Core-shell structure Au-coated CeO2 nano-catalyst as well as preparation method and application thereof

Abstract

The invention discloses a core-shell structure Au-coated CeO2 nano-catalyst and a preparation method and application thereof, and belongs to the technical field of core-shell structure catalysts.The preparation method of the catalyst comprises the following steps that S1, a chloroauric acid solution and a low-concentration cerium chloride solution are added into deionized water and stirred and mixed at the temperature of 5 DEG C, then an ammonia water solution is rapidly added, stirring and mixing are conducted at the temperature of 5 DEG C, and a mixed solution is obtained; quickly adding a high-concentration cerium chloride solution, and continuously stirring for 30 minutes to obtain a mixed solution; s2, carrying out centrifugal separation on the mixed solution to retain a precipitate, washing the precipitate with deionized water and absolute ethyl alcohol, and carrying out freeze drying to obtain a catalyst precursor; s3, performing cleaning treatment and annealing treatment on the catalyst precursor, and cooling to room temperature to obtain a core-shell structure Au-coated CeO2 nano-catalyst; when the catalyst is applied to catalytic synthesis of the BODIPY fluorescent dye, excellent catalytic performance and recycling performance are shown, and the yield of the BODIPY fluorescent dye can be remarkably increased.

Description

Technical Field

[0001] The present invention belongs to the technical field of core-shell structure catalysts, and specifically relates to a core-shell structure Au@CeO 2 Nanocatalyst and its preparation method and application. Background Art

[0002] Fluoroboron dipyrrole fluorescent dyes are compounds with fluoroboron dipyrrole as the skeleton. They have the advantages of high fluorescence quantum yield, good photostability, and easy chemical modification. They are widely used in various fields such as biology, materials, and medicine. Introducing a conjugated structure or constructing an electron donor-electron donor unit in the fluoroboron dipyrrole structure can improve the photophysical properties of fluoroboron dipyrrole fluorescent dyes; the aniline group has good photophysical properties and a small molecular weight, which is easy to chemically couple; introducing the aniline group into the fluoroboron dipyrrole structure expands the conjugated system of the fluoroboron dipyrrole molecule, which helps to increase its fluorescence quantum yield and molar absorption coefficient, thereby improving the fluorescence intensity; by introducing the aniline group, the fluoroboron dipyrrole fluorescent dye can be further functionalized and modified, and targeting groups, reactive groups, etc. can be introduced to expand its application range.

[0003] The Chinese patent with the announcement number CN113308130B discloses a method for preparing a fluoroboron dipyrrole fluorescent dye, wherein an intermediate containing a fluoroboron dipyrrole structure, allyl boric acid pinacol ester, potassium carbonate, tetrakistriphenylphosphine palladium, and an organic solvent are mixed, and the molar ratio of the intermediate, allyl boric acid pinacol ester, potassium carbonate, and tetrakistriphenylphosphine palladium is 1:1.4-1.6:5.8-6.2:0.06-0.08, and the mixture is heated to 100°C and stirred for 12 hours under a nitrogen atmosphere; after the reaction is completed, the mixture is cooled to room temperature, and after post-treatment such as extraction, washing, drying, column chromatography, and drying, a black solid fluoroboron dipyrrole fluorescent dye is obtained, and the yield is 65%. The preparation method uses tetrakistriphenylphosphine palladium as a catalyst, and its catalytic effect is general, and the catalytic selectivity is insufficient, resulting in a low yield of the reaction; and the stability of tetrakistriphenylphosphine palladium is poor, and it is easy to decompose and deactivate at high temperature, resulting in a large amount of residual palladium in the waste liquid, which is difficult to recycle.

[0004] The specific chemical reaction formula is as follows:

[0005]

[0006] There are also reports in the prior art on the use of nanogold catalysts for cross-coupling reactions, but the service life of the nanogold catalyst is a key factor affecting its catalytic performance. After a long period of reaction use, the gold particles are easily lost or agglomerated, resulting in decreased activity or even inactivation.

[0007] Therefore, it is of great significance to prepare a catalyst with good catalytic performance, high conversion rate, stable performance and the ability to be recycled and reused, and apply it to the efficient synthesis of fluoroboron dipyrrole fluorescent dyes. Summary of the invention

[0008] The purpose of the present invention is to provide a core-shell structure Au@CeO 2 The invention discloses a nanocatalyst and a preparation method and application thereof to solve the problems in the background technology.

[0009] The purpose of the present invention can be achieved through the following technical solutions:

[0010] A core-shell structure Au@CeO 2 The method for preparing a nanocatalyst comprises the following steps:

[0011] S1. Add tetrachloroauric acid solution and low concentration cerium chloride solution into deionized water, stir magnetically at 1200r / min for 30min in an ice water bath at 5℃, then quickly add ammonia solution, the mixed solution immediately turns black, then quickly add high concentration cerium chloride solution and continue stirring for 30min to obtain a mixed solution; Au 3+ and Ce 3+ Gold nanoparticles and a large amount of Ce are generated through redox reactions. 4+ After adding appropriate amount of ammonia water, Ce 4+ After hydrolysis, it is converted into cerium dioxide and quickly assembled around the gold nanoparticles to form a precipitate. After quickly adding a high concentration of cerium chloride solution, the added Ce 3+ Absorption of OH - The formation of relatively stable [Ce(OH) 2 ] + and [Ce(OH)] 2+ Ions, OH in solution - The free ceria particles that were not assembled with gold nanoparticles preferentially dissolved and released OH - Until equilibrium is reached, the core-shell structure Au@CeO 2 The boundary of the Au@CeO ... 2 ;

[0012] S2, placing the mixed solution in a centrifuge tube and centrifuging at a speed of 12000r / min for 30min. After the centrifugation, remove the upper solution of the centrifuge tube, retain the precipitate at the bottom of the centrifuge tube, wash it with deionized water for 3 times, centrifuge it for 30min to remove the upper solution, then wash it with anhydrous ethanol for at least 3 times, centrifuge it for 30min to remove the upper solution, completely remove organic matter and other impurities in the precipitate, and freeze-dry it for 12h to obtain a catalyst precursor;

[0013] S3, the catalyst precursor was cleaned, and then heated to 100°C at a heating rate of 1°C / min for annealing for 12h. After cleaning again, it was heated to 300°C at a heating rate of 1°C / min for annealing again for 6h. After cooling to room temperature, a core-shell structure Au@CeO 2 Nanocatalyst. The double annealing treatments enhanced the interaction between gold particles and cerium oxide, thus improving the stability and activity of the catalyst.

[0014] Furthermore, the dosage ratio of the tetrachloroauric acid solution, the low-concentration cerium chloride solution, the deionized water, the ammonia solution and the high-concentration cerium chloride solution is 2 mL: 4 mL: 100 mL: 6 mL: 5 mL.

[0015] Furthermore, the concentration of the tetrachloroauric acid solution is 0.02 mol / L, the concentration of the low-concentration cerium chloride solution is 0.01 mol / L, the concentration of the ammonia solution is 0.33 mol / L, and the concentration of the high-concentration cerium chloride solution is 0.05 mol / L.

[0016] Furthermore, the cleaning process is: ultrasonically dispersing the treatment object in ethanol, then centrifugally separating it, and then drying it at 25°C.

[0017] A core-shell structure Au@CeO 2 Nanocatalyst, prepared by the above preparation method; the core-shell structure Au@CeO 2 The nano catalyst has nano gold particles as the core and cerium oxide as the shell. The particle size of the core is 10nm, and the particle size of the shell is 40nm.

[0018] A core-shell structure Au@CeO 2 The application of nanocatalyst in catalytic synthesis of fluoroboron dipyrrole fluorescent dyes comprises the following steps:

[0019] Under argon protection, fluoroborane dipyrrole compounds, aminophenylboronic acid pinacol ester compounds, core-shell structure Au@CeO 2 Nanocatalyst, sodium acetate and toluene were ultrasonically mixed for 30 min to make fluoroborane dipyrrole compounds, aminophenylboronic acid pinacol ester compounds, core-shell structure Au@CeO 2 The nanocatalyst and sodium acetate are uniformly dispersed in toluene, and the Suzuki coupling reaction is carried out at 100-120°C and 1200r / min with magnetic stirring for 12-18h. After the reaction is completed, ethyl acetate is used as an extractant to extract the reaction product to obtain a fluoroboron dipyrrole fluorescent dye. The present invention greatly improves the yield of fluoroboron dipyrrole fluorescent dyes by optimizing the catalyst type, dosage, solvent type, reaction time and other conditions.

[0020] Furthermore, the fluoroborane dipyrrole compound, the aminophenylboronic acid pinacol ester compound, the core-shell structure Au@CeO 2 The usage ratio of the nano catalyst, sodium acetate and toluene is 0.1mmol:0.4mmol:5-8mg:0.4mmol:2mL.

[0021] Furthermore, the general structural formula of the fluoroborane dipyrrole compound is:

[0022]

[0023] Wherein, R1 is H, CH 3 、OCH 3 、F、Cl、Br、COOH、NH 2 Any one of; wherein R2 and R3 are H, OCH 3 , any one of Cl.

[0024] Furthermore, the general structural formula of the aminophenylboronic acid pinacol ester compound is:

[0025]

[0026] Wherein, R4 is H, CH 3 、OCH 3 、F、Cl、Br、COOH、NH 2 、NO 2 CF 3 Any one of: wherein R5 is H, CH 3 Any one of .

[0027] Furthermore, the general structural formula of the fluoroboron dipyrrole fluorescent dye is as follows:

[0028]

[0029] Wherein, R1 is H, CH 3 、OCH 3 、F、Cl、Br、COOH、NH 2 Any one of; wherein R2 and R3 are H, OCH 3 , Cl; R4 is H, CH 3 、OCH 3 、F、Cl、Br、COOH、NH 2 、NO 2 CF 3 Any one of: wherein R5 is H, CH 3 Any one of .

[0030] Beneficial effects:

[0031] The present invention directly uses a one-pot method to cause a redox reaction between tetrachloroauric acid and cerium chloride in deionized water, and after the reaction is completed, an appropriate amount of Ce is added. 3+ and annealing treatment to make the core-shell structure Au@CeO 2 The nanocatalyst has a more complete structure, and has better dispersibility, stability and catalytic activity. Moreover, the preparation method of the present invention is simple and easy to operate, has low requirements on production equipment, mild reaction conditions, and is safe and environmentally friendly.

[0032] The present invention combines the core-shell structure Au@CeO 2 Nanocatalysts are used to catalyze the coupling reaction of fluoroborane dipyrrole compounds and aminophenylboronic acid pinacol ester compounds under alkaline conditions. The core-shell structure Au@CeO 2 The nanocatalyst plays a role of heterogeneous catalysis in the reaction process, and has the advantages of high catalytic activity, strong selectivity, good stability, and recyclability. It can significantly improve the yield and can be widely used in the actual production of catalytic synthesis of fluoroboron dipyrrole fluorescent dyes. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention will be further described below in conjunction with the accompanying drawings.

[0034] Figure 1 The core-shell structure Au@CeO 2 Transmission electron microscopy (TEM) image of the nanocatalyst;

[0035] Figure 2 The core-shell structure Au@CeO prepared in Example 1 2 The final yield bar graph of the nanocatalyst recycled and reused 5 times to catalyze the synthesis of fluoroboron dipyrrole fluorescent dyes under the conditions of Example 2;

[0036] Figure 3 It is a line graph of the yield of Example 2 and Comparative Example 1 monitored in real time by GC-MS. DETAILED DESCRIPTION

[0037] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] Example 1

[0039] This embodiment provides a core-shell structure Au@CeO 2 The nanocatalyst is prepared by the following preparation method:

[0040] S1. Add 2 mL of 0.02 mol / L tetrachloroauric acid solution and 4 mL of 0.01 mol / L low-concentration cerium chloride solution to 100 mL of deionized water, stir magnetically at 1200 r / min for 30 min in an ice-water bath at 5°C, then quickly add 6 mL of ammonia solution (prepared by dissolving 0.1 mL of 20 mol / L ammonia solution in 6 mL of water), the mixed solution immediately turns black, stir for 25 s, then quickly add 5 mL of 0.05 mol / L high-concentration cerium chloride solution and continue stirring for 30 min to obtain a mixed solution;

[0041] S2, placing the mixed solution in a centrifuge tube and centrifuging at a speed of 12000r / min for 30min. After the centrifugation, remove the upper solution of the centrifuge tube, retain the precipitate at the bottom of the centrifuge tube, wash it with deionized water for 3 times, centrifuge it for 30min to remove the upper solution, then wash it with anhydrous ethanol for at least 3 times, centrifuge it for 30min to remove the upper solution, completely remove organic matter and other impurities in the precipitate, and freeze-dry it for 12h to obtain a catalyst precursor;

[0042] S3, the catalyst precursor was ultrasonically dispersed in ethanol, then centrifuged, dried at 25°C, then heated to 100°C at a heating rate of 1°C / min for annealing for 12h, ultrasonically dispersed in ethanol again, then centrifuged, dried at 25°C, then heated to 300°C at a heating rate of 1°C / min for annealing for 6h, and cooled to room temperature to obtain a core-shell structure Au@CeO 2 Nanocatalyst.

[0043] The core-shell structure of Au@CeO 2 Nanocatalysts are characterized by Figure 1 As shown in the figure, the core-shell structure Au@CeO prepared by the present invention 2 The nanocatalyst is evenly dispersed and uniform in size without agglomeration. 2 As the shell, its particle size is about 40nm, and Au as the core, its particle size is about 10nm.

[0044] Comparative Example 1

[0045] The difference between this comparative example and Example 1 is that high concentration cerium chloride solution is not added in step S1, and the other raw materials and steps are the same, which is recorded as Au@CeO 2 (1).

[0046] Comparative Example 2

[0047] The difference between this comparative example and Example 1 is that the two annealing operations in step S3 are not performed, and the other raw materials and steps are the same, which is recorded as Au@CeO2 (2).

[0048] The present invention provides a core-shell structure Au@CeO 2 The application of nanocatalyst in catalytic synthesis of fluoroboron dipyrrole fluorescent dyes comprises the following steps:

[0049] Under argon protection, 0.1 mmol of fluoroborane dipyrrole compound, 0.4 mmol of aminophenylboronic acid pinacol ester compound, 5-8 mg of the core-shell structure Au@CeO prepared in Example 1 were added. 2 The nanocatalyst, 0.4 mmol sodium acetate and 2 mL toluene were added into a 100 mL reaction tube and ultrasonically mixed for 30 min, and then magnetically stirred at 100-120° C. and 1200 r / min for 12-18 h. After the reaction, ethyl acetate was used as an extractant to extract the reaction product to obtain a fluoroboron dipyrrole fluorescent dye.

[0050] The specific chemical reaction formula is as follows:

[0051]

[0052] Wherein, R1 is H, CH 3 、OCH 3 、F、Cl、Br、COOH、NH 2 Any one of; wherein R2 and R3 are H, OCH 3 , Cl; R4 is H, CH 3 、OCH 3 、F、Cl、Br、COOH、NH 2 、NO 2 CF 3 Any one of: wherein R5 is H, CH 3 Any one of .

[0053] Example 2

[0054] The fluoroboron dipyrrole fluorescent dye is prepared by the following steps:

[0055] Under argon protection, 0.1 mmol of fluoroborane dipyrrole compound (R1 is OCH 3 , R2 and R3 are H), 0.4mmol aminophenylboronic acid pinacol ester compound (R4 and R5 are H), 5mg core-shell structure Au@CeO 2Nanocatalyst, 0.4 mmol sodium acetate and 2 mL toluene were added to a 100 mL reaction tube and ultrasonically mixed for 30 min, and then magnetically stirred at 100 ° C and 1200 r / min for 12 h. After the reaction, ethyl acetate was used as an extractant to extract the reaction product to obtain a fluoroboron dipyrrole fluorescent dye.

[0056] The yield of the fluoroborane dipyrrole fluorescent dye of this example was continuously monitored by gas chromatography and gas chromatography-mass spectrometry (GC-MS), and the final yield was recorded as 82%.

[0057] The core-shell structure Au@CeO 2 The nanocatalyst was recovered by centrifugal filtration and then recycled for 4 times under the same reaction conditions, and the final yield of fluoroboron dipyrrole fluorescent dye obtained after each cycle was recorded.

[0058] like Figure 2 As shown in the figure, after five times of recycling, the core-shell structure Au@CeO 2 The nanocatalyst can still achieve a final yield of 72% when catalyzing the synthesis of fluoroboron dipyrrole fluorescent dyes, indicating that the core-shell structure Au@CeO prepared by the present invention is 2 Nanocatalysts have good catalytic activity, stability and recycling performance.

[0059] Comparative Example 3

[0060] The difference between this comparative example and Example 2 is that after the reaction is carried out for 2 hours, centrifugal filtration is performed to remove the core-shell structure Au@CeO 2 The nanocatalyst was used and the filtrate was allowed to react for 12 h under the same reaction conditions and monitored in real time by GC-MS.

[0061] like Figure 3 As shown in the monitoring results, no further generation of fluoroborane dipyrrole fluorescent dyes was observed in Comparative Example 3, which shows that the core-shell structure Au@CeO 2 The nanocatalyst has good stability and heterogeneous catalytic properties, and the metal Au is not leached from the catalyst. The core-shell structure Au@CeO 2 The synthesis of fluoroboranedipyrrole fluorescent dyes catalyzed by nanocatalysts is a true heterogeneous catalytic process.

[0062] Example 3-Example 25

[0063] Compared with Example 2, the reaction conditions of this group of examples are the same, and only the reaction substrate is changed, as shown in Table 1.

[0064] Table 1

[0065]

[0066]

[0067] From the data in Table 1, we can see that the core-shell structure Au@CeO 2 Nanocatalysts are widely used in the catalytic synthesis of fluoroboron dipyrrole fluorescent dyes, with good functional group tolerance, good conversion rate and selectivity. Whether for ortho, meta, or para fluoroboron dipyrrole fluorescent dyes, or for electron-donating or electron-withdrawing fluoroboron dipyrrole fluorescent dyes, they have good catalytic activity and stability, and excellent catalytic effect.

[0068] Example 26-Example 28

[0069] Compared with Example 2, the reaction substrates in this group of examples are the same, and only one of the types or amounts of the catalyst, solvent and base and the reaction conditions is changed, as shown in Table 2 below.

[0070] Comparative Example 4-Comparative Example 17

[0071] Compared with Example 2, the reaction substrates in this comparative example are the same, and only one of the types or amounts of the catalyst, solvent and base and the reaction conditions is changed, as shown in Table 2.

[0072] Table 2

[0073]

[0074]

[0075] It can be seen from the data in Table 2 that under the catalyst, solvent, base and reaction conditions specified in the present invention, the catalytic synthesis of fluoroboron dipyrrole fluorescent dyes has a higher yield. The existing Au@HT (hydrotalcite-supported nanogold catalyst), Au@HAP (hydroxyapatite-supported nanogold catalyst), Au@SiO 2 The catalytic performance of the catalysts obtained in Example 1 and Example 2 is inferior to that of the core-shell structure Au@CeO prepared in the present invention. 2 Nanocatalyst.

[0076] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0077] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a core-shell structure Au@CeO2 nanocatalyst, characterized in that: The steps include: S1. Add tetrachloroauric acid solution and low concentration cerium chloride solution into deionized water, stir magnetically at 5°C for 30 minutes, then quickly add ammonia solution and stir for 25 seconds, then quickly add high concentration cerium chloride solution and continue stirring for 30 minutes to obtain a mixed solution; S2, centrifuging the mixed solution to retain the precipitate, washing the precipitate with deionized water and anhydrous ethanol for multiple times, and freeze-drying to obtain a catalyst precursor; S3. The catalyst precursor is cleaned, then heated to 100° C. and annealed for 12 h. After cleaning again, it is heated to 300° C. and annealed for 6 h. After cooling to room temperature, a core-shell structured Au@CeO2 nanocatalyst is obtained.

2. The method for preparing a core-shell Au@CeO2 nanocatalyst according to claim 1, characterized in that: The dosage ratio of the tetrachloroauric acid solution, the low-concentration cerium chloride solution, the deionized water, the ammonia solution and the high-concentration cerium chloride solution is 2 mL: 4 mL: 100 mL: 6 mL: 5 mL.

3. The method for preparing a core-shell Au@CeO2 nanocatalyst according to claim 2, characterized in that: The concentration of the tetrachloroauric acid solution is 0.02 mol / L, the concentration of the low-concentration cerium chloride solution is 0.01 mol / L, the concentration of the ammonia solution is 0.33 mol / L, and the concentration of the high-concentration cerium chloride solution is 0.05 mol / L.

4. The method for preparing a core-shell Au@CeO2 nanocatalyst according to claim 1, characterized in that: The cleaning process is as follows: ultrasonically dispersing the treated object in ethanol, then centrifugally separating the object, and then drying the object at 25°C.

5. A core-shell structure Au@CeO2 nanocatalyst, characterized in that: The core-shell structured Au@CeO2 nanocatalyst is prepared by the preparation method according to any one of claims 1 to 4, wherein the core-shell structured Au@CeO2 nanocatalyst has nano-gold particles as the core and cerium oxide as the shell, the particle size of the core is 10 nm, and the particle size of the shell is 40 nm.

6. The use of a core-shell structure Au@CeO2 nanocatalyst according to claim 5, characterized in that: The following steps are involved: Under argon protection, fluoroboron dipyrrole compounds, aminophenylboronic acid pinacol ester compounds, core-shell structure Au@CeO2 nanocatalysts, sodium acetate and toluene are ultrasonically mixed and stirred at 100-120°C for 12-18h. After the reaction, the reaction product is extracted with ethyl acetate to obtain fluoroboron dipyrrole fluorescent dyes.

7. The use of a core-shell structure Au@CeO2 nanocatalyst according to claim 6, characterized in that: The dosage ratio of the fluoroborane dipyrrole compound, the aminophenylboronic acid pinacol ester compound, the core-shell structure Au@CeO2 nanocatalyst, sodium acetate and toluene is 0.1mmol:0.4mmol:5-8mg:0.4mmol:2mL.

8. The use of a core-shell structure Au@CeO2 nanocatalyst according to claim 6, characterized in that: The general structural formula of the fluoroborane dipyrrole compound is: Wherein, R1 is any one of H, CH3, OCH3, F, Cl, Br, COOH, and NH2; and R2 and R3 are any one of H, OCH3, and Cl.

9. The use of a core-shell structure Au@CeO2 nanocatalyst according to claim 6, characterized in that: The general structural formula of the aminophenylboronic acid pinacol ester compound is: Wherein, R4 is any one of H, CH3, OCH3, F, Cl, Br, COOH, NH2, NO2, and CF3; and R5 is any one of H and CH3.

10. The use of a core-shell structure Au@CeO2 nanocatalyst according to claim 6, characterized in that: The general structural formula of the fluoroboron dipyrrole fluorescent dye is as follows: Wherein, R1 is any one of H, CH3, OCH3, F, Cl, Br, COOH, and NH2; R2 and R3 are any one of H, OCH3, and Cl; R4 is any one of H, CH3, OCH3, F, Cl, Br, COOH, NH2, NO2, and CF3; and R5 is any one of H and CH3.

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