Method for realizing organic catalysis at normal temperature and normal pressure by using gold nanowire loaded on glass fiber

Abstract

The invention relates to an organic catalysis method for loading gold nanowires on glass fibers in a fixed bed system, and belongs to the technical field of catalysts. Gold nanowires (AuNWs) synthesized by taking glass fibers as a carrier through a solution growth method are used as a catalyst filled in a fixed bed system and are successfully applied to hydrogenation reaction of aryl alkyne, NaBH4 is used as a reducing agent, methanol is used as a reaction solvent, and reduction hydrogenation reaction of 2-ethynylnaphthalene is realized in the fixed bed system. According to the method, the yield of one round of reaction in a continuous flow reaction at normal temperature and normal pressure can reach 92%, wherein the product is mainly semi-hydrogenated olefin; according to the present invention, the catalyst is used for the selective cyclization reaction of o-phenylenediamine and p-tolualdehyde, the cyclization reaction of the selective synthesis of benzimidazole from o-phenylenediamine and aldehyde in the flow system is achieved, the separation yield is as high as 84%, the catalyst performance is stable, and the catalytic activity is still high after the multiple rounds of the reaction.

Description

Technical Field

[0001] This invention relates to a green chemistry method, particularly the use of gold nanowires supported on glass fibers to catalyze small molecule organic reactions in a fixed-bed system. Under ambient temperature and pressure, we designed a simple fixed-bed system to catalyze organic reactions such as the hydrogenation of aryl alkynes and the cyclization of o-phenylenediamine, achieving good reaction efficiencies. Furthermore, the catalyst in the system exhibits stable performance and maintains good catalytic efficiency even after multiple rounds of reaction, thus belonging to the field of nano-organic catalysts. Background Technology

[0002] Flow chemistry and heterogeneous catalysis demonstrate immense potential in the fields of sustainable development and green chemistry. Industrial chemistry relies on heterogeneous catalysts to improve production efficiency, while flow chemistry can promote more environmentally friendly and efficient chemical reactions on an industrial scale. With the advancement of nanotechnology, nanomaterials have been applied to flow nanocatalysis, particularly the synthesis and immobilization of metal nanomaterials in continuous flow microreactors, forming a powerful catalytic system that utilizes and enhances the advantages of nanocatalysis and flow chemistry. The key to this catalytic system lies in the efficient immobilization and stability within microfluidic devices. The immobilized catalyst should not only enhance catalytic activity but also ensure good stability and recyclability. In recent years, researchers have developed various methods to stabilize metal catalysts and immobilize them on solid surfaces, especially within microstructured reactors. These methods help improve catalyst utilization efficiency and sustainability, reduce resource consumption and environmental pollution, and align with the principles of green chemistry. Therefore, flow nanocatalysis not only improves the efficiency and environmental friendliness of chemical reactions but also promotes the sustainable development of the chemical industry. Further research and application of these advanced technologies hold promise for achieving greener and more efficient chemical processes, contributing to environmental protection and sustainable development.

[0003] Fixed-bed systems have been successfully applied to traditional organic synthesis, such as Michael addition, Aldol reaction, Mannich reaction, and Knoevenagel condensation. For example, in 2014, Kappe's group successfully synthesized alumina-supported Fe3O4 nanoparticles and then used them under continuous flow conditions for the hydrazine-mediated heterogeneous catalytic reduction of nitroaromatics to aniline compounds. In 2016, Anders also achieved the selective semi-hydrogenation of aryl alkynes in a continuous flow reactor filled with polystyrene beads loaded with a ruthenium hydrogen catalyst. In 2020, Long's group reported a novel unsaturated impregnation-precipitation method for preparing γ-Al2O3 spheres supported on CeO2 (uip-γ-Al2O3-CeO2) and used it as a catalyst for the solvent-free synthesis of imines in a fixed-bed reactor. Therefore, the study of nano-organic catalysis in flowing systems remains a hot topic for researchers. Summary of the Invention

[0004] The technical problem solved by this invention is to propose an organocatalysis method using gold nanowires supported on a glass fiber fixed-bed system, ensuring stable catalytic performance while maintaining catalytic efficiency. The nanomaterial catalyst is not prone to aggregation and deactivation in a flow system. This method can achieve a one-round yield of 92% for the reductive hydrogenation of 2-ethynylnaphthalene in a continuous flow reaction at ambient temperature and pressure. Simultaneously, it realizes the selective synthesis of benzimidazole from o-phenylenediamine and aldehydes in this flow system, with a separation yield as high as 84%. Furthermore, the catalyst performance is relatively stable, and the catalytic activity remains high even after multiple rounds of reaction.

[0005] To solve the above-mentioned technical problems, the technical solution proposed by this invention is: a method for achieving organic catalysis using gold nanowires loaded on glass fibers at room temperature and pressure, the specific steps of which include:

[0006] Gold nanowires with a size of 100±20 nm loaded on glass fibers were prepared as catalysts for a fixed-bed system. These nanowires were packed into a fine gel chromatography column. A mixture of reactants was fed into the fixed-bed reactor using a syringe pump or gravity. The outflowing reaction solution was then continuously fed back into the reactor until the reaction was complete. For example, using 2-acetylenynaphthalene as a substrate, sodium borohydride (NaBH4) as a reducing agent, and methanol as the solvent in the mobile phase of the reaction system, the reductive hydrogenation of arylaceyne was achieved in a mobile system. Using o-phenylenediamine and p-methylbenzaldehyde as substrates, and methanol and chloroform in a 1:3 ratio as the solvent in the mobile phase of the reaction system, the selective cyclization of o-phenylenediamine to benzimidazole was achieved.

[0007] The specific reaction route is as follows:

[0008]

[0009] Preferably, the specific preparation steps of the gold nanowires on glass fibers are as follows:

[0010] Step (1): First, the mixture containing 3.1 × 10 -4 M sodium citrate and 2.5×10 -4 20 mL of an aqueous solution of HAuCl4 was added to a 50 mL round-bottom flask and stirred for 1 min. Then, 620 μL of a 0.1 M NaBH4 aqueous solution prepared with ice water was added to the flask while stirring vigorously. The color of the solution changed from pale yellow to reddish-orange. The mixture was then stirred for another 30 min and allowed to stand for at least 2 h to allow unreacted NaBH4 to be completely consumed, yielding gold nanoparticles (AuNPs) with a diameter of 4 ± 1 nm.

[0011] Step (2): To prepare AuNWs on glass fibers, the glass fibers (600 mg) were cleaned with a piranha solution (H2O2:H2SO4 = 1:3) to improve their surface hydrophilicity. Then, the surface was treated with 50 mL of 5 × 10⁻⁶ mol / L 400 mL of 400 mL ... -3 The glass fiber was functionalized with amino groups by reacting M with 3-aminopropyltrimethoxysilane APTMS solution for 0.5 hours.

[0012] Step (3): Soak the fiber in 100 mL of citrate-stabilized AuNPs (4 ± 1 nm) solution for 0.5 hours to ensure the adsorption of gold seeds.

[0013] Step (4): Rinse the glass fiber from Step 3 twice with water to remove excess gold seeds. Then, immerse the seed-adsorbed fiber in MBA 6.0×10⁻⁶ solution containing thiol ligands. -4 M, HAuCl4 1.1×10 -3 M and L-ascorbic acid 2.4 × 10 - 3 Black-purple gold nanowires were loaded onto glass fibers in 120 mL of a 1:2 water / ethanol solution for 1.5 hours.

[0014] Step (5): Rinse the glass fiber from step four twice with ethanol and dry it in the air. Store it in a dry, windless environment for later use.

[0015] Preferably, the specific steps are as follows:

[0016] 1.3 g of loaded fiber was loosely packed into a column (d = 1 cm) to a height of approximately 7 cm and then wetted by immersion in methanol. At room temperature and pressure, 2-acetylenynaphthalene was dissolved in methanol, followed by the addition of sodium borohydride (NaBH4) to prepare a solution. The solution was then passed through a gel chromatography column using a syringe pump. The reaction solution remained transparent throughout, and the reaction was monitored using a TLC plate. After the reaction was confirmed to be complete, water was added to quench the reaction. The crude mixture was then concentrated under vacuum, extracted with ethyl acetate (3 × 20 mL), washed with water (3 × 20 mL), dried over anhydrous MgSO4, concentrated under vacuum, filtered, and concentrated again under vacuum to obtain the crude product. The pure compound was then obtained by column chromatography (n-hexane / ethyl acetate).

[0017] Preferably, the molar ratio of aryl alkyne to NaBH4 is 1:3, and the mass fraction of Au nanowires is 0.42%.

[0018] Preferably, the specific steps are as follows:

[0019] 1.3 g of loaded fiber was loosely packed into a column (d = 1 cm) to a height of approximately 7 cm and then wetted by immersion in methanol solvent. At room temperature and pressure, a solution was prepared by dissolving o-phenylenediamine and p-methylbenzaldehyde in a methanol:chloroform mixture. The solution was passed through a gel chromatography column under the force of a syringe pump. The reaction solution changed from colorless to pale yellow. The reaction progress was monitored using a TLC plate. Once the reaction conversion was confirmed to be essentially constant, water was added to quench the reaction. The crude mixture was then concentrated under vacuum, extracted with ethyl acetate (3 × 20 mL), washed with water (3 × 20 mL), dried over anhydrous MgSO4, concentrated under vacuum, filtered, and concentrated again under vacuum to obtain the crude product. Purification by column chromatography (n-hexane / ethyl acetate) yielded the pure compound.

[0020] Preferably, the molar ratio of o-phenylenediamine to p-methylbenzaldehyde is 1:1.2, and the mass fraction of Au nanowires is 0.42%.

[0021] Preferably, the volume ratio of methanol to chloroform is 1:3.

[0022] Preferably, 1.3g of the loaded fiber is loosely packed into a column (d=1cm) to a height of approximately 7cm and then wetted by immersion in methanol solvent. At room temperature and pressure, at 5×10⁻⁶... -3 M2-ethynylnaphthalene was used as the substrate and dissolved in 20 mL of methanol. Then, 11.32 mg of sodium borohydride (NaBH4) was added to prepare a solution. The solution was then passed through a gel chromatography column at a flow rate of 0.55 mL / min using a syringe pump. The reaction solution remained transparent throughout the reaction, and the reaction progress was monitored using a TLC plate. After the reaction was confirmed to be complete, water was added to quench the reaction. The crude mixture was then concentrated under vacuum, extracted with ethyl acetate (3 × 20 mL), washed with water (3 × 20 mL), and dried over anhydrous MgSO4. After vacuum concentration, the HPLC yield was 92%, with most of the product being olefins. The specific route is as follows:

[0023]

[0024] Preferably, 1.3g of the loaded fiber is loosely packed into a column (d=1cm) to a height of approximately 7cm and then wetted by immersion in methanol solvent. At room temperature and pressure, at 5×10⁻⁶... -3 M-phenylenediamine and 6×10 -3M, p-methylbenzaldehyde, was dissolved in 20 mL of methanol:chloroform in a 1:3 ratio to prepare a solution. The solution was then passed through a gel chromatography column at a flow rate of 0.55 mL / min using a syringe pump. The reaction solution changed from colorless to pale yellow, and the reaction progress was monitored using a TLC plate. The above steps were repeated until the reaction conversion remained essentially constant. The reaction was then quenched with water, and the crude mixture was concentrated under vacuum. It was then extracted with 3 × 20 mL of ethyl acetate, washed with 3 × 20 mL of water, and dried over anhydrous MgSO4. After vacuum concentration, the yield was 84%. The specific route is as follows:

[0025]

[0026] The beneficial effects of this invention are:

[0027] (1) The method of this invention is simple and easy to operate. Under normal temperature and pressure, a fixed-bed system was designed and applied to conduct performance tests on the hydrogenation reaction of aryl alkynes. Using AuNWs / glass fiber as packing material, 2-ethynylnaphthalene as template substrate, methanol as solvent, and NaBH4 as reducing agent, the hydrogenation reaction of this system was tested. At a system flow rate of 0.55 mL / min, the HPLC yield in one round of reaction was 92%, with the proportion of 2-vinylnaphthalene in the product being greater than 99%.

[0028] (2) The method of this invention is also applicable to other types of organic reactions. We tested the cyclization reaction under essentially the same system parameters. Using o-phenylenediamine and p-methylbenzaldehyde as substrates and methanol and chloroform as a mixed solvent, the separation yield of the benzimidazole product synthesized by selective cyclization was 84%.

[0029] (3) The hydrogenation reaction described in this invention has the optimal concentration of reactants and the optimal flow rate in the system, resulting in the highest reaction efficiency. Excessive substrate concentration or excessively high flow rate will significantly reduce the conversion efficiency of the product. Compared to other examples and comparative examples, Example 2 is the optimal example, yielding the highest yield.

[0030] (4) Comparative Example 2 shows that the amount of reducing agent NaBH4 also has a significant impact on the reaction efficiency. As can be seen from Comparative Examples 4 and 5, the hydrogenation reaction efficiency of 2-ethynylnaphthalene in other solvent mobile phases is significantly reduced. The speculated reason is that sodium borohydride reacts violently in methanol solvent to release hydrogen gas, which is then adsorbed by the gold catalyst and reacts.

[0031] (5) Comparative Example 7 shows that the hydrogenation of non-terminal alkynes is not applicable compared to the hydrogenation of terminal alkynes. Comparative Example 8 shows that no product was found when this system was applied to the oxidation of 4-methylaniline, indicating that this system is not suitable for this type of reaction. Attached Figure Description

[0032] The present invention will be further described below with reference to the accompanying drawings.

[0033] Figure 1 This is a scanning electron microscope (SEM) image of the gold nanowires in Example 1;

[0034] Figure 2 It is 5×10 2-ethynylnaphthalene -3 The application of gold nanowires loaded on glass fibers under the conditions of M concentration, flow rate of 0.55 mL / min and sodium borohydride NaBH4 3 eq. in the catalytic reduction hydrogenation reaction of 2-ethynylnaphthalene in a fixed bed system (A), NMR (B) and HPLC (C) show the structure and conversion rate of the product, respectively.

[0035] Figure 3 It is in 5×10 -3 The concentration of M is o-phenylenediamine, 6 × 10⁻⁶. -3 The application of gold nanowires loaded on glass fibers at a flow rate of 0.55 mL / min to the selective cyclization reaction of p-methylbenzaldehyde at a concentration of M in a fixed-bed system (A), NMR spectrum (B), confirming the structure of the product;

[0036] Figure 4 This is a TLC spot pattern of the reduction hydrogenation reaction of 2-acetylenynaphthalene catalyzed in a fixed-bed system using gold nanowires loaded on glass fibers.

[0037] Figure 5 This is a TLC plot of gold nanowires loaded on glass fibers catalyzing the selective cyclization reaction of o-phenylenediamine in a fixed-bed system. Detailed Implementation

[0038] Example 1

[0039] Step (1): First, the mixture containing 3.1 × 10 -4 M sodium citrate and 2.5×10 -4 20 mL of an aqueous solution of HAuCl4 was added to a 50 mL round-bottom flask and stirred for 1 min. Then, 620 μL of a 0.1 M NaBH4 aqueous solution prepared with ice water was added to the flask while stirring vigorously. The color of the solution changed from pale yellow to reddish-orange. The mixture was then stirred for another 30 min and allowed to stand for at least 2 h to allow unreacted NaBH4 to be completely consumed, yielding gold nanoparticles (AuNPs) with a diameter of 4 ± 1 nm.

[0040] To prepare AuNWs on glass fibers, the glass fibers (600 mg) were cleaned with a piranha solution (H₂O₂:H₂SO₄ volume ratio of 1:3) to improve their surface hydrophilicity. Then, the surface was prepared by mixing with 50 mL of 5 × 10⁻⁶ mol / L mol / L 400 mL of 100 mL mol / L 400 mL mol / L 400 -3The glass fiber was functionalized with amino groups by reacting M with 3-aminopropyltrimethoxysilane APTMS solution for 0.5 h. The fiber was then immersed in 100 mL of citrate-stabilized AuNPs (4 ± 1 nm) solution for 0.5 h to ensure gold seed adsorption. The glass fiber was then rinsed twice with water to remove excess gold seeds. The seed-adsorbed fiber was then immersed in MBA containing thiol ligand 6.0 × 10⁻⁶ ppm. -4 M, HAuCl4 1.1×10 -3 M and L-ascorbic acid 2.4 × 10 -3 Blackish-purple gold nanowires were loaded onto glass fibers by incubation in 120 mL of a 1:2 water / ethanol solution for 1.5 hours. The glass fibers with the gold nanowires were then rinsed twice with ethanol and air-dried, stored in a windless, dry environment for later use. The gold nanowire catalyst was loaded onto the glass fibers at a mass fraction of 0.42%.

[0041] Example 2

[0042] The 1.3g of loaded fibers obtained in Example 1 were loosely packed into a column (d = 1cm) to a height of approximately 7cm and then wetted by immersion in methanol solvent. At room temperature and pressure, at 5 × 10⁻⁶... -3 M-2-ethynylnaphthalene was used as the substrate and dissolved in 20 mL of methanol. Then, 11.32 mg of sodium borohydride (NaBH4) was added to prepare a solution. The solution was passed through a gel chromatography column at a flow rate of 0.55 mL / min using a syringe pump. The reaction solution remained transparent throughout the reaction, and the reaction progress was monitored using a TLC plate. After the reaction was confirmed to be complete, water was added to quench the reaction. The crude mixture was then concentrated under vacuum, extracted with ethyl acetate (3 × 20 mL), washed with water (3 × 20 mL), and dried over anhydrous MgSO4. After vacuum concentration, the HPLC yield of 2-vinylnaphthalene was 92%, with a 2-vinylnaphthalene:2-ethylnaphthalene ratio greater than 99:1. The compound was purified by column chromatography (n-hexane / ethyl acetate) to obtain a pure compound.

[0043]

[0044] Example 3

[0045] The 1.3g of loaded fibers obtained in Example 1 were loosely packed into a column (d = 1cm) to a height of approximately 7cm and then wetted by immersion in methanol solvent. At room temperature and pressure, at 5 × 10⁻⁶... -3 M-phenylenediamine and 6×10 -3Using p-methylbenzaldehyde as the substrate, a solution was prepared by dissolving it in 20 mL of methanol:chloroform in a 1:3 ratio. The solution was then passed through a gel chromatography column at a flow rate of 0.55 mL / min using a syringe pump. The reaction solution changed from colorless to pale yellow as it passed through the column. The reaction progress was monitored using a TLC plate. Once the conversion rate was confirmed to be essentially constant, the reaction was quenched with water. The crude mixture was then concentrated under vacuum, extracted with 3 × 20 mL of ethyl acetate, washed with 3 × 20 mL of water, and dried over anhydrous MgSO4. After vacuum concentration, the yield of compound 6 was 84%. The compound was purified by column chromatography (n-hexane / ethyl acetate) to obtain a pure compound.

[0046]

[0047] Example 4

[0048] 1.3g of loaded fiber was loosely packed into a column (d=1cm) to a height of approximately 7cm and then wetted by immersion in methanol solvent. At room temperature and pressure, at 10... -2 M2-ethynylnaphthalene was used as the substrate and dissolved in 20 mL of methanol. Then, 11.32 mg of sodium borohydride (NaBH4) was added to prepare a solution. The solution was then passed through a gel chromatography column at a flow rate of 0.55 mL / min using a syringe pump. The reaction solution remained transparent throughout the reaction, and the reaction progress was monitored using a TLC plate. After the reaction was confirmed to be complete, water was added to quench the reaction. The crude mixture was then concentrated under vacuum, extracted with ethyl acetate (3 × 20 mL), washed with water (3 × 20 mL), and dried over anhydrous MgSO4. After vacuum concentration, the HPLC yield was 79%, with most of the product being olefins.

[0049] The reaction efficiency decreased significantly with increasing substrate concentration. However, even at higher substrate concentrations, we could still obtain a product that was predominantly 2-vinylnaphthalene using the mobile phase system, demonstrating its considerable potential application in this type of semi-hydrogenation reaction.

[0050] The specific reaction route is as follows:

[0051]

[0052] Comparative Example 1

[0053] 1.3g of loaded fiber was loosely packed into a column (d=1cm) to a height of approximately 7cm and then wetted by immersion in methanol solvent. At room temperature and pressure, at 5×10⁻⁶... -3M2-ethynylnaphthalene was used as the substrate and dissolved in 20 mL of methanol. Then, 11.32 mg of sodium borohydride (NaBH4) was added to prepare a solution. The solution was then passed through a gel chromatography column at a flow rate of 1.1 mL / min using a syringe pump. The reaction solution remained transparent throughout the reaction, and the reaction progress was monitored using a TLC plate. After the reaction was confirmed to be complete, water was added to quench the reaction. The crude mixture was then concentrated under vacuum, extracted with ethyl acetate (3 × 20 mL), washed with water (3 × 20 mL), and dried over anhydrous MgSO4. After vacuum concentration, the HPLC yield was 60%.

[0054] Compared to Example 2, the reaction efficiency decreased significantly when the flow rate was increased.

[0055] Comparative Example 2

[0056] 1.3g of loaded fiber was loosely packed into a column (d=1cm) to a height of approximately 7cm and then wetted by immersion in methanol solvent. At room temperature and pressure, at 5×10⁻⁶... -3 M2-ethynylnaphthalene was dissolved in 20 mL of methanol, followed by the addition of 7.566 mg (2 eq.) of sodium borohydride (NaBH4). The solution was then passed through a gel permeation chromatography column at a flow rate of 0.55 mL / min using a syringe pump. The reaction solution remained transparent throughout the reaction, and the reaction progress was monitored using a TLC plate. After the reaction was confirmed to be complete, water was added to quench the reaction. The crude mixture was then concentrated under vacuum, extracted with ethyl acetate (3 × 20 mL), washed with water (3 × 20 mL), and dried over anhydrous MgSO4. After vacuum concentration, the HPLC yield was 25%. This indicates that the amount of reducing agent NaBH4 significantly affects the reaction efficiency.

[0057] Comparative Example 3

[0058] 1.3g of loaded fiber was loosely packed into a column (d=1cm) to a height of approximately 7cm and then wetted by immersion in methanol solvent. At room temperature and pressure, at 5×10⁻⁶... -3 M2-ethynylnaphthalene was used as the substrate and dissolved in 20 mL of methanol. Then, 34.884 mg (3 eq.) of Et3SiH triethylsilane was added to prepare a solution. The solution was passed through a gel chromatography column at a flow rate of 0.55 mL / min using a syringe pump. The reaction solution remained transparent throughout. The reaction was monitored using a TLC plate; no target product was detected. Changing the reducing agent to other types did not result in any reaction.

[0059] Comparative Example 4

[0060] 1.3g of loaded fiber was loosely packed into a column (d=1cm) to a height of approximately 7cm and then wetted by immersion in methanol solvent. At room temperature and pressure, at 5×10⁻⁶...-3 M2-ethynylnaphthalene was used as the substrate and dissolved in 20 mL of ethyl acetate. Then, 11.32 mg (3 eq.) of sodium borohydride (NaBH4) was added to prepare a solution. The solution was then passed through a gel chromatography column at a flow rate of 0.55 mL / min using a syringe pump. The reaction solution remained transparent throughout the reaction, and the reaction progress was monitored using a TLC plate. After one round of reaction, the mixture was quenched with water, and then the crude mixture was concentrated under vacuum. It was then extracted with ethyl acetate (3 × 20 mL) and washed with water (3 × 20 mL), and dried over anhydrous MgSO4. After vacuum concentration, the HPLC yield was 30%. Changing to other types of reaction solvents significantly reduced the reaction efficiency.

[0061] Comparative Example 5

[0062] 1.3g of loaded fiber was loosely packed into a column (d=1cm) to a height of approximately 7cm and then wetted by immersion in methanol solvent. At room temperature and pressure, at 5×10⁻⁶... -3 M2-ethynylnaphthalene was used as the substrate and dissolved in 20 mL of tetrahydrofuran solvent. Then, 11.32 mg of 3 eq. of NaBH4 sodium borohydride was added to prepare a solution. The solution was passed through a gel chromatography column at a flow rate of 0.55 mL / min using a syringe pump. The reaction solution remained transparent throughout the reaction, and the reaction progress was monitored by TLC plate. After one round of reaction, water was added to quench the reaction. The crude mixture was then concentrated under vacuum, extracted with 3 × 20 mL of ethyl acetate and washed with 3 × 20 mL of water. The mixture was dried over anhydrous MgSO4. After vacuum concentration, the HPLC yield was 45%.

[0063] As can be seen from Comparative Examples 4 and 5, the hydrogenation efficiency of 4-acetylene biphenyl in other solvent mobile phases is significantly reduced. The speculated reason is that sodium borohydride reacts violently in methanol solvent, releasing hydrogen gas, which is then adsorbed by the gold catalyst and reacts.

[0064] Comparative Example 6

[0065] 1.3g of loaded fiber was loosely packed into a column (d=1cm) to a height of approximately 7cm and then wetted by immersion in methanol solvent. At room temperature and pressure, at 5×10⁻⁶... -3 M4-ethynylbiphenyl was used as the substrate and dissolved in 20 mL of methanol. Then, 11.32 mg of 3 eq. of NaBH4 sodium borohydride was added to prepare a solution. The solution was then passed through a gel chromatography column at a flow rate of 0.55 mL / min using a syringe pump. The reaction solution remained pale yellow throughout. The reaction progress was monitored using a TLC plate. After the reaction was confirmed to be complete, water was added to quench the reaction. The crude mixture was then concentrated under vacuum, extracted with 3 × 20 mL of ethyl acetate and washed with 3 × 20 mL of water. The mixture was dried over anhydrous MgSO4. After vacuum concentration, the HPLC yield was 32%.

[0066] The reaction with 4-ethynylbiphenyl as the substrate had a poor yield of only 32%.

[0067] Comparative Example 7

[0068] 1.3g of loaded fiber was loosely packed into a column (d=1cm) to a height of approximately 7cm and then wetted by immersion in methanol solvent. At room temperature and pressure, at 5×10⁻⁶... -3 Using 1-phenyl-1-acetylene as the substrate, a solution was dissolved in 20 mL of methanol, followed by the addition of 11.32 mg (3 eq.) of sodium borohydride (NaBH4). The solution was then passed through a gel chromatography column at a flow rate of 0.55 mL / min using a syringe pump. The reaction solution remained transparent throughout the reaction, and the reaction progress was monitored using a TLC plate. The above steps were repeated, but the target product was not observed after four rounds of reaction. Compared to the hydrogenation of terminal alkynes, the flow hydrogenation of non-terminal alkynes is also not applicable.

[0069] Comparative Example 8

[0070] 1.3g of loaded fiber was loosely packed into a column (d=1cm) to a height of approximately 7cm and then wetted by immersion in methanol solvent. At room temperature and pressure, at 5×10⁻⁶... -3 M 4-methylaniline was used as the substrate and dissolved in 20 mL of methanol. Then, 10.2 mg of 3 eq. of hydrogen peroxide (30% w / w solubility in water) was added to prepare a solution. The solution was then passed through a gel chromatography column at a flow rate of 0.55 mL / min using a syringe pump. The reaction solution remained transparent throughout. The reaction progress was monitored using a TLC plate. The above steps were repeated, but no target product was found after four rounds of reaction. Applying this system to the oxidation reaction of 4-methylaniline did not yield any product, indicating that this system is not suitable for this type of reaction.

Claims

1. A method for organic catalysis using gold nanowires supported on a glass fiber fixed-bed system, characterized in that... The specific steps include: Gold nanowires were prepared on glass fibers as a catalyst for the mobile phase. A gel chromatography column was used as the packing container. Gold nanowires with a length of 100±20 nm were loaded on the glass fibers as the catalyst for the fixed bed system. Sodium borohydride (NaBH4) was used as the reducing agent and methanol was used as the solvent of the mobile phase in the reaction system. The reductive hydrogenation reaction of 2-ethynylnaphthalene was realized in the mobile system. This fixed-bed system can also be used for the selective cyclization reaction of o-phenylenediamine and p-methylbenzaldehyde, and the selective synthesis of benzimidazole from o-phenylenediamine and aldehyde in a fluid system. The specific reaction route is as follows: Reaction route 1: Reaction route 2:

2. The method for organic catalysis using gold nanowires supported on a glass fiber fixed-bed system according to claim 1, characterized in that... : The specific steps for preparing gold nanowires loaded on glass fibers are as follows: Step (1): First, the mixture containing 3.1 × 10 -4 M sodium citrate and 2.5×10 -4 20 mL of HAuCl4 aqueous solution was added to a 50 mL round-bottom flask and stirred for 1 min. Then, 620 μL of 0.1 M NaBH4 aqueous solution prepared with ice water was added to the flask and stirred vigorously. The color of the solution changed from pale yellow to reddish orange. The mixture was then stirred for another 30 min and allowed to stand for at least 2 h to allow the unreacted NaBH4 to be completely consumed, yielding gold nanoparticles (AuNPs) with a diameter of 4 ± 1 nm. Step (2): To prepare AuNWs on glass fibers, 600 mg of glass fibers were cleaned with a piranha solution (H2O2:H2SO4 = 1:3) to improve their surface hydrophilicity; then, by mixing with 50 mL of 5×10 -3 The glass fiber was functionalized with amino groups by reacting M with 3-aminopropyltrimethoxysilane APTMS solution for 0.5 hours. Step (3): Immerse the glass fiber treated in step 2 in 100 mL of citrate-stabilized AuNPs (4±1 nm) solution obtained in step 1 for 0.5 hours to ensure the adsorption of gold seeds; Step (4): Rinse the glass fiber from step 3 twice with water to remove excess gold seeds; Then, the fiber adsorbed by the seed was immersed in MBA containing thiol ligand 6.0 × 10⁶. -4 M, HAuCl4 1.1×10 -3 M and L-ascorbic acid 2.4 × 10 -3 Black-purple gold nanowires were loaded onto glass fibers in 120 mL of a 1:2 water / ethanol solution for 1.5 hours. Step (5): Rinse the glass fiber from step 4 twice with ethanol and dry it in the air. Store it in a dry, windless environment for later use.

3. The method for organic catalysis using gold nanowires supported on a glass fiber fixed-bed system according to claim 2, characterized in that... The fixed-bed system utilizes gold nanowires to catalyze the reductive hydrogenation reaction of arylacetylene. The specific steps are as follows: The prepared fibers were placed in a 7 cm high (d = 1 cm) gel chromatography column; the fibers loaded with gold nanowires were packed loosely in the column (d = 1 cm) to reach a height of 7 cm. A methanol mixture of 2-ethynylnaphthalene and NaBH4 was added to a chromatographic column; the reaction flow rate was controlled by a flow pump or external pressure, and the reaction mixture remained colorless as it passed through the catalyst bed; the reaction efficiency was detected by TLC analysis. After completion, the crude mixture was concentrated under vacuum, then extracted with ethyl acetate (3 × 20 mL) and washed with water (3 × 20 mL). The combined organic layers were dried on anhydrous MgSO4, filtered, and concentrated under vacuum to obtain the crude product. After purification by column chromatography (n-hexane / ethyl acetate), the pure compound was obtained.

4. The method for organic catalysis using gold nanowires supported on a glass fiber fixed-bed system according to claim 2, characterized in that... The specific steps of the fixed-bed system for synthesizing benzimidazole by selective cyclization of o-phenylenediamine catalyzed by gold nanowires are as follows: The prepared fibers were placed in a 7 cm high (d = 1 cm) gel chromatography column. The fibers loaded with gold nanowires were loosely packed into the column (d = 1 cm) to achieve a height of 7 cm. A mixture of o-phenylenediamine and p-methylbenzaldehyde in methanol and chloroform at a volume ratio of 1:3 was added to a chromatographic column. The reaction flow rate was controlled by a flow pump or external pressure. The reaction mixture changed from colorless to pale yellow as it passed through the catalyst bed. The reaction efficiency was detected by TLC analysis. After completion, the crude mixture was concentrated under vacuum, then extracted with ethyl acetate (3×20 mL) and washed with water (3×20 mL). The combined organic layers were dried on anhydrous MgSO4, filtered, and concentrated under vacuum to obtain the crude product. The crude product was then purified by column chromatography (n-hexane / ethyl acetate) to obtain the pure compound.

5. The method for organic catalysis using gold nanowires supported on a glass fiber fixed-bed system according to claim 2, characterized in that... : In reaction route 1, the molar ratio of arylaceyne to reducing agent NaBH4 is 1:3, and in reaction route 2, the molar ratio of o-phenylenediamine to p-methylbenzaldehyde is 1:1.

2. The gold nanowire catalyst is supported on glass fiber and has a mass fraction of 0.42%.

6. The method for organic catalysis using gold nanowires supported on a glass fiber fixed-bed system according to claim 5, characterized in that... : At room temperature and pressure, the substrate concentration in 20 mL is 5 × 10⁻⁶. -3 The 2-ethynylnaphthalene of M was reacted for 36 min, and the HPLC yield was 92%, wherein the volume ratio of 2-vinylnaphthalene to 2-ethylnaphthalene was greater than 99:

1.

7. The method for organic catalysis using gold nanowires supported on a glass fiber fixed-bed system according to claim 5, characterized in that... : At room temperature and pressure, the substrate concentration in 20 mL is 5 × 10⁻⁶. -3 The o-phenylenediamine of M reacted for 36 min, and the yield of compound 6-2-(4-methylbenzene)benzimidazole was 84%.

8. The method for organic catalysis using gold nanowires supported on a glass fiber fixed-bed system according to claim 5, characterized in that... : 1.3g of loaded fiber was loosely packed into a column (d=1cm) to a height of 7cm and then wetted by immersion in methanol solvent. The column was then subjected to a process at room temperature and pressure at a rate of 5×10⁻⁶. -3 M 2-ethynylnaphthalene was used as the substrate and dissolved in 20 mL of methanol. Then, 11.32 mg of 3 eq. of NaBH4 sodium borohydride was added to prepare a solution. The solution was then passed through a gel chromatography column at a flow rate of 0.55 mL / min using a syringe pump. The reaction solution remained transparent throughout the process, and the reaction progress was monitored using a TLC plate. After the reaction was completed, water was added to quench the reaction. The crude mixture was then concentrated under vacuum, extracted with 3 × 20 mL of ethyl acetate and washed with 3 × 20 mL of water. The mixture was dried over anhydrous MgSO4. After vacuum concentration, the HPLC yield was 92%, with a volume ratio of 2-vinylnaphthalene to 2-ethylnaphthalene greater than 99:

1.

9. The method for organic catalysis using gold nanowires supported on a glass fiber fixed-bed system according to claim 2, characterized in that... : 1.3g of loaded fiber was loosely packed into a column (d=1cm) to a height of 7cm and then wetted by immersion in methanol solvent. The column was then subjected to a process at room temperature and pressure at a rate of 5×10⁻⁶. -3 M-phenylenediamine and 6×10 -3 M, using p-methylbenzaldehyde as a substrate, was dissolved in 20 mL of methanol. The solution prepared in chloroform at a volume ratio of 1:3 was passed through a gel chromatography column by a syringe pump at a flow rate of 0.55 mL / min. The reaction solution changed from colorless to pale yellow as it passed through the column. The reaction progress was monitored by TLC plate. The crude mixture was then concentrated under vacuum, extracted with ethyl acetate (3 × 20 mL), washed with water (3 × 20 mL), and dried with anhydrous MgSO4. After vacuum concentration, the yield of compound 6 was 84%.

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