Crystalline orientation type covalent organic framework film, preparation method and application

Abstract

The invention belongs to the technical field of two-dimensional covalent organic framework materials, and particularly relates to a crystal orientation type covalent organic framework film, a preparation method and application. On the basis of an interfacial polymerization method, reaction kinetics are regulated and controlled by constructing a solvent buffer layer and introducing a reaction regulator, amino monomers containing pyridine nitrogen are orderly arranged on a water / oil two-phase interface through the cation-pi action after being protonated, aldehyde monomers dissolved in an oil phase are induced to have a Schiff base reaction with the amino monomers at the interface, and the pyridine nitrogen-containing amino monomers are obtained. And a crystal-oriented two-dimensional covalent organic framework film is formed at normal temperature. The self-supporting covalent organic framework film prepared by the method disclosed by the invention is controllable in thickness, has remarkable crystal orientation, is beneficial to carrier migration, and can be used as an electrocatalyst for electrocatalytic reduction of CO2.

Description

Technical Field

[0001] The present invention belongs to the technical field of two-dimensional covalent organic framework materials, and particularly relates to a crystalline orientation covalent organic framework thin film, a preparation method and an application thereof. Background Art

[0002] Two-dimensional covalent organic frameworks are a class of crystalline organic porous materials. The ordered stacked structure within the framework is one of the key structural features that distinguish this class of materials from other organic porous materials. The stacked structure endows two-dimensional covalent organic frameworks with ordered one-dimensional pores, which can provide a path for the interlayer migration of charges. However, at present, most two-dimensional covalent organic framework materials are powder materials formed by the accumulation of polycrystalline particles, lacking crystalline orientation. This results in the disordered arrangement of their π-columnar channels and a large number of grain boundaries between grains, which not only hinder the in-plane transport of carriers within the framework but also lead to low out-of-plane transport efficiency of carriers, greatly limiting the transport of carriers and the application of covalent organic frameworks in the field of electrocatalysis.

[0003] To solve this problem, researchers have begun to explore the preparation methods of two-dimensional covalent organic framework thin films. Among them, interfacial polymerization is one of the common strategies. However, for most COF thin films prepared by interfacial polymerization, due to the lack of substrate induction, the orientation of crystals is often random. The main reason is that the monomer concentration at the two-phase interface is higher than that in the two-phase solutions, and the nucleation and growth rates are significantly accelerated, which is not conducive to the formation of a consistent crystalline orientation. Therefore, it is necessary to regulate the crystallization reaction kinetics in the interfacial polymerization system. However, when regulating the reaction kinetics to promote the in-plane dominant extended growth, the crystallization process will be inhibited and ultra-thin nanosheets rather than continuous thin films will be formed.

[0004] Therefore, it is crucial to develop a new interfacial polymerization method to prepare self-supporting, thickness-controllable, and crystalline orientation two-dimensional covalent organic framework thin films. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a crystalline orientation covalent organic framework thin film, a preparation method and an application thereof, which is a method for preparing a crystalline orientation two-dimensional covalent organic framework thin film by interfacial polymerization, and discloses its application in the electrocatalytic reduction of CO 2 aspect.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] The first technical object of the present invention is to provide a preparation method of a crystalline orientation covalent organic framework thin film. Based on the interfacial polymerization method, by constructing a solvent buffer layer and introducing a reaction regulator to control the reaction kinetics at the interface, the protonated amino monomer containing pyridine nitrogen is orderly arranged at the water / oil two-phase interface through cation-π interaction, inducing the aldehyde monomer dissolved in the oil phase to react with the amino monomer at the interface to form a Schiff base reaction, and a crystalline orientation two-dimensional covalent organic framework thin film is formed at room temperature.

[0008] Specifically, the specific steps of the method are as follows:

[0009] (1) Dissolve the aldehyde monomer sufficiently in an organic solvent immiscible with water, and the concentration of the obtained aldehyde monomer solution is 0.001 wt% to 10 wt%;

[0010] (2) Dissolve the amino monomer containing pyridine nitrogen and the reaction regulator in an aqueous mixed solvent, and the concentration of the obtained amino monomer solution is 0.001 wt% to 10 wt%;

[0011] (3) Add the amino reaction regulator to the amino monomer solution obtained in step (2), and the concentration of the amino reaction regulator is 0.001 wt% to 30 wt%;

[0012] (4) Pour the organic phase solution of the aldehyde monomer in step (1) into a flat reaction vessel, then add a deionized water layer as a spacer layer on the organic phase layer, and finally uniformly drop the aqueous phase solution obtained in step (3) on the spacer layer, and let it stand for interfacial polymerization reaction to form a film;

[0013] (5) Transfer the COF thin film formed at the two-phase interface to deionized water, tetrahydrofuran and acetone solvents in sequence for soaking and washing to remove impurities and unreacted monomers, and finally obtain a crystalline orientation two-dimensional covalent organic framework thin film.

[0014] Furthermore, the aldehyde monomer described in the above step (1) is preferably selected from the following structures:

[0015]

[0016] Furthermore, the organic solvent described in the above step (1) is dichloromethane or dichloroethane.

[0017] Furthermore, the amino monomer described in the above step (2) is preferably selected from the following structures:

[0018]

[0019] Further, the aqueous mixed solvent described in the above step (2) is prepared by mixing deionized water and an organic solvent miscible with water. The organic solvent is preferably selected from one of acetonitrile, methanol, ethanol, n-butanol, n-pentanol, n-hexanol, and isopropanol. The volume percentage of water in the mixed solvent is 50% - 90%.

[0020] Further, the amino reaction regulator described in the above step (3) is preferably selected from any one of p-toluenesulfonic acid, trifluoroacetic acid, and trifluoromethanesulfonic acid.

[0021] Further, the interfacial polymerization reaction time described in the above step (4) is 1 - 7 days, and the reaction temperature is room temperature 25°C.

[0022] The second technical object of the present invention is to provide a crystalline orientation covalent organic framework film prepared by the method as described above.

[0023] The third technical object of the present invention is to provide an application of the crystalline orientation covalent organic framework film prepared by the method as described above in the field of electrocatalysis.

[0024] Specifically, in the present invention, a composite electrode is obtained by compounding a crystalline orientation covalent organic framework film with a copper substrate. The composite copper electrode is immersed in a 1,2-dibromoethane solution, taken out after refluxing at a temperature of 130 - 160°C for 6 - 18 hours, and soaked and washed in acetone and deionized water to remove unreacted solvents, obtaining a crystalline orientation two-dimensional ionic covalent organic framework composite copper electrode. Moreover, the present invention is applied to electrocatalytic reduction of CO 2 The two-dimensional covalent organic framework film is prepared by the above method.

[0025] It is worth noting that the two-dimensional covalent organic framework film prepared by the present invention has good crystalline orientation perpendicular to the film direction, which is beneficial to mass transfer and electron transport in the electrocatalytic reaction, and promotes efficient energy conversion.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] (1) In the process of interfacial polymerization of the method of the present invention, by constructing a solvent buffer layer and introducing a reaction regulator to synergistically regulate the reaction kinetics at the interface, and at the same time using the protonation of the amino monomer containing pyridine nitrogen to be orderly arranged at the water / oil two-phase interface through cation-π interaction, enhancing the normal stacking orientation, inducing the aldehyde monomer dissolved in the oil phase to react with the amino monomer at the interface to form a Schiff base reaction, a self-supporting, thickness-controllable, and crystalline orientation two-dimensional covalent organic framework film can be formed at room temperature;

[0028] (2) The present invention has universality, the selection range of monomers used to prepare the crystalline orientation covalent organic framework film is wide, and the preparation process is simple and controllable. Brief Description of the Drawings

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings described below are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the provided drawings.

[0030] Figure 1 Schematic reaction diagram of the crystalline orientation covalent organic framework thin film prepared for Examples 1-3.

[0031] Figure 2 Infrared spectrum of the crystalline orientation covalent organic framework thin film prepared for Examples 1-3.

[0032] Figure 3 Glancing incidence wide-angle X-ray diffraction curve of the Tp-Phen-COF thin film prepared for Example 1.

[0033] Figure 4 Glancing incidence wide-angle X-ray diffraction pattern of the Tp-Phen-COF thin film prepared for Example 1.

[0034] Figure 5 Atomic force scanning electron micrograph of the Tp-Phen-COF thin film prepared for Example 1.

[0035] Figure 6 Atomic force scanning electron micrograph of the Tp-Bpy-COF thin film prepared for Example 2.

[0036] Figure 7 Atomic force scanning electron micrograph of the Tp-Pyr-COF thin film prepared for Example 3. Detailed Description of the Embodiments

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0038] The special term "embodiment" here, any embodiment described as "exemplary" does not have to be interpreted as superior or better than other embodiments. For the performance index tests in the embodiments of this application, unless otherwise specified, conventional test methods in the art are used. It should be understood that the terms described in this application are only for describing specific embodiments and are not used to limit the content disclosed in this application.

[0039] Unless otherwise specified, the technical and scientific terms used herein have the same meanings as commonly understood by those of ordinary skill in the technical field to which this application belongs; other test methods and technical means not specifically noted in this application refer to the test methods and technical means commonly adopted by those of ordinary skill in the art.

[0040] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "in", "on", "under", "rise", "fall", "vertical", "surface", "top", "bottom", "inside", "outside", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0041] To better illustrate the content of this application, numerous specific details are given in the following specific embodiments. Those skilled in the art should understand that the present application can be implemented without some specific details. In the embodiments, some methods, means, instruments, devices, etc. well-known to those skilled in the art are not described in detail in order to highlight the gist of the present application.

[0042] On the premise of no conflict, the technical features disclosed in the embodiments of the present application can be combined arbitrarily, and the obtained technical solutions belong to the content disclosed in the embodiments of the present application.

[0043] The present invention discloses a crystalline orientation type covalent organic framework film, a preparation method and an application.

[0044] To better understand the present invention, the following embodiments are used to further specifically elaborate the present invention, but it should not be construed as a limitation to the present invention. For those skilled in the art, some non-essential improvements and adjustments made according to the above-mentioned invention content are also considered to fall within the protection scope of the present invention.

[0045] Example 1: Preparation of Crystalline Orientation Tp-Phen-COF Film

[0046] Pour 100 mL of dichloromethane dissolved with 16 mg of trihydroxybenzene into an empty beaker, and then slowly add 60 mL of deionized water along the wall of the beaker as a spacer layer. Dissolve 24 mg of 3,8-diamino-1,10-phenanthroline monomer and 40 mg of p-toluenesulfonic acid in a mixed solution of 30 mL of acetonitrile and 70 mL of deionized water, and slowly and evenly drop it drop by drop above the spacer layer. Let it stand at room temperature for 3 days to carry out a Schiff base reaction at the two-phase interface to form a self-supporting Tp-Phen-COF film. Transfer the Tp-Phen-COF film to deionized water, tetrahydrofuran and acetone solvents in sequence for soaking and washing to remove impurities and unreacted monomers.

[0047] In Example 1, the reaction schematic diagram of the Tp-Phen-COF thin film is as Figure 1 shown.

[0048] The prepared Tp-Phen-COF thin film in this example was characterized by infrared spectroscopy and grazing-incidence wide-angle X-ray diffraction. As Figure 2 shown, there are obvious characteristic vibration peaks of C=O and C-N in the infrared spectrum, indicating that a covalent organic framework thin film with keto-enamine bond connection was successfully obtained in this example. As Figure 3 shown, the grazing-incidence wide-angle X-ray diffraction curve of Example 1 shows that the prepared Tp-Phen-COF thin film has good crystallinity. As Figure 4 shown, the grazing-incidence wide-angle X-ray diffraction pattern of Example 1 indicates that the prepared Tp-Phen-COF thin film in this example has a crystalline orientation perpendicular to the film direction. As Figure 5 shown, the thickness of the prepared Tp-Phen-COF thin film in this example is about 1.62 microns.

[0049] The carrier mobility of the prepared Tp-Phen-COF thin film in this example was tested, and its zero-field mobility is 0.14 cm 2 V -1 S -1 .

[0050] Example 2: Preparation of Crystalline Oriented Tp-Bpy-COF Thin Film

[0051] 100 mL of dichloromethane dissolved with 16 mg of trihydroxybenzene was poured into an empty beaker, and then 60 mL of deionized water was slowly added along the wall of the beaker as a spacer layer. 21 mg of 5-amino-2,2'-bipyridine monomer and 40 mg of p-toluenesulfonic acid were dissolved in a mixed solution of 30 mL of acetonitrile and 70 mL of deionized water, and it was slowly and evenly dropped dropwise above the spacer layer. The reaction was allowed to stand at room temperature for 3 days, and a Schiff base reaction occurred at the two-phase interface to form a self-supporting Tp-Bpy-COF thin film. The Tp-Bpy-COF thin film was successively transferred to deionized water, tetrahydrofuran, and acetone solvents for soaking and washing to remove impurities and unreacted monomers.

[0052] In Example 2, the reaction schematic diagram of the Tp-Bpy-COF thin film is as Figure 1 shown.

[0053] The prepared Tp-Bpy-COF thin film in this example was characterized by infrared spectroscopy and grazing-incidence wide-angle X-ray diffraction. As Figure 2As shown, there are obvious characteristic vibration peaks of C=O and C-N in the infrared spectrum, indicating that a Tp-Bpy-COF thin film with a keto-enamine bond connection was successfully obtained in this example. Grazing incidence wide-angle X-ray diffraction characterization shows that the Tp-Bpy.-COF thin film prepared in this example has a crystalline orientation perpendicular to the film direction. As Figure 6 shown, the thickness of the Tp-Phen-COF thin film prepared in this example is about 1.83 microns.

[0054] The carrier mobility of the Tp-Bpy-COF thin film prepared in this example was tested, and its zero-field mobility was 0.093 cm 2 V -1 S -1 .

[0055] Example 3: Preparation of a Crystalline Oriented Tp-Pyr-COF Thin Film

[0056] Pour 100 mL of dichloromethane containing 16 mg of trihydroxybenzene carbaldehyde into an empty beaker, and then slowly add 60 mL of deionized water along the wall of the beaker as a spacer layer. Dissolve 12 mg of 2,5-diaminopyridine monomer and 40 mg of p-toluenesulfonic acid in a mixed solution of 30 mL of acetonitrile and 70 mL of deionized water, and slowly and evenly drop it drop by drop above the spacer layer. Let it stand and react at room temperature for 3 days, and a Schiff base reaction occurs at the two-phase interface to form a self-supporting Tp-Pyr-COF thin film. Transfer the Tp-Pyr-COF thin film to deionized water, tetrahydrofuran, and acetone solvents in sequence for soaking and washing to remove impurities and unreacted monomers.

[0057] In Example 3, the reaction schematic diagram of the Tp-Pyr-COF thin film is as Figure 1 shown.

[0058] The Tp-Pyr-COF thin film prepared in this example was characterized by infrared spectroscopy and grazing incidence wide-angle X-ray diffraction. As Figure 2 shown, there are obvious characteristic vibration peaks of C=O and C-N in the infrared spectrum, indicating that a Tp-Pyr-COF thin film with a keto-enamine bond connection was successfully obtained in this example. Grazing incidence wide-angle X-ray diffraction characterization shows that the Tp-Pyr.-COF thin film prepared in this example has a crystalline orientation perpendicular to the film direction. As Figure 7 shown, the thickness of the Tp-Pyr-COF thin film prepared in this example is about 1.88 microns.

[0059] The carrier mobility of the Tp-Bpy-COF thin film prepared in this example was tested, and its zero-field mobility was 0.054 cm 2 V -1 S -1 .

[0060] Example 4:

[0061] Crystalline oriented covalent organic framework thin film for electrocatalytic reduction of CO 2 , this method is applicable to the covalent organic framework materials prepared in the above Examples 1-3, and here Tp-Phen-COF thin film is taken as an example.

[0062] Pretreatment of Cu electrode: Sprinkle alumina polishing powder (0.05 μm) on the suede laid flat and fixed on the surface of a smooth thick glass, and slightly moisten it with distilled water to form a paste before polishing. Then polish the copper sheet in a uniform "8" shape on the suede to form a mirror-like surface. Then rinse the polished copper sheet with deionized water to remove the residual alumina polishing powder, and ultrasonically clean it with acetone and deionized water in sequence. Then place the copper sheet electrode in an 85% phosphoric acid aqueous solution, use a carbon rod as the counter electrode, electro-polish the copper sheet electrode at a potential of 2.0 V for 5 minutes, rinse it with deionized water and dry it with a nitrogen stream to obtain a shiny Cu electrode for use.

[0063] Preparation of Cu@Tp-Phen-COF composite electrode: Transfer the Tp-Phen-COF thin film prepared in Example 1 to the surface of the above-treated Cu electrode to prepare a Cu@Tp-Phen-COF composite electrode.

[0064] Cu@Tp-Phen 2+ -COF composite electrode preparation: Immerse the Cu@Tp-Phen-COF electrode in a 1,2-dibromoethane solution, reflux at 130 °C for 12 hours, and then transfer it to acetone and deionized water in sequence for soaking and washing to remove the unreacted solvent, obtaining a Cu@Tp-Phen 2+ -COF composite electrode.

[0065] CuNC@Tp-Phen 2+ -COF composite electrode preparation: Adopt a three-electrode system, with an aqueous solution of 0.10 M KHCO 2 saturated with CO 3 as the electrolyte. Use a Pt sheet as the counter electrode, a saturated calomel electrode as the reference electrode, and Cu@Tp-Phen 2+ -COF as the working electrode. After cycling 3 times from -0.60 V to 0.75 V in the cyclic voltammetry mode, a CuNC@Tp-Phen 2+ -COF composite electrode is obtained.

[0066] Electrocatalytic reduction of CO 2 : At room temperature, the electrocatalytic reduction of CO is completed in a three-electrode H-type electrolytic cell on a CHI660E electrochemical workstation. 2The two electrolytic chambers are connected by an activated proton exchange membrane (Nafion-117). The anode chamber uses a Pt sheet as the counter electrode, the cathode chamber uses a saturated calomel electrode as the reference electrode, and the CuNC@Tp-Phen 2+ -COF composite electrode is the working electrode. The electrolyte is CO 2 Saturated 0.10M KHCO 3 Water-soluble, and CO was continuously introduced during the test 2 , CO 2 Flow rate: 30 mL min -1 .

[0067] CuNC@Tp-Phen 2+ -FE of COF C2H4 43.9%, FE C≥2 The reaction temperature was 64.4%, showing good selectivity for ethylene and multi-carbon products and good reaction stability.

[0068] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a crystal-oriented covalent organic framework film, characterized in that: Based on the interfacial polymerization method, the reaction kinetics are regulated by constructing a solvent buffer layer and introducing a reaction regulator. The amino monomers containing pyridine nitrogen are protonated and arranged in an orderly manner at the water / oil interface through the cation-π effect, inducing the aldehyde monomers dissolved in the oil phase to undergo a Schiff base reaction with the amino monomers at the interface, forming a crystalline-oriented two-dimensional covalent organic framework film at room temperature.

2. The method according to claim 1, characterized in that The specific steps are as follows: (1) fully dissolving the aldehyde monomer in an organic solvent immiscible with water, wherein the concentration of the obtained aldehyde monomer solution is 0.001 wt % to 10 wt %; (2) dissolving an amino monomer containing pyridinic nitrogen and a reaction regulator in an aqueous mixed solvent, wherein the concentration of the obtained amino monomer solution is 0.001 wt % to 10 wt %; (3) adding an amino reaction regulator to the amino monomer solution obtained in step (2), wherein the concentration of the amino reaction regulator is 0.001 wt % to 30 wt %; (4) pouring the organic phase solution of the aldehyde monomer in step (1) into a flat-bottomed reaction vessel, then adding a deionized water layer on the organic phase layer as a spacer layer, and finally evenly dropping the aqueous phase solution obtained in step (3) on the spacer layer, and allowing the interfacial polymerization reaction to form a film; (5) The COF film formed at the interface between the two phases is transferred to deionized water, tetrahydrofuran and acetone solvents for immersion and washing in turn to remove impurities and monomers that do not participate in the reaction, and finally a crystalline oriented two-dimensional covalent organic framework film is obtained.

3. The method according to claim 2, characterized in that In step (1), the aldehyde monomer is selected from the following structures: The organic solvent is dichloromethane or dichloroethane.

4. The method according to claim 2, characterized in that: In step (2), the amino monomer is selected from the following structures:

5. The method according to claim 1, characterized in that In step (2), the aqueous phase mixed solvent is prepared by mixing deionized water and an organic solvent miscible with water, the organic solvent is one of acetonitrile, methanol, ethanol, n-butanol, n-pentanol, n-hexanol, and isopropanol, and the volume percentage of water in the mixed solvent is 50% to 90%.

6. The method according to claim 1, characterized in that In step (3), the amino reaction regulator is selected from any one of p-toluenesulfonic acid, trifluoroacetic acid and trifluoromethanesulfonic acid.

7. The method according to claim 1, characterized in that In step (4), the interfacial polymerization reaction time is 1 to 7 days, and the reaction temperature is room temperature 25°C.

8. A crystal-oriented covalent organic framework film prepared by the method according to any one of claims 1 to 7.

9. Use of a crystal-oriented covalent organic framework film prepared by the method according to any one of claims 1 to 7 in the field of electrocatalysis.

10. The use according to claim 9, characterized in that: The composite electrode obtained by compounding the crystal-oriented covalent organic framework film with a copper substrate is then ionized to obtain a crystal-oriented two-dimensional ionic covalent organic framework composite copper electrode, which is used as an electrocatalyst for electrocatalytic reduction of CO2.

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