CN114100629A

CN114100629A - Multilevel-structure hybrid-loaded atomic precision gold nanocluster catalyst and preparation method thereof

Info

Publication number: CN114100629A
Application number: CN202111293447.9A
Authority: CN
Inventors: 张慧; 于淑娣; 李进; 郭佳伟; 汪青琳; 魏卓君
Original assignee: Beijing University of Chemical Technology
Current assignee: Beijing University of Chemical Technology
Priority date: 2021-11-03
Filing date: 2021-11-03
Publication date: 2022-03-01

Abstract

A multilevel-structure hybrid loaded atomic precision gold nanocluster catalyst and a preparation method thereof. Belongs to the technical field of noble metal nano-catalysts. The expression of the catalyst is Au_n/(M²⁺) Al-LDH/rGO-T, wherein LDH nanosheets in the carrier grow perpendicularly and alternately on both sides of rGO, and M²⁺Is Mg²⁺、Ni²⁺、Co²⁺Either one or both of the ions; au coating_nIs gold nanocluster, n is 25, 38 and 127,the dispersion is high at the edge position of LDH nano-sheets and the junction of LDH and rGO; t represents the calcination temperature and is 260-300 ℃. Au protected by captopril through pH double-control electrostatic adsorption method_nThe nanoclusters are loaded on a hybrid carrier, and the catalyst is obtained by removing the ligand through moderate calcination. The catalyst has the advantages that the obtained catalyst has large specific surface area and more active sites, and shows high activity and high selectivity in the process of preparing benzaldehyde by solvent-free aerobic oxidation of benzyl alcohol under the condition of no external alkali.

Description

Multilevel-structure hybrid-loaded atomic precision gold nanocluster catalyst and preparation method thereof

Technical Field

The invention belongs to the technical field of precious metal nano catalysts, and particularly relates to a nanosheet array type hierarchical structure LDH/rGO hybrid loaded atomic precision gold nanocluster catalyst and a preparation method thereof.

Background

The selective oxidation of alcohols is an important organic synthesis process since the corresponding aldehydes and ketones produced thereby are important intermediates and precursors for pharmaceuticals, pesticides, vitamins and fine chemicals, etc. The catalysts currently used to catalyze the selective oxidation of alcohols can be divided into homogeneous catalysts and heterogeneous catalysts. The homogeneous catalyst mainly comprises 2, 2, 6, 6-tetramethyl piperidine-N-oxyl (TEMPO), Ru and Pd complex and the like, has the characteristics of uniform active center, easy contact with reactants and the like, and therefore, shows higher catalytic activity. But it has a certain limitation in industrial application because it is difficult to separate from the product to cause metal contamination. Therefore, in the reaction system of alcohol catalytic oxidation, researchers are receiving more and more attention to develop a high-efficiency heterogeneous catalyst which has high activity and high selectivity and is easy to separate from reactants and recycle. Compared with other noble metal catalysts (such as Pd, Pt, Ru and the like), the supported gold catalyst has the advantages of mild reaction conditions, difficult peroxidation, poisoning by strongly adsorbed byproducts and the like, and can be used as a high-selectivity catalyst in the catalytic oxidation process of alcohol. In 2016 Zhang et al [ Wang S, Ying S, Chen G, Li L, Zhang H, Catal. Sci. technol.2016.6: 4090-.]Reporting different compositions of hydrotalcite loaded Au₂₅The nanocluster catalyst efficiently catalyzes alcohol selective oxidation reaction under the condition of not adding alkali and taking oxygen as an oxidant. Zhan of 2020g et al [ Xu Y, Li J, Zhou J, Liu Y, Wei Z, Zhang H J.Cat.2020.389: 409-420.]It is reported that the nickel-aluminum hydrotalcite loaded gold nanocluster catalyst with different atomic accuracies can efficiently catalyze the benzyl alcohol oxidation reaction under the conditions of no additional alkali, toluene as a solvent and air as an oxidant. However, single support LDH nanosheets can be severely stacked due to strong particle-particle interactions, and the use of organic solvents inevitably leads to environmental pollution. The graphene material has the characteristics of large specific surface area, high conductivity, good chemical stability and the like, and can be used in the fields of adsorption, electrochemistry, drug delivery, catalysis and the like. However, the super strong van der waals interaction force between graphene layers makes the graphene layers easy to stack, which is not beneficial to the exposure of active surface area. Based on this, 2016, Zhang et al [ Dou L, Zhang H, J.Mater.chem.A 2016,4: 18990-.]A CuMgAl-LDH/rGO hybrid with a nanosheet array structure is prepared by a simple and green citric acid assisted liquid-phase co-precipitation method, wherein LDH nanosheets are vertically and alternately grown on two sides of a rGO lamella. The unique nanosheet array morphology has a large specific surface area, can provide more active sites, is beneficial to enhancing the adsorption capacity of the nanosheet array morphology on a reaction substrate, and is expected to prepare a gold nanocluster catalyst with high atomic dispersion precision. However, no reports on the nanosheet array-like multilevel structure hydrotalcite/reduced graphene oxide (LDH/rGO) hybrid supported atomic precision gold nanocluster catalyst have been reported so far.

Disclosure of Invention

The invention aims to provide a nanosheet-like array type hierarchical structure hydrotalcite/reduced graphene oxide hybrid (LDH/rGO) loaded atomic precision gold nanocluster catalyst and a preparation method thereof, and aims to prepare captopril (Capt) ligand-protected atomic precision Au nanocluster by adopting a size focusing method and a polyacrylamide gel electrophoresis separation technology₂₅Capt₁₈、Au₃₈Capt₂₄And Au_～127-Capt nanocluster precursor, with (M)²⁺) Al-LDH/rGO hybrid (M)²⁺Is Mg²⁺、Ni²⁺、Co²⁺Any one or two of ions) as a carrier, and loading the carrier on an LDH/rGO hybrid carrier by a pH double-control electrostatic adsorption method, wherein (at the moment: (M²⁺) The pI values (10.0) of the Al-LDH/rGO hybrid carriers are greater than the pH values (pH 8.0) of the solutions, so that (M)²⁺) The surface of the Al-LDH/rGO hybrid carrier is partially positively charged, the pI (5.6) of Au NCs is less than the pH value (8.0) of the solution, so that the surface of the Au NCs is partially negatively charged, and under the condition, the gold nanoclusters with negative charges are adsorbed to the surface of the LDH/rGO nanosheets with positive charges through strong electrostatic action to obtain the catalyst precursor. The obtained catalyst precursor is subjected to subsequent moderate calcination to obtain Au with atomic precision_nNanocluster catalyst Au_n/(M²⁺) A1-LDH/rGO-T, in which Au_nThe nano-cluster (n is the number of gold atoms) is an active component, and the obtained catalyst is used for catalyzing the solventless aerobic oxidation reaction of the benzyl alcohol under the condition of no alkaline additive, so that the high-activity green catalyst which is easy to recycle is provided.

The expression of the multilevel-structure hybrid-loaded atomic precision gold nanocluster catalyst is Au_n/(M²⁺) A1-LDH/rGO-T, in which Au_nN gold atoms, n being 25, 38, 127; (M)²⁺) M in A1-LDH/rGO²⁺Is Mg²⁺、Ni²⁺、Co²⁺Either one or both of the ions; the method is characterized in that: (M) 55 to 70nm in size and 8 to 10nm in thickness²⁺) Al-LDH nanosheets vertically and alternately grow on two sides of the rGO lamella, and the nanosheet array morphology is shown. The gold nanoclusters with the sizes of 1.0 +/-0.3, 1.5 +/-0.3 and 1.8 +/-0.4 nm in the catalyst are highly dispersed at the edge of the LDH and the junction of the LDH and the rGO; the active component in the catalyst is a gold nanocluster, and the mass percentage of the gold nanocluster is 0.5-1.5 wt%. The obtained catalyst has a unique nanosheet-like array morphology, has a large specific surface area, can provide more active sites, and enhances the adsorption capacity on a reaction substrate. Has greatly improved selective oxidation performance of benzyl alcohol without solvent compared with the traditional nano gold catalyst.

The method for preparing the gold nanocluster catalyst is a pH double-control electrostatic adsorption method. Preparing atom precision gold nanocluster protected by captopril ligand as precursor by adopting size focusing method and polyacrylamide gel electrophoresis separation technology, and adopting simple and green citric acid assisted liquid phase coprecipitation methodPreparation type nano sheet array type multilevel structure (M)²⁺) A1-LDH/rGO hybrid (where M is²⁺Is Mg²⁺、Ni²⁺、Co²⁺One or two of ions) as a carrier, and loading the gold nanoclusters to (M) based on the electrostatic adsorption principle by finely regulating the pH value to 6-10²⁺) Removing ligands on an A1-LDH/rGO hybrid carrier through moderate calcination to obtain a nanosheet array type hierarchical structure LDH/rGO hybrid loaded atomic precision gold nanocluster catalyst named as Au_n/(M²⁺) A1-LDH/rGO-T. The preparation process comprises the following steps:

(1) the synthesis of gold nanocluster precursors is prepared according to the method reported in Journal of Catalysis,389(2020), 409-.

Preparation of Au by combining size focusing method and polyacrylamide gel electrophoresis technology₂₅Capt₁₈、Au₃₈Capt₂₄And Au_～127-Capt nanoclusters. Firstly, dissolving 1g of chloroauric acid tetrahydrate in 100mL of methanol to prepare a chloroauric acid methanol stock solution of 10 mg/mL; then, 8.23mL of chloroauric acid tetrahydrate (HAuCl)₄·4H₂O, 0.20mmol) in methanol and 126.8mg of tetraoctylammonium bromide (TOABr, 0.23mmol) were added to a 100mL round bottom flask containing 6.75mL of methanol and magnetically stirred at 1200rpm at room temperature, the mixture turned from orange-yellow to deep red. After 15 minutes of reaction, 130.4mg of captopril (Capt, 0.60mmol) was added to the reaction solution, and the solution rapidly turned white in color. After 30 minutes of reaction, the stirring rate was adjusted to 600rpm and 5mL of NaBH was added₄Ice-water solution (1mmol, 37.8mg dissolved in 5mL ice-water) was added quickly to the reaction and the solution immediately turned brown-green in color. After the reaction solution was continuously reacted in a water bath at 25. + -. 1 ℃ for 48 hours, the reaction solution was centrifuged (5000r/min, 20min) to remove unreacted and insoluble Au (I) Capt polymer. Collecting supernatant, and rotary steaming (30 deg.C, 20min) to obtain concentrated solution. Then 20mL of acetone is added into the concentrated solution and is kept stand for 12 hours to obtain the gold clusters. Then dried under vacuum at 30 ℃ for 12 hours to give the crude product. The crude product was extracted 6 times with methanol (0.5-1 mL each) to give a dark brown clear extract. Adding 20mL acetone into the brown black transparent extractive solution, and precipitating againGold clusters were centrifuged (3000r/min, 10min) to give a brownish black precipitate. Vacuum drying at 30 deg.C for 12 hr to obtain final brown black product Au_:Capt nanoclusters.

Polyacrylamide gel electrophoresis separation: the resulting Au: Capt products were separated by polyacrylamide gel electrophoresis (PAGE) using a vertical gel electrophoresis system at 300V. The gels and stacking gels were prepared with 30% and 4% acrylamide monomer, respectively. The Au: Capt cluster was dissolved in 10% (v/v) glycerol/water at a concentration of 30mg/mL and added to the gel at a loading of 40. mu.L/well. After 4 hours of electrophoretic separation, the clear bands cut from the gel were soaked in water for 2 hours and the nanocluster solution mixed with the gel matrix was filtered by using a 0.22 μm filter. Then adding 10% (v/v) glacial acetic acid for acidification, concentrating the acidified nano-cluster solution by using a 3kDa cut-off filter, finally precipitating the concentrated solution by using acetone and drying for 12 hours under vacuum to obtain pure Au₂₅Capt₁₈And Au₃₈Capt₂₄And larger size gold nanoclusters. For the gold nanoclusters with larger size, a simple method is used, the gold nanoclusters are assumed to be spherical and have the same density as bulk Au, and the gold nanoclusters with larger size are calculated to be Au corresponding to the gold nanoclusters with larger size of 1.6nm obtained based on TEM analysis_～127-Capt。

(2) And (3) preparing a nano sheet array-like multi-level structure hydrotalcite/reduced graphene oxide hybrid carrier.

First, a Graphene Oxide (GO) sol (ρ 8.07mg/mL) was prepared as a stock solution by an improved Hummers method using natural flake graphite powder as a raw material. Then preparing the nano-sheet array type (M) with the multilevel structure by a simple and green citric acid assisted liquid-phase coprecipitation method²⁺) Al-LDH/rGO hybrid (where M is²⁺Is Mg²⁺、Ni²⁺、Co²⁺Either one or both of the ions). The method comprises the following specific steps: dispersing 50mg of GO sol into 100mL of deionized water, ultrasonically stripping for 20 minutes, then adding 25mg of citric acid and continuing to ultrasonically treat for 5 minutes to obtain a citric acid modified GO suspension. The resulting citric acid modified GO suspension was transferred to a 500mL four-necked flask and NaOH and Na were added dropwise with vigorous stirring₂CO₃Mixed alkali solution of (a) [ OH-]/[CO₃ ²-]＝3.2、[CO₃ ²-]/[Al³⁺]2, 200mL) to pH 10.0 ± 0.1, stable for 10 min. Then 100mL (M) was added dropwise²⁺)(NO₃)₂·6H₂O (M ═ Mg, Co, Ni) (15mmol) and Al (NO)₃)₃·9H₂O (5mmol) mixed salt solution, and simultaneously dropwise adding the mixed alkali solution to ensure that the pH value of the system is 10.0 +/-0.1. After the dropwise addition, the resulting reaction solution was crystallized in a water bath at 65 ℃ for 4 hours. Finally, centrifugal separation is carried out, deionized water is washed to be neutral, and freeze drying is carried out to obtain the hybrid carrier with the nanosheet array structure, which is named as (M)²⁺)Al-LDH/rGO。

(3) Synthesis of nanosheet-like array type hierarchical structure LDH/rGO-supported atomic precision gold nanocluster catalyst

Preparation of Au by pH double-control electrostatic adsorption method_n/(M²⁺) Al-LDH/rGO-T catalyst (where M is²⁺Is Mg²⁺、Ni²⁺、Co²⁺Any one or two of ions), the specific operation steps are as follows: 0.5 to 1.0g of (M)²⁺) Adding the Al-LDH/rGO hybrid carrier into 30-50 mL of deionized water, and adding a proper amount of Na with a certain concentration₂CO₃And (3) ultrasonically dispersing the solution (0.1mol/L) for 5-15 minutes, and then adjusting to obtain a carrier dispersion liquid with the pH value of 6.0-8.0. Stirring vigorously at room temperature, adding Na with a certain concentration₂CO₃The gold nano-cluster precursor solution with the pH value of 6.0-10.0 pre-adjusted by the solution is added into the carrier dispersion liquid, the theoretical load capacity of the gold nano-cluster is 0.5-1.5 wt%, and the gold nano-cluster is magnetically stirred and reacted for 2-6 hours at 1000 rpm. The mixture was collected by centrifugation and freeze-dried to obtain a catalyst precursor. Calcining the obtained catalyst precursor for 3 hours at 260-300 ℃ in nitrogen atmosphere to obtain the catalyst, which is named as Au_n/(M²⁺)Al-LDH/rGO-T。

The nanosheet array-like hierarchical structure LDH/rGO loaded atomic precision gold nanocluster catalyst needs to be stored in a sealed mode.

The nanosheet array-like hierarchical structure LDH/rGO-supported atomic precision gold nanocluster catalyst can be applied to a benzyl alcohol solvent-free aerobic oxidation reaction.

The catalyst obtained after the reaction separation can be recycled after drying treatment.

The invention has the main advantages that:

(1) a novel nanosheet array type multilevel structure LDH/rGO loading atomic precision gold nanocluster catalyst and a preparation method thereof are provided. Wherein (M)²⁺) Al-LDH nano sheets grow on two sides of the rGO sheet layer in a vertical staggered orientation mode, and show a nano sheet array-like shape. The unique morphology structure effectively prevents self-aggregation between LDH nanosheets and rGO sheets, is beneficial to improving the specific surface area of the catalyst and exposes more effective Au active sites.

(2) The nanosheet array type hierarchical structure LDH/rGO loading atom precision gold nanocluster catalyst prepared by utilizing a pH double-control electrostatic adsorption method has the characteristics of large specific surface area, high dispersion of active components, more active sites and the like, has very obvious performance advantages in the solvent-free oxidation reaction of catalyzing benzyl alcohol under the condition of no alkaline additive and taking molecular oxygen as an oxidant, and has no obvious loss of activity after being repeatedly used for 5 times. Provides a new path for synthesizing the inorganic multi-stage structure nano composite material.

Drawings

FIG. 1 shows atomic accuracy Au in example 1₂₅Capt₁₈HRTEM images of nanoclusters.

FIG. 2 is the atomic accuracy Au in example 12₃₈Capt₂₄HRTEM images of nanoclusters.

FIG. 3 shows the atomic accuracy of the load Au of the nanosheet array type multilevel structure nickel-aluminum hydrotalcite/reduced graphene oxide hybrid obtained in example 1 under the condition of adjusting the pH to 6.0₂₅Capt₁₈HRTEM images of nanocluster catalysts.

FIG. 4 shows the atomic accuracy of the load Au of the nanosheet array type multilevel structure nickel-aluminum hydrotalcite/reduced graphene oxide hybrid obtained in example 2 under the condition of adjusting the pH to 10.0₂₅Capt₁₈HRTEM images of nanocluster catalysts.

FIG. 5 shows the nanosheet array type multilevel structure nickel obtained in example 3 under the condition of adjusting pH to 8.0Aluminum hydrotalcite/reduced graphene oxide hybrid loaded atomic precision Au₂₅Capt₁₈HRTEM images of nanocluster catalysts.

FIG. 6 shows the atomic accuracy Au loaded by the nanosheet array type multilevel structure Ni-Mg-Al hydrotalcite/reduced graphene oxide hybrid in example 12₃₈Capt₂₄HRTEM images of nanocluster catalysts.

The specific implementation mode is as follows:

the present invention will be described in detail below by way of examples, but the present invention is not limited to the following examples.

Example 1

(1)Au₂₅Capt₁₈Preparation of nanoclusters

1.0g of HAuCl was weighed₄·4H₂O to 100mL of methanol to prepare a 10mg/mL methanolic chloroauric acid solution, 24.69mL of the above solution and 0.3804g of TOABr (0.69mmol) were weighed and added to a 100mL single-neck flask containing 20.31mL of methanol, and the mixture was magnetically stirred at 1200rpm in a water bath at 25. + -. 1 ℃ until the mixture turned from orange to deep red. After 15 minutes, 0.3912g of captopril (0.60mmol) were added to the reaction solution, and the solution quickly turned white in color. After 30 minutes of reaction, the stirring rate was adjusted to 600rpm and 15mL of NaBH was added₄An ice-water solution was rapidly added to the above reaction solution, and the color of the solution immediately changed to brown-green. After the reaction mixture was reacted in a water bath at 25 ℃ for 48 hours, it was centrifuged (4800r/min, 20min) to remove unreacted and insoluble Au (I) and Capt polymer. Collecting supernatant, and rotary steaming (30 deg.C, 20min) to obtain concentrated solution. Then 20mL of acetone is added into the concentrated solution and is kept stand for 12 hours to obtain the gold clusters. Then dried under vacuum at 30 ℃ for 12 hours to give the crude product. The crude product was extracted 6 times with methanol (0.5-1 mL each) to give a dark brown clear extract. And adding 20mL of acetone into the brownish black transparent extracting solution to precipitate gold clusters again, and centrifuging (3000r/min for 10min) to obtain brownish black precipitates. Vacuum drying at 30 deg.C for 12 hr to obtain final brown black product Au_:Capt nanoclusters.

Polyacrylamide gel electrophoresis separation: the resulting Au: Capt product was fractionated by polyacrylamide gel electrophoresis (PAGE) at 300V using a vertical gel electrophoresis systemAnd (5) separating. The gels and stacking gels were prepared with 30% and 4% acrylamide monomer, respectively. The Au: Capt cluster was dissolved in 10% (v/v) glycerol/water at a concentration of 30mg/mL and added to the gel at a loading of 40. mu.L/well. After 4 hours of electrophoretic separation, the clear bands cut from the gel were soaked in water for 2 hours and the nanocluster solution mixed with the gel matrix was filtered by using a 0.22 μm filter. Then adding 10% (v/v) glacial acetic acid for acidification, concentrating the acidified nanocluster solution by using a 3kDa cut-off filter, finally precipitating the concentrated solution by using acetone and drying under vacuum to obtain pure black brown solid powder which is marked as Au₂₅Capt₁₈。

(2)Ni₃Preparation of Al-LDH/rGO hybrid carrier

Mixing Ni (NO)₃)₂·6H₂O and Al (NO)₃)₃·9H₂O massage molar ratio [ Ni²⁺]/[A1³⁺]As 3, 100mL of salt solution ([ Ni ] was made up with deionized water²⁺]+[A1³⁺]＝2mol·L^-1) NaOH and Na are added₂CO₃([OH-]/[CO₃ ^2-]＝3.2、[CO₃ ^2-]/[A1³⁺]═ 3) 100mL of mixed base solution was made up with deionized water. Dispersing 50mg of GO sol into 100mL of deionized water, ultrasonically stripping for 20 minutes to obtain stripped graphene oxide, then adding 25mg of citric acid, and continuing to ultrasonically treat for 5 minutes. The resulting citric acid modified GO suspension was transferred to a 500mL four-necked flask and the mixed base solution was added dropwise with vigorous stirring to a pH of 10.0 ± 0.1 and stabilized for 10 minutes. Then the mixed salt solution is added dropwise, and simultaneously the mixed alkali solution is added dropwise so that the pH value of the mixed system is 10.0 +/-0.1. After the dropwise addition, the resulting reaction solution was crystallized in a water bath at 65 ℃ for 4 hours. Finally, through centrifugal separation, deionized water washing to neutrality, obtaining brownish green solid powder after freeze drying, namely Ni₃Al-LDH/rGO。

(3)Au₂₅/Ni₃Preparation of Al-LDH/rGO catalyst

Mixing 25mg of Au₂₅Capt₁₈Dissolving the nano-cluster in 100mL of deionized water to prepare 0.25mg/mL of Au₂₅Capt₁₈Aqueous solution. 1.0g of Ni₃Placing the Al-LDH/rGO hybrid carrier in a 150mL beaker, adding 50mL deionized water, carrying out ultrasonic treatment for 5 minutes, and then adjusting to obtain a hybrid carrier dispersion liquid with the pH value of 6.0. 20mL of 0.25mg/mL Au was measured₂₅Capt₁₈Adding a proper amount of 0.1mol/L sodium carbonate solution into the aqueous solution to adjust the pH value to 8.0 in advance, adding the aqueous solution into the carrier dispersion liquid under vigorous stirring, wherein the theoretical loading capacity of the gold nanocluster is 0.5 wt%, and stirring at 1000rpm for 4 hours. Collecting the mixture by centrifugal separation, and freeze-drying to obtain catalyst precursor Au₂₅Capt₁₈/Ni₃Al-LDH/rGO. The obtained catalyst precursor was calcined at 270 ℃ for 3 hours in a nitrogen atmosphere to obtain a catalyst, which was named 0.5-Au₂₅/Ni₃Al-LDH/rGO-270。

Example 2

(1)Au₂₅Capt₁₈Nanoclusters were prepared as in example 1.

(2)Ni₃The Al-LDH/rGO hybrid support was prepared as in example 1.

(3)Au₂₅/Ni₃Preparation of Al-LDH/rGO catalyst

Mixing 25mg of Au₂₅Capt₁₈Dissolving the nano-cluster in 100mL of deionized water to prepare 0.25mg/mL of Au₂₅Capt₁₈An aqueous solution. 1.0g of Ni₃Putting the Al-LDH/rGO hybrid carrier into a 150mL beaker, adding 50mL deionized water and a proper amount of 0.1mol/L sodium carbonate solution, carrying out ultrasonic treatment for 15 minutes, and then adjusting to obtain a hybrid carrier dispersion liquid with the pH value of 10.0. 20mL of 0.25mg/mL Au was measured₂₅Capt₁₈Adding a proper amount of 0.1mol/L sodium carbonate solution into the aqueous solution to adjust the pH value to 8.0 in advance, adding the aqueous solution into the carrier dispersion liquid under vigorous stirring, wherein the theoretical loading capacity of the gold nanocluster is 0.5 wt%, and stirring at 1000rpm for 4 hours. Collecting the mixture by centrifugal separation, and freeze-drying to obtain catalyst precursor Au₂₅Capt₁₈/Ni₃Al-LDH/rGO. The obtained catalyst precursor was calcined at 270 ℃ for 3 hours in a nitrogen atmosphere to obtain a catalyst, which was named 0.5-Au₂₅/Ni₃Al-LDH/rGO-270。

Example 3

(1)Au₂₅Capt₁₈NanoclusterWas prepared as in example 1.

(2)Ni₃The Al-LDH/rGO hybrid support was prepared as in example 1.

(3)Au₂₅/Ni₃Preparation of Al-LDH/rGO catalyst

Mixing 25mg of Au₂₅Capt₁₈Dissolving the nano-cluster in 100mL of deionized water to prepare 0.25mg/mL of Au₂₅Capt₁₈An aqueous solution. 1.0g of Ni₃Putting the Al-LDH/rGO hybrid carrier into a 150mL beaker, adding 50mL deionized water and a proper amount of 0.1mol/L sodium carbonate solution, carrying out ultrasonic treatment for 10 minutes, and then adjusting to obtain a hybrid carrier dispersion liquid with the pH value of 8.0. 20mL of 0.25mg/mL Au was measured₂₅Capt₁₈Adding a proper amount of 0.1mol/L sodium carbonate solution into the aqueous solution to adjust the pH value to 8.0 in advance, adding the aqueous solution into the carrier dispersion liquid under vigorous stirring, wherein the theoretical loading capacity of the gold nanocluster is 0.5 wt%, and stirring at 1000rpm for 4 hours. Collecting the mixture by centrifugal separation, and freeze-drying to obtain catalyst precursor Au₂₅Capt₁₈/Ni₃Al-LDH/rGO. The obtained catalyst precursor was calcined at 270 ℃ for 3 hours in a nitrogen atmosphere to obtain a catalyst, which was named 0.5-Au₂₅/Ni₃Al-LDH/rGO-270。

Example 4

(1)Au₂₅Capt₁₈Nanoclusters were prepared as in example 1.

(2)Ni₃The Al-LDH/rGO hybrid support was prepared as in example 1.

(3)Au₂₅/Ni₃Preparation of Al-LDH/rGO catalyst

Mixing 25mg of Au₂₅Capt₁₈Dissolving the nano-cluster in 100mL of deionized water to prepare 0.25mg/mL of Au₂₅Capt₁₈An aqueous solution. 1.0g of Ni₃Putting the Al-LDH/rGO hybrid carrier into a 150mL beaker, adding 50mL deionized water and a proper amount of 0.1mol/L sodium carbonate solution, carrying out ultrasonic treatment for 10 minutes, and then adjusting to obtain a hybrid carrier dispersion liquid with the pH value of 8.0. 20mL of 0.25mg/mL Au was measured₂₅Capt₁₈Adding a proper amount of 0.1mol/L sodium carbonate solution into the aqueous solution to adjust the pH value to 6.0 in advance, adding the aqueous solution into the carrier dispersion liquid under vigorous stirring, and obtaining the theoretical loading capacity of the gold nanoclusters0.5 wt%, stirring at 1000rpm for 4 hours. Collecting the mixture by centrifugal separation, and freeze-drying to obtain catalyst precursor Au₂₅Capt₁₈/Ni₃Al-LDH/rGO. The obtained catalyst precursor was calcined at 270 ℃ for 3 hours in a nitrogen atmosphere to obtain a catalyst, which was named 0.5-Au₂₅/Ni₃Al-LDH/rGO-270。

Example 5

(1)Au₂₅Capt₁₈Nanoclusters were prepared as in example 1.

(2)Ni₃The Al-LDH/rGO hybrid support was prepared as in example 1.

(3)Au₂₅/Ni₃Preparation of Al-LDH/rGO catalyst

Mixing 25mg of Au₂₅Capt₁₈Dissolving the nano-cluster in 100mL of deionized water to prepare 0.25mg/mL of Au₂₅Capt₁₈An aqueous solution. 1.0g of Ni₃Putting the Al-LDH/rGO hybrid carrier into a 150mL beaker, adding 50mL deionized water and a proper amount of 0.1mol/L sodium carbonate solution, carrying out ultrasonic treatment for 10 minutes, and then adjusting to obtain a hybrid carrier dispersion liquid with the pH value of 8.0. 20mL of 0.25mg/mL Au was measured₂₅Capt₁₈Adding a proper amount of 0.1mol/L sodium carbonate solution into the aqueous solution to adjust the pH value to 10.0 in advance, adding the aqueous solution into the carrier dispersion liquid under vigorous stirring, wherein the theoretical loading capacity of the gold nanocluster is 0.5 wt%, and stirring at 1000rpm for 4 hours. Collecting the mixture by centrifugal separation, and freeze-drying to obtain catalyst precursor Au₂₅Capt₁₈/Ni₃Al-LDH/rGO. The obtained catalyst precursor was calcined at 270 ℃ for 3 hours in a nitrogen atmosphere to obtain a catalyst, which was named 0.5-Au₂₅/Ni₃Al-LDH/rGO-270。

Example 6

(1)Au₂₅Capt₁₈Nanoclusters were prepared as in example 1.

(2)Ni₃The Al-LDH/rGO hybrid support was prepared as in example 1.

(3)Au₂₅/Ni₃Preparation of Al-LDH/rGO catalyst

Mixing 25mg of Au₂₅Capt₁₈Dissolving the nano-cluster in 100mL of deionized water to prepare 0.25mg/mL of Au₂₅Capt₁₈An aqueous solution. 1.0g of Ni₃Putting the Al-LDH/rGO hybrid carrier into a 150mL beaker, adding 50mL deionized water and a proper amount of 0.1mol/L sodium carbonate solution, carrying out ultrasonic treatment for 10 minutes, and then adjusting to obtain a hybrid carrier dispersion liquid with the pH value of 8.0. 20mL of 0.25mg/mL Au was measured₂₅Capt₁₈Adding a proper amount of 0.1mol/L sodium carbonate solution into the aqueous solution to adjust the pH value to 8.0 in advance, adding the aqueous solution into the carrier dispersion liquid under vigorous stirring, wherein the theoretical loading capacity of the gold nanocluster is 0.5 wt%, and stirring the mixture at 1000rpm for 2 hours. Collecting the mixture by centrifugal separation, and freeze-drying to obtain catalyst precursor Au₂₅Capt₁₈/Ni₃Al-LDH/rGO. The obtained catalyst precursor was calcined at 270 ℃ for 3 hours in a nitrogen atmosphere to obtain a catalyst, which was named 0.5-Au₂₅/Ni₃Al-LDH/rGO-270。

Example 7

(1)Au₂₅Capt₁₈Nanoclusters were prepared as in example 1.

(2)Ni₃The Al-LDH/rGO hybrid support was prepared as in example 1.

(3)Au₂₅/Ni₃Preparation of Al-LDH/rGO catalyst

Mixing 25mg of Au₂₅Capt₁₈Dissolving the nano-cluster in 100mL of deionized water to prepare 0.25mg/mL of Au₂₅Capt₁₈An aqueous solution. 1.0g of Ni₃Putting the Al-LDH/rGO hybrid carrier into a 150mL beaker, adding 50mL deionized water and a proper amount of 0.1mol/L sodium carbonate solution, carrying out ultrasonic treatment for 10 minutes, and then adjusting to obtain a hybrid carrier dispersion liquid with the pH value of 8.0. 20mL of 0.25mg/mL Au was measured₂₅Capt₁₈Adding a proper amount of 0.1mol/L sodium carbonate solution into the aqueous solution to adjust the pH value to 8.0 in advance, adding the aqueous solution into the carrier dispersion liquid under vigorous stirring, wherein the theoretical loading capacity of the gold nanocluster is 0.5 wt%, and stirring at 1000rpm for 6 hours. Collecting the mixture by centrifugal separation, and freeze-drying to obtain catalyst precursor Au₂₅Capt₁₈/Ni₃Al-LDH/rGO. The obtained catalyst precursor was calcined at 270 ℃ for 3 hours in a nitrogen atmosphere to obtain a catalyst, which was named 0.5-Au₂₅/Ni₃Al-LDH/rGO-270。

Example 8

(1)Au₂₅Capt₁₈Nanoclusters were prepared as in example 1.

(2)Ni₃The Al-LDH/rGO hybrid support was prepared as in example 1.

(3)Au₂₅/Ni₃Preparation of Al-LDH/rGO catalyst

Mixing 25mg of Au₂₅Capt₁₈Dissolving the nano-cluster in 100mL of deionized water to prepare 0.25mg/mL of Au₂₅Capt₁₈An aqueous solution. 1.0g of Ni₃Putting the Al-LDH/rGO hybrid carrier into a 150mL beaker, adding 50mL deionized water and a proper amount of 0.1mol/L sodium carbonate solution, carrying out ultrasonic treatment for 10 minutes, and then adjusting to obtain a hybrid carrier dispersion liquid with the pH value of 8.0. 60mL of 0.25mg/mL Au is measured₂₅Capt₁₈Adding a proper amount of 0.1mol/L sodium carbonate solution into the aqueous solution to adjust the pH value to 8.0 in advance, adding the aqueous solution into the carrier dispersion liquid under vigorous stirring, wherein the theoretical loading capacity of the gold nanocluster is 1.5 wt%, and stirring at 1000rpm for 4 hours. Collecting the mixture by centrifugal separation, and freeze-drying to obtain catalyst precursor Au₂₅Capt₁₈/Ni₃Al-LDH/rGO. The obtained catalyst precursor was calcined at 270 ℃ for 3 hours in a nitrogen atmosphere to obtain a catalyst, which was named 1.5-Au₂₅/Ni₃Al-LDH/rGO-270。

Example 9

(1)Au₂₅Capt₁₈Nanoclusters were prepared as in example 1.

(2)Ni_1.5Mg_1.5Preparation of Al-LDH/rGO hybrid carrier

Mixing Ni (NO)₃)₂·6H₂O、Mg(NO₃)₂·6H₂O and Al (NO)₃)₃·9H₂O massage molar ratio [ M²⁺]/[A1³⁺]＝3([Ni²⁺]/[Mg³⁺]1) 100mL of saline solution ([ M ] in deionized water²⁺]+[A1³⁺]＝2mol·L^-1) NaOH and Na are added₂CO₃([OH-]/[CO₃ ²-]＝3.2、[CO₃ ²-]/[A1³⁺]═ 3) 100mL of mixed base solution was made up with deionized water. Dispersing 50mg GO sol into 100mL deionizationAnd ultrasonically stripping for 20 minutes to obtain stripped graphene oxide, and then adding 25mg of citric acid to continue the ultrasonic stripping for 5 minutes. The resulting citric acid modified GO suspension was transferred to a 500mL four-necked flask and the mixed base solution was added dropwise with vigorous stirring to a pH of 10.0 ± 0.1 and stabilized for 10 minutes. Then the mixed salt solution is added dropwise, and simultaneously the mixed alkali solution is added dropwise so that the pH value of the mixed system is 10.0 +/-0.1. After the dropwise addition, the resulting reaction solution was crystallized in a water bath at 65 ℃ for 4 hours. Finally, through centrifugal separation, deionized water washing to neutrality, obtaining brownish green solid powder after freeze drying, namely Ni_1.5Mg_1.5Al-LDH/rGO。

(3)Au₂₅/Ni_1.5Mg_1.5Preparation of Al-LDH/rGO catalyst

Mixing 25mg of Au₂₅Capt₁₈Dissolving the nano-cluster in 100mL of deionized water to prepare 0.25mg/mL of Au₂₅Capt₁₈An aqueous solution. 1.0g of Ni_1.5Mg_1.5Putting the Al-LDH/rGO hybrid carrier into a 150mL beaker, adding 50mL deionized water and a proper amount of 0.1mol/L sodium carbonate solution, carrying out ultrasonic treatment for 10 minutes, and then adjusting to obtain a hybrid carrier dispersion liquid with the pH value of 8.0. 40mL of 0.25mg/mL Au was measured₂₅Capt₁₈Adding a proper amount of 0.1mol/L sodium carbonate solution into the aqueous solution to adjust the pH value to 8.0 in advance, adding the aqueous solution into the carrier dispersion liquid under vigorous stirring, wherein the theoretical loading capacity of the gold nanocluster is 1.0 wt%, and stirring at 1000rpm for 4 hours. Collecting the mixture by centrifugal separation, and freeze-drying to obtain catalyst precursor Au₂₅Capt₁₈/Ni_1.5Mg_1.5Al-LDH/rGO. The obtained catalyst precursor was calcined at 280 ℃ for 3 hours in a nitrogen atmosphere to obtain a catalyst, which was named 1-Au₂₅/Ni_1.5Mg_1.5Al-LDH/rGO-280。

Example 10

(1)Au₂₅Capt₁₈Nanoclusters were prepared as in example 1.

(2)Ni_1.5Mg_1.5The Al-LDH/rGO hybrid support was prepared as in example 9.

(3)Au₂₅/Ni_1.5Mg_1.5Preparation of Al-LDH/rGO catalyst

Mixing 25mg of Au₂₅Capt₁₈Dissolving the nano-cluster in 100mL of deionized water to prepare 0.25mg/mL of Au₂₅Capt₁₈An aqueous solution. 1.0g of Ni_1.5Mg_1.5Putting the Al-LDH/rGO hybrid carrier into a 150mL beaker, adding 50mL deionized water and a proper amount of 0.1mol/L sodium carbonate solution, carrying out ultrasonic treatment for 10 minutes, and then adjusting to obtain a hybrid carrier dispersion liquid with the pH value of 8.0. 40mL of 0.25mg/mL Au was measured₂₅Capt₁₈Adding a proper amount of 0.1mol/L sodium carbonate solution into the aqueous solution to adjust the pH value to 8.0 in advance, adding the aqueous solution into the carrier dispersion liquid under vigorous stirring, wherein the theoretical loading capacity of the gold nanocluster is 1.0 wt%, and stirring at 1000rpm for 4 hours. Collecting the mixture by centrifugal separation, and freeze-drying to obtain catalyst precursor Au₂₅Capt₁₈/Ni_1.5Mg_1.5Al-LDH/rGO. Calcining the obtained catalyst precursor for 3 hours at 260 ℃ in nitrogen atmosphere to obtain the catalyst which is named as 1-Au₂₅/Ni_1.5Mg_1.5Al-LDH/rGO-260。

Example 11

(1)Au₂₅Capt₁₈Nanoclusters were prepared as in example 1.

(2)Ni_1.5Mg_1.5The Al-LDH/rGO hybrid support was prepared as in example 9.

(3)Au₂₅/Ni_1.5Mg_1.5Preparation of Al-LDH/rGO catalyst

Mixing 25mg of Au₂₅Capt₁₈Dissolving the nano-cluster in 100mL of deionized water to prepare 0.25mg/mL of Au₂₅Capt₁₈An aqueous solution. 1.0g of Ni_1.5Mg_1.5Putting the Al-LDH/rGO hybrid carrier into a 150mL beaker, adding 50mL deionized water and a proper amount of 0.1mol/L sodium carbonate solution, carrying out ultrasonic treatment for 10 minutes, and then adjusting to obtain a hybrid carrier dispersion liquid with the pH value of 8.0. 40mL of 0.25mg/mL Au was measured₂₅Capt₁₈Adding a proper amount of 0.1mol/L sodium carbonate solution into the aqueous solution to adjust the pH value to 8.0 in advance, adding the aqueous solution into the carrier dispersion liquid under vigorous stirring, wherein the theoretical loading capacity of the gold nanocluster is 1.0 wt%, and stirring at 1000rpm for 4 hours. Collecting the mixture by centrifugal separation, and freeze-drying to obtain catalyst precursor Au₂₅Capt₁₈/Ni_1.5Mg_1.5Al-LDH/rGO. The obtained catalyst precursor is calcined for 3 hours at 300 ℃ in nitrogen atmosphere to prepare the catalyst which is named as 1-Au₂₅/Ni_1.5Mg_1.5Al-LDH/rGO-300。

Example 12

(1)Au₃₈Capt₁₈Preparation of nanoclusters

1.0g of HAuCl was weighed₄·4H₂O to 100mL of methanol to prepare a 10mg/mL methanolic chloroauric acid solution, 24.69mL of the above solution and 0.3804g of TOABr (0.69mmol) were weighed and added to a 100mL single-neck flask containing 20.31mL of methanol, and the mixture was magnetically stirred at 1200rpm in a water bath at 25 ℃ to change the yellow color of the mixture from orange to deep red. After 15 minutes, 0.3912g of captopril (0.60mmol) were added to the reaction solution, and the solution quickly turned white in color. After 30 minutes of reaction, the stirring rate was adjusted to 600rpm and 15mL of NaBH was added₄An ice-water solution was rapidly added to the above reaction solution, and the color of the solution immediately changed to brown-green. After the reaction solution was continuously reacted in a water bath at 25. + -. 1 ℃ for 48 hours, it was centrifuged (4800r/min, 20min) to remove unreacted and insoluble Au (I) Capt polymer. Collecting supernatant, and rotary steaming (30 deg.C, 20min) to obtain concentrated solution. Then 20mL of acetone is added into the concentrated solution and is kept stand for 12 hours to obtain the gold clusters. Then dried under vacuum at 30 ℃ for 12 hours to give the crude product. The crude product was extracted 6 times with methanol (0.5-1 mL each) to give a dark brown clear extract. And adding 20mL of acetone into the brownish black transparent extracting solution to precipitate gold clusters again, and centrifuging (3000r/min for 10min) to obtain brownish black precipitates. The mixture is dried in vacuum at 30 ℃ for 12 hours to obtain a final brown black product Au: Capt nano cluster.

Polyacrylamide gel electrophoresis separation: the resulting Au: Capt products were separated by polyacrylamide gel electrophoresis (PAGE) using a vertical gel electrophoresis system at 300V. The gels and stacking gels were prepared with 30% and 4% acrylamide monomer, respectively. The Au: Capt cluster was dissolved in 10% (v/v) glycerol/water at a concentration of 30mg/mL and added to the gel at a loading of 40. mu.L/well. After 4 hours of electrophoretic separation, the clear bands cut from the gel were soaked in water for 2 hours and these combined gels were filtered by using a 0.22 μm filterNanocluster solution of gum base. Then adding 10% (v/v) glacial acetic acid for acidification, concentrating the acidified nanocluster solution by using a 3kDa cut-off filter, finally precipitating the concentrated solution by using acetone and drying under vacuum to obtain pure black brown solid powder which is marked as Au₃₈Capt₂₄。

(2)Ni_1.5Mg_1.5The Al-LDH/rGO hybrid support was prepared as in example 11.

(3)Au₃₈/Ni_1.5Mg_1.5Preparation of Al-LDH/rGO catalyst

Mixing 25mgAu₃₈Capt₂₄Dissolving the nano-cluster in 100mL of deionized water to prepare 0.25mg/mL of Au₃₈Capt₂₄An aqueous solution. 1.0g of Ni_1.5Mg_1.5Putting the Al-LDH/rGO hybrid carrier into a 150mL beaker, adding 50mL deionized water and a proper amount of 0.1mol/L sodium carbonate solution, carrying out ultrasonic treatment for 10 minutes, and then adjusting to obtain a hybrid carrier dispersion liquid with the pH value of 8.0. 40mL of 0.25mg/mL Au was measured₃₈Capt₂₄Adding a proper amount of 0.1mol/L sodium carbonate solution into the aqueous solution to adjust the pH value to 8.0 in advance, adding the aqueous solution into the carrier dispersion liquid under vigorous stirring, wherein the theoretical loading capacity of the gold nanocluster is 1.0 wt%, and stirring at 1000rpm for 4 hours. Collecting the mixture by centrifugal separation, and freeze-drying to obtain catalyst precursor Au₃₈Capt₂₄/Ni_1.5Mg_1.5Al-LDH/rGO. The obtained catalyst precursor was calcined at 280 ℃ for 3 hours in a nitrogen atmosphere to obtain a catalyst, which was named 1-Au₃₈/Ni_1.5Mg_1.5Al-LDH/rGO-280。

Example 13

(1)Au_～127Preparation of-Capt nanoclusters

1.0g of HAuCl was weighed₄·4H₂O to 100mL of methanol to prepare a 10mg/mL methanolic chloroauric acid solution, 24.69mL of the above solution and 0.3804g of TOABr (0.69mmol) were weighed and added to a 100mL single-neck flask containing 20.31mL of methanol, and the mixture was magnetically stirred at 1200rpm in a water bath at 25 ℃ to change the yellow color of the mixture from orange to deep red. After 15 minutes, 0.3912g of captopril (0.60mmol) were added to the reaction solution, and the solution quickly turned white in color. After 30 minutes of reaction, the stirring rate was adjusted to600rpm, and then 15mL of NaBH₄An ice-water solution was rapidly added to the above reaction solution, and the color of the solution immediately changed to brown-green. After the reaction solution was continuously reacted in a water bath at 25. + -. 1 ℃ for 48 hours, it was centrifuged (4800r/min, 20min) to remove unreacted and insoluble Au (I) Capt polymer. Collecting supernatant, and rotary steaming (30 deg.C, 20min) to obtain concentrated solution. Then 20mL of acetone is added into the concentrated solution and is kept stand for 12 hours to obtain the gold clusters. Then dried under vacuum at 30 ℃ for 12 hours to give the crude product. The crude product was extracted 6 times with methanol (0.5-1 mL each) to give a dark brown clear extract. And adding 20mL of acetone into the brownish black transparent extracting solution to precipitate gold clusters again, and centrifuging (3000r/min for 10min) to obtain brownish black precipitates. Vacuum drying at 30 deg.C for 12 hr to obtain final brown black product Au_:Capt nanoclusters.

Polyacrylamide gel electrophoresis separation: the resulting Au: Capt products were separated by polyacrylamide gel electrophoresis (PAGE) using a vertical gel electrophoresis system at 300V. The gels and stacking gels were prepared with 30% and 4% acrylamide monomer, respectively. The Au: Capt cluster was dissolved in 10% (v/v) glycerol/water at a concentration of 30mg/mL and added to the gel at a loading of 40. mu.L/well. After 4 hours of electrophoretic separation, the clear bands cut from the gel were soaked in water for 2 hours and the nanocluster solution mixed with the gel matrix was filtered by using a 0.22 μm filter. Then adding 10% (v/v) glacial acetic acid for acidification, concentrating the acidified nano-cluster solution by using a 3kDa cut-off filter, finally precipitating the concentrated solution by using acetone and drying in vacuum to obtain pure black-brown solid powder, and drying in vacuum to obtain black-brown solid powder with a larger size.

(2)Ni_1.5Mg_1.5The Al-LDH/rGO hybrid support was prepared as in example 11.

(3)Au_～127/Ni_1.5Mg_1.5Preparation of Al-LDH/rGO catalyst

Mixing 25mgAu_～127dissolving-Capt nano cluster in 100mL of deionized water to prepare 0.25mg/mL of Au₃₈Capt₂₄An aqueous solution. 1.0g of Ni_1.5Mg_1.5Putting the Al-LDH/rGO hybrid carrier into a 150mL beaker, adding 50mL deionized water and a proper amount of 0.1mol/L sodium carbonate solution, carrying out ultrasonic treatment for 10 minutes, and then adjusting to obtain a hybrid carrier dispersion liquid with the pH value of 8.0. 40mL of 0.25mg/mL Au was measured_～127Adding a proper amount of 0.1mol/L sodium carbonate solution into the Capt aqueous solution, adjusting the pH value to 8.0 in advance, adding the Capt aqueous solution into the carrier dispersion liquid under vigorous stirring, wherein the theoretical loading capacity of the gold nanocluster is 1.0 wt%, and stirring at 1000rpm for 4 hours. Collecting the mixture by centrifugal separation, and freeze-drying to obtain catalyst precursor Au_～127-Capt/Ni_1.5Mg_1.5Al-LDH/rGO. The obtained catalyst precursor was calcined at 280 ℃ for 3 hours in a nitrogen atmosphere to obtain a catalyst, which was named 1-Au_～127/Ni_1.5Mg_1.5Al-LDH/rGO-280。

Example 14

(1)Au₂₅Capt₁₈Nanoclusters were prepared as in example 1.

(2)Mg₃Preparation of Al-LDH/rGO hybrid carrier

Mixing Mg (NO)₃)₂·6H₂O and Al (NO)₃)₃·9H₂O massage molar ratio [ Mg²⁺]/[A1³⁺]The other synthesis steps were the same as in example 1.

(3)Au₂₅/Mg₃Preparation of Al-LDH/rGO catalyst

The synthesis procedure was the same as in example 2, and the obtained catalyst precursor, Au₂₅Capt₁₈/Mg₃Calcining Al-LDH/rGO in nitrogen atmosphere at 280 ℃ for 3 hours to prepare the catalyst, which is named as 0.5-Au₂₅/Mg₃Al-LDH/rGO-280。

Example 15

(1)Au₂₅Capt₁₈Nanoclusters were prepared as in example 1.

(2)Co₃Preparation of Al-LDH/rGO hybrid carrier

Mixing Co (NO)₃)₂·6H₂O and Al (NO)₃)₃·9H₂O massage molar ratio [ Co²⁺]/[A1³⁺]The other synthesis steps were the same as in example 1.

(3)Au₂₅/Co₃Preparation of Al-LDH/rGO catalyst

The synthesis procedure was the same as in example 2, and the obtained catalyst precursor, Au₂₅Capt₁₈/Co₃Calcining Al-LDH/rGO in nitrogen atmosphere at 280 ℃ for 3 hours to prepare the catalyst, which is named as 0.5-Au₂₅/Co₃Al-LDH/rGO-280。

Claims

1. A multilevel-structure hybrid-loaded atomic precision gold nanocluster catalyst is characterized in that the expression is Au_n/(M² ⁺) A1-LDH/rGO-T, in which Au_nN gold atoms, n being 25, 38, 127; (M)²⁺) M in A1-LDH/rGO²⁺Is Mg²⁺、Ni² ⁺、Co²⁺Either one or both of the ions; (M) 55 to 70nm in size and 8 to 10nm in thickness²⁺) Al-LDH nanosheets vertically and alternately grow on two sides of the rGO lamella, and the shape of a nanosheet-like array is shown; the gold nanoclusters with the sizes of 1.0 +/-0.3, 1.5 +/-0.3 and 1.8 +/-0.4 nm in the catalyst are highly dispersed at the edge of the LDH and the junction of the LDH and the rGO; the active component in the catalyst is a gold nanocluster, and the mass percentage of the gold nanocluster is 0.5-1.5%.

2. The preparation method of the multilevel structure hybrid supported atomic precision gold nanocluster catalyst as claimed in claim 1, which comprises the following steps:

(1) preparation of gold nanocluster precursor

Preparation of Au by combining size focusing method and polyacrylamide gel electrophoresis technology₂₅Capt₁₈、Au₃₈Capt₂₄And Au_～127-Capt nanoclusters; firstly, dissolving 1g of chloroauric acid tetrahydrate in 100mL of methanol to prepare a chloroauric acid methanol stock solution of 10 mg/mL; then, 8.23mL of chloroauric acid tetrahydrate in methanol and 126.8mg of tetraoctylammonium bromide were added to a 100mL round-bottomed flask containing 6.75mL of methanol at room temperature for 12 minutesMagnetic stirring at 00rpm, and changing the mixed solution from orange to dark red; after reacting for 15 minutes, 130.4mg of captopril, namely Capt, is added into the reaction solution, and the color of the solution is rapidly changed into white; after 30 minutes of reaction, the stirring rate was adjusted to 600rpm and 5mL of NaBH dissolved in 37.8mg₄The ice water solution is quickly added into the reaction solution, and the color of the solution immediately changes into brownish green; continuously reacting the reaction solution in a water bath at 25 +/-1 ℃ for 48 hours, centrifuging the reaction solution at 5000r/min for 20min, and removing unreacted and insoluble Au (I) and Capt polymer; collecting supernatant, and rotary steaming at 30 deg.C for 20min to obtain concentrated solution; adding 20mL of acetone into the concentrated solution, and standing for 12 hours to obtain a precipitated gold cluster; then vacuum drying is carried out for 12 hours at the temperature of 30 ℃ to obtain a crude product; continuously extracting the crude product with 0.5-1mL of methanol for 6 times to obtain a brownish black transparent extract; adding 20mL of acetone into the brownish black transparent extracting solution to precipitate gold clusters again, and centrifuging at 3000r/min for 10min to obtain brownish black precipitates; vacuum drying at 30 deg.C for 12 hr to obtain final brown black product Au_:A Capt nanocluster;

polyacrylamide gel electrophoresis separation: subjecting the obtained Au: Capt product to polyacrylamide gel electrophoresis separation by using a vertical gel electrophoresis system at 300V; preparing separation gel and stacking gel by respectively using 30% and 4% of acrylamide monomer; dissolving Au Capt cluster in 10% v/v glycerol/water at a concentration of 30mg/mL, and adding the Au cluster into the gel at a load of 40 mu L/hole; after 4 hours of electrophoretic separation, the clear bands cut from the gel were soaked in water for 2 hours and the nanocluster solution mixed with the gel matrix was filtered by using a 0.22 μm filter; then adding 10% v/v glacial acetic acid for acidification, concentrating the acidified nano-cluster solution by using a 3kDa cut-off filter, finally precipitating the concentrated solution by using acetone and drying for 12 hours under vacuum to obtain pure Au₂₅Capt₁₈And Au₃₈Capt₂₄And larger size gold nanoclusters; for the gold nanoclusters with larger size, a simple method is used, the gold nanoclusters are assumed to be spherical and have the same density as bulk Au, and the gold nanoclusters with larger size are calculated to be Au corresponding to the gold nanoclusters with larger size of 1.6nm obtained based on TEM analysis_～127-Capt；

(2) Preparation of nanosheet-like array type hierarchical structure LDH/rGO hybrid carrier

Firstly, preparing graphene oxide (GO sol) with the mass concentration of 8.07mg/mL by using natural crystalline flake graphite powder as a raw material through an improved Hummers method, wherein the graphene oxide is used as a stock solution; then preparing a nanosheet array structure (M) by a simple and green citric acid assisted liquid-phase coprecipitation method²⁺) Al-LDH/rGO hybrids; the method comprises the following specific steps: dispersing 50mg of GO sol into 100mL of deionized water, ultrasonically stripping for 20 minutes, adding 25mg of citric acid, and continuing to ultrasonically treat for 5 minutes; the resulting citric acid modified GO suspension was transferred to a 500mL four-necked flask and NaOH and Na were added dropwise with vigorous stirring₂CO₃To a pH of 10.0 ± 0.1 for 10 minutes, wherein OH^-And CO₃ ^2-The quantitative concentration ratio of the substances of (a) to (b) is 3.2; then 100mL (M) was added dropwise²⁺)(NO₃)₂·6H₂O and Al (NO)₃)₃·9H₂O mixed salt solution, and simultaneously dropwise adding mixed alkali solution to make the pH value of the mixed system be 10.0 +/-0.1, wherein CO₃ ^2-And Al³⁺The mass concentration ratio of the substances (c) is 3.2, M²⁺Is Mg²⁺、Ni²⁺、Co²⁺One or two of the ions, M²⁺And Al³⁺The amount of total substances of (2) is 20mmol, M²⁺And Al³⁺The quantitative concentration ratio of the substances of (a) to (b) is 3; after the dropwise addition is finished, crystallizing the obtained mixed solution in a water bath at 65 ℃ for 4 hours; finally, centrifugal separation is carried out, deionized water is washed to be neutral, and freeze drying is carried out to obtain the multi-level structure hybrid carrier which is named as (M)²⁺)A1-LDH/rGO；

(3) Preparation of nanosheet-like array type hierarchical structure LDH/rGO-supported atomic precision gold nanocluster catalyst

Preparation of Au by pH double-control electrostatic adsorption method_n/(M²⁺) The Al-LDH/rGO-T catalyst comprises the following specific operation steps: 0.5 to 1.0g of (M)²⁺) Adding the Al-LDH/rGO hybrid carrier into 30-50 mL of deionized water, and adding a proper amount of Na with the amount and concentration of 0.1mol/L₂CO₃Carrying out ultrasonic treatment on the solution for 5-15 minutes, and then adjusting to obtain a carrier dispersion liquid with the pH value of 6.0-10.0; play at room temperatureStirring vigorously to obtain a certain amount of Na with a concentration of 0.1mol/L₂CO₃Adding a gold nano-cluster precursor solution with the pH value of the solution being preset to 6.0-10.0 into the carrier dispersion liquid, wherein the theoretical loading capacity of the gold nano-cluster is 0.5-1.5 wt%, and carrying out magnetic stirring reaction at 1000rpm for 2-6 hours; collecting the mixture by centrifugal separation, and freeze-drying to obtain a catalyst precursor; calcining the obtained catalyst precursor for 3 hours at 260-300 ℃ in nitrogen atmosphere to obtain the catalyst, which is named as Au_n/(M²⁺)Al-LDH/rGO-T。