An Ag having an unsaturated active site 19 Pd nanoclusters, methods of making and using same

Abstract

The application belongs to the cross field of nanomaterials and coordination chemistry, and particularly relates to an Ag 19 Pd nanocluster, a preparation method and application thereof 141 H 126 Ag 19 Cl3N 18 P6Pd, which is abbreviated as Ag 19 Pd(dpa)6(dppp)3Cl3, belongs to a triclinic system; a space group is P-1, alpha=80.073(3) degrees, beta=75.948(3) degrees, gamma=88.025(3) degrees, in addition, the nanocluster has high monodispersity and stability, and contains an unsaturated mu3-Ag active site. The Ag 19 Pd nanocluster of the application has an atomic level accurate structure and an unsaturated active site, and after forming a supported catalyst with a commercially available TiO2, exhibits high catalytic activity in a p-nitrophenol reduction reaction, and a reaction rate constant is as high as 1.26 min ‑1 , and has a broad development prospect.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of nanomaterials and coordination chemistry, and in particular relates to an Ag with unsaturated active sites. 19 Pd nanoclusters, their preparation methods, and applications. Background Technology

[0002] p-Nitrophenol is listed as one of the most toxic organic pollutants due to its high stability, carcinogenicity, teratogenicity, and mutagenicity. Its high water solubility allows it to accumulate easily in organisms, inhibiting photosynthesis in aquatic plants, causing death to fish and other aquatic animals, and accumulating in aquatic organisms, amplifying its harmful effects through the food chain, ultimately posing a significant threat to human health and the ecological environment. In contrast, p-aminophenol, as a reduction product of nitrophenol, is environmentally friendly and is an important raw material for the preparation of various drugs (paracetamol, phenacetin, etc.). Converting p-nitrophenol in wastewater into high-value-added p-aminophenol, turning waste into treasure, is of great significance for promoting the circular economy and sustainable development strategies. Compared with traditional catalytic hydrogenation methods, the catalytic reduction of p-nitrophenol using sodium borohydride is widely recognized as one of the most promising technologies for industrial application due to its high efficiency, thoroughness, economy, environmental friendliness, and feasibility.

[0003] In recent years, metal nanoclusters, as a class of nanoparticles with ultra-small sizes (<3 nm), have shown significant application potential in the catalytic reduction of p-nitrophenol with sodium borohydride due to their highly tunable size, composition, and electronic / atomic structure. However, most of the metal nanoclusters reported in the literature currently exhibit low catalytic activity in this reaction, with reaction rate constants generally below 1 min. -1 This is typically due to the lack of unsaturated active sites on the surface of metal nanoclusters. Secondly, atomically precise metal nanoclusters are crucial for identifying active sites in catalytic processes and establishing the correlation between cluster structure and performance. Therefore, preparing highly active metal nanocluster catalysts with atomically precise structures and unsaturated active sites has become a key scientific problem urgently needing to be solved by researchers in this field. Summary of the Invention

[0004] This invention provides an Ag with unsaturated active sites. 19 Pd nanoclusters, Ag in this application 19 Pd nanoclusters possess atomically precise structures, unsaturated active sites, and exhibit high catalytic activity in the reduction of p-nitrophenol, effectively solving the technical problems of low catalytic activity and low reaction rate of existing metal nanoclusters in the catalytic reduction of p-nitrophenol by sodium borohydride.

[0005] To achieve the above objectives, the present invention employs the following technical solution: an Ag with unsaturated active sites. 19 Pd nanoclusters, Ag 19 The chemical formula of Pd nanoclusters is C 141 H 126 Ag 19 Cl3N 18 P6Pd, abbreviated as Ag 19 Pd(dpa)6(dppp)3Cl3, where dpa is a 2,2-dipyridinamine organic ligand and dppp is a 1,3-bis(diphenylphosphine propane) organic ligand, has a molecular weight of 4520.69 Da. The simplified structural formula of the organic ligand is as follows:

[0006]

[0007] Ag, which has unsaturated active sites 19 Further improvements to Pd nanoclusters:

[0008] Preferred, Ag 19 The crystal system of Pd(dpa)6(dppp)3Cl3 is triclinic, and its space group is P-1. α=80.073(3)°, β=75.948(3)°, γ=88.025(3)°,

[0009] Preferred, Ag 19 The precise structure of Pd(dpa)6(dppp)3Cl3 consists of 19 Ag atoms, one Pd atom, 6 dpa organic ligands, 3 dppp organic ligands, and 3 Cl halogen ligands; among them, 18 Ag atoms and one Pd atom form a twisted tetrahedral Ag atom. 18 The Pd core, with the remaining Ag atom coordinating with the N atom in 2,2-dipyridinamine, the P atom in dppp, and the Cl atom, forms an unsaturated μ3-Ag active site.

[0010] A second objective of this invention is to provide an Ag with unsaturated active sites as described in any one of the above claims. 19 The preparation method of Pd nanoclusters includes the following steps:

[0011] S1. Dissolve the silver salt, nitrogen ligand and palladium salt in a mixed solvent of dichloromethane and methanol, add triethylamine and stir, then add phosphine ligand and continue stirring to obtain a mixed solution;

[0012] S2. Add sodium borohydride aqueous solution to the mixed solution and stir thoroughly at room temperature. The mixed solution gradually turns into a brownish-red solution. Then add n-hexane to precipitate the product and separate the crude product by centrifugation.

[0013] S3. Dissolve the crude product in dichloromethane, then add n-hexane at room temperature to induce the formation of brownish-black rod-shaped crystals. Wash the crystals with n-hexane and dry them under vacuum to obtain Ag with unsaturated active sites. 19 Pd nanoclusters.

[0014] Ag, which has unsaturated active sites 19 Further improvements to the preparation method of Pd nanoclusters:

[0015] Preferably, in step S1, the volume ratio of dichloromethane to methanol in the mixed solvent is 7:1, the silver source is silver trifluoromethanesulfonate or silver hexafluoroantimonate, the nitrogen ligand is 2,2-dipyridinylamine, the palladium salt is potassium tetrachloropalladium or palladium acetate, and the phosphine ligand is 1,3-bis(diphenylphosphine)propane.

[0016] Preferably, the molar ratio of silver salt, nitrogen ligand, palladium salt, triethylamine, phosphine ligand and sodium borohydride in steps S1 and S2 is 1:(0.4-0.8):(0.1-0.4):(5-10):(1-1.5):(0.4-1.5).

[0017] A third objective of this invention is to provide an Ag with unsaturated active sites as described in any one of the above claims. 19 Application of Pd nanoclusters in the catalytic reduction of p-nitrophenol.

[0018] As the Ag with unsaturated active sites mentioned above 19 Further improvements have been made to the application of Pd nanoclusters in the catalytic reduction of p-nitrophenol:

[0019] Preferably, Ag with unsaturated active sites is used. 19 Supported silver-palladium nanoclusters catalysts, namely Ag, were prepared by loading Pd nanoclusters onto TiO2. 19 Pd@TiO2 is then applied to the catalytic reduction of p-nitrophenol.

[0020] Preferably, Ag with unsaturated active sites is used. 19 The specific method for loading Pd nanoclusters onto TiO2 is as follows: TiO2 powder is added to dichloromethane and ultrasonically dispersed, then stirred continuously. Ag with unsaturated active sites is then added at a concentration of 10 mg / mL-13 mg / mL. 19 Pd nanoclusters, TiO2 powder, and Ag with unsaturated active sites 19 The Pd nanoclusters were added at a mass ratio of 100:(0.5-1). The mixture was stirred at room temperature and pressure until fully reacted. The precipitate was then collected by centrifugation and vacuum dried at room temperature to obtain the supported silver-palladium nanocluster catalyst, i.e., Ag. 19 Pd@TiO2.

[0021] Preferably, the step of catalytic reduction of p-nitrophenol is as follows: Ag 19 A Pd@TiO2 supported silver-palladium nanocluster catalyst was added to a p-nitrophenol solution, followed by the addition of sodium borohydride. The mixture was then placed under sunlight, and the reaction process was monitored using UV-Vis absorption spectroscopy until the p-nitrophenol solution changed from yellow to colorless. The concentration of the p-nitrophenol solution was 0.15 mmol / L–0.25 mmol / L. Ag... 19 The amount of Pd@TiO2 added to the p-nitrophenol solution was 0.25-0.40 mg / ml, Ag 19 The mass ratio of Pd@TiO2 to sodium borohydride is 1:3.

[0022] The advantages of this invention compared to the prior art are as follows:

[0023] 1) This invention provides an Ag with unsaturated active sites. 19 Pd nanoclusters, with the chemical formula C 141 H 126 Ag 19 Cl3N 18 P6Pd, abbreviated as Ag 19 Pd(dpa)6(dppp)3Cl3, where dpa is 2,2-dipyridinamine and dppp is 1,3-bis(diphenylphosphine propane); its precise structure contains an unsaturated μ3-Ag active site and Ag... 18 The nanoclusters consist of a Pd core and a shell composed of two Cl ligands, six dpa ligands, and three dppp ligands. Under stirring conditions at room temperature, these nanoclusters can be effectively dispersed and adsorbed onto a commercially available TiO2 support, forming a supported catalyst. Under sunlight irradiation, this catalyst can catalytically reduce over 94% of p-nitrophenol to p-aminophenol in just 240 seconds, exhibiting high catalytic activity, a fast reaction rate, and a rate constant as high as 1.26 min. -1 It has good development prospects.

[0024] 2) This invention provides an Ag with unsaturated active sites. 19 The method for preparing Pd nanoclusters is simple, with mild reaction conditions, low cost, and no calcination required. It only requires readily available raw materials such as silver salt, 2,2-dipyridinamine ligand, 1,3-bis(diphenylphosphine)propane ligand, palladium salt, and sodium borohydride. Silver-palladium nanoclusters with unsaturated active sites can be easily and quickly prepared in a one-pot process at room temperature. The silver-palladium nanoclusters prepared by this invention have small size (~2.0 nm), good monodispersity, and high stability. Attached Figure Description

[0025] Figure 1 Ag prepared according to the present invention in Examples 1-3 19Precise structure and size diagram of Pd nanoclusters;

[0026] Figure 2 Ag prepared in Examples 1-3 19 Schematic diagram of unsaturated μ3-Ag active sites in Pd nanoclusters;

[0027] Figure 3 Ag prepared in Examples 1-3 19 High-resolution mass spectrum of Pd nanoclusters;

[0028] Figure 4 Ag prepared in Examples 1-3 19 Orbital electron binding energy of Ag and Pd elements in Pd nanoclusters;

[0029] Figure 5 Ag prepared in Examples 1-3 19 UV absorption spectra of Pd nanocluster solutions after being left for different times;

[0030] Figure 6 The Ag prepared in Example 4 19 UV-Vis absorption spectra of Pd@TiO2(a) and commercially available TiO2(b) used for the catalytic reduction of p-nitrophenol over time, where the characteristic absorption peak at 300 nm corresponds to the reduction product p-aminophenol;

[0031] Figure 7 Ag prepared in Example 4 19 Pd@TiO2 catalytic reduction of p-nitrophenol ln(C0 / C) at room temperature t The graph shows the linear relationship between C0 and different reaction times t, where C0 is the initial concentration of p-nitrophenol in the solution, and C... t It is adding Ag to the solution 19 The remaining concentration of p-nitrophenol after reaction time t using Pd@TiO2 catalyst. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0033] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Unless otherwise specified, the experimental methods described in this invention all employ conventional techniques. Furthermore, all experimental materials used, unless otherwise specified, were purchased through commercially available channels.

[0034] Example 1

[0035] This embodiment provides a silver-palladium nanocluster Ag. 19 The preparation method of Pd includes the following steps:

[0036] S1. Dissolve silver trifluoromethanesulfonate (15 mg, 0.058 mmol), 2,2-dipyridinamide (4 mg, 0.023 mmol), and palladium acetate (2.5 mg, 0.011 mmol) in a 20 mL glass bottle containing 7 mL of dichloromethane and 1 mL of methanol. Add 30 μL of triethylamine (0.42 mmol) and stir for 30 min. Then add 1,3-bis(diphenylphosphine)propane (32 mg, 0.078 mmol) to the glass bottle and continue stirring thoroughly for 40 min to obtain a mixed solution.

[0037] S2. Add 1 mg sodium borohydride (0.027 mmol) in 250 μL aqueous solution to the mixed solution in step S1. After stirring at room temperature for 12 h, the mixed solution gradually turns into a brownish-red solution. Transfer the brownish-red solution after reaction to a centrifuge tube and add n-hexane for precipitation. After centrifugation at 9500 rpm for 3 min, the crude product is obtained.

[0038] S3. Dissolve the crude product in dichloromethane, then add n-hexane at room temperature to induce crystal formation. After 1 day, brownish-black rod-shaped crystals are obtained. Wash the crystals with n-hexane, dry them under vacuum, and collect the crystal product to obtain Ag with unsaturated active sites. 19 Pd nanoclusters.

[0039] Example 2

[0040] This embodiment provides a silver-palladium nanocluster Ag 19 The preparation method of Pd includes the following steps:

[0041] S1. Dissolve silver hexafluoroantimonate (20 mg, 0.058 mmol), 2,2-dipyridinium (6 mg, 0.035 mmol), and palladium acetate (2 mg, 0.009 mmol) in a 20 mL glass bottle containing 7 mL of dichloromethane and 1 mL of methanol. Add 40 μL of triethylamine (0.54 mmol) and stir for 30 min. Then add 1,3-bis(diphenylphosphine)propane (30 mg, 0.073 mmol) to the glass bottle and continue stirring thoroughly for 40 min to obtain a mixed solution.

[0042] S2. Add 1 mg sodium borohydride (0.027 mmol) in 250 μL aqueous solution to the mixed solution in step S1. After stirring at room temperature for 15 h, the mixed solution gradually turns into a rose red solution. Transfer the rose red solution after reaction to a centrifuge tube and add n-hexane for precipitation. After centrifugation at 9500 rpm for 3 min, the crude product is obtained.

[0043] S3. Dissolve the crude product in dichloromethane, then add n-hexane at room temperature to induce crystal formation. After 1 day, brownish-black rod-shaped crystals are obtained. Wash the crystals with n-hexane, dry them under vacuum, and collect the crystal product to obtain Ag with unsaturated active sites. 19 Pd nanoclusters.

[0044] Example 3

[0045] This embodiment provides a silver-palladium nanocluster Ag. 19 The preparation method of Pd includes the following steps:

[0046] S1. Dissolve silver trifluoromethanesulfonate (15 mg, 0.058 mmol), 2,2-dipyridinium (5 mg, 0.029 mmol), and potassium tetrachloropalladium (3 mg, 0.009 mmol) in a 20 mL glass bottle containing 7 mL of dichloromethane and 1 mL of methanol. Add 25 μL of triethylamine (0.34 mmol) and stir for 30 min. Then add 1,3-bis(diphenylphosphine)propane (30 mg, 0.073 mmol) to the glass bottle and continue stirring thoroughly for 40 min to obtain a mixed solution.

[0047] S2. Add 2 mg sodium borohydride (0.054 mmol) 250 μL aqueous solution to the mixed solution in step S1. After stirring at room temperature for 14 h, the mixed solution gradually turns into a brownish-red solution. Transfer the brownish-red solution after reaction to a centrifuge tube and add n-hexane for precipitation. After centrifugation at 9500 rpm for 3 min, the crude product is obtained.

[0048] S3. Dissolve the crude product in dichloromethane, then add n-hexane at room temperature to induce crystal formation. After 1 day, brownish-black rod-shaped crystals are obtained. Wash the crystals with n-hexane, dry them under vacuum, and collect the crystal product to obtain Ag with unsaturated active sites. 19 Pd nanoclusters.

[0049] Regarding the Ag prepared in Examples 1-3 above 19 The Pd nanoclusters were characterized and their performance was tested. The specific process and results are as follows:

[0050] The crystals prepared in Examples 1-3 were tested using a Bruker SmartApex II CCD single-crystal diffractometer. Data were collected using graphite-monochromated Ga-Kα rays (λ = 1.34139) as the diffraction source, via ω-scan mode under nitrogen protection and at a low temperature of 193 K. The single-crystal structure was then solved using the ShelXT and ShelXL programs in Olex2 software. The refinement method used was the least squares F2 method. Empirical absorption correction was performed using the SADABS program, with anisotropic corrections applied to all non-hydrogen atom positions. All non-hydrogen atoms (Ag, Pd, N, P, Cl, and C) were directly identified. The refinement of hydrogen atom positions in the molecule was obtained using isotropic calculations. Detailed crystal measurement data are shown in Table 1 below.

[0051] Table 1. Main crystallographic data

[0052]

[0053]

[0054] like Figure 1 As shown, the experimental results from the Bruker SmartApex II CCD single-crystal diffractometer and the results after single-crystal analysis indicate that Ag 19 The precise structure of Pd nanoclusters is Ag 19 Pd(dpa)6(dppp)3Cl3 is composed of 19 Ag atoms, one Pd atom, 6 dpa organic ligands, 3 dppp organic ligands, and 3 Cl halogen ligands; among them, 18 Ag atoms and one Pd atom form a twisted tetrahedral Ag atom. 18 The Pd core, with the remaining Ag atom coordinating with the N atom in 2,2-dipyridinamine, the P atom in dppp, and the Cl atom, forms an unsaturated μ3-Ag active site.

[0055] Figure 2 The Ag prepared in Examples 1-3 19 A schematic diagram of the unsaturated μ3-Ag sites in Pd nanoclusters shows that Ag 19 Pd nanoclusters possess unsaturated Ag active sites, which coordinate with N atoms in 2,2-dipyridinium amine, P atoms in dppp, and Cl atoms to form unsaturated μ3-Ag active sites. This characteristic is also characteristic of Ag. 19 The key to the high catalytic activity of Pd nanoclusters lies in...

[0056] Figure 3 The Ag prepared in Examples 1-3 above is 19Pd nanoclusters dissolved in acetonitrile were analyzed by electrospray high-resolution mass spectrometry (Xevo G3 QTOF) in positive ion mode. The results showed that the nanoclusters exhibited very good monodispersity, with a very strong mass spectrum peak signal at m / z 2261.49. This molecular ion peak corresponds to [Ag] 19 Pd(dpa)6(dppp)3Cl3] 2+ Therefore, the general molecular formula of this cluster is [Ag 19 Pd(dpa)6(dppp)3Cl3] 2+ .

[0057] Figure 4 The Ag prepared in Examples 1-3 above is 19 Pd nanoclusters were dissolved in dichloromethane, then drop-coated onto a silicon wafer, dried, and subjected to X-ray photoelectron spectroscopy (Thermo Scientific K-AlphaXPS). The results confirmed that Ag... 19 In Pd nanoclusters, the valence state of Ag is between zero and +1, while the valence state of Pd is close to zero.

[0058] Figure 5 The Ag prepared in Examples 1-3 above is 19 Pd nanoclusters were dissolved in dichloromethane. The UV-Vis absorption spectra of the solution (using a METASH UV8000 microscope) were monitored at different time intervals. The results showed that Ag... 19 Pd nanoclusters exhibit distinct characteristic absorption peaks at 360 nm, 413 nm, and 512 nm. The absorption peaks did not change significantly after the solution was left to stand for one week, indicating that Ag... 19 Pd nanoclusters exhibit high stability.

[0059] Example 4

[0060] This embodiment provides an Ag 19 The method of using Pd nanoclusters supported on TiO2 for the catalytic reduction of p-nitrophenol involves the following steps:

[0061] S1. Weigh 100 mg of commercially available TiO2 powder and place it in a glass bottle containing 9 mL of dichloromethane. Disperse the powder ultrasonically for 30 minutes. Then, add 0.7 mg of Ag... 19 Pd nanoclusters were dissolved in 1 mL of dichloromethane and added to the aforementioned glass bottle. After stirring at room temperature and pressure for 3 hours, the solution was centrifuged to collect the precipitate, which was then dried under vacuum at room temperature to obtain a supported silver-palladium nanocluster catalyst with a theoretical loading of 0.7%, abbreviated as Ag. 19 Pd@TiO2.

[0062] S2. Take 1.2 mL of p-nitrophenol aqueous solution (5 mmol / L), add 30 mL of pure water and place in a 50 mL round-bottom flask. Weigh 10 mg of Ag. 19 The Pd@TiO2 supported silver-palladium nanocluster catalyst was added to a round-bottom flask, followed by the addition of 30 mg of sodium borohydride. After the reaction started, samples were taken at regular intervals, and the reaction process was monitored using UV-Vis absorption spectroscopy under sunlight until the p-nitrophenol solution changed from yellow to colorless.

[0063] Figure 6 The Ag prepared in Example 4 19 UV-Vis absorption spectra of Pd@TiO2 (a) and commercially available TiO2 (b) as catalysts for the reduction of p-nitrophenol over time. 19 The addition of Pd@TiO2 resulted in a rapid decrease in the intensity of the maximum absorption peak at 395 nm, while the characteristic absorption peak of the reduced product p-aminophenol appeared at 300 nm. This comparison shows that, compared to unloaded Ag... 19 Commercially available TiO2 and Ag nanoclusters of Pd nanoclusters 19 The Pd@TiO2 supported catalyst exhibits high catalytic activity, and under sunlight irradiation, it can catalytically reduce more than 94% of p-nitrophenol to p-aminobenzene in just 240 seconds.

[0064] Figure 7 It is Ag in Example 4 19 Pd@TiO2 catalytic reduction of ln(C0 / C) of p-nitrophenol at room temperature t The linear relationship between C0 and different time t is plotted, where C0 is the initial concentration of p-nitrophenol in the solution, and C... t It is adding Ag to the solution 19 The remaining concentration of p-nitrophenol after reaction time t using the Pd@TiO2 catalyst. It can be seen that ln(C0 / C t The reaction exhibits a good linear relationship with different time points t, conforming to the characteristics of a first-order kinetic reaction, with a fitted reaction rate constant as high as 1.26 min. -1 This indicates that Ag 19 The Pd@TiO2 catalyst exhibits high catalytic activity in the reduction reaction of p-nitrophenol.

[0065] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments. It should be noted that many modifications and improvements can be made by those skilled in the art, and all modifications or improvements not exceeding the scope of the claims should be considered within the protection scope of the present invention.

Claims

1. An Ag with unsaturated active sites 19 Pd nanoclusters, characterized in that, The Ag 19 The chemical formula of the Pd nanocluster cation host is [C 141 H 126 Ag 19 Cl3N 18 P6Pd] 2+ abbreviated as [Ag] 19 Pd(dpa)6(dppp)3Cl3] 2+ Wherein dpa is a 2,2-dipyridinamine organic ligand and dppp is a 1,3-bis(diphenylphosphine propane) organic ligand with a molecular weight of 4520.69 Da, the simplified structural formula of the organic ligand is as follows: [Ag 19 Pd(dpa)6(dppp)3Cl3] 2+ Its crystal system belongs to the triclinic crystal system, and its space group is P-1. α=80.073(3)°, β=75.948(3)°, γ=88.025(3)°, 2. An Ag-based product with unsaturated active sites as described in claim 1 19 The method for preparing Pd nanoclusters is characterized by, Includes the following steps: S1. Dissolve the silver salt, nitrogen ligand, and palladium salt in a mixed solvent of dichloromethane and methanol. Add triethylamine and stir, then add the phosphine ligand and continue stirring thoroughly to obtain a mixed solution. The silver salt is silver trifluoromethanesulfonate or silver hexafluoroantimonate, the nitrogen ligand is 2,2-dipyridinamine, the palladium salt is potassium tetrachloropalladium or palladium acetate, and the phosphine ligand is 1,3-bis(diphenylphosphine)propane. S2. Add sodium borohydride aqueous solution to the mixed solution and stir thoroughly at room temperature. The mixed solution gradually turns into a brownish-red solution. Then add n-hexane to precipitate the product and separate the crude product by centrifugation. S3. Dissolve the crude product in dichloromethane, then add n-hexane at room temperature to induce the formation of brownish-black rod-shaped crystals. Wash the crystals with n-hexane and dry them under vacuum to obtain Ag with unsaturated active sites. 19 Pd nanoclusters.

3. The Ag with unsaturated active sites according to claim 2 19 The method for preparing Pd nanoclusters is characterized by, In step S1, the volume ratio of dichloromethane to methanol in the mixed solvent is 7:

1.

4. The Ag with unsaturated active sites according to claim 2 19 The method for preparing Pd nanoclusters is characterized by, The molar ratio of silver salt, nitrogen ligand, palladium salt, triethylamine, phosphine ligand and sodium borohydride in steps S1 and S2 is 1:(0.4-0.8):(0.1-0.4):(5-10):(1-1.5):(0.4-1.5).

5. An Ag-based product with unsaturated active sites as described in any one of claims 1. 19 Application of Pd nanoclusters in the catalytic reduction of p-nitrophenol.

6. The Ag with unsaturated active sites according to claim 5 19 The application of Pd nanoclusters in the catalytic reduction of p-nitrophenol is characterized by... Ag with unsaturated active sites 19 Supported silver-palladium nanoclusters catalysts, namely Ag, were prepared by loading Pd nanoclusters onto TiO2. 19 Pd@TiO2 is then applied to the catalytic reduction of p-nitrophenol.

7. The Ag with unsaturated active sites according to claim 5 or 6 19 The application of Pd nanoclusters in the catalytic reduction of p-nitrophenol is characterized by... Ag with unsaturated active sites 19 The specific method for loading Pd nanoclusters onto TiO2 is as follows: TiO2 powder is added to dichloromethane and ultrasonically dispersed, then stirred continuously. Ag with unsaturated active sites is then added at a concentration of 10 mg / mL-13 mg / mL. 19 Pd nanoclusters, TiO2 powder, and Ag with unsaturated active sites 19 The Pd nanoclusters were added at a mass ratio of 100:(0.5-1). The mixture was stirred at room temperature and pressure until fully reacted. The precipitate was then collected by centrifugation and vacuum dried at room temperature to obtain the supported silver-palladium nanocluster catalyst, i.e., Ag. 19 Pd@TiO2.

8. The Ag with unsaturated active sites according to claim 6 19 The application of Pd nanoclusters in the catalytic reduction of p-nitrophenol is characterized by... The steps for the catalytic reduction of p-nitrophenol are as follows: Ag 19 A Pd@TiO2 supported silver-palladium nanocluster catalyst was added to a p-nitrophenol solution, followed by the addition of sodium borohydride. The mixture was then placed under sunlight, and the reaction process was monitored using UV-Vis absorption spectroscopy until the p-nitrophenol solution changed from yellow to colorless. The concentration of the p-nitrophenol solution was 0.15 mmol / L–0.25 mmol / L. Ag... 19 The amount of Pd@TiO2 added to the p-nitrophenol solution was 0.25-0.40 mg / ml, Ag 19 The mass ratio of Pd@TiO2 to sodium borohydride is 1:3.

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