Fullerene embedded with metal and preparation method thereof

Abstract

The invention provides embedded metal fullerene and a preparation method thereof. The preparation method comprises the following steps: mixing a metal source and graphite powder, and filling a hollow graphite rod with the mixture to prepare an anode; the electrode is installed at the anode end of an electric arc furnace, and on-line activation is conducted through anode and cathode short-circuit current under the inert atmosphere; then carrying out arc discharge under specific air pressure and current, and collecting generated carbon ash; performing ultrasonic extraction by using an organic solvent to obtain a fullerene crude extracting solution; and finally, performing multi-stage separation and purification by high performance liquid chromatography, and performing primary and fine separation by sequentially adopting preparative and semi-preparative chromatographic columns to obtain a high-purity product. According to the method, a complete technical path capable of efficiently and controllably preparing the ultra-high-purity embedded metal fullerene is formed through a synthesis process integrating online activation and accurate atmosphere regulation and control and a multi-stage gradient chromatography purification strategy, and a solid foundation is laid for application of atomic-scale accurate materials in the frontier fields of quantum devices and the like.

Description

Technical Field

[0001] This invention belongs to the field of preparation technology of functional carbon clusters, and in particular relates to an endohedral metal fullerene and its preparation method. Background Technology

[0002] Metal-embedded fullerenes are atomically precise carbon clusters formed by encapsulating metal atoms within carbon cages, typically ranging in size from one to several nanometers. Compared to traditional carbon nanotubes and graphene, metal-embedded fullerenes exhibit significant quantum size effects. By controlling the configuration, electronic states, and energy level structure of the metal atoms within the carbon cages using an external field, multi-state responses in their physical properties can be achieved. Metal-embedded fullerenes can serve as atomically precise response channel units for constructing atomic-scale circuits, showing significant application potential in nanoelectronics and quantum information.

[0003] Currently, many methods for synthesizing endohedral fullerenes mainly draw on the successful experience of hollow fullerenes. However, although the combustion method has achieved the highest synthesis yield of hollow fullerenes industrially, this method is difficult to apply to the synthesis of endohedral metallofullerenes. While high-frequency furnace methods or laser sputtering can prepare some single-atom endohedral fullerenes, the resulting products are relatively limited in variety, restricting their applications. In contrast, the arc discharge method, due to its advantages of lower cost and higher yield, has become the mainstream technology for synthesizing endohedral metallofullerenes in the laboratory. The advantage of this method lies in the fact that a DC arc can continuously provide a high-temperature environment exceeding 4000K, promoting the full ionization of metals or metal oxides, thereby efficiently participating in the formation process of endohedral metallofullerenes. However, limitations remain in the selection of metal types, precise structural control, and product diversity.

[0004] Studies have shown that, under an inert atmosphere, high-temperature treatment at temperatures above 1000°C on graphite rods filled with graphite powder and metal (or its oxide) powder can effectively remove water vapor adsorbed on the surface of the graphite rods and also "activate" the metal (or its oxide) to generate metal carbides (MC2). This process has been shown to help improve the yield of endohedral fullerenes. Currently, some research groups have proposed an "in-situ activation" technique, which involves short-circuiting the anode and cathode during the experiment and then applying a high current to preheat the doped carbon rods. This method has also been verified to significantly improve the synthesis efficiency of endohedral fullerenes. Furthermore, reverse discharge technology and the introduction of transition metal (compound) catalysts (such as Cu, CoO, FeN) are also effective methods. x(e.g., MNi2, where M = Y, La, Tb, Sm, etc.) are also widely used to optimize the synthesis process of endohedral metal-fullerenes. Directly using alloys formed from the target metal and transition metals (such as MNi2, where M = Y, La, Tb, Sm, etc.) can also promote the formation of endohedral metal-fullerenes to some extent. Current synthesis methods mostly focus on improving yield, while paying insufficient attention to their application needs in nanoelectronics, quantum devices, and other fields. The mechanisms of action have not yet been systematically integrated, and the repeatability and stability of the process need to be improved. Furthermore, existing methods often produce products accompanied by various byproducts such as hollow fullerenes and metal particles, making it difficult to directly obtain high-purity samples suitable for device construction.

[0005] Therefore, there is a need to provide an improved technical solution that addresses the shortcomings of the existing technology. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide an endogenous metal fullerene and its preparation method, so as to solve the problems of insufficient product diversity, poor process controllability and difficulty in obtaining atomically accurate pure samples in the existing endogenous metal fullerene synthesis methods.

[0007] To achieve the above and other related objectives, the present invention provides a method for preparing endohedral metallofullerenes, the method comprising the following steps:

[0008] S1. Mix the metal source and graphite powder in a certain proportion and fill them into a hollow graphite rod to make a doped graphite rod.

[0009] S2. Fix the doped graphite rod to the anode end of the electric arc furnace to form a graphite anode, so that the graphite electrode is in contact with the cathode. After evacuating the electric arc furnace cavity, fill it with inert gas and activate the doped graphite rod online by means of current.

[0010] S3. Under an inert atmosphere and discharge current of a certain pressure, an electric arc discharge reaction is carried out, and the carbon ash generated by the reaction is collected.

[0011] S4. The carbon ash is ultrasonically extracted with an organic solvent to obtain a crude fullerene extract.

[0012] S5. The crude fullerene extract is purified by multi-stage separation using high-performance liquid chromatography. The multi-stage separation and purification includes at least one primary separation using a preparative chromatographic column and at least one fine separation using a semi-preparative chromatographic column to obtain high-purity endogenous metal-intercalated fullerenes.

[0013] As an example, in step S1, the molar ratio between the metal element in the metal source and the carbon element in the graphite powder is 1:(12~18), wherein the metal element in the metal source is scandium.

[0014] As an example, the specific conditions for online activation in step S2 are: under inert gas protection, a current of 180~220A is passed through and heated for 20~40 minutes.

[0015] As an example, before the arc discharge reaction is carried out, step S3 requires multiple replacements of the arc furnace cavity. Specifically, the multiple replacements involve: evacuating the gas pressure inside the arc furnace cavity to below 5 Pa, and then filling it with inert gas until the gas pressure is 5 kPa, repeating this process 2 to 4 times.

[0016] As an example, the conditions for the arc discharge reaction in step S3 are: the inert atmosphere includes helium, the gas pressure is 200~400 Torr, and the discharge current is 100~150A.

[0017] As an example, step S4, which involves ultrasonically extracting the carbon ash using an organic solvent, includes the following steps:

[0018] S41. The carbon ash is immersed in an organic solvent for ultrasonic extraction. After standing, the supernatant is collected and the lower precipitate is centrifuged. Then, the supernatant and the lower centrifuged liquid are filtered to remove the carbon ash, and the solution in the filtration flask is obtained.

[0019] S42. Add the carbon ash removed by vacuum filtration back into the organic solvent, and repeat the steps of ultrasonic extraction, standing, centrifugation and vacuum filtration to remove carbon ash until the solution in the vacuum filtration flask is colorless.

[0020] S43. Collect the solution in all the filtration flasks, concentrate it, and obtain the crude fullerene extract.

[0021] As an example, the liquid-to-solid ratio of the organic solvent to the carbon ash in step S41 is 35 mL / g to 45 mL / g.

[0022] As an example, the organic solvent mentioned in step S41 includes o-xylene.

[0023] As an example, the frequency of the ultrasonic extraction is 30~80HZ, and the temperature of the ultrasonic extraction is 50~70℃.

[0024] As an example, before performing multi-stage separation and purification by high performance liquid chromatography in step S5, the crude fullerene extract is first filtered using a 0.22 μm organic filter membrane.

[0025] As an example, the preparative chromatographic column in step S5 has a specification of φ20×250mm, and the preparative chromatographic column is selected from one or a combination of Buckyprep, 5PYE, and Buckyprep-M type chromatographic columns.

[0026] As an example, the semi-preparative chromatographic column in step S5 has a specification of φ10×250mm, and the semi-preparative chromatographic column is selected from one or a combination of Buckyprep, 5PBB, 5PYE, 5NPE, and Buckyprep-M type chromatographic columns.

[0027] As an example, the multi-stage separation and purification in step S5 also includes separation using an analytical chromatographic column, wherein the analytical chromatographic column has a specification of φ2.5×250mm and is selected from one or a combination of Buckyprep and 5PYE type chromatographic columns.

[0028] As an example, the mobile phase used in the separation and purification in step S5 is one or a combination of o-xylene and toluene.

[0029] The present invention also provides an endogenous metal-fullerene, wherein the endogenous metal-fullerene is prepared by the above-described method for preparing endogenous metal-fullerene.

[0030] As described above, the endohedral metallofullerene and its preparation method of the present invention have the following beneficial effects:

[0031] This invention effectively solves the problems of unstable yield and large interference from impurities in traditional methods by introducing an online activation step and a multiple atmosphere replacement process. Online activation promotes the preferential conversion of the metal source into more reactive metal carbides and completely eliminates the adsorption of water vapor on the surface of the graphite rod. Combined with the precise control of gas pressure and discharge current in the arc discharge, a pure and controllable reaction environment is created for the nucleation and growth of the embedded metal fullerene. This not only significantly improves the synthesis yield of the target product, but also greatly enhances the reproducibility and reliability of the entire synthesis process.

[0032] The multi-stage, gradient high-performance liquid chromatography purification strategy in this invention achieves a breakthrough in obtaining atomically precise structural products from complex crude products. By dynamically using chromatographic columns with different separation mechanisms based on chromatographic peaks, the subtle physicochemical differences between the target embedded metallofullerene and impurities can be efficiently amplified, thereby achieving precise separation and ultimately obtaining samples with a purity higher than 99.5%, meeting the stringent requirements for material structural accuracy and performance consistency in high-end applications such as quantum devices.

[0033] This invention seamlessly integrates improved arc discharge synthesis with high-efficiency chromatographic purification technology, forming a complete, efficient, and scalable technical path. It not only inherits the advantages of low equipment cost and easy scale-up of the arc discharge method, but also achieves "on-demand customization" of the final product structure and performance through refined control of the entire process. This lays a solid material foundation for the practical application of embedded metal fullerenes as core functional materials in multi-field response devices such as optical, electrical, and magnetic fields. Attached Figure Description

[0034] Figure 1 The image shown is Sc2C2@C prepared in Example 1 of this invention. s (hept)-C 88 The mass spectrum.

[0035] Figure 2 The image shown is Sc2C2@C prepared in Example 1 of this invention. s (hept)-C 88 The ultraviolet-visible spectrum.

[0036] Figure 3 The image shown is Sc2C2@C prepared in Example 1 of this invention. s (hept)-C 88 Crystal structure diagram.

[0037] Figure 4 The image shown is Sc2C2@C prepared in Example 1 of this invention. s (hept)-C 88 The pure sample chromatogram.

[0038] Figure 5 The Sc2C2@C2(40)-C prepared in Example 2 of this invention is shown. 90 The mass spectrum.

[0039] Figure 6 The Sc2C2@C2(40)-C prepared in Example 2 of this invention is shown. 90 The ultraviolet-visible spectrum.

[0040] Figure 7 The Sc2C2@C2(40)-C prepared in Example 2 of this invention is shown. 90 Crystal structure diagram.

[0041] Figure 8 The Sc2C2@C2(40)-C prepared in Example 2 of this invention is shown. 90 The chromatogram.

[0042] Figure 9 The image shown is Sc3N@D3(6140)-C prepared in Example 3 of this invention. 68 The mass spectrum.

[0043] Figure 10 The image shown is Sc3N@D3(6140)-C prepared in Example 3 of this invention. 68 The ultraviolet-visible spectrum.

[0044] Figure 11The image shown is Sc3N@D3(6140)-C prepared in Example 3 of this invention. 68 Crystal structure diagram.

[0045] Figure 12 The image shown is Sc3N@D3(6140)-C prepared in Example 3 of this invention. 68 The chromatogram.

[0046] Figure 13 The figures shown are high-performance liquid chromatograms of the carbon ash prepared in Example 1 (left) and Comparative Example 1 (right).

[0047] Figure 14 The images shown are mass spectra of the carbon ash prepared in Example 1 (left) and Comparative Example 1 (right).

[0048] Figure 15 The images shown are mass spectra of the carbon ash prepared in Example 1 (left) and Comparative Example 2 (right) of this invention. Detailed Implementation

[0049] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0050] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the respective manufacturers.

[0051] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention, any prior art methods, apparatus, and materials similar to or equivalent to those described, apparatus, and materials in the embodiments of this invention may be used to implement the present invention.

[0052] Existing methods for synthesizing embedded metal fullerenes suffer from insufficient product diversity, poor process controllability, and difficulty in obtaining atomically accurate pure samples. This invention addresses these issues by optimizing preparation conditions and introducing different types of metal sources to prepare embedded metal fullerene clusters with optical, electrical, or magnetic field responses. Furthermore, it investigates the mechanisms by which the inner surface configuration, motor, and energy level structure of the carbon cage change under external field modulation, thereby achieving polymorphic regulation of the carbon cage clusters.

[0053] This invention provides a method for preparing endohedral metallofullerenes, comprising the following steps:

[0054] S1. Mix the metal source and graphite powder in a certain proportion and fill them into a hollow graphite rod to make a doped graphite rod.

[0055] S2. Fix the doped graphite rod to the anode end of the electric arc furnace to form a graphite anode, so that the graphite anode is in contact with the cathode. After evacuating the electric arc furnace cavity, fill it with inert gas and activate the doped graphite rod online by means of current.

[0056] S3. Under an inert atmosphere and discharge current of a certain pressure, an electric arc discharge reaction is carried out, and the carbon ash generated by the reaction is collected.

[0057] S4. The carbon ash is ultrasonically extracted with an organic solvent to obtain a crude fullerene extract.

[0058] S5. The crude fullerene extract is purified by multi-stage separation using high-performance liquid chromatography. The multi-stage separation and purification includes at least one primary separation using a preparative chromatographic column and at least one fine separation using a semi-preparative chromatographic column to obtain high-purity endogenous metal-intercalated fullerenes.

[0059] To better understand, the preparation method of endohedral metallofullerenes is described in detail below, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the reagents and instruments used in the present invention can be obtained commercially.

[0060] The electric arc furnace used below includes an electric arc furnace cavity, a DC motor, a stepper motor, a vacuum system, a gas path system, and a cooling water path system. The electric arc furnace used is a common piece of equipment in this field, and its specific structure will not be described in detail here.

[0061] First, in step S1, the metal source and graphite powder are mixed in a certain proportion and filled into a hollow graphite rod to form a doped graphite rod.

[0062] Specifically, the metal source and graphite powder are weighed according to a certain ratio, and the two substances are mixed evenly in an agate mortar. Then, the mixture is filled into a hollow graphite rod and compacted. In a specific embodiment of the present invention, the hollow graphite rod has an inner diameter of 8.5 mm, an outer diameter of 11 mm, a total length of 15 cm, and a hollow portion length of 11 cm.

[0063] As an example, the molar ratio between the metal element in the metal source and the carbon element in the graphite powder is 1:(12~18), wherein the metal element in the metal source is scandium (Sc).

[0064] Specifically, the molar ratio between the metal element Sc in the metal source and the carbon element in the graphite powder can be any value within a range such as 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, etc. By precisely controlling the mixing ratio of graphite powder and metal source, the optimal synergy between metal atoms and carbon atoms in the high-temperature reaction is ensured, promoting the efficient generation of metal fullerenes.

[0065] Next, in step S2, the doped graphite rod is fixed to the anode of the electric arc furnace to form a graphite anode, and the graphite anode is brought into contact with the cathode. After the electric arc furnace cavity is evacuated, an inert gas is introduced, and the doped graphite rod is activated online by means of an electric current.

[0066] Specifically, the purpose of online activation of the filled doped graphite rod is to enable the metal to form metal carbides, and also to drive away water vapor and other gases adhering to the surface of the graphite rod.

[0067] As an example, the specific conditions for online activation are: under inert gas protection, a current of 180~220A is passed through, and the mixture is heated for 20~40 minutes.

[0068] Specifically, after the doped graphite rods are loaded, the electric arc furnace door is opened, and the loaded doped graphite rods are fixed to the anode end with graphite screws to form a graphite anode. The stepper motor is started to make the graphite anode and cathode in close contact (i.e., the graphite anode and cathode are short-circuited). The electric arc furnace door is locked, and the vacuum system is turned on to evacuate the electric arc furnace cavity to below 5 Pa. Then, inert gas (preferably helium) is introduced into the electric arc furnace cavity through the gas circuit system to fill the gas pressure to 10 kPa. The cooling water circuit system and DC motor are turned on, and the current is slowly adjusted to 180~220A (e.g., 180A, 190A, 200A, 210A, 220A, etc.). During the adjustment process, the observation window is checked repeatedly until the doped graphite rods turn red and bright due to the power. However, it is necessary to ensure that the doped graphite rods do not arc. The doped graphite rods are activated online for 20~40 minutes (e.g., 20 min, 25 min, 30 min, 35 min, 40 min, etc.).

[0069] Next, step S3 is performed, in which an arc discharge reaction is carried out under an inert atmosphere and discharge current at a certain pressure, and the carbon ash generated by the reaction is collected.

[0070] Specifically, the arc discharge reaction occurs in an inert gas environment, where the high temperature (typically 3000~5000℃) generated by the arc between electrodes causes the carbon source (doped graphite rod) to evaporate into carbon vapor and metal vapor. On the one hand, the high temperature allows the metal atoms to fully vaporize and mix uniformly with the carbon vapor, providing ample reaction opportunities for the metal atoms to be encapsulated in the carbon cage. The formation of metal fullerenes requires the metal atoms and carbon clusters to recombine synergistically at high temperatures, and the high temperature significantly improves the efficiency of metal atoms embedding into the carbon cage. On the other hand, the high temperature can drive the carbon clusters to grow rapidly into hollow carbon cages of various sizes (such as C80, C82, etc.). Different metal atoms (such as Sc, Y, La) have different requirements for the size of the carbon cage. Therefore, by adjusting the size of the carbon cage to match the metal atoms, a variety of embedded metal fullerenes can be synthesized, demonstrating the advantage of product diversity.

[0071] As an example, before the electric arc discharge reaction is carried out, the electric arc furnace cavity needs to be replaced multiple times. Specifically, the gas pressure in the electric arc furnace cavity is evacuated to below 5 Pa, and then inert gas is introduced until the gas pressure is 5 kPa. This process is repeated 2 to 4 times.

[0072] Specifically, the electric arc furnace cavity is first evacuated to below 5 Pa using a vacuum system, and then an inert gas (preferably helium) is introduced into the cavity through a gas system until the pressure reaches 5 kPa. This process is repeated 2 to 4 times (e.g., 2, 3, 4 times, etc.). The purpose of pre-purifying the electric arc furnace cavity multiple times is to remove as much air and water vapor as possible so as not to affect subsequent experiments.

[0073] As an example, the conditions for the arc discharge reaction are: the inert atmosphere includes helium, the gas pressure is 200~400 Torr, and the discharge current is 100~150A.

[0074] Specifically, inert gas (preferably helium) is introduced into the electric arc furnace cavity to a pressure of 200-400 Torr (e.g., 200 Torr, 250 Torr, 300 Torr, 350 Torr, 400 Torr, etc.). The DC motor is turned on and the current is slowly adjusted to 100-150A (e.g., 100A, 110A, 120A, 130A, 140A, 150A, etc.). The stepper motor is started to slowly retract the graphite anode. An electric arc can be observed. The stepper motor is continued to be adjusted so that the distance between the cathode and the graphite anode is 0.8-1.2cm (e.g., 0.8cm, 0.9cm, 1.0cm, 1.1cm, 1.2cm, etc.) until the mixture doped with the hollow part of the graphite rod has completely reacted. After the reaction is complete, the current is adjusted to 0 and the DC motor is turned off. The stepper motor is adjusted to return the graphite anode to the initial position. Then the carbon ash generated by the reaction is collected. The carbon ash is a mixture of carbon clusters.

[0075] In addition, appropriate pressure can regulate the diffusion rate and collision probability of carbon clusters and metal atoms, which has a key impact on the structure, size distribution and yield of the product.

[0076] Next, in step S4, the carbon ash is ultrasonically extracted using an organic solvent to obtain a crude fullerene extract.

[0077] As an example, step S4, which involves ultrasonically extracting the carbon ash using an organic solvent, includes the following steps:

[0078] S41. The carbon ash is immersed in an organic solvent for ultrasonic extraction. After standing, the supernatant is collected and the lower precipitate is centrifuged. Then, the supernatant and the lower centrifuged liquid are filtered to remove the carbon ash, and the solution in the filtration flask is obtained.

[0079] Specifically, a certain amount of carbon ash is weighed and placed in a container, and an organic solvent is added to the container to immerse the carbon ash. The container is then placed in a constant-temperature ultrasonic extractor for ultrasonic extraction. After standing for a period of time, the supernatant is filtered using a vacuum funnel to remove the carbon ash. The lower sediment at the bottom of the container is separated into solid and liquid using a centrifuge, and the carbon ash is also removed by vacuum filtration using a vacuum funnel. At this point, the solution in the filtration flask is a black, high-concentration crude extract of fullerenes, which contains a variety of endohedral metallofullerenes.

[0080] As an example, the liquid-to-solid ratio of the organic solvent to the carbon ash in step S41 is 35 mL / g to 45 mL / g.

[0081] Specifically, the liquid-to-solid ratio of organic solvent to carbon ash can be any value within a range such as 35 mL / g, 38 mL / g, 40 mL / g, 42 mL / g, or 45 mL / g, and can be adjusted according to actual conditions.

[0082] As an example, the organic solvent mentioned in step S41 includes o-xylene.

[0083] As an example, the frequency of the ultrasonic extraction is 30~80HZ, and the temperature of the ultrasonic extraction is 50~70℃.

[0084] Specifically, the frequency of ultrasonic extraction can include 30 Hz, 40 Hz, 50 Hz, 60 Hz, 70 Hz, 80 Hz, etc., and the temperature of ultrasonic extraction can include any value within the range of 50℃, 55℃, 60℃, 65℃, 70℃, etc. In addition, the temperature during ultrasonic extraction is constant. Preferably, the frequency of ultrasonic extraction is 50 Hz, the temperature is 60℃, and the time is 30 minutes.

[0085] S42. Add the carbon ash removed by vacuum filtration back into the organic solvent, and repeat the steps of ultrasonic extraction, standing, centrifugation and vacuum filtration to remove carbon ash until the solution in the vacuum filtration flask is colorless.

[0086] S43. Collect the solution in all the filtration flasks, concentrate it, and obtain the crude fullerene extract.

[0087] Finally, in step S5, the crude fullerene extract is purified by multi-stage separation using high-performance liquid chromatography. The multi-stage separation and purification includes at least one primary separation using a preparative chromatographic column and at least one fine separation using a semi-preparative chromatographic column to obtain high-purity endogenous metal-intercalated fullerenes.

[0088] As an example, before performing multi-stage separation and purification by high performance liquid chromatography in step S5, the crude fullerene extract is first filtered using a 0.22 μm organic filter membrane.

[0089] As an example, the preparative chromatographic column in step S5 has a specification of φ20×250mm, and the preparative chromatographic column is selected from one or a combination of Buckyprep, 5PYE, and Buckyprep-M type chromatographic columns.

[0090] As an example, the semi-preparative chromatographic column in step S5 has a specification of φ10×250mm, and the semi-preparative chromatographic column is selected from one or a combination of Buckyprep, 5PBB, 5PYE, 5NPE, and Buckyprep-M type chromatographic columns.

[0091] As an example, the multi-stage separation and purification in step S5 also includes separation using an analytical chromatographic column, wherein the analytical chromatographic column has a specification of φ2.5×250mm and is selected from one or a combination of Buckyprep and 5PYE type chromatographic columns.

[0092] As an example, the mobile phase used in the separation and purification in step S5 is one or a combination of o-xylene and toluene.

[0093] In practical applications, the steps for multi-stage separation and purification of crude fullerene extract using high-performance liquid chromatography include:

[0094] Turn on the high performance liquid chromatograph, set the flow rate and detection wavelength, open the analysis software and turn on the deuterium lamp;

[0095] Before separation and purification, the crude extract of fullerene to be separated was filtered through a 0.22 μm organic filter membrane to prevent residual carbon ash or fullerene precipitates from clogging the chromatographic column.

[0096] The injection and separation process is as follows: For manual injection, a 2.5 mL flat-tipped syringe is used, with an injection volume of 1 mL per injection. The sample is collected and named based on the differences in chromatographic peaks and retention times. For automatic injection, the injection volume is controlled within 1.5 times the flow rate. By setting the flow rate, injection volume, elution time, and number of rounds, the sample can be automatically separated according to the size or polarity of the fullerene. Due to the large volume of the crude fullerene extract, a preparative chromatographic column with a specification of φ20×250 mm is used for the first few rounds of primary separation. The preparative chromatographic column is selected from one or a combination of Buckyprep, 5PYE, and Buckyprep-M type columns. The separation is based on the elution peaks of the sample in the column. The selection is based on the specific circumstances; the chromatographic columns used in the subsequent rounds of fine separation are semi-preparative chromatographic columns with a specification of φ10×250mm, and the semi-preparative chromatographic columns are selected from one or a combination of Buckyprep, 5PBB, 5PYE, 5NPE, and Buckyprep-M type chromatographic columns; in some specific embodiments, analytical chromatographic columns with a specification of φ2.5×250mm are also used, and the analytical chromatographic columns are selected from one or a combination of Buckyprep and 5PYE type chromatographic columns; after multiple high-performance liquid chromatography separation and purification, the endogenous metallofullerene is obtained.

[0097] In addition, regarding the multi-stage separation and purification of the crude fullerene extract in step S5 using high-performance liquid chromatography (HPLC), besides HPLC, non-chromatographic methods can also be used. Specifically, the difference in the first oxidation potential between metallofullerenes and hollow fullerenes can be utilized to selectively precipitate the target product using Lewis acids (intercalated metallofullerenes preferentially interact with Lewis acids, and this interaction leads to significant changes in the physicochemical properties of the intercalated metallofullerenes, such as a sharp decrease in solubility, thus precipitating them from the solution). Alternatively, low-symmetry metal-organic cages (MOCs) can be designed, utilizing shape matching and π-π interactions to achieve separation. The scale-up optimization of these two non-chromatographic methods (such as stirred filtration and Lewis acid precipitation) and the design of continuous production equipment may be key to industrial applications. However, based on obtaining high-purity samples, HPLC is irreplaceable. The products obtained by the method in this invention have "chromatographic purity" or "ultra-high purity," which is a prerequisite and key to applying them to the study of quantum size effects such as light, electricity, and magnetism. The present invention also provides an endogenous metal-fullerene, wherein the endogenous metal-fullerene is prepared by the above-described method for preparing endogenous metal-fullerene.

[0098] To better understand the embedded metal fullerenes and their preparation methods in this invention, specific embodiments are described below. It should be noted that these embodiments are merely descriptive and do not limit the invention in any way.

[0099] Example 1

[0100] This embodiment provides an endohedral metallofullerene and its preparation method, the preparation method including the following steps:

[0101] S1. Weigh the metal source (Sc2O3) and graphite powder according to the molar ratio of Sc to C of 1:15. Mix the two substances evenly with an agate mortar and pestle. Then fill the mixture into a hollow graphite rod (inner diameter of 8.5 mm, outer diameter of 11 mm, total length of 15 cm, and length of the hollow part of 11 cm) and compact it to make a doped graphite rod.

[0102] S2. Fix the doped graphite rod to the anode of the electric arc furnace to form a graphite anode. Start the stepper motor to bring the graphite anode into contact with the cathode. Lock the electric arc furnace door and turn on the vacuum system to evacuate the furnace cavity to below 5 Pa. Then, fill the furnace cavity with helium through the gas system to bring the pressure to 10 kPa. Turn on the cooling water system and the DC motor, and slowly adjust the current to 200 A. During the adjustment process, repeatedly check the observation window until the doped graphite rod glows red and bright due to the current. However, ensure that the doped graphite rod does not arc. Activate the doped graphite rod online for 30 minutes at 200 A. After evacuating the furnace cavity, fill it with inert gas and activate the doped graphite rod online by current. Then, turn off the DC motor.

[0103] S3. Evacuate the electric arc furnace cavity to below 5 Pa using the vacuum system, and then fill the electric arc furnace cavity with helium through the gas system until the pressure is 5 kPa. Repeat this process 3 times. Fill the electric arc furnace cavity with inert gas (preferably helium) until the pressure is 300 Torr. Turn on the DC motor and slowly adjust the current to 120 A. Start the stepper motor to slowly retract the graphite anode. An electric arc can be observed. Continue to adjust the stepper motor to make the distance between the cathode and the graphite anode 1 cm until the mixture of the hollow part of the graphite rod is completely reacted. After the reaction is complete, adjust the current to 0 and turn off the DC motor. Adjust the stepper motor to return the graphite anode to the initial position. Then collect the carbon ash generated by the reaction. The carbon ash is a mixture of carbon clusters.

[0104] S4. Weigh 200g of carbon ash and place it in a 10L glass jar. Add 8L of o-xylene to the glass jar to immerse the carbon ash. Place the glass jar in a constant temperature ultrasonic instrument at 60℃ and a frequency of 50HZ for ultrasonic extraction for 30 minutes. After standing for 10 hours, use a vacuum funnel to filter the supernatant to remove the carbon ash. Use a centrifuge to separate the solid and liquid layers of the lower precipitate at the bottom of the container. Then, use a vacuum funnel to filter and remove the carbon ash again. At this point, the solution in the filtration flask is a black, high-concentration crude fullerene extract. Add the filtered carbon ash back into o-xylene and repeat the steps of ultrasonic extraction, standing, centrifugation, and filtration to remove carbon ash until the solution in the filtration flask is colorless. Collect all the solutions in the filtration flasks and concentrate them to obtain the crude fullerene extract.

[0105] S5. The crude fullerene extract to be separated was filtered through a 0.22 μm organic filter membrane for injection into the high-performance liquid chromatography (HPLC). Then, a 5PYE preparative column (φ20×250 mm) was used with o-xylene as the mobile phase at a flow rate of 12 mL / min and a detection wavelength of 330 nm. Manual injection was employed, with an injection volume of 15 mL per sample. The target product Sc2C2@C was collected based on the UV detector signal. s (hept)-C 88 The corresponding chromatographic peak fraction; then the Sc2C2@C collected in the first round s (hept)-C 88 The fraction was concentrated, and a 5PBB semi-preparative column (φ10×250mm) was used. The mobile phase was o-xylene, and the flow rate was set to 4 mL / min. After injection and separation, the target product Sc2C2@C was collected. s (hept)-C 88 The corresponding fraction; then the Sc2C2@C collected in the second round s (hept)-C 88 The fraction was concentrated, and a Bucky-M preparative chromatographic column (φ10×250mm) was used. Toluene was used as the mobile phase, and the flow rate was set to 12 mL / min. After injection and separation, the target product Sc2C2@C was collected. s (hept)-C 88 The corresponding fraction; then the Sc2C2@C collected in the third round s (hept)-C 88 The fraction was concentrated, and a 5PBB semi-preparative column (φ10×250mm) was used. Toluene was used as the mobile phase, and the flow rate was set to 8 mL / min. After injection and separation, the target product Sc2C2@C was collected. s (hept)-C 88 The corresponding fraction; then the Sc2C2@C collected in the fourth round s (hept)-C 88The fraction was concentrated, and a 5PYE semi-preparative column (φ10×250mm) was used. The mobile phase was o-xylene, and the flow rate was set to 4 mL / min. After injection and separation, the target product Sc2C2@C was collected. s (hept)-C 88 The corresponding fractions were then collected. Finally, the fraction obtained in the fifth round was concentrated and purified using a Buckyprep analytical column (φ2.5×250mm) at a flow rate of 1mL / min to obtain high-purity endogenous metallofullerene (Sc2C2@C). s (hept)-C 88 ).

[0106] Performance characterization:

[0107] 1. Matrix-assisted laser desorption / ionization time-of-flight mass spectrometry was used to analyze the Sc2C2@C sample. s (hept)-C 88 Perform analysis;

[0108] Specifically, first check if the instrument is ready. A lit ready indicator light on the front panel indicates it is ready to use. If the indicator light is off, it means the sample target is outside the instrument or the internal pressure is higher than the normal operating range. Use a pipette to place 1 μL of matrix solution into the orifice of the target plate. Then place the test solution on top of the matrix solution. Use a pipette to quickly aspirate and drop the solution from the orifice three times to mix thoroughly. Allow it to dry. Record the position. Press "Load / Eject," wait for the inlet cover to open, then eject the target plate. Place the target holder containing the sample target onto the sample target platform, ensuring the four corners are aligned. Press "Load / Eject," close the sample inlet cover, and begin vacuuming. Be careful not to drop any debris into the sample target inlet or onto the black O-ring, as this may affect the normal operation of the instrument. Wait for the vacuum level to reach 1.0 × 10⁻⁶. -7 Based on the molecular weight and properties of the sample, an appropriate method should be selected to analyze the Sc2C2@C sample. s (hept)-C 88 Conduct tests, such as Figure 1 As shown, the mass spectrum signal of the sample is 1169.8 m / z.

[0109] 2. The Sc2C2@C sample was analyzed using a UV-Vis absorption spectrometer. s (hept)-C 88 Perform analysis;

[0110] Place 2 mg of sample in a clean, dry 20 mL sample vial, add 2 mL of CS2, and sonicate until no insoluble particles are visible to the naked eye (sonication time should be no less than 15 min). Filter through a 0.22 μm filter membrane and retain the filtrate as the sample solution. Select an appropriate cuvette based on the sample concentration and the wavelength range to be measured. Commonly used cuvette materials include quartz glass (suitable for 200-800 nm) and optical glass (suitable for 320-2500 nm). (nm), this time an optical glass cuvette was selected. The inner and outer walls of the cuvette were rinsed with CS2 and wiped clean with filter paper to ensure that no contaminants would affect the light path. The UV-Vis spectrophotometer was turned on and preheated for about 15 minutes to ensure the stability of the light source. The scanning range was set to 2000-400nm and the scanning speed to 100nm / min. In the advanced settings, the bandwidth was set to 1 and baseline correction was checked. Click OK. The cuvette was filled with blank solvent (CS2) and placed in the sample cell to calibrate the instrument with zero absorbance or 100% transmittance to eliminate solvent interference with the spectrum. The cuvette was filled with blank solution (pure solvent CS2) and placed in the sample cell to measure the baseline. The sample solution was poured into the cuvette, and the cuvette was gently shaken to distribute the solution evenly and avoid the formation of air bubbles. The sample cuvette was placed in the sample cell of the spectrometer, and then the measurement was started. Figure 2 As shown, the sample Sc2C2@C was obtained. s (hept)-C 88 The ultraviolet-visible absorption spectrum.

[0111] 3. The Sc2C2@C sample was analyzed using a Rigaku micro-focusing rotating target single-crystal diffractometer. s (hept)-C 88 The structure is analyzed.

[0112] First, the purified toluene solution containing the intercalated metallofullerene is concentrated and transferred to a conical tube with a bottom diameter of approximately 1.5 mm. A saturated toluene solution of NiII–OEP is then slowly added dropwise. The tube is then sealed with a sealing film. After approximately ten days of evaporation, the solution has completely evaporated, and black, blocky single crystals can be observed on the tube wall and bottom. For samples not containing the mother liquor, a small amount of sample should be taken and placed on a glass slide. A suitable amount of crystal-picking oil should be dropped onto the slide, and the sample should be dispersed in the oil using a needle or similar tool to prevent multiple crystals from adhering. Then, high-quality single crystals should be carefully examined under a microscope. Generally, good single crystals should be clean and uniform. A high-magnification microscope should be used for observation to avoid cracks or twins that are not visible under low-magnification microscopes. Furthermore, other impurities or even small fragments of single crystals should be avoided from adhering to the single crystal. If this is encountered, the single crystal should be repeatedly washed with a needle in clean oil until completely clean. For copper targets, the ideal crystal size should be 0.2 mm–0.55 mm. The minimum size of the crystal is not strictly limited (X-ray spot size is 0.8 mm), mainly depending on its diffraction intensity. For crystals with high X-ray absorption, ensure the minimum X-ray transmittance is 10-20%. If a suitable crystal size is unavailable, the tester can try cutting large crystals or crystal clusters with a blade, capturing a high-quality single crystal using a crystal ring, and mounting the crystal ring with the single crystal onto the base. For oddly shaped crystals, try to center the crystal's centroid. For long needle-shaped crystals, try placing them along the axis of the base to ensure diffraction points are still present at higher angles. The resolution can be adjusted as needed (0.75 Å for Mo targets, 0.83 Å step size for Cu targets). Add the calculated strategy to the experimental sequence. Longer diffraction times are always beneficial for obtaining a high signal-to-noise ratio, but they also produce overexposed points. During integration, overexposed points are deleted and replaced with diffraction points generated by fast scanning.

[0113] Finally, crystal data reconstruction and analysis were performed. The data measured by the instrument was analyzed by software to obtain Sc2C2@C. s (hept)-C 88 Please refer to the crystal structure diagram. Figure 3 .

[0114] 4. The sample Sc2C2@C was analyzed using an analytical high-performance liquid chromatograph. s (hept)-C 88 Purity was analyzed.

[0115] Weigh 2 mg (accurate to 0.1 mg) of carbon cluster sample into a clean, dry 20 mL sample vial, add 2 mL of toluene, and sonicate until no insoluble particles are visible to the naked eye (sonication time not less than 15 min). Filter through a 0.22 μm filter membrane and retain the filtrate as the carbon cluster sample solution. Turn on the high-performance liquid chromatograph (HPLC) and preheat it. Perform baseline detection on the HPLC. If the dynamic short-term baseline noise does not exceed 0.05 mAU and the dynamic baseline drift does not exceed 1 mAU / h within a detection time of not less than 15 min, the baseline detection is passed. Perform chromatographic analysis on the toluene solution of the carbon cluster sample, record the retention time, repeat the operation twice, and take the arithmetic mean of the two retention times as the result of the carbon cluster sample retention time. Use a high-performance liquid chromatography (HPLC) system for analysis, using a 5NPE column as the separation column, toluene as the mobile phase, a flow rate generally set to 2.0 mL / min, and a detection wavelength set to 330 nm. Inject the sample solution into the HPLC system using an autosampler, with an injection volume generally around 1 mL / min. Approximately mL of sample enters the chromatographic column, where it is separated based on the size and polarity differences of different carbon clusters. Each carbon cluster produces a chromatographic peak at a different retention time. Throughout the chromatographic analysis, chromatographic software is used to record and collect chromatographic data. The peak area is calculated using the integration function of the software. The peak area of ​​the target carbon cluster sample is divided by the sum of the peak areas of all other carbon clusters to obtain the target carbon cluster sample Sc2C2@C. s (hept)-C 88 The purity is 100% ( Figure 4 ).

[0116] Example 2

[0117] This embodiment provides an embedded metal fullerene and its preparation method. The preparation method is the same as in Example 1, except that the carbon cage of the final embedded metal fullerene is larger and the Sc2C2 configuration of the embedded cluster is different, which will not be described in detail here. The final result is Sc2C2@C2(40)-C 90 .

[0118] Performance characterization:

[0119] 1. Matrix-assisted laser desorption / ion-time mass spectrometry was used to analyze the sample Sc2C2@C2(40)-C. 90 Perform an analysis. See also Figure 5 As shown, the mass spectrum signal of the sample is 1193.9 m / z.

[0120] 2. The sample Sc2C2@C2(40)-C was analyzed using a UV-Vis absorption spectrometer. 90 Perform analysis, such as Figure 6 As shown, the sample Sc2C2@C2(40)-C was obtained. 90The ultraviolet-visible absorption spectrum.

[0121] 3. The Sc2C2@C2(40)-C sample was analyzed using a Rigaku micro-focusing rotating target single crystal diffractometer. 90 The structure was analyzed, and the data measured by the instrument was parsed by the software to obtain Sc2C2@C2(40)-C 90 For the structure, please refer to Figure 7 .

[0122] 4. The sample Sc2C2@C2(40)-C was analyzed using an analytical high-performance liquid chromatograph. 90 Purity analysis was performed by dividing the peak area of ​​the target carbon cluster by the sum of the peak areas of all other chromatographic peaks, yielding a purity of 99.5% for the target carbon cluster sample. (See [reference needed]). Figure 8 .

[0123] Example 3

[0124] This embodiment provides an endogenous metallofullerene and its preparation method. The difference between the preparation method and that in Embodiment 1 is that the atmosphere in step S3 is 300 Torr of helium and 30 Torr of nitrogen. Other steps and methods are the same as in Embodiment 1 and will not be repeated here.

[0125] Performance characterization:

[0126] 1. Matrix-assisted laser desorption / ionization time-of-flight mass spectrometry was used to analyze the sample Sc3N@D3(6140)-C. 68 Perform analysis, such as Figure 9 As shown, the mass spectrum signal of the sample is 966 m / z.

[0127] 2. The UV-Vis absorption spectrometer was used to analyze the sample Sc3N@D3(6140)-C. 68 Perform analysis, such as Figure 10 As shown, the sample Sc3N@D3(6140)-C was obtained. 68 The ultraviolet-visible absorption spectrum.

[0128] 3. The Sc3N@D3(6140)-C sample was analyzed using a Rigaku micro-focusing rotating target single-crystal diffractometer. 68 The structure was analyzed, and the data measured by the instrument was parsed by the software to obtain Sc3N@D3(6140)-C 68 For the structure, please refer to Figure 11 .

[0129] 4. The sample Sc3N@D3(6140)-C was analyzed using an analytical high-performance liquid chromatograph. 68 Purity analysis is performed by dividing the peak area of ​​the target carbon cluster by the sum of the peak areas of all other chromatographic peaks to obtain the purity of the target carbon cluster sample. (See [link to relevant documentation]). Figure 12 .

[0130] Comparative Example 1

[0131] This comparative example provides an endohedral metallofullerene and its preparation method. The difference between the preparation method and that in Example 1 is that the online activation step is not performed in step S2; the other steps and methods are the same as in Example 1, and will not be repeated here.

[0132] See Figure 13 The figure shows the high-performance liquid chromatography (HPLC) chromatograms of the carbon ash prepared in step S3 with and without online activation in step S2 (left figure). It is clear from the figure that the online activation step significantly increases the content of the endogenous metallofullerenes (with the most abundant being Sc2C2@C). 82 (For example).

[0133] See Figure 14 The carbon mass spectra prepared in step S3, showing the results of online activation (left) and no online activation (right) steps in step S2, also demonstrate that the online activation step significantly increases the content of the endogenous metallofullerene (in C2). 60 C 70 ,Sc2C2@C 82、 C 2n / Sc2C2@C 2n (For example).

[0134] Comparative Example 2

[0135] This comparative example provides an endogenous metallofullerene and its preparation method. The difference between the preparation method and that of Example 1 is that the multiple atmosphere replacement process is not performed in step S3; the other steps and methods are the same as those in Example 1, and will not be repeated here.

[0136] See Figure 15 The image shows the mass spectrometry data of carbon ash prepared in Example 1 with multiple atmosphere replacement process (left image), compared with the mass spectrometry data of carbon ash prepared in Comparative Example 2 without multiple atmosphere replacement process (right image). It is clear that the multiple atmosphere replacement process significantly improves the yield of the target product (intercalated metal carbide fullerene). Without atmosphere replacement, impurities such as N2, O2, and H2O are present in the chamber, leading to a decrease in the yield of intercalated metal fullerene and the generation of a large amount of Sc3N@C. 80 Sc2O@C 82 and Sc4O2@C 80 Fullerenes with embedded metal nitrogen / oxide.

[0137] In summary, this invention effectively solves the problems of unstable yield and significant impurity interference in traditional methods by introducing an online activation step and a multiple atmosphere replacement process. Online activation preferentially converts the metal source into more reactive metal carbides and completely eliminates adsorbed water vapor on the graphite rod surface. Combined with precisely controlled gas pressure and discharge current in arc discharge, a pure and controllable reaction environment is created for the nucleation and growth of endogenous metal fullerenes. This not only significantly improves the synthesis yield of the target product but also greatly enhances the reproducibility and reliability of the entire synthesis process. The multi-stage, gradient high-performance liquid chromatography purification strategy in this invention achieves a breakthrough in obtaining atomically precise structural products from complex crude products. By dynamically using chromatographic columns with different separation mechanisms based on chromatographic peaks, the subtle physicochemical differences between the target endogenous metal fullerene and impurities can be efficiently amplified, thereby achieving precise separation and ultimately obtaining samples with a purity higher than 99.5%, meeting the stringent requirements for material structural accuracy and performance consistency in high-end applications such as quantum devices. This invention seamlessly integrates improved arc discharge synthesis with high-efficiency chromatographic purification technology, forming a complete, efficient, and scalable technical path. It not only inherits the advantages of low equipment cost and easy scale-up of the arc discharge method, but also achieves "on-demand customization" of the final product's structure and properties through precise control throughout the entire process. This lays a solid material foundation for the practical application of embedded metallofullerenes as core functional materials in multi-field responsive devices such as optical, electrical, and magnetic fields. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and has high industrial application value.

[0138] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing an endohedral metallofullerene, characterized in that, The preparation method includes the following steps: S1. Mix the metal source and graphite powder in a certain proportion and fill them into a hollow graphite rod to make a doped graphite rod. S2. Fix the doped graphite rod to the anode end of the electric arc furnace to form a graphite anode, so that the graphite anode is in contact with the cathode. After evacuating the electric arc furnace cavity, fill it with inert gas and activate the doped graphite rod online by means of current. S3. Under an inert atmosphere and discharge current at a certain pressure, an electric arc discharge reaction is carried out, and the carbon ash generated by the reaction is collected. S4. The carbon ash is ultrasonically extracted using an organic solvent to obtain a crude fullerene extract. S5. The crude fullerene extract is purified by multi-stage separation using high-performance liquid chromatography. The multi-stage separation and purification includes at least one primary separation using a preparative chromatographic column and at least one fine separation using a semi-preparative chromatographic column to obtain high-purity endogenous metal-intercalated fullerenes.

2. The method for preparing endohedral metallofullerenes according to claim 1, characterized in that: In step S1, the molar ratio between the metal element in the metal source and the carbon element in the graphite powder is 1:(12~18), wherein the metal element in the metal source is scandium.

3. The method for preparing endohedral metallofullerenes according to claim 1, characterized in that: The specific conditions for online activation in step S2 are as follows: under inert gas protection, a current of 180~220A is passed through and heated for 20~40 minutes.

4. The method for preparing endohedral metallofullerenes according to claim 1, characterized in that: Before the electric arc discharge reaction, step S3 requires multiple replacements of the electric arc furnace cavity. Specifically, the gas pressure inside the electric arc furnace cavity is evacuated to below 5 Pa, and then inert gas is introduced until the gas pressure is 5 kPa. This process is repeated 2 to 4 times.

5. The method for preparing endohedral metallofullerenes according to claim 1, characterized in that: The conditions for the arc discharge reaction in step S3 are as follows: the inert atmosphere includes helium, the gas pressure is 200~400 Torr, and the discharge current is 100~150A.

6. The method for preparing endohedral metallofullerenes according to claim 1, characterized in that: Step S4, which involves ultrasonic extraction of the carbon ash using an organic solvent, includes the following steps: S41. The carbon ash is immersed in an organic solvent for ultrasonic extraction. After standing, the supernatant is collected and the lower precipitate is centrifuged. Then, the supernatant and the lower centrifuged liquid are filtered to remove the carbon ash, and the solution in the filtration flask is obtained. S42. Add the carbon ash removed by vacuum filtration back into the organic solvent, and repeat the steps of ultrasonic extraction, standing, centrifugation and vacuum filtration to remove carbon ash until the solution in the vacuum filtration flask is colorless. S43. Collect the solution in all the filtration flasks, concentrate it, and obtain the crude fullerene extract.

7. The method for preparing endohedral metallofullerenes according to claim 6, characterized in that: Includes one or a combination of the following conditions: The liquid-to-solid ratio of the organic solvent to the carbon ash is 35 mL / g to 45 mL / g; The organic solvent includes o-xylene; The ultrasonic extraction frequency is 30~80HZ, and the ultrasonic extraction temperature is 50~70℃.

8. The method for preparing endohedral metallofullerenes according to claim 1, characterized in that: Before performing multi-stage separation and purification by high performance liquid chromatography in step S5, the crude fullerene extract is first filtered using a 0.22 μm organic filter membrane.

9. The method for preparing endohedral metallofullerenes according to claim 1, characterized in that: Step S5 includes one or a combination of the following conditions: The preparative chromatographic column has a specification of φ20×250mm, and the preparative chromatographic column is selected from one or a combination of Buckyprep, 5PYE, and Buckyprep-M type chromatographic columns; The semi-preparative chromatographic column has a specification of φ10×250mm and is selected from one or a combination of Buckyprep, 5PBB, 5PYE, 5NPE, and Buckyprep-M type chromatographic columns. The multi-stage separation and purification also includes separation using an analytical chromatographic column, wherein the analytical chromatographic column has a specification of φ2.5×250mm and is selected from one or a combination of Buckyprep and 5PYE type chromatographic columns; The mobile phase used in the separation and purification is one or a combination of o-xylene and toluene.

10. An endohedral metallofullerene, characterized in that: The metal-embedded fullerene is prepared by the method described in any one of claims 1 to 9.

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