A dynamic covalent composite da@glm / mfc aerogel material and a preparation method and application thereof

Abstract

The present application relates to a kind of dynamic covalent complex DA@GLM / MFC aerogel material and its preparation method and application, belong to photo-thermal conversion material field, the present application is by: (1) preparation partially oxidized MFC frozen gel, (2) preparation hydrochloric acid dopamine modified gallium-based liquid metal DA-GLM nanodroplet, (3) DA-GLM nanodroplet is dispersed in ethanol solution, then MFC frozen gel is soaked in the solution three main steps dynamic covalent complex DA@GLM / MFC aerogel material is obtained;Dynamic covalent complex DA@GLM / MFC aerogel material obtained by the present application constructs dynamic covalent binding structure with Schiff base bond, obtains the stable liquid metal and aerosol composite material combined, and the material obtained has excellent photo-thermal performance, strong and tough mechanical performance, super stable cycle performance, as solar-driven interface evaporation material is used, can strengthen the adsorption and catalytic degradation capacity to salt ion, while improving photo-thermal conversion efficiency.

Description

Technical Field

[0001] This invention belongs to the field of photothermal conversion materials, specifically, it relates to a dynamic covalent composite DA@GLM / MFC aerogel material, its preparation method and application. Background Technology

[0002] Solar-driven interfacial water evaporation (SDIE) technology has become a preferred solution for seawater desalination and wastewater purification due to its advantages of low energy consumption and environmental friendliness. Aerogels, as the core material of this technology, have shown great potential in the field of water treatment due to their high specific surface area and three-dimensional porous structure. However, they have significant drawbacks: traditional aerogels (such as silicon-based and carbon-based aerogels) have weak mechanical properties, insufficient structural stability, and poor recyclability, which limits their large-scale application. To improve the photothermal performance of aerogels, existing technologies attempt to combine liquid metals (such as eutectic gallium indium EGaIn) with aerogels, but the following key problems exist: (1) Liquid metal nanoparticles (LMNPs) are prone to agglomeration and leakage, and the interaction between them and the aerogel matrix is ​​weak. They are prone to falling off in complex water treatment scenarios such as acid and alkali environments and water flow impact, resulting in rapid decay of material functions; (2) Existing aerogel functionalization modifications mostly use physical mixing or electrostatic interaction to achieve the combination of nanoparticles and matrix. The combination method has poor stability and cannot meet the requirements of long-term use; (3) Although dynamic covalent chemistry can achieve self-repair and self-adaptive functions of materials, existing research only focuses on the optimization of the self-repair performance of organic polymer aerogels and lacks exploration of its application in seawater desalination and wastewater purification. In addition, existing photothermal conversion materials (carbon-based materials, noble metal nanoparticles, etc.) still have problems such as high cost, easy corrosion, and complex preparation. Among solar-driven evaporators (membranes, fabrics, foams, etc.), three-dimensional porous aerogels are preferred, but how to firmly, stably, and uniformly fix liquid metal nanoparticles in the aerogel framework while endowing the material with good mechanical properties remains a current technical bottleneck. Summary of the Invention

[0003] To overcome the problems existing in the background technology, the present invention provides a dynamically covalently bonded liquid metal-biomass aerogel material. The material constructs a dynamically covalently bonded structure using Schiff base bonds to obtain a stable liquid metal-aerosol composite material. The obtained material has excellent photothermal properties, strong mechanical properties, and ultra-stable cycling performance. When used as a solar-driven interfacial evaporation material, it can enhance the purification capacity of high-concentration brine and improve the photothermal conversion efficiency.

[0004] To achieve the above objectives, the present invention is implemented through the following technical solution: The aforementioned dynamic covalent composite DA@GLM / MFC aerogel material is a three-dimensional porous structure with aldehyde-based MFC as the framework and Schiff base bonds as the dynamic covalent bonding structure supporting liquid metal nanoparticles.

[0005] Furthermore, the liquid metal is a gallium-based liquid metal modified with dopamine hydrochloride.

[0006] Furthermore, the aldehyde-modified MFC is obtained by partially oxidizing micronized cellulose MFC with sodium periodate under light-shielding conditions and then freezing.

[0007] The method for preparing the dynamic covalent composite DA@GLM / MFC aerogel material of the present invention includes the following steps: (1) Preparation of MFC cryogel NaIO4 solid was added to the MFC dispersion to partially oxidize the cellulose molecules of MFC; after stirring, an aldehyde-containing MFC dispersion was obtained. The dispersion was pre-frozen in a refrigerator and then taken out and stirred vigorously to disperse a small amount of ice crystals; thus, an MFC cryogel was obtained. (3) Preparation of gallium-based liquid metal DA-GLM nanodroplets modified with dopamine hydrochloride Gallium-based liquid metal was added to an ethanol solution and sonicated to obtain a suspension of gallium-based liquid metal nanodroplets; dopamine hydrochloride (DA) was added to the suspension and sonicated again to obtain modified DA-GLM nanodroplets; The modified DA-GLM nanodroplets were separated by centrifugation and purified by washing with ultrapure water and ethanol to obtain dopamine hydrochloride modified gallium-based liquid metal DA-GLM nanodroplets. (4) Preparation of dynamic covalent composite DA@GLM / MFC aerogel Purified DA-GLM nanodroplets were dispersed in an ethanol solution, and MFC cryogel was immersed in the solution. After shaking and incubation at 50°C, a black and robust composite DA@GLM / MFC hybrid gel was obtained. Dynamic covalent composite DA@GLM / MFC aerogel material was obtained by freeze drying.

[0008] Furthermore, in step (1), NaIO4 solid is added to 2.0% (w / w) MFC dispersion, and the cellulose molecules of MFC are oxidized at a mass ratio of NaIO4 to MFC dispersion of 0.28-0.36:12-18.

[0009] Furthermore, in step (3), the mass ratio of GLM:DA:C2H5OH is 1.6~2.4:0.8~1.2:63.2~94.8.

[0010] Furthermore, in step (4), the volume ratio of DA-GLM nanodroplets to ethanol solution is 0.6-1.4:15-40.

[0011] The present invention also provides the application of the above-mentioned dynamic covalent composite DA@GLM / MFC aerogel material as an aerogel evaporator.

[0012] The present invention also provides the application of the above-mentioned dynamic covalent composite DA@GLM / MFC aerogel material as a photocatalyst for the degradation of organic matter.

[0013] The beneficial effects of this invention are: The dynamic covalent composite DA@GLM / MFC aerogel material of this invention uses dynamic covalent bonds (Schiff base bonds) as a "bridge" to achieve covalent assembly of liquid metal nanoparticles and biomass aerogel precursors (aldehyde-modified micronized cellulose), constructing an integrated composite system of "structural stability, functional enhancement, and recyclability". The dynamic covalent bonds combine the strength of covalent bonds with the reversibility of non-covalent bonds, enabling both strong bonding between components and imparting more stable functions to the material through bond breaking and recombination. The synergistic effect of the metal active sites of the liquid metal nanoparticles and the high specific surface area of ​​the aerogel enhances the adsorption and catalytic degradation capabilities of salt ions, while simultaneously improving photothermal conversion efficiency.

[0014] The dynamic covalent composite DA@GLM / MFC aerogel material of the present invention has excellent mechanical toughness, compressibility and photothermal conversion ability, and can be prepared into different sizes.

[0015] The dynamically covalently composite DA@GLM / MFC aerogel material of this invention can be used as an aerosol evaporator with an evaporation rate of up to 7.25 kg m³. -2 h -1 The photothermal conversion efficiency is as high as 99.81%, which is 12.7 times the evaporation rate of pure water; it can also evaporate stably in high-concentration brine; it can still maintain a good evaporation rate after recycling; the ion removal rate is over 99%; it can be applied to seawater desalination and sewage treatment.

[0016] The dynamically covalently composite DA@GLM / MFC aerogel material of this invention can also be applied to the adsorption and photocatalytic degradation of organic dyes. When using DA@GLM / MFC aerogel to purify organic dyes, pure water can be collected by evaporation, and the color of the dye that was not evaporated in the beaker becomes much lighter, suggesting that the DA@GLM / MFC aerogel may have adsorbed the organic dyes or carried out photocatalytic degradation. Attached Figure Description

[0017] Figure 1 These are SEM images of MFC and the DA@GLM / MFC aerogel of the present invention (the right image shows the DA@GLM / MFC aerogel). Figure 2 This is a diagram illustrating the mechanical properties of the DA@GLM / MFC aerogel of the present invention; Figure 3The surface temperature change curves of the dry and wet aerogels of the present invention under one solar irradiation, and the temperature change of the evaporator during five cycles of heating and cooling; Figure 4 This is the evaporation performance test result of DA@GLM / MFC aerogel; Figure 5 This is the stability test result of DA@GLM / MFC aerogel; Figure 6 This is the evaporation rate of DA@GLM / MFC aerogel after 10 cycles; Figure 7 These are pictures after 10 cycles of evaporation using the DA@GLM / MFC aerogel evaporator; Figure 8 This describes the salt resistance test results of the DA@GLM / MFC aerogel of the present invention; Figure 9 These are test results of the DA@GLM / MFC aerogel simulating seawater evaporation performance and a comparison of ion concentrations before and after purification. Figure 10 The results show the evaporation rates of different dyes detected by DA@GLM / MFC aerogel. Figure 11 This is the UV-Vis-NIR absorption spectrum of DA@GLM / MFC aerogel simulating photocatalytic degradation of Congo red; Figure 12 These are the outdoor performance test results of the DA@GLM / MFC aerogel of this invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are all within the scope of protection of this invention.

[0019] To illustrate the present invention more clearly, the following embodiments will be described in detail.

[0020] Example 1 Preparation of dynamically covalently composite DA@GLM / MFC aerogel materials (hereinafter referred to as DA@GLM / MFC aerogel materials) (1) Material preparation Microcrystalline cellulose (MFC) was used as the biomass matrix, sodium periodate (NaIO4) as the oxidant, dopamine hydrochloride (DA) as the modifier, and gallium-based liquid metal (EGaIn in this example) as the photothermal functional component. All chemicals were of analytical grade and required no further purification. Functions: MFC is a renewable and environmentally friendly source, rich in active functional groups such as hydroxyl groups, providing sites for dynamic covalent reactions; gallium-based liquid metal possesses excellent electrical conductivity, thermal conductivity, and plasma properties, resulting in superior photothermal conversion performance.

[0021] (2) Preparation of MFC cryogel 0.1 M NaIO4 solid was added to a 2.0% (w / w) MFC dispersion to partially oxidize the cellulose molecules in the MFC. The dispersion was stirred at 600 rpm at room temperature in the dark for 4 hours to obtain an aldehyde-containing MFC dispersion. This dispersion was pre-frozen at -20°C for 20 minutes, then removed and vigorously stirred using an adjustable high-speed homogenizer to disperse a small amount of ice crystals. The dispersion was poured into a pre-prepared mold and frozen at -12°C for 12 hours to obtain an MFC cryogel. The cryogel process can construct a three-dimensional porous structure, providing a structural basis for subsequent loading of liquid metal nanoparticles and the formation of mass transfer channels; pre-freezing and homogenization ensure pore uniformity.

[0022] (3) Preparation of gallium-based liquid metal (DA-GLM) nanodroplets modified with dopamine hydrochloride 300 mg of gallium-based liquid metal was added to 15 ml of ethanol solution and sonicated for 2 h to obtain a suspension of gallium-based liquid metal nanodroplets. 150 mg of dopamine hydrochloride (DA) was added to the suspension, and sonication continued for 2 h. The modified DA-GLM nanodroplets were centrifuged and purified by washing with ultrapure water and ethanol. Sonication achieved nanoscale dispersion of the liquid metal, preventing particle aggregation. Dopamine hydrochloride modification introduced amino groups onto the liquid metal surface, which can form Schiff base bonds with the aldehyde groups of MFC. Simultaneously, the adhesive properties of dopamine enhanced the binding force between the liquid metal and the matrix. The purification step removed unreacted impurities, improving the purity of the composite system.

[0023] (4) Preparation of dynamic covalent composite DA@GLM / MFC aerogel Purified DA-GLM nanodroplets were dispersed in 25 ml of ethanol solution, and MFC cryogel was immersed in the solution. The mixture was incubated with shaking at 50 °C for 24 h, during which the solution gradually changed from pink to black, yielding a black and robust composite DA@GLM / MFC hybrid gel. Subsequent freeze-drying yielded the aerogel product. The 50 °C shaking incubation provided suitable conditions for the Schiff base reaction, achieving dynamic covalent anchoring between DA@GLM and MFC, resulting in a dynamically covalent composite DA@GLM / MFC aerogel material.

[0024] The composite system of this invention combines the photothermal properties of liquid metal with the porous structure advantages of aerogel, while dynamic covalent bonds endow the material with toughness and self-healing ability.

[0025] Performance study of the dynamic covalent composite DA@GLM / MFC aerogel of the present invention: (1) Characterization test: The morphology of DA@GLM / MFC aerogel was observed using field emission scanning electron microscopy, and the results (e.g.) Figure 1 The image on the left shows MFC, and the image on the right shows DA@GLM / MFC aerogel. It shows that DA@GLM / MFC aerogel has a three-dimensional porous structure with relatively uniform pore size, and a large number of spherical DA@GLM nanoparticles are attached to the pore walls of the aerogel.

[0026] Mechanical toughness testing was conducted by placing a 200g weight on a dry cylindrical DA@GLM / MFC aerogel, 1cm high and 1cm in diameter, and compressing it for 1 hour. Results (e.g.) Figure 2 The left image shows DA@GLM / MFC aerogels of different sizes, and the middle image shows the load-bearing test of DA@GLM / MFC aerogels. The results show that DA@GLM / MFC aerogels have excellent mechanical toughness, can be prepared into different sizes, and can withstand a 200g load pressure while maintaining a basically constant thickness.

[0027] (2) Photothermal performance test: Using a sunlight simulator to provide one solar illumination, the temperature change of the DA@GLM / MFC aerogel under dry and wet conditions (the aerogel was embedded in polystyrene foam, placed in a beaker, and water was added to make it float, and then the photothermal change on its surface was measured) was measured. The temperature change was recorded by an infrared thermal imager (E8). The results (e.g.) Figure 3 The results showed that the temperature of the dry DA@GLM / MFC aerogel rose from 19.7℃ to 169℃ within 60 seconds, and then balanced at 165℃ after 30 minutes; the temperature of the wet DA@GLM / MFC aerogel rose from 19.9℃ to 51.8℃ within 30 minutes. With the light source turned on, the dry DA@GLM / MFC aerogel heated to approximately 160℃ within 90 seconds. After the light source was turned off, it quickly returned to its initial temperature, and its photothermal properties were essentially undamaged. This was repeated five times, and the aerogel consistently and rapidly heated back to its initial temperature. The dry DA@GLM / MFC aerogel exhibited a rapid and stable photothermal response and demonstrated excellent recyclability throughout five heating and cooling cycles.

[0028] (3) Evaporation performance test: A solar evaporation system was constructed. MFC and DA@GLM / MFC aerogels were embedded in polystyrene foam and placed in beakers with water to make them float. The beakers were placed under a xenon lamp, and the light power of the xenon lamp source was adjusted to 1 solar irradiance (1 kW m²). -2Add water to the beaker so that the plane of the evaporator is aligned with the test plane of the optical power meter. Place the evaporator on a balance to record the mass change of the water. Measure the mass change using a precision electronic balance. The results (e.g.) Figure 4 (The left image shows the simulated equipment, and the right image shows the mass change.) This indicates that the evaporation rate of the DA@GLM / MFC aerogel evaporator can reach 7.25 kg m³. -2 h -1 The photothermal conversion efficiency is as high as 99.81%, which is lower than the evaporation rate of pure water (0.57 kg m³ / s). -2 h -1 It is 12.7 times faster than most existing similar evaporators, which is superior to most existing evaporators.

[0029] (4) Stability test: The DA@GLM / MFC aerogel was immersed in 3.5 wt.% NaCl solution for 14 days; it was then evaporated 10 times in a 20 wt% high-salt solution, irradiated for 1 hour each day, and immersed in the 20 wt% high-salt solution for the remaining time. The stability test was conducted, and the results (e.g.) Figure 5 The results show that, through brine immersion tests, the DA@GLM / MFC aerogel maintained its morphological integrity after immersion in a 3.5 wt.% NaCl solution for 14 days, with a mass reduction of only about 0.63%, and no salt crystallization occurred on the material surface. The evaporation rate remained stable at 3.20 kg / m³ after 10 cycles. -2 h -1 Left and right (e.g.) Figure 6 After 10 cycles of evaporation, the DA@GLM / MFC aerogel evaporator remained structurally intact without collapse or degradation, and only a small amount of DA@GLM / MFC aerogel fell from the bottom of the container (e.g.). Figure 7 This indicates that the dynamic covalent bonds of DA@GLM / MFC aerogel can effectively solve the problem of liquid metal shedding.

[0030] (5) Salt tolerance test: The DA@GLM / MFC aerogel evaporator was immersed in 3.5wt.%, 10wt.%, and 20wt.% NaCl solutions, respectively. The light power of the xenon lamp source was adjusted to the level of one solar irradiance (1 kW m²). -2 Afterwards, the evaporator was placed under a light source for 1 hour, and the mass loss during evaporation was recorded. The results showed that it could stably evaporate in 3.5 wt.%, 10 wt.%, and 20 wt.% NaCl solutions. Figure 8 Furthermore, there is no salt crystallization on the surface of the evaporator.

[0031] Similar to the experimental procedures described above, the evaporation rate was tested indoors using a xenon lamp to simulate sunlight, while outdoors the DA@GLM / MFC aerogel evaporator was immersed in prepared simulated seawater. Figure 9The device shown in the left figure is placed outdoors to purify simulated seawater. After purification, the seawater is collected and elemental analysis of metal ions in the simulated seawater and pure water is performed using inductively coupled plasma optical emission spectrometry (ICP-OES). After purification, the simulated seawater contains Na... + K + Ca 2+ Mg 2+ The concentrations decreased from 14776.820, 556.269, 662.657, and 1349.391 mg / L to 3.025, 0.446, 0.984, and 0.092 mg / L, respectively, with a removal rate exceeding 99%, far below the WHO and EPA safe drinking water standards (e.g., ...). Figure 9 (As shown in the right figure).

[0032] (6) Photocatalytic degradation performance test The experimental method was consistent with that used to test the evaporation rate of simulated seawater, except that the solution was replaced with organic dyes. Evaporation tests and outdoor water purification and collection capabilities were performed on Congo Red (CR), Methylene Blue (MB), Methyl Orange (MO), Alizarin Red (AR), and Rhodamine B (RhB). Characteristic absorption peaks before and after purification were then detected using a UV-Vis-NIR spectrophotometer (UV-1780). Results (e.g.) Figure 10 The results showed that the evaporation rates of all five dyes remained at a high level, and the absorption peaks of the organic dyes in the purified solution almost disappeared. DA@GLM / MFC catalyst (30 mg) was added to a Congo red (CR, 200 mg L⁻¹, 30 mL) solution. Before the reaction, the suspension was stirred in the dark for 60 min to reach adsorption equilibrium. Then, a solar photocatalytic experiment was conducted under a xenon lamp. After 2 h of reaction, the results (as shown in the figure) were obtained. Figure 11 The results showed a significant lightening of the Congo red color. Using a UV-Vis-NIR spectrophotometer (UV-1780) at the maximum absorption wavelength, its concentration was measured, revealing a significant decrease in absorbance and a substantial reduction in concentration. However, its catalytic mechanism and degradation rate are still under investigation.

[0033] (7) Outdoor performance test: using Figure 9 The apparatus shown was tested outdoors in Kunming, Yunnan Province (September 3-9, 2025). The actual outdoor temperature and humidity were recorded using an electronic thermometer and hygrometer, and the actual solar radiation intensity was measured using a power meter. After being exposed to sunlight, the temperature of the DA@GLM / MFC aerogel evaporator rose, accelerating water evaporation. Water vapor accumulated at the top of the container and then condensed at the bottom, yielding purified water. Environmental parameters and evaporation performance were recorded from 9:00 AM to 5:00 PM. Results (e.g.) Figure 12 The display showed that solar radiation reached 613.9 W / m² at 14:00. -2The peak evaporation rate was 4.62 kg m³. -2 h -1 The average freshwater yield over three days was 11.48 kg / m³. -2 The water quality is close to drinking water standards, and after seven consecutive days of testing, the evaporator still maintains a stable evaporation effect.

[0034] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A dynamic covalent composite DA@GLM / MFC aerogel material, characterized in that, The material is a three-dimensional porous structure with aldehyde-based MFC as the framework and Schiff base bonds as the dynamic covalent bonding structure supporting liquid metal nanoparticles.

2. The material according to claim 1, characterized in that, The liquid metal is a gallium-based liquid metal modified with dopamine hydrochloride.

3. The material according to claim 1, characterized in that, The aldehyde-modified MFC is obtained by partially oxidizing micronized cellulose MFC with sodium periodate under light-shielding conditions and then freezing.

4. The method for preparing the dynamic covalent composite DA@GLM / MFC aerogel material according to any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Preparation of MFC cryogel NaIO4 solid was added to the MFC dispersion to partially oxidize the cellulose molecules of MFC; after stirring, an aldehyde-containing MFC dispersion was obtained. The dispersion was pre-frozen in a refrigerator and then taken out and stirred vigorously to disperse a small amount of ice crystals; thus, an MFC cryogel was obtained. (3) Preparation of gallium-based liquid metal DA-GLM nanodroplets modified with dopamine hydrochloride Gallium-based liquid metal was added to an ethanol solution and sonicated to obtain a suspension of gallium-based liquid metal nanodroplets; dopamine hydrochloride (DA) was added to the suspension and sonicated again to obtain modified DA-GLM nanodroplets; The modified DA-GLM nanodroplets were separated by centrifugation and purified by washing with ultrapure water and ethanol to obtain dopamine hydrochloride modified gallium-based liquid metal DA-GLM nanodroplets. (4) Preparation of dynamic covalent composite DA@GLM / MFC aerogel The purified DA-GLM nanodroplets were dispersed in an ethanol solution, and the MFC cryogel was immersed in the solution. After shaking and incubation at 50°C, a black and robust composite DA@GLM / MFC hybrid gel was obtained. Dynamic covalent composite DA@GLM / MFC aerogel material was obtained by freeze-drying.

5. The preparation method according to claim 4, characterized in that, In step (1), solid NaIO4 is added to a 2.0% (w / w) MFC dispersion and the cellulose molecules of MFC are oxidized at a mass ratio of NaIO4 to MFC dispersion of 0.28-0.36:12-18.

6. The preparation method according to claim 4, characterized in that, In step (3), the mass ratio of GLM:DA:C2H5OH is 1.6~2.4:0.8~1.2:63.2~94.

8.

7. The preparation method according to claim 4, characterized in that, In step (4), the volume ratio of DA-GLM nanodroplets to ethanol solution is 0.6-1.4:15-40.

8. The dynamic covalent composite DA@GLM / MFC aerogel material obtained by the preparation method according to any one of claims 4 to 7.

9. The application of the dynamic covalent composite DA@GLM / MFC aerogel material as described in any one of claims 1 to 3 or 8 as an aerogel evaporator.

10. The application of the dynamic covalent composite DA@GLM / MFC aerogel material as described in any one of claims 1 to 3 or 8 as a photocatalyst for the degradation of organic matter.

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