NH2-UiO-66 / PyCD-COF Heterojunction Photocatalyst and Its Preparation Method and Application

Abstract

The present invention discloses an NH2-UiO-66 / PyCD-COF heterojunction photocatalyst and its preparation method and application. The preparation method includes: S1, dissolving zirconium chloride to obtain solution A; dissolving 2-aminoterephthalic acid to obtain solution B; S2, mixing and stirring, and reacting at 120-125 °C for 16-18 h to obtain NH2-UiO-66; S3, adding NH2-UiO-66, 1,3,6,8-tetrakis(4-formylphenyl)pyrene, and 2-chloro-1,4-phenylenediamine into an ortho-dichlorobenzene / n-butanol solution containing acetic acid, ultrasonic mixing in a Pyrex tube, freeze-degassing, and then vacuum-sealing; S4, reacting at 120 °C-130 °C for 3-5 days to obtain the NH2-UiO-66 / PyCD-COF heterojunction photocatalyst. The process of the present invention is simple and highly operable, and has excellent photocatalytic hydrogen production performance.

Description

Technical Field

[0001] The present invention relates to the technical field of heterojunction photocatalysts, and specifically refers to an NH2-UiO-66 / PyCD-COF heterojunction photocatalyst for photocatalytic hydrogen production, a preparation method thereof, and an application thereof. Background Art

[0002] Solar-driven photocatalytic hydrogen production (H2) is a clean, economical, and environmentally friendly strategy. Converting renewable solar energy into storable and transportable chemical energy is considered an effective strategy to alleviate global environmental pollution and energy poverty problems. Solving global energy and environmental problems through conversion. Converting inexhaustible solar energy into green and carbon-free hydrogen fuel. However, the photocatalytic hydrogen production reaction involves many steps, and the high recombination probability of photo-generated electron-hole pairs makes it difficult to occur and results in low performance. The core challenge of this promising technology lies in developing efficient, inexpensive, and reliable photocatalysts to produce H2 fuel comparable to traditional fossil fuels.

[0003] Covalent-organic framework materials (abbreviated as COFs) are a new type of visible-light-responsive non-metallic polymer that has developed rapidly in recent years. They have obvious porous structures and photochemical stabilities, adjustable porosities, modifiable skeletons, and atomically precise structures, and thus have attracted much attention. A PyCD-COF that has the ability to produce hydrogen by water photolysis under ultraviolet and visible light was first prepared. However, a single PyCD-COF photocatalyst also faces some problems, such as a high recombination probability of photo-generated electron-hole pairs and low photocatalytic hydrogen production performance. To improve this problem and enhance the photocatalytic hydrogen production performance, constructing a heterojunction photocatalyst is a simple and feasible method.

[0004] As reported by Kampouri S et al. (Kampouri S, Ebrahim F M, Fumanal M, et al. Enhanced visible-light-driven hydrogen production through MOF / MOF heterojunctions[J]. ACS Applied Materials & Interfaces, 2021, 13(12): 14239-14247.), although the MIL-167 / MIL-125-NH2 heterojunction was constructed and has relatively good optoelectronic properties, there are still problems such as a relatively complex synthesis process, a small specific surface area, a narrow light absorption range, and a relatively high recombination probability of photo-generated electrons and holes.

[0005] Therefore, it is necessary to develop a preparation process for the NH2-UiO-66 / PyCD-COF heterojunction photocatalyst that is simple, highly operable, and low-cost. Compared with single PyCD-COF, it can reduce the recombination of photogenerated electron-hole pairs during the photocatalytic process and has excellent photocatalytic hydrogen production performance. Summary of the Invention

[0006] The object of the present invention is to solve the deficiencies of the above-mentioned background technology and provide an NH2-UiO-66 / PyCD-COF heterojunction photocatalyst with a simple preparation process, strong operability, and low cost. Compared with single PyCD-COF, it can reduce the recombination of photogenerated electron-hole pairs during the photocatalytic process and has excellent photocatalytic hydrogen production performance.

[0007] The technical solution of the present invention is as follows: A preparation method for an NH2-UiO-66 / PyCD-COF heterojunction photocatalyst for photocatalytic hydrogen production, characterized by comprising the following steps:

[0008] S1. Add zirconium chloride to a mixed solution of DMF and hydrochloric acid, and ultrasonically dissolve to obtain solution A; add 2-aminoterephthalic acid to DMF and ultrasonically dissolve to obtain solution B;

[0009] S2. Mix and stir solution A and solution B, then transfer them into a hydrothermal reaction kettle with a polytetrafluoroethylene inner lining, react at 120-125°C for 16-18 hours, cool to room temperature after the reaction, collect the precipitate by centrifugation, wash, and dry to obtain NH2-UiO-66;

[0010] S3. Add the NH2-UiO-66, 1,3,6,8-tetrakis(4-formylphenyl)pyrene, and 2-chloro-1,4-phenylenediamine obtained in step S2 to an ortho-dichlorobenzene / n-butanol solution containing acetic acid, put the obtained mixture into a Pyrex tube and ultrasonically mix for 3-5 minutes, degas the test tube three times using the freeze-pump-thaw technique, and then seal it under vacuum;

[0011] S4. React the mixture obtained in step S3 at 120°C - 130°C for 3-5 days, collect the precipitate by centrifugation, wash, Soxhlet extract, and dry to obtain the NH2-UiO-66 / PyCD-COF heterojunction photocatalyst.

[0012] Preferably, in step S1, the mixed solution of DMF and hydrochloric acid is formed by mixing DMF and concentrated hydrochloric acid at a volume ratio of 5:1. For every 0.54 mmol of zirconium chloride in solution A, 30 - 50 mL of the mixed solution of DMF and hydrochloric acid is used. For every 0.54 mmol of 2-aminoterephthalic acid in solution B, 10 - 20 mL of DMF is used. In the present invention, the concentrated hydrochloric acid is commercially available concentrated hydrochloric acid with a mass fraction of 36 - 38%, of AR grade. DMF is commercially available N,N-dimethylformamide.

[0013] Preferably, in step S1, the molar ratio of zirconium chloride to 2-aminoterephthalic acid is 1:1.

[0014] Preferably, in step S2, the washing and drying include: washing the precipitate with DMF, then soaking it in anhydrous methanol for 24 h and filtering, repeating the soaking and filtering multiple times to remove DMF; drying it under vacuum at 60 - 70 °C for 12 - 15 h.

[0015] Preferably, in step S3, the mass of 1,3,6,8-tetrakis(4-formylphenyl)pyrene accounts for 50% - 90% of the total mass of NH2-UiO-66 and 1,3,6,8-tetrakis(4-formylphenyl)pyrene. The molar ratio of 2-chloro-1,4-phenylenediamine to 1,3,6,8-tetrakis(4-formylphenyl)pyrene is 0.2 - 0.3:1.

[0016] Preferably, in step S3, the o-dichlorobenzene / n-butanol solution containing acetic acid is obtained by mixing 6 mol / L aqueous acetic acid solution, o-dichlorobenzene, and n-butanol at a volume ratio of 1:9:1. For every 84 mg of 1,3,6,8-tetrakis(4-formylphenyl)pyrene, 1.1 - 2 mL of the o-dichlorobenzene / n-butanol solution containing acetic acid is used.

[0017] Preferably, in step S4, the washing, Soxhlet extraction, and drying include: washing the precipitate with anhydrous tetrahydrofuran, extracting it with a Soxhlet extractor for 10 - 12 h; drying it under vacuum at 100 - 120 °C for 24 - 30 h.

[0018] The present invention also provides an NH2-UiO-66 / PyCD-COF heterojunction photocatalyst, which is prepared by the preparation method of the NH2-UiO-66 / PyCD-COF heterojunction photocatalysis for photocatalytic hydrogen production described in any one of the above.

[0019] The present invention also provides an application of the NH2-UiO-66 / PyCD-COF heterojunction photocatalyst for photocatalytic hydrogen production.

[0020] Preferably, the steps of photocatalytic hydrogen production include:

[0021] The NH2-UiO-66 / PyCD-COF heterojunction photocatalyst was added to an ascorbic acid solution with a concentration of 0.1 mol / L. For every 30 mL of the ascorbic acid solution, 5-10 mg of the NH2-UiO-66 / PyCD-COF heterojunction photocatalyst was used. Chloroplatinic acid was added dropwise for Pt loading, and the mass of the loaded Pt was 2% of the mass of the NH2-UiO-66 / PyCD-COF composite photocatalyst. Then, nitrogen gas was introduced into the solution for half an hour to remove the oxygen in the solution. Subsequently, the quartz tube was irradiated under a 500 W xenon lamp for 6 h for the photocatalytic reaction.

[0022] Due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows:

[0023] (1) Since the preparation method of the NH2-UiO-66 / PyCD-COF heterojunction photocatalyst is in-situ growth, the synthesis method of the present invention has simple process conditions and operations, and strong repeatability; the chemical reagents used are easy to obtain, have strong applicability, high industrial application value, and are easy to promote and utilize.

[0024] (2) After NH2-UiO-66 is in-situ grown on the surface of PyCD-COF, compared with the single PyCD-COF organic framework material, the photocatalytic hydrogen production performance of the prepared NH2-UiO-66 / PyCD-COF heterojunction photocatalyst for photocatalytic hydrogen production has been significantly improved; at the same time, due to the formation of a heterojunction at the interface of the NH2-UiO-66 / PyCD-COF heterojunction photocatalyst for photocatalytic hydrogen production, the built-in electric field generated can effectively reduce the recombination of photo-generated electron-hole pairs during the photocatalytic process of single PyCD-COF, improve the separation efficiency of photo-generated electron-hole pairs, and has excellent ultraviolet-visible light water splitting hydrogen production performance. The highest photocatalytic water splitting hydrogen production performance of the prepared NH2-UiO-66 / PyCD-COF heterojunction photocatalyst for photocatalytic hydrogen production is 30.11 mmol·g -1 ·h -1 .

[0025] (3) In NH2-UiO-66 / PyCD-COF, the PyCD-COF component has excellent light absorption ability and plays a role in light harvesting under visible light irradiation. Then, the photo-generated electrons of PyCD-COF migrate from the VB to the CB, and then quickly transfer to the CB of NH2-UiO-66 through covalent connection to ensure the opposite migration of photo-generated electrons and holes. A heterojunction is formed at the interface of the NH2-UiO-66 / PyCD-COF heterojunction photocatalyst for photocatalytic hydrogen production, and the built-in electric field generated can effectively reduce the recombination of photo-generated electron-hole pairs during the photocatalytic process of single PyCD-COF, improve the separation efficiency of photo-generated electron-hole pairs, and has excellent ultraviolet-visible light water splitting hydrogen production performance.

[0026] Therefore, the process of the present invention is simple and highly operable. The prepared NH2-UiO-66 / PyCD-COF heterojunction photocatalyst for photocatalytic hydrogen production can reduce the recombination of photogenerated electron-hole pairs during the photocatalytic process compared with single PyCD-COF, and has excellent photocatalytic hydrogen production performance. Description of the Drawings

[0027] Figure 1 XRD diffraction pattern of the NH2-UiO-66 / PyCD-COF heterojunction photocatalyst prepared in Example 1

[0028] Figure 2 FT-IR spectrum of the NH2-UiO-66 / PyCD-COF heterojunction photocatalyst prepared in Example 1

[0029] Figure 3 UV-Vis spectrum of the NH2-UiO-66 / PyCD-COF heterojunction photocatalyst prepared in Example 1;

[0030] Figure 4 SEM photograph of NH2-UiO-66 prepared in Example 1;

[0031] Figure 5 SEM photograph of PyCD-COF in the comparative example;

[0032] Figure 6 SEM photograph of the NH2-UiO-66 / PyCD-COF heterojunction photocatalyst prepared in Example 1;

[0033] Figure 7 TEM photograph of the NH2-UiO-66 / PyCD-COF heterojunction photocatalyst prepared in Example 1;

[0034] Figure 8 N2 adsorption-desorption isotherms of the NH2-UiO-66 / PyCD-COF heterojunction photocatalysts prepared in Examples 1-5;

[0035] Figure 9 Photocatalytic hydrogen production performance diagrams of the NH2-UiO-66 / PyCD-COF heterojunction photocatalysts prepared in Examples 1-5;

[0036] Figure 10 Steady-state fluorescence spectra of the NH2-UiO-66 / PyCD-COF heterojunction photocatalysts prepared in Examples 1-5. Detailed Description of the Invention

[0037] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the following embodiments are used to further elaborate on the present invention in detail. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Unless otherwise specified, the drugs used in the embodiments are commercially available products, and the methods used are conventional methods in the art.

[0038] To avoid repetition, the method for measuring the photocatalytic hydrogen production performance involved is uniformly described as follows and will not be repeated in the embodiments:

[0039] Add 5 mg of the photocatalyst to 30 mL of 0.1 mol / L ascorbic acid solution, and load 2% Pt (Pt is loaded by dropping chloroplatinic acid, and the mass of the loaded Pt is 2% of the mass of the NH2-UiO-66 / PyCD-COF composite photocatalyst). Then, introduce nitrogen into the solution for half an hour to remove the oxygen in the solution. Next, irradiate the quartz tube under a 500 W xenon lamp for 6 h for the photocatalytic reaction, and take samples to detect hydrogen. During the test, use a 250 μL syringe to extract the gas from the upper layer of the quartz tube and inject it into the gas chromatograph, and convert the obtained peak area with the standard hydrogen area in the gas chromatograph to obtain the photocatalytic hydrogen production performance.

[0040] Example 1

[0041] This example provides a preparation method for an NH2-UiO-66 / PyCD-COF heterojunction photocatalyst. The steps are as follows:

[0042] S1. Add 0.54 mmol of zirconium chloride ZrCl4 to a mixed solution of 30 mL of DMF and concentrated hydrochloric acid (V DMF :V HCl = 5:1), and ultrasonically dissolve to obtain solution A; add 0.54 mmol of 2-aminoterephthalic acid (BDC-NH2) to 10 mL of DMF, and ultrasonically dissolve to obtain solution B.

[0043] S2. Mix the two solutions obtained above, stir for 2 h, transfer them to a 100 mL hydrothermal reaction kettle, and react at 120 °C for 16 h. After the reaction is completed and cooled to room temperature, centrifuge to collect the precipitate, wash the precipitate with DMF, and then soak the washed product in anhydrous methanol for 24 h, filter, and soak and filter repeatedly three times to remove DMF. Finally, put the obtained product into a vacuum drying oven and dry it at 60 °C for 12 h to obtain NH2-UiO-66.

[0044] S3. Put the obtained 9.3 mg of NH2-UiO-66, 1,3,6,8-tetrakis(4-formylphenyl)pyrene (84 mg, 0.136 mmol), 2-chloro-1,4-phenylenediamine (5.6 mg, 0.039 mmol), o-dichlorobenzene (0.9 mL), n-butanol (0.1 mL) and 6 M acetic acid aqueous solution (0.1 mL) into a 10 mL Pyrex tube, and ultrasonicate the mixture for 3 minutes. Degas the test tube three times using the freeze-pump-thaw technique and then seal it under vacuum.

[0045] S4. Heat the reactants at 120 °C for 3 days to produce a precipitate at the bottom of the test tube. Filter to obtain the precipitate, wash the precipitate with anhydrous tetrahydrofuran, extract with a Soxhlet extractor for 10 h to obtain a solid, and dry the solid under vacuum at 100 °C for 24 h to obtain the NH2-UiO-66 / PyCD-COF (1:9) heterojunction.

[0046] The NH2-UiO-66 / PyCD-COF (1:9) obtained in this example was measured for photocatalytic hydrogen production performance: the result was 19.59 mmol·g -1 ·h -1 .

[0047] Example 2

[0048] This example provides a method for preparing an NH2-UiO-66 / PyCD-COF heterojunction photocatalyst, and the steps are as follows:

[0049] S1. Add 0.54 mmol of ZrCl4 to a mixed solution of 30 mL of DMF and hydrochloric acid (V DMF :V HCl = 5:1), and ultrasonically dissolve to obtain solution A; add 0.54 mmol of 2-aminoterephthalic acid (BDC-NH2) to 10 mL of DMF, and ultrasonically dissolve to obtain solution B;

[0050] S2. Mix the above two obtained solutions, stir for 2 h, transfer to a 100 mL hydrothermal reaction kettle, and react at 120 °C for 16 h. After the reaction is completed and cooled to room temperature, centrifuge to collect the precipitate, wash the precipitate with DMF, and then soak the washed product in anhydrous methanol for 24 h, filter, and repeat three times to remove DMF. Finally, put the obtained product into a vacuum drying oven and dry at 60 °C for 12 h to obtain NH2-UiO-66;

[0051] S3. Put the obtained 21 mg of NH2-UiO-66, 1,3,6,8-tetrakis(4-formylphenyl)pyrene (84 mg, 0.136 mmol), 2-chloro-1,4-phenylenediamine (5.6 mg, 0.039 mmol), o-dichlorobenzene (0.9 mL), n-butanol (0.1 mL) and 6 M acetic acid aqueous solution (0.1 mL) into a 10 mL Pyrex tube, and ultrasonicate the mixture for 3 minutes. Degas the test tube three times using the freeze-pump-thaw technique, and then seal it under vacuum;

[0052] S4. Heat the reactants at 120 °C for 3 days, and a precipitate is formed at the bottom of the test tube. Filter to obtain the precipitate, wash the precipitate with anhydrous tetrahydrofuran, extract with a Soxhlet extractor for 10 h to obtain a solid, and dry the solid under vacuum at 100 °C for 24 h to obtain the NH2-UiO-66 / PyCD-COF(2:8) heterojunction.

[0053] The obtained NH2-UiO-66 / PyCD-COF(2:8) in this example was measured for photocatalytic hydrogen production performance: the result was 23.78 mmol·g -1 ·h -1 .

[0054] Example 3

[0055] This example provides a preparation method of an NH2-UiO-66 / PyCD-COF heterojunction photocatalyst. The steps are as follows:

[0056] S1. Add 0.54 mmol of ZrCl4 to a mixed solution of 30 mL of DMF and hydrochloric acid (V DMF :V HCl = 5:1), and ultrasonically dissolve to obtain solution A; add 0.54 mmol of 2-aminoterephthalic acid (BDC-NH2) to 10 mL of DMF, and ultrasonically dissolve to obtain solution B;

[0057] S2. Mix the above two obtained solutions, stir for 2 h, transfer to a 100 mL hydrothermal reaction kettle, and react at 120 °C for 16 h. After the reaction is completed and cooled to room temperature, centrifuge to collect the precipitate, wash the precipitate with DMF, and then soak the washed product in anhydrous methanol for 24 h, filter, and repeat three times to remove DMF. Finally, put the obtained product into a vacuum drying oven and dry at 60 °C for 12 h to obtain NH2-UiO-66;

[0058] S3. Put the obtained 36 mg of NH2-UiO-66, 1,3,6,8-tetrakis(4-formylphenyl)pyrene (84 mg, 0.136 mmol), 2-chloro-1,4-phenylenediamine (5.6 mg, 0.039 mmol), o-dichlorobenzene (0.9 mL), n-butanol (0.1 mL), and 6 M acetic acid aqueous solution (0.1 mL) into a 10 mL Pyrex tube, and ultrasonicate the mixture for 3 minutes. Degas the test tube three times using the freeze-pump-thaw technique and then seal it under vacuum;

[0059] S4. Heat the reactants at 120 °C for 3 days, and a precipitate is formed at the bottom of the test tube. Filter to obtain the precipitate, wash the precipitate with anhydrous tetrahydrofuran, extract with a Soxhlet extractor for 10 h to obtain a solid, and dry the solid under vacuum at 100 °C for 24 h to obtain the NH2-UiO-66 / PyCD-COF (3:7) heterojunction.

[0060] The NH2-UiO-66 / PyCD-COF (3:7) obtained in this example was measured for photocatalytic hydrogen production performance: 26.26 mmol·g -1 ·h -1 。

[0061] Example 4

[0062] This example provides a method for preparing an NH2-UiO-66 / PyCD-COF heterojunction photocatalyst, and the steps are as follows:

[0063] S1. Add 0.54 mmol of ZrCl4 to a mixed solution of 30 mL of DMF and hydrochloric acid (V DMF :V HCl = 5:1), and ultrasonically dissolve to obtain solution A; add 0.54 mmol of 2-aminoterephthalic acid (BDC-NH2) to 10 mL of DMF, and ultrasonically dissolve to obtain solution B.

[0064] S2. Mix the two solutions obtained above, stir for 2 h, transfer to a 100 mL hydrothermal reaction kettle, and react at 120 °C for 16 h. After the reaction is completed and cooled to room temperature, centrifuge to collect the precipitate, wash the precipitate with DMF, and then soak the washed product in anhydrous methanol for 24 h, filter, and repeat three times to remove DMF. Finally, put the obtained product into a vacuum drying oven and dry at 60 °C for 12 h to obtain NH2-UiO-66.

[0065] S3. Put the obtained 56 mg of NH2-UiO-66, 1,3,6,8-tetrakis(4-formylphenyl)pyrene (84 mg, 0.136 mmol), 2-chloro-1,4-phenylenediamine (5.6 mg, 0.039 mmol), o-dichlorobenzene (0.9 mL), n-butanol (0.1 mL), and 6 M acetic acid aqueous solution (0.1 mL) into a 10 mL Pyrex tube, and ultrasonicate the mixture for 3 minutes. Degas the test tube three times using the freeze-pump-thaw technique and then seal it under vacuum.

[0066] S4. Heat the reactants at 120 °C for 3 days, and a precipitate is formed at the bottom of the test tube. Filter to obtain the precipitate, wash the precipitate with anhydrous tetrahydrofuran, extract with a Soxhlet extractor for 10 h to obtain a solid, and dry the solid under vacuum at 100 °C for 24 h to obtain the NH2-UiO-66 / PyCD-COF (4:6) heterojunction.

[0067] The obtained NH2-UiO-66 / PyCD-COF (4:6) in this example was measured for photocatalytic hydrogen production performance: 30.11 mmol·g -1 ·h -1 。

[0068] Example 5

[0069] This example provides a method for preparing an NH2-UiO-66 / PyCD-COF heterojunction photocatalyst. The steps are as follows:

[0070] S1. Add 0.54 mmol of ZrCl4 to a mixed solution of 30 mL of DMF and hydrochloric acid (V DMF :V HCl = 5:1), and ultrasonically dissolve to obtain solution A; add 0.54 mmol of 2-aminoterephthalic acid (BDC-NH2) to 10 mL of DMF, and ultrasonically dissolve to obtain solution B.

[0071] S2. Mix the two solutions obtained above, stir for 2 h, transfer to a 100 mL hydrothermal reaction kettle, and react at 120 °C for 16 h. After the reaction is completed and cooled to room temperature, centrifuge to collect the precipitate, wash the precipitate with DMF, and then soak the washed product in anhydrous methanol for 24 h, filter, and repeat three times to remove DMF. Finally, put the obtained product into a vacuum drying oven and dry at 60 °C for 12 h to obtain NH2-UiO-66.

[0072] S3, 84mg of NH2-UiO-66, 1,3,6,8-tetrakis (4-formylphenyl) pyrene (84mg, 0.136mmol), 2-chloro-1,4-p-phenylenediamine (5.6mg, 0.039mmol), o-dichlorobenzene (0.9mL), n-butyl alcohol (0.1mL) and 6M acetic acid aqueous solution (0.1mL) were placed in a 10mL Pyrex tube, and the mixture was ultrasonicated for 3 minutes. The test tube was degassed three times with a freeze pump-thaw technique, and then sealed under vacuum.

[0073] S4. The reactants were heated at 120°C for 3 days, and a precipitate was obtained by filtration at the bottom of the test tube. The precipitate was washed with anhydrous tetrahydrofuran and extracted with a Soxhlet extractor for 10 hours to obtain a solid. The solid was dried at 100°C under vacuum for 24 hours to obtain an NH2-UiO-66 / PyCD-COF (5:5) heterojunction.

[0074] The photocatalytic hydrogen production performance of NH2-UiO-66 / PyCD-COF (5:5) obtained in this example was measured: 25.66mmol·g -1 ·h -1 .

[0075] Comparative Example

[0076] This comparative example provides a method for preparing a PyCD-COF catalyst, the steps being:

[0077] 1,3,6,8-Tetra(4-formylphenyl)pyrene (84 mg, 0.136 mmol), 2-chloro-1,4-p-phenylenediamine (5.6 mg, 0.039 mmol), o-dichlorobenzene (0.9 mL), n-butanol (0.1 mL) and 6M acetic acid aqueous solution (0.1 mL) were placed in a 10 mL Pyrex tube, and the mixture was sonicated for 3 minutes. The test tube was degassed three times using a freeze pump-thaw technique and then sealed under vacuum.

[0078] The reactants were heated at 120°C for 3 days, and a precipitate was obtained by filtration at the bottom of the test tube. The precipitate was washed with anhydrous tetrahydrofuran and extracted with a Soxhlet extractor for 10 hours to obtain a solid. The solid was dried at 100°C under vacuum for 24 hours to obtain a PyCD-COF heterojunction.

[0079] Performance Testing

[0080] Example 1 The XRD diffraction pattern of the NH2-UiO-66 / PyCD-COF heterojunction photocatalyst is as follows: Figure 1 As shown, from Figure 1It can be seen that the XRD pattern shows the typical diffraction peaks of NH2-UiO-66 in PyCD-COF and PyCD-COF / NH2-UiO-66, indicating that the crystalline phases of PyCD-COF and NH2-UiO-66 have not changed after the growth of PyCD-COF / NH2-UiO-66.

[0081] The FT-IR spectrum of the NH2-UiO-66 / PyCD-COF heterojunction photocatalyst prepared in Example 1 is as Figure 2 shown. From Figure 2 it can be seen that the FT-IR measurement shows that the infrared spectrum of PyCD-COF / NH2-UiO-66 contains the characteristic adsorption peaks of PyCD-COF and NH2-UiO-66, and the presence of C-N confirms that NH2-UiO-66 has been successfully grown on PyCD-COF. In addition, the characteristic stretching vibration peaks of PyCD-COF / NH2-UiO-66 are slightly shifted compared with those of PyCD-COF, indicating a strong interaction between PyCD-COF and NH2-UiO-66 in PyCD-COF / NH2-UiO-66.

[0082] The UV-Vis spectrum of the NH2-UiO-66 / PyCD-COF heterojunction photocatalyst prepared in Example 1 is as Figure 3 shown. From Figure 3 it can be seen that NH2-UiO-66 has a narrow light absorption range, while the light absorption range of PyCD-COF basically covers the entire UV / Vis region. The NH2-UiO-66 / PyCD-COF heterojunction photocatalyst has similar optical properties to PyCD-COF and shows a similar light absorption range to it.

[0083] The SEM photograph of NH2-UiO-66 prepared in Example 1 through S1-S2 is as Figure 4 shown. From Figure 4 it can be seen that it is in the shape of uniformly sized cubic partial spherical particles.

[0084] The SEM photograph of PyCD-COF prepared in the comparative example is as Figure 5 shown. From Figure 5 it can be seen that the morphology of the parent material PyCD-COF is a flaky morphology.

[0085] The SEM photograph of the NH2-UiO-66 / PyCD-COF heterojunction photocatalyst prepared in Example 1 is as Figure 6 shown. NH2-UiO-66 particles are attached to the surface of PyCD-COF.

[0086] The TEM photograph of the NH2-UiO-66 / PyCD-COF heterojunction photocatalyst prepared in Example 1 is asFigure 7 As shown, it can be seen more clearly through a transmission electron microscope that NH2-UiO-66 particles are attached to the surface of PyCD-COF and are in close contact.

[0087] The nitrogen adsorption-desorption isotherms of the NH2-UiO-66 / PyCD-COF heterojunction photocatalysts prepared in Examples 1-5, the NH2-UiO-66 prepared in S1-S2 of Example 1, the PyCD-COF prepared in the comparative example, and MIX (indicating the physical mixture of NH2-UiO-66 and PyCD-COF) are as Figure 8 shown, from Figure 8 it can be seen that the specific surface area of NH2-UiO-66 is 809.273 m 2 / g, and the specific surface area of the prepared NH2-UiO-66 / PyCD-COF heterojunction photocatalyst has increased.

[0088] The photocatalytic hydrogen production performance of the NH2-UiO-66 / PyCD-COF heterojunction photocatalysts prepared in Examples 1-5, the NH2-UiO-66 prepared in S1-S2 of Example 1, and the PyCD-COF prepared in the comparative example is as Figure 9 shown, it can be seen that the photocatalytic performance of the prepared NH2-UiO-66 / PyCD-COF heterojunction photocatalyst has improved compared to that of single PyCD-COF. Among them, the photocatalytic hydrogen production performance of NH2-UiO-66 / PyCD-COF (4:6) is the highest, reaching 30.11 mmol·g -1 ·h -1 .

[0089] The steady-state fluorescence spectra of the NH2-UiO-66 / PyCD-COF heterojunction photocatalysts prepared in Examples 1-5, the NH2-UiO-66 prepared in S1-S2 of Example 1, and the PyCD-COF prepared in the comparative example are as Figure 10 shown, from Figure 10 it can be seen that compared with single PyCD-COF, the fluorescence intensity of NH2-UiO-66 / PyCD-COF is significantly weakened, indicating that NH2-UiO-66 / PyCD-COF inhibits the recombination of photogenerated electron-hole pairs, which is beneficial to improving the photocatalytic hydrogen production efficiency.

Claims

1. A preparation method of an NH2-UiO-66 / PyCD-COF heterojunction photocatalyst, characterized in that, It includes the following steps: S1. Add zirconium chloride into the mixed solution of DMF and hydrochloric acid, and ultrasonically dissolve it to obtain solution A; Add 2-aminoterephthalic acid into DMF, and ultrasonically dissolve it to obtain solution B; S2. Mix solution A and solution B, stir them, and then transfer them into a hydrothermal reaction kettle with a polytetrafluoroethylene lining. React at 120-125°C for 16-18 h. After the reaction is completed, cool it to room temperature. Separate the solid product, and then wash and dry it to obtain NH2-UiO-66; S3. Add the NH2-UiO-66, 1,3,6,8-tetrakis(4-formylphenyl)pyrene, and 2-chloro-1,4-phenylenediamine obtained in step S2 into the o-dichlorobenzene / n-butanol solution containing acetic acid. Put the obtained mixture into a Pyrex tube and ultrasonically mix it for 3-5 minutes. Use the freeze-pump-thaw technique to degas the test tube three times, and then seal it under vacuum; S4. React the mixture obtained in step S3 at 120-130°C for 3-5 days. Separate the solid product, and then wash, Soxhlet extract, and dry it to obtain the NH2-UiO-66 / PyCD-COF heterojunction photocatalyst.

2. The preparation method of the NH2-UiO-66 / PyCD-COF heterojunction photocatalyst according to claim 1, characterized in that, In step S1, the mixed solution of DMF and hydrochloric acid is formed by mixing DMF and concentrated hydrochloric acid at a volume ratio of 5:

1. For every 0.54 mmol of zirconium chloride in solution A, 30-50 mL of the mixed solution of DMF and hydrochloric acid is used. For every 0.54 mmol of 2-aminoterephthalic acid in solution B, 10-20 mL of DMF is used.

3. The preparation method of the NH2-UiO-66 / PyCD-COF heterojunction photocatalyst according to claim 1, wherein, In step S1, the molar ratio of zirconium chloride to 2-aminoterephthalic acid is 1:

1.

4. The preparation method of the NH2-UiO-66 / PyCD-COF heterojunction photocatalyst according to claim 1, characterized in that, In step S2, the washing and drying include: washing the precipitate with DMF, then soaking it in anhydrous methanol for 24 h and filtering it. Repeat the soaking and filtering many times to remove DMF; drying it under vacuum at 60-70°C for 12-15 h.

5. The preparation method of the NH2-UiO-66 / PyCD-COF heterojunction photocatalyst according to claim 1, characterized in that, In step S3, the mass of 1,3,6,8-tetrakis(4-formylphenyl)pyrene is 50%-90% of the total mass of NH2-UiO-66 and 1,3,6,8-tetrakis(4-formylphenyl)pyrene. The molar ratio of 2-chloro-1,4-phenylenediamine to 1,3,6,8-tetrakis(4-formylphenyl)pyrene is 0.2-0.3:

1.

6. The preparation method of the NH2-UiO-66 / PyCD-COF heterojunction photocatalyst according to claim 1, characterized in that, In step S3, the o-dichlorobenzene / n-butanol solution containing acetic acid is obtained by mixing 6 mol / L acetic acid aqueous solution, o-dichlorobenzene, and n-butanol at a volume ratio of 1:9:

1. For every 84 mg of 1,3,6,8-tetrakis(4-formylphenyl)pyrene, 1.1-2 mL of the o-dichlorobenzene / n-butanol solution containing acetic acid is used.

7. The preparation method of the NH2-UiO-66 / PyCD-COF heterojunction photocatalyst according to claim 1, wherein, In step S4, the washing, Soxhlet extraction, and drying include: washing the precipitate with anhydrous tetrahydrofuran, and extracting it with a Soxhlet extractor for 10-12 h; drying it under vacuum at 100-120°C for 24-30 h.

8. A NH2-UiO-66 / PyCD-COF heterojunction photocatalyst, characterized in that, It is prepared by the preparation method of the NH2-UiO-66 / PyCD-COF heterojunction photocatalysis according to any one of claims 1-7.

9. Use of the NH2-UiO-66 / PyCD-COF heterojunction photocatalyst as described in claim 8, characterized in that, It is used for photocatalytic hydrogen production.

10. Use of the NH2-UiO-66 / PyCD-COF heterojunction photocatalyst according to claim 9, characterized in that, The steps of photocatalytic hydrogen production include: Add the NH2-UiO-66 / PyCD-COF composite photocatalyst to an ascorbic acid solution with a concentration of 0.1 mol / L. For every 30 mL of the ascorbic acid solution, use 5 - 10 mg of the NH2-UiO-66 / PyCD-COF composite photocatalyst. Drop in chloroplatinic acid for Pt loading, and the mass of the loaded Pt is 2% of the mass of the NH2-UiO-66 / PyCD-COF composite photocatalyst. Then, pass nitrogen into the solution for half an hour to remove the oxygen in the solution. Next, irradiate the quartz tube under a 500 W xenon lamp for 6 h for the photocatalytic reaction.

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