Preparation method of sulfonic acid type covalent organic framework material and preparation method of 5-hydroxymethylfurfural

Abstract

The invention discloses a preparation method of a sulfonic acid type covalent organic framework material and a preparation method of 5-hydroxymethylfurfural. The material is prepared by carrying out covalent condensation reaction on a monomer containing a sulfonic acid group precursor and a connecting ligand of a skeleton through a hot solvent method, and the catalyst has the characteristics of high crystallinity, large specific surface area, ordered pore structure, high sulfonic acid group density and uniform distribution. The preparation method is simple, convenient, efficient, mild in condition and high in yield. Compared with a traditional lewis acid catalyst for preparing 5-hydroxymethylfurfural through fructose dehydration, the material has the advantages of being uniform and adjustable in porosity, higher in active site, capable of promoting fructose hydrolysis and the like, efficient conversion can be achieved, side reactions and product transition polymerization are inhibited, and better industrialization prospects are shown.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of chemical industry, and particularly relates to a preparation method and catalytic application of a novel sulfonic acid type covalent organic framework material. BACKGROUND

[0002] Covalent organic frameworks (COFs) are a new class of crystalline porous materials with periodic network structures and regular channels, which are formed by organic building blocks through strong covalent bonds. Due to their high specific surface area, tunable pore structure and easy functionalization, COFs have shown great potential in gas storage, separation, catalysis, optoelectronics and other fields.

[0003] Solid acid catalysts, especially those containing sulfonic acid groups (-SO3H), are gradually replacing traditional liquid inorganic acids (such as sulfuric acid and hydrochloric acid) in chemical production due to their easy separation, reusability, environmental friendliness and other advantages. Currently, common solid sulfonic acid materials include Nafion, sulfonated resins (such as Amberlyst-15) and sulfonated carbon materials. However, these materials have some inherent defects, such as high price of Nafion, poor thermal stability of sulfonated resins, disordered pore structure and uneven distribution of sulfonic acid sites of sulfonated carbon materials, which limit their wide application. Introducing sulfonic acid groups into the framework of COFs can combine the regular and ordered channels of COF materials with the strong acidity of sulfonic acid groups, creating an ideal solid acid catalyst. However, direct use of monomers containing sulfonic acid groups for COF synthesis faces challenges, as the strong polarity of sulfonic acid groups can severely interfere with the formation and reversible equilibrium of dynamic covalent bonds such as imine bonds and boronic ester bonds, leading to decreased crystallinity of the material or even formation of amorphous polymers.

[0004] With the increasing demand for renewable energy, the development of green synthetic bio-based chemicals is constantly promoted. 5-HMF, as a key bio-based platform compound, has shown a growing market demand. However, the current industrial production of 5-HMF is mainly achieved by removing 3 molecules of water from fructose, and the catalyst is a key factor affecting the efficiency of fructose dehydration reaction and the selectivity of 5-HMF. However, the current catalysts are generally inefficient, resulting in high production cost of HMF. In order to overcome the shortcomings of homogeneous catalysts, solid acid catalysts have attracted more and more attention. Solid acid catalysts have the advantages of easy separation, recyclability, low corrosion, etc., making them have wide application prospects in industry. Common solid acid catalysts include molecular sieves, metal oxides, heteropoly acids and functional resins, etc. COF catalysts have shown great potential and significant advantages in the field of biomass catalytic conversion, especially in the reaction of preparing 5-HMF from fructose dehydration, due to their unique ordered pore structure, high specific surface area, precisely controllable active sites and good stability. With the in-depth research, through optimizing the synthesis method, reducing the cost and further improving the stability and applicability, COF catalysts are expected to play a more important role in green chemistry and sustainable chemical process.

[0005] Therefore, developing a new method for synthesizing a sulfonic acid type COF with high crystallinity, high loading of sulfonic acid groups and uniform distribution, and expanding its application field, has become a technical problem to be solved in the field. SUMMARY

[0006] Therefore, the present application provides a method for preparing a novel sulfonic acid type covalent organic framework material and its catalytic application, aiming to overcome the problems of low 5-HMF yield and poor stability faced by existing fructose dehydration catalysts. The ordered pore of the COF catalyst not only provides size selectivity, but also enables the specific sulfonic acid group functional groups on the pore wall to interact with the intermediates of the reactants, enabling the performance of the catalyst to be designed on demand, promoting the reaction-separation integration, and the ordered pore can selectively accommodate reactants, transition states and products, thereby inhibiting side reactions and facilitating the construction of a multifunctional catalytic system to reduce the reaction energy barrier.

[0007] The technical scheme of the present application is as follows in order to achieve the above-mentioned purposes:

[0008] The present application first provides a sulfonic acid group functionalized covalent organic framework material, which is prepared by condensation reaction of a monomer (A) containing a sulfonic acid group (or its precursor, such as sulfonate, which can be hydrolyzed into sulfonic acid after synthesis) and a monomer (B) containing a complementary functional group (aldehyde group or amino group) by solvothermal method; the sulfonic acid group is uniformly loaded in the material skeleton and the inner surface of the pore in the form of chemical bond. By carefully selecting the monomers and reaction conditions, the present application successfully integrates the strong polar sulfonic acid group into the highly ordered COF skeleton without sacrificing its crystallinity.

[0009] The aromatic monomer A containing sulfonic acid group or its precursor is selected from one or more of the following: sulfonated derivatives of benzene sulfonic acid derivatives containing amino or aldehyde group, sulfonated derivatives of biphenyl or polynuclear aromatic containing amino or aldehyde group, sulfonated derivatives of vinyl benzene containing amino or aldehyde group.

[0010] The aromatic monomer B containing complementary reactive functional group is selected from one or more of the following: polycarboxylic acid compound, polyaldehyde compound, nitrogen-containing heterocyclic compound, phosphorus-containing acyl group aromatic acid compound, which can form imine bond, borate ester bond, amide bond or enamine bond with the functional group of monomer A.

[0011] The technical solution of the present application is as follows: (1) Under the protection of inert gas, monomer A and monomer B are dissolved in a mixed solvent according to a certain molar ratio to form a homogeneous solution; (2) Acidic adjuvant is added to the solution, and the air in the tube is extracted after being frozen with liquid nitrogen for 5-30 min, and then nitrogen is introduced for thawing, which is repeated three times; the glass sealing reaction container is melted using a spray gun, and the reaction is carried out at 80-150℃ for 3-7 days; (3) After the reaction is completed, it is cooled to room temperature, and the solid product is collected and washed with organic solvent and water in sequence; (4) The washed product is purified by a Soxhlet extractor, and finally dried under vacuum to obtain the sulfonic acid group functionalized covalent organic framework material catalyst.

[0012] The mixed solvent in step (1) is a mixed system of mesitylene, 1,4-dioxane and acetic acid, wherein the volume fraction of acetic acid is 5% to 20%.

[0013] According to the present application, the aromatic monomer A containing sulfonic acid group or its precursor is one or more of 2,5-diaminobenzenesulfonic acid, 3-[[4-(phenylamino)phenyl]azo]benzenesulfonic acid, 1,4-benzenediamine-2-sulfonic acid, tetrakis(4-formylphenyl)ethylenebenzenesulfonic acid.

[0014] According to the present application, the aromatic monomer B containing hydrolyzable or condensable functional group is one or more of bicyclo[2.2.2]octane-1,4-dicarboxylic acid, 1,2,4,5-tetrakis(4-carboxyphenyl)benzene, bicyclo[1.1.1]pentane-1,3-dicarboxylic acid, 4,4',4''-phosphorylbenzenetricarboxylic acid, 1,2-di-(4-pyridyl)ethylene, 1,3,5-tris(1-imidazolyl)benzene.

[0015] The acid additive in the step (2) is selected from one or more of dilute hydrochloric acid, acetic acid, dilute nitric acid, p-toluenesulfonic acid, trifluoroacetic acid, oxalic acid, and ethanedioic acid, and the addition amount is 1% to 10% of the total mass of monomer A and monomer B.

[0016] The application of the sulfonic acid type covalent organic framework material as a solid acid catalyst in a reaction of catalyzing dehydration of fructose to prepare 5-hydroxymethylfurfural.

[0017] The temperature of the catalytic reaction is 120 DEG C to 200 DEG C, the reaction time is 0.5 hours to 5 hours, the reaction solvent is selected from one or more of water, an alcohol solvent, dimethyl sulfoxide, dioxane, acetonitrile, acetone, and ethyl acetate, the mass concentration of fructose in the reaction system is 10% to 80%, and the mass ratio of the catalyst to fructose is 0.1% to 10%.

[0018] A method for catalyzing dehydration of fructose to prepare 5-hydroxymethylfurfural, which adopts the sulfonic acid type covalent organic framework material as a catalyst and carries out the reaction under the conditions.

[0019] The beneficial effects of the present application are as follows: By combining the strong Br nsted acid active site (-SO3H) with the highly ordered covalent organic framework pore structure, the dehydration of fructose is precisely catalyzed and regulated at the molecular level. The dense sulfonic acid groups on the inner surface can specifically adsorb and stabilize the fructose molecules and the intermediates after ring opening through hydrogen bonding, electrostatic interaction, etc. The pore environment can stabilize this high-energy intermediate, making its configuration more conducive to the subsequent dehydration step and inhibiting isomerization into other by-products. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The infrared characterization graph of SCOF-1, SCOF-2, SCOF-3 and SCOF-4. DETAILED DESCRIPTION

[0021] The embodiments of the present application will be described in detail below with specific examples, but those skilled in the art will understand that the following examples are only for illustration of the present application and should not be regarded as limiting the scope of the present application.

[0022] The present application does not have special limitations on the addition amount of each substance, and any ratio can be used.

[0023] Example 1: Preparation of SCOF-1 Preparation of a sulfonic acid type COF (named SCOF-1): In a 50 mL Schlenk tube, 2,5-diaminobenzenesulfonic acid (0.2 mmol) and bicyclo[2.2.2]octane-1,4-dicarboxylic acid (0.3 mmol) were dissolved in a mixed solvent composed of 3 mL mesitylene, 3 mL 1,4-dioxane and 0.6 mL glacial acetic acid. The mixture was sonicated for 10 minutes until a clear solution was formed. Under argon protection, 5 mg of p-toluenesulfonic acid was added to the solution as a catalyst. Subsequently, the mixture was transferred to a 25 mL polytetrafluoroethylene-lined stainless steel autoclave, which was sealed and placed in an oven at 120 °C for 72 hours. After the reaction was completed, it was naturally cooled to room temperature, and the red precipitate obtained was collected by centrifugation. Each was washed three times with absolute ethanol, tetrahydrofuran and deionized water, respectively. Finally, the product was Soxhlet extracted in methanol for 24 hours, and vacuum dried at 80 °C for 12 hours to obtain the red powder product SCOF-1 with a yield of 85%.

[0024] Example 2 Preparation of SCOF-2 In a 50 mL Schlenk tube, 3-[[4-(phenylamino)phenyl]azo]benzenesulfonic acid (0.2 mmol) and 1,2,4,5-tetrakis(4-carboxyphenyl)benzene (0.3 mmol) were dissolved in a mixed solvent composed of 3 mL mesitylene, 3 mL 1,4-dioxane and 0.6 mL glacial acetic acid. The mixture was sonicated for 10 minutes until a clear solution was formed. Under argon protection, 5 mg of p-toluenesulfonic acid was added to the solution as a catalyst. Subsequently, the mixture was transferred to a 25 mL polytetrafluoroethylene-lined stainless steel autoclave, which was sealed and placed in an oven at 120 °C for 72 hours. After the reaction was completed, it was naturally cooled to room temperature, and the red precipitate obtained was collected by centrifugation. Each was washed three times with absolute ethanol, tetrahydrofuran and deionized water, respectively. Finally, the product was Soxhlet extracted in methanol for 24 hours, and vacuum dried at 80 °C for 12 hours to obtain the orange-red powder product SCOF-2 with a yield of 82%.

[0025] Example 3 Preparation of SCOF-3 In a 50 mL Schlenk tube, 1,4-benzenediamine-2-sulfonic acid (0.2 mmol) and 1,2-di-(4-pyridyl)ethene (0.3 mmol) were dissolved in a mixed solvent consisting of 3 mL mesitylene, 3 mL 1,4-dioxane and 0.6 mL glacial acetic acid. The mixture was sonicated for 10 minutes until a clear solution was formed. Under argon protection, 5 mg of p-toluenesulfonic acid was added to the solution as a catalyst. Subsequently, the mixture was transferred to a 25 mL polytetrafluoroethylene-lined stainless steel autoclave, which was sealed and placed in an oven at 120 °C for 72 hours. After the reaction was completed, it was naturally cooled to room temperature, and the red precipitate obtained was collected by centrifugation. Each was washed with anhydrous ethanol and deionized water three times. Finally, the product was Soxhlet extracted in methanol for 24 hours, and vacuum dried at 80 °C for 12 hours to obtain the orange powder product SCOF-3 with a yield of 80%.

[0026] Example 4 Preparation of SCOF-4 In a 50 mL Schlenk tube, 2,5-diaminobenzenesulfonic acid (0.2 mmol) and bicyclo[1.1.1]pentane-1,3-dicarboxylic acid (0.3 mmol) were dissolved in a mixed solvent consisting of 3 mL dimethyl sulfoxide and 0.6 mL acetone. The mixture was sonicated for 10 minutes until a clear solution was formed. Under argon protection, 5 mg of p-toluenesulfonic acid was added to the solution as a catalyst. Subsequently, the mixture was transferred to a 25 mL polytetrafluoroethylene-lined stainless steel autoclave, which was sealed and placed in an oven at 120 °C for 72 hours. After the reaction was completed, it was naturally cooled to room temperature, and the red precipitate obtained was collected by centrifugation. Each was washed with anhydrous ethanol, tetrahydrofuran and deionized water three times. Finally, the product was Soxhlet extracted in methanol for 24 hours, and vacuum dried at 80 °C for 12 hours to obtain the red powder product SCOF-4 with a yield of 83%.

[0027] Example 5 Application of catalyst in dehydration reaction: The prepared catalyst was applied to the reaction of fructose dehydration to prepare 5-HMF with water and dimethyl sulfoxide as a solvent system. In a 50 mL hydrothermal kettle, 10 g of fructose, 10 g of H2O, 20 g of dimethyl sulfoxide and 50 mg of SCOF catalyst were added, and hydrothermal reaction was carried out at 150°C for 1 hour. After the reaction was completed, the catalyst was separated by centrifugation, and the supernatant was analyzed by liquid chromatography (HPLC). The yield of HMF was calculated as shown in the table. The SCOF material showed high conversion rate and excellent selectivity for the fructose dehydration reaction. Compared with the SiO2 catalyst, the dense sulfonic acid groups in the inner surface of the active site of the SCOF material can specifically adsorb and stabilize the fructose molecule and its open-loop intermediate through hydrogen bonding, electrostatic interaction and the like, and the pore environment can stabilize the high-energy intermediate, so as to facilitate the dehydration reaction. Due to the stable microstructure of the material, the SCOF catalyst also has high stability, as shown in Table 2, and can be used for more than 20 hours without decreasing the catalytic activity, and can be recycled for 5 times.

[0028] Example 6 Infrared characterization of SCOF catalyst An appropriate amount of powder sample and pure KBr were finely ground and placed in a mold to press into a transparent wafer. The sample was placed in an infrared spectrometer for testing, with a wave number range of 4000~500cm -1 , a scanning number of 32 and a resolution of 4cm -1 . The results are shown in the attached Figure 1 . It can be seen that each SCOF material shows stretching vibration of SO3 - , confirming the successful introduction of sulfonic acid groups. At the same time, N-H stretching and characteristic bands related to C=C were also detected, indicating that the catalyst was successfully synthesized.

[0029] Preparation of SO3H-SiO2 catalyst 1 1g of mesoporous SiO2 was taken in a 100 mL three-necked flask, 50 mL of toluene was added, and then 0.417 mL of 1,2,2-trifluoro-2-hydroxy-1-(trifluoromethyl)-ethane sulfonic acid lactone was added dropwise. The flask was placed in an oil bath at 60°C, protected by N2, and stirred under reflux condensation for 6h. After the reaction was completed, the catalyst was washed and centrifuged with ethanol and water for 3 times, and dried in an oven at 80°C to obtain the SO3H-SiO2 catalyst.

[0030] Preparation of SO3H-SiO2 catalyst 2 In 353 K condition, 0.1 g sodium hydroxide, 180 mL water were added into a 250 mL three-necked flask and stirred vigorously to dissolve uniformly, then 0.364 g CTAB was added, 2.5 h later, 1.48 mL TEOS and 0.308 mL MPTMS were added, 2 h later, the reaction was completed. After cooling and standing, centrifugal filtration was carried out with deionized water and ethanol for 3 times, and drying was carried out in an oven at 80°C. Then 0.37 g was taken and dispersed in 112 mL ethanol solution, 0.56 g ammonium nitrate was added, and refluxing was carried out at 363 K for 3 h to remove the surfactant. Centrifugal filtration was carried out with ethanol for 3 times, and drying was carried out in a vacuum oven at 80°C to obtain the SO3H-SiO2 catalyst 2.

[0031] Table 1 Activity data of catalysts in the dehydration of fructose to 5-HMF

[0032]

[0033] Table 2 Catalytic life of catalysts in the dehydration of fructose to 5-HMF

[0034] Finally, it should be noted that the above-described embodiments are only preferred embodiments of the present application, but the present application is not limited to the specific details in the above-described embodiments. Within the technical concept of the present application, the technical solutions of the present application can be modified and improved in several ways, which all belong to the protection scope of the present application. Therefore, the protection scope of the present application patent should be subject to the appended claims.

Claims

1. A sulfonic acid-based covalent organic framework material, characterized in that, A crystalline material with a periodic porous network structure is formed by covalently linking an aromatic monomer A containing a sulfonic acid group or its precursor with an aromatic monomer B containing complementary reactive functional groups; the sulfonic acid group is uniformly loaded on the material framework and the inner surface of the pores in the form of chemical bonds.

2. The sulfonic acid-type covalent organic framework material according to claim 1, characterized in that, The aromatic monomer A containing a sulfonic acid group or its precursor is selected from one or more of the following: benzenesulfonic acid derivatives containing an amino or aldehyde group, sulfonated derivatives of biphenyl or polyphenylbenzene containing an amino or aldehyde group, and sulfonated derivatives of vinylbenzene containing an amino or aldehyde group.

3. The sulfonic acid-type covalent organic framework material according to claim 1, characterized in that, The aromatic monomer B containing the complementary reactive functional group is selected from one or more of the following: polycarboxylic acid compounds, polyaldehyde compounds, nitrogen-containing heterocyclic compounds, and aromatic acid compounds containing phosphoryl groups. The complementary reactive functional group can form an imine bond, a borate bond, an amide bond, or an enamine bond with the functional group of monomer A.

4. A method for preparing a sulfonic acid-type covalent organic framework material according to any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Under an inert atmosphere, monomer A and monomer B are dissolved in a mixed solvent to form a homogeneous reaction solution; (2) Add an acidic auxiliary agent to the reaction solution; (3) After degassing the reaction system, seal it and react at 80°C to 150°C for 3 to 7 days; (4) After the reaction is complete, the solid product is separated and collected, and after washing, purification and drying, the sulfonic acid type covalent organic framework material is obtained.

5. The preparation method according to claim 4, characterized in that, The mixed solvent in step (1) is a mixture of mesitylene, 1,4-dioxane and acetic acid, wherein the volume fraction of acetic acid is 5% to 20%.

6. The preparation method according to claim 4, characterized in that, The acidic additive in step (2) is selected from one or more of dilute hydrochloric acid, acetic acid, dilute nitric acid, p-toluenesulfonic acid, trifluoroacetic acid, oxalic acid, and oxalic acid. The amount added is 1% to 10% of the total mass of monomer A and monomer B. The degassing treatment in step (3) adopts the "freezing-vacuuming-thawing" cycle method, and the number of cycles is 2 to 4.

7. The application of a sulfonic acid-type covalent organic framework material according to any one of claims 1 to 3 as a solid acid catalyst in the catalytic dehydration of fructose to prepare 5-hydroxymethylfurfural.

8. The application according to claim 7, characterized in that, The catalytic reaction is carried out at a temperature of 120°C to 200°C for 0.5 hours to 5 hours. The reaction solvent is selected from one or more of water, alcohol solvents, dimethyl sulfoxide, dioxane, acetonitrile, acetone, and ethyl acetate. The mass concentration of fructose in the reaction system is 10% to 80%, and the mass ratio of catalyst to fructose is 0.1% to 10%.

9. A method for preparing 5-hydroxymethylfurfural by catalytic dehydration of fructose, characterized in that, The reaction is carried out under the conditions described in claim 9 or 10, using the sulfonic acid-type covalent organic framework material as a catalyst, as described in any one of claims 1 to 3.

10. The method according to claim 9, characterized in that, After the reaction is complete, the catalyst is separated by centrifugation or filtration. The catalyst can be reused after simple washing and drying.

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