A pdcu alloy nanocluster and application thereof in catalyzing suzuki-miyaura coupling reaction

Abstract

The application discloses a PdCu alloy nanocluster and application of the PdCu alloy nanocluster in catalyzing Suzuki-Miyaura coupling reaction, and belongs to the technical field of nanomaterials. The chemical formula of the PdCu alloy nanocluster is Pd2Cu2(S-Adm)1(DPPM)3, S-Adm represents adamantane mercaptan, DPPM represents bisdiphenylphosphinomethane, and the PdCu alloy nanocluster is simply denoted as Pd2Cu2-1; or the chemical formula of the PdCu alloy nanocluster is Pd2Cu2(C7H5F3S)6(DPPF)2, C7H5F3S represents 2-(trifluoromethyl)benzenethiol, and DPPF represents bisdiphenylphosphin ferrocene; and the PdCu alloy nanocluster is simply denoted as Pd2Cu2-2. The Pd2Cu2 nanocluster is loaded on a carbon nanotube to obtain a Pd2Cu2@CNT catalyst, and the Pd2Cu2@CNT catalyst is used for catalyzing Suzuki-Miyaura coupling reaction and has excellent catalytic performance.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials technology, specifically relating to a PdCu alloy nanocluster and its application in catalyzing the Suzuki-Miyaura coupling reaction. Background Technology

[0002] Over the past few decades, metal nanoclusters with extremely small sizes (1-3 nm) have attracted increasing attention due to their precise structures and broad potential applications in a wide range of fields, such as catalysis, medicine, sensing, biotechnology, and energy. Among these, the catalytic performance of nanoclusters due to their small size is one of the most attractive and compelling properties. Bimetallic nanoclusters have recently garnered significant attention not only for reducing the amount of precious metals used but also for their superior performance in catalytic reactions. Compared to traditional palladium-based catalysts, PdCu bimetallic atomic catalysts can significantly reduce catalyst costs. Furthermore, from a green chemistry perspective, PdCu alloy catalysts are a cost-effective option for Suzuki-Miyaura coupling (SMC) reactions.

[0003] The mixed Pd preparation process using commercial non-precious metals to prepare alloy catalysts has proven to be an economically feasible and efficient approach. In particular, copper is an excellent alloy catalyst for Pd-based synthetic SMC reactions. On the other hand, compared to unsupported catalysts, supported catalysts can immobilize nanoclusters in an ideal dispersion state, further reducing the size of nanoclusters and thus improving catalytic performance and durability. The Suzuki-Miyaura reaction is a typical PdCu-catalyzed coupling reaction involving the formation of C-C bonds between organoboronic acids and halides, involving the activation of carbon-halogen bonds. These reactions have attracted widespread attention due to their enormous industrial potential and wide range of applications. Summary of the Invention

[0004] This invention provides a PdCu alloy nanocluster and its application in the catalytic Suzuki-Miyaura coupling reaction. The PdCu alloy nanocluster of this invention effectively solves the problems of high usage and cost of the noble metal Pd, as well as the difficulties in the synthesis and preparation of supported catalysts.

[0005] The PdCu alloy nanoclusters of this invention are Pd2Cu2(S-Adm)1(DPPM)3, where S-Adm represents adamantane thiol and DPPM represents bis(diphenylphosphine)methane, abbreviated as Pd2Cu2-1; or Pd2Cu2(C7H5F3S)6(DPPF)2, where C7H5F3S represents 2-(trifluoromethyl)benzylthiophenol and DPPF represents bis(diphenylphosphine)ferrocene, abbreviated as Pd2Cu2-2.

[0006] The method for preparing PdCu alloy nanoclusters of the present invention includes the following steps:

[0007] Copper source and palladium metal salt were dissolved in a mixed solution of dichloromethane and methanol. Thiol ligand and bisphosphine ligand were added sequentially under stirring at room temperature to carry out an initial reaction, resulting in a mixed solution. An aqueous solution of sodium borohydride was added to the resulting mixed solution, and a one-pot reduction reaction was carried out to obtain an organic phase solution. The organic phase solution was placed at room temperature for crystallization to obtain PdCu alloy nanoclusters.

[0008] Furthermore, the copper source is copper chloride, the palladium metal salt is palladium chloride, the thiol ligand is adamantane thiol, and the bisphosphine ligand is bis(diphenylphosphine)methane, thus preparing PdCu alloy nanoclusters Pd2Cu2-1.

[0009] The specific steps are as follows: copper chloride source is dissolved in a mixed solution of dichloromethane and methanol, stirred at room temperature, then palladium source is added, followed by the sequential addition of adamantane thiol and bis(diphenylphosphine)methane for initial reaction to obtain a mixed solution. An aqueous solution of sodium borohydride is added to the mixed solution for a one-pot reduction reaction to obtain a crude product, which is then crystallized to obtain Pd2Cu2-1 alloy nanoclusters.

[0010] Furthermore, the ratio of copper source, palladium metal salt, thiol ligand, bisphosphine ligand to sodium borohydride is 60 mg:45 uL:60 mg:50 mg:10 mL (10 mg).

[0011] Furthermore, the copper source is copper tetrafluoroborate tetraacetonitrile, the palladium source is palladium chloride, the thiol ligand is 2-(trifluoromethyl)benzylthiophenol, and the bisphosphine ligand is bis(diphenylphosphine)ferrocene, thus preparing PdCu alloy nanoclusters Pd2Cu2-2.

[0012] The specific steps are as follows: copper tetrafluoroborate tetraacetonitrile is dissolved in a mixed solution of dichloromethane and methanol, stirred at room temperature, then palladium source is added, followed by 2-(trifluoromethyl)benzylthiophenol and bis(diphenylphosphine)ferrocene for initial reaction to obtain a mixed solution. A methanol solution of sodium borohydride is added to the mixed solution for one-pot reduction reaction to obtain a crude product, which is then crystallized to obtain Pd2Cu2-2 alloy nanoclusters.

[0013] Furthermore, the ratio of copper source, palladium metal salt, thiol ligand, bisphosphine ligand to sodium borohydride was 34 mg:25 uL:30 uL:50 mg:5 mL (100 mg).

[0014] Furthermore, the reaction time is 8 hours.

[0015] Furthermore, the organic phase is purified using dichloromethane, and then crystallized using dichloromethane / n-hexane (volume ratio 1:3).

[0016] The present invention relates to the application of PdCu alloy nanoclusters in the catalytic Suzuki-Miyaura coupling reaction.

[0017] Furthermore, the PdCu alloy nanoclusters were loaded onto carbon nanotubes to obtain a Pd2Cu2@CNT catalyst with a loading of 1%, which was used to catalyze the Suzuki-Miyaura coupling reaction.

[0018]

[0019] Catalytic reaction conditions: 50 mg Pd₂Cu₂@CNT catalyst, 1 mmol bromobenzene, 1.2 mmol phenylboronic acid, 2 mmol potassium carbonate, 3 mL solvent, reaction temperature 40 °C. The yield was determined by gas chromatography-mass spectrometry.

[0020] Compared with Pd2Cu2-2@CNT, Pd2Cu2-1@CNT exhibits superior catalytic performance in the Suzuki-Miyaura reaction, particularly in the activation of C-Br bonds.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] The alloy nanoclusters of this invention are Pd2Cu2(S-Adm)1(DPPM)3 (abbreviated as Pd2Cu2-1) and Pd2Cu2(C7H5F3S)6(DPPF)2 (abbreviated as Pd2Cu2-2). The Pd2Cu2-1 alloy nanocluster consists of two palladium atoms and two copper atoms, subsequently protected and linked by ligands of S-Adm and DPPM, forming a shape resembling a small turtle. However, the Pd2Cu2-2 nanocluster also consists of two palladium atoms, two copper atoms, and ligands of C7H5F3S and DPPF forming a linear structure. The two Pd2Cu2 nanoclusters prepared in this invention are loaded onto carbon nanotubes (CNTs) to form catalysts, namely Pd2Cu2-1@CNT and Pd2Cu2-2@CNT. Compared with Pd2Cu2-2@CNT, Pd2Cu2-1@CNT with Pd-Pd bonds prepared in this invention exhibits better catalytic performance in the Suzuki-Miyaura reaction, especially in the activation of C-Br bonds, showing a higher contrast, revealing the superiority of Pd-Pd bonds in the Suzuki-Miyaura catalytic reaction. Attached Figure Description

[0023] Figure 1The UV-Vis absorption spectrum (a) of Pd2Cu2(S-Adm)1(DPPM)3, abbreviated as Pd2Cu2-1, prepared in this invention, in CH2Cl2; X-ray photoelectron spectrum (XPS) (c); the UV-Vis absorption spectrum (c) of Pd2Cu2(C7H5F3S)6(DPPF)2, abbreviated as Pd2Cu2-2, prepared in this invention, in CH2Cl2; X-ray photoelectron spectrum (XPS) (d).

[0024] Figure 2 The diagram shows the overall structural breakdown of Pd₂Cu₂(S-Adm)₁(DPPM)₃ and Pd₂Cu₂(C₇H₅F₃S)₆(DPPF)₂ prepared in this invention. (a) shows the structure broken down into Pd₂Cu₂, (b) into Pd₂Cu₂(DPPM)₃, (c) into Pd₂Cu₂(S-Adm)₁(DPPM)₃, (d) into Pd₂Cu₂, (e) into Pd₂Cu₂(C₇H₅F₃S)₆, and (f) into Pd₂Cu₂(C₇H₅F₃S)₆(DPPF)₂. Color coding: Dark green represents Pd (palladium), orange represents Cu (copper), dark yellow represents Fe (iron), red represents S (sulfur), purple represents P (phosphorus), dark red represents F (fluorine), green represents Cl (chlorine), and the H atom is omitted.

[0025] Figure 3 The structural differences between Pd2Cu2(S-Adm)1(DPPM)3 (a) and Pd2Cu2(C7H5F3S)6(DPPF)2 (b) prepared in this invention are highlighted in the figure.

[0026] Figure 4 Line graphs (X=Br) showing the conversion and yield of bromobenzene and biphenyl after the Suzuki-Miyaura reaction of (a) Pd2Cu2-1@CNT prepared for this invention; (b) catalytic performance of CNT, Pd2Cu2-1@CNT, Pd2Cu2-2@CNT, DPPM, DPPF, C7H5F3S and S-Adm after the Suzuki-Miyaura reaction; (c) comparison of the conversion rates of Pd2Cu2-1@CNT and Pd2Cu2-2@CNT after the Suzuki-Miyaura reaction (X=Cl, Br, I); and (d) cyclic testing of Pd2Cu2-1@CNT in the Suzuki-Miyaura reaction (X=Br).

[0027] Figure 5 The bond length diagram of Pd2Cu2-1 prepared in the present invention is shown.

[0028] Figure 6The bond length diagram of Pd2Cu2-2 prepared in the present invention is shown.

[0029] Figure 7 The XRD pattern of Pd2Cu2-1@CNT prepared for the present invention.

[0030] Figure 8 The XRD pattern of Pd2Cu2-2@CNT prepared in the course of this invention.

[0031] Figure 9 TEM image of Pd2Cu2-1@CNT prepared in accordance with the present invention.

[0032] Figure 10 TEM image of Pd2Cu2-2@CNT prepared in accordance with the present invention. Detailed Implementation

[0033] To enable those skilled in the art to better understand and implement the technical solutions of this invention, the invention will be further described below with reference to specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the invention. Unless otherwise specified, the following test methods and detection methods are conventional methods; unless otherwise specified, the reagents and raw materials are commercially available.

[0034] The effects are explained below with reference to the specific experimental process and preparation method.

[0035] Test reagents: Palladium chloride (PdCl2), copper chloride (CuCl2), copper tetrafluoroborate tetrafluoroborate (Cu(CH3CN)4·BF4), bis(diphenyl)ferrocene (Dppf), bis(diphenylphosphine)methane (Dppm), 1-adamanthiol (HS-Adm), 2-(trifluoromethyl)benzenethiophenol (C7H5F3S), and sodium borohydride (NaBH4) were purchased from Shanghai Maclean Biochemical Co., Ltd. Solvents, including dichloromethane (DCM, HPLC grade), methanol (MeOH, HPLC grade), and n-hexane (n-Hex, HPLC grade), were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. The ultrapure water used in this study was purified using a microporous system. Example 1:

[0036] The preparation method of Pd2Cu2-1 alloy nanoclusters includes the following steps:

[0037] First, 60 mg of copper chloride was dissolved in a mixture of 5 mL of methanol and 15 mL of dichloromethane (volume ratio v / v = 1 / 3). Then, 45 μL of the prepared palladium chloride solution was slowly added dropwise while stirring. Subsequently, 50 mg of bis(diphenylphosphine)methane was introduced into the flask. Next, 60 mg of 1-adamanthiol was added to the mixture, and the mixture was stirred for another 25 minutes to allow for sufficient interaction and initial reaction between the ligand and the metal. After this time, 10 mg of NaBH4 dissolved in 1 mL of water was added to further react and form nanoclusters. The reaction mixture immediately turned into a brown solution. Notably, over 8 hours, the solution color changed from brown to reddish-brown, and finally to an orange-red state, indicating the formation of the desired nanoclusters. The next step was to extract the reaction mixture with CH2Cl2 to separate the product from the reaction solvent and byproducts. The purified CH2Cl2 organic phase was collected and crystallized at room temperature using dichloromethane / n-hexane. After 5 days, red rod-shaped single crystals were formed, yielding Pd2Cu2-1 alloy nanoclusters, namely Pd2Cu2(S-Adm)1(DPPM)3. Example 2:

[0038] The preparation method of Pd2Cu2-2 alloy nanoclusters includes the following steps:

[0039] First, 34 mg of copper tetrafluoroborate tetraacetonitrile was dissolved in a mixture of 10 mL methanol and 10 mL dichloromethane (v / v = 1 / 1). Then, 25 μL of the prepared palladium chloride solution was slowly added dropwise while stirring. Subsequently, 50 mg of bis(diphenylphosphine)ferrocene and 30 μL of 2-(trifluoromethyl)thiophenol were added to the solution, and interestingly, the solution immediately turned deep red. The mixture was stirred for another 20 minutes to allow sufficient interaction and initial reaction between the ligand and the metal. Then, 100 mg of NaBH4 dissolved in 5 mL methanol was added to the reactor. The solution color turned dark brown within 5 minutes. Notably, the solution color changed from deep red to orange, indicating the formation of the desired nanoclusters. After 8 hours, the reaction mixture was treated, and the reaction mixture was extracted with CH2Cl2 to separate the product from the reaction solvent and byproducts. The purified CH2Cl2 organic phase was collected and crystallized at room temperature using dichloromethane / n-hexane. After 15 days, black, crystalline single crystals were formed, yielding Pd2Cu2-2 alloy nanoclusters, namely Pd2Cu2(C7H5F3S)6(DPPF). 2。

[0040] The properties of the Pd2Cu2(S-Adm)1(DPPM)3 alloy nanoclusters and Pd2Cu2(C7H5F3S)6(DPPF)2 alloy nanoclusters prepared above were tested. The specific process and results are as follows:

[0041] (a) Test and detection methods

[0042] 1. The UV-Vis absorption spectra of all nanoclusters were recorded using an Agilent 8453. The samples were dissolved in dichloromethane, and background correction was performed using a dichloromethane blank sample.

[0043] 2. X-ray photoelectron spectroscopy (XPS) measurements were performed on a thermal scale ESCALAB 250, equipped with a monochromatic aluminum Kα (1486.8 Ev) 150W X-ray source, a 0.5 mm circular spot size, and a flow injector.

[0044] 3. The F200 field emission transmission electron microscope (TEM F200) test was conducted on the JEM-F200. The sample was dissolved in an ethanol solution and dropped onto a molybdenum grid for testing.

[0045] 4. Single-crystal X-ray diffraction data were acquired using a Bruker Smart APEX II CCD diffractometer at 120 K, with graphite monochromatic Cu Kα radiation (λ = 1.54186 Å).

[0046] 5. The X-ray diffraction (XRD) test uses a high-resolution θ / θ closed-loop goniometer drive system, a cross-beam optics system (CBO), and a 9.0 kW rotating cathode X-ray generator.

[0047] 6. Gas chromatography-MS (GC-MS) testing was performed using a GC-2010Pro.

[0048] (II) Test Results

[0049] 1. Synthesis and characterization of Pd₂Cu₂⁻¹ and Pd₂Cu₂⁻² nanoclusters

[0050] The Pd₂Cu₂⁻¹ and Pd₂Cu₂⁻² nanoclusters were synthesized using a one-pot method, as described in Examples 1 and 2. The overall structures of the two alloy nanoclusters are as follows: Figure 2 The c-graph and f-graphs are shown in the figure.

[0051] Single-crystal X-ray crystallography determined the crystal structures of Pd₂Cu₂⁻¹ and Pd₂Cu₂⁻², both using the P⁻¹ space group, as shown in Tables 1 and 2. The crystal structure of Pd₂Cu₂⁻¹ consists of 2 Cu atoms, 2 Pd atoms, 2 Cl atoms, 6 P atoms, and 1 S atom. The overall structure of Pd₂Cu₂(S-Adm)₁(DPPM)₃ is shown below. Figure 2c, protected and linked by adamantane-thiol ligand and bis(diphenylphosphine-methane). Structural analysis shows that two Cu atoms form a twisted Cu-Cl-Cu-Cl quadrilateral with two Cl atoms, and a Pd-Pd bond on it. Figure 2 The distances between the PdCu metal atoms are 3.074 Å and 3.090 Å, respectively, exceeding the typical bonding range of Pd-Cu bonds, and are indicated by dashed lines. Interestingly, the PdCu metal atoms rely on... Figure 2 In b, bis(diphenylphosphine)methane is attached. Subsequently, the S atom in adamantanethiol forms a triangle with two Pd atoms, serving as the head of Pd₂Cu₂⁻, which can be viewed as a "turtle" shape. Figure 2 c). One characteristic is the formation of a metallic Pd-Pd bond with a bond length of 2.638 Å. Furthermore, the remaining portion is bonded to either S or P atoms. The structure of Pd₂Cu₂⁻⁂ consists of 2 Cu atoms, 2 Pd atoms, 2 Fe atoms, 6 S atoms, 18 F atoms, and 4 P atoms. The overall structure of Pd₂Cu₂(C₇H₅F₃S)₆(DPPF)₂ is as follows... Figure 2 f, protected and linked by 2-(trifluoromethyl)benzylthiophenol and bis(diphenylphosphine)ferrocene. For example... Figure 2 The four metal atoms are linearly arranged at a twist angle. The distance between every two metal atoms is approximately 3.18 Å, preventing the formation of metallic bonds. This paves the way for the further formation of three twisted quadrilaterals with S atoms in the six thiol ligands. Figure 2 e). Two bis(diphenylphosphine)ferrocene atoms are connected to opposite sides of the structure, forming... Figure 2 Pd2Cu2-2 in f.

[0052] The UV-Vis spectrum showed three prominent peaks centered at 362 nm and 455 nm, and a weak peak at 309 nm for Pd₂Cu₂⁻ dissolved in dichloromethane. Figure 1 a. The illustration in the upper right corner shows Pd₂Cu₂⁻¹ crystals under a microscope, appearing as red rods. For Pd₂Cu₂⁻², the UV-Vis spectrum of pure Pd₂Cu₂⁻² crystals dissolved in dichloromethane shows a significant peak at 388 nm and a weak peak at 306 nm, as shown in Figure 1. Figure 1 b.

[0053] X-ray photoelectron spectroscopy confirmed the presence of Pd, Cu, S, P, and Cl in Pd₂Cu²⁻. Figure 1 X-ray photoelectron spectroscopy of Pd in ​​Pd₂Cu₂⁻ confirmed the presence of Pd, Cu, Fe, S, P, and F in Pd₂Cu₂⁻. Figure 1 c. And Figure 5 and 6As shown, Pd exhibits a +2 valence state at the center of both Pd2Cu2-1 and Pd2Cu2-2, while Cu exhibits a +1 valence state at the center of both Pd2Cu2-1 and Pd2Cu2-2.

[0054]

[0055]

[0056] 2. Characterization of catalytic performance of Pd2Cu2-1@CNT and Pd2Cu2-2@CNT

[0057] X-ray diffraction (XRD) confirmed that Pd2Cu2-1 and Pd2Cu2-2, when loaded onto carbon nanotubes and subjected to organocatalytic reactions, were identical to blank carbon nanotubes, showing almost no change, indicating that there was no aggregation before and after the reaction.

[0058] Field emission transmission electron microscopy (TEM F200) detected no aggregation in Pd2Cu2-1@CNT and Pd2Cu2-2@CNT, indicating that they had good morphology.

[0059] 3. Comparative Study on the Catalytic Performance of Pd2Cu2-1@CNT and Pd2Cu2-2@CNT

[0060] The catalytic performance of Pd₂Cu₂⁻¹@CNT was investigated via the Suzuki-Miyaura reaction in methanol solvent at 40 °C. The conversion of bromobenzene on Pd₂Cu₂⁻¹@CNT and the selectivity for biphenyl products were as follows: Figure 4a. After 4 h, the conversion of bromobenzene reached 74.02%, and the selectivity of biphenyl remained almost 100%. Therefore, the reaction exhibits high selectivity and good conversion. Notably, when the reaction time was extended to 12 h, the selectivity of biphenyl remained stable at around 100%, indicating that Pd2Cu2-1@CNT hardly catalyzed other bromobenzene products under these conditions, demonstrating good selectivity for biphenyl. The conversion rate remained almost constant over time, indicating that 4 h is the optimal and mildest reaction time. However, under the same conditions, blank carbon nanotubes (CNTs) showed a trace bromobenzene conversion of 2% within 4 h, suggesting that the Pd site acts as the catalytic center in this reaction. To investigate the property differences between Pd2Cu2-1@CNT and Pd2Cu2-2@CNT and to control halogenated benzene due to different substituents, the carbon-carbon coupling reaction between bromobenzene and phenylboronic acid esters was used as a model reaction. Therefore, we compared the catalytic activities of iodobenzene and chlorobenzene with substituents different from those of bromobenzene. For Pd₂Cu₂⁻¹@CNT, the conversion of iodobenzene reached 70%, while the selectivity for biphenyl remained at 100%. This is because the C-Cl bond energy is higher and more difficult to activate. Therefore, under the same conditions, the conversion of chlorobenzene reached 10%. Subsequently, to better reveal the superiority and catalytic activity of Pd₂Cu₂⁻¹@CNT, we plotted a bar chart to more intuitively show the differences between the two, such as... Figure 4 c. Therefore, iodobenzene and chlorobenzene exhibit almost no catalytic activity towards Pd₂Cu₂-2@CNT. As expected, due to the synergistic effect of the Pd-Pd bond and the strong metal-support interaction, Pd₂Cu₂-1@CNT demonstrates superior catalytic activity and selectivity compared to the Pd₂Cu₂-2@CNT catalyst in the Suzuki-Miyaura reaction. Next, the recyclability of Pd₂Cu₂-1@CNT was investigated to evaluate the stability of the catalyst for the Suzuki-Miyaura reaction under the same mild conditions. The results for Pd₂Cu₂-1@CNT are as follows: Figure 4 Unfortunately, the stability was maintained for only three cycles during the reaction, but after three cycles, the selectivity for biphenyl products exceeded 90%.

[0061] In summary, this invention synthesized two small-sized Pd₂Cu₂ nanoclusters, Pd₂Cu₂(S-Adm)₁(DPPM)₃ (Pd₂Cu₂-1) and Pd₂Cu₂(C₇H₅F₃S)₆(DPPF)₂ (Pd₂Cu₂-2), using a one-pot method, which were well confirmed by single-crystal X-ray crystallography (SCXRD) and X-ray photoelectron spectroscopy (XPS). SCXRD data showed that the Pd₂Cu₂-1 structure was considered to be "turtle-shaped," while the Pd₂Cu₂-2 structure was considered to be linearly arranged. The most interesting and crucial aspect is the presence of Pd-Pd bonds in both nanoclusters. Compared to Pd₂Cu₂-2@CNT, Pd₂Cu₂-1@CNT with Pd-Pd bonds exhibited better catalytic performance in the Suzuki-Miyaura reaction, particularly in C-Br bond activation. Under Pd₂Cu₂⁻¹@CNT conditions, the conversion rate of bromobenzene reached 74.02%, while the selectivity for biphenyl remained almost 100%. Considering green chemistry and cost-effectiveness, Pd₂Cu₂⁻¹@CNT shows great potential for industrial applications, laying the foundation for the subsequent development of small-sized PdCu bimetallic nanoclusters.

[0062] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A PdCu alloy nanocluster, characterized in that: The chemical formula of the PdCu alloy nanoclusters is Pd2Cu2Cl2(S-Adm)1(DPPM)3, where S-Adm represents adamantane thiol and DPPM represents bis(diphenylphosphine)methane, abbreviated as Pd2Cu2-1. Alternatively, the chemical formula of the PdCu alloy nanoclusters is Pd2Cu2(C7H5F3S)6(DPPF)2, where C7H5F3S represents 2-(trifluoromethyl)benzylthiophenol and DPPF represents bis(diphenylphosphine)ferrocene, abbreviated as Pd2Cu2-2.

2. The method for preparing the PdCu alloy nanoclusters according to claim 1, characterized in that... Includes the following steps: Copper source and palladium metal salt were dissolved in a mixed solution of dichloromethane and methanol. Thiol ligand and bisphosphine ligand were added sequentially under stirring at room temperature to carry out the initial reaction and obtain a mixed solution. An aqueous solution of sodium borohydride was added to the obtained mixed solution and a one-pot reduction reaction was carried out to obtain an organic phase solution. The organic phase solution was crystallized at room temperature to obtain PdCu alloy nanoclusters.

3. The preparation method according to claim 2, characterized in that: The copper source is copper chloride, the palladium metal salt is palladium chloride, the thiol ligand is adamantane thiol, and the bisphosphine ligand is bis(diphenylphosphine)methane, thus preparing PdCu alloy nanoclusters Pd2Cu2-1.

4. The preparation method according to claim 2, characterized in that: The copper source is copper tetrafluoroborate tetraacetonitrile, the palladium metal salt is palladium chloride, the thiol ligand is 2-(trifluoromethyl)benzylthiophenol, and the bisphosphine ligand is bis(diphenylphosphine)ferrocene, thus preparing PdCu alloy nanoclusters Pd2Cu2-2.

5. The application of the PdCu alloy nanoclusters of claim 1 in the catalytic Suzuki-Miyaura coupling reaction.

6. The application according to claim 5, characterized in that: The PdCu alloy nanoclusters were loaded onto carbon nanotubes to obtain a Pd2Cu2@CNT catalyst, which was used to catalyze the Suzuki-Miyaura coupling reaction.

7. The application according to claim 6, characterized in that: Using bromobenzene and phenylboronic acid as reaction substrates, a Suzuki-Miyaura coupling reaction was carried out in the presence of a Pd2Cu2@CNT catalyst and potassium carbonate to obtain biphenyl products.

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