CN112552206B - Azophenyl derivative, solar thermal energy fuel film composite material, and preparation method and application thereof - Google Patents

Abstract

The invention relates to an azobenzene derivative, a solar thermal energy fuel film composite material, a preparation method and application thereof, discloses a series of azobenzene derivatives, provides a method for preparing a photoinduced phase change type ready-to-use solar thermal energy fuel film through the azobenzene derivatives, and the prepared solar thermal energy fuel film composite material has good mechanical flexibility, photoinduced isomerism effect and energy storage capacity. The composite film can rapidly generate cis-trans isomerization to store energy under the irradiation of an ultraviolet lamp, the stored energy is gradually increased along with the extension of irradiation time, the full-filling state can be achieved within about 2 hours, the energy density can be more than 200J/g, and the self temperature can be continuously increased by about 5 ℃. The energy charging/discharging process has very good reversibility, and no obvious attenuation exists when the energy charging/discharging is carried out for more than 5 times in a circulating manner. The composite material has the advantages of simple preparation process, environmental friendliness, easiness in preparation, large heat release, good mechanical flexibility, strong acid-base corrosion resistance, good recycling performance and the like.

Description

A kind of azophenyl derivative, solar thermal fuel film composite material and its preparation method and use

technical field

The invention belongs to the field of clean energy and renewable energy, and mainly relates to the design and synthesis of photoresponsive materials, a method for processing and molding solar thermal fuel film composite materials, and applications for photothermal energy storage and solar energy utilization.

Background technique

In recent years, the world is facing an energy crisis, and the extensive use of fossil fuels has also caused environmental pollution. The search for new renewable clean energy has become the focus of people. Since the beginning of the 21st century, with the continuous development of solar resource utilization and people's strong demand for clean energy, light-responsive solar thermal fuels have become the focus of research in the field of clean energy. Solar thermal fuel, as a new type of energy storage device, converts solar energy into chemical energy stored in the form of molecular isomers such as cis/trans azobenzene, and releases it in the form of thermal energy under various stimuli, thereby Provides a closed loop and renewable energy storage strategy. Its energy storage has the advantages of being recyclable, pollution-free, and zero-emission, so it has been widely studied.

The solar thermal fuels that have been studied before are generally as follows: (1) spin-coated thin film, this material has the advantages of high cost performance, energy saving, and low pollution, but the disadvantage of spin-coated thin film is that it cannot be prepared in a large area; (2) Electrochemical deposition film formation can accurately control the thickness of the deposited layer and the speed of film formation, and is easy to operate, but the film made by this method is difficult to peel off, which hinders its practicability; (3) carbon nanotube composite materials, the The material is a combination of photoresponsive molecules and carbon nanotubes, which can effectively increase its potential energy density, but it needs an organic solvent to assist charging, which will undoubtedly pollute the environment, and the cost of carbon nanotube materials is expensive, so its development is also subject to certain restrictions.

Azobenzene-based photoresponsive materials have been widely studied in recent years due to their excellent photo-induced cis-trans isomerism properties, and have been widely used in optical information storage, solar thermal fuels, molecular cages, photochromism, nanoimprinting and molecular robots, etc. field. This kind of material converts from trans conformation (stable state) to cis conformation (metastable state) under ultraviolet light irradiation, with fast response and high efficiency, and can change from cis conformation to trans conformation under heat or visible light stimulation. Conformational conversion, and this cis-trans isomerization process has very good reversibility. During this process, the trans conformation in the low-energy state will absorb energy and transform into a cis conformation, and convert the energy into chemical energy and store it in the chemical bond, thereby completing the charging process and realizing the conversion of light energy into molecular internal energy; Under the induction of visible light, it reversibly returns to the trans conformation to release heat, thereby completing the energy release process, and finally completes the purpose of converting light energy into heat energy, that is, solar thermal fuel.

In the prior art, it is reported that most of the azobenzene photoresponsive materials are solid state, such as the azobenzene material containing graphene structure and corrole, which is inconvenient to use. CN111004146A discloses a liquid azobenzene "Molecular solar thermal fuel" 4-bromobutoxy-2',6'-diethylazobenzene has a melting point of -18.73°C and is liquid at room temperature. It can be used as a solvent-free solar thermal energy storage material and is easy to use , but when the product isomerization rate is 88%, the energy storage capacity is 96.65J/g, the complete energy storage capacity of the product is 42.8KJ/mol, the energy storage capacity is not high, and the energy storage life is short.

In view of this, it is particularly necessary to invent a solar thermal fuel with fast charging speed and high energy storage density.

Contents of the invention

The purpose of the present invention is to overcome the defects in the prior art, to provide an azobenzene derivative with fast charging speed and high energy storage density, and at the same time provide its preparation method and combined processing with flexible fabrics to prepare solar thermal fuel film composite Materials, methods, and uses.

For realizing above-mentioned purpose, the technical scheme that the present invention takes is:

Technical topic one

The present invention provides an azobenzene derivative, which has a liquid state in the cis conformation and a solid state in the trans conformation at room temperature, and has a structure shown in formula I:

Wherein, R is selected from isopentyl, 2-methylbutyl, pent-2-yl, but-3-en-1-yl, but-2-en-1-yl, neopentyl, 1-butene- 1-yl or 2-methylprop-1-en-1-yl.

As some preferred embodiments of the present invention, selected from the following structural compounds:

1-(4-(isoamyloxy)phenyl)-2-(p-tolyl)diazene

1-(4-(2-Methylbutoxy)phenyl)-2-(p-tolyl)diazene

1-(4-(pent-2-yloxy)phenyl)-2-(p-tolyl)diazene

1-(4-(but-3-en-1-yloxy)phenyl)-2-(p-tolyl)diazene

1-(4-((but-2-en-1-yl)oxy)phenyl)-2-(p-tolyl)diazene

1-(4-(Nivalyloxy)phenyl)-2-(p-tolyl)diazene

1-(4-((1-buten-1-yl)oxy)phenyl)-2-(p-tolyl)diazene

1-(4-((2-methylprop-1-en-1-yl)oxy)phenyl)-2-(p-tolyl)diazene.

Technical Topic II

The present invention also provides a preparation method of the above-mentioned azobenzene derivatives, which comprises the following steps:

(1) Add p-methylaniline and concentrated hydrochloric acid into the flask for mixing, add distilled water, and drop _NaNO solution at 0-5°C, and continue stirring to obtain a diazonium salt solution of p-methylaniline;

(2) Dissolve phenol, Na ₂ CO ₃ and sodium hydroxide in water, add dropwise to the diazonium salt solution of p-methylaniline obtained in step (1), continue stirring at room temperature, after the reaction is completed, wash with hydrochloric acid After adjusting the pH to 7, the precipitated product was filtered, washed with water, dried in vacuum at room temperature, and purified by chromatography column to obtain p-hydroxymethylazobenzene;

(3) p-Hydroxymethylazobenzene and R-Br are reacted by heating in a solvent in the presence of sodium hydroxide, and after the reaction is completed, the product is purified by a chromatographic column.

As some preferred embodiments of the present invention, the concentration of concentrated hydrochloric acid in the step (1) is 37%, and the ratio of p-methylaniline and concentrated hydrochloric acid is 1mmol: (0.20-0.50mL), p-methylaniline and NaNO ₂ The molar ratio is 1:(1.0-1.5).

As some preferred embodiments of the present invention, the ratio of phenol, Na ₂ CO ₃ and sodium hydroxide in the step (2) is 1:(1.0-1.5):(0.8-1.3).

As some preferred embodiments of the present invention, the operation of chromatographic column purification in the step (2) is: first use sherwood oil: dichloromethane=1: (1-5) to elute impurities, and then wash with dichloromethane Product removal and rotary steaming can give p-hydroxymethylazobenzene.

As some preferred embodiments of the present invention, the molar ratio of p-hydroxymethylazobenzene, R-Br and sodium hydroxide in the step (3) is 1:(1-5):(1-3).

As some preferred embodiments of the present invention, the solvent of the step (3) is anhydrous ethanol: water is a mixture of (5-30): 1 (V/V), and the heating temperature is (50-90) ° C, The eluent of chromatographic purification is dichloromethane:petroleum ether 1:(2-5).

Technical Topic Three

The present invention also provides an azophenyl solar thermal fuel film composite material, which is composed of the compound in the technical subject 1 and a flexible fabric.

As some preferred embodiments of the present invention, it is prepared by the following method: the azo-based solar thermal energy fuel compound in the solid state is evenly spread on the flexible fabric, and in a dark and closed environment, it is irradiated with an ultraviolet lamp, and the The above-mentioned azo-based solar thermal fuel compound is transformed into a liquid state and impregnated into the fabric to obtain a flexible film composite material.

The fabric described in the present invention is a flat and soft sheet object formed by crossing, knotting, and connecting small and long objects. Including but not limited to: cotton fabric, commercially referred to as "cotton cloth", which is a fabric woven from cotton yarn or cotton and chemical fiber blended yarn; wool fabric, commercially referred to as "wool", which is made of animal hair Fabrics made of wool-type chemical fibers; silk-type fabrics, commercially referred to as "silk", fabrics made of mulberry silk as raw materials are called real silk, and fabrics made of tussah silk as raw materials are called tussah silk; hemp-type Fabrics mainly include ramie fabrics and linen fabrics; purified fiber fabrics mainly include medium and long fiber imitation cotton, linen, wool, silk, chemical fiber filament fabrics, artificial deerskin and artificial fur; nylon; carbon cloth, etc.

Technical Topic Four

The last aspect of the present invention provides a use of the azophenyl solar thermal fuel film composite material as a solar thermal energy storage material.

The beneficial effects produced by adopting the above-mentioned technical scheme are:

The azobenzene derivatives provided by the present invention are liquid in the cis conformation and solid in the trans conformation at room temperature, and can increase the energy storage density of the azobenzene molecule in combination with the internal energy of the molecule and the latent heat of phase change.

The solar thermal fuel film composite material provided by the present invention is processed by combining the azobenzene derivatives with the characteristics of phase change through ultraviolet irradiation and flexible fabrics, because the cis conformation of the azobenzene derivatives used is in a liquid state , provides more free volume for further photoisomerization, forms a harmonious positive feedback, and greatly reduces the charging time, because the surface of the flexible fabric used is flat, dense, porous, good mechanical flexibility, and strong corrosion resistance , has strong absorption, is closely combined with the immersed azobenzene derivatives, and has strong solar heat storage characteristics. The processing and production can be completed by ultraviolet light irradiation, which saves the cumbersome operation and cost in the process of heating at high temperature to make it into a molten state.

The solar thermal fuel thin film composite material provided by the present invention has the characteristics of flat and dense surface, environment-friendly, abundant sources, simple operation, fast response speed, good mechanical flexibility, and strong reversibility. It has been verified that the highest energy density can reach 200J/ More than g, it is very suitable for the preparation of new clean energy and solar thermal fuel.

Description of drawings

In order to more clearly illustrate the specific implementation of the present invention or the technical solutions in the prior art, the following will briefly introduce the accompanying drawings that need to be used in the specific implementation or description of the prior art. Obviously, the accompanying drawings in the following description The drawings show some implementations of the present invention, and those skilled in the art can obtain other drawings based on these drawings without creative work.

Fig. 1 is the nuclear magnetic spectrum of the azobenzene derivative that the embodiment of the present invention 2 obtains;

Fig. 2 is the nuclear magnetic spectrum of the azobenzene derivative obtained in Example 5 of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the invention will be clearly and completely described below in conjunction with specific embodiments.

The preparation of embodiment 1 p-hydroxymethyl azobenzene

Mix p-methylaniline (10mmol, 1equiv) and high-concentration hydrochloric acid (37%, 2.5mL) in a 100mL round bottom flask, then add distilled water (10mL), put the round bottom flask into ice water and stir. Weigh NaNO ₂ (690mg, 10mmol, 1equiv) into a 50mL beaker, add 1.5mL of distilled water to dissolve it, then slowly inject the solution into the above round bottom flask, and stir for 4h. Then weigh phenol (940mg, 10mmol, 1equiv), Na ₂ CO ₃ (1.092mg, 10.3mmol, 1.03equiv) and sodium hydroxide (400mg, 10mmol, 1equiv) in a 50mL beaker, add 10mL of distilled water to dissolve it, and then Add drop by drop to the round bottom flask and stir for an additional 4 hours at room temperature. After adjusting the pH to 7 with hydrochloric acid, the precipitated product was filtered off, washed with water (3×20 mL), and dried under vacuum at room temperature for 24 hours. Then put the dried solid into the chromatographic column, first use petroleum ether: dichloromethane = 1: 1 to pass through the first impurity point, then use dichloromethane to pass through the product point, and rotary steam to obtain p-hydroxyformaldehyde Azobenzene, yield 61.3%, MS (m/z) 212.1.

Example 2 Preparation of 1-(4-(isoamyloxy)phenyl)-2-(p-tolyl)diazene (C ₁₈ H ₂₂ N ₂ O)

Weigh p-hydroxymethylazobenzene (1060mg, 5mmol, 1equiv), 1-bromo-3-methylbutane (2266mg, 15mmol, 3equiv) and sodium hydroxide (400mg, 10mmol, 2equiv) in a 100mL round bottom flask , and then add 45mL of absolute ethanol and 5mL of distilled water to it, then put the round bottom flask into an oil bath and heat it to 70°C, circulate the condensed water, and stir for 24h. Then add an appropriate amount of silica gel and rotary steam to form a solid, put it into a chromatography column, use dichloromethane:petroleum ether=1:3 to pass through the product point, and rotary steam to obtain 1-(4-(isoamyloxy)phenyl) -2-(p-Tolyl)diazene, yield 71%, MS (m/z) 282.1. ¹ H NMR(500MHz, CDCl ₃ ,δ):7.91-7.87(d,2H,Ar-H),7.81-7.77(d,2H,Ar-H),7.32-7.28(d,2H,Ar-H) ,7.02-6.98(d,2H,Ar-H),4.09-4.05(t,2H,O-CH ₂ ),2.44-2.41(s,3H,-CH ₃ ),1.91-1.79(m,1H,- CH), 1.75-1.69 (q, 2H, -CH ₂ ), 1.01-0.97 (d, 6H, -CH ₃ ).

Example 3 Preparation of 1-(4-(2-methylbutoxy)phenyl)-2-(p-tolyl)diazene (C ₁₈ H ₂₂ N ₂ O)

Weigh p-hydroxymethylazobenzene (1060mg, 5mmol, 1equiv), 1-bromo-2-methylbutane (2266mg, 15mmol, 3equiv) and sodium hydroxide (400mg, 10mmol, 2equiv) in a 100mL round bottom flask Add 45mL of absolute ethanol and 5mL of distilled water to it, then put the round bottom flask into an oil bath and heat it to 70°C, circulate the condensed water, and stir for 24h. Then add an appropriate amount of silica gel and rotary steam to form a solid, put it into a chromatography column, pass through the product point, and rotary steam to obtain 1-(4-(2-methylbutoxy)phenyl)-2-(p-tolyl) Diazene, yield 63%, MS (m/z) 282.1.

Example 4 Preparation of 1-(4-(pent-2-yloxy)phenyl)-2-(p-tolyl)diazene (C ₁₈ H ₂₂ N ₂ O)

Weigh p-hydroxymethylazobenzene (1060mg, 5mmol, 1equiv), 2-bromopentane (2266mg, 15mmol, 3equiv) and sodium hydroxide (400mg, 10mmol, 2equiv) in a 100mL round bottom flask, and add to it Add 45mL of absolute ethanol and 5mL of distilled water, then put the round bottom flask into an oil bath and heat to 70°C, circulate the condensed water, and stir for 24h. Then add an appropriate amount of silica gel and rotary steam to form a solid, put it into a chromatography column, pass through the product point, and rotary steam to obtain 1-(4-(pent-2-yloxy)phenyl)-2-(p-tolyl) Diazene, yield 71%, MS (m/z) 282.1.

Example 5 Preparation of 1-(4-(but-3-en-1-yloxy)phenyl)-2-(p-tolyl)diazene (C ₁₇ H ₁₈ N ₂ O)

Weigh p-hydroxymethylazobenzene (1060mg, 5mmol, 1equiv), 4-bromobut-1-ene (2025mg, 15mmol, 3equiv) and sodium hydroxide (400mg, 10mmol, 2equiv) in a 100mL round bottom flask, Add 45mL of absolute ethanol and 5mL of distilled water to it, then put the round bottom flask into an oil bath and heat to 70°C, circulate the condensed water, and stir for 24h. Then add an appropriate amount of silica gel and rotary steam to form a solid, load it into a chromatographic column, pass through the product point, and rotary steam to obtain 1-(4-(but-3-en-1-yloxy)phenyl)-2-( p-Tolyl)diazene, yield 72%, MS (m/z) 266.1. ¹ H NMR(500MHz, CDCl3,δ):7.92-7.88(d,2H,Ar-H),7.81-7.77(d,2H,Ar-H),7.32-7.28(d,2H,Ar-H), 7.03-6.99 (d, 2H, Ar-H), 5.98-5.88 (m, 1H, =CH), 5.23-5.18 (d, 1H, =CH), 5.16-5.12 (d, 1H, =CH), 4.12 -4.08(t,2H,O-CH ₂ ),2.62-2.56(q,2H,-CH ₂ ),2.45-2.42(s,3H,-CH ₃ ).

Example 6 Preparation of 1-(4-((but-2-en-1-yl)oxy)phenyl)-2-(p-tolyl)diazene (C ₁₇ H ₁₈ N ₂ O)

Weigh p-hydroxymethylazobenzene (1060mg, 5mmol, 1equiv), 1-bromobut-2-ene (2025mg, 15mmol, 3equiv) and sodium hydroxide (400mg, 10mmol, 2equiv) in a 100mL round bottom flask, Add 45mL of absolute ethanol and 5mL of distilled water to it, then put the round bottom flask into an oil bath and heat it to 70°C, circulate the condensed water, and stir for 24h. Then add an appropriate amount of silica gel and spin evaporate to a solid, put it into a chromatography column, pass through the product point, and spin steam to obtain 1-(4-((but-2-en-1-yl)oxy)phenyl)-2 -(p-Tolyl)diazene, yield 68%, MS (m/z) 266.1.

Example 7 Preparation of 1-(4-(neopentyloxy)phenyl)-2-(p-tolyl)diazene (C ₁₈ H ₂₂ N ₂ O)

Weigh p-hydroxymethylazobenzene (1060mg, 5mmol, 1equiv), 1-bromo-2,2-dimethylpropane (2266mg, 15mmol, 3equiv) and sodium hydroxide (400mg, 10mmol, 2equiv) in a 100mL circle Add 45mL of absolute ethanol and 5mL of distilled water to the bottom flask, then put the round bottom flask into an oil bath and heat to 70°C, circulate the condensed water, and stir for 24h. Then add an appropriate amount of silica gel and rotary steam to form a solid, put it into a chromatography column, pass through the product point, and rotary steam to obtain 1-(4-(neopentyloxy)phenyl)-2-(p-tolyl)diazene , yield 70%, MS (m/z) 282.1.

Example 8 Preparation of 1-(4-((1-buten-1-yl)oxy)phenyl)-2-(p-tolyl)diazene (C ₁₇ H ₁₈ N ₂ O)

Weigh p-hydroxymethylazobenzene (1060mg, 5mmol, 1equiv), 2-bromobut-2-ene (2025mg, 15mmol, 3equiv) and sodium hydroxide (400mg, 10mmol, 2equiv) in a 100mL round bottom flask, Add 45mL of absolute ethanol and 5mL of distilled water to it, then put the round bottom flask into an oil bath and heat it to 70°C, circulate the condensed water, and stir for 24h. Then add an appropriate amount of silica gel and rotary steam to form a solid, put it into a chromatography column, pass through the product point, and rotary steam to obtain 1-(4-((1-buten-1-yl)oxy)phenyl)-2- (p-Tolyl)diazene, yield 61%, MS (m/z) 266.1.

Example 9 1-(4-((2-methylprop-1-en-1-yl)oxy)phenyl)-2-(p-tolyl)diazene (C ₁₇ H ₁₈ N ₂ O) preparation of

Weigh p-hydroxymethylazobenzene (1060mg, 5mmol, 1equiv), 2-bromobut-2-ene (2025mg, 15mmol, 3equiv) and sodium hydroxide (400mg, 10mmol, 2equiv) in a 100mL round bottom flask, Add 45mL of absolute ethanol and 5mL of distilled water to it, then put the round bottom flask into an oil bath and heat it to 70°C, circulate the condensed water, and stir for 24h. Then add an appropriate amount of silica gel and spin evaporate to a solid, put it into a chromatography column, pass through the product point, and spin steam to obtain 1-(4-((2-methylprop-1-en-1-yl)oxy)benzene Base)-2-(p-tolyl)diazene, yield 69%, MS (m/z) 266.1.

The preparation of embodiment 10 solar thermal energy fuel film composite material

Use scissors to cut a piece of square fabric (cotton cloth, thickness about 1 μm) with a side length of 3 cm, put it into a glass disc, weigh 50 mg of photoresponsive azobenzene derivatives, and spread it evenly on the square fabric . Then place the glass disc in a dark and closed environment, fix the ultraviolet lamp on the iron stand, and irradiate the square fabric for two hours to obtain a flexible composite solar thermal fuel film.

Experimental example

The amyloxymethyl azobenzene that embodiment 2 is obtained utilizes the method for embodiment 10 to prepare solar thermal energy fuel film composite material, and the amyloxymethyl azobenzene that embodiment 2 obtains carries out energy density measurement respectively, The experimental results show that the energy density of isopentyloxymethyl azobenzene is 181.63J/g, while the energy density of solar thermal fuel film is 200J/g. It shows that the combination with flexible fabric increases the energy storage capacity.

When the solar thermal fuel thin film composite is irradiated with 355nm ultraviolet light, the energy is stored in the chemical bonds due to the photoinduced trans conformation → cis conformation conversion, and the stored energy gradually increases with the prolongation of the irradiation time , no change occurs after 2h. Afterwards, under light conditions, the energy is gradually released in the form of heat, and the energy release is complete after 48 hours. This light-responsive molecule has no obvious attenuation in the reversible change after more than 5 cycles.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still be Modifications are made to the technical solutions described in the foregoing embodiments, or equivalent replacements are made to some of the technical features; these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (9)

1. An azobenzene derivative, wherein at room temperature, the cis-conformation of the azobenzene derivative is liquid, and the trans-conformation of the azobenzene derivative is solid, and the azobenzene derivative has a structure shown in formula I:

wherein R is selected from isoamyl, 2-methylbutyl, pent-2-yl, but-3-en-1-yl, but-2-en-1-yl, neopentyl, 1-buten-1-yl or 2-methylprop-1-en-1-yl.

2. A method for preparing the azobenzene derivative according to claim 1, comprising the steps of:

(1) Adding p-methylaniline and concentrated hydrochloric acid into a flask, mixing, adding distilled water, and dropwise adding NaNO at 0~5 DEG C ₂ Continuously stirring the solution to obtain a diazonium salt solution of the p-methylaniline;

(2) Mixing phenol and Na ₂ CO ₃ And sodium hydroxide, adding water for dissolving, dropwise adding the solution into the diazonium salt solution of p-methylaniline obtained in the step (1), continuously stirring at room temperature, after the reaction is finished, regulating the pH value to 7 by using hydrochloric acid, filtering a precipitated product, washing with water, drying at room temperature in vacuum, and purifying by a chromatographic column to obtain p-hydroxymethylazobenzene;

(3) Heating p-hydroxy methyl azobenzene and R-Br in a solvent in the presence of sodium hydroxide for reaction, and purifying by a chromatographic column after the reaction is finished to obtain the product.

3. The method for producing an azobenzene derivative according to claim 2, wherein the concentration of concentrated hydrochloric acid in the step (1) is 37%, and the ratio of p-methylaniline to concentrated hydrochloric acid is 1mmol: (0.20-0.50) mL of p-methylaniline and NaNO ₂ The molar ratio of (1) to (1.0-1.5).

4. The method for producing azobenzene derivative according to claim 2, wherein said step (2) comprises reacting phenol with Na ₂ CO ₃ And sodium hydroxide is 1 (1.0-1.5) to 0.8-1.3.

5. The method for producing an azobenzene derivative according to claim 2, wherein the purification in the chromatography column in the step (2) is performed by: eluting impurities by using petroleum ether and dichloromethane =1 and (1-5), eluting a product by using dichloromethane, and performing rotary evaporation to obtain the p-hydroxy methyl azobenzene.

6. The method for producing an azobenzene derivative according to claim 2, wherein the molar ratio of p-hydroxymethylazobenzene, R-Br and sodium hydroxide in the step (3) is 1 (1-5) to (1-3).

7. The method for producing an azobenzene derivative according to claim 2, wherein the solvent in the step (3) is a mixture of absolute ethanol and water at a volume ratio of (5-30): 1, the heating temperature is (50-90) ° c, and the eluent for the chromatographic purification is dichloromethane: petroleum ether at a ratio of 1: (2-5).

8. An azobenzene-based solar thermal fuel film composite material, characterized in that it consists of the azobenzene derivative as described in claim 1 and a flexible fabric;

the solar thermal energy fuel film composite material is prepared by the following method: uniformly spreading the solid azo-based solar thermal fuel compound on a flexible fabric, placing the fabric in a dark closed environment, irradiating by using an ultraviolet lamp, and immersing the azo-based solar thermal fuel compound into the fabric when the azo-based solar thermal fuel compound is converted into a liquid state, thus obtaining the flexible composite film.

9. Use of the azo-phenyl solar thermal fuel film composite of claim 8 as a solar thermal storage material.

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