A hollow spherical two-dimensional covalent organic framework, its preparation method and application

Abstract

This invention discloses a hollow spherical two-dimensional covalent organic framework, its preparation method, and its applications, belonging to the field of materials science. The preparation method of the hollow spherical two-dimensional covalent organic framework provided by this invention includes the following steps: reacting a triphenyleneamine monomer with an aldehyde monomer in the presence of a solvent and a catalyst to obtain the hollow spherical two-dimensional covalent organic framework. The organic framework prepared by the method of this invention has a uniformly sized hollow spherical structure, high crystallinity, and good chemical and thermal stability.

Description

Technical Field

[0001] This invention relates to the field of materials, specifically to a hollow spherical two-dimensional covalent organic framework, its preparation method, and its applications. Background Technology

[0002] Covalent organic frameworks (COFs) are crystalline, porous organic materials with atomically precise structural designability, tunable pore size, low density, good stability, and excellent optoelectronic properties, making them promising candidates for applications in gas storage, separation, drug delivery, energy conversion, and optoelectronic devices. Since the Yaghi group first reported COFs in 2005, numerous synthetic methods have been used to prepare them, including solvothermal, ionothermal, microwave, room-temperature, mechanical polishing, and photoluminescence methods (H. Chen. Angew. Chem. Int. Ed. 2021, 60, 10820-10827; X. Guan. J. Am. Chem. Soc. 2018, 14). 0,4494-4498; W.Ji.J.Hazard.Mater.2020,397,122793; Y.Liu.Chem.Sci.2019,10,10815-10820; S.Karak,J.Am.Chem.Soc.2017,139,1856-1862; S.Kim&H.C.Choi.Comm.Chem.2019,2,60;). Considering the crystallization mechanism of reversible reaction self-repair of defects, the solvothermal method is still the most common method for preparing highly crystalline covalent organic frameworks. However, due to the rigidity of the building units, internal defects of microcrystals, and kinetic traps, the prepared covalent organic frameworks are mostly irregular powders, which seriously limits their practical application.

[0003] Although some covalent organic frameworks with characteristic morphologies have been prepared, such as thin films, spherical, tubular, and flower-like structures (K. Liu. Nat. Chem. 2019, 11, 994-1000; C.-X. Chem. Commun. 2015, 51, 12254-12257; B. Gole. Angew. Chem Int Ed. 2018, 57, 846-850; W. Wang. Adv. Funct. Mater. 2021, 2010306.), most of the obtained covalent organic frameworks are either non-uniform in morphology and size or have poor crystallinity. While templates can achieve good morphology control, template removal can lead to a series of problems such as pore blockage, incomplete template removal, and structural collapse. Therefore, how to prepare covalent organic frameworks with uniform size and morphology and high crystallinity will be a research hotspot in this field. Summary of the Invention

[0004] This invention provides a hollow spherical two-dimensional covalent organic framework, its preparation method, and its application. This invention prepares a hollow spherical two-dimensional covalent organic framework with uniform size, high crystallinity, and good chemical and thermal stability by a solvothermal method.

[0005] This invention first discloses a method for preparing a hollow spherical two-dimensional covalent organic framework, comprising the following steps:

[0006] The amine monomer and aldehyde monomer of triphenylene react in the presence of solvent and catalyst to obtain the hollow spherical two-dimensional covalent organic framework.

[0007] In the above preparation method, the structural formula of the amine monomer of triphenylene is shown in Formula 1:

[0008]

[0009] The aldehyde monomer is Wherein, A is any one of the following groups: B can be a benzene ring or N.

[0010] Specifically, the aldehyde monomer is any one of terephthalaldehyde (TPA), 3-(4-formylphenyl)-benzene (TFPB), and 3-(4-formylphenyl)-amine (TFPA).

[0011] In the above preparation method, the amine monomer of triphenylene and

[0012] The molar ratio is 1:3; the amine monomer of the triphenylene and The molar ratio is 1:2.

[0013] The ratio of the amine monomer to the solvent in the triphenylene trioxide is 2.5–20 mg / mL; specifically, it can be 5 mg / mL.

[0014] The volume of the catalyst is 0.1 to 0.2 times the volume of the solvent; specifically, it can be 0.1 times.

[0015] In the above preparation method, the solvent is any one of acetonitrile, a mixed solvent of mesitylene and dioxane, and a mixed solvent of o-dichlorobenzene and n-butanol; specifically, in the mixed solvent of mesitylene and dioxane, the volume ratio of the two is 1:1; in the mixed solvent of o-dichlorobenzene and n-butanol, the volume ratio of the two is 1:1.

[0016] Preferably, the solvent is acetonitrile;

[0017] The catalyst is 1-12M acetic acid; specifically 6M acetic acid.

[0018] In the above preparation method, the reaction temperature is 60-120℃, specifically 120℃; the reaction time is 24-96h, specifically 72h.

[0019] The reaction was carried out under anaerobic conditions;

[0020] Specifically, the reaction can be carried out in a closed polymerization tube, reaction vessel, or in an inert atmosphere.

[0021] The above preparation method specifically includes the following steps:

[0022] 1) The amine monomer and the aldehyde monomer of the triphenylene are added to the polymerization tube, then the solvent is added, ultrasonically dispersed, and then the catalyst is added and ultrasonically dispersed again.

[0023] 2) The system obtained in step 1) is subjected to freeze-dry cycle, sealed in a tube, and after the tube is sealed, the system is allowed to return to room temperature and allowed to stand for reaction to obtain the hollow spherical two-dimensional covalent organic framework.

[0024] In the above preparation method, in step 1), the ultrasonic dispersion time is 5 to 30 minutes; specifically, it can be 5 minutes or 10 minutes.

[0025] The freeze-squeeze cycle is repeated 1 to 5 times, specifically 3 times; the temperature of the freeze-squeeze cycle is 77K.

[0026] The temperature for the static reaction is 60–120°C, specifically 120°C; the time is 24–96 hours, specifically 72 hours.

[0027] In the above preparation method, there is a post-processing step after the reaction, in which the system is allowed to return to room temperature.

[0028] Specifically, the post-processing involves washing and filtering, followed by drying in a vacuum drying oven at 60–120°C overnight; the specific drying temperature can be 90°C.

[0029] The cleaning agent used for cleaning is at least one of acetone, ethanol, methanol, and tetrahydrofuran; specifically, it may be acetone.

[0030] The hollow spherical two-dimensional covalent organic framework prepared by the above method also falls within the scope of protection of this invention.

[0031] The room temperature described in this invention is known to those skilled in the art and is generally 15–35°C.

[0032] The hollow spherical two-dimensional covalent organic framework prepared by this invention has a higher specific surface area and larger pore volume compared with randomly stacked nanomaterials. It can also expose more active sites, which has greater application potential and value in gas storage, as a carrier for loading drugs or catalysts.

[0033] The present invention has the following beneficial effects:

[0034] (1) The covalent organic framework prepared by the method of the present invention is a hollow spherical structure with uniform size;

[0035] (2) The covalent organic framework prepared by the present invention has good chemical and thermal stability, high crystallinity, high specific surface area and pore volume. Attached Figure Description

[0036] Figure 1 This is a synthetic circuit diagram of the covalent organic framework in Example 1;

[0037] Figure 2 The infrared spectrum of the covalent organic framework in Example 1;

[0038] Figure 3 This is a solid-state NMR image of the covalent organic framework from Example 1;

[0039] Figure 4 This is a scanning electron microscope image of the covalent organic framework in Example 1;

[0040] Figure 5 This is a transmission electron microscope image of the covalent organic framework in Example 1;

[0041] Figure 6 High-resolution transmission electron microscope image of the covalent organic framework in Example 1;

[0042] Figure 7 A focused ion beam scanning electron microscope image of the covalent organic framework in Example 1;

[0043] Figure 8 This is a graph showing the chemical stability data of the covalent organic framework in Example 1;

[0044] Figure 9 Thermogravimetric curve of the covalent organic framework in Example 1;

[0045] Figure 10 The powder X-ray diffraction pattern of the covalent organic framework in Example 1;

[0046] Figure 11 This is a graph showing the N2 adsorption-desorption curves of the covalent organic framework in Example 1;

[0047] Figure 12The T-plot curve of the covalent organic framework in Example 1;

[0048] Figure 13 The T-plot curve of the covalent organic framework in Example 2;

[0049] Figure 14 Thermogravimetric curve of the covalent organic framework in Example 2;

[0050] Figure 15 The T-plot curve of the covalent organic framework in Example 3;

[0051] Figure 16 The thermogravimetric curve of the covalent organic framework in Example 3 is shown. Detailed Implementation

[0052] The present invention will be further described in detail below with reference to specific embodiments. The embodiments given are only for illustrating the present invention and are not intended to limit the scope of the present invention.

[0053] Unless otherwise specified, the experimental methods described in the following examples are conventional methods.

[0054] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0055] In the following examples, HAPTP (2,3,6,7,10,11-6-(4-aminophenyl)-triphenylene) was purchased from Jilin Zhongke Yanshang Technology Co., Ltd., TPA (terephthalaldehyde) was purchased from Anaiji, TFPB (3-(4-formylphenyl)-benzene) was purchased from Anaiji, and TFPA (3-(4-formylphenyl)-amine) was purchased from Shanghai Kaishu Chemical Technology Co., Ltd.

[0056] Example 1: Synthesis of HAPTP-TPA-COF

[0057] Synthesis of 2,3,6,7,10,11-hexakis(4-aminophenyl)triphenylene(HAPTP)-Terephthaldehyde(TPA)–COF:

[0058] Weigh 10 mg HAPTP and 5.2 mg TPA into a 10 mL polymerization tube, add 2 mL of acetonitrile solvent, sonicate for 10 min, add 200 μL of 6 M acetic acid, sonicate again for 5 min until homogeneous, perform freeze-vacuum cycles three times (77 K), seal the tube, and after it returns to room temperature, place it in a 120 °C forced-air oven for 72 h to stand and react. Turn off the heating, and after the system returns to room temperature, cut the polymerization tube, wash the obtained powder with acetone and filter, and place the obtained filter cake in a vacuum drying oven and dry overnight at 90 °C. The yield is 82% (12.5 mg).

[0059] Figure 1 This is a schematic diagram of the synthesis of the covalent organic framework (HAPTP-TPA-COF) in this embodiment.

[0060] Figure 2 The infrared spectrum of the covalent organic framework (HAPTP-TPA-COF) prepared in this example is shown. Compared with its monomer, the CH stretching vibration peak of the corresponding aldehyde group in the obtained HAPTP-TPA-COF (2700-2900 cm⁻¹) is also shown. -1 The peaks of the NH stretching vibration of the amino group (3300-3500 cm⁻¹) and the peaks of the NH stretching vibration of the amino group. -1 It basically disappeared, and at 1623cm -1 A new peak appears, corresponding to the formed imine bond peak, indicating the complete consumption of the monomer and the formation of the imine bond.

[0061] Figure 3 The solid-state NMR spectrum of HAPTP-TPA-COF in this embodiment shows that 123, 128, 138 and 150 ppm correspond to the aromatic carbons in the benzene ring and the triphenyl group, and 157 ppm corresponds to the chemical shift of the carbon in the formed imine bond. The solid-state NMR spectrum further confirms the formation of the imine bond.

[0062] Figure 4 The image shows a scanning electron microscope (SEM) image of HAPTP-TPA-COF. The SEM was a field emission scanning electron microscope (S-4800). The image shows that the obtained HAPTP-TPA-COF is a spherical material with a size of about 300-400 nm. The surface of these spheres is tightly wrapped by nanosheets.

[0063] Figure 5 The image shows a transmission electron microscope (TEM) image of HAPTP-TPA-COF. The image shows that the prepared HAPTP-TPA-COF consists of hollow spheres of about 300-400 nm in diameter, which is consistent with the SEM results. The wall thickness of these hollow spheres is about 100 nm, which further proves the uniformity of the hollow spheres.

[0064] Figure 6This is a high-resolution transmission electron microscope (HRTEM) image of HAPTP-TPA-COF. The HAPTP-TPA-COF nanosheets show clear lattice fringes, including some single crystal wafers, demonstrating its excellent crystallinity.

[0065] Figure 7 The image shows a focused ion beam scanning electron microscope image of HAPTP-TPA-COF. The cross-sectional image obtained after ion beam bombardment clearly shows the hollow structure of the spherical HAPTP-TPA-COF, further proving its hollow structure characteristics.

[0066] Figure 8 The graph shows the chemical stability data of HAPTP-TPA-COF. The results show that HAPTP-TPA-COF has good stability in common organic solvents, as well as in PBS aqueous solution and even 0.1M HCl and 1M KOH aqueous solution.

[0067] The stability test method is as follows: Take 5 mg of freshly prepared HAPTP-TPA-COF, place it in the corresponding 1 mL solution, let it stand for 24 h, filter it and wash it with acetone, dry it under vacuum at 90 °C, and then test the powder X-ray diffraction. Compare it with the sample without solvent treatment.

[0068] Figure 9 The thermogravimetric curves of HAPTP-TPA-COF are shown, and the results demonstrate that the degradation temperature of the material is above 400 degrees Celsius, thus HAPTP-TPA-COF has excellent thermal stability.

[0069] Figure 10 The powder X-ray diffraction pattern of HAPTP-TPA-COF shows that many diffraction peaks, 2θ = 4.00, 6.98, 8.06, 10.67, 12.09 and 16.17°, correspond to the (100), (110), (200), (120), (300) and (400) crystal planes, respectively. This result is similar to the simulated AA stacked structure, which proves its excellent crystallinity.

[0070] Figure 11 The N2 adsorption-desorption curves of HAPTP-TPA-COF are shown. The adsorption-desorption curves exhibit typical characteristics of Type I adsorption isotherms – in the low-pressure region (P / P o <0.05) has a steep absorption.

[0071] Figure 12 The T-plot of HAPTP-TPA-COF shows that, according to calculations, the specific surface area of ​​HAPTP-TPA-COF is as high as 955 m². 2 / g.

[0072] Example 2: Synthesis of HAPTP-TFPB-COF

[0073] Synthesis of 2,3,6,7,10,11-hexakis(4-aminophenyl)triphenylene(HAPTP)-tris(4-formylphenyl)benzene(TFPB)–COF:

[0074] Weigh 10 mg HAPTP and 10 mg TFPB into a 10 mL polymerization tube, add 2 mL of acetonitrile solvent, sonicate for 10 min, add 200 μL of 6 M acetic acid, sonicate again for 5 min until homogeneous, perform freeze-vacuum cycle (77 K) three times, seal the tube, and after it returns to room temperature, place it in a 120 °C forced-air oven for 72 h to stand and react. Turn off the heating, and after the system returns to room temperature, cut the polymerization tube, wash the obtained powder with acetone and filter, and place the obtained filter cake in a vacuum drying oven and dry overnight at 90 °C. The yield is 87% (17.4 mg).

[0075] Figure 13 The T-plot of HAPTP-TFPB-COF is shown. According to calculations, the specific surface area of ​​HAPTP-TFPB-COF is 531 m². 2 / g.

[0076] Figure 14 The thermogravimetric curves of HAPTP-TFPB-COF are shown, and the results demonstrate that the degradation temperature of the material is above 400℃, thus HAPTP-TFPB-COF has excellent thermal stability.

[0077] Example 3: Synthesis of HAPTP-TFPA-COF

[0078] Synthesis of 2,3,6,7,10,11-hexakis(4-aminophenyl)triphenylene(HAPTP)-tris(4-formylphenyl)amine(TFPA)–COF:

[0079] Weigh 10 mg HAPTP and 8.5 mg TFPA into a 10 mL polymerization tube, add 2 mL of acetonitrile solvent, sonicate for 10 min, add 200 μL of 6 M acetic acid, sonicate again for 5 min until homogeneous, perform freeze-vacuum cycle (77 K) three times, seal the tube, and after it returns to room temperature, place it in a 120 °C forced-air oven for 72 h to stand and react. Turn off the heating, and after the system returns to room temperature, cut the polymerization tube, wash the obtained powder with acetone and filter, and place the obtained filter cake in a vacuum drying oven and dry overnight at 90 °C. The yield is 86% (16 mg).

[0080] Figure 15 The T-plot of HAPTP-TFPA-COF is shown. According to calculations, the specific surface area of ​​HAPTP-TFPA-COF is 829 m². 2 / g.

[0081] Figure 16 The thermogravimetric curves of HAPTP-TFPA-COF show that the degradation temperature of the material is above 400℃, thus HAPTP-TFPA-COF has excellent thermal stability.

Claims

1. A method for preparing a hollow spherical two-dimensional covalent organic framework, comprising the following steps: The amine monomer and aldehyde monomer of triphenylene react in the presence of solvent and catalyst to obtain the hollow spherical two-dimensional covalent organic framework. The structural formula of the amine monomer of the triphenylene is shown in Formula 1: The aldehyde monomer is or ;in, A can be any one of the following groups: B is a benzene ring or N; The solvent is acetonitrile; The catalyst is 1-12 M acetic acid; The reaction temperature is 60~120℃; the reaction time is 24~96 h; The reaction was carried out under anaerobic conditions.

2. The preparation method according to claim 1, characterized in that: The amine monomer of the triphenylene and The molar ratio is 1:3; the amine monomer of the triphenylene and The molar ratio is 1:

2.

3. The preparation method according to claim 1 or 2, characterized in that: The ratio of the amine monomer of the triphenylene to the solvent is 2.5~20 mg / mL; The volume of the catalyst is 0.1 to 0.2 times the volume of the solvent.

4. The preparation method according to claim 1 or 2, characterized in that: The preparation method specifically includes the following steps: 1) The amine monomer and the aldehyde monomer of the triphenylene are added to the polymerization tube, then the solvent is added, and the mixture is ultrasonically dispersed. The catalyst is then added and ultrasonically dispersed again. 2) The system obtained in step 1) is subjected to freeze-dry cycle, sealed in a tube, and after the tube is sealed, the system is allowed to return to room temperature and allowed to stand for reaction to obtain the hollow spherical two-dimensional covalent organic framework.

5. The preparation method according to claim 4, characterized in that: In step 1), the ultrasonic dispersion time is 5~30 min.

6. The preparation method according to claim 1 or 2, characterized in that: The reaction is followed by a post-processing step where the system is allowed to return to room temperature.

7. The preparation method according to claim 6, characterized in that: The post-treatment involves washing and filtration, followed by drying in a vacuum drying oven at 60-120°C overnight. The cleaning agent used for cleaning is at least one of acetone, ethanol, methanol, and tetrahydrofuran.

8. The hollow spherical two-dimensional covalent organic framework prepared by the preparation method of any one of claims 1-7.

9. The application of the hollow spherical two-dimensional covalent organic framework of claim 8 in gas storage or as a drug carrier or catalyst.

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