Method for catalytically synthesizing large-size single crystal covalent triazine framework by using mercury-based quantum dot dynamic interface

Abstract

The invention relates to a method for catalytically synthesizing a large-size single crystal covalent triazine framework (CTF) by using a mercury-based quantum dot dynamic interface. According to the method, the efficient catalytic synthesis of the aromatic dinitrile monomer is realized through the dynamic action of the mercury-based quantum dots at a superacid liquid-liquid interface. The preparation method comprises the following specific steps: firstly, dispersing aromatic dinitrile monomers and oleic acid coated mercury-based quantum dots in an organic solvent to form a precursor dispersion liquid; then slowly injecting the solution into superacid to form a clear liquid-liquid two-phase interface; under the conditions of proper temperature and rotating speed, inducing the monomers to be orderly assembled and grow through active species released by the mercury-based quantum dots; and finally, cleaning and drying to obtain the large-size CTF single crystal with high crystallinity. According to the method, the soft template effect of the mercury-based quantum dots and a super-acid enhanced reversible error correction mechanism are utilized, so that the nucleation entropy change can be effectively inhibited, and the crystal quality can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of synthesis technology of porous organic materials, and in particular to a method for synthesizing large-size single-crystal covalent triazine framework by using mercury-based quantum dot dynamic interface catalysis. BACKGROUND

[0002] The present application belongs to the technical field of porous organic material preparation, and in particular relates to a method for controllably synthesizing large-size, high-crystallinity covalent triazine framework (CTFs) single crystals by using semiconductor quantum dots to in-situ release single atoms as soft templates at a liquid-liquid interface and in a superacid environment.

[0003] Covalent triazine framework (CTFs) is a kind of porous polymer containing triazine ring (C3N3) structure formed by trimerization of aromatic nitrile monomers. Due to its excellent thermal stability, nitrogen-rich structure and photoelectric performance, it has great potential in the fields of catalysis, gas adsorption, energy storage, etc.

[0004] However, the synthesis of CTFs currently faces the contradiction between "crystallinity and reactivity": traditional ionothermal method (ZnCl2 molten salt): requires high temperature above 400°C, leading to severe carbonization, uncontrolled framework structure, and the product is mostly black amorphous powder.

[0005] Conventional superacid method (TfOH): although the reaction temperature is relatively low, the nitrile group is highly active after protonation in the superacid, and the reaction rate is too fast (kinetic control), which leads to disordered accumulation of triazine rings and difficulty in lattice arrangement, and usually only micron-sized microcrystals or amorphous polymers can be obtained.

[0006] The existing synthesis strategy is extremely difficult to obtain millimeter-sized large-size single crystals, which seriously limits the in-depth study of its intrinsic physical properties (such as anisotropic conductivity, single-crystal X-ray diffraction structure analysis).

[0007] Therefore, developing a synthesis method that can inhibit explosive nucleation and introduce error correction mechanism is the key to preparing large-size CTF single crystals. SUMMARY

[0008] In order to improve the technical defects proposed in the above, the present application provides a method for synthesizing large-size single-crystal covalent triazine framework by using mercury-based quantum dot dynamic interface catalysis.

[0009] The method for synthesizing large-size single-crystal covalent triazine framework by using mercury-based quantum dot dynamic interface catalysis provided by the present application adopts the following technical scheme: A method for synthesizing large-size single-crystal covalent triazine framework by using mercury-based quantum dot dynamic interface catalysis, the method comprising the following steps: Step one: preparation of organic phase precursor dispersion aromatic dicyan monomers and oleic acid-coated mercury-based quantum dots are dispersed in an organic solvent to obtain an organic phase precursor dispersion; Step two: construction of liquid-liquid two-phase interface The organic phase precursor solution prepared in step (1) is slowly injected along the container wall into the super acid to form a liquid-liquid two-phase interface; Step three: heating growth The heating growth is carried out at 60-120°C, and the Hg-based quantum dots release active species at the two-phase interface, inducing the ordered assembly and growth of monomers; Step four: crystal collection and post-processing After the reaction is completed, the crystals are collected and washed with ethanol, deionized water and tetrahydrofuran to obtain pure covalent triazine framework (CTFs) single crystals.

[0010] By adopting the above technical solution, the entropy problem in the nucleation process is effectively inhibited, and through the soft template effect of mercury-based quantum dots and the reversible error correction mechanism in the super acid environment, synthesis of CTF single crystals with large size and high crystallinity is realized. The Hg 2 ⁺ / Hg 0 species released by mercury-based quantum dots at the liquid-liquid interface can adsorb and pre-assemble nitrile monomer molecules, promote their ordered assembly, and reduce the instability in the nucleation process; by accurately controlling the construction of the liquid-liquid two-phase interface, the heating temperature and the reaction time, the temperature and reaction rate in the synthesis process are accurately controlled, and through the washing steps of ethanol, deionized water and tetrahydrofuran, the unreacted monomers and surface residual acid in the reaction are removed, ensuring the purity of the product, and providing high-purity materials for the subsequent application of CTF single crystals (such as catalysis, gas adsorption and energy storage).

[0011] Optionally, the super acid is trifluoromethanesulfonic acid (TfOH).

[0012] By adopting the above technical solution, an efficient protonation environment can be provided at low temperature, promoting the activation of aromatic dicyan monomers and accelerating the formation of triazine rings. At the same time, the strong acidity of TfOH can change the electronic environment at the liquid-liquid interface, enhance the catalytic effect of mercury-based quantum dots, optimize the nucleation process, avoid disordered accumulation caused by too fast reaction, and ensure the synthesis of large-size, high-crystallinity covalent triazine framework (CTFs) single crystals.

[0013] Optionally, the organic solvent is selected from dichloromethane (DCM), chloroform (CHCl3) or toluene.

[0014] By adopting the technical scheme, dichloromethane (DCM), chloroform (CHCl3) or toluene is selected as the organic solvent, uniform dispersion of the aromatic dinitrile monomer and the mercury-based quantum dot in the solvent is ensured, and mutual dissolution with the super strong acid is avoided.

[0015] Optionally, the injection speed in step (2) is controlled to be within 0.5 mL / min to avoid violent mixing of the liquid-liquid two phases.

[0016] By adopting the technical scheme, the injection speed of the organic phase precursor solution in step (2) is controlled to be within 0.5 mL / min, which effectively avoids violent mixing of the liquid-liquid two phases and ensures the formation of a stable liquid-liquid interface.

[0017] Optionally, the heating condition in step (3) is 60-120°C, the duration is 1 hour, and the rotor speed is above 150 rpm. Under the heating condition in step (3), the monomer assembly induced by the active species released by the Hg-based quantum dot at the two-phase interface can improve the crystallinity and size of the CTF single crystal.

[0018] By adopting the technical scheme, the process of releasing active species by the Hg-based quantum dot at the liquid-liquid interface is accelerated, the ordered assembly of the aromatic dinitrile monomer is effectively induced, the formation of the triazine ring is promoted, the temperature control and rotation speed control of the heating process optimize the reaction rate, the diffusivity of the reactants is enhanced, the crystallinity and size of the CTF single crystal are improved, and the synthesis of large-size and high-quality single crystals is ensured.

[0019] Optionally, the monomer is an aromatic dinitrile monomer, preferably p-phenylenedinitrile (DCB).

[0020] By adopting the technical scheme, DCB is used as the preferred monomer, which has good reactivity and stability, the nitrile group (-CN) thereof reacts with the active species released by the mercury-based quantum dot, promotes ordered assembly, ensures that the covalent triazine framework (CTF) generated in the reaction system has high structural stability and crystallinity, and helps to synthesize large-size and high-quality CTF single crystals.

[0021] Optionally, the Hg monatomic soft template effect is realized by trace etching of the mercury-based quantum dot at the two-phase interface, in-situ release of Hg 2 ⁺ / Hg 0 species, adsorption of the nitrile group and pre-assembly into a geometric configuration suitable for forming a triazine ring, thereby inhibiting the nucleation entropy change.

[0022] By adopting the technical scheme, a Hg single-atom soft template effect reduces the instability of nucleation, promotes the ordered arrangement of monomers at the interface, optimizes the formation process of the triazine ring, helps to control the reaction rate, improves the crystallinity, and finally realizes the synthesis of large-size and high-quality covalent triazine framework (CTFs) single crystals.

[0023] Optionally, the reversibility in the superacid environment makes the generated C-N=C bond in a dynamic equilibrium metastable state, allowing the dislocation connection to break and recombine until the thermodynamically most stable lattice structure is formed.

[0024] By adopting the technical scheme, the reversibility of the C-N=C bond is realized in the superacid environment, the generated C-N=C bond is in a dynamic equilibrium metastable state, allowing the dislocation connection to break and recombine, and the reversible error correction mechanism effectively corrects the structural defects that may occur during the reaction process, ensuring the ordered arrangement of the triazine ring. Through repeated recombination process, the thermodynamically most stable lattice structure is finally formed, improving the crystallinity and quality of the covalent triazine framework (CTFs) single crystal, which is helpful for the synthesis of large-size and high-crystallinity CTF single crystal materials.

[0025] Optionally, the size of the CTF single crystal is millimeter level, with high crystallinity and excellent physical properties.

[0026] By adopting the technical scheme, the CTF single crystal with a size of millimeter level is synthesized, and its high crystallinity and excellent physical properties are ensured. By optimizing the construction of liquid-liquid interface, the soft template effect of mercury-based quantum dots, and the reversible error correction mechanism in the superacid environment, the quality and size of the crystal are improved, not only having a stable lattice structure, but also having good photoelectric performance and mechanical strength.

[0027] Optionally, the crystal washing in step (4) includes sequentially washing with anhydrous ethanol, deionized water and tetrahydrofuran (THF) to remove surface residual acid and unreacted monomers.

[0028] By adopting the technical scheme, the crystal is sequentially washed with anhydrous ethanol, deionized water and tetrahydrofuran (THF), effectively removing the acid and unreacted monomers that may be left over during the reaction process. The washing process not only removes impurities, but also ensures the high purity of the final product, providing high-quality materials for the subsequent application of covalent triazine framework (CTFs) single crystals.

[0029] In summary, the present application includes at least one of the following beneficial technical effects: 1. The crystal size of CTF is first increased from micrometer level to millimeter level (up to 2mm or more), which is clearly visible to the naked eye, facilitating single crystal X-ray diffraction analysis and single device processing, and realizing a great breakthrough in crystal size.

[0030] 2. The problem of poor crystallinity of traditional acid products is solved, and the product has extremely high crystallinity.

[0031] 3. Compared with ionothermal method (>400°C), the present method can be carried out at about 60°C, has low energy consumption, avoids carbonization of the skeleton, maintains the chemical structure integrity of the material, and has mild reaction conditions.

[0032] 4. The interface catalysis strategy is not only applicable to terephthalonitrile, but also can be extended to other aromatic nitrile monomers, providing a universal platform for constructing new CTF topological structures, and has strong universality.

[0033] 5. Synthesis of large-size and high-crystallinity CTF single crystals: by precisely controlling the liquid-liquid two-phase interface construction, heating temperature, injection speed and reaction time, the entropy change in the nucleation process is effectively inhibited, ensuring the synthesis of large-size and high-crystallinity covalent triazine framework (CTFs) single crystals.

[0034] 6. Hg 2 ⁺ / Hg 0 Species released at the two-phase interface can adsorb and pre-assemble nitrile monomers, promote their ordered assembly, reduce the instability in the nucleation process, and thus improve the crystallinity and size of the crystals.

[0035] 7. Through the reversibility in the superacid environment, the C-N=C bond is in a dynamic equilibrium metastable state, allowing the dislocation connection to break and recombine, ensuring the ordered arrangement of triazine rings, and finally forming a thermodynamically most stable lattice structure, thereby improving the quality of the single crystal.

[0036] 8. The crystal is washed with anhydrous ethanol, deionized water and tetrahydrofuran (THF) in sequence to remove the surface residual acid and unreacted monomers, ensuring the high purity of the CTF single crystal and providing high-quality materials for subsequent applications.

[0037] 9. By optimizing the reaction process and material synthesis method, the obtained CTF single crystal has excellent photoelectric performance and mechanical strength, and is suitable for high-performance material applications such as catalysis, gas adsorption and energy storage. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 is a flowchart of the embodiments of the present application.

[0039] Figure 2 is a partial schematic diagram of a CTF film on filter paper in the implementation of the embodiments of the present application.

[0040] Figure 3 is an XRD spectrum of CTF of the embodiments of the present application.

[0041] Figure 4 is an FTIR spectrum of CTF of the embodiments of the present application.

[0042] Figure 5 This is a TEM image of the quantum dots in an embodiment of this application. Detailed Implementation

[0043] The following is in conjunction with the appendix Figures 1-5 This application will be described in further detail.

[0044] This application discloses a method for synthesizing large-size single-crystal covalent triazine frameworks using a dynamic interface catalysis of mercury-based quantum dots.

[0045] This patent aims to solve the problems of low crystallinity and small crystal size (only powder or microcrystals) of CTF materials in the prior art. By introducing mercury-based quantum dots to construct a "single-atom soft template + dynamic acid repair" environment at the liquid-liquid interface, explosive nucleation is suppressed, and CTF single crystals with visible millimeter scale, self-support and regular surface are successfully synthesized.

[0046] Reference Figure 1 The method includes the following steps: Step 1: Preparation of Organic Phase Precursor Dispersion Raw materials: Aromatic dinitrile monomers (such as terephthalonitrile DCB). Catalyst precursor: Group II-VI semiconductor quantum dots (preferably HgTe, HgSe, or HgS QDs with an average particle size of 3-10 nm) coated with oleic acid or organic ligands. Solvent: Choose an organic solvent that is immiscible with superacids, such as dichloromethane (DCM), chloroform (CHCl3), or toluene. Procedure: Dissolve / disperse the monomer and quantum dots in an organic solvent, and sonicate for 5-15 minutes to ensure uniform dispersion; Step 2: Construction of the liquid-liquid two-phase interface The organic phase precursor solution obtained in step (1) is slowly injected into the superacid along the container wall to form a liquid-liquid two-phase interface. A superacid (preferably trifluoromethanesulfonic acid TfOH) is pre-added to the bottom of the reaction vessel (such as a glass cap tube).

[0047] Using a syringe or dropper, the organic phase precursor solution prepared in step one is injected very slowly along the container wall, so that it carefully covers the surface of the superacid solution, forming a clear, immiscible liquid-liquid interface.

[0048] During implementation, the injection rate must be strictly controlled to avoid vigorous mixing of the two phases; Step 3: Heating for Growth Heating growth was carried out at 60-120°C, during which Hg-based quantum dots released active species at the two-phase interface, inducing the ordered assembly and growth of monomers; circulating water cooling (5-10 °C) was used, and the rotor speed was above 150 rpm. During this process, Hg quantum dots release active species at the interface between the two phases, inducing monomers to assemble and grow in an orderly manner at the interface. Step 4: Crystal Collection and Post-processing After the reaction was complete, the crystals were collected and washed with ethanol, deionized water, and tetrahydrofuran to obtain pure single crystals of covalent triazine frameworks (CTFs). Transparent or translucent plate-like crystals were observed forming at the two-phase interface. The crystals were then removed and washed sequentially with anhydrous ethanol, deionized water, and tetrahydrofuran (THF) to remove residual acid and unreacted monomers from the surface. CTF single crystals were obtained by filtration through a PP membrane and vacuum drying.

[0049] Example 1 Preparation of large-size CTF-1 single crystals Raw materials: 12.8 mg terephthalonitrile (DCB, 0.1 mmol), 5 μL of oleylamine-coated HgTe quantum dots (average particle size 8 nm) dispersed in n-hexane, concentration 10 mg / ml. Solvent: 10 mL dichloromethane (DCM) Acid phase: 0.5 mL trifluoromethanesulfonic acid (TfOH), Procedure: Dissolve DCB and HgTe quantum dots in DCM and sonicate for 10 minutes. Add TfOH to a three-necked flask, set the rotor speed to 150 rpm, heat to 60°C, and cool with circulating water at 6°C. After reacting for 5 minutes, slowly add the DCM mixture dropwise. Continue the reaction for 2 hours, quench the reaction, and then wash and filter. Results: Transparent crystalline films with dimensions exceeding 2 mm × 2 mm were grown.

[0050] Example 2 Effects of different organic solvents The difference from Example 1 is that dichloromethane is replaced with toluene. Result: Single crystals were obtained in both cases, and their quality was not significantly different.

[0051] Comparative Example 1: Hg-free quantum dots Difference: No HgTe quantum dots are added.

[0052] Result: Plate-like crystals were also generated, but their size was only tens of micrometers.

[0053] Reference Figure 2 , Figure 2 This is a partial photograph of the CTF film on filter paper. The film of Example 1 has a size exceeding 2mm × 2mm.

[0054] Reference Figure 3 , Figure 3 This is the XRD pattern of a CTF.

[0055] Reference Figure 4 , Figure 4 This is the FTIR spectrum of CTF.

[0056] Reference Figure 5 , Figure 5 This is a TEM image of quantum dots, with scattered transition metal single atoms clearly visible in the pores.

[0057] This patented solution has significant technical advantages and practical value compared to existing technologies: 1. A major breakthrough in crystal size: For the first time, the crystal size of CTF has been increased from the micrometer level to the millimeter level (up to 2mm or more), making it clearly visible to the naked eye, which facilitates single-crystal X-ray diffraction analysis and single-device fabrication; 2. Extremely high crystallinity: It solves the problem of poor crystallinity of products from traditional acid processes.

[0058] 3. Mild reaction conditions: Compared with ionothermal methods (>400°C), this method can be carried out at around 60°C, which has low energy consumption and avoids skeleton carbonization, thus maintaining the chemical structure integrity of the material.

[0059] 4. High versatility: This interfacial catalysis strategy is not only applicable to terephthalonitrile, but can also be extended to other aromatic nitrile monomers, providing a universal platform for constructing novel CTF topologies.

[0060] The core technological breakthrough achieved by this patented solution compared to existing technologies is that by using Hg-based quantum dots to "slowly release" single atoms at the acidic interface as a soft template, combined with the diffusion restriction effect of the liquid-liquid interface, the explosive nucleation in the superacid system is successfully suppressed, and thermodynamically controlled growth of CTF is realized.

[0061] The protection points of this technical solution are: 1. Synthesis method: A method for synthesizing covalent triazine framework single crystals by using a two-phase interface system (organic phase / acid phase) and introducing mercury-based nanomaterials (especially quantum dots) into the organic phase as a catalytic modifier.

[0062] 2. Application of reaction mechanism: Protect and utilize the in-situ release of mercury species from mercury-based materials to coordinate with nitrile groups, thereby inducing the orderly assembly of triazine rings.

[0063] 3. Product characteristics: The synthesized CTF crystals are in the millimeter range (>0.5 mm) and have good crystallinity and are self-supporting.

[0064] Key process parameters of this technical solution: a clear interface is formed between the organic solvent and the superacid; the reaction temperature is 60-120 degrees Celsius; quantum dots are used as a catalyst and to enhance acidity.

[0065] An alternative to this technical solution is to directly use mercury salts (such as HgCl2). Alternative technical approach: Use HgCl2 instead of HgTe quantum dots dissolved in the organic phase.

[0066] Disadvantages of the alternative: The metal salts are dispersed at the molecular level, resulting in an excessively high initial ion concentration and too many nucleation sites. Although the products have a certain degree of crystallinity, they are mostly small crystals in the micrometer range (<100μm) and contain a large amount of powder, making it impossible to grow into large single crystals in the millimeter range.

[0067] The technical solution of this application uses quantum dots as "single-atom sustained-release capsules", which is the key to controlling the nucleation density.

[0068] The implementation principle of the method for synthesizing large-size single-crystal covalent triazine frameworks using dynamic interface catalysis of mercury-based quantum dots in this application embodiment is as follows: Mercury-based quantum dots (such as HgTe, HgSe, etc.) interact with nitrile monomers under a superacid environment, producing a trace amount of etching and releasing coordination-unsaturated Hg 2 ⁺ / Hg 0 In this species, the mercury atom has a strong affinity for the nitrile group (-CN), releasing Hg. 2 ⁺ / Hg 0 The species can pre-adsorb nitrile molecules and "pre-assemble" these nitrile molecules into a geometric configuration suitable for the formation of triazine rings, which effectively reduces the entropy change during the nucleation process, suppresses the explosiveness of nucleation, and helps to form large-sized, highly crystalline CTF single crystals. This method modulates the reaction environment by constructing a stable liquid-liquid interface. At this interface, the active species released from mercury-based quantum dots can interact with nitrile monomers, inducing the ordered assembly of monomers and the formation of triazine rings. By adding a superacid (such as trifluoromethanesulfonic acid, TfOH) to the bottom of the reaction vessel, the nitrile monomers in the organic solvent and the mercury-based quantum dot solution are slowly injected into the acidic solution, forming a clear liquid-liquid interface. The reaction environment at the liquid-liquid interface greatly affects the diffusion and assembly of reactants, further improving the crystallinity and size of CTF single crystals. In the presence of the superacid environment (such as TfOH), the reaction products are in a metastable state of dynamic equilibrium during the formation of CN=C bonds. The formed CN=C bonds can undergo a dynamic process of "formation-dissociation-reorganization" under reaction conditions. The reversible repair mechanism allows the misaligned connections that occur in the reaction to break and reorganize until the thermodynamically stable state is formed. The well-defined crystal lattice structure effectively corrects structural defects that may occur during synthesis, ensuring the structural stability of CTF single crystals. Using a lower reaction temperature (60-120°C) effectively reduces energy consumption and prevents skeletal carbonization of the material at high temperatures, making the reaction process more controllable and contributing to obtaining CTF single crystals with higher crystallinity and more stable structures. By precisely controlling the construction of the liquid-liquid interface, the injection rate, heating temperature, and reaction time, the nucleation and growth processes are optimized. The reactant concentration gradient at the liquid-liquid interface controls the ordered assembly of monomer molecules at the interface, avoiding disordered accumulation caused by excessively rapid reactions, thus ensuring the crystallinity and size of the CTF single crystals. After the reaction, the surface is washed sequentially with anhydrous ethanol, deionized water, and tetrahydrofuran (THF) to remove residual acid and unreacted monomers, ensuring the high purity of the obtained CTF single crystals.

[0069] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for synthesizing large-size single-crystal covalent triazine frameworks using a dynamic interface catalysis of mercury-based quantum dots, characterized in that, The method includes the following steps: Step 1: Preparation of Organic Phase Precursor Dispersion Aromatic dinitrile monomers and oleic acid-coated mercury-based quantum dots were dispersed in an organic solvent to obtain an organic phase precursor dispersion. Step 2: Construction of the liquid-liquid two-phase interface The organic phase precursor solution obtained in step (1) is slowly injected into the superacid along the container wall to form a liquid-liquid two-phase interface. Step 3: Heating for Growth Heating growth at 60-120°C induces the orderly assembly and growth of monomers by releasing active species at the interface between two phases. Step 4: Crystal Collection and Post-processing After the reaction was completed, the crystals were collected and washed with ethanol, deionized water and tetrahydrofuran to obtain pure covalent triazine framework (CTF) single crystals.

2. The method according to claim 1, characterized in that: The superacid is trifluoromethanesulfonic acid (TfOH).

3. The method according to claim 1, characterized in that: The organic solvent is selected from dichloromethane (DCM), chloroform (CHCl3), or toluene.

4. The method according to claim 1, characterized in that: The injection rate in step (2) should be controlled within 0.5 mL / min to avoid violent mixing of the liquid-liquid two phases.

5. The method according to claim 1, characterized in that: The heating conditions in step (3) are 60-120°C for 1 hour and the rotor speed is above 150 rpm; Under the heating conditions in step (3), the monomer assembly induced by the active species released by Hg-based quantum dots at the two-phase interface can improve the crystallinity and size of CTF single crystals.

6. The method according to claim 1, characterized in that: The monomer is an aromatic dinitrile monomer, preferably terephthalonitrile (DCB).

7. The method according to claim 1, characterized in that: The Hg single-atom soft template effect described herein releases Hg in situ through micro-etching at the interface between two phases using mercury-based quantum dots. 2 ⁺ / Hg 0 The species adsorbs nitrile groups and preassembles them into a geometry suitable for forming triazine rings, thereby suppressing nucleation entropy changes.

8. The method according to claim 1, characterized in that: The reversibility under the superacid environment allows the generated CN=C bonds to be in a dynamic equilibrium metastable state, enabling the breakage and recombination of misaligned connections until the thermodynamically most stable lattice structure is formed.

9. The method according to claim 1, characterized in that: The CTF single crystals are millimeter-sized and have high crystallinity and excellent physical properties.

10. The method according to claim 1, characterized in that: The crystal washing in step (4) involves sequentially washing with anhydrous ethanol, deionized water and tetrahydrofuran (THF) to remove residual acid and unreacted monomers from the surface.

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