Self-healing and regenerable photocatalytic coatings for environmentally toxic substances and their preparation methods

Abstract

This invention belongs to the field of environmental functional materials technology, and provides a self-healing, regenerable photocatalytic coating for environmentally toxic substances and its preparation method. The invention uses fluorinated polyurethane as the continuous phase, introduces reversible bonding units, and constructs a dynamic polymer network with photothermal triggering self-healing capabilities. The coating is loaded with a heterojunction composed of nitrogen-doped carbon quantum dots and bismuth tungstate, and a silica shell inhibits catalyst surface poisoning and deactivation. Furthermore, titanium carbide-based two-dimensional materials are used as conductive and photothermal aids to effectively accelerate the separation and migration of photogenerated carriers, while simultaneously generating a mild localized temperature rise under illumination, promoting the reversible bond breaking and recombination in the polyurethane network, achieving in-situ self-healing of microcracks and photo-etching damage in the coating. Additionally, the coating surface is endowed with selective enrichment and self-cleaning capabilities. The coating of this invention can maintain stable adhesion and continuous catalytic activity under long-term illumination and complex pollution environments, and has a continuous degradation capability for environmentally toxic substances such as gaseous formaldehyde.

Description

Technical Field

[0001] This invention belongs to the field of environmental functional materials technology, and relates to a self-healing and regenerable photocatalytic coating for environmental toxicants and its preparation method. Background Technology

[0002] Environmental pollutants, especially small-molecule volatile organic compounds such as formaldehyde, are slowly released into the indoor environment over a long period, becoming one of the most concerning hidden sources of pollution in building decoration and home environments. While traditional physical adsorption materials can reduce formaldehyde concentration in the short term, they are prone to saturation and failure. In contrast, photocatalysis technology can decompose organic pollutants such as formaldehyde into inorganic small molecules at normal temperature and pressure, and is considered a green and efficient environmental purification pathway.

[0003] Existing photocatalytic purification materials are mostly based on semiconductors such as titanium dioxide and bismuth oxides, and are usually prepared as powder coatings or incorporated into resin matrices to form photocatalytic coatings. However, on the one hand, conventional photocatalytic coatings rely on inorganic brittle networks or highly cross-linked organic matrices to provide adhesion and durability. Under long-term light exposure, temperature and humidity cycles, and external forces, they are prone to microcracks, peeling, and even large-area flaking, lacking the ability to self-repair crack propagation and interface damage, resulting in a significantly shortened service life. On the other hand, the strong oxidizing free radicals generated during the photocatalytic reaction not only attack pollutant molecules such as formaldehyde, but also gradually damage the carbon-containing resin matrix, causing "photo-etching" phenomena such as surface chalking, whitening, and loss of gloss, leading to rapid deterioration of the coating's structure and appearance. In addition, with prolonged use, intermediate products of formaldehyde and other organic substances tend to accumulate on the catalyst surface, forming an organic pollution layer that masks active sites, causing continuous decay of photocatalytic activity or even "poisoning" failure. Existing technologies mostly rely on increasing the amount of catalyst, increasing the light intensity, or periodic wiping to delay deactivation, but it is difficult to achieve in-situ regeneration of the catalyst surface under practical application conditions. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a self-healing and regenerable photocatalytic coating for environmentally toxic substances and its preparation method. This coating uses a fluorinated polyurethane dynamic network as a matrix, introducing reversible disulfide bonds to achieve photothermally triggered microcrack self-repair and mechanical property recovery. A nitrogen-doped carbon quantum dot bismuth tungstate heterojunction and a silicon dioxide shell are composited within the matrix, and titanium carbide-based two-dimensional materials are synergistically introduced to promote efficient separation and interfacial transport of photogenerated carriers. Simultaneously, the coating surface is endowed with selective enrichment and self-cleaning capabilities, thereby enabling continuous degradation of environmentally toxic substances such as formaldehyde under illumination and maintaining long-term stable service, thus meeting the needs of actual production.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing a self-healing, regenerable photocatalytic coating for environmentally toxic substances, the method comprising:

[0007] S1, citric acid and urea are dispersed in deionized water and subjected to hydrothermal reaction to obtain N-doped carbon quantum dot powder. Bismuth pentahydrate and N-doped carbon quantum dot powder are dispersed in acetic acid aqueous solution and subjected to hydrothermal reaction to obtain heterojunction powder. The heterojunction powder is dispersed in a mixed solvent, and bisphenol A, tetraethyl orthosilicate and 3-aminopropyltriethoxysilane are added and reacted at room temperature. After centrifugation and reflux extraction, template-free heterojunction powder is obtained. The obtained template-free heterojunction powder is dispersed in anhydrous toluene and 3-propyltriethoxysilane is added and reacted to obtain carbon quantum dot heterojunction.

[0008] S2, PTMG-2000, PFPE-1500, isophorone diisocyanate and dibutyltin dilaurate are mixed and reacted to obtain NCO-terminated prepolymer, and then trimethylolpropane, chain extender solution and furfurylamine solution are added and reacted to obtain fluorinated polyurethane solution.

[0009] S3, mix Ti3AlC2 with etching solution, etch, centrifuge, wash, and sonicate to obtain Ti3C2T X Powder, Ti3C2T X The powder was dispersed in an aqueous ethanol solution, and 3-aminopropyltriethoxysilane was added and stirred to obtain functionalized Ti3C2T. X Powder, to obtain functionalized Ti3C2T X The powder was dispersed in anhydrous DMF and reacted with propyltriethoxysilane 3-isocyanate to obtain grafted Ti3C2T. X powder;

[0010] S4, a carbon quantum dot heterojunction grafted with Ti3C2T X The powder is mixed and dispersed with methyl ethyl ketone to obtain a dispersed phase. The dispersed phase, fluorinated polyurethane solution and bismaleimide are mixed to obtain a coating. The coating is sprayed onto the substrate and dried to obtain a self-healing and regenerable photocatalytic coating against environmental pollutants.

[0011] Specifically, it includes:

[0012] S1, citric acid and urea are dispersed in deionized water and subjected to hydrothermal reaction at a first temperature. After filtration, dialyzing, and freeze-drying, N-doped carbon quantum dot powder is obtained. Bismuth pentahydrate and N-doped carbon quantum dot powder are dispersed in acetic acid aqueous solution, sodium tungstate dihydrate solution is added dropwise, and the pH is adjusted to 6.8-7.2 using sodium hydroxide aqueous solution. After hydrothermal reaction at a second temperature, the powder is centrifuged, washed, and dried to obtain heterojunction powder. The heterojunction powder is dispersed in a mixed solvent, bisphenol A is added and stirred, and then tetraethyl orthosilicate and 3-aminopropyltriethoxysilane are added dropwise and reacted at room temperature. After centrifugation, the powder is transferred to acidic ethanol solution for reflux extraction. After centrifugation, washing, and drying, template-free heterojunction powder is obtained. The template-free heterojunction powder is dispersed in anhydrous toluene, 3-propyltriethoxysilane is added, a water separator is connected, and the mixture is refluxed. After filtration, washing, and drying, carbon quantum dot heterojunction is obtained.

[0013] S2, PTMG-2000, PFPE-1500, isophorone diisocyanate and dibutyltin dilaurate are mixed and reacted under a nitrogen atmosphere at a third temperature to obtain an NCO-terminated prepolymer. Trimethylolpropane is added to continue the reaction. Then, a chain extender solution is added dropwise to the reaction system to continue the reaction. The NCO absorption peak is monitored by infrared to reduce the peak intensity to 70-80% of the initial value. Then, furfurylamine solution is added and reacted at a fourth temperature until the NCO peak in the infrared is basically gone to obtain a fluorinated polyurethane solution.

[0014] S3, mix Ti3AlC2 with etching solution, etch and stir in a water bath at temperature 5, centrifuge and wash until the pH of the supernatant is greater than 6, disperse the precipitate in deionized water, sonicate under nitrogen atmosphere, centrifuge and collect the black supernatant, freeze-dry to obtain Ti3C2T X Powder, Ti3C2T X The powder was dispersed in an aqueous ethanol solution, and 3-aminopropyltriethoxysilane was added. Under a nitrogen atmosphere, the mixture was stirred at room temperature, centrifuged, washed, and dried to obtain functionalized Ti3C2T. X Powder, to obtain functionalized Ti3C2T X The powder was dispersed in anhydrous DMF and 3-propyltriethoxysilane was added. Under a nitrogen atmosphere, the reaction was stirred at a fourth temperature. After centrifugation, washing, and drying, grafted Ti3C2T was obtained. X powder;

[0015] S4, a carbon quantum dot heterojunction grafted with Ti3C2T X The powder is mixed and dispersed with methyl ethyl ketone to obtain a dispersed phase. The dispersed phase, fluorinated polyurethane solution and bismaleimide are mixed and stirred at the fifth temperature. The mixture is then ground and degassed under reduced pressure to obtain a coating. The coating is sprayed onto a substrate and dried to obtain a self-healing and regenerable photocatalytic coating against environmental pollutants.

[0016] In the heterogeneous bonding step, citric acid and urea undergo condensation, dehydration, and preliminary carbonization under hydrothermal conditions. Citric acid provides the carbon skeleton and carboxyl groups, while urea provides the nitrogen source and part of the carbon source, forming nitrogen-doped carbon quantum dots with carboxyl, hydroxyl, and nitrogen-containing groups on their surface. Bismuth nitrate partially hydrolyzes and coordinates in an aqueous acetic acid solution, forming a carbon quantum dot heterojunction with the nitrogen-doped carbon quantum dots. The conduction and valence bands of the two are located at different positions, and after forming the heterojunction, electrons and holes are spatially separated, providing a prerequisite for the subsequent generation of reactive oxygen species. Based on this, during silica coating, bisphenol template molecules and hydrolyzed silane monomers form a pre-assembled complex through hydrogen bonding and hydrophobic interactions. Tetraacetyl orthosilicate and aminopropyltriethoxysilane hydrolyze under alkaline conditions to generate silanol, which then forms a silicon-oxygen network on the surface of the carbon quantum dot bismuth tungstate particles through a condensation reaction, fixing the template molecules and photocatalytic particles together within the inorganic shell. Aminopropyltriethoxysilane introduces amino groups to the inner and outer surfaces of the shell, providing functional groups for subsequent coupling. After acidic ethanol reflux extraction, the template molecule is removed from the shell, while the shell interior retains vacancies and polar environments that match the template molecule structure, enabling selective adsorption and enrichment of structurally similar organic pollutants during subsequent service. Subsequently, a silane coupling agent with isocyanate and triethoxysilane groups is added. The isocyanate groups preferentially add to the amino groups on the shell surface to form urea bonds, while the triethoxysilane groups retain their hydrolytic condensation properties. The resulting photocatalytic particles possess pores, urea structures, and potential siloxane network formation sites on their surface. This enhances the compatibility and interfacial anchoring between the particles and the organic matrix, and allows them to participate in further siloxane crosslinking during coating curing and service.

[0017] In the polyurethane matrix construction step, polyether polyols and fluorinated polyethers undergo addition reactions with alicyclic diisocyanates in the presence of a catalyst. Hydroxyl groups form urethane bonds with isocyanate groups, generating a prepolymer with multiple flexible segments and partially free isocyanate groups. After the introduction of trimethylolpropane, the polyhydroxy monomers react with the isocyanate groups, introducing branching points into the main chain, forming a hyperbranched or dendritic polyurethane structure, and increasing potential crosslinking nodes. Subsequently, a chain extender solution is added. The chain extender contains dihydroxy compounds with disulfide structures, hydroxy monomers with maleimide rings, and dihydroxyethyl urea with urea units and hydroxyl groups. These react with the isocyanate groups on the prepolymer, introducing urethane bonds into the main chain, along with disulfide bonds, maleimide rings, and urea structures. The disulfide bonds can undergo homolytic cleavage and recombination under certain photothermal conditions. The maleimide ring serves as the diephilic structure for the subsequent Diels-Alder reaction, and the urea structure forms a physical crosslinking network with the urethane groups through multi-point hydrogen bonds. By controlling the degree of chain extension to retain some unreacted isocyanate groups in the system, an amine molecule containing a furan ring is added. The amine group reacts with the isocyanate group to form a urea structure, and the furan ring undergoes Diels-Alder ring addition with the side-chain maleimide ring, forming reversible covalent crosslinking points between the chains. The resulting fluorinated polyurethane contains disulfide bonds, Diels-Alder bonds, and a rearrangeable hydrogen bond network. When the local temperature increases or is subjected to photothermal effects, these bonds can break and reform.

[0018] In the two-dimensional carbide preparation and grafting steps, in a fluorinated acidic system, the aluminum layer of the layered titanium-aluminum carbide preferentially forms a soluble complex, retaining the layered framework composed of titanium and carbon. During etching, the titanium surface is partially oxidized and fluorinated, forming a structure with fluorine, hydroxyl, and oxygen end groups. After washing and ultrasonic treatment, the multilayered stacked framework is peeled off into single-layer or few-layer sheet structures, forming MXene nanosheets with a large specific surface area and continuous conductive pathways. Subsequently, aminopropyltriethoxysilane is added to an alcohol solution containing trace amounts of water. The silane hydrolyzes to form silanols, which condense with surface hydroxyl groups to form titanium-oxysilicon bonds on the titanium surface, introducing organopropyl and amino groups to the sheet surface. Triethoxysilane with isocyanate groups is then introduced. The isocyanate groups undergo an addition reaction with surface amino groups to form urea bonds, while the triethoxysilane groups retain their hydrolytic condensation ability. The resulting MXene nanosheets are coated with an organic-inorganic hybrid layer containing urea structures and triethoxysilane groups. This layer forms hydrogen bonds between the urea groups and the urethane and urea groups on the polyurethane chain, and covalently connects with the silica shell or substrate through silicon-oxygen bonds. This provides favorable conditions for the dispersion of the sheets in the matrix.

[0019] In the blending film-forming step, carbon quantum dot heterojunctions and surface-grafted MXene nanosheets are mixed with a fluorinated polyurethane solution containing a dynamically cross-linked structure, and a bismaleimide cross-linking agent is added. Bismaleimide can further undergo Diels-Alder cycloaddition with the incompletely reacted furan rings on the polyurethane chains, increasing the number of reversible cross-linking nodes in the network. During the coating's service life, formaldehyde molecules in the environment first reach the coating surface through diffusion. Some are adsorbed by polar groups on the polyurethane and inorganic shell surfaces, while others are enriched near the photocatalytic particles through pores. Under illumination, bismuth tungstate and nitrogen-doped carbon quantum dots absorb photons to generate electrons and holes, producing hydroxyl radicals and other reactive oxygen species, which then react with the adsorbed formaldehyde in an oxidation reaction. The presence of the silica shell makes it easier for organic intermediates to be further oxidized and desorbed locally, slowing down the formation of a stable organic coating layer on the catalyst surface, thereby reducing the surface poisoning rate. At the same time, the MXene sheets absorb some light energy and release it as heat in a non-radiative form, causing a slight increase in local temperature. Within this temperature range, the disulfide bonds, Diels-Alder bonds, and hydrogen bonds in the polyurethane network can undergo limited breakage and recombination, which can alleviate or heal microcracks caused by photo-etching or mechanical stress.

[0020] As a preferred technical solution of the present invention, in S1, the mass ratio of citric acid, urea and deionized water is (2-3):(2-3):20, for example, it can be (2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9 or 3.0):(2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9 or 3.0):20, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0021] In some alternative embodiments, the first temperature is 180-185°C, for example, it can be 180°C, 180.5°C, 181°C, 181.5°C, 182°C, 182.5°C, 183°C, 183.5°C, 184°C, 184.5°C or 185°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0022] In some optional embodiments, the hydrothermal reaction time at the first temperature is 5-6 hours, for example, 5.0 hours, 5.1 hours, 5.2 hours, 5.3 hours, 5.4 hours, 5.5 hours, 5.6 hours, 5.7 hours, 5.8 hours, 5.9 hours, or 6.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0023] In some optional embodiments, the dialysis phase is deionized water with a molecular weight cutoff of 1000 Da, and the dialysis time is 24-48 h. For example, the dialysis phase can be deionized water with a molecular weight cutoff of 1000 Da, and the dialysis time can be (24, 26.4, 28.8, 31.2, 33.6, 36, 38.4, 40.8, 43.2, 45.6 or 48) h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] In some optional embodiments, the mass ratio of bismuth nitrate pentahydrate, N-doped carbon quantum dot powder, aqueous acetic acid solution, and sodium tungstate dihydrate solution is (0.97-1):(0.05-0.07):40:(20-21), for example, it can be (0.97, 0.973, 0.976, 0.979, 0.982, 0.985, 0.988, 0.991, 0.994, 0.997, or 1.0):(0 0.05, 0.052, 0.054, 0.056, 0.058, 0.06, 0.062, 0.064, 0.066, 0.068 or 0.07): 40: (20, 20.1, 20.2, 20.3, 20.4, 20.5, 20.6, 20.7, 20.8, 20.9 or 21), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0025] In some optional embodiments, the concentration of the sodium hydroxide aqueous solution is 1M.

[0026] In some alternative embodiments, the second temperature is 160-165°C, for example, it can be 160°C, 160.5°C, 161°C, 161.5°C, 162°C, 162.5°C, 163°C, 163.5°C, 164°C, 164.5°C or 165°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0027] In some optional embodiments, the hydrothermal reaction time at the second temperature is 20-21 hours, for example, 20.0 hours, 20.1 hours, 20.2 hours, 20.3 hours, 20.4 hours, 20.5 hours, 20.6 hours, 20.7 hours, 20.8 hours, 20.9 hours, or 21.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0028] In some alternative embodiments, the third temperature is 380-420°C, for example, it can be 380°C, 384°C, 388°C, 392°C, 396°C, 400°C, 404°C, 408°C, 412°C, 416°C or 420°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0029] In some optional embodiments, the calcination time is 1.5-2.5h, for example, it can be 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, 2.0h, 2.1h, 2.2h, 2.3h, 2.4h or 2.5h, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0030] In some optional embodiments, the mass ratio of the heterojunction powder, mixed solvent, bisphenol A, tetraethyl orthosilicate, 3-aminopropyltriethoxysilane, anhydrous toluene, and 3-propyltriethoxysilane is (0.3-0.4):71:(0.04-0.06):(0.4-0.6):(0.08-0.1):50:(0.06-0.08), for example, it can be (0.3, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, or 0.4):71:(0.04, 0.042, 0.044, 0.046, 0.048, 0.05, 0.052, 0.0...). 54, 0.056, 0.058 or 0.06: (0.4, 0.42, 0.44, 0.46, 0.48, 0.5, 0.52, 0.54, 0.56, 0.58 or 0.6): (0.08, 0.082, 0.084, 0.086, 0.088, 0.09, 0.092, 0.094, 0.096, 0.098 or 0.1): 50: (0.06, 0.062, 0.064, 0.066, 0.068, 0.07, 0.072, 0.074, 0.076, 0.078 or 0.08), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0031] In some optional embodiments, the mass ratio of anhydrous ethanol, deionized water and ammonia in the mixed solvent is 50:20:1, and the mass fraction of ammonia is 25 wt.%.

[0032] In some optional embodiments, the reflux reaction time is 24-25 hours, for example, 24.0 hours, 24.1 hours, 24.2 hours, 24.3 hours, 24.4 hours, 24.5 hours, 24.6 hours, 24.7 hours, 24.8 hours, 24.9 hours, or 25.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0033] As a preferred embodiment of the present invention, in S2, the mass ratio of PTMG-2000, PFPE-1500, isophorone diisocyanate, dibutyltin dilaurate, trimethylolpropane, chain extender solution, and furfurylamine solution is (10-12):(3-4):(3.8-4):0.02:(0.2-0.3):30:(5.4-10.5), for example, it can be (10.0, 10.2, 10.4, 10.6, 10.8, 11.0, 11.2, 11.4, 11.6, 11.8, or 12.0):(3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6). 3.7, 3.8, 3.9 or 4.0: (3.8, 3.82, 3.84, 3.86, 3.88, 3.9, 3.92, 3.94, 3.96, 3.98 or 4.0): 0.02: (0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29 or 0.3): 30: (5.4, 5.91, 6.42, 6.93, 7.44, 7.95, 8.46, 8.97, 9.48, 9.99 or 10.5), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0034] In some alternative embodiments, the third temperature is 80-85°C, for example, it can be 80°C, 80.5°C, 81°C, 81.5°C, 82°C, 82.5°C, 83°C, 83.5°C, 84°C, 84.5°C or 85°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0035] In some optional embodiments, the stirring reaction time at the third temperature is 2-3 hours, for example, 2.0 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours, or 3.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0036] In some optional embodiments, the reaction time after adding trimethylolpropane is 1-2 hours, for example, 1.0 hours, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours, or 2.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0037] In some optional embodiments, the mass ratio of 2-hydroxyethyl disulfide, N-(2-hydroxyethyl)maleimide, N,N'-bis(2-hydroxyethyl)urea to butanone in the chain extender solution is 1:0.5:0.5:25.

[0038] In some optional embodiments, the continued reaction time is 3-4 hours, for example, 3.0 hours, 3.1 hours, 3.2 hours, 3.3 hours, 3.4 hours, 3.5 hours, 3.6 hours, 3.7 hours, 3.8 hours, 3.9 hours, or 4.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0039] In some optional embodiments, the mass ratio of furfurylamine to butanone in the furfurylamine solution is (0.4-0.5):(5-10), for example, it can be (0.4, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49 or 0.5):(5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5 or 10), but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0040] In some alternative embodiments, the fourth temperature is 60-65°C, for example, it can be 60°C, 60.5°C, 61°C, 61.5°C, 62°C, 62.5°C, 63°C, 63.5°C, 64°C, 64.5°C or 65°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0041] In some optional embodiments, the solid content of the fluorinated polyurethane solution is 40-50 wt.%, for example, it can be 40 wt.%, 41 wt.%, 42 wt.%, 43 wt.%, 44 wt.%, 45 wt.%, 46 wt.%, 47 wt.%, 48 wt.%, 49 wt.%, or 50 wt.%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0042] As a preferred technical solution of the present invention, in S3, the mass ratio of Ti3AlC2, etching solution and deionized water is (1-2):21:50, for example, it can be (1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2.0):21:50, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0043] In some optional embodiments, the mass ratio of hydrochloric acid solution to lithium fluoride in the etching solution is 20:1, and the concentration of the hydrochloric acid solution is 6M.

[0044] In some alternative embodiments, the fifth temperature is 35-40°C, for example, it can be 35°C, 35.5°C, 36°C, 36.5°C, 37°C, 37.5°C, 38°C, 38.5°C, 39°C, 39.5°C or 40°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0045] In some alternative embodiments, the stirring etching time is 24-25 hours, for example, 24.0 hours, 24.1 hours, 24.2 hours, 24.3 hours, 24.4 hours, 24.5 hours, 24.6 hours, 24.7 hours, 24.8 hours, 24.9 hours, or 25.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0046] In some alternative embodiments, the ultrasound duration is 1-2 hours, for example, it can be 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2.0h, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0047] In some optional embodiments, the Ti3C2T X The mass ratio of powder, aqueous ethanol solution, 3-aminopropyltriethoxysilane, anhydrous DMF to 3-isocyanopropyltriethoxysilane is (0.2-0.3):40:(0.1-0.2):30:0.05, for example, (0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29 or 0.3):40:(0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19 or 0.2):30:0.05, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0048] In some optional embodiments, the Ti3C2TX The powder refers to Ti3C2-type MXene material obtained by etching, washing and stripping MAX phase titanium aluminum carbide Ti3AlC2. T is an end group located on the surface of Ti3C2 framework, which is one or more of -F, -OH and -O. The subscript X indicates the average number of end groups T in each Ti3C2 structural unit based on the Ti3C2 framework. This average number satisfies 0 < X ​​≤ 2.

[0049] In some optional embodiments, the mass ratio of anhydrous ethanol to deionized water in the aqueous ethanol solution is 39:1.

[0050] In some optional embodiments, the stirring time at room temperature is 24-25 hours, for example, 24.0 hours, 24.1 hours, 24.2 hours, 24.3 hours, 24.4 hours, 24.5 hours, 24.6 hours, 24.7 hours, 24.8 hours, 24.9 hours, or 25.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0051] In some alternative embodiments, the fourth temperature is 60-65°C, for example, it can be 60°C, 60.5°C, 61°C, 61.5°C, 62°C, 62.5°C, 63°C, 63.5°C, 64°C, 64.5°C or 65°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0052] In some optional embodiments, the stirring reaction time at the fourth temperature is 12-13 hours, for example, 12.0 hours, 12.1 hours, 12.2 hours, 12.3 hours, 12.4 hours, 12.5 hours, 12.6 hours, 12.7 hours, 12.8 hours, 12.9 hours, or 13.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0053] As a preferred embodiment of the present invention, in S4, the carbon quantum dot heterojunction and the grafted Ti3C2T XThe mass ratio of powder, methyl ethyl ketone (MEK), fluorinated polyurethane solution, and bismaleimide is (0.6-0.7):(0.05-0.07):10:(25-30):(0.2-0.5), for example, it can be (0.6, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, or 0.7):(0.05, 0.052, 0.054, 0.056, 0.058, 0.06, 0. 0.062, 0.064, 0.066, 0.068 or 0.07): 10: (25, 25.5, 26, 26.5, 27, 27.5, 28, 28.5, 29, 29.5 or 30): (0.2, 0.23, 0.26, 0.29, 0.32, 0.35, 0.38, 0.41, 0.44, 0.47 or 0.5), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0054] In some optional embodiments, the drying process specifically includes: allowing the coating to stand at room temperature for 1-2 hours to level, then vacuum drying at 60-65°C for 12-13 hours, followed by holding at 80-85°C for 2-3 hours, and finally cooling to room temperature. For example, it could be: allowing the coating to stand at room temperature for (1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2.0) hours to level, then vacuum drying at (60, 60.5, 61, 61.5, 62, 62.5, 63, 63.5, 64, 64.5, or 65)°C for (12.0, 12.1, 12.2, 12.3, 12.4, 12.5, 12.6, 12.7) hours. 12.8, 12.9 or 13.0) h, then keep warm at (80, 80.5, 81, 81.5, 82, 82.5, 83, 83.5, 84, 84.5 or 85) °C for (2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9 or 3.0) h, and cool to room temperature, but not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0055] In some optional embodiments, the dry film thickness of the self-healing and regenerable photocatalytic coating against environmental toxins is 30-50 μm, for example, it can be 30 μm, 32 μm, 34 μm, 36 μm, 38 μm, 40 μm, 42 μm, 44 μm, 46 μm, 48 μm or 50 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0056] Secondly, the present invention provides a self-healing and regenerable photocatalytic coating for environmental toxicants prepared by the preparation method described in the first aspect.

[0057] Compared with existing technologies, the beneficial effects of this invention are as follows: The coating of this invention uses fluorinated polyurethane as a matrix, introduces carbon quantum dot bismuth tungstate heterostructures and surface-modified titanium carbide-based two-dimensional materials, enabling continuous catalytic degradation of volatile organic compounds such as formaldehyde in the air under light irradiation; the silica shell endows the coating with selective enrichment capabilities for target pollutants and slows down the accumulation of organic intermediates on the catalyst surface, reducing the common poisoning and deactivation problems of photocatalytic coatings; the fluorinated polyurethane soft segments, inorganic shell, and photocatalytic unit work synergistically to decompose attached organic stains and formaldehyde polymers during photocatalysis, maintaining a clean and smooth surface, and weakening the effect of active free radicals on volatile organic compounds. The photo-etching effect on the substrate enhances weather resistance and appearance retention. By introducing disulfide bonds and multi-point hydrogen bonds into the polyurethane, the coating can undergo chain segment rearrangement and cross-linking reconstruction under photothermal excitation, achieving in-situ self-repair of microcracks and minor photo-etching damage, and maintaining effective exposure and adhesion of photocatalytic components. The composite nitrogen-doped carbon quantum dot bismuth tungstate heterojunction and silicon dioxide shell in the substrate, along with the synergistic introduction of titanium carbide-based two-dimensional materials, promotes efficient separation and interfacial transport of photogenerated carriers, while endowing the coating surface with selective enrichment and self-cleaning capabilities. This significantly improves the overall durability and application value of self-cleaning functional coatings in indoor air purification and building decoration. Detailed Implementation

[0058] The technical solution of the present invention will be described in detail below with reference to specific embodiments. The embodiments described herein are specific implementations of the present invention and are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be construed as limiting the implementation of the present invention or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in the claims and the specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0059] The chemical reagents used in the embodiments and comparative examples of this invention are all commercially available products and have not undergone any further purification treatment.

[0060] Example 1

[0061] This embodiment provides a self-healing, regenerable photocatalytic coating for environmentally toxic substances and its preparation method. The preparation method specifically includes the following steps:

[0062] S1, 2g of citric acid and 3g of urea were dispersed in 20g of deionized water and hydrothermally reacted at 180℃ for 6h. The mixture was then filtered and dialyzed, with deionized water as the external phase. The molecular weight cutoff was 1000Da, and the dialyzing time was 48h, during which the deionized water was replaced every 8h. The resulting N-doped carbon quantum dot powder was freeze-dried. 0.97g of bismuth nitrate pentahydrate and 0.07g of N-doped carbon quantum dot powder were dispersed in 40g of a 13wt.% acetic acid aqueous solution, and 20g of a 13wt.% acetic acid aqueous solution was added dropwise. A 2 wt.% sodium tungstate dihydrate solution was prepared, and the pH was adjusted to 7.2 using 1M sodium hydroxide aqueous solution. The mixture was then subjected to a hydrothermal reaction at 160℃ for 21 h. After centrifugation, washing, and drying, a heterojunction powder was obtained. 0.4 g of the heterojunction powder was dispersed in 71 g of a mixed solvent, wherein the mass ratio of anhydrous ethanol, deionized water, and ammonia in the mixed solvent was 50:20:1, and the mass fraction of ammonia was 25 wt.%. 0.04 g of bisphenol A was added and stirred for 2 h. Then, 0.4 g of tetraethyl orthosilicate and 0.1 g of... 3-Aminopropyltriethoxysilane was reacted at room temperature for 8 h, centrifuged, and then refluxed in an acidic ethanol solution at pH 3 for 12 h. After centrifugation, washing, and drying, template-free heterojunction powder was obtained. The template-free heterojunction powder was dispersed in 50.0 g of anhydrous toluene, and 0.06 g of 3-propyltriethoxysilane was added. A water separator was connected, and the mixture was refluxed for 25 h. After filtration, washing, and drying, carbon quantum dot heterojunctions were obtained.

[0063] S2, 12g PTMG-2000, 3g PFPE-1500, 4g of isophorone diisocyanate, and 0.02g of dibutyltin dilaurate were mixed and reacted at 85°C for 2 hours under a nitrogen atmosphere to obtain an NCO-terminated prepolymer. 0.3g of trimethylolpropane was added, and the reaction continued for 1 hour. Then, 30g of a chain extender solution was added dropwise to the reaction system, and the reaction continued for 4 hours. The mass ratio of 2-hydroxyethyl disulfide, N-(2-hydroxyethyl)maleimide, N,N'-bis(2-hydroxyethyl)urea, and butanone in the chain extender solution was 1:0.5:0.5:25. The NCO absorption peak was monitored by infrared spectroscopy, and the peak intensity was reduced to 70% of the initial value. Then, 10.5g of furfurylamine solution was added, with a furfurylamine to butanone mass ratio of 0.5:10. The reaction was carried out at 65°C until the NCO peak in the infrared spectroscopy essentially disappeared, yielding a fluorinated polyurethane solution with a solid content of 40 wt.%.

[0064] S3, 2g of Ti3AlC2 was mixed with 21g of etching solution, wherein the mass ratio of hydrochloric acid solution to lithium fluoride in the etching solution was 20:1, and the concentration of hydrochloric acid solution was 6M. The mixture was etched in a water bath at 35℃ with stirring for 25h. After centrifugation and washing until the pH of the supernatant was greater than 6, the precipitate was dispersed in 60g of deionized water, sonicated under nitrogen atmosphere for 1h, centrifuged, and the black supernatant was collected and freeze-dried to obtain Ti3C2T. X Powder, the Ti3C2TX The powder refers to Ti3C2-like MXene material obtained by etching, washing, and stripping MAX phase titanium aluminum carbide Ti3AlC2. Here, T represents an end group located on the surface of the Ti3C2 framework, which is one or more of -F, -OH, and -O. The subscript X indicates the average number of end groups T in each Ti3C2 structural unit based on the Ti3C2 framework, where the average number satisfies 0 < X ​​≤ 2. 0.3g of Ti3C2T X The powder was dispersed in 40g of ethanol aqueous solution, and 0.1g of 3-aminopropyltriethoxysilane was added. The mixture was stirred at room temperature for 25h under a nitrogen atmosphere, centrifuged, washed, and dried to obtain functionalized Ti3C2T. X Powder, to obtain functionalized Ti3C2T X The powder was dispersed in 30g of anhydrous DMF and 0.05g of propyltriethoxysilane 3-isocyanate was added. The mixture was stirred at 65℃ for 12h under a nitrogen atmosphere. After centrifugation, washing, and drying, grafted Ti3C2T was obtained. X powder;

[0065] S4, 0.7g carbon quantum dot heterojunction, 0.05g grafted Ti3C2T X The powder was mixed and dispersed with 10g of butanone to obtain a dispersed phase. The dispersed phase, 30g of fluorinated polyurethane solution and 0.2g of bismaleimide were mixed and stirred at 40°C, ground and degassed under reduced pressure to obtain a coating. The coating was sprayed onto a substrate and dried. The drying process specifically included: leveling by standing at room temperature for 1 hour after spraying, vacuum drying at 65°C for 12 hours, then holding at 80°C for 3 hours, and cooling to room temperature to obtain a self-healing and regenerable photocatalytic coating against environmental pollutants.

[0066] Example 2

[0067] This embodiment provides a self-healing, regenerable photocatalytic coating for environmentally toxic substances and its preparation method. The preparation method specifically includes the following steps:

[0068] S1, 3g of citric acid and 2g of urea were dispersed in 20g of deionized water and hydrothermally reacted at 185℃ for 5h. The mixture was then filtered and dialyzed, with deionized water as the external phase. The molecular weight cutoff was 1000Da, and the dialyzing time was 48h, during which the deionized water was replaced every 8h. The resulting N-doped carbon quantum dot powder was freeze-dried. 1g of bismuth nitrate pentahydrate and 0.05g of N-doped carbon quantum dot powder were dispersed in 40g of a 15wt.% acetic acid aqueous solution. 21g of a 1% acetic acid aqueous solution was added dropwise. A 0.5 wt.% sodium tungstate dihydrate solution was prepared, and the pH was adjusted to 6.8 using a 1M sodium hydroxide aqueous solution. The mixture was then subjected to a hydrothermal reaction at 165℃ for 20 h. After centrifugation, washing, and drying, a heterojunction powder was obtained. 0.3 g of the heterojunction powder was dispersed in 71 g of a mixed solvent, wherein the mass ratio of anhydrous ethanol, deionized water, and ammonia was 50:20:1, and the ammonia concentration was 25 wt.%. 0.06 g of bisphenol A was added and stirred for 1 h. Then, 0.6 g of tetraethyl orthosilicate and 0.08 g of... 3-Aminopropyltriethoxysilane was reacted at room temperature for 9 h, centrifuged, and then refluxed in an acidic ethanol solution at pH 2 for 13 h. After centrifugation, washing, and drying, template-free heterojunction powder was obtained. The template-free heterojunction powder was dispersed in 50.0 g of anhydrous toluene, and 0.08 g of 3-propyltriethoxysilane was added. A water separator was connected, and the mixture was refluxed for 24 h. After filtration, washing, and drying, carbon quantum dot heterojunctions were obtained.

[0069] S2, add 10g PTMG-2000 and 4g PFPE-1500, 3.8g of isophorone diisocyanate, and 0.02g of dibutyltin dilaurate were mixed and reacted at 80℃ for 3 hours under a nitrogen atmosphere to obtain an NCO-terminated prepolymer. 0.2g of trimethylolpropane was added, and the reaction continued for 2 hours. Then, 30g of a chain extender solution was added dropwise to the reaction system, and the reaction continued for another 3 hours. The mass ratio of 2-hydroxyethyl disulfide, N-(2-hydroxyethyl)maleimide, N,N'-bis(2-hydroxyethyl)urea, and butanone in the chain extender solution was 1:0.5:0.5:25. The NCO absorption peak was monitored by infrared spectroscopy, and the peak intensity was reduced to 80% of the initial value. Then, 5.4g of furfurylamine solution was added, with a furfurylamine to butanone mass ratio of 0.4:5. The reaction was carried out at 60℃ until the NCO peak in the infrared spectroscopy essentially disappeared, yielding a fluorinated polyurethane solution with a solid content of 50 wt.%.

[0070] S3, 1g of Ti3AlC2 was mixed with 21g of etching solution, wherein the mass ratio of hydrochloric acid solution to lithium fluoride in the etching solution was 20:1, and the concentration of hydrochloric acid solution was 6M. The mixture was etched in a water bath at 40℃ with stirring for 24h. After centrifugation and washing until the pH of the supernatant was greater than 6, the precipitate was dispersed in 50g of deionized water, sonicated under nitrogen atmosphere for 2h, centrifuged, and the black supernatant was collected and freeze-dried to obtain Ti3C2T. X Powder, the Ti3C2TX The powder refers to Ti3C2-like MXene material obtained by etching, washing, and exfoliation of MAX phase titanium aluminum carbide Ti3AlC2. Here, T represents an end group located on the surface of the Ti3C2 framework, which is one or more of -F, -OH, and -O. The subscript X indicates the average number of end groups T in each Ti3C2 structural unit based on the Ti3C2 framework, where the average number satisfies 0 < X ​​≤ 2. 0.2g of Ti3C2T... X The powder was dispersed in 40g of ethanol aqueous solution, and 0.2g of 3-aminopropyltriethoxysilane was added. The mixture was stirred at room temperature for 24h under a nitrogen atmosphere, centrifuged, washed, and dried to obtain functionalized Ti3C2T. X Powder, to obtain functionalized Ti3C2T X The powder was dispersed in 30g of anhydrous DMF and 0.05g of propyltriethoxysilane 3-isocyanate was added. The mixture was stirred at 60℃ for 13h under a nitrogen atmosphere. After centrifugation, washing, and drying, grafted Ti3C2T was obtained. X powder;

[0071] S4, combining 0.6g of carbon quantum dot heterojunction and 0.07g of grafted Ti3C2T X The powder was mixed and dispersed with 10g of butanone to obtain a dispersed phase. The dispersed phase, 25g of fluorinated polyurethane solution and 0.5g of bismaleimide were mixed and stirred at 35°C, ground and degassed under reduced pressure to obtain a coating. The coating was sprayed onto a substrate and dried. The drying process specifically included: leveling by standing at room temperature for 2 hours after spraying, vacuum drying at 60°C for 13 hours, then holding at 85°C for 2 hours, and cooling to room temperature to obtain a self-healing and regenerable photocatalytic coating against environmental pollutants.

[0072] Example 3

[0073] This embodiment provides a self-healing, regenerable photocatalytic coating for environmentally toxic substances and its preparation method. The preparation method specifically includes the following steps:

[0074] S1, 2.5g of citric acid and 2.5g of urea were dispersed in 20g of deionized water and hydrothermally reacted at 182℃ for 5.5h. The mixture was then filtered and dialyzed, with deionized water as the external phase. The molecular weight cutoff was 1000Da, and the dialysis time was 48h, during which the deionized water was replaced every 8h. The resulting N-doped carbon quantum dot powder was freeze-dried. 0.98g of bismuth nitrate pentahydrate and 0.06g of... Nitrogen-doped carbon quantum dot powder was dispersed in 40g of 14wt.% acetic acid aqueous solution, and 20.5g of 1.8wt.% sodium tungstate dihydrate solution was added dropwise. The pH was adjusted to 7.0 using 1M sodium hydroxide aqueous solution. The mixture was then subjected to a hydrothermal reaction at 162℃ for 20.5h. After centrifugation, washing, and drying, heterojunction powder was obtained. 0.35g of the heterojunction powder was dispersed in 71g of a mixed solvent, wherein the mass ratio of anhydrous ethanol, deionized water, and ammonia was 50:20:1, and the ammonia content was 25wt.%. 0.05g of bisphenol A was added and stirred for 1.5h, followed by the dropwise addition of 0.5g of tetraethyl orthosilicate and 0.09g of... 3-Aminopropyltriethoxysilane was reacted at room temperature for 8.5 h, centrifuged, and then refluxed in an acidic ethanol solution at pH 2.5 for 12.5 h. After centrifugation, washing, and drying, template-free heterojunction powder was obtained. The template-free heterojunction powder was dispersed in 50.0 g of anhydrous toluene, and 0.07 g of 3-propyltriethoxysilane was added. A water separator was connected, and the mixture was refluxed for 24.5 h. After filtration, washing, and drying, carbon quantum dot heterojunctions were obtained.

[0075] S2, containing 11g PTMG-2000 and 3.5g PFPE-1500, 3.9g of isophorone diisocyanate, and 0.02g of dibutyltin dilaurate were mixed and reacted at 82℃ for 2.5h under a nitrogen atmosphere to obtain an NCO-terminated prepolymer. 0.25g of trimethylolpropane was added, and the reaction continued for another 1.5h. Then, 30g of a chain extender solution was added dropwise to the reaction system, and the reaction continued for another 3.5h. The mass ratio of 2-hydroxyethyl disulfide, N-(2-hydroxyethyl)maleimide, N,N'-bis(2-hydroxyethyl)urea, and butanone in the chain extender solution was 1:0.5:0.5:25. The NCO absorption peak was monitored by infrared spectroscopy, and the peak intensity was reduced to 75% of the initial value. Then, 8g of furfurylamine solution was added, with a furfurylamine to butanone mass ratio of 0.45:8. The reaction was carried out at 62℃ until the NCO peak in the infrared spectroscopy essentially disappeared, yielding a fluorinated polyurethane solution with a solid content of 45wt.%.

[0076] S3, 1.5g Ti3AlC2 was mixed with 21g etching solution, wherein the mass ratio of hydrochloric acid solution to lithium fluoride in the etching solution was 20:1, and the concentration of hydrochloric acid solution was 6M. The mixture was etched in a water bath at 38℃ with stirring for 24.5h. After centrifugation and washing until the pH of the supernatant was greater than 6, the precipitate was dispersed in 55g deionized water, sonicated under nitrogen atmosphere for 1.5h, centrifuged, and the black supernatant was collected and freeze-dried to obtain Ti3C2T. X Powder, the Ti3C2T X The powder refers to Ti3C2-like MXene material obtained by etching, washing, and stripping MAX phase titanium aluminum carbide Ti3AlC2. Here, T represents an end group located on the surface of the Ti3C2 framework, which is one or more of -F, -OH, and -O. The subscript X indicates the average number of end groups T in each Ti3C2 structural unit based on the Ti3C2 framework, where the average number satisfies 0 < X ​​≤ 2. 0.25g of Ti3C2T X The powder was dispersed in 40g of ethanol aqueous solution, and 0.15g of 3-aminopropyltriethoxysilane was added. The mixture was stirred at room temperature under a nitrogen atmosphere for 24.5h, centrifuged, washed, and dried to obtain functionalized Ti3C2T. X Powder, to obtain functionalized Ti3C2T X The powder was dispersed in 30g of anhydrous DMF and 0.05g of propyltriethoxysilane 3-isocyanate was added. The mixture was stirred at 62℃ for 12.5h under a nitrogen atmosphere. After centrifugation, washing, and drying, grafted Ti3C2T was obtained. X powder;

[0077] S4, 0.65g carbon quantum dot heterojunction, 0.06g grafted Ti3C2T X The powder was mixed and dispersed with 10g of butanone to obtain a dispersed phase. The dispersed phase, 28g of fluorinated polyurethane solution and 0.3g of bismaleimide were mixed and stirred at 38°C, ground and degassed under reduced pressure to obtain a coating. The coating was sprayed onto a substrate and dried. The drying process specifically included: leveling by standing at room temperature for 1.5h after spraying, vacuum drying at 62°C for 12.5h, then holding at 82°C for 2.5h, and cooling to room temperature to obtain a self-healing and regenerable photocatalytic coating against environmental pollutants.

[0078] Example 4

[0079] This embodiment provides a self-healing, regenerable photocatalytic coating for environmentally toxic substances and its preparation method. The preparation method specifically includes the following steps:

[0080] S1, 2.2g of citric acid and 2.8g of urea were dispersed in 20g of deionized water and hydrothermally reacted at 184℃ for 5.2h. The mixture was then filtered and dialyzed, with deionized water as the external phase. The molecular weight cutoff was 1000Da, and the dialysis time was 48h, during which the deionized water was replaced every 8h. The resulting N-doped carbon quantum dot powder was freeze-dried. 0.98g of bismuth nitrate pentahydrate and 0.06g of... Nitrogen-doped carbon quantum dot powder was dispersed in 40g of 14.5wt.% acetic acid aqueous solution, and 20.8g of 1.6wt.% sodium tungstate dihydrate solution was added dropwise. The pH was adjusted to 7.1 using 1M sodium hydroxide aqueous solution. The mixture was then subjected to a hydrothermal reaction at 164℃ for 20.2h. After centrifugation, washing, and drying, heterojunction powder was obtained. 0.38g of the heterojunction powder was dispersed in 71g of a mixed solvent, wherein the mass ratio of anhydrous ethanol, deionized water, and ammonia was 50:20:1, and the ammonia content was 25wt.%. 0.05g of bisphenol A was added and stirred for 1.2h, followed by the dropwise addition of 0.55g of tetraethyl orthosilicate and 0.085g of... 3-Aminopropyltriethoxysilane was reacted at room temperature for 8.2 h, centrifuged, and then refluxed in an acidic ethanol solution with pH 2.2 for 12.8 h. After centrifugation, washing, and drying, template-free heterojunction powder was obtained. The template-free heterojunction powder was dispersed in 50.0 g of anhydrous toluene, and 0.075 g of 3-propyltriethoxysilane was added. A water separator was connected, and the mixture was refluxed for 24.2 h. After filtration, washing, and drying, carbon quantum dot heterojunctions were obtained.

[0081] S2, containing 11.5g PTMG-2000 and 3.2g PFPE-1500, 3.95g of isophorone diisocyanate, and 0.02g of dibutyltin dilaurate were mixed and reacted under a nitrogen atmosphere at 84℃ for 2.8h with stirring to obtain an NCO-terminated prepolymer. 0.28g of trimethylolpropane was added, and the reaction continued for another 1.8h. Then, 30g of a chain extender solution was added dropwise to the reaction system, and the reaction continued for another 3.2h. The mass ratio of 2-hydroxyethyl disulfide, N-(2-hydroxyethyl)maleimide, N,N'-bis(2-hydroxyethyl)urea, and butanone in the chain extender solution was 1:0.5:0.5:25. The NCO absorption peak was monitored by infrared spectroscopy, and the peak intensity was reduced to 72% of the initial value. Then, 8.5g of furfurylamine solution was added, with a furfurylamine to butanone mass ratio of 0.48:8.5. The reaction was carried out at 64℃ until the NCO peak in the infrared spectroscopy essentially disappeared, yielding a fluorinated polyurethane solution with a solid content of 48wt.%.

[0082] S3, 1.8g of Ti3AlC2 was mixed with 21g of etching solution, wherein the mass ratio of hydrochloric acid solution to lithium fluoride in the etching solution was 20:1, and the concentration of hydrochloric acid solution was 6M. The mixture was etched in a water bath at 39℃ with stirring for 24.8h. After centrifugation and washing until the pH of the supernatant was greater than 6, the precipitate was dispersed in 58g of deionized water, sonicated under nitrogen atmosphere for 1.8h, centrifuged, and the black supernatant was collected and freeze-dried to obtain Ti3C2T. X Powder, the Ti3C2T X The powder refers to Ti3C2-like MXene material obtained by etching, washing, and exfoliation of MAX phase titanium aluminum carbide Ti3AlC2. Here, T represents an end group located on the surface of the Ti3C2 framework, which is one or more of -F, -OH, and -O. The subscript X indicates the average number of end groups T in each Ti3C2 structural unit based on the Ti3C2 framework, where the average number satisfies 0 < X ​​≤ 2. 0.28g of Ti3C2T X The powder was dispersed in 40g of ethanol aqueous solution, and 0.18g of 3-aminopropyltriethoxysilane was added. The mixture was stirred at room temperature for 24.2h under a nitrogen atmosphere, centrifuged, washed, and dried to obtain functionalized Ti3C2T. X Powder, to obtain functionalized Ti3C2T X The powder was dispersed in 30g of anhydrous DMF and 0.05g of propyltriethoxysilane 3-isocyanate was added. The mixture was stirred at 64℃ for 12.8h under a nitrogen atmosphere. After centrifugation, washing, and drying, grafted Ti3C2T was obtained. X powder;

[0083] S4, 0.68g carbon quantum dot heterojunction, 0.065g grafted Ti3C2T X The powder was mixed and dispersed with 10g of butanone to obtain a dispersed phase. The dispersed phase, 29g of fluorinated polyurethane solution and 0.4g of bismaleimide were mixed and stirred at 39°C, ground and degassed under reduced pressure to obtain a coating. The coating was sprayed onto a substrate and dried. The drying process specifically included: leveling by standing at room temperature for 1.8h after spraying, vacuum drying at 64°C for 12.8h, then holding at 84°C for 2.2h, and cooling to room temperature to obtain a self-healing and regenerable photocatalytic coating against environmental pollutants.

[0084] Comparative Example 1

[0085] This comparative example provides a self-healing and regenerable photocatalytic coating for environmentally toxic substances and its preparation method. The difference between this example and Example 1 is that in S1, after dispersing the heterojunction powder in a mixed solvent, bisphenol A is not added, and tetraethyl orthosilicate and 3-aminopropyltriethoxysilane are directly added dropwise. Other process parameters and operating conditions are exactly the same as in Example 1.

[0086] Comparative Example 2

[0087] This comparative example provides a self-healing, regenerable photocatalytic coating for environmentally toxic substances and its preparation method. The difference between this example and Example 1 is that the 2-hydroxyethyl disulfide in the chain extender solution in S2 is replaced with an equimolar amount of 1,4-butanediol. Other process parameters and operating conditions are exactly the same as in Example 1.

[0088] Comparative Example 3

[0089] This comparative example provides a self-healing, regenerable photocatalytic coating for environmentally toxic substances and its preparation method. The difference between this and Example 1 is that Ti3C2T is grafted into S4. X The powder mass was 0, and other process parameters and operating conditions were exactly the same as in Example 1.

[0090] The test method for formaldehyde purification performance is GB / T 23761-2020. The method for the self-cleaning effect of the coating surface is ISO27448. The self-healing test method is as follows: the self-healing regenerable photocatalytic coating is placed in a laboratory environment with a temperature of 23±2℃ and a relative humidity of 50±5% for 24 hours. A scratching device with a fixed load is used to stabilize the initial scratch depth of the coating at 20±5μm. At least 3 non-intersecting scratches with a spacing greater than 5mm are made on each sample. After scratching, the sample is placed in the dark at room temperature for 30 minutes to allow the instantaneous stress to be basically released. Then, at least one representative scratch is selected on each sample using an optical microscope or a three-dimensional profilometer. The average depth of the scratch is measured at no less than 5 cross-sectional positions along the scratch length and recorded as the initial scratch depth. The sample was placed in a constant temperature light test chamber with a visible light source. The temperature was set to 40±2℃ and the relative humidity to 50±10%. The light source was a simulated sunlight or cool white LED. The illuminance at the sample plane was adjusted to 10000±1000 lx. The sample was continuously irradiated for 24 hours. The scratch depth was measured again under the same position and conditions as the initial measurement. The change in scratch depth relative to the initial value was compared. The scratch depth recovery rate was used as the characterization index of self-repair efficiency.

[0091] The test results are shown in Table 1.

[0092] Table 1. Test results of self-healing and regenerable photocatalytic coatings in Examples 1-4 and Comparative Examples 1-3

[0093]

[0094] As shown in Table 1, compared to Example 1, Comparative Example 1 showed a decrease in formaldehyde purification rate, stain removal rate, and scratch depth recovery rate; Comparative Example 2 also showed a decrease in formaldehyde purification rate, stain removal rate, and scratch depth recovery rate. This is because Comparative Example 1 did not include bisphenol A, resulting in a lack of cavities and polar environments within the shell layer, leading to a lack of selective enrichment and directional desorption of formaldehyde and intermediate products. This makes it easier for an organic coating layer to form on the surface, masking the active sites and thus reducing the formaldehyde purification rate and stain removal rate. Comparative Example 2 only used diol to replace dihydroxyethyl disulfide, eliminating exchangeable disulfide bonds in the polyurethane network and reducing self-healing performance. Comparative Example 3 did not introduce Ti3C2T. X The conductive photothermal unit and photocatalytic system lack two-dimensional electron transport channels and local photothermal enhancement effects, resulting in an increased electron-hole recombination rate and a decrease in formaldehyde purification rate. Due to insufficient local photothermal activity, the activation level of the dynamic network is reduced, and the scratch depth recovery rate is also reduced.

[0095] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a self-healing, regenerable photocatalytic coating for environmentally toxic substances, characterized in that, The preparation method includes: S1, citric acid and urea are dispersed in deionized water and hydrothermally reacted at a first temperature to obtain N-doped carbon quantum dot powder. Bismuth pentahydrate and N-doped carbon quantum dot powder are dispersed in an aqueous acetic acid solution, and sodium tungstate dihydrate solution is added dropwise. Hydrothermal reaction is carried out at a second temperature to obtain heterojunction powder. The heterojunction powder is dispersed in a mixed solvent, and bisphenol A, tetraethyl orthosilicate and 3-aminopropyltriethoxysilane are added and reacted at room temperature. After centrifugation and reflux extraction, template-free heterojunction powder is obtained. The obtained template-free heterojunction powder is dispersed in anhydrous toluene and 3-propyltriethoxysilane is added and reacted to obtain carbon quantum dot heterojunction. S2, PTMG-2000, PFPE-1500, isophorone diisocyanate and dibutyltin dilaurate are mixed and reacted to obtain NCO-terminated prepolymer, and then trimethylolpropane, chain extender solution and furfurylamine solution are added and reacted to obtain fluorinated polyurethane solution. S3, Ti3AlC2 is mixed with etching solution, etching, centrifugation, washing, ultrasonic, Ti3C2T X powder is obtained X powder is dispersed in aqueous ethanol solution, 3-aminopropyl triethoxysilane is added and stirred to obtain functionalized Ti3C2T X powder is obtained X powder is dispersed in anhydrous DMF and reacted with 3-isocyanate propyl triethoxysilane to obtain grafted Ti3C2T X powder S4, a carbon quantum dot heterojunction grafted with Ti3C2T X The powder is mixed and dispersed with methyl ethyl ketone to obtain a dispersed phase. The dispersed phase, fluorinated polyurethane solution and bismaleimide are mixed to obtain a coating. The coating is sprayed onto the substrate and dried to obtain a self-healing and regenerable photocatalytic coating against environmental pollutants. The mass ratio of citric acid, urea and deionized water is (2-3):(2-3):20; The mass ratio of bismuth nitrate pentahydrate, N-doped carbon quantum dot powder, aqueous acetic acid solution, and sodium tungstate dihydrate solution is (0.97-1):(0.05-0.07):40:(20-21). The first temperature is 180-185℃; The second temperature is 160-165℃; The mass ratio of the heterojunction powder, mixed solvent, bisphenol A, tetraethyl orthosilicate, 3-aminopropyltriethoxysilane, anhydrous toluene, and 3-propyltriethoxysilane is (0.3-0.4):71:(0.04-0.06):(0.4-0.6):(0.08-0.1):50:(0.06-0.08). The mass ratio of PTMG-2000, PFPE-1500, isophorone diisocyanate, dibutyltin dilaurate, trimethylolpropane, chain extender solution to furfurylamine solution is (10-12):(3-4):(3.8-4):0.02:(0.2-0.3):30:(5.4-10.5); The Ti3C2T X The mass ratio of powder, aqueous ethanol solution, 3-aminopropyltriethoxysilane, anhydrous DMF and 3-isocyanatepropyltriethoxysilane is (0.2-0.3):40:(0.1-0.2):30:0.05; The carbon quantum dot heterojunction, grafted Ti3C2T X The mass ratio of powder, methyl ethyl ketone, fluorinated polyurethane solution and bismaleimide is (0.6-0.7):(0.05-0.07):10:(25-30):(0.2-0.5).

2. The method for preparing a self-healing, regenerable photocatalytic coating for environmentally toxic substances according to claim 1, characterized in that, In S1: The mass ratio of anhydrous ethanol, deionized water and ammonia in the mixed solvent is 50:20:1, and the mass fraction of ammonia is 25 wt.%.

3. The method for preparing a self-healing, regenerable photocatalytic coating for environmentally toxic substances according to claim 1, characterized in that, In S2: The mass ratio of 2-hydroxyethyl disulfide, N-(2-hydroxyethyl)maleimide, N,N'-bis(2-hydroxyethyl)urea to butanone in the chain extender solution is 1:0.5:0.5:

25. The mass ratio of furfurylamine to butanone in the furfurylamine solution is (0.4-0.5):(5-10).

4. The method for preparing a self-healing, regenerable photocatalytic coating for environmentally toxic substances according to claim 1, characterized in that, In S3: The mass ratio of Ti3AlC2, etching solution and deionized water is (1-2):21:50; The etching solution contains hydrochloric acid solution in a mass ratio of 20:1 to lithium fluoride, and the concentration of the hydrochloric acid solution is 6M.

5. The method for preparing a self-healing, regenerable photocatalytic coating for environmentally toxic substances according to claim 1, characterized in that, In S3: The Ti3C2T X The powder refers to Ti3C2-type MXene material obtained by etching, washing and stripping MAX phase titanium aluminum carbide Ti3AlC2. T is an end group located on the surface of Ti3C2 framework, which is one or more of -F, -OH and -O. The subscript X indicates the average number of end groups T in each Ti3C2 structural unit based on the Ti3C2 framework. This average number satisfies 0 < X ​​≤ 2.

6. The method for preparing a self-healing, regenerable photocatalytic coating for environmentally toxic substances according to claim 1, characterized in that, In S4: The drying process specifically includes: allowing the coating to stand at room temperature for 1-2 hours to level, then vacuum drying at 60-65℃ for 12-13 hours, followed by heat treatment at 80-85℃ for 2-3 hours, and finally cooling to room temperature.

7. The self-healing, regenerable photocatalytic coating against environmental pollutants obtained by the preparation method according to any one of claims 1-6.

Images