A porphyrin-triazine based covalent organic framework photocatalyst and its preparation method and application

Abstract

The present invention discloses a porphyrin-triazine-based covalent organic framework photocatalyst and its preparation method and application, belonging to the technical field of photocatalysis. The preparation method of the porphyrin-triazine-based covalent organic framework photocatalyst is as follows: 5,15-bis(4-aminophenyl)-10,20-diphenylporphyrin, 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, mesitylene, ethanol and 6M acetic acid aqueous solution are mixed, and ultrasonic and degassing treatments are carried out in sequence, and then heated for reaction; after the reaction is completed, centrifugation, washing and drying are carried out to obtain the photocatalyst. The porphyrin-triazine-based covalent organic framework photocatalyst has excellent light absorption performance, has rich nitrogen active sites, and the donor-acceptor structure promotes carrier separation. Under the condition of not adding sacrificial agents and photosensitizers, photocatalytic CO2 reduction and H2O oxidation reactions in pure water are realized simultaneously, with high catalytic activity and good stability.

Description

Technical Field

[0001] The present invention relates to the technical field of photocatalysis, and in particular to a porphyrin-triazine based covalent organic framework photocatalyst and a preparation method and application thereof. Background Art

[0002] At present, with the improvement of industrialization and population growth, the carbon cycle in nature has been destroyed, and the content of carbon dioxide (CO2) in the atmosphere has almost reached a historical high. The excessive production and emission of CO2 every year has led to a continuous increase in the CO2 content in the environment, resulting in a greenhouse effect and global warming. This change has had an adverse impact on the ecological environment, economic development and people's daily life. Among them, photocatalytic technology has mild conditions and is green and environmentally friendly. The ultimate goal is to use solar energy as an energy donor to continuously provide light energy to reduce CO2 to valuable carbon-containing chemicals, which is sustainable. In the past few decades, people have studied various photocatalysts such as metals, metal oxides, sulfides, nitrides, phosphides and polymers for photocatalytic CO2 reduction. However, most of the reported photocatalysts for CO2 reduction need to be coordinated with photosensitizers, co-catalysts or sacrificial agents. So far, it is still a huge challenge to use only a single photocatalyst to simultaneously achieve the full reaction of CO2 reduction and H2O oxidation in a photocatalytic system. Therefore, it is necessary to explore new photocatalysts with clear structures, wide light absorption ranges and strong redox abilities.

[0003] Covalent organic frameworks (COFs) are a promising class of porous crystalline materials that can be used for artificial photosynthesis due to their structurally directional designability, high structural stability, and chemical stability. Studies have shown that structurally robust COFs can provide a permanent platform for catalytic active sites and have a large surface area to adsorb CO2. However, existing COFs are mostly used as carriers, and different metal ions need to be introduced into them to provide active sites, or to be combined with photosensitizers, co-catalysts, or sacrificial agents to achieve good catalytic effects. Summary of the invention

[0004] The purpose of the present invention is to provide a porphyrin-triazine based covalent organic framework photocatalyst which can simultaneously realize photocatalytic CO2 reduction and H2O oxidation, and a preparation method and application thereof, so as to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention is a porphyrin-triazine covalent organic framework photocatalyst (abbreviated as DPT-COF), the structural formula of the porphyrin-triazine covalent organic framework photocatalyst is shown in Formula I (it can also be represented by Formula Figure 1 The structural diagram shown is shown):

[0007]

[0008] The second technical solution of the present invention: The preparation method of the above-mentioned porphyrin-triazine based covalent organic framework photocatalyst comprises the following steps: 5,15-di(4-aminophenyl)-10,20-diphenylporphyrin (DAPor), 2,4,6-tris(4-formaldehydephenyl)-1,3,5-triazine (TFPT), mesitylene, ethanol and 6M acetic acid aqueous solution are mixed, and ultrasonic and multiple freeze-pump-thaw cycle degassing treatments are carried out in sequence, and then sealed under vacuum, and then reacted at 115-120°C for 72-75h; after the reaction is completed, centrifugation, washing and drying are carried out to obtain the porphyrin-triazine based covalent organic framework photocatalyst.

[0009] Furthermore, the 5,15-bis(4-aminophenyl)-10,20-diphenylporphyrin (structural formula: )、2,4,6-tris(4-formaldehydephenyl)-1,3,5-triazine (structural formula is ), the usage ratio of mesitylene, ethanol and 6M acetic acid aqueous solution is 0.03mmol:0.02mmol:0.3-0.5mL:0.3-0.5mL:0.1-0.15mL.

[0010] Furthermore, the ultrasonic treatment time is 5-10 min.

[0011] Furthermore, the washing is washing with 1,4-dioxane, tetrahydrofuran and acetone in sequence until colorless.

[0012] Furthermore, the drying temperature is 60-80° C. and the drying time is 11-13 hours.

[0013] Technical solution three of the present invention: Application of the above-mentioned porphyrin-triazine based covalent organic framework photocatalyst in simultaneous photocatalytic CO2 reduction and H2O oxidation.

[0014] Furthermore, the photocatalysis uses CO2 and H2O as reactants, and the porphyrin-triazine-based covalent organic framework photocatalyst simultaneously photocatalyzes CO2 reduction and H2O oxidation to generate CO and O2.

[0015] Furthermore, the specific operation of the photocatalytic experiment is as follows: 5-10 mg of porphyrin-triazine covalent organic framework photocatalyst is dispersed in water and evenly coated on a circular glass plane (with a diameter of 35-38 mm); then, the glass plane with the porphyrin-triazine covalent organic framework photocatalyst on the surface is dried in an oven at 80-100° C. for 6-8 h, and then placed on a glass support in a 150 mL photocatalytic reactor, and 3-5 mL of distilled water is added to the bottom of the photocatalytic reactor as a reducing agent; before irradiation, the air in the photocatalytic reactor is removed by gas replacement to ensure that the reactor is finally in a CO2 atmosphere; a light intensity of 16.7 mW cm -2 A 300W xenon lamp with a 420nm filter was used as the light source to simulate sunlight. After a period of irradiation, 1-2mL of gas samples were taken to determine the CO and O2 contents produced by gas chromatography (8890GC System, Agilent, USA).

[0016] The present invention discloses the following technical effects:

[0017] (1) The porphyrin-triazine based covalent organic framework photocatalyst of the present invention has excellent light absorption performance, has abundant nitrogen active sites, and the donor-acceptor structure (porphyrin as electron donor and triazine as electron acceptor) promotes carrier separation, and can simultaneously realize photocatalytic CO2 reduction and H2O oxidation.

[0018] (2) The porphyrin-triazine based covalent organic framework photocatalyst of the present invention can simultaneously realize photocatalytic CO2 reduction and H2O oxidation reactions in pure water without adding sacrificial agents and photosensitizers, and has high catalytic activity and good stability.

[0019] (3) The preparation method of the porphyrin-triazine based covalent organic framework photocatalyst provided by the present invention is simple and the post-processing is relatively easy. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] 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 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.

[0021] Figure 1 Schematic diagram of the structure of DPT-COF in the present invention;

[0022] Figure 2 This is the SEM spectrum of DPT-COF prepared in Example 1;

[0023] Figure 3The infrared spectra of DPT-COF prepared in Example 1 and raw materials 5,15-di(4-aminophenyl)-10,20-diphenylporphyrin (DAPor) and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine (TFPT);

[0024] Figure 4 The solid UV-visible absorption spectrum of DPT-COF prepared in Example 1;

[0025] Figure 5 is the Tauc curve of DPT-COF prepared in Example 1;

[0026] Figure 6 This is the XPS-VB spectrum of DPT-COF prepared in Example 1;

[0027] Figure 7 The photocatalytic performance test results of DPT-COF prepared in Example 1;

[0028] Figure 8 The photocatalytic stability test results of DPT-COF prepared in Example 1. DETAILED DESCRIPTION

[0029] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0030] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0031] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0032] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0033] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0034] Example 1

[0035] A porphyrin-triazine based covalent organic framework photocatalyst, the preparation steps of which are as follows:

[0036] (1) 5,15-bis(4-aminophenyl)-10,20-diphenylporphyrin (19.3 mg, 0.03 mmol), 2,4,6-tris(4-formylphenyl)-1,3,5-triazine (7.9 mg, 0.02 mmol), mesitylene (0.5 mL, 3.6 mmol), anhydrous ethanol (0.5 mL, 8.6 mmol) and acetic acid aqueous solution (6 M, 0.1 mL) were added to a heat-resistant glass tube, ultrasonically treated for 5 min, and then subjected to three cycles of freeze-pump-thaw cycle degassing treatment, the tube was sealed, and heated at 120°C for 72 h;

[0037] (2) After the reaction is completed, a dark purple precipitate is generated at the bottom of the tube, and the precipitate product is obtained by centrifugation; then, the precipitate product is washed with 1,4-dioxane, tetrahydrofuran and acetone in sequence until it is colorless, and then dried at 60°C for 11 hours to obtain a purple-black powder, which is the porphyrin-triazine covalent organic framework photocatalyst (DPT-COF).

[0038] Example 2

[0039] A porphyrin-triazine based covalent organic framework photocatalyst, the preparation steps of which are as follows:

[0040] (1) 5,15-bis(4-aminophenyl)-10,20-diphenylporphyrin (18.9 mg, 0.045 mmol), 2,4,6-tris(4-formylphenyl)-1,3,5-triazine (11.8 mg, 0.03 mmol), mesitylene (0.75 mL, 5.4 mmol), anhydrous ethanol (0.75 mL, 12.9 mmol) and acetic acid aqueous solution (6 M, 0.15 mL) were added to a heat-resistant glass tube, ultrasonically treated for 5 min, and then subjected to three cycles of freeze-pump-thaw cycle degassing treatment, the tube was sealed, and heated at 118°C for 73 h;

[0041] (2) After the reaction is completed, a dark purple precipitate is generated at the bottom of the tube, and the precipitate product is obtained by centrifugation; then, the precipitate product is washed with 1,4-dioxane, tetrahydrofuran and acetone in sequence until it is colorless, and then dried at 70°C for 10 h to obtain a purple-black powder, which is the porphyrin-triazine covalent organic framework photocatalyst (DPT-COF).

[0042] Test Example 1

[0043] Characterization of various properties of porphyrin-triazine based covalent organic framework photocatalyst

[0044] Figure 2 This is the SEM spectrum of DPT-COF prepared in Example 1, which shows that the morphology of DPT-COF is rod-shaped.

[0045] Figure 3 This is the infrared spectrum of DPT-COF prepared in Example 1 and the raw materials 5,15-di(4-aminophenyl)-10,20-diphenylporphyrin (DAPor) and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine (TFPT), in which the disappearance of amino and aldehyde groups and the appearance of C=N bonds indicate the successful preparation of DPT-COF.

[0046] Figure 4 This is the solid UV-visible absorption spectrum of DPT-COF prepared in Example 1. It can be seen that the light absorption range of DPT-COF is the entire visible light region.

[0047] Figure 5 The Tauc curve of DPT-COF prepared in Example 1 shows that the band gap (E g ) is 1.62eV.

[0048] Figure 6 This is the XPS-VB spectrum of DPT-COF prepared in Example 1, and it can be seen that the valence band (VB) of DPT-COF is 0.94 eV. VB =E CB +E g , the conduction band can be calculated to be -0.78 eV, which can realize photocatalytic CO2 reduction and H2O oxidation simultaneously.

[0049] The above-mentioned properties of the DPT-COF prepared in Example 2 are basically consistent with those of the DPT-COF prepared in Example 1.

[0050] Application Example 1

[0051] Photocatalytic experiment

[0052] 5 mg of the porphyrin-triazine covalent organic framework photocatalyst prepared in Example 1 was dispersed in water and uniformly coated on a circular glass plane (with a diameter of 38 mm); then, the glass plane with the porphyrin-triazine covalent organic framework photocatalyst on the surface was dried in an oven at 100° C. for 6 h, and then placed on a glass support in a 150 mL photocatalytic reactor, and 5 mL of distilled water was added to the bottom of the photocatalytic reactor as a reducing agent; before irradiation, the air in the photocatalytic reactor was removed by gas replacement to ensure that the reactor was finally in a CO2 atmosphere; a light intensity of 16.7 mW cm -2 A 300W xenon lamp with a 420nm filter was used as a light source to simulate sunlight. After a period of irradiation, 1mL of gas sample was taken to measure the content of CO and O2 before and after illumination by gas chromatography (8890GC System, Agilent, USA). Sampling tests were performed at 1, 2, 3, and 4 hours of illumination. The photocatalytic performance test results of DPT-COF are shown in Figure 2. Figure 7 As shown in the figure, the production of CO and O2 reached 49.5 and 24.5 μmol g after 4 h of reaction. -1 (meaning μmol product / g photocatalyst).

[0053] Application Example 2

[0054] Cyclic stability test

[0055] 5 mg of the porphyrin-triazine covalent organic framework photocatalyst prepared in Example 1 was dispersed in water and uniformly coated on a circular glass plane (with a diameter of 38 mm); then, the glass plane with the porphyrin-triazine covalent organic framework photocatalyst on the surface was dried in an oven at 100° C. for 6 h, and then placed on a glass support in a 150 mL photocatalytic reactor, and 5 mL of distilled water was added to the bottom of the photocatalytic reactor as a reducing agent; before irradiation, the air in the photocatalytic reactor was removed by gas replacement to ensure that the reactor was finally in a CO2 atmosphere; a light intensity of 16.7 mW cm -2A 300W xenon lamp with a 420nm filter was used as a light source to simulate sunlight. After a period of irradiation, 1 mL of gas sample was taken and the content of CO and O2 after illumination was determined by gas chromatography (8890GC System, Agilent, USA). Sampling tests were carried out at 1, 2, 3, and 4 hours of illumination, and the reaction lasted for 4 hours, which was the first photocatalytic process. After the first photocatalysis, the light source was turned off, and the glass plane with the porphyrin-triazine covalent organic framework photocatalyst on the surface was taken out, dried in an oven at 100°C for 6 hours, and then put back on the glass support in the photocatalytic reactor. 5 mL of distilled water was added to the bottom of the photocatalytic reactor, and the air in the photocatalytic reactor was removed by gas replacement to ensure that the reactor was finally in a CO2 atmosphere. The light source was turned on for the second photocatalytic reaction, and the reaction lasted for 4 hours. This process was repeated for a total of 5 photocatalytic reactions. The photocatalytic stability test results of DPT-COF are shown in the figure. Figure 8 As shown, it can be seen that the performance of DPT-COF has basically not decreased after 5 cycles, indicating its good stability.

[0056] The embodiments described are only descriptions of the preferred modes of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. Application of a porphyrin-triazine based covalent organic framework photocatalyst in simultaneous photocatalytic CO2 reduction and H2O oxidation, characterized in that: The structural formula of the porphyrin-triazine covalent organic framework photocatalyst is shown in Formula I:

2. The use according to claim 1, characterized in that The preparation method of the porphyrin-triazine based covalent organic framework photocatalyst comprises the following steps: mixing 5,15-di(4-aminophenyl)-10,20-diphenylporphyrin, 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, mesitylene, ethanol and 6M acetic acid aqueous solution, sequentially performing ultrasonic and multiple freeze-pump-thaw cycle degassing treatments, sealing under vacuum, and then reacting at 115-120° C. for 72-75 hours; and centrifuging, washing and drying after the reaction to obtain the porphyrin-triazine based covalent organic framework photocatalyst.

3. The use according to claim 2, characterized in that The usage ratio of the 5,15-bis(4-aminophenyl)-10,20-diphenylporphyrin, 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, mesitylene, ethanol and 6M acetic acid aqueous solution is 0.03mmol:0.02mmol:0.3-0.5mL:0.3-0.5mL:0.1-0.15mL.

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