Fluorinated cofs confined pd nanocluster photocatalyst and preparation method and application thereof

Abstract

The application discloses a kind of fluorinated COFs limited Pd nanocluster photocatalyst and its preparation method and application, belong to photocatalysis field.The preparation method of photocatalyst of the application includes the following steps: (1) amino organic precursor, fluorine functionalized aldehyde group organic precursor and acid catalyst are dispersed into solvent 1, reaction is carried out, and fluorinated COFs are prepared;(2) Pd precursor and the fluorinated COFs are added to solvent 2, and the reducing agent is added to reaction, and the photocatalyst is prepared.The method of the application is to limit Pd nanocluster to the ordered nanocavity structure constructed by fluorinated COFs, and the fluorine element enhances the force of Pd and COFs carrier and changes nanometer limited microenvironment, while the stability and catalytic activity of Pd nanocluster are improved;The photocatalyst prepared by the application has the advantages of high stability, high catalytic activity, simple operation, easy preparation and the like.

Description

Technical Field

[0001] This invention relates to the field of photocatalysis, specifically to a fluorinated COFs-confined Pd nanocluster photocatalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen peroxide is a green, clean, and environmentally friendly oxidant, widely used in environmental remediation, medical, and industrial fields. However, the traditional anthraquinone oxidation method for preparing hydrogen peroxide has many problems, such as high energy consumption, high pollution, and the generation of harmful byproducts. This leads to serious energy consumption and environmental problems. Therefore, developing new green methods for preparing hydrogen peroxide is urgently needed for the field. Photocatalytic hydrogen peroxide preparation utilizes sunlight to drive the reduction of oxygen. Due to its advantages of zero pollution, zero emissions, and low energy consumption, it has become a global research hotspot.

[0003] Highly stable and highly active photocatalysts are crucial for the photocatalytic production of hydrogen peroxide. Pd nanoclusters are considered the optimal active element for catalyzing hydrogen peroxide. Dispersing Pd nanoclusters onto the surface of photoactive materials is a common method for preparing high-performance photocatalysts. However, as the particle size decreases, the high specific surface energy Pd nanoclusters undergo severe aggregation, thus affecting catalytic performance. Therefore, there is an urgent need to develop novel strategies for preparing highly stable Pd-based photocatalysts. Summary of the Invention

[0004] To address the problems of easy aggregation and low activity of Pd nanoclusters in the photocatalytic production of hydrogen peroxide, this invention provides a fluorinated COFs-confined Pd nanocluster photocatalyst, its preparation method, and its application. The method of this invention involves confining Pd nanoclusters within an ordered nanocavity structure constructed from fluorinated COFs (covalent organic frameworks). Fluorine enhances the interaction between Pd and the COFs support and alters the nano-confined microenvironment, thereby improving the stability and catalytic activity of the Pd nanoclusters.

[0005] This invention first provides a method for preparing a photocatalyst, comprising the following steps:

[0006] (1) Disperse an amino organic precursor, a fluorinated aldehyde organic precursor and an acid catalyst in solvent 1 and react them to prepare fluorinated COFs.

[0007] (2) Add the Pd precursor and the fluorinated COFs to solvent 2, add a reducing agent to react, and prepare the photocatalyst.

[0008] In the above preparation method, in step (1), the amino organic precursor is at least one of 1,3,6,8-tetra-(p-aminophenyl)-pyrene, 5,10,15,20-tetra-(4-aminophenyl)-21H,23H-porphyrin, 1,3,5-tris(4-aminophenyl)benzene, and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine;

[0009] The fluorinated aldehyde organic precursors are p-2,5-difluoro-terephthalaldehyde and 2,3,5,6-tetrafluoro-terephthalaldehyde.

[0010] The acid catalyst is acetic acid or p-benzenesulfonic acid;

[0011] Solvent 1 is n-butanol and o-dichlorobenzene; specifically, the volume ratio of n-butanol to o-dichlorobenzene can be 1:3 to 3:1; specifically, it can be 1:1, 3:1 or 1:3.

[0012] In the above preparation method, the mass ratio of the amino organic precursor to the fluorinated aldehyde organic precursor is 3:2 to 2:1; specifically, it can be 3:2.

[0013] The volume-to-mass ratio of the acid catalyst to the amino organic precursor is 0.5 μL:1 mg to 3 μL:1 mg.

[0014] In the above preparation method, in step (2), the Pd precursor is at least one of sodium palladium and potassium chloropalladium;

[0015] The mass of the Pd precursor is 1% to 10% of the mass of the fluorinated COFs; specifically, it can be 1% to 7%, and more specifically, it can be 5% to 7% or 5%.

[0016] Solvent 2 is ethylene glycol;

[0017] The volume-to-mass ratio of solvent 2 to fluorinated COFs is 0.1 mL: 1 mg to 2 mL: 1 mg.

[0018] In the above preparation method, in step (2), the reducing agent is sodium borohydride and / or sodium citrate;

[0019] The mass ratio of the reducing agent to the Pd precursor is 10:1 to 100:1.

[0020] In the above preparation method, in step (1), the reaction temperature is 80℃~130℃; specifically, it can be 100℃~120℃; the time is 10h~100h; specifically, it can be 48h~72h.

[0021] In step (2), the temperature of the reaction when the reducing agent is added is 50℃~120℃; specifically, it can be 60℃~110℃; the time is 5h~20h; specifically, it can be 5h~10h.

[0022] In the above preparation method, step (1) further includes the steps of filtering after reaction and drying the obtained solid;

[0023] In step (2), the method further includes the step of adding the Pd precursor and the fluorinated COFs to solvent 2 and then stirring; specifically, the stirring speed is 100 to 500 rpm; the time is 1 h to 20 h; specifically, it can be 2 h.

[0024] The present invention also provides a photocatalyst prepared by the above preparation method.

[0025] Finally, this invention provides the application of the above-mentioned photocatalyst in the photocatalytic production of hydrogen peroxide.

[0026] Specifically, the photocatalytic production of hydrogen peroxide includes the production of hydrogen peroxide from water and oxygen under visible light.

[0027] The method of the present invention is to first prepare fluorinated COFs, then add the Pd precursor and fluorinated COFs to ethylene glycol, stir vigorously to allow the Pd precursor to enter the ordered nanocavities of the fluorinated COFs, add a reducing agent to allow the Pd to be controlled to be reduced in the ordered nanocavities of the COFs, and finally prepare a high-performance fluorinated COFs confined Pd nanocluster photocatalyst.

[0028] The fluorinated COFs-confined Pd nanocluster photocatalyst prepared by this invention has the advantages of high stability, high catalytic activity, simple operation, and easy preparation. Attached Figure Description

[0029] Figure 1 The figures show comparative performance of the catalysts in Examples 1-4 for photocatalytic hydrogen peroxide production.

[0030] Figure 2 TEM image of TAPT-TFPA COFs@5%Pd NCs in Example 3.

[0031] Figure 3 Photocatalytic stability test of TAPT-TFPA COFs@5%Pd NCs in Example 3.

[0032] Figure 4 This is a TEM image of TAPT-TFPA COFs@5%Pd NCs after photocatalysis in Example 3.

[0033] Figure 5Photocatalytic stability test of TAPT-PBA COFs@5%Pd NCs for Comparative Example 1.

[0034] Figure 6 The image shows a TEM image of TAPT-PBA COFs@5%Pd NCs after photocatalysis, which is Comparative Example 1.

[0035] Figure 7 This is a comparison chart showing the photocatalytic hydrogen peroxide production performance of the catalysts in Example 3 and Comparative Example 1. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to specific embodiments. The embodiments given are only for illustrating the present invention and are not intended to limit the scope of the present invention.

[0037] Unless otherwise specified, the experimental methods described in the following examples are conventional methods.

[0038] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0039] Example 1

[0040] 1) Weigh 30 mg of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT) and 20 mg of 2,3,5,6-tetrafluoro-p-dibenzaldehyde (TFPA) and add them to a mixed solution of 1.5 mL of o-dichlorobenzene and 1.5 mL of n-butanol. Sonicate at 50 Hz for 10 min, add 20 μL of acetic acid, and react at 120 °C for 72 h. Filter and dry the resulting solid to prepare TAPT-TFPA COFs material.

[0041] 2) Mix 50 mg of TAPT-TFPA COFs material from step 1) with 1% potassium chloropalladium (potassium chloropalladium mass accounts for 1% of the mass of TAPT-TFPA COFs material) in 20 mL of ethylene glycol and stir at 100 rpm for 2 h.

[0042] 3) Add 50 mg of sodium citrate to the solution in step 2) and heat to 60 °C for 5 h. Finally, filter to obtain TAPT-TFPA COFs confined Pd nanoclusters (TAPT-TFPA COFs@1% Pd NCs).

[0043] 4) The TAPT-TFPA COFs@1% Pd NCs catalyst prepared in step 3) was used for photocatalytic hydrogen peroxide production testing. 10 mg of catalyst was added to a 10% (v / v) ethanol aqueous solution and sonicated for 10 minutes to ensure complete dispersion. Then, oxygen was introduced for 15 minutes, and the mixture was sealed and placed under a visible light source (specifically, a xenon lamp, Microsolar300, Beijing Perfectlight, was used in this embodiment) for a photocatalytic reaction for 3 hours.

[0044] Example 2

[0045] 1) Weigh 30 mg of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT) and 20 mg of 2,3,5,6-tetrafluoro-p-dibenzaldehyde (TFPA) and add them to a mixed solution of 1 mL of o-dichlorobenzene and 3 mL of n-butanol. Sonicate at 50 Hz for 10 min, add 50 μL of acetic acid, and react at 100 °C for 48 h. Filter and dry the resulting solid to prepare TAPT-TFPA COFs material.

[0046] 2) Mix 50 mg of TAPT-TFPA COFs material from step 1) with 3% potassium chloropalladium (potassium chloropalladium mass accounts for 3% of the mass of TAPT-TFPA COFs material) in 30 mL of ethylene glycol and stir at 300 rpm for 2 h.

[0047] 3) Add 100 mg of sodium citrate to the solution in step 2) and heat to 80 °C for 10 h. Finally, filter to obtain TAPT-TFPA COFs confined Pd nanoclusters (TAPT-TFPA COFs@3% Pd NCs).

[0048] 4) The TAPT-TFPA COFs@3% Pd NCs catalyst prepared in step 3) was used for photocatalytic hydrogen peroxide production testing, and the method was the same as in Example 1.

[0049] Example 3

[0050] 1) Weigh 30 mg of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT) and 20 mg of 2,3,5,6-tetrafluoro-p-dibenzaldehyde (TFPA) and add them to a mixed solution of 3 mL of o-dichlorobenzene and 1 mL of n-butanol. Sonicate at 50 Hz for 10 min, add 30 μL of acetic acid, and react at 110 °C for 60 h. Filter and dry the resulting solid to prepare TAPT-TFPA COFs material.

[0051] 2) Mix 50 mg of TAPT-TFPA COFs material from step 1) with 5% potassium chloropalladium (potassium chloropalladium mass accounts for 5% of the mass of TAPT-TFPA COFs material) in 40 mL of ethylene glycol and stir at 200 rpm for 2 h.

[0052] 3) Add 100 mg of sodium citrate to the solution in step 2) and heat to 90 °C for 8 h. Finally, filter to obtain TAPT-TFPA COFs confined Pd nanoclusters (TAPT-TFPA COFs@5% Pd NCs).

[0053] 4) The TAPT-TFPA COFs@5% Pd NCs catalyst prepared in step 3) was used for photocatalytic hydrogen peroxide production testing, and the method was the same as in Example 1.

[0054] Example 4

[0055] 1) Weigh 30 mg of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT) and 20 mg of 2,3,5,6-tetrafluoro-p-dibenzaldehyde (TFPA) and add them to a mixed solution of 1.5 mL of o-dichlorobenzene and 1.5 mL of n-butanol. Sonicate at 50 Hz for 10 min, add 20 μL of acetic acid, and react at 110 °C for 50 h. Filter and dry the resulting solid to prepare TAPT-TFPA COFs material.

[0056] 2) Mix 50 mg of TAPT-TFPA COFs material from step 1) with 7% potassium chloropalladium (potassium chloropalladium mass accounts for 7% of the mass of TAPT-TFPA COFs material) in 40 mL of ethylene glycol and stir at 100 rpm for 2 h.

[0057] 3) Add 100 mg of sodium citrate to the solution in step 2) and heat to 110 °C for 10 h. Finally, filter to obtain TAPT-TFPA COFs confined Pd nanoclusters (TAPT-TFPA COFs@7% Pd NCs).

[0058] 4) The TAPT-TFPA COFs@7% Pd NCs catalyst prepared in step 3) was used for photocatalytic hydrogen peroxide production testing, and the method was the same as in Example 1.

[0059] Figure 1 The photocatalytic hydrogen peroxide production performance of the catalysts prepared in Examples 1-4 shows that the best catalytic performance can be obtained when the amount of Pd added is 5%.

[0060] Figure 2The image shows a TEM image of TAPT-TFPACOFs@5% Pd NCs prepared in Example 3, which shows that the particle size of the Pd nanoclusters is 2.4 nm.

[0061] Figure 3 The photocatalytic cycling stability of TAPT-TFPACOFs@5% Pd NCs prepared in Example 3 is determined by... Figure 3 It can be seen that the catalyst performance did not significantly decrease after 100 hours of photocatalysis. The photocatalytic cycle stability test method is as follows: 10 mg of catalyst was added to a 10% (v / v) ethanol aqueous solution and sonicated for 10 minutes to ensure complete dispersion of the catalyst. Then, oxygen was introduced for 15 minutes, the reaction tank was sealed, and the reaction tank was placed under a visible light source (a xenon lamp was used in this embodiment) for photocatalytic reaction. After 3 hours, the catalyst was separated by centrifugation, and then the catalyst was added back to a 10% (v / v) ethanol aqueous solution and sonicated for 10 minutes to ensure complete dispersion of the catalyst. Oxygen was introduced for 15 minutes, the reaction tank was sealed, and the reaction tank was placed under a visible light source for photocatalytic reaction. After 3 hours, the catalyst was separated by centrifugation, and the above steps were repeated.

[0062] Figure 4 This is a TEM image of TAPT-TFPACOFs@5% Pd NCs prepared in Example 3 after 102 hours of photocatalysis. Figure 4 It can be seen that no significant aggregation occurred in TAPT-TFPACOFs@5% Pd NCs after photocatalysis. This indicates that the fluorine element enhanced the interaction between Pd and TAPT-TFPACOFs, thereby improving the catalyst stability.

[0063] Comparative Example 1

[0064] 1) Weigh 30 mg of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT) and 20 mg of p-dibenzaldehyde (PBA) and add them to a mixed solution of 3 mL of o-dichlorobenzene and 1 mL of n-butanol. Sonicate at 50 Hz for 10 min, add 30 μL of acetic acid, and react at 110 °C for 60 h. Filter and dry the resulting solid to prepare TAPT-PBACOFs material.

[0065] 2) Mix 50 mg TAPT-PBA COFs from step 1) with 5% potassium chloropalladate in 40 mL of ethylene glycol and stir at 200 rpm for 2 h.

[0066] 3) Add 100 mg of sodium citrate to the solution in step 2) and heat to 90 °C for 8 h. Finally, filter to obtain TAPT-PBACOFs confined Pd nanoclusters (TAPT-PBA COFs@5% Pd NCs).

[0067] 4) The TAPT-PBA COFs@5% Pd NCs catalyst prepared in step 3) was used for photocatalytic hydrogen peroxide production testing, and the method was the same as in Example 1.

[0068] Figure 5 Photocatalytic cycling stability of TAPT-PBA COFs@5% Pd NCs prepared in Comparative Example 1 (test method and...) Figure 3 (Same method), by Figure 5 It can be seen that the catalyst underwent significant performance degradation after 50 hours of photocatalysis.

[0069] Figure 6 This is a TEM image of TAPT-PBA COFs@5% Pd NCs prepared in Comparative Example 1 after 51 hours of photocatalysis. Figure 6 It was found that TAPT-PBA COFs@5% Pd NCs underwent severe aggregation after photocatalysis. This further demonstrates that the presence of F element is beneficial to improving the stability of Pd nanoclusters.

[0070] Figure 7 This is a performance comparison chart of photocatalytic hydrogen peroxide preparation between Example 3 and Comparative Example 1. The catalytic performance of TAPT-TFPA COFs@5% Pd NCs is significantly higher than that of TAPT-PBA COFs@5% Pd NCs, indicating that the presence of F element not only improves the stability of the catalyst, but also enhances the activity of photocatalytic hydrogen peroxide preparation.

Claims

1. The application of a photocatalyst in the photocatalytic production of hydrogen peroxide, characterized in that: The preparation method of the photocatalyst includes the following steps: (1) The amino organic precursor, the fluorinated aldehyde organic precursor and the acid catalyst are dispersed in solvent 1 and reacted to prepare fluorinated COFs; In step (1), the amino organic precursor is 2,4,6-tris(4-aminophenyl)-1,3,5-triazine; The fluorinated aldehyde organic precursors are p-2,5-difluoro-terephthalaldehyde and 2,3,5,6-tetrafluoro-terephthalaldehyde. The acid catalyst is acetic acid or p-benzenesulfonic acid; (2) Add the Pd precursor and the fluorinated COFs to solvent 2, add a reducing agent to react, and prepare the photocatalyst.

2. The application according to claim 1, characterized in that: In step (1), solvent 1 is n-butanol and o-dichlorobenzene.

3. The application according to claim 2, characterized in that: The volume ratio of n-butanol to o-dichlorobenzene is 1:3 to 3:

1.

4. The application according to any one of claims 1-3, characterized in that: The mass ratio of the amino organic precursor to the fluorinated aldehyde organic precursor is 3:2 to 2:

1. The volume-to-mass ratio of the acid catalyst to the amino organic precursor is 0.5 μL:1 mg to 3 μL:1 mg.

5. The application according to any one of claims 1-3, characterized in that: In step (2), the Pd precursor is at least one of sodium palladium and potassium chloropalladium; The mass of the Pd precursor is 1% to 10% of the mass of the fluorinated COFs; Solvent 2 is ethylene glycol.

6. The application according to claim 5, characterized in that: The mass of the Pd precursor is 5% of the mass of the fluorinated COFs.

7. The application according to any one of claims 1-3, characterized in that: In step (2), the reducing agent is sodium borohydride and / or sodium citrate; The mass ratio of the reducing agent to the Pd precursor is 10:1 to 100:

1.

8. The application according to any one of claims 1-3, characterized in that: In step (1), the reaction temperature is 80 ℃~130 ℃; In step (2), the temperature of the reaction when the reducing agent is added is 50 ℃~120 ℃; the time is 5 h~20 h.

9. The application according to any one of claims 1-3, characterized in that: In step (2), the method further includes the step of adding the Pd precursor and the fluorinated COFs to solvent 2 and then stirring.

10. The application according to claim 9, characterized in that: The stirring speed is 100~500 rpm.

Images