A method of molecular isomerization based on perovskite nanocrystal sensitization

Abstract

This invention relates to a method for molecular isomerization based on perovskite nanocrystals (CsPbBr3) sensitization. The system uses a perovskite nanocrystal-organic molecule hybrid system as the sensitizer, and utilizes visible light excitation to achieve isomerization of trans-stilbene molecules and their derivatives via triplet energy transfer. Under irradiation with a 450 nm continuous-wave laser (CW laser) at a power of 2.7 W, a conversion rate of >75% can be achieved in ~30 s. With low-power (5 mW) excitation, a quantum efficiency as high as ~30% can be obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to a method of molecular isomerization based on perovskite nanocrystal sensitization. BACKGROUND

[0002] In recent years, lead halide perovskite materials have made breakthrough progress in the application of solar cells, light-emitting diodes and other photoelectric conversion fields, which is due to their high light absorption capacity, long-lived carriers and long carrier diffusion free path and other excellent photoelectric properties. At the same time, due to the simple synthesis process and the easy-to-tune physical and chemical properties of the material, perovskite materials are also used in the field of photocatalysis, such as photoredox catalysis, photopolymerization and the like. However, since these applications often involve polar solvents, and the charge transfer process will produce highly reactive intermediates, which poses a challenge to the stability of perovskite.

[0003] In addition to charge transfer, another important way to use photosensitizers for catalysis is energy transfer. In principle, compared with redox-type electron transfer, energy transfer is more gentle to photosensitizers. In the cycle reaction, the photosensitizer always remains electrically neutral, which effectively avoids the corrosion of the active intermediates produced in the charge transfer process to the photosensitizer. Therefore, it is of great significance to explore perovskite as a photosensitizer for energy transfer reactions.

[0004] Based on the traditional work of Group II- VI quantum dots as triplet photosensitizers, the triplet energy transfer from perovskite nanocrystals to organic molecules has also been continuously developed. However, most of these energy transfers are applied to triplet-state annihilation-photon upconversion systems. Considering the many application prospects of the triplet states generated by nanocrystals in photochemistry (such as driving isomerization, cycloaddition and other organic reactions), it is of great research value to use the triplet energy transfer between perovskite materials and organic molecules to drive organic reactions.

[0005] Based on this, we designed and synthesized cesium lead bromide perovskite nanocrystals (CsPbBr3), modified the surface of the nanocrystals with triplet energy acceptors, constructed a nanocrystal-organic molecule hybrid system, and used this system to catalyze the isomerization of trans-stilbene and its derivatives. Compared with direct excitation of trans-stilbene (the excitation light wavelength needs to be less than 340 nm), under the irradiation of a 450 nm continuous light laser with a power of 2.7 W, a conversion rate of >75% can be achieved in ~30 s. At the same time, the system also achieves a high quantum efficiency. This invention provides a basis for the future development of efficient organic reactions based on perovskite nanocrystal sensitization. SUMMARY

[0006] The application aims to provide a method for molecular isomerization based on perovskite nanocrystal sensitization, and to broaden the application of molecular triplet state in photocatalysis. The method for isomerization of trans-stilbene and its derivatives in the application mainly utilizes the triplet energy transfer between cesium lead bromide perovskite nanocrystals (CsPbBr3) and organic molecules. The triplet energy of the organic molecules is transferred to the substrate molecules in the solution, such as trans-stilbene molecules, through collision. The two-step energy transfer by the triplet acceptor widens the range of substrates, and no longer requires the substrate to have a carboxyl group that can be coordinated on the surface of the cesium lead bromide perovskite.

[0007] The cesium lead bromide perovskite nanocrystals are synthesized by a hot injection method. The prepared cesium source is injected into a lead source at a specific temperature, and the reaction is quenched by rapidly cooling with an ice-water mixture after 5-10 s of reaction. After the reaction product mixture is cooled to room temperature, it is separated and purified.

[0008] The cesium lead bromide perovskite nanocrystals have uniform sizes, obvious exciton peaks, and narrow fluorescence half-width.

[0009] The cesium lead bromide perovskite nanocrystals and the organic molecule coupling system modify the organic molecules on the surface of the nanocrystals through ultrasonic treatment.

[0010] The organic molecules are tunable. 9-phenylthiophene-2-carboxylic acid (9-PTA), 1-naphthalene carboxylic acid (NCA), 1-nitro-2-naphthalene acid (nitro-NCA), and 9-fluorene-2-carboxylic acid (FCA) can all be used as suitable energy acceptors to catalyze the isomerization reaction.

[0011] The reaction substrates are tunable. Trans-stilbene, 4-bromo-trans-stilbene, 4-methyl-trans-stilbene, and 4-methoxy-trans-stilbene can all be used as suitable energy acceptors to undergo isomerization reaction and be converted into the corresponding cis isomers.

[0012] To verify whether the above photocatalytic system can undergo efficient isomerization reaction under visible light irradiation, the application adopts the following verification scheme:

[0013] The electron transfer and energy transfer in the CsPbBr3 nanocrystal-organic molecule system are preliminarily characterized by steady-state absorption spectrum and steady-state fluorescence spectrum.

[0014] The electron transfer and energy transfer processes in the CsPbBr3 nanocrystal-organic molecule system are characterized by femtosecond transient absorption spectroscopy; and the energy transfer process in the CsPbBr3-organic molecule / / trans-stilbene molecule system constructed is characterized by nanosecond transient absorption spectroscopy.

[0015] The photoisomerization process in the CsPbBr3 nanocrystal-organic molecule / / trans-stilbene system is characterized by steady-state absorption spectroscopy.

[0016] The present application uses a perovskite nanocrystal-organic molecule hybrid system as a sensitizer, uses visible light excitation, and realizes the isomerization of trans-stilbene and its series of derivatives through triplet energy transfer.

[0017] In the present application, two-step triplet energy transfer from CsPbBr3 nanocrystals to organic ligands and from organic ligands to reaction substrate molecules in solution is used to realize the isomerization of substrate molecules. In the process of energy transfer, no high-reactivity free radical intermediates are generated, the reaction is mild, and the photosensitizer is friendly. And under the selective excitation of 450nm CW laser, the system realizes a conversion rate of up to ~75% and a quantum efficiency of up to ~30%. BRIEF DESCRIPTION OF DRAWINGS

[0018] CsPbBr3 nanocrystals-9-PTA with a first exciton absorption peak at 455nm are taken as an example, and the related mechanism of the photocatalytic system is characterized by steady-state and transient experiments (Example 1).

[0019] Figure 1 , a schematic diagram of energy transfer in the CsPbBr3 nanocrystal-9-PTA / / trans-stilbene (trans-stilbene or trans-SB) coupling system.

[0020] Figure 2 , an electron microscope image and a particle size statistical diagram of CsPbBr3 nanocrystals with a first exciton absorption peak at 455nm.

[0021] Figure 3 , steady-state absorption spectra of CsPbBr3 nanocrystals and CsPbBr3 nanocrystal-9-PTA with a first exciton absorption peak at 455nm, and fluorescence quenching of 9-PTA on nanocrystals when CsPbBr3 nanocrystals are selectively excited.

[0022] Figure 4, a CsPbBr3 nanocrystal sensitized reaction with the first exciton absorption peak at 455 nm, a is the femtosecond transient absorption kinetics of CsPbBr3 nanocrystals and CsPbBr3 nanocrystal-9-PTA system excited at 400 nm, b is the nanosecond transient absorption kinetics of CsPbBr3 nanocrystal-9-PTA and CsPbBr3 nanocrystal-9-PTA / / trans-stilbene system excited at 400 nm.

[0023] Figure 5 , a CsPbBr3 nanocrystal sensitized reaction with the first exciton absorption peak at 455 nm, a is the absorption spectrum of trans-stilbene in the system with time change and quantum yield under the excitation power of 450 nm, 5 mW, after deducting the absorption of CsPbBr3-9-PTA, b is the conversion rate of trans-stilbene in the system with time change under the excitation power of 450 nm, 2.7 W.

[0024] Figure 6 , a CsPbBr3 nanocrystal sensitized reaction with the first exciton absorption peak at 455 nm, a is the steady-state absorption spectrum of CsPbBr3-9-PTA / / trans-Br-substituted stilbene system with time change under the irradiation of 450 nm, 2.7 W, b is the steady-state absorption spectrum of trans-Br-substituted stilbene in the system with time change after deducting the absorption of CsPbBr3-9-PTA, c is the conversion rate of trans-Br-substituted stilbene in the system with time change.

[0025] Figure 7 , a CsPbBr3 nanocrystal sensitized reaction with the first exciton absorption peak at 455 nm, a is the steady-state absorption spectrum of CsPbBr3-9-PTA / / trans-CH3-substituted stilbene system with time change under the irradiation of 450 nm, 2.7 W, b is the steady-state absorption spectrum of trans-CH3-substituted stilbene in the system with time change after deducting the absorption of CsPbBr3-9-PTA, c is the conversion rate of trans-CH3-substituted stilbene in the system with time change.

[0026] Figure 8, the first exciton absorption peak of CsPbBr3 nanocrystals is at 455 nm, a is the time-dependent steady-state absorption spectra of CsPbBr3-9-PTA / / trans-CH3O-substituted stilbene system under 450 nm, 2.7 W irradiation, b is the time-dependent steady-state absorption spectra of trans-CH3O-substituted stilbene in the system after deducting the absorption of CsPbBr3-9-PTA, c is the conversion rate of trans-CH3O-substituted stilbene in the system over time.

[0027] Figure 9 , the first exciton absorption peak of CsPbBr3 nanocrystals is at 455 nm, a is the time-dependent steady-state absorption spectra of CsPbBr3-NCA / / trans-stilbene system under 450 nm, 2.7 W irradiation, b is the time-dependent steady-state absorption spectra of trans-stilbene in the system after deducting the absorption of CsPbBr3-NCA, c is the conversion rate of trans-stilbene in the system over time.

[0028] Figure 10 , the first exciton absorption peak of CsPbBr3 nanocrystals is at 455 nm, a is the time-dependent steady-state absorption spectra of CsPbBr3-nitro-NCA / / trans-stilbene system under 450 nm, 2.7 W irradiation, b is the time-dependent steady-state absorption spectra of trans-stilbene in the system after deducting the absorption of CsPbBr3-nitro-NCA, c is the conversion rate of trans-stilbene in the system over time.

[0029] Figure 11 , the first exciton absorption peak of CsPbBr3 nanocrystals is at 455 nm, a is the time-dependent steady-state absorption spectra of CsPbBr3-FCA / / trans-stilbene system under 450 nm, 2.7 W irradiation, b is the time-dependent steady-state absorption spectra of trans-stilbene in the system after deducting the absorption of CsPbBr3-FCA, c is the conversion rate of trans-stilbene in the system over time. DETAILED DESCRIPTION

[0030] The application is further illustrated by examples and drawings.

[0031] Example 1

[0032] The method for synthesizing perovskite nanocrystals includes the following steps:

[0033] (1) Synthesis of cesium oleate: First, take 0.814 g of Cs2CO3, 3 mL of oleic acid (OA), and 40 mL of octadecene (ODE) precursors and place them in a 100 mL three-necked round-bottom flask. Heat the system from room temperature to 120°C within 10 minutes, and then vacuumize the flask at 120°C for 30 minutes (the vacuum degree in the flask is -0.1 MPa). Blow nitrogen into the reaction flask and reduce the temperature to 100°C, and then store the system at constant temperature for later use.

[0034] (2) Synthesis of CsPbBr3 perovskite nanocrystals: Take 0.276 g of PbBr2, 20 mL of ODE, 2 mL of OA, and 2 mL of OAm (oleylamine) and mix them in a 100 mL three-necked round-bottom flask. Stir the mixture at a constant speed, vacuumize the flask at 120°C for 30 minutes (the vacuum degree in the flask is -0.1 MPa), and then blow nitrogen into the system. When the solid particles of the precursors are completely dissolved to form a light yellow transparent solution, a lead precursor solution is obtained. Set the reaction temperature of the reaction liquid (the lead precursor solution) to 100°C, and then quickly inject 1.6 mL of the above-mentioned cesium oleate stored at constant temperature into the lead precursor solution (when synthesizing nanocrystals, the temperature of the injected lead precursor solution can be 100°C-170°C. Different injection temperatures correspond to different sizes of nanocrystals, which have a first exciton absorption peak at 450 nm-490 nm. Electron microscope images show that nanocrystals with different exciton peaks have different particle sizes (3-9 nm) of cubes).

[0035] (3) Separation and purification: After centrifuging the reaction stock solution at 7800 rpm for 15 minutes, discard the precipitate, and then add 20 mL of antisolvent methyl acetate to the supernatant to obtain a suspension. Centrifuge the above-mentioned suspension at 7800 rpm for 8 minutes to obtain a precipitate and a supernatant. Disperse the precipitate in 5 mL of dry n-hexane to obtain a nanocrystal solution, and then store the solution at room temperature. The obtained CsPbBr3 nanocrystals have a first exciton absorption peak at 455 nm, and electron microscope images show (as shown in Figure 1 ) that the nanocrystals are cubes with an edge length of 3.5±0.4 nm.

[0036] Whether the CsPbBr3 nanocrystals obtained by the above preparation and having a first exciton absorption peak at 455 nm can efficiently catalyze isomerization reactions, and whether the nanocrystals can efficiently catalyze isomerization reactions after being modified with a triplet energy acceptor (as shown in Figure 2 ) need to be verified by optical detection means. The verification and detection mainly proceed from the following three aspects (taking 9-phenanthrenecarboxylic acid as an example):

[0037] (1) Preliminary characterization of electron transfer and energy transfer in CsPbBr3-9-PTA system from steady-state absorption and fluorescence spectra.

[0038] As shown in Figure 3 , the absorption and fluorescence of CsPbBr3-9-PTA system were tested by steady-state absorption and fluorescence detection methods. The absorbance of the CsPbBr3 nanocrystal solution (adjusted with n-hexane) used in the test was 0.2 OD at 455 nm in a 1 cm optical path cuvette, and after adding 2 mg of 9-PTA molecules to 5 mL of the above-mentioned n-hexane solution of CsPbBr3 nanocrystals (CsPbBr3 system), filtering with a filter membrane with a pore size of 0.22 μm, a CsPbBr3 nanocrystal-9-PTA solution was obtained. From the absorption spectrum, 9-PTA molecules and nanocrystals can be well coupled together. Compared with pure CsPbBr3, the fluorescence quenching efficiency reached 70% when the nanocrystals were excited at 450 nm in the CsPbBr3-9-PTA system, indicating that 9-PTA has good quenching on the nanocrystals. Among them, the ultraviolet-visible steady-state absorption spectrum was obtained by Agilent Cary 5000 instrument; the fluorescence spectrum was obtained by Agilent Cary Eclipse fluorescence spectrophotometer.

[0039] (2) Characterization of electron transfer and energy transfer processes in CsPbBr3-9-PTA system and CsPbBr3-9-PTA / / trans-stilbene system from transient absorption spectrum.

[0040] The absorbance of the CsPbBr3 nanocrystal solution (adjusted with n-hexane) used in the test was 0.5 OD at 455 nm in a 1 mm optical path cuvette, and after adding 2 mg of 9-PTA molecules to 2 mL of the above-mentioned n-hexane solution of CsPbBr3 nanocrystals (CsPbBr3 system), filtering with a filter membrane with a pore size of 0.22 μm, a CsPbBr3 nanocrystal-9-PTA solution (CsPbBr3-9-PTA system) was obtained. 1 mL of the CsPbBr3 nanocrystal-9-PTA solution was taken, 1 mL of the n-hexane solution of trans-stilbene (the absorbance of the trans-stilbene molecules in the n-hexane solution in the 1 mm optical path cuvette was about 2.6 OD at 295 nm) was added, and the CsPbBr3-9-PTA / / trans-stilbene system was obtained.

[0041] Femtosecond transient absorption spectroscopy and nanosecond transient absorption spectroscopy were used to test CsPbBr3, CsPbBr3-9-PTA and CsPbBr3-9-PTA / / trans-stilbene systems, respectively. As shown in Figure 4As shown, in the present application, the pump light with a wavelength of 400 nm is selected to excite CsPbBr3 in each system. Compared with CsPbBr3, the CsPbBr3-9-PTA system is observed to have a rapid decay of the CsPbBr3 ground state bleaching signal, with a rate of 2.09±0.04 ns -1 In the nanosecond transient absorption spectrum, the triplet state signal 9-PTA* of 9-PTA in the CsPbBr3-9-PTA system is observed, proving that efficient triplet state energy transfer occurs between CsPbBr3 and 9-PTA. Compared with CsPbBr3-9-PTA, the 9-PTA* in the CsPbBr3-9-PTA / / trans-stilbene system decays faster, proving that 9-PTA* in the solution has efficient energy transfer with trans-stilbene in the solution through collision.

[0042] (3) Constructing a CsPbBr3 nanocrystal-organic molecule-trans-stilbene system and a derivative system thereof, selecting to excite CsPbBr3 nanocrystals by visible light, and monitoring the isomerization process of the system by using a steady-state absorption spectrum.

[0043] The CsPbBr3 nanocrystal solution (adjusted by n-hexane) used in the system has an absorbance of 0.5 OD at 455 nm in a 1-mm cuvette, 2 mg of 9-PTA molecules is added to 2 mL of the above CsPbBr3 nanocrystal n-hexane solution, filtered by a filter membrane with a pore size of 0.22 μm, and a CsPbBr3 nanocrystal-9-PTA solution is obtained. 1 mL of the above CsPbBr3 nanocrystal-9-PTA solution is taken, 1 mL of a trans-stilbene n-hexane solution (the absorbance of the trans-stilbene molecules in the n-hexane solution in the 1-mm cuvette is about 2.6 OD at 295 nm) is added, and a CsPbBr3-9-PTA / / trans-stilbene system is obtained.

[0044] The present application uses Agilent Cary 5000 to test the ultraviolet-visible steady-state absorption spectrum. After the above CsPbBr3 nanocrystal-organic molecule-trans-stilbene system (CsPbBr3-9-PTA / / trans-stilbene system) is deoxygenated in a nitrogen glove box for 30 min, a 450 nm CW laser (continuous light laser) is selected to excite the nanocrystals, and through the two-step triplet state energy transfer process of the perovskite nanocrystals and the organic molecules and the triplet state of the organic molecules and the trans-stilbene in the solution, the system has a highly efficient isomerization process. As shown in FIG. 6, the steady-state absorption spectrum of the CsPbBr3-9-PTA / / trans-stilbene system is shown in FIG. 6. Figure 5From the steady-state spectra, the change of the absorption spectrum of trans-stilbene can be seen, and the change trend is consistent with the report in Turro, N. J.; Ramamurthy, V.; Scaiano, J. C. Modern molecular photochemistry of organic molecules; University Science Books, 2010, which proves that the trans-stilbene in the system is converted into cis-stilbene by isomerization. Through the change of the steady-state absorption spectrum, it can be concluded that the reaction can be completed in 30 s at high power (2.7 W), and the conversion rate reaches 82.7%. At low power (5 mW), we can capture the quantum efficiency of the system, and the quantum efficiency of the first 15 s is as high as 33.1%. The calculation formula of the conversion rate and the quantum efficiency is:

[0045]

[0046]

[0047] wherein, A 初始吸光度 and A 反应后的吸光度 are the absorbance of stilbene in the system at 295 nm at different times, △A 吸光度的变化 is the change of absorbance of stilbene in the system at 295 nm at the corresponding time, b 比色皿光程 is the optical path of the cuvette, V 溶液体积 is the volume of the reaction solution, p 激发功率 is the excitation power of the reaction, t 反应时间 is the reaction time of the system, A 纳米晶的吸光度 is the absorbance of nanocrystals in the system at 450 nm, N 转化的分子数 is the number of molecules of stilbene that undergo isomerization in the system, N 吸收的光子数 is the number of photons absorbed by the nanocrystals in the system, h is the Planck constant, c is the speed of light, λ is the wavelength of the excitation light, N A is Avogadro, and ε is the extinction coefficient of the molecule.

[0048] In addition, this system can also realize the tunability of organic molecules and the tunability of reaction substrates. In addition to 9-phenylacetic acid (9-PTA), 1-naphthalene carboxylic acid (NCA) (its operation process is the same as above, and the difference is that only when preparing the CsPbBr3-9-PTA / / trans-stilbene system, use equal mass of NCA instead of 9-PTA, as Figure 6As shown, the reaction conversion rate was 75.0%, the quantum efficiency was 27.9%, and the reaction could be completed in 10 s under 2.7 W irradiation), 1-nitro-2-naphthoic acid (nitro-NCA) (the operation process was the same as above, except that equal mass of nitro-NCA was used instead of 9-PTA when preparing the CsPbBr3-9-PTA / / trans-stilbene system, as shown in Figure 7 As shown, the reaction conversion rate was 80.3%, the quantum efficiency was 0.0017%, and the reaction could be completed in 45 min under 2.7 W irradiation), 9-fluorenone-2-carboxylic acid (FCA) (the operation process was the same as above, except that equal mass of FCA was used instead of 9-PTA when preparing the CsPbBr3-9-PTA / / trans-stilbene system, as shown in Figure 8 As shown, the reaction conversion rate was 84.5%, the quantum efficiency was 35.1%, and the reaction could be completed in 7.5 s under 2.7 W irradiation), and the like can all be used as suitable energy acceptors to catalyze the isomerization reaction. When constructing the CsPbBr3nanocrystal-organic molecule-trans-stilbene system and its derivative systems, the above-mentioned organic molecules were all added in an amount of 2 mg.

[0049] The system can also achieve tunable reaction substrates. For example, when 9-PTA is used as the energy acceptor to catalyze the isomerization reaction, in addition to trans-stilbene (trans-SB), 4-bromo-trans-stilbene (trans-Br-substituted stilbene) (the operation process was the same as above, except that equal volume of trans-Br-substituted stilbene was used instead of trans-stilbene when preparing the CsPbBr3-9-PTA / / trans-stilbene system, as shown in Figure 9 As shown, the reaction conversion rate was 75.5%, the quantum efficiency was 33.9%, and the reaction could be completed in 20 s under 2.7 W irradiation), 4-methyl-trans-stilbene (trans-CH3-substituted stilbene) (the operation process was the same as above, except that equal volume of trans-CH3-substituted stilbene was used instead of trans-stilbene when preparing the CsPbBr3-9-PTA / / trans-stilbene system, as shown in Figure 10The reaction conversion rate was 78.0%, the quantum efficiency was 32.6%, and the reaction was completed in 30 s under 2.7 W irradiation, as shown in FIG. 2B), 4-methoxy-trans-stilbene (the operation process was the same as above, except that an equal volume of trans-CH3O-substituted stilbene was used instead of trans-stilbene when preparing the CsPbBr3-9-PTA / / trans-stilbene system, as shown in FIG. 2C), and the like. Figure 11 The reaction conversion rate was 76.5%, the quantum efficiency was 33.0%, and the reaction was completed in 30 s under 2.7 W irradiation, as shown in FIG. 2B), 4-methoxy-trans-stilbene (the operation process was the same as above, except that an equal volume of trans-CH3O-substituted stilbene was used instead of trans-stilbene when preparing the CsPbBr3-9-PTA / / trans-stilbene system, as shown in FIG. 2C), and the like.

[0050] Example 2

[0051] The method for molecular isomerization based on perovskite nanocrystal sensitization described in this example is basically prepared in the same way as in Example 1, and the operation process is the same as in Example 1, except that the injection temperature in the preparation process step (2) is 130°C, that is, the reaction temperature of the reaction solution (lead precursor solution) is set to 130°C. Therefore, the first exciton absorption peak of the obtained CsPbBr3nanocrystal is at 470 nm, and the nanocrystal is a cube with an edge length of 4.6±0.3 nm.

[0052] We prepared the first exciton absorption peak at 470 nm CsPbBr3 nanocrystals can catalyze isomerization reaction, after modification of the nanocrystal surface triplet energy acceptor can catalyze isomerization reaction, need to use optical detection means to verify, verify detection method with example 1, the experimental results and example one basically consistent, that is, each system occurs high efficient isomerization, (each organic molecule catalytic process corresponding conversion rate is given below), but the quantum efficiency of isomerization reaction is slightly lower than example 1. In the construction of CsPbBr3 nanocrystals-organic molecule / / trans-stilbene (trans-stilbene or trans-SB) and its derivatives system (experimental process and parameters are the same as example 1), the organic molecule can be tuned and the reaction substrate can be tuned. 9-phenanthrene carboxylic acid (9-PTA) (2.7 W irradiation, 2 min can complete the reaction, the reaction conversion rate is 81.0%, the quantum efficiency is 5.6%), 1-naphthalene carboxylic acid (NCA) (2.7 W irradiation, 1.8 min can complete the reaction, the reaction conversion rate is 76.2%, the quantum efficiency is 4.5%), 1-nitro-2-naphthalene acid (nitro-NCA) (2.7 W irradiation, 1.5 h can complete the reaction, the reaction conversion rate is 79.6%, the quantum efficiency is 5.6×10 -5

[0053] In addition, the system can also realize the tuning of the reaction substrate (the experimental process and parameters are the same as example 1). Taking 9-fluorenone-2-carboxylic acid (FCA) as an energy acceptor to catalyze isomerization reaction as an example, in addition to trans-stilbene (2.7 W irradiation, 2 min can complete the reaction, the reaction conversion rate is 81.0%), 4-bromo-trans-stilbene (2.7 W irradiation, 1.5 min can complete the reaction, the reaction conversion rate is 82.7%), 4-methyl-trans-stilbene (2.7 W irradiation, 2.5 min can complete the reaction, the reaction conversion rate is 76.3%), 4-methoxy-trans-stilbene (2.7 W irradiation, 2 min can complete the reaction, the reaction conversion rate is 75.2%) and other molecules can also be suitable energy acceptors to occur isomerization reaction.

[0054] Example 3

[0055] ​The method for isomerization based on perovskite nanocrystal sensitization described in this embodiment, wherein the basic preparation steps and operation process of perovskite nanocrystal are the same as those of Example 1. Different from Example 1, in the preparation process step (2), the injection temperature of this embodiment is 170°C, i.e. the reaction temperature of the reaction solution (lead precursor solution) is set to 170°C. Therefore, the first exciton absorption peak of the obtained CsPbBr3nanocrystal is at 490 nm, and the nanocrystal is a cube with an edge length of 7.7±0.5 nm.

[0056] Whether the obtained CsPbBr3nanocrystal with a first exciton absorption peak at 490 nm can efficiently catalyze the isomerization reaction and whether it can efficiently catalyze the isomerization reaction after modifying the surface of the nanocrystal with a triplet energy acceptor need to be verified by optical detection means. The verification and detection method is the same as that of Example 1, and the experimental results are slightly different from those of Example 1, i.e. 9-phenylacetic acid and 1-naphthoic acid cannot be used as suitable energy transfer acceptor sensitized isomerization systems, and the quantum efficiency of the isomerization reaction of 1-nitro-2-naphthoic acid and 9-fluorenone-2-carboxylic acid as energy acceptor sensitized systems is slightly lower, about 0.3-1.2%. In the constructed CsPbBr3nanocrystal-organic molecule / / trans-stilbene (trans-SB) and its derivatives system (the experimental process and parameters are the same as those of Example 1), 1-nitro-2-naphthoic acid (nitro-NCA) (2.7W irradiation, 2h can complete the reaction, the reaction conversion rate is 74.3%), 9-fluorenone-2-carboxylic acid (FCA) (2.7W irradiation, 15min can complete the reaction, the reaction conversion rate is 80.5%) and other molecules can still be used as suitable energy acceptors to catalyze the isomerization reaction. However, because the triplet energy of 9-phenylacetic acid (9-PTA) and 1-naphthoic acid (NCA) is slightly higher, they cannot effectively transfer energy to CsPbBr3nanocrystal, so these two organic molecules cannot efficiently sensitize the isomerization of trans-stilbene and its derivatives.

[0057] In addition, the system can achieve reaction substrate tuning (experimental process and parameters are the same as those in Example 1). Taking 9-fluorenone-2-carboxylic acid (FCA) as an energy acceptor to catalyze isomerization reaction as an example, in addition to trans-stilbene (trans-SB) (2.7 W irradiation, 15 min can complete the reaction, and the reaction conversion rate is 80.5%), 4-bromo-trans-stilbene (2.7 W irradiation, 12 min can complete the reaction, and the reaction conversion rate is 78.3%), 4-methyl-trans-stilbene (2.7 W irradiation, 24 min can complete the reaction, and the reaction conversion rate is 76.1%), 4-methoxy-trans-stilbene (2.7 W irradiation, 15 min can complete the reaction, and the reaction conversion rate is 79.8%) and other molecules can also be used as suitable energy acceptors to undergo isomerization reaction.

[0058] Comparative Example 1

[0059] The perovskite nanocrystals described in the present comparative example cannot efficiently sensitize the molecular isomerization method, wherein the basic preparation steps and operation processes of the perovskite nanocrystals are the same as those in Example 1. Different from Example 1, when constructing the CsPbBr3 nanocrystal-organic molecule-trans-stilbene system and its derivative photocatalytic system, we use benzoic acid molecules as a triplet energy acceptor to modify the surface of CsPbBr3 nanocrystals, and the amount of the added molecules is the same as that in Example 1.

[0060] Whether the CsPbBr3 nanocrystals prepared by us can efficiently catalyze isomerization reaction and whether the triplet energy acceptor modified on the surface of the nanocrystals can efficiently catalyze isomerization reaction need to be verified by optical detection means. The verification and detection method is the same as that in Example 1, and the experimental results are different from those in Example 1, that is, benzoic acid cannot be used as a suitable energy transfer acceptor to sensitize the isomerization reaction of the system, and no isomerization reaction of stilbene occurs in the system under 450 nm CW laser irradiation.

[0061] In summary, the molecular isomerization method based on perovskite nanocrystal sensitization invented by us breaks the limitation of noble metal catalysts and can efficiently realize the isomerization of trans-stilbene molecules and their derivatives. At the same time, the organic molecules in this system are tunable, and the substrate is tunable. This application is the first to use a perovskite system to realize isomerization reaction, and the use of two-step energy transfer further reduces the limitation of the substrate, realizes a higher conversion rate, widens the application of molecular triplet state in photochemistry, and has great application prospect in the field of energy transfer type organic reactions.

Claims

1. A method of molecular isomerization based on perovskite nanocrystal sensitization, characterized by: Under visible light irradiation, the isomerization of the reaction substrate in the nanocrystal-organic molecule hybrid system is converted into the corresponding cis structure; The organic molecules in the nanocrystal-organic molecule hybrid system can be one or more than two of 9-phenanthrene carboxylic acid (9-PTA), 1-naphthalene carboxylic acid (NCA), 1-nitro-2-naphthalene acid (nitro-NCA), 9-fluorene-2-carboxylic acid (FCA) molecules, all of which can be used as suitable energy acceptors to catalyze isomerization reactions; the reaction substrate can be one or more than two of trans-stilbene ( trans -stilbene or trans -SB), 4-bromo-trans-stilbene ( trans -Br-substituted stilbene), 4-methyl-trans-stilbene ( trans -CH3-substituted stilbene), 4-methoxy-trans-stilbene ( trans -CH3O-substituted stilbene), all of which can undergo isomerization reactions as suitable energy acceptors to be converted into the corresponding cis isomers, and the perovskite nanocrystal is a cesium lead bromide perovskite nanocrystal.

2. The method of claim 1, wherein: the first exciton absorption peak of the perovskite nanocrystal is at 450-490 nm, and the nanocrystals with different first exciton peaks are cubic nanocrystals with different edge lengths, and the different edge lengths are 3-9 nm.

3. The method of claim 2, wherein: the perovskite nanocrystal is a cesium lead bromide perovskite nanocrystal, the first exciton absorption peak of the perovskite nanocrystal is at 450-470 nm, and the nanocrystals with different first exciton peaks are cubic nanocrystals with different edge lengths, and the different edge lengths are 3.1-6 nm.

4. The method of claim 2, wherein: the cubic nanocrystal with an edge length of 3-6 nm, and the organic molecule can be one or more of 9-phenanthrene carboxylic acid (9-PTA), 1-naphthalene carboxylic acid (NCA), 1-nitro-2-naphthalene acid (nitro-NCA), and 9-fluorene-2-carboxylic acid (FCA) molecules; or, the cubic nanocrystal with an edge length greater than 6 to 9 nm, and the organic molecule is one or more of 1-nitro-2-naphthalene acid (nitro-NCA) and 9-fluorene-2-carboxylic acid (FCA) molecules, which can all be used as suitable energy acceptors to catalyze the isomerization reaction.

5. The method of claim 1, wherein: the system is a non-polar organic solution system using a non-polar organic solvent, and the non-polar organic solvent is one or more of n-hexane and toluene.

6. The method of claim 1, wherein: the wavelength range of the visible light is 400-500 nm.

7. The method of claim 1, wherein: 1) Preparation process of the perovskite nanocrystal-organic molecule system: 1-5 mg of organic molecules are added to 2-3 mL of non-polar organic solution of perovskite nanocrystals, and then filtered with a filter membrane with a pore size of 0.22-0.25 µm to obtain nanocrystal-organic molecule solution passing through the filter membrane, and the organic molecules are modified on the surface of the nanocrystals by coordination; the non-polar organic solution of nanocrystals used in the system has an absorbance of 0.1-3 OD at 455 nm in a 1 mm optical path cuvette; 2) Take 1-5 mL of the above nanocrystal-organic molecule solution, add 1-5 mL of non-polar organic solution of reaction substrate to obtain a photocatalytic system, and under visible light excitation, one or more of trans-stilbene or trans-stilbene derivatives in the reaction is converted into the corresponding cis structure through isomerization; the non-polar organic solution of trans-stilbene or trans-stilbene derivatives added in the system has an absorbance of 0.1-3 OD at 295 nm in a 1 mm optical path cuvette.

8. The method of claim 7, wherein: The high-power continuous laser used in the sensitization process has a power range of 1-3 W when the volume of the reaction system is 0.3-0.4 mL.

9. The method of claim 7, wherein: The reaction time of the isomerization process is 5 s-2 h, and the conversion rate is 75%-85%.

10. The method of claim 9, wherein: The reaction time of the isomerization process is 5-60 s.

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