Silver-copper alloy nanoparticles with core-shell structure as well as preparation method and application of silver-copper alloy nanoparticles

Abstract

The invention discloses silver-copper alloy nanoparticles with a core-shell structure as well as a preparation method and application of the silver-copper alloy nanoparticles. The core of the core-shell structure silver-copper alloy nanoparticle is a silver-copper alloy nanoparticle, and the shell of the core-shell structure silver-copper alloy nanoparticle is a ZIF-8 coating layer. The preparation method of the silver-copper alloy nanoparticles with the core-shell structure comprises the following steps: 1) preparing the silver-copper alloy nanoparticles; (2) preparing surface modified silver-copper alloy nanoparticles; and 3) dispersing the surface-modified silver-copper alloy nanoparticles, zinc salt and 2-methylimidazole in methanol for reaction. The silver-copper alloy nano-particles with the core-shell structure have the advantages of rich active sites, good catalytic effect, high cycling stability, mild reaction conditions, simple preparation method and the like, can be used for carboxylation of terminal alkyne and CO2 to generate propiolic acid compounds and carboxylation of propargyl amine and CO2 to generate 2-oxazolidinone compounds; and the method has a very wide application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of photocatalysis, and in particular to a core-shell structured silver-copper alloy nanoparticle and a preparation method and application thereof. Background Art

[0002] Carbon dioxide capture and utilization (CCU) is a promising approach that aims to utilize CO2 as a carbon source (C1) to produce valuable chemicals and fuels. However, due to the high thermodynamic and kinetic stability of CO2, most catalysts used for CO2 conversion need to be used under harsh conditions (e.g., high temperature, high CO2 pressure, high catalyst loading, or the need for equivalent additives), which is not conducive to practical application.

[0003] Studies have shown that Cu and Ag nanoparticles (NPs) loaded on supports as heterogeneous catalysts can show outstanding advantages in the activation of alkynes (e.g., carboxylation of terminal alkynes with CO2, cyclization of propargylamine with CO2, carbonyl cyclization of propargyl alcohol with CO2, etc.), and have good application prospects. However, during the reaction, Cu or Ag NPs are prone to aggregation due to their high surface energy, especially when irradiated or heated, which will cause a reduction in their active sites and surface area, resulting in reduced catalytic activity and recovery capacity.

[0004] To address the above problems, an effective method is to encapsulate susceptible metal NPs into MOF materials with high stability and suitable pore size to form core-shell structure catalysts. The porous shell layer can not only protect the metal NPs from migration, aggregation and leaching, but also promote the enrichment of substrates on the surface of the core, thereby improving the catalytic efficiency. For example, Ag@ZIF-8, Cu@Ag@ZIF-8 and Cu2O@ZIF-8, these core-shell structure catalysts can promote the efficient conversion of alkynes and CO2, and the catalytic performance does not decrease significantly after repeated use. However, despite the improved stability and activity of these core-shell structure catalysts, their catalytic reactions still require high temperatures (>50°C), and the catalytic sites are single. Most of them only have a catalytic effect on a single type of alkyne, which greatly limits their practical applications.

[0005] Therefore, it is of great significance to develop a catalytic material for CO2 chemical conversion with rich active sites, good catalytic effect, strong cyclic stability, mild reaction conditions and simple preparation method. Summary of the invention

[0006] The purpose of the present invention is to provide a core-shell structured silver-copper alloy nanoparticle and a preparation method and application thereof.

[0007] The technical solution adopted by the present invention is:

[0008] A core-shell structured silver-copper alloy nanoparticle, wherein the core is the silver-copper alloy nanoparticle and the shell is a ZIF-8 coating layer.

[0009] Preferably, the molar ratio of silver to copper in the silver-copper alloy nanoparticles is 1:0.55-1.68.

[0010] Preferably, the average particle size of the silver-copper alloy nanoparticles is 40 nm to 60 nm.

[0011] Preferably, the average particle size of the core-shell structured silver-copper alloy nanoparticles is 100 nm to 500 nm.

[0012] A method for preparing the core-shell structured silver-copper alloy nanoparticles as described above comprises the following steps:

[0013] 1) dispersing a soluble silver salt, a soluble copper salt, a nonionic surfactant and a reducing agent in water for hydrothermal reaction to obtain silver-copper alloy nanoparticles;

[0014] 2) surface-modifying the silver-copper alloy nanoparticles with a polymer surfactant to obtain surface-modified silver-copper alloy nanoparticles;

[0015] 3) dispersing the surface-modified silver-copper alloy nanoparticles, zinc salt and 2-methylimidazole in a polar protic solvent for reaction to obtain core-shell structured silver-copper alloy nanoparticles.

[0016] Preferably, the soluble silver salt in step 1) is at least one of silver nitrate and silver acetate.

[0017] Preferably, the soluble copper salt in step 1) is at least one of copper chloride, copper nitrate, copper acetate and copper sulfate.

[0018] Preferably, the nonionic surfactant in step 1) is at least one of hexadecylamine, oleylamine and octadecylamine.

[0019] Preferably, the reducing agent in step 1) is at least one of glucose and maltose.

[0020] Preferably, in step 1), the molar ratio of the soluble silver salt, the soluble copper salt, the nonionic surfactant and the reducing agent is 1:0.55-1.68:6.0-6.5:2.0-2.5.

[0021] Preferably, the hydrothermal reaction in step 1) is carried out at a temperature of 96° C. to 107° C., and the reaction time is 2 h to 4 h.

[0022] Preferably, the polymer surfactant in step 2) is at least one of polyvinyl pyrrolidone, sodium carboxymethyl cellulose, methyl cellulose, sodium alginate, polyvinyl alcohol, and sodium lignin sulfonate.

[0023] Preferably, in step 2), the mass ratio of the silver-copper alloy nanoparticles to the polymer surfactant is 1:8-12.

[0024] Preferably, the surface modification in step 2) is carried out at room temperature (25°C±5°C).

[0025] Preferably, step 2) comprises the following operations: dispersing silver-copper alloy nanoparticles and a polymer surfactant in an ethanol aqueous solution for surface modification, and then separating and purifying the product.

[0026] Preferably, the zinc salt in step 3) is at least one of zinc nitrate, zinc sulfate and zinc chloride.

[0027] Preferably, in step 3), the mass ratio of the surface-modified silver-copper alloy nanoparticles to the zinc salt is 1:20-30.

[0028] Preferably, in step 3), the molar ratio of the zinc salt to 2-methylimidazole is 1:3.2-3.7.

[0029] Preferably, the polar protic solvent in step 3) is at least one of methanol, ethanol and water.

[0030] Preferably, the reaction in step 3) is carried out under a protective atmosphere at a temperature of 31° C. to 37° C., and the reaction time is 6 h to 18 h.

[0031] Preferably, the protective atmosphere is a nitrogen atmosphere or an argon atmosphere.

[0032] The core-shell structured silver-copper alloy nanoparticles as described above are used for catalyzing the carboxylation of terminal alkynes with CO2 to prepare propiolic acid compounds or for catalyzing the carboxylation of propargylamine with CO2 to prepare 2-oxazolidinone compounds.

[0033] The beneficial effects of the present invention are as follows: the core-shell structured silver-copper alloy nanoparticles of the present invention have the advantages of rich active sites, good catalytic effect, strong cyclic stability, mild reaction conditions, simple preparation method, etc., and can be used for the carboxylation of terminal alkynes with CO2 to generate propiolic acid compounds and for the carboxylation of propargylamine with CO2 to generate 2-oxazolidinone compounds, and have very broad application prospects.

[0034] Specifically:

[0035] 1) The core-shell structured silver-copper alloy nanoparticles of the present invention comprise a heterogeneous alloy structure formed by silver and copper. The more electronegative silver can obtain electrons from copper and present a negative charge, which is beneficial to the adsorption and polarization of CO2, while the copper presents a positive charge, which is beneficial to the formation of acetylene copper intermediates, thereby promoting the efficient progress of the reaction and greatly improving the catalytic activity of the catalyst;

[0036] 2) The core-shell structured silver-copper alloy nanoparticles of the present invention include a MOF shell, which can not only protect the metal nanoparticles from migration, aggregation and leaching, but also promote the enrichment of the substrate on the surface of the core, thereby improving the catalytic efficiency. The metal nanoparticle core will undergo a localized plasma resonance effect (LSPR) during light radiation, and the heat generated by the LSPR (which has the highest photothermal conversion efficiency in the visible light region) is blocked by the MOF shell, which increases the temperature around the core and reduces the bulk solution temperature, increases the solubility of CO2, and enhances the metal catalytic activity;

[0037] 3) The preparation method of the core-shell structured silver-copper alloy nanoparticles of the present invention has the advantages of being simple, environmentally friendly, low cost, and high yield, and is suitable for large-scale industrial production;

[0038] 4) The core-shell structured silver-copper alloy nanoparticles of the present invention can be used for the carboxylation reaction of terminal alkyne compounds with CO2 and for the carboxylation reaction of propargylamine compounds with CO2, and can show high stability and catalytic activity, high conversion rate of reactants, simple operation, mild reaction conditions, convenient operation, wide substrate applicability, and have very broad practical application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 1 and 2 are XRD diagrams of the silver-copper alloy nanoparticles in Examples 1 to 3, the silver nanoparticles in Comparative Example 1, and the copper nanoparticles in Comparative Example 2.

[0040] Figure 2 XRD diagrams of the core-shell structured silver-copper alloy nanoparticles in Examples 2, 4, 6, 7 and 8, the core-shell structured silver nanoparticles in Comparative Example 1, the core-shell structured copper nanoparticles in Comparative Example 2, and the ZIF-8 nanoparticles in Comparative Example 3.

[0041] Figure 3 TG curves of the core-shell structured silver-copper alloy nanoparticles in Examples 2, 6 and 7 and the ZIF-8 nanoparticles in Comparative Example 3.

[0042] Figure 4 The XPS graphs of the silver-copper alloy nanoparticles in Example 2, the silver nanoparticles in Comparative Example 1, and the copper nanoparticles in Comparative Example 2.

[0043] Figure 5 IR spectra of the core-shell structured silver-copper alloy nanoparticles in Example 6 and the ZIF-8 nanoparticles in Comparative Example 3.

[0044] Figure 6 The nitrogen adsorption-desorption isotherm curves and pore size distribution diagrams of the core-shell structured silver-copper alloy nanoparticles in Example 6 and the ZIF-8 nanoparticles in Comparative Example 3.

[0045] Figure 7 This is the carbon dioxide adsorption-desorption isotherm curve of the core-shell structured silver-copper alloy nanoparticles in Example 6.

[0046] Figure 8 The SEM images of the silver-copper alloy nanoparticles in Examples 1 to 3, the silver nanoparticles in Comparative Example 1, and the copper nanoparticles in Comparative Example 2 are shown.

[0047] Fig. 9 2. SEM images of the core-shell structured silver-copper alloy nanoparticles in Examples 2, 6 and 7.

[0048] Fig.10 This is the TEM image of the silver-copper alloy nanoparticles in Example 2.

[0049] Fig.11 This is the EDS image of the silver-copper alloy nanoparticles in Example 2.

[0050] Fig.12 TEM images and EDS images of the core-shell structured silver-copper alloy nanoparticles in Example 6.

[0051] Fig.13 TEM and EDS images of the core-shell structured silver-copper alloy nanoparticles in Comparative Example 4.

[0052] Fig.14 TEM and EDS images of the core-shell structured silver-copper alloy nanoparticles in Comparative Example 5.

[0053] Fig.15 The UV-visible absorption spectra of the silver-copper alloy nanoparticles in Examples 1 to 3, the silver nanoparticles in Comparative Example 1, and the copper nanoparticles in Comparative Example 2 are shown.

[0054] Fig.16 It is the UV-visible absorption spectra of the core-shell structured silver-copper alloy nanoparticles in Example 6 and the ZIF-8 nanoparticles in Comparative Example 3.

[0055] Fig.17 This is a thermal imaging measurement image of the core-shell structured silver-copper alloy nanoparticles in Example 6.

[0056] Fig.18This is the thermal imaging measurement image of the ZIF-8 nanoparticles in Comparative Example 3.

[0057] Fig.19 The temperature-irradiation time relationship curve of the reaction solution containing the silver-copper alloy nanoparticles in Example 2, the core-shell structure silver-copper alloy nanoparticles in Example 6 and the ZIF-8 nanoparticles in Comparative Example 3 under LED light irradiation.

[0058] Fig. 20 This is the XRD pattern of the core-shell structured silver-copper alloy nanoparticles after use in Example 6 (phenylacetylene carboxylation reaction).

[0059] Fig.21 This is the Fourier transform infrared spectrum of the core-shell structured silver-copper alloy nanoparticles in Example 6 after use (phenylacetylene carboxylation reaction).

[0060] Fig. 22 These are the SEM and TEM images of the core-shell structured silver-copper alloy nanoparticles after use in Example 6 (phenylacetylene carboxylation reaction).

[0061] Fig.23 This is a graph showing the stability test results of the core-shell structured silver-copper alloy nanoparticles in Example 6 (phenylacetylene carboxylation reaction).

[0062] Fig.24 This is the XRD pattern of the core-shell structured silver-copper alloy nanoparticles after use in Example 6 (carboxyl cyclization reaction of N-benzylprop-2-yn-1-amine compounds).

[0063] Fig.25 This is the Fourier transform infrared spectrum of the core-shell structured silver-copper alloy nanoparticles after use in Example 6 (carboxyl cyclization reaction of N-benzylprop-2-yn-1-amine compounds).

[0064] Fig.26 These are the SEM and TEM images of the core-shell structured silver-copper alloy nanoparticles after use in Example 6 (carboxyl cyclization reaction of N-benzylprop-2-yn-1-amine compounds).

[0065] Fig. 27 This is a graph showing the stability test results of the core-shell structured silver-copper alloy nanoparticles in Example 6 (carboxyl cyclization reaction of N-benzylprop-2-yn-1-amine compounds).

[0066] Fig.28 This is a diagram showing the results of a thermal filtration experiment of the core-shell structured silver-copper alloy nanoparticles in Example 6 (carboxyl cyclization reaction of N-benzylprop-2-yn-1-amine compounds). DETAILED DESCRIPTION

[0067] The present invention will be further explained and illustrated below in conjunction with specific embodiments.

[0068] Embodiment 1:

[0069] A core-shell structured silver-copper alloy nanoparticle, the preparation method of which is as follows:

[0070] 1) Add 6 mL of 20 mmol / L silver nitrate aqueous solution into a reaction container, then add 9 mg (0.067 mmol) of CuCl2, 180 mg (0.745 mmol) of hexadecylamine and 50 mg (0.278 mmol) of glucose, stir magnetically at room temperature for 5 h, then heat to 100 ° C and stir vigorously for 2 h, centrifuge, take the solid and wash it several times with acetone and dichloromethane, and then place the obtained solid in a vacuum drying oven at 55 ° C for 24 h to obtain silver-copper alloy nanoparticles (denoted as Ag2Cu1NPs);

[0071] 2) adding 60 mg of silver-copper alloy nanoparticles and 0.6 g of polyvinyl pyrrolidone (number average molecular weight of 40,000) to 50 mL of ethanol aqueous solution (volume ratio of ethanol to water is 1:1), ultrasonicating for several times and stirring at room temperature for 24 hours, centrifuging, taking the solid and washing it with ethanol for several times to obtain surface-modified silver-copper alloy nanoparticles;

[0072] 3) 7 mg of surface-modified silver-copper alloy nanoparticles, 176 mg (0.592 mmol) of zinc nitrate hexahydrate and 167 mg (2.034 mmol) of 2-methylimidazole were dispersed in 20 mL of methanol, and then reacted at 35 °C for 6 h under argon protection. The solid was centrifuged and washed several times with methanol. The obtained solid was then placed in a vacuum drying oven at 55 °C and dried for 24 h to obtain core-shell structured silver-copper alloy nanoparticles (denoted as Ag2Cu1@ZIF-8 / 6h).

[0073] Embodiment 2:

[0074] A core-shell structured silver-copper alloy nanoparticle, the preparation method of which is as follows:

[0075] 1) Add 6 mL of 20 mmol / L silver nitrate aqueous solution into a reaction container, then add 18 mg of CuCl2, 180 mg of hexadecylamine and 50 mg of glucose, stir magnetically at room temperature for 5 h, then heat to 100 °C and stir vigorously for 2 h, centrifuge, take the solid and wash it several times with acetone and dichloromethane, then dry the obtained solid in a vacuum drying oven at 55 °C for 24 h to obtain silver-copper alloy nanoparticles (denoted as Ag1Cu1 NPs);

[0076] 2) adding 60 mg of silver-copper alloy nanoparticles and 0.6 g of polyvinyl pyrrolidone (number average molecular weight of 40,000) to 50 mL of ethanol aqueous solution (volume ratio of ethanol to water is 1:1), ultrasonicating for several times and stirring at room temperature for 24 hours, centrifuging, taking the solid and washing it with ethanol for several times to obtain surface-modified silver-copper alloy nanoparticles;

[0077] 3) 7 mg of surface-modified silver-copper alloy nanoparticles, 176 mg of zinc nitrate hexahydrate and 167 mg of 2-methylimidazole were dispersed in 20 mL of methanol, and then reacted at 35°C for 6 h under argon protection. The solid was centrifuged and washed several times with methanol. The solid was then dried in a vacuum drying oven at 55°C for 24 h to obtain core-shell structured silver-copper alloy nanoparticles (denoted as Ag1Cu1@ZIF-8 / 6h).

[0078] Embodiment 3:

[0079] A core-shell structured silver-copper alloy nanoparticle, the preparation method of which is as follows:

[0080] 1) 6 mL of 20 mmol / L silver nitrate aqueous solution was added to a reaction container, and then 27 mg of CuCl2, 180 mg of hexadecylamine and 50 mg of glucose were added, and magnetic stirring was performed at room temperature for 5 h, and then the temperature was raised to 100 ° C and stirred vigorously for 2 h, and centrifuged, and the solid was washed with acetone and dichloromethane several times, and then the obtained solid was placed in a vacuum drying oven at 55 ° C for 24 h to obtain silver-copper alloy nanoparticles (denoted as Ag2Cu3 NPs);

[0081] 2) adding 60 mg of silver-copper alloy nanoparticles and 0.6 g of polyvinyl pyrrolidone (number average molecular weight of 40,000) to 50 mL of ethanol aqueous solution (volume ratio of ethanol to water is 1:1), ultrasonicating for several times and stirring at room temperature for 24 hours, centrifuging, taking the solid and washing it with ethanol for several times to obtain surface-modified silver-copper alloy nanoparticles;

[0082] 3) 7 mg of surface-modified silver-copper alloy nanoparticles, 176 mg of zinc nitrate hexahydrate and 167 mg of 2-methylimidazole were dispersed in 20 mL of methanol, and then reacted at 35°C for 6 h under argon protection. The solid was centrifuged and washed several times with methanol. The solid was then dried in a vacuum drying oven at 55°C for 24 h to obtain core-shell structured silver-copper alloy nanoparticles (denoted as Ag2Cu3@ZIF-8 / 6h).

[0083] Embodiment 4:

[0084] A core-shell structured silver-copper alloy nanoparticle, the preparation method of which is as follows:

[0085] 7 mg of surface modified silver-copper alloy nanoparticles (same as in Example 1), 176 mg of zinc nitrate hexahydrate and 167 mg of 2-methylimidazole were dispersed in 20 mL of methanol, and then reacted at 35°C for 12 h under argon protection. The solid was centrifuged and washed several times with methanol. The obtained solid was then placed in a vacuum drying oven at 55°C and dried for 24 h to obtain core-shell structured silver-copper alloy nanoparticles (denoted as Ag2Cu1@ZIF-8 / 12h).

[0086] Embodiment 5:

[0087] A core-shell structured silver-copper alloy nanoparticle, the preparation method of which is as follows:

[0088] 7 mg of surface modified silver-copper alloy nanoparticles (same as in Example 1), 176 mg of zinc nitrate hexahydrate and 167 mg of 2-methylimidazole were dispersed in 20 mL of methanol, and then reacted at 35°C for 18 h under argon protection. The solid was centrifuged and washed several times with methanol. The obtained solid was then placed in a vacuum drying oven at 55°C and dried for 24 h to obtain core-shell structured silver-copper alloy nanoparticles (denoted as Ag2Cu1@ZIF-8 / 18h).

[0089] Embodiment 6:

[0090] A core-shell structured silver-copper alloy nanoparticle, the preparation method of which is as follows:

[0091] 7 mg of surface modified silver-copper alloy nanoparticles (same as in Example 2), 176 mg of zinc nitrate hexahydrate and 167 mg of 2-methylimidazole were dispersed in 20 mL of methanol, and then reacted at 35°C for 12 h under argon protection. The solid was centrifuged and washed several times with methanol. The obtained solid was then placed in a vacuum drying oven at 55°C and dried for 24 h to obtain core-shell structured silver-copper alloy nanoparticles (denoted as Ag1Cu1@ZIF-8 / 12h).

[0092] Embodiment 7:

[0093] A core-shell structured silver-copper alloy nanoparticle, the preparation method of which is as follows:

[0094] 7 mg of surface modified silver-copper alloy nanoparticles (same as in Example 2), 176 mg of zinc nitrate hexahydrate and 167 mg of 2-methylimidazole were dispersed in 20 mL of methanol, and then reacted at 35°C for 18 h under argon protection. The solid was centrifuged and washed several times with methanol. The obtained solid was then placed in a vacuum drying oven at 55°C and dried for 24 h to obtain core-shell structured silver-copper alloy nanoparticles (denoted as Ag1Cu1@ZIF-8 / 18h).

[0095] Embodiment 8:

[0096] A core-shell structured silver-copper alloy nanoparticle, the preparation method of which is as follows:

[0097] 7 mg of surface modified silver-copper alloy nanoparticles (same as in Example 3), 176 mg of zinc nitrate hexahydrate and 167 mg of 2-methylimidazole were dispersed in 20 mL of methanol, and then reacted at 35°C for 12 h under argon protection. The solid was centrifuged and washed several times with methanol. The obtained solid was then placed in a vacuum drying oven at 55°C and dried for 24 h to obtain core-shell structured silver-copper alloy nanoparticles (denoted as Ag2Cu3@ZIF-8 / 12h).

[0098] Embodiment 9:

[0099] A core-shell structured silver-copper alloy nanoparticle, the preparation method of which is as follows:

[0100] 7 mg of surface modified silver-copper alloy nanoparticles (same as in Example 3), 176 mg of zinc nitrate hexahydrate and 167 mg of 2-methylimidazole were dispersed in 20 mL of methanol, and then reacted at 35°C for 18 h under argon protection. The solid was centrifuged and washed several times with methanol. The obtained solid was then placed in a vacuum drying oven at 55°C and dried for 24 h to obtain core-shell structured silver-copper alloy nanoparticles (denoted as Ag2Cu3@ZIF-8 / 18h).

[0101] Comparative Example 1:

[0102] A core-shell structured silver nanoparticle, the preparation method of which is as follows:

[0103] 1) Add 50 mL of ethylene glycol (EG) to a reaction vessel, place it in an oil bath, stir and heat to 150°C, quickly add 0.6 mL of 3 mmol / L sodium hydrosulfide ethylene glycol solution, add 3.9 mL of 3.84 mmol / L hydrogen chloride ethylene glycol solution 2 minutes later, add 10 mL of 25 mg / mL polyvinyl pyrrolidone (number average molecular weight 40000) ethylene glycol solution 2 minutes later, add 5 mL of 50 mg / mL silver trifluoroacetate ethylene glycol solution 2 minutes later, stir and react at 150°C for 1 hour, centrifuge, take the solid (gray particles), wash it several times with acetone, and then place the obtained solid in a vacuum drying oven at 55°C for 24 hours to obtain silver nanoparticles (denoted as Ag NPs);

[0104] 2) adding 60 mg of silver nanoparticles and 0.6 g of polyvinyl pyrrolidone (number average molecular weight of 40,000) to 50 mL of ethanol aqueous solution (volume ratio of ethanol to water is 1:1), ultrasonicating for several times and stirring at room temperature for 24 h, centrifuging, taking the solid and washing it with ethanol for several times to obtain surface-modified silver nanoparticles;

[0105] 3) 7 mg of surface-modified silver nanoparticles, 176 mg of zinc nitrate hexahydrate and 167 mg of 2-methylimidazole were dispersed in 20 mL of methanol, and then reacted at 35° C. for 12 h under argon protection, centrifuged, and the solid was washed several times with methanol. The obtained solid was then placed in a vacuum drying oven at 55° C. and dried for 24 h to obtain core-shell structured silver nanoparticles (denoted as Ag@ZIF-8 / 12h).

[0106] Comparative Example 2:

[0107] A core-shell structured copper nanoparticle, the preparation method of which is as follows:

[0108] 1) 15 mL of diethylene glycol, 250 mg of polyvinyl pyrrolidone (number average molecular weight of 40,000) and 500 mg of copper sulfate pentahydrate were added to reaction container A, and then placed in an oil bath with stirring and heated to 100°C to obtain solution A; 15 mL of diethylene glycol and 2.4 g of NaH2PO2·H2O were added to reaction container B, and then placed in an oil bath with stirring and heated to 100°C to obtain solution B; solution A and solution B were quickly mixed, rapidly stirred at 100°C for 5 min, naturally cooled to room temperature, centrifuged, and the solid was washed with deionized water and acetone several times, and then the obtained solid was placed in a vacuum drying oven at 55°C for 24 h to obtain copper nanoparticles (denoted as CuNPs);

[0109] 2) adding 60 mg of copper nanoparticles and 0.6 g of polyvinyl pyrrolidone (number average molecular weight of 40,000) to 50 mL of ethanol aqueous solution (volume ratio of ethanol to water is 1:1), ultrasonicating for several times and stirring at room temperature for 24 h, centrifuging, taking the solid and washing it with ethanol for several times to obtain surface-modified copper nanoparticles;

[0110] 3) 7 mg of surface-modified copper nanoparticles, 176 mg of zinc nitrate hexahydrate and 167 mg of 2-methylimidazole were dispersed in 20 mL of methanol, and then reacted at 35°C for 12 h under argon protection. The solid was centrifuged and washed several times with methanol. The solid was then dried in a vacuum drying oven at 55°C for 24 h to obtain core-shell copper nanoparticles (denoted as Cu@ZIF-8 / 12h).

[0111] Comparative Example 3:

[0112] A ZIF-8 nanoparticle, the preparation method thereof is as follows:

[0113] 2.381 g (8 mmol) of zinc nitrate hexahydrate was dissolved in 100 mL of methanol to obtain a zinc nitrate solution; 4.926 g (48 mmol) of 2-methylimidazole was dissolved in 100 mL of methanol to obtain a 2-methylimidazole solution; the zinc nitrate solution and the 2-methylimidazole solution were mixed, stirred at 35° C. for 18 h, centrifuged, the solid was washed several times with methanol, and the obtained solid was placed in a vacuum drying oven at 60° C. and dried for 24 h to obtain ZIF-8 nanoparticles (referred to as ZIF-8).

[0114] Comparative Example 4:

[0115] A core-shell structured silver-copper alloy nanoparticle, the preparation method of which is as follows:

[0116] 7 mg of silver-copper alloy nanoparticles (same as in Example 2), 176 mg of zinc nitrate hexahydrate and 167 mg of 2-methylimidazole were dispersed in 20 mL of methanol, and then reacted at 35°C for 6 h under argon protection. The solid was centrifuged and washed several times with methanol. The obtained solid was then placed in a vacuum drying oven at 55°C and dried for 24 h to obtain core-shell structured silver-copper alloy nanoparticles (denoted as Ag1Cu1@ZIF-8 / 6h*).

[0117] Comparative Example 5:

[0118] A core-shell structured silver-copper alloy nanoparticle, the preparation method of which is as follows:

[0119] 7 mg of silver-copper alloy nanoparticles (same as in Example 2), 176 mg of zinc nitrate hexahydrate and 167 mg of 2-methylimidazole were dispersed in 20 mL of methanol, and then reacted at 35°C for 12 h under argon protection. The solid was centrifuged and washed several times with methanol. The obtained solid was then placed in a vacuum drying oven at 55°C and dried for 24 h to obtain core-shell structured silver-copper alloy nanoparticles (denoted as Ag1Cu1@ZIF-8 / 12h*).

[0120] Performance Testing:

[0121] 1) X-ray diffraction (XRD) patterns of the silver-copper alloy nanoparticles (Ag2Cu1 NPs, Ag1Cu1 NPs and Ag2Cu3 NPs) in Examples 1 to 3, the silver nanoparticles (Ag NPs) in Comparative Example 1 and the copper nanoparticles (Cu NPs) in Comparative Example 2 are shown in FIG. Figure 1 shown.

[0122] Depend on Figure 1 It can be seen that the silver-copper alloy nanoparticles in Examples 1 to 3 contain diffraction peaks belonging to silver and copper, respectively, indicating that the silver-copper alloy nanoparticles retain the characteristic crystal forms of silver and copper.

[0123] 2) The XRD patterns of the core-shell structured silver-copper alloy nanoparticles (Ag1Cu1@ZIF-8 / 6h, Ag2Cu1@ZIF-8 / 12h, Ag1Cu1@ZIF-8 / 12h, Ag1Cu1@ZIF-8 / 18h and Ag2Cu3@ZIF-8 / 12h) in Examples 2, 4, 6, 7 and 8, the core-shell structured silver nanoparticles (Ag@ZIF-8 / 12h) in Comparative Example 1, the core-shell structured copper nanoparticles (Cu@ZIF-8 / 12h) in Comparative Example 2 and the ZIF-8 nanoparticles (ZIF-8) in Comparative Example 3 are as shown in FIG. Figure 2 (a is Ag1Cu1@ZIF-8 / 6h, Ag1Cu1@ZIF-8 / 12h, Ag1Cu1@ZIF-8 / 18h and ZIF-8, b is Ag2Cu1@ZI F-8 / 12h, Ag1Cu1@ZIF-8 / 12h, Ag2Cu3@ZIF-8 / 12h, Ag@ZIF-8 / 12h and Cu@ZIF-8 / 12h) are shown.

[0124] Depend on Figure 2 It can be seen that the crystal form of the ZIF-8 coating layer is consistent with that of the pure ZIF-8 nanoparticles, indicating that the ZIF-8 coating layer is successfully synthesized, and the diffraction intensity of the ZIF-8 coating layer increases with the increase of reaction time, indicating that the thickness of the ZIF-8 coating layer also increases.

[0125] 3) The thermal gravimetric (TG) curves of the core-shell structured silver-copper alloy nanoparticles (Ag1Cu1@ZIF-8 / 6h, Ag1Cu1@ZIF-8 / 12h and Ag1Cu1@ZIF-8 / 18h) in Examples 2, 6 and 7 and the ZIF-8 nanoparticles (ZIF-8) in Comparative Example 3 are as follows: Figure 3 (oxygen atmosphere) as shown.

[0126] Depend on Figure 3 It can be seen that the thermal stability of the core-shell structured silver-copper alloy nanoparticles is similar to that of the pure ZIF-8 nanoparticles. The mass loss after 400°C in an oxygen atmosphere is the combustion of organic ligands, and ZIF-8 is converted into zinc oxide, indicating that the core-shell structured silver-copper alloy nanoparticles can maintain good thermal stability below 400°C.

[0127] 4) The X-ray photoelectron spectroscopy (XPS) of the silver-copper alloy nanoparticles (Ag1Cu1 NPs) in Example 2, the silver nanoparticles (AgNPs) in Comparative Example 1, and the copper nanoparticles (Cu NPs) in Comparative Example 2 are as follows: Figure 4 (a is the Ag 3d spectrum, b is the Cu 2p spectrum).

[0128] Depend on Figure 4 It can be seen that the Ag 3d5 / 2 and Ag 3d 3 / 2 The binding energies are 368.4 eV and 374.4 eV, respectively, indicating that AgNPs exist mainly in the form of zero valence. Compared with pure Ag NPs, the Ag 3d 5 / 2 and Ag 3d 3 / 2 The peak shifts toward the direction of lower binding energy, indicating that due to the greater electronegativity of Ag, the electrons in Ag1Cu1 NPs are transferred from Cu to Ag; Cu NPs mainly exist in the form of 0 valence and +1 valence. Compared with pure Cu NPs, the Cu 2P 1 / 2 and Cu 2P 3 / 2 The oxidation state of Ag1Cu1 NPs increases, and the +2 valence form of Cu appears, which further indicates that the electrons in Ag1Cu1 NPs are transferred from Cu to Ag, indicating that the electronic state in Ag1Cu1 NPs has changed significantly compared with AgNPs and Cu NPs, with Ag carrying a negative charge and Cu carrying a positive charge.

[0129] 5) The infrared spectra of the core-shell structured silver-copper alloy nanoparticles (Ag1Cu1@ZIF-8 / 12h) in Example 6 and the ZIF-8 nanoparticles (ZIF-8) in Comparative Example 3 are as follows: Figure 5 shown.

[0130] Depend on Figure 5 It can be seen that Ag1Cu1@ZIF-8 / 12h has the typical band shape of ZIF-8, indicating that the ZIF-8 framework structure remains unchanged after the formation of the ZIF-8 coating layer.

[0131] 6) The nitrogen adsorption-desorption isotherm curves and pore size distribution diagrams of the core-shell structured silver-copper alloy nanoparticles (Ag1Cu1@ZIF-8 / 12h) in Example 6 and the ZIF-8 nanoparticles (ZIF-8) in Comparative Example 3 are shown in Figure 6 (a is the nitrogen adsorption-desorption isotherm of Ag1Cu1@ZIF-8 / 12h, b is the pore size distribution diagram of Ag1Cu1@ZIF-8 / 12h, c is the nitrogen adsorption-desorption isotherm of ZIF-8, and d is the pore size distribution diagram of ZIF-8).

[0132] Depend on Figure 6 It can be seen that the specific surface areas of Ag1Cu1@ZIF-8 / 12h and ZIF-8 are 1351m 2 / g and 1451m 2 / g, all show a completely reversible type I isotherm, indicating that they are microporous materials; compared with ZIF-8, the specific surface area of ​​Ag1Cu1@ZIF-8 / 12h is reduced, which is mainly attributed to the occupation of silver-copper alloy nanoparticles; the pore size distribution diagrams of Ag1Cu1@ZIF-8 / 12h and ZIF-8 are consistent, the pore size is mainly concentrated at 1.1nm, and the pore size of 1.3nm~1.6nm is due to the existence of the gating effect, indicating that the ZIF-8 coating layer of the core-shell structured silver-copper alloy nanoparticles and the pure ZIF-8 nanoparticles have the same properties.

[0133] 7) The carbon dioxide adsorption-desorption isotherm curve of the core-shell structure silver-copper alloy nanoparticles (Ag1Cu1@ZIF-8 / 12h) in Example 6 is as follows Figure 7 (Test temperature is 25°C).

[0134] Depend on Figure 7 It can be seen that the adsorption capacity of carbon dioxide by Ag1Cu1@ZIF-8 / 12h at 25°C exceeds 15 cm 3 / g, indicating that it has a strong adsorption capacity for carbon dioxide.

[0135] 8) The scanning electron microscope (SEM) images of the silver-copper alloy nanoparticles (Ag2Cu1 NPs, Ag1Cu1 NPs and Ag2Cu3 NPs) in Examples 1 to 3, the silver nanoparticles (Ag NPs) in Comparative Example 1 and the copper nanoparticles (Cu NPs) in Comparative Example 2 are as follows: Figure 8 As shown, the SEM images of the core-shell structured silver-copper alloy nanoparticles (Ag1Cu1@ZIF-8 / 6h, Ag1Cu1@ZIF-8 / 12h and Ag1Cu1@ZIF-8 / 18h) in Examples 2, 6 and 7 are shown in FIG. Fig. 9 (a is Ag1Cu1@ZIF-8 / 6h, b is Ag1Cu1@ZIF-8 / 12h, c is Ag1Cu1@ZIF-8 / 18h) as shown.

[0136] Depend on Figure 8 It can be seen that the particle sizes of silver-copper alloy nanoparticles, silver nanoparticles and copper nanoparticles are all concentrated between 40nm and 60nm.

[0137] Depend on Fig. 9 It can be seen that the core-shell structured silver-copper alloy nanoparticles are uniform rhombic dodecahedral nanocrystals, and as the growth time increases from 6h to 18h, the particle size of the nanoparticles increases from about 180nm to about 500nm, and no small silver-copper alloy nanoparticles are observed, indicating the successful synthesis of the ZIF-8 coating layer.

[0138] 9) The transmission electron microscope (TEM) image and X-ray energy dispersive spectroscopy (EDS) image of the silver-copper alloy nanoparticles (Ag1Cu1 NPs) in Example 2 are as follows: Fig.10 and Fig.11 shown.

[0139] Depend on Fig.10 and Fig.11 It can be seen that Ag1Cu1 NPs present a heterogeneous alloy morphology, and the distribution element mapping images of Ag and Cu also confirm this, indicating the successful preparation of silver-copper alloy nanoparticles.

[0140] 10) The TEM and EDS images of the core-shell structured silver-copper alloy nanoparticles (Ag1Cu1@ZIF-8 / 12h) in Example 6 are as follows: Fig.12 As shown, the TEM and EDS images of the core-shell structured silver-copper alloy nanoparticles (Ag1Cu1@ZIF-8 / 6h*) in Comparative Example 4 are as follows: Fig.13 As shown, the TEM and EDS images of the core-shell structured silver-copper alloy nanoparticles (Ag1Cu1@ZIF-8 / 12h*) in Comparative Example 5 are as follows: Fig.14 shown.

[0141] Depend on Figures 12-14 It can be seen that the Ag1Cu1 NPs in Ag1Cu1@ZIF-8 / 12h are completely wrapped by the ZIF-8 coating layer, and the thickness of the ZIF-8 coating layer is about 80nm. The distribution element mapping images of Zn, N, Ag and Cu further confirm this point. The Cu signal is slightly weakened, which is due to the etching of very small amount of Cu during the growth of the in situ ZIF-8 coating layer. During the synthesis of Ag1Cu1@ZIF-8 / 6h* and Ag1Cu1@ZIF-8 / 12h*, since the Ag1Cu1 NPs were not passivated with polyvinyl pyrrolidone (PVP), obvious Cu etching occurred, indicating the necessity of PVP passivation protection.

[0142] 11) The UV-visible absorption spectra of the silver-copper alloy nanoparticles (Ag2Cu1 NPs, Ag1Cu1 NPs and Ag2Cu3 NPs) in Examples 1 to 3, the silver nanoparticles (Ag NPs) in Comparative Example 1 and the copper nanoparticles (Cu NPs) in Comparative Example 2 are shown in FIG. Fig.15 shown.

[0143] Depend on Fig.15 It can be seen that Ag NPs have obvious absorption capacity in the range of 340nm to 560nm, and a peak appears at 420nm, while Cu nanoparticles have no obvious absorption peak in the visible light region because of their weak light absorption ability and easy oxidation, which is confirmed by XDR ( Figure 1); Silver-copper alloy nanoparticles show obvious visible light absorption band in the range of 350nm to 550nm, indicating that the light absorption capacity of silver-copper alloy nanoparticles mainly comes from Ag nanoparticles.

[0144] 12) The UV-visible absorption spectra of the core-shell structured silver-copper alloy nanoparticles (Ag1Cu1@ZIF-8 / 12h) in Example 6 and the ZIF-8 nanoparticles (ZIF-8) in Comparative Example 3 are shown in FIG. Fig.16 shown.

[0145] Depend on Fig.16 It can be seen that an obvious absorption spectrum peak is observed for Ag1Cu1@ZIF-8 / 12h in the range of 380nm to 500nm, while ZIF-8 has no absorption in the visible light region, indicating that the ZIF-8 coating layer does not affect the light absorption ability of Ag1Cu1 NPs.

[0146] 13) The thermal imaging measurement of the core-shell structured silver-copper alloy nanoparticles (Ag1Cu1@ZIF-8 / 12h) in Example 6 is shown in FIG. Fig.17 (a is 10 mg of Ag1Cu1@ZIF-8 / 12h+air; b is 10 mg of Ag1Cu1@ZIF-8 / 12h+3 mL of DMSO; LED light irradiation, power is 40 W, wavelength is 420 nm), the thermal imaging measurement of ZIF-8 nanoparticles (ZIF-8) in Comparative Example 3 is shown in Fig.18 (a is 3 mL of DMSO; b is 10 mg of ZIF-8 + 3 mL of DMSO; LED light irradiation, power is 40 W, wavelength is 420 nm).

[0147] Depend on Fig.17 and Fig.18 It can be seen that: in the air atmosphere, after irradiation with LED light (40W, 420nm) for 10 minutes, the detected temperature around Ag1Cu1@ZIF-8 / 12h reached 61°C, while the temperature in 3mL of DMSO was 56°C. In contrast, after irradiation with LED light for 10 minutes, the temperature detected in DMSO without Ag1Cu1@ZIF-8 / 12h was only 30°C. In addition, the surface temperature of ZIF-8 did not increase after irradiation with LED light for 10 minutes, indicating that Ag1Cu1@ZIF-8 / 12h has a strong photothermal conversion ability.

[0148] 14) 10 mg of the silver-copper alloy nanoparticles (Ag1Cu1 NPs) in Example 2, the core-shell structure silver-copper alloy nanoparticles (Ag1Cu1@ZIF-8 / 12h) in Example 6, and the ZIF-8 nanoparticles (ZIF-8) in Comparative Example 3 were added to a test tube, 0.5 mmol of phenylacetylene, 0.75 mmol of Cs2CO3, and 3 mL of DMSO were added, and then irradiated with LED light (40 W, 420 nm). The obtained temperature-irradiation time relationship curve is as shown in FIG. Fig.19 shown.

[0149] Depend on Fig.19 It can be seen that: in the test tube with ZIF-8 added, the temperature of the reaction solution rose to about 35°C after 10 minutes of LED illumination, which is almost the same as the temperature of the reaction solution in the test tube without ZIF-8 added. In the test tube with Ag1Cu1 NPs added, the temperature of the reaction solution in the test tube reached 40°C after 10 minutes of LED illumination, and further rose to 50°C after 30 minutes, indicating that the photothermal conversion capacity of Ag1Cu1@ZIF-8 / 12h comes from Ag1Cu1 NPs; in the test tube with Ag1Cu1@ZIF-8 / 12h added, the temperature of the reaction solution only rose to 40°C. This is because the ZIF-8 coating layer hindered heat diffusion, making it difficult for most of the solution in the test tube to be heated by the hot "spot" of Ag1Cu1NPs. Therefore, the actual temperature around the core of Ag1Cu1 NPs should be much higher than the detection value in the reaction solution.

[0150] 15) 0.5 mmol of phenylacetylene, 10 mg of catalyst, 0.75 mmol of Cs2CO3 and 3 mL of DMSO were added to a test tube, and the mixture was stirred for 24 h at 25°C, 1 atm of CO2 and irradiated with a blue LED (40 W, 420 nm). The yield of the product was calculated. The results are shown in the following table:

[0151] Table 1 Photocatalytic performance of different catalysts

[0152]

[0153] From Table 1, we can see that:

[0154] a) The yield of the target product of system 1 is highest when the molar ratio of silver to copper in the alloy reaches 1:1, which indicates that after silver and copper form a nano-alloy, the electronic state of silver and copper in the alloy is improved. The positively charged silver can adsorb and activate CO2, and the negatively charged copper can promote the formation of acetylene copper intermediates. This change in electronic state improves the catalytic efficiency, making the yield of Ag1Cu1 NPs twice that of single metal nanoparticles, thereby improving the utilization rate of the metal;

[0155] b) The yield of the target product of system 2 is also the highest when the molar ratio of silver and copper in the alloy reaches 1:1, and the catalytic activity of the core-shell structure catalyst is greatly improved compared with that of the metal nanoparticles, indicating that the ZIF-8 coating layer is conducive to the diffusion of substrates / products, while the simple physical mixing of metal particles and ZIF-8 in system 4 (Ag1Cu1 NPs+ZIF-8 refers to Ag1Cu1 NPs (2 mg) + ZIF-8 (8 mg)) cannot effectively improve the catalytic activity, indicating that there is a positive synergistic effect between the ZIF-8 shell and the metal nanoparticle core;

[0156] c) For the target product of system 3, the yield of the product decreased regardless of whether the thickness of the ZIF-8 coating layer increased or decreased. The possible reasons for these results are that too thin a ZIF-8 coating layer (6 h) would reduce the thermal insulation performance and cause heat loss, but too thick a ZIF-8 coating layer (18 h) would inhibit the diffusion of substrates / products.

[0157] The XRD pattern of the catalyst Ag1Cu1@ZIF-8 / 12h in system 2 after use is shown in Fig. 20 As shown in the Fourier infrared spectrum Fig.21 As shown, SEM and TEM images are Fig. 22 (a is SEM image, b is TEM image).

[0158] Depend on Figures 20-22 It can be seen that the crystal shape of Ag1Cu1@ZIF-8 / 12h is well maintained after use, indicating that it has high stability;

[0159] The stability test results of the catalyst Ag1Cu1@ZIF-8 / 12h in system 2 are as follows: Fig.23 shown.

[0160] Depend on Fig.23 It can be seen that Ag1Cu1@ZIF-8 / 12h can be reused at least 5 times, and the yield of the corresponding product does not decrease significantly after 5 reuses, and the yield is still over 93%.

[0161] Note:

[0162] The reaction formula is as follows:

[0163]

[0164] 16) 0.5 mmol of phenylacetylene, 10 mg of catalyst, 0.75 mmol of Cs2CO3 and 3 mL of DMSO were added to a test tube and stirred for 24 h under 1 atm of CO2. The yield of the product was calculated. The results are shown in the following table:

[0165] Table 2 Thermocatalytic performance of different catalysts

[0166]

[0167]

[0168] From Table 2, we can see that:

[0169] a) The yields of the target products of system 1 and system 2 are consistent with the room temperature photocatalytic results, indicating that the photocatalysis in the reaction is mainly photothermal catalysis, and the catalyst still has metal synergy and core-shell positive synergistic effect in thermal catalysis;

[0170] b) The solution temperature during the catalytic reaction in system 3 was 40 °C, while the temperature around the inner Ag1Cu1 NPs core was estimated to be about 50 °C, indicating that the ZIF-8 coating layer has good thermal insulation properties for Ag1Cu1 NPs.

[0171] 17) Add 0.5 mmol of phenylacetylene, 10 mg of Ag1Cu1@ZIF-8 / 12h, 0.75 mmol of Cs2CO3 and 3 mL of DMSO to a test tube, stir and react for 24 h at 25°C, 1 atm of CO2 and irradiation with a blue LED (40 W, 420 nm), and calculate the yield of the product. The results are shown in the following table:

[0172] Table 3 Effect of reaction time on yield

[0173]

[0174] It can be seen from Table 3 that the yield of the target product increases with the increase of reaction time. After 24 hours of reaction, the yield reaches 97.3%, indicating that the optimal time for the catalyst to catalyze the reaction is 24 hours.

[0175] 18) 0.5 mmol of phenylacetylene compound, 10 mg of Ag1Cu1@ZIF-8 / 12h, 0.75 mmol of Cs2CO3 and 3 mL of DMSO were added to a test tube, and the reaction was stirred for 24 h at 25°C, 1 atm of CO2 and irradiation with a blue LED (40 W, 420 nm). The yield of the product was calculated (the product was confirmed by NMR). The results are shown in the following table:

[0176] Table 4 Substrate suitability

[0177]

[0178]

[0179]

[0180] It can be seen from Table 4 that the core-shell structured silver-copper alloy nanoparticles Ag1Cu1@ZIF-8 / 122h have good catalytic performance. Regardless of the electron-donating or electron-withdrawing nature of the connecting group on phenylacetylene, Ag1Cu1@ZIF-8 / 12h can efficiently catalyze the conversion of different terminal alkynes into the corresponding acetylic acids under the optimized reaction conditions. The spatial position of the substituent (ortho, meta and para positions of phenylacetylene) has almost no effect on the yield of the product. Heteroaromatic (thiophene) alkynes can also be converted into the corresponding acetylic acids with high yield.

[0181] 19) 0.5 mmol of N-benzylprop-2-yn-1-amine, 10 mg of catalyst, 0.05 mmol of DBU (1,8-diazabicycloundec-7-ene) and 2 mL of DMSO were added to a test tube, stirred for 12 h at 25 ° C, 1 atm of CO2, and irradiated with a blue LED (40 W, 420 nm). The yield of the product was calculated. The results are shown in the following table:

[0182] Table 5 Photocatalytic performance of different catalysts

[0183]

[0184] It can be seen from Table 5 that the core-shell structured silver-copper alloy nanoparticles Ag1Cu1@ZIF-8 / 12h have excellent catalytic performance for the carboxylation cyclization reaction of N-benzylprop-2-yn-1-amine with CO2.

[0185] The XRD pattern of the core-shell structured silver-copper alloy nanoparticles Ag1Cu1@ZIF-8 / 12h in system 1 after use is shown in the figure below. Fig.24 As shown, the Fourier infrared spectrum is as follows Fig.25 As shown, SEM and TEM images are Fig.26 (a is SEM image, b is TEM image).

[0186] Depend on Figures 24-26 It can be seen that the crystal shape of Ag1Cu1@ZIF-8 / 12h is well maintained after use, indicating that it has high stability;

[0187] The stability test results of the core-shell structured silver-copper alloy nanoparticles Ag1Cu1@ZIF-8 / 12h in system 1 are shown in Figure 2. Fig. 27 shown.

[0188] Depend on Fig. 27 It can be seen that Ag1Cu1@ZIF-8 / 12h can be reused at least 5 times. After being reused 5 times, the yield of the corresponding product does not decrease significantly, and the yield retention rate is still 95%.

[0189] Note:

[0190] The reaction formula is as follows:

[0191]

[0192] 20) 0.5 mmol of N-benzylprop-2-yn-1-amine, 10 mg of Ag1Cu1@ZIF-8 / 12h, 0.05 mmol of DBU and 2 mL of DMSO were added to a test tube, and the reaction was stirred for 12 h under 1 atm of CO2. The yield of the product was calculated. The results are shown in the following table:

[0193] Table 6 Thermal catalytic performance of different catalysts

[0194]

[0195] It can be seen from Table 6 that the yield of the target product of system 1 (50°C) is consistent with the room temperature photocatalytic result, while the yield under room temperature without light is extremely low, indicating that the photocatalysis in the reaction is mainly photothermal catalysis.

[0196] 21) 0.5 mmol of N-benzylprop-2-yn-1-amine, catalyst Ag1Cu1@ZIF-8 / 12h, 0.05 mmol of DBU and 2 mL of DMSO were added to a test tube, and the reaction was stirred for 12 h at 25°C, 1 atm of CO2 and irradiated with a blue LED (40 W, 420 nm). The yield of the product was calculated. The results are shown in the following table:

[0197] Table 7 Effect of catalyst dosage on yield

[0198]

[0199] It can be seen from Table 7 that the yield of the target product shows a trend of first increasing and then decreasing with the increase of the catalyst dosage, and the optimal dosage of Ag1Cu1@ZIF-8 / 12h is 10 mg.

[0200] 22) 0.5 mmol of N-benzylprop-2-yn-1-amine, 10 mg of Ag1Cu1@ZIF-8 / 12h, 0.05 mmol of DBU and 2 mL of DMSO were added to a test tube, and the reaction was stirred at 25°C, 1 atm of CO2, and irradiated with a blue LED (40 W, 420 nm). The yield of the product was calculated. The results are shown in the following table:

[0201] Table 8 Effect of reaction time on yield

[0202]

[0203]

[0204] It can be seen from Table 8 that the yield of the target product increases with the extension of the reaction time. After 12 hours of reaction, the yield reaches 97%, indicating that the optimal time for the catalyst to catalyze the reaction is 12 hours.

[0205] 23) 0.5 mmol of N-benzylprop-2-yn-1-amine, 10 mg of Ag1Cu1@ZIF-8 / 12h, 0.05 mmol of DBU and 2 mL of DMSO were added to a test tube, stirred and reacted for 6 h at 25 °C, 1 atm of CO2 and irradiation with a blue LED (40 W, 420 nm), centrifuged, the mother liquor was separated from the catalyst, and the product yield was determined by nuclear magnetic resonance. The reaction solution was allowed to react for a period of time, and the product yield was determined by nuclear magnetic resonance. The results of the hot filtration experiment were as follows: Fig.28 (The control group did not have a filtering operation and did not separate the mother liquor from the catalyst).

[0206] Depend on Fig.28 It can be seen that after the catalyst Ag1Cu1@ZIF-8 / 12h was separated from the mother liquor, the mother liquor was allowed to continue to react, but the yield of the product did not increase significantly, which means that there was no Ag and Cu in the reaction process, indicating that the catalytic system was heterogeneous.

[0207] 24) Add 0.5 mmol of N-benzylprop-2-yn-1-amine compound, 10 mg of Ag1Cu1@ZIF-8 / 12h, 0.05 mmol of DBU and 2 mL of DMSO to a test tube, stir and react for 12 h at 25°C, 1 atm of CO2, and irradiation with a blue LED (40 W, 420 nm), and calculate the yield of the product (the product was confirmed by NMR). The results are shown in the following table:

[0208] Table 9 Substrate suitability

[0209]

[0210]

[0211] It can be seen from Table 9 that the core-shell structured silver-copper alloy nanoparticles Ag1Cu1@ZIF-8 / 12h have good catalytic performance. The substituted propargylamine derivatives with electron-donating or electron-withdrawing groups in the N-benzyl part still have good tolerance and can smoothly obtain the corresponding products. By replacing the benzyl part with a thiophene group, the corresponding product can be obtained with a yield of 97%, indicating that Ag1Cu1@ZIF-8 / 12h can effectively catalyze the carboxyl cyclization reaction of propargylamine with CO2.

[0212] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A core-shell structured silver-copper alloy nanoparticle, characterized in that: The core is silver-copper alloy nanoparticles, and the shell is a ZIF-8 coating layer.

2. The core-shell structured silver-copper alloy nanoparticles according to claim 1, characterized in that: The molar ratio of silver to copper in the silver-copper alloy nanoparticles is 1:0.55-1.

68.

3. The core-shell structured silver-copper alloy nanoparticles according to claim 1 or 2, characterized in that: The average particle size of the silver-copper alloy nanoparticles is 40nm-60nm.

4. The core-shell structured silver-copper alloy nanoparticles according to claim 1 or 2, characterized in that: The average particle size of the core-shell structured silver-copper alloy nanoparticles is 100nm to 500nm.

5. A method for preparing core-shell structured silver-copper alloy nanoparticles according to any one of claims 1 to 4, characterized in that: The following steps are involved: 1) dispersing a soluble silver salt, a soluble copper salt, a nonionic surfactant and a reducing agent in water for hydrothermal reaction to obtain silver-copper alloy nanoparticles; 2) surface-modifying the silver-copper alloy nanoparticles with a polymer surfactant to obtain surface-modified silver-copper alloy nanoparticles; 3) dispersing the surface-modified silver-copper alloy nanoparticles, zinc salt and 2-methylimidazole in a polar protic solvent for reaction to obtain core-shell structured silver-copper alloy nanoparticles.

6. The preparation method according to claim 5, characterized in that: The soluble silver salt in step 1) is at least one of silver nitrate and silver acetate; the soluble copper salt in step 1) is at least one of copper chloride, copper nitrate, copper acetate and copper sulfate; the nonionic surfactant in step 1) is at least one of hexadecylamine, oleylamine and octadecylamine; the reducing agent in step 1) is at least one of glucose and maltose; the polymer surfactant in step 2) is at least one of polyvinyl pyrrolidone, sodium carboxymethyl cellulose, methyl cellulose, sodium alginate, polyvinyl alcohol and sodium lignin sulfonate; the zinc salt in step 3) is at least one of zinc nitrate, zinc sulfate and zinc chloride; the polar protic solvent in step 3) is at least one of methanol, ethanol and water.

7. The preparation method according to claim 5 or 6, characterized in that: The molar ratio of the soluble silver salt, soluble copper salt, nonionic surfactant and reducing agent in step 1) is 1:0.55-1.68:6.0-6.5:2.0-2.5; the mass ratio of the silver-copper alloy nanoparticles and the polymer surfactant in step 2) is 1:8-12; the mass ratio of the surface-modified silver-copper alloy nanoparticles and the zinc salt in step 3) is 1:20-30; the molar ratio of the zinc salt and 2-methylimidazole in step 3) is 1:3.2-3.

7.

8. The preparation method according to claim 5 or 6, characterized in that: Step 1) The hydrothermal reaction is carried out at a temperature of 96°C to 107°C, and the reaction time is 2h to 4h.

9. The preparation method according to claim 5 or 6, characterized in that: Step 3) The reaction is carried out under a protective atmosphere at a temperature of 31° C. to 37° C., and the reaction time is 6 h to 18 h.

10. Use of the core-shell structured silver-copper alloy nanoparticles as claimed in any one of claims 1 to 4 for catalyzing the carboxylation of terminal alkynes with CO2 to prepare propiolic acid compounds or for catalyzing the carboxylation of propargylamine with CO2 to prepare 2-oxazolidinone compounds.

Images