A cofs composite aerogel and a preparation method and application thereof

Abstract

This application relates to a COFs composite aerogel, its preparation method, and its application, belonging to the field of new energy power generation materials technology. The preparation method of the COFs composite aerogel of this application includes the following steps: S1, dissolving aminated carbon nanotubes (NH2-CNTs), 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde, and 4,4'-diaminobiphenyl-3,3'-disulfonic acid in a mixed solvent and carrying out a solvothermal reaction; after washing and drying, a TB-COF@CNTs composite material is obtained; S2, dispersing cellulose nanocrystals (CNC) and chitosan (CS) in deionized water, adding the TB-COF@CNTs composite material, stirring evenly, and then adding a crosslinking agent to obtain a mixed precursor solution; S3, injecting the mixed precursor solution into a mold, solidifying it through directional freezing, and then freeze-drying to obtain the COFs composite aerogel. This multi-level structural design of the present application achieves cross-scale synergistic optimization of nanoscale ion screening and macroscale fluid transport and electron collection, significantly enhancing the charge separation efficiency of the evaporation interface under photothermal drive.

Description

Technical Field

[0001] This application relates to the field of new energy power generation materials technology, and in particular to a COFs composite aerogel, its preparation method and application. Background Technology

[0002] Hydrovoltaic power generation is a technology that converts environmental water energy into electrical energy through the direct interaction between water and functional materials (such as flow, evaporation, infiltration, or humidity gradients). Its core principle typically relies on electrokinetic effects (such as flow potential, evaporation potential, etc.) or ion gradient diffusion at the solid-liquid interface. Evaporation-driven hydrovoltaic power generation has attracted significant attention due to its ability to generate continuous electricity from the widespread and continuous evaporation process found in nature. This technology requires no external mechanical energy input, offering a promising sustainable energy solution for fields such as IoT sensors, portable devices, and low-grade waste heat recovery. Although existing hydrovoltaic materials have attempted to improve power generation performance by utilizing porous structures and surface hydrophilicity, they still face many limitations in practical applications. These materials generally suffer from limited surface charge density, insufficient ion selectivity, and inadequate coupling between ion channels and electronic conduction networks, resulting in limited ion migration efficiency and charge separation efficiency, thus restricting the steady-state current and power output of the device. Particularly in advanced applications that seek to convert light energy into heat energy to drive fluid flow and generate potential in synergy, a material system that can integrate fluid management, ion screening, and electronic conduction functions is lacking.

[0003] Covalent organic frameworks (COFs) offer an ideal platform for constructing high-performance hydroelectric power generation materials due to their precisely designable pore sizes, functionalizable pore surfaces, and excellent structural stability. Introducing charged functional groups (such as sulfonates) into the COF framework through molecular design can effectively control the charge density and polarity of the pore surface. However, COFs generally suffer from poor conductivity and light absorption, limiting their potential application as active materials in power generation devices. While combining COFs with nanomaterials possessing both conductivity and light absorption (such as carbon nanotubes and graphene) is an effective approach, achieving uniform, stable, in-situ composites at the nanoscale, and further effectively transferring these nanoscale advantages to construct integrated functional devices with specific macroscopically ordered structures (such as vertically oriented channels) to maximize the synergistic efficiency of ion transport and electron collection, remains a critical technological bottleneck that needs to be overcome.

[0004] Therefore, providing a method that integrates the ordered nanopores of COFs with tunable surface charge, as well as the high conductivity and light absorption of nanomaterials, and constructs an integral aerogel with a biomimetic directional macroscopic structure, has important scientific significance and application value for realizing efficient and stable hydrovoltaic power generation driven by photothermal enhanced evaporation. Summary of the Invention

[0005] In view of this, this application provides a COFs composite aerogel, its preparation method and application, aiming to achieve efficient and stable hydroelectric power generation, which can effectively overcome the defects of the above-mentioned prior art.

[0006] The first aspect of this application provides a method for preparing COFs composite aerogels, comprising the following steps:

[0007] S1. Aminated carbon nanotubes NH2-CNTs, 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde and 4,4'-diaminobiphenyl-3,3'-disulfonic acid were dissolved in a mixed solvent and subjected to a solvothermal reaction. After washing and drying, TB-COF@CNTs composite material was obtained.

[0008] S2. Disperse cellulose nanocrystals (CNC) and chitosan (CS) in deionized water, add the TB-COF@CNTs composite material, stir evenly, and then add a crosslinking agent to obtain a mixed precursor solution;

[0009] S3. The mixed precursor liquid is injected into a mold, solidified by directional freezing, and then freeze-dried to obtain a COFs composite aerogel with vertically oriented layered channels.

[0010] Preferably, in step S1, the temperature of the solvothermal reaction is 120°C and the reaction time is 72 h.

[0011] Preferably, in step S1, the mixed solvent is a mixture of 1,4-dioxane, mesitylene, and an aqueous solution of acetic acid.

[0012] Preferably, in step S2, the mass ratio of the cellulose nanocrystals (CNC), chitosan (CS), and TB-COF@CNTs composite material is 2:1:1.

[0013] Preferably, in step S2, the crosslinking agent is glutaraldehyde.

[0014] Preferably, in step S3, the specific process of directional freezing is as follows: using liquid nitrogen to rapidly cool the bottom of the mold to induce ice crystals to grow in a single direction.

[0015] Preferably, in step S3, the specific conditions for freeze drying are as follows: freeze drying is performed using a refrigerated dryer, and the cold trap temperature of the refrigerated dryer is -50°C, the temperature of the sample is -25.6°C, and the freeze drying time is 3 days.

[0016] Specifically, the preparation method of COFs composite aerogel includes the following steps:

[0017] The method for synthesizing TB-COF includes: weighing 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde and 4,4'-diaminobiphenyl-3,3'-disulfonic acid in a molar ratio of 2:3 into a reaction vessel, and sequentially adding mesitylene, 1,4-dioxane and 6 M acetic acid solution in a volume ratio of 4:1:1, sonicating at 200 W for 10 min, removing air from the reaction vessel through a freeze-pump-thaw cycle, sealing and reacting at 120℃ for 72 h. After the reaction is completed, the product is washed sequentially with N,N-dimethylformamide, dimethyl sulfoxide, deionized water and methanol, and then vacuum dried to obtain TB-COF.

[0018] The method for synthesizing TB-COF@CNTs includes: weighing 40 mg of NH2-CNTs and 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde and 4,4'-diaminobiphenyl-3,3'-disulfonic acid in a molar ratio of 2:3 into a reaction vessel, and sequentially adding mesitylene, 1,4-dioxane and 6 M acetic acid solution in a volume ratio of 4:1:1, sonicating at 200 W for 10 min, removing air from the reaction vessel by a freeze-pump-thaw cycle, sealing and reacting at 120 °C for 72 h. After the reaction is completed, the product is washed sequentially with N,N-dimethylformamide, dimethyl sulfoxide, deionized water and methanol, and then vacuum dried to obtain TB-COF@CNTs.

[0019] The method for preparing TB-COF@CNTs-Gel includes: weighing CNC, CS and TB-COF@CNTs composite material in a mass ratio of 2:1:1; dispersing CNC and CS in ultrapure water and stirring until completely dissolved to obtain a homogeneous solution; then adding acetic acid to the solution and stirring until homogeneous; then adding TB-COF@CNTs composite material and dispersing by ultrasonication to obtain a homogeneous mixed dispersion; finally, adding glutaraldehyde solution dropwise to the mixed dispersion under continuous stirring to initiate a crosslinking reaction; injecting the obtained crosslinked mixed precursor liquid into a mold and placing the bottom of the mold in liquid nitrogen for unidirectional freezing until completely solidified; transferring the solidified sample to a freeze dryer and freeze-drying it (using a model SJIA-10N-60A freeze dryer with a cold trap temperature of -50℃ and a sample temperature of -25.6℃; freeze-drying time of 3 days) to obtain TB-COF@CNTs-Gel aerogel with vertically oriented layered channels.

[0020] A second aspect of this application also provides a COFs composite aerogel, which is prepared by the above method.

[0021] The third aspect of this application also provides the application of the aforementioned COFs composite aerogel in hydrovoltaic power generation.

[0022] First, anionic COF (TB-COF) was synthesized on the surface of aminated carbon nanotubes (NH2-CNTs) using an in-situ covalent growth method to obtain TB-COF@CNTs composite material. Subsequently, this composite material was uniformly dispersed in an aqueous matrix of cellulose nanocrystals (CNC) and chitosan (CS), and after crosslinking and directional freeze-drying, TB-COF@CNTs-Gel aerogel was constructed, which is a hydrovoltaic power generation material.

[0023] The fourth aspect of this application also provides a water-based photovoltaic power generation device, including the aforementioned COFs composite aerogel and two conductive electrodes respectively attached to the upper and lower surfaces of the COFs composite aerogel. The conductive electrodes are copper sheets, and multiple water-based photovoltaic power generation devices are connected in series or in parallel via wires.

[0024] Compared with the prior art, this application has the following advantages:

[0025] 1. This application creatively combines TB-COF, which has ordered nanopores and tunable surface charge, with CNT, which has both high conductivity and high photothermal conversion efficiency, in situ at the nanoscale to prepare TB-COF@CNTs core-shell structured materials. This design enables the material to simultaneously possess excellent ion-selective transport capabilities and efficient electron collection and photothermal driving capabilities.

[0026] 2. This application utilizes ice-template-guided directional freezing technology to successfully construct a monolithic TB-COF@CNTs-Gel aerogel with vertically arranged, low-torsivity layered channels, featuring a biomimetic coniferous tree structure, by combining the aforementioned nanocomposite material (TB-COF@CNTs) with a biomass matrix (CNC / CS). This macroscopic structure significantly reduces fluid transport resistance, providing a rapid and directional transport path for evaporation-driven water flow and ions.

[0027] 3. TB-COF@CNTs-Gel achieves efficient coupling and conversion of multiple fields: light, heat, flow, and electricity. CNTs convert absorbed light energy into heat energy, enhancing top evaporation to drive water flow. Ions in the flowing water are selectively screened in the vertical charged channels of TB-COF@CNTs-Gel, generating a flow potential. Simultaneously, the pervasive CNT network rapidly collects and removes charge. This integrated strategy effectively alleviates the problems of mutual constraints between fluid management, ion screening, and electron conduction processes in traditional hydroelectric power generation.

[0028] 4. The hydrovoltaic device constructed based on the COFs composite aerogel of this application exhibits good electrical output performance (up to 1.0 kW m³ / s). -2(A steady-state voltage exceeding 103.6 mV and a steady-state current output of 14.2 μA were achieved under illumination using a 3.5 wt% NaCl solution). The device features modular expansion capabilities, allowing for flexible adjustment of the output voltage or current through series or parallel connection, providing convenience for practical applications.

[0029] 5. This multi-level structural design achieves cross-scale synergistic optimization of nanoscale ion screening and macroscale fluid transport and electron collection, significantly enhancing the charge separation efficiency at the evaporation interface under photothermal drive. The aerogel prepared in this application exhibits excellent steady-state electrical output performance in brine, providing a new approach for developing efficient, modular distributed hydrovoltaic energy systems. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in this application or the prior art, the drawings used in the description of this application or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0031] Figure 1 The image shows a transmission electron microscope (TEM) image of the TB-COF@CNTs composite material prepared in Example 1.

[0032] Figure 2 This is a cross-sectional scanning electron microscope (SEM) image of the TB-COF@CNTs-Gel aerogel prepared in Example 2;

[0033] Figure 3 This is a cross-sectional SEM image of the TB-COF@CNTs-Gel aerogel prepared in Example 2;

[0034] Figure 4 This is a comparison chart of the electrical output performance (voltage) of the oriented structure and the isotropic structure TB-COF@CNTs-Gel in deionized water in Example 2;

[0035] Figure 5 This is a comparison chart of the electrical output performance (current) of the oriented structure and the isotropic structure TB-COF@CNTs-Gel in deionized water in Example 2;

[0036] Figure 6 The directional structure TB-COF@CNTs-Gel in Example 2 at 1.0 kW m -2 Electrical output performance (voltage) under light and in 3.5 wt% NaCl solution;

[0037] Figure 7The directional structure TB-COF@CNTs-Gel in Example 2 at 1.0 kW m -2 Electroelectric output performance (current) under light and in 3.5 wt% NaCl solution;

[0038] Figure 8 The diagram shows the electrical output performance (voltage) of multiple TB-COF@CNTs-Gel power generation units connected in series in Example 2.

[0039] Figure 9 The diagram shows the electrical output performance (current) of multiple TB-COF@CNTs-Gel power generation units connected in parallel in Example 2. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0041] Unless otherwise specified, the experimental methods used in the embodiments of this application are all conventional methods.

[0042] In the following examples, unless otherwise specified, all raw materials can be obtained by commercial purchase or conventional methods.

[0043] Example 1: Preparation of TB-COF and TB-COF@CNTs

[0044] Step 1: Weigh 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde and 4,4'-diaminobiphenyl-3,3'-disulfonic acid in a molar ratio of 2:3 into a reaction vessel, and add mesitylene, 1,4-dioxane and 6 M acetic acid solution in a volume ratio of 4:1:1 in sequence. Sonicate at 200 W for 10 min, remove air from the reaction vessel by a freeze-pump-thaw cycle, seal and react at 120℃ for 72 h. After the reaction is completed, wash the product with N,N-dimethylformamide, dimethyl sulfoxide, deionized water and methanol in sequence, and then dry under vacuum to obtain TB-COF.

[0045] Step 2: Weigh 40 mg of NH2-CNTs and 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde and 4,4'-diaminobiphenyl-3,3'-disulfonic acid in a molar ratio of 2:3 into a reaction vessel. Then, add mesitylene, 1,4-dioxane and 6 M acetic acid solution in a volume ratio of 4:1:1 sequentially. Sonicate at 200 W for 10 min. Remove air from the reaction vessel by a freeze-pump-thaw cycle. After sealing, react at 120℃ for 72 h. After the reaction is complete, wash the product sequentially with N,N-dimethylformamide, dimethyl sulfoxide, deionized water and methanol, and then vacuum dry to obtain TB-COF@CNTs.

[0046] Example 2: Preparation of TB-COF@CNTs-Gel

[0047] CNC, CS, and TB-COF@CNTs composite materials were weighed in a mass ratio of 2:1:1. CNC and CS were dispersed in ultrapure water and stirred until completely dissolved to obtain a homogeneous solution. Acetic acid was then added to this solution, and after stirring until homogeneous, the TB-COF@CNTs composite material was added and ultrasonically dispersed to obtain a homogeneous mixed dispersion. Finally, glutaraldehyde solution was added dropwise to the mixed dispersion under continuous stirring to initiate a crosslinking reaction. The resulting crosslinked precursor solution was injected into a mold, and the bottom of the mold was placed in liquid nitrogen for unidirectional freezing until complete solidification. The solidified sample was transferred to a freeze dryer and freeze-dried (using a model SJIA-10N-60A freeze dryer with a cold trap temperature of -50°C and a sample temperature of -25.6°C; freeze-drying time was 3 days) to obtain TB-COF@CNTs-Gel aerogel with vertically oriented layered channels.

[0048] Figure 1 The image shows a TEM image of the TB-COF@CNTs composite material prepared in Example 1. Figure 1 The results show that TB-COF was successfully coated onto the surface of CNTs (the material was originally aminated carbon nanotubes (NH2-CNTs), but during the preparation of TB-COF@CNTs, the amino groups were chemically reacted and consumed. Therefore, the reacted carbon nanotubes are essentially free of amino groups and can be directly referred to as carbon nanotubes (CNTs)).

[0049] Figure 2-3 The image shows a cross-sectional SEM image of the TB-COF@CNTs-Gel aerogel prepared in Example 2. The aerogel has vertical channels with a biomimetic coniferous tree structure. The TB-COF@CNTs composite is mainly distributed on the pore walls and does not block the channels.

[0050] Example 3: Hydroelectric Power Generation Performance Test

[0051] Device assembly: Two copper electrode sheets, serving as the first and second electrodes respectively, are tightly and stably attached to the upper and lower surfaces of the TB-COF@CNTs-Gel aerogel to assemble the TB-COF@CNTs-Gel aerogel hydrovoltaic power generation device.

[0052] Performance testing: The assembled hydroelectric generator was vertically fixed, with its lower end submerged in a container filled with an electrolyte solution (such as deionized water or 3.5 wt% NaCl solution), while the upper end was exposed to air or specific light conditions (such as 1.0 kW m²). -2 Under simulated sunlight conditions, the steady-state output voltage and current between the first and second electrodes were measured using an electrochemical workstation.

[0053] Figure 4-5 This is a comparison of the electrical output performance (voltage / current) of the directional and isotropic TB-COF@CNTs-Gel structures in deionized water in Example 2. In deionized water, the directional TB-COF@CNTs-Gel (Directional-TB-COF@CNTs-Gel, 46.1 mV / 5.7 μA) exhibits excellent stable output voltage and current, significantly outperforming the isotropic comparison sample (Isotropic-TB-COF@CNTs-Gel, 34.9 mV / 2.9 μA). This performance difference demonstrates the effectiveness of the ice template strategy in constructing low-torsion charge transport paths.

[0054] Figure 6-7 The directional structure TB-COF@CNTs-Gel in Example 2 at 1.0 kW m -2 Electrooutput performance (voltage / current) under light and in 3.5 wt% NaCl solution. (From...) Figure 6-7 As shown, TB-COF@CNTs-Gel at 1.0 kW m -2 The material exhibits excellent and stable output voltage (103.6 mV) and current (14.2 μA) under both light intensity and 3.5 wt% NaCl solution conditions. This performance enhancement is mainly due to two factors: first, the material's efficient photothermal conversion capability accelerates bulk water evaporation, thereby significantly enhancing the water flow through the nanochannels; second, the salt solution provides ample ions. Driven by this enhanced water flow, more ions are transported through the charged nanochannels, and the increased ionic strength of the solution also increases the surface charge density. Both factors jointly enhance the ion dragging effect, thereby improving the electrical output.

[0055] Figure 8-9In Example 2, multiple TB-COF@CNTs-Gel power generation units are connected in series ( Figure 8 ) and parallel ( Figure 9 The electrical output performance (voltage / current) diagram when connected. (From...) Figure 8-9 As shown, when multiple units are connected in a modular fashion: in the series structure, the voltage increases linearly from approximately 103.6 mV for one unit to 340.1 mV for four units; while in the parallel structure, the current reaches 53.8 μA. These results fully demonstrate the reliable scalability and broad application prospects of TB-COF@CNTs-Gel in large-scale energy harvesting applications.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing a COFs composite aerogel, characterized in that, Includes the following steps: S1. Aminated carbon nanotubes NH2-CNTs, 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde and 4,4'-diaminobiphenyl-3,3'-disulfonic acid were dissolved in a mixed solvent and subjected to a solvothermal reaction. After washing and drying, TB-COF@CNTs composite material was obtained. S2. Disperse cellulose nanocrystals (CNC) and chitosan (CS) in deionized water, add the TB-COF@CNTs composite material, stir evenly, and then add a crosslinking agent to obtain a mixed precursor solution; S3. The mixed precursor liquid is injected into a mold, solidified by directional freezing, and then freeze-dried to obtain a COFs composite aerogel with vertically oriented layered channels.

2. The method for preparing COFs composite aerogel according to claim 1, characterized in that, In step S1, the temperature of the solvothermal reaction is 120°C and the reaction time is 72 h.

3. The method for preparing COFs composite aerogel according to claim 1, characterized in that, In step S1, the mixed solvent is a mixture of 1,4-dioxane, mesitylene, and an aqueous solution of acetic acid.

4. The method for preparing COFs composite aerogel according to claim 1, characterized in that, In step S2, the mass ratio of the cellulose nanocrystals (CNC), chitosan (CS), and TB-COF@CNTs composite material is 2:1:

1.

5. The method for preparing COFs composite aerogel according to claim 1, characterized in that, In step S2, the crosslinking agent is glutaraldehyde.

6. The method for preparing COFs composite aerogel according to claim 1, characterized in that, In step S3, the specific process of directional freezing is as follows: liquid nitrogen is used to rapidly cool the bottom of the mold, inducing ice crystals to grow in a single direction.

7. The method for preparing COFs composite aerogel according to claim 1, characterized in that, In step S3, the specific conditions for freeze drying are as follows: freeze drying is carried out using a refrigerated dryer, and the cold trap temperature of the refrigerated dryer is -50℃, the temperature of the sample is -25.6℃, and the freeze drying time is 3 days.

8. A COFs composite aerogel, characterized in that, COFs composite aerogels prepared by the method according to any one of claims 1 to 7.

9. The application of the COFs composite aerogel according to claim 8 in hydrovolt power generation.

10. A hydroelectric power generation device, characterized in that, It includes the COFs composite aerogel as described in claim 8 and two conductive electrodes respectively attached to the upper and lower surfaces of the COFs composite aerogel, wherein the conductive electrodes are copper sheets, and multiple of the water-volt power generation devices are connected in series or in parallel through wires.

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