Preparation method and application of post-modified metal organic framework material for catalytically oxidizing benzyl alcohol into benzaldehyde

Abstract

The invention discloses a preparation method and application of a post-modified metal organic framework material for catalytically oxidizing benzyl alcohol into benzaldehyde, and belongs to the technical field of photocatalytic materials. Zr-based MOF-808 is used as a parent framework, organic dye eosin Y (eosin Y, EY) is used as a functional unit, and the parent framework and the functional unit are coordinated and anchored to obtain the post-modified metal organic framework material EY-MOF-808. The post-modified metal organic framework material EY (at) MOF-808 has abundant unsaturated coordination sites, provides a way for distinguishing the combining capacity of objects with different groups and improving reactivity and selectivity, and effectively avoids excessive oxidation of benzaldehyde. The EY-coated MOF-808 is suitable for catalyzing benzyl alcohol with a plurality of substituent groups, and corresponding benzaldehyde is obtained at the selectivity of more than 99%. In addition, the EY-coated MOF-808 can be recycled for four times, the selectivity is not reduced, and toxic dyes are prevented from being released into the environment.

Description

Technical Field

[0001] The invention relates to a preparation method and application of a post-modified metal organic framework material for catalytically oxidizing benzyl alcohol to benzaldehyde, belonging to the technical field of photocatalytic materials. Background Art

[0002] As key intermediates in organic synthesis, aldehyde compounds are widely used in biomedicine, food additives, dye synthesis and other fields, and they play an important role in industrial chemistry. With the rapid development of the economy, my country's demand for high-quality benzaldehyde is increasing. In addition to extraction from natural products, the selective oxidation of alcohols to generate aldehydes is an important scientific research and industrial manufacturing method in synthetic chemistry. Traditional alcohol oxidation still relies on strong oxidants or precious metal catalysts, which are limited in their application due to high cost, harsh reaction conditions, and low atom economy. In addition, since aldehydes are more easily activated than alcohols, over-oxidation to acids greatly reduces the selectivity of the oxidation reaction. Therefore, there is an urgent need to develop a highly selective and environmentally friendly photocatalytic system to provide an effective solution for the efficient conversion of alcohols into aldehydes.

[0003] On the one hand, organic photoredox catalysts remove the restriction of redox potential through hydrogen atom transfer (HAT), and use molecular oxygen as a green terminal oxidant, providing an opportunity to activate C-H bonds under mild conditions. As a cheap and readily available heteroanthracene dye, Eosin Y (EY) has been successfully used for C-H bond activation, but it is prone to aggregation-induced quenching and photobleaching in homogeneous systems, which greatly limits its application. On the other hand, metal organic frameworks (MOFs) composed of orderly connections of organic ligands and inorganic metal ions / cluster nodes are used as heterogeneous catalysts for various organic transformations. MOFs constructed by multi-nuclear metal clusters have abundant unsaturated coordination sites, which provide a good way to distinguish the binding ability of guests with different groups and improve reactivity and selectivity. Introducing photosensitive units into MOFs is an effective way to improve photocatalytic activity in recent years. The introduction of photosensitive units as ligands has received widespread attention in the field of organic catalysis, but there are problems such as low catalyst synthesis yield and poor selectivity. Summary of the invention

[0004] In order to overcome the deficiencies in the prior art, the present invention aims to provide a preparation method and application of a post-modified metal organic framework material for highly selective catalytic oxidation of benzyl alcohol to benzaldehyde. The post-modification method provides a simple and flexible platform for the combination of MOFs and organic catalysts with excellent activation performance. The post-modified metal organic framework material EY@MOF-808 prepared by the method can be used for highly selective catalytic oxidation of benzyl alcohol to benzaldehyde. The present invention uses a solvent-assisted ligand incorporation method to anchor the functional unit eosin Y bidentate bridging coordination on the Zr6O4(OH)4 cluster of MOF-808. Importantly, the strong interaction between the potential unsaturated coordination sites close to eosin Y on the metal cluster and the substrate benzyl alcohol not only ensures the high efficiency of the HAT process to activate the CH bond, but also avoids the over-oxidation of the product benzaldehyde. Under optimized conditions, benzyl alcohol with a variety of substituents was used as a substrate, and the corresponding benzaldehyde was obtained under the catalysis of EY@MOF-808, with selectivities greater than 99%, successfully expanding the substrate range. In addition, 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 new prospect for a unique and economical highly selective MOFs photocatalyst scheme.

[0005] In order to achieve the above-mentioned invention purpose and solve the problems existing in the prior art, the technical solution adopted by the present invention is: a preparation method of a post-modified metal organic framework material for highly selective catalytic oxidation of benzyl alcohol to benzaldehyde, using Zr-based MOF-808 as a parent framework and organic dye eosin Y as a functional unit, and the two are coordinated and anchored by a solvothermal method to obtain a post-modified metal organic framework material EY@MOF-808, and the synthesis route is as follows: MOF-808 + EY → EY@MOF-808 Among them, the structure of eosin Y is: .

[0006] Some specific steps for preparing the post-modified metal organic framework material: 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 to 120 ° C, and the reaction time is 15 to 96 hours.

[0007] In some specific steps for preparing the post-modified metal organic framework material, the molar ratio of Zr-based MOF-808 and eosin Y is selected from 1:5 to 10, the reaction temperature is 60 to 120 °C, and the reaction time is 20 to 50 hours.

[0008] Some specific preparation steps of the post-modified metal organic framework material are as follows: 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.

[0009] Some specific preparation steps of the post-modified metal organic framework material are as follows: Zr-based MOF-808 and eosin Y are added to a solvent and ultrasonically treated to form a uniform suspension, and then transferred to a high-pressure reactor, heated at 80-120 °C for 20-48 hours, centrifuged or filtered, washed, and vacuum dried to obtain the post-modified metal organic framework material EY@MOF-808.

[0010] Some specific preparation steps of the post-modified metal organic framework material are as follows: Zr-based MOF-808 and eosin Y are added to DMF and ultrasonicated to form a uniform suspension, and then transferred to a high-pressure reactor, heated at 100 ° C. for 24 hours, centrifuged or filtered, washed, and vacuum dried to obtain the post-modified metal organic framework material EY@MOF-808.

[0011] A specific method for preparing a post-modified metal organic framework material comprises the following steps: According to the literature, trimesic acid (21 mg) and zirconium oxychloride octahydrate (97 mg) were dissolved in a flask containing N,N -Dimethylformamide (DMF, 3 mL) and formic acid (3 mL) solution, ultrasonic until completely dissolved, then transferred to a polytetrafluoroethylene-lined autoclave and heated at 100 °C for 24 hours. After cooling to room temperature, the white powder was collected by centrifugation and washed with DMF and acetone in turn. Finally, the white powder was vacuum dried at 100 °C overnight to obtain the mother framework MOF-808.

[0012] The metal organic framework material MOF-808 of the present invention is a known material and can be prepared with reference to the reference J. Am. Chem. Soc. 2018, 140, 18208-18216.

[0013] MOF-808 (0.0389 mmol, 53 mg) and eosin Y (0.389 mmol, 252 mg) were ultrasonically mixed in DMF (5 mL) at a molar ratio of 1:10 until a uniform suspension was formed, and then transferred to a polytetrafluoroethylene-lined autoclave and heated at 100 °C for 24 h. After cooling to room temperature, the orange-red powder was collected by centrifugation and filtered and washed several times with DMF, acetone and ethanol in sequence until the supernatant was clear and transparent with no eosin Y dye adsorption residue. Finally, the orange-red powder was vacuum dried at 100 °C overnight to obtain the post-modified metal organic framework EY@MOF-808.

[0014] The post-modified metal organic framework material is used in the reaction of preparing benzaldehyde derivatives by catalytic oxidation of benzyl alcohol containing or not containing substituents.

[0015] The substituent is selected from a fluoroalkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms, a halogen group, a nitro group, and an alkoxy group having 1 to 5 carbon atoms.

[0016] The substituent is selected from trifluoromethyl, F, Cl, Br, nitro, and methoxy.

[0017] The post-modified metal organic framework material EY@MOF-808 is used in the selective catalytic oxidation of benzyl alcohol to benzaldehyde.

[0018] The post-modified metal organic framework material catalytically oxidizes benzyl alcohol to prepare benzaldehyde under light at a wavelength selected from 400 to 520 nm.

[0019] The beneficial effects of the present invention are: a preparation method and application of a post-modified metal organic framework material for highly selective catalytic oxidation of benzyl alcohol to benzaldehyde, using Zr-based MOF-808 as the parent framework and organic dye eosin Y as the functional unit, and the two are coordinated and anchored to obtain the post-modified metal organic framework material. Compared with the existing technology, the method has mild conditions and is easy to synthesize. On the one hand, the introduction of eosin Y successfully expands the light absorption properties 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 close to eosin Y on the post-modified metal organic framework material Zr6O4(OH)4 cluster and the substrate benzyl alcohol avoids excessive oxidation of the product benzaldehyde. After optimizing the reaction conditions, under the irradiation of blue light, EY@MOF-808 catalytically oxidized benzyl alcohol to obtain benzaldehyde with a selectivity greater than 99%, and can be stably recycled four times. The post-modified metal organic framework material and method provide new ideas for expanding green organic catalytic strategies. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the powder X-ray diffraction (PXRD) of the target compound EY@MOF-808 in Example 1.

[0021] Figure 2 This is the X-ray photoelectron spectrum (XPS) of the target compound EY@MOF-808 in Example 1.

[0022] Figure 3 This is a curve chart showing the change in reaction yield over time of the compound EY@MOF-808 prepared in Example 1 under light conditions for catalytic oxidation of benzyl alcohol to produce benzaldehyde.

[0023] Figure 4 This is a fluorescence emission spectrum diagram of the titration of the compound EY@MOF-808 prepared in Example 1 with the reaction substrate benzyl alcohol and the product benzaldehyde.

[0024] Figure 5 This is a bar chart of the cycle yield of benzaldehyde produced by catalytic oxidation of benzyl alcohol by compound EY@MOF-808 prepared in Example 1. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the embodiments. Example 1

[0026] Trimellitic acid (21 mg) and zirconium oxychloride octahydrate (97 mg) were dissolved in a solution containing DMF (3 mL) and formic acid (3 mL), ultrasonicated until completely dissolved, and then transferred to a polytetrafluoroethylene-lined autoclave and heated at 100 °C for 24 h. After cooling to room temperature, the white powder was collected by centrifugation and washed with DMF and acetone in sequence. Finally, the white powder was vacuum dried at 100 °C overnight to obtain the parent framework MOF-808. Subsequently, MOF-808 (0.0389 mmol, 53 mg) and eosin Y (0.389 mmol, 252 mg) were ultrasonicated in DMF (5 mL) at a molar ratio of 1:10 until a uniform suspension was formed, and then transferred to a polytetrafluoroethylene-lined autoclave and heated at 100 °C for 24 h. After cooling to room temperature, the orange-red powder was collected by centrifugation and filtered and washed several times with DMF, acetone and ethanol in turn until the supernatant was clear and transparent with no adsorption of eosin Y dye. Finally, the orange-red powder was vacuum dried at 100 °C overnight to obtain the post-modified metal organic framework material EY@MOF-808. The X-ray diffraction of the material is shown in Figure 1The PXRD of MOF-808 and EY@MOF-808 is shown in Figure 1. The experimental instrument used is a Rigaku Smart Lab model X-ray diffractometer. This figure shows that MOF-808 was successfully synthesized and the post-coordination modification process of eosin Y did not destroy the structure of MOF-808. The X-ray photoelectron spectra of MOF-808 and EY@MOF-808 are shown in Figure 2. Figure 2 As shown in the XPS O 1s, the experimental instrument used is the Thermo ESCALAB Xi+ model X-ray photoelectron spectrometer. In EY@MOF-808, since the unsaturated nodes coordinate and anchor the eosin Y molecules in a bidentate bridging manner, compared with MOF-808, the peak area of ​​the Zr−O bond is reduced and the O−C=O signal is enhanced. Example 2

[0027] Add 3 mL of acetonitrile solution to a 20 mL photoreaction tube, then add EY@MOF-808 (5.0 μmol) and benzyl alcohol (0.2 mmol) prepared in Example 1, seal with a sealing stopper, introduce oxygen to exclude interference from other gases, connect an oxygen ball, and stir the reaction continuously at 40 °C for 12 hours under irradiation with a light source of 455 nm. After the reaction is completed, add the internal standard 1,3,5-trimethoxybenzene (0.2 mmol), centrifuge to remove the catalyst EY@MOF-808, and vacuum distill and concentrate the supernatant. 1 The yield was determined by H NMR spectroscopy. The yield curve of the reaction of EY@MOF-808 catalytic oxidation of benzyl alcohol to benzaldehyde under light conditions is shown as follows: Figure 3 As shown in the graph, the yield of benzyl alcohol increased linearly with time and stabilized within 12 h. In addition, the yield did not increase further after 3 h of removal of EY@MOF−808, indicating that EY@MOF−808 is a true heterogeneous photocatalyst and the post-modified anchored eosin Y is stable enough without shedding. Example 3

[0028] The concentration is 1.0×10 -2 3 mL of acetonitrile was added to the sample pool, and EY@MOF-808 (7.5 mg) prepared in Example 1 was evenly dispersed therein. 10 μl of the benzyl alcohol solution was quantitatively added to the sample pool each time, and the excitation wavelength was 425 nm. The absorbance change from 450 nm to 750 nm was recorded. The fluorescence emission spectrum of EY@MOF-808 titrated with the reaction substrate benzyl alcohol is shown in Figure 1. Figure 4 (a) shown.

[0029] The concentration is 1.0×10 -23 mL of acetonitrile was added to the sample pool, and EY@MOF-808 (7.5 mg) prepared in Example 1 was evenly dispersed therein. 10 μl of the benzaldehyde solution was quantitatively added to the sample pool each time, and the excitation wavelength was 425 nm. The absorbance change from 450 nm to 750 nm was recorded. The fluorescence emission spectrum of EY@MOF-808 titrated with the reaction product benzaldehyde is shown in Figure 2. Figure 4 (b) is shown.

[0030] From the fluorescence intensity of EY@MOF-808 to benzyl alcohol and benzaldehyde relative to their concentrations, we can see that EY@MOF-808 selectively coordinates with the substrate benzyl alcohol to accelerate the electron transfer process, while the product benzaldehyde cannot bind, thus providing a basis for the selectivity of catalytic oxidation. Example 4

[0031] Add 3 mL of acetonitrile to a 20 mL photoreactor tube, then add EY@MOF-808 (5.0 μmol) prepared in Example 1 and benzyl alcohol (0.2 mmol), seal it with a sealing stopper, introduce oxygen to exclude interference from other gases, connect an oxygen ball, and stir the reaction continuously at 40 °C for 12 hours under irradiation with a light source of 455 nm wavelength. After the reaction is completed, the precipitate EY@MOF-808 is obtained by centrifugation and washed with dichloromethane until no product remains in the supernatant. The washed precipitate is vacuum dried to remove solvent molecules. The dried catalyst is re-introduced into the above reaction system, and this is repeated four times. The cycle yield of EY@MOF-808 catalytic oxidation of benzyl alcohol to produce benzaldehyde is shown in the column chart. Figure 5 As shown in Figure 3, the selectivity to the product benzaldehyde did not decrease during the four cycles. Example 5

[0032] Add 3 mL of acetonitrile solution to a 20 mL photoreaction tube, then add EY@MOF-808 (5.0 μmol) prepared in Example 1 and benzyl alcohol (0.2 mmol) with fluorine, chlorine, bromine, nitro, trifluoromethyl, ethoxy and other substituents, respectively, seal with a sealing plug, pass oxygen to exclude interference from other gases, connect an oxygen ball, and stir the reaction continuously at 40 °C for 12 hours under irradiation with a light source of 455 nm wavelength. After the reaction is completed, add the internal standard 1,3,5-trimethoxybenzene (0.2 mmol), centrifuge to remove the catalyst EY@MOF-808, and vacuum distill and concentrate the supernatant. 1 The yield was determined by H NMR spectroscopy. The yields of benzyl alcohol with the above substituents catalyzed by EY@MOF-808 under light irradiation to generate the corresponding benzaldehyde are shown in Table 1. The yields are moderate and the selectivity is greater than 99%, which successfully expands the substrate range.

[0033] Table 1 Example 1 Preparation of compound EY@MOF-808 catalytic oxidation of benzyl alcohol with various substituents to produce the corresponding benzaldehyde yield

[0034] The advantages of the present invention are that the post-modified metal organic framework material prepared by the method has abundant unsaturated coordination sites with the ability to distinguish the binding of different guests, which is conducive to controlling the reactivity of chemical conversion, thereby realizing highly selective catalytic oxidation of benzyl alcohol to benzaldehyde without the generation of by-products, and showing good stability in cyclic catalysis.

Claims

1. A post-modified metal organic framework material, characterized in that: Prepared using the following steps: The post-modified metal organic framework material is obtained by using Zr-based MOF-808 as a parent framework and eosin Y as a functional unit, and the two are coordinated and anchored by a solvothermal method; Among them, the structure of eosin Y is: ； The molar ratio of Zr-based MOF-808 and eosin Y is 1:5~15.

2. The post-modified metal organic framework material according to claim 1, characterized in that: The molar ratio of Zr-based MOF-808 and eosin Y is 1:5-15, 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.

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

4. The post-modified metal organic framework material according to claim 3, characterized in that: Zr-based MOF-808 and eosin Y are added to a solvent and ultrasonically treated to form a uniform suspension, and then transferred to a high-pressure reactor, heated at 80-120 °C for 20-48 hours, centrifuged or filtered, washed, and vacuum dried to obtain the post-modified metal organic framework material EY@MOF-808.

5. Use of the post-modified metal organic framework material according to any one of claims 1 to 4 in the catalytic oxidation of benzyl alcohol containing or not containing a substituent to prepare a benzaldehyde derivative; The substituent is selected from a fluoroalkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms, a halogen group, a nitro group, and an alkoxy group having 1 to 5 carbon atoms.

6. The use according to claim 5, characterized in that: The substituent is selected from trifluoromethyl, F, Cl, Br, nitro, and methoxy.

7. The use according to claim 5, characterized in that: The post-modified metal organic framework material catalyzes the oxidation of benzyl alcohol to prepare benzaldehyde under light with a wavelength range of 400-520 nm.

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