Photothermal nanomaterials Cu 2-x Photocatalytic biosynthesis of Se and its application in photothermal distillation of seawater desalination

Abstract

The present invention discloses a photothermal nanomaterial Cu 2‑x The present invention uses a hybrid system Bio-Se to synthesize Se in situ by reducing Na2SeO3 with dissimilatory metal-reducing bacteria. 0 As a semi-artificial photosynthetic system, Cu(II)-EDTA is used as a precursor, and the enzyme catalysis system and semiconductor Se 0 Photocatalysis was carried out by Cu 2‑ x Photocatalytic biosynthesis of Se and its application in photothermal distillation membrane Cu 2‑x Preparation of Se@MR-1@PVDF and desalination of seawater. The method of the present invention removes heavy metal ions Cu(II) and generates high-value products Cu 2‑x Se not only has strong absorption of visible light, but also has a plasma resonance effect (SPR) in the near-infrared range, which makes the distillation membrane have higher photothermal performance; the doped biological components improve the hydrophilicity of the membrane.

Description

Technical Field

[0001] The present invention belongs to the technical field of photothermal metal nanomaterial synthesis and seawater desalination treatment, and particularly relates to a photothermal nanomaterial Cu 2-x Photocatalytic biosynthesis of Se and its application in photothermal distillation of seawater. Background Art

[0002] Polyvinylidene fluoride (PVDF) membranes have good mechanical strength, high thermal stability and strong chemical resistance. The PVDF composite membranes doped with metal materials prepared by the phase inversion method have the advantages of simple preparation method, convenient transportation and less metal ion leaching. Therefore, in recent years, there have been many studies using PVDF membrane as the substrate and doping with metal materials with SPR effect for photothermal distillation. However, the poor hydrophilicity of PVDF membranes makes it easy to be contaminated and the water flux is reduced. At present, some studies have doped extracellular polymers (EPS) in activated sludge into PVDF membranes, which significantly improved the pure water flux and anti-fouling performance of the membranes, but the process of extracting EPS is cumbersome and complicated, and only its secretions are extracted, and some functions of the organisms themselves are not effectively utilized. Other studies have only doped metal materials. Although the photothermal performance of the membrane has been improved, the poor hydrophilicity of the PVDF membrane has not been solved, which has hindered water exchange and ultimately made the water evaporation efficiency still low.

[0003] Cu 2-x Se nanomaterials have a high degree of copper defect structure and unique photothermal and photoelectric properties. They are widely used in photothermal anticancer, photothermal antibacterial, gas sensors, pollutant degradation, power generation and refrigeration, photothermal distillation membranes, biosensors and devices, biomedical imaging, plasma light scattering material identification, persulfate activation, adsorption and other fields. 2-x Se preparation methods include solvothermal method, microwave synthesis method, ultrasonic method and hydrothermal method, but these preparation methods have the disadvantages of complex preparation process, harsh reaction conditions, toxic reagents involved in the reaction process, high preparation cost and poor product biocompatibility. In recent years, due to the advantages of low cost and environmental friendliness of microorganisms in the fields of environment and energy, they have been studied and applied, such as microbial environmental remediation and microbial energy synthesis. Considering that the transformation of heavy metals in nature is closely related to the ubiquitous microorganisms and the various substances they secrete, a biological-abiotic system was constructed in situ to synthesize Cu 2-x Se becomes a possibility.

[0004] It is reported that Se nanoparticles have good photoconductivity. Single crystal Se has stable photocatalytic performance; amorphous Se also has a suitable band gap at room temperature, has strong absorption capacity for ultraviolet and visible light, and has high photosensitivity. 2-x Se method does not utilize Se 0 photocatalytic properties.

[0005] Currently, biosynthetic Cu 2-x The Se method mainly adds selenite and divalent copper salt precursors to the dissimilatory metal-reducing bacteria at the same time, and uses the detoxification function of the organism to synthesize. However, this method usually causes the system to be highly toxic to the organism, making the reaction unsustainable. 2-x The amount of Se synthesized is small. Summary of the Invention

[0006] In view of this, the present invention provides a photothermal nanomaterial Cu 2-x The photocatalytic biosynthesis method of Se and its application in photothermal distillation and desalination of seawater. The present invention makes full use of the detoxification function of bacteria to construct a semi-artificial system Bio-Se in situ. 0 and photocatalytically synthesized Cu by doping with this semi-artificial system. 2-x Se@MR-1 material not only improves the hydrophilicity of PVDF membrane, but also enhances its photothermal efficiency, thereby improving the photothermal distillation efficiency of the membrane.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] The present invention's photothermal nanomaterial Cu 2-x The photocatalytic biosynthesis method of Se comprises the following steps:

[0009] Step 1: Cultivate the dissimilatory metal-reducing bacteria in a culture medium until the early stage of the plateau phase;

[0010] Step 2: The dissimilatory metal-reducing bacteria cultured in step 1 to the early stage of the platform were transferred to the anaerobic culture medium, and selenite was added thereto. After anaerobic reaction, the semi-artificial system Bio-Se was successfully constructed. 0 ;

[0011] Step 3: Add the semi-artificial system Bio-Se obtained in step 2 0 Add Cu(II)-EDTA and place it under light, and Cu(II)-EDTA is obtained through photoreaction. 2-x Se nanoparticles; wherein x=0-1;

[0012] Step 4: The composite Cu obtained in step 3 2-x Se@MR-1 was freeze-dried (-40°C to -50°C, 20-30 Pa) and ground into solid powder.

[0013] Furthermore, in step 1, a single colony was picked from the plate of dissimilatory metal-reducing bacteria and cultured aerobically in LB medium for 12 hours, and then the bacterial solution was transferred to fresh LB medium at a ratio of 1:10 and continued to be aerobically cultured for 12 hours.

[0014] The dissimilatory metal-reducing bacteria is a wild-type strain of S. oneidensis MR-1.

[0015] Furthermore, in step 2, the anaerobic incubation time is 10 hours; the selenite is sodium selenite. The amount of selenite added and the reaction time can affect performance, particularly bacterial activity, and thus experimental results. The present invention optimizes the use of a final selenite concentration of 0.5 mM.

[0016] In step 2, the anaerobic culture medium is transferred to LB culture medium, and then an anaerobic environment is achieved by exposing to N2.

[0017] Furthermore, in step 3, the photocatalytic anaerobic incubation time is 24 hours. Cu(II)-EDTA is added in the form of divalent copper salt (copper chloride) and EDTA. The present invention uses a Cu(II)-EDTA complex with a final concentration of 1 mM.

[0018] In the present invention, the anaerobic environment is achieved by exposing to N2, and a xenon lamp is used to simulate the sunlight source.

[0019] The present invention's photothermal nanomaterial Cu 2-x The application of Se is based on the photothermal material Cu 2-x Se@MR-1 and PVDF are used to construct a composite membrane material, which is then used as a photothermal distillation membrane to desalinate seawater.

[0020] The specific steps include:

[0021] The photothermal material Cu 2-x Se@MR-1 solid powder, PVDF polymer mixed powder and appropriate amount of pure DMF were stirred and mixed at room temperature. After degassing, the casting solution was transferred to a glass plate and a composite film was cast using a 200 μm gap scraper. The film was then removed with ultrapure water to obtain Cu 2-x Se@MR-1@PVDF composite membrane; the Cu 2-x Se@MR-1@PVDF composite membrane is used as photothermal distillation membrane to desalinate seawater.

[0022] Among them, the mass of PVDF accounts for 15% of the total mass of the casting solution, and Cu 2-x The mass of Se@MR-1 solid powder accounts for 3-10% of the total mass of the casting solution, preferably 5-10%.

[0023] During the experiment of the present invention, as a comparison, Cu 2-x Se@MR-1@PVDF composite membrane (Cu 2-x Se@MR-1 doping amounts were 0%, 3%, 5%, and 10% in sequence and used in pure water, 0.5M NaCl, and actual seawater photothermal distillation experiments: 0.5h dark → 1h light → 1h dark; 10% Cu 2-xSe@MR-1@PVDF composite membrane was used in the photothermal distillation cycle experiment of pure water, 0.5M NaCl and actual seawater: 10 cycle experiments were carried out with 1h illumination as one cycle.

[0024] The photothermal distillation experiment recorded the evaporated water flux at 5-min intervals.

[0025] The film temperature changes in the photothermal distillation experiment were recorded using an infrared camera.

[0026] The light condition of the photothermal distillation experiment is 1 sun intensity.

[0027] Cu 2-x The valence of Cu in Se includes monovalent copper and divalent copper (x represents the proportion of divalent copper). 2+ Cu 2-x Se has been reported, but Cu 2+ The simultaneous addition of Na2SeO3 can lead to severe bacterial toxicity, Cu 2-x Se synthesis is unsustainable. According to this study, Bio-Se 0 The addition of divalent copper salts to the system resulted in better biological activity because the system was not toxic to both selenite and divalent copper salts. 2-x Se has been reported, but Bio-Se has not yet been reported. 0 As a semi-artificial system, using photosynthetic Cu 2-x Research on Se.

[0028] Therefore, the present invention proposes to use biological in situ construction of Bio-Se 0 Photocatalytic synthesis of Cu 2-x A new method for Se. Construction of Bio-Se by S. oneidensis MR-1 and sodium selenite 0 , using bacterial enzyme catalysis and Se photocatalysis to synthesize Cu 2-x Se photothermal nanomaterials, and the product Cu 2-x Se@MR-1 is used for the preparation of photothermal distillation membrane and its application in seawater desalination.

[0029] Compared with the preparation and application of reported photothermal distillation membranes, the present invention has the following advantages:

[0030] The system of the present invention has low toxicity to bacteria and can synthesize Cu efficiently and quickly. 2-xSe nanoparticles are easy to operate, environmentally friendly, and require no toxic chemicals. The doped membrane obtained by the present invention has improved hydrophilicity, increased roughness, and larger membrane pores. Highly efficient photothermal distillation can be achieved using sunlight, and the desalination effect is excellent. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 (A), (C), and (D) are the photocatalytic biosynthesis of Cu in Example 1. 2-x Soft X-ray imaging projection of the bacterial material complex formed after Se nanoparticles, high-angle annular dark field scanning transmission (HAADF-STEM) after sectioning, and the corresponding X-ray energy spectrum (EDS); (B) is the 10% Cu prepared in Example 2 2-x Soft X-ray imaging projection of Se@MR-1@PVDF composite membrane slice;

[0032] Figure 2 For the photocatalytic biosynthesis of Cu in Example 1 2-x X-ray diffraction (XRD) results of Se nanoparticles;

[0033] Figure 3 For different concentrations of Cu in Example 1 2-x Photothermal ΔT data under Se nanoparticles;

[0034] Figure 4 For the different Cu prepared in Example 2 2-x Se@MR-1@PVDF composite membrane (Cu 2-x Optical images of Se@MR-1 doping levels of 0, 3%, 5%, and 10%;

[0035] Figure 5 The Cu prepared in Example 2 2-x Se@MR-1@PVDF composite membrane (Cu 2-x Surface atomic force electron microscopy three-dimensional imaging (3D-AFM) results of Se@MR-1 (doping levels of 0, 3%, 5%, and 10%);

[0036] Figure 6 The Cu prepared in Example 2 2-x Se@MR-1@PVDF composite membrane (Cu 2-x The contact angle results of Se@MR-1 doping levels are 0%, 3%, 5%, and 10%;

[0037] Figure 7 Cu in Example 3 2-x Se@MR-1@PVDF composite membrane (Cu 2-x The film temperature variation data of photothermal distillation experiment (Se@MR-1 doping amount is 0%, 3%, 5%, and 10%);

[0038] Figure 8 Cu in Example 3 2-x Se@MR-1@PVDF composite membrane (Cu 2-x Water evaporation flux data of photothermal distillation experiment (Se@MR-1 doping levels are 0%, 3%, 5%, and 10%);

[0039] Figure 9 Cu in Example 3 2-x Se@MR-1@PVDF composite membrane (Cu 2-x Photothermal conversion efficiency data of photothermal distillation experiments (Se@MR-1 doping levels are 0%, 3%, 5%, and 10%);

[0040] Figure 10 Cu in Example 3 2-x Se@MR-1@PVDF composite membrane (Cu 2-x Photothermal conversion efficiency data of photothermal distillation cycle experiment (Se@MR-1 doping amount is 10%). DETAILED DESCRIPTION

[0041] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, the following detailed description of the specific embodiments of the present invention is provided. The following is merely an example and illustration of the concept of the present invention. Persons skilled in the art may make various modifications, additions, or substitute similar methods for the specific embodiments described. As long as these modifications or additions do not deviate from the concept of the invention or exceed the scope defined by the claims, they shall fall within the scope of protection of the present invention.

[0042] The present invention constructs S.oneidensis MR-1-Se 0 Semi-artificial system, Cu 2+ Converted into photothermal nanomaterial Cu 2- x Se, the obtained Cu 2-x Se@MR-1 is used to dope PVDF membranes for photothermal desalination. Compared to most existing chemical methods for synthesizing and doping materials, this method is environmentally friendly and does not involve toxic agents. It also provides high membrane hydrophilicity, excellent stability, and superior distillation performance.

[0043] The dissimilatory metal-reducing bacteria used in the present invention is a commercially available wild-type strain of S. oneidensis MR-1. Information for purchasing the strain is as follows: Shewanella oneidensis MR-1 (astrain of Shewanella oneidensis; Catalog Number: Shewanella oneidensis ATCC 700550, MR-1; Taxonomy ID: 211586). Purchase information is available at: Shewanella oneidensis Venkateswaran et al. - 700550 | ATCC; Shewanella oneidensis ATCC 700550, MR-1 - Biovector Plasmid Vector, Bacteria, Cell, Protein, and Antibody Gene Collection - NTCC Type Culture Collection (googbio.com). Note: ATCC (American Type Culture Collection) is a collection of American Type Cultures.

[0044] The following is a photothermal nanomaterial Cu provided by the present invention 2-x The photocatalytic biosynthesis method of Se and its application in photothermal distillation membrane desalination of seawater are further explained.

[0045] Example 1: Construction of Bio-Se by Shewanella Oneidensis MR-1 0 Semi-artificial system for photocatalytic biosynthesis of Cu 2-x Se

[0046] (1) Semi-artificial system Bio-Se 0 Construction: After the Shewanella bacteria were cultured to the early stage of the plateau, they were harvested and washed with LB medium at least three times. The centrifugation conditions were 6000 rpm, 10 min, and 4°C. The washed bacteria were resuspended and added to an anaerobic serum bottle containing LB medium (exposed to N2 gas for 30 min) to achieve an initial OD of 600 The value is 1. Sterilized Na2SeO3 was added to the serum bottle to make the final concentration of Se 0.5mM, and the culture was placed in a shaker at 200rpm and 30℃. After culturing for 10h, Bio-Se 0 Hybrid system.

[0047] (2) Photocatalytic biosynthesis of Cu 2-x Se: Bio-Se obtained in (1) 0 Hybrid system, add 1mM Cu(II)-EDTA and irradiate (xenon lamp) for 24h to obtain Cu2-x Se@MR-1 material.

[0048] (3)Cu 2-x Se@MR-1 material recovery: (2) containing Cu 2-x Se material was collected by centrifugation and washed with water three times. 2-x The Se@MR-1 precipitate was freeze-dried using a freeze dryer and ground into a powdered solid using an agate mortar for characterization such as XRD.

[0049] (4) The Cu 2-x Se@MR-1 composite system was tested for performance indicators:

[0050] ① Soft X-ray imaging sample preparation: Cu 2-x The Se@MR-1 complex was washed three times with PBS buffer at pH 7.2, and then the sample was frozen with liquid nitrogen and loaded onto a nickel mesh. All centrifugation conditions involved in the sample preparation process were 6000 rpm, 5 min, and 4°C. Figure 1 (A) It is known that there are a large number of Cu2+ photocatalytic biosynthesized extracellular 2-x Se materials.

[0051] ② Sample sectioning and high-angle annular dark field scanning transmission sample preparation: First, the sample was centrifuged and washed three times with PBS buffer at pH 7.2, and then fixed overnight with double aldehyde fixative (5% glutaraldehyde + 4% paraformaldehyde). The next day, it was washed three times with PBS buffer at pH 7.2, and then dehydrated with ethanol concentration gradient (30%, 50%, 70%, 80%, 95%, 100%), and then washed three times with acetone. The samples needed to be soaked for 20 minutes when treated with the above concentrations of ethanol and acetone. Then, it was soaked in 25% resin for 3-5 hours under light-proof conditions, and then changed to 50% resin overnight. On the morning of the third day, it was changed to 75% resin, and in the evening, it was changed to pure resin overnight. After the above samples were processed, they needed to be placed on a shaker and shaken slightly. On the morning of the fourth day, fresh pure resin was changed for soaking again and placed in an oven to polymerize. Finally, the slices were embedded and sliced ​​using an ultrathin slicer. The slices were fixed on an aluminum mesh and high-angle annular dark field scanning transmission was collected. Cu was determined by energy spectrum. 2-x Elemental composition of Se particles. All centrifugation conditions involved in the sample preparation process were 6000 rpm, 5 min, and 4°C. Figure 1 (C) and (D) are the high-angle annular dark field scanning transmission images and the corresponding energy spectrum results of the synthesized nanoparticles, respectively. It can be seen that the successfully synthesized nanoparticles are composed of Cu and Se elements.

[0052] ③ X-ray diffraction (XRD) characterization sample preparation: the sample was freeze-dried and ground into powder. Figure 2 is the test result, corresponding to Cu 2-x Se card (PDF#06-0680).

[0053] ④Cu 2-x Se@MR-1 photothermal performance test: The mixed solution was washed three times with pure water and resuspended in an EP tube with a solution volume of 200uL. A 1064nm laser with an output power of 1.0W / cm 2 The temperature change of the liquid surface was recorded by infrared camera, and the measurement time was 6 minutes. The results corresponded to Figure 3 As can be seen from the figure, within a certain Cu concentration range, as Cu 2-x As the concentration of Se@MR-1 increases, the photothermal temperature rise ΔT increases, indicating that Cu 2-x Se@MR-1 has photothermal properties.

[0054] Example 2: Preparation of Cu 2-x Se@MR-1@PVDF composite membrane

[0055] This example uses the Cu obtained in Example 1 2-x Preparation of Cu by Se@MR-1 solid powder 2-x Se@MR-1@PVDF composite membrane, the proportion of each component is shown in Table 1.

[0056] Table 1

[0057]

[0058] PVDF powder was added to the DMF solution and stirred to obtain a PVDF / DMF solution. 2-x Se@MR-1 solid powder was added to the PVDF / DMF solution prepared above and ultrasonicated to form Cu 2-x The Se@MR-1 / PVDF / DMF solution mixture was placed in a vacuum drying oven at 30°C for degassing. The casting solution was then transferred to a glass surface and Cu was cast using a 200 μm gap scraper. 2-x Se@MR-1@PVDF composite membrane. 2-x Se@MR-1@PVDF glass was soaked in deionized water for 0.5 h to remove the membrane, and the membrane was trimmed into a circular shape. According to the composition table in Table 1, Cu was obtained through the above steps. 2-x Se@MR-1 doping amount is 0%, 3%, 5%, 10% Cu 2-x Se@MR-1@PVDF composite membrane.

[0059] (1) The Cu prepared in this example 2-x Physical and chemical properties of Se@MR-1@PVDF composite membrane were tested:

[0060] ① Optical picture shooting: Figure 4 As shown, with Cu 2-x As the Se@MR-1 doping amount increases, the film color gradually becomes darker.

[0061] ② Membrane Sample Sectioning and High-Angle Annular Dark-Field Scanning Transmission Sample Preparation: The membrane was soaked in resin in the dark and placed in an oven to polymerize. Finally, the membrane was embedded and sectioned using an ultramicrotome. The sections were mounted on nickel grids and soft X-ray projections were collected. Figure 1 (B) is 10% Cu 2-x The soft X-ray imaging projection results of the Se@MR-1@PVDF composite membrane show that there are a large number of bacteria and materials, as well as a large number of holes on the composite membrane.

[0062] ③ Atomic force electron microscope three-dimensional imaging: such as Figure 5 As shown, with Cu 2-x As the Se@MR-1 doping amount increases, the film surface becomes increasingly rough.

[0063] ④Contact angle test: Figure 6 As shown, with Cu 2-x With the increase of Se@MR-1 doping amount, the hydrophilicity of the membrane is improved.

[0064] Example 3: Cu 2-x Se@MR-1@PVDF composite membrane (Cu 2-x Se@MR-1 doping amounts are 0%, 3%, 5%, and 10% in sequence)

[0065] In this example, the Cu obtained in Example 2 was used. 2-x Se@MR-1@PVDF composite membrane was used in photothermal distillation experiments.

[0066] Cu 2-x The Se@MR-1@PVDF composite membrane was subjected to a photothermal distillation experiment under 1 sun. The membrane temperature change was recorded with an infrared camera. The volume of the experimental device was weighed every 5 minutes (the difference between each measurement was the mass of water evaporated during that time period). The water evaporation rate and photothermal conversion efficiency were calculated according to the following:

[0067]

[0068] η=m′×h Lv / (3600×P in )

[0069] Where m is the water evaporation rate (kg·m -2 ·h -1), η is the photothermal conversion rate (%), Δm represents the mass change of water per unit time (kg / h), S represents the membrane evaporation area (cm 2 ), t is the irradiation time (h), m′ is the corresponding water evaporation rate in the dark (kg·m -2 ·h -1 ), h Lv is the liquid-gas enthalpy change of water (kJ / kg, ambient temperature is 20°C), P in is the incident light power.

[0070] The following photothermal distillation experiments and photothermal distillation cycle experiments were carried out:

[0071] (1)Cu 2-x Se@MR-1@PVDF composite membrane was used in pure water, 0.5M NaCl and actual seawater photothermal distillation experiments: 0.5h dark → 1h light → 1h dark. The membrane temperature change, water evaporation rate and photothermal conversion efficiency data are shown in Figure 2. Figure 7 、 Figure 8 and Figure 9 As shown, 10% Cu was found 2-x Se@MR-1@PVDF composite membrane has the best evaporation effect. Its maximum evaporation rates in pure water, 0.5M NaCl and actual seawater systems are 1.48, 1.40 and 1.38 kg / m respectively. 2 / h, and the corresponding photothermal conversion efficiencies are 93.76%, 90.39% and 88.57% respectively.

[0072] (2) 10% Cu 2-x Se@MR-1@PVDF composite membrane was used in photothermal distillation cycle experiments of pure water, 0.5M NaCl and actual seawater: 10 cycles were conducted with 1h illumination as one cycle. The photothermal conversion efficiency data are shown in Figure 2. Figure 10 As shown in the figure, 10% Cu 2-x Se@MR-1@PVDF composite membrane has good cyclic stability.

[0073] The above are merely exemplary embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. Photothermal nanomaterial Cu 2-x The photocatalytic biosynthesis method of Se@MR-1 is characterized in that The steps include: Step 1: Cultivate the dissimilatory metal-reducing bacteria in a culture medium until the early stage of the plateau phase; Step 2: The dissimilatory metal-reducing bacteria cultured in step 1 to the early stage of the platform were transferred to the anaerobic culture medium, and selenite was added thereto. After anaerobic reaction, the semi-artificial system Bio-Se was successfully constructed. 0 ; Step 3: Add the semi-artificial system Bio-Se obtained in step 2 0 Add Cu(II)-EDTA complex and place it under light, and Cu(II)-EDTA complex will be obtained through photoreaction. 2-x Se nanoparticles; where x = 0-1; Step 4: The Bio-Cu complex obtained in step 3 2-x Se was freeze-dried and ground to obtain the photothermal material Cu 2-x Se@MR-1 solid powder; The dissimilatory metal-reducing bacteria is the wild-type strain of S. oneidensis MR-1.

2. The synthesis method according to claim 1, wherein: In step 2, the dissimilatory metal-reducing bacteria are cultured anaerobically until all selenite is reduced.

3. The synthesis method according to claim 1, wherein: The amount of selenite added is between 0.1 and 5 mM.

4. The synthesis method according to claim 1, wherein: In step 3, the light culture time is greater than 12 h.

5. The synthesis method according to claim 1, wherein: In step 3, the concentration of the Cu(II)-EDTA complex in the system is 0.1-5 mM.

6. The photothermal nanomaterial Cu prepared according to any one of the synthesis methods of claims 1 to 5 2-x The application of Se@MR-1 is characterized by: With the Cu 2-x Se@MR-1 and PVDF are used to construct a composite membrane material, which is then used as a photothermal distillation membrane to desalinate seawater.

7. The use according to claim 6, characterized in that: The photothermal material Cu 2-x Se@MR-1 solid powder, PVDF polymer mixed powder and appropriate amount of pure DMF were stirred and mixed at room temperature. After degassing, the casting solution was transferred to a glass plate and a composite film was cast using a 200 μm gap scraper. The film was then removed with ultrapure water to obtain Cu 2-x Se@MR-1@PVDF composite membrane; the Cu 2-x Se@MR-1@PVDF composite membrane is used as photothermal distillation membrane to desalinate seawater.

8. The use according to claim 7, characterized in that: The mass of PVDF accounts for 15% of the total mass of the casting solution, and Cu 2-x The mass of Se@MR-1 solid powder accounts for 3-10% of the total mass of the casting solution.

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