A hydrogen bond-induced multi-level porous covalent organic framework material and its assembly method and application

Abstract

The present invention discloses a hydrogen bond-induced multi-level pore covalent organic framework material and an assembly method and application thereof. The material comprises a triphenylbenzene-type six-connected molecular module (1) and an meta-substituted benzene-type two-connected molecular module (2) interconnected in a two-dimensional space to form a two-dimensional multi-level pore structure. The present invention provides a novel assembly strategy, wherein an orderly expanded hydrogen bond-induced two-dimensional multi-level pore covalent organic framework material is obtained through [6+2] imine condensation. The material has high crystallinity, a large specific surface area and a unique pore structure, so that the novel multi-level pore covalent organic framework material generates abundant specific gas adsorption sites and has good application prospects in gas adsorption and separation.

Description

Technical Field

[0001] The present invention belongs to the field of covalent organic framework (COFs) materials, and specifically relates to a novel type of hydrogen bond-induced multi-level pore covalent organic framework material and an assembly method thereof, as well as applications in the field of gas separation. Background Art

[0002] As an important chemical raw material, acetylene is widely used in fields such as petrochemical and electronics industries. However, acetylene produced by processes such as petroleum distillation and cracking often contains some impurities, such as methane and carbon dioxide, which seriously affect its subsequent use efficiency. Since the boiling points and kinetic sizes of acetylene (C2H2), carbon dioxide (CO2) and methane (CH4) molecules are very close, their separation is extremely challenging. Therefore, achieving selective adsorption separation of C2H2 / CO2 and C2H2 / CH4 is particularly important for reducing energy consumption and purifying energy. Traditional adsorption materials are difficult to meet the market's growing demand for high-performance adsorption separation materials due to their drawbacks such as poor adsorption separation effects. Therefore, it is necessary to study porous materials with controllable pore size, excellent adsorption separation selectivity and high stability.

[0003] Covalent organic frameworks (COFs), as an emerging porous material, are widely used in energy, catalysis, and separation due to their tunable regular pore structure, rich, designable active sites, and high specific surface area. The nanosheets formed by two-dimensional COFs have atomic-level thickness and extremely low mass transfer resistance, making them a research hotspot in the field of high-throughput gas separation. Introducing functional sites, such as hydroxyl (-OH) groups, into the COFs backbone can enhance the binding affinity for C2H2. Therefore, developing a hydroxyl-functionalized two-dimensional COF material could provide a new research perspective for the adsorption separation of C2H2 / CO2.

[0004] This study successfully synthesized a series of hydrogen-bond-induced hierarchical COFs (COFs) by assembling a hexameric triphenylbenzene-based molecular module with a dimeric meta-substituted benzene-based molecular module. Leveraging the abundant hydroxyl functional groups within the pores and their one-dimensional nanochannels, these materials can be used for the selective adsorption and separation of C₂H₂ and CO₂. Summary of the Invention

[0005] The present invention provides a hydrogen bond-induced multi-level porous covalent organic framework material, its assembly method, and its application. The multi-level porous covalent organic framework material of the present invention has high crystallinity, a large specific surface area, and a specific pore structure, and has good application in acetylene purification.

[0006] The technical solutions of the present invention are as follows:

[0007] A hydrogen-bond-induced multi-level pore covalent organic framework material is formed by interconnecting triphenylbenzene-based six-connected molecular modules and meta-substituted benzene-based two-connected molecular modules in a two-dimensional space; in at least a portion of the hydrogen-bond-induced multi-level pore covalent organic framework material, each meta-substituted benzene-based two-connected molecular module is respectively connected to two adjacent triphenylbenzene-based six-connected molecular modules, and each triphenylbenzene-based six-connected molecular module is respectively connected to six adjacent meta-substituted benzene-based two-connected molecular modules, forming a two-dimensional multi-level pore structure;

[0008] The structure of the triphenylbenzene six-connected molecular module is shown in formula (1), and the structure of the meta-substituted benzene two-connected molecular module is shown in formula (2):

[0009]

[0010] In formula (1) or formula (2), "---" represents a linking position, and R = OH, COOH, SO3H, PO3H or B(OH)2.

[0011] The hydrogen bond induced multi-level pore covalent organic framework material of the present invention has a one-dimensional pore structure with two different pore sizes, and a BET specific surface area of ​​40 to 4000 m 2 / g, pore size is 0.6~6.0nm.

[0012] Preferably, in at least a portion of the hydrogen bond induced multi-level porous covalent organic framework material, the molar ratio of the triphenylbenzene six-linked molecular modules to the meta-substituted benzene two-linked molecular modules is 0.5-1.5:2.5-4.5, particularly preferably 1:3.

[0013] The connecting groups of the hydrogen bond induced multi-level porous covalent organic framework material include dynamic covalent bonds, and the connection mode is selected from any one of -C=N-, -C=NN=C-, -C=N-NH-, -C=C, and -C=C(CN)-, preferably -C=N-.

[0014] When the connection mode is -C=N-, the hydrogen bond induced multi-level porous covalent organic framework material includes a skeleton unit shown in formula (3):

[0015]

[0016] In formula (3), “---” represents a linking position, and R=OH, COOH, SO3H, PO3H or B(OH)2.

[0017] A method for preparing a hydrogen bond-induced multi-level porous covalent organic framework material, comprising:

[0018] The triphenylbenzene hexalinker molecule (I), the meta-substituted benzene dilinker molecule (II), a catalyst and an organic solvent are mixed, degassed by freeze-thaw cycles, and then sealed. The mixture is reacted at 80-180° C. (preferably 120° C.) for 72-168 hours (preferably 72 hours) to generate a solid precipitate. The precipitate is filtered to obtain a solid precipitate, and the solid precipitate is washed and dried to obtain the hydrogen bond induced hierarchical porous covalent organic framework material.

[0019] The catalyst was acetic acid, which was fed in the form of a 6M aqueous acetic acid solution;

[0020] The organic solvent is a mixed solvent of o-dichlorobenzene and n-butanol, or a mixed solvent of anisole and n-butanol;

[0021] The specific operations of washing and drying the precipitate are as follows: the precipitate is first soaked in N,N-dimethylacetamide for 6 h, repeated twice, then soaked in acetone for 6 h, repeated twice, then Soxhlet extraction is performed with tetrahydrofuran and acetone for 24 h, respectively, and then placed in a vacuum drying oven at 80°C, evacuated to 20 mTorr, and dried for 24 h;

[0022]

[0023] In formula (I) or formula (II),

[0024] X1 is an aldehyde group (CHO) or an amino group (NH2);

[0025] X2 is an aldehyde group (CHO) or an amino group (NH2);

[0026] Preferably, X1 is an amino group (NH2) and X2 is an aldehyde group (CHO);

[0027] The group R is OH, COOH, SO3H, PO3H or B(OH)2.

[0028] The hydrogen bond-induced multi-level porous covalent organic framework material of the present invention can be applied to the field of gas separation, especially the selective adsorption separation of C2H2 / CO2 and C2H2 / CH4.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] This invention provides a novel assembly strategy for hydrogen-bond-induced hierarchical porous covalent organic frameworks. This strategy employs a triphenylbenzene-based hexalinker molecular module and a meta-substituted benzene-based dilinker molecular module containing a hydroxyl functional group, resulting in an ordered, extended, hydrogen-bond-induced, two-dimensional hierarchical porous framework material through [6+2] imine condensation. This hierarchical porous covalent organic framework material exhibits high crystallinity, a large specific surface area, and a unique pore structure, resulting in abundant specific gas adsorption sites and promising application prospects in gas adsorption and separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 : Schematic diagram of the topological structure of the hydrogen bond induced multi-level porous covalent organic framework material in Example 1 of the present invention; a: TH-COF, b: TD-COF.

[0032] Figure 2 : Schematic diagram of the synthesis of hydrogen bond induced multi-level porous covalent organic framework materials TH-COF and TD-COF in Example 1 of the present invention.

[0033] Figure 3 : Scanning electron microscope photos of the hydrogen bond induced multi-level porous covalent organic framework material in Example 1 of the present invention; a: TH-COF, b: TD-COF.

[0034] Figure 4 : Powder X-ray (PXRD) test spectrum and simulated spectrum of the hydrogen bond induced multi-level porous covalent organic framework material in Example 1 of the present invention; a: TH-COF, b: TD-COF.

[0035] Figure 5 : Infrared (FT-IR) spectra of the hydrogen bond induced multi-level porous covalent organic framework material in Example 1 of the present invention; a: TH-COF, b: TD-COF.

[0036] Figure 6 : Adsorption performance diagram of acetylene and carbon dioxide of the hydrogen bond induced multi-level porous covalent organic framework material in Example 1 of the present invention at 273K; a: TH-COF, b: TD-COF. DETAILED DESCRIPTION

[0037] The following further describes the objectives, technical solutions and advantages of the present invention in detail with reference to the embodiments and drawings. The specific embodiments described are only used to explain the present invention and are not intended to limit the present invention.

[0038] In the following examples,

[0039] Triphenylbenzene hexalinker (TAPB), 5-hydroxyisophthalaldehyde (HBB), and 3,5-diformylphenylboronic acid (DBA) were purchased from Shanghai Tengqian Biotechnology Co., Ltd. with a purity of >95%.

[0040] Example 1

[0041] The preparation method of a hierarchical porous covalent organic framework compound (abbreviated as TH-COF, TD-COF) comprises the following steps:

[0042] (1) Synthesis of TH-COF:

[0043] See Figure 2In a glass ampoule, triphenylbenzene hexalinker (TAPB) (51.18 mg, 0.06 mmol) and 5-hydroxyisophthalaldehyde (HBB) (27.1 mg, 0.18 mmol) were added to a mixed solvent of o-dichlorobenzene (1.5 mL) and n-butanol (0.5 mL). After sonication for 5 minutes, a pale yellow turbid solution was obtained. 6 M acetic acid (0.3 mL) was added to the glass ampoule as a catalyst. The glass ampoule was quickly frozen at 77 K in a liquid nitrogen bath and degassed by freeze-pump-thaw cycles three times before being sealed. The glass ampoule was placed in an oven at 120°C for 3 days. The pale yellow solid was isolated by centrifugation and washed by soaking with N,N-dimethylacetamide (2×10 mL) and acetone (2×10 mL). The resulting precipitate was filtered and then thoroughly washed with tetrahydrofuran and acetone by Soxhlet extraction for 48 h. The sample was then transferred to a vacuum oven, evacuated to 20 mTorr at 80° C., and dried for 24 h to obtain TH-COF as a light yellow powder (yield: 68.2 mg, 87.2%).

[0044] (2) Synthesis of TD-COF:

[0045] See Figure 2 In a glass ampoule, triphenylbenzene hexalinker (TAPB) (51.18 mg, 0.06 mmol) and 3,5-diformylphenylboronic acid (DBA) (32.04 mg, 0.18 mmol) were added to a mixed solvent of anisole (1.5 mL) and n-butanol (0.5 mL). After sonication for 5 minutes, a light orange turbid solution was obtained. 6 M acetic acid (0.3 mL) was added to the glass ampoule as a catalyst. The glass ampoule was quickly frozen at 77 K in a liquid nitrogen bath and degassed by freeze-pump-thaw cycles three times before being sealed. The ampoule was placed in an oven at 120°C for 3 days. The pale yellow solid was centrifuged and washed by soaking with N,N-dimethylacetamide (2×10 mL) and acetone (2×10 mL). The resulting precipitate was filtered and then thoroughly washed with tetrahydrofuran and acetone by Soxhlet extraction for 48 h. The sample was then transferred to a vacuum chamber, evacuated to 20 mTorr at 80°C, and dried for 24 h to obtain TD-COF as a light yellow powder (yield: 69 mg, 82.9%).

[0046] (3) Product characterization and performance testing

[0047] See Figure 3 , Scanning electron microscopy (SEM) images showing the stick-like morphology of TH-COF (a) and the spherical morphology of TD-COF (b).

[0048] See Figure 4The successful synthesis of highly crystalline TH-COF (a) and TD-COF (b) was verified by PXRD measurements. Materials Studio software was used to simulate and analyze the crystal structures of TH-COF and TD-COF. The simulated PXRD patterns matched well with the experimentally observed PXRD patterns, further confirming the accuracy of the structures.

[0049] See Figure 5 The infrared spectra of the monomers required for synthesis and the corresponding products TH-COF (a) and TD-COF (b) were compared by Fourier transform infrared (FT-IR) spectroscopy. Both of them were at 1631 cm -1 The characteristic stretching vibration of the C=N bond was generated, proving the successful synthesis of TH-COF and TD-COF.

[0050] See Figure 6 The acetylene and carbon dioxide adsorption performance of TH-COF (a) and TD-COF (b) was tested using a gas adsorption instrument (ASAP 2020) at 273K. The results showed that both exhibited high acetylene adsorption capacity and excellent acetylene / carbon dioxide separation performance.

[0051] The embodiments described above only express the preferred embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be understood as limiting the scope of protection of the present invention. The various technical features of the embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the various technical features in the above embodiments are described, but as long as there are no contradictions in these combinations involved, they should be considered to be within the scope of this specification. For those of ordinary skill in the art, several modifications and changes can be made without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be based on the appended claims.

Claims

1. A hydrogen bond induced multi-level porous covalent organic framework material, characterized in that: The triphenylbenzene six-connected molecular modules and the meta-substituted benzene two-connected molecular modules are interconnected in a two-dimensional space; in at least a portion of the hydrogen bond induced multi-level pore covalent organic framework material, each meta-substituted benzene two-connected molecular module is respectively connected to two adjacent triphenylbenzene six-connected molecular modules, and each triphenylbenzene six-connected molecular module is respectively connected to six adjacent meta-substituted benzene two-connected molecular modules, forming a two-dimensional multi-level pore structure; The structure of the triphenylbenzene six-connected molecular module is shown in formula (1), and the structure of the meta-substituted benzene two-connected molecular module is shown in formula (2): The connection mode of the hydrogen bond induced multi-level porous covalent organic framework material is -C=N-, and includes the skeleton unit shown in formula (3): In formula (1), formula (2) or formula (3), "---" represents a linking position, and R = OH, COOH, SO3H, PO3H or B(OH)2.

2. The hydrogen bond induced multi-level porous covalent organic framework material according to claim 1, characterized in that: In at least a portion of the hydrogen bond-induced multi-level porous covalent organic framework material, the molar ratio of the triphenylbenzene six-connected molecular modules to the meta-substituted benzene two-connected molecular modules is 0.5-1.5:2.5-4.

5.

3. The hydrogen bond induced multi-level porous covalent organic framework material according to claim 2, characterized in that: In at least a portion of the hydrogen bond-induced multi-level porous covalent organic framework material, the molar ratio of the triphenylbenzene-type six-connected molecular modules to the meta-substituted benzene-type two-connected molecular modules is 1:

3.

4. A method for preparing a hydrogen bond-induced multi-level porous covalent organic framework material, characterized in that: The method comprises: The triphenylbenzene hexalinker molecule (I), the meta-substituted benzene dilinker molecule (II), a catalyst and an organic solvent are mixed, degassed by freeze-thaw cycles, and then sealed. The mixture is reacted at 80-180° C. for 72-168 hours to generate a solid precipitate. The precipitate is filtered to obtain a solid precipitate, and the solid precipitate is washed and dried to obtain the hydrogen bond induced hierarchical porous covalent organic framework material. In formula (I) or formula (II), X1 is an aldehyde group or an amino group; X2 is an aldehyde group or an amino group; R is OH, COOH, SO3H, PO3H or B(OH)2.

5. The preparation method according to claim 4, wherein: The catalyst is acetic acid.

6. The preparation method according to claim 4, characterized in that: The organic solvent is a mixed solvent of o-dichlorobenzene and n-butanol, or a mixed solvent of anisole and n-butanol.

7. Application of the hydrogen bond induced multi-level porous covalent organic framework material as claimed in claim 1 in the field of gas separation.

8. The use according to claim 7, characterized in that Application of hydrogen bond induced hierarchical porous covalent organic framework materials in the selective adsorption and separation of C2H2 / CO2 and C2H2 / CH4.

Images