Ultramicroporous fluorine-rich two-dimensional covalent organic framework material as well as preparation method and application thereof

Abstract

The invention discloses an ultramicropore fluorine-rich two-dimensional covalent organic framework material and a preparation method and application thereof.The preparation method comprises the steps that six-connection-node molecules with hexagonal symmetry and three-connection-node molecules with fluoro trilateral symmetry are adopted, and an orderly-expanded trilateral symmetry two-dimensional topological network structure is obtained through [6 + 3] imine condensation; a frame compound having a fluoro group; the material has high crystallinity and a unique ultra-microporous pore structure, so that the novel two-dimensional covalent organic framework compound generates abundant specific gas screening characteristics, and has a good application prospect in the aspects of industrial gas separation and purification; # imgabs0 #

Description

Technical Field

[0001] The present invention belongs to the field of covalent organic framework (COFs) materials, and specifically relates to a class of ultra-microporous fluorine-rich two-dimensional covalent organic framework materials and a preparation 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 electronic 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 benefits. 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, purifying energy and achieving "carbon neutrality". Traditional adsorption materials are difficult to meet the market's growing demand for high-performance adsorption and separation materials due to their drawbacks such as poor adsorption and separation effects. Therefore, it is necessary to study porous materials with adjustable pore size, excellent adsorption and separation selectivity and high stability.

[0003] Covalent organic frameworks (COFs), as an emerging porous material, are widely used in energy, catalysis, and separation fields 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, and have become a research hotspot in the field of high-throughput gas separation. Introducing functional sites, such as fluorine groups (-F), into the COFs skeleton can enhance the binding affinity to C2H2. Therefore, the development of a fluorine-functionalized two-dimensional COFs material can provide a new research perspective for the adsorption and separation of C2H2 / CO2, etc. Summary of the invention

[0004] The present invention provides a two-dimensional covalent organic framework material with an ultra-microporous fluorine-rich structure, and a preparation method and application thereof. The present invention uses a hexagonal symmetric six-connected node molecule to assemble with a fluorinated three-connected node molecule with trigonal symmetry to successfully synthesize a series of fluorinated two-dimensional COFs materials. The high crystallinity and specific ultra-microporous pore structure of the material make it have good application prospects in industrial gas separation and purification, such as industrial helium separation, acetylene or methane purification and other fields.

[0005] The technical solution of the present invention is as follows:

[0006] A fluorine-rich two-dimensional covalent organic framework material with ultra-micropores, which is formed by six hexagonal symmetric connection nodes and three fluorinated trigonal symmetric connection nodes connected by covalent bonds on a two-dimensional level and stacked in three dimensions;

[0007] In at least a portion of the two-dimensional covalent organic framework material, each hexagonal symmetric six-connected node is respectively connected to six adjacent fluorinated trigonal symmetric three-connected nodes, and each fluorinated trigonal symmetric three-connected node is respectively connected to three adjacent hexagonal symmetric six-connected nodes, forming a two-dimensional topological network structure;

[0008] in,

[0009] The six connection nodes of hexagonal symmetry and the three connection nodes of fluorinated trigonal symmetry are shown in formula (1) and formula (2) respectively:

[0010]

[0011] In formula (1) and formula (2),

[0012] R is one or more of H, OH, SH, halogen (F, Cl, Br, I);

[0013] “---” indicates a connection.

[0014] The BET specific surface area of ​​the ultra-microporous fluorine-rich two-dimensional covalent organic framework material of the present invention is 100 to 2000 m 2 / g, pore size is 0.4~1.0nm.

[0015] In at least a portion of the ultramicroporous fluorine-rich two-dimensional covalent organic framework material of the present invention, the molar ratio of six hexagonal symmetric connecting nodes to three fluorinated trigonal symmetric connecting nodes is (0.5-1.5): (0.75-2.25), preferably 1:2.

[0016] The ultra-microporous fluorine-rich two-dimensional covalent organic framework material of the present invention comprises a tripartite symmetrical two-dimensional topological network structure.

[0017] The connecting group of the ultramicroporous fluorine-rich two-dimensional covalent organic framework material described in the present invention contains a dynamic covalent bond, and the connection mode is selected from one of -C=N-, -C=NN=C-, -C=N-NH-, -C=C-, and -C=C(CN)-, preferably -C=N- (reversible imine covalent bond).

[0018] When the connection mode is -C=N-, the ultra-microporous fluorine-rich two-dimensional covalent organic framework material includes a skeleton unit shown in formula (3):

[0019]

[0020] In formula (3),

[0021] R is one or more of H, OH, SH, halogen (F, Cl, Br, I);

[0022] “---” indicates the connection bit.

[0023] The method for preparing the ultra-microporous fluorine-rich two-dimensional covalent organic framework material of the present invention comprises:

[0024] The hexagonal symmetric six-connected node molecules, the fluorinated trigonal symmetric three-connected node molecules, the reaction solvent and the catalyst are mixed, and after freeze-thaw cycle degassing, the mixture is sealed and heated to 80-180° C. for reaction for 72-168 hours, and the reaction mixture is post-treated to obtain the ultra-microporous fluorine-rich two-dimensional covalent organic framework material;

[0025] The molar ratio of the hexagonal symmetric six-connected node molecule to the fluorinated trigonal symmetric three-connected node molecule is (0.5-1.5): (0.75-2.25), preferably 1:2;

[0026] The reaction solvent is selected from one of the following mixed solvents: o-dichlorobenzene / n-butanol, anisole / n-butanol, N,N-dimethylacetamide / n-butanol;

[0027] The catalyst is acetic acid or trifluoroacetic acid;

[0028] The preferred reaction temperature is 120°C and the reaction time is 3 days;

[0029] The specific post-treatment method is as follows: after the reaction is completed, cool to room temperature, collect the solid product by centrifugation, soak it in N,N-dimethylacetamide for 6 hours, repeat twice, then soak it in acetone for 6 hours, repeat twice, then use tetrahydrofuran and acetone to Soxhlet extraction for 24 to 48 hours respectively, then place it in a vacuum drying oven, evacuate to 20mTorr at 100°C and dry it for 24 hours to obtain the target product;

[0030] The hexagonal symmetric six-connected node molecule and the fluorinated trigonal symmetric three-connected node molecule are shown in formula (4) and formula (5) respectively:

[0031]

[0032] In formula (4) and formula (5),

[0033] One of R1 and R2 is an aldehyde group (-CHO), and the other is an amino group (-NH2); preferably, R1 is an aldehyde group and R2 is an amino group;

[0034] R3 and R4 are each independently H, OH, SH, or halogen (F, Cl, Br, I); preferably, R3 and R4 are both H.

[0035] The ultra-microporous fluorine-rich two-dimensional covalent organic framework material of the present invention can be applied to the separation and purification of industrial gases.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] The present invention provides a design strategy for a two-dimensional covalent organic framework compound with a novel interlayer staggered stacking, which adopts six-connected node molecules with hexagonal symmetry and three-connected node molecules with fluorinated tripartite symmetry, and obtains an orderly extended tripartite symmetrical two-dimensional topological network structure through [6+3] imine condensation, and has a framework compound with a fluorinated group.

[0038] The two-dimensional covalent organic framework compound of the present invention has high crystallinity and unique ultra-microporous pore structure, so that this new two-dimensional covalent organic framework compound produces rich specific gas screening properties and has good application prospects in industrial gas separation and purification. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 : Schematic diagram of the topological structure of the fluorine-rich two-dimensional covalent organic framework compound in Example 1 of the present invention.

[0040] Figure 2 : Schematic diagram of the synthesis of the fluorine-rich two-dimensional covalent organic framework compound in Example 1 of the present invention.

[0041] Figure 3 : Powder X-ray (PXRD) test spectrum and simulation spectrum of the fluorine-rich two-dimensional covalent organic framework compound in Example 1 of the present invention.

[0042] Figure 4 : Infrared (FT-IR) spectrum of the fluorine-rich two-dimensional covalent organic framework compound in Example 1 of the present invention.

[0043] Figure 5 : Scanning electron microscope photograph of the fluorine-rich two-dimensional covalent organic framework compound in Example 1 of the present invention.

[0044] Figure 6 : The adsorption performance diagram of acetylene, ethylene and carbon dioxide at 298K of the fluorine-rich two-dimensional covalent organic framework compound in Example 1 of the present invention (a) and the acetylene / carbon dioxide and acetylene / ethylene separation performance diagram (b). DETAILED DESCRIPTION

[0045] The objectives, technical solutions and advantages of the present invention are further described in detail below in conjunction with the embodiments and drawings. The specific embodiments described are only used to explain the present invention but not to limit the present invention.

[0046] In the following embodiments,

[0047] The raw materials hexaaldehyde benzene (HFPB) and 1,3,5-trifluoro-2,4,6-tris(4-aminophenyl)benzene (TAFB) had a purity of >95% and were purchased from Shanghai Tengqian Biotechnology Co., Ltd.

[0048] Example 1

[0049] (1) Synthesis of TFB-COF

[0050] See also Figure 2 In a glass ampoule, hexaformaldehyde benzene (HFPB) (14 mg, 20 mmol) and 1,3,5-trifluoro-2,4,6-tri(4-aminophenyl)benzene (TAFB) (16 mg, 40 mmol) were added to a mixed solvent of anisole (0.48 mL) and n-butanol (0.12 mL). After ultrasonication for 5 minutes, a light yellow turbid solution was obtained. 9 M acetic acid (60 uL) was added to the glass ampoule as a catalyst. The glass ampoule was quick-frozen at 77 K in a liquid nitrogen bath and degassed by freeze-pump-thaw, cycled three times, and then sealed. The glass ampoule was placed in an oven at 120 ° C for 3 days. The purple-white solid was separated 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 for 48 h, respectively, by Soxhlet extraction. The sample was then transferred to a vacuum chamber, evacuated to 20 mTorr at 100° C., and dried for 24 h to obtain TFB-COF as a light yellow powder (yield: 20 mg, 66%).

[0051] (2) Product characterization

[0052] See also Figure 3 Through PXRD measurement, TFB-COF has diffraction peaks at 6.58, 10.56, 11.72, 12.62, 13.50, 15.02, 15.90, 16.50, 17.94, 20.48, 21.96 and 22.94. The crystal structure of TFB-COF was analyzed by structural simulation using Materials Studio software. The simulated PXRD pattern generated by the two-dimensional topological network structure of the corresponding fluorinated structure matched the experimental PXRD pattern well, proving the correctness of the structure.

[0053] See also Figure 4 Through Fourier transform infrared (FT-IR) spectroscopy, the required monomers and the corresponding product TFB-COF were tested at 1610 cm -1 The characteristic stretching vibration of the C=N bond was produced, proving the successful synthesis of TFB-COF.

[0054] See also Figure 5 , Scanning electron microscopy (SEM) pattern, showing that TFB-COF has a blocky morphology.

[0055] See also Figure 6The adsorption performance of acetylene, ethylene and carbon dioxide of TFB-COF was tested using a gas adsorption instrument (ASAP 2020) at 298K. The results showed that TFB-COF exhibited the best adsorption capacity for acetylene at 298K, reaching 55cm 3 / g, and the corresponding acetylene / carbon dioxide separation factor reaches 3.

[0056] Comparative Example

[0057] Our research group previously disclosed similar two-dimensional COFs materials without fluorine functional groups in CN 115894947A. Under the same gas adsorption and separation performance test conditions, the results showed that its adsorption capacity for acetylene was only 30 cm 3 / g, and the corresponding acetylene / carbon dioxide separation factor is only 1.5, which fully proves the effectiveness of the introduction of fluorinated functional groups in the present invention. This is also consistent with a research work previously reported by our research group (New Journal of Chemistry 2023, 47, 6759-6764).

[0058] The above-described embodiments only express the preferred implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of protection of the present invention. The various technical features of the embodiments can be arbitrarily combined. For the sake of brevity, all possible combinations of the various technical features in the above-described embodiments are not described, but as long as there are no contradictions in the combinations involved, they should be considered to be within the scope of the present 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 belong to the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the attached claims.

Claims

1. A fluorine-rich two-dimensional covalent organic framework material with ultra-micropores, characterized in that: It is formed by six connecting nodes of hexagonal symmetry and three connecting nodes of fluorinated trigonal symmetry connected by covalent bonds on a two-dimensional level and stacked in three dimensions; In at least a portion of the two-dimensional covalent organic framework material, each hexagonal symmetric six-connected node is respectively connected to six adjacent fluorinated trigonal symmetric three-connected nodes, and each fluorinated trigonal symmetric three-connected node is respectively connected to three adjacent hexagonal symmetric six-connected nodes, forming a two-dimensional topological network structure; in, The six connection nodes of hexagonal symmetry and the three connection nodes of fluorinated trigonal symmetry are shown in formula (1) and formula (2) respectively: In formula (1) and formula (2), R is one or more of H, OH, SH, and halogen; "---" indicates a connection.

2. The ultra-microporous fluorine-rich two-dimensional covalent organic framework material according to claim 1, characterized in that: The BET specific surface area of ​​the material is 100 to 2000 m 2 / g, pore size is 0.4~1.0nm.

3. The ultra-microporous fluorine-rich two-dimensional covalent organic framework material according to claim 1, characterized in that: In at least a portion of the material, the molar ratio of hexagonal symmetric six-connected nodes to fluorinated trigonal symmetric three-connected nodes is (0.5 to 1.5): (0.75 to 2.25).

4. The ultra-microporous fluorine-rich two-dimensional covalent organic framework material according to claim 1, characterized in that: The connecting group of the material contains a dynamic covalent bond, and the connecting mode is selected from one of -C=N-, -C=NN=C-, -C=N-NH-, -C=C-, and -C=C(CN)-.

5. The ultra-microporous fluorine-rich two-dimensional covalent organic framework material according to claim 1, characterized in that: The material includes a skeleton unit shown in formula (3): In formula (3), R is one or more of H, OH, SH, and halogen; "---" indicates the connection bit.

6. The method for preparing the ultra-microporous fluorine-rich two-dimensional covalent organic framework material according to claim 1, characterized in that: The preparation method comprises: The hexagonal symmetric six-connected node molecules, the fluorinated trigonal symmetric three-connected node molecules, the reaction solvent and the catalyst are mixed, and after freeze-thaw cycle degassing, the mixture is sealed and heated to 80-180° C. for reaction for 72-168 hours, and the reaction mixture is post-treated to obtain the ultra-microporous fluorine-rich two-dimensional covalent organic framework material; The reaction solvent is selected from one of the following mixed solvents: o-dichlorobenzene / n-butanol, anisole / n-butanol, N,N-dimethylacetamide / n-butanol; The catalyst is acetic acid or trifluoroacetic acid; The hexagonal symmetric six-connected node molecule and the fluorinated trigonal symmetric three-connected node molecule are shown in formula (4) and formula (5) respectively: In formula (4) and formula (5), One of R1 and R2 is an aldehyde group, and the other is an amino group; R3 and R4 are each independently H, OH, SH, or halogen.

7. The preparation method according to claim 6, characterized in that: The molar ratio of the hexagonal symmetric six-connected node molecule to the fluorinated trigonal symmetric three-connected node molecule is (0.5-1.5): (0.75-2.25).

8. The preparation method according to claim 6, characterized in that: The post-treatment method is as follows: after the reaction is completed, cool to room temperature, collect the solid product by centrifugation, soak it in N,N-dimethylacetamide for 6 hours, repeat twice, then soak it in acetone for 6 hours, repeat twice, then use tetrahydrofuran and acetone to Soxhlet extraction for 24 to 48 hours respectively, then place it in a vacuum drying oven, evacuate to 20mTorr at 100°C and dry it for 24 hours to obtain the target product.

9. Use of the ultra-microporous fluorine-rich two-dimensional covalent organic framework material as claimed in claim 1 in the separation and purification of industrial gases.

10. The use according to claim 9, characterized in that The ultra-microporous fluorine-rich two-dimensional covalent organic framework material is used for the adsorption and separation of acetylene / carbon dioxide.

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