An MXene-modified polysiloxane-nitrogen heterocyclic hybrid hydrogel composite atmospheric water collection material and its preparation method

Abstract

This invention discloses an MXene-modified polysiloxane-nitrogen heterocyclic hybrid hydrogel composite atmospheric water collection material and its preparation method. The water collection material is a three-dimensional porous structure of a hybrid hydrogel constructed from polysiloxane and nitrogen heterocycles. MXene is loaded into this three-dimensional porous structure, which is further impregnated with lithium chloride hygroscopic salt. This water collection material utilizes the flexible network of polysiloxane, the hydrophilic adsorption sites of nitrogen heterocycles, the photothermal conversion properties of MXene, and the high hygroscopicity of lithium chloride to achieve efficient adsorption over a wide humidity range and rapid desorption driven by sunlight. The preparation process of this invention is mild and has good cycle stability, effectively solving the problem of hygroscopic salt leakage, and can be widely applied to atmospheric water collection in arid and semi-arid regions.

Description

Technical Field

[0001] This invention belongs to the field of functional materials and atmospheric water resource collection technology, specifically relating to an MXene-modified polysiloxane-nitrogen heterocyclic hybrid hydrogel composite atmospheric water collection material and its preparation method. Background Technology

[0002] The global water shortage problem is becoming increasingly severe, making the development of efficient and sustainable freshwater acquisition technologies an urgent priority. Adsorption-based atmospheric water harvesting technology captures water molecules from the air using adsorbents and utilizes low-grade thermal energy such as solar energy for desorption and collection, offering advantages such as strong environmental adaptability and low energy consumption. However, the actual effectiveness of this technology is highly dependent on the comprehensive performance of the adsorbent material.

[0003] Currently common adsorbents, such as silica gel, zeolites, hygroscopic salts (e.g., lithium chloride), and metal-organic frameworks (MOFs), while each possessing unique characteristics, still exhibit significant drawbacks. For instance, while hygroscopic salts demonstrate outstanding adsorption potential at low humidity levels, they are prone to leakage after deliquescence, leading to loss of active ingredients and equipment corrosion. Furthermore, porous crystalline materials are costly to synthesize, hindering large-scale production. Loading salts onto porous supports is an effective improvement strategy, but existing supports, such as cellulose aerogels, often experience a decrease in mechanical strength after salt loading and lack photothermal functionality, requiring external heat sources for desorption, thus limiting energy efficiency.

[0004] It is evident that existing adsorbents fall short in achieving a balance between key performance indicators such as adsorption capacity, desorption energy consumption, long-term cycle stability, and low-cost preparation. Therefore, developing a novel composite material capable of achieving efficient adsorption, rapid desorption, and long-term stable operation has significant scientific value and application prospects. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the problems of limited adsorption capacity, high desorption energy consumption, and insufficient cycle stability of existing atmospheric water collection adsorbent materials in a wide humidity range.

[0006] Polysiloxane materials possess excellent flexibility, thermal stability, and modifiability. By introducing nitrogen-containing heterocyclic functional monomers, hybrid hydrogel networks with abundant hydrophilic sites can be constructed. Meanwhile, MXene, as a novel two-dimensional transition metal carbide / nitride, exhibits excellent photothermal conversion performance, hydrophilicity, and conductivity. To achieve the above objectives, this invention provides an MXene-modified polysiloxane-nitrogen heterocyclic hybrid hydrogel atmospheric water collection material. Through multi-component functional synergy and three-dimensional structural design, it achieves a balance between efficient adsorption, rapid desorption, and long-term stable operation.

[0007] The atmospheric water-collecting material of this invention uses a three-dimensional porous structure of a hybrid hydrogel constructed from polysiloxane and nitrogen heterocycles as a carrier. MXene photothermal nanosheets are uniformly loaded within this three-dimensional porous structure, and further impregnated with lithium chloride (LiCl) hygroscopic salt. This system utilizes the three-dimensional network structure of the hydrogel to stably lock in the hygroscopic salt, preventing its leakage; it utilizes the hydrophilic adsorption sites of the nitrogen heterocycle structure to enhance the water molecule capture ability; and it utilizes MXene to achieve efficient photothermal conversion, thereby achieving high adsorption capacity over a wide humidity range, and rapidly desorbing with the help of solar energy.

[0008] Specifically, the present invention provides an MXene-modified polysiloxane-nitrogen heterocyclic hybrid hydrogel atmospheric water collection material, wherein the water collection material is a polysiloxane-nitrogen heterocyclic hybrid hydrogel matrix loaded with MXene material and further impregnated with lithium chloride hygroscopic salt; the hydrogel matrix has a three-dimensional porous structure, and the three-dimensional porous structure is loaded with MXene material.

[0009] Furthermore, the hydrogel atmospheric water collection material is formed by mixing a dispersion of MXene material with a siloxane precursor and a nitrogen-containing heterocyclic functional monomer, followed by a hydrolysis and condensation reaction to form an MXene-modified polysiloxane-nitrogen heterocyclic hybrid hydrogel with a three-dimensional network structure, and then impregnating it with lithium chloride hygroscopic salt.

[0010] Furthermore, the siloxane precursor is selected from at least one of tetraethyl orthosilicate, methyl orthosilicate, vinyltrimethoxysilane, vinyltriethoxysilane, 3-aminopropyltriethoxysilane, or polydimethylsiloxane, methyltrimethoxysilane, and tetraethoxysilane containing terminal alkoxy groups; it forms a Si-O-Si covalent network through hydrolysis and condensation; the nitrogen-containing heterocyclic functional monomer is selected from at least one of pyrrolidone ring, imidazole ring, pyridine ring, or triazole ring; the nitrogen atom in the nitrogen heterocycle acts as a hydrogen bond acceptor, forming hydrogen bonds with hydrogen atoms in water molecules; simultaneously, the polar bonds or active hydrogen on the nitrogen heterocycle form hydrogen bonds with oxygen-containing functional groups on the MXene surface, and the lone pair electrons on the nitrogen heterocycle coordinate with transition metal sites on the MXene surface, jointly constructing a three-dimensional network structure that provides ample water storage space. MXene materials can enhance the mechanical properties of structures. The pores store a large amount of lithium chloride hygroscopic salt and adsorbed water vapor, which can efficiently adsorb water vapor in the air. In other words, MXene improves photothermal conversion efficiency and accelerates desorption rate.

[0011] Furthermore, the MXene material is preferably Ti3C2T. x T x With surface functional groups (such as -OH, -O, -F, etc.), MXene materials are uniformly dispersed in the hydrogel matrix by ultrasound.

[0012] This invention also provides a method for preparing the MXene-modified polysiloxane-nitrogen heterocyclic hybrid hydrogel atmospheric water collection material as described above. The MXene-modified polysiloxane-nitrogen heterocyclic hybrid hydrogel atmospheric water collection material is formed by crosslinking using a sol-gel method, comprising the following steps: Step S1: Disperse MXene material in deionized water to obtain MXene dispersion; Step S2: Add the siloxane precursor to the MXene dispersion; Step S3: Add nitrogen-containing heterocyclic functional monomers to the system of step S2; the siloxane precursor and nitrogen-containing heterocyclic functional monomers are mixed to give it a flexible structural network, thereby enabling the hydrogel to have the properties of efficient water molecule adsorption, rapid desorption and good cycling stability. Step S4: Perform a hydrolysis-condensation reaction on the above mixture to obtain a homogeneous sol; Step S5: Pour the homogeneous sol obtained in S4 into a mold, and after gelation, obtain a polysiloxane-nitrogen heterocyclic hybrid hydrogel loaded with MXene. Step S6: Immerse the MXene-loaded polysiloxane-nitrogen heterocyclic hybrid hydrogel in a lithium chloride solution for 6-24 hours, and then dry it to obtain the MXene-modified polysiloxane-nitrogen heterocyclic hybrid hydrogel atmospheric water collection material.

[0013] Furthermore, the mass-to-volume ratio of the MXene material to deionized water in step S1 is 0.2~1.0 g / L.

[0014] Furthermore, the mass ratio of the siloxane precursor, the nitrogen-containing heterocyclic functional monomer, and deionized water is 1–10 g: 0.5–5 g: 100 g. This ratio forms a uniform three-dimensional network with suitable mechanical properties, providing an ideal carrier for water adsorption and storage. The gelation process mainly relies on the covalent bonds formed by the hydrolysis and condensation of the siloxane, the hydrogen bonding between the nitrogen heterocycle and water molecules and MXene, and coordination interactions, collectively constructing a stable three-dimensional network structure.

[0015] Further, in step S2, the siloxane precursor is added to the MXene dispersion and then stirred at 2000-3000 r / min for 30-50 min; after adding the nitrogen-containing heterocyclic functional monomer to the system in step S2, the mixture is stirred at 2000-3000 r / min for 30-50 min.

[0016] Furthermore, the hydrolysis-condensation reaction in step S4 is carried out at a temperature of 20-80°C for 2-24 hours.

[0017] Furthermore, step S5 gelation is completed by heating at 50°C for 1 to 2 hours.

[0018] Further, the specific steps of step S6 are as follows: the hydrogel obtained in step S5 is immersed in a lithium chloride solution with a mass fraction of 3% to 20% for 6 to 24 hours, and then dried at 40 to 60°C for 12 to 24 hours to obtain MXene modified polysiloxane-nitrogen heterocyclic hybrid hydrogel atmospheric water collection material.

[0019] Compared with the prior art, the present invention has the following outstanding features and advantages: 1. Innovative Material System: This invention is the first to propose a hybrid hydrogel constructed by covalent cross-linking polysiloxane and nitrogen heterocyclic compounds as a three-dimensional matrix for atmospheric water collection materials. This system fully leverages the synergistic advantages of its multiple components: polysiloxane provides a flexible and stable network framework, endowing the material with excellent mechanical adaptability and structural integrity; nitrogen heterocyclic functional units introduce abundant hydrophilic adsorption sites (such as imidazole groups and pyridinyl groups), enhancing the water molecule capture ability; MXene nanosheets are uniformly embedded in the network, not only endowing the material with excellent photothermal conversion performance, but also enhancing structural stability through hydrogen bonding or coordination with the polymer matrix via their surface functional groups; lithium chloride, as a highly efficient hygroscopic salt, further improves the material's adsorption capacity. The organic combination of these four components constructs a three-dimensional porous network with high specific surface area, high porosity, excellent hydrophilicity, and photothermal responsiveness.

[0020] 2. Synergistic Enhancement of Functions: This invention achieves synergistic effects of moisture absorption, photothermal conversion, and structural stability through rational component design and structural regulation. Specifically, lithium chloride provides excellent moisture absorption capacity, enabling the material to achieve efficient water adsorption within a wide humidity range (30%RH to 90%RH); MXene, as a highly efficient photothermal conversion material, can rapidly heat up under simulated sunlight irradiation, driving the rapid desorption of adsorbed water and significantly reducing the energy consumption and time of the desorption process; the polysiloxane-nitrogen heterocyclic hydrogel matrix plays a role in stabilizing the load, constructing mass transfer channels, and providing structural support. The synergy of these three components exhibits excellent comprehensive water collection performance.

[0021] 3. Excellent structural stability: In this invention, lithium chloride is stably immobilized within a three-dimensional hydrogel network constructed from covalent bonds (siloxane condensation network) and non-covalent bonds (hydrogen bonds, coordination interactions, etc.), avoiding the leakage problem caused by deliquescence in traditional hygroscopic salts. The introduction of MXene not only enhances the structural strength of the network but also further inhibits salt migration and precipitation through interfacial interactions with the polymer matrix. Experimental results show that after 10 hygroscopic-photodesorption cycles, the material still retains more than 97% of its initial adsorption capacity, with a mass loss (mainly from salt leakage) of less than 2%, and the hydrogel network remains intact without significant structural damage. This excellent structural and performance stability significantly improves the cycle life of the material, providing a reliable guarantee for practical applications.

[0022] 4. Simple and controllable preparation method: The preparation method adopts the sol-gel method, which is mild, has clear parameters, and good repeatability. It avoids the use of toxic chemical crosslinking agents. Moreover, by adjusting parameters such as the precursor ratio, reaction temperature and time, and the loading of MXene and LiCl, the pore structure, mechanical properties and hygroscopic characteristics of the material can be flexibly controlled to meet different application needs. It has the potential for large-scale production and can be widely used in atmospheric water collection in arid and semi-arid regions or emergency scenarios. Attached Figure Description

[0023] Figure 1 This is a comparison chart of the changes in photothermal conversion performance (a) and moisture absorption rate (b) between adding MXene and not adding MXene in Example 3; Figure 2 The graph (a) shows the change in adsorption capacity of PSi-NH / MXene / LiCl prepared in Example 4 during 10 cycles, and the actual image (b) shows the product after 10 cycles. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. The technical solutions of the present invention will be further described below with reference to implementation examples. Unless otherwise stated, the raw materials, reagents, and instruments used in the embodiments of the present invention are all commercially available conventional products.

[0025] Example 1: Optimization of basic formulation and reaction conditions This embodiment aims to determine the optimal ratio of siloxane precursor, nitrogen-containing heterocyclic functional monomer, and water, as well as the optimal temperature and time for the sol-gel reaction. The specific steps are as follows: (1) Weigh out different mass ratios of siloxane precursor (a mixture of methyltrimethoxysilane and tetraethoxysilane in a mass ratio of 1:1), nitrogen-containing heterocyclic functional monomer (N-[3-(trimethoxysilyl)propyl]imidazole), and deionized water. The specific ratios investigated include: siloxane precursor: nitrogen heterocyclic monomer: water = 1:0.5:100, 5:2:100, and 10:5:100 (all mass ratios).

[0026] (2) MXene (Ti3C2(OH)2, i.e. hydroxylated titanium carbide) was dispersed in deionized water at a ratio of 0.5 g / L and ultrasonicated at 200 W for 1 hour to obtain MXene dispersion.

[0027] (3) Add the siloxane precursor to the MXene dispersion and stir at 2500 r / min for 30 min; then add the nitrogen-containing heterocyclic functional monomer and continue stirring at 2500 r / min for 30 min.

[0028] (4) The mixed system was placed at different temperatures (20℃, 50℃, 80℃) and reacted for different times (2 hours, 12 hours, 24 hours) to obtain a homogeneous sol.

[0029] (5) Pour the homogeneous sol into the mold and heat it at 50°C for 1.5 hours to promote gelation, and obtain the polysiloxane-nitrogen heterocyclic hybrid hydrogel loaded with MXene.

[0030] (6) The obtained MXene-loaded polysiloxane-nitrogen heterocyclic hybrid hydrogel was immersed in 10% LiCl solution for 12 hours, and then dried at 50°C for 18 hours to obtain MXene-modified polysiloxane-nitrogen heterocyclic hybrid hydrogel atmospheric water collection material.

[0031] Performance testing: The equilibrium swelling rate (soaked in deionized water for 24 hours), mechanical properties (compression modulus), and moisture absorption rate at 75% RH were tested for each group of samples.

[0032] Performance testing methods: Equilibrium swelling rate test: Weigh the dry gel sample and record the weight as follows: Soak in deionized water for 24 hours, then remove and gently blot away surface moisture with filter paper. Weigh again and record the weight. The formula for calculating the equilibrium swelling ratio is: ; Mechanical property (compression modulus) test: Using a universal testing machine, the sample was prepared as a cylinder with a diameter of 10 mm and a height of 10 mm. A compression test was carried out at a compression rate of 2 mm / min. The stress-strain curve was recorded, and the slope of the initial linear segment (strain 0~10%) was taken as the compression modulus (unit: MPa).

[0033] 75% RH moisture absorption test: Weigh the dried sample and record the weight as follows. The sample was placed in a constant temperature and humidity chamber (temperature 25℃, relative humidity 75%), and weighed every 2 hours until the weight change between two consecutive weighings was less than 0.01 g, which was recorded as 0.01 g. The formula for calculating moisture absorption rate is: ; The performance results under different ratios and reaction conditions are as follows: Following the above method, a systematic test was conducted on all 3 ratios × 3 temperatures × 3 times (a total of 27 combinations). The results for 9 representative key combinations are listed below, and the results for the remaining combinations are summarized below.

[0034] When the ratio of siloxane precursor: nitrogen heterocyclic monomer: water is 1:0.5:100 (mass ratio), the reaction temperature is 50℃, and the reaction time is 12 hours, the compression modulus is 0.6 MPa, the equilibrium swelling rate is 800%, and the moisture absorption rate at 75% RH is 1.2 g / g.

[0035] When the mass ratio is 5:2:100, the reaction temperature is 50℃, and the reaction time is 12 hours, the compression modulus is 1.2 MPa, the equilibrium swelling rate is 600%, and the moisture absorption rate at 75% RH is 1.8 g / g.

[0036] When the mass ratio is 10:5:100, the reaction temperature is 50℃, and the reaction time is 12 hours, the compression modulus is 2.0 MPa, the equilibrium swelling rate is 400%, and the moisture absorption rate at 75% RH is 1.5 g / g.

[0037] When the mass ratio is 5:2:100, the reaction temperature is 20℃, and the reaction time is 24 hours, the compression modulus is 0.8 MPa, the equilibrium swelling rate is 650%, and the moisture absorption rate at 75% RH is 1.6 g / g.

[0038] When the mass ratio is 5:2:100, the reaction temperature is 80℃, and the reaction time is 2 hours, the compression modulus is 1.5 MPa, the equilibrium swelling rate is 500%, and the moisture absorption rate at 75% RH is 1.7 g / g.

[0039] When the mass ratio is 1:0.5:100, the reaction temperature is 20℃, and the reaction time is 24 hours, the compression modulus is 0.4 MPa, the equilibrium swelling rate is 850%, and the moisture absorption rate at 75% RH is 1.0 g / g.

[0040] When the mass ratio is 1:0.5:100, the reaction temperature is 80℃, and the reaction time is 2 hours, the compression modulus is 0.9 MPa, the equilibrium swelling rate is 720%, and the moisture absorption rate at 75% RH is 1.1 g / g.

[0041] When the mass ratio is 10:5:100, the reaction temperature is 20℃, and the reaction time is 24 hours, the compression modulus is 1.6 MPa, the equilibrium swelling rate is 350%, and the moisture absorption rate at 75% RH is 1.3 g / g.

[0042] When the mass ratio is 10:5:100, the reaction temperature is 80℃, and the reaction time is 2 hours, the compression modulus is 2.5 MPa, the equilibrium swelling rate is 300%, and the moisture absorption rate at 75% RH is 1.2 g / g.

[0043] Under other reaction conditions not listed above (including but not limited to: ratio 1:0.5:100 at 20℃ / 2h, 20℃ / 12h, 50℃ / 2h, 50℃ / 24h, 80℃ / 12h, 80℃ / 24h; ratio 5:2:100 at 20℃ / 2h, 20℃ / 12h, 50℃ / 2h, 50℃ / 24h, 80℃ / 12h, 80℃ / 24h; ratio 10:5:100 at 20℃ / 2h, 20℃ / 12h, 50℃ / 2h, 50℃ / 24h, 80℃ / 12h, 80℃ / 24h), the properties of the materials obtained were not superior to the results listed above. Specifically, the compression modulus is ≤0.5 MPa or ≥2.2 MPa; the equilibrium swelling rate is ≤350% or ≥850%; and the 75% RH moisture absorption rate is ≤1.1 g / g.

[0044] The results showed that, after comprehensive comparison, the hydrogel exhibited both good mechanical strength (1.2 MPa) and high moisture absorption (1.8 g / g) when the ratio of siloxane precursor: nitrogen heterocyclic monomer: water was 5:2:100, the reaction temperature was 50℃, and the reaction time was 12 hours. Therefore, this condition was selected as the optimal process.

[0045] Example 2: Optimization of MXene Dosage In this embodiment, under the optimized conditions determined in Example 1 (siloxane precursor: nitrogen heterocyclic monomer: water mass ratio 5:2:100, reaction temperature of step (4) 50℃, reaction time of step (4) 12 hours), the effect of different MXene addition amounts (0, 0.2, 0.5, 0.8, 1.0 g / L) on material properties was investigated. The LiCl impregnation concentration was fixed at 10%.

[0046] Step 1: Prepare MXene-modified polysiloxane-nitrogen heterocyclic hybrid hydrogel atmospheric water collection materials with different amounts of MXene according to the method in Example 1.

[0047] Step 2: Test the photothermal heating performance (time required for surface temperature to rise from 25℃ to 45℃) of each sample under 1 solar intensity (1 kW / m²) and the equilibrium moisture absorption rate at 75% RH.

[0048] The performance results for different amounts of MXene are as follows: Without the addition of MXene, the time required to heat to 45°C is greater than 30 minutes, and the equilibrium moisture absorption rate at 75% RH is 1.5 g / g.

[0049] When the addition amount is 0.2 g / L, the heating time is 14 minutes, and the moisture absorption rate is 1.6 g / g.

[0050] When the addition amount is 0.5 g / L, the heating time is 8 minutes, and the moisture absorption rate is 1.8 g / g.

[0051] When the addition amount is 0.8 g / L, the heating time is 6 minutes, and the moisture absorption rate is 1.75 g / g.

[0052] When the addition amount is 1.0 g / L, the heating time is 6 minutes, and the moisture absorption rate is 1.7 g / g.

[0053] The results showed that adding MXene significantly improved the photothermal heating rate, but the heating performance plateaued after the addition amount reached 0.5 g / L. Appropriate MXene addition had a slight promoting effect on moisture absorption performance, while excessive addition may slightly affect moisture absorption due to agglomeration. Therefore, the preferred MXene addition amount is 0.5~0.8 g / L.

[0054] Example 3: Optimization of LiCl impregnation concentration In this embodiment, under the optimized conditions of Examples 1 and 2 (siloxane precursor: nitrogen heterocyclic monomer: water mass ratio 5:2:100, reaction temperature of step (4) is 50℃, reaction time of step (4) is 12 hours, MXene is added 0.5 g / L), the effects of different LiCl impregnation concentrations (0%, 3%, 7%, 10%, 15%, 20%) on the moisture absorption properties and salt leakage rate of the material were investigated.

[0055] Step 1: Prepare polysiloxane-nitrogen heterocyclic hybrid hydrogels loaded with MXene according to the method in Example 1, and immerse them in LiCl solutions of different concentrations.

[0056] Step 2: Test the equilibrium moisture absorption rate of each sample at 30% RH (low humidity), 60% RH (medium humidity), and 90% RH (high humidity).

[0057] Step 3: By placing the moisture-saturated sample at 90% RH for 7 days, weighing its mass loss, and calculating the salt leakage rate.

[0058] The performance results for different LiCl impregnation concentrations are as follows: When the impregnation concentration is 0%, the moisture absorption rate is 0.1 g / g at 30% RH, 0.2 g / g at 60% RH, and 0.3 g / g at 90% RH. The 7-day salt leakage rate cannot be calculated.

[0059] When the impregnation concentration is 3%, the moisture absorption rate is 0.5 g / g at 30% RH, 1.0 g / g at 60% RH, 1.5 g / g at 90% RH, and the salt leakage rate is 2% after 7 days.

[0060] When the impregnation concentration is 7%, the moisture absorption rate is 0.8 g / g at 30% RH, 1.5 g / g at 60% RH, and 2.2 g / g at 90% RH. The salt leakage rate is 3% after 7 days.

[0061] When the impregnation concentration is 10%, the moisture absorption rate is 1.0 g / g at 30% RH, 1.9 g / g at 60% RH, and 2.7 g / g at 90% RH. The salt leakage rate is 4% after 7 days.

[0062] When the impregnation concentration is 15%, the moisture absorption rate is 1.1 g / g at 30% RH, 2.0 g / g at 60% RH, and 2.8 g / g at 90% RH. The salt leakage rate is 10% after 7 days.

[0063] When the impregnation concentration is 20%, the moisture absorption rate is 1.1 g / g at 30% RH, 1.9 g / g at 60% RH, and 2.6 g / g at 90% RH. The salt leakage rate is 15% after 7 days.

[0064] The results showed that the moisture absorption rate increased significantly with increasing LiCl concentration, especially under low humidity conditions. However, when the concentration exceeded 15%, the increase in moisture absorption rate was limited, but the salt leakage rate increased sharply. Considering both moisture absorption performance and stability, a LiCl impregnation concentration of 10%–15% was preferred.

[0065] Figure 1 This example demonstrates a comparison of the changes in photothermal conversion performance (a) and moisture absorption rate (b) with and without MXene addition in this embodiment. Figure 1 As shown in (a), the surface temperature of the sample with added MXene rises rapidly under simulated sunlight irradiation, and the time required to reach the same temperature is significantly shortened, indicating that the introduction of MXene greatly improves the photothermal conversion efficiency of the material. Figure 1 As shown in (b), adding an appropriate amount of MXene slightly promotes the moisture absorption rate of the material, which is attributed to the enhanced water molecule trapping ability of the abundant hydrophilic functional groups on the MXene surface; however, excessive addition may lead to the aggregation of MXene sheets, which may slightly reduce the moisture absorption performance. In summary... Figure 1 As a result, the introduction of MXene achieved synergistic optimization of photothermal and moisture absorption properties.

[0066] Example 4: Comprehensive Performance Test (Optimal Sample) Based on the above optimization results, this embodiment prepared the optimal sample (siloxane precursor: nitrogen heterocyclic monomer: water mass ratio 5:2:100, reaction temperature of step (4) is 50℃, reaction time of step (4) is 12 hours, MXene is added 0.5 g / L, and 15% LiCl is impregnated), and its performance was comprehensively evaluated.

[0067] The preparation steps are as follows: Step S1: Add 60 mg of MXene (Ti3C2T) x Add the powder to 100 mL of deionized water and sonicate at 200W ultrasonic power for 1 hour.

[0068] Step S2: Add 5 g of siloxane precursor (methyltrimethoxysilane to tetraethoxysilane in a mass ratio of 1:1) to the S1 dispersion and stir at 2500 r / min for 30 minutes.

[0069] Step S3: Add 2 g of N-[3-(trimethoxysilyl)propyl]imidazolium to the system in step S2 and stir at 2500 r / min for 30 minutes.

[0070] Step S4: The above mixture is subjected to a hydrolysis-condensation reaction at 50°C for 12 hours to obtain a homogeneous sol.

[0071] Step S5: Pour the homogeneous sol obtained in S4 into a mold and heat at 50°C for 4 hours to promote gelation, thereby obtaining a polysiloxane-nitrogen heterocyclic hybrid hydrogel loaded with MXene.

[0072] Step S6: The hydrogel obtained in step S5 is immersed in a 15% lithium chloride solution for 12 hours, and then dried at 50°C for 20 hours to obtain MXene-modified polysiloxane-nitrogen heterocyclic hybrid hydrogel atmospheric water collection material (labeled as PSi-NH / MXene / LiCl).

[0073] Hygroscopic performance: The equilibrium moisture absorption rate of the sample was tested at 30%, 60%, and 90% RH at 25℃. The results showed that the adsorption capacity reached approximately 1.15 g / g at 30% RH; approximately 2.05 g / g at 60% RH; and approximately 2.85 g / g at 90% RH. This material exhibits excellent adsorption capacity over a wide humidity range (30%–90% RH), especially in low-humidity environments, outperforming many traditional adsorbents.

[0074] Photothermal and desorption performance: Under simulated sunlight (1 kW / m²), the surface temperature of the PSi-NH / MXene / LiCl sample increased from 25°C to approximately 52°C within 7 minutes, while the control sample (PSi-NH / LiCl) without MXene only increased to approximately 37°C within 30 minutes. Under the same illumination conditions, the desorption test showed that the PSi-NH / MXene / LiCl sample reached 88% of its saturated adsorption capacity within 5 hours, while the control sample only reached 40%. The desorption rate was increased by approximately 120%.

[0075] Cyclic stability: The PSi-NH / MXene / LiCl sample was subjected to 10 cycles of "hygroscopic-photodesorption" at 60% RH. Figure 2 Figure (a) shows the change in adsorption capacity of the prepared PSi-NH / MXene / LiCl during 10 cycles, and Figure (b) shows the final product after 10 cycles. As shown, after 10 cycles, the hygroscopic capacity of the sample remained above 97% of the initial value, and the sample mass loss (mainly attributed to salt leakage) was less than 2%. The hydrogel network structure remained intact without significant damage. This indicates that the polysiloxane-nitrogen heterocyclic hybrid network has good immobilization capacity for LiCl.

[0076] The above-described embodiments are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. An MXene-modified polysiloxane-nitrogen heterocyclic hybrid hydrogel atmospheric water collection material, characterized in that, The water-collecting material is a polysiloxane-nitrogen heterocyclic hybrid hydrogel matrix loaded with MXene material, and further impregnated with lithium chloride hygroscopic salt; the hydrogel matrix has a three-dimensional porous structure, and the three-dimensional porous structure is loaded with MXene material.

2. The MXene-modified polysiloxane-nitrogen heterocyclic hybrid hydrogel atmospheric water collection material according to claim 1, characterized in that, The hydrogel atmospheric water collection material is formed by mixing a dispersion of MXene material with a siloxane precursor and a nitrogen-containing heterocyclic functional monomer, followed by a hydrolysis and condensation reaction to form an MXene-modified polysiloxane-nitrogen heterocyclic hybrid hydrogel with a three-dimensional network structure, and then impregnating it with lithium chloride hygroscopic salt.

3. The MXene-modified polysiloxane-nitrogen heterocyclic hybrid hydrogel atmospheric water collection material according to claim 2, characterized in that, The siloxane precursor is selected from at least one of tetraethyl orthosilicate, methyl orthosilicate, vinyltrimethoxysilane, vinyltriethoxysilane, 3-aminopropyltriethoxysilane, or polydimethylsiloxane, methyltrimethoxysilane, or tetraethoxysilane containing terminal alkoxy groups; the nitrogen-containing heterocyclic functional monomer is selected from at least one of pyrrolidone ring, imidazole ring, pyridine ring, or triazole ring.

4. The method for preparing the MXene-modified polysiloxane-nitrogen heterocyclic hybrid hydrogel atmospheric water collection material according to any one of claims 1-3, characterized in that, Includes the following steps: Step S1: Disperse MXene material in deionized water to obtain MXene dispersion; Step S2: Add the siloxane precursor to the MXene dispersion; Step S3: Add a nitrogen-containing heterocyclic functional monomer to the system of step S2; Step S4: Perform a hydrolysis-condensation reaction on the above mixture to obtain a homogeneous sol; Step S5: Pour the homogeneous sol obtained in S4 into a mold, and after gelation, obtain a polysiloxane-nitrogen heterocyclic hybrid hydrogel loaded with MXene. Step S6: Immerse the MXene-loaded polysiloxane-nitrogen heterocyclic hybrid hydrogel in a lithium chloride solution for 6-24 hours, and then dry it to obtain the MXene-modified polysiloxane-nitrogen heterocyclic hybrid hydrogel atmospheric water collection material.

5. The method according to claim 4, characterized in that, The mass-to-volume ratio of MXene material to deionized water in step S1 is 0.2~1.0 g / L.

6. The method according to claim 4, characterized in that, The mass ratio of siloxane precursor, nitrogen-containing heterocyclic functional monomer and deionized water is 1~10 g:0.5~5 g:100 g.

7. The method according to claim 4, characterized in that, In step S2, the siloxane precursor is added to the MXene dispersion and then stirred at 2000-3000 r / min for 30-50 min; after adding the nitrogen-containing heterocyclic functional monomer to the system in step S2, the mixture is stirred at 2000-3000 r / min for 30-50 min.

8. The method according to claim 4, characterized in that, Step S4 hydrolysis-condensation reaction temperature is 20~80℃, reaction time is 2~24 hours.

9. The method according to claim 4, characterized in that, Step S5 gelation is completed by heating at 50°C for 1 to 2 hours.

10. The method according to claim 4, characterized in that, The specific steps of step S6 are as follows: the hydrogel obtained in step S5 is immersed in a lithium chloride solution with a mass fraction of 3% to 20% for 6 to 24 hours, and then dried at 40 to 60°C for 12 to 24 hours to obtain MXene modified polysiloxane-nitrogen heterocyclic hybrid hydrogel atmospheric water collection material.

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