Thermochromic smart window

Abstract

This invention discloses a thermochromic smart window, which contains at least one layer of thermochromic material. The core functional material of the thermochromic material is a core-shell structured thermochromic material, with doped vanadium dioxide nanoparticles as the core and a metal-organic framework as the shell. The thermochromic smart window of this invention exhibits high stability, good optical properties, and the ability to achieve synergistic photothermal response, making it particularly suitable for home use. Furthermore, its preparation method is simple, requires mild conditions, and is highly compatible with existing laminated glass manufacturing processes, facilitating industrialization. It not only responds to changes in ambient temperature but also sensitively responds to changes in solar radiation intensity, achieving intelligent regulation of solar thermal energy.

Description

Technical Field

[0001] This invention relates to the field of building energy conservation technology, specifically to a thermochromic smart window. Background Technology

[0002] With increasing societal demands for energy efficiency and comfort in buildings, smart window technology has become a research hotspot. A smart window is a type of functional glass based on dynamic optical adjustment technologies such as electrochromic and thermochromic displays. Thermochromic smart windows, in particular, can automatically adjust their solar transmittance according to ambient temperature, making them an ideal passive energy-saving technology.

[0003] In existing thermochromic smart windows, vanadium dioxide is typically used as the thermochromic material. Near its phase transition temperature (approximately 68°C), it undergoes a reversible transition from a semiconductor state (low temperature, transparent to infrared light) to a metallic state (high temperature, reflective of infrared light), thereby achieving intelligent control of solar radiation heat. For example, CN202210311247.X disclosed a thermochromic smart window based on highly transparent vanadium dioxide and its preparation method, which belongs to this technology of using vanadium dioxide as a thermochromic material in thermochromic smart windows.

[0004] However, vanadium dioxide-based thermochromic smart windows still face many serious challenges in practical applications: First, the phase transition temperature of vanadium dioxide (68°C) is much higher than the comfortable room temperature, requiring various elemental doping to lower it. However, this process often leads to a significant decrease in its optical properties (such as visible light transmittance and solar energy modulation capability). Second, vanadium dioxide materials have poor stability and durability. VO2 nanoparticles are easily oxidized into vanadium pentoxide (which lacks thermochromic properties) under high humidity, high temperature, and ultraviolet light conditions, resulting in rapid functional degradation. Meanwhile... Nanoparticle materials have poor dispersibility and compatibility, and are prone to agglomeration in polymer matrices (such as PVB or EVA used in laminated glass), resulting in uneven film formation, high haze, and affecting light transmittance and aesthetics. Moreover, existing vanadium dioxide-based thermochromic smart window products have limited functionality, usually only responding to temperature, and cannot cope with complex and changing environmental factors, such as the inability to activate the shading function in advance in cold and sunny weather.

[0005] A previously disclosed method under CN202510148958.3 A one-step chemical synthesis method for nanoparticles and its application in thermochromic smart windows were disclosed in CN201310692460.0. These existing patents use tungsten-doped vanadium dioxide as the thermochromic material, which can effectively reduce the sensing temperature, but still suffers from poor durability and stability. Furthermore, although some existing technologies employ... Inorganic materials Coating is used to improve stability, but it is often difficult to simultaneously achieve optical performance, low-temperature phase transition, and multifunctionality.

[0006] Therefore, developing a novel thermochromic material and device structure that combines low-temperature phase transition, high stability, excellent optical performance, and potential multifunctionality has become a problem that needs to be considered and solved by those skilled in the art. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is: how to provide a thermochromic smart window with a suitable temperature range for home use, high stability, and good optical properties.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0009] A thermochromic smart window, comprising at least one layer of thermochromic material, characterized in that the core functional material of the thermochromic material is a core-shell structured thermochromic material, wherein the core-shell structured thermochromic material is doped with vanadium dioxide. Nanoparticles form the core, and a metal-organic framework forms the shell.

[0010] Thus, the thermochromic material in this solution, with doped vanadium dioxide nanoparticles as the core, can effectively reduce the phase transition reaction temperature range, making it suitable for home use. The metal-organic framework as the shell effectively protects the vanadium dioxide, preventing oxidation and improving its stability.

[0011] More specifically, the unique advantage of this core-shell structure lies in: firstly It can act as a "stability guardian," generating dense... The shell effectively isolates oxygen, water vapor, and acidic pollutants in the environment, preventing... The oxidation of the nucleus greatly improves the material's environmental stability and lifespan. Secondly... It can be used as a "phase change modifier" by... and Inter-nuclear interactions may further optimize the electronic structure, helping to lower the phase transition temperature and improve the sharpness of the phase transition. Meanwhile... It can also serve as a "functionality expansion platform" because Its porous structure allows for the adsorption / desorption of water molecules or other small molecules, and it can respond to humidity or specific gases.

[0012] Furthermore, the thermochromic smart window comprises two outer glass layers and a thermochromic material interlayer sandwiched and fixed between the two outer glass layers. This structure is simple, easy to manufacture, and has good stability.

[0013] Furthermore, the outer glass layer uses either ordinary float glass or ultra-clear glass. Ordinary float glass is cheaper, while ultra-clear glass has stronger light transmittance.

[0014] Furthermore, the thermochromic material interlayer is obtained by chemically anchoring the core-shell structured thermochromic material as a thermochromic functional unit onto a solid transparent matrix material via covalent bonds. The solid transparent matrix material is a three-dimensional cross-linked polymer of polymethyl methacrylate. This makes it easy to prepare and provides good transparency and stability.

[0015] Furthermore, the doping element M of the doped vanadium dioxide nanoparticles is tungsten (W). Therefore, the doped vanadium dioxide nanoparticles can be characterized as follows: .

[0016] Thus, through Doping with high-valence ions can effectively reduce... Its phase change temperature is reduced to a comfortable room temperature range of 35-50℃, making it more suitable for home use.

[0017] Furthermore, the metal-organic framework material is Therefore, the core-shell structured color-changing material can be characterized as... .

[0018] This gives the metal-organic framework high visible light transmittance and excellent solar energy modulation capabilities, thus better improving the material's optical properties. Simultaneously, the ZIF-8 framework possesses natural ultraviolet absorption and shielding functions, effectively blocking high-energy ultraviolet rays from penetrating the interior. This significantly improves the material's weather resistance and chemical stability by preventing oxidation and corrosion. The porous shell of ZIF-8 creates a microscopic thermally confined space, reducing heat dissipation from the core and enhancing... The photothermal conversion efficiency is high. Therefore, the smart window has the characteristics of low phase change temperature, high stability, high visible light transmittance, and photothermal synergistic response capability.

[0019] Furthermore, the thermochromic smart window comprises the following preparation steps:

[0020] a) Obtain the doped vanadium dioxide nanoparticles (specifically...) );

[0021] b) Coating the surface of the doped vanadium dioxide nanoparticles using an in-situ growth method. Shell layer, to obtain core-shell structured nanoparticles;

[0022] c) The obtained core-shell structured nanoparticle powder material is added to a transparent liquid polymer and then injected between two outer glass layers. The thermochromic material interlayer is obtained by in-situ polymerization under the assistance of an electric field, and the thermochromic smart window is obtained.

[0023] This method is characterized by controllable processes and mild conditions, making it suitable for large-scale production.

[0024] Further, in step a), the doped vanadium dioxide Nanoparticles were obtained using the following preparation steps:

[0025] a1. A certain amount of vanadium pentoxide and ammonium metatungstate Dissolved in the addition of graphene quantum dots Oxalic acid is added to deionized water in aqueous solution. As a reducing agent and complexing agent, vanadium pentoxide is reduced to deep blue vanadium oxalate by stirring at 60-80℃. Precursor complex solution; wherein the molar ratio of vanadium atoms to tungsten atoms is . At this point, tungsten ions are uniformly dispersed in the vanadium acyl solution system and have not yet formed crystals.

[0026] a2. Add a water-soluble polymer (preferably polyethylene glycol, PEG) to the above precursor complex solution and mix thoroughly; wherein, the mass ratio of vanadium pentoxide to the polymer is... The mixed solution is transferred to a high-pressure reactor and subjected to a hydrothermal reaction at 180-220°C for 24-48 hours. During this high-temperature and high-pressure stage, the solution reaches supersaturation, inducing tungsten-doped vanadium dioxide. Nucleation and growth of the embryonic crystal.

[0027] a3. After the hydrothermal reaction is complete (in the reaction system) (The precursor grains exist as a solid precipitate). The precipitate is collected by centrifugation and washed several times with water and ethanol to remove residual reactants and solvents. Then, it is dried in a vacuum drying oven at 60-80°C to obtain tungsten-doped vanadium dioxide containing polymer. Precursor powder;

[0028] a4. The precursor powder is placed in a tube furnace, and oxygen (1-5% by volume) is introduced into a flowing inert protective atmosphere (such as high-purity nitrogen or argon). Annealing is carried out at 400-600℃. During this process, the polymer undergoes thermal decomposition and decomposes into gas. After the gas is discharged, tungsten-doped vanadium dioxide is obtained. Nanoparticles.

[0029] Thus, in step a1, the corresponding proportion of vanadium pentoxide is... and oxalic acid When the solutions are mixed, they react to produce vanadium oxalate. The reaction equation for the precursor complex solution is as follows: The graphene quantum dots added to it The abundant hydroxyl and carboxyl groups on the surface act as effective anchoring sites for vanadium and tungsten ions; Serving as heterogeneous nucleation sites helps to obtain finer and more uniform particles. Grains; the high thermal conductivity of graphene can accelerate the phase transition response, thus achieving a photothermal synergistic effect. Then, in step a2, polymers (such as polyethylene glycol, PEG) form weak coordination with vanadium ions through their functional groups (such as ether-bonded oxygen atoms), adsorbing onto the surface of the growing preform. This polymer "protective layer" generates a steric hindrance effect, preventing [the formation of vanadium ions] through repulsive forces. The crystal nuclei rapidly aggregate, thereby controlling the size uniformity and dispersion of the nanoparticles and guiding them to form the desired porous spherical microstructure, while simultaneously combining with the a1 step... As a heterogeneous nucleation site, it can The extremely fine and uniform size strongly supports the characteristics of the aforementioned nanoparticles, making them more uniform within the interlayer and improving the performance of the smart window. The polymer guides the crystal growth towards the desired morphology, ultimately resulting in porous spherical particles after polymer removal, which can better facilitate subsequent bonding with metal-organic framework materials. In this process, the crystal nuclei develop into mature nanoparticles during hydrothermal reaction in a high-pressure reactor under a polymer protective layer, followed by polymer removal through carbonization. The polymer does not affect the transformation of the crystals into nanoparticles; it only plays a guiding and protective role in this process. Then, in step a3, after the hydrothermal reaction, due to the generated... The precursor consists of water-insoluble solid particles with a density much greater than that of the solution medium, allowing for rapid sedimentation under centrifugal force. Solid-liquid separation is achieved through centrifugation, the solid precipitate is collected, and after washing and drying, the polymer-containing product is obtained. Precursor powder. Finally, annealing is performed under an inert atmosphere containing a small amount of oxygen (e.g., 1-5% by volume). During annealing, the polymer is carbonized and decomposed, causing it to decompose into gases and be released, resulting in a pure product with excellent dispersibility. Nanoparticles. The small amount of oxygen contained in the inert gas prevents PEG carbonization and the leaving of residual carbon. The ideal oxidative decomposition reaction for removing the polymer is as follows: In this way, the polymer is carbonized and decomposed into gases such as , Once evaporated, impurities can be removed, while ensuring good dispersion and size of nanoparticles and forming the desired porous shape.

[0030] Based on the information disclosed above, this invention also discloses a tungsten-doped vanadium dioxide nanoparticle material. The preparation method utilizes the steps described above. The obtained... Nanoparticles are characterized by smaller size, better size uniformity, more uniform distribution, and better dispersibility. Furthermore, the prepared particles have excellent porous properties, which facilitates the subsequent loading of other component materials (such as organometallic framework materials).

[0031] Furthermore, step b) specifically includes the following steps:

[0032] b1. Obtain tungsten-doped vanadium dioxide Nanoparticles are dispersed in ethanol, and a surface modifier (preferably a silane coupling agent containing amino or carboxyl groups, such as 3-aminopropyltriethoxysilane) is added. Or carboxyethylsilanetriol The surface is functionalized by reflux stirring at 60-80℃ for 6-12 hours, thereby enabling the modifier molecules to bind with the surface hydroxylated molecules. Nanoparticles undergo chemical bonding;

[0033] b2. Tungsten-doped vanadium dioxide with completed surface functionalization modification Nanoparticles were centrifuged and washed to remove free modifiers, then dispersed in a ZIF-8 precursor mixture containing zinc salts (such as zinc nitrate) and 2-methylimidazole, utilizing the surface-modified carboxyl groups. or amino As a metal ion scavenger, it adsorbs zinc ions in solution. ; to make zinc ions in vanadium dioxide Surface enrichment forms localized high-concentration nucleation sites, followed by coordination of 2-methylimidazole with zinc to form a framework, inducing ZIF-8 growth;

[0034] b3. After the reaction is continued at room temperature for 2-4 hours, the product is collected by centrifugation, washed several times with methanol, and dried under vacuum to obtain... Core-shell structured nanoparticle powder materials.

[0035] Thus, in the b1 preparation step, one end of the modifier molecule (such as a siloxane or carboxyl group) is connected to... Chemical bonding occurs at hydroxyl or metal sites on the surface, exposing active functional groups (such as amino, carboxyl, or pyrrolidone rings) at the other end to the outermost layer of the particle, thus completing the surface functionalization of the nanoparticles, i.e., the surface modification reaction: In the b2 preparation step, the amino groups exposed on the particle surface are utilized. or carboxyl group As metal anchoring sites, functional groups can serve as effective anchoring sites for metal ions, preferentially capturing them in solution. Subsequently, adsorbed It undergoes coordination polymerization with 2-methylimidazolium in solution: .because surface The rapid increase in concentration significantly lowers the nucleation barrier of ZIF-8 crystals, causing the ZIF-8 framework to preferentially grow along the surface of VO2 particles rather than forming independently in solution. Ultimately, as the crystals grow, a continuous and uniform ZIF-8 shell forms, which... The core is tightly enclosed, eventually forming a core-shell structure. Composite material; the ZIF-8 shell effectively blocks oxygen, water vapor, and acidic pollutants in the environment (such as... , )and The core direct contact significantly improves the long-term chemical stability of the composite material; the refractive index of ZIF-8 is between It acts as an anti-reflective layer between itself and the air, thus increasing light transmittance.

[0036] Based on the information disclosed above, this invention also discloses a core-shell structured nanoparticle powder thermochromic material, the structural-functional expression of which is as follows: The preparation is achieved using the steps described above. This step involves introducing a metal-organic framework (MOF) of ZIF-8 (zeolite imidazolium ester framework-8) to form a tungsten-doped vanadium dioxide shell, thereby endowing it with photothermal synergistic response capabilities. Simultaneously, the preparation step itself boasts significant advantages such as mild operating conditions, precise and controllable nucleation and growth, strong core-shell interface bonding, uniform product morphology, and flexible design of structural functions. Specifically, this process can be rapidly completed at room temperature. Surface functionalization modification precisely guides heterogeneous nucleation of ZIF-8, effectively suppressing impurity phases; a strong core-shell interface is achieved through chemical bonding; and the shell thickness and surface properties can be customized by controlling the modifier. The process is highly versatile and easily scalable.

[0037] Furthermore, step c) specifically includes:

[0038] c1. The prepared core-shell structured nanoparticles The powder material is dispersed in anhydrous ethanol and ultrasonically treated to ensure uniform dispersion. Then, silane coupling agent KH-570 is added, and the mixture is refluxed and stirred at 60-80℃ for 6-12 hours. After the reaction is completed, the mixture is centrifuged, washed with ethanol to remove unreacted silane, and vacuum dried to achieve surface functionalization.

[0039] c2. The surface-functionalized powder material is added to liquid methyl methacrylate (MMA) monomer and strongly ultrasonically dispersed to form a stable suspension; then ethylene glycol dimethacrylate (EGDMA) is added as a crosslinking agent and azobisisobutyronitrile (AIBN) is added as a thermal initiator to prepare a precursor solution; furthermore, the mass ratio of core-shell nanoparticles, MMA monomer, crosslinking agent and initiator is 1:10:0.2:0.05;

[0040] c3. Inject the mixed precursor solution between two glass substrates whose inner surfaces are coated with a transparent conductive film (such as ITO); use a spacer of predetermined thickness (such as polytetrafluoroethylene) at the edge between the two glass substrates. The two glass plates are separated to control the thickness of the thermochromic material interlayer; the conductive layers of the two glass plates are connected to a high-voltage AC power supply, and an electric field with a frequency of 1kHz and a strength of [missing information] is applied. The alternating electric field; maintaining the applied electric field state, so as to The temperature is slowly increased to 50-70℃ (optimal 65℃), and the electric field is maintained while the reaction is kept at a constant temperature for about 4-6 hours (this time is sufficient for most monomers to complete polymerization and form a solid composite film with sufficient mechanical strength). Then the electric field is turned off, the temperature is raised to 80-90℃, and the reaction is maintained for another 1-2 hours to complete the reaction (this ensures that the residual initiator is completely decomposed and the unreacted monomers are further polymerized, improving the stability and durability of the final product), thus obtaining the thermochromic smart window.

[0041] Thus, step c1 uses the silane coupling agent KH-570. The particles undergo surface modification by introducing polymerization-participating functional groups (vinyl or amino groups) onto their ZIF-8 shell, thus achieving surface functionalization; the reaction equation is as follows: In step c2, EGDMA and AIBN are added as crosslinking agents and initiators, respectively, which generate free radicals upon heating, initiating a chain reaction. This allows the core-shell structured nanoparticles to be uniformly dispersed in the liquid polymer monomer, achieving uniform particle dispersion within the monomer. The polymerizable functional groups on the particle surface ensure that they can form chemical bonds with the matrix during subsequent polymerization, thus obtaining a stable composite structure. In step c3, a polytetrafluoroethylene (PTFE) gasket ensures insulation to prevent short circuits caused by the electric field. Under the influence of an alternating electric field, particles with different dielectric constants... Core-shell nanoparticles undergo dielectric polarization, and the dipole-dipole interactions between the particles drive their assembly along the electric field lines, forming an ordered quasi-one-dimensional chain structure. Simultaneously, monomer polymerization is initiated by heating. After an electric field is applied and an initial ordered structure is formed, the temperature is slowly increased to the initiation temperature to minimize the damage to the ordered structure caused by thermal convection. During polymerization, monomer molecules interconnect to form a three-dimensional network structure, and the active double bonds introduced on the surface of the core-shell particles through modification with the silane coupling agent KH-570 covalently bond with the growing polymer chains. This in-situ copolymerization irreversibly locks the dynamically assembled ordered structure within the formed three-dimensional cross-linked network. After the reaction is complete, a monolithic composite smart window with a "sandwich" structure is obtained. The polymerization equation is as follows: This electric field-induced orientation and covalently anchored core-shell nanochain / polymer three-dimensional interpenetrating network structure ensures infrared blocking efficiency while minimizing lateral scattering of light as it passes through the particle layer, thus providing a structural basis for obtaining high-transmittance, low-haze composite smart window materials.

[0042] Compared with the prior art, the present invention has the following significant advantages:

[0043] 1. Low phase transition temperature and high optical performance coexist. This invention achieves this through W element doping and... The synergistic effect of interface effects, while lowering the phase transition temperature to near room temperature, due to... The shell's suppression of light scattering and its high transparency maintain a high visible light transmittance. and excellent solar modulation capabilities Furthermore, by combining innovative preparation methods, smaller-sized products can be produced. Nanoparticles are crucial for the high light transmittance and low haze of smart windows.

[0044] 2. It exhibits excellent long-term stability. In this solution... The shell is The core provides a robust physical barrier and a chemically inert environment, significantly enhancing its weather resistance and UV aging resistance, and extending device lifespan considerably. The core-shell structure, formed by chemical bonding rather than physical adsorption, is more stable and less prone to peeling off during subsequent processing or applications.

[0045] 3. This invention achieves multi-functional integration. Due to the unique properties of its shell, the intelligent window of this invention can achieve a coordinated response to ambient temperature and solar heat. Under strong solar radiation, especially ultraviolet radiation, the ZIF-8 shell not only absorbs ultraviolet light energy and converts it into heat energy, but also effectively suppresses the core. The heat dissipation. This localized heating effect enables the smart window to trigger a phase change in advance by sensing the heat generated by sunlight before the ambient temperature reaches the phase change threshold, and to activate the adaptive shading function, thus achieving intelligent and precise control of the environmental climate.

[0046] 4. Process-friendly and with broad application prospects. The preparation method of this invention is simple, the conditions are mild, it is compatible with existing laminated glass production processes, and it is easy to industrialize.

[0047] In summary, the thermochromic smart window of the present invention has the advantages of high stability, good optical properties, and the ability to achieve photothermal synergy, making it particularly suitable for home use. Moreover, the preparation method is simple, the conditions are mild, it has good compatibility with existing laminated glass production processes, and it is easy to industrialize. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the thermochromic smart window during implementation.

[0049] Figure 2 for Figure 1 A schematic diagram of the structure of a single thermochromic material interlayer.

[0050] Figure 3 for Figure 1 A single doped vanadium dioxide A magnified diagram showing the location of the nanoparticles. Figure 2 Showing a top view of the structure.

[0052] Figure 4 This is a schematic diagram of the process for preparing the thermochromic smart window of the present invention. Detailed Implementation

[0053] The present invention will now be described in further detail with reference to specific embodiments.

[0054] In specific implementation: a thermochromic smart window, see [link / reference] Figures 1-3 The thermochromic smart window contains at least one thermochromic material interlayer 2, characterized in that the core functional material of the thermochromic material interlayer is a core-shell structured thermochromic material, wherein the core-shell structured thermochromic material is doped vanadium dioxide. Nanoparticles 3 form the core, and a metal-organic framework 4 forms the shell.

[0055] Thus, the thermochromic material in this solution, with doped vanadium dioxide nanoparticles as the core, can effectively reduce the phase transition reaction temperature range, making it suitable for home use. The metal-organic framework as the shell effectively protects the vanadium dioxide, preventing oxidation and improving its stability.

[0056] More specifically, the unique advantage of this core-shell structure lies in: firstly It can act as a "stability guardian," generating dense... The shell effectively isolates oxygen, water vapor, and acidic pollutants in the environment, preventing... The oxidation of the nucleus greatly improves the material's environmental stability and lifespan. Secondly... It can be used as a "phase change modifier" by... and Inter-nuclear interactions may further optimize the electronic structure, helping to lower the phase transition temperature and improve the sharpness of the phase transition. Meanwhile... It can also serve as a "functionality expansion platform" because Its porous structure allows for the adsorption / desorption of water molecules or other small molecules, and it may respond to humidity or specific gases.

[0057] In this embodiment, see Figure 1 and Figure 2 The thermochromic smart window comprises two outer glass layers 1 and a thermochromic material interlayer 2 sandwiched and fixed between the two outer glass layers. This structure is simple, easy to manufacture, and has good stability.

[0058] In this embodiment, the outer glass 1 is made of ordinary float glass or ultra-clear glass. Ordinary float glass is cheaper, while ultra-clear glass has stronger light transmittance.

[0059] In this embodiment, see Figure 2 and Figure 3 The thermochromic material interlayer 2 is obtained by chemically anchoring the core-shell structured thermochromic material as a thermochromic functional unit onto a solid transparent matrix material 5 via covalent bonds. The solid transparent matrix material is a three-dimensional network crosslinked polymer of polymethyl methacrylate. This makes it easy to prepare and provides good transparency and stability.

[0060] In this embodiment, the doping element M of the doped vanadium dioxide nanoparticles is tungsten (W). Therefore, the doped vanadium dioxide nanoparticles can be characterized as follows: .

[0061] Thus, through Doping with high-valence ions can effectively reduce... Its phase change temperature is reduced to a comfortable room temperature range of 35-50℃, making it more suitable for home use.

[0062] In this embodiment, the metal-organic framework material is ZIF-8 (zeolite imidazolium ester framework-8). Therefore, the core-shell structured color-changing material can be characterized as... .

[0063] This gives the metal-organic framework high visible light transmittance and excellent solar energy modulation capabilities, thus better improving the material's optical properties. Simultaneously, the ZIF-8 framework possesses natural ultraviolet absorption and shielding functions, effectively blocking high-energy ultraviolet rays from penetrating the interior. This significantly improves the material's weather resistance and chemical stability by preventing oxidation and corrosion. The porous shell of ZIF-8 creates a microscopic thermally confined space, reducing heat dissipation from the core and enhancing... The photothermal conversion efficiency is high. Therefore, the smart window has the characteristics of low phase change temperature, high stability, high visible light transmittance, and photothermal synergistic response capability.

[0064] In this embodiment, the thermochromic smart window has the following preparation steps: See Figure 4 .

[0065] a) Obtain the doped vanadium dioxide nanoparticles ;

[0066] b) Coating the surface of the doped vanadium dioxide nanoparticles using an in-situ growth method. Shell layer, to obtain core-shell structured nanoparticles;

[0067] c) The obtained core-shell structured nanoparticle powder material is added to a transparent liquid polymer and then injected between two outer glass layers. The thermochromic material interlayer is obtained by in-situ polymerization under the assistance of an electric field, and the thermochromic smart window is obtained.

[0068] This method is characterized by controllable processes and mild conditions, making it suitable for large-scale production.

[0069] Further, in step a), the doped vanadium dioxide Nanoparticles were obtained using the following preparation steps:

[0070] a1. A certain amount of vanadium pentoxide and ammonium metatungstate Dissolved in the addition of graphene quantum dots Oxalic acid is added to deionized water in aqueous solution. As a reducing agent and complexing agent, vanadium pentoxide is reduced to deep blue vanadium oxalate by stirring at 60-80℃. Precursor complex solution; wherein the molar ratio of vanadium atoms to tungsten atoms is . At this point, tungsten ions are uniformly dispersed in the vanadium acyl solution system and have not yet formed crystals.

[0071] a2. Add a water-soluble polymer (preferably polyethylene glycol, PEG) to the above precursor complex solution and mix thoroughly. The molar ratio of vanadium atoms to tungsten atoms in the added material is [insert molar ratio here]. The mass ratio of vanadium pentoxide to polymer is The mixed solution was transferred to a high-pressure reactor and subjected to a hydrothermal reaction at 180-220°C for 24-48 hours. During this high-temperature and high-pressure stage, the solution reached supersaturation, inducing tungsten-doped vanadium dioxide. Nucleation and growth of the embryonic crystal.

[0072] a3. After the hydrothermal reaction is complete, in the reaction system The precursor grains existed as a solid precipitate. The precipitate was collected by centrifugation and washed several times with water and ethanol to remove residual reactants and solvents. It was then dried in a vacuum oven at 60-80°C to obtain tungsten-doped vanadium dioxide containing the polymer. Precursor powder;

[0073] a4. The precursor powder is placed in a tube furnace, and oxygen (1-5% by volume) is introduced into a flowing inert protective atmosphere (such as high-purity nitrogen or argon). Annealing is carried out at 400-600℃. During this process, the polymer undergoes thermal decomposition and decomposes into gas. After the gas is discharged, tungsten-doped vanadium dioxide is obtained. Nanoparticles.

[0074] Thus, in step a1, the corresponding proportion of vanadium pentoxide is... and oxalic acid When the solutions are mixed, they react to produce vanadium oxalate. The reaction equation for the precursor complex solution is as follows: The graphene quantum dots added to it The abundant hydroxyl and carboxyl groups on the surface act as effective anchoring sites for vanadium and tungsten ions; Serving as heterogeneous nucleation sites helps to obtain finer and more uniform particles. Grains; the high thermal conductivity of graphene can accelerate the phase transition response, thus achieving a photothermal synergistic effect. Then, in step a2, polymers (such as polyethylene glycol, PEG) form weak coordination with vanadium ions through their functional groups (such as ether-bonded oxygen atoms), adsorbing onto the surface of the growing preform. This polymer "protective layer" generates a steric hindrance effect, preventing [the formation of vanadium ions] through repulsive forces. The crystal nuclei rapidly aggregate, thereby controlling the size uniformity and dispersion of the nanoparticles and guiding them to form the desired porous spherical microstructure, while simultaneously combining with the a1 step... As a heterogeneous nucleation site, it can The extremely fine and uniform size strongly supports the characteristics of the aforementioned nanoparticles, making them more uniform within the interlayer and improving the performance of the smart window. The polymer guides the crystal growth towards the desired morphology, ultimately resulting in porous spherical particles after polymer removal, which can better facilitate subsequent bonding with metal-organic framework materials. In this process, the crystal nuclei develop into mature nanoparticles during hydrothermal reaction in a high-pressure reactor under a polymer protective layer, followed by polymer removal through carbonization. The polymer does not affect the transformation of the crystals into nanoparticles; it only plays a guiding and protective role in this process. Then, in step a3, after the hydrothermal reaction, due to the generated... The precursor consists of water-insoluble solid particles with a density much greater than that of the solution medium, allowing for rapid sedimentation under centrifugal force. Solid-liquid separation is achieved through centrifugation, the solid precipitate is collected, and after washing and drying, the polymer-containing product is obtained. Precursor powder. Finally, annealing is performed under an inert atmosphere containing a small amount of oxygen (e.g., 1-5% by volume). During annealing, the polymer is carbonized and decomposed, causing it to decompose into gases and be released, resulting in a pure product with excellent dispersibility. Nanoparticles. The small amount of oxygen contained in the inert gas prevents PEG carbonization and the leaving of residual carbon. The ideal oxidative decomposition reaction for removing the polymer is as follows: In this way, the polymer is carbonized and decomposed into gases such as , Once evaporated, impurities can be removed, while ensuring good dispersion and size of nanoparticles and forming the desired porous shape.

[0075] Based on the information disclosed above, this invention also discloses a tungsten-doped vanadium dioxide nanoparticle material. The preparation method utilizes the steps described above. The obtained... Nanoparticles are characterized by smaller size, better size uniformity, more uniform distribution, and better dispersibility. Furthermore, the prepared particles have excellent porous properties, which facilitates the subsequent loading of other component materials (such as organometallic framework materials).

[0076] Furthermore, step b) specifically includes the following steps:

[0077] b1. Obtain tungsten-doped vanadium dioxide Nanoparticles are dispersed in ethanol, and a surface modifier is added, preferably a silane coupling agent containing amino or carboxyl groups, such as 3-aminopropyltriethoxysilane. Or carboxyethylsilanetriol ,exist The surface is functionalized by reflux stirring at a constant temperature for 6-12 hours, allowing the modifier molecules to bind with the surface hydroxylated molecules. Nanoparticles undergo chemical bonding;

[0078] b2. To complete the surface functionalization modification Nanoparticles were centrifuged and washed to remove free modifiers, then dispersed in a ZIF-8 precursor mixture containing zinc salts (such as zinc nitrate) and 2-methylimidazole, utilizing the surface-modified carboxyl groups. or amino As a metal ion scavenger, it adsorbs zinc ions in solution. To allow zinc ions to... Surface enrichment forms localized high-concentration nucleation sites, followed by coordination of 2-methylimidazole with zinc to form a framework, inducing ZIF-8 growth;

[0079] b3. After the reaction is continued at room temperature for 2-4 hours, the product is collected by centrifugation, washed several times with methanol, and dried under vacuum to obtain... Core-shell structured nanoparticle powder materials.

[0080] Thus, in the b1 preparation step, one end of the modifier molecule (such as a siloxane or carboxyl group) is connected to... Chemical bonding occurs at hydroxyl or metal sites on the surface, exposing active functional groups (such as amino, carboxyl, or pyrrolidone rings) at the other end to the outermost layer of the particle, thus completing the surface functionalization of the nanoparticles, i.e., the surface modification reaction: In the b2 preparation step, the amino groups exposed on the particle surface are utilized. or carboxyl group As metal anchoring sites, functional groups can serve as effective anchoring sites for metal ions, preferentially capturing them in solution. Subsequently, adsorbed It undergoes coordination polymerization with 2-methylimidazolium in solution: .because surface The rapid increase in concentration significantly lowers the nucleation barrier of ZIF-8 crystals, causing the ZIF-8 framework to preferentially grow along the surface of VO2 particles rather than forming independently in solution. Ultimately, as the crystals grow, a continuous and uniform ZIF-8 shell forms, which... The core is tightly enclosed, eventually forming a core-shell structure. Composite material; the ZIF-8 shell effectively blocks oxygen, water vapor, and acidic pollutants in the environment (such as... , )and The core direct contact significantly improves the long-term chemical stability of the composite material; the refractive index of ZIF-8 is between It acts as an anti-reflective layer between itself and the air, thus increasing light transmittance.

[0081] Based on the information disclosed above, this invention also discloses a core-shell structured nanoparticle powder thermochromic material, the structural-functional expression of which is as follows: The preparation is achieved using the steps described above. This step involves introducing a metal-organic framework (MOF) of ZIF-8 (zeolite imidazolium ester framework-8) to form a tungsten-doped vanadium dioxide shell, thereby endowing it with photothermal synergistic response capabilities. Simultaneously, the preparation step itself boasts significant advantages such as mild operating conditions, precise and controllable nucleation and growth, strong core-shell interface bonding, uniform product morphology, and flexible design of structural functions. Specifically, this process can be rapidly completed at room temperature. Surface functionalization modification precisely guides heterogeneous nucleation of ZIF-8, effectively suppressing impurity phases; a strong core-shell interface is achieved through chemical bonding; and the shell thickness and surface properties can be customized by controlling the modifier. The process is highly versatile and easily scalable.

[0082] Furthermore, step c) specifically includes:

[0083] c1. The prepared core-shell structured nanoparticles The powder material is dispersed in anhydrous ethanol and ultrasonically treated to ensure uniform dispersion. Then, silane coupling agent KH-570 is added, and the mixture is refluxed and stirred at 60-80℃ for 6-12 hours. After the reaction is completed, the mixture is centrifuged, washed with ethanol to remove unreacted silane, and vacuum dried to achieve surface functionalization.

[0084] c2. The surface-functionalized powder material is added to liquid methyl methacrylate (MMA) monomer and strongly ultrasonically dispersed to form a stable suspension; then ethylene glycol dimethacrylate (EGDMA) is added as a crosslinking agent and azobisisobutyronitrile (AIBN) is added as a thermal initiator to prepare a precursor solution; furthermore, the mass ratio of core-shell nanoparticles, MMA monomer, crosslinking agent and initiator is 1:10:0.2:0.05;

[0085] c3. Inject the mixed precursor solution between two glass substrates whose inner surfaces are coated with a transparent conductive film (such as ITO); use a spacer of predetermined thickness (such as polytetrafluoroethylene) at the edge between the two glass substrates. The two glass plates are separated to control the thickness of the thermochromic material interlayer; the conductive layers of the two glass plates are connected to a high-voltage AC power supply, and an AC electric field with a frequency of 1kHz and a field strength of 200-500V / cm is applied; the electric field is maintained in the applied state to... The temperature is slowly increased to 50-70℃ (optimal 65℃), and the electric field is maintained while the reaction is kept at a constant temperature for about 4-6 hours (this time is sufficient for most monomers to complete polymerization and form a solid composite film with sufficient mechanical strength). Then the electric field is turned off, the temperature is raised to 80-90℃, and the reaction is maintained for another 1-2 hours to complete the reaction (this ensures that the residual initiator is completely decomposed and the unreacted monomers are further polymerized, improving the stability and durability of the final product), thus obtaining the thermochromic smart window.

[0086] Thus, step c1 uses the silane coupling agent KH-570. The particles undergo surface modification by introducing polymerization-participating functional groups (vinyl or amino groups) onto their ZIF-8 shell, thus achieving surface functionalization; the reaction equation is as follows: In step c2, EGDMA and AIBN are added as crosslinking agents and initiators, respectively, which generate free radicals upon heating, initiating a chain reaction. This allows the core-shell structured nanoparticles to be uniformly dispersed in the liquid polymer monomer, achieving uniform particle dispersion within the monomer. The polymerizable functional groups on the particle surface ensure that they can form chemical bonds with the matrix during subsequent polymerization, thus obtaining a stable composite structure. In step c3, a polytetrafluoroethylene (PTFE) gasket ensures insulation to prevent short circuits caused by the electric field. Under the influence of an alternating electric field, particles with different dielectric constants... Core-shell nanoparticles undergo dielectric polarization, and the dipole-dipole interactions between the particles drive their assembly along the electric field lines, forming an ordered quasi-one-dimensional chain structure. Simultaneously, monomer polymerization is initiated by heating. After an electric field is applied and an initial ordered structure is formed, the temperature is slowly increased to the initiation temperature to minimize the damage to the ordered structure caused by thermal convection. During polymerization, monomer molecules interconnect to form a three-dimensional network structure, and the active double bonds introduced on the surface of the core-shell particles through modification with the silane coupling agent KH-570 covalently bond with the growing polymer chains. This in-situ copolymerization irreversibly locks the dynamically assembled ordered structure within the formed three-dimensional cross-linked network. After the reaction is complete, a monolithic composite smart window with a "sandwich" structure is obtained. The polymerization equation is as follows: This electric field-induced orientation and covalently anchored core-shell nanochain / polymer three-dimensional interpenetrating network structure ensures infrared blocking efficiency while minimizing lateral scattering of light as it passes through the particle layer, thus providing a structural basis for obtaining high-transmittance, low-haze composite smart window materials.

Claims

1. A thermochromic smart window, wherein the thermochromic smart window contains at least one layer of thermochromic material, characterized in that, The core functional material of the thermochromic material is a core-shell structured thermochromic material, which uses doped vanadium dioxide nanoparticles as the core and a metal-organic framework as the shell.

2. The thermochromic smart window as described in claim 1, characterized in that, The thermochromic smart window includes two outer glass layers and a thermochromic material interlayer sandwiched between the two outer glass layers.

3. The thermochromic smart window as described in claim 2, characterized in that, The outer glass layer is made of ordinary float glass or ultra-clear glass.

4. The thermochromic smart window as described in claim 2, characterized in that, The thermochromic material interlayer is obtained by using the core-shell structured thermochromic material as the thermochromic functional unit, which is chemically anchored to a solid transparent matrix material by covalent bonds. The solid transparent matrix material is a three-dimensional network crosslinked polymer of polymethyl methacrylate.

5. The thermochromic smart window as described in claim 2, characterized in that, The doping element M of the doped vanadium dioxide nanoparticles is tungsten.

6. The thermochromic smart window as described in claim 2, characterized in that, The metal-organic framework material is ZIF-8.

7. The thermochromic smart window as described in claim 2, characterized in that, The thermochromic smart window has the following preparation steps: a) Obtain the doped vanadium dioxide nanoparticles; b) By means of in-situ growth method, MOF shell layer is coated on the surface of the doped vanadium dioxide nanoparticles to obtain core-shell structured nanoparticles; c) The obtained core-shell structured nanoparticle powder material is added to a transparent liquid polymer and then injected between two outer glass layers. The thermochromic material interlayer is obtained by in-situ polymerization under the assistance of an electric field, and the thermochromic smart window is obtained.

8. The thermochromic smart window as described in claim 7, characterized in that, In step a), the doped vanadium dioxide nanoparticles are obtained using the following preparation steps: a1. A certain amount of vanadium pentoxide and ammonium metatungstate are dissolved in deionized water containing graphene quantum dots. Oxalic acid is added as a reducing agent and complexing agent. The reaction is stirred at 60-80℃, and vanadium pentoxide is reduced to form a dark blue vanadium oxalate precursor complex solution. The molar ratio of vanadium atoms to tungsten atoms is [insert molar ratio here]. ; a2. Add the water-soluble polymer to the above precursor complex solution and mix thoroughly; wherein, the mass ratio of vanadium pentoxide to the polymer is [missing information]. The mixed solution was transferred to a high-pressure reactor and subjected to a hydrothermal reaction at 180-220°C for 24-48 hours. a3. After the hydrothermal reaction is completed, the precipitate is collected by centrifugation and washed several times with water and ethanol to remove residual reactants and solvents. Then it is dried in a vacuum drying oven at 60-80°C to obtain tungsten-doped vanadium dioxide precursor powder containing polymer. a4. The precursor powder is placed in a tube furnace, and annealing is performed at 400-600℃ under a flowing inert protective atmosphere with 1-5% oxygen by volume. During this process, the polymer undergoes thermal decomposition and decomposes into gas. After the gas is discharged, tungsten-doped vanadium dioxide is obtained. Nanoparticles.

9. The thermochromic smart window as described in claim 7, characterized in that, b) The specific steps include: b1. Disperse the obtained tungsten-doped vanadium dioxide nanoparticles in ethanol, add a surface modifier, and reflux and stir at 60-80℃ for 6-12 hours to perform surface functionalization modification, so that the modifier molecules are hydroxylated on the surface. Nanoparticles undergo chemical bonding; b2. The tungsten-doped vanadium dioxide nanoparticles with completed surface functionalization were centrifuged and washed to remove free modifiers. They were then dispersed in a mixed solution of ZIF-8 precursor containing zinc salt and 2-methylimidazole. The surface-modified carboxyl or amino groups were used as metal ion scavengers to adsorb zinc ions in the solution. This enriched zinc ions on the vanadium dioxide surface, forming local high-concentration nucleation sites. Subsequently, 2-methylimidazole coordinated with zinc to form a framework, inducing ZIF-8 growth. b3. After the reaction is continued at room temperature for 2-4 hours, the product is collected by centrifugation, washed several times with methanol, and dried under vacuum to obtain... Core-shell structured nanoparticle powder materials.

10. The thermochromic smart window as described in claim 7, characterized in that, c) The specific steps include: c1. The obtained core-shell structured nanoparticle powder material is dispersed in anhydrous ethanol and ultrasonically treated to make it uniformly dispersed; then silane coupling agent KH-570 is added, and the mixture is refluxed and stirred at 60-80℃ for 6-12 hours; after the reaction is completed, the mixture is centrifuged, washed with ethanol to remove unreacted silane, and vacuum dried to achieve its surface functionalization. c2. The surface-functionalized powder material is added to liquid methyl methacrylate monomer and strongly ultrasonically dispersed to form a stable suspension; then ethylene glycol dimethacrylate is added as a crosslinking agent and azobisisobutyronitrile is added as a thermal initiator to prepare a precursor solution. c3. The mixed precursor solution is injected between two glass substrates with transparent conductive films deposited on their inner surfaces; the edges between the two glass substrates are separated by spacers of a predetermined thickness to control the thickness of the resulting thermochromic material interlayer; the conductive layers of the two glass substrates are connected to a high-voltage AC power supply, and an AC electric field with a frequency of 1kHz and a field strength of 200-500V / cm is applied; the applied electric field is maintained to... The temperature is slowly increased to 50-70℃, the electric field is maintained and the reaction is kept at a constant temperature for about 4-6 hours, then the electric field is turned off, the temperature is increased to 80-90℃, and the reaction is maintained for another 1-2 hours to complete the reaction, thus obtaining the thermochromic smart window.

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