Bimetal-based metal organic framework Pickering emulsion Pd0. 2Ni0. 8atMIL-101 and preparation method and application thereof

Abstract

The invention relates to the technical field of catalysts, in particular to a metal organic framework Pd < 0.2 > Ni < 0.8 >-coated MIL-101 Pickering emulsion based on bimetal as well as a preparation method and application of the metal organic framework Pd < 0.2 > Ni < 0.8 >-coated MIL-101 Pickering emulsion. According to the Pickering emulsion, water and methylbenzene are adopted as solvents at the same time, Pickering emulsion Pickering emulsion Pickering emulsion Pickering emulsion Pickering emulsion Pickering emulsion Pickering emulsion Pickering emulsion Pickering emulsion Pickering emulsion Pickering emulsion Pickering emulsion Pickering emulsion Pickering emulsion Pickering emulsion Pickering emulsion Pickering emulsion Pickering emulsion Pickering emulsion Pickering emulsion Pickering emulsion Pickering emulsion Pickering emulsion Pickering emulsion Pickering emulsion Pickering emulsion Pickering emulsion Pickering emulsion Pickering The preparation method of the Pd0. 2Ni0. 8at-MIL-101 emulsifier provided by the invention is simple, and the Pd0. 2Ni0. 8at-MIL-101 emulsifier shows ultrahigh catalytic ability in a reductive amination cascade reaction of nitrobenzene.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and relates to a metal organic framework Pd based on a bimetallic 0.2 Ni 0.8 @MIL-101 Pickering emulsion and its preparation method and application, specifically, it relates to the preparation and application of a metal organic framework material stabilized Pickering emulsion that catalyzes the tandem reductive amination reaction of nitrobenzene. Background Art

[0002] Metal organic frameworks (MOFs) are three-dimensional network structure crystals formed by self-assembly through metal ions or metal clusters as nodes and nitrogen and oxygen multidentate organic ligands of aromatic acids or bases as bridges. They are also called porous crystalline materials. The crystalline porous structure of MOF can limit the migration and aggregation of metal nanoparticles. MOF-bimetallic nanoparticle materials have better catalytic activity than their monometallic counterparts. The multifunctional catalyst of bimetallic NP@MOF with three active sites (acid-metal A-metal B) not only utilizes the catalytic synergy of bimetallic nanoparticles, but also utilizes the catalytic activity of MOF itself.

[0003] Pickering emulsion is an emulsion obtained by using ultrafine solid particles as emulsifiers. It is formed by the self-assembly of solid particles at the interface of two immiscible liquids, which can prevent the merging of droplets. They form a large number of water or oil droplets, greatly expanding the interfacial area of ​​water and oil. Compared with traditional emulsions, Pickering emulsion has the advantages of low toxicity and strong stability. Pickering interfacial catalysis has broad application prospects in acid-catalyzed transesterification, oxidation and acetalization reactions.

[0004] Tandem reaction refers to an efficient, energy-saving and environmentally friendly chemical synthesis method, which is increasingly attracting the interest of chemical researchers. Tandem reaction often refers to the continuous synthesis of two or more steps of reaction without the need to separate intermediates, and the final product can be directly synthesized, which can effectively reduce the emission of pollutants. In the field of organic catalysis, tandem reaction has become a very promising reaction development direction. Amines are valuable compounds that have been widely used in dyes, rubber materials, agricultural chemicals, drugs, surfactants, etc. Direct reductive amination is one of the most convenient and widely used methods for amine synthesis, and one of the most economical and cleanest routes is to use nitroaromatics instead of amines for direct reductive amination of aldehydes and ketones. Summary of the invention

[0005] The present invention aims to provide a catalytic Pd having both acid-metal dual functional active sites. 0.2 N i0.8 @MIL-101 stabilized Pickering emulsion is used to efficiently catalyze the tandem reaction of nitrobenzene reductive amination.

[0006] The technical solution adopted by the present invention is: a metal organic framework Pd based on bimetallic 0.2 Ni 0.8 @MIL-101 emulsifier, the preparation method is as follows: MIL-101 is dispersed in n-hexane, and a methanol solution of sodium chloropalladate and nickel chloride is added dropwise under ultrasonic stirring, ultrasonic stirring and mixing to disperse evenly, and centrifugal drying is performed; sodium borohydride is added to methanol, and sodium borohydride and methanol release hydrogen, and the upper layer of bubbling liquid is quickly absorbed and added to MIL-101, sodium chloropalladate and nickel chloride, and stirring is continued for 30 minutes, and washed with methanol, and vacuum dried to obtain Pd 0.2 Ni 0.8 @MIL-101 emulsifier.

[0007] The above-mentioned bimetallic metal organic framework Pd 0.2 N i0.8 @MIL-101 emulsifier, by mass ratio, MIL-101:Pd:Ni=500:2:8.

[0008] The above-mentioned bimetallic metal organic framework Pd 0.2 N i0.8 @MIL-101 emulsifier, the preparation method of MIL-101 is as follows: add chromium nitrate nonahydrate, terephthalic acid, glacial acetic acid and ultrapure water into a hydrothermal synthesis reactor for reaction, cool to room temperature after the reaction is completed, wash with DMF and anhydrous ethanol in turn, and vacuum dry to obtain the precursor MIL-101.

[0009] The above-mentioned bimetallic metal organic framework Pd 0.2 N i0.8 @MIL-101 emulsifier, molar ratio, chromium nitrate nonahydrate: terephthalic acid = 1:1.

[0010] The above-mentioned bimetallic metal organic framework Pd 0.2 N i0.8 @MIL-101 emulsifier, the reaction is carried out in an oven at 473K for 8 hours.

[0011] A bimetallic metal-organic framework Pd 0.2 N i0.8 @MIL-101 Pickering emulsion, the preparation method is as follows: add the Pd 0.2 Ni 0.8 @MIL-101 emulsifier was added with toluene and water, and then shaken vigorously after ultrasonication to obtain Pd 0.2 Ni 0.8 @MIL-101 stabilized Pickering emulsion.

[0012] The above-mentioned bimetallic metal organic framework Pd 0.2 N i0.8 @Application of MIL-101 Pickering emulsion catalyzed tandem reductive amination of nitrobenzene.

[0013] The above application is carried out in the following method: nitrobenzene, sodium borohydride and a catalyst are reacted in a container, benzaldehyde is added, and the reaction is continued for 20 minutes, wherein the catalyst is Pd 0.2 Ni 0.8 @MIL-101 Pickering Lotion.

[0014] In the above application, the molar ratio of nitrobenzene, sodium borohydride and benzaldehyde is 1:2:1.2.

[0015] In the above application, the reaction is carried out at a temperature of 303K for 20 minutes.

[0016] Pd of the present invention 0.2 Ni 0.8 In the MIL-101-stabilized Pickering emulsion, the palladium-nickel alloy provides metal sites to catalyze the first step of nitrobenzene reduction reaction, and MIL-101 provides abundant acid sites (Cr clusters in MIL-101) to catalyze the second step reaction, thereby synergistically catalyzing the cascade reaction. The reaction formula is as follows:

[0017]

[0018] The beneficial effects of the present invention are as follows: in the PdNi@MIL-101 Pickering emulsion provided by the present invention, Pd and Ni are attached to the pores of MIL-101, effectively preventing the aggregation of nanoparticles. The electronic structure of the active site is adjusted by adding a second low-cost metal, thereby improving the catalytic activity. In addition, after 5 cycles of testing, the Pd 0.2 Ni 0.8 @MIL-101 still maintains high catalytic activity, has high stability and recyclability. 0.2 Ni 0.8 @MIL-101 has excellent catalytic performance in the tandem reductive amination reaction of nitrobenzene. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the Pd formed 0.2 Ni 0.8 Optical microscope photo of @MIL-101 Pickering emulsion.

[0020] Figure 2 The present invention Pd 0.2 Ni 0.8 @MIL-101 Pd in ​​Pickering Emulsion 0.2Ni 0.8 @TEM image of MIL-101.

[0021] Figure 3 The present invention Pd 0.2 Ni 0.8 @MIL-101 Pd in ​​Pickering Emulsion 0.2 Ni 0.8 @PXRD pattern of MIL-101 material.

[0022] Figure 4 The present invention Pd 0.2 Ni 0.8 Comparison of the catalytic activity of @MIL-101 Pickering emulsion, Pd@MIL-101 Pickering emulsion and Ni@MIL-101 Pickering emulsion for nitrobenzene reduction reaction.

[0023] Figure 5 The present invention Pd 0.2 Ni 0.8 @The catalytic activity diagram of the five-cycle catalytic reaction of MIL-101 Pickering emulsion.

[0024] Figure 6 The present invention Pd 0.2 Ni 0.8 @MIL-101 Optical micrograph of the emulsion formed by the catalyst recovered after five cycles of catalytic reaction of Pickering emulsion. DETAILED DESCRIPTION

[0025] Example 1 A metal organic framework based on bimetallic Pd 0.2 Ni 0.8 @MIL-101 The preparation method of the stabilized Pickering emulsion (I) is as follows:

[0026] 1. Synthesis of MIL-101 powder

[0027] Chromium nitrate nonahydrate (3.2 g, 0.008 mol) and terephthalic acid (1.312 g, 0.008 mol) were poured into a 80 ml hydrothermal synthesis reactor. Then 2.1708 ml of 99.95% glacial acetic acid and 40 ml of ultrapure water were accurately measured with a pipette and added to the reactor. The reactor was placed in an oven at 473 K for 8 hours. After the reaction was completed, it was cooled to room temperature, washed three times with DMF, then washed three times with ethanol, and finally placed in a vacuum drying oven and dried at 423 K for 12 hours to obtain the precursor MIL-101.

[0028] 2. Preparation of sodium chloropalladate solution and nickel chloride solution

[0029] Accurately weigh 0.12g of solid palladium chloride and 0.044g of solid sodium chloride into a 10mL glass bottle, then add 4mL of methanol to the bottle, heat slightly until completely dissolved, and stir overnight to obtain a 0.17mol / L brown sodium chloropalladate solution.

[0030] Accurately weigh 0.202 ml of nickel chloride hexahydrate solid and pour it into a 5 ml glass bottle, then add 1.85 ml of methanol to the bottle and heat it slightly until it is completely dissolved. A 1.85 mol / L light green nickel chloride solution is obtained.

[0031] 3. Pd 0.2 Ni 0.8 @MIL-101 powder synthesis

[0032] Accurately weigh 200 mg of MIL-101 and place it in a 100 mL three-necked flask. Use a pipette to accurately add 40 mL of n-hexane, ultrasonicate for 15 minutes to make it evenly dispersed, and drop 165 ul of sodium chloropalladate solution and 185 ul of nickel chloride solution under vigorous stirring. Ultrasonicate for 15 minutes and stir for 60 minutes to make it evenly mixed and dispersed, and centrifuge to dry; accurately weigh 34.48 mg of sodium borohydride solid and add it to 20 ml of methanol. Sodium borohydride and methanol release hydrogen. Quickly absorb the upper layer of bubbling liquid and add it to MIL-101, sodium chloropalladate and nickel chloride. Continue stirring for 30 minutes, wash with methanol three times, and finally dry it in a 333K vacuum oven for 6 hours to obtain Pd 0.2 Ni 0.8 @MIL-101 materials;

[0033] 4. Synthesis of Pd@MIL-101 and Ni@MIL-101 powders

[0034] Accurately weigh 200 mg of MIL-101 and place it in a 100 mL three-necked flask. Use a pipette to accurately add 40 mL of n-hexane, ultrasonicate for 15 min to make it evenly dispersed, and drop 350 ul of 0.21 mol / L sodium chloropalladate solution or 350 ul of 0.39 mol / L nickel chloride solution under vigorous stirring. Ultrasonicate for 15 min and stir for 60 min to make it evenly dispersed, and centrifuge to dry; Accurately weigh 34.48 mg of sodium borohydride solid and add it to 20 ml of methanol. Sodium borohydride and methanol release hydrogen. Quickly absorb the upper layer of bubbling liquid and add it to MIL-101, sodium chloropalladate and nickel chloride powders. Continue stirring for 30 min, wash three times with methanol, and finally dry in a 333K vacuum oven for 6 h to obtain Pd@MIL-101 and Ni@MIL-101 materials respectively;

[0035] 5. Pd 0.2 Ni 0.8Preparation of Pickering emulsions stabilized by @MIL-101, Pd@MIL-101 and Ni@MIL-101

[0036] 25 mg of Pd 0.2 Ni 0.8 2 mL of toluene and 3 mL of deionized water were added to Pd@MIL-101, Pd@MIL-101, and Ni@MIL-101, and ultrasonicated for 5 min at 100 W power and then vigorously shaken for 5 min to obtain Pd@MIL-101, Pd@MIL-101, and Ni@MIL-101, respectively. 0.2 Ni 0.8 Pickering emulsions stabilized by Pd@MIL-101, Pd@MIL-101, and Ni@MIL-101.

[0037] (II) Testing

[0038] Figure 1 The formed Pd 0.2 Ni 0.8 @MIL-101Pickering emulsion optical microscope photo. It can be seen that Pd 0.2 Ni 0.8 @MIL-101 The stable Pickering emulsion droplets are evenly dispersed and uniform in size.

[0039] Figure 2 Based on Pd 0.2 Ni 0.8 @TEM image of MIL-101 material shows that Pd and Ni nanoparticles are evenly dispersed in the Pd 0.2 Ni 0.8 @MIL-101 material.

[0040] Figure 3 Based on Pd 0.2 Ni 0.8 @MIL-101 material X-ray diffraction pattern (PXRD), indicating that Pd 0.2 Ni 0.8 @MIL-101 material has good crystallinity during the synthesis process.

[0041] Example 2 Based on Pd 0.2 Ni 0.8 @MIL-101 material catalytic function of nitrobenzene reductive amination tandem reaction (I) A bimetallic metal organic framework based on Pd prepared in Example 1 0.2 Ni 0.8 @MIL-101 stabilized Pickering emulsion as catalyst for tandem reductive amination of nitrobenzene

[0042] Here’s how:

[0043] The Pd obtained in step 5 of Example 1 was0.2 Ni 0.8 The Pickering emulsion of @MIL-101 was added to a 10 mL three-necked reaction container, and then 1.0 mmol nitrobenzene and 2 mmol sodium borohydride were added in sequence, and the reaction was carried out at a temperature of 303 K for 20 min, and then 1.2 mmol benzaldehyde was added and the reaction was carried out for 20 min to generate N-benzylidene aniline derivatives. For comparison, the Pd@MIL-101 or Ni@MIL-101 stabilized Pickering emulsion obtained in step 5 of Example 1 was added to a 10 mL three-necked reaction container, and then 1.0 mmol nitrobenzene and 2 mmol sodium borohydride were added in sequence, and the reaction was carried out at a temperature of 303 K for 20 min. The yield of the product was monitored by gas chromatography (GC).

[0044] During the reaction, Pd 0.2 Ni 0.8 @The experimental results of the catalytic performance of the MIL-101 stabilized Pickering emulsion for the tandem reaction were detected by GC. As the reaction proceeded, the yield of the reaction gradually increased. When the reaction was carried out for 40 minutes, the yield of the reaction had reached 99%.

[0045] (II) Based on Pd 0.2 Ni 0.8 @MIL-101 Recycling of stabilized Pickering emulsion

[0046] After the reaction was completed, the reaction mixture was centrifuged and filtered. 0.2 Ni 0.8 @MIL-101 is separated, washed with ethanol, filtered and dried. Recover Pd 0.2 Ni 0.8 @MIL-101 material.

[0047] Specific operation of the recycling experiment: using the recycled Pd 0.2 Ni 0.8 @MIL-101 material was used to prepare Pickering emulsion again to catalyze the reductive amination reaction of nitrobenzene.

[0048] The experimental results are as follows Figure 4 , Figure 5 and Figure 6 As shown, Figure 4 It is Pd 0.2 Ni 0.8 Comparison of catalytic activity of Pickering emulsions stabilized by Pd@MIL-101, Pd@MIL-101, and Ni@MIL-101. 0.2 Ni 0.8 The yield and conversion rate of Pd@MIL-101 Pickering emulsion are higher than those of single metal Pd@MIL-101 and Ni@MIL-101 Pickering emulsion. Figure 5 It is Pd0.2 Ni 0.8 @MIL-101 Pickering emulsion catalytic activity diagram of five cycles of catalytic reaction. After five cycles, the yield and conversion rate of the experiment were both higher than 95%, indicating that the activity of the catalyst did not decrease significantly. Figure 6 It is Pd 0.2 Ni 0.8 @MIL-101 Pickering emulsion was subjected to five cycles of catalytic reaction. The recovered catalyst formed an emulsion optical microscopic image. It can be seen from the image that the recovered catalyst can still stably form a Pickering emulsion. This indicates that Pd 0.2 Ni 0.8 @MIL-101 can be recycled as a catalyst for the reductive amination of nitrobenzene.

Claims

1. A bimetallic metal-organic framework Pd 0.2 Ni 0.8 @MIL-101 emulsifier, characterized in that The preparation method is as follows: MIL-101 is dispersed in n-hexane, and a methanol solution of sodium chloropalladate and nickel chloride is added dropwise under ultrasonic stirring, ultrasonic stirring and mixing to disperse evenly, and centrifugal drying is performed; sodium borohydride is added to methanol, and sodium borohydride and methanol release hydrogen, and the upper layer of bubbling liquid is quickly absorbed and added to MIL-101, sodium chloropalladate and nickel chloride, and stirring is continued for 30 minutes, and the mixture is washed with methanol and vacuum dried to obtain Pd 0.2 Ni 0.8 @MIL-101 emulsifier.

2. A bimetallic metal organic framework Pd according to claim 1 0.2 N i0.8 @MIL-101 emulsifier, characterized in that In terms of mass ratio, MIL-101:Pd:Ni=500:2:

8.

3. A bimetallic metal organic framework Pd according to claim 1 0.2 N i0.8 @MIL-101 emulsifier, characterized in that The preparation method of MIL-101 is as follows: adding chromium nitrate nonahydrate, terephthalic acid, glacial acetic acid and ultrapure water into a hydrothermal synthesis reactor for reaction, cooling to room temperature after the reaction is completed, washing with DMF and anhydrous ethanol in turn, and vacuum drying to obtain the precursor MIL-101.

4. A bimetallic metal organic framework Pd according to claim 3 0.2 N i0.8 @MIL-101 emulsifier, characterized in that In terms of molar ratio, chromium nitrate nonahydrate: terephthalic acid = 1:

1.

5. A bimetallic metal organic framework Pd according to claim 3 0.2 N i0.8 @MIL-101 emulsifier, characterized in that The reaction was carried out in an oven at 473K for 8h.

6. A metal-organic framework based on bimetallic Pd 0.2 N i0.8 @MIL-101 Pickering emulsion, characterized in that, The preparation method is as follows: adding the Pd 0.2 Ni 0.8 @MIL-101 emulsifier was added with toluene and water, and then shaken vigorously after ultrasonication to obtain Pd 0.2 Ni 0.8 @MIL-101 stabilized Pickering emulsion.

7. A bimetallic metal organic framework Pd according to claim 6 0.2 N i0.8 @Application of MIL-101 Pickering emulsion catalyzed tandem reductive amination of nitrobenzene.

8. The use according to claim 7, characterized in that: The method is as follows: nitrobenzene, sodium borohydride and a catalyst are placed in a container for reaction, benzaldehyde is added, and the reaction is continued for 20 minutes. The catalyst is Pd 0.2 Ni 0.8 @MIL-101 Pickering Lotion.

9. The use according to claim 8, characterized in that: The molar ratio of nitrobenzene, sodium borohydride and benzaldehyde is 1:2:1.

2.

10. The use according to claim 8, characterized in that: The reaction was carried out at a temperature of 303 K for 20 min.

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