Self-repairing renewable photocatalytic coating aiming at environmental toxicants and preparation method of self-repairing renewable photocatalytic coating

Abstract

The invention belongs to the technical field of environmental functional materials, and provides a self-repairing renewable photocatalytic coating aiming at environmental toxicants and a preparation method of the self-repairing renewable photocatalytic coating. According to the invention, fluorine-containing polyurethane is taken as a continuous phase, a reversible bonding unit is introduced, and a dynamic polymer network with photo-thermal triggered self-repairing capability is constructed; heterojunctions formed by nitrogen-doped carbon quantum dots and bismuth tungstate are loaded in the coating, and surface poisoning and inactivation of the catalyst are inhibited through a silicon dioxide shell layer. Furthermore, a titanium carbide two-dimensional material is used as a conductive and photo-thermal auxiliary agent, so that separation and migration of photon-generated carriers are effectively accelerated, mild local temperature rise is generated under illumination, breakage and recombination of reversible bonds in a polyurethane network are promoted, and in-situ self-repairing of coating microcracks and light etching damage is realized; in addition, the coating surface is endowed with selective enrichment and self-cleaning capability; the coating provided by the invention can keep stable adhesion and continuous catalytic activity under long-term illumination and complex pollution environments, and has continuous degradation capability on environmental toxicants such as gas-phase formaldehyde and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of environmental functional materials, and relates to a self-repairing renewable photocatalytic coating for environmental toxicants and a preparation method thereof. BACKGROUND

[0002] Environmental toxicants, especially small-molecule volatile organic compounds represented by formaldehyde, are slowly released in indoor environments for a long time, and have become one of the most concerned hidden pollution sources in building decoration and home environments. Although traditional physical adsorption materials can reduce the formaldehyde concentration in a short period of time, they are easy to saturate and fail. In comparison, photocatalytic technology can decompose organic pollutants such as formaldehyde into inorganic small molecules at normal temperature and pressure, and is regarded as a green and efficient environmental purification path.

[0003] Most of the existing photocatalytic purification materials are based on semiconductors such as titanium dioxide and bismuth oxides, and are usually prepared as powder coating layers or incorporated into resin matrices to form photocatalytic coatings. However, on the one hand, conventional photocatalytic coatings often rely on inorganic brittle networks or organic matrices with high cross-linking degrees to provide adhesion and durability, and are easy to produce micro-cracks, peeling and even large-area peeling under long-term light, temperature and humidity cycles and external forces, lacking self-repairing ability for crack propagation and interface damage, resulting in significantly shortened service life. On the other hand, 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 phenomena such as surface powdering, whitening and loss of luster, which rapidly deteriorate the structure and appearance of the coating. In addition, with the extension of use time, intermediate products of formaldehyde and other organic substances are easy to accumulate on the surface of the catalyst, forming an organic pollution layer, which masks the active sites and causes continuous decay of photocatalytic activity and even "poisoning" failure. Most of the existing technologies rely on increasing the amount of catalyst, increasing the light intensity or periodic scrubbing to delay deactivation, but it is difficult to achieve in-situ regeneration of the catalytic surface under actual application conditions. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application aims to provide a self-repairing renewable photocatalytic coating for environmental toxicants and a preparation method thereof. The coating uses a fluorine-containing polyurethane dynamic network as the matrix, introduces reversible disulfide bonds to realize light-heat triggered micro-crack self-repairing and mechanical property recovery; composites a nitrogen-doped carbon quantum dot bismuth tungstate heterojunction and a silica shell layer in the matrix, and cooperatively introduces titanium carbide type two-dimensional materials to promote efficient separation and interface transmission of photo-generated carriers, and at the same time endows the coating with surface selective enrichment and self-cleaning ability, so as to realize continuous degradation of formaldehyde and other environmental toxicants under light conditions and maintain long-term stable service, thereby meeting the needs of actual production.

[0005] To achieve this purpose, the present application adopts the following technical solutions:

[0006] In a first aspect, the present application provides a preparation method of a self-repairing renewable photocatalytic coating for environmental toxicants, the preparation method comprising:

[0007] S1, dispersing citric acid and urea in deionized water, and hydrothermally reacting to obtain N-doped carbon quantum dot powder, dispersing bismuth nitrate pentahydrate and the N-doped carbon quantum dot powder in an acetic acid aqueous solution, and hydrothermally reacting to obtain a heterojunction powder, dispersing the heterojunction powder in a mixed solvent, adding bisphenol A, tetraethyl orthosilicate and 3-aminopropyl triethoxysilane to react at room temperature, and after centrifugation, reflux extraction is performed to obtain a de-templated heterojunction powder, dispersing the obtained de-templated heterojunction powder in anhydrous toluene, and adding 3-isocyanate propyl triethoxysilane to obtain a carbon quantum dot heterojunction;

[0008] S2, mixing and reacting PTMG-2000, PFPE-1500, isophorone diisocyanate and dibutyltin dilaurate to obtain an NCO-terminated prepolymer, adding trimethylolpropane, a chain extender solution and a furfurylamine solution to react to obtain a fluorine-containing polyurethane solution;

[0009] S3, mixing Ti3AlC2 and an etching solution, etching, centrifuging, washing and ultrasonicating to obtain Ti3C2T X powder, dispersing the Ti3C2T X powder in an ethanol aqueous solution, adding 3-aminopropyl triethoxysilane and stirring to obtain functionalized Ti3C2T X powder, dispersing the obtained functionalized Ti3C2T X powder in anhydrous DMF and adding 3-isocyanate propyl triethoxysilane to react to obtain grafted Ti3C2T X powder;

[0010] S4, dispersing the carbon quantum dot heterojunction, grafted Ti3C2T X powder and butanone to obtain a dispersion phase, mixing the dispersion phase, the fluorine-containing polyurethane solution and bismaleimide to obtain a coating material, and spraying the coating material onto a substrate to dry to obtain a self-repairing renewable photocatalytic coating for environmental toxicants.

[0011] Specifically comprising:

[0012] S1, dispersing citric acid and urea in deionized water, hydrothermal reaction at a first temperature, filtering, dialysis, freeze-drying to obtain N-doped carbon quantum dot powder, dispersing bismuth nitrate pentahydrate and N-doped carbon quantum dot powder in acetic acid aqueous solution, adding sodium tungstate dihydrate solution dropwise, adjusting pH to 6.8-7.2 using sodium hydroxide aqueous solution, hydrothermal reaction at a second temperature, centrifugation, washing, drying to obtain a heterojunction powder, dispersing the heterojunction powder in a mixed solvent, adding bisphenol A and stirring, then adding tetraethyl orthosilicate and 3-aminopropyl triethoxysilane at room temperature, centrifuging and transferring into acidic ethanol solution for reflux extraction, centrifugation, washing, drying to obtain a template-free heterojunction powder, dispersing the obtained template-free heterojunction powder in anhydrous toluene, adding 3-isocyanatopropyl triethoxysilane, connecting a water separator, refluxing, filtering, washing, drying to obtain a carbon quantum dot heterojunction;

[0013] S2, mixing PTMG-2000, PFPE-1500, isophorone diisocyanate and dibutyltin dilaurate, stirring and reacting under a nitrogen atmosphere at a third temperature to obtain an NCO-terminated prepolymer, adding trimethylolpropane for further reaction, then adding a chain extender solution dropwise into the reaction system for further reaction, monitoring the NCO absorption peak by infrared spectroscopy, and reducing the peak intensity to 70-80% of the initial value, then adding furfurylamine solution, reacting at a fourth temperature until the NCO peak in the infrared spectrum disappears to obtain a fluorine-containing polyurethane solution;

[0014] S3, mixing Ti3AlC2 and etching solution, stirring and etching in a water bath at a fifth temperature, centrifugation, washing until the pH of the supernatant is greater than 6, dispersing the precipitate in deionized water, ultrasonicating under a nitrogen atmosphere, centrifugation, and taking the black supernatant, freeze-drying to obtain Ti3C2T X powder; X dispersing the Ti3C2T X powder in ethanol aqueous solution, adding 3-aminopropyl triethoxysilane, stirring at room temperature under a nitrogen atmosphere, centrifugation, washing, and drying to obtain functionalized Ti3C2T X powder; X dispersing the functionalized Ti3C2T X powder in anhydrous DMF and adding 3-isocyanatopropyl triethoxysilane, stirring and reacting at a fourth temperature under a nitrogen atmosphere, centrifugation, washing, and drying to obtain grafted Ti3C2T

[0015] S4, dispersing the carbon quantum dot heterojunction, grafted Ti3C2T X powder and butanone to obtain a dispersed phase, mixing the dispersed phase, fluorine-containing polyurethane solution, and bismaleimide, stirring at a fifth temperature, grinding, and degassing under reduced pressure to obtain a coating material, spraying the coating material onto a substrate, drying, and obtaining a self-repairing renewable photocatalytic coating layer for environmental toxicants.

[0016] In the step of heterojunction, citric acid and urea are condensed, dehydrated and preliminary carbonized under hydrothermal conditions. Citric acid provides carbon skeleton and carboxyl group, and urea provides nitrogen source and part of carbon source, forming nitrogen-doped carbon quantum dots with carboxyl, hydroxyl and nitrogen-containing groups on the surface. Bismuth nitrate is partially hydrolyzed and coordinated in aqueous acetic acid, and forms carbon quantum dot heterojunction with nitrogen-doped carbon quantum dots. The conduction band and valence band positions of the two are different, and after forming a heterojunction, the electrons and holes are spatially separated, providing a prerequisite for the subsequent generation of active oxygen species. On this basis, when coated with silicon dioxide, the bisphenol template molecules and the hydrolyzed silane monomers form a pre-assembled complex through hydrogen bonding and hydrophobic interaction. Tetraacetyl orthosilicate and aminopropyl triethoxysilane are hydrolyzed to form silanol under alkaline conditions, and then form a siloxane network on the surface of the carbon quantum dot bismuth tungstate particles through condensation reaction, fixing the template molecules and photocatalytic particles in the inorganic shell. Aminopropyl triethoxysilane introduces amino groups to the inner and outer surfaces of the shell, providing functional groups for subsequent coupling. After reflux extraction with acidic ethanol, the template molecules are removed from the shell, and the internal cavity of the shell retains a cavity and a polar environment matching the structure of the template molecules, producing selective adsorption and enrichment functions for organic pollutants with similar structures during subsequent service. Then, a silane coupling agent with isocyanate and triethoxysilane groups is added. The isocyanate group preferentially reacts with the amino group on the surface of the shell to form a urea bond, and the triethoxysilane group retains the hydrolyzable condensation property. The resulting photocatalytic particles have pores, urea structures and potential siloxane network formation sites on the surface, which on the one hand enhance the compatibility and interface anchoring between the particles and the organic matrix, and on the other hand can participate in further siloxane crosslinking during coating curing and service.

[0017] In the polyurethane matrix construction step, the polyether polyol and fluorine-containing polyether are added to the alicyclic diisocyanate in the presence of a catalyst to form urethane bonds between the hydroxyl groups and the isocyanate groups, generating a prepolymer with multiple flexible chain segments and some free isocyanate groups. After the introduction of trimethylolpropane, the polyhydroxyl monomer reacts with the isocyanate groups to introduce branching points in the main chain, forming hyperbranched or dendritic polyurethane structures and increasing the potential crosslinking nodes. Subsequently, a chain extender solution is added dropwise, which contains dihydroxyl compounds with disulfide structures, hydroxyl monomers with maleimide rings, and bis-hydroxyethyl urea with urea units and hydroxyl groups. The isocyanate groups on the prepolymer continue to react, introducing urethane bonds into the main chain, as well as disulfide bonds, maleimide rings, and urea structures. The disulfide bonds can undergo homolysis and recombination under certain light and heat conditions, while the maleimide rings serve as the diels-alder reaction's dienophile structure, and the urea structure forms a physical crosslinking network with the urethane groups through multiple hydrogen bonds. By controlling the degree of chain extension, some unreacted isocyanate groups remain in the system, and then 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 a diels-alder cycloaddition with the side chain maleimide ring to form a reversible covalent crosslinking point between chains. The resulting fluorine-containing polyurethane contains disulfide bonds, diels-alder bonds, and rearrangeable hydrogen bond networks. When the local temperature rises or is subjected to light and heat, these bonds can break and reform.

[0018] In the two-dimensional carbide preparation and grafting step, the layered titanium aluminum carbide is preferentially converted into a soluble complex in a fluorine-containing acidic system, leaving a layered skeleton composed of titanium and carbon. During etching, the titanium surface is partially oxidized and fluorinated, forming structures with fluorine, hydroxyl, and oxygen end groups. After washing and ultrasonic treatment, the multi-layer stacked skeleton is exfoliated into single-layer or few-layer sheet structures, forming MXene nanoplates with a large specific surface area and continuous conductive paths. Subsequently, in an alcohol solution containing a small amount of water, amino propyl triethoxysilane is added, and the silane hydrolyzes to form silanol and condenses with the surface hydroxyl groups, forming titanium-oxygen-silicon bonds on the titanium surface and introducing organic propyl and amino groups onto the sheet surface. Then, isocyanate group-containing triethoxysilane is introduced, and the isocyanate group reacts with the surface amino group to form a urea bond, and the triethoxysilane group retains the ability to hydrolyze and condense. The final MXene nanoplate is covered with an organic-inorganic hybrid layer containing urea structures and triethoxysilane groups, which forms hydrogen bonds with the urea groups on the polyurethane chain and covalent bonds with the silica shell or substrate, while also providing favorable conditions for the dispersion of the sheet in the matrix.

[0019] In the blending into film step, the carbon quantum dot heterojunction and the surface grafted MXene nanosheet are mixed with a fluorine-containing polyurethane solution containing a dynamic crosslinking structure, and a bismaleimide type crosslinking agent is added. The bismaleimide can further undergo Diels-Alder cycloaddition with the unreacted furan ring on the polyurethane chain to increase the reversible crosslinking nodes in the network. During the service stage of the coating, the formaldehyde molecules in the environment first reach the coating surface layer by diffusion, part of which is adsorbed by the polar groups on the surface of the polyurethane and inorganic shell layer, and part of which is enriched near the photocatalytic particles through the pores. Under the action of light, the bismuth tungstate and nitrogen-doped carbon quantum dots absorb photons to generate electrons and holes, generate hydroxyl radicals and other active oxygen species, and undergo oxidation reaction with the adsorbed formaldehyde. The presence of the silica shell layer makes it easier for organic intermediates to be further oxidized and desorbed, slowing down the process of forming a stable organic cover layer on the surface of the catalyst, thereby reducing the surface poisoning rate. At the same time, the MXene sheet layer absorbs part of the light energy and releases it in the form of heat without radiation, causing the local temperature to rise slightly. Within this temperature range, the disulfide bonds, Diels-Alder bonds and hydrogen bonds in the polyurethane network can undergo limited breaking and recombination, allowing microcracks caused by photo-erosion or mechanical stress to be alleviated or healed.

[0020] As a preferred technical solution of the present application, 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 not limited to the listed values, other unlisted values within this range are also applicable.

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

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

[0023] In some optional embodiments, the external phase of the dialysis is deionized water, the molecular weight cut-off is 1000 Da, and the dialysis time is 24-48 h, for example, the external phase of the dialysis can be deionized water, the molecular weight cut-off is 1000 Da, and the dialysis time is (24, 26.4, 28.8, 31.2, 33.6, 36, 38.4, 40.8, 43.2, 45.6, or 48) h, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0024] In some optional embodiments, the mass ratio of the bismuth nitrate pentahydrate, the N-doped carbon quantum dot powder, the acetic acid aqueous solution, and the sodium tungstate dihydrate solution is (0.97-1): (0.05-0.07): 40: (20-21), for example, the mass ratio 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): (0.05, 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 is not limited to the listed values, and other values not listed in the range are also applicable.

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

[0026] In some optional embodiments, the second temperature is 160-165℃, for example, the second temperature can be 160℃, 160.5℃, 161℃, 161.5℃, 162℃, 162.5℃, 163℃, 163.5℃, 164℃, 164.5℃, or 165℃, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0027] In some optional embodiments, the time of the second temperature hydrothermal reaction is 20-21 h, for example, the time can be 20.0 h, 20.1 h, 20.2 h, 20.3 h, 20.4 h, 20.5 h, 20.6 h, 20.7 h, 20.8 h, 20.9 h, or 21.0 h, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0028] In some optional embodiments, the third temperature is 380-420 °C, for example, 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 not only limited to the listed values, other values not listed in the range of values are also applicable.

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

[0030] In some optional embodiments, the mass ratio of the heterojunction powder, mixed solvent, bisphenol A, tetraethyl orthosilicate, 3-aminopropyl triethoxysilane, anhydrous toluene and 3-isocyanate propyl triethoxysilane 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, 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, 0.054, 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 only limited to the listed values, other values not listed in the range of values are also applicable.

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

[0032] In some optional embodiments, the refluxing reaction time is 24-25 h, for example, can be 24.0 h, 24.1 h, 24.2 h, 24.3 h, 24.4 h, 24.5 h, 24.6 h, 24.7 h, 24.8 h, 24.9 h or 25.0 h, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0033] As a preferred technical solution of the present application, 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, 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 only limited to the listed values, other values not listed in the range of values are also applicable.

[0034] In some optional embodiments, the third temperature is 80-85℃, for example, can be 80℃, 80.5℃, 81℃, 81.5℃, 82℃, 82.5℃, 83℃, 83.5℃, 84℃, 84.5℃ or 85℃, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0035] In some optional embodiments, the third temperature stirring reaction time is 2-3 h, for example, can be 2.0 h, 2.1 h, 2.2 h, 2.3 h, 2.4 h, 2.5 h, 2.6 h, 2.7 h, 2.8 h, 2.9 h or 3.0 h, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0036] In some optional embodiments, the time for continuing the reaction after adding trimethylolpropane is 1-2 h, for example, can be 1.0 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h, or 2.0 h, but not only limited to the listed values, other values not listed in the range of values 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 and butanone in the chain extender solution is 1:0.5:0.5:25.

[0038] In some optional embodiments, the time for continuing the reaction is 3-4 h, for example, can be 3.0 h, 3.1 h, 3.2 h, 3.3 h, 3.4 h, 3.5 h, 3.6 h, 3.7 h, 3.8 h, 3.9 h, or 4.0 h, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0039] In some optional embodiments, the mass ratio of furfurylamine and butanone in the furfurylamine solution is (0.4-0.5):(5-10), for example, 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 not only limited to the listed values, other values not listed in the range of values are also applicable.

[0040] In some optional embodiments, the fourth temperature is 60-65℃, for example, can be 60℃, 60.5℃, 61℃, 61.5℃, 62℃, 62.5℃, 63℃, 63.5℃, 64℃, 64.5℃, or 65℃, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0041] In some optional embodiments, the solid content of the fluorine-containing polyurethane solution is 40-50 wt.%, for example, 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 not only limited to the listed values, other values not listed in the range of values are also applicable.

[0042] As a preferred technical solution of the present application, 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 not limited to the listed values, other values not listed in 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 optional embodiments, the fifth temperature is 35-40℃, for example, it can be 35℃, 35.5℃, 36℃, 36.5℃, 37℃, 37.5℃, 38℃, 38.5℃, 39℃, 39.5℃ or 40℃, but not limited to the listed values, other values not listed in this range are also applicable.

[0045] In some optional embodiments, the stirring etching time is 24-25h, for example, it can be 24.0h, 24.1h, 24.2h, 24.3h, 24.4h, 24.5h, 24.6h, 24.7h, 24.8h, 24.9h or 25.0h, but not limited to the listed values, other values not listed in this range are also applicable.

[0046] In some optional embodiments, the ultrasonic time is 1-2h, 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 not limited to the listed values, other values not listed in this range are also applicable.

[0047] In some optional embodiments, the Ti3C2T X The mass ratio of powder, aqueous ethanol solution, 3-aminopropyl triethoxysilane, anhydrous DMF and 3-isocyanate propyl triethoxysilane is (0.2-0.3):40:(0.1-0.2):30:0.05, for example, it can be (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 not limited to the listed values, other values not listed in this range are also applicable.

[0048] In some optional embodiments, the Ti3C2TX The powder refers to a Ti3C2 MXene material obtained by etching, washing and exfoliating a MAX phase titanium aluminum carbide Ti3AlC2, wherein T is an end group located on the surface of the Ti3C2 skeleton, is one or more of -F, -OH and -O, and the subscript X represents the average number of end groups T carried by each Ti3C2 structural unit on the basis of the Ti3C2 skeleton, and the average number satisfies 0X≤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 24-25h, for example, it can be 24.0h, 24.1h, 24.2h, 24.3h, 24.4h, 24.5h, 24.6h, 24.7h, 24.8h, 24.9h or 25.0h, but not only limited to the listed values, other values not listed in this range are also applicable.

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

[0052] In some optional embodiments, the stirring time at the fourth temperature is 12-13h, for example, it can be 12.0h, 12.1h, 12.2h, 12.3h, 12.4h, 12.5h, 12.6h, 12.7h, 12.8h, 12.9h or 13.0h, but not only limited to the listed values, other values not listed in this range are also applicable.

[0053] As a preferred technical solution of the present application, in S4, the carbon quantum dot heterojunction, grafted Ti3C2T XThe mass ratio of the powder, butanone, fluorine-containing 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, 0.062, 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 is not limited to the listed values, and other values not listed in the range are also applicable.

[0054] In some optional embodiments, the drying specifically comprises: room temperature standing for 1-2h leveling after spraying, vacuum drying at 60-65℃ for 12-13h, and then incubating at 80-85℃ for 2-3h, and cooling to room temperature. For example, it can be room temperature standing for (1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2.0)h leveling after spraying, vacuum drying at (60, 60.5, 61, 61.5, 62, 62.5, 63, 63.5, 64, 64.5 or 65)℃ for (12.0, 12.1, 12.2, 12.3, 12.4, 12.5, 12.6, 12.7, 12.8, 12.9 or 13.0)h, and then incubating at (80, 80.5, 81, 81.5, 82, 82.5, 83, 83.5, 84, 84.5 or 85)℃ 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 cooling to room temperature, but is not limited to the listed values, and other values not listed in the range are also applicable.

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

[0056] In the second aspect, the application provides a self-repairing renewable photocatalytic coating against environmental toxicants prepared by the preparation method of the first aspect.

[0057] Compared with the prior art, the beneficial effects of the present application are that the coating of the present application takes fluorine-containing polyurethane as a matrix, introduces carbon quantum dot bismuth tungstate heterojunction and surface-modified titanium carbide two-dimensional material, and can continuously catalyze the degradation of volatile organic compounds such as formaldehyde in air under light; the silica shell layer endows the coating with the selective enrichment ability of the target pollutants, and slows down the accumulation of organic intermediates on the surface of the catalyst, thereby reducing the common problem of photocatalytic coating poisoning and inactivation; the fluorine-containing polyurethane soft segment, inorganic shell layer and photocatalytic unit cooperate, which can not only decompose the attached organic stains and formaldehyde polymers during the photocatalytic process, so as to keep the surface clean and smooth, but also can weaken the photo-etching effect of active free radicals on the organic matrix, thereby improving the weather resistance and appearance retention; by introducing disulfide bonds and multiple hydrogen bonds in the polyurethane, the coating can undergo segment rearrangement and crosslinking reconstruction under photo-thermal excitation, so as to realize in-situ self-repairing of micro-cracks and slight photo-etching damage, keep the effective exposure and adhesion of the photocatalytic components; the nitrogen-doped carbon quantum dot bismuth tungstate heterojunction and silica shell layer are compounded in the matrix, and the titanium carbide two-dimensional material is introduced to promote the efficient separation and interface transmission of photo-generated carriers, and at the same time, the coating is endowed with the selective enrichment and self-cleaning ability on the surface, so as to significantly improve the comprehensive durability and application value of the self-cleaning functional coating in the field of indoor air purification and building decoration. DETAILED DESCRIPTION

[0058] The technical solutions of the present application will be described in detail below in combination with specific embodiments. The embodiments described herein are specific specific embodiments of the present application, which are used to illustrate the concept of the present application; these descriptions are all explanatory and exemplary, and should not be understood as limiting the embodiments of the present application and the protection scope of the present application. In addition to the embodiments described herein, those skilled in the art can also employ other technical solutions that are obvious based on the content disclosed in the claims and the description of the present application, which include technical solutions that make any obvious replacement and modification to the embodiments described herein.

[0059] The chemical reagents used in the embodiments and comparative examples of the present application are all commercially available goods, and are not subjected to any further purification treatment.

[0060] Embodiment 1

[0061] The present embodiment provides a self-repairing renewable photocatalytic coating for environmental toxicants and a preparation method thereof, which specifically comprises the following steps:

[0062] S1, 2 g of citric acid and 3 g of urea were dispersed in 20 g of deionized water, and hydrothermal reaction was carried out at 180℃ for 6 h, filtration, dialysis, the outer phase of the dialysis was deionized water, the molecular weight cut-off was 1000 Da, the dialysis time was 48 h, and the deionized water was replaced every 8 h during the dialysis, and freeze-drying obtained N-doped carbon quantum dot powder, 0.97 g of bismuth nitrate pentahydrate and 0.07 g of N-doped carbon quantum dot powder were dispersed in 40 g of 13wt.% acetic acid aqueous solution, 20 g of 2wt.% sodium tungstate dihydrate solution was added dropwise, 1M sodium hydroxide aqueous solution was used to adjust the pH to 7.2, and hydrothermal reaction was carried out at 160℃ for 21 h, centrifugation, washing, drying, and obtaining a heterojunction powder, 0.4 g of the heterojunction powder was dispersed in 71 g of a mixed solvent, the mass ratio of anhydrous ethanol, deionized water and ammonia water in the mixed solvent was 50:20:1, the mass fraction of ammonia water was 25wt.%, 0.04 g of bisphenol A was added and stirred for 2 h, 0.4 g of tetraethyl orthosilicate and 0.1 g of 3-aminopropyl triethoxysilane were added and reacted at room temperature for 8 h, after centrifugation, it was transferred into an acidic ethanol solution with a pH of 3 and refluxed for 12 h, centrifugation, washing, drying, and obtaining a template-free heterojunction powder, the template-free heterojunction powder obtained was dispersed in 50.0 g of anhydrous toluene, 0.06 g of 3-isocyanatopropyl triethoxysilane was added, a water separator was connected, and reflux reaction was carried out for 25 h, filtration, washing, drying, and obtaining a carbon quantum dot heterojunction;

[0063] S2, 12 g of PTMG-2000, 3 g of PFPE-1500, 4 g of isophorone diisocyanate and 0.02 g of dibutyltin dilaurate were mixed, and NCO-terminated prepolymer was obtained by stirring reaction at 85℃ for 2 h under a nitrogen atmosphere, 0.3 g of trimethylolpropane was added and the reaction was continued for 1 h, 30 g of a chain extender solution was added dropwise into the reaction system and the reaction was continued for 4 h, 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 peak intensity of NCO absorption was reduced to 70% of the initial value by infrared monitoring, 10.5 g of a furfuryl amine solution was then added, the mass ratio of furfuryl amine and butanone in the furfuryl amine solution was 0.5:10, and the reaction was carried out at 65℃ until the NCO peak in the infrared spectrum disappeared, and a fluorine-containing polyurethane solution was obtained, the solid content of the fluorine-containing polyurethane solution was 40wt.%;

[0064] S3, 2 g of Ti3AlC2 was mixed with 21 g of etching solution, the mass ratio of hydrochloric acid solution to lithium fluoride in the etching solution was 20:1, the concentration of the hydrochloric acid solution was 6M, and the etching was carried out by stirring in a water bath at 35℃ for 25 h, centrifugation, washing until the pH of the supernatant was greater than 6, the precipitate was dispersed in 60 g of deionized water, ultrasonic treatment was carried out under a nitrogen atmosphere for 1 h, centrifugation and taking the black supernatant, and freeze-drying obtained Ti3C2T X powder, the Ti3C2TX The powder refers to a Ti3C2 MXene material obtained by etching, washing and exfoliating a MAX phase titanium aluminum carbide Ti3AlC2, wherein T is an end group located on the surface of the Ti3C2 skeleton, is one or more of -F, -OH and -O, the subscript X represents the average number of end groups T carried by each Ti3C2 structural unit on the basis of the Ti3C2 skeleton, and the average number satisfies 0 < X ≤ 2, 0.3 g of Ti3C2T X The powder is dispersed in 40 g of an ethanol aqueous solution, 0.1 g of 3-aminopropyl triethoxysilane is added, stirring is performed under a nitrogen atmosphere at room temperature for 25 h, centrifugation, washing and drying are performed, and functionalized Ti3C2T X The powder, the obtained functionalized Ti3C2T X The powder is dispersed in 30 g of anhydrous DMF and 0.05 g of 3-isocyanate propyl triethoxysilane is added, stirring is performed under a nitrogen atmosphere at 65 °C for 12 h, centrifugation, washing and drying are performed, and grafted Ti3C2T X The powder is mixed with 10 g of butanone to obtain a dispersion phase, the dispersion phase, 30 g of a fluorine-containing polyurethane solution and 0.2 g of bismaleimide are mixed, stirring is performed at 40 °C, grinding and degassing are performed under reduced pressure, a coating is obtained, the coating is sprayed onto a substrate, and drying is performed, the drying specifically including: standing for 1 h at room temperature for leveling after spraying, vacuum drying at 65 °C for 12 h, and then heat preservation at 80 °C for 3 h, and cooling to room temperature, to obtain a self-repairing renewable photocatalytic coating for environmental toxicants.

[0065] S4, 0.7 g of carbon quantum dot heterojunction, 0.05 g of grafted Ti3C2T X The powder is mixed with 10 g of butanone to obtain a dispersion phase, the dispersion phase, 30 g of a fluorine-containing polyurethane solution and 0.2 g of bismaleimide are mixed, stirring is performed at 40 °C, grinding and degassing are performed under reduced pressure, a coating is obtained, the coating is sprayed onto a substrate, and drying is performed, the drying specifically including: standing for 1 h at room temperature for leveling after spraying, vacuum drying at 65 °C for 12 h, and then heat preservation at 80 °C for 3 h, and cooling to room temperature, to obtain a self-repairing renewable photocatalytic coating for environmental toxicants.

[0066] Example 2

[0067] The present embodiment provides a self-repairing renewable photocatalytic coating for environmental toxicants and a preparation method thereof, and the preparation method specifically includes the following steps:

[0068] S1, 3 g of citric acid and 2 g of urea were dispersed in 20 g of deionized water, and hydrothermal reaction was carried out at 185℃ for 5 h, filtration, dialysis, the outer phase of the dialysis was deionized water, the molecular weight cut-off was 1000 Da, the dialysis time was 48 h, and the deionized water was replaced every 8 h during the dialysis, and freeze-drying was carried out to obtain N-doped carbon quantum dot powder, 1 g of bismuth nitrate pentahydrate and 0.05 g of N-doped carbon quantum dot powder were dispersed in 40 g of 15wt.% acetic acid aqueous solution, 21 g of 1.5wt.% sodium tungstate dihydrate solution was added dropwise, 1M sodium hydroxide aqueous solution was used to adjust the pH to 6.8, and hydrothermal reaction was carried out at 165℃ for 20 h, centrifugation, washing, and drying were carried out to obtain a heterojunction powder, 0.3 g of the heterojunction powder was dispersed in 71 g of a mixed solvent, the mass ratio of anhydrous ethanol, deionized water and ammonia water in the mixed solvent was 50:20:1, the mass fraction of ammonia water was 25wt.%, 0.06 g of bisphenol A was added and stirred for 1 h, 0.6 g of tetraethyl orthosilicate and 0.08 g of 3-aminopropyl triethoxysilane were added and reacted at room temperature for 9 h, after centrifugation, it was transferred into an acidic ethanol solution with a pH of 2 and refluxed for 13 h, centrifugation, washing, and drying were carried out to obtain a template-free heterojunction powder, and the template-free heterojunction powder was dispersed in 50.0 g of anhydrous toluene, 0.08 g of 3-isocyanatopropyl triethoxysilane was added, a water separator was connected, and reflux reaction was carried out for 24 h, filtration, washing, and drying were carried out to obtain a carbon quantum dot heterojunction;

[0069] S2, 10 g of PTMG-2000, 4 g of PFPE-1500, 3.8 g of isophorone diisocyanate, and 0.02 g of dibutyltin dilaurate were mixed, a nitrogen atmosphere was provided, and stirring reaction was carried out at 80℃ for 3 h to obtain an NCO-terminated prepolymer, 0.2 g of trimethylolpropane was added and the reaction was continued for 2 h, 30 g of a chain extender solution was added dropwise into the reaction system and the reaction was continued for 3 h, 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 peak intensity of the NCO absorption peak was reduced to 80% of the initial value by infrared monitoring, 5.4 g of a furfuryl amine solution was added, the mass ratio of furfuryl amine and butanone in the furfuryl amine solution was 0.4:5, and the reaction was carried out at 60℃ until the NCO peak in the infrared spectrum disappeared, to obtain a fluorine-containing polyurethane solution, the solid content of the fluorine-containing polyurethane solution was 50wt.%;

[0070] S3, 1 g of Ti3AlC2 was mixed with 21 g of etching solution, the mass ratio of hydrochloric acid solution to lithium fluoride in the etching solution was 20:1, the concentration of the hydrochloric acid solution was 6M, and stirring etching was carried out at 40℃ for 24 h, centrifugation, washing were carried out until the pH of the supernatant was greater than 6, the precipitate was dispersed in 50 g of deionized water, ultrasonic treatment was carried out under a nitrogen atmosphere for 2 h, centrifugation was carried out and the black supernatant was taken, and freeze-drying was carried out to obtain Ti3C2T X powder, the Ti3C2TX The powder refers to a Ti3C2 MXene material obtained by etching, washing and exfoliating a MAX phase titanium aluminum carbide Ti3AlC2, wherein T is an end group located on the surface of the Ti3C2 skeleton, is one or more of -F, -OH and -O, the subscript X represents the average number of end groups T carried by each Ti3C2 structural unit on the basis of the Ti3C2 skeleton, and the average number satisfies 0 < X ≤ 2, 0.2 g of Ti3C2T X The powder is dispersed in 40 g of an ethanol aqueous solution, 0.2 g of 3-aminopropyl triethoxysilane is added, stirring is performed under a nitrogen atmosphere at room temperature for 24 h, centrifugation, washing and drying are performed, and functionalized Ti3C2T X The powder, functionalized Ti3C2T X The powder is dispersed in 30 g of anhydrous DMF and 0.05 g of 3-isocyanate propyl triethoxysilane is added, stirring is performed under a nitrogen atmosphere at 60°C for 13 h, centrifugation, washing and drying are performed, and grafted Ti3C2T X The powder;

[0071] S4, 0.6 g of carbon quantum dot heterojunction, 0.07 g of grafted Ti3C2T X The powder is mixed and dispersed in 10 g of butanone to obtain a dispersion phase, the dispersion phase, 25 g of a fluorine-containing polyurethane solution and 0.5 g of bismaleimide are mixed, stirring is performed at 35°C, grinding and degassing are performed under reduced pressure, a coating is obtained, the coating is sprayed onto a substrate, drying is performed, the drying specifically includes: standing for 2 h for leveling at room temperature after spraying, vacuum drying at 60°C for 13 h, and then heat preservation at 85°C for 2 h, and cooling to room temperature, to obtain a self-repairing renewable photocatalytic coating for environmental toxicants.

[0072] Example 3

[0073] The present embodiment provides a self-repairing renewable photocatalytic coating for environmental toxicants and a preparation method thereof, and the preparation method specifically includes the following steps:

[0074] S1, 2.5 g of citric acid and 2.5 g of urea were dispersed in 20 g of deionized water, and hydrothermal reaction was carried out at 182℃ for 5.5 h. Filtration, dialysis, and freeze-drying were performed to obtain N-doped carbon quantum dot powder. 0.98 g of bismuth nitrate pentahydrate and 0.06 g of N-doped carbon quantum dot powder were dispersed in 40 g of 14wt.% acetic acid aqueous solution. 20.5 g of 1.8wt.% sodium tungstate dihydrate solution was added dropwise. 1M sodium hydroxide aqueous solution was used to adjust the pH to 7.0. Hydrothermal reaction was carried out at 162℃ for 20.5 h. Centrifugation, washing, and drying were performed to obtain a heterojunction powder. 0.35 g of the heterojunction powder was dispersed in 71 g of a mixed solvent, in which the mass ratio of anhydrous ethanol, deionized water, and ammonia water was 50:20:1, and the mass fraction of ammonia water was 25wt.%. 0.05 g of bisphenol A was added and stirred for 1.5 h. 0.5 g of tetraethyl orthosilicate and 0.09 g of 3-aminopropyl triethoxysilane were added and reacted at room temperature for 8.5 h. After centrifugation, the product was transferred into an acidic ethanol solution with a pH of 2.5 for reflux extraction for 12.5 h. Centrifugation, washing, and drying were performed to obtain a template-free heterojunction powder. The template-free heterojunction powder was dispersed in 50.0 g of anhydrous toluene, and 0.07 g of 3-isocyanatopropyl triethoxysilane was added. A water separator was connected, and reflux reaction was carried out for 24.5 h. Filtration, washing, and drying were performed to obtain a carbon quantum dot heterojunction;

[0075] S2, 11 g of PTMG-2000, 3.5 g of PFPE-1500, 3.9 g of isophorone diisocyanate, and 0.02 g of dibutyltin dilaurate were mixed and stirred at 82℃ for 2.5 h under a nitrogen atmosphere to obtain an NCO-terminated prepolymer. 0.25 g of trimethylolpropane was added and reacted for another 1.5 h. Then, 30 g of a chain extender solution was added dropwise into the reaction system and reacted for another 3.5 h. 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 peak intensity of the NCO absorption peak was reduced to 75% of the initial value by infrared monitoring. Then, 8 g of a furfuryl amine solution was added, in which the mass ratio of furfuryl amine to butanone was 0.45:8. The reaction was carried out at 62℃ until the NCO peak in the infrared spectrum disappeared, to obtain a fluorine-containing polyurethane solution with a solid content of 45wt.%.

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

[0077] S4, 0.65 g carbon quantum dot heterojunction, 0.06 g grafted Ti3C2T X powder was mixed and dispersed in 10 g butanone to obtain a dispersion phase. The dispersion phase, 28 g fluorine-containing polyurethane solution and 0.3 g bismaleimide were mixed, stirred at 38℃, ground and degassed under reduced pressure to obtain a coating. The coating was sprayed onto a substrate, and drying was performed, which specifically included the following steps: standing for 1.5 h at room temperature for leveling after spraying, vacuum drying at 62℃ for 12.5 h, and then incubating at 82℃ for 2.5 h, and cooling to room temperature. A self-repairing renewable photocatalytic coating for environmental toxicants was obtained.

[0078] Example 4

[0079] The present embodiment provides a self-repairing renewable photocatalytic coating for environmental toxicants and a preparation method thereof, which specifically includes the following steps:

[0080] S1, 2.2 g of citric acid and 2.8 g of urea were dispersed in 20 g of deionized water, and hydrothermal reaction was carried out at 184℃ for 5.2 h. Filtration, dialysis, and freeze-drying were performed to obtain N-doped carbon quantum dot powder. 0.98 g of bismuth nitrate pentahydrate and 0.06 g of N-doped carbon quantum dot powder were dispersed in 40 g of 14.5wt.% acetic acid aqueous solution. 20.8 g of 1.6wt.% sodium tungstate dihydrate solution was added dropwise. 1M sodium hydroxide aqueous solution was used to adjust the pH to 7.1. Hydrothermal reaction was carried out at 164℃ for 20.2 h. Centrifugation, washing, and drying were performed to obtain a heterojunction powder. 0.38 g of the heterojunction powder was dispersed in 71 g of a mixed solvent, in which the mass ratio of anhydrous ethanol, deionized water, and ammonia water was 50:20:1, and the mass fraction of ammonia water was 25wt.%. 0.05 g of bisphenol A was added and stirred for 1.2 h. 0.55 g of tetraethyl orthosilicate and 0.085 g of 3-aminopropyltriethoxysilane were added and reacted at room temperature for 8.2 h. After centrifugation, the product was transferred into an acidic ethanol solution with a pH of 2.2 and refluxed for 12.8 h. Centrifugation, washing, and drying were performed to obtain a template-free heterojunction powder. The template-free heterojunction powder was dispersed in 50.0 g of anhydrous toluene, and 0.075 g of 3-isocyanatopropyltriethoxysilane was added. A water separator was connected, and reflux reaction was carried out for 24.2 h. Filtration, washing, and drying were performed to obtain a carbon quantum dot heterojunction;

[0081] S2, 11.5 g of PTMG-2000, 3.2 g of PFPE-1500, 3.95 g of isophorone diisocyanate, and 0.02 g of dibutyltin dilaurate were mixed and stirred at 84℃ for 2.8 h to obtain an NCO-terminated prepolymer. 0.28 g of trimethylolpropane was added and reacted for 1.8 h. Then, 30 g of a chain extender solution was added dropwise into the reaction system and reacted for 3.2 h. 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 peak intensity of the NCO absorption peak was reduced to 72% of the initial value by infrared monitoring. Then, 8.5 g of a furfuryl amine solution was added, in which the mass ratio of furfuryl amine to butanone was 0.48:8.5. The reaction was carried out at 64℃ until the NCO peak in the infrared spectrum disappeared, to obtain a fluorine-containing polyurethane solution with a solid content of 48wt.%.

[0082] S3, 1.8 g Ti3AlC2 was mixed with 21 g etching solution, the mass ratio of hydrochloric acid solution to lithium fluoride in the etching solution was 20:1, the concentration of the hydrochloric acid solution was 6 M, and the etching was carried out at 39 °C water bath for 24.8 h. After centrifugation and washing until the pH of the supernatant was greater than 6, the precipitate was dispersed in 58 g deionized water, and ultrasonic treatment was carried out in a nitrogen atmosphere for 1.8 h. After centrifugation, the black supernatant was obtained and freeze-dried to obtain Ti3C2T X powder, the Ti3C2T X powder refers to a Ti3C2 MXene material obtained by etching, washing and exfoliating a MAX phase titanium aluminum carbide Ti3AlC2, wherein T is an end group located on the surface of the Ti3C2 skeleton, and is one or more of -F, -OH and -O; the subscript X represents the average number of end groups T carried by each Ti3C2 structural unit on the basis of the Ti3C2 skeleton, and the average number satisfies 0 < X ≤ 2. 0.28 g Ti3C2T X powder was dispersed in 40 g ethanol aqueous solution, 0.18 g 3-aminopropyl triethoxysilane was added, stirring was carried out in a nitrogen atmosphere at room temperature for 24.2 h, and then centrifugation, washing and drying were carried out to obtain functionalized Ti3C2T X powder, the functionalized Ti3C2T X powder was dispersed in 30 g anhydrous DMF and 0.05 g 3-isocyanate propyl triethoxysilane was added, stirring was carried out in a nitrogen atmosphere at 64 °C for 12.8 h, and then centrifugation, washing and drying were carried out to obtain grafted Ti3C2T X powder;

[0083] S4, 0.68 g carbon quantum dot heterojunction, 0.065 g grafted Ti3C2T X powder was mixed and dispersed in 10 g butanone to obtain a dispersion phase. The dispersion phase, 29 g fluorine-containing polyurethane solution and 0.4 g bismaleimide were mixed, stirred at 39 °C, ground and degassed under reduced pressure to obtain a coating material. The coating material was sprayed onto a substrate, and drying was carried out, which specifically included: standing at room temperature for 1.8 h for leveling after spraying, vacuum drying at 64 °C for 12.8 h, and then heat preservation at 84 °C for 2.2 h, and cooling to room temperature to obtain a self-repairing renewable photocatalytic coating layer for environmental toxicants.

[0084] Comparative Example 1

[0085] This comparative example provides a self-repairing renewable photocatalytic coating layer for environmental toxicants and a preparation method thereof, which is different from Example 1 in that, in S1, after the heterojunction powder was dispersed in the mixed solvent, no bisphenol A was added, and tetraethyl orthosilicate and 3-aminopropyl triethoxysilane were directly added dropwise. Other process parameters and operating conditions are exactly the same as those of Example 1.

[0086] Comparative Example 2

[0087] The comparative example provides a self-repairing renewable photocatalytic coating against environmental toxicants and a preparation method thereof, which is different from example 1 in that 2-hydroxyethyl disulfide in the chain extender solution in S2 is replaced by equimolar amount of 1,4-butanediol, and other process parameters and operating conditions are exactly the same as in example 1.

[0088] Comparative example 3

[0089] The comparative example provides a self-repairing renewable photocatalytic coating against environmental toxicants and a preparation method thereof, which is different from example 1 in that the Ti3C2T X The mass of the powder is 0, and other process parameters and operating conditions are exactly the same as in example 1.

[0090] The test method for formaldehyde purification performance is GB / T 23761-2020. The method for coating surface self-cleaning effect is ISO 27448. The self-repairing test method is as follows: the self-repairing renewable photocatalytic coating is placed in a laboratory environment with a temperature of 23±2℃ and a relative humidity of 50±5% for 24h, a scratch device with a fixed load is used to make the initial scratch depth of the coating stable at 20±5μm, and at least 3 scratches that do not intersect each other and have a spacing of more than 5mm are made on each sample. After scratching, the sample is placed in the dark at room temperature for 30min to release the instantaneous stress, and then an optical microscope or a three-dimensional profilometer is used to select at least one representative scratch on each sample, and the average depth of the scratch is measured at not less than 5 cross-section positions in the length direction of the scratch, which is recorded as the initial scratch depth. The sample is placed in a constant temperature light test box with a visible light source, the temperature is set to 40±2℃ and the relative humidity is set to 50±10%, the light source is simulated daylight or cold white LED, the illuminance at the sample plane is adjusted to 10000±1000lx, and continuous light curing is carried out for 24h. The scratch depth is measured again under the same conditions as the initial measurement, and the change of the scratch depth relative to the initial value is compared, and the scratch depth recovery rate is taken as the characterization index of the self-repairing efficiency.

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

[0092] Table 1 Test results of self-repairing renewable photocatalytic coatings of examples 1-4 and comparative examples 1-3

[0093]

[0094] As shown in Table 1, compared with Example 1, the formaldehyde purification rate, the stain removal rate and the scratch depth recovery rate of Comparative Example 1 are all decreased; the formaldehyde purification rate, the stain removal rate and the scratch depth recovery rate of Comparative Example 2 are all decreased; the formaldehyde purification rate, the stain removal rate and the scratch depth recovery rate of Comparative Example 2 are all decreased. This is because, in Comparative Example 1, no bisphenol A is added, and there is a lack of cavities and polar environment in the shell, and there is a lack of selective enrichment and directional desorption of formaldehyde and intermediate products, and the surface is more likely to form an organic cover layer, and the active sites are shielded, so the formaldehyde purification rate, the stain removal rate are decreased. In Comparative Example 2, only dihydric alcohol is used to replace dihydroxyethyl disulfide, and the polyurethane network no longer contains exchangeable disulfide bonds, and the self-repairing performance is decreased. In Comparative Example 3, Ti3C2T X The conductive photo-thermal unit, the photo-catalytic system lacks a two-dimensional electron transmission channel and a local photo-thermal enhancement effect, the electron-hole recombination rate is increased, the formaldehyde purification rate is decreased, and due to the lack of local photo-thermal effect, the degree of activation of the dynamic network is reduced, and the scratch depth recovery rate is reduced.

[0095] The above merely describes specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and those skilled in the art should understand that any changes or replacements within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. Process for the preparation of a self-repairing regenerative photocatalytic coating against environmental toxicants, characterized in that, The preparation method comprises: S1, dispersing citric acid and urea in deionized water, and hydrothermally reacting to obtain N-doped carbon quantum dot powder, dispersing bismuth nitrate pentahydrate and the N-doped carbon quantum dot powder in acetic acid aqueous solution, and hydrothermally reacting to obtain a heterojunction powder, dispersing the heterojunction powder in a mixed solvent, adding bisphenol A, tetraethyl orthosilicate and 3-aminopropyl triethoxysilane to react at room temperature, and after centrifugation, reflux extraction is performed to obtain a template-free heterojunction powder, dispersing the obtained template-free heterojunction powder in anhydrous toluene, and adding 3-isocyanate propyl triethoxysilane to react to obtain a carbon quantum dot heterojunction; S2, mixing and reacting PTMG-2000, PFPE-1500, isophorone diisocyanate and dibutyltin dilaurate to obtain an NCO-terminated prepolymer, and adding trimethylolpropane, a chain extender solution and a furfurylamine solution to react to obtain a fluorine-containing polyurethane solution; S3, Ti3AlC2 was mixed with etching solution, etched, centrifuged, washed, and ultrasonicated to obtain Ti3C2T X powder, Ti3C2T X powder was dispersed in an ethanol aqueous solution, 3-aminopropyl triethoxysilane was added, and stirring was performed to obtain functionalized Ti3C2T X powder, the obtained functionalized Ti3C2T X powder was dispersed in anhydrous DMF and reacted by adding 3-isocyanate propyl triethoxysilane to obtain grafted Ti3C2T X powder; S4, carbon quantum dots heterojunction, graft Ti3C2T X The powder is mixed and dispersed with butanone to obtain a dispersion phase, the dispersion phase, a fluorine-containing polyurethane solution, and a bismaleimide are mixed to obtain a coating, and the coating is sprayed onto a substrate to be dried to obtain a self-repairing renewable photocatalytic coating for environmental toxicants.

2. The process for the preparation of a self-healing regenerative photocatalytic coating against environmental toxicants according to claim 1, characterized in that, In S1: The mass ratio of the citric acid, urea and deionized water is (2-3):(2-3):20; The mass ratio of the bismuth nitrate pentahydrate, N-doped carbon quantum dot powder, acetic acid aqueous solution and sodium tungstate dihydrate solution is (0.97-1):(0.05-0.07):40:(20-21).

3. The method for the preparation of self-healing regenerative photocatalytic coatings against environmental toxicants according to claim 1, characterized in that, In S1: The mass ratio of the heterojunction powder, mixed solvent, bisphenol A, tetraethyl orthosilicate, 3-aminopropyl triethoxysilane, anhydrous toluene and 3-isocyanate propyl triethoxysilane 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 the anhydrous ethanol, deionized water and ammonia water in the mixed solvent is 50:20:1, and the mass fraction of the ammonia water is 25wt.%.

4. The method for the preparation of self-healing regenerative photocatalytic coatings against environmental toxicants according to claim 1, characterized in that, In S2: The mass ratio of the 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).

5. The method for the preparation of self-healing regenerative photocatalytic coatings against environmental toxicants 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 and butanone in the chain extender solution is 1:0.5:0.5:25; The mass ratio of furfurylamine and butanone in the furfurylamine solution is (0.4-0.5):(5-10).

6. The process for the preparation of a self-healing regenerative photocatalytic coating against environmental toxicants according to claim 1, characterized in that, In S3: The mass ratio of the Ti3AlC2, etching liquid and deionized water is (1-2):21:50; The mass ratio of the hydrochloric acid solution and lithium fluoride in the etching liquid is 20:1, and the concentration of the hydrochloric acid solution is 6M.

7. The process for the preparation of a self-healing regenerative photocatalytic coating against environmental toxicants according to claim 1, characterized in that, In S3: Ti3C2T X powder, aqueous ethanol solution, 3-aminopropyltriethoxysilane, anhydrous DMF and 3-isocyanatopropyltriethoxysilane in a mass ratio of (0.2-0.3):40:(0.1-0.2):30:0.05; The Ti3C2T X The powder refers to a Ti3C2 MXene material obtained by etching, washing and exfoliating a MAX phase titanium aluminum carbide Ti3AlC2, wherein T is an end group located on the surface of the Ti3C2 skeleton, is one or more of -F, -OH and -O, and the subscript X represents the average number of end groups T carried by each Ti3C2 structural unit on the basis of the Ti3C2 skeleton, and the average number satisfies 0X≤2.

8. The process for the preparation of a self-healing regenerative photocatalytic coating against environmental toxicants according to claim 1, characterized in that, In S4: The carbon quantum dot heterojunction, graft Ti3C2T X The mass ratio of the powder, butanone, fluorine-containing polyurethane solution and bismaleimide is (0.6-0.7):(0.05-0.07):10:(25-30):(0.2-0.5).

9. The process for the preparation of a self-healing regenerative photocatalytic coating against environmental toxicants according to claim 1, characterized in that, In S4: The drying specifically comprises: after spraying, standing at room temperature for 1-2h for leveling, vacuum drying at 60-65℃ for 12-13h, and then incubating at 80-85℃ for 2-3h, and cooling to room temperature.

10. A self-repairing renewable photocatalytic coating against environmental toxicants obtained by the preparation method according to any one of claims 1-9.

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