Preparation method and application of Se-rich covalent organic framework photocatalytic material

Abstract

The present invention discloses a method for preparing a Se-rich covalent organic framework photocatalytic material and its application. The method comprises the following steps: (1) preparing an amine monomer (PB) and an aldehyde monomer (BS) by a coupling reaction; (2) subjecting the PB and BS to ultrasonic dispersion and freeze-thaw degassing in a mixed solvent, and then synthesizing BS-PB-COF by a solvothermal reaction. Based on the synergistic effect of its conjugated skeleton and selenium active sites, the material significantly improves the visible light absorption capacity and photogenerated carrier separation efficiency. The present invention adopts a mild solvothermal reaction system, avoids high temperature and high pressure conditions, and has the characteristics of simple process, low energy consumption, and green environmental protection, and is suitable for large-scale production. The obtained BS-PB-COF material exhibits excellent activity in the photocatalytic production of hydrogen peroxide (H2O2) from seawater, and its performance is significantly better than that of similar COF photocatalysts, providing an efficient solution for green chemical synthesis and seawater resource utilization.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor photocatalytic materials, and in particular relates to a preparation method and application of a Se-rich covalent organic framework photocatalytic material. Background Art

[0002] Hydrogen peroxide (H2O2), a key oxidant, is widely used in the chemical industry, environmental remediation, and medical fields. Traditional preparation methods rely on high-temperature and high-pressure industrial synthesis, which is subject to high energy consumption, environmental pollution, and harsh reaction conditions. The development of new, efficient, green, and low-cost preparation methods is urgently needed.

[0003] Photocatalytic H2O2 production has attracted considerable attention due to its green nature. This process utilizes light energy to excite semiconductor materials, generating electron-hole pairs that drive the water splitting reaction to produce H2O2. Covalent organic frameworks (COFs) have become a research hotspot for novel photocatalysts due to their excellent structural controllability and photocatalytic activity. COFs possess highly ordered pore structures and large surface areas, making them suitable for gas adsorption and catalytic reactions, and hold great potential for photocatalytic H2O2 production.

[0004] However, existing COF materials have many problems: the synthesis process is complex and the cost is high, which limits large-scale production; the stability is poor and the reaction rate is slow, which restricts practical application; and the selectivity and product distribution in the photocatalytic reaction are affected by multiple factors such as light source intensity and reaction environment. Controlling these factors to improve efficiency still faces challenges.

[0005] In summary, developing an efficient, green, and low-cost method for preparing hydrogen peroxide, especially optimizing the preparation process and performance of covalent organic framework materials, has important practical significance and broad application prospects. Summary of the Invention

[0006] In view of the problems of low yield, long process, serious pollution or high cost in the existing technology, the present invention provides a preparation method and application of a Se-rich covalent organic framework photocatalytic material.

[0007] The technical solution adopted in the present invention is as follows:

[0008] A method for preparing a Se-rich covalent organic framework photocatalytic material comprises the following steps:

[0009] S1. Preparation of amine monomer (PB): 1,4-Dibromobenzene and 4-aminophenylboronic acid pinacol ester are reacted under an inert atmosphere with tetrakis(triphenylphosphine)palladium as a catalyst and potassium carbonate added. The reaction is then refluxed in a mixed solvent of 1,4-dioxane and water. After the reaction, the mixture is extracted, dried, and purified by column chromatography to obtain 4,4'-diaminobiphenyl, designated as PB.

[0010] S2. Preparation of aldehyde monomer (BS): 4,7-Dibromo-2,1,3-benzoselenadiazole and 3,5-diformylphenylboronic acid pinacol ester were dissolved in a mixed solvent of 1,4-dioxane and water. A coupling reaction was carried out under a nitrogen atmosphere using tetrakis(triphenylphosphine)palladium as a catalyst and potassium carbonate as a base. The reaction product was washed and dried to obtain 5,5'-(benzo[c][1,2,5]selenadiazole-4,7-diyl)diisophthalaldehyde, denoted as BS.

[0011] S3. Synthesis of BS-PB-COF: The PB obtained in step S1 and the BS obtained in step S2 were mixed at a molar ratio of 1-3:1, and a mixed solvent was added. After ultrasonic dispersion and freeze-thaw degassing, the mixture was reacted in a sealed environment at 110-130°C for 50-80 hours. The resulting precipitate was washed and dried to obtain a yellow powdered BS-PB-COF.

[0012] Furthermore, in step S1, the molar ratio of 1,4-dibromobenzene to 4-aminophenylboronic acid pinacol ester is 1:1.5-4, preferably 1:2-3, and the amount of tetrakis(triphenylphosphine)palladium used is 0.5%-1% of the total molar amount of the reactants.

[0013] Furthermore, in step S1, the reflux reaction time is 10-30 hours, preferably 12-24 hours.

[0014] Furthermore, in step S2, the coupling reaction temperature is 80-120° C., and the time is 18-30 hours.

[0015] Furthermore, in step S2, washing is performed sequentially with water, methanol, toluene and chloroform for 2-5 times, preferably 3-4 times.

[0016] Furthermore, in step S3, the mixed solvent is a mixed solvent consisting of n-butanol, o-dichlorobenzene and acetic acid aqueous solution, and the volume ratio of n-butanol, o-dichlorobenzene and acetic acid aqueous solution is 7-10:1:1.

[0017] Furthermore, the concentration of the acetic acid aqueous solution is 3-9 mol / L.

[0018] Furthermore, in step S3, the ultrasonic dispersion time is 1-5 minutes, preferably 2-3 minutes.

[0019] Furthermore, in step S3, freeze-thaw degassing comprises performing at least 2 freeze-pump-thaw cycles in a liquid nitrogen bath, preferably 2-5 times.

[0020] Furthermore, in step S3, washing is performed sequentially with tetrahydrofuran and acetone.

[0021] The above-mentioned Se-rich covalent organic framework photocatalytic material was used for photocatalytic production of hydrogen peroxide in seawater and exhibited excellent photocatalytic activity.

[0022] The beneficial effects of the present invention are:

[0023] (1) This invention utilizes a solvothermal reaction to prepare covalent organic frameworks (COFs), avoiding the complex high-temperature and high-pressure conditions of conventional methods. The process is simple to operate and streamlines post-processing steps. By combining a mild reaction system (e.g., a n-butanol / o-dichlorobenzene mixed solvent) with low-temperature degassing and sealing technology, energy consumption and equipment requirements are significantly reduced, resulting in a green and environmentally friendly synthesis process suitable for large-scale production.

[0024] (2) The Se-rich BS-PB-COF material prepared in this invention exhibits excellent visible light absorption ability and efficient separation efficiency of photogenerated carriers due to the synergistic effect of the unique conjugated system and Se active sites. The H2O2 production rate in seawater environment is as high as 3057.17 μmol·g -1 ·h -1 , significantly better than most similar COF photocatalysts.

[0025] (3) The introduction of selenium and the conjugated skeleton design in the present material not only enhance the photocatalytic activity but also impart chemical stability and controllability. This property gives it broad application prospects in areas such as photocatalytic H2O2 production and seawater resource utilization. Furthermore, the readily available raw materials and low synthesis cost further enhance the technical and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The XRD patterns of BS-PB-COF and BS-MB-COF obtained in Example 1 prove the successful synthesis of COF.

[0027] Figure 2 This is a scanning electron microscope (SEM) image of the BS-PB-COF obtained in Example 1, showing that the prepared BS-PB-COF is in the shape of a column.

[0028] Figure 3 The Fourier transform infrared spectra of BS-PB-COF and BS-MB-COF obtained in Example 1 show that the absorption peak of the aldehyde group disappears and the imine bond is formed.

[0029] Figure 4 Figure 2 is the rate diagram of photocatalytic H2O2 production of BS-PB-COF and BS-MB-COF obtained in Example 1 under visible light irradiation. BS-PB-COF exhibits excellent photocatalytic activity.

[0030] Figure 5The corresponding photocurrent test graphs of BS-PB-COF and BS-MB-COF obtained in Example 1 show the strong ability of BS-PB-COF in light absorption. DETAILED DESCRIPTION

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the present invention is not limited thereto.

[0032] Example 1

[0033] Step 1, synthesis of amine monomer:

[0034] 1,4-Dibromobenzene (0.55 g, 2.33 mmol) and 4-aminophenylboronic acid pinacol ester (1.29 g, 5.89 mmol) were dissolved in 1,4-dioxane (8 mL). Potassium carbonate (0.85 g, 6.16 mmol), distilled water (8 mL), and tetrakis(triphenylphosphine)palladium (0.03 g, 0.03 mmol) were added. The reaction mixture was refluxed under an argon atmosphere for 18 hours. Subsequently, the 1,4-dioxane was removed and evaporated under vacuum. The resulting residue was treated with water, extracted with dichloromethane, and dried over anhydrous sodium sulfate. The organic layer was separated and evaporated, and the resulting compound was purified by column chromatography using ethyl acetate and petroleum ether as eluents to obtain 4,4-diaminobiphenyl (PB).

[0035] Step 2, synthesis of aldehyde monomer:

[0036] A degassed mixture of 4,7-dibromo-2,1,3-benzoselenadiazole (0.10 g, 0.29 mmol), 3,5-diformylphenylboronic acid pinacol ester (0.21 g, 0.81 mmol), potassium carbonate (0.28 g, 2.04 mmol), 1,4-dioxane (6.0 mL), and H₂O (6.0 mL) was bubbled through for 30 minutes, followed by the addition of tetrakis(triphenylphosphine)palladium (0.03 g, 0.03 mmol). The resulting mixture was heated to 100°C under a nitrogen atmosphere and stirred for 24 hours. The reaction mixture was cooled to room temperature and poured into 100.0 mL of water. The residue was washed several times with excess water, methanol, toluene, and chloroform. The product was then oven-dried at 60°C to yield 5,5'-(benzo[c][1,2,5]selenadiazole-4,7-diyl)diisophthalaldehyde (BS).

[0037] Step 3, synthesis of BS-PB-COF:

[0038] A Pyrex tube was charged with BS (15 mg, 0.04 mmol), PB (19 mg, 0.08 mmol), n-butanol (1.8 mL), o-dichlorobenzene (0.2 mL), and aqueous acetic acid (6 M, 0.2 mL). The tube was sonicated for 3 minutes and then rapidly frozen and degassed using three freeze-pump-thaw cycles at 77 K using a liquid nitrogen bath. The tube was sealed under vacuum and placed in an oven at 120°C for 3 days. A yellow precipitate formed, which was isolated by filtration and washed with tetrahydrofuran and acetone, respectively. The sample was dried in a vacuum oven for 12 hours to yield BS-PB-COF.

[0039] Example 2

[0040] Step 1, synthesis of amine monomer:

[0041] Dissolve 1,4-dibromobenzene (0.55 g, 2.33 mmol) and 4-aminophenylboronic acid pinacol ester (1.29 g, 5.89 mmol) in 1,4-dioxane (16 mL). Add potassium carbonate (0.85 g, 6.16 mmol), distilled water (8 mL), and tetrakis(triphenylphosphine)palladium (0.03 g, 0.03 mmol). Reflux under argon for 10 hours. Subsequent treatment is the same as in Example 1 to obtain PB.

[0042] Step 2, synthesis of aldehyde monomer:

[0043] The reaction was controlled at 80° C. for 18 hours. The mixture was washed with water, methanol, toluene and chloroform twice each. The remaining steps were the same as in Example 1 to obtain BS.

[0044] Step 3, synthesis of BS-PB-COF:

[0045] The volume ratio of n-butanol, o-dichlorobenzene and 3 mol / L acetic acid aqueous solution in the mixed solvent was 7:1:1, ultrasonic dispersion was performed for 2 minutes, and freeze-thaw degassing was performed twice. The other conditions were the same as in Example 1 to obtain BS-PB-COF.

[0046] Example 3

[0047] Step 1, synthesis of amine monomer:

[0048] The reaction conditions were the same as in Example 1, but the reflux time was adjusted to 20 hours.

[0049] Step 2, synthesis of aldehyde monomer:

[0050] The coupling reaction was carried out at 90°C for 24 hours, and the mixture was washed with water, methanol, toluene and chloroform three times each.

[0051] Step 3, synthesis of BS-PB-COF:

[0052] The volume ratio of n-butanol, o-dichlorobenzene and 6 mol / L acetic acid aqueous solution in the mixed solvent was 8.5:1:1, ultrasonic dispersion was performed for 2 minutes, and freeze-thaw degassing was performed three times. The remaining steps were the same as in Example 1 to obtain BS-PB-COF.

[0053] Example 4

[0054] Step 1, synthesis of amine monomer:

[0055] The reaction conditions were the same as in Example 1, but the reflux time was extended to 30 hours.

[0056] Step 2, synthesis of aldehyde monomer:

[0057] The coupling reaction was carried out at 110°C for 30 hours, and the mixture was washed with water, methanol, toluene and chloroform four times each.

[0058] Step 3, synthesis of BS-PB-COF:

[0059] The volume ratio of n-butanol, o-dichlorobenzene and 9 mol / L acetic acid aqueous solution in the mixed solvent was 10:1:1, ultrasonic dispersion was performed for 5 minutes, and freeze-thaw degassing was performed 4 times. The other conditions were the same as in Example 1 to obtain BS-PB-COF.

[0060] The materials obtained in the above examples were characterized and tested, with Example 1 being a typical example. The experimental results are described as follows:

[0061] The XRD patterns of BS-PB-COF and BS-MB-COF are as follows: Figure 1 As shown, from Figure 1 It can be seen that there is a very sharp absorption peak between 2-10°, proving the successful synthesis of COF.

[0062] The scanning electron microscope (SEM) image of BS-PB-COF is as follows: Figure 2 As shown, from Figure 2 It can be seen from the figure that the prepared BS-PB-COF is in the shape of a column.

[0063] The Fourier transform infrared spectra of BS-PB-COF and BS-MB-COF are shown in Figure 2. Figure 3 As shown, from Figure 2 As can be seen, the aldehyde group (1700 cm -1 ) disappears, and the absorption peak of the imine bond (1627 cm -1 ) formation.

[0064] The photocatalytic H2O2 production rates of BS-PB-COF and BS-MB-COF under visible light irradiation are as follows: Figure 4 As shown by Figure 4 It can be seen that BS-PB-COF reached an astonishing 3057.17 μmol g -1 h -1 , surpassing most of the currently reported COF photocatalysts and showing excellent photocatalytic activity.

[0065] The corresponding photocurrent test diagrams of BS-PB-COF and BS-MB-COF are shown in the figure below. Figure 5 As shown, from Figure 5 It can be seen that BS-PB-COF has a very high response value, which indirectly proves its strong ability in light absorption.

[0066] Comparative Example 1

[0067] Preparation of Selenium-free COF

[0068] The rest is the same as Example 1, except that 4,7-dibromo-2,1,3-benzoselenadiazole is replaced by 4,7-dibromo-2,1,3-benzothiadiazole, and the other conditions remain unchanged.

[0069] The experimental results show that the H2O2 yield of the obtained BS-PB-COF (selenium-free) in seawater is 820 µmol·g -1 ·h -1 , which is significantly lower than 3057 μmol·g in Example 1 -1 ·h -1 , proving the decisive role of selenium.

[0070] Comparative Example 2

[0071] High temperature and high pressure synthesis

[0072] The rest is the same as Example 1, except that in S3 the reaction temperature is increased to 200° C. and the pressure is 2 MPa, while other conditions remain unchanged.

[0073] The experimental results show that the H2O2 yield is 3130 μmol·g -1 ·h -1 , which is similar to Example 1, but the energy consumption is significantly increased, the equipment requirements are complex, and it does not conform to the principles of green chemistry.

Claims

1. Application of a Se-rich covalent organic framework photocatalytic material in photocatalytic production of hydrogen peroxide in seawater, characterized in that: The method for preparing the Se-rich covalent organic framework photocatalytic material comprises the following steps: S1. Preparation of amine monomer: 1,4-dibromobenzene and 4-aminophenylboronic acid pinacol ester are reacted in an inert atmosphere with tetrakis(triphenylphosphine)palladium as a catalyst and potassium carbonate added, and the mixture is refluxed in a mixed solvent of 1,4-dioxane and water. After the reaction, the mixture is extracted, dried, and purified by column chromatography to obtain 4,4'-diaminoterphenyl (denoted as PB). S2. Preparation of aldehyde monomer: 4,7-Dibromo-2,1,3-benzoselenadiazole and 3,5-diformylphenylboronic acid pinacol ester were dissolved in a mixed solvent of 1,4-dioxane and water, and a coupling reaction was carried out under a nitrogen atmosphere using tetrakis(triphenylphosphine)palladium as a catalyst and potassium carbonate as a base. The reaction product was washed and dried to obtain 5,5'-(benzo[c][1,2,5]selenadiazole-4,7-diyl)diisophthalaldehyde, denoted as BS. S3. Synthesis of BS-PB-COF: PB obtained in step S1 and BS obtained in step S2 were mixed at a molar ratio of 1-3:1, a mixed solvent was added, and after ultrasonic dispersion and freeze-thaw degassing, the mixture was reacted in a sealed environment at 110-130°C for 50-80 hours. The resulting precipitate was washed and dried to obtain BS-PB-COF as a yellow powder. In step S1, the molar ratio of 1,4-dibromobenzene to 4-aminophenylboronic acid pinacol ester is 1:1.5-4, and the amount of tetrakis(triphenylphosphine)palladium used is 0.5%-1% of the total molar amount of the reactants; In step S3, the mixed solvent is a mixed solvent consisting of n-butanol, o-dichlorobenzene and acetic acid aqueous solution, and the volume ratio of n-butanol, o-dichlorobenzene and acetic acid aqueous solution is 7-10:1:

1.

2. The use according to claim 1, characterized in that In step S1, the reflux reaction time is 15-30 hours.

3. The use according to claim 1, characterized in that In step S2, the coupling reaction temperature is 80-120° C. and the reaction time is 18-30 hours.

4. The use according to claim 1, characterized in that In step S2, washing is performed sequentially with water, methanol, toluene and chloroform for 2 to 5 times.

5. The use according to claim 1, characterized in that The concentration of the acetic acid aqueous solution is 3-12 mol / L.

6. The use according to claim 1, characterized in that In step S3, the ultrasonic dispersion time is 2-5 minutes.

7. The use according to claim 1, characterized in that In step S3, freeze-thaw degassing includes performing at least two freeze-pump-thaw cycles in a liquid nitrogen bath; and washing is performed sequentially using tetrahydrofuran and acetone.

Images