Photo-thermal synergistic phase change composite film based on gradient type carbon-based heterostructure and preparation method of photo-thermal synergistic phase change composite film

Abstract

The invention relates to a photo-thermal synergistic phase change composite film based on a gradient type carbon-based heterostructure and a preparation method of the photo-thermal synergistic phase change composite film based on the gradient type carbon-based heterostructure, a gradient heterostructure metal coupling highly-graphitized carbon hybrid carrier is constructed through in-situ pyrolysis of a molecular precursor, and confinement packaging of an alcohol phase change material is achieved. The core innovation comprises the following steps: 1) exciting local plasmon resonance by using an electron tunneling effect between a graphite sphybrid orbit and a metal d orbit, and improving the photothermal conversion efficiency; 2) inhibiting thermal relaxation energy loss through a phonon confinement effect of the graded carbon-based topological skeleton; and (3) core material dynamics is regulated and controlled by means of a micro-nano porous structure, and wide-temperature-range heat energy controllable release is achieved. The material and a polymer binder are compounded and rolled through an interpenetrating network to form a flexible functional film, the preparation process is simple, the efficient heat energy storage and release synergistic performance is shown in the fields of wearable equipment, battery thermal control and building energy saving, and the problems that a traditional phase change material is low in photothermal conversion efficiency, large in heat loss and poor in temperature range adaptability are solved.

Description

Technical Field

[0001] The present invention belongs to the field of nanomaterials and composite phase change materials, and specifically relates to a photothermal synergistic phase change composite film based on a gradient carbon-based heterostructure and a preparation method thereof. Background Art

[0002] As a clean, renewable and green energy source, solar energy has been widely used in photovoltaics, photocatalysis, water purification and other fields. However, the inherent intermittent and variability of solar radiation poses a major challenge to the widespread use of solar energy. Storing solar energy in the form of heat through phase change materials has great prospects because of their high energy density and stable phase change temperature, which can promote continuous energy release even in the absence of solar radiation. However, single phase change materials are limited by their low solar absorptivity and poor photothermal conversion capabilities. To address these limitations, efficient photothermal materials must be integrated into phase change materials.

[0003] Among various photothermal materials such as nanocarbon materials, metal-based materials, and organic materials, nanocarbon materials have great potential in improving the energy storage efficiency of phase change materials. This potential is attributed to their strong photothermal conversion ability, high thermal conductivity, good stability, and low toxicity. In particular, the sp 2 Hybridization forms a planar π electron cloud structure, which enables nanocarbon materials to effectively convert solar energy into thermal energy through non-radiative transitions of π electrons. 2 The conjugated system produced by hybrid carbon narrows the energy gap between molecular orbitals, allowing the material to absorb light from almost the entire solar spectrum. However, traditional carbon materials face the challenges of poor photothermal responsiveness, complex pore structure, and difficult to adjust multi-level pores. Metal-organic framework-derived carbon materials generally retain the well-defined mesh pore structure and unique morphology of their precursors, and have unique advantages such as abundant adsorption sites, adjustable hierarchical pores, and excellent stability. In addition, catalytically active metal nanoparticles can convert amorphous carbon into graphitized carbon, and reduce the emissivity of these metal nanoparticles to carbon-based materials through the localized surface plasmon resonance effect. The mutual coupling between metal nanoparticles and highly graphitized carbon further enhances the photothermal performance. However, how to achieve effective contact between phase change materials and metal-coupled highly graphitized carbon synergistic enhancement sites remains a major challenge. Therefore, it is crucial to develop a phase change material with fast photothermal response, diverse and adjustable pore structure, and thus achieve effective contact between phase change materials and metal-coupled highly graphitized carbon synergistic enhancement sites, which is crucial to significantly improve the photothermal performance of phase change materials. Summary of the invention

[0004] The purpose of the present invention is to provide a photothermal synergistic phase change composite film based on a gradient carbon-based heterostructure and a preparation method thereof. By adopting in-situ confined growth technology, through molecular-level carbon precursor coordination regulation and pyrolysis strategy, a gradient heterostructure metal-coupled high-graphitization carbon hybrid carrier is constructed, and the three-dimensional confined encapsulation of phase change materials is successfully realized. Subsequently, it is formed into an interpenetrating network structure with a polymer binder, and a photothermal synergistic phase change composite film is obtained by directional calendering. The prepared phase change composite film has a simple preparation method and process, is efficient and suitable for large-scale production, can effectively improve the photothermal response capability, promote the efficient storage and utilization of solar energy, and has broad application prospects.

[0005] The present invention provides a photothermal synergistic phase change composite film based on a gradient carbon-based heterostructure and a preparation method thereof, the method comprising the following steps:

[0006] (1) In a metal organic framework material MOF (A), by adsorbing exogenous metal ions B, a MOF (A, B) precursor containing two metal components is obtained;

[0007] (2) carbonizing the MOF (A, B) precursor containing two metal components prepared in step (1) at high temperature under an inert atmosphere, and etching the metal nanoparticles not coated with carbon with an acid solution to obtain a gradient heterostructure metal-coupled highly graphitized carbon hybrid carrier;

[0008] (3) adding the gradient heterostructure metal-coupled highly graphitized carbon hybrid support prepared in step (2) and the hydroxyl-containing organic phase change material into an ethanol solution in a mass ratio of 4:1 to 1:4, ultrasonically treating for 20 to 60 min to ensure complete contact and sufficient mixing, and drying in a vacuum oven at 30 to 100 °C for 12 to 24 h to obtain a composite phase change material;

[0009] (4) Add the composite phase change material prepared in step (3) and the polymer binder into an agate mortar in a mass ratio of 10:1 to 5:1, mix thoroughly, and press to form a phase change composite film.

[0010] The MOF (A, B) precursor containing two metal components was synthesized by the following method:

[0011] (a) dispersing a zinc-containing metal salt and an amino-containing organic ligand in a DMF solvent at a molar ratio of 1:2 to 2:1 to form a homogeneous mixed solution;

[0012] (b) adding triethylamine to the homogeneous mixed solution of step (a) to adjust the pH value of the system to 7-8, and obtaining a colloidal suspension after stirring;

[0013] (c) sequentially centrifuging the colloidal suspension, washing with a DMF solvent for 3 to 5 times, and washing with a methanol solvent for 3 to 5 times, and then drying the colloidal suspension at 60 to 80° C. under vacuum conditions for 12 to 24 h to obtain MOF (A) powder;

[0014] (d) dispersing the MOF (A) powder and the metal salt containing catalytic properties in a DMF solvent to obtain a mixed solution, wherein the concentration of the metal salt containing catalytic properties in the mixed solution is controlled to be 25-125 mg / mL;

[0015] (e) The mixed solution of step (d) is subjected to ultrasonic dispersion for 20 to 60 min, followed by reaction under stirring for 2 to 5 h, the reaction product is separated by centrifugation, and dried under vacuum at 60 to 80 °C for 12 to 24 h to finally obtain a MOF (A, B) precursor containing two metal components.

[0016] The gradient heterostructured metal-coupled highly graphitized carbon hybrid support was synthesized by the following method:

[0017] (a) The MOF (A, B) precursor containing two metal components is placed under inert atmosphere protection, the temperature is programmed to 900-1200 °C at a heating rate of 1-5 °C / min, and carbonized at this temperature for 2-6 h;

[0018] (b) immersing the carbonized product of step (a) in a 6-12 M hydrochloric acid solution and chemically etching at room temperature for 6-24 h to remove free metal nanoparticles not coated by the carbon layer;

[0019] (c) repeatedly washing the product after etching in step (b) with deionized water until the filtrate is neutral, so as to completely remove the residual acid and metal ions to obtain a purified product;

[0020] (d) The purified product of step (c) is dried under vacuum conditions at 60 to 80° C. for 12 to 24 h to obtain a gradient heterostructure metal-coupled highly graphitized carbon hybrid support.

[0021] The zinc-containing metal salts suitable for the present invention include but are not limited to: one or more of zinc nitrate, zinc sulfate, zinc acetate, and zinc chloride; the amino-containing organic ligands include but are not limited to: one or more of 2-aminoterephthalic acid, 3-amino-1,2,4-triazole, and 2-aminobiphenyl-4,4'-dicarboxylic acid.

[0022] The metal salts with catalytic properties suitable for use in the present invention include, but are not limited to, one or more of nickel nitrate, nickel sulfate, nickel acetate, nickel chloride, cobalt nitrate, cobalt chloride, cobalt sulfate, cobalt acetate, ferric nitrate, ferric chloride, ferric sulfate, and ferric acetate.

[0023] The hydroxyl-containing organic phase change material suitable for the present invention includes any combination of one or more of n-octanol, n-decanol, octanol, lauryl alcohol, myristyl alcohol, palmityl alcohol, stearyl alcohol, cetearyl alcohol, behenyl alcohol and polyethylene glycol.

[0024] The polymer binder suitable for the present invention includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, carboxymethyl cellulose, styrene-butadiene rubber, polyvinyl alcohol, polyacrylic acid, polyimide, epoxy resin, polyurethane and polyacrylonitrile.

[0025] The beneficial effects of the present invention are as follows: the gradient heterostructure metal-coupled highly graphitized carbon hybrid carrier is successfully constructed by the method of the present invention, and the three-dimensional confined encapsulation of the phase change material is realized, thereby stably obtaining a photothermal synergistic phase change composite film based on a gradient carbon-based heterostructure. By designing a heterogeneous interface structure of graphitized carbon shells encapsulating metal nanocrystals, the graphite sp 2 The electron tunneling effect between the hybrid orbital and the metal d orbital produces a localized surface plasmon enhancement effect, which significantly improves the photothermal conversion efficiency; at the same time, the phonon confinement effect of the graded carbon skeleton significantly reduces the thermal relaxation loss of the phase change material. In addition, the alcohol phase change material containing hydroxyl groups exhibits the highest kinetic energy and diffusion coefficient after encapsulation. The gradient heterostructure metal coupled with the highly graphitized carbon hybrid carrier effectively broadens the phase change temperature and heat release time of the composite phase change material, realizing the wide temperature range and long-term thermal energy release of the composite phase change film. The preparation method is simple, efficient and suitable for large-scale production. It can effectively improve the photothermal response capability, promote the efficient storage and utilization of solar energy, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the TEM spectrum of the carrier material obtained in Example 1 of the present invention.

[0027] Figure 2 This is the XRD spectrum of the carrier material obtained in Example 1 of the present invention.

[0028] Figure 3 This is the XRD spectrum of the composite phase change material obtained in Example 1 of the present invention.

[0029] Figure 4 This is the DSC spectrum of the composite phase change material obtained in Example 1 of the present invention.

[0030] Figure 5 This is the DSC spectrum of the composite phase change material obtained in Example 1 of the present invention after 200 cycles.

[0031] Figure 6 This is the photothermal temperature change curve of the phase change composite film obtained in Example 1 of the present invention.

[0032] Figure 7 This is the photothermal temperature change curve of the phase change composite film obtained in Example 2 of the present invention.

[0033] Figure 8 This is the photothermal temperature change curve of the phase change composite film obtained in Example 3 of the present invention. DETAILED DESCRIPTION

[0034] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0035] Implementation Case 1

[0036] (1) Preparation of gradient heterostructured nickel-coupled highly graphitized carbon hybrid support materials:

[0037] Zinc nitrate hexahydrate and 2-aminoterephthalic acid were dispersed in DMF solvent at a molar ratio of 2:1 to form a homogeneous mixed solution, and then triethylamine solution was added to adjust the pH value of the system to 7. After stirring, a colloidal suspension was obtained, which was centrifuged, washed with DMF solvent 3 times and methanol solvent 3 times in sequence, and then dried at 80°C under vacuum for 24 h to obtain MOF (Zn) powder; MOF (Zn) powder and nickel nitrate were co-dispersed in DMF solvent, and the concentration of nickel nitrate in the mixed solution was controlled to be 100 mg / mL, and then the mixed solution was ultrasonically dispersed for 30 min, and reacted under stirring for 3 h. After the product was centrifuged, it was dried at 80°C under vacuum for 24 h to finally obtain a MOF (Zn, Ni) precursor containing two metal components; the MOF (Zn, Ni) precursor containing two metal components was placed under Ar gas atmosphere protection, and the temperature was programmed to 1000°C at a heating rate of 2°C / min, and carbonized at this temperature for 3 h. The carbonized product was immersed in 12 M hydrochloric acid solution and chemically etched at room temperature for 12 h to remove free nickel nanoparticles not coated by the carbon layer. The etched product was repeatedly washed with deionized water until the filtrate was neutral to completely remove residual acid and nickel ions. The purified product was dried at 80 °C under vacuum for 24 h to finally obtain a gradient heterostructure nickel-coupled highly graphitized carbon hybrid support.

[0038] (2) Preparation of photothermal synergistic phase change composite film:

[0039] The gradient heterostructure nickel-coupled highly graphitized carbon hybrid carrier prepared above and stearyl alcohol were added to an ethanol solution in a mass ratio of 3:7, ultrasonically treated for 30 min to ensure complete contact and sufficient mixing, and then dried in a vacuum oven at 80°C for 24 h to obtain a composite phase change material; the composite phase change material and polytetrafluoroethylene were added to an agate mortar in a mass ratio of 8:1, fully mixed and pressed into a photothermal synergistic phase change composite film.

[0040] We used in-situ confined growth technology, molecular-level carbon precursor coordination regulation and pyrolysis strategy to successfully construct a gradient heterostructured nickel-coupled highly graphitized carbon hybrid support. Figure 1 The nickel-coupled high-graphitization plasma-enhanced sites can be clearly observed in the TEM spectrum. Figure 2 The XRD results of the carrier show that the peaks at 44.2°, 51.5° and 76.1° correspond to the (111), (200) and (220) crystal planes of the nickel nanoparticles, respectively. In addition, a broad peak is observed at 26.6°, corresponding to the graphite carbon layer around the nickel nanoparticles. The carrier can effectively adsorb stearyl alcohol and quickly realize photothermal conversion. Figure 3 In the XRD results of the composite phase change material, the characteristic peak of stearyl alcohol can be clearly observed, which confirms that the composite phase change material with excellent crystallization performance is successfully obtained by adopting this experimental scheme. The DSC test results of the composite phase change material prepared in this implementation case are as follows: Figure 4 The results show that the melting temperature of the composite phase change material is 59.6℃, the melting enthalpy is 156.3 J / g, the solidification temperature is 53.7℃, and the solidification enthalpy is 152.5 J / g. Figure 5 The DSC test results of the composite phase change material after 200 cycles show that the phase change temperature and phase change enthalpy of the composite phase change material have only slight changes before and after the cycle, confirming that the composite phase change material obtained by this scheme has good cycle stability. Figure 6 As shown, under the light intensity simulating 1 standard sunlight, the lower surface temperature of the phase change composite film rises to 44.5°C within 60 s, and its photothermal energy storage efficiency is as high as 90.7%, confirming that the prepared phase change composite film has excellent photothermal conversion performance.

[0041] Implementation Case 2

[0042] (1) Preparation of gradient heterostructured cobalt-coupled highly graphitized carbon hybrid support materials:

[0043] Zinc nitrate hexahydrate and 2-aminoterephthalic acid were dispersed in DMF solvent at a molar ratio of 2:1 to form a homogeneous mixed solution, and then triethylamine solution was added to adjust the pH value of the system to 7. After stirring, a colloidal suspension was obtained, which was centrifuged, washed with DMF solvent 3 times and methanol solvent 3 times in sequence, and then dried at 80°C under vacuum for 24 h to obtain MOF (Zn) powder; MOF (Zn) powder and cobalt nitrate were co-dispersed in DMF solvent, and the concentration of cobalt nitrate in the mixed solution was controlled to be 100 mg / mL, and then the mixed solution was ultrasonically dispersed for 30 min, and reacted under stirring for 3 h. After the product was centrifuged, it was dried at 80°C under vacuum for 24 h to finally obtain a MOF (Zn, Co) precursor containing two metal components; The MOF (Zn, Co) precursor containing two metal components was placed under Ar gas atmosphere protection, and the temperature was programmed to 1000°C at a heating rate of 2°C / min, and was carbonized at this temperature for 3 hours. h, the carbonized product was immersed in 12 M hydrochloric acid solution and chemically etched at room temperature for 12 h to remove free cobalt nanoparticles not coated by the carbon layer. The etched product was repeatedly washed with deionized water until the filtrate was neutral to completely remove residual acid and cobalt ions. The purified product was dried at 80 °C under vacuum for 24 h to finally obtain a gradient heterostructure cobalt-coupled highly graphitized carbon hybrid support.

[0044] (2) Preparation of photothermal synergistic phase change composite film:

[0045] The gradient heterostructure cobalt-coupled highly graphitized carbon hybrid carrier prepared above and stearyl alcohol were added to an ethanol solution in a mass ratio of 3:7, ultrasonically treated for 30 min to ensure complete contact and sufficient mixing, and then dried in a vacuum oven at 80°C for 24 h to obtain a composite phase change material; the composite phase change material and polytetrafluoroethylene were added to an agate mortar in a mass ratio of 8:1, fully mixed and pressed into a photothermal synergistic phase change composite film.

[0046] The test results show that the melting temperature of the composite phase change material is 59.3°C, the melting enthalpy is 156.7 J / g, the solidification temperature is 53.1°C, and the solidification enthalpy is 151.8 J / g. At the same time, after 200 cycles, there is no obvious change in the phase change temperature and phase change enthalpy values, and it has excellent thermal cycle stability. The photothermal conversion efficiency of the phase change composite film is as high as 91.2%, which proves that the prepared phase change composite film has excellent photothermal conversion performance.

[0047] Implementation Case 3

[0048] (1) Preparation of gradient heterostructured iron-coupled highly graphitized carbon hybrid support materials:

[0049] Zinc nitrate hexahydrate and 2-aminoterephthalic acid were dispersed in DMF solvent at a molar ratio of 2:1 to form a homogeneous mixed solution, and then triethylamine solution was added to adjust the pH value of the system to 7. After stirring, a colloidal suspension was obtained, which was centrifuged, washed with DMF solvent 3 times and methanol solvent 3 times in sequence, and then dried at 80°C under vacuum for 24 h to obtain MOF (Zn) powder; MOF (Zn) powder and ferric nitrate were co-dispersed in DMF solvent, and the concentration of ferric nitrate in the mixed solution was controlled to be 100 mg / mL, and then the mixed solution was ultrasonically dispersed for 30 min, and reacted under stirring for 3 h. After the product was centrifuged, it was dried at 80°C under vacuum for 24 h to finally obtain a MOF (Zn, Fe) precursor containing two metal components; The MOF (Zn, Fe) precursor containing two metal components was placed under Ar gas atmosphere protection, and the temperature was programmed to 1000°C at a heating rate of 2°C / min, and was carbonized at this temperature for 3 hours. h, the carbonized product was immersed in 12 M hydrochloric acid solution and chemically etched at room temperature for 12 h to remove free iron nanoparticles not coated by the carbon layer. The etched product was repeatedly washed with deionized water until the filtrate was neutral to completely remove residual acid and iron ions. The purified product was dried at 80 °C under vacuum for 24 h to finally obtain a gradient heterostructure iron-coupled highly graphitized carbon hybrid support.

[0050] (2) Preparation of photothermal synergistic phase change composite film:

[0051] The gradient heterostructure iron-coupled highly graphitized carbon hybrid carrier prepared above and stearyl alcohol were added to an ethanol solution in a mass ratio of 3:7, ultrasonically treated for 30 min to ensure complete contact and sufficient mixing, and then dried in a vacuum oven at 80°C for 24 h to obtain a composite phase change material; the composite phase change material and polytetrafluoroethylene were added to an agate mortar in a mass ratio of 8:1, fully mixed and pressed into a photothermal synergistic phase change composite film.

[0052] The test results show that the melting temperature of the composite phase change material is 58.8°C, the melting enthalpy is 157.0 J / g, the solidification temperature is 53.6°C, and the solidification enthalpy is 150.9 J / g. At the same time, after 200 cycles, there is no obvious change in the phase change temperature and phase change enthalpy values, and it has excellent thermal cycle stability. The photothermal conversion efficiency of the phase change composite film is as high as 90.4%, which proves that the prepared phase change composite film has excellent photothermal conversion properties.

Claims

1. A photothermal synergistic phase change composite film based on a gradient carbon-based heterostructure, characterized in that: The invention comprises a gradient heterostructure metal-coupled highly graphitized carbon hybrid carrier, a hydroxyl-containing organic phase change material adsorbed in the pores of the gradient heterostructure metal-coupled highly graphitized carbon hybrid carrier, and a polymer binder which forms an interpenetrating network structure composite membrane with the gradient heterostructure metal-coupled highly graphitized carbon hybrid carrier and the hydroxyl-containing organic phase change material.

2. The light-thermal synergistic phase change composite film based on gradient carbon-based heterostructure according to claim 1, characterized in that: The gradient heterostructure metal-coupled highly graphitized carbon hybrid carrier has graphite sp² hybrid orbitals and metal d orbitals, forming an electron tunneling effect to excite localized plasma exciton resonance; the graded carbon-based topological skeleton phonon confinement effect of the gradient heterostructure metal-coupled highly graphitized carbon hybrid carrier suppresses thermal relaxation energy loss; an electrostatic effect is formed with the hydroxyl-containing organic phase change material to regulate its phase change dynamics; and a flexible functional film is formed with the polymer binder through interpenetrating network composite calendering.

3. The light-thermal synergistic phase change composite film based on gradient carbon-based heterostructure according to claim 1, characterized in that: The hydroxyl-containing organic phase change material is selected from one or more of octanol, decyl alcohol, octyl decyl alcohol, lauryl alcohol, myristyl alcohol, palmityl alcohol, stearyl alcohol, cetearyl alcohol, behenyl alcohol, and polyethylene glycol in any combination; the polymer binder is selected from one or more of polytetrafluoroethylene, polyvinylidene fluoride, carboxymethyl cellulose, styrene-butadiene rubber, polyvinyl alcohol, polyacrylic acid, polyimide, epoxy resin, polyurethane, and polyacrylonitrile.

4. The method for preparing a photothermal synergistic phase change composite film based on a gradient carbon-based heterostructure according to claim 1, characterized in that: The following steps are involved: (1) In a metal organic framework material MOF (A), by adsorbing exogenous metal ions B, a MOF (A, B) precursor containing two metal components is obtained; (2) carbonizing the MOF (A, B) precursor containing two metal components prepared in step (1) at high temperature under an inert atmosphere, and etching the metal nanoparticles not coated with carbon with an acid solution to obtain a gradient heterostructure metal-coupled highly graphitized carbon hybrid carrier; (3) adding the gradient heterostructure metal-coupled highly graphitized carbon hybrid support prepared in step (2) and the hydroxyl-containing organic phase change material into an ethanol solution in a mass ratio of 4:1 to 1:4, ultrasonically treating for 20 to 60 min to ensure complete contact and sufficient mixing, and drying in a vacuum oven at 30 to 100 °C for 12 to 24 h to obtain a composite phase change material; (4) Add the composite phase change material prepared in step (3) and the polymer binder into an agate mortar in a mass ratio of 10:1 to 5:1, mix thoroughly, and press to form a phase change composite film.

5. The method for preparing a photothermal synergistic phase change composite film based on a gradient carbon-based heterostructure according to claim 4, characterized in that: The preparation method of the MOF (A, B) precursor containing two metal components in step (1) is specifically as follows: (a) dispersing a zinc-containing metal salt and an amino-containing organic ligand in a DMF solvent at a molar ratio of 1:2 to 2:1 to form a homogeneous mixed solution; (b) adding triethylamine to the homogeneous mixed solution of step (a) to adjust the pH value of the system to 7-8, and obtaining a colloidal suspension after stirring; (c) sequentially centrifuging the colloidal suspension, washing with a DMF solvent for 3 to 5 times, and washing with a methanol solvent for 3 to 5 times, and then drying the colloidal suspension at 60 to 80° C. under vacuum conditions for 12 to 24 h to obtain MOF (A) powder; (d) dispersing the MOF (A) powder and the metal salt containing catalytic properties in a DMF solvent to obtain a mixed solution, wherein the concentration of the metal salt containing catalytic properties in the mixed solution is controlled to be 25-125 mg / mL; (e) The mixed solution of step (d) is subjected to ultrasonic dispersion for 20 to 60 min, followed by reaction under stirring for 2 to 5 h, the reaction product is separated by centrifugation, and dried under vacuum at 60 to 80 °C for 12 to 24 h to finally obtain a MOF (A, B) precursor containing two metal components.

6. The method for preparing a photothermal synergistic phase change composite film based on a gradient carbon-based heterostructure according to claim 5, characterized in that: The zinc-containing metal salt includes: one or more of zinc nitrate, zinc sulfate, zinc acetate, and zinc chloride; the amino-containing organic ligand includes: one or more of 2-aminoterephthalic acid, 3-amino-1,2,4-triazole, and 2-aminobiphenyl-4,4'-dicarboxylic acid; the metal salt with catalytic properties includes: one or more of nickel nitrate, nickel sulfate, nickel acetate, nickel chloride, cobalt nitrate, cobalt chloride, cobalt sulfate, cobalt acetate, ferric nitrate, ferric chloride, ferric sulfate, and ferric acetate.

7. The method for preparing a photothermal synergistic phase change composite film based on a gradient carbon-based heterostructure according to claim 4, characterized in that: The preparation method of the gradient heterostructure metal-coupled highly graphitized carbon hybrid carrier in step (2) is specifically as follows: (a) The MOF (A, B) precursor containing two metal components is placed under inert atmosphere protection, the temperature is programmed to 900-1200 °C at a heating rate of 1-5 °C / min, and carbonized at this temperature for 2-6 h; (b) immersing the carbonized product of step (a) in a 6-12 M hydrochloric acid solution and chemically etching at room temperature for 6-24 h to remove free metal nanoparticles not coated by the carbon layer; (c) repeatedly washing the product after etching in step (b) with deionized water until the filtrate is neutral, so as to completely remove the residual acid and metal ions to obtain a purified product; (d) The purified product of step (c) is dried under vacuum conditions at 60 to 80° C. for 12 to 24 h to obtain a gradient heterostructure metal-coupled highly graphitized carbon hybrid support.

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