Redox imidazole covalent organic framework material as well as preparation method and application thereof

Abstract

The invention provides a redox imidazole covalent organic framework material as well as a preparation method and application thereof, belongs to the technical field of material preparation and photocatalytic preparation of hydrogen peroxide, and aims to solve the technical problem of low activity of a current covalent organic framework in preparation of hydrogen peroxide. The preparation method of the imidazole-connected redox type imidazole covalent organic framework material comprises the following steps: respectively reacting a reactant 2, 7-di-tert-butylpyrene-4, 5, 9, 10-tetraketone monomer with 4, 4 ', 4', 4 ', 4', 4 ', 4', 4 ', 4', 4 ', 4', 4 ', 4', 4 ', 4', 4 ', 4', 4 ' The preparation method comprises the following steps: mixing 4, 4 '-(pyridine-2, 4, 6-triyl) tribenzaldehyde and a tri (4-formylphenyl) amine monomer, adding a solvent and a catalyst, uniformly stirring, and reacting to obtain the redox type imidazole covalent organic framework material after the reaction is finished. The application comprises the following steps: adding the covalent organic framework, oxygen and the sacrificial agent into water, and reacting under the irradiation of visible light. The preparation method is green, environment-friendly, simple and easy to implement, the prepared material has good thermal stability, and efficient visible light photocatalysis preparation of hydrogen peroxide can be achieved; meanwhile, the catalyst can be recycled and has good photocatalytic stability.

Description

Technical Field

[0001] The invention belongs to the technical field of photocatalysis, and in particular relates to a covalent organic framework material. Background Art

[0002] Hydrogen peroxide (H2O2) is a green energy source with an energy density comparable to that of hydrogen because it is easier to store and transport. Anthraquinone oxidation is the most commonly used method for preparing H2O2 in industry, which usually uses metal catalysts with high energy input and large waste. With the advancement of the national carbon neutrality strategy, the demand for H2O2 is very urgent from the perspectives of economy, cost-effectiveness and environmental sustainability. To achieve this goal, artificial photosynthesis of H2O2 using water, oxygen (O2), photocatalysts and visible light has important prospects.

[0003] Since stable and efficient photocatalysts have an important influence on the conversion of H2O2, in order to achieve the conversion rate of photocatalytic conversion, the study of stable and efficient photocatalysts has become one of the main contents. In recent years, metal-free organic semiconductors, such as graphitic carbon nitride, linear conjugated polymers, and covalent triazine frameworks, have become promising photocatalysts for efficient and green production of H2O2 due to their adjustable structure, light absorption capacity, and metal-free components compared with reported inorganic semiconductors. Among them, all-conjugated covalent organic frameworks (COFs), as a class of crystalline porous materials, have attracted more and more attention in recent years due to their long-range ordered conjugated structure and structural diversity. They are considered to be a new type of semiconductor material with broad photocatalytic application prospects. Specifically, COFs have the characteristics of good stability, clear structure, adjustable visible light absorption range, and structure that can be designed in advance or modified afterwards. COFs with visible light absorption ability can avoid UV-induced H2O2 decomposition and improve the utilization rate of solar energy, so they have great application prospects in H2O2 production. For example, patent publication number CN116622041A discloses a β-ketoenamine type covalent organic framework material COF-N32 having a triazine structure, its preparation method, and its application in hydrogen peroxide photosynthesis. The preparation method comprises adding 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine to a solvent system comprising 1,4-dioxane, mesitylene and 3 mol / L acetic acid solution, heating after ultrasonic vibration for reaction, washing and drying to obtain the covalent organic framework material COF-N32. The invention prepares the covalent organic framework material COF-N32, which is used as a photocatalyst for hydrogen peroxide synthesis, but the yield of hydrogen peroxide is low. Under the conditions of visible light catalysis with a dosage of 500 mg / L, the average yield in 12 hours is only 605 μmol g -1 h -1The structure of COFs affects the yield and reaction pathway of photocatalytic H2O2 generation. Precisely controlling the structure of COFs at the atomic level and studying the relationship between structure and activity will be beneficial to the development of high-performance H2O2 generation space. Summary of the invention

[0004] In view of the technical problem of low yield of covalent organic framework materials in catalyzing hydrogen peroxide photosynthesis, the present invention proposes a redox imidazole covalent organic framework material and a preparation method and application thereof. The prepared redox imidazole covalent organic framework material has an ultra-high specific surface area and pore structure, and has high photocatalytic activity in photocatalytic reactions.

[0005] In order to achieve the above object, the technical solution of the present invention is achieved as follows:

[0006] A redox imidazole covalent organic framework material, wherein the redox imidazole covalent organic framework material is composed of a plurality of repeated structural units, wherein the structural formula of the structural unit is as shown in Formula I or Formula II.

[0007]

[0008] In the formula Indicates omitted repeating structural units.

[0009] A method for preparing a redox imidazole covalent organic framework material comprises the following steps: uniformly mixing reactants 2,7-di-tert-butylpyrene-4,5,9,10-tetraketone and a nitrogen-containing monomer with a solvent and a catalyst, and then reacting the mixture to obtain a redox imidazole covalent organic framework material after the reaction is completed.

[0010] The nitrogen-containing monomer is 4,4',4"-(pyridine-2,4,6-triyl)tribenzaldehyde or tris(4-formylphenyl)amine.

[0011] The molar ratio of the nitrogen-containing monomer to 2,7-di-tert-butylpyrene-4,5,9,10-tetraone is (2-5): (2-5).

[0012] The catalyst is ammonium acetate.

[0013] The solvent includes dioxane and mesitylene; the volume mass ratio of the dioxane, mesitylene and the catalyst is (0.01-0.04) mL: (0.01-0.04) mL: 1 mg.

[0014] The solvent includes o-dichlorobenzene, dioxane and n-butanol; the volume mass ratio of o-dichlorobenzene, dioxane, n-butanol and catalyst is (0.004-0.02) mL: (0.03-0.04) mL: (0.08-0.1) mL: 1 mg.

[0015] The mass volume ratio of the reactant to the solvent is 10-30 mg / mL; the reaction temperature is 120-160°C, and the reaction time is 72-120 hours. After the reaction is completed, the product is washed with anhydrous methanol and tetrahydrofuran in sequence, and then vacuum dried at a drying temperature of 60-80°C and a drying time of 6-10 hours.

[0016] The invention discloses an application of a redox imidazole covalent organic framework material. The redox imidazole covalent organic framework material is used as a catalyst in photocatalytic preparation of hydrogen peroxide. The steps are: adding the covalent organic framework and a sacrificial agent into water, and reacting them in an oxygen-containing atmosphere under visible light irradiation.

[0017] The amount of the redox imidazole covalent organic framework material added in water is 50-250 mg / L; the sacrificial agent is benzyl alcohol, and the concentration of benzyl alcohol in water is 10-50 wt %.

[0018] Beneficial effects of the present invention:

[0019] (1) The present invention uses 2,7-di-tert-butylpyrene-4,5,9,10-tetraketone and nitrogen-containing monomers 4,4',4"-(pyridine-2,4,6-triyl) tribenzaldehyde or tri(4-formylphenyl)amine as raw materials to synthesize a novel redox imidazole covalent organic framework material. The ratio of 2,7-di-tert-butylpyrene-4,5,9,10-tetraketone and the nitrogen-containing monomer must be appropriate. The preparation method is simple and easy, and can be prepared by a common solvent thermal method. The obtained redox imidazole covalent organic framework material has functional groups such as pyrene and imidazole. By regulating the nitrogen-containing microstructure in the structure, the light absorption performance of the material and the migration ability of photogenerated carriers can be regulated. At the same time, as a photocatalytic material, the catalytic reaction is carried out at room temperature and only visible light irradiation is required. The catalytic conditions are simple and the catalytic process is green and environmentally friendly.

[0020] (2) The redox imidazole covalent organic framework material prepared by the present invention has good thermal stability and maintains structural stability below 500°C.

[0021] (3) The redox imidazole covalent organic framework material prepared by the present invention exhibits excellent performance in the photocatalytic preparation of hydrogen peroxide. The photocatalytic preparation of hydrogen peroxide by PT-COFs produces a yield of 33.21 mmol·g -1 h -1 FA-COF photocatalytic production of hydrogen peroxide yields up to 38.75mmol·g -1 h -1This is because the redox imidazole covalent organic framework material has an ultra-high specific surface area and pore structure. The high specific surface area is conducive to the exposure of more catalytic active centers, which is convenient for photocatalytic reactions. In addition, the material has different hydrophilicity and hydrophobicity, and the hydrophilicity is conducive to reactions in water systems. The COFs material connected by imidazole has a fully conjugated property, which makes this type of material conducive to improving the mobility of charge carriers, thereby possibly improving the catalytic performance of the material.

[0022] (4) The redox imidazole covalent organic framework material prepared by the present invention can be recycled. After being recycled for 4 times, the catalytic activity does not change significantly, showing good photocatalytic stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 Synthesis diagram of PT-COF and FA-COF materials;

[0025] Figure 2 Powder XRD pattern of PT-COF material;

[0026] Figure 3 FT-IR images of PT-COF material and FA-COF material;

[0027] Figure 4 This is the thermogravimetric analysis diagram of PT-COF material;

[0028] Figure 5 This is the UV-visible diffuse reflectance spectrum of PT-COF material;

[0029] Figure 6 Powder XRD pattern of FA-COF material;

[0030] Figure 7 This is the thermogravimetric analysis diagram of FA-COF material;

[0031] Figure 8 This is the UV-visible diffuse reflectance spectrum of FA-COF material;

[0032] Fig. 9 The performance diagram of visible light photocatalysis for preparing hydrogen peroxide under different ratios of sacrificial agents for PT-COF and FA-COF materials;

[0033] Fig.10The performance diagram of PT-COF and FA-COF materials in preparing hydrogen peroxide under visible light photocatalysis in different atmospheres;

[0034] Fig.11 Impedance diagrams of PT-COF and FA-COF materials;

[0035] Fig.12 Fluorescence spectra of PT-COF and FA-COF materials. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] Example 1

[0038] A method for preparing a redox imidazole covalent organic framework material, the synthesis mechanism is as follows Figure 1 As shown, the specific steps include:

[0039] (1) 12.5 mg (0.03 mmol) of 4,4',4"-(pyridine-2,4,6-triyl)benzaldehyde and 17 mg (0.048 mmol) of 2,7-di-tert-butylpyrene-4,5,9,10-tetraone were placed in a Pyrex tube, and then a mixed solution consisting of solvent dioxane (0.5 mL), mesitylene (0.5 mL) and ammonium acetate (21 mg) was added dropwise, and the mixture was stirred magnetically at room temperature and ultrasonicated;

[0040] (2) The test tube was reacted at a temperature of 150° C. for 120 h. After the reaction, the product was washed three times with anhydrous methanol and three times with tetrahydrofuran. It was then vacuum dried at 75° C. for 10 h to obtain a covalent organic framework (PT-COF) material.

[0041] The prepared PT-COF was subjected to powder X-ray diffraction (XRD) test, and the results were as follows: Figure 2 As shown. Figure 2 It can be seen that there is an obvious crystallization peak at 2θ = 3.27°, which confirms that the redox imidazole covalent organic framework material has a crystallization phenomenon. The coordination state of the amino functional group was studied using Fourier transform infrared spectroscopy (FT-IR). Figure 3-4 As shown. At 3434 and 1602cm -1The two vibration peaks at correspond to the stretching vibration peaks of the imidazole structure in PT-COF. Combined with the XRD spectrum of the sample, it can be inferred that the imidazole-linked PT-COF material (such as Figure 3 ). According to N2 adsorption-desorption analysis, the specific surface area of ​​the material is 561m 2 / g. Thermogravimetric analysis shows that the material structure is stable before 500℃ under nitrogen protection (such as Figure 4 In addition, UV-visible diffuse reflectance spectroscopy analysis (such as Figure 5 ), the light absorption range of this material is 620nm.

[0042] Example 2

[0043] A method for preparing a redox imidazole covalent organic framework material comprises the following steps:

[0044] (1) 12.5 mg (0.03 mmol) of 4,4',4"-(pyridine-2,4,6-triyl)benzaldehyde and 17 mg (0.048 mmol) of 2,7-di-tert-butylpyrene-4,5,9,10-tetraone were placed in a Pyrex tube, and then a mixed solution consisting of solvent dioxane (0.3 mL), mesitylene (0.6 mL) and ammonium acetate (21 mg) was added dropwise, and the mixture was stirred magnetically at room temperature and ultrasonicated;

[0045] (2) The test tube was reacted at a temperature of 160° C. for 120 h. After the reaction, the product was washed with anhydrous methanol 5 times and with tetrahydrofuran 5 times. It was then vacuum dried at 80° C. for 10 h to obtain a covalent organic framework (PT-COF) material.

[0046] Example 3

[0047] A method for preparing a redox imidazole covalent organic framework material comprises the following steps:

[0048] (1) 13 mg (0.031 mmol) of 4,4',4"-(pyridine-2,4,6-triyl)benzaldehyde and 17.7 mg (0.05 mmol) of 2,7-di-tert-butylpyrene-4,5,9,10-tetraone were placed in a Pyrex tube, and then a mixed solution consisting of solvent dioxane (0.6 mL), mesitylene (0.3 mL) and ammonium acetate (21 mg) was added dropwise, and the mixture was stirred magnetically at room temperature and ultrasonicated;

[0049] (2) The test tube was reacted at a temperature of 160° C. for 90 hours. After the reaction, the product was washed 3 times with anhydrous methanol and 4 times with tetrahydrofuran. It was then vacuum dried at 60° C. for 8 hours to obtain a covalent organic framework (PT-COF) material.

[0050] Example 4

[0051] A method for preparing a redox imidazole covalent organic framework material, the synthesis mechanism is as follows Figure 1 As shown, the specific steps include:

[0052] (1) Weigh 10 mg (0.03 mmol) of tri(4-formylphenyl)amine and 17 mg (0.048 mmol) of 2,7-di-tert-butylpyrene-4,5,9,10-tetraone into a Pyrex tube, then dropwise add a mixed solution consisting of solvent o-dichlorobenzene (0.2 mL), dioxane (0.8 mL), n-butanol (1.8 mL) and ammonium acetate (21 mg), and stir magnetically at room temperature and perform ultrasound.

[0053] (2) The test tube was reacted at a temperature of 150° C. for 120 h. After the reaction, the product was washed three times with anhydrous methanol and three times with tetrahydrofuran. It was then vacuum dried at 75° C. for 10 h to obtain a covalent organic framework (FA-COF) material.

[0054] The prepared FA-COF was subjected to XRD test, and the results were as follows Figure 6 As shown. Figure 6 It can be seen that there is an obvious crystallization peak at 2θ = 3.34°, which confirms that the redox imidazole covalent organic framework material has a crystallization phenomenon. -1 The two vibration peaks at correspond to the stretching vibration peaks of the imidazole structure in FA-COF. Combined with the XRD spectrum of the sample, it can be inferred that the imidazole-linked PT-COF material (such as Figure 3 ). According to N2 adsorption-desorption analysis, the specific surface area of ​​the material is 567m 2 / g. Thermogravimetric analysis shows that the material structure is stable before 500℃ under nitrogen protection (such as Figure 7 ), indicating that the catalyst material has excellent thermal stability. In addition, UV-visible diffuse reflectance spectroscopy analysis (such as Figure 8 ), the light absorption range of this material is 550nm.

[0055] Example 5

[0056] A method for preparing a redox imidazole covalent organic framework material comprises the following steps:

[0057] (1) Weigh 10 mg (0.03 mmol) of tri(4-formylphenyl)amine and 17 mg (0.48 mmol) of 2,7-di-tert-butylpyrene-4,5,9,10-tetraone into a Pyrex tube, then dropwise add a mixed solution consisting of solvent o-dichlorobenzene (0.1 mL), dioxane (0.6 mL), n-butanol (1.6 mL) and ammonium acetate (21 mg), and stir magnetically at room temperature and perform ultrasound.

[0058] (2) The test tube was reacted at a temperature of 160° C. for 100 h. After the reaction, the product was washed 4 times with anhydrous methanol and 5 times with tetrahydrofuran. It was then vacuum dried at 60° C. for 12 h to obtain a covalent organic framework (FA-COF) material.

[0059] Example 6

[0060] A method for preparing a redox imidazole covalent organic framework material comprises the following steps:

[0061] (1) Weigh 6.67 mg (0.02 mmol) of tri(4-formylphenyl)amine and 11.33 mg (0.048 mmol) of 2,7-di-tert-butylpyrene-4,5,9,10-tetraone into a Pyrex tube, then dropwise add a mixed solution consisting of solvent o-dichlorobenzene (0.3 mL), dioxane (1.0 mL), n-butanol (2.0 mL) and ammonium acetate (21 mg), and stir magnetically at room temperature and perform ultrasound.

[0062] (2) The test tube was reacted at a temperature of 120° C. for 110 hours. After the reaction, the product was washed 4 times with anhydrous methanol and 5 times with tetrahydrofuran. It was then vacuum dried at 80° C. for 8 hours to obtain a covalent organic framework (FA-COF) material.

[0063] Example 7

[0064] A method for preparing a redox imidazole covalent organic framework material comprises the following steps:

[0065] (1) Weigh 6.67 mg (0.02 mmol) of tri(4-formylphenyl)amine and 11.33 mg (0.048 mmol) of 2,7-di-tert-butylpyrene-4,5,9,10-tetraone into a Pyrex tube, then dropwise add a mixed solution consisting of solvent o-dichlorobenzene (0.2 mL), dioxane (1.0 mL), n-butanol (1.8 mL) and ammonium acetate (21 mg), and stir magnetically at room temperature and perform ultrasound.

[0066] (2) The test tube was reacted at a temperature of 150° C. for 120 h. After the reaction, the product was washed with anhydrous methanol 4 times and with tetrahydrofuran 5 times. It was then vacuum dried at 70° C. for 10 h to obtain a covalent organic framework (FA-COF) material.

[0067] Application Example 1

[0068] Application of a redox imidazole covalent organic framework material (PT-COF) in the visible light photocatalytic preparation of hydrogen peroxide system:

[0069] The PT-COF prepared in Example 1 was subjected to photocatalysis to prepare hydrogen peroxide. The covalent organic framework catalyst was added to the aqueous solution at a concentration of 50 mg / L. The photocatalytic reaction was carried out under an oxygen atmosphere and irradiated with a xenon lamp with a wavelength of λ≥420 nm.

[0070] The production of hydrogen peroxide reached 270 μmol·g after 2 h of illumination, as monitored by UV-visible diffuse reflectance spectroscopy. -1 h -1 (like Fig. 9 ).

[0071] Application Example 2

[0072] Application of a redox imidazole covalent organic framework material (PT-COF) in the visible light photocatalytic preparation of hydrogen peroxide system:

[0073] The PT-COF prepared in Example 1 was photocatalytically used to prepare hydrogen peroxide. The covalent organic framework catalyst was added to the aqueous solution at a concentration of 50 mg / L. In an oxygen atmosphere, the ratio of benzyl alcohol to water was 1:9 (v:v), and the solution was illuminated under a xenon lamp with a wavelength of λ≥420 nm to carry out a photocatalytic reaction.

[0074] The production of hydrogen peroxide reached 6.82 mmol·g after 2 h of illumination as monitored by UV-visible diffuse reflectance spectroscopy. -1 h -1 (like Fig. 9 ).

[0075] Application Example 3

[0076] Application of a redox imidazole covalent organic framework material (PT-COF) in the visible light photocatalytic preparation of hydrogen peroxide system:

[0077] The PT-COFs prepared in Example 1 were photocatalytically prepared to produce hydrogen peroxide, and the covalent organic framework catalyst was added to the aqueous solution, and the added concentration of the covalent organic framework catalyst was 50 mg / L; under an oxygen atmosphere, the ratio of benzyl alcohol to water was 1:1 (v:v), and the photocatalytic reaction was carried out under illumination with a xenon lamp with a wavelength of λ≥420nm.

[0078] The production of hydrogen peroxide reached 33.21 mmol·g after 2 h of illumination, as monitored by UV-visible diffuse reflectance spectroscopy. -1 h -1 (like Fig. 9 ).

[0079] Application Example 4

[0080] Cyclic application of a redox imidazole covalent organic framework material in the visible light photocatalytic preparation of hydrogen peroxide system:

[0081] The solution after the reaction in Application Example 1 is filtered, separated, washed and then the PT-COF material is extracted. The extracted PT-COF material is subjected to the steps in Application Example 1 again, and the PT-COF is cyclically used for photocatalytic preparation of hydrogen peroxide.

[0082] Application Example 5

[0083] Application of a redox imidazole covalent organic framework material in the visible light photocatalytic preparation of hydrogen peroxide system:

[0084] The FA-COF prepared in Example 4 was subjected to photocatalysis to prepare hydrogen peroxide. The covalent organic framework catalyst was added to the aqueous solution, and the added concentration of the covalent organic framework catalyst was 50 mg / L. The photocatalytic reaction was carried out under an oxygen atmosphere and irradiated with a xenon lamp with a wavelength of λ≥420 nm.

[0085] UV-visible diffuse reflectance spectroscopy showed that the hydrogen peroxide production reached 400 μmol g after 2 h of illumination. -1 h -1 (like Fig.10 ).

[0086] Application Example 6

[0087] Application of a redox imidazole covalent organic framework material in the visible light photocatalytic preparation of hydrogen peroxide system:

[0088] The FA-COF prepared in Example 4 was photocatalytically prepared into hydrogen peroxide, and the covalent organic framework catalyst was added into the aqueous solution, and the added concentration of the covalent organic framework catalyst was 50 mg / L; under an oxygen atmosphere, the ratio of benzyl alcohol to water was 1:9 (v:v), and the photocatalytic reaction was carried out under illumination with a xenon lamp having a wavelength of λ≥420 nm.

[0089] Monitoring by UV-Vis diffuse reflectance spectroscopy showed that the hydrogen peroxide production reached 9.67 mmol·g after 2 h of illumination. -1 h -1 (like Fig.10 ).

[0090] Application Example 7

[0091] Application of a redox imidazole covalent organic framework material in the visible light photocatalytic preparation of hydrogen peroxide system:

[0092] The FA-COF prepared in Example 4 was photocatalytically prepared into hydrogen peroxide, and the covalent organic framework catalyst was added into the aqueous solution, and the added concentration of the covalent organic framework catalyst was 50 mg / L; under an oxygen atmosphere, the ratio of benzyl alcohol to water was 1:1 (v:v), and the photocatalytic reaction was carried out under illumination with a xenon lamp having a wavelength of λ≥420 nm.

[0093] Monitoring by UV-Vis diffuse reflectance spectroscopy showed that the hydrogen peroxide production reached 38.75 mmol·g after 2 h of illumination. -1 h -1 (like Fig.10 ).

[0094] Compared with Application Example 1, the hydrogen peroxide performance of FA-COF catalyst is significantly higher than that of PT-COF catalyst. We conducted electrochemical impedance spectroscopy tests, such as Fig.11 The radian of the impedance curve of the FA-COF sample is smaller than that of the PT-COF sample, indicating that FA-COF can be more conducive to the separation efficiency of carriers, thereby improving the photocatalytic activity of the sample, which is completely consistent with the above experimental results.

[0095] In addition, from the fluorescence spectra data of PT-COF and FA-COF samples (such as Fig.12 ) It can be seen that the fluorescence intensity of the FA-COF sample is lower, indicating that the FA-COF sample has a longer photogenerated carrier lifetime and thus has a higher activity in producing hydrogen peroxide during the photocatalytic production of hydrogen peroxide.

[0096] Application Example 8

[0097] Application of a redox imidazole covalent organic framework material in the visible light photocatalytic preparation of hydrogen peroxide system:

[0098] The solution after the reaction in Application Example 4 was filtered, separated, and washed to extract the FA-COF material. The extracted FA-COF material was repeated with the application steps in Application Example 8. After being recycled 4 times, the performance remained basically unchanged.

[0099] Comparative Example 1

[0100] Application of a redox imidazole covalent organic framework material in the visible light photocatalytic preparation of hydrogen peroxide system:

[0101] The PT-COF prepared in Example 1 and the FA-COF prepared in Example 4 were photocatalytically prepared to produce hydrogen peroxide. PT-COF and FA-COF were added to an aqueous solution, respectively, and the added concentrations of PT-COF and FA-COF were both 50 mg / L. The photocatalytic reaction was carried out in the dark.

[0102] Monitoring by UV-visible diffuse reflectance spectroscopy showed that after 2 hours of illumination, almost no hydrogen peroxide was produced by these two materials.

[0103] Comparative Example 2

[0104] Application of a redox imidazole covalent organic framework material in the visible light photocatalytic preparation of hydrogen peroxide system:

[0105] The PT-COF prepared in Example 1 and the FA-COF prepared in Example 4 were photocatalytically prepared to produce hydrogen peroxide. PT-COF and FA-COF were added to an aqueous solution, respectively. The added concentrations of PT-COF and FA-COF were both 50 mg / L, and the ratio of benzyl alcohol to water was 1:1 (v:v); in an air atmosphere, the photocatalytic reaction was carried out under illumination with a xenon lamp with a wavelength of λ≥420 nm.

[0106] UV-visible diffuse reflectance spectroscopy showed that the hydrogen peroxide production of PT-COF and FA-COF reached 12.58 and 15.01 mmol·g, respectively, after 2 h of illumination. -1 h -1 .

[0107] Comparative Example 3

[0108] Application of a redox imidazole covalent organic framework material in the visible light photocatalytic preparation of hydrogen peroxide system:

[0109] The PT-COF prepared in Example 1 and the FA-COF prepared in Example 4 were photocatalytically prepared to produce hydrogen peroxide. PT-COF and FA-COF were added to an aqueous solution, respectively. The added concentrations of PT-COF and FA-COF were both 50 mg / L, and the ratio of benzyl alcohol to water was 1:1 (v:v); under a nitrogen atmosphere, the photocatalytic reaction was carried out under illumination with a xenon lamp with a wavelength of λ≥420 nm.

[0110] UV-visible diffuse reflectance spectroscopy showed that the hydrogen peroxide production of PT-COF and FA-COF reached 3.66 and 6.33 mmol·g, respectively, after 2 h of illumination. -1 h -1 .

[0111] It can be seen from Application Examples 1-3, 5-7 and Comparative Examples 1, 2, and 3 that the imidazole-linked redox imidazole covalent organic framework material can be used in combination with a sacrificial agent and oxygen to efficiently prepare hydrogen peroxide under a certain ratio. This is due to the fully conjugated properties of the imidazole-linked COFs material, which makes this type of material conducive to improving the mobility of charge carriers, thereby potentially improving the catalytic performance of the material.

[0112] Comparative Example 4

[0113] A method for preparing a covalent organic framework material comprises the following steps:

[0114] (1) 11.7 mg (0.03 mmol) of 1,3,5-tri(p-formylphenyl)benzene and 17 mg (0.048 mmol) of 2,7-di-tert-butylpyrene-4,5,9,10-tetraone were placed in a Pyrex tube, and then a mixed solution consisting of solvent dioxane (0.5 mL), mesitylene (0.5 mL) and ammonium acetate (21 mg) was added dropwise, and the mixture was stirred magnetically at room temperature and ultrasonicated;

[0115] (2) The test tube was reacted at a temperature of 150° C. for 120 h. After the reaction, the product was washed three times with anhydrous methanol and three times with tetrahydrofuran. It was then vacuum dried at 75° C. for 10 h to obtain a covalent organic framework material.

[0116] The covalent organic framework material prepared in Comparative Example 4 was photocatalytically used to prepare hydrogen peroxide. The covalent organic framework catalyst was added to an aqueous solution, and the added concentration of the covalent organic framework catalyst was 50 mg / L. In an oxygen atmosphere, the ratio of benzyl alcohol to water was 1:1 (v:v), and the photocatalytic reaction was carried out under illumination with a xenon lamp with a wavelength of λ≥420 nm.

[0117] The production of hydrogen peroxide was 25.3 mmol g after 2 h of illumination as monitored by UV-visible diffuse reflectance spectroscopy. -1 h -1 .

[0118] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A redox imidazole covalent organic framework material, characterized in that: The redox imidazole covalent organic framework material is composed of a plurality of repeated structural units, wherein the structural formula of the structural unit is as shown in Formula I or Formula II. In the formula Indicates omitted repeating structural units.

2. The method for preparing the redox imidazole covalent organic framework material according to claim 1, characterized in that: The method comprises the following steps: uniformly mixing reactants 2,7-di-tert-butylpyrene-4,5,9,10-tetraketone and a nitrogen-containing monomer with a solvent and a catalyst, and then reacting the mixture; after the reaction is completed, a redox imidazole covalent organic framework material is obtained.

3. The method for preparing the redox imidazole covalent organic framework material according to claim 2, characterized in that: The nitrogen-containing monomer is 4,4',4"-(pyridine-2,4,6-triyl)tribenzaldehyde or tris(4-formylphenyl)amine.

4. The method for preparing the redox imidazole covalent organic framework material according to claim 3, characterized in that: The molar ratio of the nitrogen-containing monomer to 2,7-di-tert-butylpyrene-4,5,9,10-tetraone is (2-5):(2-5).

5. The method for preparing the redox imidazole covalent organic framework material according to any one of claims 2 to 4, characterized in that: The catalyst is ammonium acetate.

6. The method for preparing the redox imidazole covalent organic framework material according to claim 5, characterized in that: The solvent includes dioxane and mesitylene; the volume mass ratio of the dioxane, mesitylene and the catalyst is (0.01-0.04) mL: (0.01-0.04) mL: 1 mg.

7. The method for preparing the redox imidazole covalent organic framework material according to claim 5, characterized in that: The solvent includes o-dichlorobenzene, dioxane and n-butanol; the volume mass ratio of o-dichlorobenzene, dioxane, n-butanol and catalyst is (0.004-0.02) mL: (0.03-0.04) mL: (0.08-0.1) mL: 1 mg.

8. The method for preparing the redox imidazole covalent organic framework material according to claim 2, characterized in that: The mass volume ratio of the reactant to the solvent is 10-30 mg / mL; the reaction temperature is 120-160° C., and the reaction time is 72-120 h.

9. The use of the redox imidazole covalent organic framework material according to claim 1, characterized in that: The redox imidazole covalent organic framework material is used as a catalyst in the photocatalytic preparation of hydrogen peroxide, and the steps are: adding the covalent organic framework into water, and reacting in an oxygen-containing atmosphere under visible light irradiation.

10. The use of the redox imidazole covalent organic framework material according to claim 9, characterized in that: The amount of the redox imidazole covalent organic framework material added to the water is 50-250 mg / L; a sacrificial agent is also added to the water, and the sacrificial agent is 10-50% of the water volume; the sacrificial agent is benzyl alcohol.

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