Double-network synergistically enhanced composite aerogel and preparation method thereof
By constructing a TOCNF/CS dual-network aerogel and growing UiO-66-NH2 nanoparticles in situ within the pores, the problems of insufficient adsorption efficiency and poor structural stability of the TOCNF system were solved, achieving high mechanical resilience and long-term stability, making it suitable for complex environments such as wastewater treatment.
Patent Information
- Application Number
- CN202511112645.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-09
- Publication Date
- 2025-10-31
AI Technical Summary
In practical applications, the TOCNF system has insufficient adsorption efficiency and poor structural stability. MOF materials are prone to agglomeration and destruction of porous structure during the composite process, which leads to a decline in the performance of traditional adsorption materials in complex environments.
By constructing a TOCNF/CS dual-network aerogel matrix and growing UiO-66-NH2 nanoparticles in situ within the pores, a three-dimensional interpenetrating network structure is formed, which enhances mechanical strength and stability through electrostatic attraction and hydrogen bonding.
It significantly improves the mechanical resilience and structural durability of the material, enhances its stability and adsorption performance in humid environments, and expands its application scenarios.
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Figure CN120865610A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of polymer composite materials technology, specifically relating to a composite aerogel material based on TOCNF / CS dual-network synergistic reinforcement and its preparation method. Background Technology
[0002] In recent years, with the increasing demand for environmental protection and sustainable resource utilization, cellulose nanofiber (CNF), as a green and biodegradable new material, has gradually attracted widespread attention from academia and industry. In particular, cellulose nanofiber (TOCNF) prepared by the TEMPO oxidation method, due to the selective oxidation of its surface hydroxyl groups to carboxyl groups, significantly enhances the colloidal stability and surface reactivity of the material, making it a high-performance adsorbent material widely used in environmental treatment and other fields.
[0003] However, the single TOCNF system still faces certain challenges in practical applications. First, although TOCNF possesses a certain adsorption capacity, the relatively few active sites on its surface limit its adsorption efficiency, often resulting in insufficient adsorption capacity when treating high concentrations of pollutants. Second, in complex water treatment media, the TOCNF network structure is prone to collapse, leading to poor long-term stability, especially during repeated use. Structural changes cause a decline in adsorption performance because the high-density carboxyl groups on the TOCNF surface ionize upon contact with water, disrupting the inter-fiber hydrogen bond network and causing the gel skeleton to lose its mechanical integrity. Green Chemistry 2011,13(4): 807–814, DOI:10.1039 / C0GC00771J), thus failing to form a stable aerogel. Therefore, how to further improve the adsorption performance and stability of TOCNF through functional modification or composite structure design has become a current research hotspot.
[0004] Metal-organic frameworks (MOFs) are considered ideal adsorption-enhancing components due to their designable pore structures and high specific surface area. However, their nanoscale characteristics present two major challenges in practical applications: first, powdered MOFs are prone to agglomeration, posing a risk of secondary pollution during recycling; second, traditional loading processes easily damage the porous support structure, reducing the accessibility of active sites. In-situ growth strategies can improve MOF dispersibility and strengthen support binding strength. Zr-MOF materials, represented by UiO-66, have become preferred for composite system design due to their excellent hydrothermal stability and tunable pore size distribution. UiO-66-NH2, prepared through amino functionalization modification, further enriches the surface chemical functional groups, providing an active interface for hierarchical structure design.
[0005] Therefore, this invention proposes a composite aerogel, which uses TOCNF and chitosan (CS) to construct a dual-network aerogel matrix. Utilizing the electrostatic attraction and hydrogen bonding between the amino groups in the CS molecular chain and the carboxyl groups on the TOCNF surface, a three-dimensional interpenetrating network structure is formed, significantly improving the material's mechanical strength. Furthermore, amino-functionalized UiO-66-NH2 particles are uniformly loaded into the aerogel channels via in-situ growth, resulting in a TOCNF / CS@UiO-66-NH2 composite aerogel system with excellent mechanical resilience and durability. This multi-level structure not only maintains the material's high porosity but also significantly enhances its mechanical resilience and cycling stability through component synergistic effects, providing a new approach for developing high-performance porous composite materials. Summary of the Invention
[0006] This invention addresses the shortcomings and improvement needs of existing technologies by proposing a dual-network synergistic reinforced composite aerogel with excellent mechanical resilience and structural durability, along with its preparation method. It utilizes the electrostatic attraction and hydrogen bonding between the amino groups in the CS molecular chain and the carboxyl groups on the TOCNF surface to form a three-dimensional interpenetrating network structure. Simultaneously, an in-situ growth method is employed to uniformly load amino-functionalized MOF particles (UiO-66-NH2) within the aerogel's pores. This results in a TOCNF / CS@UiO-66-NH2 composite aerogel possessing excellent hydrophilicity, high mechanical strength, and wet-state resilience. Furthermore, the coupling effect between its dual-network structure and the MOF matrix interface synergistically ensures the long-term structural stability of the material in air and water environments, improving the plastic deformation and structural stability degradation problems that traditional adsorbent materials easily encounter under complex conditions. This provides a new option for solving the problem of insufficient material durability in humid environments.
[0007] To achieve the above objectives, the present invention adopts the following technical solution: A dual-network synergistic reinforced composite aerogel exhibiting both mechanical resilience and structural durability is developed. It is constructed by first modifying TEMPO oxidized cellulose with polyethyleneimine, and then utilizing the intermolecular hydrogen bonds and electrostatic interactions between the modified cellulose and chitosan to create a structurally stable TOCNF / CS dual-network aerogel substrate in air, oil, and water environments. UiO-66-NH2 nanoparticles are then grown in situ on this substrate, followed by thorough cleaning and freeze-drying to form the TOCNF / CS@UiO-66-NH2 composite aerogel. This dual-network system significantly enhances the material's compressive resilience and fatigue resistance in humid environments through the synergistic effect between its components, enabling it to maintain stable deformation recovery under complex wet conditions and providing a highly durable basic material for various applications.
[0008] The preparation method of the dual-network synergistic reinforced composite aerogel specifically includes the following steps: S1: TEMPO oxidized cellulose nanoparticle (TOCNF) dispersion was mixed with polyethyleneimine (PEI) aqueous solution, and then chitosan (CS) acetic acid solution was added. The mixture was homogenized at room temperature to form a mixed system. S2: Add polyvinyl alcohol (PVA) to the mixture obtained in step S1, perform thermal crosslinking treatment, cool to room temperature, add citric acid (CCA) as a crosslinking agent, stir evenly, pour into a mold, freeze dry to obtain TOCNF / CS aerogel, and soak and clean it. S3: Immerse the TOCNF / CS aerogel washed in step S2 in an environment containing Zr. 4+ UiO-66-NH2 nanoparticles were grown in situ on an N,N-dimethylformamide (DMF) solution containing ions and 2-aminoterephthalic acid (BDC-NH2) was added. S4: The product from step S3 was soaked, washed, and freeze-dried to obtain TOCNF / CS@UiO-66-NH2 composite aerogel.
[0009] Furthermore, the mass concentration of the TEMPO-oxidized nanocellulose dispersion in step S1 is 1.2 wt.%.
[0010] Further, the mass concentration of the polyethyleneimine aqueous solution in step S1 is 5.8-6.2 wt.%.
[0011] Further, the mass concentration of the chitosan acetate solution in step S1 is 1.8-2.2 wt.%.
[0012] Further, the volume ratio of the TEMPO oxidized nanocellulose dispersion, the polyethyleneimine aqueous solution, and the chitosan acetate solution used in step S1 is (1.8-2.2):(0.9-1.1):(0.9-1.1).
[0013] Furthermore, the homogenization process in step S1 takes 1 hour and rotates at a speed of 500 r / min.
[0014] Furthermore, the amount of polyvinyl alcohol added in step S2 is 0.80-1.25 mg·mL. -1 .
[0015] Furthermore, the temperature of the thermal crosslinking treatment in step S2 is 95 °C and the time is 2 h.
[0016] Furthermore, the amount of citric acid added in step S2 is 0.57-0.97 mg·mL. -1 .
[0017] Further, in step S3, 60-75 mg of TOCNF / CS aerogel is soaked in 8-12 mL of N,N-dimethylformamide solution containing 22.3-24.3 mg ZrCl4 for 1 h, so that Zr... 4+ After complete coordination, 25.2-27.2 mg of 2-aminoterephthalic acid was added, and the mixture was soaked at room temperature for 2 h before being transferred to a reaction vessel and reacted solvothermically at 120 °C for 24 h.
[0018] Furthermore, the freeze-drying described in steps S2 and S4 involves evacuating to below 10 Pa at -75 °C and maintaining this state for 24 h.
[0019] Furthermore, the soaking and cleaning described in steps S2 and S4 involves ultrasonic soaking in water for at least 4 hours, with the water changed every 30 minutes.
[0020] This invention innovatively modifies TOCNF using PEI, utilizing the electrostatic interaction between TOCNF's surface carboxyl groups and PEI amine groups, as well as the confinement effect of nanofibers, to construct a hydrogen-bonded-electrostatic synergistic dual-network structure with chitosan (CS). This achieves excellent stability of the fully bio-based aerogel in air and water (wet compression recovery rate >90%). Subsequently, UiO-66-NH2 is grown in situ on the substrate surface, and its porous structure and active groups are used to successfully anchor MOF nanoparticles, ensuring uniform dispersion of MOF particles. This method overcomes the technical bottlenecks of single-function and poor wet performance of natural-based aerogels, endowing them with excellent mechanical toughness, environmental friendliness, and adsorption-catalysis multifunctionality, providing a new material for wastewater, waste oil, or waste gas treatment.
[0021] Compared with the prior art, the technical solution of the present invention has the following advantages: (1) This invention constructs a TOCNF / CS dual-network interpenetrating structure and grows UiO-66-NH2 particles in situ within the aerogel channels to prepare a composite aerogel material with mechanical resilience and structural durability. Specifically, TOCNF is first used as a rigid framework, and a stable dual-network matrix is formed through the triple synergistic effect of electrostatic attraction, hydrogen bonding, and coordination bonds between its surface carboxyl groups and the amino groups of chitosan (CS) molecular chains. Then, UiO-66-NH2 is generated in situ within the channels via a solvothermal method, which can utilize the nano-confined coupling effect between its rigid framework and the polymer network. The resulting material maintains a high stress retention rate after 50 compression cycles at 50% strain; it can maintain structural integrity in air, oil, and water environments, breaking through the structural collapse bottleneck of traditional aerogels under dynamic wet conditions and expanding its application scenarios.
[0022] (2) The synergistic mechanism of the dual network structure and MOF in situ composite described in this invention plays a positive role in performance improvement: the TOCNF fiber skeleton provides elastic recovery force, the CS / PVA crosslinking network dissipates energy through molecular chain slip, and the uniformly distributed UiO-66-NH2 particles inhibit pore collapse through interface coupling effect. The synergistic effect of the three enables the material to maintain structural rigidity in a humid environment.
[0023] (3) Compared with the prior art, the technical solution of in-situ coordination growth of MOF in aerogel channels of the present invention effectively improves the problem of easy aggregation and deactivation of MOF in traditional processes, and provides a new type of high-performance material for wet environment applications such as sewage treatment and intelligent sensing. Attached Figure Description
[0024] Figure 1 Optical photographs of the TOCNF / CS@UiO-66-NH2 composite aerogel prepared in Example 5 (a); optical photographs of the TOCNF / CS@UiO-66-NH2 composite aerogel at 50% compressive strain (b); and optical photographs of the TOCNF / CS@UiO-66-NH2 composite aerogel after 50% compression release (c).
[0025] Figure 2 The images show scanning electron microscope (SEM) images of the upper and lower surfaces (a, b) of the TOCNF / CS@UiO-66-NH2 composite aerogel prepared in Example 5, and the fracture surfaces (d) after being quenched in liquid nitrogen and then exposed to air (c) and after being soaked and squeezed in water.
[0026] Figure 3 XRD comparison diagrams (a) of TOCNF / CS aerogel prepared in Example 2, TOCNF / CS@UiO-66-NH2 composite aerogel prepared in Example 5, and UiO-66-NH2 synthesized separately by the solvothermal method described in Example 5, and XRD comparison diagrams (b) of TOCNF / CS@UiO-66-NH2 composite aerogel after immersion and extrusion in air and water.
[0027] Figure 4 FTIR comparison images of TOCNF / CS aerogel prepared in Example 2, TOCNF / CS@UiO-66-NH2 composite aerogel prepared in Example 5, and UiO-66-NH2 synthesized alone by the solvothermal method described in Example 5.
[0028] Figure 5 The N2 isothermal adsorption curves of the TOCNF / CS aerogel prepared in Example 2, the TOCNF / CS@UiO-66-NH2 composite aerogel prepared in Example 5, and the UiO-66-NH2 synthesized separately by the solvothermal method described in Example 5.
[0029] Figure 6 Pore size distribution diagrams of the TOCNF / CS aerogel prepared in Example 2, the TOCNF / CS@UiO-66-NH2 composite aerogel prepared in Example 5, and the UiO-66-NH2 synthesized alone by the solvothermal method described in Example 5.
[0030] Figure 7 The stress-strain diagrams (a, c) of the TOCNF / CS aerogel prepared in Example 2 and the TOCNF / CS@UiO-66-NH2 composite aerogel prepared in Example 5 after 50 compression cycles at 50% deformation, and the stress-strain diagrams (b, d) of the TOCNF / CS aerogel prepared in Example 2 and the TOCNF / CS@UiO-66-NH2 composite aerogel prepared in Example 5, and the TOCNF / CS@UiO-66-NH2 composite aerogel prepared in Example 5 under different compressive strains (10%, 30%, 50%, 70% and 90%).
[0031] Figure 8 Photographs of the TOCNF / CS@UiO-66-NH2 composite aerogel (a) prepared for Example 5 and the BC / CS@UiO-66-NH2 composite aerogel (b) prepared for the comparative example after 3 cycles under 50% compressive strain. Detailed Implementation
[0032] A dual-network synergistic reinforced composite aerogel is prepared by the following steps: S1: A TEMPO oxidized nanocellulose (TOCNF) dispersion with a mass concentration of 1.2 wt.%, a polyethyleneimine (PEI) aqueous solution with a mass concentration of 5.8-6.2 wt.%, and a chitosan (CS) acetic acid solution with a mass concentration of 1.8-2.2 wt.% were mixed at a volume ratio of (1.8-2.2):(0.9-1.1):(0.9-1.1) and homogenized at room temperature and 500 r / min for 1 h to form a mixed system; S2: 0.80-1.25 mg·mL -1 Polyvinyl alcohol (PVA) was added to the mixture obtained in step S1, and after thermal crosslinking treatment at 95 °C for 2 h, it was cooled to room temperature, and then added at a rate of 0.57-0.97 mg·mL⁻¹. -1 Add the amount of crosslinking agent citric acid (CCA), stir evenly, pour into a mold, vacuum at -75 ℃ to below 10 Pa and dry for 24 h to obtain TOCNF / CS aerogel, then put it in water and ultrasonically soak for at least 4 h (change the water every 30 min) for cleaning. S3: Soak 60-75 mg of TOCNF / CS aerogel washed in step S2 in 8-12 mL of N,N-dimethylformamide solution containing 22.3-24.3 mg ZrCl4 for 1 h, then add 25.2-27.2 mg of 2-aminoterephthalic acid, soak at room temperature for 2 h, then transfer to a reaction vessel and solvothermal reaction at 120 ℃ for 24 h to grow UiO-66-NH2 nanoparticles in situ on it; S4: Place the product obtained in step S3 into water and ultrasonically soak it for at least 4 hours (changing the water every 30 minutes) to clean it, thus obtaining TOCNF / CS@UiO-66-NH2 composite aerogel.
[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other. The invention will be further described in detail below with reference to specific embodiments.
[0034] In the performance tests of the examples, the specific surface area was determined using the N2 isothermal adsorption-desorption method (BET method).
[0035] The wet compression rebound rate is determined by completely immersing the aerogel in water to ensure thorough wetting, then compressing the sample at a constant rate (10 mm / min) to 50% strain (i.e., the height becomes 50% of the original height) using a mechanical testing machine. After removing the pressure, the height of the sample when it returns to equilibrium is recorded, and then calculated using the following formula: Rebound rate (%) = (H1 / H0) × 100% Where H0 is the initial height of the sample, and H1 is the height recovered after the sample is depressurized.
[0036] The method for determining the stress retention rate after 50 cycles involves immersing the aerogel in water until completely wetted, then compressing the sample at a constant rate (10 mm / min) to 50% strain using a mechanical testing machine, followed by unloading to zero stress. This process is repeated 50 times, with stress-strain data recorded continuously for each cycle. The stress-strain ratio is then calculated using the following formula: Retention rate (%) = Maximum stress in the 50th cycle / Maximum stress in the 1st cycle × 100%.
[0037] Example 1 The following describes the preparation method of TOCNF / CS aerogel as an example. The preparation method includes the following steps: 1) Preparation of the mixture: Take 1.8 mL of TOCNF dispersion with a mass concentration of 1.2 wt.% and mix it with 0.9 mL of PEI aqueous solution with a mass concentration of 5.8 wt.%, then slowly add 0.9 mL of CS acetic acid solution with a mass concentration of 1.8 wt.%, and homogenize it at room temperature and 500 r / min for 1 h to form a mixed system; 2) Preparation of TOCNF / CS composite aerogel: Add 3.5 mg PVA to the mixture obtained in step 1), heat and stir at 95℃ for 2 h, cool to room temperature, add 2.5 mg CCA, stir evenly, pour into a silicone mold, pre-freeze in a -20℃ refrigerator for 4 h, then vacuum at -75℃ to below 10 Pa and maintain for 24 h to obtain TOCNF / CS aerogel. Then place it in water and ultrasonically soak for at least 4 h (change the water every 30 min) for cleaning.
[0038] Example 2 The following describes the preparation method of TOCNF / CS aerogel as an example. The preparation method includes the following steps: 1) Preparation of the mixture: Take 2 mL of TOCNF dispersion with a mass concentration of 1.2 wt.% and mix it with 1 mL of PEI aqueous solution with a mass concentration of 6 wt.%, then slowly add 1 mL of CS acetic acid solution with a mass concentration of 2 wt.%, and homogenize it at room temperature and 500 r / min for 1 h to form a mixed system; 2) Preparation of TOCNF / CS composite aerogel: Add 4 mg PVA to the mixture obtained in step 1), heat and stir at 95 °C for 2 h, cool to room temperature, add 3 mg CCA, stir evenly, pour into a silicone mold, pre-freeze in a -20 °C refrigerator for 4 h, then vacuum at -75 °C to below 10 Pa and maintain for 24 h to obtain TOCNF / CS aerogel. Then place it in water and ultrasonically soak for at least 4 h (change the water every 30 min) for cleaning.
[0039] Example 3 The following describes the preparation method of TOCNF / CS aerogel as an example. The preparation method includes the following steps: 1) Preparation of the mixture: Take 2.2 mL of TOCNF dispersion with a mass concentration of 1.2 wt.% and mix it with 1.1 mL of PEI aqueous solution with a mass concentration of 6.2 wt.%, then slowly add 1.1 mL of CS acetic acid solution with a mass concentration of 2.2 wt.%, and homogenize it at room temperature and 500 r / min for 1 h to form a mixed system; 2) Preparation of TOCNF / CS composite aerogel: Add 4.5 mg PVA to the mixture obtained in step 1), heat and stir at 95℃ for 2 h, cool to room temperature, add 3.5 mg CCA, stir evenly, pour into a silicone mold, pre-freeze in a -20℃ refrigerator for 4 h, then vacuum at -75℃ to below 10 Pa and maintain for 24 h to obtain TOCNF / CS aerogel. Then place it in water and ultrasonically soak for at least 4 h (change the water every 30 min) for cleaning.
[0040] Example 4 Based on the TOCNF / CS aerogel prepared in Example 1, UiO-66-NH2 was further synthesized in situ through coordination, ultimately forming a dual-network synergistic reinforced composite aerogel TOCNF / CS@UiO-66-NH2 with both mechanical resilience and structural durability. The preparation method includes the following steps: 60 mg of the TOCNF / CS aerogel prepared in Example 1 was soaked in 8 mL of DMF solution containing 22.3 mg ZrCl4 for 1 h to allow Zr to mature. 4+ After thorough coordination, 25.2 mg of BDC-NH2 was added, and the mixture was soaked at room temperature for 2 h before being transferred to a reaction vessel and reacted at 120 ℃ for 24 h. The resulting aerogel was then placed in water and ultrasonically soaked for at least 4 h (with water changed every 30 min) for thorough cleaning. It was then pre-frozen in a -20 ℃ freezer for 4 h, and then vacuumed to below 10 Pa at -75 ℃ for 24 h. The resulting TOCNF / CS@UiO-66-NH2 composite aerogel was stored at room temperature for subsequent experimental operations.
[0041] Example 5 Based on the TOCNF / CS aerogel prepared in Example 2, UiO-66-NH2 was further synthesized in situ through coordination, ultimately forming a dual-network synergistic reinforced composite aerogel TOCNF / CS@UiO-66-NH2 with both mechanical resilience and structural durability. The preparation method includes the following steps: 60 mg of the TOCNF / CS aerogel prepared in Example 2 was soaked in 10 mL of DMF solution containing 23.3 mg ZrCl4 for 1 h to allow Zr to mature. 4+After thorough coordination, 26.2 mg of BDC-NH2 was added, and the mixture was soaked at room temperature for 2 h before being transferred to a reaction vessel and reacted at 120 ℃ for 24 h. The resulting aerogel was then placed in water and ultrasonically soaked for at least 4 h (with water changed every 30 min) for thorough cleaning. It was then pre-frozen in a -20 ℃ freezer for 4 h, and then vacuumed to below 10 Pa at -75 ℃ for 24 h. The resulting TOCNF / CS@UiO-66-NH2 composite aerogel was stored at room temperature for subsequent experimental operations.
[0042] Example 6 Based on the TOCNF / CS aerogel prepared in Example 3, UiO-66-NH2 was further synthesized in situ through coordination, ultimately forming a dual-network synergistic reinforced composite aerogel TOCNF / CS@UiO-66-NH2 with both mechanical resilience and structural durability. The preparation method includes the following steps: 60 mg of the TOCNF / CS aerogel prepared in Example 3 was soaked in 12 mL of DMF solution containing 24.3 mg ZrCl4 for 1 h to allow Zr to mature. 4+ After thorough coordination, 27.2 mg of BDC-NH2 was added, and the mixture was soaked at room temperature for 2 h before being transferred to a reaction vessel and reacted at 120 ℃ for 24 h. The resulting aerogel was then placed in water and ultrasonically soaked for at least 4 h (with water changed every 30 min) to ensure thorough cleaning. It was then pre-frozen in a -20 ℃ freezer for 4 h, and then vacuumed to below 10 Pa at -75 ℃ for 24 h. The resulting TOCNF / CS@UiO-66-NH2 composite aerogel was stored at room temperature for subsequent experimental operations.
[0043] Table 1 shows a comparison of the properties of the TOCNF / CS@UiO-66-NH2 composite aerogels obtained in Examples 4-6.
[0044] Table 1. Performance comparison of TOCNF / CS@UiO-66-NH2 composite aerogels prepared in different embodiments
[0045] As shown in Table 1, the composite aerogel prepared in Example 5 is significantly better than that in Examples 4 and 6 in terms of specific surface area, wet compression rebound rate, and cycle stability.
[0046] Morphology and structural characterization of composite aerogels 1. Morphological characterization of TOCNF / CS@UiO-66-NH2 composite aerogel Figure 1Optical photographs of the TOCNF / CS@UiO-66-NH2 composite aerogel prepared in Example 5, and optical photographs before and after 50% compressive strain. As can be seen from the figures, the material exhibits a typical porous structure and can still achieve complete shape recovery after being subjected to 50% compressive strain, demonstrating excellent mechanical resilience and structural durability.
[0047] The TOCNF / CS@UiO-66-NH2 composite aerogel prepared in Example 5 was quenched in liquid nitrogen to obtain a smooth fracture surface. The fracture surface and its upper and lower surfaces were then sputtered with gold, and appropriate areas were selected for morphological characterization. Simultaneously, to clarify the sample's state in water, the quenched sample was thoroughly immersed in deionized water and gently squeezed. The sample was carefully removed, excess water was absorbed with filter paper, and then dried. The fracture surface was then sputtered with gold, and appropriate areas were selected for morphological characterization. The results are shown in [Figure number missing]. Figure 2 .like Figure 2 As shown, the in-situ grown UiO-66-NH2 particles are uniformly distributed on the aerogel surface, with consistent particle size, allowing for the exposure of more active sites (a, b). Meanwhile, the fracture surface of the TOCNF / CS@UiO-66-NH2 aerogel exhibits a sponge-like or honeycomb-like structure, with irregularly interwoven pores on a large scale and denser pores on a small scale. The size, shape, and distribution of the pore structure are random (c), and its morphology does not significantly change after immersion and compression in water (d).
[0048] 2. Structural characterization of TOCNF / CS@UiO-66-NH2 composite aerogel UiO-66-NH2 was synthesized separately using the solvothermal method described in Example 5 (26.2 mg BDC-NH2 was added to 10 mL of DMF solution containing 23.3 mg ZrCl4, soaked at room temperature for 2 hours, and then transferred to a reaction vessel and reacted at 120 °C for 24 h). The synthesized UiO-66-NH2 was then ground into powder. The TOCNF / CS aerogel obtained in Example 2 and the TOCNF / CS@UiO-66-NH2 aerogel obtained in Example 5 were cut into small pieces and flattened, and X-ray diffraction and infrared spectroscopy were performed. The results are shown in the figures below. Figure 3 , 4 .
[0049] like Figure 3As shown, the main characteristic diffraction peaks of the separately synthesized UiO-66-NH2 are at 7.3°, 8.5°, and 25.7°, corresponding to the (111), (200), and (222) crystal planes, respectively, which is consistent with the standard characteristic peaks in the literature. The XRD pattern of the TOCNF / CS aerogel shows a broad peak at 22.3°, which is attributed to the amorphous arrangement of the polymer chains. The characteristic peak of UiO-66-NH2 can still be observed on the XRD pattern of the TOCNF / CS@UiO-66-NH2 composite aerogel, which strongly indicates that UiO-66-NH2 has been successfully loaded onto the TOCNF / CS aerogel (a). At the same time, after the TOCNF / CS@UiO-66-NH2 composite aerogel was pressed in water multiple times (no less than 30 times) to fully exchange the solvent, its XRD pattern did not change significantly compared with that in air, proving that its structure has good stability (b).
[0050] exist Figure 4 In the middle, the TOCNF / CS@UiO-66-NH2 composite aerogel at 3000-3500 cm⁻¹ -1 A broad absorption peak appears at 1636 cm⁻¹, which is presumably related to the stretching and bending vibrations of the -OH and -NH₂ groups in TOCNF and CS, as well as the aromatic amino group of UiO-66-NH₂; -1 and 1560 cm -1 The absorption peak at 1065 cm⁻¹ is caused by the stretching vibrations of the C=O and O=CO groups; -1 The absorption peak appearing at this location corresponds to the COC bond in TOCNF. Furthermore, the 770 cm⁻¹ peak in the TOCNF / CS@UiO-66-NH₂ composite aerogel... -1 (Zr-O bond), 1216 cm -1 (CN key), 1500 cm -1 The characteristic peak of (C=C bond) further confirms the effective loading of UiO-66-NH2.
[0051] 3. Specific surface area of TOCNF / CS@UiO-66-NH2 composite aerogel Take 100 mg each of the TOCNF / CS aerogel prepared in Example 2, the TOCNF / CS@UiO-66-NH2 composite aerogel prepared in Example 5, and UiO-66-NH2 synthesized separately by the solvothermal method described in Example 5, place them in a vacuum drying oven, activate them at 120 °C for 48 hours, and then perform N2 isothermal adsorption-desorption tests. The results are shown in […]. Figure 5 .
[0052] like Figure 5As shown, the specific surface areas of the TOCNF / CS aerogel and the UiO-66-NH2 sample are 3.6299 m². 2 ·g -1 and 284 m 2 ·g -1 The specific surface area of the TOCNF / CS@UiO-66-NH2 composite aerogel grown in situ from UiO-66-NH2 was 151.33 m². 2 ·g -1 This demonstrates that the inherent microporous structure of MOF effectively compensates for the low porosity defect caused by the macroporous dominance of TOCNF / CS aerogel.
[0053] 4. Pore size distribution diagram of TOCNF / CS@UiO-66-NH2 composite aerogel like Figure 6 As shown, the TOCNF / CS aerogel is mainly composed of mesopores and macropores, with no obvious micropores observed. The pore size distribution of UiO-66-NH2 is highly concentrated in the micropore regions of 0.78 nm, 1.17 nm, and 1.35 nm. However, the TOCNF / CS@UiO-66-NH2 composite aerogel exhibits both micropores and mesopores. This is because, on the one hand, the introduction of UiO-66-NH2 increases the proportion of micropores (<2 nm), providing abundant active sites; on the other hand, the macroporous and mesoporous (2-50 nm) structures of the TOCNF / CS substrate are preserved, forming a hierarchical pore network. This synergistic effect allows the composite material to have an adsorption capacity far exceeding that of a single component.
[0054] 5. Stress-strain curves of TOCNF / CS@UiO-66-NH2 composite aerogel like Figure 7As shown, the TOCNF / CS aerogel prepared in Example 2 retained 81.1% of its stress after 50 cycles at 50% compressive strain (a), while the TOCNF / CS@UiO-66-NH2 composite aerogel retained 92.7% of its stress after 50 cycles at 50% compressive strain (c). This indicates that the TOCNF / CS@UiO-66-NH2 composite aerogel has a better resilience. This is because its sponge-like porous structure can effectively transfer compressive stress, achieving a high stress retention rate, thus giving it excellent compressibility and elasticity. Meanwhile, both TOCNF / CS aerogel and TOCNF / CS@UiO-66-NH2 composite aerogel materials exhibit unique strain response characteristics. In the low strain range below 50%, the materials exhibit near-linear elastic behavior. When the strain exceeds 50%, the system undergoes strain hardening (b, d). The strengthening mechanism involves multi-scale synergistic effects, such as the collapse and compression of the macroporous framework into a dense structure, forming a continuous rigid support network that effectively transfers external loads; at the molecular scale, the dense packing of polymer chains multiplies the hydrogen bond density, increasing the compressive strength.
[0055] Comparative Example The TOCNF used in step 1) of Example 2 was replaced with nano-sized bacterial cellulose (BC), and other operations were the same as in Example 2 to prepare BC / CS aerogel. Then, based on this, UiO-66-NH2 was further synthesized in situ according to the steps described in Example 5 to finally form BC / CS@UiO-66-NH2.
[0056] Testing revealed that the wet compression resilience of the obtained BC / CS@UiO-66-NH2 was only 32%; furthermore, it collapsed after three cycles at 50% compressive strain (see...). Figure 8 It is evident that the composite aerogel prepared using BC does not possess good mechanical properties.
[0057] It is understood that the embodiments of the system described above are merely illustrative, and the units described as separate components may or may not be physically separated; they may be located in one place or distributed across different network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any inventive effort.
[0058] Furthermore, those skilled in the art should understand that in the application documents of this invention, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0059] Numerous specific details are set forth in the specification of embodiments of the present invention. However, it should be understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification. Similarly, it should be understood that, in order to streamline the disclosure of embodiments of the present invention and aid in the understanding of one or more of the various inventive aspects, various features of the embodiments of the present invention are sometimes grouped together in a single embodiment, figure, or description thereof in the above description of exemplary embodiments of the present invention. However, this method of disclosure should not be construed as reflecting an intention that the claimed embodiments of the present invention require more features than those expressly recited in each claim. Rather, as reflected in the claims, inventive aspects lie in fewer than all features of a single foregoingly disclosed embodiment. Therefore, the claims following the detailed description are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the present invention.
[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the embodiments of the present invention, and are not intended to limit them. Although the embodiments of the present invention have 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 of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A dual-network synergistic reinforced composite aerogel with mechanical resilience and structural durability, characterized in that: The process involves first modifying TEMPO oxidized cellulose with polyethyleneimine, and then constructing a TOCNF / CS dual-network aerogel substrate by utilizing the intermolecular hydrogen bonds and electrostatic interactions between the modified cellulose and chitosan. UiO-66-NH2 nanoparticles are then grown in situ on the substrate, followed by thorough cleaning and freeze-drying to form a TOCNF / CS@UiO-66-NH2 composite aerogel.
2. A method for preparing the dual-network synergistic reinforced composite aerogel as described in claim 1, characterized in that: Includes the following steps: S1: TEMPO oxidized cellulose nanoparticle dispersion was mixed with polyethyleneimine aqueous solution, and then chitosan acetate solution was added. The mixture was homogenized at room temperature to form a mixed system. S2: Add polyvinyl alcohol to the mixture obtained in step S1, and after thermal cross-linking treatment, add citric acid, stir evenly, pour into a mold, freeze dry to obtain TOCNF / CS aerogel, and soak and clean it. S3: Immerse the TOCNF / CS aerogel washed in step S2 in an environment containing Zr. 4+ In an N,N-dimethylformamide solution containing ions, 2-aminoterephthalic acid was added, and then UiO-66-NH2 nanoparticles were grown in situ on it by a solvothermal method. S4: The product from step S3 was soaked, washed, and freeze-dried to obtain TOCNF / CS@UiO-66-NH2 composite aerogel.
3. The method for preparing the dual-network synergistic reinforced composite aerogel according to claim 2, characterized in that: In step S1, the mass concentration of the TEMPO oxidized nanocellulose dispersion is 1.2 wt.%, the mass concentration of the polyethyleneimine aqueous solution is 5.8-6.2 wt.%, and the mass concentration of the chitosan acetate solution is 1.8-2.2 wt.%; the volume ratio of the three is (1.8-2.2):(0.9-1.1):(0.9-1.1).
4. The method for preparing the dual-network synergistic reinforced composite aerogel according to claim 2, characterized in that: The homogenization process in step S1 takes 1 hour and rotates at a speed of 500 r / min.
5. The method for preparing the dual-network synergistic reinforced composite aerogel according to claim 2, characterized in that: In step S2, the amount of polyvinyl alcohol added is 0.80-1.25 mg·mL. -1 .
6. The method for preparing the dual-network synergistic reinforced composite aerogel according to claim 2, characterized in that: The temperature for the thermal crosslinking treatment in step S2 is 95 °C and the time is 2 h.
7. The method for preparing the dual-network synergistic reinforced composite aerogel according to claim 2, characterized in that: In step S2, the amount of citric acid added is 0.57-0.97 mg·mL. -1 .
8. The method for preparing the dual-network synergistic reinforced composite aerogel according to claim 2, characterized in that: In step S3, 60-75 mg of TOCNF / CS aerogel is soaked in 8-12 mL of N,N-dimethylformamide solution containing 22.3-24.3 mg ZrCl4 for 1 h. Then, 25.2-27.2 mg of 2-aminoterephthalic acid is added, and the mixture is soaked at room temperature for 2 h. Finally, the mixture is transferred to a reaction vessel and solvothermal reacted at 120 °C for 24 h.
9. The method for preparing the dual-network synergistic reinforced composite aerogel according to claim 2, characterized in that: The freeze-drying described in steps S2 and S4 involves evacuating to below 10 Pa at -75 °C and maintaining this state for 24 h.
10. The method for preparing the dual-network synergistic reinforced composite aerogel according to claim 2, characterized in that: The soaking and cleaning described in steps S2 and S4 involves ultrasonic soaking in water for at least 4 hours, with the water changed every 30 minutes.