A gold-silver alloy nanocluster and application thereof in catalyzing carboxylation reaction of an epoxide compound

Abstract

The application discloses a gold-silver alloy nanocluster and application of the gold-silver alloy nanocluster in catalyzing carboxylation of an epoxy compound. 13 Ag 12 (PPh3) 10 Cl8] + (PF6) ‑ wherein PPh3 is triphenylphosphine. The catalyst provided by the application exhibits high catalytic activity in a carbon dioxide carboxylation reaction. The catalytic yield of the gold-silver alloy nanocluster catalyst without a carrier is less than 5%, the catalytic yield of the gold-silver alloy nanocluster catalyst with a carrier is up to 90%, and the TON is up to 3.06*10 4 The catalytic condition is mild, the catalyst is easy to recycle, and the catalyst can be used for multiple catalytic cycle experiments. Meanwhile, the catalyst is suitable for carboxylation reactions of various different epoxy substrates, and the purity of the corresponding cyclic carbonate product is high, and the number of impurities is small.

Description

Technical Field

[0001] This invention belongs to the field of chemical synthesis, specifically relating to a gold-silver alloy nanocluster and its application in the catalytic carboxylation reaction of epoxides. Background Technology

[0002] There is a growing interest in the capture and utilization of carbon dioxide, a strategy known as carbon dioxide utilization (CDU). Its advantage lies in using non-toxic, inexpensive, and energy-rich C1 chemical feedstocks to produce value-added products such as fuels, chemicals, and materials (10.1021 / cr4002758). Therefore, vigorously developing green carbon dioxide utilization technologies is of great significance. In recent years, ligand-protected, atomically precise gold nanoclusters (typically using Au) have become increasingly important. n (L) m (To describe) One or more foreign metal atoms (Ag, Cu, Pd, Pt) can be doped to maintain the size of the nanoclusters, while the synergistic effect of gold and silver in the gold-silver alloy nanoclusters triggers highly efficient catalytic activity (10.1021 / acscatal.0c05681). The ligand-protected nanoclusters, as a whole, have a well-defined composition and structure, facilitating the study of the influence of composition and structure on catalysis at the atomic scale. Zhu's research group discovered (AuAg) 21 The catalytic activity of alloy clusters in the carboxylation reaction of epoxides and carbon dioxide conforms to Au 19 Ag4(S-Adm) 15 Au 21 (S-Adm) 15 Au 20 Ag1(S-Adm) 15 The reason for this phenomenon is that the degree of silver atom exposure varies in different clusters (10.1002 / anie.202100071). Therefore, efficient and mild strategies for the effective utilization of carbon dioxide have attracted much attention. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention provides a gold-silver alloy nanocluster and its application in the catalytic carboxylation reaction of epoxides. The preparation method of the gold-silver alloy nanocluster of this invention is simple and exhibits excellent stability. This gold-silver alloy nanocluster catalyst demonstrates high catalytic activity (TON) of 3.06 × 10⁻⁶ in the carbon dioxide carboxylation reaction. 4 The catalytic conditions are mild, the catalyst is easy to recover and reuse, multiple catalytic cycle experiments can be carried out, and it is suitable for carboxylation reactions of a variety of different epoxy substrates. The corresponding cyclic carbonate products have high purity and few impurities.

[0004] This invention relates to gold-silver alloy nanoclusters with the molecular formula [Au].13 Ag 12 (PPh3) 10 Cl8] + (PF6) - PPh3 is triphenylphosphine.

[0005] The method for preparing gold-silver alloy nanoclusters of the present invention includes the following steps:

[0006] S1: Adding excess dimethyl sulfide to a methanol solution of chloroauric acid and stirring yields a white precipitate. After centrifugation, the precipitate is washed three times with ethanol, and then filtered under reduced pressure and dried to obtain a white solid of gold sulfide.

[0007] S2: Dissolve the gold sulfide obtained in S1 in dichloromethane, add triphenylphosphine ligand, centrifuge, wash, filter, collect the precipitate and dry to obtain a white solid gold-phosphine complex.

[0008] S3: The white solid gold-phosphine complex obtained in S2 was added to an organic solvent and mixed thoroughly. Then, a silver source was added, and the solution was stirred at room temperature and in air. Sodium borohydride solution was then added dropwise to the system, and the mixture was stirred at room temperature in the dark for 15 hours. Subsequently, the black precipitate was removed by centrifugation, and the solid was dried by vacuum evaporation. The resulting solid was washed with an organic solvent to remove impurities, yielding a purple-red solution. The organic solvent was then removed by vacuum evaporation to obtain Au. 13 Ag 12 Clusters, which are purplish-red solids.

[0009] In S3, the silver source is silver nitrate, and the molar ratio of the gold phosphine complex to the silver source is 1:2.

[0010] The organic solvent is a mixture of methanol and dichloromethane.

[0011] This invention relates to the application of gold-silver alloy nanoclusters in the carboxylation reaction of epoxides.

[0012] Specifically, the gold-silver alloy nanoclusters are loaded onto activated carbon to obtain a supported gold-silver alloy nanocluster catalyst, Au. 13 Ag 12 / Ac, using this supported catalyst to catalyze the carboxylation reaction of epoxy substrates.

[0013] The loading process includes the following steps: 49 mg of activated carbon is uniformly dispersed in dichloromethane solvent to form a suspension, and then 1 mg of purple-red solid Au dispersed in dichloromethane solvent is added. 13 Ag 12 Clusters were stirred at room temperature for 1 hour, and the black solid was collected by centrifugation. After vacuum filtration and drying, the supported gold-silver alloy nanocluster catalyst Au was obtained. 13 Ag12 / Ac, with a load of 2wt%.

[0014] The synthetic route for the carboxylation reaction of epoxy substrates is shown below:

[0015]

[0016] R is selected from phenyl, allyloxy, or 4-fluorophenyl.

[0017] The co-catalyst is selected from tetrabutylammonium bromide, tetrabutylammonium iodide or potassium iodide.

[0018] The carboxylation reaction includes the following steps:

[0019] Au supported gold-silver alloy nanocluster catalyst 13 Ag 12 Ac and epoxide were mixed, stirred, and heated, with carbon dioxide introduced at atmospheric pressure. The reaction was carried out at 65-75°C for 10 hours. After the reaction was completed, the reaction mixture was cooled to room temperature, and the catalyst Au was separated by centrifugation. 13 Ag 12 / Ac, ethyl acetate extraction yields cyclic carbonate products.

[0020] This invention employs a thermochemical strategy to immobilize carbon dioxide. The gold-silver alloy nanocluster catalyst, supported on activated carbon, has a significantly increased specific surface area, which greatly enhances the catalytic performance of the carboxylation reaction between epoxides and carbon dioxide. The resulting cyclic carbonate can be used as an electrolyte, exhibiting high conductivity and providing sufficient ion transport rates to ensure lithium-ion migration between the positive and negative electrodes. Furthermore, the cyclic carbonate electrolyte also possesses low viscosity and good chemical stability, improving the safety and cycle life of lithium-ion batteries. Therefore, cyclic carbonate is a commonly used electrolyte for lithium-ion batteries.

[0021] The beneficial effects of this invention are reflected in:

[0022] 1. Compared with cobalt, zinc, and nickel complex catalysts, the gold-silver alloy nanocluster catalyst of this invention is basically non-toxic. As a highly efficient heterogeneous catalyst, it has a high specific surface area and can exhibit high recyclability and long-term stability under many harsh conditions.

[0023] 2. The gold-silver alloy nanocluster catalyst of this invention exhibits high catalytic activity in the carbon dioxide carboxylation reaction. The catalytic yield of the unsupported gold-silver alloy nanocluster catalyst is less than 5%, while the catalytic yield of the supported gold-silver alloy nanocluster catalyst reaches 90%, with a TON of 3.06 × 10⁻⁶. 4 .

[0024] 3. The catalytic conditions of this invention are mild, overcoming the problems of harsh conditions, poor selectivity, and low yield in carbon dioxide carboxylation reactions. The catalyst can be recycled and can undergo more than 8 carbon dioxide carboxylation reactions, resulting in high economic and environmental benefits.

[0025] 4. The gold-silver alloy nanocluster catalyst of this invention is suitable for the carboxylation reaction of a variety of different epoxy substrates, and the corresponding cyclic carbonate products have high purity and few impurities. Attached Figure Description

[0026] Figure 1 This is a single-crystal structure diagram of the gold-silver alloy nanoclusters of the present invention.

[0027] Figure 2 This is the ultraviolet absorption spectrum of the gold-silver alloy nanoclusters of the present invention.

[0028] Figure 3 The 1H NMR spectrum of styrene carbonate prepared in Example 8.

[0029] Figure 4 The 1H NMR spectrum of 4-((allyloxy)methyl)-1,3-dioxolane-2-one prepared in Example 9.

[0030] Figure 5 The 1H NMR spectrum of 4-(4-fluorophenyl)-1,3-dioxolane-2-one prepared in Example 10. Detailed Implementation

[0031] The technical solution of the present invention will be further explained and illustrated below with reference to specific embodiments.

[0032] Example 1: Gold-silver alloy nanoclusters Au 13 Ag 12 Preparation

[0033] 1. Adding excess 200 µL of Me2S dimethyl sulfide to a methanol solution of 400 µL HAuCl4·4H2O chloroauric acid and stirring yields a white precipitate. After centrifugation, the precipitate is washed three times with ethanol, and then filtered under reduced pressure and dried to obtain a white solid gold sulfide Au(Me2S)Cl.

[0034] 2. Dissolve 301 mg of Au(Me2S)Cl gold sulfide in 20 mL of dichloromethane, add 334 mg of (PPh3)triphenylphosphine ligand, centrifuge, wash, filter, collect the precipitate and dry to obtain a white solid Au(PPh3)Cl gold phosphine complex.

[0035] 3. Add 50 mg of Au(PPh3)Cl gold-phosphine complex to a mixed solution of 10 mL dichloromethane and 10 mL methanol, stir well, then add 32 mg of AgNO3 silver nitrate, stir the solution at room temperature and in air atmosphere, then add 5 mL of NaBH4 (6 mg) sodium borohydride methanol solution dropwise to the system, place in the dark and stir at room temperature for 15 hours, then centrifuge to remove the black precipitate, and evaporate to dryness under vacuum. The obtained solid is washed with a 1:2 (v / v) mixture of dichloromethane and methanol to remove impurities, giving a purple-red solution, which is then evaporated under vacuum to remove the organic solvent, yielding Au. 13 Ag 12 Clusters, which are purplish-red solids.

[0036] Example 2: Supported gold-silver alloy nanocluster catalyst Au 13 Ag 12 Preparation of / Ac

[0037] 1. Disperse 49 mg of activated carbon evenly in 15 mL of dichloromethane solvent to form a suspension. Then add 1 mg of purple-red solid Au dispersed in dichloromethane solvent. 13 Ag 12 Clusters were stirred at room temperature for 1 hour, and the black solid was collected by centrifugation. After vacuum filtration and drying, the supported gold-silver alloy nanocluster catalyst Au was obtained. 13 Ag 12 / Ac, with a load of 2wt%.

[0038] Example 3: Unsupported gold-silver alloy nanocluster catalyst Au 13 Ag 12 Catalytic synthesis of styrene carbonate

[0039] 1. Add 600 mg of styrene oxide and 160 mg of tetrabutylammonium bromide co-catalyst at a molar ratio of 10:1 to a 10 mL Schlenk tube, then add unsupported gold-silver alloy nanocluster catalyst Au. 13 Ag 12 (1 mg, 0.145 µmol). The Schlenk tube was sealed with a rubber stopper and evacuated using a vacuum pump to remove any residual air. A carbon dioxide balloon was attached. After stirring at 65 °C for 10 hours, the reaction mixture was cooled to room temperature, and the carbon dioxide balloon was removed.

[0040] 2. Dissolve the reaction mixture in a solvent (such as ethyl acetate), remove the catalyst by centrifugation (10,000 rpm), and obtain the target product styrene carbonate. The yield was determined to be less than 5% by gas chromatography (GC).

[0041] Example 4: Au 13Ag 12 Ac-catalyzed synthesis of styrene carbonate (co-catalyst: tetrabutylammonium bromide)

[0042] 1. Add 600 mg of styrene oxide and 160 mg of tetrabutylammonium bromide co-catalyst at a molar ratio of 10:1 to a 10 mL Schlenk tube, and then add the supported gold-silver alloy nanocluster catalyst Au. 13 Ag 12 / Ac (20 mg, 2 wt%). The Schlenk tubes were sealed with rubber stoppers and evacuated using a vacuum pump to remove any residual air. A carbon dioxide balloon was attached. After stirring at 65 °C for 10 hours, the reaction mixture was cooled to room temperature, and the carbon dioxide balloon was removed.

[0043] 2. Dissolve the reaction mixture in a solvent (such as ethyl acetate), remove the catalyst by centrifugation (10,000 rpm), and obtain the target product styrene carbonate. The yield was determined to be 90% by gas chromatography (GC).

[0044] Example 5: Au 13 Ag 12 Ac-catalyzed synthesis of styrene carbonate (co-catalyst is tetrabutylammonium iodide)

[0045] 1. Add 600 mg of styrene oxide and 184 mg of tetrabutylammonium iodide co-catalyst at a molar ratio of 10:1 to a 10 mL Schlenk tube, then add the supported gold-silver alloy nanocluster catalyst Au. 13 Ag 12 / Ac (20 mg, 2 wt%). The Schlenk tube was sealed with a rubber stopper and evacuated using a vacuum pump to remove any residual air. A carbon dioxide balloon was attached. After stirring at 65 °C for 10 hours, the reaction mixture was cooled to room temperature, and the carbon dioxide balloon was removed.

[0046] 2. The reaction mixture was dissolved in a solvent (such as ethyl acetate), and the catalyst was removed by centrifugation (10,000 rpm) to obtain the target product, styrene carbonate. The yield was determined to be 46% by gas chromatography (GC).

[0047] Example 6: Au 13 Ag 12 / Ac-catalyzed synthesis of styrene carbonate (potassium iodide as co-catalyst)

[0048] 1. Add 600 mg of styrene oxide and 83 mg of potassium iodide co-catalyst at a molar ratio of 10:1 to a 10 mL Schlenk tube, then add the supported gold-silver alloy nanocluster catalyst Au. 13 Ag12 / Ac (20 mg, 2 wt%). The Schlenk tube was sealed with a rubber stopper and evacuated using a vacuum pump to remove any residual air. A carbon dioxide balloon was attached. After stirring at 65 °C for 10 hours, the reaction mixture was cooled to room temperature, and the carbon dioxide balloon was removed.

[0049] 2. The reaction mixture was dissolved in a solvent (such as ethyl acetate), and the catalyst was removed by centrifugation (10,000 rpm) to obtain the target product, styrene carbonate. The yield was determined to be 14% by gas chromatography (GC).

[0050] Example 7: Cyclic Experiment: Au Recovery 13 Ag 12 / Ac Synthetic styrene carbonate

[0051] 1. After completing the fresh experiment of synthesizing styrene carbonate, centrifuge the separated Au... 13 Ag 12 The solution was washed three times with dichloromethane and vacuum dried at 60°C for 8 hours. Then, 600 mg of fresh styrene oxide and 160 mg of tetrabutylammonium bromide co-catalyst were added, using recycled gold-silver alloy nanoclusters as the catalyst. The Schlenk tube was sealed with a rubber stopper and evacuated using a vacuum pump to remove residual air. A carbon dioxide balloon was attached. The solution was dried at 65°C. o After stirring at C for 10 hours, the reaction mixture was cooled to room temperature, and the carbon dioxide balloon was removed. The reaction mixture was dissolved in a solvent (such as ethyl acetate), and the catalyst was removed by centrifugation (10,000 rpm) to obtain the target product, styrene carbonate. The yield was determined to be 88% by gas chromatography (GC).

[0052] 2. The recovered catalyst was repeated under the above reaction conditions until the 8th cycle. The reaction mixture was dissolved in a solvent (such as ethyl acetate). The catalyst was removed by centrifugation (10,000 rpm) to obtain the target product, styrene carbonate. The yield was determined to be 80% by gas chromatography (GC).

[0053] Example 8: Au 13 Ag 12 / Ac-catalyzed synthesis of styrene carbonate

[0054] 1. Add 600 mg of styrene oxide and 160 mg of tetrabutylammonium bromide co-catalyst at a molar ratio of 10:1 to a 10 mL Schlenk tube, and then add the supported gold-silver alloy nanocluster catalyst Au. 13 Ag 12 / Ac (20 mg, 2 wt%). The Schlenk tube was sealed with a rubber stopper and evacuated using a vacuum pump to remove any residual air. A carbon dioxide balloon was attached. After stirring at 65°C for 10 hours, the reaction mixture was cooled to room temperature, and the carbon dioxide balloon was removed.

[0055] 2. Dissolve the reaction mixture in a solvent (such as ethyl acetate), remove the catalyst by centrifugation (10,000 rpm), and obtain the target product, styrene carbonate. The yield was determined to be 90% by gas chromatography (GC). Subsequent purification of the sample was performed using an appropriate separation method (such as silica gel column chromatography).

[0056] Figure 3 This is the 1H NMR spectrum of styrene carbonate ester of the present invention.

[0057] 1H NMR (400 MHz, CDCl3) δ 7.58 - 7.17 (m, 5H), 5.67 (t, J = 8.0 Hz, 1H), 4.80 (t, J = 8.4 Hz, 1H), 4.34 (t, J = 8.3 Hz, 1H).

[0058] Example 9: Au 13 Ag 12 Ac-catalyzed synthesis of 4-((allyloxy)methyl)-1,3-dioxolane-2-one

[0059] 1. Add 570 mg of allyl glycidyl ether and 160 mg of tetrabutylammonium bromide co-catalyst to a 10 mL Schlenk tube at a molar ratio of 10:1, and then add the supported gold-silver alloy nanocluster catalyst Au. 13 Ag 12 / Ac (20 mg, 2 wt%). The Schlenk tube was sealed with a rubber stopper and evacuated using a vacuum pump to remove any residual air. A carbon dioxide balloon was attached. After stirring at 65°C for 10 hours, the reaction mixture was cooled to room temperature, and the carbon dioxide balloon was removed.

[0060] 2. The reaction mixture was dissolved in a solvent (such as ethyl acetate). After removing the catalyst by centrifugation (10,000 rpm), the target product 4-((allyloxy)methyl)-1,3-dioxolane-2-one was obtained. The yield was determined to be 97% by gas chromatography (GC). The sample was then purified using an appropriate separation method (such as silica gel column chromatography).

[0061] Figure 4 The 1H NMR spectrum of 4-((allyloxy)methyl)-1,3-dioxolane-2-one.

[0062] 1 H NMR (400 MHz, CDCl3) δ 5.86 (m, 1H), 5.27 (d, J = 17.1 Hz, 1H), 5.21 (d, J = 10.3 Hz, 1H), 4.82 (p, J = 7.9, 4.0, 1.9 Hz, 1H), 4.49 (t, J =8.4 Hz, 1H), 4.39 (t, J = 7.2 Hz, 1H), 4.07 - 4.00 (m, 2H), 3.68 (dd, J =11.0, 3.7 Hz, 2H), 3.60 (dd, J = 11.0, 3.8 Hz, 1H).

[0063] Example 10: Au 13 Ag 12 Ac-catalyzed synthesis of 4-(4-fluorophenyl)-1,3-dioxolane-2-one

[0064] 1. 690 mg of the raw material 4-fluorostyrene epoxide and 160 mg of the co-catalyst tetrabutylammonium bromide were added to a 10 mL Schlenk tube at a molar ratio of 10:1, followed by the addition of the supported gold-silver alloy nanocluster catalyst Au. 13 Ag 12 / Ac (20 mg, 2 wt%). The Schlenk tube was sealed with a rubber stopper and evacuated using a vacuum pump to remove any residual air. A carbon dioxide balloon was attached. After stirring at 65°C for 10 hours, the reaction mixture was cooled to room temperature, and the carbon dioxide balloon was removed.

[0065] 2. The reaction mixture was dissolved in a solvent (such as ethyl acetate). After centrifugation (10,000 rpm) to remove the catalyst, the target product 4-(4-fluorophenyl)-1,3-dioxolane-2-one was obtained. The yield was determined to be 75% by gas chromatography (GC). The sample was then purified using an appropriate separation method (such as silica gel column chromatography).

[0066] Figure 5 The 1H NMR spectrum of 4-(4-fluorophenyl)-1,3-dioxolane-2-one.

[0067] 1H NMR (400 MHz, CD2Cl2) δ 7.69 - 6.74 (m, 4H), 5.66 (t, J = 8.0 Hz, 1H), 4.78 (t, J = 8.4 Hz, 1H), 4.31 (t, J = 8.0 Hz, 1H).

Claims

1. A gold-silver alloy nanocluster, characterized in that: The molecular formula of the gold-silver alloy nanoclusters is [Au 13 Ag 12 (PPh3) 10 Cl8] + (PF6) - , where PPh3 represents triphenylphosphine.

2. The method for preparing the gold-silver alloy nanoclusters according to claim 1, characterized in that... Includes the following steps: S1: Add excess dimethyl sulfide to a methanol solution of chloroauric acid and stir to obtain a white precipitate. After centrifugation, wash with ethanol, filter under reduced pressure and dry to obtain gold sulfide. S2: The gold sulfide obtained in S1 was dissolved in dichloromethane, and triphenylphosphine ligand was added. After 30 minutes, the mixture was centrifuged, washed, filtered, and the precipitate was collected and dried to obtain a white solid gold-phosphine complex. S3: The white solid gold-phosphine complex obtained in S2 was added to an organic solvent and mixed thoroughly. Then, a silver source was added, and the solution was stirred at room temperature and in air. Sodium borohydride solution was then added dropwise to the system, and the mixture was stirred at room temperature in the dark for 15 hours. Subsequently, the black precipitate was removed by centrifugation, and the solid was dried by vacuum evaporation. The resulting solid was washed with an organic solvent to remove impurities, yielding a purple-red solution. The organic solvent was then removed by vacuum evaporation to obtain Au. 13 Ag 12 Clusters, which are purplish-red solids.

3. The preparation method according to claim 2, characterized in that: In S3, the silver source is silver nitrate.

4. The preparation method according to claim 3, characterized in that: The molar ratio of the gold-phosphine complex to the silver source is 1:

2.

5. The application of the gold-silver alloy nanoclusters according to claim 1 in the catalytic carboxylation reaction of epoxides, characterized in that: Using activated carbon as a support, the gold-silver alloy nanoclusters were loaded onto the support to obtain a supported gold-silver alloy nanocluster catalyst Au. 13 Ag 12 / Ac, using this supported catalyst to catalyze the carboxylation reaction of epoxides; The carboxylation reaction includes the following steps: In the presence of a co-catalyst, the supported gold-silver alloy nanocluster catalyst Au 13 Ag 12 / Ac was mixed with the epoxide and stirred and heated, with carbon dioxide introduced at normal pressure. The reaction was carried out at 65-75°C. After the reaction was completed, the reaction mixture was cooled to room temperature, and the catalyst Au was separated by centrifugation. 13 Ag 12 / Ac, dichloromethane extraction yields cyclic carbonate products; The synthesis route is shown below: ； Wherein, R is selected from phenyl, allyl or 4-fluorophenyl; The co-catalyst is selected from tetrabutylammonium bromide.

6. The application according to claim 5, characterized in that: The loading process includes the following steps: 49 mg of activated carbon is uniformly dispersed in dichloromethane solvent to form a suspension, and then 1 mg of purple-red solid Au dispersed in dichloromethane solvent is added. 13 Ag 12 Clusters were stirred at room temperature for 1 hour, and the black solid was collected by centrifugation. After vacuum filtration and drying, the supported gold-silver alloy nanocluster catalyst Au was obtained. 13 Ag 12 / Ac, with a load of 2 wt%.

Images