Highly crystalline perylene imide-naphthalene imide heterojunction and preparation method and application thereof

Abstract

The application belongs to the technical field of photocatalytic materials, and relates to a high-crystalline perylene imide-naphthalene imide heterojunction, a preparation method and application thereof, and comprises the following steps: 3,4,9,10-perylene tetracarboxylic dianhydride, 1,4,5,8-naphthalene tetracarboxylic anhydride, ammonium sulfate and imidazole are mixed and heated, so that the two substances synchronously undergo terminal amidation in the presence of ammonium sulfate to generate perylene imide and naphthalene imide respectively; after the reaction is completed, hydrochloric acid solution is added to the reaction system to remove the imidazole, so that the reaction system is changed from a good solvent environment to a poor solvent environment, and the perylene imide and the naphthalene imide are synchronously self-assembled through a pi-pi stacking effect to form a high-crystalline perylene imide-naphthalene imide heterojunction. The preparation method is simple, controllable, green and environment-friendly, the obtained heterojunction has high crystallinity and good dispersity, and can be widely applied to the field of photocatalytic overall water splitting.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic materials technology, and relates to a highly crystalline perylene imide-naphthalene imide heterojunction, its preparation method, and its application. Background Technology

[0002] Organic semiconductor photocatalytic materials have become a new hot research area in the field of photocatalysis in the past decade. 3,4,9,10-perylenetetracarboxylic acid diimide (peryleneimide, abbreviated as PDINH) and its derivatives are among the best n-type organic semiconductor materials currently available, possessing very unique photoelectrochemical properties and excellent light and thermal stability.

[0003] In recent years, PDINH and its derivatives have attracted widespread attention from photocatalysis researchers due to their broad spectral response range and excellent carrier migration performance. Modified materials based on PDINH exhibit excellent photocatalytic water splitting and oxygen production performance, showing broad application prospects in the environmental and energy fields.

[0004] However, due to the intrinsic band structure of PDINH, molecular modification alone is insufficient to meet the thermodynamic requirements for photocatalytic water splitting (simultaneous oxygen and hydrogen production). 1,4,5,8-Naphthalenetetracarboxylic acid diimide (NDINH) possesses a similar molecular structure and packing characteristics to PDINH, and its intrinsic band structure meets the requirements for hydrogen production in photocatalytic water splitting. Theoretically, if an effective composite of PDINH and NDINH can be achieved to construct a Z-shaped heterojunction, complete water splitting may be realized.

[0005] Inspired by plant photosynthesis, semiconductor-based Z-shaped artificial photosynthesis systems have been widely used for photocatalytic water splitting. Currently reported important Z-shaped heterojunctions include SrTiO3 / BiVO4, SrTiO3 / WO3, Ta3N5 / WO3, metal sulfides / TiO2, and black phosphorus / BiVO4. However, most of these Z-shaped heterojunctions contain transition metals, resulting in high preparation costs and potential heavy metal pollution. Therefore, in the field of photocatalytic water splitting, the development of metal-free, all-organic Z-shaped heterojunctions has shown great potential and has become one of the current research hotspots. Despite the advantages of all-organic Z-shaped heterojunctions, effectively combining PDINH and NDINH materials to form a heterojunction with high crystallinity, tight interfacial contact, and high charge separation efficiency remains a pressing technical problem to be solved in this field. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a highly crystalline perylene imide-naphthalene imide heterojunction, its preparation method, and its application, thereby overcoming the technical defects of existing inorganic Z-type heterojunctions, such as high preparation cost, easy heavy metal pollution, and difficulty in achieving efficient simultaneous amidation and self-assembly crystallization in existing all-organic heterojunctions.

[0007] This invention is achieved through the following technical solution: The first aspect provides a method for preparing highly crystalline peryleneimide-naphthaleneimide heterojunctions, comprising: 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) and 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA) were added to imidazole. Under the action of ammonium sulfate, PTCDA and NTCDA underwent a terminal amidation reaction to generate 3,4,9,10-perylenetetracarboxylic diimide (peryleneimide, PDINH) and 1,4,5,8-naphthalenetetracarboxylic diimide (naphthaleneimide, NDINH), respectively. After the amidation reaction is complete, hydrochloric acid solution is added to the reaction system to remove imidazole, thereby inducing perylene imide and naphthalene imide to self-assemble through π-π stacking to obtain a highly crystalline perylene imide-naphthalene imide heterojunction.

[0008] Preferably, the molar ratio of 3,4,9,10-perylenetetracarboxylic dianhydride and 1,4,5,8-naphthalenetetracarboxylic anhydride is 1:10 to 10:1.

[0009] Preferably, the mass ratio of imidazole to ammonium sulfate is 5:1 to 30:1.

[0010] Preferably, the imidazole acts as a good solvent during the reaction stage to disperse 3,4,9,10-perylenetetracarboxylic dianhydride and 1,4,5,8-naphthalenetetracarboxylic anhydride into a monomolecular state. The hydrochloric acid solution acts as a poor solvent to amplify the π-conjugation interaction between molecules after removing the imidazole, inducing peryleneimide and naphthaleneimide to undergo simultaneous intermolecular π-π stacking self-assembly, forming a highly crystalline peryleneimide-naphthaleneimide heterojunction.

[0011] Preferably, the specific conditions for the amidation reaction are: reaction temperature of 140~160 ℃, reaction stirring speed of 400~600 r / min, and reaction time of 4~5 h.

[0012] Preferably, the specific operation for removing imidazole with hydrochloric acid solution is as follows: cooling the reaction system to 90~100 ℃, adding hydrochloric acid solution, and stirring to dissolve imidazole; the stirring speed is 400~600 r / min, and the stirring time is 12~16 h.

[0013] Preferably, the concentration of hydrochloric acid in the hydrochloric acid solution is 3~5 mol / L.

[0014] Preferably, the highly crystalline perylene imide-naphthalene imide heterojunction has a Z-shaped band structure.

[0015] The second aspect provides a highly crystalline perylene imide-naphthalene imide heterojunction, which is prepared by the aforementioned method for preparing a highly crystalline perylene imide-naphthalene imide heterojunction.

[0016] The third aspect provides an application of highly crystalline perylene imide-naphthalene imide heterojunction in photocatalytic water splitting.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects: This invention proposes a method for preparing highly crystalline perylene imide-naphthalene imide heterojunctions. A one-pot method is employed to simultaneously complete the terminal amidation reaction of two acid anhydrides (PTCDA and NTCDA) in an imidazole medium in the presence of ammonium sulfate. This avoids the component inhomogeneity and interfacial defects caused by stepwise synthesis or physical mixing, significantly simplifying the preparation process and reducing production costs. After the reaction, the imidazole is removed using hydrochloric acid solution, abruptly changing the system from a favorable solvent environment to a unfavorable solvent environment. This amplifies the intermolecular π-π interactions, inducing the simultaneous self-assembly of the in-situ generated perylene imide and naphthalene imide, thus successfully constructing a highly crystalline perylene imide-naphthalene imide heterojunction for photocatalytic water splitting. This heterojunction possesses excellent carrier migration capabilities due to its high crystallinity and achieves effective separation of photogenerated electron-hole pairs due to its Z-type band structure. The PDINH component meets the thermodynamic requirements for photocatalytic oxygen production, while the NDINH component meets the thermodynamic requirements for photocatalytic hydrogen production. The Z-type charge transport mechanism between the two components enables complete water splitting.

[0018] Furthermore, imidazole, as a good solvent and reaction medium, exhibits strong interactions with PTCDA and NTCDA molecules, dispersing them into unimolecular states. Simultaneously, ammonium sulfate, acting as a nitrogen source, transforms into a molten salt state under heating conditions, activating the ammonium and amidating the terminal O of PTCDA and NTCDA with N, generating the corresponding perylene imide (PDINH) and naphthalene imide (NDINH). Due to the good dispersibility and similar reactivity of the two anhydrides in imidazole, they can undergo simultaneous amidation reactions, avoiding the product heterogeneity issues that may result from stepwise synthesis. After the amidation reaction is complete, hydrochloric acid solution is added, dissolving and removing the imidazole, transforming the reaction system from a good solvent environment to a poor solvent environment. In the poor solvent, the interactions between solvent molecules and PDINH and NDINH molecules are significantly weakened, while the π-conjugation interactions between PDINH molecules (perylene nuclei), between NDINH molecules (naphthalene nuclei), and between PDINH and NDINH molecules (perylene nuclei and naphthalene nuclei) are amplified and become the dominant driving force. Driven by the aforementioned π-π stacking interaction, PDINH and NDINH molecules simultaneously undergo self-assembly, arranging themselves in an orderly manner along the π-π stacking direction to form a supramolecular heterojunction structure with a clearly defined donor-acceptor interface. Because the self-assembly process proceeds slowly and uniformly in a poor solvent, the resulting heterojunction exhibits high crystallinity, and the close molecular-level contact between PDINH and NDINH facilitates rapid separation of photogenerated carriers.

[0019] Furthermore, the preparation method of this invention is simple, highly controllable, reproducible, uses inexpensive and widely available raw materials, is green, safe, and environmentally friendly, improves production efficiency, reduces production costs, and is suitable for large-scale production. This invention utilizes an easy-to-operate heating and stirring method to achieve the efficient synthesis of highly crystalline peryleneimide-naphthaleneimide heterojunctions. The resulting Z-type heterojunction system exhibits excellent photocatalytic water splitting performance, good dispersibility, and stable storage. This method does not involve heavy metal chemical reagents during the reaction process, effectively avoiding environmental pollution problems. Moreover, due to the properties of PDINH and NDINH, it can be widely used in photocatalytic water splitting, artificial photosynthesis, organic pollutant degradation, and gas oxidation / reduction. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1The X-ray diffraction patterns of the highly crystalline PDINH-NDINH heterojunctions of Examples 1 to 5 of the present invention and Comparative Example 3 are shown. Figure 2 The X-ray diffraction patterns of the commercial PDINH of Comparative Example 1 and the PDINH of Example 6 are shown below. Figure 3 The X-ray diffraction patterns of the commercial NDINH of Comparative Example 2 and the NDINH of Example 7 are shown below. Figure 4 The images show the photocatalytic water splitting performance of the highly crystalline PDINH-NDINH heterojunction of Examples 1 to 5, the PDINH of Example 6, the NDINH of Example 7, and Comparative Example 3. Figure 5 This is a transmission electron microscope image of the highly crystalline PDINH-NDINH heterojunction of Example 1 of the present invention; Figure 6 The high-resolution transmission electron microscope images of the highly crystalline PDINH-NDINH heterojunction interface lattice fringes in Example 1 of this invention. Figure 7 The selected area diffraction spot of PDINH in the highly crystalline PDINH-NDINH heterojunction of Example 1 of the present invention; Figure 8 This is a schematic diagram of the band arrangement of PDINH and NDINH in Embodiments 6 and 7 of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0023] A method for preparing a highly crystalline peryleneimide-naphthaleneimide heterojunction includes: 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) and 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA) were added to imidazole. Under the action of ammonium sulfate, PTCDA and NTCDA underwent a simultaneous terminal amidation reaction to generate 3,4,9,10-perylenetetracarboxylic diimide (PDINH) and 1,4,5,8-naphthalenetetracarboxylic diimide (NDINH), respectively. After the amidation reaction is complete, hydrochloric acid solution is added to remove imidazole, thereby inducing perylene imide and naphthalene imide to self-assemble synchronously through π-π stacking to form a highly crystalline perylene imide-naphthalene imide heterojunction.

[0024] Ammonium sulfate plays multiple key roles in this invention: Ammonium sulfate, as a nitrogen source, transforms into a molten salt state under heating conditions and participates in the terminal amidation reaction of PTCDA and NTCDA, promoting their simultaneous conversion into PDINH and NDINH. Ammonium sulfate is used as a reaction promoter to optimize the amidation reaction efficiency and ensure that the two acid anhydrides are converted synchronously and uniformly in the imidazole medium. Ammonium sulfate also acts as a crystallization inducer. Its introduction helps to regulate the subsequent π-π stacking self-assembly process, and in conjunction with the conversion strategy from good solvent to poor solvent, promotes the formation of highly ordered supramolecular heterojunction structures with excellent crystallinity between PDINH and NDINH molecules.

[0025] Explained, imidazole is a good solvent for both PDINH and NDINH. After the amidation reaction, PDINH and NDINH remain molecularly dispersed in the imidazole system. Upon addition of hydrochloric acid solution (hydrochloric acid / water system), the imidazole is dissolved and removed, transforming the reaction system from a good solvent environment to a poor solvent environment. In the poor solvent, the interactions between solvent molecules and PDINH and NDINH molecules are significantly weakened, while the π-conjugation interactions between PDINH molecules (between perylene nuclei), between NDINH molecules (between naphthalene nuclei), and between PDINH and NDINH molecules (between perylene nuclei and naphthalene nuclei) are amplified and become the dominant driving force.

[0026] Driven by the aforementioned π-π stacking interaction, PDINH and NDINH molecules simultaneously undergo self-assembly, arranging themselves in an orderly manner along the π-π stacking direction to form a supramolecular heterojunction structure with a clearly defined donor-acceptor interface. Because the self-assembly process proceeds slowly and uniformly in a poor solvent, the resulting heterojunction exhibits high crystallinity, and the close molecular-level contact between PDINH and NDINH facilitates rapid separation of photogenerated carriers.

[0027] The resulting highly crystalline peryleneimide-naphthaleneimide heterojunction has a Z-shaped band structure, in which the PDINH component meets the thermodynamic requirements for photocatalytic oxygen production, and the NDINH component meets the thermodynamic requirements for photocatalytic hydrogen production. The Z-shaped charge transport mechanism between the two components enables complete water splitting.

[0028] As a preferred technical solution, the molar ratio of PTCDA to NTCDA is 1:10 to 10:1.

[0029] As a preferred technical solution, the mass ratio of imidazole to ammonium sulfate is 5:1 to 30:1.

[0030] As a preferred technical solution, the specific conditions for the amidation reaction are: reaction temperature of 140~160 ℃, stirring speed of 400~600 r / min, and reaction time of 4~5 h. This invention employs a one-pot synthesis method, eliminating the need for complex step-by-step operations or expensive equipment. The target product can be obtained through simple heating, stirring, and acid washing. The reaction conditions are mild, the raw materials are inexpensive and readily available, and the production efficiency is high, making it suitable for large-scale industrial production.

[0031] Explanatoryly, this invention employs a one-pot method to prepare highly crystalline perylene imide. Naphthalimide heterojunction is a synthesis process that uses imidazole as the reaction medium and ammonium sulfate as the nitrogen source, and mixes and heats the raw materials in one pot to achieve simultaneous amidation and self-assembly crystallization.

[0032] As a preferred technical solution, the specific operation for removing imidazole with hydrochloric acid solution is as follows: the mixture after reaction is cooled to 90~100 ℃, a hydrochloric acid solution with a concentration of 3~5 mol / L is added, and the mixture is stirred at 400~600 r / min for 12~16 h to fully dissolve the imidazole. In this invention, the hydrochloric acid solution acts as a poor solvent medium. By dissolving and removing imidazole (a good solvent) from the reaction system, the solvent environment changes from a strong intermolecular interaction (affinity solvation between imidazole and perylene imide and naphthalene imide molecules) to a weak interaction system. This amplifies the π-π conjugation driving force between perylene imide and naphthalene imide molecules, inducing them to simultaneously undergo intermolecular self-assembly behavior, forming a heterojunction with a supramolecular structure. Simultaneously, the acidic environment of the hydrochloric acid solution helps dissolve residual imidazole and promotes product purification, ensuring the uniformity of the crystallization process and improving crystallinity.

[0033] Explanatoryly, self-assembly refers to the process by which two or more different molecules spontaneously and collaboratively assemble under the drive of non-covalent interactions (such as π-π stacking) to jointly form a single crystalline phase (co-crystallization) heterostructure.

[0034] As a preferred technical solution, the preparation method further includes the steps of filtering the product, washing it with water until the supernatant is neutral, and then vacuum drying it.

[0035] The present invention also provides a highly crystalline perylene imide-naphthalene imide heterojunction, which is prepared by the above preparation method.

[0036] The highly crystalline peryleneimide-naphthaleneimide heterojunction of this invention possesses a Z-shaped band structure. PDINH and NDINH undergo simultaneous self-assembly at the molecular level, forming a tight donor-acceptor interface contact, which is beneficial for the effective separation of photogenerated electron-hole pairs. Compared with traditional inorganic Z-shaped heterojunctions, the preparation method of this invention does not use any transition metal or heavy metal reagents. The entire reaction process is green and safe, avoiding heavy metal pollution problems and meeting the requirements of green chemistry and sustainable development.

[0037] This invention also provides the application of the above-mentioned highly crystalline perylene imide-naphthalene imide heterojunction in photocatalytic water splitting.

[0038] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Example 1: Preparation of a highly crystalline peryleneimide-naphthaleneimide heterojunction (PN-1) Step 1: Mix 0.4 mmol PTCDA, 1.6 mmol NTCDA, 2 g ammonium sulfate and 25 g imidazole in a reaction vessel; heat and stir at 150 °C for 4 h at 500 r / min to obtain mixture A1.

[0040] Step 2: Cool mixture A1 to 90 °C, add 100 mL of 4 mol / L hydrochloric acid solution, and continue stirring at 500 r / min for 14 h to obtain mixture B1. Filter mixture B1, wash the filter cake repeatedly with deionized water until the supernatant is neutral, and finally vacuum dry to remove water to obtain the target product, denoted as PN-1.

[0041] The X-ray diffraction pattern of PN-1 is shown below. Figure 1 As shown, the morphology and structure under high-resolution transmission electron microscopy are as follows: Figure 5 As shown, the photocatalytic water splitting performance is as follows: Figure 4 As shown.

[0042] Example 2: Preparation of highly crystalline peryleneimide-naphthaleneimide heterojunction (PN-2) Step 1: Mix 1.0 mmol PTCDA, 1.0 mmol NTCDA, 3 g ammonium sulfate and 30 g imidazole in a reaction vessel; heat and stir at 150 °C for 5 h at 600 r / min to obtain mixture A2.

[0043] Step 2: Cool mixture A2 to 90 °C, add 100 mL of 5 mol / L hydrochloric acid solution, and continue stirring at 500 r / min for 16 h to obtain mixture B2. Filter mixture B2, wash with water until the supernatant is neutral, and vacuum dry to remove water to obtain the target product, denoted as PN-2.

[0044] The X-ray diffraction pattern of PN-2 is shown below. Figure 1 As shown, the photocatalytic water splitting performance is as follows: Figure 4 As shown.

[0045] Example 3: Preparation of highly crystalline peryleneimide-naphthaleneimide heterojunction (PN-3) Step 1: Mix 0.2 mmol PTCDA, 2.0 mmol NTCDA, 2 g ammonium sulfate and 18 g imidazole in a reaction vessel; heat and stir at 150 °C for 4 h at 500 r / min to obtain mixture A3.

[0046] Step 2: Cool mixture A3 to 90 °C, add 100 mL of 4 mol / L hydrochloric acid solution, and continue stirring at 500 r / min for 14 h to obtain mixture B3. Filter mixture B3, wash with water until the supernatant is neutral, and vacuum dry to remove water to obtain the target product, denoted as PN-3.

[0047] The X-ray diffraction pattern of PN-3 is shown below. Figure 1 As shown, the photocatalytic water splitting performance is as follows: Figure 4 As shown.

[0048] Example 4: Preparation of highly crystalline peryleneimide-naphthaleneimide heterojunction (PN-4) Step 1: Mix 1.2 mmol PTCDA, 1.8 mmol NTCDA, 3 g ammonium sulfate and 15 g imidazole in a reaction vessel; heat and stir at 140 °C and 600 r / min for 4.5 h to obtain mixture A4.

[0049] Step 2: Cool mixture A4 to 95 °C, add 100 mL of 5 mol / L hydrochloric acid solution, and continue stirring at 600 r / min for 12 h to obtain mixture B4. Filter mixture B4, wash with water until the supernatant is neutral, and vacuum dry to remove water to obtain the target product, denoted as PN-4.

[0050] The X-ray diffraction pattern of PN-4 is shown below. Figure 1 As shown, the photocatalytic water splitting performance is as follows: Figure 4 As shown.

[0051] Example 5: Preparation of highly crystalline peryleneimide-naphthaleneimide heterojunction (PN-5) Step 1: Mix 2.0 mmol PTCDA, 0.2 mmol NTCDA, 1 g ammonium sulfate and 30 g imidazole, place in a reaction vessel, and heat and stir at 400 r / min for 5 h at 160 °C to obtain mixture A5.

[0052] Step 2: Cool mixture A5 to 100 °C, add 100 mL of 3 mol / L hydrochloric acid solution, and continue stirring at 400 r / min for 16 h to obtain mixture B5. Filter mixture B5, wash with water until the supernatant is neutral, and vacuum dry to remove water to obtain the target product, denoted as PN-5.

[0053] The X-ray diffraction pattern of PN-5 is shown below. Figure 1 As shown, the photocatalytic water splitting performance is as follows: Figure 4 As shown.

[0054] Example 6: Preparation of highly crystalline perylene imide (PDINH) Step 1: Mix 25 g imidazole, 2 mmol PTCDA and 2 g ammonium sulfate in a reaction vessel, heat and stir at 150 °C for 4 h at 500 r / min to obtain mixture A6.

[0055] Step 2: Cool mixture A6 to 90 °C, add 100 mL of 4 mol / L hydrochloric acid solution, and continue stirring at 500 r / min for 14 h to obtain mixture B6. Filter mixture B6, wash with water until the supernatant is neutral, and vacuum dry to remove water to obtain the target product, denoted as PDINH.

[0056] Among them, the X-ray diffraction pattern of PDINH is as follows: Figure 2 As shown, the photocatalytic water splitting performance is as follows: Figure 4 As shown.

[0057] Example 7: Preparation of highly crystalline naphthaleneimide (NDINH) Step 1: Mix 25 g imidazole, 2 mmol NTCDA and 2 g ammonium sulfate in a reaction vessel, heat and stir at 150 °C for 4 h to obtain mixture A7.

[0058] Step 2: Cool mixture A7 to 90 °C, add 100 mL of 4 mol / L hydrochloric acid solution, and continue stirring at 500 r / min for 14 h to obtain mixture B7. Filter mixture B7, wash with water until the supernatant is neutral, and vacuum dry to remove water to obtain the target product, denoted as NDINH.

[0059] Among them, the X-ray diffraction pattern of NDINH is as follows: Figure 3 As shown, the photocatalytic water splitting performance is as follows: Figure 4 As shown.

[0060] Comparative Example 1: Commercial Perylene Imidamine (PDINH) Manufacturer: McLean, Product No.: N867094, Purity ≥95%.

[0061] Among them, the X-ray diffraction pattern of Commercial PDINH, such as Figure 2 As shown.

[0062] Comparative Example 2: Commercial NDINH Manufacturer: McLean, Product No.: P816993, Purity ≥99%.

[0063] Among them, the X-ray diffraction pattern of Commercial NDINH, such as Figure 3 As shown.

[0064] Comparative Example 3: Preparation of a commercial peryleneimide-naphthaleneimide heterojunction (C-PN-1) Using a rapid solvent dispersion method, a PDINH-NDINH heterojunction was synthesized as a control sample, named C-PN-1, using commercial perylene imide (Commercial PDINH) and commercial naphthalene imide (Commercial NDINH) as raw materials.

[0065] The specific steps are as follows: Take 0.4 mmol of commercial PDINH and 1.6 mmol of commercial NDINH, and disperse them together in 200 mL of concentrated sulfuric acid (98% by mass). Place the above mixture in an ultrasonic disperser and sonicate for 0.5 h to form a homogeneous mixed solution; Take another 1 L of deionized water and place it in a large-capacity beaker. Add the above mixed solution dropwise into the deionized water, controlling the dropping rate to 1~2 drops / second. Stir mechanically at a speed of 1000 r / min to make the mixed solution precipitate out quickly when it comes into contact with the unsuitable solvent (water).

[0066] After the addition was complete, the stirring was turned off, and the mixture was allowed to stand for 3 hours to precipitate. The precipitate was collected by centrifugation (8000 r / min, 10 min), and the supernatant was discarded. The precipitate was washed repeatedly with deionized water 3-5 times to remove residual sulfuric acid. The washed precipitate was placed in a freeze dryer and dried at -80 ℃ and a vacuum degree of less than 10 Pa for 24 hours to obtain the powdered target product, which is the control sample C-PN-1.

[0067] X-ray diffraction analysis of C-PN-1 yielded the following results: Figure 1 As shown (compared with the XRD spectrum of the embodiment of the present invention). The photocatalytic water splitting performance test results are as follows. Figure 4 As shown.

[0068] Testing and Characterization: Figure 1 The X-ray diffraction (XRD) patterns of the highly crystalline PDINH-NDINH heterojunctions prepared in Examples 1 to 5 of this invention and the sample of Comparative Example 3 are shown in the patterns. It can be clearly seen from the patterns that the PDINH-NDINH heterojunction samples of the PN-1, PN-2, PN-3, PN-4, and PN-5 series prepared by the one-pot method of this invention all simultaneously exhibit sharp, strong diffraction peaks at 24.94° and 27.07°, belonging to the supramolecular π-π stacking structure of PDINH, and a sharp diffraction peak at 28.13°, belonging to the supramolecular π-π stacking structure of NDINH. This indicates that the preparation method of this invention successfully constructs the heterojunctions. The sample yielded a stable PDINH-NDINH heterojunction structure, and the diffraction peaks of all the sample examples exhibited sharp peak shapes and high signal intensity, demonstrating excellent crystallinity. Furthermore, the sample examples with different raw material ratios and ammonium sulfate dosages all maintained a stable high crystallinity state, proving that the preparation process of this invention has good stability and universality. In contrast, the C-PN-1 control sample prepared by the rapid solvent dispersion method in Comparative Example 3 showed significantly broadened diffraction peaks and extremely low signal intensity, indicating crystallinity far inferior to the heterojunction prepared in the examples of this invention. This clearly demonstrates the significant advantage of the preparation process of this invention in improving the crystallinity of the material.

[0069] Figure 2The X-ray diffraction patterns of the commercial PDINH in Comparative Example 1 and the PDINH in Example 6 of this invention are shown. These patterns compare the crystallinity of the highly crystalline PDINH in Example 6 with that of the commercial PDINH in Comparative Example 1. The commercial PDINH generally exhibits lower peak heights and wider peak widths, especially the π-π packing diffraction peaks at 2θ of 24.94° and 27.07°, indicating lower crystallinity and poorer molecular packing order. In contrast, the highly crystalline PDINH in Example 6 exhibits significantly sharper diffraction peaks within the same 2θ range, with two particularly strong peaks at 24.94° and 27.07°, corresponding to the π-π packing characteristic diffraction of the supramolecular structure of PDINH. Compared to the commercial PDINH, the diffraction peak intensity of Example 6 is significantly increased, and the full width at half maximum (FWHM) is significantly reduced, indicating that the PDINH synthesized in this invention has higher crystallinity and a more regular molecular arrangement.

[0070] Figure 3 The X-ray diffraction patterns of the commercial NDINH from Comparative Example 2 and the NDINH from Example 7 are shown below. These patterns compare the crystallinity of the NDINH prepared by the molten salt substitution method in Example 7 with that of the commercial NDINH component in Comparative Example 2. The commercial NDINH generally exhibits lower peak heights and wider peak widths, especially the π-π packing diffraction peak at 28.13°, indicating poor crystallinity and disordered molecular packing. In contrast, the highly crystalline NDINH from Example 7 exhibits sharper and stronger characteristic diffraction peaks within the same 2θ range, with the peak at 28.13° being particularly prominent. This peak is attributed to the π-π packing structure of the NDINH supramolecular structure, indicating long-range order in molecular arrangement. This demonstrates that the NDINH synthesized in this invention also possesses excellent high crystallinity properties, far superior to commercial NDINH, laying a material foundation for constructing highly crystalline PDINH-NDINH heterojunctions.

[0071] Figure 4 The figures show the photocatalytic water splitting performance of the highly crystalline PDINH-NDINH heterojunctions of Examples 1 to 5, the highly crystalline PDINH of Example 6, the highly crystalline NDINH of Example 7, and Comparative Example 3. Performance test results show that the highly crystalline PDINH prepared in Example 6 and the highly crystalline NDINH prepared in Example 7 could not achieve photocatalytic water splitting in a pure water system, and could not produce hydrogen and oxygen products. However, the series of highly crystalline PDINH-NDINH heterojunctions prepared in this invention could successfully achieve photocatalytic water splitting, and simultaneously generate hydrogen and oxygen in a stoichiometric ratio strictly according to 2:1. Among them, the PN-1 sample prepared in Example 1 showed the most outstanding photocatalytic water splitting performance, with a hydrogen production rate of 18.26 μmolg. -1 h -1The oxygen production rate reached 9.15 μmol g. -1 h -1 The catalytic activity was 4.8 times that of the low-crystallinity control sample C-PN-1 in Comparative Example 3, which fully demonstrates that the high-crystallinity heterojunction structure is the core factor in improving the performance of photocatalytic water splitting, and also directly verifies the excellent application value of the heterojunction prepared in this invention in the field of photocatalytic water splitting.

[0072] comprehensive Figure 1 , Figure 2 , Figure 3 and Figure 4 Together, these findings demonstrate that the one-pot method employed in this invention not only enables the simultaneous amidation synthesis of heterojunction materials from PDINH and NDINH, but also produces materials with a crystallinity far exceeding that of commercially available samples. This high crystallinity provides the structural basis for forming a tight heterojunction interface, ultimately resulting in a highly crystalline Z-shaped heterojunction with efficient photocatalytic water splitting performance, thus achieving superior photocatalytic water splitting performance.

[0073] Figure 5 This is a transmission electron microscope (TEM) image of the highly crystalline PDINH-NDINH heterojunction of Example 1 of the present invention. The microstructure of the PN-1 heterojunction can be clearly observed by TEM characterization. The PDINH component exhibits a regular one-dimensional nanorod structure, while the NDINH component aggregates to form a nanoparticle morphology. The two components with different morphologies are uniformly distributed and in close contact within the material, and there is no obvious phase separation phenomenon, forming a continuous and complete heterojunction interface. Figure 6 The high-resolution transmission electron microscope (HRTEM) images of the highly crystalline PDINH-NDINH heterojunction interface in Embodiment 1 of this invention clearly show the lattice structure and interface features of the PN-1 heterojunction. The images show no disordered amorphous regions, but rather continuous and clear lattice fringes, further confirming the high crystallinity of the material at the microscopic level. The lattice fringes with a spacing of 0.738 nm correspond to the (020) crystal plane of PDINH, and the lattice fringes with a spacing of 0.597 nm belong to the (110) crystal plane of NDINH. The crystal planes of the two components achieve seamless connection at the heterojunction interface, forming an extremely tight interfacial contact. This lattice feature is consistent with... Figure 1 The XRD diffraction peak position analysis results are in high agreement, which verifies from the microscopic lattice structure level that the present invention has successfully prepared a highly crystalline PDINH-NDINH heterojunction.

[0074] Figure 7The selected area diffraction (SAED) pattern of PDINH in the highly crystalline PDINH-NDINH heterojunction of Example 1 of this invention shows a series of clear and regular diffraction spots, rather than diffuse diffraction rings, which directly demonstrates that the PDINH component in the heterojunction has good crystalline order. After precise calibration of the diffraction spots, it can be seen that these spots correspond to the PDINH ⁻¹(NDINH ⁻¹) of the heterojunction. ), ( ), ( )and( The crystal planes were further examined, and crystal diffraction confirmed that the PDINH component maintains a highly crystalline supramolecular structure in the heterojunction, providing a solid crystal structure guarantee for efficient charge transport and separation in photocatalytic reactions.

[0075] Figure 8 This diagram illustrates the band structure of highly crystalline PDINH and highly crystalline NDINH in Examples 6 and 7 of this invention. PDINH has a band gap of 1.72 eV, a conduction band potential of 0.06 V, a valence band potential of 1.78 V, and a Fermi level of 0.19 V. NDINH has a band gap of 2.62 eV, a conduction band potential of -0.95 V, a valence band potential of 1.67 V, and a Fermi level of -0.01 V. The two exhibit an alternating band structure with close Fermi levels, satisfying the band matching requirements of a Z-type heterojunction. After the heterojunction is formed, photogenerated electrons in the PDINH conduction band recombine with holes in the NDINH valence band, ultimately retaining the strong reducing power of the NDINH conduction band and the strong oxidizing power of the PDINH valence band. This simultaneously satisfies the thermodynamic potential requirements for photocatalytic water splitting to produce hydrogen and oxygen, providing an electronic structure basis for the high-efficiency photocatalytic performance of the heterojunction.

[0076] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0077] Unless otherwise specified, all the technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0078] In this invention, unless otherwise specified, percentage (%) or parts refer to weight percentage or parts relative to the composition.

[0079] Unless otherwise specified, the components or preferred components involved in this invention can be combined with each other to form new technical solutions.

[0080] In this invention, unless otherwise specified, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "6~22" indicates that all real numbers between "6~22" have been listed in this document, and "6~22" is simply a shortened representation of these numerical combinations.

[0081] The "scope" disclosed in this invention can be in the form of a lower limit and an upper limit, and can be one or more lower limits and one or more upper limits, respectively.

[0082] In this invention, the term "and / or" as used herein refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes such combinations.

[0083] In this invention, unless otherwise stated, the various reactions or operation steps may be performed sequentially or in a particular order. Preferably, the reaction methods described herein are performed sequentially.

[0084] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be used in this invention.

[0085] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing a highly crystalline peryleneimide-naphthaleneimide heterojunction for photocatalytic water splitting, characterized in that, include: When 3,4,9,10-perylenetetracarboxylic dianhydride and 1,4,5,8-naphthalenetetracarboxylic anhydride are added to imidazole, under the action of ammonium sulfate, 3,4,9,10-perylenetetracarboxylic dianhydride and 1,4,5,8-naphthalenetetracarboxylic anhydride undergo terminal amidation reaction to generate peryleneimide and naphthaleneimide, respectively. After the amidation reaction is complete, hydrochloric acid solution is added to the reaction system to remove imidazole, thereby inducing perylene imide and naphthimide to self-assemble through π-π stacking to obtain highly crystalline perylene imide-naphthalene imide heterojunction; The molar ratio of the 3,4,9,10-perylenetetracarboxylic anhydride and the 1,4,5,8-naphthalenetetracarboxylic anhydride is 1:

4. The imidazole acts as a good solvent during the reaction stage to disperse 3,4,9,10-perylenetetracarboxylic dianhydride and 1,4,5,8-naphthalenetetracarboxylic anhydride into a unimolecular state. The hydrochloric acid solution, acting as a poor solvent, amplifies the π-conjugation interaction between molecules after removing imidazole, inducing perylene imide and naphthalene imide to simultaneously undergo intermolecular π-π stacking self-assembly, forming a highly crystalline perylene imide-naphthalene imide heterojunction.

2. The method for preparing a highly crystalline peryleneimide-naphthaleneimide heterojunction for photocatalytic water splitting according to claim 1, characterized in that, The mass ratio of imidazole to ammonium sulfate is 5:1 to 30:

1.

3. The method for preparing a highly crystalline peryleneimide-naphthaleneimide heterojunction for photocatalytic water splitting according to claim 1, characterized in that, The specific conditions for the amidation reaction are: reaction temperature of 140~160 ℃, stirring speed of 400~600 r / min, and reaction time of 4~5 h.

4. The method for preparing a highly crystalline peryleneimide-naphthaleneimide heterojunction for photocatalytic water splitting according to claim 1, characterized in that, The specific operation for removing imidazole with hydrochloric acid solution is as follows: the reaction system is cooled to 90~100℃, hydrochloric acid solution is added, and the imidazole is dissolved by stirring; the stirring speed is 400~600 r / min, and the stirring time is 12~16 h.

5. The method for preparing a highly crystalline peryleneimide-naphthaleneimide heterojunction for photocatalytic water splitting according to claim 4, characterized in that, The concentration of hydrochloric acid in the hydrochloric acid solution is 3~5 mol / L.

6. The method for preparing a highly crystalline peryleneimide-naphthaleneimide heterojunction for photocatalytic water splitting according to claim 1, characterized in that, The highly crystalline perylene imide-naphthalene imide heterojunction has a Z-shaped band structure.

7. A highly crystalline peryleneimide-naphthaleneimide heterojunction for photocatalytic water splitting, characterized in that, It is prepared by any one of the methods for preparing a highly crystalline peryleneimide-naphthaleneimide heterojunction for photocatalytic water splitting according to any one of claims 1 to 6.

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