Preparation method of a heteroporous covalent organic framework photocatalyst

Abstract

This invention proposes a method for preparing a heteroporous covalent organic framework photocatalyst. The method involves uniformly dispersing tetra-(4-aminophenyl)ethylene and 4,4'-(thiazo[5,4-d]thiazolyl-2,5-diyl)dibenzaldehyde in an organic solvent and then sonicating them at room temperature to obtain a first mixed organic solution. Acetic acid is added to the mixed organic solution, followed by sonication to obtain a second mixed organic solution. The second mixed organic solution is then subjected to a freeze-vacuum-thaw treatment to obtain a thawed product. The thawed product is placed in an oven for a solvothermal reaction to obtain a crude reactant. The crude reactant is then washed and vacuum-dried to obtain the heteroporous covalent organic framework photocatalyst. The heteroporous covalent organic framework photocatalyst prepared by this invention possesses advantages such as low density, high specific surface area, highly regular nanopore size, high stability, chemical stability, and thermal stability.

Description

Technical Field

[0001] This invention relates to the field of hydrogen peroxide preparation technology, and in particular to a method for preparing a heteroporous covalent organic framework photocatalyst. Background Technology

[0002] hydrogen peroxide ( Anthraquinone, as a green oxidant and a promising liquid fuel, is attracting increasing research interest. Currently, its industrial production mainly relies on the anthraquinone process, but this process suffers from high energy consumption and the generation of hazardous waste. In recent years, photocatalytic synthesis based on water and oxygen has provided a new route to replace the traditional anthraquinone process, including the use of metal semiconductors and metal-organic frameworks (MOFs). ) and graphitic carbon nitride ( Materials such as these have attracted much attention due to their excellent properties.

[0003] However, traditional inorganic metal semiconductors (such as , and In photocatalytic production While it has some effect in this regard, it is difficult to overcome its poor visible light absorption capacity. Metal catalysts suffer from inherent drawbacks such as low selectivity and poor stability. Furthermore, metal catalysts may cause secondary pollution, while organic polymer catalysts generally suffer from insufficient visible light absorption. Therefore, developing efficient, economical, and environmentally friendly catalysts is crucial. Photosynthesis strategies are therefore particularly urgent. Summary of the Invention

[0004] In view of the above, the main objective of this invention is to provide a method for preparing a heteroporous covalent organic framework photocatalyst to solve the aforementioned technical problems.

[0005] This invention proposes a method for preparing a heteroporous covalent organic framework photocatalyst, the method comprising the following steps: Step 1: Tetra-(4-aminophenyl)ethylene and 4,4'-(thiazo[5,4-d]thiazolyl-2,5-dimethyl)dibenzaldehyde are uniformly dispersed in an organic solvent and subjected to ultrasonic treatment at room temperature to obtain a first mixed organic solution; Step 2: Add acetic acid to the first mixed organic solution and then sonicate to obtain the second mixed organic solution; Step 3: The second mixed organic solution is subjected to freezing-vacuuming-thawing treatment to obtain the thawed product; the thawed product is placed in an oven for solvothermal reaction to obtain the crude reactant. Step 4: Wash and vacuum dry the crude reactants to obtain a heteroporous covalent organic framework photocatalyst.

[0006] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The preparation process of the heteroporous covalent organic framework photocatalyst of the present invention is simple, energy-saving and has a high yield. The prepared heteroporous covalent organic framework photocatalyst has the advantages of low density, high specific surface area, highly regular nanopore size, high stability, chemical stability and thermal stability. Compared with the indirect synthesis of hydrogen peroxide by anthraquinone in industry, the present invention has low energy consumption and high safety.

[0007] 2. The heteroporous covalent organic framework photocatalyst prepared by this invention can greatly promote the separation of photogenerated charge carriers and suppress the recombination of charge carriers, thereby improving photocatalytic efficiency. However, the DA-type imine bonds in the ethanol-water solution... It can achieve a greater number of charge transfer channels, which is beneficial for enhanced charge carrier separation, suppressed recombination, and strong oxygen absorption energy, thus improving the photocatalytic production of DA-type COF. The yield of hydrogen peroxide is significantly improved. In particular, this invention proposes for the first time a method for producing hydrogen peroxide using a heteroporous covalent organic framework photocatalyst. Compared with other photocatalytic hydrogen peroxide production techniques using porous materials, the yield of hydrogen peroxide per unit time is significantly improved. Attached Figure Description

[0008] Figure 1 The X-ray diffraction patterns are those of the heteroporous covalent organic framework photocatalysts prepared in Examples 4 to 6 of this invention. Figure 2 This is a scanning electron microscope image of the heteroporous covalent organic framework photocatalyst prepared in Example 4 of the present invention; Figure 3 This is a transmission electron microscope image of the heteroporous covalent organic framework photocatalyst prepared in Example 4 of the present invention; Figure 4 The infrared spectrum of the heteroporous covalent organic framework photocatalyst prepared in Example 4 of this invention; Figure 5 The nitrogen adsorption-desorption curve of the heteroporous covalent organic framework photocatalyst prepared in Example 4 of this invention at 77 K; Figure 6 This is a schematic diagram of the pore size distribution curve of the heteroporous covalent organic framework photocatalyst prepared in Example 4 of the present invention; Figure 7 The figure shows the hydrogen peroxide yield of the heteroporous covalent organic framework photocatalyst prepared in Example 4 of this invention. Figure 8 This is a comparison chart of the hydrogen peroxide yield of the heteroporous covalent organic framework photocatalyst prepared in Example 4 of the present invention and existing photocatalysts. Detailed Implementation

[0009] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0010] Example 1 This embodiment provides a method for preparing a heteroporous covalent organic framework photocatalyst, the method comprising the following steps: 30 mg of tetra-(4-aminophenyl)ethylene and 35 mg of 4,4'-(thiazo[5,4-d]thiazolyl-2,5-diyl)dibenzaldehyde were uniformly dispersed in 1 mL of a mixed organic solvent of o-dichlorobenzene / n-butanol (volume ratio 2:1), and the mixture was sonicated at room temperature for 2 min to obtain the first mixed organic solution. The mixed organic solution was added to 300 μL of acetic acid (6 mol / L) and then sonicated for 1 min to obtain a second mixed organic solution. The second mixed organic solution was subjected to a freeze-vacuum-thaw cycle three times to obtain the thawed product; the thawed product was placed in an oven at 140℃ for a solvothermal reaction for 72 hours to obtain the crude reactant. The crude reactants were washed three times alternately with tetrahydrofuran, ethanol, and water, and then vacuum dried at 60°C for 12 hours to obtain a heteroporous covalent organic framework photocatalyst.

[0011] Example 2 This embodiment provides a method for preparing a heteroporous covalent organic framework photocatalyst, the method comprising the following steps: 50 mg of tetra-(4-aminophenyl)ethylene and 50 mg of 4,4'-(thiazo[5,4-d]thiazolyl-2,5-diyl)dibenzaldehyde were uniformly dispersed in 1 mL of a mixed organic solvent of o-dichlorobenzene / n-butanol (volume ratio 2:1), and the mixture was sonicated at room temperature for 2 min to obtain the first mixed organic solution. The mixed organic solution was added to 500 μL of acetic acid (6 mol / L) and then sonicated for 1 min to obtain a second mixed organic solution. The second mixed organic solution was subjected to a freeze-vacuum-thaw cycle three times to obtain the thawed product; the thawed product was placed in an oven at 180℃ for a solvothermal reaction for 72 hours to obtain the crude reactant. The crude reactants were washed three times alternately with tetrahydrofuran, ethanol, and water, and then vacuum dried at 60°C for 12 hours to obtain a heteroporous covalent organic framework photocatalyst.

[0012] Example 3 This embodiment provides a method for preparing a heteroporous covalent organic framework photocatalyst, the method comprising the following steps: 11.75 mg of tetra-(4-aminophenyl)ethylene and 20.7 mg of 4,4'-(thiazo[5,4-d]thiazolyl-2,5-diyl)dibenzaldehyde were uniformly dispersed in 1 mL of a mixed organic solvent of o-dichlorobenzene / n-butanol (volume ratio 2:1), and the mixture was sonicated at room temperature for 2 min to obtain the first mixed organic solution. The mixed organic solution was added to 100 μL of acetic acid (6 mol / L) and then sonicated for 1 min to obtain a second mixed organic solution. The second mixed organic solution was subjected to a freeze-vacuum-thaw cycle three times to obtain the thawed product; the thawed product was placed in an oven at 120°C for a solvothermal reaction for 72 hours to obtain the crude reactant. The crude reactants were washed three times alternately with tetrahydrofuran, ethanol, and water, and then vacuum dried at 60°C for 12 hours to obtain a heteroporous covalent organic framework photocatalyst.

[0013] Example 4 This embodiment provides a method for preparing a heteroporous covalent organic framework photocatalyst, the method comprising the following steps: 11.75 mg of tetra-(4-aminophenyl)ethylene and 20.7 mg of 4,4'-(thiazo[5,4-d]thiazolyl-2,5-diyl)dibenzaldehyde were uniformly dispersed in 1 mL of a mixed organic solvent of o-dichlorobenzene / n-butanol (volume ratio 2:1), and the mixture was sonicated at room temperature for 2 min to obtain the first mixed organic solution. The mixed organic solution was added to 100 μL of acetic acid (6 mol / L) and then sonicated for 1 min to obtain a second mixed organic solution. The second mixed organic solution was subjected to a freeze-vacuum-thaw cycle three times to obtain the thawed product; the thawed product was placed in an oven at 120°C for a solvothermal reaction for 72 hours to obtain the crude reactant. The crude reactants were washed three times alternately with tetrahydrofuran, ethanol, and water, and then vacuum dried at 60°C for 12 hours to obtain a heteroporous covalent organic framework photocatalyst, denoted as ETTA-TTDB-1COF.

[0014] Example 5 This embodiment provides a method for preparing a heteroporous covalent organic framework photocatalyst, the method comprising the following steps: 11.75 mg of tetra-(4-aminophenyl)ethylene and 20.7 mg of 4,4'-(thiazo[5,4-d]thiazolyl-2,5-diyl)dibenzaldehyde were uniformly dispersed in 1 mL of a mixed organic solvent of o-dichlorobenzene / n-butanol (volume ratio 1:1), and the mixture was sonicated at room temperature for 2 min to obtain the first mixed organic solution. The mixed organic solution was added to 100 μL of acetic acid (6 mol / L) and then sonicated for 1 min to obtain a second mixed organic solution. The second mixed organic solution was subjected to a freeze-vacuum-thaw cycle three times to obtain the thawed product; the thawed product was placed in an oven at 120°C for a solvothermal reaction for 72 hours to obtain the crude reactant. The crude reactants were washed three times alternately with tetrahydrofuran, ethanol, and water, and then vacuum dried at 60°C for 12 hours to obtain a heteroporous covalent organic framework photocatalyst, denoted as ETTA-TTDB-2COF.

[0015] Example 6 This embodiment provides a method for preparing a heteroporous covalent organic framework photocatalyst, the method comprising the following steps: 11.75 mg of tetra-(4-aminophenyl)ethylene and 20.7 mg of 4,4'-(thiazo[5,4-d]thiazolyl-2,5-diyl)dibenzaldehyde were uniformly dispersed in 1 mL of a mixed organic solvent of mesitylene / dioxane (volume ratio 1:1), and the mixture was sonicated at room temperature for 2 min to obtain the first mixed organic solution. The mixed organic solution was added to 100 μL of acetic acid (6 mol / L) and then sonicated for 1 min to obtain a second mixed organic solution. The second mixed organic solution was subjected to a freeze-vacuum-thaw cycle three times to obtain the thawed product; the thawed product was placed in an oven at 120°C for a solvothermal reaction for 72 hours to obtain the crude reactant. The crude reactants were washed three times alternately with tetrahydrofuran, ethanol, and water, and then vacuum dried at 60°C for 12 hours to obtain a heteroporous covalent organic framework photocatalyst, denoted as ETTA-TTDB-3COF.

[0016] like Figure 1 The image shows the X-ray diffraction patterns of the heteroporous covalent organic framework photocatalysts prepared in Examples 4 to 6. pass Figure 1X-ray diffraction is a diffraction phenomenon produced by the interaction of X-rays with crystalline materials. It is used to study and determine the crystal structure, phase identification, grain size, and crystallinity of a substance. By measuring the diffraction angle and intensity, information such as the crystal structure and phase composition of the material can be obtained. In Example 4, a more obvious diffraction peak appeared at 1.8°, corresponding to the (100) crystal plane. The results show that the heteroporous covalent organic framework photocatalyst prepared in Example 4 has better crystalline COF materials.

[0017] like Figure 2 The image shown is a scanning electron microscope (SEM) image of the heteroporous covalent organic framework photocatalyst prepared in Example 4. The SEM analysis is performed by scanning the sample surface with a high-energy electron beam and obtaining the microstructure and structural information of the sample through the signal generated by the interaction between electrons and sample atoms. pass Figure 2 As can be seen, the heteroporous covalent organic framework photocatalyst prepared in Example 4 has an irregular polyhedral structure. By combining the following transmission electron microscopy characterization, it can be concluded that the heteroporous covalent organic framework material has good crystallinity. Combined with other characterization, other structures can be further excluded, confirming the successful synthesis of the photocatalyst.

[0018] like Figure 3 The image shown is a transmission electron microscope (TEM) image of the heteroporous covalent organic framework photocatalyst prepared in Example 4. TEM images are obtained by using a high-energy electron beam to penetrate a thin sample and detecting transmitted and scattered electrons to obtain the sample's microstructure and crystal structure.

[0019] pass Figure 3 It can be seen that the heteroporous covalent organic framework photocatalyst prepared in Example 4 is a continuous porous channel with a lattice size of about 4.0 nm, indicating that the prepared heteroporous covalent organic framework photocatalyst is a nanomaterial; the clearer the stripes and the wider the continuous range, the higher the crystal quality of the material, and the continuous lattice stripes indicate that the material has good crystallinity.

[0020] like Figure 4 The image shows the infrared spectrum of the heteroporous covalent organic framework photocatalyst prepared in Example 4. Infrared spectroscopy is based on the principle of characteristic absorption of infrared radiation by molecular vibrations. When infrared light of a specific frequency interacts with sample molecules, if the vibrational mode causes a change in the molecular dipole moment, resonance absorption will occur, producing characteristic absorption bands corresponding to the molecular structure. By analyzing the position, intensity, and shape of the absorption peaks, qualitative identification and quantitative characterization of the types of functional groups, chemical bonds, and molecular configuration of the material can be achieved. Figure 4 It can be seen that the characteristic absorption peak of the imine bond (-C=N-) appears at ~1625. The characteristic absorption peaks can be attributed to the characteristic stretching vibrations of the imine bond (–C=N–), confirming that a Schiff base condensation reaction successfully occurred between the aldehyde group and the amino group, forming the expected covalent organic framework structure, thus indicating that ETTA-TTDB-1 COF was successfully synthesized.

[0021] like Figure 5 The figure shows the nitrogen adsorption-desorption curve of the heteroporous covalent organic framework photocatalyst prepared in Example 4 at 77 K. The nitrogen adsorption-desorption curve at 77 K, obtained by measuring specific surface area using techniques such as gas adsorption, can quantitatively evaluate the pore structure, dispersion, and surface activity of materials, and is one of the key physical indicators for evaluating catalyst performance. The adsorption-desorption curve results show that the specific surface area of ​​ETTA-TTDB-1 COF reaches 123.4. This indicates that there are abundant nanoscale pores inside the heteroporous covalent organic framework photocatalyst.

[0022] like Figure 6 The image shows a schematic diagram of the pore size distribution curve of the heteroporous covalent organic framework photocatalyst prepared in Example 4. The pore size distribution curve is a quantitative spectrum characterizing the internal pore structure of porous materials. It is measured and plotted using gas physical adsorption technology and is used to describe the proportion of pores of different sizes in the total pore volume of the material. Figure 6 It can be seen that the heteroporous covalent organic framework photocatalyst has a uniform pore size of 1.4 nm and 4.5 nm, indicating that the heteroporous covalent organic framework photocatalyst is a porous material.

[0023] like Figure 7 As shown, this illustrates the photocatalytic product of the heteroporous covalent organic framework photocatalyst prepared in Example 4. Activity testing; Produce Specific steps: Place 5 mg ETTA-TTDB-1 COF, 2 mL ethanol and 18 mL water into a 150 mL beaker, sonicate for 10 min to make the catalyst evenly dispersed in the ethanol aqueous solution, aerate under dark conditions, and fill the solution with high-purity oxygen for 30 min to make the reaction solution reach dissolved oxygen saturation. The light source was xenon gas (MC-PF300C, Beijing Magnesium Rayson Light Source, 300 W), and visible light irradiation (λ > 420 nm) was achieved using a cutoff filter. A cooling water circulation system was used to maintain the reaction solution at approximately 6 °C. Samples were taken every 15 min, and the catalyst was filtered using a 0.22 μm filter. The concentrations of the catalyst in the reaction solution were detected using a UV-Vis spectrophotometer and iodometric titration. The content of.

[0024] pass Figure 7It can be seen that the ETTA-TTDB-1 COF (heteroporous covalent organic framework photocatalyst) prepared in Example 4 exhibits an average photocatalytic rate of 3360 μmol g⁻¹ h⁻¹ under visible light irradiation under the condition of ethanol as a sacrificial agent, demonstrating excellent photocatalytic activity. It not only has a high photocatalytic yield but also provides a basis for designing photocatalytic synthesis... Porous catalysts provide a new research direction.

[0025] pass Figure 8 It can be seen that, based on the existing photocatalyst (ETTA-TTBP COF), the photocatalytic rate of hydrogen peroxide production is 1718.63. By optimizing the structure of the functional groups, the photocatalyst (ETTA-TTDB-1COF) prepared in Example 4 achieved a photocatalytic hydrogen peroxide production rate of 3360. This increases the catalytic efficiency of photocatalysts by more than two times.

[0026] Photocatalysts based on thiazole-structured heteroporous covalent organic frameworks, with their precise band structure design, efficient charge dynamics, and excellent structural stability, have made significant contributions to the photocatalytic synthesis of... Its overall performance is significantly better than that of traditional porous materials, providing a useful reference for designing novel heteroporous covalent organic framework photocatalysts with high efficiency and stability in photocatalytic systems.

[0027] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0028] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing a heteroporous covalent organic framework photocatalyst, characterized in that, The method includes the following steps: Step 1: Tetra-(4-aminophenyl)ethylene and 4,4'-(thiazo[5,4-d]thiazolyl-2,5-dimethyl)dibenzaldehyde are uniformly dispersed in an organic solvent and subjected to ultrasonic treatment at room temperature to obtain a first mixed organic solution; Step 2: Add acetic acid to the first mixed organic solution and then sonicate to obtain the second mixed organic solution; Step 3: The second mixed organic solution is subjected to freezing-vacuuming-thawing treatment to obtain the thawed product; the thawed product is placed in an oven for solvothermal reaction to obtain the crude reactant. Step 4: Wash and vacuum dry the crude reactants to obtain a heteroporous covalent organic framework photocatalyst.

2. The method for preparing the heteroporous covalent organic framework photocatalyst according to claim 1, characterized in that, In step 1, the amount of tetra-(4-aminophenyl)ethylene added is 10~50 mg, and the amount of 4,4'-(thiazo[5,4-d]thiazolyl-2,5-dimethyl)dibenzaldehyde added is 20~50 mg.

3. The method for preparing the heteroporous covalent organic framework photocatalyst according to claim 2, characterized in that, In step 1, the ultrasonic treatment time at room temperature is 2 minutes, and the organic solvents are 1 mL of a mixed organic solvent of o-dichlorobenzene / n-butanol (volume ratio 2:1), 1 mL of a mixed organic solvent of o-dichlorobenzene / n-butanol (volume ratio 1:1), or 1 mL of a mixed organic solvent of mesitylene / dioxane (volume ratio 1:1).

4. The method for preparing the heteroporous covalent organic framework photocatalyst according to claim 3, characterized in that, In step 2, the amount of acetic acid added is 100~500μL, and the concentration is 6mol / L.

5. The method for preparing the heteroporous covalent organic framework photocatalyst according to claim 4, characterized in that, In step 2, the ultrasonic treatment time is 1 minute.

6. The method for preparing the heteroporous covalent organic framework photocatalyst according to claim 5, characterized in that, In step 3, the freezing-evacuation-thawing process is repeated 3 times, the oven temperature is 100~180℃, and the solvothermal reaction time is 72h.

7. The method for preparing the heteroporous covalent organic framework photocatalyst according to claim 6, characterized in that, In step 4, the washing conditions are tetrahydrofuran, ethanol, and water, which are used to wash the product three times alternately. The vacuum drying temperature is 60°C, and the vacuum drying time is 12 hours.

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