CN113200526B - Method for preparing boron nitride nanosheets by stripping method and boron nitride nanosheets - Google Patents

Abstract

The present invention proposes a method for preparing boron nitride nanosheets by exfoliation, boron nitride nanosheets, and a method of using CPs as a ball milling agent to assist the exfoliation of hexagonal boron nitride h-BN into boron nitride nanosheets BNNS. Including: (1) Add h-BN, CPs and agate pellets into the ball milling tank, and ball-mill at a speed of 500 rpm for 2-24 hours. (2) Disperse the mixture obtained after ball milling into isopropyl alcohol and sonicate for 1 hour. (3) Remove unstripped h-BN and CPs by centrifugation to obtain boron nitride nanosheets. The present invention uses the shear force and heat generated under ball milling to cause the CPs to undergo phase transformation, causing the CPs to transform from a crystalline state into a molten liquid, forming a similar ionic liquid, which is intercalated into h-BN in the form of ion fragments to assist h-BN. ‑BN exfoliation to prepare BNNS. The CPs used in the present invention only include systems that can undergo solid-liquid phase transition under ball milling. This method is simple to operate, low in cost, does not require complex and expensive equipment, and is conducive to large-scale production of BNNS.

Description

A method for preparing boron nitride nanosheets by exfoliation method, boron nitride nanosheets

Technical field

The invention belongs to the technical field of two-dimensional material exfoliation and preparation, specifically relates to a method for preparing boron nitride nanosheets by exfoliation, boron nitride nanosheets, and specifically a method for preparing BNNS by using CPs as a ball milling agent to assist h-BN exfoliation. .

Background technique

Since graphene was obtained from graphite by mechanical exfoliation in 2004, two-dimensional materials have attracted widespread attention from researchers due to their special properties. Hexagonal boron nitride (h-BN) is a two-dimensional material with a graphene-like structure that has high thermal conductivity, low density, low thermal expansion, high chemical stability and excellent electrical insulation. Compared with graphene, graphene only has covalent bonds connecting C-C bonds and has no polarity. However, h-BN has different electronegativities between B and N atoms, resulting in the existence of partial ionic bonds in the B-N bonds in the h-BN layer. , has a certain polarity, which makes the van der Waals interaction between h-BN layers stronger than that of graphite, so it is more difficult to peel off than graphite.

The main methods for preparing ultra-thin BNNS are mechanical exfoliation (Yang G, Zhang .), liquid phase exfoliation method (Deshmukh A R, Jeong J W, Lee S J, et al. Ultrasound-assisted facile green synthesis of hexagonal boronnitride nanosheets and their applications [J]. ACS Sustainable Chemistry&Engineering, 2019, 7(20): 17114- 17125.), chemical vapor deposition method (Geng D, Zhao ): 1801493.).

However, the yield of ordinary mechanical stripping methods is very low; liquid phase stripping requires the use of a large amount of solvents for a long time, and commonly used organic solvents can easily cause environmental pollution; the chemical vapor deposition method has complex equipment and is expensive, making it difficult to achieve large-scale preparation .

Contents of the invention

Purpose of the invention: In order to overcome the shortcomings of large-scale preparation of boron nitride nanosheets in the prior art, the present invention provides a method for preparing boron nitride nanosheets by exfoliation, boron nitride nanosheets, specifically using high-energy ball milling. A method to promote solid-liquid phase transition of coordination polymer CPs to assist h-BN exfoliation. Compared with traditional ionic liquid exfoliation, the coordination polymer phase transition generates ion fragments of different sizes, multi-level ion fragments The intercalation and peeling effect is better.

Technical solution: In order to achieve the above purpose, the first purpose of the present invention is to use CPs that are prone to solid-liquid phase transition to assist in the mechanical ball milling method to peel off h-BN, including the following steps:

(1) Ball milling peeling: ball mill hexagonal boron nitride h-BN, coordination polymer CPs and agate balls. The CPs is a system in which solid-liquid phase transition occurs under the action of ball milling;

(2) Ultrasonic: Disperse the mixture obtained after ball milling in an organic solvent including any one of ethanol, isopropyl alcohol, N,N-dimethylformamide, and N-methylpyrrolidone, and perform ultrasonic treatment;

(3) Collection: centrifuge once to obtain the organic solvent dispersion of boron nitride nanosheets; centrifuge twice to obtain the solid phase, and collect after drying to obtain boron nitride nanosheets BNNS.

Optionally, in step (2), the CPs include but are not limited to [Zn(HPO ₄ )(H ₂ PO ₄ )] ₂ (imH ₂ ) ₂ , [M(1,2,4-triazole)(H ₂ PO ₄ ) ₂ ], ZIF-4, Zn-ZIF-62, Co-ZIF-62, ZIF-76, ZIF-76-mbim, Cu(isopropylimidazolate), [Zn ₃ (H ₂ PO ₄ ) ₆ (H ₂ O ₃ )]·bimH, [Zn ₃ (H ₂ PO ₄ ) ₆ (H ₂ O ₃ )]·H(2Mebim), [Zn2(HPO ₄ ) ₂ (H ₂ PO ₄ )(5ClbimH) ₂ ]( H ₂ PO ₄ )(MeOH), [Cd ₃ (SCN) ₂ Br ₆ (C ₂ H ₉ N ₂ ) ₂ ], [Cu ₂ (SCN) ₃ (C ₂ bpy)], [Cu ₂ (SCN) ₃ (C ₄ bpy)], [Cu ₂ (SCN) ₁₂ (Phbpy) ₄ ], [Cu ₂ (SCN) ₃ (3-Pybpy)], (1-butyl-4-methylpyridinium)[Cu(SCN) ₂ ] At least one of them, wherein M includes any one of Zn ²⁺ , Cd ²⁺ , Cr ²⁺ , and Mn ²⁺ , im=imidazole, bim=benzimidazole, triazole=triazole, 5-Clbim= 5-chlorobenzimidazole, 2Mebim=2-methylbenzimidazole, C ₂ bpy=1-ethylbipyridine, C ₄ bpy=1-butylbipyridine, Phbpy=1-phenylbipyridine, 3- Pybpy=terpyridine, isopropylimidazolate=isopropylimidazole, methylpyridinium=methylpyridine, mbim=5-methylbenzimidazole, 1-butyl-4-methylpyridinium=1-butyl-4-methylpyridine.

The CPs are a type of CPs that undergo solid-liquid phase transition after ball milling. The main types, their melting points and glass transition temperatures are shown in Table 1 below:

Table 1 List of CPs for solid-liquid phase transition during ball milling

im=imidazole, bim=benzimidazole, 5-Clbim=5-chlorobenzimidazole, 2Mebim=2-methylbenzimidazole, C ₂ bpy=1-ethylbipyridine, C ₄ bpy=1-butyl Bipyridine, Phbpy=1-phenylbipyridine, 3-Pybpy=terpyridine.

Optionally, in step (1), the mass ratio of the hexagonal boron nitride h-BN and coordination polymer CPs is 1:0.1-0.5.

Optionally, in step (1), the ball milling speed is 300-600rpm, and the ball milling time is 2-24h.

Optionally, in step (2), the mixture obtained after ball milling is dispersed in an organic solvent at a concentration of 1-10 mg/ml; the ultrasonic treatment time is 1 h, and the ultrasonic treatment power is 100W.

Optionally, in step (3), the centrifugation speed is 1000-3000 rpm, and the centrifugation time is 10-30 min.

Optionally, in step (3), the speed of the second centrifugation is 9000-12000 rpm, and the centrifugation time is 10-30 minutes.

On the other hand, the present invention also provides a boron nitride nanosheet prepared according to the above method.

Optionally, the lateral size of the boron nitride nanosheets is 3-5 μm, and 30-40% of the boron nitride nanosheets have a lateral size of 5 μm; and the boron nitride nanosheets are thin, with a thickness of 1-5 nm. ; The edges of the boron nitride nanosheets are curled, and there are upright boron nitride nanosheets.

On the other hand, the boron nitride nanosheets of the present invention can be used as inorganic fillers and filled in polymers to prepare thermally conductive and electrically insulating polymers, which can be used in a variety of scenarios such as aerospace, 5G base stations, and small electronic equipment.

Beneficial effects: The present invention uses high-energy ball milling to promote solid-liquid phase transition of coordination polymer CPs to assist h-BN peeling. Compared with traditional ionic liquid peeling, the phase transition of coordination polymers generates particles with different sizes. Ion fragments, multi-stage ion fragment intercalation and stripping effects are better. In addition, the preparation method of the present invention is simple, has high yield, rich raw materials, low cost, low equipment requirements, and is conducive to large-scale production.

Description of the drawings

Figure 1 is a scanning electron microscope photograph of boron nitride nanosheets prepared in Example 1.

Detailed ways

The present invention utilizes CPs, which is prone to solid-liquid phase transition, to assist in mechanical ball milling to peel off h-BN, which includes the following steps:

(1) First, take 500mg h-BN and 50-250mg CPs and put them into the ball milling tank. Put the agate pellets with a total mass of about 50g into the ball milling tank and ball-mill at a speed of 500rpm for 2-24h.

(2) Disperse the ball-milled mixture in isopropyl alcohol at a concentration of 3 mg/ml, and use an ultrasonic cell disrupter (650W × 15%, about 100W) to sonicate for 1 hour.

(3) Centrifuge the ultrasonic dispersion for 15 minutes at 2000 rpm to remove unstripped boron nitride and CPs.

(4) Centrifuge the supernatant at 9000 rpm for 15 minutes, discard the isopropyl alcohol, and dry overnight to collect boron nitride nanosheets.

The CPs used in the present invention only include systems that can undergo solid-liquid phase transition under the action of ball milling. The shear force and heat generated by ball milling are used to cause the CPs to undergo a phase transition, causing the CPs to transform from a crystalline state into a molten liquid, forming a similar ionic liquid, which is intercalated into h-BN in the form of ion fragments to assist h-BN. Exfoliation to prepare BNNS. This method is simple to operate, low in cost, does not require complex and expensive equipment, and is conducive to large-scale production of BNNS.

The following examples use different CPs-assisted mechanical ball milling methods to peel off h-BN, which are used to specifically illustrate and explain the technical solution of the present invention. According to the following examples, the present invention can be better understood. However, those skilled in the art can easily understand that the specific material ratios, process conditions and results described in the examples are only for illustrating the present invention, and should not and will not limit the invention as described in detail in the claims. . The compounds in the aforementioned Table 1 all belong to CPs substances that undergo phase transformation of CPs due to the shear force and heat generated by ball milling. Therefore, they are also consistent with the principles of the embodiments of the present invention.

Example 1

Preparation of phase transition CPs:

Preparation of [Zn(HPO ₄ )(H ₂ PO ₄ ) ₂ ](imH ₂ ) ₂ : Place zinc oxide (81 mg, 1 mmol), imidazole (136 mg, 2 mmol), ethanol (500 μL), and phosphoric acid (205 μL, 3 mmol). Grind in a mortar for 10 minutes. The obtained powder was centrifuged and washed three times with ethanol (8000 rpm for 5 min), transferred to vacuum drying at 100°C overnight, and a dry pure phase was obtained.

Preparation of boron nitride nanosheets:

First, take 500mg h-BN and 100mg of the obtained [Zn(HPO ₄ )(H ₂ PO ₄ ) ₂ ](imH ₂ ) ₂ and put them into the ball mill jar. Add 3 agate pellets with a diameter of 1.2cm and 15 agate pellets with a diameter of 1cm. 10 8mm agate pellets and 50 6mm agate pellets (the total mass of all agate pellets is about 50g) are put into the ball milling tank and milled at a speed of 500 rpm for 24 hours.

The ball-milled mixture was dispersed in isopropyl alcohol at a concentration of 3 mg/mL, and ultrasonicated with an ultrasonic cell disrupter at a power of 100 W for 1 hour.

The ultrasonic dispersion was centrifuged at 2000 rpm for 15 min to remove the unpeeled boron nitride nanosheets. The supernatant was then centrifuged at a high speed of 9000 rpm for 15 min and dried overnight to obtain boron nitride nanosheets with a yield of 34.1%.

Figure 1 is a scanning electron microscope photo of the boron nitride nanosheets prepared in this embodiment. It can be seen from the picture that large and thin boron nitride nanosheets are obtained, with a lateral size of 3-5 μm and a 30-40% The boron nitride nanosheets have a lateral dimension of 5 μm. The edges of this boron nitride nanosheet are curled, and there are vertical boron nitride nanosheets with a thickness of 2-5nm. The size and thickness of the boron nitride nanosheets obtained by exfoliation are important indicators for evaluating boron nitride nanosheets. The boron nitride nanosheets obtained in this example are larger in size and thinner, and are a high-quality nitride nanosheet. Boron nanosheets. In this embodiment, CPs is used to transform from large scale to small scale under the action of ball milling to assist boron nitride exfoliation, which is beneficial to obtaining large-sized and thin-thickness boron nitride nanosheets.

Example 2

Preparation of phase transition CPs:

Preparation of [Zn(1,2,4-triazole) ₂ (H ₂ PO ₄ ) ₂ ]: Combine zinc oxide (81 mg, 1 mmol), 1,2,4-triazole (138 mg, 2 mmol) and phosphoric acid (85 %, 134 μL, 2 mmol) into the ball mill. The mixture was ground at 500 rpm for 60 minutes. The resulting powder was washed with methanol, transferred and dried at 100°C overnight to obtain a dry pure phase.

Preparation of boron nitride nanosheets:

First, take 500mg h-BN and 100mg of the obtained [Zn(1,2,4-triazole) ₂ (H ₂ PO ₄ ) ₂ ] and put them into the ball milling tank. Add 3 agate pellets with a diameter of 1.2cm and 1cm agate pellet. 15 pcs, 10 8mm agate pellets and 50 6mm agate pellets (the total mass of all agate pellets is about 50g) were put into the ball milling tank and milled at a speed of 500 rpm for 24 hours.

The ball-milled mixture was dispersed in 30 mL of isopropanol using an ultrasonic cell disrupter at a power of 100 W for 1 hour, with a concentration of 3 mg/mL.

The ultrasonic dispersion was centrifuged at 2000 rpm for 15 min to remove the unpeeled boron nitride nanosheets. The supernatant was then centrifuged at a high speed of 9000 rpm for 15 min and dried overnight to obtain boron nitride nanosheets with a yield of 28.1%.

The results of the boron nitride nanosheets obtained in this example are the same as those in Example 1. The lateral size is 3-5 μm, and about 30-40% of the boron nitride nanosheets have a lateral size of 5 μm. The edges of the boron nitride nanosheets are curled, and there are vertical boron nitride nanosheets with a thickness of 1-3 nm.

Example 3

Preparation of phase transition CPs:

Preparation of ZIF-4: Put 1.2g zinc nitrate hexahydrate, 0.9g imidazole, and 90ml N, N-dimethylformamide into a 100ml reaction kettle, react at 100°C for 72h, cool naturally, and use N , N-dimethylformamide and dichloromethane were washed three times each, transferred and dried at 100°C overnight to obtain a dry pure phase.

Preparation of boron nitride nanosheets:

First, take 500mg h-BN and 100mg ZIF-4 obtained and put them into the ball milling tank. Add 3 agate pellets with a diameter of 1.2cm, 15 agate pellets with a diameter of 1cm, 10 agate pellets with a diameter of 8mm, and 50 agate pellets with a diameter of 6mm ( The total mass of all agate pellets is about 50g) and put into the ball milling tank, and ball milled at a speed of 500rpm for 24h.

The ball-milled mixture was dispersed in 30 ml of isopropyl alcohol using an ultrasonic cell disrupter at a power of 100 W for 1 hour, with a concentration of 3 mg/mL.

The ultrasonic dispersion was centrifuged at 2000 rpm for 15 min to remove the unpeeled boron nitride nanosheets. The supernatant was then centrifuged at a high speed of 9000 rpm for 15 min and dried overnight to obtain boron nitride nanosheets with a yield of 12.1%.

The results of the boron nitride nanosheets obtained in this example are the same as those in Example 1. The lateral size is 3-5 μm, and about 30-40% of the boron nitride nanosheets have a lateral size of 5 μm. The edges of this boron nitride nanosheet are curled, and there are vertical boron nitride nanosheets with a thickness of about 2-5nm.

Comparative example 1

Preparation of boron nitride nanosheets:

First, take 500 mg h-BN and 100 mg of urea and put them into the ball mill tank. Place 3 agate pellets with a diameter of 1.2cm, 15 agate pellets with a diameter of 1cm, 10 agate pellets with a diameter of 8mm, and 50 agate pellets with a diameter of 6mm (all agate pellets The total mass of the balls is about 50g) and put into the ball milling tank, and ball milled at a speed of 500rpm for 24h.

The ball-milled mixture was dispersed in 30 ml of isopropyl alcohol using an ultrasonic cell disrupter at a power of 100 W for 1 hour, with a concentration of 3 mg/mL.

The ultrasonic dispersion was centrifuged at 2000 rpm for 15 min to remove the unpeeled boron nitride nanosheets. The supernatant was then centrifuged at a high speed of 9000 rpm for 15 min and dried overnight to obtain boron nitride nanosheets with a yield of 11.3%.

The results of the boron nitride nanosheets obtained in this comparative example show that the lateral size is 3-5 μm, and about 20-30% of the boron nitride nanosheets have a lateral size of 5 μm. The edges of the boron nitride nanosheets are curled, and there are vertical boron nitride nanosheets with a thickness of 5-10nm.

Comparative example 2

Preparation of boron nitride nanosheets:

Put 100 mg h-BN and 30 ml of isopropyl alcohol into a centrifuge tube, and use an ultrasonic cell disrupter to sonicate at a power of 100 W for 1 hour.

The ultrasonic dispersion was centrifuged at 2000 rpm for 15 min to remove the unpeeled boron nitride nanosheets. The supernatant was then centrifuged at a high speed of 9000 rpm for 15 min and dried overnight to obtain boron nitride nanosheets with a yield of 0.2%.

The results of the boron nitride nanosheets obtained in this comparative example are no different from those of the original boron nitride, and their lateral dimensions are 30-50 μm. The boron nitride nanosheets are very thick, with a thickness of 1-2 μm.

Comparative example 3

Preparation of boron nitride nanosheets:

Put 100 mg h-BN and 30 ml of isopropyl alcohol into a centrifuge tube, and use an ultrasonic cell disrupter to sonicate at a power of 100 W for 24 hours.

The ultrasonic dispersion was centrifuged at 2000 rpm for 15 min to remove the unpeeled boron nitride nanosheets. The supernatant was then centrifuged at a high speed of 9000 rpm for 15 min and dried overnight to obtain boron nitride nanosheets with a yield of 16.3%.

The results of the boron nitride nanosheets obtained in this comparative example show that the lateral size is 1-3 μm, and about 20-30% of the boron nitride nanosheets have a lateral size of 3 μm. The edges of the boron nitride nanosheets are curled, and there are vertical boron nitride nanosheets with a thickness of 1-10nm.

Example results and analysis

Table 2 Comparison of yield and CPs melting point of boron nitride nanosheets obtained in Examples and Comparative Examples

Based on the experimental results of the above Examples 1-3 and Comparative Examples 1-3, it can be seen that using CPs ball milling to assist h-BN peeling has a higher yield than using isopropyl alcohol ultrasonic and urea ball milling to peel off, especially for long-distance h-BN peeling. Higher than the effect of pure isopropyl alcohol ultrasound, the results of Comparative Example 3 show that pure isopropyl alcohol ultrasound can barely achieve the lowest level of the embodiment of the present invention after 24 hours. This undoubtedly greatly shortens the time and improves the efficiency. Production yield. Compared with the use of urea ball milling in Comparative Example 1, the peeling yield and effect of Examples 1-3 using the method of the present invention have been improved, especially the [Zn(HPO ₄ )(H ₂ PO) used in Examples 1 and 2 ₄ ) ₂ ] (imH ₂ ) ₂ and [Zn (1, 2, 4-triazole) ₂ (H ₂ PO ₄ ) ₂ ], compared with Comparative Example 1, an efficiency improvement of nearly 3 times was achieved.

The above yield comparison results fully illustrate that the present invention uses CPs to assist h-BN exfoliation, which is more conducive to h-BN exfoliation than conventional isopropyl alcohol ultrasonic and urea ball milling, and obtains boron nitride nanosheets with a higher yield;

At the same time, by comparing the efficiency of CPs-assisted h-BN peeling with different melting points Tm, as the melting point increases, the efficiency of CPs-assisted h-BN peeling also becomes lower. Using lower melting point [Zn(HPO ₄ )(H ₂ PO ₄ ) ₂ ](imH ₂ ) ₂ obtained the highest peeling efficiency. This shows that when low melting point CPs ball milling is used to assist h-BN exfoliation, the exfoliation yield is greatly improved.

The reason for this phenomenon is that the energy generated during ball milling is not enough to convert high melting point CPs into ion fragments, while low melting point CPs can be converted into a large number of ion fragments under the action of ball milling to assist h-BN peeling. This results in higher yields.

In addition, the products obtained by the method of the present invention are large and thin boron nitride nanosheets, which achieve excellent h-BN peeling effect, especially in terms of size distribution breadth and multi-level ion fragment intercalation compared with the use of isopropyl alcohol ultrasound and urea. Ball mill peeling has made more significant progress. Significant progress has been made in terms of lateral size and thickness. Specifically, the lateral size is 3-5 μm, and about 30-40% of boron nitride nanosheets have a lateral size of 5 μm; and this boron nitride nanosheet has a lateral size of 5 μm. The edges are curled, and there are erected boron nitride nanosheets with a thickness of about 2-5nm. It can be seen that the boron nitride nanosheets prepared by the method of the present invention obtain a larger proportion of laterally large-sized products and have a thinner thickness.

In summary, the present invention discloses a method for preparing boron nitride nanosheets by a peeling method. The layered boron nitride is peeled off by ball milling, and a coordination polymer is added as a ball milling agent. The selected coordination polymerization Materials will undergo phase transition during the ball milling process. The shear and frictional heat of ball milling prompt the coordination polymer to undergo phase transition from crystal to liquid. The coordination polymer plays a role similar to that of ionic liquids in peeling off two-dimensional materials, but it stops Transformed into solid after ball milling. Compared with traditional ionic liquid exfoliation, coordination polymer phase transition generates ion fragments of varying sizes, and multi-level ion fragment intercalation and exfoliation effects are better.

The above are only the preferred embodiments of the present invention. It should be pointed out that those of ordinary skill in the art can make several improvements and modifications without departing from the principles of the present invention. These improvements and modifications can also be made. should be regarded as the protection scope of the present invention.

Claims (8)

1. A method for preparing boron nitride nanosheets by a stripping method, the method comprising the steps of:

(1) Ball milling stripping: hexagonal boron nitride h-BN and coordination polymer CPs are mixed according to the mass ratio of 1: ball milling is carried out at 0.1-0.5, CPs is a system which is subjected to solid-liquid phase inversion under the action of ball milling, the ball milling speed is 300-600rpm, and the ball milling time is 2-24 h;

(2) Ultrasonic: dispersing the mixture obtained after ball milling in an organic solvent, and carrying out ultrasonic treatment;

(3) And (3) collecting: obtaining an organic solvent dispersion liquid of the boron nitride nanosheets through one-time centrifugation; performing secondary centrifugation to obtain a solid phase, and collecting the solid phase after drying to obtain boron nitride nano-sheets BNNS;

the CPs include [ Zn (HPO) ₄ )(H ₂ PO ₄ ) ] ₂ (imH ₂ ) ₂ 、[M(1,2,4-triazole)(H ₂ PO ₄ ) ₂ ]、ZIF-4、Zn-ZIF-62、Co-ZIF-62、ZIF-76、ZIF-76-mbim、Cu(isopropylimidazolate)、[Zn ₃ (H ₂ PO ₄ ) ₆ (H ₂ O ₃ )]·bimH、[Zn ₃ (H ₂ PO ₄ ) ₆ (H ₂ O ₃ )]·H(2Mebim)、

[Zn ₂ (HPO ₄ ) ₂ (H ₂ PO ₄ )(5ClbimH) ₂ ](H ₂ PO ₄ )(MeOH)、[Cd ₃ (SCN) ₂ Br ₆ (C ₂ H ₉ N ₂ ) ₂ ]、[Cu ₂ (SCN) ₃ (C ₂ bpy)]、[Cu ₂ (SCN) ₃ (C ₄ bpy)]、[Cu ₂ (SCN) ₁₂ (Phbpy) ₄ ]、[Cu ₂ (SCN) ₃ (3-Pybpy)]、(1-butyl-4-methylpyridinium)[Cu(SCN) ₂ ]At least one of (1), wherein M comprises

Zn ²⁺ , Cd ²⁺ ,Cr ²⁺ ,Mn ²⁺ Any of im=imidazole, bim=benzimidazole, triazole=triazole, 5-clbim=5-chlorobenzoimidazole, 2 mebim=2-methylbenzimidazole, C ₂ bpy=1-ethylbipyridine, C ₄ bpy=1-butylbipyridine, phbpy=1-phenylbipyridine, 3-ppy=terpyridine, isopropropylimidozolate=isopropylimidazole, methylpyridinium=picoline, mbim=5-methylbenzimidazole, 1-butyl-4-methylpyridinium=1-butyl-4-picoline.

2. The method for producing boron nitride nanoplatelets according to claim 1, wherein in step (2), the mixture obtained after ball milling is dispersed in an organic solvent at a concentration of 1-10mg/ml, the organic solvent comprising any one of ethanol, isopropanol, N-dimethylformamide, N-methylpyrrolidone.

3. The method for producing boron nitride nanosheets according to claim 1, wherein in step (2), the time of the ultrasonic treatment is 1h, and the power of the ultrasonic treatment is 100W.

4. The method for producing boron nitride nanosheets according to claim 1, wherein in step (3), the speed of the primary centrifugation is 1000 to 3000rpm, and the centrifugation time is 10 to 30min.

5. The method for producing boron nitride nanosheets according to claim 1, wherein in step (3), the secondary centrifugation is performed at 9000 to 12000rpm for 10 to 30 minutes.

6. Boron nitride nanoplatelets, characterized in that they are prepared according to the method of any one of claims 1 to 5.

7. The boron nitride nanoplatelets of claim 6, wherein the boron nitride nanoplatelets have a lateral dimension of 3-5 μm, and 30-40% of the boron nitride nanoplatelets have a lateral dimension of 5 μm; the edges of the boron nitride nano-sheets are curled, and the thickness of the boron nitride nano-sheets is 1-5 nm.

8. Use of the boron nitride nanoplatelets according to claim 6 or 7, characterized in that the boron nitride nanoplatelets as inorganic fillers for the preparation of thermally conductive electrically insulating polymers, including applications in aerospace, 5G base stations, small electronic devices.