Ternary organic eutectic P-TS-TC and preparation and application thereof

Abstract

The invention provides preparation of a ternary organic eutectic and application of the ternary organic eutectic in photocatalysis. The molecular formula of the ternary organic eutectic crystal P-TS-TC is (Pyrene) 0.1 (TSB) 0.9 (TCNB), Pyrene is pyrene, TSB is trans-1, 2-stilbene, and TCNB is 1, 2, 4, 5-benzene tetraacetonitrile. The preparation method of the P-TS-TC comprises the following steps: dissolving pyrene, TSB and TCNB in an acetonitrile solvent, and naturally volatilizing the acetonitrile solvent to obtain the orange-yellow P-TS-TC single crystal. The ternary eutectic prepared by the invention has a charge transfer state (CT state), so that the light absorption range of the ternary eutectic has obvious red shift compared with three monomer molecules pyrene, TSB and TCNB. And meanwhile, the energy levels of the three monomer molecules are arranged in a gradient manner, so that hole transfer in P-TS-TC can be effectively promoted, and the CT state delocalization in the eutectic can be regulated and controlled. Compared with binary organic eutectic crystals P-TC and TS-TC, the ternary organic eutectic crystal P-TS-TC prepared by the preparation method disclosed by the invention has longer carrier life and higher photocatalytic water splitting hydrogen production performance.

Description

Technical Field

[0001] The present invention relates to a preparation method of a ternary organic eutectic P-T S -T C and its application in photocatalysis. Specifically, it is to prepare a ternary organic eutectic material with an energy level gradient arrangement, belonging to the field of organic crystal materials. Background Art

[0002] Organic eutectics are crystal materials formed by the self-assembly of two or more organic monomer molecules. Due to their characteristics of light weight, low defects, and easy regulation, they have attracted extensive attention in the fields of optics, electronics, pharmaceuticals, etc. The self-assembly of eutectics mainly occurs through non-covalent supramolecular interactions, including charge transfer (CT) interactions, π-π interactions, hydrogen bond interactions, etc. When the eutectic contains electron-rich donor molecules and electron-deficient acceptor molecules, CT interactions will occur, thereby forming a molecular heterojunction in the eutectic. CT interactions endow CT eutectics with many peculiar properties, such as bipolar charge transport, nonlinear optics, photoconductivity, and ferroelectric properties. Developing CT eutectic materials with a long-lived CT state is of great significance for their further development and application.

[0003] Currently, binary organic eutectic materials are the most common, and there are mainly three strategies for regulating their CT interactions: (1) reasonably select donor and acceptor molecules according to the molecular configuration, ionization energy of the donor molecule, and electron affinity energy of the acceptor molecule; (2) modify the donor and acceptor molecules with functional groups; (3) adjust the ratio and / or stacking mode of the donor and acceptor molecules, such as separated stacking or mixed stacking. By regulating the CT interaction, the charge transport properties and luminescence properties of binary CT eutectics can be controlled (Small 2015, 11, 2150; Adv. Opt. Mater. 2022, 10, 2200286). However, since the CT state excitons are localized at the interface of the donor and acceptor molecules and are prone to rapid recombination, it is difficult to obtain binary CT eutectic materials with a long carrier lifetime, which limits the application of CT eutectic materials in the field of light conversion.

[0004] Compared with binary eutectic materials, multi-component eutectics have greater advantages in functional regulation and have attracted extensive attention in recent years (Angew. Chem. Int. Ed. 2019, 58, 12027; J. Am. Chem. Soc. 2020, 142, 20772; Adv. Mater. 2023, 2211160). The successful preparation of multi-component eutectic materials has also brought new opportunities for the regulation of CT states. By introducing a third organic monomer, it may be possible to regulate the delocalization of CT states and extend the carrier lifetime, but relevant regulation strategies have not been reported yet. At the same time, ternary organic eutectic materials that can be used as photocatalysts to achieve photocatalytic water splitting for hydrogen production have not been reported in Chinese patents. Summary of the Invention

[0005] One of the objectives of the present invention is to provide a preparation method for a ternary organic eutectic P-T S -T C crystal material.

[0006] Another objective of the present invention is to provide a method for regulating the delocalization of CT states in organic eutectics.

[0007] The third objective of the present invention is to provide the application of the above-mentioned ternary organic eutectic P-T S -T C in photocatalytic water splitting for hydrogen production.

[0008] To achieve the above objectives, the present invention adopts the following technical solutions:

[0009] A ternary organic eutectic P-T S -T C , with the molecular formula (Pyrene) 0.1 (TSB) 0.9 (TCNB), where Pyrene is pyrene, TSB is trans-1,2-distyrene, and TCNB is 1,2,4,5-benzenetetracarbonitrile.

[0010] Preferably, the P-T S -T C crystal material belongs to the monoclinic system, space group C 2 / m, and the distances between TCNB and pyrene, TSB are both Its single crystal structure is as Figure 1 shown.

[0011] The preparation method of the ternary organic eutectic P-T S -T C includes the following steps:

[0012] (1) Add pyrene, TSB, and TCNB to a beaker;

[0013] (2) Add anhydrous acetonitrile and methanol to the beaker in step (1), and stir until completely dissolved;

[0014] (3) Evaporate the solvent in step (2) and collect the orange-yellow rectangular single crystal product.

[0015] Preferably, the molar ratio of pyrene, TSB, and TCNB in step (1) is 1:1.5:1.5.

[0016] Preferably, the mixing volume ratio of acetonitrile and methanol in step (2) is 9:1.

[0017] Preferably, the dosage of the solvent in step (2) is 10 ml per 0.1 mmol of pyrene.

[0018] A method for regulating the delocalization of CT states in organic co-crystals. Specifically, by reasonably selecting organic monomer molecules with an energy level gradient arrangement to construct an energy level gradient in the ternary organic co-crystal, carrier separation is promoted, thereby enhancing the delocalization of CT state excitons.

[0019] Preferably, select three organic monomers, pyrene, TSB, and TCNB, and prepare the P-T S -T C crystal according to the preparation method of the ternary organic co-crystal P-T S -T C crystal.

[0020] Preferably, the hole transfer rate in the P-T S -T C crystal is 283 ps.

[0021] Preferably, the CT state exciton lifetime of the P-T S -T C crystal is 60.2 ns.

[0022] The application of the ternary organic co-crystal P-T S -T C in photocatalytic water splitting for hydrogen production. The application method is to add P-T S -T C to a mixed solution of ascorbic acid, methanol, and water, with platinum as a co-catalyst, and react under irradiation with a 300 W xenon lamp.

[0023] Preferably, the addition amount of the P-T S -T C crystal material is 20 mg, the mixed solution is 10 - 20 mM ascorbic acid, 60 - 100 ml methanol, and 10 - 30 ml water, and the dosage of platinum is 0.5 - 1.5 wt% of the P-T S -T C crystal material.

[0024] Compared with the binary organic eutectic P-T C and T S -T C the ternary organic eutectic P-T S -T C prepared in the present invention has a longer carrier lifetime and higher photocatalytic water splitting performance for hydrogen production.

[0025] The advantages of the present invention are as follows:

[0026] 1. The method for preparing the ternary organic eutectic P-T S -T C crystal material in the present invention has mild conditions, simple operation and low cost. The prepared P-T S -T C crystal material has high crystallinity and a wide light absorption range, and has good optical properties.

[0027] 2. The method for regulating the delocalization of CT states in the organic eutectic in the present invention is simple and easy to implement. The prepared P-T S -T C crystal material has a longer carrier lifetime and photocatalytic water splitting performance for hydrogen production compared with the binary organic eutectic T S -T C and P-T C crystal materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 FIG. is a structural diagram of the ternary organic eutectic P-T S -T C crystal material;

[0029] Figure 2 FIG. is the S -T C H-NMR spectra of the P-T 1 crystal and three organic monomers pyrene, TSB and TCNB;

[0030] Figure 3 FIG. is the XRD pattern of the P-T S -T C crystal material;

[0031] Figure 4 The UV-visH of the P-T S -T C crystal material and the UV-vis diagrams of three organic monomers pyrene, TSB and TCNB, where (a) is the UV-vis diagram of the P-T S -T C crystal material; (b) is the UV-vis diagram of three organic monomers pyrene, TSB and TCNB;

[0032] Figure 5 For P-T S -T C PL diagram of the crystal material;

[0033] Figure 6 For P-T S -T C Energy level arrangement diagram of three organic monomers pyrene, TSB and TCNB in;

[0034] Figure 7 For the ternary organic eutectic P-T S -T C and the binary organic eutectic T S -T C 、P-T C Ultrafast fluorescence kinetic curve comparison diagram of;

[0035] Figure 8 For the ternary organic eutectic P-T S -T C and the binary organic eutectic T S -T C 、P-T C Fluorescence kinetic curve comparison diagram of;

[0036] Figure 9 For the ternary organic eutectic P-T S -T C Schematic diagram of the carrier dynamics process in;

[0037] Figure 10 For the ternary organic eutectic P-T S -T C and the binary organic eutectic T S -T C 、P-T C Activity data diagram for photocatalytic water splitting to produce hydrogen. Specific implementation mode

[0038] To further illustrate the present invention, the following examples are listed, but it does not limit the scope of the invention defined by the appended claims.

[0039] Example 1: Preparation of the ternary organic eutectic P-T S -T C Preparation of the crystal material

[0040] Weigh pyrene (20.2 mg, 0.1 mmol), TSB (27.0 mg, 0.15 mmol), and TCNB (26.7 mg, 0.15 mmol) and add them to a 25 ml beaker. Add 9 ml of acetonitrile and 1 ml of methanol, stir until completely dissolved, and then allow the solvent to evaporate naturally at room temperature to obtain the target material P-T S-T C ,P-T S -T C is an orange-yellow rectangular single crystal, 50 - 80 μm in length, 20 - 40 μm in width, and the yield is about 10% (calculated based on pyrene).

[0041] The prepared ternary organic eutectic P-T S -T C The crystal material structure is as Figure 1 shown, belonging to the monoclinic system, space group C 2 / m. The distances between TCNB and pyrene, and TSB are both The prepared P-T S -T C The 1 1H-NMR spectrum of the crystal material is shown in Figure 2 . By comparing the 1 1H-NMR spectra of the three organic monomers pyrene, TSB, and TCNB, it can be determined that the molar ratio of pyrene, TSB, and TCNB in P-T S -T C is 1:9:10. From this, the molecular formula of P-T S -T C is (Pyrene) 0.1 (TSB) 0.9 (TCNB). The XRD result of the P-T S -T C crystal material is shown in Figure 3 . This figure shows that the measured X-ray powder diffraction curve of the P-T S -T C crystal material is basically consistent with the simulated curve of the CIF file of X-ray single crystal diffraction, indicating that the crystal has good crystallinity and high purity. The difference in diffraction intensity between the two is due to the preferred orientation of the crystal.

[0042] Comparative Example 1: Preparation of the binary organic eutectic P-T C crystal material

[0043] Weigh pyrene (20.2 mg, 0.1 mmol) and TCNB (17.8 mg, 0.1 mmol) and add them to a 25 ml beaker. Add 15 ml of acetonitrile and stir until completely dissolved. Then let the solvent evaporate naturally at room temperature to obtain the target material P-T C , P-T C is an orange rod-shaped single crystal product, 0.1 - 2 mm in length, 5 - 500 μm in width, and the yield is about 100% (calculated based on pyrene).

[0044] Comparative Example 2: Preparation of the binary organic eutectic T S -T C crystal material

[0045] Weigh TSB (18.0 mg, 0.1 mmol) and TCNB (35.6 mg, 0.2 mmol), add them to a 25 ml beaker, add 10 ml of acetonitrile, stir until completely dissolved, and then let the solvent evaporate naturally at room temperature to obtain the target material T S -T C , T S -T C is a yellow rod-shaped single crystal, 0.1 - 2 mm in length, 5 - 500 μm in width, and the yield is about 95% (calculated based on TSB).

[0046] Example 2: Ternary organic eutectic P-T S -T C 's optical properties

[0047] This example mainly examines the optical properties of the ternary organic eutectic P-T S -T C , mainly including light absorption and fluorescence emission.

[0048] Perform solid UV-vis spectroscopy on the ternary organic eutectic P-T S -T C . The test results are shown in Figure 4 . This figure is obtained by scanning the ternary organic eutectic P-T S -T C through a solid ultraviolet spectrophotometer with white barium sulfate as the blank control group in the wavelength range of 350 - 700 nm. Figure 4 a shows that the ternary organic eutectic P-T S -T C has good absorption in the visible light region, and the light absorption range reaches 583 nm. Comparing the three organic monomers pyrene, TSB, and TCNB, P-T S -T C 's absorption edge ( Figure 4 b) is significantly redshifted, and this feature indicates that in P-T S -T C , a charge transfer state (CT state) is formed due to the interaction between the donor (pyrene, TSB) and acceptor (TCNB) molecules. The fluorescence emission spectrum of the ternary organic eutectic P-T S -T C is shown in Figure 5 . This figure is obtained by scanning the single crystal material of P-T S -T C at an excitation light wavelength of 405 nm and a fluorescence spectrum collection range of 450 - 780 nm. This figure shows that the center of the fluorescence emission peak of P-T S -T C is located at 580 nm.

[0049] Example 3: Energy Level Gradient Regulation of Ternary Organic Eutectic P-T S -T C Delocalization of the CT State in

[0050] This example mainly examines the regulation of the delocalization of the CT state in the ternary organic eutectic P-T by reasonably selecting organic monomers and constructing an energy level gradient. S -T C

[0051] P-T S -T C The energy level arrangements of the three monomers pyrene, TSB, and TCNB in P-T are shown in Figure 6 . This figure shows that there may be two CT states simultaneously generated in P-T S -T C , namely the CT state composed of the lowest unoccupied molecular orbital (LUMO orbital) of the TCNB molecule and the highest occupied molecular orbital (HOMO orbital) of pyrene, and the CT 1 state composed of the LUMO orbital of the TCNB molecule and the HOMO orbital of the TSB molecule. Due to the existence of the energy level gradient, there may be a hole transfer process from the CT 2 state to the CT 2 state. 1

[0052] Perform fluorescence up-conversion testing on the ternary organic eutectic P-T S -T C . Figure 7 Figure S -T C shows the ultrafast fluorescence kinetic curve of P-T, which is measured by a femtosecond up-conversion fluorescence spectrometer. The excitation light wavelength is 405 nm, and the fluorescence test range is greater than 650 nm. Compared with the binary organic eutectic T S -T C , P-T C , the kinetic curve of the ternary organic eutectic P-T S -T C shows an obvious rising process, indicating that there is a hole transfer process from the CT S -T C state to the CT 2 state in P-T 1 , proving that constructing an energy level gradient can effectively promote charge separation in the ternary organic eutectic P-T S -T C . Performing double-exponential fitting on the ultrafast fluorescence kinetic curve of P-T S -T C , the hole transfer time can be obtained as 283 ps.

[0053] Perform relevant tests on the ternary organic eutectic P-T S-T C The carrier lifetime of was measured. Specifically, a fluorescence kinetic curve was collected using a laser scanning confocal imaging system coupled with time-correlated single-photon counting technology (TCSPC). The ternary organic eutectic P-T S -T C The fluorescence kinetic curve of can be seen in Figure 8 , which was collected under the conditions of an excitation light wavelength of 405 nm and a fluorescence collection range of 540 - 580 nm. By performing a single-exponential fit on this PL kinetic curve, the carrier lifetime of the ternary organic eutectic P-T S -T C was found to be 60.2 ns. Using the same testing method, conditions, and fitting method, the carrier lifetimes of the binary organic eutectics T S -T C and P-T C were found to be 28.4 ns and 27.7 ns respectively, as shown in Figure 8 . Compared with the binary organic eutectics T S -T C and P-T C , the carrier lifetime of the ternary organic eutectic P-T S -T C was significantly prolonged, indicating that the charge transfer process driven by the energy level gradient in P-T S -T C led to an enhanced delocalization of CT-state carriers.

[0054] According to the above kinetic characterization, the carrier dynamics process in the ternary organic eutectic P-T S -T C is as shown in Figure 9 , which shows that constructing an energy level gradient can effectively promote hole transfer in the ternary organic eutectic P-T S -T C and regulate the delocalization of the CT state, thereby prolonging its carrier lifetime.

[0055] Example 4: Photocatalytic water splitting hydrogen production reaction

[0056] Weigh 20 mg of the ternary organic eutectic P-T S -T C crystal material prepared in Example 1 and add it to a mixed solution composed of 15 mM ascorbic acid, 80 ml of methanol, and 20 ml of water. Then add 270 μl of chloroplatinic acid solution (0.74 mg / ml, calculated as platinum). After evacuating the reaction system, irradiate it with a 300 W xenon lamp under full-spectrum wavelength light for 3 h for platinum deposition. Then evacuate again and irradiate it with a 300 W xenon lamp under full-spectrum wavelength light for 1 h, and analyze the hydrogen content generated by gas chromatography sampling. As shown in Figure 10As shown, the prepared ternary organic eutectic P-T S -T C has significantly improved photocatalytic hydrogen production performance from water splitting compared to the binary organic eutectic T S -T C (the process and conditions are the same as those of the aforementioned ternary organic eutectic P-T S -T C in the photocatalytic hydrogen production reaction from water splitting), P-T C (the process and conditions are the same as those of the aforementioned ternary organic eutectic P-T S -T C in the photocatalytic hydrogen production reaction from water splitting). They are 29.6 times and 5.4 times the hydrogen production activities of T S -T C and P-T C respectively, indicating that the enhanced delocalization and extended lifetime of the CT state in the ternary organic eutectic P-T S -T C are beneficial to the improvement of its photocatalytic hydrogen production performance from water splitting.

Claims

1. A ternary organic eutectic P-T S -T C , It is characterized in that The molecular formula is (Pyrene) 0.1 (TSB) 0.9 (TCNB), where Pyrene is pyrene, TSB is trans-1,2-distyrene, and TCNB is 1,2,4,5-benzenetetracarbonitrile.

2. The ternary organic eutectic P-T as described in claim 1 S -T C , It is characterized in that Belonging to the monoclinic system, space group C 2 / m, the spacing between TCNB and pyrene, and TSB is 3. The ternary organic eutectic P-T as claimed in claim 1 or 2 S -T C , It is characterized in that Ternary organic eutectic P-T S -T C It has a charge transfer state (CT state), and the light absorption is significantly redshifted compared to pyrene, TSB, and TCNB; The energy levels of pyrene, TSB, and TCNB are arranged in a gradient, which can effectively promote the hole transfer process, thereby improving the delocalization of CT state excitons in P-T S -T C ​ 4. The ternary organic eutectic P-T as claimed in claim 1 or 2 S -T C , It is characterized in that By selecting organic monomer molecules with energy levels arranged in a gradient in a ternary organic eutectic, an energy level gradient is constructed to promote charge separation, thereby realizing the regulation of the delocalization of CT-state excitons.

5. A preparation method of the ternary organic eutectic P-T according to any one of claims 1-4 S -T C ​ It is characterized in that It includes the following steps: (1) Add pyrene, TSB, and TCNB into a beaker; (2) Add acetonitrile and methanol to the beaker in step (1), and stir until completely dissolved; (3) Let the solvent in step (2) volatilize, and collect the orange-yellow rectangular single crystal product.

6. According to the preparation method described in claim 5, It is characterized in that The molar ratio of pyrene, TSB, and TCNB described in step (1) is 0.5 - 1:1 - 1.5:1.5 - 2, and preferably the molar ratio of pyrene, TSB, and TCNB is 1:1.5:1.

5.

7. According to the preparation method described in claim 5, It is characterized in that The mixing volume ratio of acetonitrile and methanol described in step (2) is 8 - 10:0 - 2, and preferably the mixing volume ratio of acetonitrile and methanol is 9:

1.

8. According to the preparation method described in claim 5 or 6 or 7, It is characterized in that The dosage of the solvent in step (2) is 8 - 10 ml per 0.1 mmol of pyrene, and preferably 10 ml per 0.1 mmol of pyrene.

9. Use of any one of the ternary organic eutectics P-T according to claims 1-4 S -T C in photocatalytic water splitting for hydrogen production.

10. According to the application described in claim 9, It is characterized in that P-T S -T C The crystal material is added to a mixed solution of ascorbic acid, methanol and water, with platinum as a cocatalyst, and the reaction is carried out under the irradiation of a xenon lamp.

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