A hollow nano covalent organic framework and preparation method thereof

Abstract

The present invention relates to the field of nanomaterial technology, and in particular to a hollow nano covalent organic framework and a preparation method thereof. The preparation method comprises the following steps: A) mixing imine bond COF nanospheres with a first organic solvent to obtain a nanosphere dispersion; B) mixing the nanosphere dispersion, glacial acetic acid, a metal salt solution and a hydrogen peroxide solution, and performing a Fenton reaction to obtain a hollow nano covalent organic framework. The preparation method of the hollow nano covalent organic framework provided by the present invention is an imine bond oxidation method, which does not require the use of a template and does not require subsequent template removal; the operation steps are simple, the reaction conditions are milder, and the time is short, and the hollow nano covalent organic framework can be obtained in as little as 10 minutes of reaction; at the same time, the preparation method provided by the present invention has universality, and can synthesize a variety of hollow nano covalent organic frameworks connected by imine bonds, and can obtain a hollow nano covalent organic framework with regular morphology and uniform size.

Description

Technical Field

[0001] The invention relates to the technical field of nanomaterials, and in particular to a hollow nano covalent organic framework and a preparation method thereof. Background Art

[0002] Covalent organic frameworks (COFs), a class of crystalline porous organic polymers with permanent porosity and highly ordered structures, are a new type of porous organic material that has attracted much attention. Compared with traditional organic polymers and inorganic zeolites, COFs have low density, precisely tunable pores and structures, and good stability. The combination of customizable functions and crystalline porous structures provides great potential for the application of COFs materials in many research fields, including gas adsorption and separation, energy storage, catalysis, and biomedicine. In general, the successful application of nanomaterials depends not only on their physicochemical properties, but also on their structural morphology. Since the performance of COFs materials is highly dependent on their morphology, controlling the morphology is crucial to improving the performance of COFs materials.

[0003] In the past few years, COFs in various shapes such as nanospheres, nanosheets, nanotubes and nanofibers have been prepared and have shown excellent performance. Among various forms, hollow nanostructures have unique advantages in guest loading and imparting multifunctionality, so the research on hollow structures has attracted much attention. However, although the strategy of synthesizing various functional COFs by controlling different structural units has gradually matured, the precise control of COFs morphology still faces considerable challenges. Therefore, the development of synthetic strategies for hollow nano COFs is of great significance for exploring their further applications.

[0004] The patent with publication number CN112625254A discloses a surface-modifiable pH-responsive hollow covalent organic framework nanosphere and a synthesis method, which adopts a hard template method, that is, using PEI-modified mesoporous silica as a template, growing COF on its surface, and then removing the template silicon with tetrahydrofuran to prepare hollow COF nanospheres. This hard template method has complex steps and requires four steps of reaction; the reaction time is long, up to 23 to 33 hours; the reaction temperature is high, and the maximum temperature reaches 100°C. Summary of the invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a hollow nano covalent organic framework and a preparation method thereof, which is simple to operate and can obtain a hollow nano covalent organic framework with regular morphology and uniform size.

[0006] The present invention provides a method for preparing a hollow nano covalent organic framework, comprising the following steps:

[0007] A) mixing imine bond COF nanospheres with a first organic solvent to obtain a nanosphere dispersion;

[0008] B) mixing the nanosphere dispersion, glacial acetic acid, a metal salt solution and a hydrogen peroxide solution, and performing a Fenton reaction to obtain a hollow nano covalent organic framework.

[0009] Preferably, in step A), the imine bond COF nanospheres are prepared from raw materials including monomers containing amino groups and monomers containing aldehyde groups.

[0010] Preferably, the amino group-containing monomer includes at least one of 1,3,5-tris(4-aminophenyl)benzene, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, p-phenylenediamine and tris(4-aminophenyl)amine;

[0011] The monomer containing an aldehyde group includes at least one of 2,5-divinylterephthalaldehyde, 2,5-dimethoxyterephthalaldehyde, 2,5-dihydroxyterephthalaldehyde, 1,3,5-tris(p-formylphenyl)benzene and trimesic acid;

[0012] The molar ratio of the monomer containing an amino group to the monomer containing an aldehyde group is 2-3:2-3.

[0013] Preferably, the preparation method of the imine bond COF nanospheres comprises the following steps:

[0014] a) mixing a monomer containing an amino group, a monomer containing an aldehyde group and a second organic solvent to obtain a mixed solution;

[0015] b) mixing the mixed solution with glacial acetic acid, and removing the second organic solvent to obtain imine bond COF nanospheres.

[0016] Preferably, in step a), the second organic solvent comprises at least one of acetonitrile, dichloromethane, chloroform and ethyl acetate;

[0017] In step b), the ratio of the sum of the molar amounts of the monomer containing an amino group and the monomer containing an aldehyde group to the glacial acetic acid is 0.02-0.05 mmol: 0.5-5 mL;

[0018] The method for removing the second organic solvent includes: stirring at room temperature until the second organic solvent is completely volatilized, or heating at 40-70° C. until the second organic solvent is completely volatilized.

[0019] Preferably, in step A), the first organic solvent comprises at least one of acetonitrile, ethanol, N,N-dimethylformamide and N,N-dimethylacetamide.

[0020] Preferably, in step B), the metal salt comprises at least one of ferric chloride, ferric nitrate, cupric chloride, cupric nitrate and manganese chloride;

[0021] The solvent of the metal salt solution is acetonitrile and / or ethanol;

[0022] The mass concentration of the metal salt solution is 45-55 mg / mL;

[0023] The mass concentration of the hydrogen peroxide solution is 3% to 30%.

[0024] Preferably, the usage ratio of the imine bond COF nanospheres, glacial acetic acid, metal salt and hydrogen peroxide solution is 0.5-5 mg: 0.05-0.5 mL: 1-10 mg: 0.2-2 mL.

[0025] Preferably, in step B), the temperature of the Fenton reaction is 40-80° C. and the time is 10 min-4 h.

[0026] The present invention also provides a hollow nano covalent organic framework prepared by the preparation method described above.

[0027] The present invention provides a method for preparing a hollow nano covalent organic framework, comprising the following steps: A) mixing imine bond COF nanospheres with a first organic solvent to obtain a nanosphere dispersion; B) mixing the nanosphere dispersion, glacial acetic acid, a metal salt solution and a hydrogen peroxide solution, and performing a Fenton reaction to obtain a hollow nano covalent organic framework. The method for preparing the hollow nano covalent organic framework provided by the present invention is an imine bond oxidation method, which does not require the use of a template and does not require subsequent template removal; the operation steps are simple, the reaction conditions are milder (for example, the temperature of the Fenton reaction is 40 to 80° C.), the reaction time is short, and the hollow nano covalent organic framework can be obtained in as little as 10 minutes; at the same time, the preparation method provided by the present invention is universal, and can synthesize a variety of imine bond-connected hollow nano covalent organic frameworks, and can obtain a hollow nano covalent organic framework with regular morphology and uniform size. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 TEM image of TAPB-DVA-COF of Example 1 of the present invention;

[0029] Figure 2 TEM image of TAPB-DVA-HCOF of Example 1 of the present invention;

[0030] Figure 3 TEM image of TAPB-DMTP-HCOF of Example 2 of the present invention;

[0031] Figure 4TEM image of TAPB-DHTP-HCOF of Example 3 of the present invention;

[0032] Figure 5 TEM image of TAPB-TFPB-HCOF of Example 4 of the present invention;

[0033] Figure 6 TEM image of TAPTA-DMTP-HCOF of Example 5 of the present invention;

[0034] Figure 7 TEM image of TAPTA-TFPB-HCOF of Example 6 of the present invention;

[0035] Figure 8 is the X-ray powder diffraction pattern of the imine bond COF nanospheres of Examples 1 to 7 of the present invention;

[0036] Fig. 9 This is the TEM image of TAPTA-BTCA-HCOF of Example 7 of the present invention. DETAILED DESCRIPTION

[0037] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] The present invention provides a method for preparing a hollow nano covalent organic framework, comprising the following steps:

[0039] A) mixing imine bond COF nanospheres with a first organic solvent to obtain a nanosphere dispersion;

[0040] B) mixing the nanosphere dispersion, glacial acetic acid, a metal salt solution and a hydrogen peroxide solution, and performing a Fenton reaction to obtain a hollow nano covalent organic framework.

[0041] In step A):

[0042] The imine bond COF nanospheres are mixed with a first organic solvent to obtain a nanosphere dispersion.

[0043] In certain embodiments of the present invention, the mixing is blending.

[0044] In certain embodiments of the present invention, the imine bond COF nanospheres are prepared from raw materials including monomers containing amino groups and monomers containing aldehyde groups. The monomers containing amino groups include at least one of 1,3,5-tris(4-aminophenyl)benzene (TAPB), 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPTA), p-phenylenediamine (PDA) and tris(4-aminophenyl)amine (TAPA). The monomers containing aldehyde groups include at least one of 2,5-divinylterephthalaldehyde (DVA), 2,5-dimethoxyterephthalaldehyde (DMTP), 2,5-dihydroxyterephthalaldehyde (DHTP), 1,3,5-tris(p-formylphenyl)benzene (TFPB) and trimesic acid (BTCA). The molar ratio of the monomers containing amino groups to the monomers containing aldehyde groups is 2 to 3:2 to 3.

[0045] In certain embodiments of the present invention, the method for preparing the imine bond COF nanospheres comprises the following steps:

[0046] a) mixing a monomer containing an amino group, a monomer containing an aldehyde group and a second organic solvent to obtain a mixed solution;

[0047] b) mixing the mixed solution with glacial acetic acid, and removing the second organic solvent to obtain imine bond COF nanospheres.

[0048] In step a):

[0049] In certain embodiments of the present invention, the second organic solvent comprises at least one of acetonitrile, dichloromethane, chloroform and ethyl acetate. The present invention has no particular limitation on the amount of the second organic solvent, as long as it can completely dissolve the monomer containing amino groups and the monomer containing aldehyde groups. In certain embodiments, the molar sum of the monomer containing amino groups and the monomer containing aldehyde groups and the amount ratio of the second organic solvent is 0.04-0.06mmol:5-20mL; specifically 0.05mmol:10mL or 0.04mmol:10mL.

[0050] In certain embodiments of the present invention, after the mixing, the step further includes: completely dissolving the monomer containing an amino group and the monomer containing an aldehyde group in the second organic solvent by ultrasonic treatment.

[0051] In step b):

[0052] Glacial acetic acid acts as a catalyst to trigger the Schiff base reaction between the amino monomer and the aldehyde monomer.

[0053] In certain embodiments of the present invention, the usage ratio of the monomer containing an amino group to the glacial acetic acid is 0.02-0.05 mmol:0.5-5 mL; specifically 0.02 mmol:1 mL, 0.02 mmol:0.5 mL or 0.02 mmol:2 mL.

[0054] In some embodiments of the present invention, the method of removing the second organic solvent comprises: stirring at room temperature until the second organic solvent is completely volatilized, or heating at 40-70° C. until the organic solvent is completely volatilized. In some embodiments, heating at 60° C. until the organic solvent is completely volatilized.

[0055] The time for heating at 40-70° C. until the organic solvent is completely volatilized is 0.5-12 hours, specifically 0.5-3 hours, more specifically 30 minutes, 1 hour or 3 hours.

[0056] After removing the second organic solvent, the method further comprises: centrifuging and washing the precipitate obtained by centrifugation. The washing is performed with anhydrous ethanol. The washing may be performed three times.

[0057] In certain embodiments of the present invention, the particle size of the imine bond COF nanospheres is 240-1700 nm; specifically, 290-310 nm, 490-510 nm, 1500-1700 nm, 240-260 nm, 890-910 nm, 500-520 nm or 280-300 nm.

[0058] After obtaining the imine bond COF nanospheres, the imine bond COF nanospheres are mixed with the first organic solvent to obtain a nanosphere dispersion.

[0059] In some embodiments of the present invention, the first organic solvent includes at least one of acetonitrile, ethanol, N,N-dimethylformamide and N,N-dimethylacetamide. The amount ratio of the imine bond COF nanospheres to the first organic solvent is 0.5-5 mg: 1-20 mL; specifically 0.5 mg: 1 mL.

[0060] In step B):

[0061] The nanosphere dispersion, glacial acetic acid, metal salt solution and hydrogen peroxide solution are mixed and then subjected to Fenton reaction to obtain a hollow nano covalent organic framework.

[0062] In certain embodiments of the present invention, the metal salt comprises at least one of an iron salt, a copper salt and a manganese salt; specifically, at least one of ferric chloride, ferric nitrate, copper chloride, copper nitrate and manganese chloride. The solvent of the metal salt solution is acetonitrile and / or ethanol. The mass concentration of the metal salt solution is 45-55 mg / mL; specifically, 50 mg / mL.

[0063] In certain embodiments of the present invention, the mass concentration of the hydrogen peroxide solution is 3% to 30%, specifically 3%; and the solvent is deionized water.

[0064] In certain embodiments of the present invention, the dosage ratio of the imine bond COF nanospheres, glacial acetic acid, metal salt and hydrogen peroxide solution is 0.5-5 mg: 0.05-0.5 mL: 1-10 mg: 0.2-2 mL; specifically 0.5 mg: 0.05 mL: 1 mg: 0.2 mL, 0.5 mg: 0.05 mL: 1 mg: 0.5 mL, 0.5 mg: 0.05 mL: 2.5 mg: 0.3 mL or 0.5 mg: 0.05 mL: 2.5 mg: 0.5 mL.

[0065] In certain embodiments of the present invention, the temperature of the Fenton reaction is 40-80° C., specifically 60° C.; the time is 10 min-4 h, specifically 10 min, 4 h or 1 h.

[0066] In certain embodiments of the present invention, after the Fenton reaction, the method further comprises: centrifuging and washing the precipitate obtained by centrifugation. The washing is performed using anhydrous ethanol. The number of times of washing can be 3 times.

[0067] The present invention also provides a hollow nano covalent organic framework prepared by the preparation method described above.

[0068] In certain embodiments of the present invention, the particle size of the hollow nano covalent organic framework is 160-1200 nm; specifically, 250-270 nm, 450-470 nm, 1000-1200 nm, 230-250 nm, 590-610 nm, 490-510 nm or 160-180 nm.

[0069] By adopting the preparation method of the hollow nano covalent organic framework provided by the present invention, a hollow nano covalent organic framework with regular morphology and uniform size can be obtained.

[0070] The present invention utilizes the Schiff base reaction of monomers containing amino groups and monomers containing aldehyde groups, and prepares a variety of highly crystalline, uniformly sized, and regularly morphological imine bond COF nanospheres through a solvent volatilization method. Different from the traditional solvent thermal method, the solvent volatilization method in the present invention has mild reaction conditions, simple operation steps, and the reaction can be carried out at room temperature or low temperature heating at normal pressure; the reaction is fast, and the reaction time is shortened from 1 to 9 days to 0.5 to 12 hours, which greatly saves time costs; and this preparation method has fewer influencing factors, strong repeatability, and can achieve large-scale preparation of COFs.

[0071] The preparation method of the hollow nano covalent organic framework provided by the present invention is an imine bond oxidation method, which does not require the use of a template and does not require subsequent template removal; the operation steps are simple, the reaction conditions are mild, and the reaction time is short, and the hollow nano covalent organic framework can be obtained after the fastest reaction of only 10 minutes; at the same time, the preparation method provided by the present invention is universal and can synthesize a variety of hollow nano covalent organic frameworks connected by imine bonds.

[0072] The hollow nano covalent organic framework prepared by the present invention has a variety of structures. For COFs formed by connecting different monomers, hollow bowl-shaped, hollow sphere-shaped, hollow eggshell-shaped, and hollow flower-shaped nanoparticles can be obtained.

[0073] The present invention has no particular limitation on the sources of the raw materials used above, and they can be generally commercially available.

[0074] In order to further illustrate the present invention, a hollow nano covalent organic framework and a preparation method thereof provided by the present invention are described in detail below in conjunction with examples, but it should not be construed as limiting the scope of protection of the present invention.

[0075] Example 1

[0076] 1) Preparation of TAPB-DVA-COF nanospheres:

[0077] Weigh 0.02mmol (7mg) of 1,3,5-tris(4-aminophenyl)benzene (TAPB) and 0.03mmol (5.5mg) of 2,5-divinylterephthalaldehyde (DVA), add 10mL of acetonitrile, dissolve the two monomers completely by ultrasound, add 1mL of glacial acetic acid, stir at room temperature for 30min to completely evaporate the acetonitrile. Collect the precipitate by centrifugation, wash it with anhydrous ethanol three times, and you can get regular morphology, highly crystalline imine bond COF nanospheres (TAPB-DVA-COF nanospheres).

[0078] The TAPB-DVA-COF was analyzed by transmission electron microscopy. Figure 1 As shown, Figure 1 TEM image of TAPB-DVA-COF of Example 1 of the present invention. Figure 1 It can be seen that the TAPB-DVA-COF is uniform spherical nanoparticles with a size of 290 to 310 nm.

[0079] 2) Preparation of hollow nanocovalent organic frameworks:

[0080] 0.5 mg of the TAPB-DVA-COF nanospheres and 1 mL of N,N-dimethylformamide (DMF) were mixed, and 0.05 mL of glacial acetic acid, 0.02 mL of acetonitrile solution of ferric chloride (50 mg / mL), and 0.2 mL of 3% aqueous hydrogen peroxide solution were added, and the mixture was placed in an oven at 60° C. to react for 10 min. The precipitate was collected by centrifugation and washed three times with anhydrous ethanol to obtain hollow nanosphere TAPB-DVA-HCOF.

[0081] The TAPB-DVA-HCOF was analyzed by transmission electron microscopy, and the results were as follows: Figure 2 As shown, Figure 2 TEM image of TAPB-DVA-HCOF of Example 1 of the present invention. Figure 2 It can be seen that the TAPB-DVA-HCOF is a hollow spherical nanoparticle with a size of 250 to 270 nm.

[0082] Example 2

[0083] 1) Preparation of TAPB-DMTP-COF nanospheres:

[0084] Weigh 0.02mmol (7mg) of 1,3,5-tris (4-aminophenyl) benzene (TAPB) and 0.03mmol (5.8mg) of 2,5-dimethoxyterephthalaldehyde (DMTP), add 10mL of acetonitrile, and completely dissolve the two monomers by ultrasound. Then add 0.5mL of glacial acetic acid and stir at room temperature for 30min to completely evaporate the acetonitrile. Collect the precipitate by centrifugation and wash it with anhydrous ethanol three times to obtain imine bond COF nanospheres (TAPB-DMTP-COF nanospheres) with regular morphology and high crystallinity.

[0085] The TAPB-DMTP-COF was analyzed by transmission electron microscopy, and the results showed that the TAPB-DMTP-COF was uniform spherical nanoparticles with a size of 490 to 510 nm.

[0086] 2) Preparation of hollow nanocovalent organic frameworks:

[0087] 0.5 mg of the TAPB-DMTP-COF nanospheres and 1 mL of N,N-dimethylformamide (DMF) were mixed, and 0.05 mL of glacial acetic acid, 0.02 mL of acetonitrile solution of ferric chloride (50 mg / mL), and 0.2 mL of 3% aqueous hydrogen peroxide solution were added, and the mixture was placed in an oven at 60° C. to react for 10 min. The precipitate was collected by centrifugation and washed three times with anhydrous ethanol to obtain a hollow nano-bowl-shaped TAPB-DMTP-HCOF.

[0088] The TAPB-DMTP-HCOF was analyzed by transmission electron microscopy. Figure 3 As shown, Figure 3 TEM image of TAPB-DMTP-HCOF of Example 2 of the present invention. Figure 3 It can be seen that the TAPB-DMTP-HCOF is a hollow bowl-shaped nanoparticle with a size of 450 to 470 nm.

[0089] Example 3

[0090] 1) Preparation of TAPB-DHTP-COF nanospheres:

[0091] Weigh 0.02mmol (7mg) of 1,3,5-tris (4-aminophenyl) benzene (TAPB) and 0.03mmol (5mg) of 2,5-dihydroxyterephthalaldehyde (DHTP), add 10mL of acetonitrile, and completely dissolve the two monomers by ultrasound. Then, add 1mL of glacial acetic acid and heat in an oven at 60℃ for 3h to completely evaporate the acetonitrile. Collect the precipitate by centrifugation and wash it with anhydrous ethanol three times to obtain imine bond COF nanospheres (TAPB-DHTP-COF nanospheres) with regular morphology and high crystallinity.

[0092] Transmission electron microscopy analysis of the TAPB-DHTP-COF showed that the TAPB-DHTP-COF was uniform spherical nanoparticles with a size of 1500 to 1700 nm.

[0093] 2) Preparation of hollow nanocovalent organic frameworks:

[0094] 0.5 mg of the TAPB-DHTP-COF nanospheres and 1 mL of N,N-dimethylformamide (DMF) were mixed, 0.05 mL of glacial acetic acid, 0.2 mL of ethanol solution of ferric nitrate (50 mg / mL), and 0.5 mL of 30% aqueous hydrogen peroxide solution were added, and the mixture was placed in an oven at 60° C. for reaction for 4 h. The precipitate was collected by centrifugation and washed three times with anhydrous ethanol to obtain hollow nano-eggshell-shaped TAPB-DHTP-HCOF.

[0095] The TAPB-DHTP-HCOF was analyzed by transmission electron microscopy. Figure 4 As shown, Figure 4 TEM image of TAPB-DHTP-HCOF of Example 3 of the present invention. Figure 4 It can be seen that the TAPB-DHTP-HCOF is a hollow eggshell-shaped nanoparticle with a size of 1000 to 1200 nm.

[0096] Example 4

[0097] 1) Preparation of TAPB-TFPB-COF nanospheres:

[0098] Weigh 0.02mmol (7mg) of 1,3,5-tri(4-aminophenyl)benzene (TAPB) and 0.02mmol (7.8mg) of 1,3,5-tri(p-formylphenyl)benzene (TFPB), add 7.5mL of acetonitrile and 2.5mL of chloroform, dissolve the two monomers completely by ultrasound, add 2mL of glacial acetic acid, heat in an oven at 60℃ for 1h to completely evaporate the acetonitrile. Collect the precipitate by centrifugation and wash it with anhydrous ethanol three times to obtain imine bond COF nanospheres (TAPB-TFPB-COF nanospheres) with regular morphology and high crystallinity.

[0099] The TAPB-TFPB-COF was analyzed by transmission electron microscopy, and the results showed that the TAPB-TFPB-COF was uniform spherical nanoparticles with a size of 240 to 260 nm.

[0100] 2) Preparation of hollow nanocovalent organic frameworks:

[0101] 0.5 mg of the TAPB-TFPB-COF nanospheres were mixed with 1 mL of N,N-dimethylformamide (DMF), and 0.05 mL of glacial acetic acid, 0.02 mL of an ethanol solution of iron nitrate (50 mg / mL), and 0.2 mL of a 3% aqueous hydrogen peroxide solution were added. The mixture was placed in an oven at 60° C. for reaction for 1 h, and the precipitate was collected by centrifugation and washed three times with anhydrous ethanol to obtain a hollow nano-bowl-shaped TAPB-TFPB-HCOF.

[0102] The TAPB-TFPB-HCOF was analyzed by transmission electron microscopy, and the results were as follows: Figure 5 As shown, Figure 5 TEM image of TAPB-TFPB-HCOF of Example 4 of the present invention. Figure 5 It can be seen that the TAPB-TFPB-HCOF is a hollow bowl-shaped nanoparticle with a size of 230 to 250 nm.

[0103] Example 5

[0104] 1) Preparation of TAPTA-DMTP-COF nanospheres:

[0105] Weigh 0.02mmol (7mg) of 2,4,6-tris (4-aminophenyl) -1,3,5-triazine (TAPTA) and 0.03mmol (5.8mg) of 2,5-dimethoxyterephthalaldehyde (DMTP), add 10mL of acetonitrile, and completely dissolve the two monomers by ultrasound. Then, add 2mL of glacial acetic acid and heat in an oven at 60℃ for 3h to completely evaporate the solvent. Collect the precipitate by centrifugation and wash it with anhydrous ethanol three times to obtain imine bond COF nanospheres (TAPTA-DMTP-COF nanospheres) with regular morphology and high crystallinity.

[0106] Transmission electron microscopy analysis of the TAPTA-DMTP-COF showed that the TAPTA-DMTP-COF was uniform spherical nanoparticles with a size of 890 to 910 nm.

[0107] 2) Preparation of hollow nanocovalent organic frameworks:

[0108] 0.5 mg of the TAPTA-DMTP-COF nanospheres were mixed with 1 mL of N,N-dimethylformamide (DMF), and 0.05 mL of glacial acetic acid, 0.02 mL of acetonitrile solution of ferric chloride (50 mg / mL), and 0.2 mL of 3% aqueous hydrogen peroxide solution were added. The mixture was placed in an oven at 60° C. for reaction for 1 h, and the precipitate was collected by centrifugation and washed three times with anhydrous ethanol to obtain hollow nanosphere-shaped TAPTA-DMTP-HCOF.

[0109] The TAPTA-DMTP-HCOF was analyzed by transmission electron microscopy, and the results were as follows: Figure 6 As shown, Figure 6 TEM image of TAPTA-DMTP-HCOF of Example 5 of the present invention. Figure 6 It can be seen that the TAPTA-DMTP-HCOF is a hollow spherical nanoparticle with a size of 590 to 610 nm.

[0110] Example 6

[0111] 1) Preparation of TAPTA-TFPB-COF nanospheres:

[0112] Weigh 0.02mmol (7mg) of 2,4,6-tris (4-aminophenyl) -1,3,5-triazine (TAPTA) and 0.02mmol (7.8mg) of 1,3,5-tris (p-formylphenyl) benzene (TFPB), add 7.5mL acetonitrile and 2.5mL chloroform, and completely dissolve the two monomers by ultrasound. Then add 0.5mL glacial acetic acid and heat in an oven at 60℃ for 3h to completely evaporate the solvent. Collect the precipitate by centrifugation and wash it with anhydrous ethanol three times to obtain imine bond COF nanospheres (TAPTA-TFPB-COF nanospheres) with regular morphology and high crystallinity.

[0113] Transmission electron microscopy analysis of the TAPTA-TFPB-COF showed that the TAPTA-TFPB-COF was uniform spherical nanoparticles with a size of 500 to 520 nm.

[0114] 2) Preparation of hollow nanocovalent organic frameworks:

[0115] 0.5 mg of the TAPTA-TFPB-COF nanospheres were mixed with 1 mL of N,N-dimethylformamide (DMF), and 0.05 mL of glacial acetic acid, 0.05 mL of an ethanol solution of iron nitrate (50 mg / mL), and 0.3 mL of a 3% aqueous hydrogen peroxide solution were added. The mixture was placed in an oven at 60° C. for reaction for 1 h, and the precipitate was collected by centrifugation and washed three times with anhydrous ethanol to obtain hollow nanosphere-shaped TAPTA-TFPB-HCOF.

[0116] The TAPTA-TFPB-HCOF was subjected to transmission electron microscopy analysis, and the results were as follows: Figure 7 As shown, Figure 7 TEM image of TAPTA-TFPB-HCOF of Example 6 of the present invention. Figure 7 It can be seen that the TAPTA-TFPB-HCOF is a hollow spherical nanoparticle with a size of 490 to 510 nm.

[0117] Example 7

[0118] 1) Preparation of TAPTA-BTCA-COF nanospheres:

[0119] Weigh 0.02mmol (7mg) of 2,4,6-tris (4-aminophenyl) -1,3,5-triazine (TAPTA) and 0.02mmol (3mg) of trimesic acid (BTCA), add 10mL of acetonitrile, dissolve the two monomers completely by ultrasound, add 0.5mL of glacial acetic acid, heat in an oven at 60℃ for 1h to completely evaporate the solvent. Collect the precipitate by centrifugation and wash it with anhydrous ethanol three times to obtain imine bond COF nanospheres (TAPTA-BTCA-COF nanospheres) with regular morphology and high crystallinity.

[0120] Transmission electron microscopy analysis of the TAPTA-BTCA-COF showed that the TAPTA-BTCA-COF was uniform spherical nanoparticles with a size of 280 to 300 nm.

[0121] Figure 8 is the X-ray powder diffraction pattern of the imine bond COF nanospheres of Examples 1 to 7 of the present invention. Figure 8 It can be seen that the TAPB-DVA-COF, TAPB-DMTP-COF, TAPB-DHTP-COF, TAPB-TFPB-COF, TAPTA-DMTP-COF, TAPTA-TFPB-COF, and TAPTA-BTCA-COF all have good crystallinity.

[0122] 2) Preparation of hollow nanocovalent organic frameworks:

[0123] 0.5 mg of the TAPTA-BTCA-COF nanospheres were mixed with 1 mL of N,N-dimethylformamide (DMF), and 0.05 mL of glacial acetic acid, 0.05 mL of ferric nitrate ethanol solution (50 mg / mL), and 0.5 mL of 3% hydrogen peroxide aqueous solution were added. The mixture was placed in an oven at 60°C for 4 h, and the precipitate was collected by centrifugation and washed three times with anhydrous ethanol to obtain hollow nanoflower-shaped TAPTA-BTCA-HCOF.

[0124] The TAPTA-BTCA-HCOF was subjected to transmission electron microscopy analysis, and the results were as follows: Fig. 9 As shown, Fig. 9 TEM image of TAPTA-BTCA-HCOF of Example 7 of the present invention. Fig. 9 It can be seen that the TAPTA-BTCA-HCOF is a hollow flower-shaped nanoparticle with a size of 160 to 180 nm.

[0125] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a hollow nano covalent organic framework, comprising the following steps: A) mixing imine bond COF nanospheres with a first organic solvent to obtain a nanosphere dispersion; The first organic solvent comprises at least one of acetonitrile, ethanol, N,N-dimethylformamide and N,N-dimethylacetamide; The preparation method of the imine bond COF nanospheres comprises the following steps: a) mixing a monomer containing an amino group, a monomer containing an aldehyde group and a second organic solvent to obtain a mixed solution; b) mixing the mixed solution with glacial acetic acid, and removing the second organic solvent to obtain imine bond COF nanospheres; The method for removing the second organic solvent comprises: stirring at room temperature until the second organic solvent is completely volatilized, or heating at 40-70° C. until the second organic solvent is completely volatilized; B) After mixing the nanosphere dispersion, glacial acetic acid, metal salt solution and hydrogen peroxide solution, a Fenton reaction is carried out to obtain a hollow nano covalent organic framework.

2. The preparation method according to claim 1, characterized in that: The amino group-containing monomer includes at least one of 1,3,5-tris(4-aminophenyl)benzene, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, p-phenylenediamine and tris(4-aminophenyl)amine; The monomer containing an aldehyde group includes at least one of 2,5-divinylterephthalaldehyde, 2,5-dimethoxyterephthalaldehyde, 2,5-dihydroxyterephthalaldehyde, 1,3,5-tris(p-formylphenyl)benzene and trimesic acid; The molar ratio of the monomer containing an amino group to the monomer containing an aldehyde group is 2-3:2-3.

3. The preparation method according to claim 1, characterized in that: In step a), the second organic solvent comprises at least one of acetonitrile, dichloromethane, chloroform and ethyl acetate; In step b), the ratio of the amino group-containing monomer to the glacial acetic acid is 0.02-0.05 mmol: 0.5-5 mL.

4. The preparation method according to claim 1, characterized in that: In step B), the metal salt comprises at least one of ferric chloride and ferric nitrate; The solvent of the metal salt solution is acetonitrile and / or ethanol; The mass concentration of the metal salt solution is 45-55 mg / mL; The mass concentration of the hydrogen peroxide solution is 3% to 30%.

5. The preparation method according to claim 1, characterized in that: The dosage ratio of the imine bond COF nanospheres, glacial acetic acid, metal salt and hydrogen peroxide solution is 0.5-5 mg: 0.05-0.5 mL: 1-10 mg: 0.2-2 mL.

6. The preparation method according to claim 1, characterized in that: In step B), the temperature of the Fenton reaction is 40-80°C and the time is 10 min-4 h.

7. The hollow nano covalent organic framework obtained by the preparation method according to any one of claims 1 to 6.

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