A ZIF-based nano-hybrid flame retardant, its preparation method and application

Abstract

This invention relates to the field of flame retardant materials technology, and discloses a ZIF-based nano-hybrid flame retardant, its preparation method, and its application. The preparation method is as follows: cobalt nitrate hexahydrate is dissolved in a solvent, aluminum diethylphosphinate is added, and the mixture is stirred at room temperature; then 2-methylimidazole solution is added, and the mixture is stirred at room temperature; after the reaction is complete, the mixture is centrifuged, the precipitate is washed, and the precipitate is vacuum dried to obtain the ZIF-based nano-hybrid flame retardant. This invention achieves structural coupling between MOFs and phosphorus-based flame retardants by in-situ growing ZIF-67 on the surface of ADP, thereby overcoming the problems of insufficient flame retardant efficiency, poor char layer quality, and poor interfacial compatibility in the prior art. In the application of epoxy resins, it can significantly improve the flame retardant performance, smoke suppression performance, and comprehensive mechanical properties of epoxy resins.

Description

Technical Field

[0001] This invention relates to the field of flame retardant materials technology, specifically to a ZIF-based nano-hybrid flame retardant, its preparation method, and its application. Background Technology

[0002] Epoxy resin (EP) is a commonly used thermosetting resin with advantages such as high strength, impact resistance, water resistance, electrical insulation, and good thermal stability, making it widely used in construction, coatings, and electronic packaging materials. However, EP is flammable and releases large amounts of toxic gases when burned, posing a serious threat to its practical applications. Adding flame retardants to EP composites is considered an effective method to improve their flame retardancy.

[0003] Aluminum diethylphosphonate (ADP) is a widely used flame retardant with good thermal stability and flame retardant effect. Compared with the traditionally used ammonium polyphosphate, the ethyl group in the molecular structure of ADP can significantly improve its hydrophobic properties and enhance its interfacial compatibility with EP. Moreover, its thermal decomposition temperature is higher than that of ammonium polyphosphate (APP), making it more suitable for high-temperature processing environments. However, when ADP is used alone, it still faces the problems of insufficient flame retardant efficiency and decreased mechanical properties.

[0004] Metal-organic frameworks (MOFs) exhibit potential advantages in catalysis, adsorption, and flame retardancy due to their high specific surface area, porous structure, and tunable composition. However, direct doping of MOFs into polymer matrices often leads to aggregation and poor interfacial compatibility, hindering the full realization of their synergistic flame-retardant effects. Zeolite imidazole ester framework material (ZIF-67) is composed of transition metal ions (Co... 2+ Metal-organic frameworks (MOFs) formed by the self-assembly of imidazole organic ligands via coordination bonds have crystal structures similar to traditional zeolites, but with imidazole-based ligands replacing the oxygen bridges in the silicon-oxygen tetrahedra, resulting in a highly symmetric hierarchical porous structure. The pore size is tunable in the range of 0.3-3.4 nm, and the specific surface area typically reaches 1000-2000 m² / g. ZIF-67's unique advantage lies in its chemical designability: by selecting different metal nodes (Co in ZIF-67...), 2+ZIF-67 can be precisely controlled by using functionalized imidazole ligands (such as 2-methylimidazole) to regulate its porosity, thermal stability, and surface functional groups (such as -NH2 and -OH). Furthermore, ZIF-67 has mild synthesis conditions (atmospheric pressure and room temperature) and can be mass-produced via solvothermal, microwave, or mechanochemical methods, demonstrating excellent potential for industrial applications. In the flame retardant field, the porous structure and chemical activity of ZIF-67 endow it with dual functions: on the one hand, its high specific surface area can adsorb pyrolysis gases and delay heat transfer; on the other hand, the metal nodes can catalyze the formation of a dense char layer in polymers at high temperatures, while the nitrogen-containing gases released by the thermal decomposition of imidazole ligands can dilute the oxygen concentration, achieving synergistic flame retardancy between the condensed and gas phases.

[0005] However, ZIF-67 has limited flame retardant efficiency when used alone, and there is currently no research on combining ADP with ZIF-67 to improve the synergistic flame retardant effect, especially in terms of in-situ composite and interface control at the nanoscale, there is a lack of systematic methods. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the existing technology and provide an ADP-coated ZIF-67 ZIF-based nano-hybrid flame retardant, its preparation method and application.

[0007] To achieve the above objectives, the technical solution of the present invention is: a method for preparing a ZIF-based nano-hybrid flame retardant, characterized by comprising the following steps: (1) Dissolve cobalt nitrate hexahydrate in a solvent to prepare a cobalt nitrate solution; (2) Add aluminum diethylphosphinate to the cobalt nitrate solution and stir the reaction at room temperature; (3) Dissolve 2-methylimidazole in a solvent to prepare a 2-methylimidazole solution, and then add the 2-methylimidazole solution to the reaction solution in step (2) and stir the reaction at room temperature; (4) After the reaction is complete, centrifuge and wash the precipitate multiple times with anhydrous ethanol. The light purple powder after vacuum drying of the precipitate is the ZIF-based nano-hybrid flame retardant.

[0008] Further; the mass-to-volume ratio of the cobalt nitrate hexahydrate solution to the solvent in step (1) is (0.5~1) g: 100 mL.

[0009] Further; in step (2), the mass ratio of aluminum diethylphosphonate to cobalt nitrate hexahydrate is 4:(1~2), and the reaction time is 2~3h.

[0010] Further; in step (3), the mass ratio of 2-methylimidazole to cobalt nitrate hexahydrate is (5~6):1, the reaction time is 10~12h, and the molar concentration of the 2-methylimidazole solution is 1~2mol / L.

[0011] Further; in step (4), centrifuge at 5000 rpm and vacuum dry at 60℃ for 10~15h.

[0012] Furthermore, the solvent is anhydrous ethanol.

[0013] Another technical solution of the present invention is: a ZIF-based nano-hybrid flame retardant prepared by a method for preparing the aforementioned ZIF-based nano-hybrid flame retardant.

[0014] Another technical solution of the present invention is: the application of the ZIF-based nano-hybrid flame retardant in epoxy resin: the ZIF-based nano-hybrid flame retardant and epoxy resin are mixed and stirred at 90°C for 30 min, then a curing agent is added to defoam and a curing reaction is carried out to obtain flame-retardant epoxy resin.

[0015] The beneficial effects of this invention are: (1) The addition of ZIF-67@ADP improved the mechanical properties of EP composite material. The tensile strength, flexural strength and flexural modulus of 10ZIF-67@ADP / EP were increased by 24.6%, 20.1% and 32.9% respectively compared with pure EP.

[0016] (2) The addition of ZIF-67@ADP improved the thermal stability of the EP composite material. The maximum pyrolysis temperature and char rate of 10ZIF-67@ADP / EP decreased to 419.3 ℃ and 12.5 % / min, respectively, and the glass transition temperature was increased.

[0017] (3) ZIF-67@ADP can effectively improve the thermal conductivity of EP composite material. The heating rate of 10ZIF-67@ADP / EP during the heating stage (0.099 ℃ / s) is 110.6% higher than that of pure EP (0.047 ℃ / s).

[0018] (4) The addition of ZIF-67@ADP can effectively improve the flame retardant properties of EP composite materials. The LOI of 10ZIF-67@ADP / EP is increased to 28.7%, reaching the V-0 rating of UL-94. Compared with pure EP, the PHRR, THR, PSPR, TSP, PCOP and PCO2P of 10ZIF-67@ADP / EP are reduced by 68.7%, 49.3%, 60.0%, 59.9%, 41.7% and 72.5% respectively. This shows that the addition of ZIF-67@ADP improves the flame retardant properties and safety of EP composite materials, and is suitable for fires caused by the combustion of thermosetting materials.

[0019] (5) The structure is stable. The ZIF-67 and ADP are tightly bound together through in-situ growth, avoiding the problems of MOF aggregation and shedding.

[0020] (6) By growing ZIF-67 in situ on the surface of ADP, the structural coupling of MOFs and phosphorus flame retardants is realized, thereby overcoming the problems of insufficient flame retardant efficiency, poor char layer quality and poor interfacial compatibility in the existing technology. In the application of epoxy resin, the flame retardant performance, smoke suppression performance and comprehensive mechanical properties of epoxy resin can be significantly improved. Attached Figure Description

[0021] Figure 1 These are the mechanical property diagrams of EP and flame-retardant epoxy resin samples; Figure 2 These are the TGA curves of EP and flame-retardant epoxy resin samples under a nitrogen atmosphere: (a) TGA curve; (b) TGA partial magnification curve; (c) DTG curve; (d) TGA curve. 5% and T max ;(e)R max and W 600℃ (f) DSC curve; Figure 3 (a) Schematic diagram of infrared thermal imaging device for EP and flame-retardant epoxy resin samples; (b) Temperature change curves during the heating process and (c) Cooling process. Figure 4 These are infrared thermal images of the heating and cooling processes of EP and flame-retardant epoxy resin samples. Figure 5 (a) LOI test diagrams for EP and flame-retardant epoxy resin samples; (b) photographs of the UL-94 test process and UL-94 test results. Figure 6 The following are the HRR plots, THR plots, SPR plots, and TSP plots of the EP and flame-retardant epoxy resin samples. Detailed Implementation

[0022] Example:

[0023] A method for preparing a ZIF-based nano-hybrid flame retardant 1.45 g (0.005 mol) of cobalt nitrate hexahydrate (Co(NO3)2·6H2O) was dissolved in 200 mL of anhydrous ethanol (EtOH). 4.00 g (0.010 mol) of aluminum diethylphosphonate (ADP) was added to the solution, and the mixture was stirred at room temperature for 2 h. 8.20 g (0.100 mol) of 2-methylimidazole (2-MIZ) was dissolved in 100 mL of anhydrous ethanol and added to the solution. The mixture was stirred at room temperature for 12 h. The mixture was centrifuged at 5000 rpm for 10 min, and the precipitate was washed five times with anhydrous ethanol to remove impurities. The precipitate was then dried in a vacuum oven at 60 °C for 12 h to obtain a light purple powder, which is the ZIF-based nano-hybrid flame retardant (ZIF-67@ADP).

[0024] Preparation of flame-retardant epoxy resin: Weigh each raw material according to the raw material ratio in Table 1. Add ZIF-67@ADP to EP (E-44, Yantai Yuandong Fine Chemical Co., Ltd.) and mix thoroughly. Stir at 90℃ for 30 min. Add polyamide resin (PA-650, Shanghai Aotun Chemical Technology Co., Ltd.) to the above mixture and stir evenly. Pour the mixture into a mold and transfer it to a vacuum oven (60℃) for defoaming treatment. Finally, place the defoamed mixture in an oven at 60℃ for curing for 24 h to obtain flame-retardant epoxy resin.

[0025] Table 1. Mass ratio of flame-retardant epoxy resin raw materials

[0026] Performance tests were performed on pure EP and flame-retardant epoxy resin samples. 1. Mechanical property analysis The tensile and flexural strengths of the samples were tested using a universal testing machine (RMES-100B). The tensile test was conducted at a speed of 10 mm / min, and the flexural test at a speed of 2 mm / min, in accordance with ASTM D638 and ASTM D790 standards.

[0027] like Figure 1As shown, the tensile strength of pure EP is 28.4 MPa, the flexural strength is 56.6 MPa, and the flexural modulus is 1440.9 MPa. With the addition of ZIF-67@ADP, the mechanical properties of the composite material gradually improve. The tensile strength, flexural strength, and flexural modulus of 4ZIF-67@ADP / EP are 28.9 MPa, 46.7 MPa, and 1191.1 MPa, respectively. The tensile strength (35.4 MPa), flexural strength (67.6 MPa), and flexural modulus (1914.6 MPa) of 10ZIF-67@ADP / EP are 24.6%, 20.1%, and 32.9% higher than those of pure EP, respectively. This is mainly because ZIF-67@ADP acts as a reinforcing agent in the EP matrix, improving the overall mechanical properties of the material. Comparing 10ZIF-67@ADP / EP and 10ADP / EP, it can be seen that the tensile strength of 10ZIF-67@ADP / EP is 11.7% higher than that of 10ADP / EP (31.7 MPa); the flexural strength is 29.2% higher than that of 10ADP / EP (52.0 MPa); and the flexural modulus is 11.7% higher than that of 10ADP / EP (1714.3 MPa). This indicates that ZIF-67@ADP is superior to ADP alone in improving the mechanical properties of composite materials. This is due to the special structure and chemical properties of ZIF-67@ADP, which gives it better dispersibility and interfacial compatibility in the EP matrix, thus more effectively transferring stress and improving the mechanical properties of the material. In conclusion, the addition of ZIF-67@ADP improves the mechanical properties of EP composite materials and has a good effect on the EP matrix.

[0028] 2. Thermal stability analysis Thermogravimetric analysis was used to test the thermal stability of the samples. Samples weighing approximately 5 mg were heated from 30 °C to 700 °C in a nitrogen atmosphere at a heating rate of 20 °C / min.

[0029] The glass transition temperature of the sample was measured using differential scanning calorimetry. A sample weighing approximately 10 mg was heated from -40 °C to 150 °C at a heating rate of 10 °C / min under nitrogen atmosphere.

[0030] like Figure 2 As shown, the initial decomposition temperature of pure EP (T) 5% The maximum decomposition temperature is 337.5 ℃, and the maximum decomposition temperature (T) is 337.5 ℃. max The temperature was 426.8℃, and the char residue rate (R) was... max The carbon residue at 600 °C was 18.6%. 600℃The thermal decomposition behavior indicates that EP begins thermal degradation at 337.5 °C, reaches its peak decomposition rate at 426.8 °C, and ultimately forms 4.1% char residue. The introduction of ZIF-67@ADP significantly alters the thermal stability parameters of the composite material. For 4ZIF-67@ADP / EP, its T1... 5% Temperature dropped to 321.0℃, T max R slightly increased to 425.8 ℃, R max Reduced to 17.5% / min, W 600℃ The Tdecomposition increased to 6.7%. Compared to pure EP, although the initial decomposition temperature shifted earlier, the decrease in the maximum decomposition rate and the increase in residual char indicate that the addition of ZIF-67@ADP slowed down the thermal decomposition kinetics through a physical barrier effect and promoted the formation of the char layer. When the addition amount increased to 10 wt.%, its Tdecomposition increased to 6.7%. 5% Temperature rose to 338.1 °C, an increase of 0.6 °C compared to pure EP. max It dropped to 419.3 ℃, R max Further reduced to 12.5% / min (a 32.8% decrease compared to pure EP), W 600℃ The content increased to 9.8% (an increase of 139%). This phenomenon reveals that under high loading, ZIF-67@ADP not only improves the thermal stability of the matrix through heterogeneous nucleation, but its porous structure also effectively promotes the construction of cross-linked carbon layers during pyrolysis. Compared with 10ADP / EP, its T... 5% (319.0 ℃) is 19.1 ℃ lower than 10ZIF-67@ADP / EP, R max (15.9% / min) 27.2% higher, W 600℃ (6.8%) 30.6% lower. This confirms that ZIF-67@ADP, compared to single ADP, possesses the enhanced mass transfer barrier effect of ZIFs' hierarchical porous structure; the catalytic effect of Co²⁺ promotes the formation of a dense carbon layer; and the interfacial synergy between ADP and ZIF-67 improves the thermal stability of the carbon layer. In summary, the introduction of ZIF-67@ADP enables the EP composite material to achieve triple optimization: initial decomposition temperature control, suppression of decomposition kinetics, and improvement of residual carbon content.

[0031] Glass transition temperature (T) g The temperature at which a material transitions from a glassy state to a highly elastic state is a key parameter for evaluating its properties. The temperature at which a material transitions from a glassy state to a highly elastic state is [not specified]. For pure polypropylene (EP), the temperature at which [temperature is specified] is [not specified]. g The temperature was 66.4 °C. After adding ZIF-67@ADP, T... g Significant changes have occurred in the T of 4ZIF-67@ADP. g The temperature was 69.9 °C. With increasing ZIF-67@ADP content, T... g Gradually increasing, T of 10ZIF-67@ADPg The temperature was 74.6 °C, indicating a good interaction between ZIF-67@ADP and the EP matrix, which restricts the movement of polymer chain segments and thus improves the thermal stability of the material. The T0 of ZIF-67@ADP / EP... g The temperature was significantly higher than that of 10ADP / EP (73.3 °C), attributed to the porous structure of ZIF-67@ADP providing more interfacial interactions, further restricting the movement of chain segments, compared to the T0 of 10ADP / EP. g The lower value indicates that ADP alone is less effective than ZIF-67@ADP in improving the thermal stability of EP. In conclusion, the addition of ZIF-67@ADP improves the thermal stability of EP composites. g This enhances its thermal stability.

[0032] 3. Thermal conductivity analysis like Figure 3 and Figure 4 As shown, the sample material was vertically fixed on a flat table. A 200 W heat source and an infrared camera were placed 30 cm from the front and 15 cm from the back of the material, respectively. A thermocouple was installed on the coating surface to detect the temperature. The experiment first heated the composite material, then cooled it to obtain relevant data. Under constant power irradiation, all samples were gradually heated from room temperature. The results showed that during the heating phase, the temperature of pure EP gradually increased from 24.7 °C to 59.8 °C, with a heating rate of 0.047 °C / s; while during the cooling phase, the temperature decreased from 100.5 °C to 28.5 °C, with a cooling rate of 0.096 °C / s. Its thermal conductivity was relatively stable but not very efficient. The addition of ZIF-67@ADP improved the thermal conductivity of the composite material. During the heating phase, the temperature of 10ZIF-67@ADP / EP rapidly increased from 24.8 ℃ to 99.1 ℃, with a heating rate (0.099 ℃ / s) increasing by 110.6%, and a maximum temperature difference of 39.3 ℃. During the cooling phase, the temperature rapidly decreased from 100.3 ℃ to 23.0 ℃, with a cooling rate (0.103 ℃ / s) increasing by 7.3%, and a maximum temperature difference of 5.5 ℃. This is mainly attributed to the porous structure of ZIF-67@ADP and the high thermal conductivity of ADP, which together facilitated rapid heat transfer. Further comparison of the thermal conductivity of 10ZIF-67@ADP / EP and 10ADP / EP revealed that 10ZIF-67@ADP / EP exhibited a more rapid temperature change during both heating and cooling processes. This indicates that ZIF-67@ADP not only retains the thermal conductivity of ADP but also further enhances the thermal conductivity efficiency of the composite material through its unique structure.

[0033] 4. Flame retardant performance analysis The flame retardant properties of the samples were tested using a limiting oxygen index tester and a vertical combustion tester. The sample dimensions were set to 100×6.5×3.2 mm³ and 130×13×3.2 mm³, respectively, according to ASTM D2863-10 and ASTM D3801-10 standards.

[0034] like Figure 5 As shown, the limiting oxygen index (LOI) of pure EP was 18.0%, failing to meet the UL-94 standard, exhibiting poor flame retardant performance. However, with the increase of ZIF-67@ADP addition, the LOI gradually increased, and the burning time gradually shortened. The LOI of 4 ZIF-67@ADP was 25.5%; the LOI of 6 ZIF-67@ADP increased to 26.7%, and the first ignition to extinguishing time (t1) and the second ignition to extinguishing time (t2) were shortened to 21 s and 20 s, respectively; the LOI of 8 ZIF-67@ADP reached 27.8%, and t1 and t2 were shortened to 7 s and 12 s, respectively, achieving the UL-94 V-1 rating; the LOI of 10 ZIF-67@ADP increased to 28.7%, and t1 and t2 were shortened to 2 s and 5 s, respectively, achieving the UL-94 V-0 rating. The addition of ZIF-67@ADP improves the flame retardant properties of the composite material. It forms a protective film on the material surface, effectively isolating oxygen and inhibiting the combustion reaction. Furthermore, the porous structure of ZIF-67@ADP helps improve the material's thermal stability and flame retardant properties. The LOI of 10ADP / EP is only 25.5%, with t1 and t2 of 14 s and 10 s, respectively, achieving the UL-94 V-1 rating. This indicates that the addition of ZIF-67@ADP not only improves the flame retardant properties of the composite material but also outperforms the effect of using ADP alone. This is likely due to the porous structure and synergistic effect of ZIF-67@ADP, which allows for more uniform dispersion of the flame retardant in the material, thereby improving flame retardant efficiency.

[0035] 5. Combustion Behavior Analysis The combustion performance of the samples was tested using a cone calorimeter. The combustion behavior of EP and its composites was simulated under a thermal radiation condition of 35 kW / m² according to ASTM E1354. The sample size was 100×100×3 mm³.

[0036] like Figure 6As shown in Table 2, the peak heat release rate (PHRR) of pure EP is 1292.8 kW / m², and the total heat release (THR) is 166.2 MJ / m², indicating that it releases a high amount of heat and burns at a fast rate, posing a certain safety hazard. After adding ZIF-67@ADP, both PHRR and THR gradually decreased with increasing addition amount. The PHRR of 4ZIF-67@ADP / EP was 704.1 kW / m², and the THR was 124.1 MJ / m²; the PHRR of 10ZIF-67@ADP / EP decreased to 404.8 kW / m², and the THR was 84.3 MJ / m². Compared with pure EP, the PHRR and THR of 10ZIF-67@ADP / EP decreased by 68.7% and 49.3%, respectively. This indicates that the addition of ZIF-67@ADP improved the flame retardant properties of the composite material and effectively reduced the heat release rate and total heat release during combustion. The flame retardant resistance (PHRR) of 10ADP / EP was 598.2 kW / m², and the flame retardant resistance (THR) was 117.4 MJ / m². Compared with 10ADP / EP, the PHRR and THR of 10ZIF-67@ADP / EP decreased by 32.3% and 28.2%, respectively. In conclusion, adding ZIF-67@ADP to EP can improve the flame retardant properties of the composite material. As the amount of ZIF-67@ADP added increases, the PHRR and THR gradually decrease, indicating that the flame retardant properties of the composite material are improved.

[0037] During polymer combustion, the release of smoke poses a serious threat to human life. The peak smoke release rate (PSPR) of pure EP is 0.210 m² / s, and the total smoke production (TSP) is 28.2 m². After adding ZIF-67@ADP, both PSPR and TSP show a decreasing trend with the increase of the amount added. The PSPR of 4ZIF-67@ADP / EP decreased to 0.116 m² / s, and the TSP decreased to 18.5 m². The PSPR of 6ZIF-67@ADP / EP further decreased to 0.111 m² / s, and the TSP decreased to 20.4 m². The PSPR of 8ZIF-67@ADP / EP was 0.103 m² / s, and the TSP was 17.7 m². The lowest PSPR was found in 10ZIF-67@ADP / EP, at 0.084 m² / s, with a TSP of 11.3 m². The PSPR decreased by 60.0%, and the TSP decreased by 59.9%. These data indicate that the addition of ZIF-67@ADP reduced the PSPR and TSP of the composite material. This is because ZIF-67@ADP can form a dense protective film during combustion, effectively suppressing smoke generation. The PSPR of 10ADP / EP is 0.092 m² / s, and the TSP is 16.8 m². Compared with 10ADP / EP, the PSPR of 10ZIF-67@ADP / EP is reduced by 8.7%, and the TSP is reduced by 32.7%. In conclusion, by adding ZIF-67@ADP to EP, the smoke release of EP composite materials during combustion can be reduced, and the smoke suppression capability of the material can be improved.

[0038] Table 2. Cone calorimeter test data for EP and flame-retardant epoxy resins.

[0039] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications may be made without departing from the technical solutions described in the claims.

Claims

1. A method for preparing a ZIF-based nano-hybrid flame retardant, characterized in that, Includes the following steps: (1) Dissolve cobalt nitrate hexahydrate in a solvent to prepare a cobalt nitrate solution; (2) Add aluminum diethylphosphinate to the cobalt nitrate solution and stir the reaction at room temperature; (3) Dissolve 2-methylimidazole in a solvent to prepare a 2-methylimidazole solution, and then add the 2-methylimidazole solution to the reaction solution in step (2) and stir the reaction at room temperature; (4) After the reaction is complete, centrifuge and wash the precipitate multiple times with anhydrous ethanol. The light purple powder after vacuum drying of the precipitate is the ZIF-based nano-hybrid flame retardant.

2. The method for preparing the ZIF-based nano-hybrid flame retardant according to claim 1, characterized in that: The mass-to-volume ratio of cobalt nitrate hexahydrate solution to solvent in step (1) is (0.5~1) g: 100 mL.

3. The method for preparing the ZIF-based nano-hybrid flame retardant according to claim 1, characterized in that: In step (2), the mass ratio of aluminum diethylphosphonate to cobalt nitrate hexahydrate is 4:(1~2), and the reaction time is 2~3h.

4. The method for preparing the ZIF-based nano-hybrid flame retardant according to claim 1, characterized in that: In step (3), the mass ratio of 2-methylimidazole to cobalt nitrate hexahydrate is (5~6):1, the reaction time is 10~12h, and the molar concentration of the 2-methylimidazole solution is 1~2mol / L.

5. The method for preparing the ZIF-based nano-hybrid flame retardant according to claim 1, characterized in that: In step (4), centrifuge at 5000 rpm and vacuum dry at 60℃ for 10~15h.

6. The method for preparing the ZIF-based nano-hybrid flame retardant according to claim 1, characterized in that: The solvent is anhydrous ethanol.

7. A ZIF-based nano-hybrid flame retardant prepared by the method of any one of claims 1-6.

8. The application of the ZIF-based nano-hybrid flame retardant of claim 7 in epoxy resin, characterized in that: The ZIF-based nano-hybrid flame retardant and epoxy resin were mixed and stirred at 90°C for 30 min. Then, a curing agent was added to defoam and the mixture was cured to obtain flame-retardant epoxy resin.

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