MOFs-COFs composite material based on covalent bond combination as well as preparation method and application of MOFs-COFs composite material

Abstract

The invention relates to an MOFs-COFs composite material based on covalent bond combination, a preparation method of the MOFs-COFs composite material and application of the MOFs-COFs composite material in the field of photocatalytic hydrogen peroxide production, and belongs to the field of green chemical engineering. The invention aims to provide a method for efficiently producing hydrogen peroxide by photocatalysis based on a covalent bond combination MOFs (at) COFs composite material, and provides an application of the composite material in preparation of hydrogen peroxide. According to the novel method for preparing hydrogen peroxide through photocatalysis, a sacrificial agent and a cocatalyst are not used, so that the method is green, environment-friendly and pollution-free; high yield can be obtained without a pure oxygen environment and an air environment, visible light is used as an energy source, energy consumption is low, safety is high, operation is easy and convenient, reaction conditions are mild, the reaction mechanism is novel, and the yield of hydrogen peroxide in unit time is higher than that of similar prototype materials.

Description

TECHNICAL FIELD

[0001] The application relates to an application of a MOFs@COFs composite material based on covalent bond combination in the field of photocatalytic hydrogen peroxide production, and belongs to the field of green chemical industry. BACKGROUND

[0002] In the prior art, hydrogen peroxide (aqueous solution, also known as hydrogen peroxide) is mainly produced by the following two methods: anthraquinone (AO) method and thermal catalysis method. Although the two methods have the advantages of low cost and large synthesis amount, they also have respective disadvantages. The AO method needs to use a palladium catalyst, and once it leaks into the oxidation system or the extraction system, it will cause the hydrogen peroxide to decompose violently, with very serious consequences. Although the anthraquinone method has been improved for many times, it is still essentially a high-energy-consumption synthesis method, and it also affects the service life of the equipment. The thermal catalysis is to use H2 / O2 mixed gas to heat and catalyze to directly prepare hydrogen peroxide. Since the mixed gas is explosive in a wide concentration range, it has greater safety hazards. At the same time, most thermal catalysis uses noble metal catalysts such as gold, palladium or platinum, which has high production cost, and uses mixed gas as raw material, which further increases the risk. Therefore, it is extremely challenging to produce hydrogen peroxide safely, efficiently, and energy-savingly and environmentally.

[0003] The emerging photocatalytic technology uses H2O and O2 as raw materials, uses inexhaustible sunlight as an energy source, avoids the mixing of H2 and O2, is safe and green, and has received extensive attention in recent years. However, the common problem at present is that the MOFs material has weak light absorption capacity and low photoelectric charge separation efficiency, and the COFs material needs a sacrificial agent and has poor crystallinity, which is difficult to be reused. SUMMARY

[0004] The MOFs@COFs composite material based on covalent bond combination is used as a photocatalyst to promote the photocatalytic efficient preparation of hydrogen peroxide using H2O and O2 as raw materials, which meets the current compatibility of chemical industry and ecological environment and the realistic demand for sustainable development, and thus has important industrial application value and social significance.

[0005] The application aims to provide a method for using a MOFs@COFs composite material based on covalent bond combination to efficiently produce hydrogen peroxide by photocatalysis, and to provide the application of the method in the preparation of hydrogen peroxide. The new method for photocatalytic preparation of hydrogen peroxide disclosed in the application does not use a sacrificial agent or a catalyst, is green, environmentally friendly and pollution-free, does not need a pure oxygen environment and can obtain a high yield in an air environment, uses visible light as an energy source, has low energy consumption, high safety, simple and convenient operation, mild reaction conditions, and a novel reaction mechanism. The catalyst has excellent catalytic activity in multiple catalysis and has a wide application prospect.

[0006] The technical scheme of the application is as follows.

[0007] A MOFs@COFs composite material based on covalent bond combination, the chemical structural formula of the MOFs@COFs composite material is as follows: .

[0008] The application discloses a preparation method of the MOFs@COFs composite material based on covalent bond combination.

[0009] The application discloses application of the MOFs@COFs composite material based on covalent bond combination in production of hydrogen peroxide.

[0010] In the application, the hydrogen peroxide is produced by photocatalysis.

[0011] In the application, the raw material for producing the hydrogen peroxide is a solution containing water; further, the solution containing water includes water, water containing organic matter or other solutions containing water. The application discloses a new method for preparing hydrogen peroxide, which does not use a sacrificial agent and a cocatalyst, is green, environmentally friendly and pollution-free, does not need a pure oxygen environment, and can obtain a high yield in an air environment.

[0012] The application discloses a method for producing hydrogen peroxide by using the MOFs@COFs composite material based on covalent bond combination, which comprises the following steps: mixing the MOFs@COFs composite material based on covalent bond combination with a solution containing water, then irradiating to produce hydrogen peroxide.

[0013] Preferably, the method for producing hydrogen peroxide by using the MOFs@COFs composite material based on covalent bond combination comprises the following steps: mixing the MOFs@COFs composite material based on covalent bond combination with a solution containing water, then adsorbing in the dark, and then irradiating to produce hydrogen peroxide.

[0014] In the application, the irradiation is carried out at room temperature in an air atmosphere.

[0015] Preferably, the time for adsorbing in the dark is 10-60 minutes, and the time for irradiating is 30-120 minutes.

[0016] In the application, the MOFs@COFs composite material based on covalent bond combination is used as a photocatalyst.

[0017] Preferably, in the mixed solution formed by mixing the covalent bond-based MOFs@COFs composite material with a solution containing water, the concentration of the covalent bond-based MOFs@COFs composite material is 0.1-0.3 g / L.

[0018] In the present application, no sacrificial agent and cocatalyst are needed when producing hydrogen peroxide.

[0019] The beneficial effects of the present application mainly include: (1) The present application provides a method for photocatalytic production of hydrogen peroxide based on a covalent bond-based MOFs@COFs composite material, which does not use organic solvents (ethanol, isopropanol, benzyl alcohol, etc.) as a sacrificial agent, and is green, environmentally friendly and non-polluting. (2) The present application provides a method for photocatalytic production of hydrogen peroxide based on a covalent bond-based MOFs@COFs composite material, which does not need to introduce saturated oxygen as an oxygen source in the reaction system, and uses sunlight (visible light) as an energy source. Compared with the industrial anthraquinone method for indirect synthesis of hydrogen peroxide, the method of the present application has low energy consumption and high safety. (3) The present application provides a method for photocatalytic production of hydrogen peroxide based on a covalent bond-based MOFs@COFs composite material, which is safer than directly preparing hydrogen peroxide from a mixture of oxygen and hydrogen, and has no noble metal pollution. (4) The present application provides a method for photocatalytic production of hydrogen peroxide based on a covalent bond-based MOFs@COFs composite material, which can simultaneously act on wastewater treatment.

[0020] (5) Compared with the traditional photocatalytic preparation of hydrogen peroxide, this method eliminates the problem of difficult separation of organic sacrificial agents and their oxidation products from the source. (6) The present application first proposes a method for photocatalytic production of hydrogen peroxide based on a covalent bond-based MOFs@COFs composite material. Compared with the photocatalytic production of hydrogen peroxide by the same MOFs or COFs alone, the yield of hydrogen peroxide per unit time is greatly improved.

[0021] (7) The method for preparing hydrogen peroxide of the present application has mild reaction conditions and simple operation. Only the composite material needs to be uniformly dispersed with ultrapure water. Under the conditions of room temperature, air reaction atmosphere, no stirring of sacrificial agent and cocatalyst, after visible light irradiation for a period of time, the reaction solution is taken and filtered to obtain a hydrogen peroxide solution with high concentration. The method of the present application for preparing hydrogen peroxide has the advantages of high yield, high and stable catalytic performance, and good application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1NU-66, TpTapt and a series of gradient composite NU-66 x @TpTapt( x X-ray powder diffraction pattern and Fourier infrared spectrum of NU-66, TpTapt and a series of gradient composite NU-66 (Example 1-Example 6).

[0023] Figure 2 It is a schematic diagram of photocatalytic reaction device.

[0024] Figure 3 NU-66, TpTapt and a series of gradient composite NU-66 x @TpTapt( x The relationship diagram of photocatalytic hydrogen peroxide production rate and time of NU-66, TpTapt and a series of gradient composite NU-66 (Example 1-Example 6).

[0025] Figure 4 It is NU-66 obtained in Example 7 0.4 The five catalytic repeated use performance diagram of TpTapt.

[0026] Figure 5 It is a diagram of in-situ generated hydrogen peroxide obtained in Example 8 applied to wastewater treatment. DETAILED DESCRIPTION

[0027] The application discloses a new MOFs@COFs composite material, which is obtained by covalently combining MOFs and COFs materials, has the advantages of unique large specific surface area, excellent adsorption capacity, excellent light absorption capacity, high efficient photo-generated charge separation efficiency and stable structure, and the like, and is further applied to efficient preparation of hydrogen peroxide by photocatalysis with H2O and O2 as raw materials as a high efficient photocatalyst for the first time, and the atomic utilization rate of the reaction system is high, and in particular, the in-situ generated hydrogen peroxide can be applied to wastewater treatment.

[0028] The application discloses a MOFs@COFs composite material based on covalent bond combination, which is prepared from 2-amino terephthalic acid, zirconium chloride, triformylphloroglucinol and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine. Specifically, the 2-amino terephthalic acid and the zirconium chloride are reacted to prepare a NU-66 compound; and the NU-66 compound, the triformylphloroglucinol and the 2,4,6-tris(4-aminophenyl)-1,3,5-triazine are reacted to prepare the MOFs@COFs composite material based on covalent bond combination.

[0029] The application discloses a method for efficiently producing hydrogen peroxide by photocatalysis based on a MOFs@COFs composite material based on covalent bond combination, which comprises the following steps: ultrasonic dispersion of the MOFs@COFs composite material in water to obtain a dispersion liquid with a catalyst concentration of 0.2 g / L, and illumination at room temperature for photocatalytic production of hydrogen peroxide.

[0030] Further, the obtained reaction product is filtered, and the filtrate is obtained as an aqueous hydrogen peroxide solution (hydrogen peroxide).

[0031] As a preferred embodiment of the present application, the photocatalyst used in step (1) is at least one of NU-66, TpTapt and NU-66 x @TpTapt, x = 0.2-0.5). Further preferably, the MOFs@COFs composite is NU-66 0.4 @TpTapt, and the performance is the best, and the best composite ratio is x:1. Wherein, x is the mass ratio of NU-66 to TpTapt, i.e. the mass ratio of NU-66 to TpTapt is x:1.

[0032] As a preferred embodiment of the present application, the photocatalytic reaction for producing hydrogen peroxide is carried out in an air atmosphere.

[0033] As a preferred embodiment of the present application, no additional sacrificial agent and cocatalyst is needed in the photocatalytic reaction system for producing hydrogen peroxide.

[0034] As a preferred embodiment of the present application, the light irradiation time for photocatalytic production of hydrogen peroxide is 1 h.

[0035] As a preferred embodiment of the present application, the light irradiation is visible light irradiation, and further preferably, the visible light for photocatalytic production of hydrogen peroxide comes from a xenon lamp with an additional 420 nm cut-off filter (λ≥420 nm).

[0036] As a preferred embodiment of the present application, the detection of the photocatalytically produced hydrogen peroxide is carried out by KI solution color reaction.

[0037] As a preferred embodiment of the present application, after the photocatalytic production of hydrogen peroxide is completed, the catalyst is recovered by centrifugal washing and drying, and its recycling performance is detected.

[0038] As a preferred embodiment of the present application, the water for photocatalytic production of hydrogen peroxide can be pure water or wastewater, and the in-situ produced hydrogen peroxide can be used for wastewater treatment.

[0039] In order to make the technical solutions and advantages of the present application clearer, the present application will be further described below in conjunction with specific examples, but the protection scope of the present application is not limited thereto. The raw materials used in the present application are existing products, and the specific preparation operation and performance test are conventional technologies. In addition, the technical features involved in each embodiment of the present application described below can be combined as long as they do not conflict with each other.

[0040] Methods for testing hydrogen peroxide concentration: The amount of hydrogen peroxide was analyzed by iodometric titration. 1 mL of 0.1 mol∙L⁻¹ hydrogen peroxide was added. -1 C8H5KO4 aqueous solution and 1 mL 0.4 mol∙L -1 Add KI aqueous solution to the resulting solution, then let stand for 30 min. Hydrogen peroxide molecules react under acidic conditions (H₂O₂ + 3I⁻). - +2H + →I 3- + 2H2O) and iodide anion (I - The reaction generates triiodide anion (I2), which has a strong absorption near 350 nm. 3- ). I 3- The amount of hydrogen peroxide was determined by UV-Vis spectrophotometry based on the absorbance at 350 nm, and the amount of hydrogen peroxide produced in each reaction was estimated accordingly.

[0041] The source of the medicine used in this invention: 2-Aminoterephthalic acid, zirconium chloride, trialdehyde phloroglucinol and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine were all purchased from TCI (Shanghai) Chemical Industry Development Co., Ltd.

[0042] Synthesis example Synthesis of NU-66: 2-Amino-terephthalic acid (0.543 g, 3.0 mmol) and zirconium chloride (0.5 g, 2.16 mmol) were added separately to DMF (50 mL), and the mixture was sonicated for 30 min to disperse the reaction solution evenly until it became transparent. The solution was then transferred to a round-bottom flask, and glacial acetic acid (8.3 mL) was added. The mixture was again sonicated to disperse the solution evenly. Finally, the reaction mixture was heated at 120 °C for 24 hours. After the reaction was complete, the solid powder was collected by centrifugation using methanol as solvent, and then dried overnight at 80 °C to obtain the product, which was labeled NU-66.

[0043] Synthesis of TpTapt: Trialdehyde phloroglucinol (Tp 0.2 mmol, 42 mg) and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (Tapt 0.2 mmol, 71 mg) were mixed and placed in ampoules. A mixed solvent consisting of glacial acetic acid, mesitylene, and 1,4-dioxane (1 / 3 / 3 by vol) was added. The ampoules were placed in liquid nitrogen to freeze. After the reactants were completely frozen, the air in the ampoules was evacuated. Then, the evacuation valve was closed and the ampoules were placed in natural water to thaw the reactants. Finally, the ignition valve was opened to fill the ampoules with nitrogen. This freeze-thaw cycle was repeated three times to remove gases present in the ligands and solvent. The ampoules were then sealed and allowed to cool to room temperature. The reactants were then sonicated to disperse them evenly. Finally, the ampoules were placed in an oven, and the heating rate was controlled at 1 °C / min. The reaction was carried out at a constant temperature of 120 °C for 96 h. After the reaction was completed, the ampoules were allowed to cool naturally to room temperature. The ampoules were then removed, filtered, and the solid product was collected and washed sequentially with solvents such as ethanol, DMF, and acetone. The product was further purified by Soxhlet extraction. After the above operations were completed, the product was dried overnight in an oven at 100 °C to obtain a yellow solid powder, which was labeled as TpTapt.

[0044] Synthesis of composite material NU-66x@TpTapt (x=0.2~0.5): The composite material was synthesized according to the TpTapt synthesis method. Before adding the mixed solvent, NU-66 was added based on the mass ratio of NU-66 to TpTapt and the yield of TpTapt. NU-66 was covalently bonded to TpTapt during the formation process. After the reaction, the solid was washed, Soxhlet extracted, and dried. Composite materials of different proportions were collected and labeled as NU-66x@TpTapt (x=0.2~0.5), representing the covalently bonded MOFs@COFs composite material of this invention.

[0045] Figure 1 NU-66, TpTapt, and a series of gradient composite materials for NU-66 x @TpTapt( x X-ray powder diffraction pattern (a) and Fourier transform infrared spectrum (b) of 0.2~0.5 were used to characterize the structure of the prepared material.

[0046] Application Examples For example Figure 2 The schematic diagram of the reaction apparatus is shown to carry out the photocatalytic reaction. 10 mg of NU-66, TpTapt, or NU-66 is added. x @TpTapt( x=0.2~0.5) composite materials were added to 100 mL quartz reactor, then 50 mL deionized water was added, and the catalyst was dispersed uniformly by ultrasonic for 5 min. Dark adsorption for 30 min in the dark to reach adsorption-desorption equilibrium, then the reactor was irradiated with a xenon lamp equipped with a 420 nm filter, and the sample was taken at a fixed time and filtered with a 0.22 μm filter to obtain a filtrate containing hydrogen peroxide, and the content of hydrogen peroxide in the solution was quantitatively analyzed by potassium iodide colorimetry; adsorption and irradiation were carried out under conventional stirring.

[0047] Example 1 Reference application: the catalyst used was NU-66.

[0048] Example 2 Reference application: the catalyst used was TpTapt.

[0049] Example 3 Reference application: the catalyst used was NU-66 0.2 @TpTapt.

[0050] Example 4 Reference application: the difference lies in the use of NU-66 0.3 @TpTapt.

[0051] Example 5 Reference application: the catalyst used was NU-66 0.4 @TpTapt.

[0052] Example 6 Reference application: the catalyst used was NU-66 0.5 @TpTapt.

[0053] Figure 3 NU-66, TpTapt and a series of gradient composite materials NU-66 x @TpTapt( x =0.2~0.5) (Example 3~Example 6) The relationship between the photocatalytic hydrogen peroxide production rate and time. Among them, the photocatalytic hydrogen peroxide production performance of NU-66 0.4 @TpTapt is the best, reaching 1092 μM / h.

[0054] Example 7 After Example 5 is completed (1 hour), NU-66 0.4 @TpTapt is recovered by centrifugal washing and drying, and its recycling performance is further detected.

[0055] Figure 4 NU-660.4 TpTapt's five catalytic repeated cycle performance, NU-66 0.4 TpTapt shows excellent cycle performance.

[0056] Example 8 The in-situ generated hydrogen peroxide is applied to wastewater treatment, by respectively preparing 50 ppm of bisphenol A, phenol or 2,4-dichlorophenol aqueous solution to simulate real wastewater. The reference application is distinguished in that the reaction solution is the above-mentioned simulated real wastewater solution, wherein the control group needs to additionally add 0.1 mmol of catalase.

[0057] Figure 5 NU-66 0.4 The in-situ generated hydrogen peroxide obtained by TpTapt is applied to wastewater treatment figure, the present application can effectively in-situ treat the organic matter in real wastewater.

[0058] The above only describes the preferred embodiments of the present application, and any equivalent changes and modifications made within the scope of the patent application of the present application shall be included in the scope of the present application.

[0059] The present application provides a kind of for efficient photocatalytic production of hydrogen peroxide composite material, simultaneously is the first report in the field of photocatalytic production of hydrogen peroxide of this kind of composite material application.This application uses catalyst is metal organic framework (MOFs) and covalent organic framework (COFs) by covalent bond effect combination and form composite material NU-66 x TpTapt( x =0.2~0.5), the material photocatalytic production of hydrogen peroxide method is simple, green and environmentally friendly, high safety.In the irradiation of 300 W xenon lamp (with 420 nm cut-off filter) as light source, in the absence of sacrificial agent and co-catalyst condition, only in air atmosphere can show efficient photocatalytic production of hydrogen peroxide activity.This application not only improves atomic utilization, while in-situ generated hydrogen peroxide wastewater treatment effect is remarkable.The composite material is the first report application in this field, has important research value and significance, has broad application prospect.

Claims

1. A MOFs@COFs composite material based on covalent bonding, characterized in that, The chemical structural formula of the MOFs@COFs composite material is as follows: 。 2. The method for preparing the MOFs@COFs composite material based on covalent bonding as described in claim 1, characterized in that, The MOFs@COFs composite material based on covalent bonding was prepared using 2-aminoterephthalic acid, zirconium chloride, trialdehyde phloroglucinol and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine as raw materials.

3. The application of the MOFs@COFs composite material based on covalent bonding as described in claim 1 in the production of hydrogen peroxide.

4. The application according to claim 3, characterized in that, Hydrogen peroxide is produced by photocatalysis.

5. The application according to claim 3, characterized in that, The raw material for producing hydrogen peroxide is a solution containing water.

6. A method for producing hydrogen peroxide using the covalently bonded MOFs@COFs composite material as described in claim 1, characterized in that, The process includes the following steps: mixing the covalently bonded MOFs@COFs composite material with an aqueous solution, followed by light irradiation to produce hydrogen peroxide.

7. The method according to claim 6, characterized in that, The illumination is carried out at room temperature and in an airy atmosphere.

8. The method according to claim 6, characterized in that, The MOFs@COFs composite material based on covalent bonding is used as a photocatalyst.

9. The method according to claim 6, characterized in that, Aqueous solutions include water, water containing organic matter, or other aqueous solutions.

10. The method according to claim 6, characterized in that, No sacrificial agents or co-catalysts are required when producing hydrogen peroxide.

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