Multi-component covalent organic framework material for producing hydrogen peroxide based on photocatalysis as well as preparation method and application of multi-component covalent organic framework material

Abstract

The invention discloses a multi-component covalent organic framework material for producing hydrogen peroxide based on photocatalysis and a preparation method and application thereof.The preparation method comprises the steps that a catalyst is added into turbid liquid containing an organic monomer, styrene, etherified boron trifluoride, 2, 3-dichloro-5, 6-dichloro-p-benzoquinone and an organic solvent, the mixture is mixed to be uniform, then the mixture is frozen and subjected to a reaction under vacuum after exhausting, and the multi-component covalent organic framework material is obtained; the multi-component covalent organic framework material for producing hydrogen peroxide based on photocatalysis is obtained. The material has the characteristics of adjustable structure height, abundant active centers, good porosity and the like, can be recycled for multiple times, and is a good catalyst for H2O2 production.

Description

Technical Field

[0001] The invention belongs to the technical field of covalent organic framework material synthesis, and particularly relates to a multi-component covalent organic framework material based on photocatalytic hydrogen peroxide production, a preparation method and an application thereof. Background Art

[0002] Hydrogen peroxide (H2O2) is a versatile and environmentally friendly oxidant with water and oxygen as byproducts, which has a wide range of applications in wastewater treatment, medical disinfection, chemical synthesis and other fields. Industrial H2O2 production has traditionally adopted the anthraquinone oxidation process, which is an energy-intensive process involving large infrastructure, complex processes, and produces toxic byproducts. In contrast, photocatalytic H2O2 production has become the focus of research with excellent efficiency and selectivity, meeting the growing demand for green and sustainable energy development. By utilizing the abundant water and air on earth as raw materials, photocatalytic H2O2 production via the two-electron oxygen reduction reaction (ORR) is now considered a promising alternative to the traditional energy-intensive anthraquinone process. In particular, artificial photosynthesis can be based on actual application needs, avoiding the safety hazards and high costs of concentrated H2O2 in transportation, storage and use. To this end, the development of low-cost, high-efficiency and environmentally friendly catalysts for H2O2 production is a current development trend.

[0003] COFs are an emerging class of crystalline porous polymer materials with relatively stable covalent bonds. Multicomponent reactions are a suitable tool to form strong connectivity within COFs while maintaining their framework stacking. Multicomponent COFs are different functional groups introduced into the framework. The obtained quinoline bond-connected COFs show good stability and photocatalytic activity, can maintain their framework crystallinity, and can be reused under harsh conditions such as acidic, alkaline and strong oxidizing conditions. Compared with traditional imine-connected COFs, their catalytic activity is higher. Due to their highly ordered and π-conjugated structure, COFs show semiconductor properties and are therefore promising materials for photocatalysis.

[0004] However, during the photocatalytic reaction of COFs, a sacrificial agent needs to be added to maintain the hydrogen peroxide content. After ten hours of continuous production, the crystallinity decreases, and continuous and stable production of hydrogen peroxide cannot be achieved. Summary of the invention

[0005] In order to overcome the technical problem of COFs materials in the prior art to achieve continuous and stable production of hydrogen peroxide, the present invention aims to provide a multi-component covalent organic framework material based on photocatalytic hydrogen peroxide production, a preparation method and an application thereof. S It has the characteristics of highly adjustable structure, rich active centers, good porosity, etc. It can be recycled many times and is a good catalyst for H2O2 production.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A method for preparing a multi-component covalent organic framework material based on photocatalytic hydrogen peroxide production comprises the following steps: A catalyst is added to a suspension containing an organic monomer, styrene, boron trifluoride etherate, 2,3-dichloro-5,6-dichlorobenzoquinone and an organic solvent, the mixture is evenly mixed, and then the mixture is frozen, vented and reacted under vacuum to obtain a multi-component covalent organic framework material based on photocatalytic production of hydrogen peroxide.

[0007] A further improvement of the present invention is that the organic solvent is a mixture of n-butanol and o-dichlorobenzene.

[0008] A further improvement of the present invention is that the volume ratio of n-butanol to o-dichlorobenzene is 1:1.

[0009] A further improvement of the present invention is that the organic monomer is a mixture of 4,4',4"-nitrotribenzaldehyde and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine in a molar ratio of 1:1 or a mixture of tris(4-aminophenyl)amine and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine.

[0010] A further improvement of the present invention is that the usage ratio of the organic monomer, styrene, boron trifluoride etherate, 2,3-dichloro-5,6-dichloro-p-benzoquinone and the organic solvent is 0.16-0.32 mmol: 60 μL: 4 μL: 8 mg: 1-6 mL.

[0011] A further improvement of the present invention is that the catalyst is a catalyst having a concentration of 6 mol·L –1 of acetic acid solution.

[0012] A further improvement of the present invention is that the molar ratio of the organic monomer to the catalyst is 0.16-0.32:1.2.

[0013] A further improvement of the present invention is that the reaction temperature is 110-130 ° C and the time is 3-5 days.

[0014] A multi-component covalent organic framework material based on photocatalytic hydrogen peroxide production, the specific surface area of ​​the material is 900-1000m 2 g -1 .

[0015] A multi-component covalent organic framework material based on photocatalytic hydrogen peroxide production is used in the preparation of hydrogen peroxide.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The organic monomers of aldehyde and amino groups used in the present invention are used to construct COFs with opposite C=N bond orientations through the Schiff base reaction for basic condensation, and the dynamic imine bond is converted into a solid quinoline bond by performing a Povarov reaction. The use of triazine and N monomers can make the synthesized COFs have different torsion angles, and the two COFs have different planarities, which leads to different stacking energies and different interlayer spacings, affecting the efficiency of the two to produce hydrogen peroxide. The present invention realizes the preparation of COFs connected by quinoline bonds that are easy to quickly recycle and can be recycled for multiple times, and successfully prepares two multi-component COFs with different planarities. The two show significant differences in photocatalytic H2O2 production. It is initially believed that the difference in planarity and conjugation is caused by the distortion of the benzene rings of the two. The enhanced planarity and conjugation promote charge generation and separation, which further promotes the performance of the photocatalyst.

[0017] Furthermore, the content of 2,3-dichloro-5,6-dichlorobenzoquinone has a significant effect on the reaction, and too high or too low a content will affect the crystallinity of COFs.

[0018] The multi-component COFs prepared by the present invention are a type of COFs constructed by multi-component reactions involving more than two monomers. This strategy creates more complex and diverse structures, and the resulting COFs have higher stability, high crystallinity, structural and functional diversity, making them a potential platform for wide application. By introducing multiple components into COFs, the obtained quinoline bond-connected COFs show good stability and photocatalytic activity, can maintain their framework crystallinity, and can be reused under harsh conditions such as acidic, alkaline and strong oxidizing conditions. In particular, the multi-components play a vital role in their electronic properties such as band gap, light absorption and charge separation and transfer behavior, thereby affecting their photocatalytic performance. In addition, COFs have different torsion angles, resulting in different dihedral angles and stacking energies between the two, further affecting the charge transfer and transport within the COFs, thereby producing different efficiencies in the photocatalytic production of hydrogen peroxide. Compared with traditional imine-connected COFs, it has higher catalytic activity and can be widely used in fields such as photocatalytic production of H2O2. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the process of preparing PAPT-COF and PTPA-COF in Example 1 and Example 2 using 4,4',4"-nitrobenzaldehyde, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, styrene and tris(4-aminophenyl)amine, 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, styrene as monomers; Figure 2 is a scanning electron micrograph of the PAPT-COF synthesized in Example 1; Figure 3is a scanning electron micrograph of the PTPA-COF synthesized in Example 2; Figure 4 is the XRD pattern of PAPT-COF in Example 1; Figure 5 for Figure 4 Enlarged image of the 001 crystal plane; Figure 6 is the XRD pattern of PTPA-COF in Example 2; Figure 7 for Figure 6 Enlarged image of the 001 crystal plane; Figure 8 is the N2 adsorption isotherm of PAPT-COF in Example 1; Fig. 9 is the pore size distribution diagram of PAPT-COF in Example 1; Fig.10 is the N2 adsorption isotherm of PTPA-COF in Example 2; Fig.11 is the pore size distribution diagram of PTPA-COF in Example 2; Fig.12 It is the photocatalytic H2O2 production performance diagram of PAPT-COF and PTPA-COF in Example 1 and Example 2. DETAILED DESCRIPTION

[0020] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly and comprehensively understood.

[0021] The concept of the present invention is to provide an alternative to the traditional anthraquinone scheme for the catalytic synthesis of H2O2 from water and oxygen using semiconductor photocatalysts, which is due to its low energy consumption, pollution-free and high safety. Although inorganic semiconductor photocatalysts, such as TiO2, ZnO and BiVO4, show good performance for photocatalytic production of hydrogen peroxide, the inherent defects of the materials themselves, such as poor visible light absorption and relatively low stability, are difficult to overcome. COFs have received great attention because they consume low energy, are safe, and produce little pollution. The multi-component COFs studied in the present invention are different functional groups introduced into the skeleton. The obtained quinoline bond-connected COFs show good stability and photocatalytic activity, can maintain their framework crystallinity, and the planarity of the two COFs is greatly different. The increase in planarity enhances the π-π stacking interaction and electron delocalization of COFs, so that it has a superior band structure and a lower exciton binding energy. It can be reused under harsh conditions such as acidic, alkaline and strong oxidizing conditions.

[0022] Different bonding structures lead to different photoelectrochemical properties, multi-component COF S The change of microstructure improves the COF S Photocatalytic activity for the photocatalytic production of H2O2.

[0023] The present invention provides a method for preparing a multi-component covalent organic framework material based on photocatalytic hydrogen peroxide production, comprising the following steps: (1) A certain amount of organic monomer was weighed and dispersed in an ampoule containing a mixed solution of styrene, boron trifluoride etherate, 2,3-dichloro-5,6-dichlorobenzoquinone, n-butanol and o-dichlorobenzene. The mixture was ultrasonically treated for 3 minutes to obtain a suspension. Acetic acid solution was then added dropwise and ultrasonicated again for 10 minutes.

[0024] The concentration of acetic acid solution is 6 mol·L –1 The organic monomer is a mixture of 4,4',4"-nitrotribenzaldehyde and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine or a mixture of tris(4-aminophenyl)amine and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine in a molar ratio of 1:1. The amount ratio of the organic monomer, styrene, boron trifluoride etherate, 2,3-dichloro-5,6-dichlorobenzoquinone, n-butanol and o-dichlorobenzene is 0.16-0.32mmol: 60μL: 4μL: 8mg: 1-3mL: 1-3mL. n-Butanol and o-dichlorobenzene are used as solvents, and the volume ratio of n-butanol and o-dichlorobenzene is 1:1.

[0025] (2) The suspension prepared in step (1) was rapidly frozen at 77 K (liquid nitrogen bath) and degassed by three freeze-pump-thaw cycles. The tube was sealed under vacuum and heated at 110-130 °C for 3-5 days.

[0026] (3) The flocculent precipitate obtained in step (2) is washed several times with acetone and anhydrous ethanol, and the obtained solid product is dried by supercritical carbon dioxide, and then vacuum dried at 80°C to obtain a reddish-brown solid powder, which is a multi-component covalent organic framework material based on photocatalytic hydrogen peroxide production. The material has a high degree of crystallinity and a specific surface area of ​​900-1000m 2 g -1 It can be recycled many times and can produce hydrogen peroxide by photocatalysis under harsh conditions such as acid or alkaline.

[0027] The monomers used in step (1) include a third component, styrene, which reacts with the other two monomers under vacuum-sealed heating to construct COFs with opposite C=N bond orientations under Schiff base reaction-based conditions. After the third component styrene is introduced, the dynamic imine bond is converted into a strong quinoline bond, forming two COFs with different planarities, which have high crystallinity, high specific surface area, and a clear and adjustable pore structure.

[0028] The multi-component COFs of the present invention introduce different functional groups into the framework, and the obtained quinoline bond-connected COFs show good stability and photocatalytic activity, can maintain its framework crystallinity, and the planarity of the two COFs is greatly different. The increase in planarity enhances the π-π stacking interaction and electron delocalization of the COFs, so that it has a superior band structure and lower exciton binding energy. It can be reused under harsh conditions such as acidic, alkaline and strong oxidizing conditions.

[0029] The following are specific embodiments.

[0030] Example 1 See also Figure 1 , the preparation process of PAPT-COF includes the following steps: a: Add 4,4',4"-nitrotribenzaldehyde (52.69 mg, 0.16 mmol), 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (56.7 mg, 0.16 mmol), styrene (60 μL), boron trifluoride etherate (4 μL), 2,3-dichloro-5,6-dichlorobenzoquinone (8 mg), n-butanol (1 mL), and o-dichlorobenzene (1 mL) into a 10 mL ampoule and mix by ultrasonication for 3 minutes to obtain a suspension.

[0031] b: After obtaining the suspension, 0.2 mL of 6 mol / L acetic acid solution was added dropwise while ultrasonicating. After ultrasonicating again for 10 min, the ampoule was placed in a liquid nitrogen bath at -196°C (77K) for rapid freezing. The ampoule was degassed through three freeze-pump-thaw cycles and flame-sealed under vacuum.

[0032] c: The ampoule was placed at room temperature and then in an oven at 120°C for reaction for 3 days to obtain a reddish-brown flocculent precipitate.

[0033] d: After cooling to room temperature, the product was collected by filtration and washed several times with anhydrous acetone and anhydrous ethanol respectively. The obtained solid product was supercritically dried with carbon dioxide and vacuum dried at 80°C to obtain a reddish-brown solid powder, which is a multi-component covalent organic framework material based on photocatalytic production of hydrogen peroxide.

[0034] Depend on Figure 2 It can be seen that PAPT-COF shows a flocculent structure.

[0035] Depend on Figure 4 and Figure 5 It can be seen that the PAPT-COF sample was successfully prepared.

[0036] Depend on Figure 8 and Fig. 9 It can be seen that the pore size of PAPT-COF is 1.22nm, and the specific surface area is between 900-1000m 2 g -1 .

[0037] Example 2 The PTPA-COF preparation process includes the following steps: a: Add tris(4-aminophenyl)amine (46.46 mg, 0.16 mmol), 2,4,6-tris(4-formylphenyl)-1,3,5-triazine (62.94 mg, 0.16 mmol), styrene (60 μL), boron trifluoride etherate (4 μL), 2,3-dichloro-5,6-dichlorobenzoquinone (8 mg), n-butanol (1 mL), and o-dichlorobenzene (1 mL) into a 10 mL ampoule and mix by ultrasonication for 3 minutes to obtain a suspension.

[0038] b: After obtaining the suspension, 0.2 mL of 6 mol / L acetic acid solution was added dropwise while ultrasonicating. After ultrasonicating again for 10 min, the ampoule was placed in a liquid nitrogen bath at -196°C (77K) for rapid freezing. The ampoule was degassed through three freeze-pump-thaw cycles and flame-sealed under vacuum.

[0039] c: The ampoule was placed at room temperature and then placed in an oven at 120°C for reaction for 3 days to obtain a brown flocculent precipitate.

[0040] d: After cooling to room temperature, the product was collected by filtration and washed several times with anhydrous acetone and anhydrous ethanol respectively. The solid product was supercritically dried with carbon dioxide and vacuum dried at 80°C to obtain a brown solid powder, which is a multi-component covalent organic framework material based on photocatalytic production of hydrogen peroxide.

[0041] Depend on Figure 1 It can be seen that the preparation of PAPT-COF and PTPA-COF materials requires the use of five monomers: 4,4',4"-nitrotribenzaldehyde, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, styrene and tris(4-aminophenyl)amine, 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, and styrene.

[0042] Depend on Figure 3 It can be seen that PTPA-COF shows a rod-like structure.

[0043] Depend on Figure 6 and Figure 7 It can be seen that the PTPA-COF sample was successfully prepared.

[0044] Depend on Fig.10 and Fig.11 It can be seen that the pore size of PTPA-COF is 1.02nm, and the specific surface area is between 900-1000m 2 g -1 .

[0045] Photocatalytic production of hydrogen peroxide: Under the irradiation of λ>420 nm Xe lamp, hydrogen peroxide can be produced in a mixed solution of water and isopropanol. Under sacrificial oxidant conditions, hydrogen peroxide can also be effectively produced in pure water and oxygen or air atmosphere.

[0046] Depend on Fig.12 It can be seen that both COFs can efficiently produce H2O2 under the irradiation of λ>420 nm Xe lamp, and the performance of PAPT-COF is higher than that of PTPA-COF.

[0047] Example 3 a: Add 4,4',4"-nitrotribenzaldehyde (26.345 mg, 0.08 mmol), 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (28.35 mg, 0.08 mmol), styrene (60 μL), boron trifluoride etherate (4 μL), 2,3-dichloro-5,6-dichlorobenzoquinone (8 mg), n-butanol (3 mL), and o-dichlorobenzene (3 mL) into a 10 mL ampoule and mix by ultrasonication for 3 minutes to obtain a suspension.

[0048] b: After obtaining the suspension, 0.2 mL of 6 mol / L acetic acid solution was added dropwise while ultrasonicating. After ultrasonicating again for 10 min, the ampoule was placed in a liquid nitrogen bath at -196°C (77K) for rapid freezing. The ampoule was degassed through three freeze-pump-thaw cycles and flame-sealed under vacuum.

[0049] c: The ampoule was placed at room temperature and then in an oven at 110°C for reaction for 5 days to obtain a reddish-brown flocculent precipitate.

[0050] d: After cooling to room temperature, the product was collected by filtration and washed several times with anhydrous acetone and anhydrous ethanol respectively. The obtained solid product was supercritically dried with carbon dioxide and vacuum dried at 80°C to obtain a reddish-brown solid powder, which is a multi-component covalent organic framework material based on photocatalytic production of hydrogen peroxide.

[0051] Example 4 a: Add 4,4',4"-nitrotribenzaldehyde (0.1mmol), 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (0.15mmol), styrene (60μL), boron trifluoride etherate (4μL), 2,3-dichloro-5,6-dichlorobenzoquinone (8 mg), n-butanol (2mL), and o-dichlorobenzene (2mL) into a 10mL ampoule and mix by ultrasonication for 3 minutes to obtain a suspension.

[0052] b: After obtaining the suspension, 0.2 mL of 6 mol / L acetic acid solution was added dropwise while ultrasonicating. After ultrasonicating again for 10 min, the ampoule was placed in a liquid nitrogen bath at -196°C (77K) for rapid freezing. The ampoule was degassed through three freeze-pump-thaw cycles and flame-sealed under vacuum.

[0053] c: The ampoule was placed at room temperature and then in an oven at 130°C for reaction for 3 days to obtain a reddish-brown flocculent precipitate.

[0054] d: After cooling to room temperature, the product was collected by filtration and washed several times with anhydrous acetone and anhydrous ethanol respectively. The obtained solid product was supercritically dried with carbon dioxide and vacuum dried at 80°C to obtain a reddish-brown solid powder, which is a multi-component covalent organic framework material based on photocatalytic production of hydrogen peroxide.

[0055] The two multi-component COFs prepared by the present invention are a type of COFs constructed by multi-component reactions involving more than two monomers. This strategy creates more complex and diverse structures, and the resulting COFs have higher stability, high crystallinity, structural and functional diversity, making them a potential platform for wide application. By introducing multiple components into COFs, the obtained quinoline bond-connected COFs show good stability and photocatalytic activity, can maintain their framework crystallinity, and can be reused under harsh conditions such as acidic, alkaline and strong oxidizing conditions. In particular, the multiple components play a vital role in their electronic properties such as band gap, light absorption and charge separation and transfer behavior, thereby affecting their photocatalytic performance. In addition, the two COFs have different torsion angles, resulting in different dihedral angles and stacking energies between the two, which further affects the charge transfer and transport inside the COFs, thereby producing different efficiencies in the photocatalytic production of hydrogen peroxide. Compared with traditional imine-connected COFs, it has higher catalytic activity and can be widely used in fields such as photocatalytic production of H2O2.

[0056] The above description is only for the best embodiment of the present invention, but it should not be understood as limiting the claims. The present invention is not limited to the above embodiments, and its specific structure is allowed to be changed. However, all changes made within the protection scope of the independent claims of the present invention are within the protection scope of the present invention.

[0057] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

Claims

1. A method for preparing a multi-component covalent organic framework material based on photocatalytic hydrogen peroxide production, characterized in that: The following steps are involved: A catalyst is added to a suspension of an organic monomer containing aldehyde and amino groups, styrene, boron trifluoride etherate, 2,3-dichloro-5,6-dichloro-p-benzoquinone and an organic solvent, the mixture is evenly mixed, and then the mixture is frozen, vented and subjected to a Povarov reaction under vacuum to obtain a multi-component covalent organic framework material based on photocatalytic production of hydrogen peroxide.

2. According to the preparation method of multi-component covalent organic framework material based on photocatalytic hydrogen peroxide production, it is characterized in that: The organic solvent is a mixture of n-butanol and o-dichlorobenzene.

3. According to the preparation method of multi-component covalent organic framework material based on photocatalytic hydrogen peroxide production, it is characterized in that: The volume ratio of n-butanol to o-dichlorobenzene is 1:

1.

4. According to the preparation method of multi-component covalent organic framework material based on photocatalytic hydrogen peroxide production, it is characterized in that: The organic monomer is a mixture of 4,4',4"-nitrobenzaldehyde and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine in a molar ratio of 1:1 or a mixture of tris(4-aminophenyl)amine and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine.

5. According to the preparation method of multi-component covalent organic framework material based on photocatalytic hydrogen peroxide production, it is characterized in that: The usage ratio of the organic monomer, styrene, boron trifluoride etherate, 2,3-dichloro-5,6-dichloro-p-benzoquinone and the organic solvent is 0.16-0.32 mmol: 60 μL: 4 μL: 8 mg: 1-6 mL.

6. According to the preparation method of multi-component covalent organic framework material based on photocatalytic hydrogen peroxide production, it is characterized in that: The catalyst concentration was 6 mol·L –1 of acetic acid solution.

7. According to the preparation method of multi-component covalent organic framework material based on photocatalytic hydrogen peroxide production, it is characterized in that: The molar ratio of the organic monomer to the catalyst is 0.16-0.32:1.

2.

8. According to the preparation method of multi-component covalent organic framework material based on photocatalytic hydrogen peroxide production, it is characterized in that: The reaction temperature is 110-130 ° C and the reaction time is 3-5 days.

9. A multi-component covalent organic framework material based on photocatalytic hydrogen peroxide production prepared according to the method of any one of claims 1 to 8, characterized in that: The specific surface area of ​​this material is 900-1000m 2 g -1 .

10. Use of a multi-component covalent organic framework material based on photocatalytic hydrogen peroxide production prepared according to the method of any one of claims 1 to 8 in the preparation of hydrogen peroxide.

Images