Mxene@uiO-66@pap nanocomposite and preparation method, flame-retardant composite and application

Abstract

The present application relates to the field of functional nanomaterial preparation technology, in particular to MXene@UiO-66@PAP nanocomposite and preparation method, flame-retardant composite and application. The nanocomposite is obtained by loading UiO-66 on the surface of MXene through hydrothermal method, constructing MXene@UiO-66 heterostructure, and then loading hydrochloric acid dopamine doped adenosine triphosphate on the surface of MXene@UiO-66 through interface self-assembly. The flame-retardant composite is obtained by blending the nanocomposite with epoxy resin, curing agent and intumescent flame-retardant system, and then coating and curing. The present application significantly improves the flame retardancy and smoke suppression of the flame-retardant composite through the physical barrier of MXene, the gas adsorption / catalysis of UiO-66 and the phosphorus-nitrogen synergistic flame-retardant effect of PAP, and the residual carbon content is 39.0%, the steel plate back temperature is reduced by 94.6 DEG C, and the present application is suitable for fireproof scenes such as building steel structure.

Description

Technical Field

[0001] This invention relates to the field of functional nanomaterial preparation technology, specifically to MXene@UiO-66@PAP nanocomposites and their preparation methods, flame-retardant composites and their applications. Background Technology

[0002] In fields such as building steel structures and transportation, water-based intumescent fire-retardant coatings are of significant value in replacing traditional solvent-based fire-retardant coatings due to their excellent adhesion, environmental performance, and weather resistance. These coatings expand at high temperatures to form a porous char layer, effectively blocking flame contact with steel and delaying the thermal degradation of the substrate. However, existing technologies still have the following significant drawbacks: insufficient fire resistance under extreme fire conditions, poor stability in high-temperature and high-humidity environments, poor adhesion to steel structures, and difficulty in achieving a good balance between environmental friendliness and flame retardancy.

[0003] In recent years, researchers have turned their attention to novel nano-flame retardant fillers, among which MXene has become a research hotspot due to its unique layered structure and excellent physicochemical properties. However, MXene itself lacks active flame retardant groups (such as phosphorus and nitrogen elements), and it mainly relies on physical barrier effects, making it difficult to achieve "gas-solid dual-phase synergistic flame retardancy," resulting in limited suppression effects on smoke and toxic gases. At the same time, the synergistic effect between MXene and the intumescent flame retardant system (IFR) is insufficient, leading to low density and poor oxidation resistance of the formed intumescent char layer, which is prone to structural damage at high temperatures.

[0004] Although researchers have attempted to overcome these limitations by constructing novel nano-hybrids using a "multi-component composite" strategy, the currently available MXene@UiO-66 still suffers from the following problems when used in composite coatings: First, it fails to effectively address the lack of active flame-retardant groups in MXene, resulting in limited synergistic flame-retardant effects; second, it cannot significantly improve the density and oxidation resistance of the expanded char layer, making it difficult to meet fire protection requirements under extreme high-temperature conditions. These problems limit the effectiveness of existing technologies in complex fire environments. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides an MXene@UiO-66@PAP nanocomposite, its preparation method, a flame-retardant composite, and its applications. Based on the porous structure of a metal-organic framework and the synergistic flame-retardant mechanism of phosphorus and nitrogen, this invention prepares an MXene@UiO-66@PAP nanohybrid by self-assembly loading dopamine hydrochloride-doped adenosine triphosphate (ATP) onto the surface of MXene@UiO-66. Subsequently, the MXene@UiO-66@PAP nanohybrid is mixed with epoxy resin, a curing agent, ammonium polyphosphate, melamine, and dipentaerythritol to obtain a flame-retardant composite. When used in water-based intumescent fire-retardant coatings, the flame-retardant properties and smoke suppression of the composite are significantly improved through the physical barrier of MXene, the gas adsorption / catalysis of UiO-66, and the synergistic flame-retardant effect of PAP.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: The first objective of this invention is to provide a method for preparing MXene@UiO-66@PAP nanocomposites, comprising the following steps: Using MXene@UiO-66 heterostructures as the matrix and dopamine hydrochloride and adenosine triphosphate (ATP) as raw materials, interfacial assembly was carried out at room temperature. In this process, the catechol groups of dopamine hydrochloride coordinated with the phosphate groups of ATP, and the cations of dopamine hydrochloride and the anions of ATP were electrostatically attracted. At the same time, the hydroxyl and amino groups between dopamine hydrochloride and ATP interacted through hydrogen bonds, thus forming a dopamine hydrochloride-doped ATP complex. This complex was then self-assembled on the surface of MXene@UiO-66 to obtain the MXene@UiO-66@PAP nanocomposite.

[0007] In a preferred embodiment of the present invention, the mass ratio of MXene@UiO-66 heterojunction, dopamine hydrochloride, and adenosine triphosphate is 2:3:6.

[0008] In a preferred embodiment of the present invention, the interface assembly time is 20h~25h.

[0009] In a preferred embodiment of the present invention, the preparation process of the MXene@UiO-66 heterojunction includes the following steps: using MXene as a substrate, zirconium chloride as a metal source, and 2-aminoterephthalic acid as an organic ligand, a hydrothermal reaction is carried out in a reaction system of solvent and acetic acid, wherein the hydroxyl groups of MXene react with the Zr groups of zirconium chloride. 4+ Coordination, followed by Zr 4+ The UiO-66 crystal nucleus is formed by coordinating with the carboxyl group of 2-aminoterephthalic acid, and then UiO-66 is grown in situ on the MXene surface to form an MXene@UiO-66 heterostructure.

[0010] In a preferred embodiment of the present invention, the mass ratio of MXene to zirconium chloride is 15:16, and the mass ratio of zirconium chloride to 2-aminoterephthalic acid is 32:25.

[0011] In a preferred embodiment of the present invention, the mass-to-volume ratio of MXene to solvent is 0.3g:60mL, the solvent is N,N-dimethylformamide, and the mass-to-volume ratio of MXene to acetic acid is 0.3g:6mL.

[0012] A second objective of this invention is to provide an MXene@UiO-66@PAP nanocomposite prepared by the above method.

[0013] A third object of the present invention is to provide a flame-retardant composite material made from the following parts by weight of raw materials: 36 to 40 parts epoxy resin, 18 to 20 parts curing agent, 1 to 5 parts of the MXene@UiO-66@PAP nanocomposite as described in claim 7, 19 to 21 parts ammonium polyphosphate, 19 to 21 parts melamine and 8 to 12 parts dipentaerythritol.

[0014] A fourth objective of this invention is to provide an application of the above-mentioned flame-retardant composite in the preparation of water-based intumescent fire-retardant coatings.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention provides an MXene@UiO-66@PAP nanocomposite, which is based on the porous structure of a metal-organic framework and the synergistic flame-retardant mechanism of phosphorus and nitrogen. The preparation process employs a stepwise functionalization strategy. First, a zirconium-based metal-organic framework (UiO-66) is loaded onto the MXene surface using a hydrothermal method to construct an MXene@UiO-66 heterostructure to integrate gas adsorption and catalytic char formation functions. Subsequently, dopamine hydrochloride-doped adenosine triphosphate (PAP) is loaded onto the MXene@UiO-66 surface via interfacial self-assembly to obtain the MXene@UiO-66@PAP nanohybrid. The aim is to achieve multi-scale synergistic enhancement through the physical barrier of MXene, the gas adsorption / catalysis of UiO-66, and the phosphorus and nitrogen synergistic flame retardancy of PAP. PAP is prepared by dissolving dopamine hydrochloride and adenosine triphosphate separately in buffer solutions to ensure sufficient dispersion and a certain concentration. The catechol groups of dopamine bind to the phosphate groups or other functional groups in adenosine triphosphate through coordination interactions. Simultaneously, the cationic nature of dopamine creates an electrostatic attraction with the anionic portion of adenosine triphosphate (ATP). Polar groups such as hydroxyl and amino groups exist between dopamine and ATP, and these groups further enhance the bond between them through hydrogen bonding interactions.

[0016] 2. This invention provides a flame-retardant composite, prepared by blending MXene@UiO-66@PAP nanohybrids and an intumescent flame-retardant system with an aqueous epoxy resin. Specifically, the Zr-O clusters in UiO-66 catalyze the decomposition of ammonium polyphosphate to generate polyphosphoric acid, promoting the dehydration and carbonization of the epoxy resin to form a dense carbon layer. The two-dimensional layered structure of MXene preferentially oxidizes at high temperatures to form a continuous carbon layer, which, together with the ZrO2 nanoparticles generated from the pyrolysis of UiO-66, constructs a multi-level barrier structure, effectively blocking the transfer of heat and oxygen to the matrix. The polydopamine in PAP carbonizes at high temperatures to form a graphitized carbon layer, further enhancing the density and oxidation resistance of the carbon layer. Furthermore, the Zr nodes in UiO-66 catalyze the crosslinking and dehydration of the intumescent flame-retardant system, further promoting the formation of a dense, intumescent carbon layer.

[0017] 3. The char residue and T of the flame-retardant composite provided by this invention, namely the MXene@UiO-66@PAP / EP coating... max The values ​​were 39.0% and 346.2℃, respectively. When the addition amount of MXene@UiO-66@PAP was 3wt.%, the final back surface temperature of the coated steel plate was 170.8℃, which was 94.6℃ lower than that of the EP coating. The expansion height and expansion ratio of this composite coating were 28.7mm and 19.26, respectively. The smoke density rating of the MXene@UiO-66@PAP / EP coating was 34.6%. Compared with the EP coating, the pHRR, THR, pSPR, TSP, pCO, and pCO2 of the 3wt.% MXene@UiO-66@PAP / EP coating were reduced by 52.6%, 37.3%, 58.1%, 59.1%, 43.6%, and 38.7%, respectively, indicating that the MXene@UiO-66@PAP nano-hybrid improved the flame retardant and smoke suppression properties of the waterborne epoxy coating. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating the preparation process of the MXene@UiO-66@PAP nanocomposite of the present invention.

[0019] Figure 2 The images are SEM images of UiO-66, MXene@UiO-66 and MXene@UiO-66@PAP from Embodiment 1 of the present invention. Figure 2 Figure (a) is a SEM image of UiO-66, Figure (b) is a SEM image of MXene@UiO-66, and Figure (c) is a SEM image of MXene@UiO-66@PAP.

[0020] Figure 3 This is a TGA diagram of MXene, UiO-66, MXene@UiO-66 and MXene@UiO-66@PAP in Embodiment 1 of the present invention.

[0021] Figure 4 The diagram shows the dispersion stability of MXene, UiO-66, MXene@UiO-66 and MXene@UiO-66@PAP in water after 3 h and 24 h, according to Example 1 of the present invention. Figure 4 Figure (a) shows the dispersion stability of MXene after 3 hours; Figure (b) shows the dispersion stability of UiO-66 after 3 hours; Figure (c) shows the dispersion stability of MXene@UiO-66 after 3 hours; Figure (d) shows the dispersion stability of MXene@UiO-66@PAP after 3 hours; Figure (a1) shows the dispersion stability of MXene after 24 hours; Figure (b1) shows the dispersion stability of UiO-66 after 24 hours; Figure (c1) shows the dispersion stability of MXene@UiO-66 after 24 hours; Figure (d1) shows the dispersion stability of MXene@UiO-66@PAP after 24 hours.

[0022] Figure 5 The images shown are SEM images of the fracture sections of the composite coatings of Embodiment 2 and Comparative Examples 1 to 4 of the present invention. Figure 5 Figure (a) is the SEM image of EP, Figure (b) is the SEM image of MXene / EP, Figure (c) is the SEM image of UiO-66 / EP, Figure (d) is the SEM image of MXene@UiO-66 / EP, and Figure (e) is the SEM image of MXene@UiO-66@PAP / EP.

[0023] Figure 6 These are post-combustion morphology diagrams of the composite coatings of Embodiment 2 and Comparative Examples 1 to 4 of the present invention. Figure 6 Figure (a) shows the post-combustion morphology of EP, Figure (b) shows the post-combustion morphology of MXene / EP, Figure (c) shows the post-combustion morphology of UiO-66 / EP, Figure (d) shows the post-combustion morphology of MXene@UiO-66 / EP, and Figure (e) shows the post-combustion morphology of MXene@UiO-66@PAP / EP.

[0024] Figure 7 The diagram shows the expansion height and expansion ratio of the composite coatings in Embodiment 2 and Comparative Examples 1 to 4 of the present invention.

[0025] Figure 8 These are digital photographs of the composite coatings of Example 2 and Comparative Examples 1 to 4 of the present invention before and after combustion experiments. Figure 8Figure (a) shows the pre-combustion morphology of EP, Figure (b) shows the pre-combustion morphology of MXene / EP, Figure (c) shows the pre-combustion morphology of UiO-66 / EP, Figure (d) shows the pre-combustion morphology of MXene@UiO-66 / EP, Figure (e) shows the pre-combustion morphology of MXene@UiO-66@PAP / EP, Figure (f) shows the post-combustion morphology of EP, Figure (g) shows the post-combustion morphology of MXene / EP, Figure (h) shows the post-combustion morphology of UiO-66 / EP, Figure (i) shows the post-combustion morphology of MXene@UiO-66 / EP, and Figure (j) shows the post-combustion morphology of MXene@UiO-66@PAP / EP.

[0026] Figure 9 The image shows the back temperature curves of the steel plates coated with the composite coatings of Example 2 and Comparative Examples 1 to 5 of this invention.

[0027] Figure 10 The graphs show the cone calorimetric test data of the composite coatings of Embodiment 2 and Comparative Examples 1 to 4 of the present invention. Figure 10 Figure a shows the HRR curve, figure b shows the THR curve, figure c shows the SPR curve, figure d shows the TSP curve, figure e shows the CO2 generation rate, and figure f shows the CO generation rate.

[0028] Figure 11 The diagram shows the smoke exhaust characteristics of the composite coatings in Embodiment 2 and Comparative Examples 1 to 4 of the present invention. Figure 11 Figure a shows the light absorption diagram, and Figure b shows the smoke density level diagram.

[0029] Figure 12 The TGA and DTG curves of the composite coatings of Example 2 and Comparative Examples 1 to 4 of the present invention under a nitrogen atmosphere are shown. Figure 12 Figure a is the TGA graph, and figure b is the DTG curve graph. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0032] First, this invention provides a method for preparing MXene@UiO-66@PAP nanocomposites, comprising the following steps: Using MXene@UiO-66 heterostructures as the matrix and dopamine hydrochloride and adenosine triphosphate (ATP) as raw materials, interfacial assembly was carried out at room temperature in a buffer system. In this process, the catechol groups of dopamine hydrochloride coordinated with the phosphate groups of ATP, and the cations of dopamine hydrochloride and the anions of ATP were electrostatically attracted. At the same time, the hydroxyl and amino groups between dopamine hydrochloride and ATP were combined through hydrogen bonding, thus forming a dopamine hydrochloride-doped ATP complex. The complex was then functionalized on the surface of MXene@UiO-66 through interfacial self-assembly to obtain the MXene@UiO-66@PAP nanocomposite.

[0033] It should be noted that the reaction mechanism of the MXene@UiO-66@PAP nanocomposite is as follows: (1) MXene possesses excellent electrical conductivity, mechanical strength, and a layered structure, providing a physical barrier and enhancing flame retardant properties. Its abundant carbon skeleton can form a stable carbon layer at high temperatures, while its edge functional groups (such as -OH, -O, etc.) can interact with the zirconium oxide clusters (Zr-O) in UiO-66. UiO-66 has a high specific surface area and a regular pore structure, which can adsorb pyrolysis gases generated during combustion and slow down flame propagation. Its metal nodes (Zr-O clusters) can catalyze the graphitization process of the carbon layer at high temperatures, enhancing the oxidation resistance and stability of the carbon layer. The strong interactions between MXene and UiO-66 (such as van der Waals forces and chemical bonding) form a stable heterostructure. This structure not only enhances the thermal stability and mechanical properties of the material but also achieves a synergistic effect of "gas-phase flame retardancy" and "solid-phase flame retardancy".

[0034] (2) Dopamine hydrochloride is a small molecule compound containing catecholamine groups. These catechol groups possess good surface affinity and cross-linking ability, enabling them to chemically bond with the surface of the MXene@UiO-66 heterostructure (e.g., hydrogen bonds, π-π interactions), thereby improving the adhesion of the coating to the steel substrate. In an aqueous environment, dopamine molecules can form a polydopamine layer through oxidative or reductive polymerization. This polymer network not only enhances the coating's weather resistance and corrosion resistance but also provides a stable carrier for the flame-retardant components.

[0035] (3) Adenosine triphosphate (ATP) decomposes at high temperatures to generate phosphate and carbon-based products. The phosphate component can catalyze the formation of a stable phosphorylation interface on the surface of the MXene@UiO-66 heterostructure, further enhancing its antioxidant properties and thermal stability. The carbon-based products participate in the construction of the carbon layer, improving the density of the expanded carbon layer. The interaction between ATP and the MXene@UiO-66 heterostructure can regulate the gas-phase and solid-phase reactions in the flame-retardant process. During a fire, the decomposition products of ATP can promote the catalytic formation of a graphitized carbon layer by MXene@UiO-66, thereby improving the fire resistance of the coating.

[0036] (4) The mechanism of action of the dopamine hydrochloride-doped adenosine triphosphate (PAP) complex is as follows: Dopamine hydrochloride and adenosine triphosphate are dissolved separately in appropriate buffer solutions to ensure that they are fully dispersed and reach a certain concentration. The catechol groups in dopamine can bind to the phosphate group or other functional groups in the adenosine triphosphate molecule through coordination interactions. At the same time, the cationic nature of dopamine may generate electrostatic attraction with the anionic part of adenosine triphosphate. There are polar groups such as hydroxyl and amino groups between dopamine and adenosine triphosphate, which can further enhance the binding between the two through hydrogen bonding interactions.

[0037] The mass ratio of the MXene@UiO-66 heterostructure, dopamine hydrochloride, and adenosine triphosphate is 2:3:6.

[0038] The buffer solution is an aqueous solution of tris(hydroxymethyl)aminomethane hydrochloride, consisting of 0.12 g of tris(hydroxymethyl)aminomethane hydrochloride and 100 mL of water, with a mass ratio of dopamine hydrochloride to tris(hydroxymethyl)aminomethane hydrochloride in the buffer solution of 2.5:1.

[0039] The interface assembly time is 20h~25h.

[0040] The preparation process of the MXene@UiO-66 heterojunction includes the following steps: using MXene as a substrate, zirconium chloride as a metal source, and 2-aminoterephthalic acid as an organic ligand, a hydrothermal reaction is carried out in a reaction system of solvent and acetic acid. The hydroxyl groups on the surface of MXene react with the Zr in zirconium chloride. 4+ Coordination, followed by Zr 4+ The UiO-66 crystal nucleus is coordinated with the carboxyl group of 2-aminoterephthalic acid, and finally UiO-66 is grown in situ on the MXene surface to form an MXene@UiO-66 heterojunction.

[0041] The mass ratio of MXene to zirconium chloride is 15:16, and the mass ratio of zirconium chloride to 2-aminoterephthalic acid is 32:25.

[0042] The mass-to-volume ratio of MXene to solvent is 0.3 g: 60 mL, and the solvent is N,N-dimethylformamide; the mass-to-volume ratio of MXene to acetic acid is 0.3 g: 6 mL.

[0043] The MXene preparation method involves placing 2g of LiF and 40mL of 9M HCl solution in a polytetrafluoroethylene mold and stirring magnetically for 30min until completely dissolved. Then, 2g of MAX phase (titanium aluminum carbide) powder is slowly added, and the mixture is magnetically stirred at a constant temperature of 40℃ for 24h. After the reaction is complete, the supernatant is removed by centrifugation, followed by alternating washing with 2M HCl solution and deionized water until the supernatant is neutral. The resulting precipitate is ultrasonically treated with ethanol for 1h and then collected by centrifugation. To promote layered exfoliation, the precipitate is ultrasonically treated in deionized water for 1h, followed by centrifugation at 3500r / min for 15min to obtain an MXene nanosheet suspension. Finally, MXene powder is obtained by freeze-drying.

[0044] Secondly, the present invention provides an MXene@UiO-66@PAP nanocomposite prepared by the above method.

[0045] Then, the present invention provides a flame retardant composite comprising 36-40 parts epoxy resin, 18-20 parts curing agent, 1-5 parts MXene@UiO-66@PAP nanocomposite as described in claim 7, 19-21 parts ammonium polyphosphate, 19-21 parts melamine and 8-12 parts dipentaerythritol.

[0046] The preparation method of the flame-retardant composite includes the following steps: dissolving epoxy resin, curing agent, MXene@UiO-66@PAP nanocomposite, ammonium polyphosphate, melamine, and dipentaerythritol in water, coating the solution onto the substrate surface, and curing it at room temperature for 7 days to obtain the flame-retardant composite coating MXene@UiO-66@PAP / EP. The epoxy resin and curing agent are water-based epoxy resin AB glue produced by Hangzhou Wuhuigang Adhesive Co., Ltd., and the substrate is a steel plate.

[0047] It should be noted that the flame-retardant mechanism of the MXene@UiO-66@PAP / EP composite coating in this invention is a multi-level synergistic effect. Under heat or flame impact, the two-dimensional sheet structure of MXene first exerts a physical barrier effect, effectively delaying the pyrolysis process of the substrate by extending the heat penetration path. Simultaneously, the Zr-O clusters of UiO-66 undergo a synergistic catalytic reaction with phosphorus and nitrogen-containing components in PAP (such as adenosine triphosphate and polydopamine), promoting the formation of a porous char layer with expansion properties. During this process, gases such as NH3, H2O, and CO2 released from the thermal degradation of PAP reduce the combustion intensity by diluting the concentration of combustibles and through endothermic effects, while the released phosphorus-containing free radicals (PO·, HPO·) interrupt the combustion chain reaction by capturing active free radicals. The high specific surface area of ​​UiO-66 and the Zr metal centers significantly improve the catalytic char formation efficiency, synergistically constructing a high-strength, dense char layer with the CNP crosslinking structure in PAP, effectively preventing the escape of combustible volatiles. Furthermore, the UiO-66 loaded on the MXene surface partially decomposes into ZrO2 nanoparticles at high temperatures. These nanoparticles, together with the CNP network formed by PAP carbonization, constitute an inorganic-organic hybrid char skeleton, further enhancing thermal insulation performance by increasing thermal reflectivity and the density of the char layer. Ultimately, this system, through the physical barrier of MXene, the catalytic char formation of UiO-66, and the synergistic gas-solid dual-phase flame retardant effect of PAP, forms a triple protection mechanism of combustion inhibition, smoke reduction, and char reinforcement, significantly improving the fire resistance of the composite coating.

[0048] Finally, the present invention provides an application of the above-mentioned flame-retardant composite in the preparation of water-based intumescent fire-retardant coatings.

[0049] The following specific examples will provide further explanation.

[0050] In this invention, the abbreviation for N,N-dimethylformamide is DMF, the abbreviation for tris-hydroxymethylaminomethane hydrochloride is Tris-HCl, the abbreviation for adenosine triphosphate is ATP, the abbreviation for ammonium polyphosphate is APP, the abbreviation for melamine is MEL, the abbreviation for dipentaerythritol is DPER, and the abbreviation for epoxy resin is EP.

[0051] Example 1 A method for preparing MXene@UiO-66@PAP nanocomposite includes the following steps: S1. 2g of LiF and 40mL of 9M HCl solution were placed in a polytetrafluoroethylene mold and magnetically stirred for 30min until completely dissolved. Then, 2g of titanium aluminum carbide powder was slowly added, and the mixture was magnetically stirred at a constant temperature of 40℃ for 24h. After the reaction was complete, the supernatant was removed by centrifugation, followed by alternating washing with 2M HCl solution and deionized water until the supernatant was neutral. The resulting precipitate was ultrasonically treated with ethanol for 1h and then collected by centrifugation. To promote layered exfoliation, the precipitate was ultrasonically treated in deionized water for 1h, and then centrifuged at 3500r / min for 15min to obtain an MXene nanosheet suspension. Finally, MXene powder was obtained by freeze-drying.

[0052] S2. 0.3 g of MXene powder was dispersed in 60 mL of DMF and ultrasonically dispersed for 1 h. Then, 0.32 g of ZrCl4 and 0.25 g of 2-aminoterephthalic acid were added sequentially, and the mixture was magnetically stirred until homogeneous. 6 mL of acetic acid was then added. The mixture was transferred to a polytetrafluoroethylene-lined high-pressure reactor and reacted in a 120°C oven for 24 h. After the reaction system cooled naturally, it was washed several times with DMF and vacuum dried at 60°C for 24 h to obtain MXene@UiO-66.

[0053] S3. Dissolve 0.12 g of Tris-HCl in 100 mL of deionized water and stir magnetically for 10 min. Then, add 0.2 g of MXene@UiO-66, 0.3 g of dopamine hydrochloride, and 0.6 g of ATP sequentially. Adjust the pH to 8.5 with sodium hydroxide solution. Stir continuously at room temperature for 24 h to complete interfacial assembly. After washing three times with deionized water, dry the product in a vacuum oven at 60 °C for 24 h to finally obtain the hierarchical MXene@UiO-66@PAP nanocomposite.

[0054] Example 2 A method for preparing a flame-retardant composite includes the following steps: S1. 3g of MXene@UiO-66 was dispersed in 10mL of deionized water by ultrasonic vibration to obtain a uniform nanofiller dispersion. MXene@UiO-66 is denoted as MUP.

[0055] S2. Weigh 20g of APP, 10g of MEL and 10g of DPER, mix them together in 20mL of deionized water, and stir with high-speed magnetic force for 30min to obtain a suspension of evenly dispersed expanded components.

[0056] S3. Add 38g of waterborne epoxy resin and 19g of curing agent to the suspension of the expanding component prepared in S2 and stir for 10min.

[0057] S4. Add the nanofiller dispersion prepared in S1 to the prepared suspension and stir continuously for 10 minutes to mix it evenly, thus obtaining the composite slurry.

[0058] S5. Apply the composite slurry to the surface of the pretreated steel plate (100mm×100mm×5mm) and cure at room temperature for 7 days to obtain the flame retardant composite material, i.e., the composite coating MUP / EP.

[0059] Comparative Example 1 A method for preparing a coating EP includes the following steps: S1. Weigh 20g of APP, 10g of MEL and 10g of DPER, mix them together in 20mL of deionized water, and stir with high-speed magnetic force for 30min to obtain a suspension of evenly dispersed expanded components.

[0060] S2. Add 40g of waterborne epoxy resin and 20g of curing agent to the suspension of the expanding component obtained in S1 and stir for 10 minutes to obtain a composite slurry.

[0061] S3. Apply the composite slurry to the surface of the pretreated steel plate (100mm×100mm×5mm) and cure at room temperature for 7 days to obtain the water-based epoxy coating EP.

[0062] Comparative Example 2 A method for preparing a composite coating MXene / EP includes the following steps: S1. Disperse 3g of MXene into 10mL of deionized water by ultrasonic vibration to obtain a uniform nanofiller dispersion.

[0063] S2. Weigh 20g of APP, 10g of MEL and 10g of DPER, mix them together in 20mL of deionized water, and stir with high-speed magnetic force for 30min to obtain a suspension of evenly dispersed expanded components.

[0064] S3. Add 38g of waterborne epoxy resin and 19g of curing agent to the suspension of the expanding component prepared in S2 and stir for 10min.

[0065] S4. Add the nanofiller dispersion prepared in S1 to the prepared suspension and stir continuously for 10 minutes to mix it evenly, thus obtaining the composite slurry.

[0066] S5. Apply the composite slurry to the surface of the pretreated steel plate (100mm×100mm×5mm) and cure at room temperature for 7 days to obtain the composite coating MXene / EP.

[0067] Comparative Example 3 A method for preparing a composite coating UiO-66 / EP includes the following steps: S1. Disperse 3g of UiO-66 into 10mL of deionized water by ultrasonic vibration to obtain a uniform nanofiller dispersion.

[0068] S2. Weigh 20g of APP, 10g of MEL and 10g of DPER, mix them together in 20mL of deionized water, and stir with high-speed magnetic force for 30min to obtain a suspension of evenly dispersed expanded components.

[0069] S3. Add 38g of waterborne epoxy resin and 19g of curing agent to the suspension of the expanding component prepared in S2 and stir for 10min.

[0070] S4. Add the nanofiller dispersion prepared in S1 to the prepared suspension and stir continuously for 10 minutes to mix it evenly, thus obtaining the composite slurry.

[0071] S5. Apply the composite slurry to the surface of the pretreated steel plate (100mm×100mm×5mm) and cure at room temperature for 7 days to obtain the composite coating UiO-66 / EP.

[0072] Comparative Example 4 A method for preparing a composite coating MU / EP includes the following steps: S1. 3g of MXene@UiO-66 was dispersed in 10mL of deionized water by ultrasonic vibration to obtain a uniform nanofiller dispersion. MXene@UiO-66 is denoted as MU.

[0073] S2. Weigh 20g of APP, 10g of MEL and 10g of DPER, mix them together in 20mL of deionized water, and stir with high-speed magnetic force for 30min to obtain a suspension of evenly dispersed expanded components.

[0074] S3. Add 38g of waterborne epoxy resin and 19g of curing agent to the suspension of the expanding component prepared in S2 and stir for 10min.

[0075] S4. Add the nanofiller dispersion prepared in S1 to the prepared suspension and stir continuously for 10 minutes to mix it evenly, thus obtaining the composite slurry.

[0076] S5. Apply the composite slurry to the surface of the pretreated steel plate (100mm×100mm×5mm) and cure at room temperature for 7 days to obtain the composite coating MU / EP.

[0077] The structures and performance of Examples 1 to 2 and Comparative Examples 1 to 4 were characterized.

[0078] Figure 2The images are SEM images of UiO-66, MXene@UiO-66 and MXene@UiO-66@PAP from Embodiment 1 of the present invention. Figure 2 Figure (a) is a SEM image of UiO-66, Figure (b) is a SEM image of MXene@UiO-66, and Figure (c) is a SEM image of MXene@UiO-66@PAP. (From...) Figure 2 As can be seen, UiO-66 exhibits a regular cubic structure, and its regular geometric contour and clear edges verify the high crystallinity of the zirconium-based metal-organic framework. UiO-66 nanoparticles are uniformly dispersed on the MXene surface without significant aggregation, which is attributed to the interaction between the functional groups on the MXene surface and Zr. 4+ The strong coordination effect. A continuous coating layer is formed on the surface of MXene@UiO-66@PAP and island-like protrusions are attached. This hierarchical morphology is due to the synergistic regulation of π-π stacking and hydrogen bonding during the self-assembly of PDA and ATP.

[0079] Next, the thermal degradation behavior of MXene, UiO-66, MXene@UiO-66 and MXene@UiO-66@PAP under nitrogen atmosphere was investigated by TGA. Figure 3 This is a TGA diagram of MXene, UiO-66, MXene@UiO-66, and MXene@UiO-66@PAP from Embodiment 1 of the present invention. Figure 3 MXene exhibits excellent thermal stability, retaining a high residual mass of 98.8% at 800℃. This is attributed to the three-dimensional network structure of Ti-C covalent bonds within the MXene sheets and the thermal resistance effect of interlayer van der Waals forces. UiO-66, due to the pyrolysis of its organic ligand (terephthalic acid) in the 200℃-550℃ range, ultimately retains 43.0% ZrO2 crystalline phase. The residual rate of MXene@UiO-66 prepared via hydrothermal reaction is 65.2%, and its enhanced thermal stability stems from the synergistic effect of two factors: the physical coating of UiO-66 nanocrystals by the MXene sheets delays ligand pyrolysis, while the Zr-O-Ti heterostructure enhances structural rigidity. The residual rate of MXene@UiO-66@PAP decreases to 63.5%, reflecting the dual influence of the PAP component. On the one hand, the phosphate groups in ATP dehydrate at 300-450℃ to generate polyphosphoric acid, which promotes the formation of the carbon layer. On the other hand, the gaseous products (NH3, H2O) generated by the pyrolysis of polydopamine cause the microporous structure to expand at 500℃-700℃. The dynamic balance between the two results in the final residual mass being between UiO-66 and MXene@UiO-66.

[0080] In this invention, to evaluate the dispersion stability of the nanofillers, MXene, UiO-66, MXene@UiO-66 and MXene@UiO-66@PAP were uniformly dispersed in deionized water by ultrasonic dispersion, and observed after standing at different time points. Figure 4 The diagram shows the dispersion stability of MXene, UiO-66, MXene@UiO-66 and MXene@UiO-66@PAP in water after 3 h and 24 h, according to Example 1 of the present invention. Figure 4 Figure (a) shows the dispersion stability of MXene after 3 hours; Figure (b) shows the dispersion stability of UiO-66 after 3 hours; Figure (c) shows the dispersion stability of MXene@UiO-66 after 3 hours; Figure (d) shows the dispersion stability of MXene@UiO-66@PAP after 3 hours; Figure (a1) shows the dispersion stability of MXene after 24 hours; Figure (b1) shows the dispersion stability of UiO-66 after 24 hours; Figure (c1) shows the dispersion stability of MXene@UiO-66 after 24 hours; Figure (d1) shows the dispersion stability of MXene@UiO-66@PAP after 24 hours. Figure 4 It was observed that MXene exhibited significant aggregation and bottom sedimentation after 3 hours, and completely settled after 24 hours, indicating that its interlayer van der Waals forces easily induce aggregation. UiO-66, due to its porous structure and hydrophilic surface, maintained good dispersibility after 3 hours, but some particles settled after 24 hours. MXene@UiO-66 did not show significant sedimentation after 3 hours, but the amount of sediment decreased significantly after 24 hours, indicating that the loading of UiO-66 effectively suppressed the interlayer stacking of MXene. MXene@UiO-66@PAP maintained excellent dispersion stability throughout 24 hours, attributed to PAP significantly improving the aqueous dispersion stability of the nanofiller through steric hindrance and surface charge repulsion.

[0081] Figure 5 The images shown are SEM images of the fracture sections of the composite coatings of Embodiment 2 and Comparative Examples 1 to 4 of the present invention. Figure 5 Figure (a) is a SEM image of EP, (b) is a SEM image of MXene / EP, (c) is a SEM image of UiO-66 / EP, (d) is a SEM image of MXene@UiO-66 / EP, and (e) is a SEM image of MXene@UiO-66@PAP / EP. Figure 5It is evident that the fracture cross-section of EP exhibits brittle fracture characteristics. For MXene / EP, the surface roughness increases significantly, with localized stacking and agglomeration observed. Localized aggregation of Zr-based MOF particles is observed in UiO-66 / EP, leading to micron-sized pore defects in the fracture surface, indicating limited dispersibility of UiO-66 in EP. No obvious aggregates were observed in MXene@UiO-66 / EP, because UiO-66 nanoparticles are anchored to the surface of MXene sheets via hydrothermal reaction, forming a stable heterostructure that effectively inhibits UiO-66 agglomeration. MXene@UiO-66@PAP / EP exhibits the best dispersibility. Dopamine molecules in PAP regulate the interfacial compatibility between the filler and EP through π-π interactions and hydrogen bonds, ensuring uniform distribution of the MXene@UiO-66@PAP nanofiller in the matrix, confirming the synergistic effect of the multi-level composite strategy on improving filler dispersibility.

[0082] Next, the expansion properties of EP and its composite coating were characterized by muffle furnace calcination experiments. The specific calcination process was as follows: the sample was placed in a muffle furnace, and the temperature was increased from 25°C to 800°C at a rate of 20°C / min for 60 min to ensure complete combustion of the coating.

[0083] Figure 6 These are post-combustion morphology diagrams of the composite coatings of Embodiment 2 and Comparative Examples 1 to 4 of the present invention. Figure 6 Figure (a) shows the post-combustion morphology of EP, Figure (b) shows the post-combustion morphology of MXene / EP, Figure (c) shows the post-combustion morphology of UiO-66 / EP, Figure (d) shows the post-combustion morphology of MXene@UiO-66 / EP, and Figure (e) shows the post-combustion morphology of MXene@UiO-66@PAP / EP. Figure 7 This diagram shows the expansion height and expansion ratio of the composite coatings in Example 2 and Comparative Examples 1-4 of the present invention. Table 1 shows the expansion parameters of the composite coatings in Example 2 and Comparative Examples 1-4. Figures 6-7As shown in Table 1, the expansion height and expansion ratio of the EP coating are 6.5 mm and 4.36, respectively. Its lower expansion ratio may be due to the loose carbon layer structure of the single resin system at high temperatures, which cannot effectively prevent gas escape. The expansion performance of the MXene / EP coating is significantly improved (14.8 mm and 9.87), thanks to the layered structure of MXene forming a physical barrier at high temperatures, delaying gas diffusion and enhancing the density of the carbon layer. The expansion height and expansion ratio of UiO-66 / EP increase to 12.2 mm and 8.08, respectively. Although the hierarchical porous structure of UiO-66 can promote carbonization, its expansion efficiency under its sole effect is still lower than that of the MXene system, which may be related to the insufficient structural stability of the single porous material. The expansion height and expansion ratio of MXene@UiO-66 / EP reached 22.8 mm and 15.2, respectively. This is attributed to the combination of MXene two-dimensional nanosheets and the porous framework of UiO-66. The former provides framework support, while the latter traps decomposition gases through its porous structure, jointly enhancing the stability of the expanded char layer. MXene@UiO-66@PAP / EP exhibited the best expansion performance (28.7 mm and 19.26), which is attributed to PAP promoting the formation of a cross-linked dense char layer during pyrolysis, while the heterostructure of MXene@UiO-66 prolongs gas retention time through a multi-layered barrier mechanism. This triple synergistic effect ultimately improved the expansion performance of the composite coating, verifying the effectiveness of multi-component composite strategies in flame-retardant coating design.

[0084] Table 1. Expansion parameters of the composite coatings in Example 2 and Comparative Examples 1 to 5 Figure 8 These are digital photographs of the composite coatings of Example 2 and Comparative Examples 1 to 4 of the present invention before and after combustion experiments. Figure 8 Figure (a) shows the pre-combustion morphology of EP; Figure (b) shows the pre-combustion morphology of MXene / EP; Figure (c) shows the pre-combustion morphology of UiO-66 / EP; Figure (d) shows the pre-combustion morphology of MXene@UiO-66 / EP; Figure (e) shows the pre-combustion morphology of MXene@UiO-66@PAP / EP; Figure (f) shows the post-combustion morphology of EP; Figure (g) shows the post-combustion morphology of MXene / EP; Figure (h) shows the post-combustion morphology of UiO-66 / EP; Figure (i) shows the post-combustion morphology of MXene@UiO-66 / EP; Figure (j) shows the post-combustion morphology of MXene@UiO-66@PAP / EP. Figure 8It is evident that after combustion, the EP coating exhibits a large-area depression in the central region of the char layer and wide cracks at the edges, indicating low char layer strength and poor thermal insulation performance. For the MXene / EP coating, the physical barrier effect of MXene nanosheets promotes increased char layer density, but local microcracks still appear on the surface, which is related to the incomplete orientation of the two-dimensional nanosheets. For the UiO-66 / EP coating, the porous framework characteristics of Zr-based MOFs lead to the formation of a continuous honeycomb char layer structure; however, the high microporosity exposes the self-aggregation defect of UiO-66. The MXene@UiO-66 / EP char layer shows reduced cracks and refined pores, attributed to the synergistic effect of the heterogeneous interface between MXene and UiO-66, forming a three-dimensional interpenetrating network structure that effectively suppresses crack propagation. The char layer surface of MXene@UiO-66@PAP / EP is intact and defect-free. This is attributed to the catalytic cross-linking effect of dopamine hydrochloride-doped PAP during combustion, which synergistically forms a dense char layer barrier with MXene@UiO-66. At the same time, MXene inhibits the excessive expansion of PAP pyrolysis products, ultimately achieving high-efficiency fire resistance.

[0085] The composite coatings of Example 2 and Comparative Examples 1 to 4 were applied to the surface of the steel plate.

[0086] Figure 9 This is a back-side temperature profile of the steel plate coated with the composite coatings of Example 2 and Comparative Examples 1 to 5 of the present invention. Figure 9 It is known that the temperature of the bare steel plate without any coating rapidly exceeds 500℃ within 10 minutes of combustion, leading to a sharp decrease in steel strength. In contrast, the temperature on the back side of the steel plate coated with EP coating stabilizes at 265.4℃ after 60 minutes of combustion. The slower heating rate indicates that although the carbon layer has an insulating effect, its loose structure makes it difficult to effectively block heat penetration. The introduction of MXene nanosheets (MXene / EP) significantly reduced the temperature on the back side of the steel plate to 200.4℃ due to the physical barrier effect of the two-dimensional sheets on heat flow and the reinforcing effect of the carbon layer skeleton. For the UiO-66 / EP coating containing Zr-based MOF, the temperature on the back side of the steel plate (226.2℃) is higher than that of the MXene / EP coating. This is because although the hierarchical porous structure of Zr-based MOF can adsorb pyrolysis gases, the continuity of the carbon layer is poor when used alone. The MXene@UiO-66 / EP coating, through the synergistic effect of two-dimensional layers and a porous framework, forms a gradient-blocked thermal diffusion path, further reducing the temperature to 182.3℃, demonstrating that the heterogeneous interface structure can significantly improve the density of the carbon layer. The temperature on the back side of the steel plate with the MXene@UiO-66@PAP / EP coating decreased to 170.8℃. This is attributed to the formation of a conjugated structure between phosphorus-containing free radicals generated from the pyrolysis of adenosine triphosphate and the carbonization products of dopamine, synergistically constructing a dense carbon layer with excellent antioxidant properties.

[0087] The flame retardant and smoke suppression properties of EP and its composite coating were analyzed using a cone calorimeter (CCT), including heat release rate (HRR), total heat release (THR), smoke generation rate (SPR), total smoke volume (TSP), CO2 generation rate, and CO generation rate. Table 2 shows the cone calorimeter test results for EP and its composite coating.

[0088] Table 2. Cone calorimetry test results of EP and its composite coating Figure 10 The graphs show the cone calorimetric test data of the composite coatings of Embodiment 2 and Comparative Examples 1 to 4 of the present invention. Figure 10 Figure a shows the HRR curve, figure b shows the THR curve, figure c shows the SPR curve, figure d shows the TSP curve, figure e shows the CO2 formation rate, and figure f shows the CO formation rate. Figure 10 As shown in Table 2, the pHRR and THR of EP are 268.4 kW / m³. 2 and 27.1 MJ / m 2 This indicates that it releases heat rapidly during combustion. The pHRR of UiO-66 / EP is 212.4 kW / m³. 2 ) and THR (24.4 MJ / m 2 The pHRR and THR of MXene / EP further decreased, thanks to the catalytic char formation of Zr-O clusters in UiO-66 and the adsorption capacity of the metal-organic framework for free radicals. After the introduction of MXene, the pHRR and THR of MXene / EP decreased to 154.1 kW / m³. 2 and 23.9 MJ / m 2 This is attributed to the continuous physical barrier formed by the two-dimensional layered structure of MXene at high temperatures, effectively slowing down the diffusion of heat and oxygen. The pHRR of MXene@UiO-66 / EP is 148.7 kW / m³. 2 ) and THR (20.2 MJ / m 2 Compared to EP, the flame retardancy and smoke suppression effects were reduced by 44.6% and 25.4%, respectively, indicating that the physical barrier effect of MXene and the chemical catalysis effect of UiO-66 play complementary roles in char layer formation. MXene@UiO-66@PAP / EP exhibited the best flame retardant and smoke suppression effects, with a pHRR of 125.2 kW / m³. 2 ) and THR (17.1 MJ / m 2Compared to EP, the peak CO generation rate (pCO) and peak CO2 generation rate (pCO2) of MXene@UiO-66@PAP / EP decreased by 52.6% and 37.3%, respectively, while the peak smoke generation rate (pSPR) and total smoke production (TSP) decreased by 58.1% and 59.1%, respectively. This is because PAP promotes the rapid formation of a dense, expanded char layer, effectively suppressing the escape of pyrolysis gases and the diffusion of smoke particles. Furthermore, the peak CO generation rate (pCO) and peak CO2 generation rate (pCO2) of MXene@UiO-66@PAP / EP were 0.0028 g / s and 0.039 g / s, respectively, which were 43.6% and 38.7% lower than those of EP (0.0049 g / s and 0.065 g / s), indicating that the composite filler significantly reduced the formation of incomplete combustion products by enhancing the stability of the char layer. These results demonstrate that the multi-level composite structure of MXene@UiO-66@PAP provides an efficient solution for waterborne intumescent fire-retardant coatings through a multi-synergistic mechanism of physical barrier, catalytic char formation, and gas-phase free radical quenching.

[0089] Figure 11 The diagram shows the smoke exhaust characteristics of the composite coatings in Embodiment 2 and Comparative Examples 1 to 4 of the present invention. Figure 11 Figure a shows the light absorption map, and figure b shows the smoke density level map. Figure 11 It can be seen that the EP coating maintains the highest light absorption value during combustion, indicating that it releases the most smoke during combustion. With the addition of MXene-based nanofillers, the light absorption value of the composite coating shows a significant decreasing trend during combustion. Among them, the light absorption value of MXene@UiO-66@PAP / EP remains at the lowest value, indicating that it produces the least smoke throughout the entire combustion stage. The smoke density rating (SDR) of EP is as high as 60.5%, consistent with the trend of the light absorption curve. The SDR of MXene / EP decreases to 40.3%, mainly because the introduction of MXene hinders the further decomposition of thermal degradation products, thereby reducing smoke production. The SDR of UiO-66 / EP further decreases, attributed to the adsorption of pyrolysis gases by the hierarchical porous structure of UiO-66, which prolongs the smoke diffusion path. The SDR of the MXene@UiO-66 / EP coating is significantly reduced to 36.7% through the synergistic effect of two-dimensional barrier and porous adsorption. In contrast, the SDR of MXene@UiO-66@PAP / EP was further reduced to a minimum (34.6%), which is mainly attributed to the catalytic char formation of N and P elements in PAP, the dual barrier of heterostructure to volatile products, the promotion of dense char layer formation, and the inhibition of the release of combustible volatiles, thereby achieving optimal smoke suppression performance.

[0090] Figure 12 The TGA and DTG curves of the composite coatings of Example 2 and Comparative Examples 1 to 4 of the present invention under a nitrogen atmosphere are shown. Figure 12Figure a shows the TGA curve, and figure b shows the DTG curve. Table 3 shows the TGA and DTG data for EP and its composite coating under nitrogen atmosphere. Figure 12 As shown in Table 3, the initial decomposition temperature of EP (T) 5% The temperature at which the maximum decomposition rate is 209.2℃ is the highest. max The thermal stability was 321.3℃, and the residual char content was 20.3%, indicating poor thermal stability and low char formation efficiency. MXene / EP benefits from the physical barrier constructed by the two-dimensional layers, T 5% Increased to 242.1℃, T max Upon reaching 337.3℃, the residual char content significantly increased to 35.8%, confirming its effective delay in the thermal decomposition process of the matrix. UiO-66 / EP, through the catalytic char formation effect of the metal-organic framework, achieved a residual char content of 31.2%, with its T... 5% (237.7℃) and T max The improvement in T (331.5℃) was slightly less than that of MXene / EP. MXene@UiO-66 / EP exhibited a synergistic enhancement effect; the combination of the two-dimensional barrier structure and porous catalytic sites improved its T 5% and T max The temperatures reached 245.2℃ and 339.8℃ respectively, with the residual char content increasing to 37.7%. MXene@UiO-66@PAP / EP exhibited the best thermal performance (T... 5% T max The residual char content was 248.6℃, 346.2℃ and 39.0% respectively. This is due to the synergistic effect of PAP catalytic char formation and the composite barrier effect of MXene@UiO-66 promoting the formation of a dense char layer, which significantly improves the thermal stability and flame retardant efficiency of the char layer.

[0091] Table 3. TGA and DTG data of EP and its composite coating under nitrogen atmosphere. It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of this invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended scope of protection is intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of this invention.

[0092] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of protection of this invention and its equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing MXene@UiO-66@PAP nanocomposite, characterized in that, Includes the following steps: Using MXene@UiO-66 heterojunctions as the matrix and dopamine hydrochloride and adenosine triphosphate (ATP) as raw materials, interfacial assembly was performed at room temperature. The catechol groups of dopamine hydrochloride coordinated with the phosphate groups of ATP, and the cations of dopamine hydrochloride and the anions of ATP were electrostatically attracted. Simultaneously, the hydroxyl and amino groups of dopamine hydrochloride and ATP interacted through hydrogen bonds, forming a dopamine-doped ATP complex. This complex was then self-assembled onto the surface of MXene@UiO-66 to obtain the MXene@UiO-66@PAP nanocomposite. The mass ratio of MXene@UiO-66 heterojunctions, dopamine hydrochloride, and ATP was 2:3:

6.

2. The method for preparing the MXene@UiO-66@PAP nanocomposite according to claim 1, characterized in that, The interface assembly time is 20-25 hours.

3. The method for preparing the MXene@UiO-66@PAP nanocomposite according to claim 1, characterized in that, The preparation process of MXene@UiO-66 heterojunction includes the following steps: using MXene as a substrate, zirconium chloride as a metal source, and 2-aminoterephthalic acid as an organic ligand, a hydrothermal reaction is carried out in a reaction system of solvent and acetic acid. The hydroxyl groups of MXene react with the Zr groups of zirconium chloride. 4+ Coordination, followed by Zr 4+ The UiO-66 crystal nucleus is formed by coordinating with the carboxyl group of 2-aminoterephthalic acid, and then UiO-66 is grown in situ on the MXene surface to form an MXene@UiO-66 heterojunction.

4. The method for preparing the MXene@UiO-66@PAP nanocomposite according to claim 3, characterized in that, The mass ratio of MXene to zirconium chloride is 15:16, and the mass ratio of zirconium chloride to 2-aminoterephthalic acid is 32:

25.

5. The method for preparing the MXene@UiO-66@PAP nanocomposite according to claim 3, characterized in that, The mass-to-volume ratio of MXene to solvent was 0.3 g: 60 mL, and the solvent was N,N-dimethylformamide; the mass-to-volume ratio of MXene to acetic acid was 0.3 g: 6 mL.

6. An MXene@UiO-66@PAP nanocomposite, characterized in that, It is prepared by the method described in any one of claims 1 to 5.

7. A flame-retardant compound, characterized in that, It is made from the following raw materials in parts by weight: 36-40 parts epoxy resin, 18-20 parts curing agent, 1-5 parts MXene@UiO-66@PAP nanocomposite as described in claim 6, 19-21 parts ammonium polyphosphate, 19-21 parts melamine and 8-12 parts dipentaerythritol.

8. The use of the flame-retardant composite of claim 7 in the preparation of water-based intumescent fire-retardant coatings.

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