydrogel photothermal interface evaporator ΔH is calculated by Equation 3 equ , and then the latent heat H of the aqueous gel photothermal interface evaporator is estimated by Equation 4 LV，Absorber , Sensible heat of aqueous gel photothermal interface evaporator It can be calculated by Equation 5. The total energy H required for water evaporation in the hydrogel photothermal interface evaporator total = ...

[0164]

[0165] ΔH vap m0=ΔH equ m g #(3)

[0166] Among them, H LV represents the latent heat of bulk water, BW represents bulk water, T s Represents the evaporator surface temperature, C p，l is the heat capacity of liquid water, C p，v is the heat capacity of steam water. C p，l =4.18JK -1 g -1 , H LV，373.15K =2257.2 J g -1 , C p，v =(3.47+1.45×10 -3 ×T+1.21×10 4 ×T-2 )×R / M(JK -1 g -1 ),R=8.314JK -1 mol -1 ,M=18.02Jmol -1 ,ΔH vap m0 is the evaporation enthalpy and mass change of water in the blank evaporator, ΔH equ m g is the equivalent evaporation enthalpy and mass change of the photothermal interface evaporator containing water gel. LV，Absorber is the latent heat required for water evaporation in the hydrogel photothermal interface evaporator, H is the sensible heat required for water evaporation in the hydrogel photothermal interface evaporator. total is the total energy required for water evaporation in the hydrogel photothermal interface evaporator, V is the evaporation rate of the evaporator, and E in is the total solar radiation intensity received by the evaporator.

[0167] Table 1 shows the evaporation rate and photothermal conversion efficiency of the photothermal interface evaporator described in the above embodiments and comparative examples in pure water.

[0168] Table 1

[0169]

[0170]

[0171] From Table 1 we can see that:

[0172] (1) It can be seen from Examples 1 and 4-7 that the loading amount of the photothermal material in the hydrogel evaporator has an optimal value. As the loading amount increases from 0 to 30 mg, the evaporation rate of the evaporator shows a trend of first increasing and then decreasing. The optimal loading amount is around 24 mg, and its evaporation rate can reach 2.27 kg / m 2 / h, this is because RE-MOF@PDA has good absorbance and photothermal conversion ability. The increase in loading will improve the absorbance and photothermal conversion efficiency of the entire evaporator. However, as the content of photothermal material further increases, the performance of the evaporator decreases. This is because the amount of photothermal material added is too high, which causes the internal pores of the hydrogel to be blocked, affecting its water transmission performance, thereby reducing the evaporation rate and photothermal conversion efficiency of the entire evaporator.

[0173] (2) It can be seen from Examples 1 and 8-9 that in the photothermal material of the present invention, the mass ratio of the rare earth MOF material to polydopamine is preferably within a specific range, which is beneficial to further improve the performance of the evaporator; It can be seen from Examples 1 and 10 that the introduction of directional freezing technology in the hydrogel synthesis process can effectively improve the evaporation efficiency. This is because the vertically arranged channels generated by directional freezing can effectively improve the ability of the hydrogel to transport water, further improving the evaporation efficiency. At the same time, the porous channels can also increase the refraction and reflection of sunlight inside them, thereby improving light absorption, etc.

[0174] (3) It can be seen from Example 1 and Comparative Examples 1-3 that the photothermal conversion ability of RE-MOF@PDA is stronger than that of pure RE-MOF and pure polydopamine. This is because polydopamine can not only protect the RE-MOF material, but also produce a synergistic effect with RE-MOF to improve the photothermal conversion ability. Among them, the comparison of the evaporator surface temperature during the evaporation process of Example 1 and Comparative Examples 1-3 is shown in the figure below. Figure 8 As shown by Figure 8 It can be seen that the surface temperature of Example 2 is higher than that of Comparative Examples 1 and 2, which can also effectively prove that the photothermal conversion ability of RE-MOF / PDA is stronger than that of pure RE-MOF material or pure polydopamine material.

[0175] In addition, the pure water in the beaker of the above system was replaced with simulated salt water of a certain concentration, and the above solar simulated evaporation test was repeated to obtain the photothermal evaporation performance of the evaporator in salt water. Table 2 is the test results of Example 2 in salt water of different concentrations.

[0176] Table 2

[0177]

[0178] It can be seen from Table 2 that in low-concentration salt water, the evaporation performance of the hydrogel evaporator only decreases slightly and is not affected too much. The evaporation rate is not much different from that in pure water. However, as the concentration of salt water increases, the evaporation performance of the evaporation device will decrease to a certain extent.

[0179] In order to further explore the anti-salt deposition performance of the evaporator, the photothermal interface evaporator described in Example 2 was irradiated in a 15% salt water evaporation system for 8 hours, and the surface salt accumulation during the evaporation process was observed. Fig. 9 The salt accumulation changes shown in the figure show that before 2 hours, there was basically no salt deposition on the evaporator surface, and after 4 hours, salt deposition gradually appeared on the evaporator.

[0180] Salt was added to the surface of the evaporator under no light conditions to explore the salt dissolving capacity of the evaporator. The schematic diagram of the salt dissolving process on the surface of the photothermal interface evaporator described in Example 2 is shown in FIG. Fig.10 As shown in the figure, the evaporator has good salt dissolving ability and can completely dissolve the salt particles on the surface within 1 hour. The excellent salt dissolving ability of the evaporator is due to the vertically arranged pores in the hydrogel. When the surface water evaporates and causes the salt concentration in the top layer to rise, the vertically arranged channels can transport the high-concentration salt ions on the top to the bottom, thereby avoiding salt deposition on the surface to a large extent.

[0181] In summary, the present invention provides a RE-MOF-based photothermal material, a photothermal interface evaporator, and a preparation method and application thereof. The RE-MOF-based photothermal material adopts polydopamine to coat the rare earth MOF material, so that the photothermal material has higher light absorption capacity and hydrothermal stability, which can effectively improve the evaporation efficiency and photothermal conversion capacity of the photothermal interface evaporator.

[0182] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A photothermal material based on RE-MOF, characterized in that: The RE-MOF-based photothermal material includes a two-dimensional nanosheet-shaped rare earth MOF material and a polydopamine coating layer on the surface of the rare earth MOF material.

2. The RE-MOF-based photothermal material according to claim 1, characterized in that: The mass ratio of the rare earth MOF material to the polydopamine coating layer is 1:(0.1-10); Preferably, the rare earth atoms in the rare earth MOF material include any one or a combination of at least two of cerium, neodymium, erbium or ytterbium, preferably ytterbium; Preferably, the organic ligand in the rare earth MOF material includes porphyrin and / or porphyrin derivatives.

3. A method for preparing a photothermal material based on RE-MOF as claimed in claim 1 or 2, characterized in that: The preparation method comprises the following steps: The rare earth MOF material, dopamine and the first solvent are mixed, and then the pH of the system is adjusted to polymerize dopamine on the surface of the rare earth MOF material, and then solid-liquid separation, washing and drying are performed to obtain the RE-MOF-based photothermal material.

4. The preparation method according to claim 3, characterized in that: The mass ratio of the rare earth MOF material to dopamine is 1:(1-2); Preferably, the pH of the regulating system is 8-13; Preferably, the mixing time is 8-24h; Preferably, the mixing includes dispersing the rare earth MOF material in deionized water to form a rare earth MOF dispersion, adding dopamine to a mixed solution including Tris-HCL buffer, deionized water and ethanol to form a dopamine solution, and then mixing the rare earth MOF dispersion and the dopamine solution.

5. The preparation method according to claim 3 or 4, characterized in that: The method for preparing the rare earth MOF material comprises the following steps: Mixing an organic ligand, a rare earth salt and a second solvent to obtain a reaction precursor solution, then heating the reaction precursor solution, and then performing solid-liquid separation and washing to obtain the rare earth MOF material; Preferably, the heating method includes microwave heating; Preferably, the microwave heating has a power of 100-700 W and a time of 5-30 min; Preferably, the mass ratio of the organic ligand, the rare earth salt and the second solvent is (1-10):(1-10):(1000-2000); Preferably, the rare earth salt comprises any one of cerium nitrate hexahydrate, neodymium nitrate hexahydrate, erbium nitrate pentahydrate or ytterbium nitrate pentahydrate, or a combination of at least two thereof; Preferably, the organic ligand comprises porphyrin and / or porphyrin derivatives; Preferably, the second solvent includes any one of N,N-dimethylformamide, N,N-dimethylacetamide or deionized water, or a combination of at least two thereof.

6. A photothermal interface evaporator based on RE-MOF, characterized in that: The RE-MOF-based photothermal interface evaporator comprises a hydrogel and the RE-MOF-based photothermal material according to claim 1 or 2, and the photothermal interface evaporator has a pore structure; Preferably, the photothermal interface evaporator has a vertically arranged pore structure; Preferably, in the photothermal interface evaporator, the content of the photothermal material is 0.01-1 wt %.

7. A method for preparing a photothermal interface evaporator based on RE-MOF as claimed in claim 6, characterized in that: The preparation method comprises the following steps: (1) mixing a water-soluble polymer material, the photothermal material according to claim 1 or 2, a cross-linking agent and a third solvent to obtain a mixed solution; (2) transferring the mixed solution into a mold for directional freezing, wherein the mold has a temperature gradient in a vertical and horizontal direction during the directional freezing, and thawing after the directional freezing; (3) The directional freezing and thawing process of step (2) is repeated, and the product of the directional freezing obtained last time is freeze-dried to obtain the RE-MOF-based photothermal interface evaporator.

8. The preparation method according to claim 7, characterized in that: The mixing in step (1) comprises: adding a water-soluble polymer material into water and heating and dissolving it to obtain a hydrogel precursor solution; mixing the photothermal material with deionized water to obtain a photothermal material dispersion, and adding the photothermal material dispersion and a cross-linking agent into the hydrogel precursor solution and heating and stirring; Preferably, the concentration of the photothermal material dispersion is 0-10 mg / mL, excluding 0 mg / mL, and preferably 6-10 mg / mL; Preferably, the content of the water-soluble polymer material in the hydrogel precursor solution is 1-10wt%; Preferably, the temperature for heating and dissolving the water-soluble polymer material is 90-120° C. and the time is 0.5-4 h; Preferably, the heating and stirring temperature is 90-120°C and the time is 10-30min; Preferably, the water-soluble polymer material includes any one of polyvinyl alcohol, agar, sodium alginate or chitosan, or a combination of at least two thereof; Preferably, the cross-linking agent includes KH560 silane coupling agent or a hydrochloric acid-glutaraldehyde mixed solution.

9. The preparation method according to claim 7 or 8, characterized in that: The bottom of the mold in step (2) is made of metal, and the side walls are made of plastic; Preferably, the mold in step (2) is a cylindrical mold with an inner diameter of 2-4 cm and a height of 2-4 cm; Preferably, the freezing source of the directional freezing in step (2) is located at the bottom of the mold; Preferably, the directional freezing method in step (2) includes placing the bottom of the mold in liquid nitrogen to allow the hydrogel ice crystals in the mixed liquid to grow vertically upward; Preferably, the vacuum degree of the freeze-drying in step (3) is 5-30 Pa, the temperature is -80 to -40°C, and the time is 12-48 hours.

10. An application of the photothermal interface evaporator based on RE-MOF as claimed in claim 6, characterized in that: The applications include use in seawater desalination.

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