Heterostructure two-dimensional covalent organic framework diaphragm, preparation method thereof and application of heterostructure two-dimensional covalent organic framework diaphragm in battery

Abstract

The invention belongs to the technical field of aqueous batteries, and particularly relates to a heterostructure two-dimensional covalent organic framework diaphragm, a preparation method thereof and application of the heterostructure two-dimensional covalent organic framework diaphragm in a battery. The diaphragm is formed by self-assembly of a water-phase monomer and an organic-phase monomer through double-activation interface polymerization, the water phase monomers are p-phenylenediamine and 2, 5-diaminobenzene sulfonic acid; the monomer of the organic phase is 1, 3, 5-triformyl phloroglucinol; the molar ratio of the water-phase monomer to the organic-phase monomer is (1-2): 1. According to the invention, a covalent organic framework structure with asymmetric interface orientation is constructed as the diaphragm, so that the two sides of the diaphragm have significant differences in pore orientation, surface morphology and wetting characteristics, directional regulation and control of zinc ion migration behaviors are realized, and the limitation of passive adaptation of a traditional homogeneous diaphragm to ion transmission is broken through; the diaphragm does not need an additional supporting substrate or a composite layer, is high in structural stability, is beneficial to simplifying the structural design of the battery, and improves the overall safety and reliability of the battery.

Description

Technical Field

[0001] This invention belongs to the field of aqueous battery technology, specifically relating to a heterogeneous two-dimensional covalent organic framework separator, its preparation method, and its application in batteries. Background Technology

[0002] With the rapid development of the new energy industry, aqueous zinc anode batteries, which combine high safety, low cost, and environmental friendliness, have become a research hotspot in the field of electrochemical energy storage. However, in practical applications, these batteries still face the challenge of poor stability at the zinc anode interface. This is because during charging and discharging, Zn... 2+ Uneven deposition is prone to occur, inducing zinc dendrite growth, accompanied by side reactions such as hydrogen evolution and corrosion, ultimately leading to battery capacity decay, reduced coulombic efficiency, and even safety hazards such as short circuits.

[0003] As a key component for regulating ion transport, the membrane's structure and performance directly affect the stability of the zinc anode. Currently, commonly used membranes in aqueous zinc batteries, such as glass fiber membranes and polyolefin membranes, generally suffer from the following defects:

[0004] Traditional diaphragm membranes have a wide pore size distribution and irregular pore arrangement, making it impossible to accurately guide Zn. 2+ The directional migration of ions can easily lead to excessively high local current density, exacerbating dendrite growth; the hydrophilic / hydrophobic properties are difficult to match with the electrolyte characteristics, easily forming interface wetting dead zones, further amplifying the non-uniformity of ion transport; existing technologies mostly use strategies such as surface coatings and composite functional layers to improve membrane performance, but there are problems such as complex preparation processes, high costs, and weak interfacial bonding; the functional layers are prone to detachment under long-cycle or high-rate conditions, leading to rapid performance degradation.

[0005] Covalent organic frameworks (COFs) have shown promise in the field of ion-selective transport due to their advantages such as highly ordered structure, precisely designable pore size, and functionalizable framework. However, existing COF-based membranes are mostly symmetrical structures or have a single interface morphology, making it difficult to simultaneously meet the multiple requirements of rapid electrolyte wetting, low ion transport impedance, and stability of the zinc anode interface; existing COF materials also have limitations regarding Zn... 2+ The specific adsorption and directional conduction capabilities are insufficient, making it unable to effectively suppress dendrite formation; under complex electrolyte environments and long-term mechanical stress, COF membranes are prone to structural collapse or performance degradation, making it difficult to meet the requirements of industrial applications. Summary of the Invention

[0006] The purpose of this invention is to provide a heterogeneous two-dimensional covalent organic framework separator, its preparation method, and its application in batteries, thereby overcoming the shortcomings of existing technologies and preparing a self-supporting covalent organic framework separator with an asymmetric interfacial orientation structure. This separator can achieve interfacial functional partitioning within a single membrane, synergistically regulating the transmembrane transport behavior of zinc ions, thereby effectively suppressing zinc dendrite growth and side reactions, and improving the cycle stability and rate performance of aqueous zinc anode batteries.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: In a first aspect, the present invention provides a heterostructured two-dimensional covalent organic framework membrane, wherein the heterostructured two-dimensional covalent organic framework membrane is self-assembled by polymerization of aqueous phase monomers and organic phase monomers through a dual-activation interface; The aqueous monomers include one or more of p-phenylenediamine (Pa), 4,4′-diaminobiphenyl, 2,4,6-triamino-1,3,5-triazine, 4,4'-diamino-[1,1'-biphenyl]-3,3'-disulfonic acid (BD-(SO3H)2), and 2,5-diaminobenzenesulfonic acid (Pa-SO3H); The monomers of the organic phase include one or more of 1,3,5-tricarboxyloylphloroglucinol (Tp), 1,3,5-benzenetricarboxaldehyde, 2,5-dimethoxyterephthalaldehyde (DMDD), 2,5-dihydroxyterephthalaldehyde (OPA), 2,6-pyridinedicarboxaldehyde, 2,4,6-tricarboxy-1,3,5-triazine, and pyrazindicarboxaldehyde.

[0008] The heterostructured two-dimensional covalent organic framework membrane of this invention is constructed through dual-activated interfacial polymerization of aqueous monomers (such as p-phenylenediamine, aminosulfonic acid monomers, triazine derivatives, etc.) and organic monomers (such as pyrogallol, benzaldehyde derivatives, pyridinedicarboxaldehyde, etc.), forming a self-supporting membrane with an asymmetric interfacial orientation. The structural advantages of this membrane are: dual-activated polymerization significantly enhances monomer reactivity, promoting the formation of a highly crystalline, ordered porous structure; the self-supporting characteristic avoids substrate dependence and simplifies the preparation process; the differentiated selection of aqueous and organic monomers (such as hydrophilic / hydrophobic, acidic / basic functional groups) creates a gradient distribution of chemical composition and pore size within the membrane, endowing it with excellent ion-selective sieving ability. This membrane can achieve interfacial functional partitioning within a single membrane, synergistically regulating the transmembrane transport behavior of zinc ions, thereby effectively inhibiting zinc dendrite growth and side reactions, and significantly improving the cycle stability and rate performance of aqueous zinc anode batteries.

[0009] In some other embodiments, the aqueous monomer is p-phenylenediamine or 2,5-diaminobenzenesulfonic acid; The organic phase monomer is 1,3,5-tricarboxymethylphloroglucinol; The molar ratio of the aqueous phase monomer to the organic phase monomer is (1-2):1.

[0010] Specifically, the molar ratio of the aqueous phase monomer to the organic phase monomer is any one or a range of values ​​from 1:1, 1.25:1, 1.5:1, 1.75:1, or 2:1.

[0011] This invention employs p-phenylenediamine or 2,5-diaminobenzenesulfonic acid as the aqueous phase monomer and 1,3,5-triformylphloroglucinol as the organic phase monomer, controlling their molar ratio. This allows for the construction of a hydrophilic interface rich in amino and sulfonic acid groups on the aqueous side and a hydrophobic structure rich in phenolic hydroxyl groups on the organic phase side. This results in a clear chemical gradient and functional partitioning within the membrane, effectively regulating ion transport pathways and improving ion selective sieving efficiency. Simultaneously, through dual-activated interface polymerization and optimized monomer ratios, the membrane is ensured to possess high crystallinity, an ordered porous structure, and stable self-supporting properties, providing a reliable guarantee for the efficient separation of lithium / zinc ions and the optimization of battery performance.

[0012] In some other embodiments, the heterostructured two-dimensional covalent organic framework membrane has a gradient porous structure with a thickness of 30-50 μm, a porosity of 15%-30%, and a pore size distribution range of 1.6-1.9 nm.

[0013] Specifically, a thickness of 30-35 μm is preferred. COF films of this thickness exhibit more significant effects in regulating interfacial ion conduction, which is beneficial for leveraging their interfacial regulation role.

[0014] In a second aspect, the present invention provides a method for preparing the heterostructure two-dimensional covalent organic framework membrane described in the first aspect, comprising the following steps: mixing an aqueous monomer, a catalyst, and an aqueous solvent to form an aqueous solution; mixing an organic monomer and an organic solvent to form an organic solution; adding the organic solution dropwise to the aqueous solution, allowing the reaction to proceed at room temperature, and then washing and drying to obtain the heterostructure two-dimensional covalent organic framework membrane.

[0015] In some other embodiments, the aqueous monomer comprises one or more of p-phenylenediamine (Pa), 4,4′-diaminobiphenyl, 2,4,6-triamino-1,3,5-triazine, 4,4'-diamino-[1,1'-biphenyl]-3,3'-disulfonic acid, and 2,5-diaminobenzenesulfonic acid; The monomers of the organic phase include one or more of 1,3,5-tricarboxyloyl-phloroglucinol, 1,3,5-benzenetricarboxaldehyde, 2,5-dimethoxy-terephthalaldehyde, 2,5-dihydroxy-terephthalaldehyde, 2,6-pyridinedicarboxaldehyde, 2,4,6-tricarboxy-1,3,5-triazine, and pyrazindicarboxaldehyde. Specifically, the aqueous monomer is p-phenylenediamine or 2,5-diaminobenzenesulfonic acid; The organic phase monomer is 1,3,5-tricarboxymethylphloroglucinol; The aqueous solvent is deionized water; the catalyst is one or more of sodium formate or acetonitrile. The organic solvent is one or more of octanoic acid or 1,3,5-trimethylbenzene.

[0016] The study found that the catalysts added during the dual-activated interfacial polymerization reaction have a significant impact on the structure of the product. Among them, sodium formate, with its weak base catalytic properties, can neutralize by-products, lower the reaction energy barrier, promote the reversible reaction in the forward direction, and induce the ordered arrangement of monomers. Acetonitrile, through its polar solvent effect, regulates monomer diffusion and the reaction interface, forming a reaction gradient, and ultimately constructs a bifacial heterostructure in the interfacial polymerization, achieving precise control of pore size and function.

[0017] In some other embodiments, the settling reaction time is 20-50 h; the washing solvent is deionized water and ethanol.

[0018] Specifically, the settling time can be any value or range from 20, 24, 30, 36, 40, 48, or 50 hours. The thickness of the COF membrane can be effectively controlled by adjusting the interfacial reaction time.

[0019] In some other embodiments, the molar ratio of the aqueous phase monomer to the organic phase monomer is 1.5:1; and the settling time is 20-25 h.

[0020] Specifically, the static reaction time is 24 hours. COF membranes of this thickness exhibit a more significant effect in regulating interfacial ion conduction, which is beneficial for exerting their interfacial regulation role.

[0021] Thirdly, the present invention provides the application of the heterostructure two-dimensional covalent organic framework separator described in the first aspect in an aqueous battery, wherein the aqueous battery includes an aqueous zinc battery.

[0022] Fourthly, the present invention provides an aqueous zinc battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the separator is the heterostructure two-dimensional covalent organic framework separator described in the first aspect.

[0023] This heterogeneous two-dimensional covalent organic framework membrane exhibits a distinct bifacial heterostructure. The organic phase side has a relatively smooth and dense surface with no obvious defects. This morphology helps reduce interfacial resistance during ion transport, thus ensuring the continuity and stability of the ion transport path. In contrast, the aqueous phase side displays a relatively loose porous structure with a certain degree of structural toughness. This morphology mainly stems from the diffusion behavior of monomers within the aqueous phase during interfacial polymerization. The loose porous structure provides ample transport channels for the rapid diffusion of ions within the membrane.

[0024] In some other embodiments, the electrolyte is zinc sulfate electrolyte; the negative electrode is zinc metal foil; and the positive electrode is one or more of sodium vanadate, polyaniline, manganese dioxide, ammonium vanadate, and vanadium pentoxide.

[0025] The beneficial effects of this invention are: This invention utilizes a covalent organic framework structure with asymmetrical interface orientation as a separator, resulting in significant differences on both sides of the separator in terms of pore orientation, surface morphology, and wettability. This enables directional control of zinc ion migration behavior, overcoming the limitation of traditional homogeneous separators that passively adapt to ion transport. Furthermore, this separator can be used independently without additional supporting substrates or composite layers, exhibits high structural stability, simplifies battery structure design, and improves the overall safety and reliability of aqueous zinc anode batteries. Attached Figure Description

[0026] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0027] Figure 1 The Fourier transform infrared (FT-IR) spectra and XRD patterns of the TpPa film and the TpPa-SO3H film in the embodiments of the present invention are shown, wherein a is the FT-IR spectrum of the TpPa film, b is the FT-IR spectrum of the TpPa-SO3H film, c is the XRD pattern of the TpPa film, and d is the XRD pattern of the TpPa-SO3H film. Figure 2 The following are illustrations of nitrogen adsorption-desorption isotherms and pore size distribution of TpPa membrane and TpPa-SO3H membrane in the embodiments of the present invention, wherein a is the nitrogen adsorption-desorption isotherm and pore size distribution of TpPa membrane and b is the nitrogen adsorption-desorption isotherm and pore size distribution of TpPa-SO3H membrane. Figure 3These are scanning electron microscope (SEM) images of the TpPa membrane and the TpPa-SO3H membrane in the embodiments of the present invention at a scale bar of 5 μm; a is a scanning electron microscope (SEM) image of the TpPa membrane and b is a scanning electron microscope (SEM) image of the TpPa-SO3H membrane. Figure 4 The images shown are scanning electron microscope (SEM) images of TpPa membranes and TpPa-SO3H membranes prepared at different reaction times in the embodiments of the present invention; a is the SEM image of the TpPa membrane prepared after 48 h of reaction, b is the SEM image of the TpPa membrane prepared after 24 h of reaction, and c is the SEM image of the TpPa-SO3H membrane prepared after 24 h of reaction. Figure 5 The diagrams show the dynamic wetting behavior of the TpPa membrane and the TpPa-SO3H membrane in the organic and aqueous phases, respectively, in embodiments of the present invention. Specifically, a is the dynamic wetting behavior of the TpPa membrane (organic phase), b is the dynamic wetting behavior of the TpPa membrane (aqueous phase), c is the dynamic wetting behavior of the TpPa-SO3H membrane (organic phase), and d is the dynamic wetting behavior of the TpPa-SO3H membrane (aqueous phase). Figure 6 In the embodiments of the present invention, the TpPa membrane and the TpPa-SO3H membrane are at 2 mol·L⁻¹ -1 Zn 2p XPS spectrum and C 1s XPS spectrum after immersion in ZnSO4 electrolyte, where a represents the concentration of Zn in 2 mol·L⁻¹ electrolyte. -1 a) Zn2p XPS spectrum after soaking in ZnSO4 electrolyte; b) C1s XPS spectrum at TpPa; c) C1s XPS spectrum of TpPa-SO3H. Figure 7 The figures show the AC impedance spectra of bare Zn cells, TpPa@Zn cells, and TpPa-SO3H@Zn cells in embodiments of the present invention, as well as the Ea calculation (organic phase measurement) graph based on Arrhenius curve fitting. Specifically, a is the AC impedance spectrum of the bare Zn cell, b is the AC impedance spectrum of the TpPa@Zn cell, c is the AC impedance spectrum of the TpPa-SO3H@Zn cell, and d is the Ea calculation (organic phase measurement) graph of the bare Zn cell, TpPa@Zn cell, and TpPa-SO3H@Zn cell based on Arrhenius curve fitting. Figure 8 In the embodiments of the present invention, the bare Zn battery, the TpPa@Zn battery, and the TpPa-SO3H@Zn battery are used at 0.1 mA cm⁻¹. -2 0.1mAh cm -2 SEM images of the surface of the negative electrode after zinc deposition under cycling conditions, where a is bare Zn, b is TpPa@Zn, and c is TpPa-SO3H@Zn; Figure 9 These are in-situ optical images of bare Zn cells, TpPa@Zn cells, and TpPa-SO3H@Zn cells at different deposition times in embodiments of the present invention. The scale bar is 100µm, where a represents bare Zn, b represents TpPa@Zn, and c represents TpPa-SO3H@Zn. Figure 10 In this embodiment of the invention, the bare Zn negative electrode and the zinc negative electrode with the heterostructure membrane are at 0.1 mA·cm⁻¹. -2 and 0.1mAh·cm -2 XRD diffraction pattern after cycling in a symmetrical cell under certain conditions; Figure 11 The diagram shows the coulombic efficiency of zinc deposition / stripping in Zn / / Cu batteries and the rate performance of different Zn / / Zn batteries in the embodiments of the present invention, wherein a is the coulombic efficiency diagram of zinc deposition / stripping in Zn / / Cu batteries and b is the rate performance diagram of different Zn / / Zn batteries. Figure 12 In this embodiment of the invention, the Zn / / Zn battery is at 0.1 mA cm -2 0.1mAh cm -2 Long-cycle test diagram under current density. Detailed Implementation

[0028] Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be construed as limiting the scope of the invention. Specific conditions not specified in the embodiments were performed under conventional conditions or conditions recommended by the manufacturer. Components not specifying their manufacturers are all commercially available conventional products. The synthesis method and electrochemical performance of the present invention are further illustrated below with reference to the embodiments.

[0029] Example 1 This embodiment provides a heterogeneous two-dimensional covalent organic framework membrane and its preparation method, specifically including the following steps: First, prepare the lower phase aqueous solution of the reaction system: using deionized water as solvent, weigh different masses of sulfonic acid-functionalized amine monomers Pa-SO3H (0.0364 g, 0.0464 g, 0.0564 g, 0.0664 g, and 0.0764 g) and add them to a clean, dry beaker, along with an appropriate amount of sodium formate as a catalyst for the imine condensation reaction. Sonicate the resulting mixture for at least 15 min until Pa-SO3H and the catalyst are completely dissolved, obtaining a homogeneous and transparent aqueous solution, which serves as the lower phase of the interfacial reaction system.

[0030] Subsequently, the upper organic phase solution of the reaction system was prepared: 0.0424 g of aldehyde monomer 1,3,5-tricarboxymethylphloroglucinol (Tp) was weighed, dissolved in 20 mL of octanoic acid, and subjected to sonication for no less than 30 min until the monomer was completely dissolved, resulting in a clear and transparent Tp organic phase solution.

[0031] The lower phase aqueous solution was transferred to a reaction vessel, and the upper phase Tp organic solution was slowly added dropwise along the inner wall of the vessel to form a stable and clear liquid-liquid interface between the two phases. The reaction was allowed to stand at room temperature for 24 h or 48 h. A continuous, self-supporting thin-film covalent organic framework material gradually formed at the interface.

[0032] After the reaction was completed, the resulting film was carefully removed from the interface and thoroughly washed with deionized water and ethanol in sequence to remove unreacted monomers and residual impurities, resulting in a TpPa-SO3H covalent organic framework membrane with continuous structure, good mechanical strength and controllable thickness.

[0033] Finally, the COF film was transferred to the zinc foil surface using the dip-coating transfer method to prepare the COF@Zn composite electrode, or transferred to other substrates for subsequent structural characterization and performance testing.

[0034] Example 2 Unlike Example 1, the monomer Pa-SO3H in the lower phase aqueous solution was replaced with Pa to prepare a TpPa membrane. The specific preparation process is as follows: First, an aqueous solution of Pa containing 16 wt% acetonitrile was used as the lower phase, with Pa concentrations of 0.20 mmol, 0.25 mmol, 0.30 mmol, 0.35 mmol, and 0.40 mmol. The solutions were thoroughly mixed and sonicated to obtain a homogeneous lower phase solution.

[0035] Subsequently, 0.20 mmol of Tp monomer was dissolved in a mixed organic solvent consisting of octanoic acid and 1,3,5-trimethylbenzene to form the upper phase solution. This organic phase was then slowly added dropwise along the container wall above the lower phase solution, forming a stable interface at the liquid-liquid interface.

[0036] The reaction system was allowed to stand at room temperature for 24 or 48 hours. After the reaction was complete, the generated TpPa covalent organic framework membrane was removed from the interface and washed sequentially with deionized water and ethanol to remove unreacted monomers and residual impurities. The washed TpPa membrane was used for subsequent structural characterization and electrochemical performance testing.

[0037] Comparative Example 1 Unlike Example 1, sodium formate was not added to the lower phase aqueous solution. The specific preparation steps are as follows: First, prepare the lower phase aqueous solution of the reaction system: using deionized water as solvent, weigh different masses of sulfonic acid-functionalized amine monomer Pa-SO3H (0.0564 g) and add them to clean, dry beakers, along with an appropriate amount of sodium formate as a catalyst for the imine condensation reaction. Sonicate the resulting mixture for at least 15 min until Pa-SO3H and the catalyst are completely dissolved, obtaining a homogeneous and transparent aqueous solution, which serves as the lower phase of the interfacial reaction system.

[0038] Subsequently, the upper organic phase solution of the reaction system was prepared: 0.0424 g of aldehyde monomer 1,3,5-tricarboxymethylphloroglucinol (Tp) was weighed, dissolved in 20 mL of octanoic acid, and subjected to sonication for no less than 30 min until the monomer was completely dissolved, resulting in a clear and transparent Tp organic phase solution.

[0039] The lower phase aqueous solution was transferred to a reaction vessel, and the upper phase Tp organic solution was slowly added dropwise along the inner wall of the vessel to form a stable and clear liquid-liquid interface between the two phases. The reaction was allowed to stand at room temperature for 24 hours. A continuous, self-supporting thin-film covalent organic framework material gradually formed at the interface.

[0040] Studies have found that omitting the addition of a catalyst significantly reduces the reaction rate, leading to a decrease in structural regularity, crystallinity, and the efficiency of sulfonic acid group functionalization. This manifests as disordered nanochannels, wider pore size distribution, and insufficient negative charge density, which in turn weakens the synergistic effect of size sieving and electrostatic repulsion, ultimately resulting in poorer mechanical strength and long-term stability.

[0041] Comparative Example 2 Unlike Comparative Example 1, the lower phase aqueous solution was transferred to a reaction vessel, and the upper phase Tp organic solution was slowly added dropwise along the inner wall of the vessel. The mixture was then heated to 60°C and reacted for 24 hours.

[0042] Studies have found that when the reaction temperature is increased from room temperature to 60 °C, the reaction rate is too fast, leading to an imbalance between monomer diffusion and interfacial polymerization. This easily results in the formation of disordered structures with excessive local cross-linking, which not only causes uneven distribution of angstrom-sized pore channels and a reduction in effective sieving area, but may also cause partial decomposition of sulfonic acid groups due to high temperature, weakening the electrostatic repulsion effect. Furthermore, the increased solvent evaporation at high temperatures can easily generate macroscopic cracks, seriously affecting the mechanical strength and separation stability of the membrane.

[0043] Comparative Example 3 Unlike the previous example, a commercially available glass fiber diaphragm was used.

[0044] Studies have found that during the charging and discharging process, Zn 2+In traditional separators, the zinc exhibits a disordered migration state and uneven ion flux distribution, easily leading to significant concentration polarization at the electrode / electrolyte interface. With cycling, uneven deposition gradually appears on the zinc anode surface, forming dendritic structures, resulting in a continuous increase in interfacial impedance and intensified battery polarization. In long-term cycling tests, this system exhibits poor battery cycle stability, significant capacity decay, and ultimately fails due to zinc dendrites piercing the separator or interfacial instability.

[0045] Comparative Example 4 Unlike the previous examples, a single-structure COF membrane without heterogeneous structures was used as the separator material. This COF membrane consists of a single organic framework structure, with its pore structure and chemical environment being essentially homogeneous along the membrane thickness direction, without forming an interfacial gradient or multiphase synergistic structure. This single-structure COF membrane was placed between the zinc anode and cathode, and its zinc ion transport behavior and zinc anode stability were tested under the same electrolyte conditions and test conditions as in the previous examples.

[0046] Studies have found that single-structure COF membranes improve Zn absorption to some extent compared to traditional membranes. 2+ The transport of Zn is controllable, but due to the uniform distribution of the membrane pore environment and chemical interaction sites, Zn... 2+ The migration of ions still primarily relies on a single transport mechanism. During charge and discharge, localized ion enrichment and uneven deposition still exist at the zinc anode interface. With increasing cycle count, an uneven deposition structure gradually appears on the zinc anode surface, the interfacial impedance increases, and cycle stability is limited.

[0047] Performance testing: (1) FT-IR and XRD tests FT-IR testing method: Before testing, the COF film sample to be tested is thoroughly dried to remove residual solvent and moisture from the surface. Measurements are taken using a Bruker ALPHA II spectrometer in the wavelength range of 4000-400 cm⁻¹. -1 XRD testing method: Obtained using a RigakuSmartLab 9 kW X-ray diffractometer (Cu Kα radiation), with a scanning range of 2θ = 4-90° and a scanning speed of 20°·min. -1 .

[0048] Depend on Figure 1 The FT-IR results in a and b show that the characteristic absorption peaks of the precursor monomers in the COF membrane disappear, while new skeletal characteristic absorption peaks appear, indicating that the membrane mainly exists in the form of keto tautomers. With increasing monomer concentration, the intensity of the relevant skeletal characteristic absorption peaks gradually increases, indicating that the COF skeletal structure is formed more fully, and the structural integrity and order of the membrane are correspondingly improved.

[0049] Depend on Figure 1XRD patterns c and d show that when the monomer reaction concentration of the TpPa membrane is controlled at 0.3 mmol, a sharp and clear characteristic diffraction peak appears at 2θ≈4.4°. This diffraction peak can be attributed to the (100) crystal plane in the COF crystal structure, indicating that a covalent organic framework membrane with a long-range ordered structure is formed under these reaction conditions. Similarly, for the TpPa-SO3H membrane, when the amount of sulfonic acid functionalized amine monomer is 0.0564 g, a characteristic diffraction peak corresponding to the (100) crystal plane also appears in its XRD pattern, indicating that the membrane material obtained under these conditions also has good crystallinity. The above results show that by reasonably controlling the monomer reaction concentration, the formation of an ordered crystal structure in both COF membranes can be effectively promoted. Good crystallinity helps to construct a regular and continuous pore system, thereby providing a stable structural basis for the directional transport and uniform migration of ions in the membrane.

[0050] Based on the above structural characterization and performance analysis results, and considering the crystallinity, structural integrity, and controllability of the membranes, the optimal monomer feed concentrations for the two COF membranes were finally determined. Specifically, the optimal concentration of Pa monomer in the TpPa membrane was 0.3 mmol, while the optimal monomer mass of Pa-SO3H monomer in the TpPa-SO3H membrane was 0.0564 g. These were used as the standard preparation conditions for subsequent structural characterization and performance testing.

[0051] (2) Test method for nitrogen adsorption-desorption isotherms: The isotherms were measured at 77 K using a multi-station extended specific surface area and porosity analyzer (ASAP 2460-4MP). The corresponding pore size distribution was calculated using NLDFT theory, and the existence of large-scale pores was confirmed using BJH analysis.

[0052] from Figure 2 As can be seen from the data, in the lower relative pressure range P / P0, both COF membranes exhibit typical porous material adsorption characteristics, confirming that the materials possess a regular porous structure and excellent gas adsorption performance, making them suitable as Zn adsorption materials. 2+ The transport pore channels. Fitting the nonlocal density functional theory (NLDFT) model, the pore size distribution curves of both COF films exhibit a narrow distribution characteristic, indicating their regular and uniform pore structure; specifically, the main pore size peak of the TpPa film is 1.79 nm, and that of the TpPa-SO3H film is 1.74 nm. This uniform pore size at this scale can impart Zn... 2+ An ordered transport path is established, and the ion transport rate is regulated through the size sieving effect.

[0053] (3) Scanning electron microscopy test The prepared covalent organic framework (COF) membrane was extracted from the interface using a pull-out method. The membrane sample was then cleaned with ethanol and deionized water to remove surface impurities, and subsequently dried. Before SEM testing, the COF membrane sample was sprayed with a 3 kV coating to improve conductivity for 60 s. Following this, the membrane sample was characterized using a tungsten filament as the electron source at an accelerating voltage of 10 kV, and surface and cross-sectional morphology images were acquired at different magnifications.

[0054] from Figure 3 It is evident that both types of COF membranes exhibit distinct bifacial heterogeneous structures. Specifically, the organic phase side of the membrane surface is generally smooth and dense, with no obvious defects observed. This morphology helps reduce interfacial resistance during ion transport on the membrane surface, thereby ensuring the continuity and stability of the ion conduction path. In contrast, the aqueous phase side exhibits a relatively loose porous structure with a certain degree of structural toughness. This morphology mainly stems from the diffusion behavior of monomers within the aqueous phase during interfacial polymerization. This loose porous structure provides ample transport channels for the rapid diffusion of ions within the membrane.

[0055] Furthermore, through Figure 4 The thicknesses of three COF films were measured using SEM cross-sectional images, and the results showed that: Taking the TpPa covalent organic framework membrane as an example, the relationship between interfacial reaction time and membrane thickness was investigated. When the interfacial reaction time was 48 h, the thickness of the obtained COF membrane was approximately 49 μm. Figure 4 (a) When the reaction time was shortened to 24 h, the film thickness decreased to approximately 34 μm. Figure 4 (b). The thickness of the TpPa-SO3H membrane is approximately 32 μm. Figure 4 (c). It is evident that the thickness of the COF membrane can be effectively controlled by adjusting the interfacial reaction time. A thinner COF membrane exhibits a more significant effect in regulating interfacial ion conduction, which is beneficial for its interfacial regulation function. Therefore, in this invention, the interfacial reaction time is preferentially controlled to 24 h to obtain a covalent organic framework membrane with moderate thickness and excellent interfacial regulation performance.

[0056] (4) Test method for WCA: The test was conducted using a JC2000C contact angle measuring instrument (POWEREACH®, China).

[0057] from Figure 5As can be seen, the surface facing the organic phase is smooth, allowing water droplets to be gradually absorbed, and the hydrophilicity of the membrane is significantly enhanced after the introduction of sulfonic acid groups; the surface facing the aqueous phase is rough and porous, allowing droplets to spread completely upon contact. The differences in surface morphology and chemical composition on both sides of the membrane result in a significant asymmetry in its wetting behavior. This wetting characteristic, synergistically regulated by surface structure and functional groups, facilitates the full wetting of the electrolyte at the COF@Zn interface, providing a suitable environment for Zn... 2+ Uniform desolvation, stable migration, and uniform deposition provide a favorable interfacial environment.

[0058] (5) XPS testing method: During testing, the prepared COF membrane sample was immersed in a solution with a concentration of 2 mol·L⁻¹. -1 The membrane samples were soaked in an aqueous solution of zinc sulfate (ZnSO4) for 24 h. After soaking, the membrane samples were removed, vacuum dried, and then subjected to XPS testing to analyze the interaction between zinc ions and the COF membrane.

[0059] from Figure 6 It can be seen that in the original ZnSO4 sample, Zn 2p 3 / 2 and Zn 2p 1 / 2 The characteristic peaks were located at 1023.0 eV and 1046.0 eV, respectively. When the ZnSO4 solution came into contact with the COF membrane, these characteristic peaks shifted to approximately 1021.5 eV and 1044.6 eV, respectively, indicating that the ZnSO4 solution... 2+ The change in the electronic environment on the COF film surface confirms that Zn 2+ There is coordination or interaction between the TpPa-SO3H membrane and the COF membrane framework. Further analysis of the C1s energy spectrum of the TpPa-SO3H membrane revealed three characteristic peaks in the 282–290 eV range, corresponding to C=C (approximately 284.2 eV), C─N (approximately 285.9 eV), and C=O (approximately 287.6 eV), respectively. After immersion in ZnSO4 solution, the aforementioned C1s characteristic peaks shifted towards lower binding energies, indicating that electron-rich functional groups (including sulfonic acid groups and imine bonds) in the COF membrane interact with Zn. 2+ There is a strong interaction between them. In contrast, the TpPa membrane without sulfonic acid groups also showed a similar binding energy shift trend after being immersed in ZnSO4 solution, but its shift amplitude was significantly smaller, further verifying the role of sulfonic acid group modification in enhancing the zinc-loving coordination ability of COF membranes.

[0060] (6) Electrochemical performance testing A Zn / / Zn battery was prepared by using a COF membrane with its smooth side facing the zinc anode as the separator. Impedance tests were then performed on each battery using an electrochemical workstation, and desolvation energy was obtained through post-processing. Preferably, the separator used in this invention is a self-synthesized covalent organic framework (COF) membrane with a heterostructure, while the separator used in the bare zinc system is a glass fiber separator.

[0061] Zn / / Zn battery assembly method: Both the positive and negative electrodes are zinc sheets, the separator is a COF film with different heterostructures, and the electrolyte is 2 mol·L⁻¹. -1 The amount of ZnSO4 aqueous solution used was 100 μL.

[0062] from Figure 7 It can be seen that the COF film-assembled Zn / / Zn battery prepared in Example 1 has the smallest desolvation energy barrier. This indicates that the battery assembled using Example 1 can help improve the kinetic performance at the interface.

[0063] Zinc anode at 0.1 mA cm -2 0.1mAh cm -2 SEM images of the surface of the negative electrode after zinc deposition under cyclic conditions. From Figure 8 It can be seen that, compared with other embodiments, the battery in Example 1 produces fewer byproducts during operation.

[0064] In-situ optical microscopy testing method: Real-time imaging was performed using an optical microscope. During the test, a dedicated in-situ electrochemical cell (LIB-MS-II, Beijing Sike Technology Co., Ltd.) was used to conduct a continuous deposition reaction. From Figure 9 It is known that uneven deposition and bubbles easily appear on the surface of bare Zn electrodes, which can induce dendrite growth and reduce mechanical stability. In contrast, when a COF film is used as a separator, the Zn surface maintains a uniform and dense deposition state, with the TpPa-SO3H film showing particularly significant effects, effectively improving Zn deposition. 2+ The deposition behavior inhibits corrosion and dendrite formation, thereby protecting the stability of the zinc anode interface.

[0065] XRD patterns of the zinc anode after 50 cycles in Examples 1 and 2. Figure 10 It can be seen that, compared with other embodiments, the battery in Example 1 produces fewer byproducts during operation. This indicates that Example 1 is more effective than other embodiments in suppressing hydrogen evolution side reactions and dendrite formation.

[0066] Figure 11The figures for a) Coulombic efficiency of zinc deposition / stripping in Zn / / Cu batteries in Examples 1 and 2; and b) Rate performance of different Zn / / Zn batteries. Example 1 achieved a higher Coulombic efficiency, indicating that Example 1 is more effective than other examples in suppressing hydrogen evolution side reactions and dendrite formation.

[0067] Examples 1 and 2 were assembled into Zn / / Zn batteries at 0.1 mA cm -2 0.1mAh cm -2 Long-cycle testing was conducted at current densities. Figure 12 It can be seen that, compared with other embodiments, the battery of Example 1 has less polarization and a longer cycle life. This indicates that, due to the series of characterization tests shown in the preceding series, Example 1 can effectively suppress the generation of battery side reactions, thus demonstrating a longer cycle life and greater durability in long-cycle tests.

[0068] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A heterogeneous two-dimensional covalent organic framework membrane, characterized in that, The heterostructured two-dimensional covalent organic framework membrane is self-assembled by the polymerization of aqueous monomers and organic monomers through a dual-activation interface. The aqueous monomers include one or more of p-phenylenediamine, 4,4′-diaminobiphenyl, 2,4,6-triamino-1,3,5-triazine, 4,4'-diamino-[1,1'-biphenyl]-3,3'-disulfonic acid, and 2,5-diaminobenzenesulfonic acid; The organic phase monomers include one or more of 1,3,5-tricarboxyloyl-phloroglucinol, 1,3,5-benzenetriformaldehyde, 2,5-dimethoxy-terephthalaldehyde, 2,5-dihydroxy-terephthalaldehyde, 2,6-pyridinediformaldehyde, 2,4,6-tricarboxy-1,3,5-triazine, and pyrazindiformaldehyde.

2. The heterogeneous two-dimensional covalent organic framework membrane according to claim 1, characterized in that, The aqueous phase monomers are p-phenylenediamine and 2,5-diaminobenzenesulfonic acid; The organic phase monomer is 1,3,5-tricarboxymethylphloroglucinol; The molar ratio of the aqueous phase monomer to the organic phase monomer is (1-2):

1.

3. The heterogeneous two-dimensional covalent organic framework membrane according to claim 1, characterized in that, The heterostructured two-dimensional covalent organic framework membrane has a gradient porous structure with a thickness of 30-50 μm, a porosity of 15%-30%, and a pore size distribution range of 1.6-1.9 nm.

4. A method for preparing a heterogeneous two-dimensional covalent organic framework membrane according to any one of claims 1-3, characterized in that, Includes the following steps: An aqueous solution is prepared by mixing an aqueous monomer, a catalyst, and an aqueous solvent; an organic solution is prepared by mixing an organic monomer and an organic solvent; the organic solution is added dropwise to the aqueous solution, and the mixture is allowed to stand at room temperature for reaction. After washing and drying, a heterostructured two-dimensional covalent organic framework membrane is obtained.

5. The method for preparing a heterogeneous two-dimensional covalent organic framework membrane according to claim 4, characterized in that, The aqueous monomers include one or more of p-phenylenediamine (Pa), 4,4′-diaminobiphenyl, 2,4,6-triamino-1,3,5-triazine, 4,4'-diamino-[1,1'-biphenyl]-3,3'-disulfonic acid and 2,5-diaminobenzenesulfonic acid; The organic phase monomers include one or more of 1,3,5-tricarboxyloyl-phloroglucinol, 1,3,5-benzenetricarboxaldehyde, 2,5-dimethoxyterephthalaldehyde, 2,5-dihydroxyterephthalaldehyde, 2,6-pyridinedicarboxaldehyde, 2,4,6-tricarboxy-1,3,5-triazine, and pyrazindicarboxaldehyde. The aqueous solvent is deionized water; the catalyst is one or more of sodium formate and acetonitrile. The organic solvent is one or more of octanoic acid and 1,3,5-trimethylbenzene.

6. The method for preparing a heterogeneous two-dimensional covalent organic framework membrane according to claim 4, characterized in that, The settling time is 20-50 h; the solvent used for washing is deionized water and ethanol.

7. The method for preparing a heterogeneous two-dimensional covalent organic framework membrane according to claim 4, characterized in that, The molar ratio of the aqueous phase monomer to the organic phase monomer is 1.5:1; the static reaction time is 20-25 h.

8. The application of a heterogeneous two-dimensional covalent organic framework separator according to any one of claims 1-5 in an aqueous battery, characterized in that, The aqueous battery includes an aqueous zinc battery.

9. An aqueous zinc battery, characterized in that, It includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the separator is a heterostructure two-dimensional covalent organic framework separator as described in any one of claims 1-5.

10. The aqueous zinc battery according to claim 9, characterized in that, The electrolyte is zinc sulfate electrolyte; the negative electrode is zinc metal foil; and the positive electrode is one or more of sodium vanadate, polyaniline, manganese dioxide, ammonium vanadate, and vanadium pentoxide.

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