Heterojunction composite material and preparation method and application thereof

Abstract

The invention relates to a heterojunction composite material and a preparation method and application thereof, and belongs to the technical field of catalysts. The preparation method of the heterojunction composite material comprises the following steps: dispersing nano cadmium sulfide in water to obtain a nano cadmium sulfide dispersion liquid, then adding a triazinyl covalent organic framework, fully reacting at 75-85 DEG C, centrifuging, precipitating, washing and drying to obtain the heterojunction composite material. The narrow-band-gap semiconductor cadmium sulfide and the wide-band-gap semiconductor triazinyl covalent organic framework are compounded to form the heterojunction structure composite material photocatalyst, and the narrow-band-gap semiconductor cadmium sulfide and the wide-band-gap semiconductor triazinyl covalent organic framework interact with each other, so that the response range of sunlight is widened, separation and transfer of photo-induced electrons and holes are promoted, and the photoelectric conversion efficiency is improved. Therefore, the photocatalytic oxidation-reduction capacity of the catalyst is improved, and the photocatalytic performance of the catalyst is finally improved. The heterojunction composite material can be applied to the field of cleaning and environmental protection as a photocatalyst, and has excellent hydrogen production efficiency.

Description

Technical Field

[0001] The present invention relates to the field of catalyst technology, and in particular to a heterojunction composite material and a preparation method and application thereof. Background Art

[0002] Photocatalysis is the process of accelerating reactions using photocatalysts. When exposed to light, the catalyst absorbs the photon energy and becomes excited, producing active species such as photogenerated electrons and holes, which exhibit high redox activity. Consequently, scientists have been exploring different materials as photocatalysts to improve their efficiency and extend their light absorption capabilities from the ultraviolet range to the visible spectrum. Consequently, photocatalytic technology has found widespread application in environmental remediation, water treatment, energy generation, and self-cleaning surfaces.

[0003] Despite decades of research and progress in photocatalysis, its practical application remains challenging due to low light utilization efficiency. Therefore, improving the efficiency of light absorption and charge carrier separation to make photocatalysis economically viable for large-scale applications is currently a key research and development priority in this field. Photocatalysis holds promise as a sustainable solution to environmental and energy challenges.

[0004] In view of this, this application is filed. Summary of the Invention

[0005] The present invention aims to overcome the shortcomings of the prior art and provide a heterojunction composite material and its preparation method and application. The heterojunction composite material has excellent hydrogen production efficiency and can be used as a photocatalyst in the production of clean energy.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] In a first aspect, the present invention provides a method for preparing a heterojunction composite material, comprising dispersing nano-cadmium sulfide (CdS) in water to obtain a nano-cadmium sulfide dispersion, adding a triazine-based covalent organic framework (Tr-COF), and fully reacting at 75-85°C, centrifuging, washing the precipitate, and then drying to obtain the heterojunction composite material; the mass ratio of the nano-cadmium sulfide to the triazine-based covalent organic framework is 100:(10-30).

[0008] This invention creatively combines a wide-bandgap semiconductor (CdS) with a narrow-bandgap semiconductor (Tr-COF) to form a heterojunction composite photocatalyst. The interaction between the two creates a composite material that not only broadens the solar light response range but also promotes the separation and transfer of light-induced electrons and holes, thereby enhancing the catalyst's photocatalytic redox capacity and ultimately improving its photocatalytic performance. This composite material can be used as a photocatalyst in clean and environmentally friendly applications, demonstrating excellent hydrogen production efficiency.

[0009] The triazine units in Tr-COF are highly conjugated and nitrogen-rich, providing efficient electron conduction pathways and facilitating the transfer of photogenerated electrons from CdS to COF. Furthermore, the band structures of Tr-COF and CdS may form a more efficient charge separation interface (e.g., electrons from the CdS CB are injected into the LUMO of Tr-COF), reducing the recombination rate. The rigid porous structure of Tr-COF makes it easier to control the size and distribution of CdS compared to conventional COFs, forming uniform quantum dots (e.g., confined within ~2 nm pores) and increasing active site exposure. Tr-COF has a narrow band gap (e.g., 2.0-2.5 eV), which facilitates a broad spectral response synergistic effect with CdS (~2.4 eV), improving solar light utilization. The nitrogen atoms in the triazine ring of Tr-COF can serve as proton reduction sites, directly participating in HER (hydrogen evolution) or CO2 reduction without the need for additional co-catalysts.

[0010] The present invention uses nano-CdS and Tr-COF to form a heterojunction, but there are many difficulties that need to be overcome: First, the nano-CdS precursor (such as Cd 2+ 、S 2- ) usually needs to react in the aqueous phase, but Tr-COF is highly hydrophobic, and the two have poor compatibility, which can easily lead to the agglomeration of CdS nanoparticles or the collapse of the Tr-COF structure; secondly, in order to make the nano-CdS nucleate uniformly in the pores or surface of Tr-COF rather than randomly deposit and block the pores, it is necessary to precisely control the reaction conditions; thirdly, the strong electron-withdrawing property of Tr-COF may aggravate the charge imbalance on the CdS surface, thereby leading to the oxidation of photogenerated holes. The triazine ring can anchor CdS through coordination. 2 +, inhibiting CdS photocorrosion. The present invention utilizes water as a solvent and combines low-temperature hydrothermal reaction conditions (75-85°C) to slow the CdS nucleation rate, avoid agglomeration, and prevent the collapse of the Tr-COF framework. This transforms the inherent advantages of CdS and Tr-COF into synergistic performance, rather than simply physically mixing them. This allows nano-CdS to uniformly nucleate within the pores or surface of Tr-COF, resulting in a CdS / Tr-COF heterojunction composite material.

[0011] The present invention uses water as a solvent, which can form nano-CdS into uniform nanoparticles and avoid hydrolysis of Tr-COF. However, replacing it with anhydrous ethanol or other organic solvents, strong acids, etc. may cause problems such as rapid agglomeration of nano-CdS and hydrolysis of Tr-COF, thereby failing to obtain a heterojunction composite material. At the same time, water molecules can participate in surface hydroxylation (-OH modification) and optimize the CdS / Tr-COF interface band structure. Moreover, water is non-toxic, cheap, and easily available, and does not require recycling and treatment, which meets the requirements of sustainable development and avoids the environmental risks of organic solvents (such as ethanol) or strong acids (such as HCl).

[0012] As a preferred embodiment of the preparation method of the present invention, the reaction time for the sufficient reaction is 10-15 hours.

[0013] As a preferred embodiment of the preparation method of the present invention, the pH value of the nano-cadmium sulfide dispersion is adjusted to 8-9 before adding the triazine-based covalent organic framework (Tr-COF). 2 + Strong coordination with the triazine nitrogen of Tr-COF to avoid destruction of the Tr-COF structure.

[0014] As a preferred embodiment of the preparation method of the present invention, the solid-liquid ratio of the nano-cadmium sulfide (CdS) and water is 100 mg: (100-120) mL.

[0015] As a preferred embodiment of the preparation method of the present invention, the preparation method of the nano cadmium sulfide (CdS) is as follows: cadmium acetate dihydrate (Cd(OAc)2·2H2O) and dimethyl sulfoxide (DMSO) are dissolved in water to obtain a cadmium acetate solution and a dimethyl sulfoxide solution, respectively, the dimethyl sulfoxide solution is added to the cadmium acetate solution, mixed, dried, and sintered to obtain nano cadmium sulfide (CdS).

[0016] The invention uses water as a medium and utilizes cadmium acetate dihydrate (Cd(OAc)2·2H2O) and dimethyl sulfoxide (DMSO) as reaction raw materials to prepare nano-cadmium sulfide. The preparation method utilizes simple raw materials and has simple operation steps. Compared with the existing preparation method of nano-cadmium sulfide, the preparation method has wider application value.

[0017] As a preferred embodiment of the preparation method of the present invention, in the preparation method of nano-cadmium sulfide (CdS), the molar ratio of cadmium acetate dihydrate to dimethyl sulfoxide is (2-10):(4-20).

[0018] As a preferred embodiment of the preparation method of the present invention, in the preparation method of nano-cadmium sulfide (CdS), the drying temperature is 60-65° C., the sintering temperature is 120-200° C., and the sintering time is 10-15 hours.

[0019] As a preferred embodiment of the preparation method of the present invention, the preparation method of the triazine-based covalent organic framework (Tr-COF) is as follows: 1,2-acenaphthenequinone and 4,4',4"-(1,3,5-triazine-2,4,6-triyl)triphenylamine are added to water to obtain a mixture A; triphenylamine is added to water to obtain a mixture B, and then the mixture B is added to the mixture A, mixed, dried, and sintered to obtain a triazine-based covalent organic framework (Tr-COF).

[0020] The present method for preparing triazine-based covalent organic frameworks (Tr-COFs) utilizes an aqueous system and an interfacial self-assembly strategy to induce directional polycondensation of the hydrophobic Tr-COF precursor in a microemulsion environment. This method eliminates the need for highly polar solvents, resulting in a green solvent environment. Compared to traditional methods that rely on highly toxic solvents (such as nitrobenzene and dioxane), resulting in complex post-processing and environmental pollution, the present Tr-COF preparation method offers significant advancements and advantages.

[0021] As a preferred embodiment of the preparation method of the present invention, in the preparation method of the triazine-based covalent organic framework (Tr-COF), the molar ratio of the 1,2-acenaphthenequinone, 4,4',4"-(1,3,5-triazine-2,4,6-triyl)triphenylamine and triphenylamine is: (0.1-0.3): (0.1-0.3): (0.1-0.2); the ratio of the 1,2-acenaphthenequinone to water is (0.1-0.3) mmol: (10-50) mL; the ratio of the triphenylamine to water is (0.1-0.2) mmol: (30-100) mL.

[0022] As a preferred embodiment of the preparation method of the present invention, in the preparation method of the triazine-based covalent organic framework (Tr-COF), the drying temperature is 60-65°C, the sintering temperature is 100-200°C, and the sintering time is 10-15h.

[0023] Existing Tr-COF synthesis requires high temperatures (120-180°C) and strong acid catalysts (such as concentrated sulfuric acid and trifluoroacetic acid), which can easily lead to problems such as partial triazine ring hydrolysis and amorphization. However, the present invention can catalyze polycondensation at relatively low temperatures (around 100°C), promote the reversible equilibrium of the cyano trimerization reaction, repair defects, and improve the crystallinity of Tr-COF under milder reaction conditions. The preparation method of Tr-COF of the present invention has significant improvements and advantages compared to existing Tr-COF preparation methods.

[0024] Furthermore, conventional Tr-COF functionalization requires pre-modification of monomers, a complex process (e.g., the introduction of -SO3H requires multiple steps). However, the Tr-COF synthesized in the present invention retains active end groups (e.g., unreacted -CN), allowing for the direct introduction of functional groups such as -SH and -COOH via "click chemistry" (e.g., thiol-ene reactions). This allows for flexible functionalization and the control of pore size and surface chemistry. The present Tr-COF preparation method enables continuous synthesis of Tr-COF in a microchannel reactor, shortening the reaction time to 2 hours and achieving batch-to-batch variability of less than 5%. This shortens the synthesis time and improves batch reproducibility, making it suitable for large-scale production.

[0025] In a second aspect, the present invention provides a heterojunction composite material prepared using the above preparation method.

[0026] In a third aspect, the present invention provides the use of the above heterojunction composite material as a photocatalyst in the preparation of clean energy.

[0027] As a preferred embodiment of the application of the present invention, the clean energy is hydrogen. The heterojunction composite material of the present invention can decompose water to produce hydrogen under the action of photocatalysis.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] This invention combines a narrow-bandgap semiconductor (CdS) with a wide-bandgap semiconductor (Tr-COF) to form a heterojunction composite material. Through the interaction of the two, the designed composite material not only broadens the response range to sunlight but also promotes the separation and transfer of light-induced electrons and holes, thereby enhancing the catalyst's photocatalytic redox capacity and ultimately improving its photocatalytic performance. This material can be used as a photocatalyst in clean and environmentally friendly applications, with excellent hydrogen production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is the stability effect of the heterojunction composite material of Example 1 in the test example of the present invention. DETAILED DESCRIPTION

[0031] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0032] Unless otherwise specified, other materials and reagents used in the examples can be obtained from commercial sources.

[0033] Example 1

[0034] A method for preparing a heterojunction composite material comprises the following steps:

[0035] (1) Preparation of nano-CdS

[0036] Cadmium acetate dihydrate (Cd(OAc)2·2H2O) is dissolved in water to obtain a cadmium acetate solution; dimethyl sulfoxide is dissolved in water to obtain a dimethyl sulfoxide solution, the dimethyl sulfoxide solution is added to the cadmium acetate solution, the molar ratio of cadmium acetate dihydrate to dimethyl sulfoxide is 2:4, the mixture is stirred evenly, dried (60°C), and sintered at 120°C for 15 hours to obtain nano-cadmium sulfide (CdS).

[0037] (2) Preparation of Tr-COF

[0038] 0.1 mmol of 1,2-acenaphthenequinone and 0.1 mmol of 4,4',4"-(1,3,5-triazine-2,4,6-triyl)triphenylamine were added to 20 mL of water to obtain mixture A; 0.1 mmol of triphenylamine was added to 40 mL of water to obtain mixture B, which was added to mixture A, stirred evenly, dried (60°C), and sintered at 100°C for 15 h to obtain Tr-COF.

[0039] (3) Preparation of CdS / Tr-COF heterojunction composite materials

[0040] 100 mg of nano-cadmium sulfide (CdS) was dispersed in 100 mL of deionized water to obtain a nano-cadmium sulfide dispersion. The pH was adjusted to 9, and then 25 mg of Tr-COF was slowly added to the nano-cadmium sulfide dispersion. The resulting mixture was stirred continuously at 80°C for 12 hours. The mixture was centrifuged, the precipitate was collected, washed with deionized water, and vacuum-dried (at approximately 60°C) to obtain a CdS / Tr-COF heterojunction composite.

[0041] Example 2

[0042] A method for preparing a heterojunction composite material comprises the following steps:

[0043] (1) Preparation of nano-CdS

[0044] Cadmium acetate dihydrate (Cd(OAc)2·2H2O) is dissolved in water to obtain a cadmium acetate solution; dimethyl sulfoxide is dissolved in water to obtain a dimethyl sulfoxide solution, the dimethyl sulfoxide solution is added to the cadmium acetate solution, the molar ratio of cadmium acetate dihydrate to dimethyl sulfoxide is 2:20, the mixture is stirred evenly, dried (60°C), and sintered at 200°C for 10 hours to obtain nano-cadmium sulfide (CdS).

[0045] (2) Preparation of Tr-COF

[0046] 0.2 mmol of 1,2-acenaphthenequinone and 0.2 mmol of 4,4',4"-(1,3,5-triazine-2,4,6-triyl)triphenylamine were added to 30 mL of water to obtain mixture A; 0.1 mmol of triphenylamine was added to 60 mL of water to obtain mixture B, which was added to mixture A, stirred evenly, dried (60°C), and sintered at 200°C for 10 h to obtain Tr-COF.

[0047] (3) Preparation of CdS / Tr-COF heterojunction composite materials

[0048] 100 mg of nano-cadmium sulfide (CdS) was dispersed in 100 mL of deionized water to obtain a nano-cadmium sulfide dispersion. The pH was adjusted to 8, and then 10 mg of Tr-COF was slowly added to the nano-cadmium sulfide dispersion. The resulting mixture was stirred continuously at 75°C for 15 hours. The mixture was centrifuged, the precipitate was collected, washed with deionized water, and vacuum-dried (around 60°C) to obtain a CdS / Tr-COF heterojunction composite.

[0049] Example 3

[0050] A method for preparing a heterojunction composite material comprises the following steps:

[0051] (1) Preparation of nano-CdS

[0052] Cadmium acetate dihydrate (Cd(OAc)2·2H2O) is dissolved in water to obtain a cadmium acetate solution; dimethyl sulfoxide is dissolved in water to obtain a dimethyl sulfoxide solution, the dimethyl sulfoxide solution is added to the cadmium acetate solution, the molar ratio of cadmium acetate dihydrate to dimethyl sulfoxide is 10:20, the mixture is stirred evenly, dried (60°C), and sintered at 120°C for 15 hours to obtain nano-cadmium sulfide (CdS).

[0053] (2) Preparation of Tr-COF

[0054] 0.3 mmol of 1,2-acenaphthenequinone and 0.3 mmol of 4,4',4"-(1,3,5-triazine-2,4,6-triyl)triphenylamine were added to 50 mL of water to obtain mixture A; 0.2 mmol of triphenylamine was added to 80 mL of water to obtain mixture B. Mixture B was added to mixture A, stirred evenly, dried (about 60°C), and sintered at 110°C for 14 h to obtain Tr-COF.

[0055] (3) Preparation of CdS / Tr-COF heterojunction composite materials

[0056] 100 mg of nano-cadmium sulfide (CdS) was dispersed in 100 mL of deionized water to obtain a nano-cadmium sulfide dispersion. The pH was adjusted to 9, and then 30 mg of Tr-COF was slowly added to the nano-cadmium sulfide dispersion. The resulting mixture was stirred continuously at 85°C for 10 hours. The mixture was centrifuged, the precipitate was collected, washed with deionized water, and vacuum-dried (at approximately 60°C) to obtain a CdS / Tr-COF heterojunction composite.

[0057] Example 4

[0058] A method for preparing a heterojunction composite material comprises the following steps:

[0059] (1) Preparation of nano-CdS

[0060] Same as Example 1.

[0061] (2) Preparation of Tr-COF

[0062] 0.1 mmol of 1,2-acenaphthenequinone and 0.1 mmol of 4,4',4"-(1,3,5-triazine-2,4,6-triyl)triphenylamine were added to 10 mL of water to obtain mixture A; 0.1 mmol of triphenylamine was added to 30 mL of water to obtain mixture B, which was added to mixture A, stirred evenly, dried (60°C), and sintered at 100°C for 15 h to obtain Tr-COF.

[0063] (3) Preparation of CdS / Tr-COF heterojunction composite materials

[0064] Same as Example 1.

[0065] Example 5

[0066] A method for preparing a heterojunction composite material comprises the following steps:

[0067] (1) Preparation of nano-CdS

[0068] Same as Example 1.

[0069] (2) Preparation of Tr-COF

[0070] 0.1 mmol of 1,2-acenaphthenequinone and 0.1 mmol of 4,4',4"-(1,3,5-triazine-2,4,6-triyl)triphenylamine were added to 50 mL of water to obtain mixture A; 0.1 mmol of triphenylamine was added to 100 mL of water to obtain mixture B, which was added to mixture A, stirred evenly, dried (60°C), and sintered at 100°C for 15 h to obtain Tr-COF.

[0071] (3) Preparation of CdS / Tr-COF heterojunction composite materials

[0072] Same as Example 1.

[0073] Example 6

[0074] (1) Preparation of nano-CdS

[0075] Same as Example 1.

[0076] (2) Preparation of Tr-COF

[0077] Same as Example 1.

[0078] (3) Preparation of CdS / Tr-COF heterojunction composite materials

[0079] 100 mg of nano-cadmium sulfide (CdS) was dispersed in 120 mL of deionized water to obtain a nano-cadmium sulfide dispersion. The pH was adjusted to 9, and then 25 mg of Tr-COF was slowly added to the nano-cadmium sulfide dispersion. The resulting mixture was stirred continuously at 80°C for 12 hours. The mixture was centrifuged, the precipitate was collected, washed with deionized water, and vacuum-dried (at approximately 60°C) to obtain a CdS / Tr-COF heterojunction composite.

[0080] Comparative Example 1

[0081] A method for preparing a heterojunction composite material is the same as that in Example 1, except that the amount of Tr-COF added in the preparation step of the CdS / Tr-COF heterojunction composite material is replaced with 2 mg. The method specifically comprises the following steps:

[0082] (1) Preparation of nano-CdS

[0083] Same as Example 1.

[0084] (2) Preparation of Tr-COF

[0085] Same as Example 1.

[0086] (3) Preparation of CdS / Tr-COF heterojunction composite materials

[0087] 100 mg of nano-cadmium sulfide (CdS) was dispersed in 100 mL of deionized water to obtain a nano-cadmium sulfide dispersion. The pH was adjusted to 9, and then 2 mg of Tr-COF was slowly added to the nano-cadmium sulfide dispersion. The resulting mixture was stirred continuously at 80°C for 12 hours. The mixture was centrifuged, the precipitate was collected, washed with deionized water, and vacuum-dried (at approximately 60°C) to obtain a CdS / Tr-COF heterojunction composite.

[0088] Comparative Example 2

[0089] A method for preparing a heterojunction composite material is the same as that in Example 1, except that the amount of Tr-COF added in the preparation step of the CdS / Tr-COF heterojunction composite material is replaced with 50 mg. The method specifically comprises the following steps:

[0090] (1) Preparation of nano-CdS

[0091] Same as Example 1.

[0092] (2) Preparation of Tr-COF

[0093] Same as Example 1.

[0094] (3) Preparation of CdS / Tr-COF heterojunction composite materials

[0095] 100 mg of nano-cadmium sulfide (CdS) was dispersed in 100 mL of deionized water to obtain a nano-cadmium sulfide dispersion. The pH was adjusted to 9, and then 50 mg of Tr-COF was slowly added to the nano-cadmium sulfide dispersion. The resulting mixture was stirred continuously at 80°C for 12 hours. The mixture was centrifuged, the precipitate was collected, washed with deionized water, and vacuum-dried (at approximately 60°C) to obtain a CdS / Tr-COF heterojunction composite.

[0096] Comparative Example 3

[0097] The difference between Comparative Example 3 and Example 1 is that, in Comparative Example 3, nano-CdS is not added, and an equal amount of Tr-COF is used instead, and specifically comprises the following steps:

[0098] (1) Preparation of Tr-COF

[0099] Same as Example 1.

[0100] (2) Preparation of catalytic materials

[0101] 125 mg of Tr-COF was dispersed in 100 mL of deionized water, the pH was adjusted to 9, and the mixture was stirred continuously at 80° C. for 12 hours. The mixture was centrifuged, the precipitate was collected, washed with deionized water, and vacuum dried (at about 60° C.) to obtain the catalytic material.

[0102] Comparative Example 4

[0103] The difference between Comparative Example 4 and Example 1 is that Tr-COF is not added in Comparative Example 4, and an equal amount of nano-CdS is used instead. Specifically, the following steps are included:

[0104] (1) Preparation of nano-CdS

[0105] Same as Example 1.

[0106] (2) Preparation of catalytic materials

[0107] 125 mg of nano-CdS was dispersed in 100 mL of deionized water, the pH value was adjusted to 9, and the mixture was stirred continuously at 80° C. for 12 hours. The mixture was centrifuged, the precipitate was collected, washed with deionized water, and vacuum dried (at about 60° C.) to obtain a catalytic material.

[0108] Comparative Example 5

[0109] The difference between Comparative Example 5 and Example 1 is that, in the preparation step of the CdS / Tr-COF heterojunction composite material in Example 1, the deionized water is replaced with anhydrous ethanol in Comparative Example 5, and specifically comprises the following steps:

[0110] (1) Preparation of nano-CdS

[0111] Same as Example 1.

[0112] (2) Preparation of Tr-COF

[0113] Same as Example 1.

[0114] (3) Preparation of CdS / Tr-COF heterojunction composite materials

[0115] 100 mg of nano-cadmium sulfide (CdS) was dispersed in 100 mL of anhydrous ethanol to obtain a nano-cadmium sulfide dispersion. The pH was adjusted to 9, and then 25 mg of Tr-COF was slowly added to the nano-cadmium sulfide dispersion. The resulting mixture was stirred continuously at 80°C for 12 hours. After centrifugation, the precipitate was collected, washed with anhydrous ethanol, and vacuum dried (around 60°C). The results showed that it was impossible to obtain a CdS / Tr-COF heterojunction composite material. Nano-CdS formed large particles (>50 nm) in anhydrous ethanol rather than uniform quantum dots. Anhydrous ethanol easily adsorbed on the CdS surface, hindering the exposure of active sites. At the same time, Tr-COF has poor solubility in anhydrous ethanol, making it difficult to achieve uniform composite.

[0116] Test Case

[0117] 1. Determination of hydrogen production capacity

[0118] The hydrogen production capacity of the materials in the examples and comparative examples was evaluated using a photocatalytic reactor system designed for visible light irradiation. The steps are as follows:

[0119] (1) Ensure that the glass reactor is completely clean. Disperse 20 mg of heterojunction composite material (or catalytic material) in 10 mL of aqueous solution. After ultrasonic dispersion for 30 minutes, add 1 mL of lactic acid as a sacrificial donor. Stir the reaction solution continuously to make the entire mixture uniform. Then, completely evacuate the entire assembly.

[0120] (2) Place at 100mW / cm 2 The mixture was irradiated with a xenon lamp. After 4 hours of reaction, the gases collected during the reaction were analyzed by gas chromatography equipped with a molecular sieve 5A column and a TCD detector; the hydrogen production was calculated.

[0121] The hydrogen production of the CdS / Tr-COF heterojunction composite materials of the examples was 16 to 55 mmol / g, while the hydrogen production of the heterojunction composite materials (or catalytic materials) of the comparative examples was less than 13 mmol / g. The hydrogen production of the heterojunction composite materials (or catalytic materials) of Examples 1-3 and Comparative Examples 1-4 is shown in Table 1 below.

[0122] Table 1

[0123] Hydrogen production (mmol / g) Example 1 50.32 Example 2 39.82 Example 3 16.63 Comparative Example 1 6.42 Comparative Example 2 12.87 Comparative Example 3 0.44 Comparative Example 4 1.32

[0124] According to Example 1 and Comparative Examples 1 and 2, the mass ratio of nano-CdS to Tr-COF must be in the range of 100: (10-30). If it is lower or higher than this range, the hydrogen production of the heterojunction composite material will be reduced, that is, the catalytic hydrogen production performance will be reduced.

[0125] 2. Determination of stability

[0126] Following the aforementioned method for measuring hydrogen production capacity, after 4 hours of illumination in step (2), the first cycle ends, the light source is turned off, nitrogen is purged for 10 minutes, solvent water is replenished, and step 2 is repeated for the second, third, and fourth cycles (a total of 16 hours). The hydrogen production is measured once per hour during each cycle. The stability of the heterojunction composite material is plotted based on the hydrogen production.

[0127] The results show that the stability of the heterojunction composite material of the embodiment is good. The stability effect of the heterojunction composite material of Example 1 is as follows: Figure 1 shown.

[0128] In summary, the heterojunction composite material of the present invention can be used as a photocatalyst in the field of clean energy and has excellent hydrogen production capacity.

[0129] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a heterojunction composite material, characterized in that: Dispersing nano-cadmium sulfide in water to obtain a nano-cadmium sulfide dispersion, then adding a triazine-based covalent organic framework, fully reacting at 75-85° C., centrifuging, washing the precipitate, and then drying to obtain the heterojunction composite material; The mass ratio of the nano-cadmium sulfide to the triazine-based covalent organic framework is 100:(10-30).

2. The preparation method according to claim 1, wherein The reaction time for the full reaction is 10-15 hours.

3. The preparation method according to claim 1, wherein Before adding the triazine-based covalent organic framework, the pH value of the nano-cadmium sulfide dispersion is adjusted to 8-9.

4. The preparation method according to claim 1, wherein The solid-liquid ratio of the nano-cadmium sulfide to water is 100 mg: (100-120) mL.

5. The preparation method according to claim 1, wherein The preparation method of the nano-cadmium sulfide comprises the following steps: dissolving cadmium acetate dihydrate and dimethyl sulfoxide in water to obtain a cadmium acetate solution and a dimethyl sulfoxide solution respectively; adding the dimethyl sulfoxide solution to the cadmium acetate solution; mixing; drying; and sintering to obtain the nano-cadmium sulfide.

6. The preparation method according to claim 5, wherein The molar ratio of the cadmium acetate dihydrate to dimethyl sulfoxide is (2-10):(4-20); And / or, the sintering temperature is 120-200°C; And / or, the sintering time is 10 to 15 hours.

7. The preparation method according to claim 1, wherein The preparation method of the triazine-based covalent organic framework comprises: adding 1,2-acenaphthenequinone and 4,4',4"-(1,3,5-triazine-2,4,6-triyl)triphenylamine to water to obtain a mixture A; adding triphenylamine to water to obtain a mixture B; then adding the mixture B to the mixture A, mixing, drying, and sintering to obtain the triazine-based covalent organic framework.

8. The preparation method according to claim 7, wherein The molar ratio of 1,2-acenaphthenequinone, 4,4',4"-(1,3,5-triazine-2,4,6-triyl)triphenylamine and triphenylamine is: (0.1-0.3): (0.1-0.3): (0.1-0.2); and / or, the ratio of 1,2-acenaphthenequinone to water is (0.1-0.3) mmol: (10-50) mL; and / or, the ratio of triphenylamine to water is (0.1-0.2) mmol: (30-100) mL; and / or, the sintering temperature is 100-200° C.; And / or, the sintering time is 10 to 15 hours.

9. The heterojunction composite material prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the heterojunction composite material according to claim 9 as a photocatalyst in the preparation of clean energy.

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