A composite material loaded with gold nanoclusters, a preparation method and applications thereof

Abstract

This invention provides a composite material loaded with gold nanoclusters, its preparation method, and its application. The preparation method includes mixing a prescribed amount of ZIF powder with an aqueous solution of the composite material loaded with gold nanoclusters, reacting under ultrasonic conditions at a certain temperature for a certain time, and then centrifuging and vacuum drying to obtain the final product. This invention prepares the composite material loaded with gold nanoclusters by ultrasonically blending ZIFs and gold nanoclusters. The material exhibits uniform size and morphology, achieving high dispersion loading of gold nanoclusters while maintaining the long-range order of ZIFs. The composite material has good recyclability, conforming to the concept of green chemistry. As a catalyst, the composite material loaded with gold nanoclusters provided by this invention, based on the strong confinement effect of ZIFs on gold nanoclusters and its high dispersion loading, greatly enhances the catalytic activity of gold nanoclusters, achieving highly efficient catalytic reduction of p-nitrophenol.

Description

Technical Field

[0001] This invention belongs to the field of catalytic materials technology, and relates to a composite material loaded with gold nanoclusters, its preparation method and application. Background Technology

[0002] p-Nitrophenol is a highly toxic pollutant widely found in chemical wastewater, and its reduction product, p-aminophenol, is an important pharmaceutical intermediate. Traditional methods for treating p-nitrophenol (such as biodegradation and physical adsorption) suffer from low efficiency, high cost, and secondary pollution. In contrast, catalytic hydrogenation reduction has become a research hotspot due to its advantages of mild reaction conditions and high product added value.

[0003] Currently, although noble metal catalysts (such as Pt and Pd) can efficiently catalyze the reduction of p-nitrophenol, they suffer from high cost and poor cycle stability; non-noble metal catalysts (such as Co and Ni) are insufficient in activity to meet industrial needs.

[0004] Composite materials loaded with gold nanoclusters exhibit excellent catalytic potential due to their unique surface quantum effects and electronic properties, but their application is limited by two major bottlenecks: they are prone to severe aggregation, reducing the utilization rate of active sites; and conventional supports (such as activated carbon and alumina) have weak confinement effects, making it impossible to achieve highly dispersed loading. In addition, the catalytic reduction reaction of p-nitrophenol in existing technologies often requires a long reaction time (>30 min), making it difficult to achieve high catalytic conversion efficiency at room temperature and pressure.

[0005] In summary, developing a green, low-cost, and highly stable composite catalyst for supporting gold nanoclusters, and achieving high dispersion loading of the composite material (<2nm) of gold nanoclusters and efficient reduction of p-nitrophenol under mild conditions, is a technical challenge that urgently needs to be overcome. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a composite material loaded with gold nanoclusters, its preparation method, and its application, thereby solving the technical problems in existing technologies where composite catalysts loaded with gold nanoclusters are difficult to achieve high dispersion loading and have unsatisfactory reduction effects on nitrophenol under mild conditions.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A method for preparing a composite material loaded with gold nanoclusters includes mixing a prescribed amount of ZIF powder with a gold nanocluster solution, reacting under ultrasonic conditions, and then drying by centrifugation and vacuum drying.

[0009] The present invention also has the following technical features: Specifically, the molar ratio of the ZIFs powder to the gold nanoclusters is (9~11):1.

[0010] Furthermore, the molar ratio of the ZIFs powder to the gold nanoclusters is 10:1.

[0011] Furthermore, the reaction under ultrasonic conditions specifically includes: ultrasonic power of 300~500W, reaction temperature of 20~27℃, and reaction time of 1~2h.

[0012] Furthermore, the centrifugal vacuum drying process specifically includes: a centrifugal force of 8500~9000g, a centrifugation time of 10~20min; a vacuum drying temperature of 50~55℃, and a drying time of 12~14h.

[0013] Furthermore, the ZIFs are selected from any one of ZIF-67, ZIF-7, ZIF-8, ZIF-10, ZIF-20, ZIF-68, ZIF-81, ZIF-90 and ZIF-100.

[0014] Furthermore, the ligands of the gold nanoclusters are thiol ligands containing carboxylic acid groups.

[0015] Furthermore, the thiol ligand is selected from any one of glutathione, cysteine, and mercaptopropionic acid.

[0016] The present invention also protects the composite material of gold nanoclusters prepared by the above method.

[0017] This invention also protects the application of the composite material with gold nanoclusters prepared by the above method in the catalytic reduction of p-nitrophenol.

[0018] Compared with the prior art, the present invention has the following technical effects: (1) The present invention prepares a composite material loaded with gold nanoclusters by ultrasonic blending reaction of ZIFs and gold nanoclusters. The material has uniform size and morphology, and achieves high dispersion loading of gold nanoclusters while maintaining the long-range order of ZIFs. The composite material has good recyclability and conforms to the concept of green chemistry.

[0019] (2) The composite material with gold nanoclusters supported by the present invention is used as a catalyst. Based on the strong confinement effect of ZIFs on gold nanoclusters and the high dispersion and loading, the catalytic activity of gold nanoclusters is greatly enhanced, and the efficient catalytic reduction of p-nitrophenol is achieved.

[0020] (3) The preparation method of the present invention is simple, highly operable, and suitable for efficient mass production. Attached Figure Description

[0021] Figure 1 This is a transmission electron microscope image of the gold nanoclusters in Example 1; Figure 2 The image shows a scanning electron microscope image of the ZIF-67 in Example 1. Figure 3 This is a scanning electron microscope image of the gold nanocluster composite material in Example 1; Figure 4 This is an elemental distribution diagram of the gold nanocluster composite material in Example 1; Figure 5 The powder X-ray diffraction pattern of ZIF-67 and gold nanocluster composite material in Example 1; Figure 6 The UV-Vis absorption spectrum of the gold nanocluster composite material used as a catalyst in Example 1 for the catalytic reduction of p-nitrophenol; Figure 7 The UV-Vis absorption spectrum of the reduction of p-nitrophenol by gold nanoclusters as a catalyst in Example 1; Figure 8 This is a graph showing the relationship between ln (C / CO) and reaction time (t) on different catalysts in Example 1; Figure 9 This is a comparison chart of the TOF values ​​of different catalysts in Example 1; Figure 10 This is a cyclic experiment diagram of the gold nanocluster composite material used as a catalyst in Example 1.

[0022] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0023] It should be noted that, unless otherwise specified, all raw materials used in this invention are those known in the prior art.

[0024] The technical concept of this invention is as follows: ZIFs and gold nanoclusters undergo an ultrasonic blending reaction. Through strong hydrogen bonding interactions between the carboxylic acid groups in the ligands on the gold nanoclusters and the imidazole groups in the ZIFs, efficient synergistic assembly of the two is achieved, resulting in a composite material with uniform size and morphology of gold nanoclusters. Based on the strong confinement effect and high dispersion loading of the gold nanoclusters by ZIFs, the catalytic activity of the gold nanoclusters is enhanced, achieving highly efficient catalytic reduction of nitrophenol.

[0025] The coordinating metal in ZIFs can be selected from any one of cobalt (Co), zinc (Zn), and potassium (K).

[0026] In this invention, scanning electron microscopy and transmission electron microscopy are used to study the size and morphology of gold nanoclusters, ZIF, and the prepared products; energy dispersive spectroscopy is used to analyze the elemental distribution of the products; and powder X-ray diffraction is used to study the crystallinity of the products.

[0027] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0028] Example 1 Following the above technical solution, this embodiment provides a method for preparing a composite material loaded with gold nanoclusters, specifically including: taking a 5 mL centrifuge tube and adding 4.4 mg of ZIF-67 powder; adding 1 mL of glutathione-protected gold nanoclusters (GSH-AuNCs) with a concentration of 2 mM; ultrasonically reacting at room temperature (25℃) for 1 h; after the reaction, the blue ZIF-67 powder at the bottom of the centrifuge tube turns yellow, and the supernatant is colorless and transparent; centrifuging at 9000 g for 10 min, then washing the precipitate three times with ultrapure water, and drying the precipitate product under vacuum at 50℃ for 12 h, the resulting red powder is the composite material loaded with AuNCs.

[0029] The morphology and structure of the product obtained in this embodiment were studied. By comparing and analyzing the performance differences of the composite material and gold nanoclusters prepared in this embodiment as catalysts for the catalytic reduction of p-nitrophenol, the potential mechanism of the strong confinement effect of ZIFs on AuNCs and the high dispersion loading on improving the catalytic activity of AuNCs was revealed.

[0030] The size and morphology of GSH-AuNCs and ZIF-67 as raw materials were studied using scanning electron microscopy and transmission electron microscopy, as well as the prepared composite materials. The elemental distribution in the materials was studied using energy dispersive spectroscopy. The long-range order of the composite materials and ZIF-67 was compared and analyzed using powder X-ray diffraction. The results are as follows Figure 1-5 As shown: from Figure 1 It can be seen that the size of the prepared GSH-AuNCs is about 1.7 nm, and the size distribution is uniform.

[0031] from Figure 2 It can be seen that the size of the prepared ZIF-67 is about 1 μm, and the size distribution is uniform.

[0032] from Figure 3 and Figure 4It can be seen that the size and morphology of GSH-AuNCs and ZIF-67 changed significantly after the blending reaction, and the resulting composite material consisted of microspheres of about 500 nm, indicating that GSH-AuNCs and ZIF-67 underwent synergistic assembly. The elemental distribution diagram shows that the characteristic element Au of GSH-AuNCs and the characteristic element Co of ZIF-67 are uniformly distributed within the structure of the assembly, and the Au element signal is very strong, indicating that the prepared composite material efficiently loads AuNCs.

[0033] Powder X-ray diffraction characterization was performed on ZIF-67 and GSH-AuNCs before and after assembly, and the results are as follows: Figure 5 As shown, the X-ray diffraction peak shape and position of the composite powder loaded with AuNCs are consistent with those of ZIF-67, indicating that the composite material maintains the long-range order of ZIF-67.

[0034] The composite material prepared in this embodiment was used as a catalyst for the catalytic reduction of p-nitrophenol. The specific steps are as follows: Step 1: Mix p-nitrophenol (0.3 mL, 1 mM) aqueous solution, GSH-AuNCs@ZIF-67 (20 μL, 1 mM) dispersion / aqueous solution prepared in this example, and 1 mL of ultrapure water in a quartz test tube to obtain mixed solution A; Step 2: After mixing solution A uniformly for 10 minutes at room temperature (25℃), place the cuvette in a UV-Vis spectrophotometer and add sodium borohydride (1 mL, 0.25 M) aqueous solution to the mixed solution to obtain mixed solution B. Step 3: Measure the UV-Vis absorption spectrum of mixed solution B. By monitoring the change in the intensity of the p-nitrophenol peak at 400 nm over time, the progress of the reduction reaction is tracked to examine the catalytic ability of the composite material.

[0035] like Figure 6 and Figure 7 As shown, after the addition of the catalyst, the transition from a bright yellow aqueous solution of p-nitrophenol to a colorless aqueous solution of p-aminophenol was detected at the absorption band of 400 nm. The absorption intensity of the solution at 400 nm decreased rapidly and disappeared within 3 minutes, indicating a 100% conversion from p-nitrophenol to p-aminophenol, accompanied by the fading of the solution color.

[0036] The kinetics of the catalytic reaction were studied by plotting ln(C / C0) as a function of reaction time (t), where C is the concentration of p-nitrophenol in the solution at time t, and C0 is the initial concentration of p-nitrophenol in the solution. The results are as follows: Figure 8 As shown. The apparent kinetic constant of the reaction (K) app The value is calculated based on the slope obtained from linear fitting. Further, based on K... appBased on the value and the amount of catalyst, the catalyst activity index (TOF) value is calculated. In this embodiment, the calculated K... app The value is 1.04 x 10 -2 The TOF value is 272 s. -1 mmol -1 .

[0037] To verify the changes in catalytic performance before and after AuNCs loading, GSH-AuNCs were used instead of GSH-AuNCs@ZIF-67, and a control experiment was conducted using the above method.

[0038] The catalytic activity of the catalyst was investigated using UV-Vis absorption spectroscopy. The results showed that the rate of decrease in absorption intensity at 400 nm was significantly slower, ultimately achieving 100% conversion of p-nitrophenol to p-aminophenol within 6 minutes. The calculated K... app The value is 2.54 x 10 -2 s -1 The TOF value is 665 s. -1 mmol -1 .

[0039] Comparative experiments show that loading AuNCs onto ZIF-67 significantly enhances their catalytic activity. This indicates that the AuNCs-supported composite material exhibits high catalytic activity against p-nitrophenol, thanks to the strong confinement effect and high dispersion of GSH-AuNCs by ZIF-67.

[0040] In addition, Table 1 lists the comparison of the catalytic ability of the composite catalyst prepared in this embodiment with other noble metal catalysts reported in the existing literature. The results show that the composite material supported on AuNCs exhibits excellent performance in the catalytic reduction of p-nitrophenol.

[0041]

[0042] Table 1: Comparison of AuNCs-supported composite catalysts with other catalysts Since the recyclability of a catalyst is one of the important indicators for evaluating its industrial application, this example also verified the recyclability of the AuNCs-supported composite material, and the results are as follows: Figure 10 As shown, from Figure 10 The results show that the catalyst still has good catalytic activity after being recycled 5 times, indicating its potential for industrial application.

[0043] Example 2 This embodiment provides a method for preparing a composite material loaded with gold nanoclusters. The preparation method and steps used in this embodiment are the same as those in Example 1. The difference is that ZIF-67 is replaced with ZIF-8 as the raw material in this embodiment, and a composite material loaded with gold nanoclusters is obtained.

[0044] The composite material was used as a catalyst for the catalytic reduction of p-nitrophenol; the operation method was the same as in Example 1. The composite material was tested and found to have excellent performance in the catalytic reduction of p-nitrophenol.

[0045] Example 3 This embodiment provides a method for preparing a composite material loaded with gold nanoclusters. The preparation method and steps used in this embodiment are the same as those in Example 1. The difference is that ZIF-67 is replaced with ZIF-90 as the raw material in this embodiment, and a composite material loaded with gold nanoclusters is obtained.

[0046] The composite material was used as a catalyst for the catalytic reduction of p-nitrophenol; the operation method was the same as in Example 1. The composite material was tested and found to have excellent performance in the catalytic reduction of p-nitrophenol.

[0047] Example 4 This embodiment provides a method for preparing a composite material loaded with gold nanoclusters. The preparation method and steps used in this embodiment are the same as those in Example 1. The difference is that the raw material ZIF-67 is replaced with Lcy-AuNCs in this embodiment, and a composite material loaded with gold nanoclusters is obtained.

[0048] The composite material was used as a catalyst for the catalytic reduction of p-nitrophenol; the operation method was the same as in Example 1. The composite material was tested and found to have excellent performance in the catalytic reduction of p-nitrophenol.

[0049] Example 5 This embodiment provides a method for preparing a composite material loaded with gold nanoclusters. The preparation method and steps used in this embodiment are the same as those in Example 1. The difference is that the raw material ZIF-67 is replaced with MPA-AuNCs in this embodiment, and a composite material loaded with gold nanoclusters is obtained.

[0050] The composite material was used as a catalyst for the catalytic reduction of p-nitrophenol; the operation method was the same as in Example 1. The composite material was tested and found to have excellent performance in the catalytic reduction of p-nitrophenol.

[0051] As can be seen from Examples 1-5: A composite material loaded with gold nanoclusters was obtained by blending ZIF and gold nanoclusters. This composite material exhibits uniform size and morphology, maintaining the original crystallinity of ZIF while achieving high dispersion loading of gold nanoclusters. Based on the strong confinement effect of ZIFs on the gold nanoclusters and the high dispersion loading, this composite material demonstrates excellent catalytic reduction activity of p-nitrophenol. The composite material also shows good recyclability, indicating promising prospects for industrial applications.

[0052] The specific technical features described in the above embodiments can be combined in any suitable manner without contradiction, as long as they do not violate the spirit of the present invention, and should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing a composite material loaded with gold nanoclusters, characterized in that, The process involves mixing a prescribed amount of ZIF powder with a gold nanocluster solution, reacting the mixture under ultrasonic conditions, and then centrifuging and vacuum drying to obtain the final product.

2. The method for preparing the composite material loaded with gold nanoclusters as described in claim 1, characterized in that, The molar ratio of ZIFs powder to gold nanoclusters is (9~11):

1.

3. The method for preparing the composite material loaded with gold nanoclusters as described in claim 1, characterized in that, The molar ratio of ZIFs powder to gold nanoclusters is 10:

1.

4. The method for preparing the composite material loaded with gold nanoclusters as described in claim 1, characterized in that, The reaction under ultrasonic conditions specifically includes: ultrasonic power of 300~500W, reaction temperature of 20~27℃, and reaction time of 1~2h.

5. The method for preparing the composite material loaded with gold nanoclusters as described in claim 1, characterized in that, The centrifugal vacuum drying process specifically includes: a centrifugal force of 8500~9000g, a centrifugation time of 10~20min; a vacuum drying temperature of 50~55℃, and a drying time of 12~14h.

6. The method for preparing the composite material loaded with gold nanoclusters as described in claim 1, characterized in that, The ZIFs are selected from any one of ZIF-67, ZIF-7, ZIF-8, ZIF-10, ZIF-20, ZIF-68, ZIF-81, ZIF-90 and ZIF-100.

7. The method for preparing the composite material loaded with gold nanoclusters as described in claim 1, characterized in that, The ligands of the gold nanoclusters are thiol ligands containing carboxylic acid groups.

8. The method for preparing the composite material loaded with gold nanoclusters as described in claim 1, characterized in that, The thiol ligand is selected from any one of glutathione, cysteine, and mercaptopropionic acid.

9. The composite material of gold nanoclusters prepared by any one of claims 1 to 8.

10. The application of the composite material with gold nanoclusters prepared by any one of claims 1 to 8 in the catalytic reduction of p-nitrophenol.

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