Preparation method of post-modified metal-organic framework material for catalytic oxidation of benzyl alcohol into benzaldehyde and application thereof

Abstract

The application relates to a preparation method of a post-modified metal organic framework material for catalytically oxidizing benzyl alcohol into benzaldehyde and application thereof, and belongs to the technical field of photocatalytic materials. A Zr-based MOF-808 is taken as a matrix framework, organic dye eosin Y (EY) is taken as a functional unit, and the two are coordinated and anchored to prepare a post-modified metal organic framework material EY@MOF-808. The post-modified metal organic framework material EY@MOF-808 has rich unsaturated coordination sites, provides a path for distinguishing the guest binding capacity with different groups, improving reactivity and selectivity, and effectively avoids the excessive oxidation of benzaldehyde. The EY@MOF-808 is suitable for catalyzing benzyl alcohol with various substituents, and corresponding benzaldehyde is obtained with a selectivity of greater than 99%. In addition, the EY@MOF-808 can be recycled for four times and the selectivity is not reduced, and the release of toxic dyes into the environment is prevented.

Description

Technical Field

[0001] This invention relates to a method for preparing a post-modified metal-organic framework material for the catalytic oxidation of benzyl alcohol to benzaldehyde and its application, belonging to the field of photocatalytic materials technology. Background Technology

[0002] Aldehydes, as key intermediates in organic synthesis, have wide applications in biomedicine, food additives, and dye synthesis, playing a vital role in industrial chemistry. With rapid economic development, my country's demand for high-quality benzaldehyde is increasing. Besides extraction from natural products, the selective oxidation of alcohols to aldehydes is an important scientific research and industrial manufacturing method in synthetic chemistry. Traditional alcohol oxidation still relies on strong oxidants or noble metal catalysts, which are limited in application due to high cost, harsh reaction conditions, and low atom economy. Furthermore, because aldehydes are more easily activated than alcohols, excessive oxidation to acids significantly reduces the selectivity of the oxidation reaction. Therefore, there is an urgent need to develop highly selective and environmentally friendly photocatalytic systems to provide an effective solution for the efficient conversion of alcohols to aldehydes.

[0003] On the one hand, organic photoredox catalysts, through hydrogen atom transfer (HAT), remove the limitations on redox potentials and utilize molecular oxygen as a green terminal oxidant, providing an opportunity to activate CH bonds under mild conditions. Eosin Y (EY), an inexpensive and readily available anthracene dye, has been successfully applied to CH bond activation, but its application is greatly limited by its susceptibility to aggregation-induced quenching and photobleaching in homogeneous systems. On the other hand, metal-organic frameworks (MOFs), composed of ordered connections of organic ligands and inorganic metal ions / clusters, serve as heterogeneous catalysts for various organic transformations. MOFs constructed from polynuclear metal clusters possess abundant unsaturated coordination sites, providing a good way to distinguish the binding ability of guests with different groups and improve reactivity and selectivity. Introducing photosensitive units into MOFs has been an effective way to improve photocatalytic activity in recent years, and the introduction of photosensitive units as ligands has received widespread attention in the field of organic catalysis; however, problems such as low catalyst synthesis yield and poor selectivity remain. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, the present invention aims to provide a method for preparing a post-modified metal-organic framework (MOF) material for the highly selective catalytic oxidation of benzyl alcohol to benzaldehyde, and its application. The post-modification method provides a simple and flexible platform for combining MOFs with organocatalysts possessing excellent activation properties. The post-modified MOF material EY@MOF-808 prepared using this method can be used for the highly selective catalytic oxidation of benzyl alcohol to benzaldehyde. This invention employs a solvent-assisted ligand incorporation method to anchor the functional unit eosin Y in a bidentate bridging coordination onto the Zr6O4(OH)4 cluster of MOF-808. Importantly, the strong interaction between the potential unsaturated coordination sites near eosin Y on the metal cluster and the substrate benzyl alcohol not only ensures the high efficiency of the HAT process in activating the CH bond but also avoids the over-oxidation of the product benzaldehyde. Under optimized conditions, benzyl alcohol with various substituents was used as a substrate, and the corresponding benzaldehyde was obtained under the catalysis of EY@MOF-808, with selectivity greater than 99%, successfully expanding the substrate range. Furthermore, EY@MOF-808 can be recycled four times without loss of selectivity, preventing the release of toxic dyes into the environment. This approach represents a promising new approach for uniquely economical and highly selective MOF photocatalysts.

[0005] To achieve the aforementioned objectives and address the problems existing in the prior art, the technical solution adopted by this invention is: a method for preparing a post-modified metal-organic framework material for the highly selective catalytic oxidation of benzyl alcohol to benzaldehyde. Using Zr-based MOF-808 as the parent framework and the organic dye eosin Y as the functional unit, the two are coordinated and anchored via a solvothermal method to obtain the post-modified metal-organic framework material EY@MOF-808. The synthetic route is as follows:

[0006] MOF-808 + EY → EY@MOF-808

[0007] The structure of eosin Y is as follows:

[0008] .

[0009] Some specific preparation steps of the post-modified metal-organic framework materials, the molar ratio of Zr-based MOF-808 and eosin Y is selected from 1:5 to 15, and the reaction solvent is selected from N,N - At least one of dimethylformamide, acetonitrile, and dimethylacetamide, the reaction temperature is 60~120 °C, and the reaction time is 15~96 hours.

[0010] Some specific steps for preparing the post-modified metal-organic framework material include a molar ratio of Zr-based MOF-808 and eosin Y selected from 1:5 to 10, a reaction temperature of 60 to 120 °C, and a reaction time of 20 to 50 hours.

[0011] Some specific steps for preparing the post-modified metal-organic framework material include: the molar ratio of Zr-based MOF-808 and eosin Y is selected from 1:8 to 10; the reaction temperature is 80 to 120 °C; and the reaction time is 20 to 30 hours.

[0012] Some specific steps for preparing the post-modified metal-organic framework material include adding Zr-based MOF-808 and eosin Y to a solvent and sonicating until a uniform suspension is formed. Then, the suspension is transferred to a high-pressure reactor and heated at 80-120 °C for 20-48 hours. After centrifugation or filtration, washing, and vacuum drying, the post-modified metal-organic framework material EY@MOF-808 is obtained.

[0013] Some specific steps for preparing the post-modified metal-organic framework material include adding Zr-based MOF-808 and eosin Y into DMF and sonicating until a uniform suspension is formed. Then, the suspension is transferred to a high-pressure reactor and heated at 100 °C for 24 hours. After centrifugation or filtration, washing, and vacuum drying, the post-modified metal-organic framework material EY@MOF-808 is obtained.

[0014] A specific method for preparing post-modified metal-organic framework materials includes the following steps:

[0015] According to the literature, pyromellitic acid (21 mg) and zirconium oxychloride octahydrate (97 mg) were dissolved in a solution containing... N,N The solution was dissolved in dimethylformamide (DMF, 3 mL) and formic acid (3 mL) by sonication until completely dissolved. The solution was then transferred to a high-pressure reactor lined with polytetrafluoroethylene (PTFE) and heated at 100 °C for 24 hours. After cooling to room temperature, the white powder was collected by centrifugation and washed sequentially with DMF and acetone. Finally, the white powder was vacuum-dried overnight at 100 °C to obtain the parent framework MOF-808.

[0016] The metal-organic framework material MOF-808 of the present invention is a known material and can be prepared with reference to J. Am. Chem. Soc. 2018, 140, 18208-18216.

[0017] MOF-808 (0.0389 mmol, 53 mg) and eosin Y (0.389 mmol, 252 mg) were sonicated in DMF (5 mL) at a molar ratio of 1:10 until a homogeneous suspension was formed. The suspension was then transferred to a high-pressure reactor with a polytetrafluoroethylene liner and heated at 100 °C for 24 hours. After cooling to room temperature, the orange-red powder was collected by centrifugation and filtered and washed several times with DMF, acetone, and ethanol sequentially until the supernatant was clear and transparent with no eosin Y dye adsorption residue. Finally, the orange-red powder was vacuum dried overnight at 100 °C to obtain the post-modified metal-organic framework EY@MOF-808.

[0018] The application of the post-modified metal-organic framework material in the catalytic oxidation of benzyl alcohol with or without substituents to prepare benzaldehyde derivatives.

[0019] The substituents are selected from fluoroalkyl groups with 1-5 carbon atoms, alkyl groups with 1-5 carbon atoms, halogens, nitro groups, and alkoxy groups with 1-5 carbon atoms.

[0020] The substituents are selected from trifluoromethyl, F, Cl, Br, nitro, and methoxy.

[0021] The application of the post-modified metal-organic framework material EY@MOF-808 in the selective catalytic oxidation of benzyl alcohol to benzaldehyde.

[0022] The wavelength of light used to catalytically oxidize benzyl alcohol to prepare benzaldehyde using the post-modified metal-organic framework material is selected from 400~520 nm.

[0023] The beneficial effects of this invention are: a method for preparing a post-modified metal-organic framework (MOF) material for the highly selective catalytic oxidation of benzyl alcohol to benzaldehyde and its application. Using Zr-based MOF-808 as the parent framework and the organic dye eosin Y as the functional unit, the post-modified MOF material is obtained through coordination anchoring. Compared with existing technologies, this method is milder and easier to synthesize. On the one hand, the introduction of eosin Y successfully expands the light absorption performance of the parent framework MOF-808, and the excellent CH bond activation and oxygen activation properties of EY@MOF-808 make the oxidation reaction of benzyl alcohol possible. On the other hand, the strong binding force between the potential unsaturated coordination sites near eosin Y on the Zr6O4(OH)4 cluster of the post-modified MOF material and the substrate benzyl alcohol avoids over-oxidation of the product benzaldehyde. After optimization of reaction conditions, under blue light irradiation, EY@MOF-808 catalyzes the oxidation of benzyl alcohol to benzaldehyde with a selectivity greater than 99%, and can be stably recycled four times. This post-modified MOF material and method provide a new approach for expanding green organic catalysis strategies. Attached Figure Description

[0024] Figure 1 This is the powder X-ray diffraction (PXRD) of the target compound EY@MOF-808 in Example 1.

[0025] Figure 2 This is the X-ray photoelectron spectroscopy (XPS) of the target compound EY@MOF-808 in Example 1.

[0026] Figure 3 This is a graph showing the change in the yield of compound EY@MOF-808 prepared in Example 1 for the catalytic oxidation of benzyl alcohol to benzaldehyde under light conditions over time.

[0027] Figure 4 This is the fluorescence emission spectrum of compound EY@MOF-808 prepared in Example 1, titrated with the reaction substrate benzyl alcohol and the product benzaldehyde.

[0028] Figure 5 This is a bar chart showing the cyclic yield of benzaldehyde produced by the catalytic oxidation of benzyl alcohol by compound EY@MOF-808 prepared in Example 1. Detailed Implementation

[0029] The present invention will be further described below with reference to the embodiments. Example 1

[0030] Tristyric acid (21 mg) and zirconium oxychloride octahydrate (97 mg) were dissolved in a solution containing DMF (3 mL) and formic acid (3 mL), and sonicated until completely dissolved. The solution was then transferred to an autoclave lined with polytetrafluoroethylene (PTFE) and heated at 100 °C for 24 hours. After cooling to room temperature, the white powder was collected by centrifugation and washed sequentially with DMF and acetone. Finally, the white powder was vacuum-dried overnight at 100 °C to obtain the parent framework MOF-808. Subsequently, MOF-808 (0.0389 mmol, 53 mg) and eosin Y (0.389 mmol, 252 mg) were sonicated in DMF (5 mL) at a molar ratio of 1:10 until a homogeneous suspension was formed. This suspension was then transferred to an autoclave lined with PTFE and heated at 100 °C for 24 hours. After cooling to room temperature, the orange-red powder was collected by centrifugation and filtered successively with DMF, acetone, and ethanol, and washed several times until the supernatant was clear and transparent, with no residual eosin Y dye adsorption. Finally, the orange-red powder was vacuum dried overnight at 100 °C to obtain the post-modified metal-organic framework material EY@MOF-808. The X-ray diffraction of this material is as follows: Figure 1The PXRD pattern, shown in the figure, is from a Rigaku Smart Lab X-ray diffractometer. This pattern demonstrates the successful synthesis of MOF-808 and that the post-coordination modification with eosin Y did not disrupt the structure of MOF-808. The X-ray photoelectron spectra of MOF-808 and EY@MOF-808 are shown below. Figure 2 As shown in the XPS O 1s, the experimental instrument used was a Thermo ESCALAB Xi+ X-ray photoelectron spectrometer. In EY@MOF-808, due to the unsaturated nodes being coordinated and anchored to the eosin Y molecule in a bidental bridging manner, the peak area of ​​the Zr−O bond was reduced and the signal of O−C=O was enhanced compared to MOF-808. Example 2

[0031] Add 3 mL of acetonitrile solution to a 20 mL photoreaction tube, then add 5.0 μmol of EY@MOF-808 and 0.2 mmol of benzyl alcohol prepared in Example 1. Seal the tube with a stopper, purge with oxygen to eliminate interference from other gases, and connect an oxygen bulb. Under irradiation with a 455 nm wavelength light source, continuously stir the reaction at 40 °C for 12 hours. After the reaction is complete, add 0.2 mmol of the internal standard 1,3,5-trimethoxybenzene, centrifuge to remove the catalyst EY@MOF-808, and concentrate the supernatant by vacuum distillation. 1 Yield determined by 1H NMR spectroscopy. The yield versus time curve for the catalytic oxidation of benzyl alcohol to benzaldehyde using EY@MOF-808 under illumination is shown below. Figure 3 As shown, the yield of benzyl alcohol increased linearly with time and stabilized within 12 h. In addition, the yield did not increase further after 3 hours of removing EY@MOF−808, indicating that EY@MOF−808 is a true heterogeneous photocatalyst and that the post-modified anchored eosin Y is sufficiently stable and did not detach. Example 3

[0032] The concentration was set at 1.0 × 10⁻⁶. -2 An acetonitrile solution of benzyl alcohol (M) was added to the sample cell. 3 mL of acetonitrile was added, and 7.5 mg of EY@MOF-808 prepared in Example 1 was uniformly dispersed in it. 10 μL of the benzyl alcohol solution was added quantitatively to the sample cell each time. The excitation wavelength was 425 nm, and the absorbance change from 450 nm to 750 nm was recorded. The fluorescence emission spectrum of the titration of EY@MOF-808 with the substrate benzyl alcohol is shown below. Figure 4 As shown in (a).

[0033] The concentration was set at 1.0 × 10⁻⁶. -2A benzaldehyde acetonitrile solution of M was prepared. 3 mL of acetonitrile was added to the sample cell, and 7.5 mg of EY@MOF-808 prepared in Example 1 was uniformly dispersed in it. 10 μL of the benzaldehyde solution was added quantitatively to the sample cell each time. The excitation wavelength was 425 nm, and the absorbance change from 450 nm to 750 nm was recorded. The fluorescence emission spectrum of the titration of EY@MOF-808 with the reaction product benzaldehyde is shown below. Figure 4 As shown in (b).

[0034] Based on the fluorescence intensity of EY@MOF-808 for benzyl alcohol and benzaldehyde in response to concentration, it can be seen that EY@MOF-808 selectively coordinates with the substrate benzyl alcohol, accelerating the electron transfer process, while the product benzaldehyde cannot bind, thus providing a basis for the selectivity of catalytic oxidation. Example 4

[0035] 3 mL of acetonitrile was added to a 20 mL photocatalytic reaction tube, followed by 5.0 μmol of EY@MOF-808 and 0.2 mmol of benzyl alcohol prepared in Example 1. The tube was sealed with a stopper, oxygen was introduced to eliminate interference from other gases, and an oxygen bulb was connected. The reaction was carried out under a 455 nm light source at 40 °C with continuous stirring for 12 hours. After the reaction was completed, the precipitate EY@MOF-808 was obtained by centrifugation and washed with dichloromethane until no product residue remained in the supernatant. The washed precipitate was vacuum dried to remove solvent molecules. The dried catalyst was then reintroduced into the above reaction system, and this process was repeated four times. The cyclic yield of the oxidation of benzyl alcohol to benzaldehyde by EY@MOF-808 is shown in the column graph. Figure 5 As shown, the selectivity for the product benzaldehyde did not decrease in the four cycles. Example 5

[0036] Add 3 mL of acetonitrile solution to a 20 mL photoreaction tube, then add 5.0 μmol of EY@MOF-808 prepared in Example 1 and 0.2 mmol of benzyl alcohol with substituents such as fluorine, chlorine, bromine, nitro, trifluoromethyl, and ethoxy. Seal the tube with a stopper, purge with oxygen to eliminate interference from other gases, and connect an oxygen bulb. React under a 455 nm light source at 40 °C with continuous stirring for 12 hours. After the reaction is complete, add 0.2 mmol of the internal standard 1,3,5-trimethoxybenzene, centrifuge to remove the catalyst EY@MOF-808, and concentrate the supernatant by vacuum distillation. 1 The yields were determined by ¹H NMR spectroscopy. Table 1 shows the yields of benzyl alcohol with the above substituents catalyzed by EY@MOF-808 to the corresponding benzaldehyde under light irradiation. The yields were moderate and the selectivity was greater than 99%, successfully expanding the substrate range.

[0037] Table 1. Yields of benzaldehyde produced by the catalytic oxidation of benzyl alcohol with multiple substituents using compound EY@MOF-808 in Example 1.

[0038]

[0039] The advantages of this invention are as follows: the post-modified metal-organic framework material prepared by this method has abundant unsaturated coordination sites that can distinguish the binding of different guests, which is beneficial to controlling the reactivity of chemical transformation, thereby achieving highly selective catalytic oxidation of benzyl alcohol to benzaldehyde without the generation of by-products, and exhibiting good stability in cyclic catalysis.

Claims

1. An application of a post-modified metal-organic framework material, characterized in that: Application of the post-modified metal-organic framework material in the catalytic oxidation of benzyl alcohol with or without substituents to prepare benzaldehyde derivatives; The substituents are selected from fluoroalkyl groups with 1-5 carbon atoms, alkyl groups with 1-5 carbon atoms, halogens, nitro groups, and alkoxy groups with 1-5 carbon atoms; The post-modified metal-organic framework material is prepared by the following steps: using Zr-based MOF-808 as the parent framework and eosin Y as the functional unit, the two are coordinated and anchored by a solvothermal method to obtain the post-modified metal-organic framework material. The structure of eosin Y is as follows: ； The molar ratio of Zr-based MOF-808 to eosin Y is 1:5-15.

2. The application according to claim 1, characterized in that, The molar ratio of Zr-based MOF-808 to eosin Y is 1:5-15. In the solvothermal method, the reaction solvent is selected from at least one of N,N-dimethylformamide, acetonitrile, and dimethylacetamide. The reaction temperature is 60-120 °C, and the reaction time is 15-96 hours.

3. The application according to claim 1, characterized in that, The molar ratio of Zr-based MOF-808 and eosin Y is selected from 1:5-10, and the reaction temperature in the solvothermal method is 60-120 °C, and the reaction time is 20-50 hours.

4. The application according to claim 3, characterized in that, Zr-based MOF-808 and eosin Y were added to a solvent and sonicated until a uniform suspension was formed. The suspension was then transferred to a high-pressure reactor and heated at 80-120 °C for 20-48 hours. After centrifugation or filtration, washing, and vacuum drying, the post-modified metal-organic framework material EY@MOF-808 was obtained.

5. The application according to claim 1, characterized in that, The substituents are selected from trifluoromethyl, F, Cl, Br, nitro, and methoxy.

6. The application according to claim 1, characterized in that, The wavelength range of light irradiation for the catalytic oxidation of benzyl alcohol to benzaldehyde by the post-modified metal-organic framework material is 400-520 nm.

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