Azobenzene-based photothermal energy storage molecule, method for preparing the same and use thereof

Abstract

Provided is an azobenzene-based photothermal energy storage molecule represented by Formula I which contains two types of azobenzene unit: two biscarboxyl azobenzene units and one monoamino azobenzene unit. By utilizing the energy difference between the two configurations of the azobenzene units, energy is stored during the transition from trans to cis, and in reverse, energy is released. The carboxyl and amino groups on different azobenzene units can form strong intermolecular and intramolecular hydrogen bonds, which leads to a great improvement in energy density and reversion half-life compared with the traditional azobenzene materials in which a single type of an azobenzene unit is grafted. Moreover, the release of thermal energy can be controlled by light and heating, which is beneficial to fully utilize the solar energy for photothermal energy conversion and storage, and used as a solar thermal fuel to the field of heating technology and new generation of light-driven spacecrafts. ##STR00001##

Claims

1. An azobenzene-based photothermal energy storage molecule having a structure represented by Formula I: ##STR00007##

2. A method for preparing the azobenzene-based photothermal energy storage molecule according to claim 1, comprising: subjecting trimethyl 1,3,5-benzenetricarboxylate to a hydrolysis reaction to obtain an intermediate represented by Formula II; activating the intermediate represented by Formula II with oxalyl chloride, and then reacting with Disperse Orange 3 to obtain an intermediate represented by Formula III; subjecting the intermediate represented by Formula III to a hydrolysis reaction to obtain an intermediate represented by Formula IV; activating the intermediate represented by Formula IV with oxalyl chloride, and then reacting with biscarboxyl azobenzene to obtain an intermediate represented by Formula V; and reacting the intermediate represented by Formula V with Na.sub.2S to obtain the azobenzene-based photothermal energy storage molecule represented by Formula I; ##STR00008## ##STR00009##

3. The method according to claim 2, wherein the subjecting trimethyl 1,3,5-benzenetricarboxylate to a hydrolysis reaction is: subjecting trimethyl 1,3,5-benzenetricarboxylate to a hydrolysis reaction under an alkaline condition, followed by acidification.

4. The method according to claim 3, wherein the alkaline condition is provided by an alkaline compound, and the molar ratio of the alkaline compound to trimethyl 1,3,5-benzenetricarboxylate is (11.2): 1.

5. The method according to claim 2, wherein the subjecting the intermediate represented by Formula III to a hydrolysis reaction is: subjecting the intermediate represented by Formula III to a hydrolysis reaction under an alkaline condition, followed by acidification.

6. The method according to claim 5, wherein the alkaline condition is provided by an alkaline compound, and the molar ratio of the alkaline compound to the intermediate represented by Formula III is (22.4): 1.

7. A method of using the azobenzene-based photothermal energy storage molecule according to claim 1 as a solar thermal fuel, comprising applying the azobenzene-based photothermal energy storage molecule to the solar thermal fuel.

8. The method according to claim 7, wherein the solar thermal fuel is used in the field of heating technology and light-driven spacecrafts.

9. A method of using the azobenzene-based photothermal energy storage molecule produced by the method according to claim 2 as a solar thermal fuel, comprising applying the azobenzene-based photothermal energy storage molecule to the solar thermal fuel.

10. The method according to claim 9, wherein the solar thermal fuel is used in the field of heating technology and light-driven spacecrafts.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a diagram showing reversion of isomerization by ultraviolet absorption spectroscopy for an azobenzene-based photothermal energy storage material after light irradiation at 500600 nm;

(2) FIG. 2 is a DSC diagram of an azobenzene-based photothermal energy storage material;

(3) FIG. 3 is an infrared spectrum of the azobenzene-based photothermal energy storage material prepared in Example 1.

DETAILED DESCRIPTION OF EMBODIMENTS

(4) Hereinafter, the azobenzene-based photothermal energy storage molecule and preparation method and use thereof of aspects of the present invention will be described in detail in combination with examples in order to further illustrate aspects of the present invention.

Example 1

(5) Synthesis of Product 1

(6) 3.7515 g of trimethyl 1,3,5-benzenetricarboxylate and 0.5798 g of NaOH were dissolved in 110 ml of methanol, and slowly warmed to a reflux temperature with stirring for 12 hours, and then the solvent was removed by rotary evaporation. The product was dissolved with dichloromethane and then extracted with a saturated sodium bicarbonate solution. The extracted aqueous phase was washed twice with dichloromethane and then adjusted to pH=1 with HCl, and a precipitate was produced. The precipitate was washed with water until neutral and the product was dried in a vacuum oven to obtain product 1.

(7) 2.856 g of product 1 was dissolved in 100 ml of acetonitrile, and 1.78 ml of oxalyl chloride (1.2 equivalents) and 50 L of DMF were added thereto under nitrogen protection, to perform a reaction at normal temperature for 4 hours. 4.18 ml of triethylamine and 2.9 g of Disperse Orange 3 were then added to the system, which was reacted in an ice bath for 10 hours. The product was poured into water to generate a precipitate. The precipitate was washed successively with dilute hydrochloric acid, aqueous phase sodium bicarbonate and water, respectively. The obtained precipitate was dried in a vacuum oven at 60 C. to obtain product 2.

(8) 22 mmol of product 2 was dissolved in a mixed solution of 150 ml of THF and 50 ml of water. 2.4 equivalents of NaOH was dissolved in 40 ml of water, and the resulting solution was added dropwise to the above mixed solution, to perform a reaction at reflux for 10 hours. THF in the solution was removed by rotary evaporation, and the residue was dissolved in water. The resultant was adjusted to pH=2 with hydrochloric acid, and a precipitate was generated. The precipitate was washed with water until neutral and dried in a vacuum oven at 60 C. to obtain product 3.

(9) 3.9 g (9 mmol) of product 3 was dissolved in 100 ml of dichloromethane, and 1.34 ml of oxalyl chloride and 40 L of DMF were added thereto under nitrogen protection, to perform a reaction at normal temperature for 4 hours. Then, 4.18 ml of triethylamine (30 mmol) and 5.13 g of biscarboxyl azobenzene were added to the system, which was reacted in an ice bath for 40 hours. The solvent was removed from the product by rotary evaporation, and then the product was washed three times with dichloromethane/diethyl ether (volume ratio 1:1) to obtain a crude product. The crude product was dissolved in a large amount of distilled water, and adjusted to pH=2 in an ice bath to generate a precipitate. The precipitate was dried in a vacuum oven at 60 C. to obtain product 4.

(10) The product 4 (4.76 g, 5 mmol) was dissolved in a mixed solution of 100 ml of water and 30 ml of DMF. NaS.9H.sub.2O (2.4 g, 10 mmol) was then dissolved in 100 ml of water, and added dropwise to the above system and refluxed for 36 hours. When the reaction was completed, the solvent was removed by rotary evaporation. The precipitate was re-dissolved in a large amount of water and adjusted to pH=8 with an ammonium salt, and the aqueous phase was extracted with dichloromethane. The dichloromethane was spin-dried, and the obtained solid was maintained in a vacuum oven until constant weight to obtain a three-branched azobenzene. Yield: 65%, purity: 98%.

(11) The three-branched azobenzene was detected to have an energy density of 63 Wh/kg.

(12) The prepared azobenzene-based photothermal energy storage material was irradiated with light at 500600 nm, and the diagram of reversion of isomerization by ultraviolet absorption spectroscopy thereof is shown in FIG. 1, in which curve a is a curve of light irradiation for 10 min, curve b is a curve of light irradiation for 5 min, and curve c is a curve of light irradiation for 1 min.

(13) As can be seen from FIG. 1, the cis three-branched azobenzene material undergoes a change in ultraviolet absorption due to reversion of isomerization from cis to trans over time under the irradiation of light at a wavelength of 500600 nm. It can be seen that as the light irradiation time increases, the trans characteristic absorption peak is significantly enhanced, representing the reversion of isomerization from cis to trans.

(14) The curves from c to a are of structure reversion after 1 min to 10 min, and the trend of change is that the trans characteristic absorption peak is significantly enhanced, representing the reversion from cis to trans, which indicates that the above cis three-branched azobenzene material has a short half-life of 10 min.

(15) The three-branched azobenzene was detected for its exotherm using differential scanning calorimetry, and the DSC diagram is shown in FIG. 2.

(16) The exothermic curves of the three-branched azobenzene by a differential scanning calorimeter (DSC) can be seen from FIG. 2, in which a distinct exothermic peak is observed in B which is the first heating curve, while no exothermic peak is observed in both D which is the first cooling curve and F which is the second heating curve.

(17) The three-branched azobenzene was detected for its structure using infrared spectroscopy, and the results are shown in FIG. 3.

Example 2

(18) Synthesis of Product 1

(19) 3.9231 g of trimethyl 1,3,5-benzenetricarboxylate and 0.6453 g of NaOH were dissolved in 110 ml of methanol, and slowly warmed to a reflux temperature with stirring for 13 hours, and then the solvent was removed by rotary evaporation. The product was dissolved with dichloromethane and then extracted with a saturated sodium bicarbonate solution. The extracted aqueous phase was washed twice with dichloromethane and then adjusted to pH=1.2 with HCl, and a precipitate was produced. The precipitate was washed with water until neutral and the product was dried in a vacuum oven to obtain product 1.

(20) 2.648 g of product 1 was dissolved in 90 ml of acetonitrile, and 1.62 ml of oxalyl chloride (1.2 equivalents) and 42 L of DMF were added thereto under nitrogen protection, to perform a reaction at normal temperature for 3.4 hours. 3.85 ml of triethylamine and 2.8 g of Disperse Orange 3 were then added to the system, which was reacted in an ice bath for 10 hours. The product was poured into water to generate a precipitate. The precipitate was washed successively with dilute hydrochloric acid, aqueous phase sodium bicarbonate and water, respectively. The obtained precipitate was dried in a vacuum oven at 60 C. to obtain product 2.

(21) 21 mmol of product 2 was dissolved in a mixed solution of 135 ml of THF and 45 ml of water. 2.4 equivalents of NaOH was dissolved in 38 ml of water, and the resulting solution was added dropwise to the above mixed solution, to perform a reaction at reflux for 9 hours. THF in the solution was removed by rotary evaporation, and the residue was dissolved in water. The resultant was adjusted to pH=1.8 with hydrochloric acid, and a precipitate was generated. The precipitate was washed with water until neutral and dried in a vacuum oven at 60 C. to obtain product 3.

(22) 3.8 g of product 3 was dissolved in 90 ml of dichloromethane, and 1.25 ml of oxalyl chloride and 38 L of DMF were added thereto under nitrogen protection, to perform a reaction at normal temperature for 3.8 hours. Then, 4.18 ml of triethylamine (30 mmol) and 5.13 g of biscarboxyl azobenzene were added to the system, which was reacted in an ice bath for 40 hours. The solvent was removed from the product by rotary evaporation, and then the product was washed three times with dichloromethane/diethyl ether (volume ratio 1:1) to obtain a crude product. The crude product was dissolved in a large amount of distilled water, and adjusted to pH=1.8 in an ice bath to generate a precipitate. The precipitate was dried in a vacuum oven at 60 C. to obtain product 4.

(23) 4.55 g of product 4 was dissolved in a mixed solution of 90 ml of water and 25 ml of DMF. 2.5 g of NaS.9H.sub.2O was then dissolved in 90 ml of water, and added dropwise to the above system and refluxed for 33 hours. When the reaction was completed, the solvent was removed by rotary evaporation. The precipitate was re-dissolved in a large amount of water and adjusted to pH=8.2 with an ammonium salt, and the aqueous phase was extracted with dichloromethane. The dichloromethane was spin-dried, and the obtained solid was maintained in a vacuum oven until constant weight to obtain a three-branched azobenzene. Yield: 57%, purity: 86%.

(24) The three-branched azobenzene was detected to have an energy density of 52 Wh/kg.

Example 3

(25) Synthesis of Product 1

(26) 3.7768 g of trimethyl 1,3,5-benzenetricarboxylate and 0.7439 g of NaOH were dissolved in 110 ml of methanol, and slowly warmed to a reflux temperature with stirring for 11 hours, and then the solvent was removed by rotary evaporation. The product was dissolved with dichloromethane and then extracted with a saturated sodium bicarbonate solution. The extracted aqueous phase was washed twice with dichloromethane and then adjusted to pH=1.3 with HCl, and a precipitate was produced. The precipitate was washed with water until neutral and the product was dried in a vacuum oven to obtain product 1.

(27) 2.976 g of product 1 was dissolved in 96 ml of acetonitrile, and 1.78 ml of oxalyl chloride (1.2 equivalents) and 49 L of DMF were added thereto under nitrogen protection, to perform a reaction at normal temperature for 4.5 hours. 4.15 ml of triethylamine and 2.86 g of Disperse Orange 3 were then added to the system, which was reacted in an ice bath for 10 hours. The product was poured into water to generate a precipitate. The precipitate was washed successively with dilute hydrochloric acid, aqueous phase sodium bicarbonate and water, respectively. The obtained precipitate was dried in a vacuum oven at 60 C. to obtain product 2.

(28) 23 mmol of product 2 was dissolved in a mixed solution of 144 ml of THF and 46 ml of water. 2.4 equivalents of NaOH was dissolved in 43 ml of water, and the resulting solution was added dropwise to the above mixed solution, to perform a reaction at reflux for 8.8 hours. THF in the solution was removed by rotary evaporation, and the residue was dissolved in water. The resultant was adjusted to pH=2.1 with hydrochloric acid, and a precipitate was generated. The precipitate was washed with water until neutral and dried in a vacuum oven at 60 C. to obtain product 3.

(29) 3.93 g of product 3 was dissolved in 113 ml of dichloromethane, and 1.33 ml of oxalyl chloride and 39 L of DMF were added thereto under nitrogen protection, to perform a reaction at normal temperature for 3.9 hours. Then, 4.18 ml of triethylamine (30 mmol) and 5.13 g of biscarboxyl azobenzene were added to the system, which was reacted in an ice bath for 40 hours. The solvent was removed from the product by rotary evaporation, and then the product was washed three times with dichloromethane/diethyl ether (volume ratio 1:1) to obtain a crude product. The crude product was dissolved in a large amount of distilled water, and adjusted to pH=1.9 in an ice bath to generate a precipitate. The precipitate was dried in a vacuum oven at 60 C. to obtain product 4.

(30) 4.67 g of product 4 was dissolved in a mixed solution of 94 ml of water and 26 ml of DMF. 2.3 g of NaS.9H.sub.2O was then dissolved in 90 ml of water, and added dropwise to the above system and refluxed for 35 hours. When the reaction was completed, the solvent was removed by rotary evaporation. The precipitate was re-dissolved in a large amount of water and adjusted to pH=8.1 with an ammonium salt, and the aqueous phase was extracted with dichloromethane. The dichloromethane was spin-dried, and the obtained solid was maintained in a vacuum oven until constant weight to obtain a three-branched azobenzene. Yield: 72%, purity: 93%.

(31) The three-branched azobenzene was detected to have an energy density of 48 Wh/kg.

(32) As can be seen from the above examples, the azobenzene-based photothermal energy storage molecule prepared by an aspect of the present invention has a high energy density and a short half-life.

(33) The foregoing description of the examples is provided merely to help understanding the method of an aspect of the present invention and the core idea thereof. It should be pointed out that those skilled in the art can also make several improvements and modifications without departing from the principle of aspects of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the aspects of the present invention.