COF-SO3H-coated N-MoOx composite material as well as preparation method and application thereof

Abstract

The invention provides a COF-SO3H-coated N-MoOx composite material as well as a preparation method and application thereof. The preparation method comprises the following steps: (1) dispersing melamine and ammonium molybdate tetrahydrate in water to obtain a suspension, evaporating the suspension to obtain a solid, calcining the solid, and cooling to obtain N-doped molybdenum oxide; (2) dispersing the N-doped molybdenum oxide prepared in the step (1), 1, 3, 5-trialdehyde-phloroglucinol and biphenyl diamine in a first organic solvent, adding an acid catalyst, and washing and drying the obtained solid after reaction to obtain COF (at) N-MoOx; and (3) dispersing the COF (at) N-MoOx in toluene, then adding 1, 3-propane sultone, carrying out a reaction in a nitrogen atmosphere, and after the reaction, washing and drying the obtained solid to obtain the COF-SO3H (at) N-MoOx composite material. As a bifunctional catalyst, the COF-SO3H-coated N-MoOx composite material disclosed by the invention has the advantages of stable structure, easiness in separation and recovery and reusability, and has relatively high catalyst utilization efficiency.

Description

Technical Field

[0001] This invention relates to the field of catalyst synthesis technology, and in particular to a COF-SO3H@N-MoO x Composite materials, their preparation methods, and applications. Background Technology

[0002] In recent years, with the increasing scarcity of fossil resources and the growing severity of environmental pollution, traditional chemical production models are facing challenges, prompting the chemical industry to adopt biomass as a sustainable development solution for producing chemicals and biofuels. Biomass, as the most abundant renewable carbon resource on Earth, has advantages such as wide availability, low cost, and sustainable acquisition, and can be used to produce a wide variety of high-value-added chemicals. Among numerous biomass-derived platform compounds, 2,5-dicarboxyfuran (DFF) is an important furan compound with excellent industrial value. DFF can be oxidized to prepare chemicals such as 2,5-furandicarboxylic acid (FDCA), and can also be used as an intermediate to synthesize pharmaceuticals, fluorescent agents, antibacterial agents, and other fine chemicals. Furthermore, DFF can be used to synthesize various novel bio-based polymer materials, such as bio-based polyesters, fluorescent materials, and urea polyesters.

[0003] Due to the significant application prospects of DFF compounds, their synthesis methods are constantly being enriched. Using fructose as a raw material to synthesize DFF is one of the most important routes for DFF preparation. Currently, there are two main schemes for preparing DFF from fructose. One scheme involves first dehydrating fructose to generate 5-hydroxymethylfurfural (HMF), then separating and purifying the HMF before selectively catalytically oxidizing it to obtain DFF. The other scheme involves a one-pot method that directly dehydrates and oxidizes fructose to obtain DFF, including a "one-pot two-step method" and a "one-pot one-step method." This method avoids the HMF separation process and simplifies the operation. For example, Halliday et al. reported a "one-pot two-step method" using Dowex-type ion exchange resin as a catalyst to catalyze the dehydration of fructose to generate HMF, followed by the addition of a vanadium-based catalyst to achieve the conversion of fructose to DFF. Org. Lett . 2003, 5(11):2003-2005.];Wei et al. developed a magnetically separable catalytic system, using two different catalysts, Fe3O4@SiO2-SO3H and ZnFeRuøO2, to achieve the conversion of fructose to DFF,[ J.Colloid Interface Sci [2021, 602:146-158.]; Yang et al. reported Fe3O4-RGO-SO3H and ZnFe 1.65 Ru 0.35 O4 catalyst enables fructose conversion to DFF [ Energy and Fuels2016, 31(1):533-541.];Takagaki developed a one-pot catalytic system that combines Amberlyst-15 with a Ru / HT catalyst to achieve the direct conversion of fructose to DFF[ ACS. Catal . 2011, 1(11):1562-1565.];Ghezali et al. reported a bifunctional acid / redox catalytic system for the synthesis of DFF [ ] Green Chem. [2015, 17(8):4459-4464]; Zhao et al. prepared binary oxides (MZS) with different Mo / Zr ratios to catalyze the conversion of fructose to DFF; Wang et al. studied a catalyst with vanadium oxide (V2O5@MOF) supported on MOF material to achieve the conversion of fructose to DFF. Chinese patent CN120774871A discloses a series reaction of fructose dehydration and selective oxidation under the action of nitrogen-doped carbon supported Fe / Co bimetallic single-atom catalyst to obtain DFF, FDCA or 5-formyl-2-furanoic acid (FFCA).

[0004] In the above-mentioned synthesis methods, the "one-pot two-step" synthesis of DFF from fructose requires a catalyst with acidic sites during the dehydration of fructose to HMF, while the oxidation of HMF requires a catalyst with oxidizing properties. These two different catalysts are often difficult to coordinate under the same conditions in the two-step reaction. The "one-pot one-step" synthesis of DFF from fructose uses catalysts that can simultaneously achieve fructose dehydration and HMF oxidation. However, such catalysts often suffer from poor selectivity and stability, short service life, and complex product separation and purification processes. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the object of the present invention is to provide a COF-SO3H@N-MoO x Composite materials, their preparation methods, and applications are used to address the problems of existing catalysts that simultaneously achieve fructose dehydration and HMF oxidation, such as poor selectivity and stability, short service life, and complex product separation and purification processes.

[0006] To achieve the above and other related objectives, the present invention provides a COF-SO3H@N-MoO x A method for preparing composite materials, characterized in that it includes: (1) Melamine and ammonium molybdate tetrahydrate are dispersed in water to obtain a suspension. The suspension is evaporated to obtain a solid. The solid is calcined and cooled to obtain N-doped molybdenum oxide (N-MoO). x ); (2) The N-doped molybdenum oxide, 1,3,5-trialdehyde-phloroglucinol and benzidine obtained in step (1) are dispersed in a first organic solvent, an acid catalyst is added, and the resulting solid is washed and dried after the reaction to obtain COF@N-MoO x ; (3) COF@N-MoOx was dispersed in toluene, followed by the addition of 1,3-propanesulfonate lactone. The reaction was carried out under a nitrogen atmosphere. After the reaction, the resulting solid was washed and dried to obtain COF-SO3H@N-MoO x Composite materials.

[0007] The COF-SO3H@N-MoO of the present invention x The composite material is formed by the integrated construction of a sulfonated covalent organic framework (COF-SO3H) and a nitrogen-doped molybdenum oxide (N-MoOx), achieving synergistic catalysis of different reaction steps. The COF-SO3H@N-MoOx prepared in this invention... x The composite material can simultaneously promote the dehydration of fructose to the intermediate HMF and the selective oxidation of HMF to DFF under relatively mild reaction conditions, exhibiting high product selectivity and yield. Furthermore, the catalyst has a stable structure, is easy to separate and recover, and can be reused, thus improving catalyst utilization efficiency.

[0008] The present invention also provides a COF-SO3H@N-MoO x The method for preparing composite materials includes the following steps: (1) Add an appropriate amount of deionized water to melamine and ammonium molybdate tetrahydrate, and disperse them thoroughly by ultrasonic oscillation. Stir and heat the resulting suspension at a certain temperature until the water is completely evaporated; calcine the resulting solid in a muffle furnace under air atmosphere at a constant temperature for a certain time; cool to room temperature to obtain a black powder product, denoted as N-doped molybdenum oxide (N-MoO). x ); (2) 1,3,5-trialdehyde-phloroglucinol (Tp) and benzidine (BD) were dispersed in a certain amount of methanol and sonicated until completely dissolved. Then, the N-MoO2 obtained in step (1) was... x Add the Tp solution and ultrasonically disperse for 10 min. Then, slowly add the BD solution dropwise to the mixture under continuous stirring. Next, add a certain amount of acetic acid as a catalyst and stir the reaction at room temperature. After the reaction is complete, collect the solid product, wash repeatedly with methanol until the washings are colorless, and then dry to obtain COF@N-MoO. x ; (3) The obtained product COF@N-MoOx was further dispersed in a certain amount of toluene solvent, and then 1,3-propanesulfonate lactone was added. The reaction was carried out under a nitrogen atmosphere at a certain temperature. After the reaction was completed, the product was cooled to room temperature, the solid product was collected, and washed repeatedly with acetone to remove unreacted raw materials and by-products. After vacuum drying, COF-SO3H@N-MoO was obtained. x Composite materials.

[0009] The COF-SO3H@N-MoO of the present invention x The specific synthesis route for the composite material is shown below: .

[0010] Preferably, in step (1), the molar ratio of melamine to ammonium molybdate tetrahydrate is 1:(18~30), more preferably 1:(20~26).

[0011] Preferably, in step (1), the calcination temperature is 500~600℃ and the calcination time is 3~6h.

[0012] Preferably, in step (2), the molar ratio of 1,3,5-trialdehyde-phloroglucinol and benzidine is 1:(1.5~2.1), more preferably 1:(1.5~1.7).

[0013] Preferably, in step (2), the mass ratio of the N-doped molybdenum oxide to 1,3,5-trialdehyde-phloroglucinol is 1:(1~10).

[0014] Preferably, in step (2), the first organic solvent is selected from one or more of acetonitrile, methanol, dichloroethane, tetrahydrofuran and N,N-dimethylformamide; more preferably, it is methanol.

[0015] Preferably, in step (2), the mass ratio of the first organic solvent to 1,3,5-trialdehyde-phloroglucinol is (50~100):1.

[0016] Preferably, in step (2), the acid catalyst is acetic acid, and the concentration of the acetic acid is 5~8 mol / L.

[0017] Preferably, in step (2), the mass ratio of acetic acid to 1,3,5-trialdehyde-phloroglucinol is (30~70):1.

[0018] Preferably, in step (2), after adding the acid catalyst, the mixture is stirred at room temperature for 8 to 14 hours.

[0019] Preferably, in step (2), the drying temperature is 90~110℃ and the drying time is 8~12h.

[0020] Preferably, in step (3), the toluene reacts with COF@N-MoO x The mass ratio is (100~300):1.

[0021] Preferably, in step (3), the 1,3-propanesulfonate lactone reacts with COF@N-MoO x The mass ratio is (4~10):1.

[0022] Preferably, in step (3), the reaction temperature is 100~120℃ and the reaction time is 6~10h.

[0023] Preferably, in step (3), the drying temperature is 90~110℃ and the drying time is 8~12 h.

[0024] The present invention also provides a COF-SO3H@N-MoO prepared by the above preparation method. x Composite materials.

[0025] The present invention also provides the above-mentioned COF-SO3H@N-MoO x Application of composite materials as bifunctional catalysts in the direct preparation of 2,5-dicarboxyfuran from fructose.

[0026] Preferably, in an air atmosphere, fructose is used as a raw material, and the COF-SO3H@N-MoO is used. x Using the composite material as a catalyst, 2,5-diformylfuran was prepared by dehydration and oxidation in a second organic solvent under normal pressure.

[0027] Preferably, the second organic solvent is dimethyl sulfoxide. Preferably, the mass ratio of the second organic solvent to fructose is (20-70):1.

[0028] Preferably, the COF-SO3H@N-MoO x The mass ratio of the composite material to fructose is 1:(3-8).

[0029] Preferably, the reaction temperature is 100–160°C and the reaction time is 2–9 h.

[0030] Preferably, after the reaction is complete, the COF-SO3H@N-MoO x The composite material can be reused after filtration, separation, and washing.

[0031] As described above, the present invention has the following beneficial effects: (1) The COF-SO3H@N-MoO of the present invention x The composite material consists of a sulfonated covalent organic framework (COF-SO3H) and nitrogen-doped molybdenum oxide (N-MoO).x Through its integrated structure, the catalyst of this invention achieves synergistic catalysis of different reaction steps, enabling simultaneous catalysis of fructose dehydration and HMF oxidation. (2) The COF-SO3H@N-MoO of the present invention x Composite materials, as bifunctional catalysts, can simultaneously catalyze the dehydration of fructose and the oxidation of HMF, exhibiting high product selectivity and yield. (3) The COF-SO3H@N-MoO of the present invention x Composite materials, as bifunctional catalysts, have the advantages of structural stability, easy separation and recovery, and reusability, and have high catalyst utilization efficiency. Attached Figure Description

[0032] Figure 1 The N-doped molybdenum oxide (N-MoO) prepared in Example 3 of this invention x SEM image.

[0033] Figure 2 The COF-SO3H@N-MoO prepared in Example 3 of this invention x SEM image. Detailed Implementation

[0034] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0035] It should be noted that the process equipment or apparatus not specifically mentioned in the following embodiments are all conventional equipment or apparatus in the art.

[0036] Furthermore, it should be understood that the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, does not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise stated. It should also be understood that the combined connection relationship between one or more devices / apparatus mentioned in this invention does not preclude the existence of other devices / apparatus before or after the combined devices / apparatus, or the insertion of other devices / apparatus between these explicitly mentioned devices / apparatus, unless otherwise stated. Moreover, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or limiting the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0037] Example 1 (1) A suspension system was prepared by adding an appropriate amount of deionized water to 5.00 g of melamine and 1 mmol of ammonium molybdate tetrahydrate, and then sonicated for 10 min to achieve full dispersion. The resulting suspension was stirred and heated at 100 °C in air until the water was completely evaporated. The resulting solid was calcined at 550 °C for 4 h in a muffle furnace in air; after cooling to room temperature, a black powder product was obtained, which was denoted as N-doped molybdenum oxide (N-MoOx). (2) 1,3,5-trialdehyde-phloroglucinol (Tp, 42 mg, 0.2 mmol) and benzidine (BD, 55 mg, 0.3 mmol) were dispersed in 4 mL of methanol and sonicated until completely dissolved; then, 5 mg of N-MoO2 obtained in step (1) was weighed. x The solution was added to Tp solution and sonicated for 10 min to achieve uniform dispersion. Under continuous stirring, BD solution was slowly added dropwise to the mixture. After the addition was complete, 2 mL of 6 mol / L acetic acid solution was added, and the mixture was stirred at room temperature for 12 h. After the reaction was complete, the solid product was collected and washed repeatedly with methanol until the washings were colorless. The solid was then dried at 100 °C for 12 h to obtain 55 mg COF@N-MoO. x ; (3) The COF@N-MoOx obtained in step (2) was dispersed in 20 mL of toluene, followed by the addition of 500 mg of 1,3-propanesulfonate lactone. The mixture was heated at 110 °C for 8 h under a nitrogen atmosphere. After the reaction was completed, the solid product was collected and washed repeatedly with acetone to remove unreacted raw materials and byproducts. The solid was dried at 100 °C for 12 h to obtain COF-SO3H@N-MoO x Composite materials.

[0038] Testing revealed that the COF-SO3H@N-MoO prepared in this embodiment... x The mass fraction of the COF-SO3H shell in the composite material is approximately 91.0%, and the mass fraction of N-MoO is... x The core mass fraction is approximately 9.0%.

[0039] Example 2 (1) A suspension system was prepared by adding an appropriate amount of deionized water to 5.00 g of melamine and 1 mmol of ammonium molybdate tetrahydrate, and then sonicated for 10 min to achieve full dispersion. The resulting suspension was stirred and heated at 100 °C in air until the water was completely evaporated. The resulting solid was calcined at 550 °C for 4 h in a muffle furnace in air; after cooling to room temperature, a black powder product was obtained, denoted as N-doped molybdenum oxide (N-MoO). x ); (2) 1,3,5-trialdehyde-phloroglucinol (Tp, 42 mg, 0.2 mmol) and benzidine (BD, 55 mg, 0.3 mmol) were separately dispersed in 4 mL of methanol and sonicated until completely dissolved. Then, 10 mg of N-MoO2 obtained in step (1) was weighed. x The solution was added to Tp solution and sonicated for 10 min to achieve uniform dispersion. Under continuous stirring, BD solution was slowly added dropwise to the mixture. After the addition was complete, 2 mL of 6 mol / L acetic acid solution was added, and the mixture was stirred at room temperature for 12 h. After the reaction was complete, the solid product was collected and washed repeatedly with methanol until the washings were colorless. The solid was then dried at 100 °C for 12 h to obtain 60 mg of COF@N-MoO. x ; (3) Take the COF@N-MoO obtained in step (2) x The product was dispersed in 20 mL of toluene, followed by the addition of 500 mg of 1,3-propanesulfonate lactone. The mixture was heated at 110 °C for 8 h under a nitrogen atmosphere. After the reaction was complete, the solid product was collected and washed repeatedly with acetone to remove unreacted starting materials and byproducts. The solid was dried at 100 °C for 12 h to obtain COF-SO3H@N-MoO x Composite materials.

[0040] Testing revealed that the COF-SO3H@N-MoO prepared in this embodiment... x The mass fraction of the COF-SO3H shell in the composite material is approximately 83.3%, and the mass fraction of N-MoO is... x The core mass fraction is approximately 16.7%.

[0041] Example 3 (1) A suspension system was prepared by adding an appropriate amount of deionized water to 5.00 g of melamine and 1 mmol of ammonium molybdate tetrahydrate, and then sonicated for 10 min to achieve full dispersion. The resulting suspension was stirred and heated at 100 °C in air until the water was completely evaporated. The resulting solid was calcined at 550 °C for 4 h in a muffle furnace in air; after cooling to room temperature, a black powder product was obtained, denoted as N-doped molybdenum oxide (N-MoO). x ).

[0042] (2) 1,3,5-trialdehyde-phloroglucinol (Tp, 42 mg, 0.2 mmol) and benzidine (BD, 55 mg, 0.3 mmol) were separately dispersed in 4 mL of methanol and sonicated until completely dissolved. Then, 20 mg of N-MoO2 obtained in step (1) was weighed. xThe solution was added to Tp solution and sonicated for 10 min to achieve uniform dispersion. Under continuous stirring, BD solution was slowly added dropwise to the mixture. After the addition was complete, 2 mL of 6 mol / L acetic acid solution was added, and the mixture was stirred at room temperature for 12 h. After the reaction was complete, the solid product was collected and washed repeatedly with methanol until the washings were colorless. The solid was then dried at 100 °C for 12 h to obtain 70 mg COF@N-MoO. x .

[0043] (3) Take the COF@N-MoO obtained in step (2) x The product was dispersed in 20 mL of toluene, followed by the addition of 500 mg of 1,3-propanesulfonate lactone. The mixture was heated at 110 °C for 8 h under a nitrogen atmosphere. After the reaction was complete, the solid product was collected and washed repeatedly with acetone to remove unreacted raw materials and byproducts. The solid was dried at 100 °C for 12 h to obtain the COF-SO3H@N-MoOx composite material.

[0044] Testing revealed that the COF-SO3H@N-MoO prepared in this embodiment... x The mass fraction of the COF-SO3H shell in the composite material is approximately 71.5%, and the mass fraction of N-MoO is... x The core mass fraction is approximately 28.5%.

[0045] The N-MoO prepared in this embodiment x SEM image as follows Figure 1 As shown, from Figure 1 It can be seen that N-MoO x It exhibits an aggregated nanoblock-like morphology; The COF-SO3H@N-MoO prepared in this embodiment x SEM image as follows Figure 2 As shown, from Figure 2 It can be seen that in the composite material COF-SO3H@N-MoO x Medium-fiber polycrystalline COF-SO3H coated with N-MoO x Surface. Some COF-SO3H particles are dispersed in N-MoO. x around.

[0046] Example 4 (1) A suspension system was prepared by adding an appropriate amount of deionized water to 5.00 g of melamine and 1 mmol of ammonium molybdate tetrahydrate, and then sonicated for 10 min to achieve full dispersion. The resulting suspension was stirred and heated at 100 °C in air until the water was completely evaporated. The resulting solid was calcined at 550 °C for 4 h in a muffle furnace in air; after cooling to room temperature, a black powder product was obtained, denoted as N-doped molybdenum oxide (N-MoO). x ); (2) 1,3,5-trialdehyde-phloroglucinol (Tp, 42 mg, 0.2 mmol) and benzidine (BD, 55 mg, 0.3 mmol) were dispersed separately in 4 mL of methanol and sonicated until completely dissolved. Then, 30 mg of N-MoO2 obtained in step (1) was weighed. x The solution was added to Tp solution and sonicated for 10 min to achieve uniform dispersion. Under continuous stirring, BD solution was slowly added dropwise to the mixture. After the addition was complete, 2 mL of 6 mol / L acetic acid solution was added, and the mixture was stirred at room temperature for 12 h. After the reaction was complete, the solid product was collected and washed repeatedly with methanol until the washings were colorless. The solid was then dried at 100 °C for 12 h to obtain 80 mg of COF@N-MoO. x ; (3) Take the COF@N-MoO obtained in step (2) x The product was dispersed in 20 mL of toluene, followed by the addition of 500 mg of 1,3-propanesulfonate lactone. The mixture was heated at 110 °C for 8 h under a nitrogen atmosphere. After the reaction was complete, the solid product was collected and washed repeatedly with acetone to remove unreacted starting materials and byproducts. The solid was dried at 100 °C for 12 h to obtain COF-SO3H@N-MoO x Composite materials.

[0047] Testing revealed that the COF-SO3H@N-MoO prepared in this embodiment... x The mass fraction of the COF-SO3H shell in the composite material is approximately 62.5%, and the mass fraction of N-MoO is... x The core mass fraction is approximately 37.5%.

[0048] Example 5 (1) A suspension system was prepared by adding an appropriate amount of deionized water to 5.00 g of melamine and 1 mmol of ammonium molybdate tetrahydrate, and then sonicated for 10 min to achieve full dispersion. The resulting suspension was stirred and heated at 100 °C in air until the water was completely evaporated. The resulting solid was calcined at 550 °C for 4 h in a muffle furnace in air; after cooling to room temperature, a black powder product was obtained, denoted as N-doped molybdenum oxide (N-MoO). x ); (2) 1,3,5-trialdehyde-phloroglucinol (Tp, 42 mg, 0.2 mmol) and benzidine (BD, 55 mg, 0.3 mmol) were separately dispersed in 4 mL of methanol and sonicated until completely dissolved. Then, 40 mg of N-MoO2 obtained in step (1) was weighed. xThe solution was added to Tp solution and sonicated for 10 min to achieve uniform dispersion. Under continuous stirring, BD solution was slowly added dropwise to the mixture. After the addition was complete, 2 mL of 6 mol / L acetic acid solution was added, and the mixture was stirred at room temperature for 12 h. After the reaction was complete, the solid product was collected and washed repeatedly with methanol until the washings were colorless. The solid was then dried at 100 °C for 12 h to obtain 90 mg of COF@N-MoO. x ; (3) Take the COF@N-MoO obtained in step (2) x The product was dispersed in 20 mL of toluene, followed by the addition of 500 mg of 1,3-propanesulfonate lactone. The mixture was heated at 110 °C for 8 h under a nitrogen atmosphere. After the reaction was complete, the solid product was collected and washed repeatedly with acetone to remove unreacted starting materials and byproducts. The solid was dried at 100 °C for 12 h to obtain COF-SO3H@N-MoO x Composite materials.

[0049] Testing revealed that the COF-SO3H@N-MoO prepared in this embodiment... x The mass fraction of the COF-SO3H shell in the composite material is approximately 56.0%, and the mass fraction of N-MoO is... x The core mass fraction is approximately 44.0%.

[0050] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that N-MoO was not added. x The target catalyst, COF-SO3H, was obtained. The mass fraction of the COF-SO3H shell was approximately 100%, and the N-MoO content was [missing information]. x The core mass fraction is 0%. Application Examples The COF-SO3H@N-MoO prepared in Examples 1-5 were respectively... x The composite material and the COF-SO3H material prepared in Comparative Example 1 were used as catalysts for the direct preparation of DFF from fructose.

[0051] 100 mg fructose, 20 mg catalyst, and 5 mL dimethyl sulfoxide were sequentially added to a 25 mL Shrek tube equipped with a magnetic stirrer and sealed. The reaction was carried out in an air atmosphere inside the Shrek tube, and the reaction system was placed in a constant temperature oil bath at 140 °C for 7 h. After the reaction was completed, an internal standard was added to the system, and after centrifugation, the supernatant was diluted with acetonitrile and then analyzed by gas chromatography with internal standard method. The results are shown in Table 1: Table 1. Quantitative analysis results of reaction products in each example and comparative example.

[0052] As can be seen from Table 1: with the increase of N-MoOx With increasing proportion of N-MoO in the overall catalyst, the DFF yield shows an upward trend; however, when the proportion of N-MoO increases, the yield of DFF also increases. x As the proportion increased in Examples 4 and 5, the DFF yield showed a decreasing trend. This is attributed to the N-MoO content in Examples 4 and 5. x The component ratio was higher than in Example 3. The final experiment showed that when N-MoO x The DFF yield of this conversion reaction was optimal when the proportion of the catalyst in the total catalyst was as in Example 3.

[0053] Under optimized reaction conditions, the bifunctional COF-SO3H@N-MoO x The reusability of the composite material was evaluated. After the catalytic conversion of fructose to DFF, the catalyst was recovered in solid phase by centrifugation. The recovered catalyst was washed with methanol and deionized water to remove adsorbed organic impurities from its surface. After drying, the catalyst could be reused. The results are shown in Table 2. Table 2 Performance of the recycled catalyst

[0054] As shown in Table 2, the yield of DFF remained stable after five consecutive reaction cycles without significant decline, indicating good catalytic stability and reusability.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any form or substance. It should be noted that those skilled in the art can make various improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention. Any modifications, alterations, and equivalent changes made by those skilled in the art based on the above-disclosed technical content without departing from the spirit and scope of the present invention are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and evolutions made to the above embodiments based on the essential technology of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A COF-SO3H@N-MoO x A method for preparing composite materials, characterized in that, include: (1) Melamine and ammonium molybdate tetrahydrate are dispersed in water to obtain a suspension, the suspension is evaporated to obtain a solid, the solid is calcined and cooled to obtain N-doped molybdenum oxide; (2) The N-doped molybdenum oxide, 1,3,5-trialdehyde-phloroglucinol and benzidine obtained in step (1) are dispersed in a first organic solvent, an acid catalyst is added, and the resulting solid is washed and dried after the reaction to obtain COF@N-MoO x ; (3) COF@N-MoOx was dispersed in toluene, followed by the addition of 1,3-propanesulfonate lactone. The reaction was carried out under a nitrogen atmosphere. After the reaction, the resulting solid was washed and dried to obtain COF-SO3H@N-MoO x Composite materials.

2. The preparation method according to claim 1, characterized in that: In step (1), the molar ratio of melamine to ammonium molybdate tetrahydrate is 1:(18~30); the calcination temperature is 500~600℃, and the calcination time is 3~6h.

3. The preparation method according to claim 1, characterized in that: In step (2), the molar ratio of 1,3,5-trialdehyde-phloroglucinol and benzidine is 1:(1.5~2.1); the mass ratio of N-doped molybdenum oxide to 1,3,5-trialdehyde-phloroglucinol is 1:(1~10).

4. The preparation method according to claim 1, characterized in that: In step (2), the first organic solvent is selected from one or more of acetonitrile, methanol, dichloroethane, tetrahydrofuran and N,N-dimethylformamide; the mass ratio of the first organic solvent to 1,3,5-trialdehyde-phloroglucinol is (50~100):

1.

5. The preparation method according to claim 1, characterized in that: In step (2), the acid catalyst is acetic acid, and the concentration of the acetic acid is 5~8 mol / L; the mass ratio of the acetic acid to 1,3,5-trialdehyde-phloroglucinol is (30~70):1; after adding the acid catalyst, the mixture is stirred at room temperature for 8~14h; the drying temperature is 90~110℃, and the drying time is 8~12h.

6. The preparation method according to claim 1, characterized in that: In step (3), the toluene reacts with COF@N-MoO x The mass ratio is (100~300):1; the 1,3-propanesulfonate lactone and COF@N-MoO x The mass ratio is (4~10):1; the reaction temperature is 100~120℃, the reaction time is 6~10h; the drying temperature is 90~110℃, and the drying time is 8~12h.

7. A COF-SO3H@N-MoO prepared by the preparation method according to any one of claims 1 to 6 x Composite materials.

8. A COF-SO3H@N-MoO as described in claim 7 x Application of composite materials as bifunctional catalysts in the direct preparation of 2,5-dicarboxyfuran from fructose.

9. The application according to claim 8, characterized in that: In an air atmosphere, using fructose as a raw material, the COF-SO3H@N-MoO x Using the composite material as a catalyst, 2,5-diformylfuran was prepared by dehydration and oxidation in a second organic solvent under normal pressure.

10. The application according to claim 9, characterized in that: The second organic solvent is dimethyl sulfoxide; the mass ratio of the second organic solvent to fructose is (20-70):1; the COF-SO3H@N-MoO x The mass ratio of the composite material to fructose is 1:(3-8); the reaction temperature is 100-160℃, and the reaction time is 2-9 h; after the reaction, the COF-SO3H@N-MoO x The composite material can be reused after filtration, separation, and washing.

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