Pyrrolopyrrole organic small molecular photothermal material with high photothermal conversion efficiency and preparation method and application thereof

Abstract

The invention relates to a pyrrolopyrrole organic micromolecular photothermal material with high photothermal conversion efficiency and a preparation method and application thereof, and belongs to the field of organic micromolecular photothermal materials. The problems that an existing photo-thermal material is poor in thermal stability and low in photo-thermal conversion efficiency are solved. The preparation method comprises the following steps: mixing BrDPPBr, R-boric acid ester, potassium carbonate and a high-boiling-point solvent, heating, adding a phosphine compound, continuously heating and stirring, reacting, cooling to room temperature, adding pure water to separate out a solid, recrystallizing and purifying to obtain the pyrrolopyrrole organic small molecule photo-thermal material. The evaporator is applied to water evaporation. The invention relates to the pyrrolopyrrole organic small molecule photo-thermal material with high photo-thermal conversion efficiency and the preparation and application of the pyrrolopyrrole organic small molecule photo-thermal material.

Description

Technical Field

[0001] The invention belongs to the field of organic small molecule photothermal materials. Background Art

[0002] Although the water resources on the earth are relatively abundant, the fresh water available for direct human use is very limited. Moreover, with the continuous expansion of the industrial economy and the continuous increase in population, fresh water resources are becoming increasingly scarce due to pollution and abuse, which seriously threatens the sustainable development of social economy. Therefore, seawater desalination will be an indispensable means to alleviate the shortage of fresh water resources. To solve the above problems, a variety of traditional seawater desalination strategies have emerged in recent years, including multi-stage flash evaporation technology, vacuum distillation technology, reverse osmosis and nanofiltration. However, these methods are costly, have serious secondary pollution and huge energy consumption, which seriously hinders their large-scale commercial application. Therefore, the development of efficient, low-cost and eco-friendly freshwater production technology remains a major challenge. Among the many seawater desalination technologies, solar energy is the most promising renewable energy. Solar interfacial evaporation technology uses clean and renewable solar energy as energy input to convert solar energy into thermal energy. It has higher evaporation efficiency and heating rate, in which solar heat conversion and heating are limited to the air-water interface, which can effectively utilize the absorbed sunlight and avoid heat transfer to the surrounding environment, resulting in higher photothermal conversion efficiency. Therefore, solar interfacial evaporation technology is a promising technology for freshwater acquisition due to its high conversion efficiency, great potential for industrial application, and environmental sustainability. However, this evaporation system is a complex coupling process affected by many factors such as photothermal conversion materials, thermal management, and structural design.

[0003] Among these factors, photothermal conversion materials play a key role in the system. So far, there are three popular photothermal conversion mechanisms, including plasma local heating, electron-hole generation and relaxation, and molecular thermal vibration. At present, the most reported photothermal materials are mainly concentrated in plasma metal nanoparticles, semiconductor materials, carbon materials, and polymer materials. However, due to the poor thermal stability effect, the photothermal conversion efficiency is relatively low, and there are few reports on the use of organic dye molecules for solar interfacial seawater evaporation. Therefore, in order to obtain excellent photothermal conversion performance and study its working mechanism, it is necessary to develop a photothermal conversion system based on new organic dye molecules. Summary of the invention

[0004] The present invention aims to solve the problems of poor thermal stability and low photothermal conversion efficiency of existing photothermal materials, and further provide a pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency, and a preparation method and application thereof.

[0005] A pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency, its general chemical formula is:

[0006] The R is

[0007] A method for preparing a pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency is carried out according to the following steps:

[0008] BrDPPBr, R-boric acid ester, potassium carbonate and a high boiling point solvent are mixed, and then heated to 70°C to 90°C under a nitrogen atmosphere and stirring conditions, and then a phosphine compound is added, and heating and stirring are continued for 7h to 9h under a nitrogen atmosphere and a temperature of 70°C to 90°C, and after the reaction, the mixture is cooled to room temperature, and then pure water is added to precipitate a solid, and the solid is recrystallized and purified to obtain a pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency;

[0009] The structural formula of the BrDPPBr is The R-boric acid ester is 4-(9H-carbazole-9-yl)phenylboronic acid pinacol ester or 4-(diphenylamino)phenylboronic acid pinacol ester.

[0010] The invention discloses an application of a pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency, which is used for water evaporation.

[0011] The beneficial effects of the present invention are:

[0012] The present invention provides a pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency, and a preparation method and application thereof. First, the desired target organic small molecule-electron donor-acceptor (DA) type pyrrolopyrrole organic small molecule photothermal material is synthesized through a simple one-step organic reaction. This type of organic small molecule photothermal material exhibits unique properties and strong solid-state π-π stacking. Through intramolecular charge transfer transitions and π-π* and n-π* wide absorption spectrum characteristics, the large conjugated structure is conducive to improving the molar extinction coefficient. In addition, strong intermolecular interactions and multi-phenyl rotor units improve the non-radiative transition efficiency, which is conducive to photothermal conversion. The pyrrolopyrrole organic small molecule photothermal material of the present invention has the characteristics of high molar extinction coefficient and wide spectrum absorption.

[0013] The pyrrolopyrrole organic small molecule photothermal material is loaded on polyurethane foam (PU) to form a loose and porous photothermal conversion composite material. The synthesized organic small molecules have strong light absorption ability, and PU is loose and porous. The composite material of the two can better improve the evaporation rate and light absorption rate, thereby effectively promoting multiple absorption of sunlight and increasing light capture. Under 1 light condition, the water evaporation rate is 1.08kg·m -2 ·h -1The photothermal conversion efficiency is 71.23%, and the performance remains stable after multiple cycles, with excellent thermal stability. The molecular design concept proposed in this invention can be applied to solar interfacial evaporation, providing more ideas for the research of organic photothermal conversion small molecule materials and promoting the rapid development of seawater desalination.

[0014] The present invention is used for a pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency, and a preparation method and application thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of CzDPPCz prepared in Example 1;

[0016] Figure 2 This is the carbon NMR spectrum of CzDPPCz prepared in Example 1;

[0017] Figure 3 This is a mass spectrometry analysis of CzDPPCz prepared in Example 1;

[0018] Figure 4 The UV-visible absorption spectra of CzDPPCz prepared in Example 1 in different solvents;

[0019] Figure 5 The fluorescence emission spectra of CzDPPCz prepared in Example 1 in different solvents;

[0020] Figure 6 The 365nm ultraviolet light irradiation diagram of CzDPPCz prepared in Example 1 in different solvents;

[0021] Figure 7 The solid-state fluorescence emission spectrum and solution fluorescence emission spectrum of CzDPPCz prepared in Example 1;

[0022] Figure 8 The scanning electron micrographs of CzDPPCz and polyurethane foam prepared in Example 1 and CzDPPCz@PU (40 mg) prepared in Example 3, a and b are CzDPPCz, c and d are polyurethane foams, and e and f are CzDPPCz@PU (40 mg);

[0023] Fig. 9 This is a solid ultraviolet diffuse reflection test graph of CzDPPCz@PU with different loading amounts prepared in Example 3;

[0024] Fig.10 This is a simulated seawater circulation test diagram of CzDPPCz@PU (40 mg) prepared in Example 3;

[0025] Fig.11This is a comparison chart of the photothermal conversion efficiency of CzDPPCz@PU with different loading amounts prepared in Example 3. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is not limited to the specific implementation modes listed below, but also includes any combination of the specific implementation modes.

[0027] Specific implementation method 1: This implementation method is a pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency, and its chemical formula is:

[0028] The R is

[0029] In this specific embodiment, R is a triphenylamine unit or an N-phenylcarbazole unit.

[0030] The beneficial effects of this embodiment are:

[0031] This specific embodiment provides a pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency, and its preparation method and application. First, the desired target organic small molecule-electron donor-acceptor (DA) type pyrrolopyrrole organic small molecule photothermal material is synthesized through a simple one-step organic reaction. This type of organic small molecule photothermal material exhibits unique properties and strong solid-state π-π stacking. Through intramolecular charge transfer transitions and π-π* and n-π* wide absorption spectrum characteristics, the large conjugated structure is conducive to improving the molar extinction coefficient. In addition, strong intermolecular interactions and multi-phenyl rotor units improve the non-radiative transition efficiency, which is conducive to photothermal conversion. The pyrrolopyrrole organic small molecule photothermal material of this specific embodiment has the characteristics of high molar extinction coefficient and wide spectrum absorption.

[0032] The pyrrolopyrrole organic small molecule photothermal material is loaded on polyurethane foam (PU) to form a loose and porous photothermal conversion composite material. The synthesized organic small molecules have strong light absorption ability, and PU is loose and porous. The composite material of the two can better improve the evaporation rate and light absorption rate, thereby effectively promoting multiple absorption of sunlight and increasing light capture. Under 1 light condition, the water evaporation rate is 1.08kg·m -2 ·h -1 The photothermal conversion efficiency is 71.23%, and the performance remains stable after multiple cycles, with excellent thermal stability. The molecular design concept proposed in this specific embodiment can be applied to solar interfacial evaporation, providing more ideas for the research of organic photothermal conversion small molecule materials and promoting the rapid development of seawater desalination.

[0033] Specific embodiment 2: This embodiment is a method for preparing a pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency, which is carried out according to the following steps:

[0034] BrDPPBr, R-boric acid ester, potassium carbonate and a high boiling point solvent are mixed, and then heated to 70°C to 90°C under a nitrogen atmosphere and stirring conditions, and then a phosphine compound is added, and heating and stirring are continued for 7h to 9h under a nitrogen atmosphere and a temperature of 70°C to 90°C, and after the reaction, the mixture is cooled to room temperature, and then pure water is added to precipitate a solid, and the solid is recrystallized and purified to obtain a pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency;

[0035] The structural formula of the BrDPPBr is The R-boric acid ester is 4-(9H-carbazole-9-yl)phenylboronic acid pinacol ester or 4-(diphenylamino)phenylboronic acid pinacol ester.

[0036] The preparation reaction equation of the pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency in this specific embodiment is:

[0037] The R is

[0038] Specific implementation method 3: This implementation method is different from specific implementation method 2 in that the high boiling point solvent is a mixed solution of toluene, tetrahydrofuran or methanol and water. Other aspects are the same as those of specific implementation method 2.

[0039] Specific embodiment 4: This embodiment is different from specific embodiment 2 or 3 in that the phosphine compound is PCl2, PCl3, PCl5, POCl3 or tetrakis(triphenylphosphine)palladium. Others are the same as specific embodiment 2 or 3.

[0040] Specific embodiment 5: This embodiment is different from specific embodiments 2 to 4 in that the molar ratio of BrDPPBr to R-boric acid ester is 1:(2.5-3). Other aspects are the same as specific embodiments 2 to 4.

[0041] Specific embodiment 6: This embodiment is different from specific embodiments 2 to 5 in that the molar ratio of BrDPPBr to potassium carbonate is 1:(2.5-3). Other aspects are the same as specific embodiments 2 to 5.

[0042] Specific embodiment 7: This embodiment is different from specific embodiments 2 to 56 in that the volume ratio of the mole of BrDPPBr to the high boiling point solvent is 1 mol: (20-30) mL. The rest is the same as specific embodiments 2 to 56.

[0043] Specific embodiment 8: This embodiment is different from specific embodiments 2 to 57 in that the molar ratio of BrDPPBr to the phosphine compound is 1:(0.005-0.015). Other aspects are the same as specific embodiments 2 to 57.

[0044] Specific implementation method 9: This implementation method is an application of a pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency, which is used for water evaporation.

[0045] Specific embodiment 10: This embodiment is different from specific embodiment 9 in that it is used for water evaporation, specifically, pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency is loaded in polyurethane foam. Other aspects are the same as specific embodiment 9.

[0046] The following examples are used to verify the beneficial effects of the present invention:

[0047] Embodiment 1:

[0048] A pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency, its chemical formula is:

[0049] The R is

[0050] The method for preparing the pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency is carried out according to the following steps:

[0051] BrDPPBr, R-boric acid ester, potassium carbonate and a high boiling point solvent were mixed, and then heated to 85°C under a nitrogen atmosphere and stirring conditions, and then a phosphine compound was added, and heating and stirring were continued for 8 hours under a nitrogen atmosphere and a temperature of 85°C. After the reaction, the mixture was cooled to room temperature, and then pure water was added to precipitate a solid, which was purified by recrystallization to obtain a pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency, named CzDPPCz;

[0052] The structural formula of the BrDPPBr is The R-boric acid ester is 4-(9H-carbazole-9-yl)phenylboronic acid pinacol ester;

[0053] The high boiling point solvent is toluene.

[0054] The phosphine compound is tetrakis(triphenylphosphine)palladium.

[0055] The molar ratio of BrDPPBr to R-boric acid ester is 1:3.

[0056] The molar ratio of BrDPPBr to potassium carbonate is 1:3.

[0057] The molar ratio of BrDPPBr to the high boiling point solvent is 1 mol:20 mL.

[0058] The molar ratio of BrDPPBr to the phosphine compound is 1:0.01.

[0059] The preparation reaction equation of the pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency in this embodiment is:

[0060]

[0061] Embodiment 2:

[0062] A pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency, its chemical formula is:

[0063] The R is

[0064] The method for preparing the pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency is carried out according to the following steps:

[0065] BrDPPBr, R-boric acid ester, potassium carbonate and a high boiling point solvent were mixed, and then heated to 85°C under a nitrogen atmosphere and stirring conditions, and then a phosphine compound was added, and heating and stirring were continued for 8 hours under a nitrogen atmosphere and a temperature of 85°C. After the reaction, the mixture was cooled to room temperature, and then pure water was added to precipitate a solid, which was purified by recrystallization to obtain a pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency, named TPADPPTPA;

[0066] The structural formula of the BrDPPBr is The R-boric acid ester is 4-(diphenylamino)phenylboronic acid pinacol ester;

[0067] The high boiling point solvent is toluene.

[0068] The phosphine compound is tetrakis(triphenylphosphine)palladium.

[0069] The molar ratio of BrDPPBr to R-boric acid ester is 1:3.

[0070] The molar ratio of BrDPPBr to potassium carbonate is 1:3.

[0071] The molar ratio of BrDPPBr to the high boiling point solvent is 1 mol:25 mL.

[0072] The molar ratio of BrDPPBr to the phosphine compound is 1:0.01.

[0073] The preparation reaction equation of the pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency in this embodiment is:

[0074]

[0075] Example 3: The pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency prepared in Example 1 is used for water evaporation. Specifically, the pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency is loaded in polyurethane foam. The preparation method is as follows:

[0076] 1. Place a cylindrical polyurethane foam with a diameter of 2.6 cm and a thickness of 1 cm in a watch glass;

[0077] 2. Dissolve 10 mg, 20 mg, 30 mg, 40 mg and 50 mg of CzDPPCz in 1 mL of dichloromethane to obtain CzDPPCz solutions;

[0078] 3. Drop the CzDPPCz solution drop by drop on the surface of the cylindrical polyurethane foam, and finally dry it at 60°C for 3 hours to obtain CzDPPCz@PU (10 mg, 20 mg, 30 mg, 40 mg and 50 mg).

[0079] Figure 1 The H NMR spectrum of CzDPPCz prepared in Example 1; its structure was identified by H NMR spectrum. 1 H NMR (400MHz, CDCl3) δ9.04 (d, J=4.2Hz, 2H), 8.16 (dd, J=7.6, 1.1Hz, 4H), 7.94-7.8 9(m,4H),7.69-7.65(m,4H),7.58(d,J=4.1Hz,2H),7.50-7.43(m,8H),7.34-7.30(m ,4H),4.12(d,J=7.2Hz,5H),3.72(q,J=7.0Hz,2H),2.96-2.73(m,2H),2.71-2.50( m, 2H), 2.34 (q, J = 8.6, 8.0Hz, 2H), 1.33 (s, 5H), 0.96 (s, 7H), 0.89 (d, J = 6.5Hz, 7H).

[0080] Figure 2 The carbon NMR spectrum of CzDPPCz prepared in Example 1; its structure was identified by carbon NMR spectrum. 13C NMR (101MHz, CDCl3) δ155.53,141.41,130.03,128.76,125.88,123.10,120.28,1 19.65,116.68,109.76,53.50,49.99,31.69,30.90,30.02,29.77,29.73,17.62.

[0081] Figure 3 The mass spectrum analysis diagram of CzDPPCz prepared in Example 1; the relative molecular weight was analyzed by mass spectrometry, and C 66 H 62 The relative molecular weight of N4O2S2 is 1007.43956.

[0082] Select a quartz cuvette with two sides transparent to UV light and add 3 mL of 1×10 -5 The CzDPPCz solutions of 100 M were prepared in dichloromethane (DCM), tetrahydrofuran (THF), chloroform (CHCl3), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), acetone (ACE), ethyl acetate (EA) and toluene, and the UV-visible absorption spectra of the solutions were tested in different solvents. Figure 4 This is the UV-visible light absorption spectrum of CzDPPCz prepared in Example 1 in different solvents; as can be seen from the figure, this type of fluorescent dye has a broader emission, and can thus better absorb light energy, providing a prerequisite for achieving materials with high photothermal conversion efficiency.

[0083] Select a fluorescent quartz cuvette with four sides transparent to light and add 3 mL of 1×10 -5 M CzDPPCz solution, the solvents are dichloromethane (DCM), tetrahydrofuran (THF), chloroform (CHCl3), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), acetone (Acetone), ethyl acetate (EtOAc) and toluene (Toluene), and the fluorescence emission spectra under different solvents are tested; Figure 5 This is the fluorescence emission spectrum of CzDPPCz prepared in Example 1 in different solvents; it can be seen from the figure that the compound has strong fluorescence emission in different solvents and is a good fluorescent dye.

[0084] Select a dark environment and shoot under 365nm ultraviolet light with a concentration of 1×10 -5M CzDPPCz solution, the solvents are dichloromethane (DCM), tetrahydrofuran (THF), chloroform (CHCl3), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), acetone (Acetone), ethyl acetate (EtOAc) and toluene (Toluene). Figure 6 The 365nm ultraviolet light irradiation diagram of CzDPPCz prepared in Example 1 in different solvents; it can be seen from the figure that as the polarity of the solvent increases, the fluorescence intensity begins to increase and then decreases, but the overall fluorescence intensity does not decrease significantly.

[0085] The solid-state fluorescence emission spectrum of CzDPPCz prepared in Example 1 and the solution (solvent: tetrahydrofuran, concentration: 1×10 -5 M) fluorescence emission spectrum. Figure 7 The solid-state fluorescence emission spectrum and solution fluorescence emission spectrum of CzDPPCz prepared in Example 1; as can be seen from the figure, the quantum yield of the solution state is 29.9%, the solid state hardly emits light, and the weaker fluorescence in the solid state indicates that it has better light absorption ability.

[0086] The organic small molecules, polyurethane foam (PU), and the loading (40 mg) of both were observed using SEM; Figure 8 Scanning electron microscope images of CzDPPCz and polyurethane foam prepared in Example 1 and CzDPPCz@PU (40 mg) prepared in Example 3, a and b are CzDPPCz, c and d are polyurethane foams, e and f are CzDPPCz@PU (40 mg); it can be seen from the figure that the prepared organic small molecules and polyurethane foam are successfully doped into the desired composite material.

[0087] Solid ultraviolet diffuse reflection test was performed on CzDPPCz@PU with different loading amounts prepared in Example 3; Fig. 9 This is a solid ultraviolet diffuse reflection test graph of CzDPPCz@PU with different loading amounts prepared in Example 3; it can be seen from the figure that the composite material of the two also has a broader absorption.

[0088] The CzDPPCz@PU with different loading amounts prepared in Example 3 was subjected to a simulated seawater circulation test, and the test process was as follows:

[0089] Step 1: Prepare two identical evaporating dishes, fill them with the same volume of seawater, and add an appropriate amount of CzDPPCz@PU (10 mg, 20 mg, 30 mg, 40 mg or 50 mg) into one of them;

[0090] Step 2: Use a simulated sunlight source to illuminate the two samples with a light intensity of 1000W / m 2 , each illumination time is 60min;

[0091] Step 3: Use a thermometer to regularly measure and record the surface temperature of the two groups of samples and the amount of water evaporation within a certain period of time;

[0092] Step 4: Compare the temperature difference and evaporation rate between the seawater with added photothermal conversion materials and the control group.

[0093] Fig.10 This is a simulated seawater circulation test diagram of CzDPPCz@PU (40 mg) prepared in Example 3; Fig.11 The photothermal conversion efficiency comparison chart of CzDPPCz@PU with different loading amounts prepared in Example 3 is shown in the figure. It can be seen from the figure that the water evaporation rate of CzDPPCz@PU (40 mg) is 1.08 kg·m -2 ·h -1 The photothermal conversion efficiency can reach 71.23%, and the performance remains stable after multiple cycles, with excellent thermal stability.

Claims

1. A pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency, characterized in that Its general chemical formula is: The R is 2. A method for preparing a pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency as claimed in claim 1, characterized in that It is carried out in the following steps: BrDPPBr, R-boric acid ester, potassium carbonate and a high boiling point solvent are mixed, and then heated to 70°C to 90°C under a nitrogen atmosphere and stirring conditions, and then a phosphine compound is added, and heating and stirring are continued for 7h to 9h under a nitrogen atmosphere and a temperature of 70°C to 90°C, and after the reaction, the mixture is cooled to room temperature, and then pure water is added to precipitate a solid, and the solid is recrystallized and purified to obtain a pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency; The structural formula of the BrDPPBr is The R-boric acid ester is 4-(9H-carbazole-9-yl)phenylboronic acid pinacol ester or 4-(diphenylamino)phenylboronic acid pinacol ester.

3. The method for preparing a pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency according to claim 2, characterized in that The high boiling point solvent is a mixed solution of toluene, tetrahydrofuran or methanol and water.

4. The method for preparing a pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency according to claim 2, characterized in that The phosphine compound is PCl2, PCl3, PCl5, POCl3 or tetrakis(triphenylphosphine)palladium.

5. The method for preparing a pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency according to claim 2, characterized in that The molar ratio of BrDPPBr to R-boric acid ester is 1:(2.5-3).

6. The method for preparing a pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency according to claim 2, characterized in that The molar ratio of BrDPPBr to potassium carbonate is 1:(2.5-3).

7. The method for preparing a pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency according to claim 2, characterized in that The volume ratio of the mole of BrDPPBr to the high boiling point solvent is 1 mol: (20-30) mL.

8. The method for preparing a pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency according to claim 2, characterized in that The molar ratio of BrDPPBr to the phosphine compound is 1:(0.005-0.015).

9. The use of a pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency as claimed in claim 1, characterized in that It is used for water evaporation.

10. The use of a pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency according to claim 9, characterized in that It is used for water evaporation, specifically loading pyrrolopyrrole organic small molecule photothermal material with high photothermal conversion efficiency into polyurethane foam.

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