Heterojunction laminated covalent organic framework material as well as preparation method and application thereof

Abstract

The invention discloses a heterojunction laminated covalent organic framework material and a preparation method and application thereof, and belongs to the technical field of covalent organic framework materials, the covalent organic framework material is a laminated covalent organic framework composed of single-layer covalent organic frameworks of a layer of donor unit and a layer of acceptor unit, and a heterojunction is formed between layers; according to the covalent organic framework, a single-layer donor and acceptor covalent organic framework is synthesized through reaction, and then the single-layer covalent organic framework material is synthesized into the heterojunction laminated covalent organic framework material through reaction. High-performance donor and acceptor units are introduced into the laminated covalent organic framework, so that the laminated covalent organic framework has excellent characteristics of heterojunction on the basis of keeping the covalent organic framework. The material is unique in design strategy, and can be applied to the fields of photoelectric devices, energy storage and conversion, sensing and detection, environmental governance, biomedicine and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of covalent organic framework materials, and in particular relates to a heterojunction laminated covalent organic framework material and a preparation method and application thereof. Background Art

[0002] Covalent organic frameworks (COFs) are a class of extended crystalline organic materials with unique structures, which have high structural controllability, porosity and chemical stability. Compared with traditional adsorption materials, the controllability and diversity of covalent organic framework materials also provide a wide range of possibilities for their application in the field of materials science. Researchers can achieve optimized performance and wide application in various fields by precisely regulating their structure and composition. They have high structural controllability, porosity and chemical stability. Due to the limited development of covalent organic framework materials in the optoelectronic field, it is difficult to achieve large-scale application in the optoelectronic field. Therefore, it is necessary to design and introduce heterojunctions into stacked covalent organic framework materials to achieve the excellent performance of heterojunctions in COFs.

[0003] Therefore, the research goal of this invention is to design and synthesize materials with excellent optical properties, apply them to optoelectronic devices, and expand their applications in sensing and detection, environmental governance, biomedicine and other fields. Summary of the Invention

[0004] The present invention provides a preparation method and application of a heterojunction stacked covalent organic framework material. The present invention synthesizes the material through a Suzuki coupling reaction and a nucleophilic substitution reaction, and studies its photoelectric properties after the synthesis. Different donor and acceptor units are introduced into the COF, and a single layer of COF is synthesized into a stacked COF through reaction to form a heterojunction, thereby obtaining a stacked covalent organic framework material with different luminescence properties. By controlling the introduced donor and acceptor units, the high photoelectric performance of the stacked covalent organic framework material is improved, thereby solving the problem of its limited application in the optoelectronic field and expanding its application in sensing and detection, environmental management, biomedicine and other fields.

[0005] In a first aspect, the present invention provides a heterojunction stacked covalent organic framework material, which is formed by directly covalently connecting layers of a single-layer covalent organic framework material through a substitution reaction. The general structural formula of the heterojunction stacked covalent organic framework material is as follows:

[0006] Among them, Ar1 is the electron donor unit, Ar2 is the electron acceptor unit, Ar3 is the connecting skeleton unit, and X is the chemical connecting bond; the above structural formula represents the smallest structural unit in the organic framework material, and the dotted line represents the connecting bond between the structural units.

[0007] Preferably, in the heterojunction stacked covalent organic framework material, the structural formula of the electron donor unit Ar1 is one of the following structures:

[0008] Wherein, the dotted line represents the bond connecting Ar1 and Ar3; R is selected from C0-C 30 Alkyl chain.

[0009] Preferably, in the heterojunction stacked covalent organic framework material, the structural formula of the electron acceptor unit Ar2 is one of the following structures:

[0010] Wherein, the dotted line represents the bond connecting Ar2 and Ar3, and R=C0-C30 alkyl chain.

[0011] Preferably, the structural formula of the connecting skeleton unit Ar3 in the heterojunction stacked covalent organic framework material is one of the following structures:

[0012] The dotted line represents the bond connecting Ar3 to Ar1 or Ar2, and * represents the position where Ar3 is connected to X.

[0013] Preferably, the chemical linker X is (ether bond).

[0014] In a second aspect, the present invention provides a method for preparing the heterojunction stacked covalent organic framework material according to the first aspect, comprising the following steps: In the first step, a reactant containing a donor unit Ar1 and a reactant containing a connecting skeleton unit Ar3 undergo a Suzuki coupling reaction to obtain a single-layer donor COF material.

[0015] The first step is to dissolve the reactant containing the donor unit Ar1, the reactant containing the connecting skeleton unit Ar3, and the catalyst in a solvent in proportion until the solid is completely dissolved, and then heat the reactant to 60°C-180°C by a solvothermal method for 1-10 days, or microwave heating at 40-120°C for 1-6 hours, and then wash to obtain a single-layer donor COF material. In the second step, a reactant containing an acceptor unit Ar2 and a reactant containing a connecting skeleton unit Ar3 undergo a Suzuki coupling reaction to obtain a single-layer acceptor COF material; The second step is as follows: dissolving the reactant containing the acceptor unit Ar2, the reactant containing the connecting skeleton unit Ar3, and the catalyst in a solvent in proportion until the solid is completely dissolved, heating the reactant to 60°C-180°C by a solvothermal method for 1-10 days, or heating the reactant to 40-120°C by a microwave method for 1-6 hours, and then washing to obtain a single-layer acceptor COF material; The third step is to make the donor COF material and the acceptor COF material undergo affinity substitution reaction to obtain a heterojunction stacked covalent organic framework material; The specific operation of the third step is: dissolving the obtained donor COF material, acceptor COF material, and catalyst in a solvent in proportion until the solid is completely dissolved, heating the reactants to 60°C-180°C by a solvent thermal method for 1-10 days, or heating them at 40-120°C by a microwave method for 1-6 hours, and then washing to obtain a heterojunction stacked covalent organic framework material.

[0016] The structural formula of the donor COF material is as follows:

[0017] The structural formula of the acceptor COF material is as follows:

[0018] Wherein, L1 and L2 are selected from -OH or -Br, and L1 and L2 are different.

[0019] Preferably, in the first step, the molar ratio of the reactant containing the donor unit Ar1 to the reactant containing the linker skeleton unit Ar3 is 2:3, and the mass fraction of the catalyst is 5% (the mass of the catalyst accounts for 5% of the reactant containing the donor unit Ar1 and the reactant containing the linker skeleton unit Ar3); In the second step, the molar ratio of the reactant containing the acceptor unit Ar2 to the reactant containing the linker skeleton unit Ar3 is 2:3, and the mass fraction of the catalyst is 5% (the mass of the catalyst accounts for 5% of the mass of the reactant containing the acceptor unit Ar2 and the reactant containing the linker skeleton unit Ar3); In the third step, the molar ratio of the donor COF material, the acceptor COF material and the catalyst is 1:1:12.

[0020] Preferably, in the first and second steps, the solvent is a mixed solvent of an organic solvent and deionized water, and the volume ratio of the organic solvent to the deionized water is 3:1. The organic solvent is one of toluene, dichloromethane, N,N-dimethylformamide, N,N-dimethylacetamide, acetone, methanol, tetrahydrofuran, dimethyl sulfoxide, and 1,4-dioxane.

[0021] Preferably, in the first and second steps, the catalyst is one of palladium(II)dichloride-bis(triphenylphosphine) complex, tetrakis(triphenylphosphine)palladium(0), palladium(II) acetate, bis(dibenzylideneacetone)palladium(0), bis(dibenzylideneacetone)palladium(0)-tri(o-methoxyphenyl)phosphine, palladium(II)dichloride·dichloromethane complex, bis(triphenylphosphine)palladium(II)dichloride, bis(acetonitrile)bis(acetate)palladium(II), bis(cyclooctadiene)palladium(0), and bis(tributylphosphine)palladium(II)dichloride; Preferably, in the third step, the solvent is one of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, toluene, methanol, ethanol, tetrahydrofuran, dichloromethane, acetone, 1,4-dioxane, and water, and the catalyst is one of triethylamine, sodium methoxide, potassium tert-butoxide, cesium carbonate, sodium fluoride, sodium hydroxide, potassium hydroxide, and barium hydroxide.

[0022] Preferably, in the third step, the washing liquid used for washing is one of acetone, toluene, methanol, tetrahydrofuran, dichloromethane, 1,4-dioxane or deionized water.

[0023] In a third aspect, the present invention provides an application of the heterojunction stacked covalent organic framework material described in the first aspect, wherein the heterojunction stacked covalent organic framework material can be used for optoelectronic devices, superconductors, ferromagnets, ferroelectrics, sensors, photovoltaics, energy storage, gas adsorption, and memristors.

[0024] Beneficial Effects: The method for preparing heterojunction laminated covalent organic framework materials prepared by the present invention enhances the photoelectric effect of COFs, producing highly efficient luminescent COF materials and addressing the limited application scope of COFs in the optoelectronics field. The heterojunction laminated covalent organic framework materials can also be used in electronics applications including organic electroluminescent devices, organic photovoltaics, field-effect transistors (FETs), optoelectronics, sensors, catalysis, and energy storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the powder X-ray diffraction characterization pattern of the prepared M-COF1; Figure 2 The scanning electron microscope characterization image of the prepared M-COF1; Figure 3 Comparison of Fourier transform infrared spectra of prepared M-COF1 and raw material COF; Figure 4 This is the UV absorption diagram of the prepared M-COF1.

[0026] Figure 5 is the fluorescence emission spectrum of the prepared M-COF1; Figure 6This is the spectrum of the organic electroluminescent device of the prepared M-COF1; Figure 7 is the fluorescence emission spectrum of the prepared M-COF2; Figure 8 is the fluorescence emission spectrum of the prepared M-COF3; Figure 9 The figure shows the organic electroluminescent device of the prepared M-COF5; Figure 10 Powder X-ray diffraction characterization patterns of the prepared M-COF4, 6, 7, 8, 9, and 10. DETAILED DESCRIPTION

[0027] The technical solutions of the present invention are described in detail below through examples, but the protection scope of the present invention is not limited to the examples.

[0028] Example 1 The first step is to weigh (0.1mol,1 equiv.), (0.15 mol, 1.5 equiv.) and tetrakis(triphenylphosphine)palladium(0), TBAB were added to the reaction tube, and then 6 mL of toluene and 2 mL of deionized water were added. The mixture was ultrasonicated for 30 min until the solid was completely dissolved. After heating to 110 °C for 3 days, it was naturally cooled to room temperature, then centrifuged and washed three times. The solid was dried in air to obtain a donor monolayer material, numbered D-COF1; The second step is to weigh (0.1mol,1 equiv.), (0.15 mol, 1.5 equiv.) and tetrakis(triphenylphosphine)palladium(0) and TBAB were added to the reaction tube, and then 6 mL of toluene and 2 mL of deionized water were added. The mixture was sonicated for 30 min until the solid was completely dissolved. After heating to 120 °C for 2 days, it was naturally cooled to room temperature, then centrifuged and washed three times. The solid was dried in air to obtain a receptor monolayer material, numbered A-COF1; In the third step, D-COF1 (20.00 mg), A-COF1 (25.82 mg), and triethylamine were weighed and added to a reaction tube. 10 mL of dimethyl sulfoxide was then added. The mixture was sonicated for 30 minutes until the solid was completely dissolved. After heating to 120°C for 4 days, the mixture was naturally cooled to room temperature and then centrifuged and washed three times. The solid was then air-dried to obtain the target product, designated M-COF1, with a yield of approximately 43%. Its structure is shown below:

[0029] The above structural formula represents the smallest structural unit in the organic framework material, and the wavy lines represent the connecting bonds between the structural units.

[0030] Example 2 The first step is to weigh (0.1mol,1 equiv.), (0.15 mol, 1.5 equiv.) and bis(dibenzylideneacetone)palladium(0), TBAB were added to the reaction tube, and then 6 mL of dichloromethane and 2 mL of deionized water were added. The mixture was ultrasonicated for 30 min until the solid was completely dissolved, heated to 100 °C for 2 days, and then naturally cooled to room temperature. It was then centrifuged and washed three times. The solid was dried in air to obtain a donor monolayer material, numbered D-COF2; The second step is to weigh (0.1mol,1 equiv.), (0.15 mol, 1.5 equiv.) and bis(tributylphosphine)palladium(II) dichloride and TBAB were added to a reaction tube, followed by the addition of 6 mL of N,N-dimethylformamide and 2 mL of deionized water. The mixture was sonicated for 30 min until the solid was completely dissolved. After heating to 100°C for 3 days, it was naturally cooled to room temperature, centrifuged and washed three times, and the solid was dried in air to obtain a receptor monolayer material, numbered A-COF2. In the third step, D-COF2 (20.00 mg), A-COF1 (21.82 mg), and sodium methoxide were weighed and added to a reaction tube. 10 mL of acetone was then added, and the mixture was sonicated for 30 minutes until the solid was completely dissolved. The mixture was heated to 120°C for 5 days, then naturally cooled to room temperature. The mixture was then centrifuged and washed three times, and the solid was air-dried to obtain the target product, designated M-COF2, with a yield of approximately 44%. Its structure is shown below:

[0031] Example 3 The first step is to weigh (0.1mol,1 equiv.), (0.15 mol, 1.5 equiv.) and bis(triphenylphosphine)palladium(II) dichloride and TBAB were added to the reaction tube, and then 6 mL of methanol and 2 mL of deionized water were added. The mixture was ultrasonicated for 30 min until the solid was completely dissolved. After heating to 125 °C for 2 days, it was naturally cooled to room temperature, then centrifuged and washed three times. The solid was dried in air to obtain a donor monolayer material, numbered D-COF3; The second step is to weigh (0.1mol,1 equiv.), (0.15 mol, 1.5 equiv.) and bis(acetonitrile)bis(acetate)palladium(II) and TBAB were added to a reaction tube, followed by the addition of 6 mL of N,N-dimethylformamide and 2 mL of deionized water. The mixture was sonicated for 30 min until the solid was completely dissolved. The mixture was heated to 120°C for 3 days and then naturally cooled to room temperature. The mixture was then centrifuged and washed three times. The solid was dried in air to obtain a receptor monolayer material, numbered A-COF3. In the third step, D-COF3 (20 mg), A-COF1 (20.30 mg), and potassium tert-butoxide were weighed and added to a reaction tube. 10 mL of methanol was then added, and the mixture was sonicated for 30 minutes until the solid was completely dissolved. After heating to 110°C for 5 days, the mixture was naturally cooled to room temperature, centrifuged, washed three times, and air-dried to obtain the target product. M-COF3 was obtained with a yield of approximately 54%, and its structure is shown below: .

[0032] Example 4 The first step is to weigh (0.1mol,1 equiv.), (0.15 mol, 1.5 equiv.) and bis(tributylphosphine)palladium(II) dichloride, TBAB were added to the reaction tube, and then 6 mL of tetrahydrofuran and 2 mL of deionized water were added. The mixture was ultrasonicated for 30 min until the solid was completely dissolved, heated to 90 °C for 2 days, and then naturally cooled to room temperature. It was then centrifuged and washed three times. The solid was dried in air to obtain a donor monolayer material, numbered D-COF4; The second step is to weigh (0.1mol,1 equiv.), (0.15 mol, 1.5 equiv.) and tetrakis(triphenylphosphine)palladium(0) and TBAB were added to the reaction tube, and then 6 mL of toluene and 2 mL of deionized water were added. The mixture was sonicated for 30 min until the solid was completely dissolved. After heating to 120 °C for 2 days, it was naturally cooled to room temperature, then centrifuged and washed three times. The solid was dried in air to obtain a receptor monolayer material, numbered A-COF1; In the third step, D-COF4 (20 mg), A-COF1 (11.62 mg), and cesium carbonate were weighed and added to a reaction tube. 10 mL of methanol was then added, and the mixture was sonicated for 30 minutes until the solid was completely dissolved. The mixture was then heated to 110°C for four days, cooled naturally to room temperature, and then centrifuged and washed three times. The solid was then air-dried to obtain the target product, designated M-COF4. The yield was approximately 43%, and its structure is shown below: .

[0033] Example 5 The first step is to weigh (0.1mol,1 equiv.), (0.15 mol, 1.5 equiv.) and bis(tributylphosphine)palladium(II) dichloride, TBAB were added to the reaction tube, and then 6 mL of tetrahydrofuran and 2 mL of deionized water were added. The mixture was sonicated for 30 min until the solid was completely dissolved, heated to 90 °C for 2 days, and then naturally cooled to room temperature. It was then centrifuged and washed three times. The solid was dried in air to obtain a donor monolayer material, numbered D-COF5; Weigh (0.1mol,1 equiv.), (0.15 mol, 1.5 equiv.) Bis(dibenzylideneacetone)palladium(0)-tri(o-methoxyphenyl)phosphine) and TBAB were added to a reaction tube, followed by 6 mL of toluene and 2 mL of deionized water. The mixture was sonicated for 30 min until the solid was completely dissolved. The mixture was heated to 90°C for 5 days and then naturally cooled to room temperature. The mixture was then centrifuged and washed three times. The solid was dried in air to obtain a receptor monolayer material, numbered A-COF4. In the second step, D-COF5 (20 mg), A-COF1 (16.75 mg), and sodium fluoride were weighed and added to a reaction tube. 10 mL of methanol was then added and the mixture was sonicated for 30 minutes until the solid was completely dissolved. The mixture was heated to 120°C for 5 days, then naturally cooled to room temperature. The mixture was then centrifuged and washed three times. The solid was then air-dried to obtain the target product, designated M-COF5, with a yield of approximately 43%. Its structure is shown below: .

[0034] Example 6 The first step is to weigh (0.1 mol,1 equiv.), (0.15 mol, 1.5 equiv.) and bis(cyclooctadiene)palladium(0) and TBAB were added to the reaction tube, and then 6 mL of methanol and 2 mL of deionized water were added. The mixture was ultrasonicated for 30 min until the solid was completely dissolved. After heating to 110 °C for 2 days, it was naturally cooled to room temperature, then centrifuged and washed three times. The solid was dried in air to obtain a donor monolayer material, numbered D-COF6; The second step is to weigh (0.1mol,1 equiv.), (0.15 mol, 1.5 equiv.) and palladium(II) chloride·dichloromethane complex, TBAB were added to a reaction tube, and then 6 mL of toluene and 2 mL of deionized water were added. The mixture was sonicated for 30 min until the solid was completely dissolved. After heating to 120°C for 2 days, it was naturally cooled to room temperature, then centrifuged and washed three times. The solid was dried in air to obtain a receptor monolayer material, numbered A-COF5; In the third step, D-COF6 (20.00 mg), A-COF2 (24.96 mg), and sodium hydroxide were weighed and added to a reaction tube. 10 mL of water was then added, and the mixture was sonicated for 30 minutes until the solid was completely dissolved. After heating to 100°C for 5 days, the mixture was naturally cooled to room temperature, centrifuged, washed three times, and air-dried to obtain the target product. M-COF6 was obtained with a yield of approximately 71%, and its structure is shown below: .

[0035] Example 7 The first step is to weigh (0.1 mol, 1 equiv.) 、 (0.15 mol, 1.5 equiv.) and bis(tributylphosphine)palladium(II) dichloride, TBAB were added to the reaction tube, and then 6 mL of tetrahydrofuran and 2 mL of deionized water were added. The mixture was sonicated for 30 min until the solid was completely dissolved, heated to 90 °C for 2 days, and then naturally cooled to room temperature. It was then centrifuged and washed three times. The solid was dried in air to obtain a donor monolayer material, numbered D-COF7; The second step is to weigh (0.1 mol, 1 equiv.) 、 (0.15 mol, 1.5 equiv.) and tetrakis(triphenylphosphine)palladium(0), TBAB were added to the reaction tube, and then 6 mL of 1,4-dioxane and 2 mL of deionized water were added. The mixture was sonicated for 30 min until the solid was completely dissolved, heated to 120 °C for 2 days, and then naturally cooled to room temperature. Subsequently, the mixture was centrifuged and washed three times. The solid was dried in air to obtain a receptor monolayer material, numbered A-COF5; In the third step, D-COF7 (20 mg), A-COF2 (23.34 mg), and potassium hydroxide were weighed and added to a reaction tube. 10 mL of methanol was then added, and the mixture was sonicated for 30 minutes until the solid was completely dissolved. The mixture was then heated to 120°C for 5 days, cooled naturally to room temperature, and then centrifuged and washed three times. The solid was then air-dried to obtain the target product, designated M-COF7. The yield was approximately 43%, and its structure is shown below: .

[0036] Example 8 The first step is to weigh (0.1 mol, 1 equiv.) 、 (0.15 mol, 1.5 equiv.) and tetrakis(triphenylphosphine)palladium(0), TBAB were added to the reaction tube, and then 6 mL of toluene and 2 mL of deionized water were added. The mixture was ultrasonicated for 30 min until the solid was completely dissolved. After heating to 120 °C for 2 days, it was naturally cooled to room temperature, then centrifuged and washed three times. The solid was dried in air to obtain a donor monolayer material, numbered D-COF8; The second step is to weigh (0.1mol,1 equiv.), (0.15 mol, 1.5 equiv.) and palladium (II) acetate and TBAB were added to a reaction tube, and then 6 mL of toluene and 2 mL of deionized water were added. The mixture was sonicated for 30 min until the solid was completely dissolved. After heating to 120 °C for 2 days, it was naturally cooled to room temperature, then centrifuged and washed three times. The solid was dried in air to obtain a receptor monolayer material, numbered A-COF6; In the third step, D-COF8 (20.00 mg), A-COF3 (21.30 mg), and barium hydroxide were weighed and added to a reaction tube. 10 mL of dimethyl sulfoxide was then added. The mixture was sonicated for 30 minutes until the solid was completely dissolved. After heating to 120°C for four days, the mixture was naturally cooled to room temperature and then centrifuged and washed three times. The solid was then air-dried to obtain the target product, designated M-COF8, with a yield of approximately 43%. Its structure is shown below: .

[0037] Example 9 The first step is to weigh (0.1mol,1 equiv.), (0.15 mol, 1.5 equiv.) and tetrakis(triphenylphosphine)palladium(0), TBAB were added to the reaction tube, and then 6 mL of toluene and 2 mL of toluene were added. The mixture was ultrasonicated for 30 min until the solid was completely dissolved, heated to 120 °C for 2 days, and then naturally cooled to room temperature. It was then centrifuged and washed three times. The solid was dried in air to obtain a donor monolayer material, numbered D-COF9; The second step is to weigh (0.1mol,1 equiv.), (0.15 mol, 1.5 equiv.) and tetrakis(triphenylphosphine)palladium(0) and TBAB were added to the reaction tube, and then 6 mL of toluene and 2 mL of detoxified toluene were added. The mixture was ultrasonicated for 30 min until the solid was completely dissolved. After heating to 120 °C for 2 days, it was naturally cooled to room temperature, then centrifuged and washed three times. The solid was dried in air to obtain a receptor monolayer material, numbered A-COF7; In the second step, D-COF8 (20.00 mg), A-COF3 (22.98 mg), and potassium tert-butoxide were weighed and added to a reaction tube. 10 mL of dimethyl sulfoxide was then added. The mixture was sonicated for 30 minutes until the solid was completely dissolved. After heating to 120°C for 4 days, the mixture was naturally cooled to room temperature and then centrifuged and washed three times. The solid was air-dried to obtain the target product, designated M-COF9, with a yield of approximately 41%. Its structure is shown below: .

[0038] Example 10 The first step is to weigh (0.1mol,1 equiv.), (0.15 mol, 1.5 equiv.) and tetrakis(triphenylphosphine)palladium(0), TBAB were added to the reaction tube, and then 6 mL of toluene and 2 mL of toluene were added. The mixture was ultrasonicated for 30 min until the solid was completely dissolved, heated to 120 °C for 2 days, and then naturally cooled to room temperature. It was then centrifuged and washed three times. The solid was dried in air to obtain a donor monolayer material, numbered D-COF10; The second step is to weigh (0.1mol,1 equiv.), (0.15 mol, 1.5 equiv.) and palladium(II) chloride·dichloromethane complex, TBAB were added to a reaction tube, and then 6 mL of toluene and 2 mL of detoxified toluene were added. The mixture was sonicated for 30 min until the solid was completely dissolved. After heating to 120 °C for 2 days, it was naturally cooled to room temperature, then centrifuged and washed three times. The solid was dried in air to obtain a receptor monolayer material, numbered A-COF8; In the third step, D-COF8 (20.00 mg), A-COF3 (24.32 mg), and potassium hydroxide were weighed and added to a reaction tube. 10 mL of dimethyl sulfoxide was then added. The mixture was sonicated for 30 minutes until the solid was completely dissolved. After heating to 130°C for 4 days, the mixture was naturally cooled to room temperature and then centrifuged and washed three times. The solid was then air-dried to obtain the target product, designated M-COF10, with a yield of approximately 41%. Its structure is shown below: .

[0039] Figure 1 This is the X-ray diffraction characterization diagram of M-COF1. There is an obvious crystallization peak at about 2°, indicating that the synthesized heterojunction stacked covalent organic framework material has good crystallinity; Figure 2 This is the SEM characterization image of M-COF1, showing a lamellar structure; Figure 3 The Fourier transform infrared spectrum comparison of M-COF1, Fourier transform infrared spectrum (FT-IR) at 1005cm -1 and 1122 cm -1 There is a vibration peak of ether bond at , which proves that the layers are successfully connected; Figure 4 is the UV absorption graph of M-COF1; Figure 5 is the fluorescence emission spectrum of M-COF1, with an emission wavelength of 460 nm, blue light emission, and an intensity of 17000; Figure 6 An organic electroluminescent device was prepared for M-COF1 and successfully lit up. The luminescent color was blue, which matched the fluorescence emission spectrum.

[0040] Figure 7 This is the fluorescence emission spectrum of M-COF2. The emission wavelength is 430nm, it is blue light emission, and the intensity is 80000, which proves that it has a high luminescence effect.

[0041] Figure 8 This is the fluorescence emission spectrum of M-COF3. The emission wavelength is 450nm, it is blue light emission, and the intensity is 45000, which proves that it has a good luminescence effect.

[0042] Figure 9An organic electroluminescent device prepared for M-COF5 was successfully lit up, and the luminescent color was blue-green.

[0043] Figure 10 Powder X-ray diffraction characterization patterns of prepared M-COF4, 6, 7, 8, 9, and 10.

[0044] As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the present invention itself. Various changes may be made to the form and details without departing from the spirit and scope of the present invention.

Claims

1. A heterojunction stacked covalent organic framework material, characterized in that: The heterojunction stacked covalent organic framework material is formed by directly covalently connecting layers of a single-layer covalent organic framework material through a substitution reaction. The general structural formula of the heterojunction stacked covalent organic framework material is as follows: ； Wherein, Ar1 is an electron donor unit, Ar2 is an electron acceptor unit, Ar3 is a connecting skeleton unit, and X is a chemical connecting bond.

2. The heterojunction stacked covalent organic framework material according to claim 1, characterized in that: Ar1 is one of the following structures: ； Wherein, R is selected from C0-C 30 Alkyl chain.

3. The heterojunction stacked covalent organic framework material according to claim 1, characterized in that: Ar2 is one of the following structures: ； Wherein, R is selected from C0-C 30 Alkyl chain.

4. The heterojunction stacked covalent organic framework material according to claim 1, characterized in that: Ar3 is one of the following structures: ； The dotted line represents the bond connecting Ar3 to Ar1 or Ar2, and * represents the position where Ar3 is connected to X.

5. The heterojunction stacked covalent organic framework material according to claim 1, characterized in that: Preferably, X is .

6. The method for preparing the heterojunction stacked covalent organic framework material according to claim 1, characterized in that: The steps include: In the first step, a reactant containing a donor unit Ar1 and a reactant containing a connecting skeleton unit Ar3 undergo a Suzuki coupling reaction to obtain a single-layer donor COF material; In the second step, a reactant containing an acceptor unit Ar2 and a reactant containing a connecting skeleton unit Ar3 undergo a Suzuki coupling reaction to obtain a single-layer acceptor COF material; The third step is to make the donor COF material and the acceptor COF material undergo affinity substitution reaction to obtain a heterojunction stacked covalent organic framework material.

7. The preparation method according to claim 6, characterized in that In the first step, the molar ratio of the reactant containing the donor unit Ar1 to the reactant containing the linker skeleton unit Ar3 is 2:3; In the second step, the molar ratio of the reactant containing the acceptor unit Ar2 and the reactant containing the connecting skeleton unit Ar3 is 2:3; In the third step, the molar ratio of the donor COF material to the acceptor COF material is 1:

1.

8. The preparation method according to claim 6, characterized in that The first step is to dissolve the reactant containing the donor unit Ar1, the reactant containing the connecting skeleton unit Ar3, and the catalyst in a solvent in proportion until the solid is completely dissolved, and then heat the reactant to 60°C-180°C by a solvothermal method for 1-10 days, or microwave heating at 40-120°C for 1-6 hours, and then wash to obtain a single-layer donor COF material. The second step is as follows: dissolving the reactant containing the acceptor unit Ar2, the reactant containing the connecting skeleton unit Ar3, and the catalyst in a solvent until the solid is completely dissolved, heating the reactant to 60°C-180°C by a solvothermal method for 1-10 days, or heating the reactant to 40-120°C by a microwave method for 1-6 hours, and then washing to obtain a single-layer acceptor COF material; The specific operation of the third step is: dissolving the obtained donor COF material, acceptor COF material and catalyst in a solvent in proportion until the solid is completely dissolved, heating the reactants to 60°C-180°C by a solvent thermal method for 1-10 days, or heating them at 40-120°C by a microwave method for 1-6 hours, and then washing to obtain a heterojunction stacked covalent organic framework material.

9. The preparation method according to claim 6, characterized in that The structural formula of the donor COF material is as follows: ； The structural formula of the acceptor COF material is as follows: ； Wherein, L1 and L2 are selected from -OH or -Br, and L1 and L2 are different.

10. The use of the heterojunction stacked covalent organic framework material according to claim 1, characterized in that: Used to prepare organic electroluminescent devices.

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