A hydrophobic covalent organic framework material based on 4,4'-diaminooctafluorobiphenyl and a preparation method and application thereof

Abstract

This invention relates to a hydrophobic covalent organic framework material based on 4,4'-diaminooctafluorobiphenyl, its preparation method, and its applications, belonging to the technical field of porous materials and organic framework materials. The invention involves the condensation reaction of 4,4'-diaminooctafluorobiphenyl with an aldehyde monomer in a one-pot system under organic acid catalysis to generate a fluorinated COF, denoted as F-COF. The product is then filtered, washed, and activated to obtain the hydrophobic covalent organic framework material F-COF. The hydrophobic covalent organic framework material F-COF prepared by this invention has a periodic pore structure with fluorinated groups enriched on the pore walls or surface. It exhibits excellent hydrophobicity, high specific surface area, and good thermal stability, and can be synthesized in a large-scale one-step process. This solves the problems of cumbersome preparation steps, high cost, difficulty in scale-up, and unstable performance in existing fluorinated COF preparation technologies, and can be further used for the protection of the negative electrode in aqueous zinc-ion batteries.

Description

Technical Field

[0001] This invention belongs to the technical field of porous materials and organic framework materials, specifically relating to a hydrophobic covalent organic framework material based on 4,4'-diaminooctafluorobiphenyl, its preparation method, and its application. Background Technology

[0002] Covalent organic frameworks (COFs) are a class of crystalline porous materials formed by organic units linked by covalent bonds. They possess advantages such as designable framework structures, tunable pores, high specific surface area, and great functionalization potential, showing promising applications in separation, adsorption, catalysis, corrosion protection, and sensing. For applications requiring low surface energy, resistance to water corrosion, and interfacial stability, the development of highly hydrophobic COF materials is of great significance.

[0003] In existing technologies, improving the hydrophobicity of COFs typically relies on the construction of fluorinated monomers or subsequent fluorination modifications. While these methods can improve the hydrophobic properties of materials to some extent, they still have significant drawbacks: First, the raw material routes are complex, the cost of fluorinated monomers is high, and some require multiple synthesis and purification steps; second, the preparation steps are numerous, often involving multiple condensations, post-fluorination modifications, or harsh reaction conditions, leading to complex processes and increased costs; third, problems such as decreased crystallinity, pore structure collapse, and large batch-to-batch variations are prone to occur during scale-up preparation, hindering large-scale applications.

[0004] Therefore, there is an urgent need to develop a method that uses readily available raw materials, simplifies the steps, ensures stable processing, is suitable for scale-up, and can prepare highly hydrophobic fluorinated COF materials. Summary of the Invention

[0005] The purpose of this invention is to provide a hydrophobic covalent organic framework material based on 4,4'-diaminooctafluorobiphenyl, its preparation method, and its application. The hydrophobic covalent organic framework material of this invention can be synthesized in a large-scale one-step process, thereby solving the problems of cumbersome preparation steps, high cost, difficulty in scale-up, and unstable performance in the prior art of fluorinated COF preparation.

[0006] To achieve the above objectives, this invention involves the condensation reaction of 4,4'-diaminooctafluorobiphenyl with an aldehyde monomer in a one-pot system under organic acid catalysis to generate a fluorinated COF with a periodic pore structure, denoted as F-COF; subsequently, the product is filtered, washed, and activated to obtain the hydrophobic covalent organic framework material F-COF, the steps of which are as follows:

[0007] 1) Add 4,4'-diaminooctafluorobiphenyl and aldehyde monomers to the reactor, then add solvent, and sonicate at room temperature to dissolve all the solids; then add acid catalyst to form a homogeneous or quasi-homogeneous reaction system.

[0008] 2) The reaction system of step 1) is reacted at 30~120℃ for 72~168h to allow 4,4'-diaminooctafluorobiphenyl to undergo a condensation reaction with aldehyde monomers to generate fluorinated covalent organic framework materials.

[0009] 3) The fluorinated covalent organic framework material obtained in step 2) is filtered to collect the solid, and the solid is washed sequentially with solvent. Then, the washed solid is activated to obtain the hydrophobic covalent organic framework material F-COF, whose structural formula and reaction formula are as follows:

[0010]

[0011] Aldehyde monomers include, but are not limited to, one or more of the following molecular structures;

[0012]

[0013]

[0014] The acid catalyst is one or more of formic acid, acetic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, and p-benzenesulfonic acid;

[0015] The solvent is one or more of alcohol solvents, ether solvents, nitrile solvents, ketone solvents, amide solvents, aromatic solvents, halogenated hydrocarbon solvents, and water, preferably a binary or ternary mixture of alcohol / aromatic solvents and aromatic / ether solvents;

[0016] The molar ratio of 4,4'-diaminooctafluorobiphenyl to aldehyde monomer is 1:3~5; the molar amount of acid catalyst is 1~150 times the total molar amount of 4,4'-diaminooctafluorobiphenyl and aldehyde monomer; the concentration of 4,4'-diaminooctafluorobiphenyl in the solvent is 0.04~0.1 mol / L.

[0017] The activation treatment is one or more of vacuum drying, supercritical CO2 activation, or freeze-drying activation.

[0018] The prepared hydrophobic covalent organic framework material F-COF has a periodic pore structure with fluorine-containing groups enriched on the pore walls or surface; it exhibits excellent hydrophobicity, high specific surface area, and good thermal stability. The water contact angle of the prepared hydrophobic covalent organic framework material F-COF is 110~150°, preferably 115~140°; among them, the product obtained from 4,4'-diaminooctafluorobiphenyl and 2,4-dihydroxy-1,3,5-pyromellitic methylaldehyde has a water contact angle of 110.3°; the product obtained from 4,4'-diaminooctafluorobiphenyl and trialdehyde-resorcinol has a water contact angle of 147.8°. Figure 1The prepared hydrophobic covalent organic framework material F-COF has a specific surface area of ​​300~550 m² / g; 4,4'-diaminooctafluorobiphenyl and trialdehyde phloroglucinol yield a product with a specific surface area of ​​375 m² / g. Figure 2 The product obtained by reacting 4,4'-diaminooctafluorobiphenyl with 2,4-dihydroxy-1,3,5-pyromellitic methylaldehyde has a specific surface area of ​​510.95 m² / g. Figure 3 Thermogravimetric analysis showed that no decomposition was observed before 180℃, but the structure began to collapse after 400℃, indicating that the prepared hydrophobic covalent organic framework material F-COF has good thermal stability. Figure 4 ).

[0019] The hydrophobic covalent organic framework material F-COF prepared in this invention can be used for negative electrode protection in aqueous zinc-ion batteries. F-COF is mixed with polyvinylidene fluoride (mass ratio 1-10:1) and then coated onto the surface of zinc foil using a coater (the thickness of the F-COF protective layer on the zinc foil surface can be adjusted to 1-10 µm using the coater), resulting in a modified zinc foil denoted as F-COF@Zn. Using a 2 mol / L zinc sulfate solution as the electrolyte, F-COF@Zn is assembled into an F-COF@Zn || F-COF@Zn symmetric battery, operating at 1 mAh / cm². 2 1mA / cm 2 Under these conditions, it can be cycled for over 2500 hours, far exceeding the 110 hours of ordinary zinc sheets. Figure 5 The mass ratio of hydrophobic covalent organic framework material F-COF-1 to polyvinylidene fluoride is 10:1, and the thickness of the F-COF-1 protective layer on the zinc foil surface is 5 µm.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) One-step one-pot process: From feeding to obtaining hydrophobic covalent organic framework material F-COF, no multiple post-modification steps are required, and the process is short;

[0022] (2) Scalable: It covers a wide range of monomer types and can use readily available monomers; the solvent system and reactor type are adapted for industrial scale-up;

[0023] (3) Strong hydrophobicity: Fluorine-containing groups are enriched on the pore walls / surface, which significantly reduces the surface energy and improves the water repellency. Attached Figure Description

[0024] Figure 1 Photographs of water droplet contact angles on the F-COF-1 surface prepared in Example 1;

[0025] Figure 2 Nitrogen adsorption-desorption isotherm of F-COF-1 prepared in Example 1;

[0026] Figure 3 Nitrogen adsorption-desorption isotherm of F-COF-2 prepared in Example 2;

[0027] Figure 4 Thermogravimetric curve of F-COF-1 prepared in Example 1;

[0028] Figure 5 Cyclic performance diagram of the F-COF-1 symmetric battery prepared in Example 1;

[0029] Figure 6 : Powder X-ray diffraction pattern of F-COF-1 prepared in Example 1;

[0030] Figure 7 Infrared spectrum of F-COF-1 prepared in Example 1. Detailed Implementation

[0031] Example 1

[0032] 1) Add 98.5 mg of 4,4'-diaminooctafluorobiphenyl and 42 mg of trialdehyde phloroglucinol to a reaction flask, then add 1.5 mL of tetrahydrofuran, and sonicate at room temperature for 20 minutes to dissolve the solid completely; then add 5.1 mL of trifluoroacetic acid to form a homogeneous or quasi-homogeneous reaction system.

[0033] 2) The reaction system of step 1) was reacted at 50°C for 120 h to allow 4,4'-diaminooctafluorobiphenyl to undergo a condensation reaction with trialdehyde pyrogallol to generate fluorinated covalent organic framework material.

[0034] 3) The fluorinated covalent organic framework material obtained in step 2) was filtered and the solid was collected. The solid was then washed sequentially with DMF, THF, and acetone solvents. The washed solid was then activated by heating at 80°C under vacuum for 12 hours to obtain hydrophobic covalent organic framework material F-COF-1 powder with a yield of 87%. Powder X-ray diffraction was performed, and the weighted residual factor was 2.48% and the residual factor was 1.96%, indicating that the measured curves were in high agreement with the simulated structure, proving that it has good crystallinity. Figure 6 In infrared spectroscopy testing, C=O (-1640cm) -1 ) and NH (-3200-3500cm) -1 ) disappears, C=C (-1580cm) -1 ) and CN (-1255cm -1 The generation of these monomers proves that both monomers have been fully reflected. Figure 7 ).

[0035] Example 2

[0036] 1) Add 98.5 mg of 4,4'-diaminooctafluorobiphenyl and 39 mg of 2,4-dihydroxy-1,3,5-pyromellitic methylaldehyde to a reaction flask, then add 1.5 mL of tetrahydrofuran, and sonicate for 20 minutes to dissolve the solid completely; then add 3.5 mL of trifluoroacetic acid to form a homogeneous or quasi-homogeneous reaction system.

[0037] 2) The reaction system of step 1) was reacted at 80℃ for 120h to allow 4,4'-diaminooctafluorobiphenyl and 2,4-dihydroxy-1,3,5-pyromellitic methylaldehyde to undergo a condensation reaction to generate a fluorinated covalent organic framework material.

[0038] 3) The fluorinated covalent organic framework material obtained in step 2) was filtered to collect the solid. The solid was then washed sequentially with DMF, THF and acetone solvents. The washed solid was then activated under vacuum at 80°C for 12 hours to obtain hydrophobic covalent organic framework material F-COF-2 powder with a yield of 81%.

Claims

1. A hydrophobic covalent organic framework material based on 4,4'-diaminooctafluorobiphenyl, the structural formula of which is as follows: 。 2. The method for preparing a hydrophobic covalent organic framework material based on 4,4'-diaminooctafluorobiphenyl as described in claim 1, comprising the following steps: 1) Add 4,4'-diaminooctafluorobiphenyl and aldehyde monomers to the reactor, then add solvent, and sonicate at room temperature to dissolve all the solids; then add acid catalyst to form a homogeneous or quasi-homogeneous reaction system. 2) The reaction system of step 1) is reacted at 30~120℃ for 72~168h to allow 4,4'-diaminooctafluorobiphenyl to undergo a condensation reaction with aldehyde monomers to generate fluorinated covalent organic framework materials. 3) The solid obtained in step 2) is filtered and collected, and the solid is washed with solvent in sequence. Then the washed solid is activated to obtain the hydrophobic covalent organic framework material F-COF.

3. The method for preparing a hydrophobic covalent organic framework material based on 4,4'-diaminooctafluorobiphenyl as described in claim 2, characterized in that: The acid catalyst is one or more of formic acid, acetic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, and p-benzenesulfonic acid.

4. The method for preparing a hydrophobic covalent organic framework material based on 4,4'-diaminooctafluorobiphenyl as described in claim 2, characterized in that: The solvent is one or more of the following: alcohol solvents, ether solvents, nitrile solvents, ketone solvents, amide solvents, aromatic solvents, halogenated hydrocarbon solvents, and water.

5. The method for preparing a hydrophobic covalent organic framework material based on 4,4'-diaminooctafluorobiphenyl as described in claim 4, characterized in that: The solvent is a binary or ternary mixture of alcohol / aromatic solvents or aromatic / ether solvents.

6. The method for preparing a hydrophobic covalent organic framework material based on 4,4'-diaminooctafluorobiphenyl as described in claim 2, characterized in that: The molar ratio of 4,4'-diaminooctafluorobiphenyl to aldehyde monomer is 1:3~5; the molar amount of acid catalyst is 1~150 times the total molar amount of 4,4'-diaminooctafluorobiphenyl and aldehyde monomer; the concentration of 4,4'-diaminooctafluorobiphenyl in the solvent is 0.04~0.1 mol / L.

7. The method for preparing a hydrophobic covalent organic framework material based on 4,4'-diaminooctafluorobiphenyl as described in claim 2, characterized in that: The activation treatment is one or more of vacuum drying, supercritical CO2 activation, or freeze-drying activation.

8. The method for preparing a hydrophobic covalent organic framework material based on 4,4'-diaminooctafluorobiphenyl as described in claim 2, characterized in that: Aldehyde monomers are one or more of the following molecular structures; 。 9. The application of the hydrophobic covalent organic framework material based on 4,4'-diaminooctafluorobiphenyl as described in claim 1 in the negative electrode protection of aqueous zinc-ion batteries.

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