Au and Pt catalyst with stable crown ether material as well as preparation and application of Au and Pt catalyst

Abstract

The invention provides a crown ether-based solid material stable Au and Pt monatomic catalyst as well as a preparation method and application thereof, and the preparation method comprises the following steps: taking a bdc ligand of crown ether as a protective agent of the Au and Pt monatomic catalyst, and synthesizing the heterogeneous crown ether-based solid material stable Au and Pt monatomic catalyst. The heterogeneous Pt monatomic catalyst is applied to a hydrosilylation reaction. The heterogeneous Au monatomic catalyst is adopted to catalyze reduction of nitrophenol compounds.

Description

Technical Field

[0001] The invention belongs to the field of catalysts and relates to a crown ether-based solid material-stabilized Au and Pt single-atom catalyst and a preparation method and application thereof. Background Art

[0002] Single-atom catalysts stabilized by homogeneous complexes occupy an important position in the development of industries such as industry and medicine due to their excellent activity and selectivity. However, since these homogeneous catalysts are in the same phase as the reaction substrate, they are often difficult to recover and separate from the products, which significantly increases costs; more importantly, the catalysts remaining in the products will pollute the environment and reduce product quality. For precious metal catalysts, achieving catalyst reuse is the key to reducing costs. Immobilizing homogeneous catalysts to obtain heterogeneous catalysts is an important way to achieve their effective separation and reuse. This method has also been widely used.

[0003] There are two main methods for heterogeneous catalysis: the first is to prepare a solid-phase catalyst by loading the homogeneous catalyst on an inorganic carrier with a large specific surface area, such as silica, alumina, zeolite, etc., through different physical adsorption or chemical adsorption methods on the basis of the homogeneous catalyst, but this method is difficult to solve the problem of the loss of metal active centers. The second is to chemically bond the active component with the solid phase or a liquid phase substance that is immiscible with the solvent, and anchor the metal active component on the solid material through chemical bonds through a solid-phase synthesis method. Alternatively, the active component is first bonded to the precursor of the solid material, and then the material is synthesized to complete the synthesis of the solid-phase catalyst.

[0004] In the mid-1980s, people proposed a two-phase hydroformylation reaction technology for propylene. Because it uses water-soluble phosphine ligand tri-m-sulfonic acid triphenylphosphine sodium salt (TPPTS) and other materials as catalysts, this technology has been rapidly promoted and applied. Minkee Choi reported that the catalytic activity of the catalyst was improved by using homogeneous heterogeneity to anchor single-atom Pt on a S-doped porous carbon support and change the ORR reaction mechanism of Pt. The reaction generates H2O instead of following the traditional homogeneous catalysis to generate H2O2 ·Similarly, Javier Pérez-Ramírez et al. anchored single-atom Pd on N-containing graphitic carbon nitride, which showed better reaction activity than homogeneous catalysis in the Suzuki coupling reaction. Xiao Fengshou et al. have conducted long-term research and discussion on the heterogeneity of homogeneous catalysts. In recent years, they have copolymerized ionic liquids and divinylbenzene to develop high-performance and super-hydrophobic porous catalysts. The material was then tested and the results showed that the material not only maintained a super-hydrophobic polymer skeleton structure, but also had strong acidity. The research team also conducted an ester exchange reaction to produce biodiesel and found that the catalyst had a very ideal conversion rate because it had good hydrophobic properties. In this case, the reactants can be adsorbed in the nanopores. This research result has attracted widespread attention in the academic community and provides a reference for human practice. In 2019, Ding Yunjie's team proposed a single-atom-level dispersion method for precious metal nanoparticles and prepared an activated carbon-supported single-atom Rh-based catalyst, which showed catalytic activity superior to nanoparticles and homogeneous catalysts in the methanol carbonylation reaction. The carbonyl (-C=O) oxygen functional group on the surface of the carbon support was analyzed and proved to be the most likely anchoring site for single-atom Rh in this catalysis. The lone pair of electrons on the carbonyl group successfully promoted the catalytic activity of single-atom Rh in multiphase through the interaction with the metal support.

[0005] In the above, we synthesized supported Au and Pt single-atom catalysts by method 1. However, when we reused the catalysts three times, we found that the reaction activity decreased significantly. From the above work, we know that the stability of Pt and Au single atoms depends on H + , Cl - and the coordination of the two oxygen atoms on the crown ether, so in this work, we used solid-phase crown ether-based solid material compounds to stabilize the Au and Pt single-atom catalysts, in order to achieve the recycling of the catalyst while maintaining high catalytic activity in the characteristic reaction. Summary of the invention

[0006] The purpose of the invention is to provide a method for preparing Au and Pt single-atom catalysts stabilized by crown ether-based solid materials, using the bdc ligand of the crown ether as a protective agent for the Au and Pt single-atom catalysts to synthesize the heterogeneous Au and Pt single-atom catalysts stabilized by the crown ether-based solid materials.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] The first aspect of the present invention provides a method for preparing Au and Pt single-atom catalysts stabilized by crown ether-based solid materials, characterized in that it comprises the following steps:

[0009] The bdc ligand of the crown ether is used as a protective agent for Au and Pt single-atom catalysts to synthesize Au and Pt single-atom catalysts stabilized by the crown ether-based solid material in a heterogeneous phase.

[0010] Furthermore, the precursor of the bdc ligand of the crown ether is dibromotetraethylene glycol ether;

[0011] The synthesis of the dibromotetraethylene glycol ether comprises the following steps:

[0012] 200 mL of dichloromethane (DCM) was cooled to -78°C using a mixture of liquid nitrogen / isopropanol, and N-bromosuccinimide and triphenylphosphine were added under stirring; 10 minutes later, tetraethylene glycol was added and stirred overnight, and then the temperature was slowly raised to room temperature; DCM was removed under vacuum, and purified by column chromatography (hexane / ethyl acetate = 4:1); after the solvent was removed under vacuum, a colorless oily product was isolated, and vacuum dried overnight to obtain the product dibromotetraethylene glycol ether.

[0013] Further, the dibromotriethylene glycol ether is subjected to a dehydrobromination reaction with dimethyl 2,3-dihydroxyterephthalate to synthesize 1,4-dicarboxybenzo-15-crown-5; the process specifically comprises the following steps:

[0014] First, anhydrous potassium carbonate and dimethyl 2,3-dihydroxyterephthalate 20 are added and dissolved in N,N-dimethylformamide (DMF); dibromotetraethylene glycol ether compound is added under vigorous stirring; the mixture is heated at 85°C overnight and filtered to remove K2CO3; then DMF in the mixture is removed in vacuo; the remaining part is purified by silica gel (hexane / ethyl acetate gradient: 80 / 20), and then the solvent is removed by rotary evaporation; water and KOH are added to the resulting solid, and the solution is heated to reflux overnight; after cooling to room temperature, HCl solution is added to acidify the ice bath; after observing that the solution becomes turbid, rotary evaporation is performed until the water volume is reduced to less than 5mL, and an off-white solid is precipitated and cooled in an ice bath; the precipitate is filtered out, washed and vacuum dried overnight to obtain the product 1,4-dicarboxybenzo-15-crown-5.

[0015] Further, 1,4-dicarboxybenzo-15-crown-5, ethanol and ultrapure water were stirred at 280 rpm in a round-bottom flask at room temperature; after 10 minutes, H2PtCl6 solution was added, and the mixture was stirred for 10 minutes; the solution was refluxed at 70°C for 8 hours, and then cooled to room temperature; the reaction solvents ethanol and water were removed by reduced pressure distillation on a rotary evaporator (the heating temperature was set to 45°C) to obtain a heterogeneous Pt single atom catalyst.

[0016] Furthermore, 1,4-dicarboxybenzo-15-crown-5, ethanol and ultrapure water were stirred at 280 rpm in a round-bottom flask at room temperature; after 10 minutes, HAuCl4 solution was added, and the mixture was stirred for 10 minutes; the solution was refluxed at 70°C for 40 hours and then cooled to room temperature; the reaction solvents ethanol and water were removed by reduced pressure distillation on a rotary evaporator (the heating temperature was set to 45°C) to obtain a heterogeneous Au single-atom catalyst.

[0017] A second aspect of the present invention provides a heterogeneous Pt single-atom catalyst prepared by any one of the above preparation methods.

[0018] A third aspect of the present invention provides an application of a heterogeneous Pt single-atom catalyst, wherein the heterogeneous Pt single-atom catalyst is applied to a hydrosilylation reaction.

[0019] A fourth aspect of the present invention provides a heterogeneous Au single-atom catalyst prepared by any one of the above preparation methods.

[0020] A fifth aspect of the present invention provides an application of a heterogeneous Au single-atom catalyst, wherein the heterogeneous Au single-atom catalyst is used to catalyze the reduction of nitrophenol compounds.

[0021] Beneficial effects of the present invention:

[0022] 1. The invention provides a method for preparing Au and Pt single-atom catalysts stabilized by crown ether-based solid materials, using the bdc ligand of the crown ether as a protective agent for the Au and Pt single-atom catalysts to synthesize the heterogeneous Au and Pt single-atom catalysts stabilized by the crown ether-based solid materials.

[0023] 2. For the hydrosilylation reaction of 1-octene and 1,1,1,3,5,5,5-heptamethylsiloxane, Pt1@15-crown-5 can achieve 1.2×10 7 We applied the synthesized heterogeneous single-atom catalyst to the hydrosilylation reaction.

[0024] 3. Catalytic reduction of toxic nitrobenzene compounds to less toxic aminobenzene compounds is one of the most important applications of Au. We continue to use the synthesized Au1@(COOH)2Ph(15-crown-5) for the reduction of nitrophenol compounds. The reaction of Au1@15-crown-5 to reduce nitrobenzene compounds has achieved high activity, but during the reaction we observed that the catalyst agglomerates to a certain extent, so we did not achieve good results in the catalyst cycle performance test. Here, we focus on testing the activity and reaction cyclability of heterogeneous catalysts for this type of reaction.

[0025] Similarly, 4-nitrophenol will form 4-nitrophenolate ions in an alkaline environment, with a UV absorption peak at 400nm and a yellow-green color of the solution. We first tested whether a mixture of 4-NP and NaBH4 could react when only 1,4-dicarboxybenzo-15-crown-5 was added. The results showed that the intensity of the UV absorption peak at 400nm remained constant for a long time (600 minutes), and the solution also remained yellow-green. This indicates that NaBH4 itself cannot reduce 4-nitrophenol.

[0026] 4. The heterogeneous Pt single atom catalyst is used in a hydrosilylation reaction. The heterogeneous Au single atom catalyst is used to catalyze the reduction of nitrophenol compounds. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a typical synthesis process of the crown ether bdc derivatives in the embodiments of the present invention;

[0028] Figure 2 This is the nuclear magnetic spectrum of dibromotetraethylene glycol ether in the embodiment of the present invention;

[0029] Figure 3 This is the nuclear magnetic spectrum of 1,4-dicarboxybenzo-15-crown-5 in the embodiment of the present invention;

[0030] Figure 4 This is the XPS spectrum of the heterogeneous Pt single atom catalyst in the embodiment of the present invention;

[0031] Figure 5 This is the XPS spectrum of the heterogeneous Au single atom catalyst in the embodiment of the present invention;

[0032] Figure 6 In the figure, (a): DRIFT of CO adsorbed on Pt1@1,4-dicarboxybenzo-15-Crown-5 / SiO2; (b): DRIFT of CO adsorbed on 1,4-dicarboxybenzo-15-Crown-5 / SiO2;

[0033] Figure 7 This is a cycle test of a heterogeneous Pt single atom catalyst in an embodiment of the present invention;

[0034] Figure 8 This is a cycle test of the heterogeneous Au single atom catalyst in the embodiment of the present invention; DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0037] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0038] Crown ether or macrocyclic polyether-based linkers can usually form complexes with guest species through coordination or hydrogen bonding. However, the preparation of some macrocyclic polyether compounds has always been difficult due to their high cost, low yield, and complex steps. However, this situation has been improved to a certain extent through the development of CC cross-coupling reactions and dynamic covalent chemistry. In previous studies, Chen and colleagues synthesized bdc derivatives containing 12-crown-4, 15-crown-5, and thiocrown ethers. The typical synthesis process is as follows: Figure 1 As shown, the typical IR MOF-1 (also known as MOF-5 [ZnO4 (bdc) 3] n ;bdc 2- = terephthalate) and UiO-66 (University of Oslo, [Zr6(OH)4O4(bdc)6] n ) structure. In view of these studies, we attempted to develop a simple synthetic method to synthesize heterogeneous Au and Pt single-atom stabilizers using the bdc ligands of crown ethers as protectors for Au and Pt single-atom catalysts.

[0039] The embodiment of the present invention provides a method for preparing Au and Pt single-atom catalysts stabilized by crown ether-based solid materials, using the bdc ligand of the crown ether as a protective agent for the Au and Pt single-atom catalysts to synthesize the heterogeneous Au and Pt single-atom catalysts stabilized by the crown ether-based solid materials.

[0040] The following are specific embodiments

[0041] Example 1

[0042] Embodiment 1 of the present invention provides a method for preparing a Pt single-atom catalyst stabilized by a crown ether-based solid material, comprising the following steps:

[0043] (1) Preparation of dibromotetraethylene glycol ether (precursor of the BDC ligand of crown ether)

[0044] To synthesize the bdc ligand of the crown ether, we first need to synthesize the precursor dibromotriethylene glycol ether.

[0045] First, use a mixture of liquid nitrogen / isopropanol (liquid nitrogen is passed into isopropanol to make isopropanol enter a solid-liquid mixed state, which only serves as a cooling function) to cool 200mL of dichloromethane (DCM) to -78°C, and add N-bromosuccinimide (NBS, 8.72g, 49mmol) and triphenylphosphine (PhP3, 12.84g, 49mmol) under stirring. After 10 minutes, add tetraethylene glycol (4.27g, 22mmol) and stir overnight (12 hours), then raise the temperature to room temperature. Remove DCM by vacuum distillation and purify by column chromatography (column chromatography manufacturer: Huanghai Chemical Industry Research Institute, column length 15cm, diameter 2cm, filler silica gel 200-300 mesh. Mobile phase: hexane / ethyl acetate = 4:1, volume ratio). After vacuum distillation to remove the solvent, a colorless oily product was separated and vacuum dried overnight (12 hours) to obtain the product dibromotriethylene glycol ether. The NMR spectrum is shown in Figure 2. After comparison with the NMR results of the literature (Chen TH, Schneemann A, Fischer RA, et al. Metal-organic frameworks constructed from crown ether-based 1,4-benzenedicarboxylic acid derivatives [J]. Dalton Transactions, 2016, 45 (7): 3063-3069.), the synthesis was confirmed to be successful.

[0046] (2) Preparation of 1,4-dicarboxybenzo-15-crown ether-5

[0047] Take the above-mentioned dibromo triethylene glycol ether that has been synthesized, according to Figure 1 In the next step, it is subjected to a dehydrobromination reaction with dimethyl 2,3-dihydroxyterephthalate to synthesize 1,4-dicarboxybenzo-15-crown-5.

[0048] Specific process: First, add anhydrous potassium carbonate (1.10g, 7.90mmol) and dimethyl 2,3-dihydroxyterephthalate (1.5g, 6.64mmol) to a container and dissolve them in 100mL of N,N-dimethylformamide (DMF). Add dibromotetraethylene glycol ether (2.12g, 6.64mmol) under vigorous stirring. The mixture is heated at 85°C overnight (12 hours) and filtered to remove K2CO3. Then, DMF in the mixture is removed by vacuum distillation. The remaining part is purified by silica gel (column chromatography) (Huanghai Chemical Industry Research Society, column length 15cm, diameter 2cm, silica gel 200-300 mesh. Mobile phase: hexane / ethyl acetate: 80 / 20, volume ratio), and then the solvent is removed by rotary evaporation. Add KOH aqueous solution (mixed by 100ml of water and 600mg of KOH) to the obtained solid, and the solution is heated to reflux at 155°C overnight (12 hours). After cooling to room temperature, place in an ice-water bath and add 5 ml of 1M HCl solution to acidify. After observing that the solution becomes turbid, evaporate until the amount of water is reduced to 4 mL, and a gray-white solid is precipitated and cooled in an ice-water bath. Filter the precipitate, wash and vacuum dry overnight (12 hours). The product 1,4-dicarboxybenzo-15-crown-5 (1,4-dicarboxybenzo-15-crown-5, the same below) is obtained. The product is 1 H NMR confirmed. The NMR spectrum is shown in Figure 3. After comparing with the NMR results of the literature (Chen TH, Schneemann A, Fischer RA, et al. Metal-organic frameworks constructed from crown ether-based 1,4-benzenedicarboxylic acid derivatives [J]. Dalton Transactions, 2016, 45 (7): 3063-3069.), it was confirmed that the synthesis was successful.

[0049] (3) Preparation of heterogeneous Pt single-atom catalysts

[0050] 1,4-Dicarboxybenzo-15-crown-5 (0.12 g), ethanol (45 mL) and ultrapure water (5 mL) were stirred at 280 rpm in a round-bottom flask at room temperature. After 10 minutes, 0.8 mL of H2PtCl6 aqueous solution (1.84 × 10 –2 mol / L), and the mixture was stirred for 10 minutes. The solution was treated at 70°C for 8 hours and then cooled to room temperature. The reaction solvent ethanol and water were removed by reduced pressure distillation on a rotary evaporator (the heating temperature was set to 45°C) to obtain the product, and the infrared absorption peak of CO did not blue shift during the CO adsorption process of CO-DRIFTS, proving that the heterogeneous Pt single atom catalyst was successfully synthesized.

[0051] Example 2

[0052] Embodiment 2 of the present invention provides a method for preparing a Pt single-atom catalyst stabilized by a crown ether-based solid material, comprising the following steps:

[0053] (1) Preparation of dibromotetraethylene glycol ether (precursor of the BDC ligand of crown ether)

[0054] The process and conditions are the same as those in step (1) of Example 1: preparation of dibromotetracetetral glycol (precursor of the bdc ligand of the crown ether).

[0055] (2) Preparation of 1,4-dicarboxybenzo-15-crown ether-5

[0056] The process and conditions are the same as those of step (2) of Example 1 for the preparation of 1,4-dicarboxybenzo-15-crown-5, except that:

[0057] Take the above-mentioned dibromo triethylene glycol ether that has been synthesized, according to Figure 1 In the next step, it is subjected to a dehydrobromination reaction with dimethyl 2,3-dihydroxyterephthalate to synthesize 1,4-dicarboxybenzo-15-crown-5.

[0058] Specific process: First, anhydrous potassium carbonate (1.10 g, 7.90 mmol) and dimethyl 2,3-dihydroxyterephthalate (1.5 g, 6.64 mmol) were added to a container and dissolved in 100 mL of N,N-dimethylformamide (DMF). Under vigorous stirring, dibromotetraethylene glycol ether (2.12 g, 6.64 mmol) was added. The mixture was heated at 80°C overnight (12 hours) and filtered to remove K2CO3. DMF in the mixture was then removed by vacuum distillation. The remaining part was purified by silica gel (Huanghai Chemical Industry Research Society, column length 15 cm, diameter 2 cm, silica gel 200-300 mesh. Mobile phase: hexane / ethyl acetate: 80 / 20, volume ratio), and then the solvent was removed by rotary evaporation. KOH aqueous solution (mixed from 100 ml of water and 600 mg of KOH) was added to the obtained solid, and the solution was heated to reflux at 155°C overnight (12 hours). After cooling to room temperature, place in an ice-water bath and add 5 ml of 1M HCl solution to acidify. After the solution becomes turbid, evaporate until the amount of water is reduced to 4 mL, and a gray-white solid is precipitated and cooled in an ice-water bath. Filter the precipitate, wash it, and vacuum dry it overnight (12 hours). The product 1,4-dicarboxybenzo-15-crown-5 is obtained. 1H NMR confirmed. The NMR spectrum is shown in Figure 3. After comparing with the NMR results of the literature (Chen TH, Schneemann A, Fischer RA, et al. Metal-organic frameworks constructed from crown ether-based 1,4-benzenedicarboxylic acid derivatives [J]. Dalton Transactions, 2016, 45 (7): 3063-3069.), it was confirmed that the synthesis was successful.

[0059] (3) Preparation of heterogeneous Pt single-atom catalysts

[0060] The process and conditions are the same as those of step (3) of Example 1 for the preparation of heterogeneous Pt single-atom catalyst, except that:

[0061] 1,4-Dicarboxybenzo-15-crown-5 (0.12 g), ethanol (45 mL) and ultrapure water (5 mL) were stirred at 280 rpm in a round-bottom flask at room temperature. After 10 minutes, 0.8 mL of H2PtCl6 aqueous solution (1.84 × 10 –2 mol / L), and the mixture was stirred for 10 minutes. The solution was treated at 75°C for 8 hours and then cooled to room temperature. The reaction solvent ethanol and water were removed by reduced pressure distillation on a rotary evaporator (the heating temperature was set to 40°C) to obtain the product, and the infrared absorption peak of CO did not blue shift during the CO adsorption process of CO-DRIFTS, proving that the heterogeneous Pt single atom catalyst was successfully synthesized.

[0062] Example 3

[0063] Embodiment 3 of the present invention provides a method for preparing a Pt single-atom catalyst stabilized by a crown ether-based solid material, comprising the following steps:

[0064] (1) Preparation of dibromotetraethylene glycol ether (precursor of the BDC ligand of crown ether)

[0065] The process and conditions are the same as those in step (1) of Example 1: preparation of dibromotetracetetral glycol (precursor of the bdc ligand of the crown ether).

[0066] (2) Preparation of 1,4-dicarboxybenzo-15-crown ether-5

[0067] The process and conditions are the same as those of step (2) of Example 1 for the preparation of 1,4-dicarboxybenzo-15-crown-5, except that:

[0068] Take the above-mentioned dibromo triethylene glycol ether that has been synthesized, according to Figure 1In the next step, it is subjected to a dehydrobromination reaction with dimethyl 2,3-dihydroxyterephthalate to synthesize 1,4-dicarboxybenzo-15-crown-5.

[0069] Specific process: First, add anhydrous potassium carbonate (1.10g, 7.90mmol) and dimethyl 2,3-dihydroxyterephthalate (1.5g, 6.64mmol) to a container and dissolve them in 100mL of N,N-dimethylformamide (DMF). Add dibromotetraethylene glycol ether (2.12g, 6.64mmol) under vigorous stirring. The mixture is heated at 85°C overnight (12 hours) and filtered to remove K2CO3. Then, DMF in the mixture is removed by vacuum distillation. The remaining part is purified by silica gel (Huanghai Chemical Industry Research Society, column length 15cm, diameter 2cm, silica gel 200-300 mesh. Mobile phase: hexane / ethyl acetate: 80 / 20, volume ratio), and then the solvent is removed by rotary evaporation. Add KOH aqueous solution (mixed by 100ml of water and 600mg of KOH) to the obtained solid, and the solution is heated to reflux at 160°C overnight (12 hours). After cooling to room temperature, place in an ice-water bath and add 5 ml of 1M HCl solution to acidify. After the solution becomes turbid, evaporate until the amount of water is reduced to 4 mL, and a gray-white solid is precipitated and cooled in an ice-water bath. Filter the precipitate, wash it, and vacuum dry it overnight (12 hours). The product 1,4-dicarboxybenzo-15-crown-5 is obtained. 1 H NMR confirmed. The NMR spectrum is shown in Figure 3. After comparing with the NMR results of the literature (Chen TH, Schneemann A, Fischer RA, et al. Metal-organic frameworks constructed from crown ether-based 1,4-benzenedicarboxylic acid derivatives [J]. Dalton Transactions, 2016, 45 (7): 3063-3069.), it was confirmed that the synthesis was successful.

[0070] (3) Preparation of heterogeneous Pt single-atom catalysts

[0071] The process and conditions are the same as those of step (3) of Example 1 for the preparation of heterogeneous Pt single-atom catalyst, except that:

[0072] 1,4-Dicarboxybenzo-15-crown-5 (0.12 g), ethanol (45 mL) and ultrapure water (5 mL) were stirred at 280 rpm in a round-bottom flask at room temperature. After 10 minutes, 0.8 mL of H2PtCl6 aqueous solution (1.84 × 10 –2mol / L), and the mixture was stirred for 10 minutes. The solution was treated at 78°C for 8 hours and then cooled to room temperature. The reaction solvent ethanol and water were removed by reduced pressure distillation on a rotary evaporator (the heating temperature was set to 42°C) to obtain the product, and the infrared absorption peak of CO did not blue shift during the CO adsorption process of CO-DRIFTS, proving that the heterogeneous Pt single atom catalyst was successfully synthesized.

[0073] Example 4

[0074] Embodiment 4 of the present invention provides a method for preparing a Pt single-atom catalyst stabilized by a crown ether-based solid material, comprising the following steps:

[0075] (1) Preparation of dibromotetraethylene glycol (precursor of the BDC ligand of crown ether)

[0076] The process and conditions are the same as those in step (1) of Example 1: preparation of dibromotetracetetral glycol (precursor of the bdc ligand of the crown ether).

[0077] (2) Preparation of 1,4-dicarboxybenzo-15-crown ether-5

[0078] The process and conditions are the same as those in step (2) of Example 1 for the preparation of 1,4-dicarboxybenzo-15-crown ether-5.

[0079] (3) Preparation of heterogeneous Pt single-atom catalysts

[0080] The process and conditions are the same as those of step (3) of Example 1 for the preparation of heterogeneous Pt single-atom catalyst, except that:

[0081] 1,4-Dicarboxybenzo-15-crown-5 (0.12 g), ethanol (45 mL) and ultrapure water (5 mL) were stirred at 280 rpm in a round-bottom flask at room temperature. After 10 minutes, 0.8 mL of H2PtCl6 aqueous solution (1.84 × 10 –2 mol / L), and the mixture was stirred for 10 minutes. The solution was treated at 78°C for 8 hours and then cooled to room temperature. The reaction solvent ethanol and water were removed by reduced pressure distillation on a rotary evaporator (the heating temperature was set to 43°C) to obtain the product, and the infrared absorption peak of CO did not blue shift during the CO adsorption process of CO-DRIFTS, proving that the heterogeneous Pt single atom catalyst was successfully synthesized.

[0082] Example 5

[0083] Embodiment 5 of the present invention provides a method for preparing a Pt single-atom catalyst stabilized by a crown ether-based solid material, comprising the following steps:

[0084] (1) Preparation of dibromotetraethylene glycol (precursor of the BDC ligand of crown ether)

[0085] The process and conditions are the same as those in step (1) of Example 1: preparation of dibromotetracetetral glycol (precursor of the bdc ligand of the crown ether).

[0086] (2) Preparation of 1,4-dicarboxybenzo-15-crown ether-5

[0087] The process and conditions are the same as those in step (2) of Example 1 for the preparation of 1,4-dicarboxybenzo-15-crown ether-5.

[0088] (3) Preparation of heterogeneous Pt single-atom catalysts

[0089] The process and conditions are the same as those of step (3) of Example 1 for the preparation of heterogeneous Pt single-atom catalyst, except that:

[0090] 1,4-Dicarboxybenzo-15-crown-5 (0.12 g), ethanol (45 mL) and ultrapure water (5 mL) were stirred at 280 rpm in a round-bottom flask at room temperature. After 10 minutes, 0.8 mL of H2PtCl6 aqueous solution (1.84 × 10 –2 mol / L), and the mixture was stirred for 10 minutes. The solution was treated at 76 ° C for 8 hours and then cooled to room temperature. The reaction solvent ethanol and water were removed by reduced pressure distillation on a rotary evaporator (the heating temperature was set to 45 ° C) to obtain the product, and the infrared absorption peak of CO did not blue shift during the CO adsorption process of CO-DRIFTS, proving that the heterogeneous Pt single atom catalyst was successfully synthesized.

[0091] Example 6

[0092] Embodiment 6 of the present invention provides a method for preparing a crown ether-based solid material-stabilized Au single-atom catalyst, comprising the following steps:

[0093] (1) Preparation of dibromotetraethylene glycol (precursor of the BDC ligand of crown ether)

[0094] The process and conditions are the same as those of step (1) of Example 1, preparation of dibromotriethylene glycol (precursor of the bdc ligand of the crown ether), except that:

[0095] To synthesize the bdc ligand of the crown ether, we first need to synthesize the precursor dibromotriethylene glycol ether.

[0096] First, use a mixture of liquid nitrogen / isopropanol (liquid nitrogen is passed into isopropanol to make isopropanol enter a solid-liquid mixed state, which only serves as a cooling function) to cool 200mL of dichloromethane (DCM) to -77°C, and add N-bromosuccinimide (NBS, 8.72g, 49mmol) and triphenylphosphine (PhP3, 12.84g, 49mmol) under stirring. After 10 minutes, add tetraethylene glycol (4.27g, 22mmol) and stir overnight (12 hours), then raise the temperature to room temperature. Remove DCM by vacuum distillation and purify by column chromatography (column chromatography manufacturer: Huanghai Chemical Industry Research Society, column length 15cm, diameter 2cm, filler silica gel 200-300 mesh. Mobile phase: hexane / ethyl acetate = 4:1, volume ratio). After the solvent was removed by vacuum, a colorless oily product was separated and dried in vacuum overnight (10 hours) to obtain the product dibromotriethylene glycol ether. The NMR spectrum is shown in Figure 2. After comparison with the NMR results of the literature (Chen TH, Schneemann A, Fischer RA, et al. Metal-organic frameworks constructed from crown ether-based 1,4-benzenedicarboxylic acid derivatives [J]. Dalton Transactions, 2016, 45 (7): 3063-3069.), the synthesis was confirmed to be successful.

[0097] (2) Preparation of 1,4-dicarboxybenzo-15-crown ether-5

[0098] The process and conditions are the same as those in step (2) of Example 3 for the preparation of 1,4-dicarboxybenzo-15-crown ether-5.

[0099] (3) Preparation of heterogeneous Au single-atom catalysts

[0100] The process and conditions are the same as those of step (3) of Example 1 for the preparation of heterogeneous Au single-atom catalyst, except that:

[0101] 1,4-Dicarboxybenzo-15-crown-5 (0.12 g), ethanol (45 mL) and ultrapure water (5 mL) were stirred at 400 rpm in a round-bottom flask at room temperature. After 10 minutes, 0.6 mL of HAuCl4 aqueous solution (2.43 × 10 –2mol / L), and the mixture was stirred for 10 minutes. The solution was treated at 80°C for 40 hours and then cooled to room temperature. The reaction solvent ethanol and water were removed by reduced pressure distillation on a rotary evaporator (the heating temperature was set to 45°C) to obtain the product, and the HAADF-STEM characterization results showed that obvious single-atom bright spots were found on the catalyst surface, and no nanoparticles or clusters were observed, proving that the heterogeneous Au single-atom catalyst was successfully synthesized.

[0102] Example 7

[0103] Embodiment 7 of the present invention provides a method for preparing a crown ether-based solid material-stabilized Au single-atom catalyst, comprising the following steps:

[0104] (1) The process and conditions are the same as those of step (1) of Example 1, preparation of dibromotriethylene glycol (precursor of the bdc ligand of the crown ether), except that:

[0105] To synthesize the bdc ligand of the crown ether, we first need to synthesize the precursor dibromotriethylene glycol ether.

[0106] First, use a mixture of liquid nitrogen / isopropanol (liquid nitrogen is passed into isopropanol to make isopropanol enter a solid-liquid mixed state, which only serves as a cooling function) to cool 200mL of dichloromethane (DCM) to -76°C, and add N-bromosuccinimide (NBS, 8.72g, 49mmol) and triphenylphosphine (PhP3, 12.84g, 49mmol) under stirring. After 10 minutes, add tetraethylene glycol (4.27g, 22mmol) and stir overnight (14 hours), then raise the temperature to room temperature. Remove DCM by vacuum distillation and purify by column chromatography (column chromatography manufacturer: Huanghai Chemical Industry Research Society, column length 15cm, diameter 2cm, filler silica gel 200-300 mesh. Mobile phase: hexane / ethyl acetate = 4:1, volume ratio). After the solvent was removed by vacuum, a colorless oily product was separated and dried in vacuum overnight (12 hours) to obtain the product dibromotriethylene glycol ether. The NMR spectrum is shown in Figure 2. After comparison with the NMR results of the literature (Chen TH, Schneemann A, Fischer RA, et al. Metal–organic frameworks constructed from crown ether-based 1,4-benzenedicarboxylic acid derivatives [J]. Dalton Transactions, 2016, 45 (7): 3063-3069.), the synthesis was confirmed to be successful.

[0107] (2) Preparation of 1,4-dicarboxybenzo-15-crown ether-5

[0108] Take the above-mentioned dibromo triethylene glycol ether that has been synthesized, according to Figure 1 In the next step, it is subjected to a dehydrobromination reaction with dimethyl 2,3-dihydroxyterephthalate to synthesize 1,4-dicarboxybenzo-15-crown-5.

[0109] Specific process: First, add anhydrous potassium carbonate (1.10g, 7.90mmol) and dimethyl 2,3-dihydroxyterephthalate (1.5g, 6.64mmol) to a container and dissolve them in 100mL of N,N-dimethylformamide (DMF). Add dibromotetraethylene glycol ether (2.12g, 6.64mmol) under vigorous stirring. The mixture is heated at 85°C overnight (12 hours) and filtered to remove K2CO3. Then, DMF in the mixture is removed by vacuum distillation. The remaining part is purified by silica gel (Huanghai Chemical Industry Research Society, column length 15cm, diameter 2cm, silica gel 200-300 mesh. Mobile phase: hexane / ethyl acetate: 80 / 20, volume ratio), and then the solvent is removed by rotary evaporation. Add KOH aqueous solution (mixed by 100ml of water and 600mg of KOH) to the obtained solid, and the solution is heated to reflux at 165°C overnight (12 hours). After cooling to room temperature, place in an ice-water bath and add 5 ml of 1M HCl solution to acidify. After observing that the solution becomes turbid, evaporate until the amount of water is reduced to 4 mL, and a gray-white solid is precipitated and cooled in an ice-water bath. Filter the precipitate, wash it, and vacuum dry it overnight (12 hours). The product 1,4-dicarboxybenzo-15-crown-5 is obtained. The product is 1 H NMR confirmed. The NMR spectrum is shown in Figure 3. After comparing with the NMR results of the literature (Chen TH, Schneemann A, Fischer RA, et al. Metal-organic frameworks constructed from crown ether-based 1,4-benzenedicarboxylic acid derivatives [J]. Dalton Transactions, 2016, 45 (7): 3063-3069.), it was confirmed that the synthesis was successful.

[0110] (3) The process and conditions are the same as those of step (3) of Example 6 for the preparation of the heterogeneous Au single-atom catalyst, except that:

[0111] 1,4-Dicarboxybenzo-15-crown-5 (0.12 g), ethanol (45 mL) and ultrapure water (5 mL) were stirred at 400 rpm in a round-bottom flask at room temperature. After 10 minutes, 0.6 mL of HAuCl4 aqueous solution (2.43 × 10 –2mol / L), and the mixture was stirred for 10 minutes. The solution was treated at 82°C for 40 hours and then cooled to room temperature. The reaction solvent ethanol and water were removed by reduced pressure distillation on a rotary evaporator (the heating temperature was set to 43°C) to obtain the product, and the HAADF-STEM characterization results showed that obvious single-atom bright spots were found on the catalyst surface, and no nanoparticles or clusters were observed, proving that the heterogeneous Au single-atom catalyst was successfully synthesized.

[0112] Example 8

[0113] Embodiment 8 of the present invention provides a method for preparing a crown ether-based solid material-stabilized Au single-atom catalyst, comprising the following steps:

[0114] (1) Preparation of dibromotetraethylene glycol (precursor of the BDC ligand of crown ether)

[0115] The process and conditions are the same as those in step (1) of Example 1: preparation of dibromotetracetetral glycol (precursor of the bdc ligand of the crown ether).

[0116] (2) Preparation of 1,4-dicarboxybenzo-15-crown ether-5

[0117] The process and conditions are the same as those of step (2) of Example 3 for the preparation of 1,4-dicarboxybenzo-15-crown-5, except that:

[0118] Take the above-mentioned dibromo triethylene glycol ether that has been synthesized, according to Figure 1 In the next step, it is subjected to a dehydrobromination reaction with dimethyl 2,3-dihydroxyterephthalate to synthesize 1,4-dicarboxybenzo-15-crown-5.

[0119] Specific process: First, add anhydrous potassium carbonate (1.10g, 7.90mmol) and dimethyl 2,3-dihydroxyterephthalate (1.5g, 6.64mmol) to a container and dissolve them in 100mL of N,N-dimethylformamide (DMF). Add dibromotetraethylene glycol ether (2.12g, 6.64mmol) under vigorous stirring. The mixture is heated at 95°C overnight (12 hours) and filtered to remove K2CO3. Then, DMF in the mixture is removed by vacuum distillation. The remaining part is purified by silica gel (Huanghai Chemical Industry Research Society, column length 15cm, diameter 2cm, silica gel 200-300 mesh. Mobile phase: hexane / ethyl acetate: 80 / 20, volume ratio), and then the solvent is removed by rotary evaporation. Add KOH aqueous solution (mixed by 100ml of water and 600mg of KOH) to the obtained solid, and the solution is heated to reflux at 170°C overnight (12 hours). After cooling to room temperature, place in an ice-water bath and add 5 ml of 1M HCl solution to acidify. After the solution becomes turbid, evaporate until the amount of water is reduced to 4 mL, and a gray-white solid is precipitated and cooled in an ice-water bath. Filter the precipitate, wash it, and vacuum dry it overnight (12 hours). The product 1,4-dicarboxybenzo-15-crown-5 is obtained. 1 H NMR confirmed. The NMR spectrum is shown in Figure 3. After comparing with the NMR results of the literature (Chen TH, Schneemann A, Fischer RA, et al. Metal-organic frameworks constructed from crown ether-based 1,4-benzenedicarboxylic acid derivatives [J]. Dalton Transactions, 2016, 45 (7): 3063-3069.), it was confirmed that the synthesis was successful.

[0120] (3) Preparation of heterogeneous Au single-atom catalysts

[0121] 1,4-Dicarboxybenzo-15-crown-5 (0.12 g), ethanol (45 mL) and ultrapure water (5 mL) were stirred at 280 rpm in a round-bottom flask at room temperature. After 10 minutes, 0.6 mL of HAuCl4 aqueous solution (2.43 × 10 –2 mol / L), and the mixture was stirred for 10 minutes. The solution was treated at 65°C for 40 hours and then cooled to room temperature. The reaction solvent ethanol and water were removed by reduced pressure distillation on a rotary evaporator (the heating temperature was set to 45°C) to obtain the product, and the HAADF-STEM characterization results showed that obvious single-atom bright spots were found on the catalyst surface, and no nanoparticles or clusters were observed, proving that the heterogeneous Aut single-atom catalyst was successfully synthesized.

[0122] Example 9

[0123] Embodiment 9 of the present invention provides a method for preparing a crown ether-based solid material-stabilized Au single-atom catalyst, comprising the following steps:

[0124] (1) Preparation of dibromotetraethylene glycol (precursor of the BDC ligand of crown ether)

[0125] The process and conditions are the same as those in step (1) of Example 1: preparation of dibromotetracetetral glycol (precursor of the bdc ligand of the crown ether).

[0126] (2) Preparation of 1,4-dicarboxybenzo-15-crown ether-5

[0127] The process and conditions are the same as those in step (2) of Example 3 for the preparation of 1,4-dicarboxybenzo-15-crown ether-5.

[0128] (3) Preparation of heterogeneous Au single-atom catalysts

[0129] 1,4-Dicarboxybenzo-15-crown-5 (0.12 g), ethanol (45 mL) and ultrapure water (5 mL) were stirred at 280 rpm in a round-bottom flask at room temperature. After 10 minutes, 0.6 mL of HAuCl4 aqueous solution (2.43 × 10 –2 mol / L), and the mixture was stirred for 10 minutes. The solution was treated at 75°C for 40 hours and then cooled to room temperature. The reaction solvent ethanol and water were removed by reduced pressure distillation on a rotary evaporator (the heating temperature was set to 50°C) to obtain the product, and the HAADF-STEM characterization results showed that obvious single-atom bright spots were found on the catalyst surface, and no nanoparticles or clusters were observed, proving that the heterogeneous Au single-atom catalyst was successfully synthesized.

[0130] Example 10

[0131] Embodiment 10 of the present invention provides a method for preparing a crown ether-based solid material-stabilized Au single-atom catalyst, comprising the following steps:

[0132] (1) Preparation of dibromotetraethylene glycol (precursor of the BDC ligand of crown ether)

[0133] The process and conditions are the same as those in step (1) of Example 1: preparation of dibromotetracetetral glycol (precursor of the bdc ligand of the crown ether).

[0134] (2) Preparation of 1,4-dicarboxybenzo-15-crown ether-5

[0135] The process and conditions are the same as those in step (2) of Example 1 for the preparation of 1,4-dicarboxybenzo-15-crown ether-5.

[0136] (3) Preparation of heterogeneous Au single-atom catalysts

[0137] 1,4-Dicarboxybenzo-15-crown-5 (0.12 g), ethanol (45 mL) and ultrapure water (5 mL) were stirred at 280 rpm in a round-bottom flask at room temperature. After 10 minutes, 0.6 mL of HAuCl4 aqueous solution (2.43 × 10 –2 mol / L), and the mixture was stirred for 10 minutes. The solution was treated at 60°C for 40 hours and then cooled to room temperature. The reaction solvent ethanol and water were removed by reduced pressure distillation on a rotary evaporator (the heating temperature was set to 55°C) to obtain the product, and the HAADF-STEM characterization results showed that obvious single-atom bright spots were found on the catalyst surface, and no nanoparticles or clusters were observed, proving that the heterogeneous Au single-atom catalyst was successfully synthesized.

[0138] The following are the catalyst characterizations:

[0139] UV-Vis Characterization

[0140] The reduction process of step 3 of Example 6 was monitored by UV-Vis. UV-Vis detection was performed at the beginning of the reaction and samples were taken for detection after 8 hours. Since the ligand 1,4-dicarboxybenzo-15-crown-5 can be dissolved in ethanol solution, an interference peak appeared at 200-350nm, and we could not accurately observe [AuCl4] - The characteristic UV absorption peak is at 330nm. However, during the entire reduction process, the reaction solution changes from light yellow to nearly colorless, which can be used as one of the evidences that the precursor is reduced. At the same time, the reaction solution remains clear and transparent. If nanoparticles are generated during this period, the solution should turn dark gray or black. Therefore, we can reasonably infer that no nanoparticles are generated in the solution. In addition, the UV spectrum is a horizontal straight line in the range of 400-800nm, which means that no Au nanoparticles are generated in the system. However, it should be pointed out that the peripheral temperature should be strictly controlled not to exceed the boiling point of ethanol during operation, because the boiling solution may cause metal aggregation due to more intense transmission.

[0141] For the synthesis of heterogeneous Pt single atom catalysts, the reduction process of step 3 in Example 1 was detected, and the situation was similar, [PtCl6] 2- The UV absorption peak at 265nm could not be observed, but the color of the reaction solution gradually became lighter to nearly colorless and remained clear and transparent, and the UV spectrum did not show an absorption peak at 400-800nm. It is speculated that H2PtCl6 has also been reduced.

[0142] XPS characterization of heterogeneous Pt single atom catalysts:

[0143] In order to further confirm the reduction state of Pt1, the heterogeneous Pt single atom catalyst synthesized in Example 1 above was selected for XPS analysis, and it was diluted with TiO2 (particle size 50-200nm) (mass ratio Pt1@1,4-dicarboxybenzo15-crown-5:TiO2=1:10, recorded as (Pt1@(COOH)2Ph(15-crown-5) / TiO2). The tablets were pressed in a glove box and then characterized by XPS.

[0144] The XPS results are as follows: Figure 4 As shown. First, the spectrum was corrected with the C1s binding energy obtained from the spectrum. Due to the presence of interfering C in the carrier, the C 1s binding energy showed multiple absorption peaks. After fitting, we obtained that the electron binding energy of C1s was 284.8eV. Taking the C1s binding energy of 284.6eV as the benchmark, the Pt 4f spectrum was shifted 0.2eV to the high electron binding energy, and we obtained Figure 4 b. From the figure, we observed that Pt 4f 7 / 2 The electron binding energy is (72.20eV), which is 1eV higher than the binding energy of Pt metal (71.20eV), close to the electron binding energy of monovalent Pt (72.2eV), and 1.0eV lower than the electron binding energy of divalent Pt (73.20eV), so we believe that the existence form of reduced Pt is close to +1 valence.

[0145] XPS Characterization of Heterogeneous Au Single Atom Catalysts

[0146] In order to further confirm the reduction state of Au1, we selected the heterogeneous Au single-atom catalyst synthesized in Example 6 above for XPS analysis, and also diluted it with TiO2 (particle size 50-200nm) (mass ratio Au1@1,4-dicarboxybenzo-15-crown-5:TiO2=1:10, recorded as (Au1@(COOH)2Ph(15-crown-5) / TiO2). The tablets were pressed in a glove box and then characterized by XPS.

[0147] The results are as follows Figure 5 As shown, Au@15-crown-5 appears at 89.3ev(4f5 / 2) and 85.2ev(4f 1 / 2 ), which is slightly lower than the monovalent gold sample (Au(PPh3)NO3(I), 85.34 eV). It is 1.5 eV higher than the zero-valent Au standard sample (83.7 eV). These results confirm that Au1@(COOH)2Ph(15-crown-5) / TiO2 is close to monovalent and carries more positive charges.

[0148] CO-DRIFT Characterization of Heterogeneous Pt Single Atom Catalysts

[0149] Through XPS characterization, we can confirm the reduced state of the synthesized heterogeneous Pt single atom catalyst, but we need to use CO-DRIFT to further confirm whether the distribution state of Pt in the system is monodisperse. CO-DRIFT is widely used to identify the distribution state of Pt atoms.

[0150] Therefore, a heterogeneous Pt single atom catalyst (Pt1@(COOH)2Ph(15-crown-5) / TiO2) was used. CO was used as a probe. The catalyst was placed in an infrared sample cell. Ar gas was first passed to replace the air in the sample chamber, and then CO was slowly introduced. In situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy was performed to study the adsorption state of CO on the reduced Pt species to determine its distribution state. The results are shown in the figure. Figure 6 shown.

[0151] Figure 6 In the figure, (a): DRIFT of CO adsorbed on Pt1@1,4-dicarboxybenzo-15-Crown-5 / SiO2. (b): DRIFT of CO adsorbed on 1,4-dicarboxybenzo-15-Crown-5 / SiO2. We must first exclude the effects of the support and ligand. First, the CO-DRIFT spectrum of 1,4-dicarboxybenzo-15-Crown-5 without Pt species is studied ( Figure 6 b), it is clear that there is no absorption peak of CO adsorbed on Pt species in the figure, which indicates that 1,4-dicarboxybenzo-15-Crown-5 itself cannot adsorb CO, which can exclude the influence of carrier and ligand on CO adsorption experiment. Then we studied the CO adsorption peak of Pt1@(COOH)2Ph(15-crown-5) / TiO2. After Ar purge, CO only appeared at the wavelength of 2084cm -1 A peak appears at 1800 cm, which corresponds to the linear adsorption of CO on the catalyst Pt species. From the above, we can see that if there are a large number of Pt-Pt connections in the system (i.e., Pt nanoparticles), CO will form a peak on Pt at a wavelength of 1800 cm -1 and 1900cm -1 There is no bridge adsorption peak between 2084cm and 2084cm, but there is no CO adsorption peak in this interval, which means that there are no large number of Pt clusters and nanoparticles, which is consistent with our experimental phenomenon above. -1 The peak at did not undergo a “blue shift”, which means that the reduced Pt species is indeed Pt1 (Pt1@(COOH)2Ph(15-crown-5) / TiO2).

[0152] After analysis, we know that:

[0153] The peak positions of CO adsorption on Pt1@1,4-dicarboxybenzene and Pt1@15-Crown-5 / SiO215-Crown-5 / SiO2 are roughly the same. It can be concluded that the microscopic chemical environment of the central Pt atom is similar.

[0154] The following is the catalyst activity test:

[0155] Hydrosilylation reaction process of heterogeneous Pt single atom catalyst:

[0156]

[0157] In view of the sensitivity of silane to water, all weighings and reactions were carried out in a hand box (under nitrogen protection). The steps of olefin hydrosilylation reaction are as follows: First, the heterogeneous Pt single-atom catalyst synthesized in Example 1 is diluted and mixed with nano-TiO2 (15-200nm), and the mass fraction of the mixed catalyst calculated as Pt is 0.1wt.%. A certain proportion (the molar ratio of Pt to olefin is 1:10, respectively) is weighed. -5 , 1:10 -7 ) The mixed platinum single atom catalyst is added to the reaction vial, the reaction bottle is transferred to the hand operation box, 4.4mmol olefin (1-octene) is weighed and added to the reaction vial, magnetically stirred at room temperature for 5 minutes to mix the catalyst and olefin evenly, and then 4mmol silane (heptamethylsiloxane) is added. The reaction vial is sealed and placed in a heating block that has reached the set temperature and heated with an IKA heater. The magnetic stirring speed is 400-1000r / min (here 800r / min). After the reaction is completed, the temperature is quickly cooled to room temperature. 2mmol N,N-dimethylaniline is added as an internal standard. After the internal standard is fully mixed with the reaction system, some of the liquid is taken for nuclear magnetic resonance detection. Unless otherwise specified, the reaction temperature is set to 70°C.

[0158] We first optimized the reaction time and catalyst dosage of heterogeneous catalysts. 1-octene was selected as the olefin substrate and 1,1,1,3,5,5,5-heptamethylsiloxane was selected as the silane substrate. The results are shown in Table 1. It is not difficult to find that when the catalyst dosage is 10% of the olefin addition amount, -6 In the case of , the catalysis can be completed within one minute, and the corresponding TOF value (Turover frequency, the number of reaction substrates converted per catalytic active site per unit time) is 6×10 6 h -1When the amount of catalyst material is reduced, the selectivity remains constant. However, the TOF value of the material decreases during this process. This may be due to the inactivation of part of the catalyst by impurities in the reactants. As the reaction continues, the raw materials are completely converted. During this period, the selectivity of the product does not change (Table 1), which indicates that the product is stable in the system.

[0159] Table 1. Hydrosilylation reactions catalyzed by heterogeneous Pt single-atom catalysts.

[0160]

[0161] Catalyst cyclability test

[0162] After the reaction was completed, the obtained reaction product solution was centrifuged, and the solid catalyst was subjected to a second reaction (the reaction process and conditions were the same as above (above: olefin hydrosilylation reaction)). The supernatant was analyzed by NMR. The results were as follows: Figure 7 shown.

[0163] Figure 7 This is a cycle test of the heterogeneous Pt single atom catalyst in the embodiment of the present invention. It is not difficult to find that after three cycles, the activity and selectivity of the catalyst can still maintain a high level (100% conversion rate, 98% selectivity).

[0164] The stability of heterogeneous catalysts is a necessary property of catalysts. After the material is reused, its activity and selectivity do not decrease significantly. This shows that the material has good recycling performance. For precious metal catalysts, the key to reducing costs is to achieve the reuse of catalysts. We immobilize homogeneous catalysts to obtain heterogeneous catalysts, and achieve their effective separation and reuse. This is of great significance to the industrial application of the reaction.

[0165] Catalyst substrate universality study

[0166] In previous work, we have investigated the catalytic activity of Pt1@15-crown-5 in the hydrosilylation reaction of 1-octene, 1,1,1,3,5,5,5-heptamethylsiloxane and phenyldimethylsilane. Next, we expanded the scope of olefins and siloxanes. The reaction process and conditions were the same as above (above: olefin hydrosilylation reaction) except for the change of substrate type. The difference is that the olefin substrate in the above process (above olefin hydrosilylation reaction process) was replaced with styrene, cyclohexene, p-methylstyrene or n-dodecene, and diphenylmethylsilane (heptamethylsiloxane or diphenylmethylsilane) was added to the silane substrate. The results are shown in Table 2. 4 mg of Pt1@(COOH)2Ph(15-crown-5) / TiO2 catalyst was weighed and added to the reaction vial. The ratio of catalyst Pt species to substrate olefin was 10-5 We set the reaction time to 1 min and the reaction temperature to 70 °C.

[0167] From the table, we can see that when using 1,1,1,3,5,5,5-heptamethylsiloxane as the silane substrate for the hydrosilylation reaction of styrene, we also obtained a high yield of 3.2×10 6 h -1 The TOF of diphenylmethylsilane was as high as 1.4×10 6 h -1 (Table 3, Entry 2), the catalytic activity is not only not weakened compared to the homogeneous Pt1@15-crown-5, but also slightly enhanced. We speculate that this is because the phenyl group in the ligand enriches the phenyl group in the reaction substrate. Similarly, a similar conclusion was drawn when the olefin substrate was p-methylstyrene (Entry5-6, Table 2). For cyclic olefins (cyclohexene), the catalyst also obtained a higher TOF value, but its activity was reduced relative to that of chain olefins. In addition, we also tested the hydrosilylation activity of longer chain olefins, and 1-dodecene also followed Markovnikov's rule for addition. The results showed that its TOF for 1,1,1,3,5,5,5-heptamethylsiloxane also reached 1.4×10 6 h -1 (Entry 7, Table 3), its activity is slightly lower than that of 1-octene with a shorter chain length. At the same time, the hydrosilylation reaction of olefins has always maintained a high selectivity. Although the α-addition product is difficult to generate due to the steric effect, our catalyst has good control over the isomerization and decomposition of olefins. In addition, the catalyst showed no signs of deactivation at the end of the reaction, which means that TON can be further improved with the extension of reaction time. This also shows the stability of the high activity of the catalyst during the reaction.

[0168] In addition, the hydrosilylation reaction of alkynes has always been a major challenge in hydrosilylation. Studies have shown that the catalyst activity and selectivity in this reaction are not very ideal. Therefore, this paper studied Pt1@(COOH)2Ph(15-crown-5) / TiO2. The results are shown in Table 3. It is not difficult to see that its reaction activity is high but the selectivity is poor.

[0169] Table 2 Study on the universality of substrates for hydrosilylation reaction catalyzed by Pt1@(COOH)2Ph(15-crown-5) / TiO2

[0170]

[0171] Table 3 Study on the hydrosilylation of alkynes catalyzed by Pt1@(COOH)2Ph(15-crown-5) / TiO2

[0172]

[0173] Heterogeneous Au single-atom catalyst for the reduction of nitrophenols

[0174] One of the most important applications of Au is to catalytically reduce toxic nitrobenzene compounds to less toxic aminobenzene compounds. We continue to use Au1@(COOH)2Ph(15-crown-5) synthesized in Example 6 of the present invention to reduce nitrophenol compounds. In previous work, the reaction of Au1@15-crown-5 to reduce nitrobenzene compounds has achieved high activity, but during the reaction we observed that the catalyst agglomerated to a certain extent, so no good results were achieved in the catalyst cycle performance test ( Xing Shen ,Kairui Liu*,DiscreteAu1(0)stabilized by 15-crown-5for high-efficiency catalytic reduction of nitrophenol and nitroaniline[J],Catalysts.2023,13(4),776.). Here, we focused on testing the activity and reaction cyclability of heterogeneous catalysts for this type of reaction.

[0175] 4-Nitrophenol will form 4-nitrophenol ions in an alkaline environment, and the ultraviolet absorption peak will appear at 400nm, and the color of the solution will be yellow-green. We first tested whether the mixture of 4-NP and NaBH4 could react when only 1,4-dicarboxybenzo-15-crown-5 was added. We added 4-NP aqueous solution (150ml, 0.2mM, 4-nitrophenol), NaBH4 aqueous solution (150ml, 0.1M) and 2.5mg of 1,4-dicarboxybenzo-15-crown-5 to a flask and let it react at room temperature. The results showed that the intensity of the ultraviolet absorption peak at 400nm remained unchanged for a long time (600 minutes), and the solution was also yellow-green. This shows that NaBH4 itself cannot reduce 4-nitrophenol.

[0176] We added the catalyst synthesized in Example 6 above for reduction. Due to the limitation of solid catalyst weighing, the molar ratio of catalyst to substrate was adjusted to a certain extent.

[0177] Reduction process of nitrophenol compounds catalyzed by heterogeneous Au single-atom catalyst: The catalyst synthesized in Example 6 was diluted and mixed with nano-TiO2 (15-200nm), and the mass fraction of the mixed catalyst calculated by Au was 0.1wt.% (recorded as: Au1@(COOH)2Ph(15-crown-5) / TiO2). The mixed catalyst (2.5mg), 4-NP aqueous solution (150ml, 0.2mM, 4-nitrophenol), and NaBH4 aqueous solution (150ml, 0.1M) were added to the flask. The color of the mixture changed from yellow-green to colorless in about 20 minutes at room temperature. The UV spectrum also showed the corresponding results: the absorption peak of p-nitrophenol at 400nm dropped to 0, and the product p-aminophenol (4-AP) appeared at 300nm. It shows that the Au1@(COOH)2Ph(15-crown-5) catalyst prepared in this work can effectively catalyze the reduction of 4-NP to generate 4-AP.

[0178] We then continued to explore the applicability of this reaction to other nitrophenols and nitroanilines. We then used Au1@(COOH)2Ph(15-crown-5) / TiO2 to catalyze the reduction of 2-NP, 2-NA, and 4-NA (nitroaniline). The reaction process and conditions were the same as above except for the change of substrate type (the above heterogeneous Au single-atom catalyst catalyzed the reduction process of nitrophenol compounds), with the difference being that 4-NP (4-nitrophenol) was replaced by 2-NA (2-nitroaniline), 4-NA (4-nitroaniline), and 2-NP (2-nitrophenol), respectively; the reduction of 2-NA, 4-NA, and 2-NP could also be easily monitored by UV-Vis. The results are also listed in Table 4, which shows that this catalyst also has high activity for other nitroaromatics. The results showed that these compounds could be well reduced, and the catalytic rates followed the order of 4-NP>2-NP>2-NA>4-NA, with TOFs of 22075, 12614, 11038, and 11038 h, respectively. -1 , indicating the universality of the catalyst in the reduction of nitrophenol and nitroaniline. At the same time, compared with the homogeneous Au1@15-crown-5 catalyst, the heterogeneous catalyst showed comparable activity.

[0179] Table 4 Hydrogenation reaction of nitrobenzene compounds over heterogeneous Au single atom catalyst

[0180]

[0181] After the reaction was completed, the obtained reaction product solution was centrifuged, 80% of the upper layer liquid was taken out, and 20 ml of 4-nitrophenol solution and 20 ml of sodium borohydride solution were added. The second reaction was carried out. The supernatant was analyzed by UV-Vis. The results are as follows: Figure 8 shown.

[0182] It should be noted that, in this article, terms such as "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of more restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0183] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a crown ether-based material-stabilized Au and / or Pt catalyst, characterized in that: The steps include: Using the bdc ligand of the crown ether as a protective agent for the Au and / or Pt catalyst, synthesizing the Au and / or Pt catalyst stabilized by the crown ether-based solid material in a heterogeneous phase; 1,4-dicarboxybenzo-15-crown-5, ethanol and water are mixed in a container, and the volume ratio of the reducing agent ethanol to water is 1:10000-30:1 (preferably 20:1-5:1); then the noble metal precursor H2PtCl6 and / or HAuCl4 is added, and the concentration of the noble metal precursor in the solution after addition should be 10 -5 -5×10 -2 M (preferably 10 -2 -5×10 -2 ), and the molar ratio of the protective agent 1,4-dicarboxybenzo-15-crown-5 to the noble metal precursor is 1:2-1:100 (preferably 1:2-1:12); the solution is heated at 55°C-100°C (preferably 70°C-80°C) for 8-40 hours (preferably 8-15 hours), and then cooled to room temperature; the reaction solvents ethanol and water are removed to obtain a heterogeneous Pt and / or Au catalyst.

2. The preparation method according to claim 1, characterized in that: 1,4-dicarboxybenzo-15-crown-5, ethanol and water are stirred and mixed in a round-bottom flask at room temperature at 80-900 rpm for not less than 10 minutes; Then, H2PtCl6 and / or HAuCl4 are added, and the mixture is stirred for not less than 10 minutes; the solution is heated and then cooled to room temperature; the reaction solvent ethanol and water are removed by reduced pressure distillation using a rotary evaporator (the heating temperature is set to 40-60°C, preferably 45°C-50°C) to obtain a heterogeneous Pt and / or Au catalyst.

3. The preparation method according to claim 1, characterized in that: The method comprises the following steps: performing a dehydrobromination reaction of dibromotriethylene glycol ether and dimethyl 2,3-dihydroxyterephthalate to synthesize 1,4-dicarboxybenzo-15-crown-5; Anhydrous potassium carbonate (5mmol-20mmol, preferably 6mmol-10mmol) and dimethyl 2,3-dihydroxyterephthalate (5mmol-20mmol, preferably 6mmol-10mmol) are dissolved in N,N-dimethylformamide (DMF, 80-300ml, preferably 80-150ml); dibromotetraethylene glycol ether (the molar ratio of dibromotetraethylene glycol ether to dimethyl 2,3-dihydroxyterephthalate is 1:1-1:2, preferably 1:1-1:1.1) is added under stirring, the mixture is heated at 60-150°C (preferably 75°C-100°C) for 8-24 hours (preferably 10-15 hours), and K2CO3 is removed by filtration; DMF in the mixture is then removed by distillation; the remaining part is purified by column chromatography (Huanghai Chemical Industry Research Society, column length 10-30cm, diameter 1-3cm, filler: silica gel 200-300 mesh) purification (volume ratio: hexane / ethyl acetate: 75 / 25-85 / 15), remove the solvent; add KOH aqueous solution to the obtained solid, the concentration of KOH solution should be 0.05M-0.2M (preferably 0.08M-0.12M), the amount added is 50-200ml (preferably 80ml-120ml), the solution is heated (temperature range 150-200℃, preferably 155℃-160℃) and refluxed for 8-24 hours (preferably 10-15 hours); after cooling to room temperature, add HCl solution in an ice water bath for acidification, the concentration of HCl solution is 0.5-2M (preferably 0.8-1.2M), and the amount added should be 1-10ml (preferably 2-5ml); After the solution becomes turbid, the solution is evaporated until the amount of water is reduced to 1-5 mL (preferably 2-3 mL), and an off-white solid is precipitated and cooled in an ice-water bath; the precipitate is filtered, washed and dried to obtain the product 1,4-dicarboxybenzo-15-crown-5.

4. The preparation method according to claim 3, characterized in that: The precursor of the bdc ligand of the crown ether is dibromotetraethylene glycol ether; The synthesis of the dibromotetraethylene glycol ether comprises the following steps: Cool 20-1000 mL (preferably 100-300 ml) of dichloromethane (DCM) to -76°C to -78°C, and add 5-300 mmol (preferably 40-60 mmol) of N-bromosuccinimide and triphenylphosphine (with a molar ratio of 1:1-1:1.2 to N-bromosuccinimide, preferably 1:1-1:1.1) under stirring; after 5-60 minutes (preferably 10-20 minutes), add 2-100 ml of tetraethylene glycol; mol (preferably 15-30 mmol) and stirred for 6-24 hours (preferably 10-15 hours), then the temperature was raised to room temperature; DCM was removed by distillation under reduced pressure, and purified by column chromatography (column length 10-30 cm, diameter 1-3 cm, filler: silica gel 200-300 mesh) (volume ratio: hexane / ethyl acetate = 4:1-4:1.1); after distilling off the solvent, a colorless oily product was separated and dried to obtain the product dibromotetrace ...

5. A heterogeneous Pt catalyst, characterized in that: Prepared by any one of the preparation methods of claims 1-4.

6. Use of the heterogeneous Pt catalyst according to claim 5, characterized in that: The heterogeneous Pt catalyst is applied to the hydrosilylation reaction.

7. The use according to claim 6, characterized in that: Under nitrogen protection, weigh a platinum single atom catalyst (the molar ratio of platinum to olefin is 1:10000-1:1000000) into a reaction bottle, weigh and add 0.4-40mmol olefin (for example, one or more of chain olefins such as 1-octene, n-dodecene, styrene, p-methylstyrene, cyclohexene, etc.) or alkyne into the reaction bottle, stir at room temperature (preferably 1-10min) to mix the catalyst and olefin evenly, and then add 0.4-40mmol silane (for example, one or more of heptamethylsiloxane, diphenylmethylsilane, etc.); seal the reaction bottle and heat it to a reaction temperature of 40-90°C, stir (stirring speed is 400-1000r / min), and the reaction time is 1-100min (preferably 1-5min).

8. A heterogeneous Au catalyst, characterized in that: Prepared by any one of the preparation methods of claims 1-4.

9. A use of the heterogeneous Au catalyst as claimed in claim 8, characterized in that: The heterogeneous Au catalyst is used to catalyze the reduction of nitroaromatic compounds.

10. The use according to claim 9, characterized in that: A nitroaromatic compound (one or more of o-nitrophenol (2-NP), m-nitrophenol (3-NP), p-nitrophenol (4-NP), o-nitroaniline (2-NA), m-nitroaniline (3-NA), p-nitroaniline (4-NA), etc.) (2-300 ml, preferably 25 ml-150 ml, the concentration of its aqueous solution is 0.01-20 mM, preferably 0.1-1 mM), a reducing agent (one or more of NaBH4, hydrazine hydrate, etc.) (2-300 ml, preferably 25 ml-150 ml, the concentration of its aqueous solution is 0.01-1000 mM, preferably 10-100 mM) is added to a container, and then a catalyst (the molar ratio of Au to the substrate 4-NP is in the range of 1:10 2 -1:10 6 , preferably 1:10 3 -1:10 5 ); The reaction is carried out at room temperature, and the reaction time is greater than 10 min (preferably 15-30 min).

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