Composite heterojunction photocatalyst as well as preparation method and application thereof

Abstract

The invention discloses a composite heterojunction photocatalyst as well as a preparation method and application thereof. The preparation method comprises the following steps: carrying out pre-reaction on a first mixed system at least containing an aldehyde substance, an amine substance, a two-dimensional nanosheet and a catalyst, and then heating in a vacuum or inert atmosphere for continuous reaction to prepare the covalent organic framework nanotube / two-dimensional nanosheet composite heterojunction photocatalyst. According to the method, no soft / hard template is used, reversible Schiff base chemical bonds and proton tautomerization are utilized, hollow nanotubes are constructed on the surface of a two-dimensional nanosheet layer material in situ through a one-pot method which is easy to operate from bottom to top, the composite heterojunction photocatalyst is obtained, and meanwhile the composite heterojunction photocatalyst is high in crystallinity and good in photocatalytic performance. And the material has a large specific surface area, and has potential application value in the fields of adsorption, separation and photocatalytic antibiosis and antifouling.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanomaterials, and in particular relates to a composite heterojunction photocatalyst and a preparation method and application thereof. Background Art

[0002] The adhesion and growth of microorganisms on engineering equipment, medical equipment and daily necessities has caused great trouble to the efficient and safe operation of equipment and human health. For example, bacteria and fungi can survive for hours or even days on the surface of items such as gloves, urethral catheters, and hemostatic gauze, and spread between individuals after contact with the host, which increases the risk of infection. In the marine environment, biofouling is also a serious problem. It will increase the friction resistance of the hull surface, accelerate metal corrosion, block the ventilation holes of aquaculture cages, and cause additional fuel consumption and excessive maintenance costs. According to statistics, marine biofouling causes losses of more than US$15 billion to the global marine industry each year. However, traditional antibacterial and antifouling coatings kill fouling organisms by releasing tributyltin, antibiotics, and cuprous oxide toxic antibacterial and antifouling agents, which cause serious damage to the ecological environment.

[0003] Photocatalytic technology is an environmentally friendly technology that uses solar energy for environmental purification and energy conversion. It has the characteristics of environmental friendliness and sustainable development. Covalent organic framework materials (COFs), as lightweight porous crystalline polymer materials, have excellent photocatalytic activity due to their unique chemical structure and photophysical properties, and have received extensive attention in the fields of degradation of organic pollutants and photocatalytic antibacterial. However, the photogenerated electrons and holes generated by common COFs after absorbing light energy have a fast recombination rate, resulting in low carrier utilization, and problems such as photoinactivation seriously reduce the photocatalytic efficiency of COFs. At present, most COFs research focuses on designing synthesis strategies, adjusting the constituent units and framework structures, and there are still certain difficulties and challenges in the controlled synthesis of COFs with uniform morphology and good crystallinity. For example, the patent with publication number CN111171369A introduces a method for constructing tubular COFs using silica nanowires as a hard template, but this method requires subsequent removal of the template; the patent with publication number CN114874451A uses trimesic acid as a morphology directing agent for tubular COFs, but this method may require the use of more organic acids. Nevertheless, the photocatalytic efficiency of single-component COFs is still low and needs to be further improved. Summary of the invention

[0004] The main purpose of the present invention is to provide a composite heterojunction photocatalyst and a preparation method and application thereof, so as to overcome the deficiencies of the prior art.

[0005] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes: An embodiment of the present invention provides a method for preparing a composite heterojunction photocatalyst, which comprises: A first mixed system containing at least aldehyde substances, amine substances, two-dimensional nanosheets and catalysts is pre-reacted, and then the temperature is raised in a vacuum or inert atmosphere to continue the reaction to obtain a covalent organic framework nanotube / two-dimensional nanosheet composite heterojunction photocatalyst.

[0006] An embodiment of the present invention also provides a composite heterojunction photocatalyst obtained by the aforementioned preparation method, wherein the composite heterojunction photocatalyst includes covalent organic framework nanotubes and two-dimensional nanosheets, wherein a heterojunction is formed between the covalent organic framework nanotubes and the two-dimensional nanosheets; the covalent organic framework nanotubes are dispersed on the surface of the two-dimensional nanosheets in at least one of a coating, an inlay, and an adsorption manner, or the two-dimensional nanosheets are dispersed on the surface of the covalent organic framework nanotubes in at least one of a coating, an inlay, and an adsorption manner.

[0007] The embodiments of the present invention also provide applications of the aforementioned composite heterojunction photocatalyst in the fields of adsorption, separation or photocatalytic antibacterial.

[0008] The embodiment of the present invention further provides an antibacterial and antifouling agent, which at least includes the aforementioned composite heterojunction photocatalyst.

[0009] Compared with the prior art, the present invention has the following beneficial effects: (1) The method provided by the present invention does not use any soft / hard templates, but uses an easy-to-operate solvothermal method to in-situ construct hollow nanotubes on the surface of a two-dimensional sheet material "from bottom to top" to obtain a composite heterojunction photocatalyst of covalent organic framework nanotubes / two-dimensional nanosheets. The obtained covalent organic framework nanotubes have uniform morphology and size, high crystallinity, large specific surface area, and good stability. (2) Compared with other covalent organic framework materials, the composite heterojunction photocatalyst of the covalent organic framework nanotube / two-dimensional nanosheet prepared by the present invention has the advantage of the generated heterojunction interface, which has the ability to quickly separate photogenerated electrons and holes and has a higher light absorption capacity, thereby improving the photocatalytic performance of the single-component covalent organic framework; (3) The process provided by the present invention is simple to operate, controllable, and has a certain degree of universality; the ratio of the two-dimensional sheet material to the covalent organic framework nanotube is adjustable, and the band structure and photocatalytic performance of the binary composite heterojunction photocatalyst can be regulated by different ratios to better meet actual needs; (4) The covalent organic framework nanotube / two-dimensional nanosheet composite heterojunction photocatalyst of the present invention has a faster and better antibacterial and antifouling effect compared with a single component covalent organic framework material. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] 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 recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0011] Figure 1 It is a flow chart for preparing a covalent organic framework nanotube / two-dimensional nanosheet composite heterojunction photocatalyst in a typical embodiment of the present invention; Figure 2A-2E It is a two-dimensional nanosheet Ti3C2T prepared in a typical embodiment of the present invention. x Nanosheets, SEM images of graphene-phase carbon nitride nanosheets, TEM images of tungsten selenide nanosheets, SEM images and TEM images of covalent organic framework nanotubes; Figure 3 is an X-ray powder diffraction pattern of a covalent organic framework nanotube in a typical embodiment of the present invention; Figure 4A-4B A typical embodiment of the present invention is a covalent organic framework nanotube / Ti3C2T x SEM image of nanosheet composite heterojunction photocatalyst; Figure 5A-Figure 5B is a scanning electron microscope image of a covalent organic framework nanotube / graphite phase carbon nitride nanosheet composite heterojunction photocatalyst in a typical embodiment of the present invention; Figure 6 It is a scanning electron microscope image of a covalent organic framework nanotube / tungsten selenide nanosheet composite heterojunction photocatalyst in a typical embodiment of the present invention. DETAILED DESCRIPTION

[0012] In view of the defects of the prior art, the inventor of this case has proposed the technical solution of the present invention after long-term research and extensive practice. The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. 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.

[0013] Specifically, as one aspect of the technical solution of the present invention, a method for preparing a composite heterojunction photocatalyst includes: A first mixed system containing at least aldehyde substances, amine substances, two-dimensional nanosheets and catalysts is pre-reacted, and then the temperature is raised in a vacuum or inert atmosphere to continue the reaction to obtain a covalent organic framework nanotube / two-dimensional nanosheet composite heterojunction photocatalyst.

[0014] In some preferred embodiments, the preparation method specifically includes: under the condition of -10~35°C, mixing the aldehyde substance, the two-dimensional nanosheets and the first solvent to form a first dispersion, mixing the amine substance with the first solvent to form a second dispersion, and then mixing the second dispersion with the first dispersion under stirring conditions and adding a catalyst to form a first mixed system for pre-reaction for 2~60 min.

[0015] In some preferred embodiments, the preparation method specifically includes: under the condition of -10~35°C, mixing the amine substance, the two-dimensional nanosheet and the first solvent to form a third dispersion; mixing the aldehyde substance with the first solvent to form a fourth dispersion, and then mixing the fourth dispersion with the third dispersion under stirring conditions and adding a catalyst to form a first mixed system for pre-reaction for 2~60 min.

[0016] Further, the aldehyde substance includes a dialdehyde or a polyaldehyde containing an aromatic ring structure, and the dialdehyde or polyaldehyde containing an aromatic ring structure includes any one or more combinations of terephthalaldehyde, o-phthalaldehyde, isophthalaldehyde, trimesic acid, 1,3,5-triazine-2,4,6-tricarbaldehyde, 2-hydroxy-1,3,5-benzenetricarbaldehyde, 2,4-dihydroxy-1,3,5-tribenzenetricarbaldehyde, and 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde, and is not limited thereto.

[0017] Furthermore, the dialdehyde or polyaldehyde containing an aromatic ring structure includes any one or more combinations of 2-hydroxy-1,3,5-benzenetricarbaldehyde, 2,4-dihydroxy-1,3,5-pyrimidinecarbaldehyde, and 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde, but is not limited thereto.

[0018] Furthermore, the amine substance includes a diamine or polyamine containing an aromatic ring structure, and the diamine or polyamine containing an aromatic ring structure includes any one or more combinations of p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, benzidine, tris(4-aminophenyl)amine, and (2,4,6-trimethylbenzene-1,3,5-triyl)trimethylamine, and is not limited thereto.

[0019] Furthermore, the diamine or polyamine containing an aromatic ring structure includes any one or more combinations of p-phenylenediamine, o-phenylenediamine, and m-phenylenediamine, but is not limited thereto.

[0020] Furthermore, the two-dimensional nanosheets include any one or more combinations of graphite-phase carbon nitride, MXene, WSe2, graphene, boron nitride, transition metal sulfides, black scale, and phosphorene, wherein the MXene includes any one or more combinations of transition metal carbides, nitrides, and carbonitrides, and is not limited thereto.

[0021] Furthermore, the two-dimensional nanosheets include graphite phase carbon nitride, Ti3C2T x , WSe2, or any one or more combinations thereof, and is not limited thereto.

[0022] Furthermore, the catalyst includes any one or more combinations of hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, formic acid, and benzenesulfonic acid, but is not limited thereto.

[0023] Furthermore, the catalyst includes any one or more combinations of acetic acid, formic acid, and hydrochloric acid, but is not limited thereto.

[0024] Further, the first solvent includes any one or more combinations of N,N-dimethylformamide, dimethyl sulfoxide, dichloromethane, mesitylene, 1,4-dioxane, tetrahydrofuran, chloroform, chloroform, and toluene, and is not limited thereto.

[0025] Furthermore, the first solvent includes any one or more combinations of dichloromethane, mesitylene, and 1,4-dioxane, but is not limited thereto.

[0026] Furthermore, the concentration of the catalyst is 0.1-15 mol / L.

[0027] Furthermore, the molar ratio of the amine functional group to the aldehyde functional group in the first mixed reaction system is 1:0.5-1.5.

[0028] Furthermore, the mass ratio of the sum of the aldehyde substance and the amine substance in the first mixed reaction system to the two-dimensional nanosheets is 1:0.1-10.

[0029] Furthermore, the mass ratio of the two-dimensional nanosheets to the first solvent in the first dispersion is 1:5-100.

[0030] Furthermore, the mass ratio of the two-dimensional nanosheets to the first solvent in the third dispersion is 1:5-100.

[0031] Furthermore, the volume ratio of the catalyst to the sum of the first dispersion and the second dispersion is 1-3:3-10.

[0032] Furthermore, the volume ratio of the catalyst to the sum of the third dispersion and the fourth dispersion is 1-3:3-10.

[0033] Furthermore, the stirring speed used in the stirring is 50-1000 rpm.

[0034] In some preferred embodiments, the preparation method specifically comprises: after the pre-reaction is completed, heating to 60-160° C. in a vacuum or inert atmosphere and continuing the reaction for 1-120 hours, and then separating, purifying, and drying to obtain a composite heterojunction photocatalyst of covalent organic framework nanotubes / two-dimensional nanosheets; Wherein, the purification treatment includes any one or more combinations of solution washing, solvent exchange, vacuum drying, and air drying; the reagents used in the purification treatment include any one or more combinations of acetone, methanol, ethanol, isopropanol, tetrahydrofuran, N,N-dimethylformamide, and N,N-dimethylacetamide, but are not limited thereto.

[0035] In some more specific embodiments, the preparation method of the composite heterojunction photocatalyst (flow chart as shown in FIG. Figure 1 shown) include: Provide A component precursors: amine substances (di / polyamines containing aromatic ring structures) and aldehyde substances (di / polyaldehydes containing aromatic ring structures); Providing a B-component two-dimensional nanosheet; Pre-reaction: at -10~35°C, the precursor aldehyde substance of component A, the nanosheets of component B and the first solvent are mixed to form a uniform dispersion C1, and the amine substance and the first solvent are mixed to form a uniform dispersion D1; then, the dispersion D1 is dripped into the dispersion C1 under stirring, and a catalyst is dripped to accelerate the condensation reaction, so as to form a first mixed reaction system; Alternatively, at -10 to 35° C., the precursor amine substance of component A, the nanosheets of component B and the first solvent are mixed to form a uniform dispersion D2, and the aldehyde substance and the first solvent are mixed to form a uniform dispersion C2; then, the dispersion C2 is dripped into the dispersion D2 under stirring, and a catalyst is dripped to accelerate the condensation reaction, so as to form a first mixed reaction system; Subsequent reaction: in a non-reactive gas environment, increasing the reaction temperature of the first mixed reaction system and extending the reaction time to increase the degree of reaction and the crystallinity of the Schiff base covalent organic framework; Separation and purification: After the reaction is completed, the mixture is cooled to room temperature, and then separated, purified and dried to obtain a composite heterojunction photocatalyst of covalent organic framework nanotubes / two-dimensional nanosheets.

[0036] Preferably, the di- / polyamine containing an aromatic ring structure includes any one or more combinations of p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, benzidine, tris(4-aminophenyl)amine, (2,4,6-trimethylbenzene-1,3,5-triyl)trimethylamine, but is not limited thereto; Preferably, the di- / poly-aldehyde containing an aromatic ring structure includes any one or more combinations of terephthalaldehyde, o-phthalaldehyde, isophthalaldehyde, trimesicaldehyde, 1,3,5-triazine-2,4,6-tricarbaldehyde, 2-hydroxy-1,3,5-benzenetricarbaldehyde, 2,4-dihydroxy-1,3,5-tribenzenetricarbaldehyde, and 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde, and is not limited thereto.

[0037] Preferably, the molar ratio of amine functional groups to aldehyde functional groups in the first mixed reaction system is 1:0.5~1.5; the mass ratio of the sum of aldehyde substances and amine substances in the first mixed reaction system to the two-dimensional nanosheets is 1:0.1~10; the mass ratio of the two-dimensional nanosheets to the first solvent is 1:5~100.

[0038] Preferably, the first solvent includes any one or a combination of two or more of N,N-dimethylformamide, dimethyl sulfoxide, dichloromethane, mesitylene, 1,4-dioxane, tetrahydrofuran, chloroform, chloroform, and toluene, but is not limited thereto.

[0039] Preferably, the catalyst includes any one or a combination of two or more of hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, formic acid, and benzenesulfonic acid, but is not limited thereto.

[0040] Preferably, the stirring state includes magnetic stirring, ultrasonic stirring, vortex stirring, shaking table stirring, and mechanical stirring. Preferably, the stirring state is vortex stirring, magnetic stirring, and the stirring speed is 50-1000 rpm.

[0041] Preferably, the reaction temperature of the subsequent reaction is 80-150°C.

[0042] Preferably, the reaction time of the subsequent reaction is 24 to 72 hours.

[0043] Preferably, after the reaction is completed, the obtained product is separated and purified; preferably, the purification treatment includes any one or more combinations of solution washing, solvent exchange, vacuum drying, and air drying; preferably, the reagents used in the purification treatment include any one or more combinations of acetone, methanol, ethanol, isopropanol, tetrahydrofuran, N,N-dimethylformamide, and N,N-dimethylacetamide, but are not limited thereto.

[0044] Preferably, the concentration of the catalyst solution is 1-15 mol / L, and the volume ratio of the catalyst to the mixed organic solvent is 1-3:3-10.

[0045] Another aspect of an embodiment of the present invention also provides a composite heterojunction photocatalyst obtained by the aforementioned preparation method, wherein the composite heterojunction photocatalyst includes covalent organic framework nanotubes and two-dimensional nanosheets, and a heterojunction is formed between the covalent organic framework nanotubes and the two-dimensional nanosheets; the covalent organic framework nanotubes are dispersed on the surface of the two-dimensional nanosheets in at least one of a coating, an inlay, and an adsorption manner, or the two-dimensional nanosheets are dispersed on the surface of the covalent organic framework nanotubes in at least one of a coating, an inlay, and an adsorption manner.

[0046] In some preferred embodiments, the covalent organic framework nanotube has a hollow channel with a diameter of 10 to 1000 nm, and the length of the covalent organic framework nanotube is 0.5 to 30 μm.

[0047] In some preferred embodiments, the two-dimensional nanosheet has a thickness of 0.1-100 nm and a sheet diameter of 0.01-50 μm.

[0048] Specifically, the composite heterojunction photocatalyst in the present invention is mainly composed of component A and component B, wherein component A is a covalent organic framework nanotube, the precursor of component A is a diamine or polyamine containing an aromatic ring structure and a dialdehyde or polyaldehyde containing an aromatic ring structure; component B is a two-dimensional nanosheet.

[0049] Another aspect of the embodiments of the present invention further provides the application of the aforementioned composite heterojunction photocatalyst in the field of adsorption, separation or photocatalytic antibacterial.

[0050] Another aspect of the embodiments of the present invention further provides an antibacterial and antifouling agent, which at least includes the aforementioned composite heterojunction photocatalyst.

[0051] The technical solution of the present invention is further described in detail below in conjunction with several preferred embodiments and drawings. This embodiment is implemented on the premise of the technical solution of the invention, and a detailed implementation method and specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

[0052] Unless otherwise specified, the experimental materials used in the following examples can be purchased from conventional biochemical reagent companies.

[0053] Example 1 Step 1: 160 mg of 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde and 120 mg of p-phenylenediamine were dispersed in 6 mL of a mixed solvent of mesitylene and 1,4-dioxane (volume ratio of 1:1), and ultrasonically dispersed to form uniform dispersion A and dispersion B; The dispersion A is added dropwise into the dispersion B at -10-35°C, with stirring at a speed of 50-1000 rpm, to form a first mixed reaction system, and a 6M acetic acid aqueous solution is added to carry out a condensation reaction.

[0054] Step 2: The first mixed reaction system was rapidly and vigorously stirred, and the mixed solution was quickly frozen at 77.3 K (liquid nitrogen bath) before heating, and degassed through three freeze-pump-thaw cycles.

[0055] Step 3: After degassing, the reaction system is reacted at 100° C. for 72 h under vacuum or inert gas atmosphere.

[0056] Step 4: After filtering the solid after the reaction, the COFs tubes were purified by solvent exchange with acetone, methanol, and DMF. Finally, the purified sample was filtered and vacuum dried at 90°C to obtain covalent organic framework nanotubes; the covalent organic framework nanotubes have a diameter of about 200 nanometers, a wall thickness of about 50 nanometers, and a length of about 4 micrometers (such as Figure 2C , Figure 2E By X-ray powder diffraction analysis (as shown); Figure 3 As shown), it is proved that the covalent organic framework nanotubes prepared by the present invention have a crystal structure and crystallinity similar to those of traditional COFs; in the BET specific surface area test, the specific surface area of ​​tubular COFs is about 5 times that of traditional COFs.

[0057] Technical description of this embodiment: Through the preparation method of this experiment, using Schiff base chemical reaction and proton tautomerism, covalent organic framework nanotubes can be directly constructed in one pot without soft / hard templates; compared with traditional COFs, the prepared covalent organic framework nanotubes have good crystallinity and a larger specific surface area.

[0058] Example 2 Step 1: Preparation of Ti3C2T x Nanosheets; 0.5 g of multilayer Ti3C2T x The two-dimensional sheet material Ti3C2T was obtained by stirring in 50 mL tetrabutylammonium hydroxide solution under nitrogen atmosphere for 21 hours, and then through ultrasonication, washing, filtration and other steps. x Nanosheets, such as Figure 2A , Figure 2B , Figure 2D shown.

[0059] Step 2: 80 mg 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde, 160 mg p-phenylenediamine, 50 mg prepared Ti3C2T xThe nanosheets were dispersed in 3 mL of a mixed solvent of mesitylene and 1,4-dioxane (volume ratio of 1:1) to form uniform dispersions A, B, and C; At -10-35°C, the dispersion B and the dispersion C are uniformly mixed, and then dispersion A is added dropwise while stirring at a speed of 50-1000 rpm to form a first mixed reaction system, and a 6M acetic acid aqueous solution is added to carry out a condensation reaction.

[0060] Step 3: The mixed reaction system was rapidly and vigorously stirred, and the mixed solution was quickly frozen at 77.3 K (liquid nitrogen bath) before heating and degassed through three freeze-pump-thaw cycles.

[0061] Step 4: After degassing, the reaction system is reacted at 100° C. for 72 h under vacuum or inert gas atmosphere.

[0062] Step 5: After filtering the solid after the reaction, the COFs tube was purified by solvent exchange with acetone, methanol, and DMF. Finally, the purified sample was filtered and vacuum dried at 90 ° C to obtain covalent organic framework nanotubes / Ti3C2T x Nanosheet composite heterojunction photocatalyst; coated / embedded / adsorbed on Ti3C2T x The covalent organic framework nanotubes on the surface of the nanosheets are about 200 nanometers in diameter and 10 micrometers in length. x The lateral size of the nanosheets is 1 to 7 microns (e.g. Figure 2A , Figure 2B , Figure 2D , Figure 4A , Figure 4B As shown); prepared covalent organic framework nanotube / Ti3C2T x Compared with the single-component traditional COFs, the nanosheet composite heterojunction photocatalyst has stronger light absorption performance. In the anti-bacterial fouling test, the single-component traditional COFs and the single-component Ti3C2T x Nanosheets and covalent organic framework nanotubes / Ti3C2T x Nanosheet composite heterojunction photocatalysts, under light conditions, have inhibition rates of approximately 67%, 35%, and 99.4% on bacterial growth, respectively.

[0063] Technical description of this example: Through Schiff base chemical reaction and proton tautomerism, Ti3C2T x Covalent organic framework nanotubes were constructed on the nanosheets to obtain covalent organic framework nanotubes / Ti3C2T x Nanosheet composite heterojunction photocatalyst; covalent organic framework nanotube and Ti3C2T xThe nanosheets form heterojunctions, and the bonding between them is that the covalent organic framework nanotubes are coated / embedded / adsorbed on the Ti3C2T x Nanosheet surface, and compared with single-component traditional COFs and single-component Ti3C2T x The nanosheets have enhanced antibacterial and antifouling capabilities.

[0064] Example 3 This embodiment is basically the same as Embodiment 2, except that: Step 1: Prepare a semiconductor two-dimensional material: graphite phase carbon nitride nanosheets; 10g of melamine and 30g of sodium chloride were ground for 10 minutes and then placed in a quartz crucible. In an air atmosphere, the temperature was raised to 500°C in a muffle furnace at a heating rate of 15°C / min and kept for 3 hours, then cooled with the furnace. The obtained solid was washed and filtered three times with deionized water and ethanol, and the obtained flake graphite phase carbon nitride was ultrasonically exfoliated in an isopropanol solvent. Finally, two-dimensional sheet material graphite phase carbon nitride nanosheets were obtained through washing, filtering and other steps.

[0065] Step 2: 80 mg of 2,4,6-trihydroxybenzene-1,3,5-triformaldehyde, 160 mg of p-phenylenediamine, and 50 mg of the prepared graphite phase carbon nitride nanosheets were dispersed in 3 mL of a mixed solvent of mesitylene and 1,4-dioxane (volume ratio of 1:1) to form uniform dispersions A, B, and C; At -10-35°C, the dispersion B and the dispersion C are uniformly mixed, and then dispersion A is added dropwise while stirring at a speed of 50-1000 rpm to form a first mixed reaction system, and a 6M acetic acid aqueous solution is added to carry out a condensation reaction.

[0066] Step 3: The mixed reaction system was rapidly and vigorously stirred, and the mixed solution was quickly frozen at 77.3K (liquid nitrogen bath) before heating, and degassed through three freeze-pump-thaw cycles.

[0067] Step 4: After degassing, the reaction system is reacted at 100° C. for 72 h under vacuum or inert gas atmosphere.

[0068] Step 5: After filtering the solid after the reaction is completed, the COFs tube is purified by solvent exchange with acetone, methanol and DMF. Finally, the purified sample is filtered and vacuum dried at 90°C to obtain a covalent organic framework nanotube / graphite phase carbon nitride nanosheet composite heterojunction photocatalyst.

[0069] In this way, a covalent organic framework nanotube / graphite phase carbon nitride nanosheet composite heterojunction photocatalyst was obtained; the lateral size of the graphite phase carbon nitride nanosheet is about 5-20 microns, the diameter of the covalent organic framework nanotube is about 50 nanometers, and the length is about 6 microns. Figure 5A , Figure 5B As shown; a heterojunction is formed between the covalent organic framework nanotubes and the graphite phase carbon nitride nanosheets, and the bonding mode between them is that the covalent organic framework nanotubes are coated / embedded / adsorbed on the surface of the graphite phase carbon nitride nanosheets; the obtained covalent organic framework nanotube / graphite phase carbon nitride nanosheet composite heterojunction photocatalyst has a stronger reduction performance than the band structure corresponding to the single-component traditional COFs; the anti-bacterial fouling test shows that compared with the blank control group, the single-component traditional COFs, the single-component graphite phase carbon nitride nanosheets and the covalent organic framework nanotube / graphite phase carbon nitride nanosheet composite heterojunction photocatalyst, under light, the inhibition rates of the three on bacterial growth are approximately 67%, 34% and 98.2%, respectively.

[0070] Technical description of this embodiment: By changing the type of two-dimensional sheet material, binary composite heterojunction photocatalysts with different heterogeneous structures can be obtained. The prepared covalent organic framework nanotube / graphite phase carbon nitride nanosheet composite heterojunction photocatalyst has enhanced antibacterial and antifouling properties compared to traditional single-component COFs.

[0071] Example 4 This embodiment is basically the same as Embodiment 2, except that: Step 1: Prepare a two-dimensional transition metal chalcogenide: tungsten selenide nanosheet; 0.5 g of tungsten selenide was ultrasonically treated in isopropanol solvent, peeled off, and finally washed, filtered and other steps to obtain a two-dimensional layer material tungsten selenide nanosheet.

[0072] Step 2: 80 mg of 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde, 160 mg of p-phenylenediamine, and 50 mg of the prepared tungsten selenide nanosheets were dispersed in 3 mL of a mixed solvent of mesitylene and 1,4-dioxane (volume ratio of 1:1) to form uniform dispersions A, B, and C; At -10-35°C, the dispersion B and the dispersion C are uniformly mixed, and then dispersion A is added dropwise while stirring at a speed of 50-1000 rpm to form a first mixed reaction system, and a 6M acetic acid aqueous solution is added to carry out a condensation reaction.

[0073] Step 3: The mixed reaction system was rapidly and vigorously stirred, and the mixed solution was quickly frozen at 77.3K (liquid nitrogen bath) before heating, and degassed through three freeze-pump-thaw cycles.

[0074] Step 4: After degassing, the reaction system is reacted at 100° C. for 72 h under vacuum or inert gas atmosphere.

[0075] Step 5: After filtering the solid after the reaction is completed, the COFs tube is purified by solvent exchange with acetone, methanol and DMF. Finally, the purified sample is filtered and vacuum dried at 90°C to obtain a covalent organic framework nanotube / tungsten selenide nanosheet composite heterojunction photocatalyst.

[0076] In this way, a covalent organic framework nanotube / tungsten selenide nanosheet composite heterojunction photocatalyst was obtained; the lateral size of the tungsten selenide nanosheet is 200-400 nanometers, the diameter of the covalent organic framework nanotube is about 50 nanometers, and the length is about 7 micrometers. Figure 6 As shown; a heterojunction is formed between the covalent organic framework nanotube and the tungsten selenide nanosheet, and the bonding method between them is that the tungsten selenide nanosheet is coated / embedded / adsorbed on the surface of the covalent organic framework nanotube; the obtained covalent organic framework nanotube / tungsten selenide nanosheet composite heterojunction photocatalyst has the strongest reduction performance and enhanced light absorption performance compared with the band structure corresponding to the single-component traditional COFs; the anti-bacterial fouling test shows that compared with the blank control group, the single-component traditional COFs, the single-component tungsten selenide nanosheet and the covalent organic framework nanotube / tungsten selenide nanosheet composite heterojunction photocatalyst, under light, the inhibition rates of the three on bacterial growth are approximately 67%, 41% and 99.6%, respectively.

[0077] Technical description of this embodiment: By changing the type and size of the two-dimensional sheet material, not only can binary composite heterojunction photocatalysts with different heterostructures be obtained, but also the bonding mode between the covalent organic framework nanotube and the two-dimensional sheet material can be changed; the prepared covalent organic framework nanotube / tungsten selenide nanosheet composite heterojunction photocatalyst has enhanced antibacterial and antifouling properties compared to traditional COFs with a single component.

[0078] Example 5 This embodiment is basically the same as embodiments 2, 3, and 4, except that: the added two-dimensional sheet material (Ti3C2T x , graphite phase carbon nitride, tungsten selenide) is doubled, and 100 mg Ti3C2T x , graphite carbon nitride, and tungsten selenide nanosheets were dispersed in 3 mL of a mixed solvent of mesitylene and 1,4-dioxane to form dispersions C1, C2, and C3, respectively, and other conditions remained the same.

[0079] This method was used to obtain covalent organic framework nanotubes / Ti3C2T xNanosheet-2 composite heterojunction photocatalyst, covalent organic framework nanotube / graphite phase carbon nitride nanosheet-2 composite heterojunction photocatalyst, covalent organic framework nanotube / tungsten selenide nanosheet-2 composite heterojunction photocatalyst; the newly prepared binary composite heterojunction photocatalyst has the difference from the binary composite heterojunction photocatalyst prepared in Examples 2, 3, and 4 in that: in Ti3C2T x , the number of covalent organic framework nanotubes coated / embedded / adsorbed on the surface of graphene-phase carbon nitride nanosheets decreased; the number of tungsten selenide nanosheets coated / embedded / adsorbed on the surface of covalent organic framework nanotubes increased; the band structure of the newly prepared binary composite heterojunction photocatalyst changed; the anti-bacterial fouling test showed that compared with the blank control group, the single-component traditional COFs, covalent organic framework nanotubes / Ti3C2T x Nanosheet-2 composite heterojunction photocatalyst, covalent organic framework nanotube / graphite phase carbon nitride nanosheet-2 composite heterojunction photocatalyst, and covalent organic framework nanotube / tungsten selenide nanosheet-2 composite heterojunction photocatalyst, under light conditions, the four have inhibition rates on bacterial growth of approximately 67%, 99.8%, 99.9%, and 99.9%, respectively.

[0080] Technical description of this embodiment: By changing the ratio of two-dimensional sheet materials and covalent organic framework nanotubes, binary composite heterojunction photocatalysts with different photocatalytic properties can be obtained; the newly prepared binary composite heterojunction photocatalysts have enhanced antibacterial and antifouling properties compared with traditional COFs with a single component.

[0081] Comparative Example 1 This embodiment is basically the same as embodiment 1, except that in step 1, the dispersion B is added dropwise to the dispersion A, and other conditions remain the same. The covalent organic framework nanofibers obtained by this method have a diameter of about 50 nanometers and a length of about 15 micrometers.

[0082] Technical description of this embodiment: By comparing the order of dropping the precursor dispersion in Example 1, covalent organic framework nanofibers with different morphologies can be prepared.

[0083] Comparative Example 2 Step 1: Add 160 mg of 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde and 120 mg of p-phenylenediamine to 12 mL of a mixed solvent of mesitylene and 1,4-dioxane (volume ratio of 1:1), and add 6 M acetic acid aqueous solution to carry out condensation reaction.

[0084] Step 2: The first mixed reaction system was subjected to ultrasonic treatment, and the mixed solution was quickly frozen at 77.3 K (liquid nitrogen bath) and degassed through three freeze-pump-thaw cycles.

[0085] Step 3: After degassing, the reaction system is reacted at 100° C. for 72 h under vacuum or inert gas atmosphere.

[0086] Step 4: After filtering the solid after the reaction, the COFs tube is purified by solvent exchange with acetone, methanol and DMF. Finally, the purified sample is filtered and vacuum dried at 90°C to obtain a covalent organic framework nanosheet; Technical description of this embodiment: Compared with the preparation method in Example 1, a covalent organic framework nanosheet can be obtained.

[0087] SEM and TEM analysis The covalent organic framework nanotubes, Ti3C2T prepared in Examples 1, 2, 3, and 4 of the present invention x , graphite carbon nitride, covalent organic framework nanotubes / two-dimensional nanosheets (Ti3C2T x , graphite phase carbon nitride, tungsten selenide nanosheets) composite heterojunction photocatalyst, and were analyzed by scanning electron microscope respectively; and the covalent organic framework nanotube photocatalyst and tungsten selenide nanosheets prepared in Examples 1 and 4 were analyzed by transmission electron microscope.

[0088] The results are as follows Figure 2A-2E , Figure 4A-4B , Figure 5A-Figure 5B , Figure 6 As shown in the figure, it can be seen that the directly generated covalent organic framework nanotube photocatalyst is similar to the covalent organic framework nanotube / two-dimensional nanosheet (Ti3C2T x , Graphite Carbon Nitride x The morphological characteristics of the composite heterojunction photocatalyst (Ti3C2T) and tungsten selenide nanosheets) are shown in Figure 2, which proves the universality of the preparation method of binary heterojunction photocatalysts in this experiment. x , graphite phase carbon nitride surface coating / inlay / adsorption; tungsten selenide is coated / inlay / adsorbed on the surface of covalent organic framework nanotubes.

[0089] X-ray powder diffraction analysis The covalent organic framework nanotubes prepared in Example 1 of the present invention were subjected to X-ray powder diffraction analysis, and the results were as follows: Figure 3 As shown. It can be seen that the obtained sample presents typical COFs diffraction peaks at 4.5°, 7.9°, and 26.9°, corresponding to 100, 110, and 001 crystal plane reflections, respectively. This indicates that the covalent organic framework nanotubes prepared by the present invention have a crystal structure and crystallinity similar to those of traditional COFs.

[0090] Example 6 Step 1: providing graphene nanosheets; Step 2: 100 mg of 2-hydroxy-1,3,5-benzenetricarboxaldehyde, 150 mg of (2,4,6-trimethylbenzene-1,3,5-triyl)trimethylamine, and 50 mg of graphene nanosheets were dispersed in 3 mL of a mixed solvent of dichloromethane and tetrahydrofuran (volume ratio of 1:1) to form uniform dispersions A, B, and C; At -10-35°C, the dispersion B and the dispersion C are uniformly mixed, and then the dispersion A is added dropwise while stirring at a speed of 50-1000 rpm to form a first mixed reaction system, and a 15M hydrochloric acid aqueous solution is added to carry out a condensation reaction.

[0091] Step 3: The mixed reaction system was rapidly and vigorously stirred, and the mixed solution was quickly frozen at 77.3 K (liquid nitrogen bath) before heating and degassed through three freeze-pump-thaw cycles.

[0092] Step 4: After degassing, the reaction system is reacted at 60° C. for 120 h under vacuum or inert gas atmosphere.

[0093] Step 5: After filtering the solid after the reaction is completed, the COFs tube is purified by solvent exchange with acetone, methanol and DMF. Finally, the purified sample is filtered and vacuum dried at 90°C to obtain a covalent organic framework nanotube / graphene nanosheet composite heterojunction photocatalyst.

[0094] Example 7 Step 1: providing a boron nitride nanosheet; Step 2: 100 mg of 2,4-dihydroxy-1,3,5-benzene trimesaldehyde, 80 mg of tris(4-aminophenyl)amine, and 50 mg of boron nitride nanosheets were dispersed in 3 mL of a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide (volume ratio of 1:1) to form uniform dispersions A, B, and C; At -10-35°C, the dispersion B and the dispersion C are uniformly mixed, and then the dispersion A is added dropwise while stirring at a speed of 50-1000 rpm to form a first mixed reaction system, and a 0.1 M benzenesulfonic acid aqueous solution is added to carry out a condensation reaction.

[0095] Step 3: The mixed reaction system was rapidly and vigorously stirred, and the mixed solution was quickly frozen at 77.3K (liquid nitrogen bath) before heating, and degassed through three freeze-pump-thaw cycles.

[0096] Step 4: After degassing, the reaction system is reacted at 160° C. for 1 h under vacuum or inert gas atmosphere.

[0097] Step 5: After filtering the solid after the reaction is completed, the COFs tube is purified by solvent exchange with acetone, methanol and DMF. Finally, the purified sample is filtered and vacuum dried at 90°C to obtain a covalent organic framework nanotube / boron nitride nanosheet composite heterojunction photocatalyst.

[0098] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments with other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0099] It should be understood that the technical solution of the present invention is not limited to the above-mentioned specific implementation cases. Any technical deformation made according to the technical solution of the present invention without departing from the scope of protection of the purpose of the present invention and the claims shall fall within the protection scope of the present invention.

Claims

1. A method for preparing a composite heterojunction photocatalyst, characterized in that: include: A first mixed system containing at least aldehyde substances, amine substances, two-dimensional nanosheets and catalysts is pre-reacted, and then the temperature is raised in a vacuum or inert atmosphere to continue the reaction to obtain a covalent organic framework nanotube / two-dimensional nanosheet composite heterojunction photocatalyst.

2. The preparation method according to claim 1, characterized in that: Specifically include: Under the condition of -10~35℃, the aldehyde substance, the two-dimensional nanosheets and the first solvent are mixed to form a first dispersion, the amine substance and the first solvent are mixed to form a second dispersion, and then the second dispersion is mixed with the first dispersion under stirring conditions and a catalyst is added to form a first mixed system for pre-reaction for 2~60 min.

3. The preparation method according to claim 1, characterized in that: Specifically include: Under the condition of -10~35℃, the amine substance, the two-dimensional nanosheets and the first solvent are mixed to form a third dispersion; the aldehyde substance is mixed with the first solvent to form a fourth dispersion, and then the fourth dispersion is mixed with the third dispersion under stirring and a catalyst is added to form a first mixed system for pre-reaction for 2~60 minutes.

4. The preparation method according to claim 2 or 3, characterized in that: The aldehyde substance includes a dialdehyde or polyaldehyde containing an aromatic ring structure, and the dialdehyde or polyaldehyde containing an aromatic ring structure includes any one or more combinations of terephthalaldehyde, o-phthalaldehyde, isophthalaldehyde, trimesic acid, 1,3,5-triazine-2,4,6-tricarbaldehyde, 2-hydroxy-1,3,5-benzenetricarbaldehyde, 2,4-dihydroxy-1,3,5-benzenetricarbaldehyde, and 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde; And / or, the amine substance includes a diamine or polyamine containing an aromatic ring structure, and the diamine or polyamine containing an aromatic ring structure includes any one or more combinations of p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, benzidine, tris(4-aminophenyl)amine, and (2,4,6-trimethylbenzene-1,3,5-triyl)trimethylamine; And / or, the two-dimensional nanosheets include any one or more combinations of graphite-phase carbon nitride, MXene, WSe2, graphene, boron nitride, transition metal sulfide, black scale, phosphorene, wherein the MXene includes any one or more combinations of transition metal carbides, nitrides, and carbonitrides; And / or, the catalyst includes any one or more combinations of hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, formic acid, and benzenesulfonic acid; And / or, the first solvent includes any one or more combinations of N,N-dimethylformamide, dimethyl sulfoxide, dichloromethane, mesitylene, 1,4-dioxane, tetrahydrofuran, chloroform, chloroform, and toluene; And / or, the concentration of the catalyst is 0.1-15 mol / L; And / or, the molar ratio of amine functional groups to aldehyde functional groups in the first mixed reaction system is 1:0.5-1.5; And / or, the mass ratio of the sum of the aldehyde substance and the amine substance in the first mixed reaction system to the two-dimensional nanosheet is 1:0.1-10; and / or, the mass ratio of the two-dimensional nanosheets to the first solvent in the first dispersion is 1:5-100; And / or, the mass ratio of the two-dimensional nanosheets to the first solvent in the third dispersion is 1:5-100; And / or, the volume ratio of the catalyst to the sum of the first dispersion and the second dispersion is 1-3:3-10; And / or, the volume ratio of the catalyst to the sum of the third dispersion and the fourth dispersion is 1-3:3-10; And / or, the stirring speed adopted in the stirring is 50-1000 rpm.

5. The preparation method according to claim 4, characterized in that: The dialdehyde or polyaldehyde containing an aromatic ring structure includes any one or more combinations of 2-hydroxy-1,3,5-benzene trimaldehyde, 2,4-dihydroxy-1,3,5-pyromellitic trimaldehyde, and 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde; And / or, the diamine or polyamine containing an aromatic ring structure includes any one or more combinations of p-phenylenediamine, o-phenylenediamine, and m-phenylenediamine; And / or, the two-dimensional nanosheets include graphite phase carbon nitride, Ti3C2T x , any one or more combinations of WSe2; And / or, the catalyst comprises any one or more combinations of acetic acid, formic acid, and hydrochloric acid; And / or, the first solvent includes any one or more combinations of dichloromethane, mesitylene, and 1,4-dioxane.

6. The preparation method according to claim 1, characterized in that: Specifically include: After the pre-reaction is completed, the temperature is raised to 60-160° C. in a vacuum or inert atmosphere to continue the reaction for 1-120 hours, and then separated, purified and dried to obtain a composite heterojunction photocatalyst of covalent organic framework nanotubes / two-dimensional nanosheets; The purification treatment includes any one or more combinations of solution washing, solvent exchange, vacuum drying, and air drying; the reagents used in the purification treatment include any one or more combinations of acetone, methanol, ethanol, isopropanol, tetrahydrofuran, N,N-dimethylformamide, and N,N-dimethylacetamide.

7. The composite heterojunction photocatalyst prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The composite heterojunction photocatalyst includes covalent organic framework nanotubes and two-dimensional nanosheets, and a heterojunction is formed between the covalent organic framework nanotubes and the two-dimensional nanosheets; the covalent organic framework nanotubes are dispersed on the surface of the two-dimensional nanosheets in at least one of a coating, an inlay, and an adsorption manner, or the two-dimensional nanosheets are dispersed on the surface of the covalent organic framework nanotubes in at least one of a coating, an inlay, and an adsorption manner.

8. The composite heterojunction photocatalyst according to claim 7, characterized in that: The covalent organic framework nanotube has a hollow channel with a diameter of 10 to 1000 nm, and the length of the covalent organic framework nanotube is 0.5 to 30 μm; And / or, the two-dimensional nanosheet has a thickness of 0.1-100 nm and a sheet diameter of 0.01-50 μm.

9. Use of the composite heterojunction photocatalyst according to claim 7 or 8 in the field of adsorption, separation or photocatalytic antibacterial.

10. An antibacterial antifouling agent, characterized in that: At least includes the composite heterojunction photocatalyst described in claim 7 or 8.

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