Covalent organic framework material as well as preparation method and application thereof

Abstract

The invention discloses a covalent organic framework material as well as a preparation method and application thereof, and belongs to the technical field of polymer preparation. The covalent organic framework material provided by the invention is applied to adsorption of furfural and / or acetic acid in hydrolysate, and has a relatively good adsorption effect. Specifically, the covalent organic framework material provided by the invention can adsorb furfural, acetic acid and other compounds, which are not beneficial to subsequent fermentation of carbohydrates in hydrolysate to produce ethanol, in the hydrolysate; compared with an existing traditional covalent organic framework material, the covalent organic framework material has the advantages of being high in adsorption capacity, good in adsorption selectivity, fast in adsorption equilibrium, high in crystallinity, high in specific surface area and the like. The adsorption process is simple and mild, only at room temperature, the operation is simple, the safety is high, the efficiency is high, and good economic benefits are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer preparation, and in particular relates to a covalent organic framework material and a preparation method and application thereof. Background Art

[0002] In the context of achieving "dual carbon", finding efficient and renewable alternative energy sources is crucial to overcoming global energy challenges. Biomass and biomass-derived materials are the only sustainable sources of organic carbon on Earth, and ethanol is the world's most important biofuel, mainly produced by biomass fermentation, and is considered one of the most promising alternatives to fossil fuels and fine chemicals.

[0003] Lignocellulosic biomass is a complex organic polysaccharide, mainly composed of cellulose (35-50%), hemicellulose (20-35%) and lignin (10-25%). Lignocellulosic residues from agriculture, forestry or urban environments are ideal raw materials for converting cellulose and hemicellulose into fermentable sugars and finally fermenting to produce ethanol. Among them, pretreatment of lignocellulosic raw materials by high-temperature hydrolysis is one of the methods to produce hydrolyzate, improve downstream enzymatic hydrolysis efficiency, and promote ethanol production from lignocellulose. However, high-temperature hydrolysis will decompose and produce toxic substances such as furfural and acetic acid, which are not conducive to subsequent fermentation and ethanol production. Moreover, these substances have low concentrations, are easily soluble in water, are difficult to separate, and have high separation costs. Therefore, the development of a new adsorbent with efficient adsorption and separation capabilities for acetic acid and furfural has important practical significance for the detoxification of biomass hydrolyzate. In view of the shortcomings of traditional adsorbents, such as low adsorption capacity, poor adsorption selectivity and slow adsorption equilibrium (most of them require more than 4 hours to reach adsorption equilibrium), it is necessary to design a new adsorbent with the characteristics of large specific surface area, high porosity, and easy functionalization. Based on the above considerations, covalent organic framework materials (COFs), a porous material, are used as adsorbents to adsorb fermentation inhibitors (furfural, acetic acid) in biomass hydrolysate. However, the covalent organic framework materials prepared by the prior art have limited adsorption performance for furfural and / or acetic acid. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the defects and shortcomings of the prior art and provide a covalent organic framework material.

[0005] Another object of the present invention is to provide a method for preparing the covalent organic framework material.

[0006] Another object of the present invention is to provide applications of the covalent organic framework material.

[0007] Another object of the present invention is to provide a method for removing furfural and / or acetic acid.

[0008] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0009] The present invention provides a covalent organic framework material, the structure of which is shown below:

[0010]

[0011] The present invention provides a covalent organic framework material with a new structure, and the covalent organic framework material has high chemical activity -NH 2 groups, which is beneficial to subsequent adsorption and catalysis.

[0012] Furthermore, the present invention also provides a method for preparing the covalent organic framework material, comprising the following steps: dissolving 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene and trimesic acid in n-butanol, adding an acetic acid aqueous solution, and carrying out a condensation reaction at 25 to 120° C. to obtain the covalent organic framework material.

[0013] The present invention adopts green and cheap n-butanol as a reaction solvent and acetic acid aqueous solution as a catalyst to prepare an imine covalent organic framework material with high crystallinity, high specific area and high yield under mild conditions. Compared with the prior art, the n-butanol used in the method of the present invention is a reaction solvent, and the synthesis conditions are mild and the operation is simple. It is not necessary to add other toxic and harmful organic solvents, and it is not necessary to perform complex operations such as freeze-pump-thaw cycles and high-temperature flame sealing to synthesize a covalent organic framework material with high crystallinity. In addition, n-butanol can be derived from biomass fermentation, which is in line with the concept of sustainable development. Compared with traditional synthesis methods, this method has low pollution, mild reaction conditions, simple operation, good universality, high yield, and is conducive to industrial large-scale production.

[0014] Preferably, the molar ratio of 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene to trimesicaldehyde is (0.5-1): 1. Specifically, the molar ratio of 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene to trimesicaldehyde may be 0.5:1, 0.6:1, 0.67:1, 0.7:1, 0.8:1, 0.9:1, 1:1, or an interval range consisting of any two of the above ratios, such as 0.5-0.67:1, 0.6-0.9:1, 0.6-1:1, etc., but the present invention is not limited thereto.

[0015] Preferably, the concentration of acetic acid in the acetic acid aqueous solution is 3 to 12 mol / L. Specifically, the concentration of acetic acid in the acetic acid aqueous solution may be 3 mol / L, 6 mol / L, or 12 mol / L.

[0016] Preferably, the concentration of 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene in the n-butanol is 0.01 to 0.03 mol / L.

[0017] Preferably, the concentration of trimesaldehyde in the n-butanol is 0.01-0.04 mol / L.

[0018] Preferably, the condensation reaction time is 1 to 24 hours. Specifically, the condensation reaction time is 1 hour, 12 hours, or 24 hours.

[0019] Preferably, the temperature of the condensation reaction is 25-70° C. Specifically, the temperature of the condensation reaction is 25° C., 30° C., 40° C., 50° C., 60° C., or 70° C.

[0020] Preferably, after the condensation reaction, purification treatment and post-treatment are also included.

[0021] Furthermore, the purification treatment method is: taking the reaction liquid after the condensation reaction for solid-liquid separation, taking the solid matter, and performing Soxhlet extraction with tetrahydrofuran and ethanol in sequence.

[0022] Preferably, the Soxhlet extraction time is 12 to 24 hours.

[0023] Furthermore, the post-treatment method is: soaking the product after Soxhlet extraction in n-hexane and drying it to obtain the covalent organic framework material. The post-treatment is to prevent the covalent organic framework from structural collapse during the drying process.

[0024] Furthermore, the present invention also protects the use of the above-mentioned covalent organic framework material in the adsorption of furfural and / or acetic acid, or in the separation of furfural and levulinic acid.

[0025] A method for removing furfural and / or acetic acid comprises dispersing the covalent organic framework material of the invention in a solution containing furfural and / or acetic acid; or dispersing the covalent organic framework material in a solution containing furfural and levulinic acid.

[0026] Preferably, the volume mass ratio of the solution containing furfural and / or acetic acid to the covalent organic framework is (5-10) mL: (0.01-0.1) g.

[0027] Preferably, the solution containing furfural and / or acetic acid is obtained by subjecting the lignocellulosic raw material to high-temperature hydrothermal reaction and enzymatic hydrolysis.

[0028] Furthermore, the lignocellulosic raw material includes but is not limited to one or more of bagasse, wood, bamboo or straw.

[0029] Preferably, the covalent organic framework material needs to be shaken for 0.5 to 4 hours after being dispersed in the solution containing furfural and / or acetic acid.

[0030] Compared with the prior art, the present invention has at least the following beneficial effects:

[0031] The present invention provides a covalent organic framework material, and applies it to adsorb furfural and / or acetic acid in a hydrolyzate, and has a good adsorption effect. Specifically, the covalent organic framework material provided by the present invention can adsorb furfural and acetic acid in the hydrolyzate, and other compounds that are not conducive to the subsequent fermentation of sugar substances in the hydrolyzate to produce ethanol. At the same time, the covalent organic framework material of the present invention has the advantages of high adsorption capacity, good adsorption selectivity, fast adsorption equilibrium, high crystallinity, high specific surface area, and high synthesis yield compared to the existing traditional covalent organic framework materials. The adsorption process of the present invention is simple and mild, only needs to be at room temperature, is simple to operate, has high safety and high efficiency, and has good economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the PXRD spectrum of the covalent organic framework material obtained in Example 1 of the present invention.

[0033] Figure 2 This is a nitrogen adsorption-desorption curve spectrum of the covalent organic framework material obtained in Example 1 of the present invention.

[0034] Figure 3 This is the solid NMR spectrum of the covalent organic framework material obtained in Example 1 of the present invention.

[0035] Figure 4 This is a scanning electron microscope image of Example 1 of the present invention.

[0036] Figure 5 This is the PXRD spectrum of the covalent organic framework material obtained in Comparative Example 1 of the present invention.

[0037] Figure 6 This is the PXRD spectrum of the covalent organic framework material obtained in Comparative Example 2 of the present invention.

[0038] Figure 7 This is the solid NMR spectrum of the covalent organic framework material obtained in Comparative Example 2 of the present invention.

[0039] Figure 8 This is a nitrogen adsorption-desorption curve spectrum of the covalent organic framework material obtained in Comparative Example 2 of the present invention.

[0040] Fig. 9 It is the scanning electron microscope image of comparative example 2 of the present invention.

[0041] Fig.10 It is a graph of the adsorption capacity of Example 1, Comparative Example 1 and Comparative Example 2 in the hydrolyzate of the present invention;

[0042] Fig.11 It is the adsorption selectivity diagram of Example 1, Comparative Example 1 and Comparative Example 2 in the hydrolyzate of the present invention. DETAILED DESCRIPTION

[0043] The present invention is further described below in conjunction with specific examples and accompanying drawings, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0044] Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0045] Example 1

[0046] The present embodiment provides a method for preparing a covalent organic framework material, comprising the following steps: first, 0.0130 g (0.06 mmol) of trimesaldehyde (CAS No. 3163-76-6) and 0.0227 g (0.04 mmol) of 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene (CAS No. 1610471-69-6) are added to a 10 mL plastic centrifuge tube, and then 2 mL of n-butanol is added as a reaction medium and 0.2 mL of 12M acetic acid aqueous solution is added as a catalyst. After mixing evenly, the mixed solution is kept at a constant temperature of 70° C. for 24 hours. After the reaction is completed, the obtained solid precipitate is Soxhlet extracted with tetrahydrofuran and ethanol respectively. Finally, the extracted solid is immersed in n-hexane and placed in a vacuum drying oven for 12 hours to obtain a covalent organic framework material (yield is 95%).

[0047] The structural formula of the covalent organic framework material is as follows:

[0048]

[0049] Figure 1 is the PXRD pattern of the covalent organic framework material (COF) prepared in Example 1 of the present invention. Figure 1 It can be seen that the characteristic diffraction peaks of the COF characteristic crystal plane are very obvious, indicating that the material has a high degree of crystallinity.

[0050] Figure 2 This is the nitrogen adsorption-desorption curve of the covalent organic framework material prepared in Example 1 of the present invention. It can be seen that the prepared covalent organic framework has a high adsorption capacity for nitrogen, and the specific surface area obtained by fitting is very high, which is 1338 m 2 / g.

[0051] Figure 3 This is the solid NMR image of the covalent organic framework material prepared in Example 1 of the present invention. It can be seen that the carbon peak position of the prepared covalent organic framework product corresponds to the theoretical one, indicating that the product is consistent with the theoretical framework structure.

[0052] Figure 4This is a scanning electron microscope image of the covalent organic framework material prepared in Example 1 of the present invention. It can be seen that the material has a regular overall structure.

[0053] Comparative Example 1

[0054] This comparative example provides a method for preparing a covalent organic framework material, comprising the following steps: first, 0.0100 g (0.06 mmol) of 2,5-dihydroxy-1,4-benzenedicarbaldehyde (DHA) and 0.0141 g (0.04 mmol) of 1,3,5-tris(4-aminophenyl)benzene (TAPB) are added to a 10 mL plastic centrifuge tube, and then 2 mL of n-butanol is added as a reaction medium and 0.2 mL of 6M acetic acid aqueous solution is added as a catalyst. After mixing evenly, the mixed solution is kept at a constant temperature of 70°C for 24 hours. After the reaction is completed, the obtained solid precipitate is Soxhlet extracted with tetrahydrofuran and ethanol, respectively. Finally, the extracted solid is immersed in n-hexane and placed in a vacuum drying oven for 12 hours to obtain a covalent organic framework material.

[0055] The structure of the covalent organic framework material is shown below:

[0056]

[0057] Among them, R 1 is a benzene ring, R 2 is H or OH.

[0058] Figure 5 This is the PXRD pattern of the covalent organic framework material prepared in Comparative Example 1 of the present invention. Figure 5 It can be seen that the obtained product has obvious diffraction peaks at 2.7°, 4.7°, 5.5° and 7.4°, corresponding to the (100), (110), (200) and (210) crystal planes, respectively, indicating that the material has a high degree of crystallinity.

[0059] Comparative Example 2

[0060] This comparative example provides a method for preparing a covalent organic framework material. The difference from the preparation steps of Example 1 is that 0.0130 g (0.06 mmol) of trimesicaldehyde is replaced by 0.0102 g (0.06 mmol) of 2,5-difluoro-1,4-benzenedicarbaldehyde, and 0.0227 g (0.04 mmol) of 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene is replaced by 0.0141 g (0.04 mmol) of 1,3,5-tris(4-aminophenyl)benzene (TAPB), and the remaining experimental methods and steps are consistent with Example 1.

[0061] The structure of the covalent organic framework material is shown below:

[0062]

[0063] Where R 1 is a benzene ring, R 2 It is H or F.

[0064] Figure 6 is the PXRD pattern of the covalent organic framework material prepared in Comparative Example 2 of the present invention. Figure 6 It can be seen that the characteristic diffraction peaks of the characteristic crystal planes (100), (110), (200) and (210) of COF are very obvious, indicating that the material has a high degree of crystallinity.

[0065] Figure 7 This is the solid NMR image of the covalent organic framework material prepared in comparative example 2 of the present invention. It can be seen that the carbon peak position of the prepared covalent organic framework product corresponds to the theoretical one, indicating that the product is consistent with the theoretical framework structure.

[0066] Figure 8 This is the nitrogen adsorption-desorption curve of the covalent organic framework material prepared in comparative example 2 of the present invention. It can be seen that the prepared covalent organic framework has a high adsorption capacity for nitrogen, and the specific surface area obtained by fitting is very high, which is 1401m 2 / g.

[0067] Fig. 9 This is a scanning electron microscope image of the covalent organic framework material prepared in comparative example 2 of the present invention. It can be seen that the morphology of the prepared covalent organic framework product is "sea urchin flower" shaped, and the overall structure is relatively regular.

[0068] Application Example 1

[0069] Biomass hydrolysate system: To simulate the hydrolysate, specifically: the concentration of 5-hydroxymethylfurfural is 0.53 g / L, the concentration of furfural is 1.61 g / L, the concentration of levulinic acid is 0.069 g / L, the concentration of formic acid is 1.34 g / L, the concentration of acetic acid is 5.66 g / L, and the pH value of the solution is not additionally adjusted.

[0070] The covalent organic framework materials prepared in Example 1, Comparative Example 1 and Comparative Example 2 were applied to the adsorption and separation of furfural in the hydrolyzate, and the specific operation steps were as follows:

[0071] Weigh 0.05 g of the covalent organic framework material and add it to 5 mL of the biomass hydrolyzate system, and place the sample in a shaking incubator at 25°C for 240 min, with the speed set at 120 rpm. After reaching adsorption equilibrium, separate the covalent organic framework material from the solution.

[0072] The adsorption capacity and selectivity were calculated using the following equations:

[0073]

[0074] Where: q i,e is the adsorption capacity of adsorbate i on the covalent organic framework material when the adsorption reaches equilibrium; C i,0 and C i,e represents the concentration of adsorbate i in the hydrolyzate under the initial and equilibrium conditions; V is the volume of the hydrolyzate; m is the mass of the covalent organic framework material; where adsorbate i is formic acid, acetic acid, furfural, 5-hydroxymethylfurfural, levulinic acid; when adsorbate i is furfural, q i,e Represented as q Furfural,e , C i,0 and C i,e Represented as C FA,0 and C FA,e .

[0075] It represents the selectivity factor of furfural to adsorbate i (excluding furfural).

[0076] The adsorption performance of the adsorbent was measured by adsorption capacity and selectivity factor. The experimental results are as follows:

[0077] The components in the hydrolyzate are formic acid (FA), acetic acid (AA), furfural, 5-hydroxymethylfurfural (5-HMF), and levulinic acid (LA) solution. Fig.10 : This is a graph of the adsorption capacity of each component of the embodiments of the present invention (wherein PTTA-BTCA represents the covalent organic framework material prepared in Example 1, TAPB-DHA represents the covalent organic framework material prepared in Comparative Example 1, and TAPB-2F represents the covalent organic framework material prepared in Comparative Example 2). It can be seen from the figure that the covalent organic framework materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 have adsorption capacities of 77, 66, and 73 mg / g for furfural, respectively, and adsorption capacities of 93, 19, and 10 mg / g for acetic acid, respectively, indicating that only the covalent organic framework prepared in the embodiments of the present invention has a high adsorption capacity for both furfural and acetic acid in the hydrolyzate, and can reach adsorption equilibrium within 4 hours.

[0078] Fig.11 The figure is an adsorption selectivity diagram of each component of the embodiments of the present invention. It can be seen from the figure that in the process of adsorbing furfural by the covalent organic framework materials prepared in Example 1, Comparative Example 1 and Comparative Example 2, the furfural / levulinic acid selectivity factor of Example 1 is the highest, which is 384.27, which is significantly different from Comparative Examples 1 and 2, indicating that the material has obvious selective adsorption in the adsorption process, can more effectively separate or enrich the target substance from a complex mixture, while the adsorption effect on non-target substances is weak.

[0079] The present invention uses the green solvent n-butanol as a solvent and acetic acid as a catalyst to achieve green synthesis of high-crystallinity imine COFs under mild conditions. The specific covalent organic framework prepared in the embodiment of the present invention has a good adsorption effect on furfural, acetic acid and other substances in the hydrolyzate that are not conducive to the subsequent fermentation and utilization of the hydrolyzate, and the adsorption capacity is significantly better than that of the comparative example.

[0080] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited to the above specific embodiment. Obviously, those skilled in the art can easily make various changes or modifications within the scope of the claims of the present invention, which does not affect the essential content of the present invention.

Claims

1. A covalent organic framework material, characterized in that: The structure is as follows:

2. The method for preparing the covalent organic framework material according to claim 1, comprising the following steps: 1,3,6,8-Tetrakis-(p-aminophenyl)-pyrene and trimesic acid aldehyde are dissolved in n-butanol, and an acetic acid aqueous solution is added to carry out a condensation reaction at 25-120° C. to obtain a covalent organic framework material.

3. The preparation method according to claim 2, characterized in that: The molar ratio of the 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene to trimesic acid is (0.5-1):

1.

4. The preparation method according to claim 2, characterized in that: The concentration of acetic acid in the acetic acid aqueous solution is 3-12 mol / L.

5. The preparation method according to claim 2, characterized in that: The volume ratio of n-butanol to the acetic acid aqueous solution is 1:0.05-0.

15.

6. The preparation method according to claim 2, characterized in that: The concentration of 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene in the n-butanol is 0.01-0.03 mol / L.

7. The preparation method according to claim 2, characterized in that: The condensation reaction time is 1 to 24 hours.

8. The preparation method according to claim 2, characterized in that: After the condensation reaction, purification treatment and post-treatment are also included.

9. Use of the covalent organic framework material according to claim 1 in the adsorption of furfural and / or acetic acid, or in the separation of furfural and levulinic acid.

10. A method for removing furfural and / or acetic acid, characterized in that: Dispersing the covalent organic framework material according to claim 1 in a solution containing furfural and / or acetic acid; or The covalent organic framework material according to claim 1 is dispersed in a solution containing furfural and levulinic acid.

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