Preparation method of alkaline earth metal atom intercalation doped fullerene molecule covalent polymer single crystal

Abstract

The invention relates to the field of composite material preparation, in particular to a preparation method of an alkaline earth metal atom intercalation doped fullerene molecule covalent polymer single crystal. The preparation method comprises the following steps: A) sealing an alkaline earth metal source and fullerene molecular crystal polycrystal powder in a container in a protective atmosphere and under a vacuum condition, and then carrying out a heating reaction to obtain a reaction product; and B) taking out a single crystal product in the reaction product, and washing to obtain the alkaline earth metal atom intercalation doped fullerene molecule covalent polymer single crystal, wherein the alkaline earth metal source is alkaline earth metal and / or an alkaline earth metal compound; alkaline earth metal in the alkaline earth metal source is Mg, Ca, Sr or Ba; the temperature of the heating reaction is 300 to 1000 DEG C. According to the preparation method, the size of the single crystal can be increased, the yield is improved, the time is shortened, and the preparation efficiency is improved.

Description

Technical Field

[0001] The invention relates to the field of composite material preparation, and in particular to a method for preparing alkaline earth metal atom intercalation doped fullerene molecule covalent polymer single crystal. Background Art

[0002] As an allotrope of carbon, fullerene molecules have clear molecular structures and unique physical and chemical properties. They are often used as basic structural units for constructing new carbon materials or composite materials. Fullerene molecules can be assembled into molecular crystals through van der Waals interactions at room temperature and pressure, showing unique structures and properties. The introduction of other element atoms or small molecules can further expand the possibilities of the crystal structure and properties of fullerene molecular crystals. Among them, the uniform intercalation of metal atoms into the gaps of fullerene molecular crystals can construct a series of new carbon-based composite crystal materials containing ionic bonds, especially active metal (alkali metal and alkaline earth metal) atoms that can donate electrons. They show great potential for regulating the lattice and electronic structure of carbon-based composite crystals and each low-dimensional structural unit therein, thereby hoping to obtain unique lattice structures and transcendent intrinsic properties. For example, alkali metal A (A = K, Rb, Cs) intercalated into the center-centered cubic C 60 Molecular crystals, formed by A3C 60 The composite crystal exhibits superconducting properties at low temperatures, and the superconducting transition temperature can reach above 30K; alkali metal Li, Na and alkaline earth metal Mg intercalation C 60 Molecular crystals can induce covalent bonds between adjacent molecules to form Li4C 60 、Na4C 60 and Mg2C 60 The crystal is a type of superionic conductor that exhibits excellent properties for conducting metal ions.

[0003] Currently, A3C 60 The preparation method of the composite crystal is mainly based on gas curing reaction. At a certain temperature, alkali metal atomic vapor slowly penetrates into the fullerene molecular crystal to form A3C 60 Composite crystals, mostly polycrystalline thin film structures; Li4C 60 、Na4C 60 and Mg2C 60 The preparation method of crystals is mainly based on solid-solid chemical reaction, but the preparation time is generally long, requiring 7 days or more. In the middle, it is necessary to grind multiple times in an inert atmosphere to improve the reaction efficiency. The operation is relatively complicated, and the products are mostly polycrystalline materials with poor uniformity and crystallinity, which is not conducive to the study of intrinsic properties. In 2018, a literature reported that Japanese scholars used dual gas phase transport technology to prepare Mg2C 60 Crystal 500 micron size single crystal material, that is, at 500-600℃ and vacuum conditions, metal atoms and C 60The molecules migrate from the high temperature end to the low temperature end in the form of gas, forming Mg2C 60 Composite crystal single crystal, but the single crystal size is small, the yield is low, and the reproducibility is poor; In 2022, a literature reported that scholars from the Institute of Chemistry of the Chinese Academy of Sciences and Columbia University used dual gas phase transport technology to prepare Mg4C 60 The single crystal material with a size of 200 to 300 microns is also a problem of small single crystal size and low yield. In summary, there is an urgent need for a universal method that can efficiently prepare large-sized single crystals of metal fullerene or metal fullerene molecule covalent polymer composite crystals. Summary of the invention

[0004] In view of the problems that the previous preparation of alkaline earth metal atom intercalation doped fullerene molecule covalent polymers often has a polycrystalline structure, a small size, a low yield, and a long time consumption, the present invention provides a method for preparing single crystals of alkaline earth metal atom intercalation doped fullerene molecule covalent polymers, which can increase the size of the single crystal, improve the yield, shorten the time and improve the preparation efficiency, and is a fast and efficient preparation method.

[0005] The present invention provides a method for preparing an alkaline earth metal atom intercalation doped fullerene molecule covalent polymer single crystal, comprising the following steps:

[0006] A) sealing an alkaline earth metal source and fullerene molecular crystal polycrystalline powder in a container under a protective atmosphere and vacuum conditions, and then heating and reacting to obtain a reaction product;

[0007] B) taking out the single crystal product from the reaction product, washing it, and obtaining a single crystal of a covalent polymer of alkaline earth metal atoms intercalated and doped fullerene molecules;

[0008] in,

[0009] The alkaline earth metal source is an alkaline earth metal and / or an alkaline earth metal compound;

[0010] The alkaline earth metal in the alkaline earth metal source is Mg, Ca, Sr or Ba;

[0011] The temperature of the heating reaction is 300-1000°C.

[0012] Preferably, the fullerene molecular crystal is selected from C 60 , C 70 , C 78 , C 80 , C 82 , C 84 and C 90 At least one of the molecular crystals;

[0013] The alkaline earth metal source is at least one of magnesium, calcium, strontium, magnesium hydride, calcium hydride, strontium hydride, magnesium nitride, calcium nitride and strontium nitride.

[0014] Preferably, the molar ratio of the alkaline earth metal atoms in the alkaline earth metal source to the molecules in the fullerene molecule crystal is (1-50):1.

[0015] Preferably, the solvent used for the washing is at least one of cyclopentane, cyclohexane, chloroform, carbon tetrachloride, carbon disulfide, benzene, toluene, xylene, trimethylbenzene, chlorobenzene, isopropanol, acetone and anhydrous ethanol.

[0016] Preferably, step A) specifically comprises:

[0017] A1) adding an alkaline earth metal source and fullerene molecular crystal polycrystalline powder into a quartz tube under a protective atmosphere, and then sealing the quartz tube under vacuum conditions;

[0018] A2) placing the quartz tube into a heating furnace, so that the raw materials in the quartz tube are at the center of the temperature zone, and undergoing heating reaction to obtain a reaction product.

[0019] Preferably, step A1) specifically comprises: adding the alkaline earth metal source and the fullerene molecular crystal polycrystalline powder into a quartz tube with one end sealed under a protective atmosphere, and then sealing the other end of the quartz tube under vacuum conditions.

[0020] Preferably, the quartz tube has a length of 10 to 50 cm and an inner diameter of 5 to 50 mm.

[0021] Preferably, the vacuum degree of the vacuum condition is 0.01-100Pa.

[0022] Preferably, the reaction time is 1 to 50 hours;

[0023] The heating reaction temperature rise rate is 1-20°C / min.

[0024] Preferably, the alkaline earth metal source is in powder or block form;

[0025] The purity of the alkaline earth metal source is above 99.9%;

[0026] The purity of the fullerene molecular crystal polycrystalline powder is above 99%.

[0027] The present invention provides a solid phase synthesis method for rapidly preparing large-sized single crystals of alkaline earth metal atom intercalation doped fullerene molecule covalent polymers. Fullerene molecule crystal polycrystalline powder is mixed with alkaline earth metal source powder or block or compound powder and vacuum sealed at one end of a quartz tube, a solid phase chemical reaction occurs at a certain temperature for a certain period of time, and after the reaction is complete, a single crystal product is found in the reaction area, and the single crystal product is washed with a specific solvent to obtain a large-sized single crystal of alkaline earth metal atom intercalation doped fullerene molecule covalent polymer. The method of the present invention successfully prepares large-sized single crystals, and the above-mentioned solid phase synthesis method is simple and easy to operate, takes a short time, has a high yield, and can be prepared in batches.

[0028] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention adopts two or more solid powders to mix for solid phase chemical reaction, the alkaline earth metal source and the fullerene molecular crystal are in close contact, the preparation time is short, and the preparation efficiency is improved; (2) The alkaline earth metal atom intercalation doped fullerene molecular covalent polymer single crystal material prepared by the present invention is relatively large in size, which can reach more than 2.3 mm; the size refers to the longest dimension in the length direction of the crystal. In the prior art, the material is mostly in the form of amorphous powder, and the largest reported crystal sample is only about a few hundred microns, which is relatively small in size. Compared with this, the present invention significantly increases the crystal size; (3) The yield of the preparation method of the present invention is relatively high, which can reach more than 16%; the yield of the reported crystal sample is usually no more than 10%, and the present invention greatly improves the yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0030] Figure 1 This is an optical image of the alkaline earth metal atom intercalation doped fullerene molecule covalent polymer single crystal obtained in Example 1;

[0031] Figure 2 The X-ray diffraction pattern of the alkaline earth metal atom intercalation doped fullerene molecule covalent polymer single crystal obtained in Example 1;

[0032] Figure 3 This is a Raman spectrum of the alkaline earth metal atom intercalation doped fullerene molecule covalent polymer single crystal obtained in Example 1;

[0033] Figure 4 This is an optical image of the alkaline earth metal atom intercalation doped fullerene molecule covalent polymer single crystal obtained in Example 2;

[0034] Figure 5 This is an optical image of the alkaline earth metal atom intercalation doped fullerene molecule covalent polymer single crystal obtained in Example 3. DETAILED DESCRIPTION

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0036] In this article, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0037] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0038] Herein, when it comes to numerical ranges, unless otherwise specified, the numerical ranges are deemed to be continuous and include the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0039] In this article, when referring to the unit of a data range, if there is a unit only after the right endpoint, it means that the units of the left and right endpoints are the same. For example, 300~1000℃ means that the units of the left endpoint "300" and the right endpoint "1000" are both ℃.

[0040] The present invention provides a method for preparing an alkaline earth metal atom intercalation doped fullerene molecule covalent polymer single crystal, comprising the following steps:

[0041] A) sealing an alkaline earth metal source and fullerene molecular crystal polycrystalline powder in a container under a protective atmosphere and vacuum conditions, and then heating and reacting to obtain a reaction product;

[0042] B) taking out the single crystal product from the reaction product, washing it, and obtaining a single crystal of a covalent polymer of alkaline earth metal atoms intercalated and doped fullerene molecules;

[0043] in,

[0044] The alkaline earth metal source is an alkaline earth metal and / or an alkaline earth metal compound;

[0045] The alkaline earth metal in the alkaline earth metal source is Mg, Ca, Sr or Ba;

[0046] The temperature of the heating reaction is 300-1000°C.

[0047] [About Step A]:

[0048] A) An alkaline earth metal source and fullerene molecular crystal polycrystalline powder are sealed in a container under a protective atmosphere and vacuum conditions, and then heated to react to obtain a reaction product.

[0049] In the present invention, the alkaline earth metal source is an alkaline earth metal and / or an alkaline earth metal compound. Wherein, the alkaline earth metal is Mg (magnesium), Ca (calcium), Sr (strontium) or Ba (barium). In the present invention, preferably, the alkaline earth metal source is at least one of magnesium, calcium, strontium, magnesium hydride, calcium hydride, strontium hydride, magnesium nitride, calcium nitride and strontium nitride. In the present invention, the alkaline earth metal source is in powder or block form. In the present invention, the purity of the alkaline earth metal source is preferably above 99.9%.

[0050] In the present invention, the fullerene molecular crystal is preferably C 60 , C 70 , C 78 , C 80 , C 82 , C 84 and C 90 At least one of the molecular crystals. In the present invention, the purity of the fullerene molecular crystal polycrystalline powder is preferably above 99%.

[0051] In the present invention, the molar ratio of the alkaline earth metal atoms in the alkaline earth metal source to the molecules in the fullerene molecule crystal is preferably (1-50):1, specifically 1:1, 3:1, 5:1, 9:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, 50:1, more preferably (1-20):1.

[0052] In the present invention, the above two raw materials are sealed in a container under a protective atmosphere and vacuum conditions. Specifically, the above two raw materials can be mixed in advance and then sealed in a container under a protective atmosphere and vacuum conditions; or the above two raw materials can be put into a container and mixed, and then the container is sealed. In the present invention, the container is preferably a quartz tube. In the present invention, the length of the quartz tube is preferably 10 to 50 cm, more preferably 10 to 30 cm. The inner diameter of the quartz tube is preferably 5 to 50 mm, more preferably 10 to 30 mm.

[0053] In the present invention, step A) preferably specifically comprises:

[0054] A1) adding an alkaline earth metal source and fullerene molecular crystal polycrystalline powder into a quartz tube under a protective atmosphere, and then sealing the quartz tube under vacuum conditions;

[0055] A2) placing the quartz tube into a heating furnace, so that the raw materials in the quartz tube are at the center of the temperature zone, and undergoing heating reaction to obtain a reaction product.

[0056] Regarding step A1): Preferably, the specific steps are as follows: add the alkaline earth metal source and fullerene molecular crystal polycrystalline powder into a quartz tube sealed at one end under a protective atmosphere, and then seal the other end of the quartz tube under vacuum conditions. The present invention has no special restrictions on the type of gas providing a protective atmosphere, and it can be a conventional inert gas in the field, such as nitrogen, argon, etc. Add the materials into a quartz tube sealed at one end under a protective atmosphere and mix them evenly, and then seal the other end of the quartz tube under vacuum conditions. Among them, the vacuum degree of the vacuum condition is preferably 0.01 to 100 Pa, and more preferably 0.01 to 10 Pa. When the sealing is performed after the loading is completed, it is preferably a high-temperature seal; the sealing temperature is preferably 1000 to 3000°C.

[0057] Regarding step A2): Place the sealed quartz tube into a heating furnace so that the raw materials in the quartz tube are in the center of the temperature zone. Among them, the heating furnace is preferably a tubular furnace. When placing the sealed quartz tube into the heating furnace, it is preferably placed horizontally, and ensure that the raw materials in the quartz tube are in the center of the temperature zone. After loading the furnace, a heating reaction is carried out. The heating furnace is preferably in a protective atmosphere, that is, heat treatment is carried out under a protective atmosphere; more preferably, an argon atmosphere. The temperature of the heating reaction is 300 to 1000°C, specifically 300°C, 400°C, 500°C, 600°C, 680°C, 700°C, 800°C, 900°C, 1000°C, and more preferably 400 to 800°C. The heating rate of the heating is preferably 1 to 20°C / min, specifically 1°C / min, 5°C / min, 15°C / min, 20°C / min. The holding time of the heating reaction is preferably 1 to 50 hours, specifically 1 hour, 5 hours, 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 45 hours, 50 hours. The above heating causes a solid phase reaction between the raw materials to generate an alkaline earth metal atom intercalation doped fullerene molecule covalent polymer single crystal material.

[0058] [About step B]:

[0059] In the present invention, after the reaction in step A) is completed, the single crystal product in the obtained reaction product is picked out and washed. The present invention preferably uses a specific organic solvent for ultrasonic cleaning. Among them, the organic solvent is preferably at least one of cyclopentane, cyclohexane, chloroform, carbon tetrachloride, carbon disulfide, benzene, toluene, xylene, trimethylbenzene, chlorobenzene, acetone, isopropanol and anhydrous ethanol; the use of the above solvents can well remove unreacted fullerene molecules. The time for ultrasonic cleaning of each solvent is preferably 10 to 200 minutes. After ultrasonic cleaning, vacuum filtration is preferably performed to obtain a clean alkaline earth metal atom intercalation doped fullerene molecule covalent polymer single crystal material.

[0060] The present invention provides a solid phase synthesis method for rapidly preparing large-sized single crystals of alkaline earth metal atom intercalation doped fullerene molecule covalent polymers. Fullerene molecule crystal polycrystalline powder is mixed with alkaline earth metal source powder or block or compound powder and vacuum sealed at one end of a quartz tube, a solid phase chemical reaction occurs at a certain temperature for a certain period of time, and after the reaction is complete, a single crystal product is found in the reaction area, and the single crystal product is washed with a specific solvent to obtain a large-sized single crystal of alkaline earth metal atom intercalation doped fullerene molecule covalent polymer. The method of the present invention successfully prepares large-sized single crystals, and the above-mentioned solid phase synthesis method is simple and easy to operate, takes a short time, has a high yield, and can be prepared in batches.

[0061] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention adopts two or more solid powders to mix for solid phase chemical reaction, the alkaline earth metal source and the fullerene molecular crystal are in close contact, the preparation time is short, and the preparation efficiency is improved; (2) The alkaline earth metal atom intercalation doped fullerene molecular covalent polymer single crystal material prepared by the present invention is relatively large in size, which can reach more than 2.3 mm; the size refers to the longest dimension in the length direction of the crystal. In the prior art, the material is mostly in the form of amorphous powder, and the largest reported crystal sample is only about a few hundred microns, which is relatively small in size. Compared with this, the present invention significantly increases the crystal size; (3) The yield of the preparation method of the present invention is relatively high, which can reach more than 16%; the yield of the reported crystal sample is usually no more than 10%, and the present invention greatly improves the yield.

[0062] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0063] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods. Among them, the purity of the alkaline earth metal source is above 99.9%, and the purity of the fullerene molecular crystal polycrystalline powder is above 99%.

[0064] Example 1

[0065] A1) In an argon atmosphere glove box, 120 mg of magnesium hydride powder and 360 mg of fullerene C60 molecular crystal powder (molar ratio of metal atoms to crystal molecules 9:1) were added to a quartz tube with a length of 25 cm, an inner diameter of 16 mm, and a wall thickness of 2 mm, mixed evenly, and subjected to high-temperature vacuum packaging with a vacuum degree of 0.1 Pa.

[0066] A2) Place the above quartz tube into a tube furnace, place the raw materials in the quartz tube at the center of the temperature zone, set the heating rate to 8°C / min, react at 680°C for 10 hours, and the argon flow rate to 120 sccm.

[0067] B) After the reaction is completed, the temperature is naturally lowered to room temperature, the quartz tube is taken out and opened in an argon atmosphere glove box, and the single crystal product is picked out from the reactants; the single crystal product is ultrasonically washed with carbon disulfide, chloroform and isopropanol organic solvents in sequence, each ultrasonic washing lasts for 20 minutes, and then vacuum filtered to obtain a clean alkaline earth metal atom intercalated doped fullerene molecule covalent polymer single crystal.

[0068] Based on the raw material input amount and the obtained product amount, the product yield was calculated to be 16.7%.

[0069] Figure 1 This is an optical image of the alkaline earth metal atom intercalation doped fullerene molecule covalent polymer single crystal obtained in Example 1. The size of the obtained single crystal material is 4 mm.

[0070] Figure 2 This is the X-ray diffraction pattern (XRD pattern) of the alkaline earth metal atom intercalation doped fullerene molecule covalent polymer single crystal obtained in Example 1. It can be seen that the two sharp diffraction peaks also correspond to the exposed crystal planes of the crystal.

[0071] Figure 3 This is the Raman spectrum of the alkaline earth metal atom intercalated fullerene molecule covalent polymer single crystal obtained in Example 1. It can be seen that the abundant Raman absorption peaks correspond to the vibration modes of the chemical bonds between fullerene molecules or between fullerene molecules and metal atoms.

[0072] Example 2

[0073] A1) 200 mg of calcium nitride powder and 500 mg of fullerene C were mixed in an argon atmosphere glove box. 70 Molecular crystal powder (the molar ratio of metal atoms to fullerene molecular crystals is 3:1) is added into a quartz tube with a length of 30 cm, an inner diameter of 20 mm, and a wall thickness of 2.5 mm, mixed evenly, and sealed in a high-temperature vacuum with a vacuum degree of 0.5 Pa.

[0074] A2) The quartz tube was placed in a tube furnace, and the raw materials in the quartz tube were placed in the center of the temperature zone. The heating rate was set to 6°C / min, and the reaction was carried out at 600°C for 12 hours with an argon flow rate of 80 sccm.

[0075] B) After the reaction is completed, the temperature is naturally lowered to room temperature, the quartz tube is taken out and opened in an argon atmosphere glove box, and the single crystal product is picked out from the reactants; the single crystal product is ultrasonically washed with toluene, xylene and acetone organic solvents in sequence, each ultrasonic washing lasts for 30 minutes, and then vacuum filtered to obtain a clean alkaline earth metal atom intercalated doped fullerene molecule covalent polymer single crystal.

[0076] Based on the raw material input amount and the obtained product amount, the product yield was calculated to be 19.1%.

[0077] Figure 4 This is an optical image of the alkaline earth metal atom intercalation doped fullerene molecule covalent polymer single crystal obtained in Example 2. The size of the obtained single crystal material is 2.3 mm.

[0078] Example 3

[0079] A1) In an argon atmosphere glove box, 150 mg of metallic strontium and 700 mg of fullerene C were added. 78 Molecular crystal powder (the molar ratio of metal atoms to fullerene molecular crystals is 1:1) is added into a quartz tube with a length of 40 cm, an inner diameter of 12 mm, and a wall thickness of 1.5 mm, mixed evenly, and sealed in a high-temperature vacuum with a vacuum degree of 0.5 Pa.

[0080] A2) Place the above quartz tube into a tube furnace, place the raw materials in the quartz tube at the center of the temperature zone, set the heating rate to 9°C / min, react at 700°C for 10 hours, and the argon flow rate to 50 sccm.

[0081] B) After the reaction is completed, the temperature is naturally lowered to room temperature, the quartz tube is taken out and opened in an argon atmosphere glove box, and the single crystal product is picked out from the reactants; the single crystal product is ultrasonically washed with chlorobenzene, carbon tetrachloride and anhydrous ethanol organic solvents in sequence, each ultrasonic washing lasts for 10 minutes, and then vacuum filtered to obtain a clean alkaline earth metal atom intercalated doped fullerene molecule covalent polymer single crystal.

[0082] Based on the raw material input amount and the obtained product amount, the product yield was calculated to be 18.3%.

[0083] Figure 5 This is an optical image of the alkaline earth metal atom intercalation doped fullerene molecule covalent polymer single crystal obtained in Example 3. The size of the obtained single crystal material is 3 mm.

[0084] Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas, including the best mode, and also enable any technician in the field to practice the present invention, including making and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, the present invention can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements similar to the literal expression of the claims, or if they include equivalent structural elements that are not substantially different from the literal expression of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. A method for preparing a single crystal of alkaline earth metal atom intercalation doped fullerene molecule covalent polymer, characterized in that: The following steps are involved: A) sealing an alkaline earth metal source and fullerene molecular crystal polycrystalline powder in a container under a protective atmosphere and vacuum conditions, and then heating and reacting to obtain a reaction product; B) taking out the single crystal product from the reaction product, washing it, and obtaining a single crystal of a covalent polymer of alkaline earth metal atoms intercalated and doped fullerene molecules; in, The alkaline earth metal source is an alkaline earth metal and / or an alkaline earth metal compound; The alkaline earth metal in the alkaline earth metal source is Mg, Ca, Sr or Ba; The temperature of the heating reaction is 300-1000°C.

2. The preparation method according to claim 1, characterized in that: The fullerene molecular crystal is selected from C 60 , C 70 , C 78 , C 80 , C 82 , C 84 and C 90 At least one of the molecular crystals; The alkaline earth metal source is at least one of magnesium, calcium, strontium, magnesium hydride, calcium hydride, strontium hydride, magnesium nitride, calcium nitride and strontium nitride.

3. The preparation method according to claim 1, characterized in that: The molar ratio of the alkaline earth metal atoms in the alkaline earth metal source to the molecules in the fullerene molecule crystal is (1-50):

1.

4. The preparation method according to claim 1, characterized in that: The solvent used for the washing is at least one of cyclopentane, cyclohexane, chloroform, carbon tetrachloride, carbon disulfide, benzene, toluene, xylene, trimethylbenzene, chlorobenzene, isopropanol, acetone and anhydrous ethanol.

5. The preparation method according to claim 1, characterized in that: Step A) specifically includes: A1) adding an alkaline earth metal source and fullerene molecular crystal polycrystalline powder into a quartz tube under a protective atmosphere, and then sealing the quartz tube under vacuum conditions; A2) placing the quartz tube into a heating furnace, so that the raw materials in the quartz tube are at the center of the temperature zone, and undergoing heating reaction to obtain a reaction product.

6. The preparation method according to claim 5, characterized in that: Step A1) specifically includes: adding an alkaline earth metal source and fullerene molecular crystal polycrystalline powder into a quartz tube with one end sealed under a protective atmosphere, and then sealing the other end of the quartz tube under vacuum conditions.

7. The preparation method according to claim 5 or 6, characterized in that: The length of the quartz tube is 10 to 50 cm, and the inner diameter is 5 to 50 mm.

8. The preparation method according to claim 5 or 6, characterized in that: The vacuum degree of the vacuum condition is 0.01-100Pa.

9. The preparation method according to claim 1, characterized in that: The reaction time is 1 to 50 hours; The heating reaction temperature rise rate is 1-20°C / min.

10. The preparation method according to claim 1, characterized in that: The alkaline earth metal source is in powder or block form; The purity of the alkaline earth metal source is above 99.9%; The purity of the fullerene molecular crystal polycrystalline powder is above 99%.

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