Phenanthrenequinone-based conjugated organic polymer photocatalyst as well as preparation method and application thereof

Abstract

The invention discloses a quinonyl conjugated organic polymer photocatalyst as well as a preparation method and application thereof, and belongs to the technical field of preparation of photocatalyst materials. The quinonyl conjugated organic polymer photocatalyst disclosed by the invention is formed by imine bond connection formed by a phenanthrenequinone group-containing aldehyde monomer and an amine monomer through a Schiff base condensation reaction, and the photocatalytic efficiency is improved by constructing an electron donor block and an electron acceptor block to initiate a push-pull electron effect in a material. According to the photocatalyst, pure water and air are subjected to photocatalysis under the condition that a sacrificial agent is not needed, and hydrogen peroxide can be efficiently generated.

Description

Technical Field

[0001] The present invention relates to a phenanthraquinone-based conjugated organic polymer photocatalyst, a preparation method thereof, and an application thereof, belonging to the technical field of preparation of photocatalyst materials. Background Art

[0002] As an important inorganic chemical raw material and fine chemical product, hydrogen peroxide plays a key role in many fields such as chemical synthesis, pulp and textile bleaching, metal ore treatment, environmental protection, electronics, military, and aerospace. With the rapid development of the global economy, the production of hydrogen peroxide is moving forward in the direction of large scale, high technology, and automatic control. Especially since the 1990s, with the continuous expansion of its application scope in the paper-making, environmental protection, and electronics industries, the market demand for hydrogen peroxide has been continuously increasing.

[0003] At present, the main methods for industrial production of hydrogen peroxide are anthraquinone autoxidation method, electrolysis method, oxygen cathode reduction method, isopropanol method, and direct synthesis of hydrogen and oxygen. Among them, the autoxidation method of anthraquinone compounds is the mainstream production method, which includes multiple steps such as hydrogenation, oxidation, extraction, and purification. However, this manufacturing process has significant drawbacks. It not only requires the construction of complex infrastructure, consumes a large amount of energy, but also causes serious environmental pollution. In addition, the use of noble metal catalysts and high-pressure hydrogen in the hydrogenation reaction stage not only greatly increases the production cost of hydrogen peroxide, but also adds many safety risks.

[0004] Therefore, it is of great significance to develop a catalyst for the preparation of hydrogen peroxide with high efficiency, low cost, and environmental friendliness. Summary of the Invention

[0005] Aiming at the defects existing in the prior art, the purpose of the present invention is to provide a phenanthraquinone-based conjugated organic polymer photocatalyst, a preparation method thereof, and an application thereof. The phenanthraquinone-based conjugated organic polymer is formed by connecting an aldehyde monomer containing a phenanthraquinone group and an amine monomer through a Schiff base condensation reaction to form an imine bond. By constructing an electron-donating building block and an electron-accepting building block, the push-pull electron effect inside the material is induced to improve the photocatalytic efficiency. Without the need for a sacrificial agent, this photocatalyst can perform photocatalysis on pure water and air to efficiently generate hydrogen peroxide.

[0006] In order to achieve the above purpose, the following technical solutions are provided:

[0007] The present invention provides a phenanthraquinone-based conjugated organic polymer photocatalyst for photocatalytic generation of hydrogen peroxide. The structural unit of the phenanthraquinone-based conjugated organic polymer has the following structural formula:

[0008]

[0009] Any one of

[0010] The present invention also provides a preparation method of the phenanthraquinone-based conjugated organic polymer photocatalyst described above, and the preparation method includes the following steps:

[0011] (1) Add 2,7-dibromophenanthraquinone into a mixed solution of 1,4-dioxane and water, and add p-formylphenylboronic acid, tetrakis(triphenylphosphine)palladium, and anhydrous potassium carbonate. Stir and react, add ethanol and water for quenching, then centrifuge and filter, and take the precipitate for drying to obtain a red solid powder product A;

[0012] (2) Mix the product A obtained in step (1) with an ammonia monomer molecule, place it in a reactor, and add a mixed solution composed of acetic acid solution, n-butanol, and o-dichlorobenzene. Freeze it in liquid nitrogen, evacuate, and then thaw. Repeat the freezing-evacuation-thawing operation 3 to 5 times. After the reactor is cooled to room temperature, carry out a heating reaction. After the reaction ends, cool it to room temperature, filter and wash the product in the reactor to obtain the phenanthraquinone-based conjugated organic polymer photocatalyst.

[0013] In one embodiment, the volume ratio of 1,4-dioxane to water in the mixed solution in step (1) is 6 to 8:1.

[0014] In one embodiment, the molar ratio of 2,7-dibromophenanthraquinone, p-formylphenylboronic acid, tetrakis(triphenylphosphine)palladium, and anhydrous potassium carbonate in step (1) is 0.2 to 0.5:2:0.05:2.

[0015] In one embodiment, the temperature of the stirring reaction in step (1) is 80 to 90 °C, and the time is 24 to 36 h.

[0016] In one embodiment, the centrifugation parameters in step (1) are: 1000 to 3000 rpm, and the time is 5 to 10 min.

[0017] In one embodiment, the drying temperature in step (1) is 80 to 90 °C.

[0018] In one embodiment, the ammonia monomer molecule in step (2) is 1,3,5-tris(4-aminophenyl)benzene or 1,3,6,8-tetra-(p-aminophenyl)pyrene.

[0019] In one embodiment, the molar ratio of the product A to the ammonia monomer molecule in step (2) is 3 to 4:2.

[0020] In one embodiment, the concentration of the acetic acid solution in step (2) is 3 to 6 mol / L.

[0021] In one embodiment, the volume ratio of the acetic acid solution, n-butanol, and o-dichlorobenzene in the mixed solution in step (2) is 0.2 to 0.5:1:1.

[0022] In one embodiment, the solid-liquid ratio in the reactor in step (2) is 0.02-0.06:2-5; g / mL.

[0023] In one embodiment, the temperature of the heating reaction in step (2) is 80-90 °C, and the time is 24-36 h.

[0024] The present invention also provides the application of the above-mentioned phenanthraquinone-based conjugated organic polymer photocatalyst in the catalytic production of hydrogen peroxide.

[0025] The present invention also provides a method for photocatalytic production of hydrogen peroxide, and the method includes:

[0026] In a Pyrex glass bottle, water and a phenanthraquinone-based conjugated organic polymer photocatalyst are added, the opening is sealed with a rubber stopper, ultrasonic treatment is carried out, then oxygen is introduced into the water through a needle to keep the pressure in the bottle balanced, and an oxygen balloon is connected to ensure the oxygen atmosphere inside the glass bottle. After that, the glass bottle is irradiated with a xenon lamp equipped with a 420 nm filter for reaction.

[0027] In one embodiment, the ultrasonic treatment time is 20-30 min.

[0028] In one embodiment, the addition amount of the phenanthraquinone-based conjugated organic polymer photocatalyst is 0.1-0.2 mg added to each milliliter of water.

[0029] The present invention also provides a method for improving the efficiency of photocatalytic production of hydrogen peroxide, and the method includes:

[0030] In a Pyrex glass bottle, water and a phenanthraquinone-based conjugated organic polymer photocatalyst are added, the opening is sealed with a rubber stopper, ultrasonic treatment is carried out, then oxygen is introduced into the water through a needle to keep the pressure in the bottle balanced, and an oxygen balloon is connected to ensure the oxygen atmosphere inside the glass bottle. After that, the glass bottle is irradiated with a xenon lamp equipped with a 420 nm filter for reaction.

[0031] Beneficial effects:

[0032] (1) In the present invention, the synthesized ligand product A and 1,3,6,8-tetra-(p-aminophenyl)-pyrene or 1,3,5-tris(4-aminophenyl)benzene are used in a n-butanol / o-dichlorobenzene / acetic acid aqueous solution system, and two conjugated organic polymers containing phenanthraquinone imine bonds are obtained by a solvothermal method. The polymer has a large specific surface area (usually between 30-40 m 2 ·g -1 between), and it can achieve an oxygen reduction reaction under an oxygen atmosphere through light irradiation to efficiently produce hydrogen peroxide (the rate is between 700-1600 μmol·g -1 ·h-1 )。

[0033] (2) The conjugated organic polymer linked by phenanthraquinone imine bonds provided by the present invention combines the electron push-pull effect between the extended two-dimensional π-conjugated skeleton, the electron-donating tetraphenylpyrene, and the electron-withdrawing phenanthraquinone, which can not only improve the visible light capture ability, but also accelerate the separation and migration of photo-generated charges. At the same time, the phenanthraquinone part as the redox center can accept the photo-generated electrons in the conduction band and transfer them to the adsorbed O2 molecules to generate hydrogen peroxide, thereby improving the photocatalytic activity. The clear structure of the conjugated organic polymer with a specific structure of the phenanthraquinone redox center provides molecular-level insights into the mechanism of efficient photocatalytic H2O2 production;

[0034] (3) The synthesis method of the present invention is simple and easy to implement, the reagents and raw materials used are easily obtained, and it has high industrial application value and is easy to promote and apply. Description of the Drawings

[0035] Figure 1 1H NMR spectrum of the phenanthraquinone-based PQ monomer obtained in Example 1;

[0036] Figure 2 Fourier transform infrared spectroscopy comparison chart of the photocatalyst PQ-PTB-COP prepared in Example 1 and the monomers used in the synthesis;

[0037] Figure 3 Fourier transform infrared spectroscopy comparison chart of the photocatalyst PQ-TPB-COP material prepared in Example 2 and the monomers used in the synthesis;

[0038] Figure 4 N2 adsorption-desorption isotherm diagram of the photocatalyst PQ-PTB-COP prepared in Example 1;

[0039] Figure 5 N2 adsorption-desorption isotherm diagram of the photocatalyst PQ-TPB-COP prepared in Example 2;

[0040] Figure 6 Solid-state 13C NMR spectrum of the photocatalyst PQ-PTB-COP prepared in Example 1;

[0041] Figure 7 Solid-state 13C NMR spectrum of the photocatalyst PQ-TPB-COP prepared in Example 2;

[0042] Figure 8 Relationship diagram of the photocatalytic hydrogen peroxide production yield and time of PQ-PTB-COP and PQ-TPB-COP prepared in Examples 1 and 2, and QP-PTB-COP and QP-TPB-COP prepared in Comparative Examples 1 and 2 under an oxygen atmosphere. Detailed Description of the Invention

[0043] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention. The following specific embodiments further describe the present invention.

[0044] Example 1

[0045] The preparation of the photocatalyst PQ-PTB-COP includes the following steps:

[0046] (1) 0.183 g (0.5 mmol) of 2,7-dibromophenanthraquinone was added to a mixed solution of 6 mL of 1,4-dioxane and 1 mL of water, and 0.3 g (2 mmol) of p-formylphenylboronic acid, 0.05 g (0.05 mmol) of tetrakis(triphenylphosphine)palladium, and 0.276 g (2 mmol) of anhydrous potassium carbonate were added. After stirring and reacting at 90 °C for 24 h, 10 mL of ethanol and 10 mL of water were added for quenching, and then centrifuged at 1000 rpm / min for 10 min. The precipitate was taken and dried at 90 °C to obtain a red solid powder product, the PQ monomer; the reaction formula is as follows:

[0047]

[0048] (2) 0.033 g (0.08 mmol) of the PQ monomer was mixed with 0.023 g (0.04 mmol) of 1,3,6,8-tetra-(p-aminophenyl)-pyrene and placed in a 10 mL glass tube. A mixed solution composed of 0.2 mL of 6 mol / L acetic acid solution, 1 mL of n-butanol and 1 mL of o-dichlorobenzene was added. It was frozen in liquid nitrogen, then evacuated to remove air, and then thawed. The freezing-evacuation-thawing operation was repeated 3 times. Then the glass tube was sealed. After the glass tube was cooled to room temperature, it was placed in an oven and reacted at 90 °C for 48 h. After it was cooled to room temperature, the product in the tube was filtered, washed and dried to obtain 0.048 g of PQ-PTB-COP. The reaction formula is as follows:

[0049]

[0050] Example 2

[0051] The preparation of the photocatalyst PQ-TPB-COP includes the following steps:

[0052] (1) 0.183 g (0.5 mmol) of 2,7-dibromophenanthraquinone was added to a mixed solution of 6 mL of 1,4-dioxane and 1 mL of water. Then, 0.3 g (2 mmol) of 4-formylphenylboronic acid, 0.05 g (0.05 mmol) of tetrakis(triphenylphosphine)palladium, and 0.276 g (2 mmol) of anhydrous potassium carbonate were added. After stirring at 90 °C for 24 h, 10 mL of ethanol and 10 mL of water were added for quenching. Then, it was centrifuged at 1000 rpm / min for 10 min, and the precipitate was taken and dried at 90 °C to obtain a red solid powder product, the PQ monomer; the reaction formula is as follows:

[0053]

[0054] (2) 0.025 g (0.06 mmol) of the PQ monomer and 0.014 g (0.04 mmol) of 1,3,5-tris(4-aminophenyl)benzene were mixed and placed in a 10 mL glass tube. A mixed solution composed of 0.2 mL of 6 mol / L acetic acid solution, 1 mL of n-butanol, and 1 mL of o-dichlorobenzene was added. It was frozen in liquid nitrogen, then the air was removed by vacuum pumping, and then thawed. The freezing-vacuum pumping-thawing operation was repeated 3 times. Then, the glass tube was sealed. After the glass tube was cooled to room temperature, it was placed in an oven and reacted at 90 °C for 48 h. After it was cooled to room temperature, the product in the tube was filtered, washed, and dried to obtain 0.03 g of PQ-TPB-COP. The reaction formula is as follows:

[0055]

[0056] Comparative Example 1

[0057] (1) 4,4'-Dibromobiphenyl (156 mg, 0.5 mmol, 1.0 eq.), 4-formylphenylboronic acid (300 mg, 2.0 mmol, 4 eq.), K2CO3 (276 mg, 2.0 mmol, 4 eq.), and Pd(PPh3)4 (50 mg, 0.05 mmol, 10 mol%) were added to a mixed solution of 6 mL of 1,4-dioxane and 1.5 mL of H2O. It was heated under reflux at 90 °C in a 25 mL Schlenk tube for 24 h. After cooling to room temperature, the precipitate was collected by filtration and washed with water and ethanol until the washing liquid was clear. Then, the product was dried in a vacuum drying oven to obtain a gray powder, the QP monomer; the reaction formula is as follows:

[0058]

[0059] (2) Add QP monomer (29.0 mg, 0.08 mmol) and 1,3,6,8-tetra-(p-aminophenyl)-pyrene (22.6 mg, 0.04 mmol) into a 25 mL Schlenk tube, then add a mixed solution of 1.5 mL of o-dichlorobenzene and 1.5 mL of n-butanol, ultrasonically disperse for 15 min, then add 0.2 mL of 6 mol / L acetic acid solution, continue to ultrasonically disperse for 15 min. Freeze the Schlenk tube in liquid nitrogen and evacuate, then thaw, repeat this step 3 times. After the glass tube returns to room temperature, place it in an oven, and then react at 90 °C for 48 h. After it cools to room temperature, filter the product in the tube, wash and dry it to obtain 0.04 g of QP-PTB-COP; the reaction formula is as follows:

[0060]

[0061] Comparative Example 2

[0062] (1) Add 4,4'-dibromobiphenyl (156 mg, 0.5 mmol, 1.0 eq.), 4-formylphenylboronic acid (300 mg, 2.0 mmol, 4 eq.), K2CO3 (276 mg, 2.0 mmol, 4 eq.) and Pd(PPh3)4 (50 mg, 0.05 mmol, 10 mol%) into a mixture of 6 mL of 1,4-dioxane and 1.5 mL of H2O, heat and reflux at 90 °C in a 25 mL Schlenk tube for 24 h. After cooling to room temperature, collect the precipitate by filtration and wash it with water and ethanol until the washing liquid is clear; dry the product in a vacuum drying oven to obtain a gray powder of QP monomer; the reaction formula is as follows:

[0063]

[0064] (2) Add QP monomer (21.7 mg, 0.06 mmol) and 1,3,5-tris(4-aminophenyl)benzene (14.0 mg, 0.04 mmol) into a 25 mL Schlenk tube, then add a mixed solution of 1.5 mL of o-dichlorobenzene and 1.5 mL of n-butanol, ultrasonically disperse for 15 min, then add 0.2 mL of 6 mol / L acetic acid solution, continue to ultrasonically disperse for 15 min. Freeze the Schlenk tube in liquid nitrogen and evacuate, then thaw, repeat this step 3 times. After the glass tube returns to room temperature, place it in an oven, and then react at 90 °C for 48 h. After it cools to room temperature, filter the product in the tube, wash and dry it to obtain 0.03 g of QP-TPB-COP; the reaction formula is as follows:

[0065]

[0066] Performance Analysis

[0067] Figure 11H NMR spectrum of the PQ monomer prepared in Example 1. The characteristic peaks of the monomer in the figure prove that the reaction proceeded smoothly and the corresponding structure was synthesized.

[0068] Figure 2 and Figure 3 are the comparative Fourier transform infrared spectra of the phenanthraquinone-based imine bond-linked conjugated organic polymers and the monomers used in the synthesis prepared in Examples 1 and 2, respectively. The presence of the characteristic peaks corresponding to the carbon-nitrogen double bonds in the figure proves the formation of the imine bond.

[0069] Figure 4 and Figure 5 are the N2 adsorption-desorption isotherms of the phenanthraquinone-based imine bond-linked conjugated organic polymers PQ-PTB-COP and PQ-TPB-COP prepared in Examples 1 and 2.

[0070] Figure 6 and Figure 7 are the solid-state 13C NMR spectra of the phenanthraquinone-based imine bond-linked conjugated organic polymers PQ-PTB-COP and PQ-TPB-COP prepared in Examples 1 and 2; the correct structure of the material was determined according to the positions of the carbon peaks in the spectra.

[0071] Example 3

[0072] 10 mg of the photocatalysts PQ-PTB-COP, PQ-TPB-COP, QP-PTB-COP, and QP-TPB-COP prepared in Examples 1 and 2 and Comparative Examples 1 and 2 were respectively added into Pyrex glass bottles, and then 50 ml of deionized water was added. The openings were sealed with rubber stoppers and ultrasonicated for 30 min. Then, oxygen was passed into the water through a needle to maintain the pressure balance in the bottle. The oxygen was passed for 30 min, and an oxygen balloon was connected to ensure the oxygen atmosphere inside the glass bottle. Next, the glass bottles were irradiated with a xenon lamp equipped with a 420 nm filter. Every hour, 0.5 ml of the sample was taken through the needle and filtered. The filtered liquid was mixed with 1.5 ml of potassium titanyl oxalate solution. After gently shaking in the dark for 30 min, the peak of the solution was measured using liquid ultraviolet, and compared with the potassium titanyl oxalate standard solution. The amount of hydrogen peroxide was calculated through the corresponding relationship between the peak value and the concentration and the reaction ratio of the chemical reaction equation.

[0073] The results are as Figure 8 shown. It can be seen from the results that when the reaction proceeded for 1 hour, using the photocatalyst PQ-PTB-COP prepared in Example 1, the hydrogen peroxide yield was 1550 μmol·g -1 ·h -1 ; using the photocatalyst PQ-TPB-COP prepared in Example 2, the hydrogen peroxide yield was 748 μmol·g -1 ·h-1 ; Using the photocatalyst QP-PTB-COP prepared in Comparative Example 1, the yield of hydrogen peroxide was 224 μmol·g -1 ·h -1 ; Using the photocatalyst QP-TPB-COP prepared in Comparative Example 2, the yield of hydrogen peroxide was 86 μmol·g -1 ·h -1 ;

[0074] When the reaction proceeded for 4 hours, using the photocatalyst PQ-PTB-COP prepared in Example 1, the total yield of hydrogen peroxide was 4100 μmol·g -1 , using the photocatalyst PQ-TPB-COP prepared in Example 2, the total yield of hydrogen peroxide was 2800 μmol·g -1 ; Using the photocatalyst QP-PTB-COP prepared in Comparative Example 1, the total yield of hydrogen peroxide was 718 μmol·g -1 ; Using the photocatalyst QP-TPB-COP prepared in Comparative Example 2, the total yield of hydrogen peroxide was 316 μmol·g -1 ;

[0075] The results show that the photocatalysts PQ-PTB-COP and PQ-TPB-COP have higher catalytic activities and can effectively improve the yield of hydrogen peroxide under the same reaction conditions.

[0076] The embodiments provided above are not intended to limit the scope covered by the present invention, nor are the described steps intended to limit their execution order. Obvious improvements made by those skilled in the art in combination with the existing common general knowledge also fall within the protection scope defined by the claims of the present invention.

Claims

1. A phenanthraquinone-based conjugated organic polymer photocatalyst for photocatalytic generation of hydrogen peroxide, characterized in that, The structural formula of the structural unit of the phenanthraquinone-based conjugated organic polymer is as follows: Any one of 2. The preparation method of the phenanthraquinone-based conjugated organic polymer photocatalyst according to claim 1, characterized in that, The preparation method includes the following steps: (1) Add 2,7-dibromophenanthraquinone to a mixed solution of 1,4-dioxane and water, and add p-formylphenylboronic acid, tetrakis(triphenylphosphine)palladium, and anhydrous potassium carbonate. Stir and react, add ethanol and water for quenching, then centrifuge and filter, and take the precipitate for drying to obtain a red solid powder product A; (2) Mix the product A obtained in step (1) with an amino monomer molecule and place it in a reactor. Then add a mixed solution composed of acetic acid solution, n-butanol, and o-dichlorobenzene. Freeze in liquid nitrogen, evacuate, and then thaw. Repeat the freezing-evacuation-thawing operation 3-5 times. After the reactor cools to room temperature, carry out a heating reaction. After the reaction ends and cools to room temperature, filter and wash the product in the reactor to obtain the phenanthraquinone-based conjugated organic polymer photocatalyst.

3. The preparation method according to claim 2, characterized in that, In the mixed solution in step (1), the volume ratio of 1,4-dioxane to water is 6-8:

1.

4. The preparation method according to claim 2, characterized in that, In step (1), the molar ratio of 2,7-dibromophenanthraquinone, p-formylphenylboronic acid, tetrakis(triphenylphosphine)palladium, and anhydrous potassium carbonate is 0.2-0.5:2:0.05:

2.

5. The preparation method according to claim 2, characterized in that, The amino monomer molecule in step (2) is 1,3,5-tris(4-aminophenyl)benzene or 1,3,6,8-tetra-(p-aminophenyl)pyrene.

6. The preparation method according to claim 2, characterized in that, In step (2), the molar ratio of product A to the amino monomer molecule is 3-4:

2.

7. The preparation method according to claim 2, characterized in that, In the mixed solution in step (2), the volume ratio of acetic acid solution, n-butanol, and o-dichlorobenzene is 0.2-0.5:1:

1.

8. Application of the phenanthraquinone-based conjugated organic polymer photocatalyst according to claim 1 in the catalytic production of hydrogen peroxide.

9. A method for photocatalytic production of hydrogen peroxide, characterized in that, The method includes: In a Pyrex glass bottle, add water and the phenanthraquinone-based conjugated organic polymer photocatalyst according to claim 1, seal the opening with a rubber stopper, perform ultrasonic treatment, then pass oxygen into the water through a needle to maintain the pressure balance in the bottle, ensure the oxygen atmosphere inside the glass bottle by connecting an oxygen balloon, and then irradiate the glass bottle with a xenon lamp equipped with a 420 nm filter for reaction.

10. A method for improving the efficiency of photocatalytic production of hydrogen peroxide, characterized in that, The method includes: In a Pyrex glass bottle, add water and the phenanthraquinone-based conjugated organic polymer photocatalyst according to claim 1, seal the opening with a rubber stopper, perform ultrasonic treatment, then pass oxygen into the water through a needle to maintain the pressure balance in the bottle, ensure the oxygen atmosphere inside the glass bottle by connecting an oxygen balloon, and then irradiate the glass bottle with a xenon lamp equipped with a 420 nm filter for reaction.

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