A sulfonic acid group modified naphthalimide photocatalyst and a preparation method and application thereof
By generating a sulfonic acid-modified naphthalimide photocatalyst through a one-step condensation reaction, the problems of light absorption and carrier separation in existing photocatalytic systems are solved, and a highly efficient photocatalytic total water splitting reaction in the aqueous phase is realized.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NORTHEAST GASOLINEEUM UNIV
- Filing Date
- 2026-01-21
- Publication Date
- 2026-05-29
Smart Images
Figure CN122103142A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of photocatalytic materials technology, and in particular to a sulfonic acid-modified naphthalimide photocatalyst, its preparation method, and its application. Background Technology
[0002] With the development of solar energy conversion technology, photocatalytic whole-phase water splitting is considered a sustainable way to obtain clean hydrogen energy. However, currently available photocatalytic systems still face many performance bottlenecks, such as limited visible light absorption, difficulty in effectively separating photogenerated carriers, and slow overall reaction kinetics, making it difficult for practical catalytic efficiency to meet application requirements. To overcome these limitations, developing novel photocatalytic materials with tunable bandgap, good interfacial reaction characteristics, and stable aqueous phase behavior has become a research focus.
[0003] Naphthalimide (NDI)-based organic semiconductor materials have attracted attention in photocatalytic reaction systems due to their high electron affinity, low LUMO energy level, and good structural designability. However, unmodified NDI molecules often exhibit weak aqueous dispersion and lack sufficient active sites, which hinders carrier migration and surface redox reactions, thus limiting their further application in overall water splitting systems. Functionalization modification is an important strategy for improving the performance of NDI materials.
[0004] Currently reported NDI-based photocatalytic systems rely on complex organic synthesis routes, multi-step modification procedures, or metal ion-assisted assembly methods, which are detrimental to structure control, yield improvement, and large-scale preparation. Furthermore, some systems struggle to achieve continuous, regular, and tunable π–π stacking structures during self-assembly, affecting electron transport efficiency. The lack of clear crystal structure information also makes it difficult to establish structure-performance correlation mechanisms, thus limiting further optimization of the material systems. Summary of the Invention
[0005] In view of this, the purpose of this invention is to provide a sulfonic acid-modified naphthalimide photocatalyst, its preparation method and application. The prepared naphthalimide photocatalyst has good aqueous phase stability, excellent light absorption, electron separation and surface reaction activity, and can be applied to photocatalytic total water splitting reaction.
[0006] The following is a summary of the disclosure of this invention to provide a basic understanding of some aspects. This summary is not intended to identify key or important elements, nor is it intended to limit the implementation or any limitations of the claims. Furthermore, this summary provides a simplified overview of some aspects that may be described in more detail in other parts of the disclosure of this invention.
[0007] The present invention solves the above-mentioned technical problems through the following technical means: In a first aspect, embodiments of the present invention provide a method for preparing a sulfonic acid-modified naphthalimide photocatalyst. The preparation method uses 1,4,5,8-naphthalenetetracarboxylic anhydride and aminosulfonic acid as basic building blocks, generates a precursor through a one-step condensation reaction, and then induces crystallization using a poor solvent to obtain a nanorod-structured naphthalimide photocatalyst.
[0008] In conjunction with the first aspect, in some embodiments, the preparation method includes the following steps: (1) Take aminosulfonic acid and 1,4,5,8-naphthalenetetracarboxylic anhydride and place them in N,N-dimethylformamide solvent, and condense them at 110-140℃ for 6-12h to obtain a precursor solution; (2) The precursor solution was naturally cooled to room temperature, and then a poor solvent was added to promote precipitation, resulting in a suspension; (3) The suspension was filtered, and the collected solid product was washed and dried to obtain the naphthalimide photocatalyst.
[0009] In conjunction with the first aspect, in some embodiments, the molar ratio of the aminosulfonic acid and 1,4,5,8-naphthalenetetracarboxylic anhydride is 2:1.
[0010] In conjunction with the first aspect, in some embodiments, the molar volume ratio of the 1,4,5,8-naphthyltetracarboxylic anhydride and N,N-dimethylformamide is 2 mmol: (25-35) mL.
[0011] In conjunction with the first aspect, in some embodiments, the precursor solution is prepared as follows: Aminosulfonic acid was added to N,N-dimethylformamide and stirred, then ultrasonically dispersed. Subsequently, 1,4,5,8-naphthalenetetracarboxylic anhydride was added and stirred, then ultrasonically mixed. The resulting mixture was subjected to a condensation reaction at 110–140 °C for 6–12 h under reflux conditions to obtain a precursor solution.
[0012] In conjunction with the first aspect, in some embodiments, the solid product is washed with tetrahydrofuran 2 to 4 times.
[0013] In conjunction with the first aspect, in some embodiments, the solid product is washed and then vacuum dried at 55–70°C for 5–10 h to obtain a naphthalimide photocatalyst.
[0014] In conjunction with the first aspect, in some embodiments, the undesirable solvent is isopropanol or tert-butanol.
[0015] The present invention discloses a method for preparing sulfonic acid-modified naphthalimide photocatalysts. Using 1,4,5,8-naphthalenetetracarboxylic anhydride and aminosulfonic acid as basic building blocks, a functionalized precursor is generated through a one-step condensation reaction. This precursor is then combined with a poor solvent-induced crystallization strategy to achieve supramolecular ordered assembly, resulting in a well-defined nanorod structure. This preparation method is simple, mild, and controllable. By controlling the reaction conditions and the solvent-induced crystallization process, the π–π packing degree, molecular dipole arrangement, and surface active site distribution of the catalyst can be optimized, thereby improving the efficiency of photogenerated electron-hole separation, the light absorption range, and the overall water splitting activity.
[0016] Secondly, embodiments of the present invention provide a sulfonic acid-modified naphthalimide photocatalyst, which is prepared using the preparation method described in the first aspect.
[0017] The sulfonic acid-modified naphthalimide photocatalyst of this invention achieves synergistic optimization of the material's molecular dipole, hydrophilicity, photogenerated carrier separation efficiency, and surface reactive sites by introducing sulfonic acid functional groups onto the naphthalimide framework. This allows its band structure to simultaneously meet the thermodynamic requirements of water reduction (hydrogen production) and oxidation (oxygen production). The introduction of sulfonic acid groups not only enhances the material's stability in the aqueous phase but also promotes surface proton transfer and intermediate adsorption, thereby improving the overall water splitting efficiency. The sulfonic acid-modified naphthalimide photocatalyst of this invention has the advantages of tunable structure and scalable preparation.
[0018] Thirdly, embodiments of the present invention also provide the application of the sulfonic acid-modified naphthalimide photocatalyst described in the second aspect in the photocatalytic total water splitting reaction.
[0019] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages: (1) The synthesis path is simple and efficient with high integration. In existing technologies, the functionalization of organic semiconductors such as naphthalimide often requires a multi-step synthetic strategy of "first constructing the core framework, then introducing functional groups step by step." This process is lengthy, limits overall yield, and each step may introduce new purification challenges. The preparation method of this invention employs a "one-step condensation" strategy, directly reacting a monomer containing a functional group (aminosulfonic acid) with 1,4,5,8-naphthalenetetracarboxylic anhydride, integrating functionalization and molecular framework construction into a single reaction step. Aminosulfonic acid possesses both an amino group that reacts with the anhydride and a sulfonic acid group that provides functionality, making it an ideal "multifunctional monomer." The preparation method of this invention fundamentally simplifies the process route (reducing it from multiple steps to one), reduces intermediate separation and purification steps, significantly improves synthetic efficiency, reduces time and material costs, and avoids the accumulation of byproducts that may occur in multi-step reactions, thus facilitating the acquisition of a final product with higher purity and a more defined structure.
[0020] (2) The reaction conditions are mild and controllable, and the environmental protection is good. Some condensation reactions in existing technologies may require strong acid catalysts, high-boiling-point toxic solvents (such as quinoline), or extremely high reaction temperatures (>180°C), placing high demands on equipment, consuming large amounts of energy, and resulting in complex post-treatment and the generation of large quantities of environmentally unfriendly waste liquid. The preparation method of this invention uses N,N-dimethylformamide (DMF) as a solvent, carrying out a reflux reaction at a relatively mild temperature. Post-treatment employs precipitation with a poor solvent (e.g., isopropanol) followed by washing with tetrahydrofuran (THF), avoiding frequent adjustments of strong acid / base. DMF is a common and excellent polar aprotic solvent, effectively dissolving reactants and promoting condensation reactions at moderate temperatures, reducing energy consumption and safety risks. Using isopropanol as a green, low-toxicity solvent to precipitate the product replaces the harsh acid-base treatments of traditional methods, reducing equipment corrosion and greatly simplifying the waste liquid treatment process.
[0021] (3) The introduction of functional groups is precise, and the product performance is promising. In existing technologies, simultaneously introducing photoactive units and hydrophilic or surface reaction sites into photocatalysts often relies on complex molecular design or multi-step copolymerization processes, making it difficult to achieve efficient and controllable structural regulation. The preparation method of this invention achieves directional functionalization modification by precisely introducing aminosulfonic acid groups into the core of naphthalimide (NDI) in a one-step condensation reaction, thereby bringing about multiple performance optimizations: ① Improved hydrophilicity and interfacial reaction performance: The sulfonic acid group (-SO3H) is a strongly polar functional group, which significantly enhances the dispersibility of the catalyst in the aqueous phase and increases the contact area between water molecules and the catalyst. At the same time, its acidic hydrogen can act as a proton transfer medium, promoting the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) through hydrogen bonding, and reducing the surface reaction energy barrier.
[0022] ② Enhanced molecular dipole and photogenerated carrier separation: The introduction of sulfonic acid groups increases the dipole moment of NDI molecules, which can form a built-in electric field in supramolecular assembly, thereby driving the directional migration of photogenerated electrons and holes, improving charge separation efficiency, and suppressing carrier recombination.
[0023] ③ Optimize light absorption performance: The electron attraction effect of S element and sulfonic acid group can adjust the energy level structure of NDI framework, slightly reduce LUMO energy level and appropriately adjust HOMO energy level, so that the material absorbs more light in the visible light range. At the same time, thermodynamically, it is beneficial to drive proton reduction hydrogen production (HER) and water oxidation oxygen production (OER) reaction simultaneously, so as to achieve the efficient progress of the overall water splitting reaction.
[0024] ④ Regulation of π–π stacking and electron transport channels: The steric hindrance of sulfonic acid groups and intermolecular forces help to form a regular π–π stacking structure, build efficient electron transport channels, improve the migration efficiency of photogenerated electrons in the catalyst, and provide a guarantee for the overall improvement of photocatalytic water splitting performance.
[0025] ⑤ Small size morphology and high crystallinity: By precisely controlling the self-assembly conditions, a regular morphology and a highly crystalline structure at the nanoscale can be obtained. This small size morphology and highly ordered crystal structure not only increase the specific surface area of the material and expose more reactive sites, but also shorten the migration path of photogenerated carriers and promote rapid electron conduction, thereby significantly improving the overall photocatalytic water splitting reaction activity.
[0026] (4) The process flow is stable and easy to scale up. The preparation method of this invention employs standardized unit operations such as conventional solution heating and reflux, precipitation, filtration, washing, and drying. All reagents and conditions are common chemical options. The homogeneous reaction system in DMF facilitates heat and mass transfer during large-scale production. Simple isopropanol precipitation allows for broader and easier control of solid-liquid separation conditions. THF washing effectively removes unreacted monomers and oligomers, and the purification operation is simple and reliable. The entire process has high tolerance for error at each stage, and the process parameters have a selectable range, exhibiting excellent repeatability and potential for large-scale production. Attached Figure Description
[0027] Figure 1 It is the reaction formula of 1,4,5,8-naphthalenetetracarboxylic anhydride and aminosulfonic acid; Figure 2 It is the reaction formula of 1,4,5,8-naphthalenetetracarboxylic anhydride and 2-aminobenzenesulfonic acid; Figure 3 It is the reaction formula of 1,4,5,8-naphthalenetetracarboxylic anhydride and 3-aminobenzenesulfonic acid; Figure 4 This is a scanning electron microscope image of the naphthalimide photocatalyst NDI-SO3H in Example 1; Figure 5 This is a scanning electron microscope image of the naphthalimide photocatalyst NDI-2ABSA in Example 2; Figure 6 This is a scanning electron microscope image of the naphthalimide photocatalyst NDI-3ABSA in Example 3; Figure 7 This is a transmission electron microscope image of the naphthalimide photocatalyst NDI-SO3H in Example 1; Figure 8 These are the X-ray diffraction patterns of NDI-SO3H from Example 1, NDI-2ABSA from Example 2, and NDI-3ABSA from Example 3; Figure 9 The X-ray diffraction pattern of NDI-SO3H in Example 1 and its refined pattern are shown below. Figure 10 The X-ray diffraction pattern and its refined pattern of NDI-2ABSA in Example 2 are shown. Figure 11 The X-ray diffraction pattern and its refined pattern of NDI-3ABSA in Example 3 are shown. Figure 12 The crystal structures are those of NDI-SO3H in Example 1, NDI-2ABSA in Example 2, and NDI-3ABSA in Example 3; Figure 13 This is a comparison chart of the photocatalytic hydrogen production performance of NDI-SO3H (Example 1), NDI-2ABSA (Example 2), and NDI-3ABSA (Example 3) with g-C3N4. Figure 14 This is a comparison chart of the photocatalytic oxygen production performance of NDI-SO3H (Example 1), NDI-2ABSA (Example 2), and NDI-3ABSA (Example 3) with g-C3N4; Figure 15 This is a graph showing the photocatalytic water splitting performance of NDI-SO3H in Example 1; Figure 16 This is a comparison chart of the photocatalytic water splitting performance of NDI-SO3H (Example 1), NDI-2ABSA (Example 2), and NDI-3ABSA (Example 3) with g-C3N4. Detailed Implementation
[0028] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.
[0029] Where specific experimental steps or conditions are not specified in the examples, they can be performed according to the conventional experimental steps or conditions described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.
[0030] The method for preparing the sulfonic acid-modified naphthalimide photocatalyst of this application includes the following steps: In step S1, the molar ratio of aminosulfonic acid to 1,4,5,8-naphthalenetetracarboxylic anhydride is 2:1, and the molar volume ratio of 1,4,5,8-naphthalenetetracarboxylic anhydride to N,N-dimethylformamide is 2 mmol:(25-35) mL. Aminosulfonic acid is added to N,N-dimethylformamide and stirred, then ultrasonically dispersed. Subsequently, 1,4,5,8-naphthalenetetracarboxylic anhydride is added and stirred, then ultrasonically mixed. The resulting mixture is then subjected to a condensation reaction at 110-140℃ for 6-12 h under reflux conditions to obtain the precursor solution. This step introduces the aminosulfonic acid group into the naphthalimide skeleton through the condensation reaction of amino groups and anhydrides, achieving functional modification of the molecular structure.
[0031] In step S2, the precursor solution is naturally cooled to room temperature, and then a poor solvent is added to promote precipitation, resulting in a suspension. This step, by adding a poor solvent to induce crystallization, facilitates the separation of the final product from the reaction solution and improves the recovery rate. The molar volume ratio of 1,4,5,8-naphthalenetetracarboxylic anhydride to the poor solvent is 2 mmol : (25–35) mL.
[0032] In step S3, the suspension is filtered through a 0.45 μm organic filter membrane, and the collected solid product is washed 2–4 times with tetrahydrofuran. The washed solid product is then vacuum dried at 55–70 °C for 5–10 h to obtain the naphthalimide photocatalyst. This step involves washing the obtained solid three times with tetrahydrofuran to remove residual reactants and solvent impurities.
[0033] The above preparation method uses aminosulfonic acid as an "integrated functional monomer" and reacts with 1,4,5,8-naphthalenetetracarboxylic anhydride in N,N-dimethylformamide solvent under mild heating conditions of 110℃ to 140℃ in a one-step condensation reaction to directly prepare functionalized naphthaleneimide derivatives. On the one hand, it integrates the amino group (reaction site) and the sulfonic acid group (functional group) into the same molecule, simultaneously completing the construction of the covalent skeleton (forming imide bonds) and the precise introduction of the functional group (-SO3H) in a single reaction step. On the other hand, the limitation of the condensation reaction temperature ensures the full dissolution and activation of the reactants, efficiently driving the condensation reaction while avoiding high-temperature side reactions. This is a direct technical guarantee for achieving the advantages of "mild" and "controllable" operation. The above preparation method uses poor solvent-induced crystallization, completely eliminating the complex post-processing steps of traditional pH adjustment and extraction. It utilizes the solvation difference between isopropanol and the reaction system (DMF) to achieve efficient and selective product separation; moreover, the operation is extremely simple, significantly reducing waste liquid generation and product loss. The above preparation method introduces aminosulfonic acid groups into the NDI framework through a one-step condensation reaction, achieving the simultaneous construction of the molecular framework and functional groups. The introduction of sulfonic acid groups not only enhances the hydrophilicity and hydrogen bonding ability of the material, but also increases the molecular dipole moment, which is beneficial for aqueous phase dispersion, ordered intermolecular interactions, and separation of photogenerated carriers. Subsequently, under suitable solvent conditions, molecular self-assembly is promoted to form a nanoscale ordered stacked structure, while simultaneously achieving π–π stacking arrangement and optimized crystal crystallinity.
[0034] The following examples 1-10 will provide a detailed description of the sulfonic acid-modified naphthalimide photocatalyst of the present invention and its preparation method.
[0035] Example 1 The reaction formula involved in this embodiment is as follows: Figure 1 As shown. The preparation method of the sulfonic acid-modified naphthalimide photocatalyst in this embodiment is as follows: In a three-necked flask equipped with a magnetic stirrer, 4 mmol (388.4 mg) of aminosulfonic acid and 30 mL of N,N-dimethylformamide were added. The mixture was stirred at room temperature for 5 min, followed by sonication for 10 min to ensure complete dispersion and dissolution of the raw materials. Then, 2 mmol (536.4 mg) of 1,4,5,8-naphthalenetetracarboxylic anhydride was added, and the mixture was stirred at room temperature for another 5 min, followed by sonication for 10 min. The resulting mixture was placed in an oil bath preheated to 125°C and heated under reflux with continuous stirring for 10 h. After the reaction was complete, a precursor solution was obtained. The oil bath was removed, and the precursor solution was allowed to cool naturally to room temperature. 30 mL of isopropanol was added to the cooled precursor solution to promote complete precipitation of the product, resulting in a suspension. The solid product precipitate was collected from the suspension using an organic filter membrane with a pore size of 0.45 μm. The collected solid product was washed three times with tetrahydrofuran. The washed solid product was placed in a vacuum drying oven and dried under vacuum at 60°C for 6 h to obtain the target product, sulfonic acid side chain modified naphthalimide photocatalyst, labeled as NDI-SO3H.
[0036] The scanning electron microscope image of the naphthimide photocatalyst NDI-SO3H prepared in this embodiment is as follows: Figure 4 As shown, the transmission electron microscope image is as follows: Figure 7 As shown. From Figure 4 As can be seen, the NDI-SO3H prepared in this embodiment exhibits a uniform nanorod structure under scanning electron microscopy, with regular morphology and basically uniform size, and the diameter is within the nanoscale range. The regular structure reflects its high crystallinity. The reason for this formation is that: – The SO3H groups are small in size, having limited influence on the stacking between NDI cores, allowing π-π stacking to dominate the self-assembly process. – The hydrogen bonds between SO3H groups and between SO3H groups and water molecules mainly play a stabilizing role, without significantly guiding the growth direction, thus promoting one-dimensional growth of the material along the π-π stacking direction to form a nanorod structure. This one-dimensional structure is beneficial for constructing continuous electron transport channels, promoting the directional migration of photogenerated carriers, reducing the recombination probability during transport, and thus improving carrier utilization efficiency. Figure 7 As can be seen, NDI-SO3H possesses a highly crystalline nanorod structure with clear edges and continuous internal lattice fringes, indicating that the molecules formed a highly ordered stack during self-assembly. This crystalline integrity provides an ideal pathway for the rapid separation and transport of photogenerated electron-hole pairs, while also facilitating the full exposure of active sites on the surface.
[0037] Example 2 The reaction formula involved in this embodiment is as follows: Figure 2 As shown. The preparation method of the sulfonic acid-modified naphthalimide photocatalyst in this embodiment is as follows: In a three-necked flask equipped with a magnetic stirrer, 4 mmol (692.7 mg) of 2-aminobenzenesulfonic acid and 30 mL of N,N-dimethylformamide were added. The mixture was stirred at room temperature for 5 min, followed by sonication for 10 min to ensure complete dispersion and dissolution of the raw materials. Then, 2 mmol (536.4 mg) of 1,4,5,8-naphthalenetetracarboxylic anhydride was added, and the mixture was stirred at room temperature for another 5 min, followed by sonication for 10 min. The resulting mixture was placed in an oil bath preheated to 125°C and heated under reflux with continuous stirring for 10 h. After the reaction was complete, a precursor solution was obtained. The oil bath was removed, and the precursor solution was allowed to cool naturally to room temperature. 30 mL of isopropanol was added to the cooled precursor solution to promote complete precipitation of the product, resulting in a suspension. The solid product precipitate was collected from the suspension using an organic filter membrane with a pore size of 0.45 μm. The collected solid product was washed three times with tetrahydrofuran. The washed solid product was placed in a vacuum drying oven and dried under vacuum at 60°C for 6 h to obtain the target product, a naphthaleneimide photocatalyst modified with an ortho-benzenesulfonic acid side chain, labeled as NDI-2ABSA.
[0038] The scanning electron microscope image of the naphthimide photocatalyst NDI-2ABSA prepared in this embodiment is as follows: Figure 5 As shown. From Figure 5 It can be seen that although NDI-2ABSA also forms nanostructures, its morphological uniformity and regularity are lower than those of NDI-SO3H, with some regions showing aggregation or morphological inhomogeneity. The reason for this is that the introduction of the 2-aminobenzenesulfonic acid group increases steric hindrance due to the benzene ring structure in the side group and the ortho-sulfonic acid functional group, weakening the regularity of the π-π stacking between NDI cores. This allows π-π interactions and non-covalent interactions such as hydrogen bonding to participate in the self-assembly process, resulting in decreased material morphological uniformity and the formation of heterogeneous nanostructures. This structure may introduce more defects or interfacial barriers, affecting the directional transport of charges and the exposure of surface reaction sites.
[0039] Example 3 The reaction formula involved in this embodiment is as follows: Figure 3 As shown. The preparation method of the sulfonic acid-modified naphthalimide photocatalyst in this embodiment is as follows: In a three-necked flask equipped with a magnetic stirrer, 4 mmol (692.7 mg) of 3-aminobenzenesulfonic acid and 30 mL of N,N-dimethylformamide were added. The mixture was stirred at room temperature for 5 min, followed by sonication for 10 min to ensure complete dispersion and dissolution of the raw materials. Then, 2 mmol (536.4 mg) of 1,4,5,8-naphthalenetetracarboxylic anhydride was added, and the mixture was stirred at room temperature for another 5 min, followed by sonication for 10 min. The resulting mixture was placed in an oil bath preheated to 125°C and heated under reflux with continuous stirring for 10 h. After the reaction was complete, a precursor solution was obtained. The oil bath was removed, and the precursor solution was allowed to cool naturally to room temperature. 30 mL of isopropanol was added to the cooled precursor solution to promote complete precipitation of the product, resulting in a suspension. The solid product precipitate was collected from the suspension using an organic filter membrane with a pore size of 0.45 μm. The collected solid product was washed three times with tetrahydrofuran. The washed solid product was placed in a vacuum drying oven and dried under vacuum at 60°C for 6 h to obtain the target product, a naphthaleneimide photocatalyst modified with a meta-benzenesulfonic acid side chain, labeled as NDI-3ABSA.
[0040] The scanning electron microscope image of the naphthalimide photocatalyst NDI-3ABSA prepared in this embodiment is as follows: Figure 6 As shown, from Figure 6 As can be seen, NDI-3ABSA also forms a nanosheet structure, which can provide a certain active reaction interface. However, its size distribution is relatively wide, and there is obvious adhesion and stacking between the sheets, resulting in a relatively reduced effective specific surface area and potentially hindering sufficient contact between reactants and active sites. This is because the introduction of the 3-aminobenzenesulfonic acid group leads to a spatially expanded distribution of the benzene ring structure and meta-sulfonic acid functional groups in the side groups, forming more significant steric hindrance. This results in a stronger inhibitory effect on the long-range π-π stacking between NDI cores, causing the directional hydrogen bonding interactions between hydrophilic side chains and the water-mediated hydrogen bond network to dominate the self-assembly process. This structural inhomogeneity makes carrier recombination more likely during transport, thus limiting its further improvement in photocatalytic water splitting activity compared to NDI-SO3H.
[0041] Example 4 The reaction formula involved in this embodiment is as follows: Figure 1 As shown. The preparation method of the sulfonic acid-modified naphthalimide photocatalyst in this embodiment is as follows: In a three-necked flask equipped with a magnetic stirrer, 4 mmol (388.4 mg) of aminosulfonic acid and 30 mL of N,N-dimethylformamide were added. The mixture was stirred at room temperature for 5 min, followed by sonication for 10 min to ensure complete dispersion and dissolution of the raw materials. Then, 2 mmol (536.4 mg) of 1,4,5,8-naphthalenetetracarboxylic anhydride was added, and the mixture was stirred at room temperature for another 5 min, followed by sonication for 10 min. The resulting mixture was placed in an oil bath preheated to 125°C and heated under reflux with continuous stirring for 6 h. After the reaction was complete, a precursor solution was obtained. The oil bath was removed, and the precursor solution was allowed to cool naturally to room temperature. 30 mL of isopropanol was added to the cooled precursor solution to promote complete precipitation of the product, resulting in a suspension. The solid product precipitate was collected from the suspension using an organic filter membrane with a pore size of 0.45 μm. The collected solid product was washed three times with tetrahydrofuran. The washed solid product was placed in a vacuum drying oven and dried under vacuum at 60°C for 6 h to obtain the target product NDI-SO3H.
[0042] Example 5 The reaction formula involved in this embodiment is as follows: Figure 1 As shown. The preparation method of the sulfonic acid-modified naphthalimide photocatalyst in this embodiment is as follows: In a three-necked flask equipped with a magnetic stirrer, 4 mmol (388.4 mg) of aminosulfonic acid and 30 mL of N,N-dimethylformamide were added. The mixture was stirred at room temperature for 5 min, followed by sonication for 10 min to ensure complete dispersion and dissolution of the raw materials. Then, 2 mmol (536.4 mg) of 1,4,5,8-naphthalenetetracarboxylic anhydride was added, and the mixture was stirred at room temperature for another 5 min, followed by sonication for 10 min. The resulting mixture was placed in an oil bath preheated to 125°C and heated under reflux with continuous stirring for 8 h. After the reaction was complete, a precursor solution was obtained. The oil bath was removed, and the precursor solution was allowed to cool naturally to room temperature. 30 mL of isopropanol was added to the cooled precursor solution to promote complete precipitation of the product, resulting in a suspension. The solid product precipitate was collected from the suspension using an organic filter membrane with a pore size of 0.45 μm. The collected solid product was washed three times with tetrahydrofuran. The washed solid product was placed in a vacuum drying oven and dried under vacuum at 60°C for 6 h to obtain the target product NDI-SO3H.
[0043] Example 6 The reaction formula involved in this embodiment is as follows: Figure 1 As shown. The preparation method of the sulfonic acid-modified naphthalimide photocatalyst in this embodiment is as follows: In a three-necked flask equipped with a magnetic stirrer, 4 mmol (388.4 mg) of aminosulfonic acid and 30 mL of N,N-dimethylformamide were added. The mixture was stirred at room temperature for 5 min, followed by sonication for 10 min to ensure complete dispersion and dissolution of the raw materials. Then, 2 mmol (536.4 mg) of 1,4,5,8-naphthalenetetracarboxylic anhydride was added, and the mixture was stirred at room temperature for another 5 min, followed by sonication for 10 min. The resulting mixture was placed in an oil bath preheated to 125°C and heated under reflux with continuous stirring for 12 h. After the reaction was complete, a precursor solution was obtained. The oil bath was removed, and the precursor solution was allowed to cool naturally to room temperature. 30 mL of isopropanol was added to the cooled precursor solution to promote complete precipitation of the product, resulting in a suspension. The solid product precipitate was collected from the suspension using an organic filter membrane with a pore size of 0.45 μm. The collected solid product was washed three times with tetrahydrofuran. The washed solid product was placed in a vacuum drying oven and dried under vacuum at 60°C for 6 h to obtain the target product NDI-SO3H.
[0044] Example 7 The reaction formula involved in this embodiment is as follows: Figure 1 As shown. The preparation method of the sulfonic acid-modified naphthalimide photocatalyst in this embodiment is as follows: In a three-necked flask equipped with a magnetic stirrer, 4 mmol (388.4 mg) of aminosulfonic acid and 30 mL of N,N-dimethylformamide were added. The mixture was stirred at room temperature for 5 min, followed by sonication for 10 min to ensure complete dispersion and dissolution of the raw materials. Then, 2 mmol (536.4 mg) of 1,4,5,8-naphthalenetetracarboxylic anhydride was added, and the mixture was stirred at room temperature for another 5 min, followed by sonication for 10 min. The resulting mixture was placed in an oil bath preheated to 110°C and heated under reflux with continuous stirring for 10 h. After the reaction was complete, a precursor solution was obtained. The oil bath was removed, and the precursor solution was allowed to cool naturally to room temperature. 30 mL of isopropanol was added to the cooled precursor solution to promote complete precipitation of the product, resulting in a suspension. The solid product precipitate was collected from the suspension using an organic filter membrane with a pore size of 0.45 μm. The collected solid product was washed three times with tetrahydrofuran. The washed solid product was placed in a vacuum drying oven and dried under vacuum at 60°C for 6 h to obtain the target product NDI-SO3H.
[0045] Example 8 The reaction formula involved in this embodiment is as follows: Figure 1 As shown. The preparation method of the sulfonic acid-modified naphthalimide photocatalyst in this embodiment is as follows: In a three-necked flask equipped with a magnetic stirrer, 4 mmol (388.4 mg) of aminosulfonic acid and 30 mL of N,N-dimethylformamide were added. The mixture was stirred at room temperature for 5 min, followed by sonication for 10 min to ensure complete dispersion and dissolution of the raw materials. Then, 2 mmol (536.4 mg) of 1,4,5,8-naphthalenetetracarboxylic anhydride was added, and the mixture was stirred at room temperature for another 5 min, followed by sonication for 10 min. The resulting mixture was placed in an oil bath preheated to 140°C and heated under reflux with continuous stirring for 10 h. After the reaction was complete, a precursor solution was obtained. The oil bath was removed, and the precursor solution was allowed to cool naturally to room temperature. 30 mL of isopropanol was added to the cooled precursor solution to promote complete precipitation of the product, resulting in a suspension. The solid product precipitate was collected from the suspension using an organic filter membrane with a pore size of 0.45 μm. The collected solid product was washed three times with tetrahydrofuran. The washed solid product was placed in a vacuum drying oven and dried under vacuum at 60°C for 6 h to obtain the target product NDI-SO3H.
[0046] Example 9 The reaction formula involved in this embodiment is as follows: Figure 1 As shown. The preparation method of the sulfonic acid-modified naphthalimide photocatalyst in this embodiment is as follows: In a three-necked flask equipped with a magnetic stirrer, 4 mmol (388.4 mg) of aminosulfonic acid and 25 mL of N,N-dimethylformamide were added. The mixture was stirred at room temperature for 5 min, followed by sonication for 10 min to ensure complete dispersion and dissolution of the raw materials. Then, 2 mmol (536.4 mg) of 1,4,5,8-naphthalenetetracarboxylic anhydride was added, and the mixture was stirred at room temperature for another 5 min, followed by sonication for 10 min. The resulting mixture was placed in an oil bath preheated to 140°C and heated under reflux with continuous stirring for 10 h. After the reaction was complete, a precursor solution was obtained. The oil bath was removed, and the precursor solution was allowed to cool naturally to room temperature. 25 mL of tert-butanol was added to the cooled precursor solution to promote complete precipitation of the product, resulting in a suspension. The solid product precipitate was collected from the suspension using an organic filter membrane with a pore size of 0.45 μm. The collected solid product was washed twice with tetrahydrofuran and then placed in a vacuum drying oven and dried under vacuum at 55°C for 10 h to obtain the target product NDI-SO3H.
[0047] Example 10 The reaction formula involved in this embodiment is as follows: Figure 1 As shown. The preparation method of the sulfonic acid-modified naphthalimide photocatalyst in this embodiment is as follows: In a three-necked flask equipped with a magnetic stirrer, 4 mmol (388.4 mg) of aminosulfonic acid and 35 mL of N,N-dimethylformamide were added. The mixture was stirred at room temperature for 5 min, followed by sonication for 10 min to ensure complete dispersion and dissolution of the raw materials. Then, 2 mmol (536.4 mg) of 1,4,5,8-naphthalenetetracarboxylic anhydride was added, and the mixture was stirred at room temperature for another 5 min, followed by sonication for 10 min. The resulting mixture was placed in an oil bath preheated to 140°C and heated under reflux with continuous stirring for 10 h. After the reaction was complete, a precursor solution was obtained. The oil bath was removed, and the precursor solution was allowed to cool naturally to room temperature. 35 mL of tert-butanol was added to the cooled precursor solution to promote complete precipitation of the product, resulting in a suspension. The solid product precipitate was collected from the suspension using an organic filter membrane with a pore size of 0.45 μm. The collected solid product was washed four times with tetrahydrofuran. The washed solid product was placed in a vacuum drying oven and dried under vacuum at 70°C for 5 h to obtain the target product NDI-SO3H.
[0048] Performance testing: Using NDI-SO3H from Example 1, NDI-2ABSA from Example 2, and NDI-3ABSA from Example 3 as samples, the following performance tests were performed: (1) X-ray diffraction pattern The X-ray diffraction patterns of NDI-SO3H from Example 1, NDI-2ABSA from Example 2, and NDI-3ABSA from Example 3 are shown below. Figure 8 As shown. From Figure 8 As can be seen, NDI-SO3H in Example 1, NDI-2ABSA in Example 2, and NDI-3ABSA in Example 3 all exhibit a series of sharp, clear, and reproducible diffraction peaks, indicating that all products are crystalline materials with well-defined and ordered structures. Further comparison reveals that the diffraction peaks of NDI-SO3H are significantly more intense and sharper overall, indicating that it possesses the highest crystallinity and a more regular molecular packing. Especially in the diffraction region corresponding to the π–π packing characteristics (marked by the dashed line in the figure), NDI-SO3H exhibits the strongest diffraction signal, indicating that its molecular plane packing is more compact and orderly, which is conducive to the formation of effective π–π electronic coupling. This highly ordered packing structure helps to construct continuous intermolecular charge transport channels, improving the separation and migration efficiency of photogenerated electrons and holes, thereby enhancing photocatalytic performance. Therefore, the XRD results suggest that NDI-SO3H possesses a superior crystal structure and potential carrier transport capability among the three materials, providing a structural basis for its higher photocatalytic activity.
[0049] The X-ray diffraction pattern and its refined pattern of NDI-SO3H in Example 1 are shown below. Figure 9 As shown, from Figure 9 As can be seen, the refined results are in high agreement with the experimental data, indicating that the established structural model is reliable. This spectrum verifies that the NDI-SO3H material prepared by the method of this invention has high crystallinity and a certain degree of ordered structure, which provides a structural basis for the effective migration and separation of photogenerated carriers and is beneficial to the material's excellent performance in photocatalytic applications.
[0050] The X-ray diffraction pattern and its refined pattern of NDI-2ABSA in Example 2 are shown below. Figure 10 As shown, from Figure 10 It can be seen that the refined results are in high agreement with the experimental data, indicating that the structural model is reliable.
[0051] The X-ray diffraction pattern and its refined pattern of NDI-3ABSA in Example 3 are shown below. Figure 11 As shown, from Figure 11 It can be seen that the refined results are in high agreement with the experimental data, indicating that the structural model is reliable.
[0052] (2) Crystal structure Based on the aforementioned XRD data, the crystal structures were determined. The crystal structures of NDI-SO3H in Example 1, NDI-2ABSA in Example 2, and NDI-3ABSA in Example 3 are as follows: Figure 12 As shown, (a) is the crystal structure diagram of the photocatalyst NDI-SO3H prepared in Example 1, (b) is the crystal structure diagram of the photocatalyst NDI-2ABSA prepared in Example 2, and (c) is the crystal structure diagram of the photocatalyst NDI-3ABSA prepared in Example 3. This crystal structure was analyzed based on experimentally obtained XRD data. Currently, no corresponding record has been found in the CCDC database, indicating that this supramolecular material possesses unique and novel structural characteristics. The experimental powder XRD patterns were compared with simulated patterns (see attached diagram). Figure 9-11 The two showed a high degree of consistency, which further verified the reliability of the resolved crystal structure and the accuracy of the results.
[0053] (3) Detection of photocatalytic activity The catalysts prepared in Examples 1-8 were used as samples for photocatalytic activity testing. The photocatalytic water splitting reaction under full-spectrum light irradiation was carried out in a quartz-top irradiated reactor, with the reaction temperature maintained at 5°C, and connected to a closed glass circulating gas system (Labsolar-6A, PerfectLight). Pt and CoO xThe co-catalyst was loaded onto the photocatalyst surface using in-situ photodeposition. In the photocatalytic water splitting reaction experiment, 25 mg of the photocatalyst loaded with the above-mentioned co-catalyst was dispersed in 100 mL of deionized water without sacrificial agents. After thorough degassing, the reaction was carried out under 300 W xenon lamp irradiation. For the photocatalytic oxygen production half-reaction, CoO2 was used as the catalyst. x 25 mg of photocatalyst, acting as a co-catalyst, was dispersed in 100 mL of aqueous solution containing 5 mmol / L AgNO3 as a sacrificial agent, and 0.1 g La2O3 was added to maintain the pH of the solution. For the photocatalytic hydrogen production half-reaction, 25 mg of photocatalyst, using Pt as a co-catalyst, was dispersed in 100 mL of aqueous solution containing 10 vol% triethanolamine (TEOA) as a sacrificial agent. The generated gas was analyzed by an online gas chromatograph (GC-2002 N / TFF, TCD detector, Ar carrier gas, 5 Å molecular sieve column) at set time intervals.
[0054] Table 1. Reaction results of photocatalytic hydrogen production rates of the catalysts in Examples 1-8
[0055] As shown in Table 1, under the same test conditions, the NDI-SO3H provided in Example 1 has both the highest hydrogen production activity and the best preparation economy, and is determined to be the preferred technical solution of the present invention.
[0056] The comparison of the photocatalytic hydrogen production performance of NDI-SO3H (Example 1), NDI-2ABSA (Example 2), and NDI-3ABSA (Example 3) with g-C3N4 is shown in the figure below. Figure 13 As shown. From Figure 13 It can be seen that the hydrogen production rate of NDI-SO3H in Example 1 is 15.9 times, 3.2 times, and 12.5 times that of NDI-2ABSA, NDI-3ABSA, and g-C3N4, respectively. This indicates that by introducing sulfonic acid groups onto NDI, the separation efficiency of photogenerated carriers can be significantly enhanced, thereby improving the photocatalytic hydrogen production activity.
[0057] A comparison of the photocatalytic oxygen production performance of NDI-SO3H (Example 1), NDI-2ABSA (Example 2), and NDI-3ABSA (Example 3) with g-C3N4 is shown in the figure below. Figure 14 As shown. From Figure 14 It can be seen that the oxygen production rate of NDI-SO3H in Example 1 is 4.7 times, 1.6 times, and 2.3 times that of NDI-2ABSA, NDI-3ABSA, and g-C3N4, respectively. This indicates that the introduction of sulfonic acid groups effectively modulates the band structure of NDI, significantly enhancing its oxidation reaction driving force and overall photo-oxidation capacity, thereby significantly improving the photocatalytic oxygen production efficiency.
[0058] The photocatalytic water splitting performance of NDI-SO3H in Example 1 is shown in the figure below. Figure 15 As shown, from Figure 15 It can be seen that the molar ratio of H2 to O2 produced by NDI-SO3H in Example 1 is close to 2:1, which is consistent with the theoretical stoichiometric ratio of water splitting. This result shows that NDI-SO3H can stably achieve simultaneous hydrogen and oxygen production without sacrificial agents and complete the water splitting reaction in a stoichiometric manner, demonstrating its good photocatalytic water splitting capability.
[0059] The comparison of the photocatalytic water splitting performance of NDI-SO3H (Example 1), NDI-2ABSA (Example 2), and NDI-3ABSA (Example 3) with g-C3N4 is shown in the figure below. Figure 16 As shown, from Figure 16 As can be seen, the hydrogen production rate of NDI-SO3H in Example 1 is approximately 13.8 times, 2.6 times, and 5.8 times that of NDI-2ABSA, NDI-3ABSA, and g-C3N4, respectively. This performance improvement is mainly due to the stronger intermolecular forces brought about by the introduction of sulfonic acid groups, such as enhanced π–π stacking, the formation of hydrogen bond networks, and a more ordered crystal structure. These factors together improve the carrier migration behavior, enabling the material to achieve highly efficient photocatalytic water splitting.
[0060] Therefore, the sulfonic acid-modified naphthalimide photocatalyst prepared by this invention has good aqueous phase stability, excellent light absorption, electron separation and surface reaction activity, and can be applied to photocatalytic water splitting reaction.
[0061] The foregoing description includes examples from this specification. Of course, for the purposes of describing this specification, it is impossible to describe every conceivable combination of components or methods; however, those skilled in the art will understand that many other combinations and arrangements are possible. Therefore, this specification is intended to cover all such changes, modifications, and variations that fall within the spirit and scope of the appended claims. Furthermore, with regard to the use of the term "comprising" in the detailed description or claims, the term is intended to be inclusive in a manner similar to the term "including," as interpreted when "comprising" is used as a transitional word in the claims.
[0062] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.
Claims
1. A method for preparing a sulfonic acid-modified naphthalimide photocatalyst, characterized in that, The preparation method uses 1,4,5,8-naphthalenetetracarboxylic anhydride and aminosulfonic acid as basic building blocks to generate a precursor through a one-step condensation reaction, and then uses a poor solvent to induce crystallization to obtain a nanorod-structured naphthalimide photocatalyst.
2. The preparation method according to claim 1, characterized in that, The preparation method includes the following steps: Aminosulfonic acid and 1,4,5,8-naphthalenetetracarboxylic anhydride were placed in N,N-dimethylformamide solvent and condensed at 110–140 °C for 6–12 h to obtain a precursor solution. The precursor solution was naturally cooled to room temperature, and then a poor solvent was added to promote precipitation, resulting in a suspension. The suspension was filtered, and the collected solid product was washed and dried to obtain the naphthalimide photocatalyst.
3. The preparation method according to claim 2, characterized in that, The molar ratio of aminosulfonic acid to 1,4,5,8-naphthalenetetracarboxylic anhydride is 2:
1.
4. The preparation method according to claim 3, characterized in that, The molar volume ratio of 1,4,5,8-naphthalenetetracarboxylic anhydride and N,N-dimethylformamide is 2 mmol: (25-35) mL.
5. The preparation method according to claim 2, characterized in that, The precursor solution is prepared as follows: Aminosulfonic acid was added to N,N-dimethylformamide and stirred, then ultrasonically dispersed. Subsequently, 1,4,5,8-naphthalenetetracarboxylic anhydride was added and stirred, then ultrasonically mixed. The resulting mixture was subjected to a condensation reaction at 110–140 °C for 6–12 h under reflux conditions to obtain a precursor solution.
6. The preparation method according to claim 2, characterized in that, The solid product was washed with tetrahydrofuran 2 to 4 times.
7. The preparation method according to claim 6, characterized in that, The solid product was washed and then vacuum dried at 55–70°C for 5–10 h to obtain a naphthalimide photocatalyst.
8. The preparation method according to claim 1, characterized in that, The unsuitable solvents are isopropanol and tert-butanol.
9. A sulfonic acid-modified naphthalimide photocatalyst, characterized in that, It is prepared by the preparation method described in any one of claims 1-8.
10. The application of the sulfonic acid-modified naphthalimide photocatalyst according to claim 9 in the photocatalytic total water splitting reaction.