A self-healing covalent organic framework-based composite membrane and its preparation method and application

Abstract

The present invention relates to a self-healing covalent organic framework-based composite membrane, its preparation method and application. By dehydrating boric acid with the hydroxyl groups on polyvinyl alcohol, a boron-crosslinked PVA / KCl hydrogel membrane is obtained; then the covalent organic framework is composited onto the boron-crosslinked PVA / KCl hydrogel membrane by in-situ polymerization growth. Based on the designability of the COFs structure and the high toughness of the hydrogel membrane, the application of the self-healing covalent organic framework-based composite membrane in supercapacitors not only achieves excellent electrochemical performance, but also exhibits excellent toughness, strength and self-healing behavior under strong mechanical deformations such as stretching or bending, and has good application prospects.

Description

Technical Field

[0001] The present invention belongs to the field of supercapacitor electrode materials, and particularly relates to a self-healing covalent organic framework-based composite film, a preparation method thereof, and an application thereof. Background Art

[0002] Wearable electronic devices based on hydrogels have good self-healing performance and high flexibility, and thus have attracted particular attention from researchers. The advantages of hydrogels are as follows: 1) Hydrogels have a cross-linked network of viscoelastic, flexible, and hydrophilic polymer chains; 2) Electrolytic ions can be effectively attracted and positioned by the hydrogel network, and the hydrogel exhibits good ionic conductivity; 3) Hydrogel materials have a good water-locking function, which can effectively avoid the volatilization and leakage of water; 4) Based on dynamic covalent bonds and non-covalent bonds, hydrogels (such as polyvinyl alcohol PVA) can establish a dynamic equilibrium of bond formation and dissociation in the hydrogel network, thereby endowing them with self-healing properties.

[0003] Covalent organic frameworks (COFs) are emerging crystalline porous materials formed by connecting light organic molecular building blocks through covalent bonds to form two-dimensional or three-dimensional network structures. Therefore, they have excellent structural tailoring and functional tunability, as well as advantages such as low framework density, high porosity, and open pore structures, and have broad application prospects in multiple fields. Applying COFs to energy storage devices can regulate the structure of COFs through structural design to enable them to obtain more redox-active organic functional groups and further improve their electrochemical performance. However, COFs have some obvious disadvantages, such as easy stacking, poor conductivity, etc., which seriously affect their further wide application.

[0004] Currently, although there are many studies on the application of COF-based composite films in supercapacitors, they mainly involve the composites of COFs with carbon nanotubes (such as patents CN111540620A, CN110164716A), graphene (such as patent CN107230557A), conductive polymers (such as Nano letters, 2010, 10, 4025-4031, publication date September 10, 2010), carbon fibers (such as Journal of Colloid and Interface Science, 2022, 622, 11-20, publication date September 15, 2022), etc., and none of them have self-healing ability. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a self-healing covalent organic framework-based composite film, a preparation method thereof, and an application thereof, which overcomes the current situation that COF-based composite films in the prior art do not have self-healing ability.

[0006] The present invention provides a self-healing covalent organic framework-based composite membrane. By dehydrating boric acid with the hydroxyl groups on polyvinyl alcohol, a boron-crosslinked PVA / KCl hydrogel membrane is obtained; then the covalent organic framework is composited onto the boron-crosslinked PVA / KCl hydrogel membrane by in-situ polymerization growth.

[0007] The present invention also provides a preparation method of the self-healing covalent organic framework-based composite membrane, comprising the following steps:

[0008] (1) Add a potassium chloride KCl solution to the PVA gel solution and continuously stir, then obtain a PVA / KCl hydrogel membrane through freeze-thaw cycles, and then immerse it in a boric acid / ammonia solution to obtain a boron-crosslinked PVA / KCl hydrogel membrane;

[0009] (2) Through in-situ growth, make an amino monomer and an aldehyde monomer react on the surface of the above-mentioned boron-crosslinked PVA / KCl hydrogel membrane to synthesize a covalent organic framework, and then take out the composite hydrogel membrane and wash it to obtain the self-healing covalent organic framework-based composite membrane.

[0010] The concentration of the PVA gel solution in the step (1) is 5-20 wt%; the concentration of the potassium chloride solution is 1-6 mol / L.

[0011] The freeze-thaw cycles in the step (1) include: pouring the stirred mixture into a mold (1.5×2×0.1 cm 3 ), freezing at -15 °C for 12-36 h, and thawing at room temperature for 12 h, and repeating this cycle 2-5 times.

[0012] The concentration of the boric acid / ammonia solution in the step (1) is 0.5-2 mg / mL; the immersion time is 12-36 h.

[0013] The amino monomer in the step (2) is one or more of p-phenylenediamine, 3,3'-dihydroxy-4,4'-biphenyldiamine, tris(4-aminophenyl)amine, 2,3,5,6-tetra(amino)benzoquinone. The chemical formulas are as follows;

[0014]

[0015] The aldehyde monomer in the step (2) is one or more of phloroglucinol trialdehyde, 3,3',5,5'-tetraaldehyde-4,4'-dihydroxybiphenyl, 2,6-dialdehyde-1,5-dihydroxynaphthalene, 1,3,5-tris(2-formylpyridin-5-yl)benzene. The chemical formulas are as follows;

[0016]

[0017] The aldehyde monomer in the step (2) is one or more of phloroglucinol trialdehyde, 3,3',5,5'-tetraaldehyde-4,4'-dihydroxybiphenyl, 2,6-dialdehyde-1,5-dihydroxynaphthalene, 1,3,5-tris(2-formylpyridin-5-yl)benzene.

[0018] The molar ratio of the amino monomer to the aldehyde monomer in the step (2) is 1-2:1.

[0019] The in-situ growth in the step (2) is specifically as follows: By using the room-temperature solution synthesis method, the boron-crosslinked PVA / KCl hydrogel film, the amino monomer, the aldehyde monomer and ethanol are stirred at room temperature for 0.5-6 h, and then the hydrogel film is taken out and washed three times with deionized water.

[0020] The selection of the above in-situ growth method determines the morphology, structure and properties of the composite film.

[0021] The present invention also provides an application of the self-healing covalent organic framework-based composite film in a quasi-solid-state symmetric supercapacitor.

[0022] The present invention prepares a flexible and self-healable polyvinyl alcohol hydrogel substrate by combining physical crosslinking and chemical crosslinking, and then prepares a covalent organic framework-based composite film with a controllable chemical structure, excellent electrochemical properties, flexibility and self-healing ability, which can be directly applied to the electrode material of a supercapacitor; and this self-healing ability can greatly extend the service life of the supercapacitor, providing a new idea for designing a new generation of flexible electronic devices.

[0023] Beneficial effects

[0024] (1) The method of the present invention has mild conditions, simple operation, and wide sources of instruments and equipment, and can be industrially produced.

[0025] (2) The present invention combines the advantages of two materials, hydrogel and covalent organic framework: The covalent organic framework material has strong structural designability, and at the same time has rich open pore structures and redox groups to store charges; while the hydrogel has a hierarchical porous structure, good ionic conductivity, high mechanical flexibility and self-healing ability, and can effectively solve problems such as easy stacking and poor conductivity of COFs.

[0026] (3) The covalent organic framework-based composite film prepared by the present invention has good flexibility and can be directly applied to the preparation of supercapacitor devices without complex electrode pretreatment steps.

[0027] (4) The covalent organic framework-based composite film prepared by the present invention is used for the preparation of a flexible quasi-solid-state symmetric supercapacitor, shows good electrochemical properties, and exhibits great application potential in the energy storage field.

[0028] (5) The covalent organic framework-based composite membrane prepared by the present invention has good self-healing ability, which can greatly extend the service life of supercapacitors. Specific Embodiments

[0029] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0030] Example 1

[0031] Preparation of boron-crosslinked PVA / KCl hydrogel membrane: 10 mL of 10 wt.% transparent PVA gel solution was stirred at 85 °C for 2 h, then 3 mL of 3 mol / L potassium chloride (KCl) solution was added and stirred continuously for 30 min. The stirred mixture was poured into a mold (1.5 × 2 × 0.1 cm 3 ), frozen at -15 °C for 24 h, and thawed at room temperature for 12 h, and this cycle was repeated 3 times to obtain the PVA / KCl hydrogel membrane. Then it was immersed in 1 mg / mL boric acid / ammonia solution for 24 h, and the boron-crosslinked PVA / KCl hydrogel membrane was obtained after taking it out.

[0032] Preparation of self-healing covalent organic framework-based composite membrane: The above-prepared boron-crosslinked PVA / KCl hydrogel membrane, 0.74 g (4 mmol) of p-phenylenediamine, 0.60 g (2 mmol) of 3,3',5,5'-tetraformyl-4,4'-dihydroxybiphenyl and 10 mL of ethanol were stirred at room temperature for 3 h. The hydrogel membrane was taken out and washed three times with deionized water to obtain the self-healing covalent organic framework-based composite membrane. Then, the boron-crosslinked PVA / KCl hydrogel membrane (1.8 × 2.2 × 0.1 cm 3 ) was used as the electrolyte and separator and placed between two prepared self-healing covalent organic framework-based composite membranes (1.5 × 2 × 0.1 cm 3 ) as the electrode materials, and two identical carbon cloths were used as current collectors. The device was encapsulated under a pressure of ~0.5 MPa to obtain a quasi-solid-state symmetric supercapacitor. The prepared quasi-solid-state symmetric supercapacitor exhibited a specific capacitance of 244 mF cm -2 at a current density of 2 mA cm -2 and a power density of 34 μW cm -2The energy density. Moreover, three series-connected quasi-solid-state symmetric supercapacitors can easily power an LED and remain bright after strong mechanical deformations such as stretching and bending. To test its self-healing ability, one of the series-connected quasi-solid-state symmetric supercapacitors was cut, and the LED light went out. Then, the two broken pieces were closely aligned and heated to 85 °C for 20 s, and the surfaces could adhere tightly to each other, and then the LED became bright again. Meanwhile, continued stretching or bending deformations were carried out, and the brightness change of the self-healing device was negligible, indicating that the prepared covalent organic framework-based composite film not only has excellent electrochemical performance but also has good self-healing performance.

[0033] Example 2

[0034] Preparation of boron-crosslinked PVA / KCl hydrogel film: 10 mL of 5 wt.% transparent PVA gel solution was stirred at 85 °C for 2 h, and then 3 mL of 1 mol / L potassium chloride (KCl) solution was added and stirred continuously for 30 min. The stirred mixture was poured into a mold (1.5×2×0.1 cm 3 ), frozen at -15 °C for 12 h, and thawed at room temperature for 12 h, and this cycle was carried out 2 times to obtain the PVA / KCl hydrogel film. Then it was immersed in 0.5 mg / mL boric acid / ammonia solution for 12 h, and the boron-crosslinked PVA / KCl hydrogel film was obtained after taking it out.

[0035] Preparation of self-healing covalent organic framework-based composite film: The above-prepared boron-crosslinked PVA / KCl hydrogel film, 0.65 g (3 mmol) of 3,3'-dihydroxy-4,4'-biphenyldiamine, 0.79 g (2 mmol) of 1,3,5–tris(2-formylpyridin-5-yl)benzene, and 10 mL of ethanol were stirred at room temperature for 0.5 h. The hydrogel film was taken out and washed three times with deionized water to obtain the self-healing covalent organic framework-based composite film. Then, the boron-crosslinked PVA / KCl hydrogel film (1.8×2.2×0.1 cm 3 ) was used as the electrolyte and separator and placed between two prepared self-healing covalent organic framework-based composite films (1.5×2×0.1 cm 3 ) as the electrode materials, and two identical carbon cloths were used as current collectors. The device was encapsulated under a pressure of ~0.5 MPa to obtain a quasi-solid-state symmetric supercapacitor. The prepared quasi-solid-state symmetric supercapacitor exhibited a specific capacitance of 313 mF cm -2 at a current density of 2 mA cm -2 and an energy density of 44 μWh cm -2 . Moreover, three series-connected quasi-solid-state symmetric supercapacitors can easily power an LED and remain bright after strong mechanical deformations such as stretching and bending. After testing, the obtained self-healing covalent organic framework-based composite film also has good self-healing performance.

[0036] Example 3

[0037] Preparation of boron-crosslinked PVA / KCl hydrogel film: 10 mL of 20 wt.% transparent PVA gel solution was stirred at 85 °C for 2 h, then 3 mL of 6 mol / L potassium chloride (KCl) solution was added and stirred continuously for 30 min. The stirred mixture was poured into a mold (1.5×2×0.1 cm 3 ), frozen at -15 °C for 36 h, and thawed at room temperature for 12 h. This cycle was repeated 5 times to obtain the PVA / KCl hydrogel film. Then it was immersed in 2 mg / mL boric acid / ammonia solution for 36 h, and the boron-crosslinked PVA / KCl hydrogel film was obtained after taking it out.

[0038] Preparation of self-healing covalent organic framework-based composite film: The above-prepared boron-crosslinked PVA / KCl hydrogel film, 0.18 g (1 mmol) of p-phenylenediamine, 0.17 g (1 mmol) of 2,3,5,6-tetra(amino)-p-benzoquinone, 0.42 g (2 mmol) of triformylphloroglucinol and 10 mL of ethanol were stirred at room temperature for 6 h. The hydrogel film was taken out and washed three times with deionized water to obtain the self-healing covalent organic framework-based composite film. Then, the boron-crosslinked PVA / KCl hydrogel film (1.8×2.2×0.1 cm 3 ) was used as the electrolyte and separator and placed between two prepared self-healing covalent organic framework-based composite films (1.5×2×0.1 cm 3 ) as the electrode materials. Two identical carbon cloths were used as current collectors, and the device was encapsulated under a pressure of ~0.5 MPa to obtain a quasi-solid-state symmetric supercapacitor. The prepared quasi-solid-state symmetric supercapacitor exhibited a specific capacitance of 276 mF cm -2 at a current density of 2 mA cm -2 and an energy density of 39 μW cm -2 . Moreover, three series-connected quasi-solid-state symmetric supercapacitors could easily power an LED and remained bright after strong mechanical deformations such as stretching and bending. After testing, the obtained self-healing covalent organic framework-based composite film also had good self-healing performance.

[0039] Example 4

[0040] Preparation of boron-crosslinked PVA / KCl hydrogel film: 10 mL of 5 wt.% transparent PVA gel solution was stirred at 85 °C for 2 h, then 3 mL of 5 mol / L potassium chloride (KCl) solution was added and stirred continuously for 30 min. The stirred mixture was poured into a mold (1.5×2×0.1 cm 3) It was frozen at -15 °C for 30 h and thawed at room temperature for 12 h, and this cycle was repeated 4 times to obtain the PVA / KCl hydrogel film. Then it was immersed in 1.5 mg / mL boric acid / ammonia solution for 30 h, and taken out to obtain the boron-crosslinked PVA / KCl hydrogel film.

[0041] Preparation of self-healing covalent organic framework-based composite film: The above-prepared boron-crosslinked PVA / KCl hydrogel film, 0.58 g (2 mmol) tris(4-aminophenyl)amine, 0.30 g (1 mmol) 3,3',5,5'-tetraformyl-4,4'-dihydroxybiphenyl, 0.22 g (1 mmol) 2,6-diformyl-1,5-dihydroxynaphthalene and 10 mL of ethanol were stirred at room temperature for 4 h. The hydrogel film was taken out and washed three times with deionized water to obtain the self-healing covalent organic framework-based composite film. Then, the boron-crosslinked PVA / KCl hydrogel film (1.8×2.2×0.1 cm 3 ) was used as the electrolyte and separator and placed between two prepared self-healing covalent organic framework-based composite films (1.5×2×0.1 cm 3 ) as the electrode materials. Two identical carbon cloths were used as current collectors, and the device was encapsulated under a pressure of ~0.5 MPa to obtain a quasi-solid-state symmetric supercapacitor. The prepared quasi-solid-state symmetric supercapacitor exhibited a specific capacitance of 413 mF cm -2 at a current density of 2 mA cm -2 and an energy density of 58 μW cm -2 . And three series-connected quasi-solid-state symmetric supercapacitors could easily power an LED and remained bright after strong mechanical deformations such as stretching and bending. After testing, the obtained self-healing covalent organic framework-based composite film also had good self-healing performance.

[0042] Example 5

[0043] Preparation of boron-crosslinked PVA / KCl hydrogel film: 10 mL of 10 wt.% transparent PVA gel solution was stirred at 85 °C for 2 h, then 3 mL of 2 mol / L potassium chloride (KCl) solution was added and stirred continuously for 30 min. The stirred mixture was poured into a mold (1.5×2×0.1 cm 3 ), frozen at -15 °C for 15 h, and thawed at room temperature for 12 h. This cycle was repeated 3 times to obtain the PVA / KCl hydrogel film. Then it was immersed in 1.2 mg / mL boric acid / ammonia solution for 24 h, and taken out to obtain the boron-crosslinked PVA / KCl hydrogel film.

[0044] Preparation of self-healing covalent organic framework-based composite film: The boron-crosslinked PVA / KCl hydrogel film prepared above, 0.33 g (2 mmol) of 2,3,5,6-tetra(amino)benzoquinone, 0.60 g (2 mmol) of 3,3',5,5'-tetraformyl-4,4'-dihydroxybiphenyl and 10 mL of ethanol were stirred at room temperature for 5 h. The hydrogel film was taken out and washed three times with deionized water to obtain the self-healing covalent organic framework-based composite film. Then, the boron-crosslinked PVA / KCl hydrogel film (1.8×2.2×0.1 cm 3 ) was used as the electrolyte and separator and placed between two prepared self-healing covalent organic framework-based composite films (1.5×2×0.1 cm 3 ) as the electrode materials, and two identical carbon cloths were used as current collectors. The device was encapsulated under a pressure of ~0.5 MPa to obtain a quasi-solid-state symmetric supercapacitor. The prepared quasi-solid-state symmetric supercapacitor exhibited a specific capacitance of 478 mF cm -2 and an energy density of 67 μW cm -2 at a current density of 2 mA cm -2 . Moreover, three series-connected quasi-solid-state symmetric supercapacitors could easily power an LED and remained bright after strong mechanical deformations such as stretching and bending. After testing, the obtained self-healing covalent organic framework-based composite film also had good self-healing properties.

Claims

1. A self-healing covalent organic framework-based composite membrane, characterized in that: Add potassium chloride (KCl) solution to the PVA gel solution and stir continuously. Then, obtain the PVA / KCl hydrogel film through freeze-thaw cycles, and immerse it in boric acid / ammonia solution to obtain the boron-crosslinked PVA / KCl hydrogel film. Then, the covalent organic framework is composited onto the boron-crosslinked PVA / KCl hydrogel film by in-situ polymerization growth.

2. A preparation method of a self-healing covalent organic framework-based composite membrane, comprising the following steps: (1) Add potassium chloride (KCl) solution to the PVA gel solution and stir continuously. Then, obtain the PVA / KCl hydrogel film through freeze-thaw cycles, and immerse it in boric acid / ammonia solution to obtain the boron-crosslinked PVA / KCl hydrogel film. (2) Through in-situ growth, react amino monomers and aldehyde monomers on the surface of the above boron-crosslinked PVA / KCl hydrogel film to synthesize a covalent organic framework. Then, take out the composite hydrogel film and wash it to obtain the self-healing covalent organic framework-based composite membrane.

3. The preparation method according to claim 2, wherein: The concentration of the PVA gel solution in step (1) is 5-20 wt%; the concentration of the potassium chloride solution is 1-6 mol / L.

4. The preparation method according to claim 2, characterized in that: The freeze-thaw cycle in step (1) includes: pouring the stirred mixture into a mold, freezing it at -15 °C for 12-36 h, and thawing it at room temperature for 12 h, and repeating this cycle 2-5 times.

5. The preparation method according to claim 2, characterized in that: The concentration of the boric acid / ammonia solution in step (1) is 0.5-2 mg / mL; the immersion time is 12-36 h.

6. The preparation method according to claim 2, wherein: The amino monomers in step (2) are one or more of p-phenylenediamine, 3,3'-dihydroxy-4,4'-biphenyldiamine, tris(4-aminophenyl)amine, 2,3,5,6-tetra(amino)benzoquinone.

7. The preparation method according to claim 2, characterized in that: The aldehyde monomers in step (2) are one or more of phloroglucinol trialdehyde, 3,3',5,5'-tetraaldehyde-4,4'-dihydroxybiphenyl, 2,6-dialdehyde-1,5-dihydroxynaphthalene, 1,3,5-tris(2-formylpyridin-5-yl)benzene.

8. The preparation method according to claim 2, characterized in that: The molar ratio of the amino monomers to the aldehyde monomers in step (2) is 1-2:

1.

9. Application of a self-healing covalent organic framework-based composite membrane as described in claim 1 in a quasi-solid-state symmetric supercapacitor.

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