Preparation method of bromine lead deuteride methylamine perovskite single crystal

Abstract

The invention discloses a preparation method of a bromine lead deuteride methylamine perovskite single crystal, and belongs to the technical field of crystal growth. The preparation method comprises the following steps: performing multiple deuteration on bromomethylamine, performing heavy water separation and recovery on a mixed solution containing bromomethylamine and heavy water generated after each deuteration, and synthesizing a bromine lead methylamine deuteride single crystal. Bromomethylamine and heavy water are subjected to multiple times of deuteration in a certain proportion to generate bromomethylamine deuteride, then bromomethylamine deuteride and lead bromide are subjected to inverse temperature crystallization in an organic solvent, and the bromolead deuteride methylamine perovskite single crystal is synthesized. The preparation method provided by the invention has the advantages that the synthesis process is efficient, safe and controllable, heavy water can be recycled, the synthesis cost is greatly reduced, and the stability of the synthesized bromine lead deuteride methylamine perovskite single crystal is greatly improved.

Description

Technical Field

[0001] This application relates to a method for preparing deuterated lead bromide methylamine perovskite single crystals, belonging to the field of crystal growth technology. Background Technology

[0002] In recent years, organic-inorganic hybrid perovskites have been considered the most promising semiconductor materials. These materials have a series of advantages, such as variable optical band gap, longer carrier diffusion length, higher absorption coefficient and lower defect density. Lead methylamine bromide (CH3NH3PbBr3, abbreviated as MAPbBr3) is a representative perovskite material among them.

[0003] However, intrinsic defects in perovskites significantly limit their application in many key fields, including photodetectors and solar cells. Therefore, new methods are urgently needed to improve the current situation. Summary of the Invention

[0004] To address the poor stability issue in existing organic-inorganic hybrid perovskite technologies, this application proposes a preparation technique for deuterated lead bromide methylamine perovskite single crystals. This involves multiple deuteration reactions of methyl bromide and heavy water in a specific ratio to generate deuterated methyl bromide. Subsequently, deuterated methyl bromide and lead bromide are crystallized counter-temperature in an organic solvent to synthesize deuterated lead bromide methylamine perovskite single crystals. Furthermore, given the high cost of D2O and its adverse environmental impact from air volatilization, this application also incorporates a heavy water recovery system, reducing costs while protecting the environment.

[0005] The technical solution adopted in this application is as follows:

[0006] According to a first aspect of this application, a method for preparing deuterated lead bromide methylamine perovskite single crystals is provided, characterized by comprising the following steps:

[0007] The method involves multiple deuteration of methyl bromide and the separation and recovery of heavy water from the mixed solution containing methyl bromide and heavy water generated after each deuteration. The heavy water separation and recovery includes reacting the mixed solution containing methyl bromide and heavy water with an alkali to convert methyl bromide into an alkali metal bromide, and then distilling the mixed solution containing the alkali metal bromide and heavy water to recover the heavy water.

[0008] The growth solution containing lead bromide, methyl bromide that has undergone multiple deuteration, and a solvent is reacted to obtain the deuterated lead bromide methyl bromide perovskite single crystal.

[0009] Optionally, the multiple deuteration of methyl bromide includes:

[0010] S1. After mixing methyl bromide with heavy water to obtain a mixture, a deuteration process is carried out.

[0011] The deuteration process is as follows: the mixture is heated until a white film appears on the surface of the mixture and then disappears. The mixture is kept at this temperature until it becomes viscous. Heating is then stopped until the mixture is completely evaporated and crystallized to obtain the deuterated methyl bromide product.

[0012] S2. The deuterated methyl bromide product is used as methyl bromide material and the deuteration process in step S1 is repeated at least once to obtain the deuterated methyl bromide.

[0013] Optionally, in step S1, the deuterium content of the heavy water is ≥99.9%.

[0014] Optionally, in step S1, the volume ratio of the methyl bromide material to heavy water is 1:3-5.

[0015] Optionally, in step S1, the step of keeping the mixture warm until it becomes viscous includes keeping the mixture warm until its volume is 15-30% of the original volume, preferably 20%.

[0016] Optionally, in step S1, the heating conditions include a heating rate of 3–3.5 °C / min. This heating refers to starting from room temperature and heating until a relatively high temperature, close to 200 °C, is reached when the white film appears and disappears in the mixed solution. At this point, the solution volume is small, and the residual heat allows the mixed solution to completely evaporate and crystallize.

[0017] Optionally, step S2 includes: repeating the deuterated methyl bromide product as methyl bromide material for 3-4 times the deuteration process in step S1 to obtain the deuterated methyl bromide. Too many deuteration times waste heavy water and increase costs, while too few deuteration times make it difficult for methyl bromide to be deuterated, resulting in a low deuterium content in the product.

[0018] Optionally, the molar mass ratio of lead bromide to methyl bromide that has undergone multiple deuteration is 1:1.

[0019] Optionally, the reaction conditions include: a heating rate of 2–2.3 °C / min, a reaction temperature of 65–71 °C, and a reaction time of 1–2 h. This reaction time refers to the time it takes for crystals to grow after the growth solution reaches the reaction temperature. This step is crucial; if the heating rate is too low, the heating time will be too long, leading to a decrease in the deuterium content of the methylamine bromide lead crystals; if the heating rate is too high, the heating time will be too short, resulting in crystals that are too small.

[0020] Optionally, the reaction process further includes filtering the growth solution, wherein the filtration conditions include: the filter element size is less than or equal to 0.1 μm. If the size is too large, the filtration effect will be poor, and a large amount of spontaneous nucleation will occur in the solution during crystal growth. The lower limit of the size is sufficient to ensure that the growth solution can pass through the filter element smoothly without clogging it.

[0021] Optionally, the preparation method further includes:

[0022] The mixed solution containing methyl bromide and heavy water collected during the evaporation process after the mixture is completely evaporated and crystallized during the deuteration process is separated and recovered.

[0023] The separation and recovery steps include:

[0024] The mixed solution containing methyl bromide and heavy water is heated, and during the heating process, an alkaline solid is gradually added to the mixed solution containing methyl bromide and heavy water and stirred until the pH value of the mixed solution is greater than 7, so as to completely react the methyl bromide in the mixed solution to an alkali metal bromide to obtain a mixed solution containing an alkali metal bromide and heavy water.

[0025] Preferably, the pH value is 7–9;

[0026] In this process, methylamine gas is generated during the heating of the mixed solution containing methylbromoamine and heavy water, and the methylamine gas is then passed into an aqueous HBr solution to react and generate an aqueous methylbromoamine solution.

[0027] The mixed solution of alkali metal bromide and heavy water is distilled until the mixed solution of alkali metal bromide and heavy water is completely evaporated, and the distillate is collected to obtain the recovered heavy water.

[0028] Optionally, the heating temperature during the heating of the mixed solution containing methyl bromide and heavy water is 45-60°C. If the temperature is too high, the reaction is too vigorous, making it difficult to collect the generated methyl amine gas; if the temperature is too low, the reaction is too slow, resulting in too little methyl amine gas being produced.

[0029] Optionally, during the distillation of the mixed solution containing alkali metal bromide and heavy water, the heating temperature is 150–170°C.

[0030] Optionally, the alkali solid is a soluble alkali; for example, the alkali solid is sodium hydroxide or potassium hydroxide.

[0031] Existing technologies do not recover heavy water. Instead, they directly distill the mixed solution containing methyl bromide and heavy water collected after the complete evaporation and crystallization of the mixture during the deuteration process. This results in some methyl bromide dissolving back into the distilled heavy water as a gas, and the distillation process also produces methylamine gas, which also dissolves into the heavy water. The technical solution of this application converts methyl bromide into sodium bromide, which is then distilled to obtain heavy water free of other substances.

[0032] The beneficial effects of this application include:

[0033] The method for preparing deuterated lead bromide methylamine perovskite single crystals provided in this application has the advantages of efficient and convenient synthesis process, safe and controllable process, and the waste of heavy water can be recycled and reused, which greatly reduces the synthesis cost. The stability of the synthesized deuterated lead bromide methylamine perovskite single crystals is greatly improved. Attached Figure Description

[0034] Figure 1 For D in this application x Schematic diagram of the MABr synthesis apparatus;

[0035] Figure 2 This refers to the D2O separation device in this application;

[0036] Figure 3 This is the deuteration experiment of methyl bromide in this application, where (a) is a mixture of heavy water and methyl bromide before deuteration, and (b) is the crystallized product after deuteration;

[0037] Figure 4 For different deuteration numbers D in this application x Fourier transform infrared spectrum of MABr;

[0038] Figure 5 For different deuteration numbers D in this application x The deuterium content of the recovered heavy water after MABr treatment is shown in (a) for the heavy water before deuteration, (b) for the heavy water after one deuteration, (c) for the heavy water after two deuteration, and (d) for the heavy water after three deuteration.

[0039] Figure 6 The D with different deuterium contents synthesized in this application x MAPbBr3;

[0040] Figure 7 SEM images of the natural surfaces of MAPbBr3 and D3MAPbBr3; (a) SEM image of the natural surface of newly prepared D3MAPbBr3; (b) SEM image of the natural surface of newly prepared MAPbBr3; (c) SEM image of the natural surface of D3MAPbBr3 after being placed in air for 60 days; (d) SEM image of the natural surface of MAPbBr3 after being placed in air for 60 days.

[0041] Attached Figure Labels

[0042] 1. Heating platform; 2. Mixed solution of D2O and MABr; 3. Distillation flask; 4. Condenser; 5. Collection bottle; 6. Mixed solution of MABr and D2O; 7. Separation device reactor; 8. Left gas delivery tube; 9. Moistened pH test paper; 10. Right gas delivery tube; 11. One-way gas valve; 12. Beaker; 13. MABr aqueous solution. Detailed Implementation

[0043] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0044] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0045] Unless otherwise specified, all test methods are standard and all instrument settings are those recommended by the manufacturer.

[0046] According to one embodiment of this application, the preparation method of deuterated lead bromide methylamine perovskite single crystal includes:

[0047] Methyl bromide undergoes multiple deuteration;

[0048] Single-crystal synthesis of deuterated lead bromide methylamine.

[0049] In one embodiment, the multiple deuteration steps of the methyl bromide are as follows:

[0050] (1) Add pure heavy water (D2O) and methyl bromide (CH3NH3Br, abbreviated as MABr) to a distillation flask at a volume ratio of 3:1-5:1, preferably a volume ratio of 5:1 for D2O to MABr;

[0051] (2) Place the distillation flask on the heating platform, connect the upper end of the distillation flask to the condenser tube, and place the collection bottle below the condenser tube.

[0052] (3) Observe the appearance of a white film on the surface of the liquid in the distillation flask and its gradual disappearance. Keep the heating temperature unchanged until the solution becomes thick. Then turn off the heating and use the residual heat of the equipment to completely evaporate and crystallize the solution. The white blocky solid in the distillation flask at this time is primary deuterated methyl bromide (D1MABr).

[0053] (4) Collect the condensed liquid, which is a mixed solution of MABr and D2O;

[0054] (5) Repeat the distillation of D1MABr in step (4) according to steps (1)-(3) to obtain secondary deuterated methyl bromide (D2MABr);

[0055] (6) Repeat the distillation of D2MABr in step (5) according to steps (1)-(3) to obtain triple deuterated methyl bromide (D3MABr).

[0056] In one embodiment, the single-crystal synthesis steps of deuterated lead bromide methylamine are as follows:

[0057] (1) Dissolve the D1MABr, D2MABr, and D3MABr described in claim 2 with lead bromide (PbBr2) in N,N-dimethylformamide (DMF) at a molar ratio of 1:1 to obtain a deuterated lead bromide methylamine crystal growth solution;

[0058] (2) The deuterated lead bromide methylamine crystal growth solution is filtered, and crystallization is carried out by rapid heating within 1-2 hours to obtain deuterated lead bromide methylamine single crystals (D). x (MAPbBr3). In this step, the heating time is preferably 1 hour. Since DMF is a weak acid, it readily undergoes "deuterium exchange," reducing the D... X MAPbBr3 deuterium content.

[0059] In one embodiment, the method for preparing deuterated lead bromide methylamine perovskite single crystals further includes: heavy water recovery.

[0060] In one embodiment, the heavy water recovery step is as follows:

[0061] (1) The mixed solution of MABr and D2O obtained in the deuteration step is placed in the reactor of the separation device. The reactor has two gas delivery pipes at the top. The left gas delivery pipe is equipped with a valve, and a moistened pH test paper is placed at the end of the gas delivery pipe to test the pH of the solution. The right gas delivery pipe is connected to a one-way gas valve, which is sealed to a beaker. A solution is placed in the beaker to recover the gas. The solution is either H2O or an acidic solution.

[0062] (2) Place the reactor of the separation device on a heating platform and set the heating temperature to 50-60℃;

[0063] (3) Gradually add an alkaline solid to the reactor of the separation device, wherein the alkaline solid is either sodium hydroxide or potassium hydroxide;

[0064] (4) Observe the color of the moist pH test paper until it turns blue, indicating that there is an excess of alkaline solid. At this time, the MABr in the mixed solution of MABr and D2O is completely reacted, and the generated gas is absorbed by the solution in the beaker. The remaining solution in the reactor is a mixed solution of NaBr, D2O and H2O. The alkaline solid is preferably sodium hydroxide.

[0065] The equation for the reaction is:

[0066] CH3NH3Br+NaOH=CH3NH2↑+NaBr+H2O;

[0067] (5) The mixture in step (4) is placed in a distillation flask for distillation, and the distilled liquid is the recovered D2O.

[0068] (6) Testing different deuteration times D x The amount of deuterium recovered from the MABr treatment.

[0069] Example 1: Synthesis of deuterated lead bromide methylamine perovskite single crystal (D x MABr, where x = 1-3)

[0070] (1) Synthesis of primary deuterated methyl bromide (D1MABr)

[0071] Adopting such Figure 1 The synthesis apparatus shown will produce a deuterium content ≥99.9% (deuterium content test results are as follows). Figure 5 (a) D₂O and MABr were added to distillation flask 3 at a volume ratio of 5:1. Heating platform 1 was turned on, and the temperature was increased from room temperature at a rate of 3.2℃ / min. A white film appeared on the surface of the mixed solution 2 in distillation flask 1 and then gradually disappeared. The temperature of heating platform 1 was kept constant until solution 2 became viscous (the volume decreased to 1 / 5 of the original). Then heating platform 1 was turned off, and the residual heat of the apparatus was used to completely evaporate and crystallize solution 2. The white blocky solid in distillation flask 1 at this time is primary deuterated methyl bromide (D₁MABr). The contents of the distillation flask before and after the deuteration experiment of methyl bromide are as follows: Figure 3 As shown in (a) and (b), Fourier transform infrared spectroscopy was performed on D1MABr, and the test results are as follows. Figure 4 As shown.

[0072] (2) Synthesis of secondary deuterated methyl bromide (D2MABr)

[0073] Adopting such Figure 1 The synthesis apparatus shown was used to add D₂O (≥99.9% deuterium content) and D₁MABr to a distillation flask 3 at a volume ratio of 5:1. Heating platform 1 was turned on, and the temperature was increased from room temperature at a rate of 3.2℃ / min. A white film appeared on the surface of the mixed solution 2 in distillation flask 1 and then gradually disappeared. The temperature of heating platform 1 was kept constant until solution 2 became viscous. Heating platform 1 was then turned off, and the residual heat of the apparatus was used to completely evaporate and crystallize solution 2. The white lumpy solid in distillation flask 1 at this point is secondary deuterated methyl bromide (D₂MABr). Fourier transform infrared spectroscopy was performed on D₂MABr, and the results are shown below. Figure 4 As shown.

[0074] (3) Synthesis of trideuterated methyl bromide (D3MABr)

[0075] Adopting such Figure 1The synthesis apparatus shown was used to add D₂O (≥99.9% deuterium content) and D₂MABr to a distillation flask 3 at a volume ratio of 5:1. Heating platform 1 was turned on, and the temperature was increased from room temperature at a rate of 3.2℃ / min. A white film appeared on the surface of the mixed solution 2 in distillation flask 1 and then gradually disappeared. The temperature of heating platform 1 was kept constant until solution 2 became viscous. Heating platform 1 was then turned off, and the residual heat of the apparatus was used to completely evaporate and crystallize solution 2. The white lumpy solid in distillation flask 1 at this point is trideuterated methyl bromide (D₃MABr). Fourier transform infrared spectroscopy was performed on D₃MABr, and the results are shown below. Figure 4 As shown.

[0076] (4) Synthesis of deuterated lead bromide methylamine single crystals

[0077] The obtained D1MABr, D2MABr, and D3MABr were dissolved in N,N-dimethylformamide (DMF) at a molar ratio of 1:1 to obtain three deuterated lead bromide methylamine crystal growth solutions with different deuterium contents at a concentration of 1 mol / L.

[0078] Three deuterated lead bromide methylamine crystal growth solutions were filtered through a 0.1 μm filter. The solutions were then heated to 70 °C at a rate of 2.3 °C / min and held at this temperature for 1 h to complete crystallization, yielding three single crystals of deuterated lead bromide methylamine with different deuterium contents: D1MAPbBr3, D2MAPbBr3, and D3MAPbBr3. The actual crystal images are shown below. Figure 6 As shown, from left to right, they are deuterated lead bromide methylamine single crystals D1MAPbBr3, D2MAPbBr3, and D3MAPbBr3. The differences between the different orders are as follows: Figure 4 MABr powders with different deuteration degrees exhibit different peak intensities. SEM images of the natural surfaces of MAPbBr3 and D3MAPbBr3 are shown below. Figure 7 As shown, (a) is a SEM image of the natural surface of the newly prepared D3MAPbBr3; (b) is a SEM image of the natural surface of the newly prepared MAPbBr3; (c) is a SEM image of the natural surface of D3MAPbBr3 after being placed in air for 60 days; and (d) is a SEM image of the natural surface of MAPbBr3 after being placed in air for 60 days. It can be seen from the figures that the surface of the newly prepared D3MAPbBr3 is smoother and has fewer macroscopic defects than that of the newly prepared MAPbBr3. After being stored for 60 days, the crystal surface turns white as a whole and white particles are generated, but there are fewer white particles on the surface of D3MAPbBr3, which proves that the stability of the crystal is improved after deuteration.

[0079] Because D2O is expensive and its volatilization into the air has adverse environmental impacts, this application also allows for the recovery of the MABr and D2O mixed solution collected after deuteration in the aforementioned steps. The specific processes involved in each step are as follows:

[0080] (a) Recovery of heavy water after the synthesis of primary deuterated methyl bromide (D1MABr)

[0081] Adopting such Figure 2 The D2O separation and recovery device shown in the diagram involves adding 200 mL of HBr aqueous solution (concentration 55%-57%) to beaker 12, and then placing 120 mL of the MABr and D2O mixed solution 6 collected after the first MABr deuteration in step (1) into the separation device reactor 7. The heating platform 1 is turned on, and the heating temperature is set to 50°C. Subsequently, solid NaOH is gradually added to the separation device reactor 7 while stirring, and the color of the moist pH test paper 9 is observed until it turns blue, indicating the reaction is complete. The remaining solution in the separation device reactor 7 is a mixed solution of NaBr, D2O, and H2O. The generated gas CH3NH2 reacts with the HBr aqueous solution in beaker 12 to generate MABr aqueous solution 13. The remaining mixed solution of NaBr, D2O, and H2O in the separation device reactor 7 is placed in… Figure 1 In the distillation flask 3 of the apparatus shown, the heating stage 1 is turned on, and the heating temperature is set to 160℃ until the mixed solution of NaBr, D2O, and H2O in the distillation flask 3 is completely evaporated. At this point, the distillation flask 3 contains solid NaBr, and the recovered heavy water is condensed in the collection bottle 5. The deuterium content of the recovered heavy water is then tested. Figure 5 As shown in (b).

[0082] (b) Recovery of heavy water after synthesis of secondary deuterated methyl bromide (D2MABr)

[0083] Adopting such Figure 2 The D2O separation and recovery device shown in the diagram involves adding 200 mL of HBr aqueous solution (concentration 55%-57%) to beaker 12, and placing 130 mL of the MABr and D2O mixed solution 6 collected after the second MABr deuteration in step (2) into the separation device reactor 7. The heating platform 1 is turned on, and the heating temperature is set to 50℃. NaOH solid is then gradually added to the separation device reactor 7 while stirring, and the color of the moist pH test paper 9 is observed until it turns blue, indicating the reaction is complete. The remaining solution in the separation device reactor 7 is a mixed solution of NaBr, D2O, and H2O. The generated gas CH3NH2 reacts with the HBr aqueous solution in beaker 12 to generate MABr aqueous solution 13. The remaining mixed solution of NaBr, D2O, and H2O in the separation device reactor 7 is placed in… Figure 1In the distillation flask 3 of the apparatus shown, the heating stage 1 is turned on, and the heating temperature is set to 160℃ until the mixed solution of NaBr, D2O, and H2O in the distillation flask 3 is completely evaporated. At this point, the distillation flask 3 contains solid NaBr, and the recovered heavy water is condensed in the collection bottle 5. The deuterium content of the recovered heavy water is then tested. Figure 5 As shown in (c).

[0084] (c) Recovery of heavy water after synthesis of methyl bromide trideuterated (D3MABr)

[0085] Adopting such Figure 2 The D2O separation and recovery device shown in the diagram involves adding 200 mL of HBr aqueous solution (concentration 55%-57%) to beaker 12, and placing 140 mL of the MABr and D2O mixed solution 6 collected after the third MABr deuteration in step (2) into the separation device reactor 7. The heating platform 1 is turned on, and the heating temperature is set to 50℃. NaOH solid is then gradually added to the separation device reactor 7 while stirring, and the color of the moist pH test paper 9 is observed until it turns blue, indicating the reaction is complete. The remaining solution in the separation device reactor 7 is a mixed solution of NaBr, D2O, and H2O. The generated gas CH3NH2 reacts with the HBr aqueous solution in beaker 12 to generate MABr aqueous solution 13. The remaining mixed solution of NaBr, D2O, and H2O in the separation device reactor 7 is placed in… Figure 1 In the distillation flask 3 of the apparatus shown, the heating stage 1 is turned on, and the heating temperature is set to 160℃ until the mixed solution of NaBr, D2O, and H2O in the distillation flask 3 is completely evaporated. At this point, the distillation flask 3 contains solid NaBr, and the recovered heavy water is condensed in the collection bottle 5. The deuterium content of the recovered heavy water is then tested. Figure 5 As shown in (d).

[0086] Figure 5 The gradually increasing deuterium content in the recovered heavy water in (b)-(d) indicates that the required heavy water content decreases with the increase of the number of deuteration cycles, meaning that the deuterium content in deuterated MABr gradually increases with the increase of the number of deuteration cycles.

[0087] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing a deuterated bromopinamide perovskite single crystal, characterized by, Includes the following steps: The method involves multiple deuteration of methyl bromide and the separation and recovery of heavy water from the mixed solution containing methyl bromide and heavy water generated after each deuteration. The heavy water separation and recovery includes reacting the mixed solution containing methyl bromide and heavy water with an alkali to convert methyl bromide into an alkali metal bromide, and then distilling the mixed solution containing the alkali metal bromide and heavy water to recover the heavy water. The growth solution containing lead bromide, methyl bromide that has undergone multiple deuteration, and a solvent is reacted to obtain the deuterated lead bromide methyl bromide perovskite single crystal.

2. The production method according to claim 1, characterized by, The multiple deuteration of methyl bromide includes: S1. After mixing methyl bromide with heavy water to obtain a mixture, a deuteration process is carried out. The deuteration process is as follows: the mixture is heated until a white film appears on the surface of the mixture and then disappears. The mixture is kept at this temperature until it becomes viscous. Heating is then stopped until the mixture is completely evaporated and crystallized to obtain the deuterated methyl bromide product. S2. The deuterated methyl bromide product is used as methyl bromide material and the deuteration process in step S1 is repeated at least once to obtain the deuterated methyl bromide.

3. The preparation method according to claim 2, characterized in that, In step S1, the deuterium content of the heavy water is ≥99.9%.

4. The production method according to claim 2, characterized by, In step S1, the volume ratio of the methyl bromide material to heavy water is 1:3-5.

5. The preparation method according to claim 2, characterized in that, In step S1, the heating conditions include a heating rate of 3 to 3.5 °C / min.

6. The method of claim 2, wherein, Step S2 includes: repeating the deuterated methyl bromide product as methyl bromide material 3 to 4 times in step S1 to obtain the deuterated methyl bromide.

7. The preparation method according to claim 1, characterized in that, The molar ratio of lead bromide to methyl bromide that has undergone multiple deuteration is 1:

1.

8. The method of claim 1, wherein, The reaction conditions include: a heating rate of 2–2.3 °C / min, a reaction temperature of 65–71 °C, and a reaction time of 1–2 h.

9. The method of claim 1, wherein, The reaction process includes filtering the growth solution, wherein the filtration conditions include that the filter element has a filter size of less than or equal to 0.1 μm.

10. The method of claim 2, wherein, The process of separating and recovering heavy water from the mixed solution containing methyl bromide and heavy water generated after each deuteration includes: The mixed solution containing methyl bromide and heavy water collected during the evaporation process after the mixture is completely evaporated and crystallized during the deuteration process is separated and recovered. The separation and recovery steps include: The mixed solution containing methyl bromide and heavy water is heated, and during the heating process, an alkaline solid is gradually added to the mixed solution while stirring until the pH value of the mixed solution is greater than 7, so as to completely react the methyl bromide in the mixed solution to an alkali metal bromide to obtain a mixed solution containing an alkali metal bromide and heavy water; wherein, during the heating process of the mixed solution containing methyl bromide and heavy water, monomethylamine gas is generated, and the monomethylamine gas is passed into an HBr aqueous solution to react and generate an aqueous solution of methyl bromide; The mixed solution of alkali metal bromide and heavy water is distilled until the mixed solution of alkali metal bromide and heavy water is completely evaporated, and the distillate is collected to obtain the recovered heavy water.

Images