A biomimetic sea urchin-like asymmetric composite phase change chitosan aerogel supported on TiO2 / rGO heterostructure, its preparation method and application

Abstract

The application discloses a biomimetic urchin-shaped asymmetric structure composite phase change chitosan aerogel loaded with TiO2 / rGO heterojunction and a preparation method and application thereof, adopts argon plasma etching GO, step-by-step dropwise adding tetrabutyl titanate to prepare TiO2 / rGO heterojunction; prepares a multi-level structure phase change microcapsule by an interfacial polymerization method; mixes the heterojunction with a chitosan solution, and prepares a biomimetic urchin-shaped asymmetric chitosan aerogel framework through a customized asymmetric mold and a unidirectional freezing process; fixes the phase change microcapsule by a vacuum-assisted impregnation method, and then performs in-situ coating through polydopamine to obtain the biomimetic urchin-shaped asymmetric structure composite phase change chitosan aerogel loaded with TiO2 / rGO heterojunction, the removal rate of VOCs of the biomimetic urchin-shaped asymmetric structure composite phase change chitosan aerogel loaded with TiO2 / rGO heterojunction is greater than or equal to 80% at low temperature, the phase change microcapsule dispersion rate is less than or equal to 3% after 100 cycles, the structural stability and the cycle durability are excellent, and the biomimetic urchin-shaped asymmetric structure composite phase change chitosan aerogel loaded with TiO2 / rGO heterojunction is suitable for efficient purification of VOCs in low-temperature closed scenes such as cold chain workshops and indoor environments in winter.

Description

Technical Field

[0001] This invention relates to the field of functional aerogel materials technology, specifically to a biomimetic sea urchin-like asymmetric composite phase change chitosan aerogel with a TiO2 / rGO heterostructure, its preparation method, and its application. Background Technology

[0002] Volatile organic pollutants (VOCs), as one of the main sources of air pollution, pose a critical challenge to environmental governance in low-temperature, enclosed environments (such as cold chain workshops, indoor spaces in winter, and low-temperature storage spaces). These environments typically operate at temperatures between -10°C and 15°C, significantly reducing the thermal activity of VOC molecules. This makes them easily adsorbed onto aerosol particles or the condensation surfaces of equipment, leading to multiple bottlenecks in traditional purification technologies: Traditional adsorption technologies (such as activated carbon adsorption) possess a certain initial adsorption capacity at low temperatures, but are prone to adsorption saturation failure, and adsorbent regeneration requires significant heat energy, posing a risk of secondary pollution; simple thermocatalysis technologies require maintaining a high-temperature reaction environment (typically ≥50°C), and in low-temperature scenarios, heat dissipates rapidly, resulting in a sharp drop in energy efficiency, failing to meet actual purification needs; photocatalysis relies on photogenerated carriers on the catalyst surface to oxidize and degrade VOCs, but molecular activity is insufficient at low temperatures, and traditional photocatalysts (such as pure TiO2) have high photogenerated electron-hole recombination rates and low photothermal conversion efficiency, further limiting catalytic performance.

[0003] To address the aforementioned issues, Chinese patent CN113416345A discloses a chitosan-diatomaceous earth composite phase change aerogel. While it achieves low-temperature heat storage and release, it lacks a photothermal catalytic functional component, resulting in a separation between catalytic and energy storage functions and an inability to achieve synergistic effects in VOCs degradation and heat regulation. Chinese patent CN113398904A discloses a catalyst for the synergistic catalysis of VOCs using photothermal and electrochemical methods at medium and low temperatures. However, it lacks a phase change energy storage synergy mechanism, leading to rapid heat loss at low temperatures. Furthermore, its substrate, titanium dioxide nanotubes, exhibits poor biocompatibility and is difficult to degrade. Chinese patent CN113070073A discloses a PtCu / TiO2 photothermal catalyst, which requires a high-temperature environment of 77 ℃ to achieve an 80% toluene degradation rate. Its suitable temperature range is 25-200 ℃, and its catalytic efficiency is almost zero at low temperatures of -10 ℃ to 15 ℃, completely failing to meet the VOCs treatment needs of low-temperature scenarios such as cold chain workshops.

[0004] In addition, existing technologies also have the following common problems: First, the functional synergy is insufficient. Photothermal catalysis and phase change energy storage have not formed an effective synergistic system, which cannot solve the core contradiction of low molecular activity and easy heat loss at low temperatures. Second, the structural design is unreasonable. Most materials adopt symmetrical porous structures, resulting in disordered VOCs mass transfer pathways, low contact rate of catalyst active sites, and limited purification efficiency. Third, stability and environmental protection are lacking. Phase change microcapsules mostly adopt physical filling methods, which are prone to disintegration during recycling. Moreover, most materials rely on precious metal components (such as Pt and Cu) or non-biomass substrates, resulting in defects such as high cost, high energy consumption, poor biocompatibility, and easy secondary pollution.

[0005] Therefore, developing a composite aerogel material that combines low-temperature high-efficiency catalysis, photothermal-energy storage synergy, mass transfer path optimization, and green environmental protection characteristics to achieve efficient and stable purification of VOCs in a low-temperature closed environment of -10 ℃ to 15 ℃ has become an urgent technical problem to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to solve the technical problems of existing VOCs purification materials, such as the sharp drop in catalytic efficiency in low-temperature closed environments of -10~15 ℃, insufficient synergy between photothermal catalysis and phase change energy storage, disordered mass transfer pathways caused by symmetrical porous structures, easy disintegration of phase change microcapsules and poor environmental performance due to reliance on precious metals or non-biomass substrates, and high cost and energy consumption. The invention provides a biomimetic sea urchin-like asymmetric composite phase change chitosan aerogel with a titanium dioxide / reduced graphene oxide (TiO2 / rGO) heterostructure, its preparation method and application, to achieve efficient and stable purification of VOCs at low temperatures.

[0007] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0008] The first aspect of this invention provides a method for preparing a biomimetic sea urchin-like asymmetric composite phase change chitosan aerogel loaded with titanium dioxide / reduced graphene oxide heterostructure, comprising the following steps:

[0009] (1) Argon (Ar) plasma etching was performed on the graphene oxide (GO) dispersion to form dual-scale defects in the graphene oxide; tetrabutyl titanate was added dropwise to the etched graphene oxide dispersion in two steps at different rates to form titanium dioxide nanoribbons and titanium dioxide microcrystals respectively; the pH of the system was adjusted to acidic and catechol was added, and titanium dioxide / reduced graphene oxide (rGO) heterojunction was obtained through hydrothermal reaction;

[0010] (2) Using epoxidized soybean oil acrylate as the core material, chitosan-polyurea-nano titanium dioxide composite as the shell material, chitosan-dopamine copolymer as the tenon and tooth material, and titanium dioxide microcrystals as the anchor material; the core material and shell material are mixed at a mass ratio of (6-8):(2-4), and emulsifier and toluene are added and stirred evenly to obtain an oil phase; melamine is dissolved in water, formaldehyde solution is added, and the resulting melamine-formaldehyde (MF) prepolymer aqueous solution is used as the aqueous phase; the oil phase is dropped into the aqueous phase and stirred to disperse, and then the tenon and tooth material and anchor material are added. After shear emulsification, polymerization at 70-80 ℃, and curing at 80-100 ℃, and after separation, washing and drying, a phase change microcapsule is obtained, consisting of a core layer, a shell layer covering the outside of the core layer, tenon and tooth protruding from the surface of the shell layer, and anchor points loaded on the surface of the tenon and tooth.

[0011] (3) Disperse the titanium dioxide / reduced graphene oxide heterojunction obtained in step (1) in water to obtain a titanium dioxide / reduced graphene oxide heterojunction dispersion with a concentration of 0.5-1 g / L; dissolve chitosan powder in dilute acetic acid solution to obtain a chitosan solution with a concentration of 1-3 % w / v; mix the titanium dioxide / reduced graphene oxide heterojunction dispersion and the chitosan solution at a volume ratio of 1:(3-5) to obtain a composite sol; pour the composite sol into a custom mold containing a planar side and a protrusion array side, and perform unidirectional freezing treatment from top to bottom to allow chitosan and titanium dioxide / reduced graphene oxide heterojunction to self-assemble into biomimetic sea urchin-shaped nanofiber bundles; after freeze-drying, perform thermal crosslinking or glutaraldehyde vapor chemical crosslinking treatment to obtain a biomimetic sea urchin-shaped asymmetric structure chitosan aerogel skeleton loaded with titanium dioxide / reduced graphene oxide heterojunction.

[0012] (4) The phase change microcapsules obtained in step (2) are dispersed in ethanol at a solid-liquid ratio of 1:(9-11) to obtain a phase change microcapsule suspension; the biomimetic sea urchin-like asymmetric structure chitosan aerogel framework with titanium dioxide / reduced graphene oxide heterostructure obtained in step (3) is immersed in the phase change microcapsule suspension for 30-60 min under vacuum conditions of -0.05 MPa ~ -0.15 MPa, the vacuum is released and then immersed for 3-5 h, and after vacuum drying, a biomimetic sea urchin-like asymmetric structure composite phase change chitosan aerogel framework with titanium dioxide / reduced graphene oxide heterostructure is obtained, wherein the loading of phase change microcapsules is 30-40 wt%;

[0013] (5) Dissolve dopamine hydrochloride in a Tris-HCl buffer solution with a pH of 8.0-8.8 to obtain a dopamine solution with a concentration of 0.5-4 mg / mL; immerse the biomimetic sea urchin-like asymmetric structure composite phase change chitosan aerogel skeleton with titanium dioxide / reduced graphene oxide heterostructure obtained in step (4) in the dopamine solution, so that dopamine is polymerized in situ on the surface of the biomimetic sea urchin-like asymmetric structure composite phase change chitosan aerogel skeleton with titanium dioxide / reduced graphene oxide heterostructure to form a polydopamine coating layer with a thickness of 50-100 nm, and obtain the biomimetic sea urchin-like asymmetric structure composite phase change chitosan aerogel with titanium dioxide / reduced graphene oxide heterostructure after drying.

[0014] This invention uses chitosan as a substrate and constructs a biomimetic sea urchin-like microstructure and macroscopic asymmetric ladder-like channels through a customized mold and unidirectional freezing process. TiO2 / rGO heterojunctions are uniformly loaded in the framework, and phase change microcapsules are then "stuck" into secondary branch pores through vacuum impregnation. The elastic deformation of the shell forms a "ring buckle" to prevent the microcapsules from falling off. Finally, a polydopamine coating layer is formed on the outer layer of the aerogel through in-situ polymerization of dopamine, which enhances the surface adsorption and structural integrity, while synergistically improving photothermal efficiency.

[0015] This invention addresses the low catalytic efficiency at low temperatures by constructing a synergistic mechanism of "photothermal catalysis-phase change energy storage." It utilizes a TiO2 / rGO heterojunction to achieve photothermal conversion, relying on phase change microcapsules to store heat and maintain a catalytic reaction temperature of 25-30 °C, thus solving the problems of insufficient molecular activity and rapid heat loss at low temperatures. To address the issues of microcapsule detachment and chaotic mass transfer pathways, a biomimetic asymmetric channel and a dual fixation structure of "core-shell-mortise and tenon teeth-anchor point" are designed. Macroscopically, the microcapsules are fixed by a "ring snap" through secondary branch holes; microscopically, the mechanical interlocking of the mortise and tenon teeth chemically bonds with the TiO2 anchor point, while directional channels shorten the mass transfer path. To address the issues of poor environmental friendliness and high energy consumption, biodegradable natural raw materials such as chitosan, soybean oil, and dopamine are used, avoiding the use of precious metals and non-biomass substrates. Furthermore, the preparation process does not require high-temperature calcination, effectively reducing energy consumption and costs.

[0016] Further, in step (1), the graphene oxide dispersion is prepared by dispersing graphene oxide in water, and the concentration of the graphene oxide dispersion is 1-3 g / L.

[0017] Further, in step (1), the parameters of the argon plasma etching are: power 45-55 W, time 8-12 min, vacuum degree 0.05-0.2 Pa, and argon flow rate 5-15 sccm.

[0018] Further, in step (1), before adding tetrabutyl titanate, anhydrous ethanol is added to the etched graphene oxide dispersion, and the volume ratio of the anhydrous ethanol to the etched graphene oxide dispersion is (1-1.5):10.

[0019] Further, in step (1), tetrabutyl titanate is first added at a rate of 0.5-1 mL / min to form titanium dioxide (TiO2) nanoribbons, and then tetrabutyl titanate is added at a rate of 2-3 mL / min to form titanium dioxide microcrystals; the volume ratio of tetrabutyl titanate added at a rate of 0.5-1 mL / min to the etched graphene oxide dispersion is (2-4):100, and the volume ratio of tetrabutyl titanate added at a rate of 2-3 mL / min to the etched graphene oxide dispersion is (1-3):100.

[0020] Furthermore, in step (1), hydrochloric acid is used to adjust the pH of the system to 2-3.

[0021] Further, in step (1), the mass ratio of catechol to graphene oxide is (0.2-0.4):100.

[0022] Furthermore, in step (1), the temperature of the hydrothermal reaction is 170-190 °C and the time is 10-14 h.

[0023] Further, in step (1), the mass ratio of titanium dioxide to reduced graphene oxide in the titanium dioxide / reduced graphene oxide heterojunction is (3-4):1.

[0024] Further, in step (1), the particle size of the titanium dioxide / reduced graphene oxide heterojunction is 80-150 nm.

[0025] Furthermore, in step (1), the titanium dioxide crystal form in the heterojunction is anatase phase. Anatase phase TiO2 has excellent photocatalytic activity and photothermal conversion efficiency, which is suitable for the low-temperature VOCs purification requirements.

[0026] This invention constructs a dual-scale defect structure for graphene oxide using Ar plasma etching. This design retains the high conductivity of rGO while providing sufficient anchoring sites for TiO2 loading, effectively solving the technical problems of easy TiO2 detachment and low charge transport efficiency in traditional processes. Subsequently, the growth morphology of TiO2 is precisely controlled by stepwise addition of tetrabutyl titanate. The slow dropping process forms TiO2 nanoribbons with a width of 30-50 nm and a length of 500-800 nm, while the fast dropping process forms TiO2 microcrystals with a particle size of 8-12 nm. The synergistic effect of the two morphologies avoids the problem of easy aggregation and pore blockage of TiO2 with a single morphology, and at the same time, it constructs a dual channel for photon capture and charge transport. Finally, catechol is added as a grain boundary promoter to catalyze the formation of Ti-C covalent bonds and Ti-OC grain boundary fusion structure between Ti and rGO, realizing the three-dimensional interlocking of TiO2 and rGO, forming a scale intercalation-grain boundary interlocking TiO2 / rGO composite structure, so that the product has both excellent photothermal conversion efficiency and structural stability.

[0027] In a specific embodiment, in step (1), 0.1-0.3 g of GO is added to 100 mL of deionized water and ultrasonically dispersed for 20-40 min to obtain a GO dispersion. The dispersion is then subjected to Ar plasma etching with the following parameters: power 45-55 W, time 8-12 min, vacuum 0.05-0.2 Pa, and argon flow rate 5-15 sccm, to construct dual-scale defects on and inside the GO sheet. 10-15 mL of anhydrous ethanol is added to the etched GO dispersion and magnetically stirred at 200-400 rpm for 10 min to ensure uniform mixing. Then, tetrabutyl titanate is added in a stepwise dropping manner: first, 2-4 mL is slowly added at a rate of 0.5-1 mL / min, and then 1-3 mL is quickly added at a rate of 2-3 mL / min to precisely control the growth morphology of TiO2. The pH of the system was adjusted to 2-3 using 1 mol / L hydrochloric acid solution, and the mixture was stirred at 40-60 °C for 1-3 h. Simultaneously, 0.2-0.4 wt% catechol (based on GO mass) was added to enhance the bonding between Ti and the subsequently reduced rGO. The system was then transferred to a hydrothermal reactor and reacted at 170-190 °C for 10-14 h. After the reaction, the mixture was cooled to room temperature and washed three times by centrifugation at 7000-9000 rpm to obtain a TiO2 / rGO heterojunction. The mass ratio of TiO2 to rGO in this heterojunction was (3-4):1, and the particle size was 80-150 nm.

[0028] Furthermore, in step (2), the epoxidized soybean oil acrylate is of industrial grade, with an iodine value ≤ 5 gI2 / 100 g and an acid value ≤ 1 mg KOH / g.

[0029] Furthermore, in step (2), the crystal form of the nano-titanium dioxide and the crystal form of the titanium dioxide microcrystals used for anchoring are both anatase phase. Their high specific surface area and active sites can enhance the mechanical strength and catalytic synergy of the shell, avoid leakage of core layer phase change material, and improve VOCs degradation efficiency.

[0030] Further, in step (2), the preparation method of the chitosan-polyurea-nano titanium dioxide composite is as follows: chitosan is dissolved in dilute acetic acid solution, nano titanium dioxide is added and dispersed evenly, isophorone diisocyanate is added, and after heating and stirring reaction, separation, washing and drying treatment, the chitosan-polyurea-nano titanium dioxide composite is obtained.

[0031] Further, in step (2), the preparation method of the chitosan-dopamine copolymer is as follows: chitosan is dissolved in dilute acetic acid solution, dopamine compounds are added and the pH is adjusted to acidic, a crosslinking agent is added and the reaction is stirred, and the mixture is purified by dialysis and freeze-dried to obtain the chitosan-dopamine copolymer.

[0032] Further, in step (2), the preparation method of the chitosan-polyurea-nano titanium dioxide composite is as follows: 1-2 g of chitosan is dissolved in 100 mL of 1% v / v dilute acetic acid solution, 0.3-0.5 g of nano titanium dioxide (particle size of 10-20 nm) is added, and ultrasonically dispersed for 20-30 min; 0.5-1 mL of isophorone diisocyanate (IPDI) is added dropwise to the system, and the mixture is stirred and reacted at 50-55 ℃ for 3-4 h, centrifuged and washed (8000 rpm, 10 min) 3 times, and vacuum dried at 60-70 ℃ for 3-4 h to obtain the chitosan-polyurea-nano titanium dioxide composite.

[0033] Further, in step (2), the preparation method of the chitosan-dopamine copolymer is as follows: 1-2 g of chitosan is dissolved in 50 mL of 1% v / v dilute acetic acid solution, 0.2-0.3 g of dopamine hydrochloride is added, and the pH is adjusted to 5.0-6.0; 0.1-0.2 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) is added as a crosslinking agent, the mixture is stirred at room temperature for 10-12 h, dialyzed (molecular weight cutoff 8 kDa) for 24-30 h, and freeze-dried at -50 ℃ ~ -55 ℃ (vacuum degree 5-5.5 Pa) to obtain the chitosan-dopamine copolymer. Further, in step (2), the total mass of the core material and the shell material to the volume ratio of toluene is 1 g : 2-3 mL.

[0034] Further, in step (2), the emulsifier is Span-80, and the mass ratio of the total mass of the core material and the shell material to the mass of the emulsifier is 100:(0.4-0.6).

[0035] Further, in step (2), the mass ratio of melamine to water is 1 g : 15-20 mL, the molar ratio of melamine to formaldehyde is 1:(2-3), and the concentration of the formaldehyde solution is 30-40 wt%.

[0036] Further, in step (2), melamine is dissolved in water, formaldehyde solution is added, the pH is adjusted to 4.5-5.0 and reacted at 60-80 °C to obtain an aqueous solution of melamine-formaldehyde prepolymer.

[0037] Further, in step (2), the volume ratio of toluene to water is 1:(2-3).

[0038] Further, in step (2), the total mass ratio of the core material and shell material to the mortise and tenon material is 100:(4-6), and the total mass ratio of the core material and shell material to the anchor material is 100:(2-4).

[0039] Further, in step (2), shear emulsification is performed at a rotation speed of 14,000-16,000 rpm for 5-10 min.

[0040] Furthermore, in step (2), the polymerization time is 1-3 h and the curing time is 1-2 h.

[0041] Further, in step (2), the specific operation of the separation, washing and drying process is as follows: centrifuge at 5000-7000 rpm for 10-20 min to wash until neutral, and vacuum dry at 50-70 ℃ for 5-7 h.

[0042] Furthermore, in step (2), the core diameter of the phase change microcapsule is 8-11 μm and the shell thickness is 150-250 nm.

[0043] Furthermore, in step (2), the particle size of the phase change microcapsules is 8-12 μm.

[0044] Further, in step (2), the surface of the phase change microcapsule has 4-6 tenon teeth, the length of the tenon teeth is 3-5 μm, the width is 80-100 nm and the height is 50-80 nm; each tenon tooth surface is loaded with 6-8 anchor points with a spacing of 10-15 nm.

[0045] This invention employs interfacial polymerization to prepare phase change microcapsules, achieving functional optimization through precise material ratios and process design: epoxidized soybean oil acrylate serves as the core material, ensuring sufficient phase change enthalpy to meet energy storage requirements; the chitosan-polyurea-nano titanium dioxide composite serves as the shell material, guaranteeing the mechanical strength and compatibility of the microcapsules and effectively preventing core material leakage; the added Span-80 is a hydrophobic emulsifier that significantly reduces the interfacial tension between the oil phase (core material, shell material, toluene) and the aqueous phase (MF prepolymer aqueous solution), allowing the oil phase to be uniformly dispersed into 8-11 μm droplets, suitable for the subsequent aerogel secondary branch pores (12-15 μm); the chitosan-dopamine copolymer forms a tenon-and-mortise structure on the microcapsule surface, with titanium dioxide microcrystals acting as anchors on the tenon-and-mortise surface. The synergistic effect of these two—the tenon-and-mortise achieves mechanical interlocking, and the titanium dioxide anchors form a chemical bond—solves the technical defect of traditional microcapsules that rely solely on physical filling and are prone to detachment. By employing a shear emulsification process, the diameter of the microcapsule core layer is precisely controlled within 8-11 μm. This avoids both excessively large particle sizes that prevent entry into the secondary branch pores of the aerogel and insufficient phase transition enthalpy due to excessively small particle sizes. The subsequent polymerization and curing process fully crosslinks the MF prepolymer with the chitosan-dopamine copolymer, further enhancing the compactness of the microcapsule shell, reducing the initial delamination rate, and ensuring the structural stability and reliability of the microcapsules.

[0046] Further, in step (3), the method for preparing the chitosan solution includes the following steps: dissolving chitosan powder in a 1-2% v / v dilute acetic acid solution and magnetically stirring at a speed of 1000-2000 rpm to obtain the chitosan solution.

[0047] Further, in step (3), the titanium dioxide / reduced graphene oxide heterojunction dispersion is mixed with the chitosan solution at a volume ratio of 1:(3-5) and stirred vigorously at a speed of 700-900 rpm for 20-40 min to obtain a composite sol.

[0048] Furthermore, in step (3), the material of the customized mold is polytetrafluoroethylene.

[0049] Further, in step (3), the customized mold includes a planar side and a protrusion array side arranged opposite to each other, a closed baffle vertically connecting the two, and a detachable upper cover plate and a lower cover plate; the protrusion array side is provided with cylindrical protrusions, the diameter of the cylindrical protrusions is 0.2-0.3 mm, the height is 0.3-0.5 mm, the protrusion spacing is 0.5-0.8 mm, and the arrangement is an equilateral triangle arrangement.

[0050] Furthermore, in step (3), the thickness of the sealing baffle is 5-7 mm, and it is vertically connected to the planar side and the protrusion array side to form a sealed cavity.

[0051] Furthermore, in step (3), the upper cover plate is a perforated plate and the lower cover plate is a cold source contact plate.

[0052] Furthermore, in step (3), the temperature of the unidirectional freezing treatment is -80 ℃ ~ -100 ℃, and the time is 4-6h.

[0053] Furthermore, in step (3), the freeze-drying temperature is -50 ℃ ~ -60 ℃, the vacuum degree is 5-10 Pa, and the time is 48-72 h.

[0054] Further, in step (3), the temperature of the thermal crosslinking is 120-150 °C and the time is 1-3 h; the specific operation of the glutaraldehyde vapor chemical crosslinking treatment is as follows: a glutaraldehyde aqueous solution with a mass fraction of 25% is used as the steam source, and the aerogel skeleton and the glutaraldehyde aqueous solution are placed alternately in a sealed container to avoid direct contact, and the vapor crosslinking treatment is carried out at room temperature for 1-3 h.

[0055] Furthermore, in step (3), the biomimetic asymmetric chitosan aerogel skeleton has a macroscopic asymmetric pore structure with ladder-like or multi-level pores oriented in a single direction.

[0056] Furthermore, in step (3), the biomimetic asymmetric chitosan aerogel skeleton has primary main pores with a pore size of 80-100 μm and secondary branch pores with a pore size of 12-15 μm.

[0057] This invention selects a chitosan solution of a specific concentration, balancing the spinnability and gelling properties of the sol. Dilute acetic acid is used as a solvent to dissolve the chitosan, avoiding the problem of decreased cross-linking efficiency caused by excessive acidity. The TiO2 / rGO heterojunction dispersion is mixed with the chitosan solution at a volume ratio of 1:(3-5), ensuring sufficient photothermal catalytic sites in the system without damaging the chitosan gel network structure. Stirring effectively eliminates agglomeration within the system, ensuring the uniformity of the composite sol. A custom mold with a flat side and a raised array on the other side induces the formation of ladder-like asymmetric channels oriented in a single direction. During freezing, the top of the mold is exposed to room temperature, while the bottom is in close contact with the cold source, creating a stable temperature gradient. Unidirectional freezing at -80℃ to -100℃ promotes the directional growth of ice crystals from the bottom to the top of the mold. The chitosan molecular chains and TiO2 / rGO heterojunctions are squeezed into the ice crystal gaps and self-assemble to form particles with a size of 1-10 mm. The use of μm-sized biomimetic sea urchin-shaped nanofiber bundles (radial nanoneedle-like microspheres) significantly increases the specific surface area of ​​the aerogel, providing ample adsorption sites and diffusion space for VOCs molecules. The freeze-drying process allows ice crystals to sublimate directly under low temperature and low pressure conditions, preventing the aerogel framework from collapsing due to liquid phase surface tension and preserving its porous structure. Subsequent thermal crosslinking or glutaraldehyde vapor crosslinking treatments not only strengthen the hydrogen and covalent bonds between chitosan molecules but also prevent high temperatures from damaging the structure of the TiO2 / rGO heterojunction. The mechanical strength of the crosslinked aerogel framework is significantly improved while maintaining good structural integrity, ultimately constructing a biomimetic sea urchin-shaped asymmetric chitosan aerogel framework loaded with TiO2 / rGO heterojunctions.

[0058] Specifically, after the TiO2 / rGO heterojunction is mixed with the chitosan solution, it undergoes unidirectional freeze-induced self-assembly and is uniformly loaded onto the surface of the chitosan nanofiber bundle and the inner wall of the pores. During the subsequent freeze-drying to remove the ice crystal template and thermal or chemical cross-linking to strengthen the framework structure, the loading state of the TiO2 / rGO heterojunction remains intact, and it always maintains stable dispersion and firm bonding.

[0059] Further, in step (4), the phase change microcapsules are dispersed in ethanol at a solid-liquid ratio of 1:(9-11) and sonicated at a power of 150-250W for 10-30 min to obtain a phase change microcapsule suspension.

[0060] Furthermore, in step (4), the vacuum drying temperature is 50-60 ℃ and the time is 2-4 h.

[0061] This invention ensures uniform dispersion of microcapsules and avoids agglomeration by controlling the solid-liquid ratio of phase change microcapsules. Combined with ultrasonic treatment to break the van der Waals forces between microcapsules, the stability of the suspension is further improved. When the aerogel framework is placed in a vacuum environment, the air in its pores can be fully expelled, opening permeation channels for the phase change microcapsule suspension, allowing the suspension to smoothly penetrate into the primary pores and secondary branch pores. Continued impregnation after releasing the vacuum significantly improves the microcapsule filling rate. The drying temperature is lower than the microcapsule phase change temperature, effectively removing ethanol solvent from the system while preventing microcapsule melting and leakage, and ensuring a tight bond between the microcapsules and the aerogel framework. A vacuum-assisted impregnation method is used to introduce phase change microcapsules into the three-dimensional network of the aerogel framework, ultimately controlling the phase change microcapsule loading at 30-40 wt%. 30 wt% is the lower limit to ensure phase change energy storage efficiency, and 40 wt% is the upper limit to avoid pore blockage, preventing excessive phase change microcapsules from filling and clogging the pores, thus affecting the mass transfer efficiency of VOCs. The secondary branch pores of the aerogel framework exhibit a differentiated structure with inlet pore diameters slightly smaller than the main pore diameters. The main pore diameter within the channels is 12-15 μm, while the inlet pore diameter connected to the primary main pore is 10-11 μm. This structure is formed using a unidirectional freezing process. Due to the compression effect of the mold's protrusion array at the inlet location, the directional growth of ice crystals is limited by the gaps between the protrusions, ultimately resulting in the pore size difference. This gradient pore size design can adapt to the size and deformation characteristics of phase change microcapsules. Utilizing the 10-12% elastic deformation capacity of the phase change microcapsule shell, the microcapsules are inserted into the channels, forming a ring-shaped mechanical fixing structure. This effectively prevents the microcapsules from detaching during repeated use, improving structural stability.

[0062] Further, in step (5), dopamine hydrochloride is dissolved in a 10 mM Tris-HCl buffer solution with a pH of 8.0-8.8 to obtain a dopamine solution with a concentration of 0.5-4 mg / mL. This concentration and pH provide the optimal reaction environment for the in-situ self-polymerization of dopamine: when the pH is below 8.0, the dopamine polymerization rate is too slow, making it difficult to form a complete coating layer on the aerogel surface; when the pH is above 8.8, the polymerization reaction is too fast and easily causes dopamine aggregation, making it impossible to prepare a coating layer of uniform thickness. If the dopamine concentration is too low, a continuous coating layer cannot be formed on the aerogel surface, making it difficult to exert the adsorption synergistic effect of hydroxyl and amino groups and the interface strengthening effect; if the concentration is too high, it will lead to an excessively thick polydopamine coating layer, which will not only block the hierarchical pores of the aerogel and affect the mass transfer of VOCs and the stability of microcapsule loading, but also reduce the photothermal response efficiency of the aerogel due to the accumulation of the coating layer.

[0063] Further, in step (5), the biomimetic sea urchin-like asymmetric composite phase change chitosan aerogel framework loaded with titanium dioxide / reduced graphene oxide heterostructure is immersed in the dopamine solution and stirred at 25-40 °C for 24-30 h at a speed of 40-60 rpm, so that dopamine is polymerized in situ on the surface of the biomimetic sea urchin-like asymmetric composite phase change chitosan aerogel framework loaded with titanium dioxide / reduced graphene oxide heterostructure to form a polydopamine coating layer with a thickness of 50-100 nm; after rinsing, it is freeze-dried at -40 °C to -50 °C for 20-24 h to obtain the biomimetic sea urchin-like asymmetric composite phase change chitosan aerogel loaded with titanium dioxide / reduced graphene oxide heterostructure.

[0064] In this invention, the polydopamine coating layer possesses multiple synergistic effects: First, the hydroxyl and amino active groups abundant in the coating layer can form hydrogen bonds and van der Waals forces with VOCs molecules, significantly enhancing the adsorption capacity of the aerogel for VOCs; Second, polydopamine strengthens the interfacial bonding between the phase change microcapsules and the aerogel framework through CN covalent bonds and homologous hydrogen bonds with chitosan, further reducing the risk of microcapsule detachment; Third, the excellent light absorption characteristics of polydopamine itself can form a synergistic effect with the TiO2 / rGO heterojunction, greatly improving the photothermal conversion efficiency of the aerogel and significantly improving the problem of low photothermal response efficiency of a single TiO2 / rGO heterojunction under weak light conditions.

[0065] The second aspect of this invention provides a biomimetic sea urchin-like asymmetric composite phase change chitosan aerogel with a titanium dioxide / reduced graphene oxide heterostructure prepared by the preparation method described in the first aspect.

[0066] The present invention provides a biomimetic sea urchin-like asymmetric composite phase change chitosan aerogel with a titanium dioxide / reduced graphene oxide heterostructure, the specific composition of which is as follows: a biomimetic sea urchin-like asymmetric chitosan aerogel framework with a TiO2 / rGO heterostructure, a "core-shell-mortise and tenon-anchor" type phase change microcapsule (mortise and tenon width is 80-100 nm) embedded in the secondary branch channels of the framework and in the nanoneedle gaps (gap width 100-200 nm) of the biomimetic sea urchin-like microspheres, and a polydopamine coating layer covering the surface of the aerogel.

[0067] The third aspect of this invention provides the application of the biomimetic sea urchin-like asymmetric composite phase change chitosan aerogel with a titanium dioxide / reduced graphene oxide heterostructure as described in the second aspect in the purification of volatile organic pollutants.

[0068] The biomimetic sea urchin-like asymmetric composite phase change chitosan aerogel with a titanium dioxide / reduced graphene oxide heterostructure provided by this invention is suitable for low-temperature closed environments of -10 ℃ to 15 ℃ (such as cold chain workshops and indoor spaces in winter), and can achieve photothermal catalysis-phase change energy storage synergistic purification of VOCs such as toluene and formaldehyde.

[0069] The biomimetic sea urchin-like asymmetric composite phase change chitosan aerogel with a titanium dioxide / reduced graphene oxide heterostructure provided by this invention achieves highly efficient VOCs purification in low-temperature environments through a triple synergistic mechanism: the photothermal conversion capability of the TiO2 / rGO heterostructure provides a heat source for phase change energy storage, maintaining the catalytic reaction temperature of 25-30 °C using the phase change energy storage module; the biomimetic asymmetric channels directionally guide VOCs diffusion, significantly shortening the mass transfer path; and the high specific surface area of ​​the aerogel itself, combined with the strong adsorption effect of the polydopamine coating, promotes rapid enrichment of VOCs and their contact with TiO2 catalytic sites, significantly improving degradation efficiency. The synergistic effect of these three mechanisms ultimately achieves a VOCs removal rate of ≥80% in the -10 °C to 15 °C low-temperature range, and a phase change microcapsule desorption rate of ≤3% after 100 cycles, exhibiting excellent structural stability and cycle durability. It is suitable for highly efficient VOCs purification in low-temperature, enclosed environments such as cold chain workshops and indoor spaces during winter.

[0070] Compared with the prior art, the above-described technical solution of the present invention has the following advantages:

[0071] 1. The TiO2 / rGO heterojunction prepared in this invention possesses a scale-intercalation-grain boundary interlocking structure. GO is bombarded with Ar plasma, forming a dual-scale defect structure on its surface consisting of macroscopic trenches (200-300 nm) and microscopic mesopores (5-10 nm). This structure retains the high conductivity of rGO while also creating dual channels for photon capture and charge transport. Further stepwise addition of tetrabutyl titanate induces the formation of dual-morphology TiO2, consisting of nanoribbons and microcrystals, effectively preventing the aggregation and pore blockage of single-morphology TiO2. Subsequent catechol catalysis promotes the formation of a Ti-C covalent bond and Ti-OC grain boundary fusion structure, ultimately achieving a stereochemical interlock between TiO2 and rGO. This TiO2 / rGO heterojunction effectively solves the technical problems of easy TiO2 detachment and low charge transport efficiency, significantly improving photothermal catalytic performance.

[0072] 2. This invention employs a customized mold to induce the formation of macroscopic asymmetric channels, combined with a -80℃ to -100℃ unidirectional freezing process, to promote the self-assembly of chitosan nanofibers into 1-10 μm biomimetic sea urchin-like microsphere structures, significantly increasing the specific surface area of ​​the aerogel and providing ample adsorption sites and diffusion channels for VOCs molecules. TiO2 / rGO heterojunctions undergo unidirectional freeze-induced self-assembly, uniformly loading onto the surface of the chitosan nanofiber bundles and the inner walls of the channels. The mechanical strength of the aerogel framework is enhanced through thermal or chemical crosslinking, followed by in-situ polydopamine coating modification. The hydroxyl and amino groups abundant in the coating layer form hydrogen bonds and van der Waals forces with VOCs molecules, significantly enhancing the aerogel's adsorption affinity for VOCs. Ultimately, the aerogel achieves an adsorption capacity of ≥15 mg / g for VOCs, while the directional channels guide the orderly diffusion of VOCs molecules, preventing localized pollutant aggregation and ensuring the stability of the catalytic degradation process.

[0073] 3. This invention prepares phase change microcapsules with a targeted anchoring "core-shell-mortise and tenon-anchor" structure. The structural design achieves a dual stable combination of microcapsules and aerogel framework: At the macroscopic level, the particle size of the microcapsule core layer (8-11 μm) is precisely matched with the secondary branch channels of the aerogel (12-15 μm). With the help of the elastic deformation of the shell, the microcapsule can firmly "lock" into the pore entrance with a pore size of 10-11 μm, forming a mechanical locking structure, which effectively prevents the microcapsule from falling off axially. At the microscopic level, the mortise and tenon of the chitosan-dopamine copolymer on the surface of the microcapsule tightly interlocks with the micro-indentations on the surface of the biomimetic sea urchin-shaped nanoneedles. At the same time, the TiO2 microcrystalline anchors are embedded in the rGO mesopores, and the chemical bonding effect of CN covalent bonds and homologous hydrogen bonds between polydopamine and chitosan further strengthens the interfacial bonding force. After 100 cycles of phase change-adsorption-desorption combined testing, the phase change microcapsule showed a desorption rate of ≤3%, solving the technical problems of high desorption rate (≥30%) and rapid performance degradation of traditional filled microcapsules.

[0074] 4. The biomimetic sea urchin-like asymmetric composite phase change chitosan aerogel with a titanium dioxide / reduced graphene oxide heterostructure provided by this invention combines environmental friendliness and low energy consumption with adaptability to low-temperature environments. The raw materials used are biodegradable natural substances such as chitosan, soybean oil, and dopamine, reducing costs by more than 30% compared to precious metal-based photothermal materials. The purification process requires no external heating equipment, relying on the light energy capture and photothermal conversion capabilities of the TiO2 / rGO heterostructure under weak light / low temperature environments, combined with the heat storage function of soybean oil-based phase change microcapsules, achieving both high purification efficiency and economical use. Addressing the problem of a sharp drop in photocatalytic activity under low-temperature environments, the phase change microcapsules can slowly release the stored heat, stabilizing the catalytic reaction temperature inside the aerogel at 25-30 ℃, achieving synergistic purification of volatile organic pollutants through photothermal catalysis and phase change energy storage in low-temperature environments. This effectively avoids the technical defects of traditional filled microcapsules, such as high detachment rates and rapid performance degradation during low-temperature purification cycles. Attached Figure Description

[0075] Figure 1 This is a schematic diagram of the protrusion arrangement on the protrusion array side of the customized mold in this invention.

[0076] Figure 2 This is a schematic diagram of the phase change microcapsule in Example 1.

[0077] Figure 3 This is a schematic diagram of the biomimetic sea urchin-like asymmetric chitosan aerogel framework loaded with TiO2 / rGO heterojunctions in Example 1.

[0078] Figure 4 This is a schematic diagram of the biomimetic sea urchin-like asymmetric composite phase change chitosan aerogel framework loaded with TiO2 / rGO heterojunction in Example 1.

[0079] Figure reference numerals: 11. Epoxidized soybean oil acrylate (core layer); 12. Chitosan-polyurea-nano TiO2 composite (shell layer); 13. TiO2 microcrystals (anchor points); 14. Chitosan-dopamine copolymer (mortise and tenon joints); 21. Primary main pore; 22. Secondary branch pore; 23. TiO2 / rGO heterojunction; 24. Biomimetic sea urchin-like nanofiber bundle loaded with TiO2 / rGO heterojunction; 31. Phase change microcapsule. Detailed Implementation

[0080] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0081] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0082] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are commercially available.

[0083] The graphene oxide used in the following examples was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with a purity ≥99% and a sheet diameter of 0.5-3 μm; tetrabutyl titanate was purchased from Sinopharm Chemical Reagent Co., Ltd., with analytical grade purity; catechol was purchased from Suzhou Senfida Chemical Co., Ltd., with analytical grade purity; chitosan was purchased from Shanghai Enzyme-Linked Biotechnology Co., Ltd., with a degree of deacetylation ≥90% and a viscosity of 100-200 mPa·s; epoxidized soybean oil acrylate was purchased from Jiangsu Sirbang Petrochemical Co., Ltd., with industrial grade purity, iodine value ≤5 g I2 / 100 g, and acid value ≤1 mg KOH / g; melamine was purchased from Sinopharm Chemical Reagent Co., Ltd., with analytical grade purity; formaldehyde solution was purchased from Sinopharm Chemical Reagent Co., Ltd., with analytical grade purity and a concentration of 37%. wt%, containing 10% methanol stabilizer; dopamine hydrochloride was purchased from Shanghai Yuanye Biotechnology Co., Ltd., with analytical grade purity; tris(hydroxymethyl)aminomethane (Tris) was purchased from Beijing Solarbio Technology Co., Ltd., with analytical grade purity; Span-80 was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with analytical grade purity; anhydrous ethanol was purchased from Sinopharm Chemical Reagent Co., Ltd., with analytical grade purity; hydrochloric acid was purchased from Sinopharm Chemical Reagent Co., Ltd., with analytical grade purity.

[0084] The Ar plasma etching machine used in the following examples is an OXFORD PlasmaPro 100 Cobra; the high-speed shearing machine is a Fluke FA25; the ultrasonic disperser is a Ningbo Xinzhi SB-5200DT; the vacuum freeze dryer is a Beijing Sihuan Qihang LGJ-12A; the vacuum impregnation equipment is a Shanghai Yanzheng YZPR-100; the vacuum drying oven is a Shanghai Yiheng DZF-6050; and the thermal crosslinking oven is a Shanghai Jinghong DHG-9070A.

[0085] In the following test examples, scanning electron microscopy (SEM) was used to observe the microstructure, microcapsule morphology, and distribution of the aerogel (HITACHI TM3030, Japan); differential scanning calorimetry (DSC) was used to test the specific heat capacity and phase transition enthalpy of the aerogel (TA Discovery 250); thermogravimetric analysis (TG / DTA) was used to test the thermal stability and microcapsule loading of the aerogel (PE Diamond TG / DTA); specific surface area (BET) and pore distribution of the aerogel were tested using a specific surface area and pore size analyzer (McMerritt ASAP 2460); gas chromatography (GC) was used to detect the toluene adsorption capacity and calculate the VOCs adsorption performance (PCF BTX530, Italy); and an infrared thermal imager was used to monitor the surface temperature change of the aerogel in real time during the photothermal test (Flir). Ti400; the incident light power density in the photothermal test was calibrated using an optical power meter, model PM100D, Thorlabs; a xenon lamp light source (simulating natural light) was used to provide the light source required for the photothermal test (400-800 nm), model Beijing PLS-SXE300D; the sample mass was accurately weighed using an electronic balance, model Mettler Toledo PL2002; and the sample environment was pretreated before testing using a constant temperature and humidity chamber (25 ℃, 50% relative humidity), model Shanghai Yiheng BPS-50CH.

[0086] The preparation method of the chitosan-polyurea-nano titanium dioxide composite in the following examples is as follows: 1 g of chitosan was dissolved in 100 mL of 1% v / v dilute acetic acid solution, and 0.4 g of nano titanium dioxide (anatase phase with a particle size of 10-20 nm) was added and ultrasonically dispersed for 20 min; 1 mL of IPDI was added dropwise to the system, and the mixture was stirred at 50 ℃ for 3 h, centrifuged and washed (8000 rpm, 10 min) 3 times, and vacuum dried at 60 ℃ for 4 h to obtain the chitosan-polyurea-nano titanium dioxide composite; The preparation method of the chitosan-dopamine copolymer is as follows: 1 g of chitosan was dissolved in 50 mL of 1% v / v dilute acetic acid solution, and 0.3 g of dopamine hydrochloride was added to adjust the pH to 6.0; 0.2 g of EDC was added as a crosslinking agent, and the mixture was stirred at room temperature for 12 h, dialyzed (molecular weight cutoff 8 kDa) for 24 h, and freeze-dried at -50 ℃ (vacuum degree 5 Pa) to obtain the chitosan-dopamine copolymer.

[0087] The custom mold used in the following embodiments is made of polytetrafluoroethylene (PTFE) and has an overall four-sided enclosed cavity structure. One side of the mold is a planar structure with an area of ​​5 cm × 5 cm and a thickness of 5 mm; the opposite side is a raised array structure, also with an area of ​​5 cm × 5 cm. The raised protrusions are cylindrical, with a diameter of 0.3 mm and a height of 0.3-0.5 mm. The spacing between adjacent protrusions is 0.7 mm, and they are arranged in an equilateral triangle pattern, such as... Figure 1 As shown; the remaining two sides are 5 mm thick closed baffles, which are vertically connected to the flat side and the raised array side to form a sealed cavity to avoid leakage of composite sol; the upper and lower sides are equipped with detachable cover plates, of which the upper cover plate is a vent plate and the lower cover plate is a cold source contact plate, which is adapted to the requirements of unidirectional freezing process.

[0088] Example 1

[0089] A method for preparing a biomimetic sea urchin-like asymmetric composite phase change chitosan aerogel loaded with TiO2 / rGO heterostructure includes the following steps:

[0090] (1) Take 0.2 g of GO and add it to 100 mL of deionized water. Disperse the GO mixture by ultrasonication for 30 min to obtain a uniform GO dispersion. The GO dispersion was etched by an Ar plasma etching machine with the following etching parameters: power 50 W, time 10 min, vacuum degree 0.1 Pa, and Ar gas flow rate 10 sccm. The GO dispersion was etched to construct a dual-scale defect structure of macro-grooves and micro-mesopores on the GO surface. 10 mL of anhydrous ethanol was added to the etched GO dispersion and the mixture was magnetically stirred at 300 rpm for 10 min to make the system uniform. Then, tetrabutyl titanate was added in a stepwise manner: first, 3 mL of tetrabutyl titanate was slowly added at a rate of 0.8 mL / min to induce the formation of TiO2 nanoribbons; then, 2 mL of tetrabutyl titanate was rapidly added at a rate of 2.5 mL / min to promote the formation of TiO2 microcrystals. After the addition was complete, the pH of the system was adjusted to 2.5 using 1 mol / L hydrochloric acid solution, and the mixture was stirred at 50 °C for 2 h. Simultaneously, 0.3 wt% (based on the mass of GO) of catechol was added to strengthen the bonding. The mixture was then transferred to a hydrothermal reactor and reacted at 180 °C for 12 h. After natural cooling to room temperature, the mixture was centrifuged and washed three times at 8000 rpm to remove impurities, yielding a TiO2 / rGO heterojunction with a particle size of 110 nm, where the mass ratio of TiO2 to rGO was 3.5:1. SEM characterization confirmed that the TiO2 / rGO heterojunction exhibited a unique morphology of "groove-locked bands and mesoporous intercalation," forming a stable structure integrating scale intercalation and grain boundary interlocking.

[0091] (2) Weigh 10 g of epoxidized soybean oil acrylate (core material) and chitosan-polyurea-nano TiO2 composite (shell material) at a mass ratio of 7:3. After mixing, add 0.05 g of Span-80 emulsifier and dissolve in 20 mL of toluene. Stir magnetically at 500 rpm for 10 min to prepare a homogeneous oil phase. Separately, dissolve 3 g of melamine in 50 mL of deionized water, add 5 mL of 37 wt% formaldehyde solution (melamine to formaldehyde molar ratio 1:2.8), adjust the pH of the system to 5.0, and stir at 70 ℃ for 30 min to obtain an aqueous solution of MF prepolymer (aqueous phase). Slowly add the above oil phase dropwise to the aqueous phase and continue stirring for 10 min to make the oil and water dispersed evenly. Then, based on the total mass of epoxidized soybean oil acrylate and chitosan-polyurea-nano TiO2 composite, add 5 wt% of chitosan-dopamine copolymer (mortise and tenon material) and 3 g of melamine to the system. wt% TiO2 microcrystals (anchor material) were sheared and emulsified at 15000 rpm for 8 min using a high-speed shear machine to form a stable emulsion. The emulsion was then stirred at 75 ℃ for 2 h to carry out interfacial polymerization, followed by curing at 90 ℃ for 1 h to strengthen the microcapsule shell structure. After the reaction was completed, the microcapsule was centrifuged at 6000 rpm for 15 min, the precipitate was collected and washed until neutral, and finally vacuum dried at 60 ℃ for 6 h to obtain targeted anchoring phase change microcapsules. These microcapsules consist of a core layer, a shell layer covering the outer side of the core layer, tenon and mortise teeth protruding from the surface of the shell layer, and anchor points loaded on the surface of the tenon and mortise teeth. The structural diagram is shown below. Figure 2 As shown, the phase change microcapsule has a core diameter of 11 μm, a shell thickness of 200 nm, and an overall particle size of 11.4 μm. Each microcapsule has 5 tenon-and-mortise teeth distributed on its surface (tenon-and-mortise teeth dimensions: length 3-5 μm, width 80-100 nm, height 50-80 nm), and each tenon-and-mortise teeth surface is loaded with 7 TiO2 microcrystal anchor points (anchor point spacing 12 nm).

[0092] (3) The above TiO2 / rGO heterojunctions were dispersed in deionized water to obtain a TiO2 / rGO heterojunction dispersion; chitosan powder was dissolved in a 2% v / v dilute acetic acid solution and magnetically stirred at 1500 rpm until completely dissolved to obtain a chitosan solution with a concentration of 2% w / v. The above TiO2 / rGO heterojunction dispersion and chitosan solution were mixed at a volume ratio of 1:4 and stirred vigorously at 800 rpm for 30 min using an ultrasonic disperser to obtain a uniform composite sol. The composite sol was poured into a custom mold with a 0.4 mm high protrusion array and treated with a unidirectional freezing process: the bottom of the mold was brought into close contact with a -90 ℃ cold source and left to stand for 5 h until the composite sol was completely frozen and formed, forming a biomimetic sea urchin-shaped nanofiber bundle loaded with TiO2 / rGO heterojunctions. The frozen composite sol was transferred to a vacuum freeze dryer and freeze-dried for 48 h at -50 ℃ and 8 Pa. The porous structure was preserved using a sublimated ice crystal template. Subsequently, the dried framework was thermally crosslinked at 130 ℃ for 2 h to obtain a biomimetic sea urchin-like asymmetric chitosan aerogel framework loaded with TiO2 / rGO heterostructures. The structural schematic diagram is shown below. Figure 3 As shown, its primary pore diameter is 90 μm and its secondary branch pore diameter is 13 μm, exhibiting a typical biomimetic sea urchin-like morphology and asymmetrical pore structure.

[0093] (4) Take 5 g of the above-mentioned biomimetic sea urchin-shaped asymmetric chitosan aerogel framework loaded with TiO2 / rGO heterojunction and place it in a vacuum impregnation device; disperse the phase change microcapsules in ethanol at a solid-liquid ratio of 1:10 (g / mL) and sonicate at 200 W for 20 min to obtain a uniform and stable phase change microcapsule suspension; take 50 mL of the suspension and pour it into the vacuum impregnation device to ensure complete immersion of the aerogel framework; keep it under a vacuum of -0.09 MPa for 30 min to remove the air in the pores of the framework, so that the microcapsule suspension can fully penetrate into the primary pores and enter the secondary branch pores, and be microscopically embedded in the nanoneedle gaps of the biomimetic sea urchin-shaped microspheres; after releasing the vacuum, continue to soak for 4 h to improve the microcapsule filling rate, and then vacuum dry in a vacuum drying oven at 55 ℃ for 3 h to obtain the biomimetic sea urchin-shaped asymmetric composite phase change chitosan aerogel framework loaded with TiO2 / rGO heterojunction, the structural schematic diagram is shown below. Figure 4 As shown, the microcapsule loading was tested using a thermogravimetric analyzer (TG / DTA, model PE Diamond TG / DTA). The test conditions were: nitrogen atmosphere (flow rate 50 mL / min), heating rate 10 ℃ / min, and test temperature range 30-600℃. By comparing the microcapsule thermal decomposition peak area with the standard curve, the phase change microcapsule loading was determined to be 35 wt%.

[0094] (5) Prepare a 10 mM Tris-HCl buffer (pH=8.5), add dopamine hydrochloride to it, stir to dissolve, and obtain a dopamine solution with a concentration of 2 mg / mL. Take 60 mL of the dopamine solution and pour it into a container. Immerse the biomimetic sea urchin-like asymmetric composite phase change chitosan aerogel framework with TiO2 / rGO heterojunction obtained in step (4) into the dopamine solution. Use an ultrasonic disperser to slowly stir at 50 rpm at room temperature for 24 h, so that dopamine polymerizes in situ on the surface of the framework to form a polydopamine coating layer with a thickness of 80 nm. After the reaction is completed, take it out and rinse it thoroughly to remove the unpolymerized dopamine on the surface. Then freeze-dry it in vacuum at -50 ℃ for 24 h to finally obtain the biomimetic sea urchin-like asymmetric composite phase change chitosan aerogel with TiO2 / rGO heterojunction.

[0095] Example 2

[0096] A method for preparing a biomimetic sea urchin-like asymmetric composite phase change chitosan aerogel loaded with TiO2 / rGO heterojunction is basically the same as in Example 1, except that: in step (1), 0.1 g of GO is added to 100 mL of deionized water, and the Ar plasma etching parameters are: power 45 W, time 8 min. Tetrabutyl titanate is added in a stepwise dropping manner: first, 2 mL of tetrabutyl titanate is slowly added at a rate of 0.5 mL / min, and then 2 mL of tetrabutyl titanate is rapidly added at a rate of 2 mL / min. The pH of the system is adjusted to 2.2 using 1 mol / L hydrochloric acid solution, and 0.2 wt% (based on the mass of GO) of catechol is added to obtain TiO2 / rGO heterojunction with a particle size of 80 nm, wherein the mass ratio of TiO2 to rGO is 3:1; in step (2), high-speed shearing emulsification is performed at a speed of 14000 rpm for 5 min, and the core layer diameter of the phase change microcapsule is 8 nm. μm, shell thickness of 150 nm, overall particle size of 8.3 μm; each microcapsule surface is distributed with 4 tenon teeth, each tenon tooth surface is loaded with 6 TiO2 microcrystal anchor points; in step (3), the composite sol is poured into a custom mold with a 0.3 mm protrusion array and treated with a unidirectional freezing process: the bottom of the mold is in close contact with a cold source of -100 ℃, and the dried skeleton is placed at 135 ℃ for thermal crosslinking for 2 h, and the secondary branch pore diameter of the aerogel skeleton is 12 μm; in step (4), after releasing the vacuum, it is soaked for 4 h to improve the microcapsule filling rate, and then vacuum dried in a vacuum drying oven at 50 ℃ for 2 h. After drying, the phase change microcapsule loading is measured by TG / DTA to be 30 wt%; in step (5), 10 mM Tris-HCl buffer (pH=8) is prepared, dopamine hydrochloride is added to it, and after stirring and dissolving, a dopamine solution with a concentration of 0.5 mg / mL is obtained, and finally a thickness of 50 A nm-sized polydopamine coating.

[0097] Example 3

[0098] A method for preparing a biomimetic sea urchin-like asymmetric composite phase change chitosan aerogel loaded with TiO2 / rGO heterojunction is basically the same as that in Example 1, except that:

[0099] In step (1), 0.3 g of GO was added to 100 mL of deionized water. The Ar plasma etching parameters were: power 55 W, time 12 min. Tetrabutyl titanate was added in a stepwise dropping manner: first, 2 mL of tetrabutyl titanate was slowly added at a rate of 1 mL / min, and then 2 mL of tetrabutyl titanate was rapidly added at a rate of 3 mL / min. 0.4 wt% (based on the mass of GO) of catechol was added to obtain a TiO2 / rGO heterojunction with a particle size of 150 nm, wherein the mass ratio of TiO2 to rGO was 4:1. In step (2), the phase change microcapsules were sheared and emulsified for 10 min at a high-speed shear machine at a speed of 16000 rpm. The core diameter of the phase change microcapsules was 9 μm, the shell thickness was 250 nm, and the overall particle size was 9.5 μm. μm; 6 tenon teeth are distributed on the surface of each microcapsule, and 8 TiO2 microcrystal anchors are loaded on the surface of each tenon tooth; In step (3), the composite sol is poured into a custom mold with a 0.5 mm protrusion array and treated with a unidirectional freezing process: the bottom of the mold is in close contact with a cold source of -80 ℃, and freeze-dried for 72 h at -50 ℃ and <10 Pa. The dried skeleton is placed at 150 ℃ for 2 h for thermal crosslinking. The secondary branch pore diameter of the aerogel skeleton is 15 μm; In step (4), after releasing the vacuum, it is soaked for 4 h to improve the microcapsule filling rate. Then it is vacuum dried in a vacuum drying oven at 60 ℃ for 4 h. After drying, the phase change microcapsule loading is measured to be 40 wt% by TG / DTA; In step (5), 10 mM Tris-HCl buffer (pH=8.8) is prepared, dopamine hydrochloride is added to it, and after stirring and dissolving, a dopamine solution with a concentration of 4 mg / mL is prepared. Polymerization is carried out for 30 h, ultimately forming a polydopamine coating layer with a thickness of 100 nm.

[0100] Comparative Example 1

[0101] A method for preparing a biomimetic sea urchin-like asymmetric composite phase change chitosan aerogel loaded with TiO2 / rGO heterojunction is basically the same as that in Example 1, except that: in step (1), the GO dispersion was not subjected to Ar plasma etching treatment.

[0102] Comparative Example 2

[0103] A method for preparing a biomimetic sea urchin-like asymmetric composite phase change chitosan aerogel loaded with TiO2 / rGO heterojunction is basically the same as that in Example 1, except that in step (1), tetrabutyl titanate is not added in a stepwise dropwise manner, but 5 mL of tetrabutyl titanate is added directly at once.

[0104] Comparative Example 3

[0105] A method for preparing a biomimetic sea urchin-like asymmetric composite phase change chitosan aerogel loaded with TiO2 / rGO heterojunction is basically the same as that in Example 1, except that in step (2), 5 wt% of chitosan-dopamine copolymer and 3 wt% of TiO2 microcrystals are not added, and the resulting phase change microcapsules only have a core-shell structure.

[0106] Comparative Example 4

[0107] The preparation method of a symmetrical composite phase change chitosan aerogel loaded with TiO2 / rGO heterojunction is basically the same as that in Example 1, except that: in step (3), a common planar mold without protrusion array is used to form a symmetrical porous structure; at the same time, its pore arrangement is a disordered porous structure with uniform pore size (50-80 μm), no distinction between primary main pores and secondary branch pores, and the VOCs mass transfer path is disordered.

[0108] Comparative Example 5

[0109] The preparation method of a biomimetic sea urchin-like asymmetric composite phase change chitosan aerogel loaded with TiO2 / rGO heterojunction is basically the same as that in Example 1, except that the polydopamine coating in step (5) is not performed.

[0110] Test case

[0111] The biomimetic sea urchin-like asymmetric composite phase change chitosan aerogels with TiO2 / rGO heterojunctions prepared in Examples 1-3 and Comparative Examples 1-5 were subjected to performance tests, including: toluene removal rate, formaldehyde removal rate, VOCs adsorption capacity, initial phase change microcapsule desorption rate, phase change microcapsule desorption rate after 100 phase change-adsorption-desorption combined cycles, initial phase change enthalpy, phase change enthalpy retention rate after 100 phase change-adsorption-desorption combined cycles, photothermal conversion efficiency, and specific surface area. The test methods are as follows:

[0112] (a) VOCs (toluene, formaldehyde) removal rate test: performed in accordance with GB / T 18883-2022 "Indoor Air Quality Standard", with a test temperature of -10 ℃ to 15 ℃.

[0113] (b) VOCs (toluene) adsorption capacity test: The test was conducted in accordance with GB / T 18883-2022 "Indoor Air Quality Standard" and the toluene adsorption capacity was determined by GC.

[0114] (c) Phase change microcapsule desorption rate test: The test was conducted in accordance with T / CTES 1005-2017 "Evaluation of the Functional Effect of Phase Change Temperature Regulating Microcapsules for Textiles and Their Applications". The test included the initial phase change microcapsule desorption rate (i.e., the proportion of the mass of the microcapsules that fell off after the material preparation was completed, without any cycling and adsorption treatment, by centrifugation (5000 rpm, 10 min) to the total load, reflecting the initial fixation stability of the microcapsules) and the phase change microcapsule desorption rate after 100 phase change-adsorption-desorption combined cycles.

[0115] The specific procedure for the 100-cycle phase change-adsorption-desorption combined test is as follows: a single combined cycle consists of one phase change cycle and one adsorption-desorption cycle, and this cycle is repeated 100 times to complete the overall test; the phase change cycle is -10℃ (solidification and energy storage, 2 h) → 30℃ (melting and heat release, 2 h); the adsorption-desorption cycle involves placing the test material in a VOCs atmosphere (toluene concentration 50 mg / m³) between -10℃ and 15℃. 3 Adsorbed in light for 1 h, and then photothermally desorbed under 3000 lux illumination for 1 h.

[0116] (d) Phase transition enthalpy and retention rate test: The test was conducted according to GB / T 19466.3-2004 "Differential Scanning Calorimetry (DSC) for Plastics - Part 3", using a differential scanning calorimeter (DSC, model TA Discovery 250). Test conditions were: nitrogen atmosphere (flow rate 50 mL / min), 5 mg of test material, heating rate 10 ℃ / min, and a test temperature range of -20 ℃ to 50 ℃ (covering the phase transition temperature range of the phase change microcapsules). Three parallel tests were performed, and the average value was taken. The test included the initial phase transition enthalpy and the phase transition enthalpy retention rate after 100 phase transition-adsorption-desorption combined cycles (phase transition enthalpy retention rate = (phase transition enthalpy after 100 phase transition-adsorption-desorption combined cycles / initial phase transition enthalpy) × 100%). Phase transition enthalpy of the phase change microcapsule monomer = enthalpy of the core layer material epoxidized soybean oil acrylate (178 J·g). -1 The ratio of core material to the total mass of the microcapsule is calculated as (core layer / (core layer + shell + tenon and mortise teeth + anchor points)). The tenon and mortise teeth and anchor points have no phase change characteristics and are not included in the phase change enthalpy calculation. Since the core-shell mass ratio is 7:3, and the tenon and mortise teeth and anchor points account for 8% of the total core-shell mass, the core layer accounts for approximately 70% / (1 + 8%) ≈ 64.81% of the total microcapsule mass. Therefore, the phase change enthalpy of the microcapsule monomer is 178 × 64.81% ≈ 115.36 J·g. -1 The initial phase transition enthalpy is the overall phase transition enthalpy of the composite aerogel, calculated using the formula: Initial phase transition enthalpy = Phase transition enthalpy of the microcapsule monomer (115.36 J·g) -1 ) × Microcapsule loading (wt%).

[0117] (e) Photothermal conversion efficiency test:

[0118] Test equipment: infrared thermal imager, optical power meter, xenon lamp light source, electronic balance;

[0119] Test conditions: Under simulated light conditions of 3000 lux, the surface temperature of the sample was monitored in real time, and the dynamic temperature change was continuously recorded within 10 min; the specific heat capacity was tested by DSC under a nitrogen atmosphere (flow rate 50 mL / min), with a sample volume of 5 mg, a heating rate of 10 ℃ / min, a test temperature range of 20-40 ℃, and three parallel tests were conducted. The average value was used as the basis for calculating the specific heat capacity of the sample.

[0120] Test Method: A constant temperature and humidity chamber was used for sample pretreatment before testing. The pretreated sample was fixed on a quartz fixture, ensuring the light-receiving surface was flat and unobstructed, and perpendicular to the incident direction of the light source. An infrared thermal imager was used to target the central area of ​​the sample, and the initial surface temperature (denoted as T0) was recorded. After the temperature stabilized for 3 minutes, the xenon lamp light source was turned on. During the illumination process, the average surface temperature of the sample was recorded every 1 minute using data acquisition software (referred to as T1-T). 10 Simultaneously, the incident light power density is monitored in real time using a power meter. If the fluctuation exceeds ±5%, the test is repeated. After 10 minutes of illumination, the light source is turned off, and the final sample surface temperature (i.e., T) is recorded. 10 ), calculate the maximum change in sample surface temperature within 10 minutes (ΔT = T). 10 - T0); the photothermal conversion efficiency is calculated according to the following formula: Photothermal conversion efficiency = (Heat required for sample heating / Total incident light energy) × 100%; where the heat required for sample heating is calculated based on the specific heat capacity, sample mass and temperature change value (ΔT) measured by differential scanning calorimeter.

[0121] (f) Specific surface area test: The test shall be conducted in accordance with GB / T 19587-2017 "Determination of specific surface area of ​​solid substances by gas adsorption BET method" and a specific surface area and pore size analyzer shall be used.

[0122] The test results are shown in Table 1:

[0123]

[0124] As shown in Table 1, the biomimetic sea urchin-like asymmetric composite phase change chitosan aerogels with TiO2 / rGO heterojunctions prepared in Examples 1-3 all exhibited toluene and formaldehyde removal rates ≥80% and toluene adsorption capacities ≥15.3 mg / g, significantly superior to the comparative examples. This successfully achieved the core objective of efficient VOCs purification at low temperatures of -10 ℃ to 15 ℃. Furthermore, the initial phase change enthalpy of the aerogels prepared in Examples 1-3 was 40.38 J·g.-1 34.61 J·g -1 46.14 J·g -1 The value is positively correlated with the microcapsule loading (35 wt%, 30 wt%, 40 wt%), consistent with the theoretical relationship between phase transition enthalpy and loading. This value matches the energy storage characteristics of the core material itself (monomer microcapsule phase transition enthalpy 115.36 J·g). -1 This design ensures that the aerogel can stably maintain the 25-30 °C required for the catalytic reaction through phase change heat release at low temperatures, providing sufficient heat support for the synergistic purification of photothermal catalysis and phase change energy storage. After 100 cycles of phase change-adsorption-desorption, the phase change microcapsule desorption rate was ≤2.8% and the phase change enthalpy retention rate was ≥94.5%, far superior to Comparative Example 3 (desorption rate 28.7%, phase change enthalpy retention rate 82.6%). This fully demonstrates that the dual fixation structure of the "core-shell-mortise and tenon-anchor" phase change microcapsule of this invention can effectively solve the technical pain point of easy desorption of traditional phase change microcapsules and significantly improve the cycling stability of the material. In addition, the aerogel prepared in Example 1 has a photothermal conversion efficiency of 78.3% and a specific surface area of ​​386 m². 2 / g, which is significantly improved compared to each control ratio, highlights the synergistic effect of TiO2 / rGO scale intercalation-grain boundary interlocking structure and biomimetic sea urchin-like asymmetric channels, and also verifies the auxiliary effect of polydopamine coating on photothermal conversion efficiency.

[0125] Furthermore, in Comparative Example 1, GO was not subjected to Ar plasma etching, resulting in a significant decrease in toluene and formaldehyde removal rates and photothermal conversion efficiency compared to Example 1. The photothermal conversion efficiency decreased by 25.7%, demonstrating that the construction of dual-scale defects on the GO surface can effectively improve photon trapping ability and charge transport efficiency. In Comparative Example 2, tetrabutyl titanate was not added using a stepwise dropwise method, leading to TiO2 agglomeration and a specific surface area of ​​only 243 m². 2 / g, the removal rates of toluene and formaldehyde decreased simultaneously, verifying the key role of the dual-morphology TiO2 (nanoribbons and microcrystals) design in inhibiting agglomeration and ensuring unobstructed pores. Comparative Example 3, without the addition of tenon and anchor materials, retained only the core-shell structure of the microcapsules, and its monomeric phase transition enthalpy was consistent with that of the examples (115.36 J·g). -1 Furthermore, the microcapsule loading is 35 wt%, therefore the initial phase transition enthalpy is 40.38 J·g. -1(Same as Example 1), but due to the lack of a dual fixation structure of mechanical interlocking and chemical bonding, the microcapsule decomposition rate reached 28.7% after 100 cycles, and the phase change enthalpy retention rate decreased to 82.6%, verifying the key role of tenon and anchor points in the cycle stability of microcapsules, rather than affecting the phase change function itself. Comparative Example 4 used a common planar mold, which did not form asymmetric directional channels, resulting in a disordered VOCs mass transfer path. After 100 cycles, the microcapsule decomposition rate reached 11.2%, which was 3.8 times that of Example 1, fully demonstrating the significant advantages of directional channels in enhancing the fixation stability of microcapsules and optimizing VOCs diffusion efficiency. Comparative Example 5 did not undergo polydopamine coating treatment, and its toluene and formaldehyde removal rates were significantly lower than those of Example 1, confirming that the polydopamine coating layer can effectively enhance the surface adsorption performance and structural integrity of materials.

[0126] In summary, the biomimetic sea urchin-like asymmetric composite phase change chitosan aerogel with a TiO2 / rGO heterostructure prepared in this invention possesses excellent photothermal conversion efficiency and low-temperature catalytic performance, exhibiting outstanding removal rates for VOCs such as toluene and formaldehyde. Simultaneously, through a dual-fixation structure of "core-shell-mortise and tenon-anchor point" and an asymmetric directional pore design, the technical problem of easy disintegration during the recycling of phase change microcapsules is effectively solved, significantly improving structural stability and cycle durability. This composite phase change chitosan aerogel is highly adaptable to low-temperature closed environments of -10℃ to 15℃ (such as cold chain workshops and indoor spaces in winter), achieving stable and efficient purification of VOCs through the synergistic effect of photothermal catalysis and phase change energy storage, showing broad application prospects.

[0127] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art should understand that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a biomimetic sea urchin-like asymmetric composite phase change chitosan aerogel loaded with titanium dioxide / reduced graphene oxide heterostructure, characterized in that, Includes the following steps: (1) Argon plasma etching was performed on the graphene oxide dispersion to form dual-scale defects in the graphene oxide; tetrabutyl titanate was added dropwise to the etched graphene oxide dispersion in two steps at different rates to form titanium dioxide nanoribbons and titanium dioxide microcrystals respectively; the pH of the system was adjusted to acidic and catechol was added, and titanium dioxide / reduced graphene oxide heterojunction was obtained through hydrothermal reaction. (2) Using epoxidized soybean oil acrylate as the core material, chitosan-polyurea-nano titanium dioxide composite as the shell material, chitosan-dopamine copolymer as the tenon and tooth material, and titanium dioxide microcrystals as the anchor material; the core material and shell material are mixed at a mass ratio of (6-8):(2-4), and emulsifier and toluene are added and stirred evenly to obtain an oil phase; melamine is dissolved in water, formaldehyde solution is added, and the resulting melamine-formaldehyde prepolymer aqueous solution is used as the aqueous phase; the oil phase is dropped into the aqueous phase and stirred to disperse, and then the tenon and tooth material and anchor material are added. After shear emulsification, polymerization at 70-80 ℃, and curing at 80-100 ℃, the core layer, shell layer covering the outer side of the core layer, tenon and tooth protruding from the surface of the shell layer, and anchor points loaded on the surface of the tenon and tooth are obtained as phase change microcapsules. (3) Disperse the titanium dioxide / reduced graphene oxide heterojunction obtained in step (1) in water to obtain a titanium dioxide / reduced graphene oxide heterojunction dispersion with a concentration of 0.5-1 g / L; dissolve chitosan powder in dilute acetic acid solution to obtain a chitosan solution with a concentration of 1-3 % w / v; mix the titanium dioxide / reduced graphene oxide heterojunction dispersion and the chitosan solution at a volume ratio of 1:(3-5) to obtain a composite sol; pour the composite sol into a custom mold containing a planar side and a protrusion array side, and perform unidirectional freezing treatment from top to bottom to allow chitosan and titanium dioxide / reduced graphene oxide heterojunction to self-assemble into biomimetic sea urchin-shaped nanofiber bundles; after freeze-drying, perform thermal crosslinking or glutaraldehyde vapor chemical crosslinking treatment to obtain a biomimetic sea urchin-shaped asymmetric structure chitosan aerogel skeleton loaded with titanium dioxide / reduced graphene oxide heterojunction. (4) The phase change microcapsules obtained in step (2) are dispersed in ethanol at a solid-liquid ratio of 1:(9-11) to obtain a phase change microcapsule suspension; the biomimetic sea urchin-like asymmetric structure chitosan aerogel framework with titanium dioxide / reduced graphene oxide heterostructure obtained in step (3) is immersed in the phase change microcapsule suspension for 30-60 min under vacuum conditions of -0.05 MPa ~ -0.15 MPa, the vacuum is released and then immersed for 3-5 h, and after vacuum drying, a biomimetic sea urchin-like asymmetric structure composite phase change chitosan aerogel framework with titanium dioxide / reduced graphene oxide heterostructure is obtained, wherein the loading of phase change microcapsules is 30-40 wt%; (5) Dissolve dopamine hydrochloride in a tris(hydroxymethyl)aminomethane hydrochloride buffer solution with a pH of 8.0-8.8 to obtain a dopamine solution with a concentration of 0.5-4 mg / mL; immerse the biomimetic sea urchin-like asymmetric structure composite phase change chitosan aerogel skeleton with titanium dioxide / reduced graphene oxide heterostructure obtained in step (4) in the dopamine solution, so that dopamine is in situ polymerized on the surface of the biomimetic sea urchin-like asymmetric structure composite phase change chitosan aerogel skeleton with titanium dioxide / reduced graphene oxide heterostructure to form a polydopamine coating layer with a thickness of 50-100 nm, and obtain the biomimetic sea urchin-like asymmetric structure composite phase change chitosan aerogel with titanium dioxide / reduced graphene oxide heterostructure after drying.

2. The preparation method according to claim 1, characterized in that, In step (1), the concentration of the graphene oxide dispersion is 1-3 g / L; the parameters of the argon plasma etching are: power 45-55 W, time 8-12 min, vacuum degree 0.05-0.2 Pa, and argon flow rate 5-15 sccm.

3. The preparation method according to claim 1, characterized in that, In step (1), tetrabutyl titanate is first added dropwise at a rate of 0.5-1 mL / min to form titanium dioxide nanoribbons, and then tetrabutyl titanate is added dropwise at a rate of 2-3 mL / min to form titanium dioxide microcrystals; the volume ratio of tetrabutyl titanate added dropwise at a rate of 0.5-1 mL / min to the etched graphene oxide dispersion is (2-4):100, and the volume ratio of tetrabutyl titanate added dropwise at a rate of 2-3 mL / min to the etched graphene oxide dispersion is (1-3):100; the mass ratio of catechol to graphene oxide is (0.2-0.4):100; the hydrothermal reaction temperature is 170-190 ℃, and the time is 10-14 h.

4. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of titanium dioxide to reduced graphene oxide in the titanium dioxide / reduced graphene oxide heterojunction is (3-4):1; the particle size of the titanium dioxide / reduced graphene oxide heterojunction is 80-150 nm.

5. The preparation method according to claim 1, characterized in that, In step (2), the preparation method of the chitosan-polyurea-nano titanium dioxide composite is as follows: chitosan is dissolved in dilute acetic acid solution, nano titanium dioxide is added and dispersed evenly, isophorone diisocyanate is added, and the mixture is heated, stirred, reacted, separated, washed and dried to obtain the chitosan-polyurea-nano titanium dioxide composite; the preparation method of the chitosan-dopamine copolymer is as follows: chitosan is dissolved in dilute acetic acid solution, dopamine compounds are added and the pH is adjusted to acidic, a crosslinking agent is added and stirred, purified by dialysis and freeze-dried to obtain the chitosan-dopamine copolymer; the mass ratio of the total mass of the core material and the shell material to the mass of the tenon tooth material is 100:(4-6), and the mass ratio of the total mass of the core material and the shell material to the mass of the anchor point material is 100:(2-4).

6. The preparation method according to claim 1, characterized in that, In step (2), the core diameter of the phase change microcapsule is 8-11 μm and the shell thickness is 150-250 nm; the particle size of the phase change microcapsule is 8-12 μm; the surface of the phase change microcapsule has 4-6 tenon teeth, the length of the tenon teeth is 3-5 μm, the width is 80-100 nm and the height is 50-80 nm; each tenon tooth surface is loaded with 6-8 anchor points with a spacing of 10-15 nm.

7. The preparation method according to claim 1, characterized in that, In step (3), the customized mold includes a planar side and a protrusion array side arranged opposite to each other, a closed baffle vertically connecting the two, and a detachable upper cover plate and a lower cover plate; the protrusion array side is provided with cylindrical protrusions, the diameter of the cylindrical protrusions is 0.2-0.3 mm, the height is 0.3-0.5 mm, the protrusion spacing is 0.5-0.8 mm, and the arrangement is an equilateral triangle; the temperature of the unidirectional freezing treatment is -80 ℃ ~ -100 ℃, and the time is 4-6 h; the temperature of the thermal crosslinking is 120-150 ℃, and the time is 1-3 h.

8. The preparation method according to claim 1, characterized in that, In step (3), the biomimetic sea urchin-like asymmetric chitosan aerogel skeleton has primary main pores with a diameter of 80-100 μm and secondary branch pores with a diameter of 12-15 μm.

9. A biomimetic sea urchin-like asymmetric composite phase change chitosan aerogel with a titanium dioxide / reduced graphene oxide heterostructure prepared by the preparation method according to any one of claims 1-8.

10. The application of the biomimetic sea urchin-like asymmetric composite phase change chitosan aerogel with a titanium dioxide / reduced graphene oxide heterostructure as described in claim 9 in the purification of volatile organic pollutants.

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