Preparation method and application of 3D hydrogel constructed by semiconductor-heteropolyblue superstructure assembled by polyoxometallate

Abstract

The invention relates to a preparation method and application of 3D hydrogel constructed by a semiconductor-heteropolyblue superstructure assembled by polyoxometallate, the preparation method comprises the following steps: dissolving polyoxometallate and metal chloride in a mixed solvent system of oleic acid, oleylamine and ethanol, uniformly stirring, transferring to a stainless steel high-pressure reaction kettle, and reacting under sealing; after cooling to room temperature, centrifuging and collecting a solid product; washing and drying overnight to obtain a metal oxide-heteropolyblue-superlattice; the preparation method comprises the following steps: dispersing metal oxide-heteropolyblue-superlattice in a mixed system of a polyvinyl alcohol aqueous solution and glutaraldehyde, carrying out water bath ultrasonic full mixing, adding a hydrochloric acid solution, carrying out ultrasonic full mixing and gelation reaction at room temperature again, carrying out freeze-drying soaking treatment on the obtained gel twice, and carrying out freeze drying to obtain the metal oxide-heteropolyblue-superlattice hydrogel. The three-dimensional metal oxide-heteropolyblue-superlattice hydrogel is obtained. The material realizes efficient solar steam generation through the advantages of improving the photothermal conversion performance, optimizing the water evaporation process and reducing the energy transfer loss.

Description

Technical Field

[0001] This invention belongs to the field of solar thermal seawater desalination, specifically relating to a method for preparing a 3D hydrogel constructed from a semiconductor-heteropolyblue superstructure assembled from polyoxometalates and its application in driving solar steam generation. Background Technology

[0002] Faced with the dual challenges of the global water crisis and the goal of carbon neutrality, the development of solar-driven interfacial evaporation (SSG) technology can become a direction for solving the water crisis and promoting the development of green energy. Solar-driven water evaporation technology can directly utilize abundant solar energy to produce clean freshwater, avoiding the high energy consumption problems of traditional reverse osmosis and multi-stage flash desalination technologies. Its core lies in photothermal conversion materials; therefore, high photothermal conversion efficiency is fundamental to achieving high freshwater production. Simultaneously, by constructing hydrophilic groups and water transport channel structures, the freshwater production rate can be increased by reducing the enthalpy of evaporation. Furthermore, hydrophobic structures are crucial for preventing salt crystallization and hindering evaporation, thus enabling continuous evaporation and freshwater production.

[0003] Semiconductor materials, with their advantages of material diversity, relatively low cost, tunable structural morphology, and excellent photothermal stability, have become a research hotspot in the field of solar thermal evaporation. However, traditional semiconductor materials, due to their narrow solar spectrum absorption range and insufficient intrinsic hydrophilicity, severely restrict further improvements in photothermal conversion efficiency and water evaporation rate.

[0004] Polyoxometalates (POMs) possess semiconductor-like properties, with their intervalence charge transfer (IVCT) transitions of local / non-local "blue electrons" at the metal center endowing them with excellent photothermal conversion performance. In particular, due to their excellent hydrophilicity and favorable active sites for in-situ photothermal-water evaporation, POMs can not only construct hydrophilic management structures but also reduce the vaporization enthalpy during evaporation through hydrogen bonding, thereby increasing the evaporation rate. Furthermore, the unique redox properties and highly negatively charged surface of POMs can drive spontaneous assembly processes with conventional semiconductors, potentially optimizing the electronic structure of semiconductors and significantly enhancing light absorption and photothermal conversion efficiency, thus enabling the construction of continuous and efficient solar evaporation systems. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing and applying a 3D hydrogel constructed from a semiconductor-heteropolyblue superstructure assembled from polyoxometalates, which significantly improves photothermal conversion efficiency and evaporation rate.

[0006] The technical solution of this invention is: A method for preparing a 3D hydrogel constructed from a semiconductor-heteropolyblue superstructure assembled from polyoxometalates includes the following steps: Step 1: Preparation of metal oxide-heteropolyblue-superlattice Polyoxometalate and metal chloride were dissolved in a mixed solvent system of oleic acid, oleylamine and ethanol at a molar ratio of 1:10 to 1:5. The metal chloride was tin chloride, cerium chloride or bismuth chloride. The mixture was stirred for 5 min to 30 min. Then the mixture was transferred to a polytetrafluoroethylene liner in a stainless steel high-pressure reactor, which was then sealed. The reactor was reacted at 120 °C to 200 °C for 0.5 h to 2 h. After cooling to room temperature, the solid product was collected by centrifugation. The product was washed and then dried overnight under vacuum at 50 °C to obtain a metal oxide-heteropolyblue-superlattice. Step 2: Preparation of three-dimensional metal oxide-heteropolyblue-superlattice hydrogel Metal oxide-heterocyanate-superlattice was dispersed in a mixture of polyvinyl alcohol aqueous solution and glutaraldehyde, and thoroughly mixed by ultrasonication in a water bath. Hydrochloric acid solution was added at a mass-to-volume ratio of 3:16 mg / mL to the metal oxide-heterocyanate-superlattice dispersion and hydrochloric acid solution, and the mixture was thoroughly mixed again by ultrasonication at room temperature. The gelation reaction lasted for 120 min. The resulting gel was subjected to two freeze-drying soaking treatments and then freeze-dried to obtain a three-dimensional metal oxide-heterocyanate-superlattice hydrogel.

[0007] Furthermore, the molar ratio of the polyoxometalate to the metal chloride is 1:5.

[0008] Furthermore, the polyoxometalate is [n-(C4H9)4N]2Mo6O 19 [n-(C4H9)4N]4Mo8O 26 [n-(C4H9)4N]4H3PMo 11 O 39 or H3PMo 12 O 40 The metal chloride is SnCl4, SnCl2, CeCl3 or BiCl3.

[0009] Furthermore, the polyoxometalate is H3PMo. 12 O 40 The metal chloride is SnCl4; the molar volume ratio of the metal chloride to the mixed solvent is 1:24 mmol / mL.

[0010] Further preferred, the volume ratio of oleylamine to oleic acid is 1:8; the volume ratio of oleylamine to ethanol is 1:5.4.

[0011] Furthermore, in step one, the stirring time is 15 minutes, the reaction temperature is 180°C, and the reaction time is 2 hours.

[0012] Furthermore, in step two, the volume ratio of the metal oxide-heterocyanate-superlattice to glutaraldehyde is 1:1 mg / mL, and the volume ratio of the polyvinyl alcohol aqueous solution to glutaraldehyde is 10:1.

[0013] Further preferred, in step two, the concentration of the polyvinyl alcohol aqueous solution is 7.5 wt%, and the concentration of the hydrochloric acid solution is 3 wt%.

[0014] Furthermore, in step one, during washing, a mixed solution of ethanol and cyclohexane with a volume ratio of 3:1 is used.

[0015] Application of 3D hydrogels constructed from semiconductor-heteropolyblue superstructures assembled with polyoxometalates prepared by the above method in solar photothermal evaporation.

[0016] The principle of this invention is as follows: by employing a molybdate-based polyoxometalate ([n-(C4H9)4N]2Mo6O) 19 [n-(C4H9)4N]4Mo8O 26 [n-(C4H9)4N]4H3PMo 11 O 39 H3PMo 12 O 40 ) and metal chlorides (TCl) n Using SnCl4, SnCl2, CeCl3, and BiCl3 as raw materials, a simple one-step solvothermal method was used to successfully construct a two-dimensional (2D) superlattice self-assembled structure (denoted as T) composed of ordered metal oxide nanocrystals and HPB clusters. x O y -HPB-SL). Taking SnO2-HPB-SL as an example, in the high-temperature synthesis system, polyoxometalates (POMs) are reduced to HPB molecules with stronger electronegativity, while Sn... 4+ The process transforms the material into SnO2 nanocrystals / quantum dots. Under the dual influence of strong electrostatic interactions and the assistance of oleic acid and oleylamine ligands, electron donor HPB and electron acceptor SnO2 nanocrystals grow into sub-nanowires and self-assemble into a highly ordered two-dimensional superlattice structure. In these T... x O y In HPB-SL, SnO2-HPB-SL exhibits excellent stability and photothermal properties.

[0017] Based on this, a three-dimensional (3D) hydrogel evaporator was successfully constructed using SnO2-HPB-SL via a hydrogel strategy. The 3D SnO2-HPB-SL hydrogel possesses a multi-level porous structure, promoting multiple refractions and reflections of sunlight and significantly improving light capture efficiency. Simultaneously, the three-dimensional interconnected pores facilitate water molecule transport and vapor escape, enhancing the overall system's energy utilization efficiency.

[0018] The beneficial effects of this invention are: (1) Main body POM([n-(C4H9)4N]2Mo6O 19 [n-(C4H9)4N]4Mo8O 26 [n-(C4H9)4N]4H3PMo 11 O 39 H3PMo 12 O 40 ) and guest metal cations (TCl) n Using the anionic, redox, and nanoscale characteristics of POM (SnCl4, SnCl2, CeCl3, and BiCl3), a 2D superstructure of semiconductor-heteropolyblue subnanowires (labeled T) was synthesized by self-assembly with metal cations in a hydrophobic oleic acid and oleylamine solvent system with metal cations. x O y -HPB-SL).

[0019] (2) In this structure, the composite of semiconductor and HPB significantly enhances light absorption and photothermal conversion performance. The hydrophilic inner core (HPB) and hydrophobic outer structure (oleic acid and oleylamine molecules) of the nanowire not only provide hydrophilic transport channels to promote in-situ photothermal evaporation of water molecules, but also prevent heat loss to the volumetric water. The SnO2-HPB-SL hydrogel evaporator of this invention can be directly used as an evaporator for solar seawater desalination and wastewater purification. Under one solar irradiation, the 3DSnO2-HPB-SL hydrogel evaporator achieved a heat output of up to 3.6 kg·m³. -2 ·h -1 It boasts an ultra-high evaporation rate and an energy conversion efficiency of 94.3%.

[0020] (3) The SnO2-HPB-S hydrogel evaporator of this invention also exhibits excellent stability and solar desalination capability. After solar desalination, the salinity of the produced water is reduced by 3-4 orders of magnitude compared to the original seawater (3.5wt% and 10.0wt%). This hydrogel also demonstrates excellent purification performance when treating heavy metal wastewater and dye wastewater samples. The quality of the obtained freshwater is comparable to that of local residents' drinking water and far superior to the initial seawater sample, providing a solution to the problem of freshwater shortage.

[0021] In summary, this invention discloses a method for preparing 3D hydrogels constructed from semiconductor-heteropolyblue superstructures assembled from polyoxometalates. This material achieves highly efficient solar steam generation through several advantages, including improved photothermal conversion performance, optimized water evaporation process, and reduced energy transfer losses. Compared to traditional seawater desalination processes, this invention uses solar energy as the core driving energy source, embodying the concept of green, low-carbon, and sustainable development. Furthermore, this achievement has broad scientific prospects for advancing solar photothermal conversion technology in applications such as seawater desalination, wastewater treatment, steam power generation, and humidifiers. Attached Figure Description

[0022] Figure 1 The figures show transmission electron microscopy (TEM) images of SnO2 nanowires prepared according to different PMA dosages in Examples 1 and 2, Comparative Examples 1 and 2 of this invention. In the figures, a. TEM image of SnO2 nanowires in the 0.00 mmol PMA synthesis system (corresponding to Comparative Example 1), b. High-resolution TEM image of SnO2-HPB-SL-1 in the 0.15 mmol PMA synthesis system (corresponding to Example 1), c. TEM image of SnO2-HPB-SL-2 in the 0.3 mmol PMA synthesis system (corresponding to Example 2), and d. TEM image of SnO2-HPB-SL-3 in the 0.3 mmol PMA synthesis system (corresponding to Comparative Example 2). Figure 2 The figures are X-ray powder diffraction (XRD) characterization patterns of different PMA doses prepared in Examples 1 and 2, Comparative Examples 1 and 2 of the present invention. In the figures, a. wide-angle X-ray powder diffraction patterns of different PMA synthesis systems, b. small-angle X-ray powder diffraction patterns of different PMA synthesis systems; Figure 3 This is a high-resolution transmission electron microscope (TEM) characterization image of SnO2-HPB-SL prepared in Example 2 of this invention, solid state. 31 P-NMR spectrum and Fourier transform infrared (FTIR) characterization, in which a. transmission electron microscopy (TEM) image of SnO2-HPB-SL, b. high-resolution TEM image of SnO2-HPB-SL, c. solid-state image of SnO2-HPB-SL. 31 P-NMR characterization image, Fourier transform infrared (FTIR) characterization image of d.SnO2-HPB-SL, yellow line: PMA; blue line: HPB; red line: corresponding to Example 2; Figure 4 These are high-resolution transmission electron microscopy (TEM) characterization images of Examples 6, 7, and 8 of the present invention. In the images, a. SnO2-Mo6O 19 Transmission electron microscopy characterization of SL, b. SnO2-Mo8O 26Transmission electron microscopy characterization of -SL, c. SnO2-PMo 11 Transmission electron microscopy characterization of -SL; Figure 5 These are high-resolution transmission electron microscopy (TEM) and X-ray powder diffraction (XRD) characterization images of Examples 4 and 5 of the present invention. In the images, a. Ce7O 12 - Transmission electron microscopy characterization image of HPB-SL, b. Ce7O 12 - Wide-angle XRD characterization of HPB-SL, c. Ce7O 12 d. Small-angle XRD characterization of Bi2O3-HPB-SL, e. Wide-angle XRD characterization of Bi2O3-HPB-SL, f. Small-angle XRD characterization of Bi2O3-HPB-SL. Figure 6 The image shows the X-ray photoelectron spectroscopy (XPS) spectrum of SnO2-HPB-SL prepared in Example 2 of this invention; in the image, a. the 1s peak of C in SnO2-HPB-SL, b. the 1s peak of N in SnO2-HPB-SL, c. the 2s peak of O in SnO2-HPB-SL, d. the 3d peak of Sn in SnO2-HPB-SL, e. the 3d peak of Mo in SnO2-HPB-SL, and f. the 2p peak of P in SnO2-HPB-SL. Figure 7 The images show scanning electron microscope (SEM) images of the SnO2-HPB-SL hydrogel in Example 2 of this invention; in the images, a. C element distribution in SnO2-HPB-SL, b. N element distribution in SnO2-HPB-SL, c. O element distribution in SnO2-HPB-SL, d. Mo element distribution in SnO2-HPB-SL, e. P element distribution in SnO2-HPB-SL, and f. Sn element distribution in SnO2-HPB-SL. Figure 8 The figure shows the solar photothermal evaporation performance of the SnO2-HPB-SL hydrogel in Example 2 of this invention. In the figure, a. Scanning electron microscopy characterization of the SnO2-HPB-SL hydrogel, b. High-resolution scanning electron microscopy characterization of the SnO2-HPB-SL hydrogel, c. UV-Vis-NIR absorption spectrum of the SnO2-HPB-SL hydrogel, d. Photothermal response of the SnO2-HPB-SL hydrogel in the dry state, e. Photothermal response of the SnO2-HPB-SL hydrogel in the evaporation state, f. Evaporation rate of the SnO2-HPB-SL hydrogel under 1 Sun irradiation, g. Evaporation rate and energy efficiency of different evaporators, h. Evaporation rate of the SnO2-HPB-SL hydrogel under 0-2 Sun irradiation. Figure 9 This figure illustrates the solar thermal performance of the SnO2-HPB-SL hydrogel in Example 2 of this invention for seawater desalination and wastewater purification. Figure a shows a comparison of the solar evaporation performance of the SnO2-HPB-SL hydrogel in deionized water, simulated seawater, and the Dead Sea system; b shows a comparison of salinity before and after solar desalination in simulated seawater and the Dead Sea system; c shows the main ion concentrations of the purified water obtained by the SnO2-HPB-SL hydrogel in simulated seawater; d shows the purification performance of the SnO2-HPB-SL hydrogel in industrial wastewater; e shows the purification performance of the SnO2-HPB-SL hydrogel in dye wastewater; f shows the stability experiment of the SnO2-HPB-SL hydrogel in seawater desalination; and gj shows the water quality assessment of the purified water obtained by the SnO2-HPB-SL hydrogel in seawater desalination. Detailed Implementation

[0023] The present invention will be further illustrated below with reference to the embodiments.

[0024] Example 1 Step 1: Preparation of SnO2-HPB-SL-1 SnCl4 (1.5 mmol) was added to an oleic acid (20 mL) system under stirring at room temperature, followed by the addition of oleylamine (2.5 mL) and anhydrous ethanol (13.5 mL) until the SnCl4 was completely dissolved. Then, phosphomolybdic acid (0.15 mmol) was added, and the mixture was stirred at room temperature for another 15 minutes. The solution was then transferred to a stainless steel high-pressure reactor and reacted at 180 °C for 2 hours. After cooling to room temperature, the product was collected by centrifugation, washed three times with an organic solution of ethanol and cyclohexane (ethanol to cyclohexane volume ratio of 3:1), and then dried overnight under vacuum at 50 °C to obtain tin dioxide-heteropolyblue-superlattice (SnO2-HPB-SL-1). Example 2 Step 1: Preparation of SnO2-HPB-SL-2 SnCl4 (1.5 mmol) was added to an oleic acid (20 mL) system under stirring at room temperature, followed by the addition of oleylamine (2.5 mL) and anhydrous ethanol (13.5 mL) until SnCl4 was completely dissolved. Then, phosphomolybdic acid (0.3 mmol) was added, and the mixture was stirred at room temperature for another 15 minutes. The solution was then transferred to a stainless steel high-pressure reactor and reacted at 180 °C for 2 hours. After cooling to room temperature, the product was collected by centrifugation, washed three times with an organic solution of ethanol and cyclohexane (ethanol to cyclohexane volume ratio of 3:1), and then dried overnight under vacuum at 50 °C to obtain the blue-black product tin dioxide-heteropolyblue-superlattice (SnO2-HPB-SL-2). Step 2: Fabrication of a three-dimensional SnO2-HPB-SL hydrogel evaporator using a typical synthesis strategy. A 7.5 wt% aqueous solution of polyvinyl alcohol (PVA) (15 mL), 0.15 mL of glutaraldehyde, and 0.15 mg of SnO2-HPB-SL-2 prepared in step one were thoroughly mixed by sonication at room temperature (solution A). Subsequently, 0.8 mL of 3 wt% hydrochloric acid solution was added to solution A, and the mixture was thoroughly mixed by sonication again at room temperature. The gelation reaction was carried out for 120 minutes. The resulting gel was subjected to two freeze-drying soaking treatments and then freeze-dried to obtain a three-dimensional tin dioxide-heteropolyblue-superlattice (SnO2-HPB-SL) hydrogel.

[0025] Example 3 In Example 2, SnCl4 was replaced with SnCl2, and everything else remained the same as in Example 2. SnO2-HPB-SL could also be obtained in the reaction system.

[0026] Example 4 Step 1: Preparation of Bi2O3-HPB-SL In Example 2, SnCl4 was replaced with BiCl3, and the rest was the same as in Example 2. Bi2O3-HPB-SL could also be obtained in the reaction system. Step 2: Prepare a three-dimensional Bi2O3-HPB-SL hydrogel evaporator using a typical synthesis strategy. 15 mL of PVA aqueous solution (7.5 wt%), 0.15 mL of glutaraldehyde, and 0.15 mg of Bi2O3-HPB-SL were thoroughly mixed in a water bath using ultrasonication (solution A). Subsequently, 0.8 mL of hydrochloric acid solution (3 wt%) was added to solution A, and the mixture was thoroughly mixed again by ultrasonication in a water bath. The gelation reaction was carried out for 120 minutes. The resulting gel was subjected to two freeze-drying soaking treatments and then freeze-dried to obtain a three-dimensional Bi2O3-HPB-SL hydrogel.

[0027] Example 5 Step 1: Preparation of Ce7O 12 -HPB-SL In Example 2, SnCl4 was replaced with CeCl3, and all other steps remained the same as in Example 2. Ce7O was also obtained in the reaction system. 12 -HPB-SL; Step 2: Prepare three-dimensional Ce7O using a typical synthesis strategy. 12 -HPB-SL Hydrogel Evaporator Add 15 mL of PVA aqueous solution (7.5 wt%), 0.15 mL of glutaraldehyde, and 0.15 mg of Ce7O 12HPB-SL was thoroughly mixed in a water bath using ultrasonication (solution A); then 0.8 mL of hydrochloric acid solution (3 wt%) was added to solution A, and the mixture was thoroughly mixed again by ultrasonication in a water bath. The gelation reaction was continued for 120 minutes; the resulting gel was subjected to two lyophilization soaking treatments followed by freeze-drying to obtain three-dimensional Ce7O. 12 -HPB-SL hydrogel.

[0028] Comparative Example 1 Step 1: Preparation of SnO2 nanowires SnCl4 (1.5 mmol) was added to an oleic acid (20 mL) system under stirring at room temperature, followed by the addition of oleylamine (2.5 mL) and anhydrous ethanol (13.5 mL), and stirring was continued at room temperature for 15 minutes. The solution was then transferred to a stainless steel high-pressure reactor and reacted at 180 °C for 2 hours. After cooling to room temperature, the product was collected by centrifugation. The product was washed three times with an organic solution of ethanol and cyclohexane (volume ratio of ethanol to cyclohexane 3:1) and then dried overnight under vacuum at 50 °C to obtain SnO2 nanowires.

[0029] Comparative Example 2 Step 1: Preparation of SnO2-HPB-SL-3 SnCl4 (1.5 mmol) was added to an oleic acid (20 mL) system under stirring at room temperature, followed by the addition of oleylamine (2.5 mL) and anhydrous ethanol (13.5 mL). The mixture was stirred at room temperature for 15 minutes. The solution was then transferred to a stainless steel high-pressure reactor and reacted at 180 °C for 0.5 h. After cooling to room temperature, the SnO2 quantum dots were collected by centrifugation. The collected SnO2 quantum dots were dispersed in a system of oleic acid (20 mL), oleylamine (2.5 mL), and anhydrous ethanol (13.5 mL), and then phosphomolybdic acid (0.3 mmol) was added. The mixture was stirred at room temperature for 15 minutes. The solution was then transferred to a stainless steel high-pressure reactor and reacted at 180 °C for 2 hours. After cooling to room temperature, the product was collected by centrifugation. The product was washed three times with an organic solution of ethanol and cyclohexane (ethanol to cyclohexane volume ratio of 3:1) and then dried overnight under vacuum at 50 °C to obtain the blue-black product SnO2-HPB-SL-3.

[0030] Comparative Example 3 In Example 2, the dosage of SnCl4 chloride was adjusted to zero, while other aspects remained the same as in Example 2. The semiconductor-heterocyanate self-assembled superstructure could not be obtained in the reaction system.

[0031] Comparative Example 4 Replacing oleic acid with ethanol in Example 2, while keeping everything else the same as in Example 2, failed to synthesize a highly ordered semiconductor-heterocyanate self-assembled superstructure.

[0032] Comparative Example 5 Replacing oleylamine with ethanol in Example 2, while keeping everything else the same as in Example 2, failed to synthesize the novel semiconductor-heterocyanate self-assembled superstructure.

[0033] Comparative Example 6 Replacing phosphomolybdic acid with phosphotungstic acid in Example 2, while keeping everything else the same as in Example 2, failed to synthesize the novel semiconductor-heterocyanate self-assembled superstructure.

[0034] Comparative Example 7 Replacing phosphomolybdic acid with silicotungstic acid in Example 2, while keeping everything else the same as in Example 2, failed to synthesize the novel semiconductor-heteropolyblue self-assembled superstructure.

[0035] Example 6 The phosphomolybdic acid from Example 2 was treated with [n-(C4H9)4N]2Mo6O 19 Alternatively, the same as in Example 2 can be used to synthesize a blue-green semiconductor-heteropolyblue self-assembled superstructure. However, in a long-term air environment, the reduced HPB in the structure will be oxidized to the POM state, losing its strong light absorption and photothermal conversion capabilities.

[0036] Example 7 The phosphomolybdic acid from Example 2 was treated with [n-(C4H9)4N]4Mo8O 26 Alternatively, the same as in Example 2 can be used to synthesize a blue-green semiconductor-heteropolyblue self-assembled superstructure. However, in a long-term air environment, the reduced HPB in the structure will be oxidized to the POM state, losing its strong light absorption and photothermal conversion capabilities.

[0037] Example 8 The phosphomolybdic acid from Example 2 was treated with [n-(C4H9)4N]4H3PMo 11 O 39 Alternatively, the same as in Example 2 can be used to synthesize a blue-green semiconductor-heteropolyblue self-assembled superstructure. However, in a long-term air environment, the reduced HPB in the structure will be oxidized to the POM state, losing its strong light absorption and photothermal conversion capabilities.

[0038] The SnO2-HPB-SL prepared in Example 2 of this invention was characterized and its performance was tested. 1. The assembly process and structural morphology of SnO2-HPB-SL were observed using transmission electron microscopy (TEM). Figure 1 It can be seen that, under the condition that phosphomolybdic acid (PMA) is not added to the system, Sn 4+ Random SnO2 nanowires with diameters of 2.0–3.0 nm are generated through hydrolysis; from Figure 1As shown in b, when 0.05 mmol PMA was introduced into the system (corresponding to Example 1), TEM observed the presence of SnO2-HPB-SL, accompanied by a certain amount of random SnO2 nanowires. From Figure 1 As can be seen from c, when the PMA dose is increased to 0.10 mmol (corresponding to Example 2), the obtained SnO2-HPB-SL has a highly ordered superstructure. Figure 1 As can be seen from d, the morphology of SnO2-HPB-SL-3 is completely consistent with that of SnO2-HPB-SL-2. The two-step synthesis results once again confirm the key guiding role of POM clusters in the directional assembly of superstructures. 2. By combining X-ray diffraction (XRD) and small-angle X-ray diffraction (SAXRD) characterization, the composition of SnO2-HPB-SL was effectively confirmed. Figure 2 As can be clearly observed, with increasing PMA dosage, SnO2-HPB-SL contains characteristic peaks of both SnO2 and HPB. Figure 2 As can be seen from b, the intensity of the small-angle XRD diffraction peak changes significantly and the peak shape tends to be sharper. This feature directly confirms the gradual evolution of the system from a disordered structure to an ordered structure.

[0039] 3. Using high-resolution transmission electron microscopy (TEM), solid-state... 31 The composition and structure of SnO2-HPB-SL were analyzed using P-NMR and Fourier transform infrared (FTIR) spectroscopy characterization. Figure 3 As can be seen from a, SnO2-HPB-SL exhibits a highly ordered 2D layered structure. From... Figure 3 As can be seen in Figure b, SnO2-HPB-SL exhibits distinct SnO2 lattice fringes (0.23 nm corresponds to the 111 crystal plane), and clearly visible amorphous layers exist between the SnO2-HPB nanowires, with a spacing of approximately 2.0 nm, which is almost equivalent to the size of oleic acid (OA) and oleylamine (OAm) molecules (1.96 nm). Figure 3 c solid 31 The P-NMR results show that the chemical shifts of SnO2-HPB-SL and HPB are basically the same, indicating that the composition and structure of HPB in SnO2-HPB-SL are well preserved. Figure 3 As can be seen from the data in section d, the infrared spectrum of the SnO2-HPB-SL sample perfectly matches the characteristic absorption peaks of the reduced HPB standard, while the 1703 cm⁻¹ peak... -1 The -C=O stretching vibration peak at 1654 cm⁻¹ confirms that oleic acid (OA) molecules participate in self-assembly. -1 The NH stretching vibration peak at 2922.4 cm⁻¹ confirms the involvement of the oleylamine (OAm) molecule; -1and 2850.7cm -1 The two characteristic peaks are located at 1461.6 cm⁻¹. -1 and 1377.7cm -1 The two characteristic peaks further strongly support the existence of OAm and OA molecules with carbon chain structures in the superlattice.

[0040] 4. The Bi₂O₃-HPB-SL of Example 4 and the Ce₇O₃ of Example 5 were further observed using high-resolution transmission electron microscopy (TEM). 12 -The morphology of HPB-SL. From Figure 4 As can be seen from 'a', Ce7O 12 -HPB-SL also exhibits a highly ordered 2D structure, from Figure 4 As can be seen from b, Ce7O 12 -HPB-SL has HPB and Ce7O 12 Composition, from Figure 4 As can be seen from c, Ce7O 12 The small-angle XRD of HPB-SL also indicates the same highly ordered 2D structure. Figure 4 As can be seen from d, Bi2O3-HPB-SL also exhibits a highly ordered 2D structure. Figure 4 As can be seen from e, Bi2O3-HPB-SL is composed of HPB and Bi2O3. Figure 4 As can be seen from c, the small-angle XRD of Bi2O3-HPB-SL also shows that it has the same 2D highly ordered structure.

[0041] 5. The SnO2-Mo6O in Example 6 was further observed using high-resolution transmission electron microscopy (TEM). 19 -SL, SnO2-Mo8O from Example 7 26 -SL and SnO2-PMo of Example 8 11 -SL's morphology. From Figure 5 As can be seen from a, b, and c, SnO2-Mo6O in Example 6 19 -SL, SnO2-Mo8O from Example 7 26 -SL and SnO2-PMo of Example 8 11 -SL all have highly ordered 2D structures, consistent with the results observed in SnO2-HPB-SL, demonstrating the universality of PMA-guided self-assembly synthesis strategies.

[0042] 6. SnO2-HPB-SL was characterized by X-ray photoelectron spectroscopy (XPS). Figure 6It can be seen that C, N, O, Sn, Mo and P elements are all present, and Sn is in the +4 valence state, while Mo is in the +6 and +5 valence states, indicating the coexistence of SnO2 and HPB.

[0043] 7. The composition and structure of SnO2-HPB-SL were analyzed by scanning electron microscopy (SEM). Figure 7 As can be seen from a, b, c, d, e, and f, elements C, N, O, Sn, Mo, and P are all present, further verifying the compositional structure of SnO2-HPB-SL.

[0044] 8. The structure of the three-dimensional SnO2-HPB-SL hydrogel was characterized by scanning electron microscopy (SEM). Figure 8 As shown in a and b, the SnO2-HPB-SL hydrogel structure contains a large number of micron-sized pore networks, which not only facilitates light capture but also water vapor escape. The solar light absorption capacity of the SnO2-HPB-SL hydrogel was observed using ultraviolet-visible-near-infrared absorption spectroscopy (UV-VIS-NIR). Figure 8 As can be seen from c, the SnO2-HPB-SL hydrogel exhibits excellent light absorption in the wavelength range of 200-2500 nm. From... Figure 8 As can be seen from d, the photothermal conversion of SnO2-HPB-SL hydrogel is superior to that of Ce7O. 12 -HPB-SL hydrogel and Bi2O3-HPB-SL hydrogel. From Figure 8 As can be seen from e, the surface temperature of the SnO2-HPB-SL hydrogel during evaporation is significantly lower than that of the surface. Figure 8 The temperature in d indicates that a significant amount of temperature is used to drive the water evaporation process. From Figure 8 As can be seen from f, under one sun irradiation, the water evaporation rate of the three-dimensional SnO2-HPB-SL hydrogel is as high as 3.6 kg·m³. -2 ·h -1 .from Figure 8 As can be seen from the expression g, the three-dimensional SnO2-HPB-SL hydrogel exhibits excellent performance, successfully joining the ranks of high-performance materials for photothermal evaporation. From Figure 8 As can be seen from h, even under different standard light intensities, the evaporation rate of SnO2-HPB-SL hydrogel remains stable. This not only confirms its applicability to all scenarios from arid regions to high-radiation environments, but also provides a core material solution for the practical application of solar interface evaporation technology.

[0045] 9. The properties of SnO2-HPB-SL hydrogel were evaluated by solar photothermal evaporation of deionized water, simulated seawater, and Dead Sea samples. Figure 9As can be seen from a, the SnO2-HPB-SL hydrogel exhibits almost identical evaporation rates and energy conversion efficiencies, and is virtually unaffected by salinity. From Figure 9 As can be seen from b, the SnO2-HPB-SL hydrogel exhibits excellent purification performance in seawater environments with salinities of 3.5 wt% and 10.0 wt%, resulting in a significant reduction in water salinity of 3–4 orders of magnitude after purification. Figure 9 As can be seen from c, in the purified water collected by evaporation, K + Na + Ca 2+ Mg 2+ The concentrations of the four main ions also decreased by three to four orders of magnitude. From Figure 9 As can be seen from d and e, the SnO2-HPB-SL hydrogel also exhibits excellent purification performance in the treatment of heavy metal wastewater and dye wastewater. From Figure 9 As can be seen from f, the SnO2-HPB-SL hydrogel possesses good stability. From Figure 9 As can be seen from the gj data, the purified water obtained through this hydrogel desalination treatment almost meets the standard requirements for domestic water quality.

[0046] Obviously, the above embodiments are merely examples for clear illustration and are not intended to limit the embodiments. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all embodiments here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a 3D hydrogel constructed from a semiconductor-heteropolyblue superstructure assembled from polyoxometalates, characterized in that: Includes the following steps: Step 1: Preparation of metal oxide-heteropolyblue-superlattice Polyoxometalate and metal chloride are dissolved in a mixed solvent system of oleic acid, oleylamine and ethanol at a molar ratio of 1:10 to 1:

5. The metal chloride is tin chloride, cerium chloride or bismuth chloride. The mixture is stirred for 5 min to 30 min. Then it is transferred to the polytetrafluoroethylene lining of a stainless steel high-pressure reactor, the reactor is sealed, and the reaction is carried out at 120℃ to 200℃ for 0.5 h to 2 h. After cooling to room temperature, the solid product is collected by centrifugation. Wash, and then dry overnight under vacuum at 50°C to obtain metal oxide-heteropolyblue-superlattice; Step 2: Preparation of three-dimensional metal oxide-heteropolyblue-superlattice hydrogel Metal oxide-heterocyanate-superlattice was dispersed in a mixture of polyvinyl alcohol aqueous solution and glutaraldehyde, and thoroughly mixed by ultrasonication in a water bath. Hydrochloric acid solution was added at a mass-to-volume ratio of 3:16 mg / mL to the metal oxide-heterocyanate-superlattice dispersion and hydrochloric acid solution, and the mixture was thoroughly mixed again by ultrasonication at room temperature. The gelation reaction lasted for 120 min. The resulting gel was subjected to two freeze-drying soaking treatments and then freeze-dried to obtain a three-dimensional metal oxide-heterocyanate-superlattice hydrogel.

2. The method for preparing 3D hydrogels constructed from semiconductor-heteropolyblue superstructures assembled from polyoxometalates according to claim 1, characterized in that: The molar ratio of the polyoxometalate to the metal chloride is 1:

5.

3. The method for preparing 3D hydrogels constructed from semiconductor-heteropolyblue superstructures assembled from polyoxometalates according to claim 1, characterized in that: The polyoxometalate is [n-(C4H9)4N]2Mo6O 19 [n-(C4H9)4N]4Mo8O 26 [n-(C4H9)4N]4H3PMo 11 O 39 or H3PMo 12 O 40 The metal chloride is SnCl4, SnCl2, CeCl3 or BiCl3.

4. The method for preparing 3D hydrogels constructed from semiconductor-heteropolyblue superstructures assembled from polyoxometalates according to claim 1, characterized in that: The polyoxometalate is H3PMo 12 O 40 The metal chloride is SnCl4; the molar volume ratio of the metal chloride to the mixed solvent is 1:24 mmol / mL.

5. The method for preparing 3D hydrogels constructed from semiconductor-heteropolyblue superstructures assembled from polyoxometalates according to claim 4, characterized in that: The volume ratio of oleylamine to oleic acid is 1:8; the volume ratio of oleylamine to ethanol is 1:5.

4.

6. The method for preparing a 3D hydrogel constructed from a semiconductor-heteropolyblue superstructure assembled from polyoxometalates according to claim 1, characterized in that: In step one, the stirring time is 15 minutes, the reaction temperature is 180℃, and the reaction time is 2 hours.

7. The method for preparing 3D hydrogels constructed from semiconductor-heteropolyblue superstructures assembled from polyoxometalates according to claim 1, characterized in that: In step two, the volume ratio of the metal oxide-heterocyanate-superlattice to glutaraldehyde is 1:1 mg / mL, and the volume ratio of the polyvinyl alcohol aqueous solution to glutaraldehyde is 10:

1.

8. The method for preparing a 3D hydrogel constructed from a semiconductor-heteropolyblue superstructure assembled from polyoxometalates according to claim 7, characterized in that: In step two, the concentration of the polyvinyl alcohol aqueous solution is 7.5 wt%, and the concentration of the hydrochloric acid solution is 3 wt%.

9. The method for preparing a 3D hydrogel constructed from a semiconductor-heteropolyblue superstructure assembled from polyoxometalates according to claim 1, characterized in that: In step one, the washing process uses a mixed solution of ethanol and cyclohexane with a volume ratio of 3:

1.

10. The application of a 3D hydrogel constructed from a semiconductor-heteropolyblue superstructure assembled from polyoxometalates prepared by the preparation method as described in claim 1 in solar photothermal evaporation.

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