Ag19Pd nano-cluster with unsaturated active sites as well as preparation method and application of Ag19Pd nano-cluster

Abstract

The invention belongs to the field of crossing of nano-materials and coordination chemistry, and particularly relates to an Ag19Pd nano-cluster with unsaturated active sites and a preparation method and application of the Ag19Pd nano-cluster. The chemical formula of the nano-cluster is C141H126Ag19Cl3N18P6Pd, the chemical formula is abbreviated as Ag19Pd (dpa) 6 (dppp) 3Cl3, and the nano-cluster belongs to a triclinic system; the nano-cluster has a space group of P-1, # imgabs 0 # alpha = 80.073 (3) degrees, beta = 75.948 (3) degrees, gamma = 88.025 (3) degrees and # imgabs 1 #, and in addition, the nano-cluster has high monodispersity and stability and contains an unsaturated mu3-Ag active site. The Ag19Pd nano-cluster disclosed by the invention has an atomic-scale accurate structure and unsaturated active sites, and shows high catalytic activity in a p-nitrophenol reduction reaction after being formed with commercially available TiO2 to form a supported catalyst, the reaction rate constant is up to 1.26 min <-1 >, and the Ag19Pd nano-cluster has a wide development prospect.

Description

Technical Field

[0001] The present invention belongs to the cross-field of nanomaterials and coordination chemistry, and in particular relates to an Ag with unsaturated active sites. 19 Pd nanoclusters and preparation methods and applications thereof. Background Art

[0002] p-Nitrophenol is listed as one of the most toxic organic pollutants due to its high stability, carcinogenicity, teratogenicity and mutagenicity. The high water solubility of p-nitrophenol makes it easy to accumulate in organisms, inhibit the photosynthesis of aquatic plants, and has a lethal effect on aquatic animals such as fish. It will also be enriched in aquatic organisms, amplifying its harm through the food chain, and ultimately posing a huge threat to human health and the ecological environment. In contrast, p-aminophenol, as a reduction product of nitrophenol, is harmless to the environment and is an important raw material for the preparation of a variety of drugs (paracetamol, phenacetin, etc.). Converting p-nitrophenol in wastewater into high-value-added p-nitrophenol and turning waste into treasure is of great significance to promoting the circular economy and sustainable development strategy. Compared with traditional catalytic hydrogenation methods, the reduction of p-nitrophenol by sodium borohydride catalyzed by catalyst is widely regarded as one of the technologies with the greatest potential for industrial application because of its high efficiency, thoroughness, economy, environmental protection and feasibility.

[0003] In recent years, metal nanoclusters, as a type of nanoparticles with ultra-small size (<3nm), have shown significant application potential in the catalytic reduction of p-nitrophenol by sodium borohydride due to their precise and highly tunable size, composition, and electronic / atomic structure. However, most of the metal nanoclusters reported in the literature show low catalytic activity in this reaction, and their reaction rate constants are generally less than 1min. -1 , which is usually caused by the lack of unsaturated active sites on the surface of metal nanoclusters. Secondly, metal nanoclusters with atomic-level precision are essential for identifying active sites in catalytic processes and establishing the relationship between cluster structure and performance. Therefore, the preparation of highly active metal nanocluster catalysts with atomic-level precise structures and unsaturated active sites has become a key scientific issue that researchers in this field need to solve urgently. Summary of the invention

[0004] The present invention provides an Ag having unsaturated active sites. 19 Pd nanoclusters, Ag in this application 19 Pd nanoclusters have atomically precise structures, unsaturated active sites and exhibit high catalytic activity in the reduction reaction 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 object, the present invention adopts the following technical solution: an Ag with unsaturated active sites 19 Pd nanoclusters, the Ag 19 The chemical formula of Pd nanocluster is C 141 H 126 Ag 19 Cl 3 N 18 P 6 Pd, abbreviated as Ag 19 Pd(dpa) 6 (dppp) 3 Cl 3 , where dpa is 2,2-dipyridylamine organic ligand, dppp is 1,3-bis(diphenylphosphino)propane organic ligand, molecular weight is 4520.69Da, and the simplified structure formula of organic ligand is as follows:

[0006]

[0007] As Ag with unsaturated active sites 19 Further improvements of Pd nanoclusters:

[0008] Preferably, Ag 19 Pd(dpa) 6 (dppp) 3 Cl 3 The crystal system belongs to the triclinic system, and the space group is P-1. α=80.073(3)°, β=75.948(3)°, γ=88.025(3)°,

[0009] Preferably, Ag 19 Pd(dpa) 6 (dppp) 3 Cl 3 The precise structure of the Ag complex consists of 19 Ag atoms, one Pd atom, 6 dpa organic ligands, 3 dppp organic ligands and 3 Cl halogen ligands; 18 Ag atoms and one Pd atom form a distorted tetrahedral Ag 18 The Pd core, the remaining Ag atom coordinates with the N atom in 2,2-bipyridylamine, the P atom in dppp and the Cl atom to form an unsaturated μ 3 -Ag active sites.

[0010] The second object of the present invention is to provide an Ag having unsaturated active sites as described in any one of the above 19 The preparation method of Pd nanoclusters comprises the following steps:

[0011] S1, dissolving the silver salt, nitrogen ligand and palladium salt in a mixed solvent of dichloromethane and methanol, adding triethylamine and stirring, then adding the phosphine ligand, and continuing to stir fully to obtain a mixed solution;

[0012] S2. Add sodium borohydride aqueous solution to the mixed solution, stir thoroughly at room temperature, the mixed solution gradually turns into a brown-red solution, then add n-hexane for precipitation, and separate the crude product after centrifugation;

[0013] S3, dissolving the crude product with dichloromethane, and then adding n-hexane at room temperature to induce the formation of brown-black rod-shaped crystals, washing the crystals with n-hexane and vacuum drying, thus obtaining Ag with unsaturated active sites. 19 Pd nanoclusters.

[0014] As Ag with unsaturated active sites 19 Further improvements in the preparation method of Pd nanoclusters:

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

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

[0017] The third object of the present invention is to provide an Ag having unsaturated active sites as described in any one of the above 19 Application of Pd nanoclusters in catalytic reduction of p-nitrophenol.

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

[0019] Preferably, Ag with unsaturated active sites 19 Pd nanoclusters supported on TiO 2 The supported silver palladium nanocluster catalyst, Ag 19 Pd@TiO 2 , and then applied to the catalytic reduction of p-nitrophenol.

[0020] Preferably, Ag with unsaturated active sites 19 Pd nanoclusters supported on TiO 2 The specific method is as follows: TiO 2The powder was added to dichloromethane and ultrasonically dispersed, and then stirred continuously. Then, Ag with unsaturated active sites at a concentration of 10 mg / mL-13 mg / mL was added. 19 Pd nanoclusters, TiO 2 Powder and Ag with unsaturated active sites 19 The mass ratio of Pd nanoclusters added was 100:(0.5-1), stirred at room temperature and pressure, and after sufficient reaction, the precipitate was collected by centrifugation and vacuum dried at room temperature to obtain a supported silver palladium nanocluster catalyst, namely Ag 19 Pd@TiO 2 .

[0021] Preferably, the steps of catalytic reduction of p-nitrophenol are as follows: 19 Pd@TiO 2 The supported silver palladium nanocluster catalyst was added to the p-nitrophenol solution, and then sodium borohydride was added. The reaction was monitored by UV-visible absorption spectroscopy under sunlight until the p-nitrophenol solution changed from yellow to colorless. The concentration of the p-nitrophenol solution was 0.15mmol / L-0.25mmol / L, and the Ag 19 Pd@TiO 2 The amount of Ag added to the p-nitrophenol solution is 0.25-0.40 mg / ml. 19 Pd@TiO 2 The mass ratio with sodium borohydride is 1:3.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1) The present invention provides an Ag having unsaturated active sites 19 Pd nanoclusters, chemical formula: C 141 H 126 Ag 19 Cl 3 N 18 P 6 Pd, abbreviated as Ag 19 Pd(dpa) 6 (dppp) 3 Cl 3 , where dpa is 2,2-dipyridylamine and dppp is 1,3-bis(diphenylphosphino)propane; its precise structure has an unsaturated μ 3 -Ag active sites, Ag 18 The nanoclusters are composed of a Pd core and a shell consisting of two Cl ligands, six dpa ligands, and three dppp ligands. Under room temperature stirring conditions, the nanoclusters can be effectively dispersed and adsorbed on commercially available TiO 2The catalyst is loaded on the carrier to form a supported catalyst. Under sunlight, it takes only 240 seconds to catalytically reduce more than 94% of p-nitrophenol to p-aminophenol. It has high catalytic activity and a fast reaction rate. The reaction rate constant is as high as 1.26min -1 , with good development prospects.

[0024] 2) The present invention provides an Ag having unsaturated active sites 19 The preparation method of Pd nanoclusters has a simple operation process, mild reaction conditions, low cost, and no need for calcination. It only requires the selection of readily available raw materials such as silver salt, 2,2-dipyridylamine ligand, 1,3-bis(diphenylphosphine)propane ligand, palladium salt and sodium borohydride, and a one-pot method can be used to simply and quickly prepare silver-palladium nanoclusters with unsaturated active sites at room temperature. The silver-palladium nanoclusters prepared by the present invention are small in size (~2.0nm), have good monodispersity, and are highly stable. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0026] Figure 2 Ag prepared in Example 1-3 19 Unsaturated μ of Pd nanoclusters 3 -Schematic diagram of Ag active sites;

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

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

[0029] Figure 5 is the Ag prepared in Example 1-3 19 UV absorption spectra of Pd nanocluster solutions after being placed for different time periods;

[0030] Figure 6 is the Ag prepared in Example 4 19 Pd@TiO 2 (a) and commercially available TiO 2 (b) a UV-visible absorption spectrum of the catalytic reduction of p-nitrophenol over time, wherein the characteristic absorption peak at 300 nm corresponds to the reduction product p-aminophenol;

[0031] Figure 7 The Ag prepared in Example 4 19 Pd@TiO2 Catalytic reduction of p-nitrophenol ln(C 0 / C t ) and different reaction times t, where C 0 is the initial concentration of p-nitrophenol in the solution, C t Ag is added to the solution 19 Pd@TiO 2 The residual concentration of p-nitrophenol after the catalyst has reacted for t time. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0033] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. Unless otherwise specified, the experimental methods described in the present invention all adopt conventional technical means. At the same time, all experimental materials used, unless otherwise specified, are purchased through commercial channels.

[0034] Example 1

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

[0036] S1. Silver trifluoromethanesulfonate (15 mg, 0.058 mmol), 2,2-dipyridylamine (4 mg, 0.023 mmol) and palladium acetate (2.5 mg, 0.011 mmol) were dissolved in a 20 mL glass bottle containing 7 mL of dichloromethane and 1 mL of methanol, 30 μL of triethylamine (0.42 mmol) was added and stirred for 30 min, 1,3-bis(diphenylphosphine)propane (32 mg, 0.078 mmol) was added to the glass bottle, and the mixture was stirred for 40 min to obtain a mixed solution;

[0037] S2. Add 1 mg sodium borohydride (0.027 mmol) and 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 brown-red solution. Transfer the brown-red solution after the reaction to a centrifuge tube, add n-hexane for precipitation, and centrifuge at 9500 rpm for 3 min to obtain a crude product.

[0038] S3, dissolving the crude product with dichloromethane, and then adding n-hexane at room temperature to induce crystal formation, obtaining brown-black rod-shaped crystals after 1 day, washing the crystals with n-hexane, and collecting the crystal products after vacuum drying, thus obtaining 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 comprises the following steps:

[0041] S1. Silver hexafluoroantimonate (20 mg, 0.058 mmol), 2,2-dipyridylamine (6 mg, 0.035 mmol) and palladium acetate (2 mg, 0.009 mmol) were dissolved in a 20 mL glass bottle containing 7 mL of dichloromethane and 1 mL of methanol, 40 μL of triethylamine (0.54 mmol) was added and stirred for 30 min, 1,3-bis(diphenylphosphine)propane (30 mg, 0.073 mmol) was added to the glass bottle, and the mixture was stirred for 40 min to obtain a mixed solution;

[0042] S2. Add 1 mg sodium borohydride (0.027 mmol) and 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. The rose red solution after the reaction is transferred to a centrifuge tube, and n-hexane is added for precipitation. The crude product is obtained after centrifugation at 9500 rpm for 3 min.

[0043] S3, dissolving the crude product with dichloromethane, and then adding n-hexane at room temperature to induce crystal formation, obtaining brown-black rod-shaped crystals after 1 day, washing the crystals with n-hexane, and collecting the crystal products after vacuum drying, thus obtaining 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 comprises the following steps:

[0046] S1. Silver trifluoromethanesulfonate (15 mg, 0.058 mmol), 2,2-dipyridylamine (5 mg, 0.029 mmol) and potassium tetrachloropalladate (3 mg, 0.009 mmol) were dissolved in a 20 mL glass bottle containing 7 mL of dichloromethane and 1 mL of methanol, 25 μL of triethylamine (0.34 mmol) was added and stirred for 30 min, 1,3-bis(diphenylphosphine)propane (30 mg, 0.073 mmol) was added to the glass bottle, and the mixture was stirred for 40 min to obtain a mixed solution;

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

[0048] S3, dissolving the crude product with dichloromethane, and then adding n-hexane at room temperature to induce crystal formation, obtaining brown-black rod-shaped crystals after 1 day, washing the crystals with n-hexane, and collecting the crystal products after vacuum drying, thus obtaining Ag with unsaturated active sites. 19 Pd nanoclusters.

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

[0050] The crystals prepared in Examples 1-3 were tested using a Bruker SmartApexⅡCCD single crystal diffractometer. The data were collected using graphite monochromatized Ga-Kα rays (λ=1.34139) as the diffraction source, and the data were collected by ω scanning under nitrogen protection and 193K low temperature bar; then the single crystal structure was solved using ShelXT and ShelXL programs in Olex2 software, the refinement method used the least squares method F2, and the empirical absorption correction used the SADABS program for all non-hydrogen atom positions and anisotropic corrections. All non-hydrogen atoms Ag, Pd, N, P, Cl and C atoms were directly discovered, and the refinement process of the hydrogen atom position in the molecule was obtained using isotropic calculation processing. Detailed crystal measurement data are shown in Table 1 below:

[0051] Table 1 Main crystallographic data

[0052]

[0053]

[0054] like Figure 1 As shown in the figure, the experimental results of Bruker SmartApexⅡCCD single crystal diffractometer and the results after single crystal analysis show that Ag 19 The precise structure of Pd nanoclusters as Ag 19 Pd(dpa) 6 (dppp) 3 Cl 3 , which is composed of 19 Ag atoms, one Pd atom, 6 dpa organic ligands, 3 dppp organic ligands and 3 Cl halogen ligands; 18 Ag atoms and one Pd atom form a distorted tetrahedral Ag 18The Pd core, the remaining Ag atom coordinates with the N atom in 2,2-bipyridylamine, the P atom in dppp and the Cl atom to form an unsaturated μ 3 -Ag active sites.

[0055] Figure 2 The Ag prepared in Example 1-3 19 Unsaturated μ of Pd nanoclusters 3 -Schematic diagram of Ag site, it can be seen that Ag 19 The Pd nanoclusters have unsaturated Ag active sites and coordinate with the N atom in 2,2-bipyridylamine, the P atom in dppp, and the Cl atom to form unsaturated μ 3 -Ag active site, this feature is also Ag 19 Pd nanoclusters are the key to exhibiting high catalytic activity.

[0056] Figure 3 The Ag prepared in the above examples 1-3 is 19 Pd nanoclusters were dissolved in acetonitrile and tested by electrospray high-resolution mass spectrometry (model Xevo G3 QTOF) in positive ion mode. The results showed that the nanoclusters had very good monodispersity. The mass spectrum peak signal at m / z 2261.49 was very strong. The molecular ion peak corresponded to [Ag 19 Pd(dpa) 6 (dppp) 3 Cl 3 ] 2+ , so the molecular formula of the cluster is [Ag 19 Pd(dpa) 6 (dppp) 3 Cl 3 ] 2+ .

[0057] Figure 4 The Ag prepared in the above examples 1-3 is 19 Pd nanoclusters were dissolved in dichloromethane and then drop-coated on a silicon wafer. After drying, X-ray photoelectron spectroscopy (Thermo Scientific K-AlphaXPS) was performed. The results confirmed that Ag 19 The valence state of Ag in Pd nanoclusters is between zero and positive one, and the valence state of Pd is close to zero.

[0058] Figure 5 The Ag prepared in the above examples 1-3 is 19 Pd nanoclusters were dissolved in dichloromethane, and the UV-visible absorption spectra (model METASH UV8000) of the solution were monitored at different time intervals. The results showed that Ag 19Pd nanoclusters have obvious characteristic absorption peaks at 360nm, 413nm and 512nm. The absorption peaks of the solution did not change significantly after being placed for one week, indicating that Ag 19 Pd nanoclusters have high stability.

[0059] Example 4

[0060] This embodiment provides an Ag 19 Pd nanoclusters supported on TiO 2 The method for catalytic reduction of p-nitrophenol is described above, and the specific steps are as follows:

[0061] S1, weigh 100 mg of commercially available TiO 2 The powder was placed in a glass bottle containing 9 mL of dichloromethane and ultrasonically dispersed for 30 minutes. 19 The 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, and then dried under vacuum at room temperature to obtain a supported silver palladium nanocluster catalyst with a theoretical loading rate of 0.7%, referred to as Ag. 19 Pd@TiO 2 .

[0062] S2, take 1.2mL of p-nitrophenol aqueous solution (5mmol / L) and add 30mL of pure water into a 50mL round-bottom flask, weigh 10mg of Ag 19 Pd@TiO 2 The supported silver palladium nanocluster catalyst was added to a round-bottom flask, and then 30 mg of sodium borohydride was added. After the reaction started, samples were taken at regular intervals, and the reaction process was monitored by UV-visible absorption spectroscopy under daylight conditions until the p-nitrophenol solution changed from yellow to colorless.

[0063] Figure 6 is the Ag prepared in Example 4 19 Pd@TiO 2 (a) and commercially available TiO 2 (b) UV-visible absorption spectrum of the catalytic reduction of p-nitrophenol over time. 19 Pd@TiO 2 With the addition of Ag, the maximum absorption peak intensity at 395nm rapidly weakened, and the characteristic absorption peak of the reduced product p-aminophenol appeared at 300nm. 19 Commercially available TiO of Pd nanoclusters 2 , Ag 19 Pd@TiO 2The supported catalyst has high catalytic activity and can catalytically reduce more than 94% of p-nitrophenol to p-aminobenzene in only 240 seconds under sunlight.

[0064] Figure 7 is the Ag in Example 4 19 Pd@TiO 2 Catalytic reduction of ln(C) of p-nitrophenol at room temperature 0 / C t ) and different time t, where C 0 is the initial concentration of p-nitrophenol in the solution, C t Ag is added to the solution 19 Pd@TiO 2 The residual concentration of p-nitrophenol after the catalyst reacts for t time. It can be seen that ln(C 0 / C t ) has a good linear relationship with different time t, which conforms to the first-order reaction characteristics of kinetics, and the fitted reaction rate constant is as high as 1.26min -1 , indicating that Ag 19 Pd@TiO 2 The catalyst has high catalytic activity in the reduction reaction of p-nitrophenol.

[0065] Those skilled in the art should understand that the above are only some specific embodiments of the present invention, rather than all embodiments. It should be noted that for those of ordinary skill in the art, many modifications and improvements can be made, and all modifications or improvements that do not exceed the scope of protection of the present invention should be regarded as the scope of protection 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 Pd nanocluster is C 141 H 126 Ag 19 Cl3N 18 P6Pd, abbreviated as Ag 19 Pd(dpa)6(dppp)3Cl3, where dpa is 2,2-dipyridylamine organic ligand, dppp is 1,3-bis(diphenylphosphino)propane organic ligand, molecular weight is 4520.69Da, and the simplified structure of organic ligand is as follows:

2. The Ag with unsaturated active sites according to claim 1 19 Pd nanoclusters, characterized in that Ag 19 The crystal system of Pd(dpa)6(dppp)3Cl3 belongs to the triclinic system, and the space group is P-1. α=80.073(3)°, β=75.948(3)°, γ=88.025(3)°, 3. The Ag with unsaturated active sites according to claim 1 or 2 19 Pd nanoclusters, characterized in that Ag 19 The precise structure of 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; 18 Ag atoms and one Pd atom form a distorted tetrahedral Ag 18 The Pd core and the remaining Ag atom coordinate with the N atom in 2,2-dipyridylamine, the P atom in dppp and the Cl atom to form an unsaturated μ3-Ag active site.

4. An Ag having unsaturated active sites as claimed in any one of claims 1 to 3 19 The method for preparing Pd nanoclusters is characterized by: The steps include: 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, continue to stir well, and obtain a mixed solution; S2. Add sodium borohydride aqueous solution to the mixed solution, stir thoroughly at room temperature, the mixed solution gradually turns into a brown-red solution, then add n-hexane for precipitation, and separate the crude product after centrifugation; S3, dissolving the crude product with dichloromethane, and then adding n-hexane at room temperature to induce the formation of brown-black rod-shaped crystals, washing the crystals with n-hexane and vacuum drying, thus obtaining Ag with unsaturated active sites. 19 Pd nanoclusters.

5. The Ag with unsaturated active sites according to claim 4 19 The method for preparing Pd nanoclusters is characterized by: The volume ratio of dichloromethane to methanol in the mixed solvent in step S1 is 7:1, the silver source is silver trifluoromethanesulfonate or silver hexafluoroantimonate, the nitrogen ligand is 2,2-dipyridylamine, the palladium salt is potassium tetrachloropalladate or palladium acetate, and the phosphine ligand is 1,3-bis(diphenylphosphine)propane.

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

7. An Ag having unsaturated active sites as claimed in any one of claims 1 to 3 19 Application of Pd nanoclusters in catalytic reduction of p-nitrophenol.

8. The Ag with unsaturated active sites according to claim 7 19 The application of Pd nanoclusters in catalytic reduction of p-nitrophenol is characterized in that: Ag with unsaturated active sites 19 Pd nanoclusters are loaded on TiO2 to prepare supported silver palladium nanocluster catalysts, namely Ag 19 Pd@TiO2 is then used for the catalytic reduction of p-nitrophenol.

9. The Ag with unsaturated active sites according to claim 7 or 8 19 The application of Pd nanoclusters in catalytic reduction of p-nitrophenol is characterized in that: Ag with unsaturated active sites 19 The specific method of loading Pd nanoclusters on TiO2 is as follows: TiO2 powder is added to dichloromethane for ultrasonic dispersion and stirred continuously, and then Ag with unsaturated active sites at a concentration of 10 mg / mL-13 mg / mL is added. 19 Pd nanoclusters, TiO2 powder, and Ag with unsaturated active sites 19 The mass ratio of Pd nanoclusters added was 100:(0.5-1), stirred at room temperature and pressure, and after sufficient reaction, the precipitate was collected by centrifugation and vacuum dried at room temperature to obtain a supported silver palladium nanocluster catalyst, namely Ag 19 Pd@TiO2.

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

Images