A cof / polyacrylonitrile composite fiber and a method for preparing the same

Abstract

The application provides a COF / polyacrylonitrile composite fiber and a preparation method thereof, and the preparation method comprises the following steps: (1) dissolving p-phenylenediamine and polyacrylonitrile in an organic solvent to obtain a spinning solution; (2) performing fiberization on the spinning solution to obtain a p-phenylenediamine / polyacrylonitrile composite fiber; and (3) adding the p-phenylenediamine / polyacrylonitrile composite fiber into a precursor solution to perform a solvothermal reaction, and obtaining a COF / polyacrylonitrile composite fiber; wherein the precursor solution contains trihydroxybenzophenone. The COF / polyacrylonitrile composite fiber provided by the application has high strength and high COF loading rate, and the preparation method is simple and has high production efficiency.

Description

Technical Field

[0001] This invention relates to the field of functional fiber technology, and in particular to a COF / polyacrylonitrile composite fiber and its preparation method. Background Technology

[0002] Covalent organic frameworks (COFs) are porous crystalline polymer materials consisting of repeating structural units linked by covalent bonds, extending into a regular geometric framework. Their structure is similar to that of inorganic materials such as zeolites and coordination materials such as organometallic frameworks. They have controllable crystal structures, high chemical and thermal stability, ordered pore structures, and large specific surface areas, and can be used for applications such as gas storage and separation, energy storage, catalysis, and molecular separation.

[0003] Furthermore, COF's excellent crystallinity gives it superior theoretical mechanical strength at the molecular level, making it a promising candidate for producing high-strength functional fibers. However, COF's high molecular weight and high crystallinity make it difficult to dissolve in solvents to form high-viscosity solutions, which makes spinning extremely difficult and hinders the preparation of COF fibers with both high strength and high loading capacity. Summary of the Invention

[0004] This invention provides a COF / polyacrylonitrile composite fiber and its preparation method. The COF / polyacrylonitrile composite fiber has both high strength and high COF loading rate, and the preparation method is simple and has high production efficiency.

[0005] In a first aspect, the present invention provides a method for preparing COF / polyacrylonitrile composite fibers, the method comprising the following steps:

[0006] (1) Dissolve p-phenylenediamine and polyacrylonitrile in an organic solvent to obtain a spinning solution;

[0007] (2) The spinning solution is subjected to fiber formation to obtain p-phenylenediamine / polyacrylonitrile composite fiber;

[0008] (3) The p-phenylenediamine / polyacrylonitrile composite fiber is added to the precursor solution for a solvothermal reaction to obtain the COF / polyacrylonitrile composite fiber; wherein the precursor solution contains trialdehyde phloroglucinol.

[0009] Preferably, in step (1), the mass ratio of p-phenylenediamine to polyacrylonitrile in the spinning solution is (1-3):1.

[0010] Preferably, in step (1), the mass concentration of polyacrylonitrile in the spinning solution is 10-15 wt%.

[0011] Preferably, in step (1), the organic solvent is at least one of dimethyl sulfoxide and N,N-dimethylformamide.

[0012] Preferably, in step (2), the fiber forming is performed using a fiber spinning device.

[0013] More preferably, the spinning speed is 2500-4500 rpm.

[0014] Preferably, in step (2), the diameter of the p-phenylenediamine / polyacrylonitrile composite fiber is 20-50 μm.

[0015] Preferably, in step (2), the spinning solution is spun to obtain nascent fibers; the nascent fibers are placed in a coagulation bath to precipitate the p-phenylenediamine / polyacrylonitrile composite fiber.

[0016] More preferably, the coagulation bath is water.

[0017] Preferably, in step (3), the precursor solution is obtained by dissolving trialdehyde phloroglucinol in a solvent;

[0018] The concentration of trialdehyde phloroglucinol in the precursor solution is 0.015–0.024 mol / L.

[0019] More preferably, the solvent is dichloromethane.

[0020] Preferably, in step (3), the molar ratio of p-phenylenediamine and trialdehyde-resorcinol in the p-phenylenediamine / polyacrylonitrile composite fiber is 3:2.

[0021] Preferably, in step (3), the temperature of the solvothermal reaction is 120-150°C and the time is 3-5 days.

[0022] Preferably, step (3) further includes: after the solvothermal reaction, a pre-made composite fiber is obtained, and the pre-made composite fiber is washed and dried in sequence to obtain the COF / polyacrylonitrile composite fiber.

[0023] In a second aspect, the present invention also provides COF / polyacrylonitrile composite fibers prepared by the method for preparing COF / polyacrylonitrile composite fibers provided in the first aspect above.

[0024] Preferably, the diameter of the COF / polyacrylonitrile composite fiber is 10–30 μm.

[0025] Compared with the prior art, the present invention has at least the following beneficial effects:

[0026] This invention proposes a two-step method for preparing COF / polyacrylonitrile composite fibers using immersion spinning and solvothermal methods. This method not only solves the problem of poor COF solubility and difficulty in spinning, but also increases the COF loading in the composite fiber while maintaining its high strength. Furthermore, the preparation method provided by this invention does not require high pressure, uses simple equipment, and has high production efficiency, showing promising application prospects in the industrialization of COF fibers.

[0027] This invention utilizes a spinning and heating device to prepare COF / polyacrylonitrile composite fibers, resulting in a simple process. Furthermore, polyacrylonitrile raw materials are relatively inexpensive, making this preparation method cost-effective. The coagulation bath uses water, making the fiber-forming process green and non-toxic. This invention allows for the preparation of spinning solutions with a wide range and varying mass ratios, enabling the control of the viscosity of the spinning solution and spinning parameters, thereby controlling the overall performance of the composite fibers.

[0028] The COF / polyacrylonitrile composite fiber prepared by this invention has a tensile strength of not less than 320 MPa and a diameter of 10–30 μm, showing potential for industrial production. COF / polyacrylonitrile composite fibers have broad application prospects in gas storage and separation, as well as in wearable smart sensors. Attached Figure Description

[0029] Figure 1 This is a flowchart of a method for preparing COF / polyacrylonitrile composite fiber provided in an embodiment of the present invention;

[0030] Figure 2 This is a physical image of a p-phenylenediamine / polyacrylonitrile composite fiber provided in an embodiment of the present invention;

[0031] Figure 3 This is a SEM image of a p-phenylenediamine / polyacrylonitrile composite fiber provided in an embodiment of the present invention;

[0032] Figure 4 This is a physical image of a COF / polyacrylonitrile composite fiber provided in an embodiment of the present invention;

[0033] Figure 5 This is a SEM image of a COF / polyacrylonitrile composite fiber provided in an embodiment of the present invention;

[0034] Figure 6 This is a cross-sectional SEM image of a COF / polyacrylonitrile composite fiber provided in an embodiment of the present invention;

[0035] Figure 7 This is a mechanical tensile property diagram of a COF / polyacrylonitrile composite fiber provided in an embodiment of the present invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0037] This invention provides a method for preparing COF / polyacrylonitrile composite fibers, such as... Figure 1 As shown, it includes the following steps:

[0038] (1) Dissolve p-phenylenediamine and polyacrylonitrile in an organic solvent to obtain a spinning solution;

[0039] (2) The spinning solution is subjected to fiber formation to obtain p-phenylenediamine / polyacrylonitrile composite fiber;

[0040] (3) The p-phenylenediamine / polyacrylonitrile composite fiber is added to the precursor solution for a solvothermal reaction to obtain COF / polyacrylonitrile composite fiber; wherein the precursor solution contains trialdehyde phloroglucinol.

[0041] Currently, COF fiber preparation methods include electrospinning and wet spinning. Electrospinning typically requires high-pressure conditions, uses toxic solvents, and has a low COF loading rate; while wet spinning results in low COF fiber yield and insufficient mechanical properties, and neither method allows for rapid, large-scale production. This invention proposes a two-step method for preparing COF / polyacrylonitrile composite fibers using immersion spinning and a solvothermal method. The spinning solution containing p-phenylenediamine is used to form p-phenylenediamine / polyacrylonitrile composite fibers. These fibers are then subjected to a solvothermal reaction with trialdehyde-resorcinol to obtain continuous COF / polyacrylonitrile composite fibers. This preparation method not only solves the problem of poor COF solubility and difficulty in spinning but also increases the COF loading rate while maintaining the high strength of the composite fiber. Furthermore, the preparation method provided by this invention does not require high pressure, uses simple equipment, and has high production efficiency, showing promising application prospects in the industrialization of COF fibers.

[0042] According to some preferred embodiments, in step (1), the mass concentration of polyacrylonitrile in the spinning solution is 10-15 wt% (for example, it can be 10 wt%, 10.5 wt%, 11 wt%, 11.5 wt%, 12 wt%, 12.5 wt%, 13 wt%, 13.5 wt%, 14 wt%, 14.5 wt%, or 15 wt%).

[0043] In this invention, experiments have confirmed that, in order to obtain p-phenylenediamine / polyacrylonitrile composite fibers, if the mass concentration of polyacrylonitrile in the spinning solution is below 10 wt%, the viscosity of the spinning solution is too low, resulting in poor fiber continuity, or even failure to form fibers or electrospraying. If the mass concentration of polyacrylonitrile is above 15 wt%, the concentration of the spinning solution is too high, resulting in high viscosity. Subsequent addition of p-phenylenediamine will further increase the viscosity, leading to a large number of droplets during fiber formation and making fiber formation difficult. Therefore, by adjusting the mass concentration of polyacrylonitrile in the spinning solution, p-phenylenediamine / polyacrylonitrile composite fibers with different diameters can be obtained, thus determining the final COF / polyacrylonitrile composite fiber.

[0044] According to some preferred embodiments, in step (1), the mass ratio of p-phenylenediamine to polyacrylonitrile in the spinning solution is (1-3):1 (for example, it can be 1:1, 1.05:1, 1.1:1, 1.15:1, 1.2:1, 1.25:1, 1.3:1, 1.35:1, 1.4:1, 1.45:1, 1.5:1, 1.55:1, 1.6:1, 1.65:1, 1.7:1, 1.75:1, 1.8:1, 1.85:1, 1.9:1, 1.95:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1 or 3:1).

[0045] In this invention, experiments have confirmed that if the amount of p-phenylenediamine in the spinning solution is too low, the content of organic monomers used to prepare COF will be too low, which will reduce the loading rate of COF in the final COF / polyacrylonitrile composite fiber; if the amount of p-phenylenediamine in the spinning solution is too high, it will increase the viscosity of the spinning solution, affect the continuity of fiber formation, and even make it difficult to form fibers.

[0046] According to some preferred embodiments, in step (1), the organic solvent is at least one of dimethyl sulfoxide and N,N-dimethylformamide.

[0047] According to some preferred embodiments, in step (2), fiber formation is performed by a spinning device.

[0048] According to some preferred embodiments, the spinning speed is 2500 to 4500 rpm (for example, it can be 2500 rpm, 2600 rpm, 2800 rpm, 3000 rpm, 3200 rpm, 3500 rpm, 3800 rpm, 4000 rpm, 4200 rpm, 4400 rpm or 4500 rpm).

[0049] According to some preferred embodiments, in step (2), the spinning solution is spun to obtain nascent fibers; the nascent fibers are placed in a coagulation bath to precipitate p-phenylenediamine / polyacrylonitrile composite fibers.

[0050] According to some preferred embodiments, the coagulation bath is water.

[0051] Specifically, a spinning solution with a certain viscosity is ejected through a high-speed rotating spinneret of a spinning equipment. The spinning solution jet comes into contact with a coagulation bath, which causes the nascent fiber to coagulate and solidify. The fiber is collected and then washed and dried to obtain continuous p-phenylenediamine / polyacrylonitrile composite fiber.

[0052] In this invention, immersion spinning is achieved using a spinning device, eliminating the need for high-pressure and toxic solvent coagulation baths, thus enabling the preparation of continuous COF / polyacrylonitrile fibers with high loading rates. Furthermore, this process boasts extremely high production efficiency, achieving a fiber production rate of 2g per minute compared to electrospinning, and holds immense promise for the industrialization of COF fibers.

[0053] According to some preferred embodiments, in step (2), the diameter of the p-phenylenediamine / polyacrylonitrile composite fiber is 20 to 50 μm (for example, it can be 20 μm, 22 μm, 25 μm, 28 μm, 30 μm, 35 μm, 40 μm, 42 μm, 45 μm, 48 μm or 50 μm).

[0054] In this invention, by adjusting the composition of the spinning solution and the spinning parameters, p-phenylenediamine / polyacrylonitrile composite fibers with different diameters can be obtained, thereby determining the final COF / polyacrylonitrile composite fiber.

[0055] According to some preferred embodiments, in step (3), the precursor solution is obtained by dissolving trialdehyde phloroglucinol in a solvent;

[0056] The concentration of trialdehyde phloroglucinol in the precursor solution is 0.015–0.024 mol / L (e.g., 0.015 mol / L, 0.0155 mol / L, 0.016 mol / L, 0.017 mol / L, 0.018 mol / L, 0.019 mol / L, 0.02 mol / L, 0.021 mol / L, 0.022 mol / L, 0.023 mol / L, or 0.024 mol / L).

[0057] According to some preferred embodiments, the solvent is dichloromethane.

[0058] According to some preferred embodiments, in step (3), the molar ratio of p-phenylenediamine and trialdehyde phloroglucinol in the p-phenylenediamine / polyacrylonitrile composite fiber is 3:2.

[0059] In this invention, based on the above molar ratio of p-phenylenediamine and trialdehyde phloroglucinol and the mass ratio of p-phenylenediamine and polyacrylonitrile in the spinning solution, the loading rate of COF in the prepared COF / polyacrylonitrile composite fiber is theoretically calculated to be approximately 69.63 wt% to 81.77 wt%.

[0060] According to some preferred embodiments, in step (3), the temperature of the solvothermal reaction is 120-150°C (e.g., 120°C, 125°C, 130°C, 135°C, 140°C, 145°C or 150°C), and the time is 3-5 days (e.g., 3 days, 3.5 days, 4 days, 4.5 days or 5 days).

[0061] In this invention, p-phenylenediamine and trialdehyde phloroglucinol are used as organic monomers for preparing COF. After a solvothermal reaction, the two organic monomers are covalently linked to obtain COF. Since p-phenylenediamine is uniformly distributed on the surface and inside of the p-phenylenediamine / polyacrylonitrile composite fiber, and the p-phenylenediamine / polyacrylonitrile composite fiber is placed in a trialdehyde phloroglucinol solution, COF will grow in situ on the surface and inside of the composite fiber, resulting in COF / polyacrylonitrile composite fiber with COF uniformly distributed on the surface and inside.

[0062] According to some preferred embodiments, step (3) further includes: after the solvothermal reaction, a pre-made composite fiber is obtained, and the pre-made composite fiber is washed and dried in sequence to obtain COF / polyacrylonitrile composite fiber.

[0063] Specifically, the precursor solution is placed in a reaction vessel, and p-phenylenediamine / polyacrylonitrile composite fibers are weighed and added to the vessel. The reaction vessel is then sealed and placed in an oven at 120–150°C for a solvothermal reaction for 3–5 days. After the reaction, the fibers are separated from the solution and washed sequentially with deionized water and ethanol, then dried in a vacuum oven at 60°C for 12 hours to obtain COF / polyacrylonitrile composite fibers. It should be noted that washing is to remove solvent and unreacted organic monomers.

[0064] The present invention also provides a COF / polyacrylonitrile composite fiber, which is prepared by the above preparation method.

[0065] According to some preferred embodiments, the diameter of the COF / polyacrylonitrile composite fiber is 10 to 30 μm (e.g., it can be 10 μm, 10.5 μm, 11 μm, 12 μm, 14 μm, 15 μm, 16 μm, 18 μm, 20 μm, 22 μm, 24 μm, 25 μm, 26 μm, 28 μm or 30 μm).

[0066] The COF / polyacrylonitrile composite fiber prepared by this invention has a tensile strength of not less than 320 MPa and a diameter of 10-30 μm, and has the potential for industrial production.

[0067] To more clearly illustrate the technical solution and advantages of the present invention, the following examples provide a detailed description of a COF / polyacrylonitrile composite fiber and its preparation method.

[0068] The spun wire equipment used in the following examples and comparative examples is a high-speed rotary shear machine, model: Pingxuan Scientific AD300L-H.

[0069] Example 1

[0070] s1. Dissolve 3g of p-phenylenediamine and 1.5g of polyacrylonitrile in 10mL of dimethyl sulfoxide and stir magnetically for 2h to ensure complete dissolution, thereby obtaining a spinning solution;

[0071] s2. Prepare the coagulation bath by using 2L of deionized water.

[0072] s3. Preparation of p-phenylenediamine / polyacrylonitrile composite fibers: The spinning solution is injected into a spinning device and spun at 3000 rpm. Simultaneously, the fibers are collected using a coagulation bath collection device. After washing and drying, p-phenylenediamine / polyacrylonitrile composite fibers are obtained (e.g., Figure 2 , Figure 3 (as shown);

[0073] s4. Weigh 85.5 mg of trialdehyde phloroglucinol and dissolve it in 20 mL of dichloromethane. After sonication for 5 min, obtain the precursor solution and pour it into a 100 mL reaction vessel. Weigh 100 mg of the p-phenylenediamine / polyacrylonitrile composite fiber prepared in s3 and add it to the reaction vessel. Then seal the reaction vessel.

[0074] s5. Place the reactor from s4 in a 120℃ forced-air drying oven for a solvothermal reaction. After 3 days of reaction, separate the fibers from the solution, then wash with deionized water and ethanol, and dry in a 60℃ vacuum oven for 12 hours to obtain COF / polyacrylonitrile composite fibers (e.g. Figure 4 , Figure 5 and Figure 6 (As shown).

[0075] Example 2

[0076] s1. Dissolve 3g of p-phenylenediamine and 1g of polyacrylonitrile in 10mL of dimethyl sulfoxide and stir magnetically for 2h to ensure complete dissolution, thereby obtaining a spinning solution;

[0077] s2. Prepare the coagulation bath by using 2L of deionized water.

[0078] s3. Preparation of p-phenylenediamine / polyacrylonitrile composite fiber: The spinning solution is injected into the spinning equipment and spun at 3000 rpm. At the same time, the fiber is collected by the coagulation bath collection device. After washing and drying, p-phenylenediamine / polyacrylonitrile composite fiber is obtained.

[0079] s4. Weigh 97.2 mg of trialdehyde phloroglucinol and dissolve it in 20 mL of dichloromethane. After sonication for 5 min, the precursor solution is obtained and poured into a 100 mL reaction vessel. Weigh 100 mg of p-phenylenediamine / polyacrylonitrile composite fiber prepared in s3 and add it to the reaction vessel. Then seal the reaction vessel.

[0080] s5. Place the reactor in s4 in a 120℃ drying oven for a solvothermal reaction. After 3 days of reaction, separate the fiber from the solution, wash it with deionized water and ethanol, and then dry it in a 60℃ vacuum oven for 12 hours to obtain COF / polyacrylonitrile composite fiber.

[0081] Example 3

[0082] s1. Dissolve 1.5g of p-phenylenediamine and 1.5g of polyacrylonitrile in 10mL of dimethyl sulfoxide and stir magnetically for 2h to ensure complete dissolution, thereby obtaining a spinning solution;

[0083] s2. Prepare the coagulation bath by using 2L of deionized water.

[0084] s3. Preparation of p-phenylenediamine / polyacrylonitrile composite fiber: The spinning solution was injected into the spinning equipment and spun at 4500 rpm. At the same time, the fiber was collected using a coagulation bath collection device. After washing and drying, p-phenylenediamine / polyacrylonitrile composite fiber was obtained.

[0085] s4. Weigh 64.8 mg of trialdehyde phloroglucinol and dissolve it in 20 mL of dichloromethane. After sonication for 5 min, the precursor solution is obtained and poured into a 100 mL reaction vessel. Weigh 100 mg of p-phenylenediamine / polyacrylonitrile composite fiber prepared in s3 and add it to the reaction vessel. Then seal the reaction vessel.

[0086] s5. Place the reactor in s4 in a 120℃ drying oven for a solvothermal reaction. After 3 days of reaction, separate the fiber from the solution, wash it with deionized water and ethanol, and then dry it in a 60℃ vacuum oven for 12 hours to obtain COF / polyacrylonitrile composite fiber.

[0087] Example 4

[0088] Example 4 is basically the same as Example 1, except that:

[0089] The solvothermal reaction in step s5 is carried out at 120°C for 5 days.

[0090] Example 5

[0091] Example 5 is basically the same as Example 1, except that:

[0092] The solvothermal reaction in step s5 is carried out at 150°C for 3 days.

[0093] Comparative Example 1

[0094] s1. Dissolve 3g of p-phenylenediamine and 1.5g of polyacrylonitrile in 10mL of dimethyl sulfoxide and stir magnetically for 2h to ensure complete dissolution, thereby obtaining a spinning solution;

[0095] s2. Prepare the coagulation bath by using 2L of deionized water.

[0096] s3. Preparation of p-phenylenediamine / polyacrylonitrile composite fibers: The spinning solution is injected into a spinning device and spun at 3000 rpm. Simultaneously, the fibers are collected using a coagulation bath collection device. After washing and drying, p-phenylenediamine / polyacrylonitrile composite fibers are obtained (e.g., Figure 2 , Figure 3 (As shown).

[0097] The tensile strength properties of the COF / polyacrylonitrile composite fibers prepared in Examples 1 to 5 and the fiber in Comparative Example 1 were tested, and the performance data are shown in Table 1.

[0098] Specifically, the tensile strength test method is uniaxial tensile test, and the standard is GB / T14337-2022.

[0099] Table 1

[0100]

[0101] As shown in Table 1, the tensile strength of the COF / polyacrylonitrile composite fiber prepared in the embodiments of the present invention is not less than 320 MPa. Compared with Comparative Example 1, the COF / polyacrylonitrile composite fiber in Example 1, due to the addition of COF and the mechanical interlocking effect between the COF and polyacrylonitrile molecular chains, has significantly improved the overall mechanical properties of the fiber. Meanwhile, through comparison... Figure 3 and Figure 5 It can be observed that before the solvothermal reaction, the surface of the p-phenylenediamine / polyacrylonitrile composite fiber is smooth, but after the solvothermal reaction, the formation of COF results in a spherical structure on the fiber surface; and as... Figure 6 As shown, the cross-sectional surface of the COF / polyacrylonitrile composite fiber exhibits a uniform spherical structure, thus confirming that COF is uniformly distributed both inside and on the surface of the COF / polyacrylonitrile composite fiber. The COF / polyacrylonitrile composite fiber prepared by this invention has a high COF loading, and the process equipment is simple yet complex, enabling rapid mass production.

[0102] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these 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. The parts of the present invention not described in detail are techniques known to those skilled in the art.

Claims

1. A method for producing a COF / polyacrylonitrile composite fiber, characterized by, The preparation method comprises the following steps: (1) dissolving p-phenylenediamine and polyacrylonitrile in an organic solvent to obtain a spinning solution; (2) performing fiberization on the spinning solution to obtain p-phenylenediamine / polyacrylonitrile composite fibers with a diameter of 20-50 μm; the fiberization is performed by using a spinning device at a rotation speed of 2500-4500 rpm; (3) adding the p-phenylenediamine / polyacrylonitrile composite fibers into a precursor solution to perform a solvothermal reaction, so as to obtain COF / polyacrylonitrile composite fibers with COFs uniformly distributed on the surface and inside; the precursor solution comprises triformylphloroglucinol, and the molar ratio of p-phenylenediamine to triformylphloroglucinol in the p-phenylenediamine / polyacrylonitrile composite fibers is 3:2; the solvothermal reaction is performed at a temperature of 120-150 ℃ for 3-5 days; the precursor solution is obtained by dissolving triformylphloroglucinol in a solvent.

2. The production method according to claim 1, characterized by, In step (1), the mass ratio of p-phenylenediamine to polyacrylonitrile in the spinning solution is (1-3):

1.

3. The preparation method according to claim 1, characterized in that, In step (1), the mass concentration of polyacrylonitrile in the spinning solution is 10-15 wt%.

4. The method of claim 1, wherein, In step (1), the organic solvent is at least one of dimethyl sulfoxide and N,N-dimethylformamide.

5. The method of claim 1, wherein, In step (2), the spinning solution is spun to obtain nascent fibers; the nascent fibers are placed in a coagulation bath to precipitate the p-phenylenediamine / polyacrylonitrile composite fibers.

6. The preparation method according to claim 5, characterized in that, The coagulation bath is water.

7. The preparation method according to claim 1, characterized in that, In step (3), the concentration of triformylphloroglucinol in the precursor solution is 0.015-0.024 mol / L.

8. The production method according to claim 7, characterized by, The solvent in the precursor solution is dichloromethane.

9. The method of claim 1, wherein, In step (3), further comprising: after the solvothermal reaction, a preformed composite fiber is obtained, and the preformed composite fiber is sequentially washed and dried to obtain the COF / polyacrylonitrile composite fibers.

10. A COF / polyacrylonitrile composite fiber, characterized by, The preparation method is prepared by using any one of the preparation methods in claims 1-9.

Images