Multifunctional layered composite film of MXene@h-bn and preparation method and application thereof

Abstract

The application discloses a multifunctional layered composite film of MXene@h-BN and a preparation method and application thereof, and relates to the field of water treatment. The multifunctional layered composite film of MXene@h-BN is a layered composite film formed by assembling MXene@h-BN composite multifunctional material obtained by mixing MXene and h-BN through ball milling as a top layer on a base film. The MXene@h-BN obtained by mixing MXene and h-BN through ball milling is used as the top layer, a polysulfone film (PS) is used as the base, and the above two materials are coupled by using an interfacial cross-linking polymerization method, so that the multifunctional layered composite film of MXene@h-BN is prepared. After the multifunctional layered composite film of MXene@h-BN is coupled with a sunlight introduction device, the multifunctional layered composite film of MXene@h-BN is applied to the field of water treatment and has the following advantages: 1. the base PS film is assembled with the MXene@h-BN composite material, so that the membrane pore size is reduced, and the physical interception effect on pollutants is enhanced; 2. h-BN and MXene are excellent adsorption materials, and the adsorption and enrichment performance on micro-pollutants is enhanced; and 3. a heterojunction is formed between h-BN and MXene, the response to sunlight and the utilization efficiency are improved, so that the photocatalytic degradation of water micro-pollutants and membrane pollutants is realized, and the membrane self-cleaning function is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to a multifunctional layered composite film of MXene@h-BN and a preparation method and application thereof. BACKGROUND

[0002] In recent years, the production and use of various drugs have shown an upward trend, but most of the drugs cannot be completely absorbed by organisms, but are excreted out of the body with metabolism and then enter natural water bodies. Some drugs have strong durability and biological accumulation, making it difficult for conventional water treatment processes to remove them, becoming one of the persistent micro-pollutants in surface water, thereby destroying the water ecosystem, making pathogenic microorganisms resistant, and even accumulating through the food chain to harm human health. Therefore, it is urgent to develop new efficient, low-cost and sustainable water drug removal technologies.

[0003] Photocatalytic oxidation is a clean and low-energy wastewater treatment method, but most photocatalytic materials are powder particles, which are easily affected by environmental factors, leading to a decline in catalytic performance and difficulty in recovery, making it difficult to be applied in practice.

[0004] Among the many emerging materials, hexagonal boron nitride (h-BN) has a similar layered structure to graphene, so it has a large specific surface area, thus having the potential to be an excellent adsorbent. In addition, its nitrogen-boron bond has polarity, which can prevent mineral scale deposition to some extent. However, its wide band gap (4.5eV-5.2eV) makes it difficult to be excited by visible light or sunlight, so it is difficult to achieve photocatalytic oxidation. Therefore, it is necessary to couple with corresponding materials to form a heterojunction to improve the solar response and thus enhance the photocatalytic performance.

[0005] MXene, also an emerging two-dimensional material, has high carrier migration efficiency and exhibits conductor properties, thus having the potential to form a heterojunction with h-BN, thereby enhancing its photocatalytic oxidation performance; in addition, the high specific surface area of MXene and the surface end groups (such as hydroxyl groups) can also enhance the chemical adsorption performance of h-BN.

[0006] Therefore, the present application plans to couple h-BN with MXene to form a MXene@h-BN composite material, and assemble the material with a polysulfone (PS) base film, so that the modified film has both adsorption and photocatalytic self-cleaning functions; at the same time, its pollutant interception performance is also enhanced. The application field of the present application is the control of new pollutants in water bodies, and can be applied to water purification pretreatment and wastewater advanced treatment.

[0007] Chinese patent CN 114456443A proposes a flexible cellulose / boron nitride / MXene "sandwich" structure composite film preparation method, which assembles the structure of the composite film by alternating vacuum suction filtration. But it is mainly applied in the fields of heat dissipation and electromagnetic shielding, and MXene and h-BN belong to different layers of "sandwich" structure, without forming a corresponding heterojunction structure, and cannot be applied to the field of photocatalysis, which is significantly different from the present invention.

[0008] Chinese patent CN 112552681A proposes a boron nitride nanosheet / MXene / polybenzimidazole (PBI) high-thermal-conductivity composite film preparation method, which uses polymer formation as a skeleton to solve the problem of material easy to fall off. But it is mainly applied in the field of heat dissipation, and the network formed by the bridging of MXene and boron nitride is to reduce the agglomeration of h-BN as a heat dissipation material, without forming a corresponding heterojunction structure, and cannot be applied to the field of photocatalysis, which is significantly different from the present invention. In the present invention, we choose the more hydrophilic and anti-fouling polydopamine (PDA) to replace PBI as an adhesive between the composite material and the substrate film. SUMMARY

[0009] In view of the above technical problems existing in the prior art, the purpose of the present application is to provide a multifunctional layered composite film of MXene@h-BN and its preparation method and application. The present invention proposes a preparation method of MXene@h-BN composite material and an assembly method with PS substrate film to realize efficient and low-carbon removal of new pollutants in water body and at the same time play the role of alleviating membrane fouling. The present invention has the advantages of low energy consumption in preparation process, no toxic and harmful by-products, simple preparation process, etc. In addition, the modified membrane prepared by the present invention has the functions of strengthening adsorption, interception and photocatalytic degradation, etc., and solves the problem of secondary pollution caused by the difficulty of recycling water treatment reagents, realizes low-carbon, harmless and sustainability in the water treatment process.

[0010] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0011] This invention uses an MXene@h-BN composite multifunctional material obtained by ball milling a mixture of MXene and h-BN as raw materials as the top layer, and a polysulfone membrane (PS) as the substrate. The two materials are coupled using an interfacial crosslinking polymerization method. The resulting MXene@h-BN multifunctional layered composite membrane, after being coupled with a sunlight-guiding device, is applied to water treatment and has the following three functions: 1. The assembly of the MXene@h-BN composite material at the PS membrane interface leads to a reduction in membrane pore size, enhancing the retention of pollutants; 2. Both h-BN and MXene are excellent adsorbent materials, strengthening the adsorption and enrichment performance of micro-pollutants; 3. The formation of a heterojunction between h-BN and MXene improves the response to and utilization efficiency of sunlight, thereby achieving photocatalytic degradation of micro-pollutants and membrane contaminants in water, and ultimately realizing the membrane's self-cleaning function.

[0012] A multifunctional layered composite membrane of MXene@h-BN is formed by using MXene@h-BN composite multifunctional material obtained by ball milling MXene and h-BN as the top layer and then bonding it to a supporting substrate.

[0013] Furthermore, the raw materials required for preparing h-BN include urea and boric acid, with the mass ratio of urea to boric acid being 5:1 to 24:1, preferably 6 to 8:1; and the mass ratio of h-BN to MXene being 5:1 to 40:1, preferably 10 to 12:1.

[0014] Furthermore, the preparation method of the h-BN includes the following steps:

[0015] 1) Dissolve boric acid and urea in deionized water, heat in a water bath at 60-85°C until dry, to obtain a homogeneous mixture of boric acid and urea;

[0016] 2) Add the mixture from step 1) to a tube furnace and calcine at 800-950℃ for 2-6 hours under a nitrogen atmosphere. Wash the crude material obtained by washing it several times with water and methanol alternately, and then dry it to obtain h-BN.

[0017] Furthermore, h-BN and MXene are mixed in a certain proportion and ball-milled at a speed of 400-700 r / min for 1-4 h. The resulting powder is the MXene@h-BN composite multifunctional material.

[0018] Furthermore, the method for preparing the MXene includes the following steps:

[0019] S1: Add lithium fluoride to concentrated hydrochloric acid, then quickly add titanium aluminum carbide, and stir at 30-40℃ for 20-30 hours;

[0020] S2: After the reaction is complete, wash and centrifuge several times until the pH of the supernatant is neutral; disperse the precipitate ultrasonically in an ice-water bath for 10-40 minutes to obtain a mixed solution, centrifuge, and freeze-dry to obtain crude MXene;

[0021] S3: Crude MXene is ultrasonically dispersed in anhydrous methanol for 10-40 minutes, centrifuged, the supernatant is discarded, washed with water, and the resulting precipitate is freeze-dried to obtain layered MXene.

[0022] Further, in step S1, the concentration of concentrated hydrochloric acid is 8-12 mol / L, the solid-liquid feeding ratio of lithium fluoride to concentrated hydrochloric acid is 1 g: 5-30 mL, and the mass ratio of titanium aluminum carbide to lithium fluoride is 0.5-3:1, preferably 1-1.2:1.

[0023] Furthermore, the supporting substrate is a polysulfone membrane (PS). First, dopamine (DA) is polymerized on the surface of the PS membrane to generate polydopamine (PDA). The polymerized PS membrane is then filtered with a dispersion of MXene@h-BN material to obtain the multifunctional layered composite membrane of MXene@h-BN.

[0024] The method for preparing the multifunctional layered composite membrane of MXene@h-BN includes the following steps:

[0025] (1) A dopamine solution with pH 8-9 was subjected to a polymerization reaction on the surface of a PS filter membrane for 0.5-3 hours to obtain a polymerized PS membrane;

[0026] (2) The MXene@h-BN composite multifunctional material was ultrasonically dispersed in an ethanol aqueous solution to obtain an MXene@h-BN material dispersion;

[0027] (3) The dispersion of the MXene@h-BN material is filtered through a polymerized PS membrane, vacuum dried, and then immersed in deionized water for at least 10 minutes. The resulting modified membrane is the multifunctional layered composite membrane of the MXene@h-BN.

[0028] The concentration of the dopamine solution mentioned in step (1) is 1-3 g / L. The dopamine solution is prepared by adding dopamine to Tris-HCl buffer solution (DA polymerization needs to be carried out in a weakly alkaline environment). The amount of dopamine used per unit area of ​​PS filter membrane is 10-15 g / m². 2 In step (2), the mass concentration of the ethanol aqueous solution is 20-40%, and the mass ratio of MXene@h-BN composite multifunctional material to dopamine is in the range of 1.6:1-3.4:1.

[0029] Furthermore, in step (1), the PS filter membrane needs to be soaked in deionized water for at least 12 hours before use.

[0030] This invention also provides the application of the aforementioned MXene@h-BN multifunctional layered composite membrane in the catalytic degradation of organic pollutants in water under sunlight irradiation. Under sunlight irradiation, the modified membrane of this invention exhibits enhanced separation of photogenerated carriers in the MXene@h-BN composite multifunctional material, resulting in the generation of a large number of active species. This degrades the pollutants adsorbed on the membrane surface, greatly mitigating membrane fouling, releasing adsorption sites, and extending the membrane's service life.

[0031] The beneficial effects achieved by this invention are:

[0032] a) The purpose of adding urea as a nitrogen source in the preparation method of the present invention is that urea is a substance that decomposes into ammonia and carbon dioxide when heated at low temperature. The generation of a large amount of gas helps to expand the structure of h-BN and increase the specific surface area of ​​the material.

[0033] b) Ball milling is a simple and easy-to-operate method for preparing MXene@h-BN composite multifunctional materials.

[0034] c)h-BN and MXene are both materials with large specific surface areas and have extremely strong adsorption properties.

[0035] d) Doping h-BN with MXene forms a heterojunction structure, which narrows the band gap of h-BN and reduces the excitation energy required for photocatalysis, thus achieving energy saving. At the same time, it promotes carrier separation, improves electron-hole migration efficiency, and improves the poor photocatalytic performance of h-BN.

[0036] e) The photocatalytic oxidation of MXene@h-BN materials degrades a large number of pollutants adsorbed on the membrane surface, which slows down membrane fouling and releases adsorption sites, thus extending the membrane's service life.

[0037] f) Photocatalytic materials are attached to the membrane, which solves the problem of the difficulty in recycling the powder particles of the catalytic materials.

[0038] g) Polydopamine not only acts as an adhesive on the membrane, enabling the composite material to be firmly cross-linked on the base membrane, but also enhances hydrophilicity and has a certain antifouling effect, thereby improving hydrophilicity and membrane flux.

[0039] h) The material of this invention has the characteristics of efficient removal of pollutants, low cost, sustainability and simple production in the field of environmental water treatment, and therefore has important practical application value. Attached Figure Description

[0040] Figure 1 Scanning electron microscope (SEM) image and EDS energy dispersive spectroscopy (EDS) image of the MXene@h-BN composite multifunctional material.

[0041] Figure 2 The valence band X-ray photoelectron spectra of 1:10MXene@h-BN and h-BN are shown.

[0042] Figure 3 To detect the signal spectrum of active species with redox properties generated by MXene@h-BN composite multifunctional materials during water treatment using electron paramagnetic (spin) resonance spectroscopy.

[0043] Figure 4 This diagram illustrates the specific structure and mechanism of action of the MXene@h-BN composite multifunctional material.

[0044] Figure 5 This is a comparison chart of the removal rates of TMP and CLQ by the MXene@h-BN layered composite membrane in Application Example 1.

[0045] Figure 6 Comparison of TMP removal rates between MXene@h-BN layered composite membrane and ball-milled h-BN layered composite membrane under light irradiation.

[0046] Figure 7 Comparison of TMP removal rates under light irradiation between MXene@h-BN layered composite membrane and (MXene+h-BN) modified membrane without ductile iron.

[0047] Figure 8 (Figure ac) shows the changes in membrane flux of the MXene@h-BN layered composite membrane at different time points under different pollutant (bovine serum albumin, humic acid, sodium alginate) environments in Application Example 2. Detailed Implementation

[0048] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0049] Example 1:

[0050] The preparation method of MXene@h-BN composite multifunctional material includes the following steps:

[0051] 1) Based on the required mass of h-BN, boric acid and urea are dissolved in deionized water at a mass ratio of 1:6, and heated in a water bath at 80°C until dry to obtain a homogeneous mixture of boric acid and urea.

[0052] 2) A mixture of boric acid and urea was added to a tube furnace and calcined at 900°C under a nitrogen atmosphere for 5 hours. The crude material obtained was washed several times with water and methanol alternately and dried to obtain h-BN.

[0053] 3) Add 1g of lithium fluoride solution to 20mL of 9M concentrated hydrochloric acid, then quickly add 1g of titanium aluminum carbide within 1 minute, and stir at 35℃ for 24h.

[0054] 4) After the reaction is complete, wash and centrifuge several times until the pH of the supernatant is neutral. Disperse and wash the precipitate in ice water using ultrasound for 20 min, then centrifuge the resulting mixed solution at 4000 rpm for 15 min.

[0055] 5) The centrifuged sediment was freeze-dried for 24 hours to obtain crude MXene;

[0056] 6) Crude MXene was ultrasonically dispersed in anhydrous methanol for 20 min, the dispersion was centrifuged at 4000 rpm for 15 min, the supernatant was discarded, and the mixture was washed with water. The resulting precipitate was freeze-dried for 24 h to obtain layered MXene.

[0057] 7) Mix 0.3g MXene with 3g h-BN and ball mill at a speed of 600r / min for 2h. The resulting powder is a 1:10 MXene@h-BN composite multifunctional material.

[0058] The properties of the prepared MXene@h-BN composite multifunctional material are as follows:

[0059] Scanning electron microscope (SEM) images and EDS spectra of the MXene@h-BN composite multifunctional material are shown below. Figure 1 , Figure 1 In (a), a smooth sheet is inserted into the rough sheet plane, indicating that MXene is partially embedded in the h-BN surface. Figure 1 (b) The uniform distribution of each element in the EDS spectrum indicates that MXene@h-BN is uniformly assembled on the basement membrane.

[0060] The valence band X-ray photoelectron spectra of the 1:10MXene@h-BN composite multifunctional material and h-BN are shown in [reference needed]. Figure 2 Compared to h-BN, the distribution of Ti and C elements is relatively uneven. Figure 2 This study verified the structure of Mxene (Ti3C2X) embedded in h-BN.

[0061] Electron paramagnetic (spin resonance) spectroscopy was used to detect redox-active species generated by the MXene@h-BN composite multifunctional material during water treatment. ● OH and 1 Typical signal of O2 ( Figure 3 This indicates that the main active species of the modified membrane after excitation by sunlight are... ● OH and 1O2. When the n-type semiconductor h-BN comes into contact with MXene, the difference in the Fermi level causes electrons to flow from h-BN to MXene until an equilibrium state is reached, forming an internal electric field and creating an ohmic contact heterojunction between the interface of h-BN and MXene. Figure 4 This greatly shortens the band gap, thereby forming an internal electric field, which causes the energy band to bend, thus improving the photoresponse and photocatalytic performance.

[0062] Application Example 1.

[0063] Using the 1:10 MXene@h-BN composite multifunctional material prepared in Example 1, an MXene@h-BN layered composite film was further prepared. The specific steps are as follows:

[0064] 1) Before using the PS filter membrane, soak it in deionized water for 12 hours.

[0065] 2) Prepare a dopamine solution by adding 0.06 g of dopamine to 30 mL of Tris-HCl buffer solution (pH 8.5, 0.05 mol / L Tris, 0.0147 mol / L HCl). Polymerize the dopamine solution on the surface of an 8 cm diameter PS filter membrane for 1 hour, then rinse thoroughly with deionized water. The concentration of the dopamine solution is approximately 2 g / L. The amount of dopamine solution used depends on the area of ​​the PS membrane; approximately 6 L / m² is used per unit area of ​​the PS filter membrane. 2 .

[0066] 3) Add 0.1g of MXene@h-BN composite multifunctional material to 30mL of 30% ethanol solution, ultrasonically disperse for 15min, and then filter the dispersion using the filter membrane from step 2) after polymerization is complete.

[0067] 4) After vacuum drying the filter membrane at 60°C for 20 min, immerse it in deionized water for 30 min to obtain MXene@h-BN layered composite membrane.

[0068] The MXene@h-BN layered composite membrane is placed in a cross-flow module. The membrane testing device consists of a solar tubular lighting system, a high-pressure diaphragm pump, inlet and outlet water pipes, a feed chamber with an illumination channel, and a permeation chamber. The feed chamber and the permeation chamber are separated by the MXene@h-BN layered composite membrane. Feed liquid is introduced into the feed chamber, and the outlet water pipe of the feed chamber is connected to the inlet water pipe of the feed chamber through the high-pressure diaphragm pump, realizing the circulation of the feed liquid between the feed chamber and the high-pressure diaphragm pump. The solar tubular lighting system is used to provide illumination to the feed chamber.

[0069] After the feed liquid is retained by the MXene@h-BN layered composite membrane, it enters the permeate chamber above the module. The pure water flux of the permeate from the composite membrane is measured to be approximately 15.5 L / (m²).2 *h), the feed solution contained 17.0 μM of newly emerging contaminants (TMP or CLQ). The pH was maintained at 7.0 by adjusting the ratio of borax and boric acid solution, while supplementing with 42 mW / cm 2 Irradiation was applied. Before sample collection, the modified membrane was pre-compacted with pure water cross-flow at 4 bar for 20 minutes. Then, the removal of organic pollutants was tested at a membrane pressure of 4 bar for 180 minutes. Figure 5 This is a comparison chart of the removal rates of TMP and CLQ by the MXene@h-BN layered composite membrane. In the 160-minute retention and removal experiment of organic pollutants, the MXene@h-BN layered composite membrane achieved removal rates of over 90% for both trimethoprim (TMP) and chloroquine (CLQ) in the water, essentially achieving complete removal of drug pollution from the water.

[0070] Comparative Example 1.

[0071] Repeat the steps 1) of Example 1 for synthesizing MXene@h-BN composite multifunctional material, except that "0.3g MXene and 3g h-BN are replaced with 3.3g h-BN", and the other operating conditions remain unchanged, to obtain ball-milled h-BN.

[0072] The assembly steps of the layered composite membrane in Example 1 were repeated using ball-milled h-BN instead of MXene@h-BN composite multifunctional material. The modified membrane assembled with the above composite material was placed in a membrane testing device and passed through a pH=7 boric acid-borax buffer solution containing 0.017 mmol / L TMP, supplemented with 42 mW / cm 2 The membrane was irradiated with light for 180 min. Before sample collection, the modified membrane was pre-compacted with pure water cross-flow at 4 bar for 20 min. Then, the removal of organic pollutants was tested at a membrane pressure of 4 bar for 180 min.

[0073] Figure 6 This is a comparison of the TMP removal rates of the MXene@h-BN layered composite membrane in Example 1 and the ball-milled h-BN layered composite membrane in Comparative Example 1 under light irradiation. Within 160 minutes of the organic pollutant removal experiment, the ball-milled h-BN modified membrane (… Figure 6 The removal rate of TMP (30%) of the control group under light irradiation was much lower than that of the MXene@h-BN layered composite membrane, indicating that the MXene-doped h-BN modified membrane in the examples has excellent photocatalytic performance.

[0074] Comparative Example 2.

[0075] Repeat the steps 1) of Example 1 for synthesizing the MXene@h-BN composite multifunctional material, except that the step of mixing and ball milling 0.3g MXene and 3g h-BN in "step 7)" is replaced by directly grinding 0.3g MXene and 3g h-BN into powder (without ball milling). The other operating conditions remain unchanged, and the resulting catalyst is labeled as MXene+h-BN.

[0076] The catalyst MXene+h-BN, prepared by directly grinding MXene and h-BN into powder (without ball milling), was used to replace the assembly steps of the layered composite membrane in Example 1 for the repeated application of the MXene@h-BN composite multifunctional material. The modified membrane assembled with the above composite material was placed in a membrane testing device and passed through a pH=7 boric acid-borax buffer solution containing 0.017 mmol / L TMP, supplemented with 42 mW / cm². 2 The membrane was irradiated with light for 180 min. Before sample collection, the modified membrane was pre-compacted with pure water cross-flow at 4 bar for 20 min. Then, the removal of organic pollutants was tested at a membrane pressure of 4 bar for 180 min.

[0077] Figure 7 This image shows a comparison of the TMP removal rates of the MXene@h-BN layered composite membrane in Example 1 and the un-spheroidized (MXene+h-BN) modified membrane in Comparative Example 2 under illumination. During the 160-minute retention and removal experiment of organic pollutants, the TMP removal rate of the un-spheroidized (MXene+h-BN) modified membrane under illumination was significantly lower than that of the MXene@h-BN layered composite membrane. This indicates that the spheroidization process forms a new chemical structure between MXene and h-BN, greatly improving the photocatalytic effect of the material.

[0078] Application Example 2.

[0079] The modified membrane from Application Example 1 was placed in a membrane testing device. The feed solution contained 200 mg / L of simulated pollutants (bovine serum albumin BSA / humic acid HA / sodium alginate SA). The pH was maintained at 7.0 by adjusting the ratio of borax and boric acid solution. The experimental conditions for photocatalytic degradation are the same as in Application Example 1. Figure 8 (Figure ac) shows the changes in membrane flux of the MXene@h-BN layered composite membrane at different time points under the influence of different membrane contaminants. The initial pure water flux of the MXene@h-BN layered composite membrane is approximately 15.5 L / (m²). 2*h), the modified membrane was pre-compacted under 4 bar pressure with pure water cross-flow for 30 min, and then subjected to an experiment to remove organic pollutants under a 4 bar permeability. After 90 min of simulated pollutant fouling, the membrane flux decreased significantly and could not be fully recovered after 30 min of water flushing. After repeating the 90 min of membrane fouling and 30 min of water flushing, followed by 30 min of visible light irradiation, the flux decrease caused by BSA and SA fouling recovered rapidly. The rate of flux recovery under light irradiation was significantly higher than that under water flushing, and the membrane flux essentially returned to its initial state after half an hour. This indicates that the MXene@h-BN layered composite membrane can achieve self-cleaning through light irradiation.

[0080] The above examples and comparative examples demonstrate that the multifunctional modified membrane possesses the functions of adsorbing and removing new pollutants and membrane self-cleaning. The formation of a composite material from h-BN and MXene, followed by assembly with a substrate membrane using interfacial polymerization, showcases a synergistic effect in treating water pollutants.

[0081] The contents described in this specification are merely an enumeration of the implementation forms of the inventive concept, and the scope of protection of this invention should not be regarded as limited to the specific forms described in the embodiments.

Claims

1. The application of a multifunctional layered composite membrane of MXene@h-BN in the catalytic degradation of organic pollutants in water under sunlight irradiation, characterized in that... Under sunlight, the separation of photogenerated carriers in the MXene@h-BN composite multifunctional material is intensified, a large number of active species are generated, and a large number of pollutants adsorbed on the membrane surface are degraded, which greatly reduces membrane fouling, releases a large number of adsorption sites, and extends the membrane's service life. The MXene@h-BN multifunctional layered composite membrane is formed by using MXene@h-BN composite multifunctional material obtained by ball milling MXene and h-BN as the top layer and then bonding it to a supporting substrate to form a layered composite membrane. The raw materials required for the preparation of h-BN include urea and boric acid; The supporting substrate is a polysulfone membrane (PS). First, dopamine (DA) is used to polymerize the PS membrane to obtain a polymerized PS membrane. Then, the PS membrane is filtered with a dispersion of MXene@h-BN material to obtain the multifunctional layered composite membrane of MXene@h-BN.

2. The application as described in claim 1, characterized in that, The mass ratio of urea to boric acid is 5:1 to 24:1; the mass ratio of h-BN to MXene is 5:1 to 40:

1.

3. The application as described in claim 2, characterized in that, The mass ratio of urea to boric acid is 6~8:1; the mass ratio of h-BN to MXene is 10~12:

1.

4. The application as described in claim 1, characterized in that... The preparation method of h-BN includes the following steps: 1) Dissolve boric acid and urea in deionized water, heat in a water bath at 60-85°C until dry, to obtain a homogeneous mixture of boric acid and urea; 2) Add the mixture from step 1) into a tube furnace and calcine it at 800-950℃ for 2-6 hours under a nitrogen atmosphere. Wash the crude material with water and methanol alternately several times and dry it to obtain h-BN.

5. The application as described in claim 1, characterized in that... h-BN and MXene are mixed in a certain proportion and ball-milled at a speed of 400-700 r / min for 1-4 h. The resulting powder is the MXene@h-BN composite multifunctional material.

6. The application as described in claim 1, characterized in that... The method for preparing MXene includes the following steps: S1: Add lithium fluoride to concentrated hydrochloric acid, then quickly add titanium aluminum carbide, and stir at 30-40℃ for 20-30 hours; S2: After the reaction is complete, wash and centrifuge several times until the pH of the supernatant is neutral; disperse the precipitate ultrasonically in an ice-water bath for 10-40 minutes to obtain a mixed solution, centrifuge, and freeze-dry to obtain crude MXene; S3: Crude MXene is ultrasonically dispersed in anhydrous methanol for 10-40 minutes, centrifuged, the supernatant is discarded, washed with water, and the resulting precipitate is freeze-dried to obtain layered MXene.

7. The application as described in claim 6, characterized in that... In step S1, the concentration of concentrated hydrochloric acid is 8-12 mol / L, the solid-liquid feeding ratio of lithium fluoride to concentrated hydrochloric acid is 1 g: 5-30 mL, and the mass ratio of titanium aluminum carbide to lithium fluoride is 0.5-3:

1.

8. The application as described in claim 7, characterized in that... In step S1, the mass ratio of titanium aluminum carbide to lithium fluoride is 1-1.2:

1.

9. The application as described in claim 1, characterized in that... The specific preparation method of the multifunctional layered composite membrane of MXene@h-BN includes the following steps: (1) A dopamine solution with pH 8-9 was subjected to a polymerization reaction on the surface of a PS filter membrane for 0.5-3 hours to obtain a polymerized PS membrane; (2) The MXene@h-BN composite multifunctional material was ultrasonically dispersed in an ethanol aqueous solution to obtain an MXene@h-BN material dispersion; (3) The dispersion of the MXene@h-BN material is filtered through a polymerized PS membrane, vacuum dried, and then immersed in deionized water for at least 10 minutes. The resulting modified membrane is the multifunctional layered composite membrane of the MXene@h-BN. The concentration of the dopamine solution mentioned in step (1) is 1-3 g / L, and the amount of dopamine used per unit area of ​​the PS filter membrane is 10-15 g / m². 2 ; In step (2), the mass concentration of the ethanol aqueous solution is 20-40%, and the mass ratio of MXene@h-BN composite multifunctional material to dopamine is in the range of 1.6:1-3.4:1.

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