A ruthenium carbon hydrogenation catalyst based on chiral diphosphine ligand modification, and a preparation method and application thereof

Abstract

The present application relates to the technical field of catalyst, in particular to a ruthenium carbon hydrogenation catalyst based on chiral diphosphine ligand modification and its preparation method and application. The method comprises the following steps: preparing a nitrogen-defect-containing carbon carrier; loading ruthenium and reducing; pre-coating a confinement layer by using ionic liquid A; introducing a chloride ion template microenvironment; coordinating with a chiral diphosphine ligand; achieving weakly coordinated anion shaping by treating with bis(trifluoromethanesulfonyl) imide silver; and finally introducing chiral ionic liquid B to construct an outer network. The catalyst realizes high enantioselective conversion of prochiral substrates through the synergistic effect of multi-level chiral microenvironments while maintaining high hydrogenation activity, and has excellent cycle stability, solving the technical problem that the activity and selectivity of non-homogeneous chiral catalysts are difficult to balance.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to a ruthenium-carbon hydrogenation catalyst based on chiral diphosphine ligand modification, its preparation method, and its application. Background Technology

[0002] Chiral hydrogenation catalysts have significant applications in drug synthesis and fine chemical preparation, with the core being the achievement of highly enantioselective conversion. While homogeneous chiral catalysts offer high enantioselectivity, they suffer from challenges such as separation difficulties, poor cycling stability, and precious metal loss, limiting their industrial application. To address the shortcomings of homogeneous catalysts, researchers have attempted to immobilize chiral ligands and metal active centers on heterogeneous supports. However, such methods often face problems such as incomplete chiral microenvironment construction and disordered ligand distribution. For example, direct physical adsorption or simple covalent anchoring of chiral ligands easily leads to heterogeneous spatial configurations of active sites, resulting in a gradual decay of chiral induction effects during the reaction.

[0003] Furthermore, the complexity of the surface chemistry of the support further increases the difficulty of constructing chiral centers. Although traditional carbon supports possess high specific surface area and stability, the types and distribution of their surface functional groups are difficult to precisely control, making it difficult to achieve directional assembly of chiral ligands and metal sites. Some studies have attempted to optimize the local microenvironment by introducing ionic liquids or template agents, but challenges such as anion competitive coordination and insufficient stability of the chiral network remain. Especially under high hydrogen pressure or continuous reaction conditions, chiral centers are prone to structural relaxation or ligand desorption, leading to a significant decrease in enantioselectivity.

[0004] In existing technologies, it is often difficult to synergistically improve the activity and enantioselectivity of heterogeneous chiral catalysts. To achieve high reaction rates, it is often necessary to increase the metal loading or reaction temperature, but this may exacerbate dynamic fluctuations in chiral configuration. Conversely, focusing on enantioselectivity control may lead to reduced catalytic activity due to excessive ligand coverage of active sites or mass transfer limitations. This contradictory relationship restricts the practical application of chiral hydrogenation catalysts in efficient synthesis. Summary of the Invention

[0005] In view of this, the purpose of this invention is to propose a ruthenium-carbon hydrogenation catalyst based on chiral diphosphine ligand modification, its preparation method and application, in order to solve the problem that existing heterogeneous chiral hydrogenation catalysts are difficult to achieve stable and high enantioselective conversion while maintaining high reactivity, and that their chiral microenvironment construction is incomplete and the active site structure is prone to dynamic drift, resulting in a significant decrease in enantioselectivity during recycling.

[0006] To achieve the above objectives, this invention provides a method for preparing a ruthenium-carbon hydrogenation catalyst modified with a chiral diphosphine ligand, comprising the following steps:

[0007] (1) Preparation of carbon supports with nitrogen defects;

[0008] (2) Ruthenium is loaded onto a nitrogen-defective carbon support and reduced to form ruthenium sites, thus obtaining a ruthenium-supported nitrogen-containing carbon catalyst;

[0009] (3) The ruthenium-supported nitrogen-containing carbon catalyst is pre-coated with ionic liquid A, wherein the ionic liquid A is an imidazolium bis(trifluoromethanesulfonyl)imine salt ionic liquid;

[0010] (4) Introducing chloride ions into the pre-coated confinement system to form a templated microenvironment, wherein the chloride ions are derived from imidazolium chloride-based ionic liquids;

[0011] (5) Introduce chiral diphosphine ligands into the chloride ion templated microenvironment for coordination modification to obtain a ruthenium-supported nitrogen-containing carbon intermediate modified with chiral diphosphine ligands;

[0012] (6) The intermediate was treated with bis(trifluoromethanesulfonyl)imide silver to obtain ruthenium-supported nitrogen-containing carbon modified with weakly coordinated anion-shaped chiral diphosphine ligand;

[0013] (7) Introduce chiral ionic liquid B to construct an outer network to obtain a ruthenium-carbon hydrogenation catalyst based on chiral diphosphine ligand modification, wherein the chiral ionic liquid B is a proline salt type chiral ionic liquid.

[0014] Preferably, step (1) includes:

[0015] (1-1) Acid oxidation treatment of carbon materials;

[0016] (1-2) Dopamine self-polymerization coating was carried out in alkaline buffer solution;

[0017] (1-3) Heat treatment under an inert atmosphere to obtain a carbon support with nitrogen defects.

[0018] Preferably, the acid oxidation treatment in step (1-1) uses an aqueous nitric acid solution as the oxidizing acid, with a nitric acid mass fraction of 50% to 70%, a reflux temperature of 70 to 85°C, a reflux time of 3 to 5 hours, and a liquid-to-solid ratio of 20 to 40 mL / g between the carbon material and the nitric acid solution, and a stirring speed of 300 to 600 rpm.

[0019] Preferably, the buffer solution in step (1-2) is a Tris buffer solution with a Tris concentration of 0.5-1.5 mol / L and a pH of 8.3-8.8; the mass ratio of dopamine to the acid-oxidized carbon material is 1:1-3:1; the reaction temperature is 20-30℃; the reaction time is 6-10 h; and the stirring speed is 400-600 rpm.

[0020] Preferably, the inert gas in steps (1-3) is nitrogen, the heating rate is 3-7℃ / min, the heat treatment temperature is 550-800℃, the holding time is 1.5-3h, and the nitrogen purging flow rate is 100-300mL / min.

[0021] Preferably, the ruthenium precursor in step (2) is ruthenium chloride hydrate, and the ruthenium loading is 4 to 6 wt% based on Ru.

[0022] Preferably, in step (2), the liquid-to-solid ratio of the impregnation solution to the carrier is 10-25 mL / g carrier, the impregnation time is 1-3 h, and the stirring speed is 400-600 rpm.

[0023] Preferably, the reducing atmosphere in step (2) is a mixture of hydrogen and inert gas, with a hydrogen gas fraction of 5% to 15%, a reduction temperature of 200 to 300°C, a holding time of 2 to 4 hours, a heating rate of 3 to 7°C / min, and a gas flow rate of 100 to 300 mL / min.

[0024] Preferably, in step (3), the amount of ionic liquid A is 2% to 12% of the mass of the ruthenium-supported nitrogen-containing carbon catalyst, the pre-coating confinement treatment temperature is 20 to 30°C, and the treatment time is 1 to 3 hours.

[0025] Preferably, the solvent used in step (3) is acetone, and the solvent is removed by depressurization after the pre-coating confinement treatment.

[0026] Preferably, in step (4), the amount of imidazolium chloride ionic liquid used is 1% to 6% of the mass of the pre-coated confinement material obtained in step (3), the template treatment temperature is 20 to 30°C, and the treatment time is 0.5 to 2 hours.

[0027] Preferably, the chiral diphosphine ligand in step (5) is (S)-(-)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl ((S)-BINAP), and the molar ratio of the chiral diphosphine ligand to ruthenium is 0.05 to 0.30.

[0028] Preferably, step (5) is carried out under an inert atmosphere, the coordination solvent is toluene, the coordination temperature is 50-70°C, and the coordination time is 2-6 hours.

[0029] Preferably, in step (6), the silver bis(trifluoromethanesulfonyl)imide treatment is carried out under light-protected conditions, with a treatment temperature of 2-10°C and a treatment time of 10-30 min. The treatment solvent is acetonitrile, and the amount of silver bis(trifluoromethanesulfonyl)imide is 3%-10% of the mass of the intermediate.

[0030] Preferably, in step (7), the chiral ionic liquid B is a proline salt-type chiral ionic liquid obtained by neutralizing L-proline with imidazolium base. The amount of chiral ionic liquid B added is 2% to 8% of the mass of the solid obtained in step (6). The treatment temperature is 20 to 30°C, the treatment time is 0.5 to 2 hours, and the solvent used is anhydrous ethanol.

[0031] Preferably, ionic liquid A is 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt, imidazolium chloride ionic liquid in step (4) is 1-butyl-3-methylimidazolium chloride, and chiral ionic liquid B is 1-ethyl-3-methylimidazolium proline salt.

[0032] Furthermore, the present invention also provides a ruthenium-carbon hydrogenation catalyst based on chiral diphosphine ligand modification, which is prepared by the above-described method.

[0033] Furthermore, the present invention also provides an application of a ruthenium-carbon hydrogenation catalyst modified with a chiral diphosphine ligand for hydrogenation of a prochiral substrate, wherein the prochiral substrate is a prochiral ketone, a prochiral imine, and / or a prochiral olefin.

[0034] Preferably, the prochiral substrate is acetophenone, the reaction solvent is toluene, the hydrogen pressure is 2.0 MPa, the reaction temperature is 40°C, the stirring speed is 800 rpm, and the reaction time is 2.0 h.

[0035] This invention utilizes a nitrogen-deficient carbon support and dopamine self-polymerization-carbonization treatment to construct abundant nitrogen-deficient sites and ordered pore structures on the carbon surface, effectively improving the anchoring strength and dispersion uniformity of metallic ruthenium. This support not only provides a stable coordination environment for the metal active centers but also enhances the intrinsic activity of ruthenium sites through the electronic regulation of nitrogen vacancies, laying a structural foundation for the precise construction of subsequent chiral microenvironments.

[0036] By utilizing the pre-coating confinement effect of ionic liquid A, localized hydrophobic-lipophilic microregions are formed on the carbon support surface, effectively guiding chiral diphosphine ligands to preferentially accumulate near ruthenium sites and avoiding disordered spreading of ligands on the support surface. This confinement effect significantly improves the utilization efficiency of chiral ligands, enabling the formation of more active centers with effective chiral induction capabilities per unit amount of ligand, while reducing the ligand's obstruction to the reaction mass transfer process.

[0037] A chloride ion templating strategy was employed to create an exchangeable anion microenvironment in the metal neighborhood, promoting the directional coordination of chiral diphosphine ligands with ruthenium sites. Chloride ion templating not only enhanced the spatial selectivity of the coordination process but also strengthened the structural rigidity of the chiral center through a pre-organization mechanism, enabling the catalyst to maintain the stability of its chiral configuration even under high-pressure hydrogen atmosphere, thus achieving sustained and efficient enantioselectivity.

[0038] Extractive dechlorination and weakly coordinating anion fixation were achieved using bis(trifluoromethanesulfonyl)imide silver treatment, effectively eliminating the occupation and poisoning of ruthenium active sites by strongly coordinating chloride ions. The introduction of the weakly coordinating anion reduced the steric hindrance of the metal center, making it easier for substrate molecules to access the chiral active site, while avoiding competition for coordination between the anion and the chiral ligand, thus achieving a synergistic improvement in both high reaction rate and high chiral induction efficiency.

[0039] By introducing a proline salt-type chiral ionic liquid B into the outer layer, a dynamic chiral network was further constructed on the catalyst surface. This network enhances chiral recognition ability by regulating the orientation and diffusion path of substrate molecules through the outer sphere interaction, and avoids deactivation due to the non-direct participation in metal coordination. The synergistic effect of this multi-level chiral microenvironment enables the catalyst to maintain excellent enantioselectivity stability during recycling. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0041] This invention provides a method for preparing a ruthenium-carbon hydrogenation catalyst based on chiral diphosphine ligand modification, the method comprising at least the following steps:

[0042] a) Preparation of carbon supports containing nitrogen defects;

[0043] b) Load ruthenium onto the nitrogen-defect-containing carbon support and reduce it to form ruthenium sites to obtain a ruthenium-supported nitrogen-containing carbon catalyst;

[0044] c) The ruthenium-supported nitrogen-containing carbon catalyst is pre-coated and confined using ionic liquid A;

[0045] d) Introducing chloride ions into the confined system to form a templated microenvironment;

[0046] e) Introduce chiral diphosphine ligands into the chloride ion microenvironment for coordination modification to obtain a ruthenium-supported nitrogen-containing carbon intermediate modified with chiral diphosphine ligands;

[0047] f) Dechlorination was carried out by silver salt extraction and shaping with weakly coordinating anions to obtain ruthenium-supported carbon modified with weakly coordinating anions;

[0048] g) Introduce chiral ionic liquid B to construct an outer network to obtain the target catalyst.

[0049] 1) Step a: Preparation of carbon support with nitrogen defects

[0050] In step a) provided by the present invention, a preferred combination of acid oxidation to activate carbon, dopamine self-polymerization coating in alkaline buffer solution, and inert atmosphere heat treatment is used to simultaneously construct on the carbon surface: nitrogen-containing defect / nitrogen-containing functional group sites that facilitate subsequent metal anchoring; hydrophilic / oxygen-containing functional groups that facilitate impregnation and dispersion; and a microporous / mesoporous surface environment that balances stability and dispersibility.

[0051] a1. Acid oxidation conditions:

[0052] In the acid oxidation treatment provided by this invention, the oxidizing acid is preferably an aqueous nitric acid solution; the mass fraction of nitric acid is preferably 50%–70%, more preferably 60%–67%, and specifically 65%. The liquid-to-solid ratio of activated carbon to nitric acid solution is preferably 10–50 mL / g, more preferably 20–40 mL / g. The reflux temperature is preferably 60–90°C, more preferably 70–85°C; the time is preferably 2–6 h, more preferably 3–5 h; and the stirring speed is preferably 200–800 rpm, more preferably 300–600 rpm.

[0053] a2. Dopamine self-polymerization coating conditions:

[0054] In the dopamine self-polymerization process provided by this invention, the buffer system is preferably Tris buffer solution; the Tris concentration is preferably 0.1-2 mol / L, more preferably 0.5-1.5 mol / L, specifically 1 mol / L; the pH is preferably 8.0-9.0, more preferably 8.3-8.8, specifically 8.5. The ultrasonic dispersion time is preferably 5-30 min, more preferably 8-15 min. The mass ratio of dopamine (calculated as dopamine hydrochloride) to oxidized activated carbon is preferably 0.5:1-5:1, more preferably 1:1-3:1. The reaction temperature is preferably 15-35℃, more preferably 20-30℃; the stirring speed is preferably 200-800 rpm, more preferably 400-600 rpm; the atmosphere is preferably air or an oxygen-containing atmosphere; the reaction time is preferably 2-12 h, more preferably 6-10 h.

[0055] a3. Inert atmosphere heat treatment conditions:

[0056] In the heat treatment provided by this invention, the inert gas is preferably nitrogen; the purging flow rate is preferably 50-500 mL / min, more preferably 100-300 mL / min; the purging time is preferably 10-60 min, more preferably 20-40 min. The heating rate is preferably 1-10 °C / min, more preferably 3-7 °C / min; the heat treatment temperature is preferably 500-900 °C, more preferably 550-800 °C; and the holding time is preferably 1-4 h, more preferably 1.5-3 h.

[0057] 2) Step b: Loading and reducing to form ruthenium sites

[0058] In step b) provided by the present invention, the preferred route is aqueous impregnation, dry immobilization, and reduction with a hydrogen / inert gas mixture.

[0059] The ruthenium precursor is preferably ruthenium chloride hydrate; the liquid-to-solid ratio of the impregnation solution is preferably 5-30 mL / g carrier, more preferably 10-25 mL / g carrier; the stirring speed during the dropwise addition or addition process is preferably 200-800 rpm, more preferably 400-600 rpm; the impregnation time is preferably 0.5-6 h, more preferably 1-3 h.

[0060] The loading amount (in Ru) is preferably 0.5 to 10 wt%, more preferably 2 to 8 wt%, and even more preferably 4 to 6 wt%.

[0061] The hydrogen gas fraction in the reducing atmosphere is preferably 1% to 20%, more preferably 5% to 15%, and specifically 10%; the gas flow rate is preferably 50 to 500 mL / min, more preferably 100 to 300 mL / min; the reducing temperature is preferably 150 to 350℃, more preferably 200 to 300℃; the holding time is preferably 1 to 6 h, more preferably 2 to 4 h; and the heating rate is preferably 1 to 10℃ / min, more preferably 3 to 7℃ / min.

[0062] 3) Steps c to e: Ionic liquid A confinement + chloride ion templated + chiral diphosphine ligand coordination

[0063] In step c) of this invention, the ionic liquid A is preferably an imidazolium bis(trifluoromethanesulfonyl)imide salt (such as 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt); its amount is preferably 0.5% to 20% of the catalyst mass, more preferably 2% to 12%. The solvent used is preferably a volatile solvent such as acetone; the stirring temperature is preferably 15 to 35°C, more preferably 20 to 30°C; the stirring time is preferably 0.5 to 6 h, more preferably 1 to 3 h.

[0064] The formation of a thin layer / local confinement of ionic liquid A on the carbon surface can reduce the ineffective spreading and random adsorption of diphosphine ligands on the carbon support, promote the preferential enrichment of ligands in the metal neighborhood and the formation of effective chiral centers, increase the proportion of effective chiral sites per unit amount of ligand, and reduce the risk of inactivation caused by excessive coverage of metal active sites.

[0065] In step d) of the present invention, the chloride ion source is preferably an imidazolium chloride-based ionic liquid (such as 1-butyl-3-methylimidazolium chloride); the amount of chloride ion is preferably 0.5% to 10% of the catalyst mass, more preferably 1% to 6%; the processing temperature is preferably 15 to 35°C, more preferably 20 to 30°C; and the processing time is preferably 0.2 to 4 h, more preferably 0.5 to 2 h.

[0066] Chloride ion templating can create an exchangeable anion microenvironment around the metal, increasing the probability of selective anchoring of diphosphine ligands to metal sites and reducing batch fluctuations caused by random adsorption / spreading away from metal sites, thereby enhancing reproducibility and the potential for improved enantioselectivity.

[0067] In step e) of this invention, the chiral diphosphine ligand is preferably (S)-BINAP; the coordination solvent is preferably a nonpolar solvent such as toluene; and the reaction is preferably carried out under an inert atmosphere. The coordination temperature is preferably 40–80°C, more preferably 50–70°C; and the time is preferably 1–12 h, more preferably 2–6 h. The molar ratio of the chiral diphosphine ligand to ruthenium (calculated as Ru) is preferably 0.01–1.0, more preferably 0.05–0.30.

[0068] Coordination temperature and molar ratio affect the degree and stability of diphosphine coordination at ruthenium sites, which in turn affects the strength and accessibility of the chiral microenvironment of the catalytic center. Insufficient coordination results in limited improvement of ee, while excessive ligands or overly strong coordination may lead to the occupation of active sites and a decrease in conversion. Therefore, confinement + templated coordination can achieve a high effective coordination ratio with a low amount of ligand.

[0069] 4) Steps f to g: Extractive dechlorination + weakly coordinating anion shaping + outer chiral ionic liquid network

[0070] In step f) of this invention, the dechlorination and anion-fixing reagent is preferably bis(trifluoromethanesulfonyl)imide silver, and it is preferably carried out under light-protected conditions. The processing temperature is preferably 0–15°C, more preferably 2–10°C; the processing time is preferably 5–60 min, more preferably 10–30 min. The amount of bis(trifluoromethanesulfonyl)imide silver is preferably 1%–15% of the catalyst mass, more preferably 3%–10%.

[0071] Ag + With Cl - The formation of sparingly soluble AgCl and its removal by washing achieve "extraction-based dechlorination"; at the same time, the introduction of weakly coordinating anions helps to reduce the occupancy of metal sites by anions, avoiding the sacrifice of activity in pursuit of high ee, and balancing the stability of chiral centers with substrate accessibility.

[0072] In step g) provided in this invention, the chiral ionic liquid B is preferably a proline salt-type chiral ionic liquid (such as 1-ethyl-3-methylimidazolium proline salt) obtained by neutralizing L-proline with an imidazolium base; its addition amount is preferably 0.5% to 15% of the catalyst mass, more preferably 2% to 8%; the solvent is preferably anhydrous ethanol; the treatment temperature is preferably 15 to 35°C, more preferably 20 to 30°C; and the time is preferably 0.5 to 4 h, more preferably 0.5 to 2 h.

[0073] Chiral ionic liquid B is preferably introduced after the weakly coordinating anion is shaped, so that it tends to accumulate at the outer interface and form an outer spherical chiral network, thereby enhancing enantioselectivity through interface confinement and orientation sieving; since it does not preferentially compete for metal centers by direct coordination, it can reduce the risk of deactivation and retain hydrogenation activity, achieving a simultaneous improvement in high ee and high conversion rate.

[0074] The following detailed description is provided with reference to the embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0075] Example 1:

[0076] The activated carbon used in this embodiment is from Merck, 100 mesh, product number 242276. The (S)-BINAP used is from Merck, product number 693057.

[0077] Preparation of nitrogen-defect-containing carbon support: 2.5 g of activated carbon powder was weighed and added to 80 mL of 65% nitric acid solution. The mixture was refluxed and stirred at 80 °C and 400 rpm for 4 h. After the reaction, the solid was separated by vacuum filtration and washed with deionized water until the pH of the filtrate was 6.8. The solid was then dried in a vacuum drying oven at 110 °C for 12 h to obtain oxidized activated carbon. 2 g of oxidized activated carbon was added to 100 mL of Tris buffer (1 mol / L, pH 8.5) and ultrasonically dispersed for 10 min. Then, 5 g of dopamine hydrochloride was added and stirred at 25 °C, 500 rpm, and air for 8 h. After the reaction, the mixture was filtered and washed three times with deionized water. It was then vacuum dried at 60 °C for 12 h to obtain polydopamine-coated carbon material. The material was placed in a quartz boat and purged with nitrogen at 200 mL / min for 30 min. The temperature was then increased to 750 °C at 5 °C / min and held for 2 h. The material was then naturally cooled to room temperature under nitrogen protection to obtain a nitrogen-defect-containing carbon support.

[0078] Ruthenium sites were loaded and reduced on nitrogen-containing anchoring sites: 2g of nitrogen-defective carbon support was weighed and added to 30mL of deionized water to form a slurry. 259mg of ruthenium chloride hydrate was dissolved in 20mL of deionized water to obtain a ruthenium salt impregnation solution. The impregnation solution was added dropwise to the support slurry at 500rpm and stirred for 2h. Then, the water was removed by rotary evaporation under reduced pressure at 60℃ and vacuum dried at 80℃ for 12h to obtain a ruthenium salt-supported precursor. The precursor was placed in a tubular furnace quartz tube and purged with nitrogen at 200mL / min for 30min. Then, the flow rate was switched to a 10% hydrogen / 90% nitrogen mixture at 200mL / min. The temperature was increased to 250℃ at 5℃ / min and held for 3h. After cooling to room temperature, the catalyst was removed under nitrogen protection to obtain a ruthenium-supported nitrogen-containing carbon catalyst.

[0079] Preparation of chiral diphosphine ligand-modified ruthenium-supported nitrogen-containing carbon intermediate: 2g of ruthenium-supported nitrogen-containing carbon catalyst was weighed and placed in a dry beaker. 150mg of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and 20mL of acetone were added to form a suspension. The mixture was stirred at 25℃ and 500rpm for 2h. Then, the acetone was removed by rotary evaporation under reduced pressure at 40℃, and the mixture was vacuum dried at 60℃ for 2h to obtain ionic liquid-pre-coated ruthenium-supported nitrogen-containing carbon material. 50mg of 1-butyl-3-methylimidazolium chloride and 10mL of acetonitrile were added to this material. The mixture was stirred at 25℃ and 500rpm for 1h, then the acetonitrile was removed by rotary evaporation and vacuum dried at 60℃ for 2h to obtain a solid containing a chloride ion microenvironment. 62mg of... (S)-BINAP was dissolved in 20 mL of toluene, and the solid containing the above chloride ion microenvironment was added under nitrogen protection and stirred at 60 °C for 4 h. After the reaction, the mixture was filtered and washed twice each with toluene and n-hexane, and dried under vacuum at 60 °C for 6 h to obtain a ruthenium-supported nitrogen-containing carbon intermediate modified with chiral diphosphine ligands.

[0080] Preparation of chiral ionic liquid: Weigh 102 mg L-proline and place it in a beaker. Add 1140 mg of 1-ethyl-3-methylimidazolium hydroxide solution (concentration 10 wt%) and stir at 25 °C for 1 h to complete acid-base neutralization and generate an aqueous system of 1-ethyl-3-methylimidazolium proline salt type chiral ionic liquid. Then evaporate the water under reduced pressure at 60 °C to constant weight and dry under vacuum at 80 °C for 12 h to obtain chiral ionic liquid B.

[0081] Weakly coordinating anion shaping and introduction of a chiral ionic liquid outer layer network: 2g of chiral diphosphine ligand-modified ruthenium-supported nitrogen-containing carbon intermediate was weighed, added to 10mL of acetonitrile, and placed in an ice-water bath to maintain the system temperature at 5℃. Then, 120mg of bis(trifluoromethanesulfonyl)imide silver was added, and the mixture was stirred for 20min under light-protected conditions. The mixture was filtered and washed twice with acetonitrile, and then dried under vacuum at 60℃ for 4h to obtain weakly coordinating anion-shaped chiral diphosphine ligand-modified ruthenium-supported nitrogen-containing carbon. 80mg of chiral ionic liquid was dissolved in 10mL of anhydrous ethanol and added to the above weakly coordinating anion-shaped chiral diphosphine ligand-modified ruthenium-supported nitrogen-containing carbon. The mixture was stirred at 25℃ and 500rpm for 1h, then the ethanol was removed under reduced pressure at 40℃ and dried under vacuum at 60℃ for 6h to obtain a ruthenium carbon hydrogenation catalyst based on chiral diphosphine ligand modification.

[0082] Example 2 (with a change in the amount of diphosphine ligand; otherwise the same as in Example 1):

[0083] Compared with Example 1, this example only adjusts the dosage of (S)-BINAP in step (3) from 62mg to 93mg. The dosage of other raw materials, the order of addition, the stirring conditions, the temperature and time, the atmosphere, and the washing and drying conditions are the same as in Example 1.

[0084] Example 3 (with altered chloride ion template intensity; otherwise the same as Example 1):

[0085] Compared with Example 1, this example only adjusts the amount of 1-butyl-3-methylimidazolium chloride in step (3) from 50 mg to 80 mg, and adjusts the template stirring time from 1 h to 2 h; the other conditions are the same as in Example 1.

[0086] Example 4 (Change in dechlorination / setting strength; otherwise the same as Example 1):

[0087] Compared with Example 1, this example only adjusts the amount of bis(trifluoromethanesulfonyl)imide silver in step (5) from 120mg to 180mg, and adjusts the stirring time from 20min to 30min (the temperature is still kept at 5℃ and the protection from light remains unchanged); the other conditions are the same as in Example 1.

[0088] Comparative Example 1:

[0089] The difference between Comparative Example 1 and Example 1 is that in the step of preparing the nitrogen-defect-containing carbon support, the addition of 5g of dopamine hydrochloride and stirring at 25°C, 500rpm, and air for 8h to form polydopamine-coated carbon material is not performed, nor is the inert atmosphere heat treatment of purging with nitrogen at 200mL / min for 30min followed by raising the temperature to 600°C at 5°C / min and holding for 2h to obtain the nitrogen-defect-containing carbon support. Instead, the oxidized activated carbon obtained in Example 1, which was refluxed and stirred at 80°C and 400rpm for 4h, acid-oxidized, filtered, washed with deionized water until the pH of the filtrate was 6.8, and vacuum-dried at 110°C for 12h, is directly used as the support for loading and reducing the nitrogen-containing anchoring sites to form ruthenium sites; the other conditions are the same as in Example 1.

[0090] Comparative Example 2:

[0091] The difference between Comparative Example 2 and Example 1 is that in the preparation step of the chiral diphosphine ligand modified ruthenium-supported nitrogen-containing carbon intermediate, 150 mg of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt is not added. Instead, 2 g of ruthenium-supported nitrogen-containing carbon catalyst is weighed and placed in a dry beaker, and only 20 mL of acetone is added to form a suspension. The mixture is stirred at 25 °C and 500 rpm for 2 h. Then, the acetone is removed by rotary evaporation under reduced pressure at 40 °C and the mixture is vacuum dried at 60 °C for 2 h to obtain ruthenium-supported nitrogen-containing carbon material without ionic liquid pre-coating treatment. Then, the following steps are performed as in Example 1: adding 50 mg of 1-butyl-3-methylimidazolium chloride and 10 mL of acetonitrile for template formation, adding (S)-BINAP / toluene for coordination at 60 °C, silver salt treatment, and introducing the chiral ionic liquid B outer layer network. The remaining conditions are the same as in Example 1.

[0092] Comparative Example 3:

[0093] The difference between Comparative Example 3 and Example 1 is that in the step of introducing chloride ions into the ruthenium-supported nitrogen-containing carbon material pre-coated with ionic liquid to form a templated microenvironment, 50 mg of 1-butyl-3-methylimidazolium chloride is not added. That is, only 10 mL of acetonitrile is added to the ruthenium-supported nitrogen-containing carbon material pre-coated with ionic liquid and stirred at 25°C and 500 rpm for 1 h. After removing acetonitrile by rotary evaporation and vacuum drying at 60°C for 2 h, the process is directly carried out according to the steps of Example 1: (S)-BINAP / toluene coordination at 60°C for 4 h, filtration, washing and drying, silver salt treatment to remove chloride and weak coordination anion shaping, and introduction of chiral ionic liquid B outer layer network. The remaining conditions are the same as in Example 1.

[0094] Comparative Example 4:

[0095] The difference between Comparative Example 4 and Example 1 is that in the steps of weakly coordinating anion shaping and introducing the chiral ionic liquid outer layer network, 120 mg of bis(trifluoromethanesulfonyl)imide silver is not added. Instead, 2 g of chiral diphosphine ligand-modified ruthenium-supported nitrogen-containing carbon intermediate is weighed, added to 10 mL of acetonitrile, and placed in an ice-water bath to maintain the system temperature at 5°C. After stirring for 20 min under light-protected conditions, it is directly filtered and washed twice with acetonitrile, and then dried under vacuum at 60°C for 4 h. Subsequently, following the steps of Example 1, 80 mg of chiral ionic liquid is dissolved in 10 mL of anhydrous ethanol, added, stirred at 25°C and 500 rpm for 1 h, ethanol is removed under reduced pressure at 40°C, and then dried under vacuum at 60°C for 6 h to introduce the chiral ionic liquid outer layer network. The remaining conditions are the same as in Example 1.

[0096] Comparative Example 5:

[0097] The difference between Comparative Example 5 and Example 1 is that in the step of introducing the chiral ionic liquid outer layer network, 80 mg of chiral ionic liquid B is not added. That is, after the silver salt treatment to remove chloride and the weakly coordinating anion is fixed, the obtained solid is weighed and 10 mL of anhydrous ethanol is added and stirred at 25°C and 500 rpm for 1 h. Then, the ethanol is removed under reduced pressure at 40°C and dried under vacuum at 60°C for 6 h to obtain a sample without the introduction of the chiral ionic liquid outer layer network. The other conditions are the same as in Example 1.

[0098] Performance testing:

[0099] Test Item 1: Determination of Ruthenium Content and Ruthenium Leaching Amount After Reaction

[0100] Inductively coupled plasma atomic emission spectrometry (ICP-AES) was performed according to GB / T 23942-2009. 20.0 mg of each sample was weighed and placed in a polytetrafluoroethylene digestion vessel. 6.0 mL of hydrochloric acid (36% by mass) and 2.0 mL of nitric acid (65% by mass) were added, followed by microwave digestion (heating to 180℃ for 10 min, holding at 180℃ for 20 min). After cooling, the samples were transferred to 50.00 mL volumetric flasks and diluted to volume. 0.50 mL solutions of ruthenium standard solution were prepared. Working curves were established using a series of calibration solutions of 1.00, 2.00, 5.00, and 10.00 mg / L. The ruthenium emission line at 240.272 nm was selected for quantification to obtain the ruthenium content (wt%) of each sample. The ruthenium leaching amount was tested using the hydrogenation reaction filtrate of test item 3. 1.00 mL of filtrate was added to 1.00 mL of nitric acid for digestion for 10 min, and the volume was adjusted to 10.00 mL. The Ru concentration (mg / L) in the filtrate was then determined according to the same curve.

[0101] Test Item 2: Characterization of Specific Surface Area and Pore Structure (Gas Adsorption BET Method)

[0102] Gas adsorption BET method was performed according to GB / T 19587-2017; approximately 200 mg of each sample was weighed and placed in a sample tube, degassed at 200℃ under vacuum for 6 h, cooled to room temperature, and then subjected to nitrogen adsorption-desorption test at 77 K. The specific surface area (m²) was obtained by BET linear fitting of data with relative pressure P / P0 ranging from 0.05 to 0.30. 2 / g), and the pore volume (cm³) was calculated using the BJH method from the desorption branch. 3 (g) and average pore size (nm).

[0103] Test Item 3: Evaluation of the activity and selectivity of asymmetric hydrogenation reaction (conversion rate, selectivity, initial rate)

[0104] The heterogeneous hydrogenation of the chiral ketone acetophenone was evaluated using it as a model substrate. A 50 mL stainless steel high-pressure reactor was used, with 10.00 mmol of acetophenone and 20.0 mL of toluene added. The catalyst was weighed according to the ruthenium content measured in test item 1, ensuring a constant ruthenium amount of 0.0100 mmol added in each reaction. After sealing, the reactor was purged with hydrogen three times and then purged to 2.0 MPa. The reaction was carried out at 40 °C and 800 rpm for 2.0 h with stirring. After the reaction, the reactor was cooled, depressurized, and filtered to separate the solids. The filtrate was quantitatively analyzed by gas chromatography to calculate the acetophenone conversion rate (%) and target alcohol selectivity (%). The initial rate (mmol·g) was obtained by fitting the data from 0-30 min sampling. cat -1 ·h -1Gas chromatography analysis was performed according to the general requirements of GB / T 9722-2023. The instrument was configured and calibrated using a DB-5 capillary column (30m×0.25mm×0.25μm), with an injection port temperature of 250℃, a detector temperature of 280℃, a split ratio of 20:1, and a programmed temperature increase of 60℃ for 2 min followed by a 10℃ / min increase to 220℃ for 5 min.

[0105] Test Item 4: Determination of Enantiomeric Excess (ee) (Chiral High Performance Liquid Chromatography)

[0106] Perform high-performance liquid chromatography (HPLC) tests according to GB / T 16631-2008, using a chiral stationary phase column to achieve enantiomer separation. Take 1.00 mL of the filtrate obtained from test item three, remove the solvent under reduced pressure at 40℃, and reconstitute to 2.00 mL with n-hexane / isopropanol at a volume ratio of 90 / 10. Filter through a 0.22 μm filter membrane before injection. Use a CHIRALPAK AD-H column (250 mm × 4.6 mm, 5 μm), with a mobile phase of n-hexane / isopropanol = 90 / 10, a flow rate of 1.0 mL / min, a column temperature of 25℃, a detection wavelength of 254 nm, and an injection volume of 10 μL. Record the peak areas A of the two enantiomers. R With A S And according to ee(%)=|A R -A S | / (A R +A S Calculate by multiplying by 100.

[0107] Test item 5: Recyclability and structural retention (five cycles, activity / ee retention rate)

[0108] The hydrogenation reaction of test item 3 was used as a cycle evaluation unit, and each sample was subjected to 5 consecutive reactions. After each reaction, the solid catalyst was recovered by filtration, washed with 20 mL of toluene and 20 mL of anhydrous ethanol in sequence, dried under vacuum at 60 °C for 6 h and used for the next reaction. The conversion rate (%) and ee (%) of the 1st and 5th reactions were recorded, and the conversion rate retention rate and ee retention rate (%) were calculated.

[0109] The test results for each of the above test items are shown in Table 1.

[0110] Table 1 Summary of key parameters for intrinsic characterization and application performance testing of the examples and comparative samples

[0111]

[0112] Data Analysis:

[0113] As can be seen from the data in Table 1, the ruthenium metal catalyst supported on a carbon support prepared in this invention maintains high reactivity while achieving a high enantiomeric excess value, and retains good activity and enantioselectivity stability even after recycling. With the adjustment of (S)-BINAP, chloride ion templating treatment intensity, and silver salt dechlorination / weakly coordinating anion shaping intensity, the catalyst activity and enantioselectivity show a trend of synergistic optimization, rather than a simple trade-off. The reasons are speculated to be as follows: on the one hand, the nitrogen-deficient carbon support and the pre-confined layer of ionic liquid A jointly improve the dispersion and anchoring strength of metallic ruthenium, reducing migration and leaching during the reaction process; on the other hand, chloride ion templating and chiral diphosphine coordination construct a more ordered chiral microenvironment at the pores and interfaces, and the silver salt dechlorination and introduction of weakly coordinating anions further weaken the interference of chloride ions on active sites, making chiral induction more stable and controllable; at the same time, the secondary regulation of microenvironment polarity and local solvation structure by the outer network of ionic liquid B is conducive to maintaining stereoselectivity under high activity conditions, thus demonstrating a comprehensive improvement effect.

[0114] As can be seen from the data in Table 1 for Example 1 and Comparative Example 1, when the nitrogen-deficient carbon support formed by polydopamine-coated carbonization is missing, the reactivity, enantiomeric excess value, and cycle retention rate of the samples all show a systematic decrease, accompanied by a more pronounced ruthenium leaching trend. The main reason for this is that nitrogen-deficient sites and nitrogen-containing functional groups can provide stronger coordination anchoring and electronic regulation for ruthenium, making it easier for the active metal to form stable and dispersed effective sites. When this structure is missing, ruthenium is more prone to aggregation or weak binding desorption, leading to a simultaneous decrease in the number and stability of effective chiral sites. Therefore, the nitrogen-deficient carbon support not only improves loading stability but also provides a crucial foundation for the subsequent microenvironment constructed by ionic liquids and chiral diphosphine, laying the groundwork for subsequent multi-factor synergy.

[0115] As can be seen from the data in Table 1 for Example 1 and Comparative Examples 2 and 5, the samples may exhibit higher apparent activity or faster initial reaction rates when either the ionic liquid A pre-confined layer or the ionic liquid B outer layer network is missing, but the enantiomeric excess and cycle retention are difficult to maintain at a high level simultaneously. The main reason is that the ionic liquid A pre-confined layer helps to form a stable solvation / ion-pair environment at the pores and interfaces, inhibiting the disordered migration and site rearrangement of chiral diphosphine under reaction conditions; while the ionic liquid B outer layer network further modulates local polarity, substrate enrichment, and configuration recognition processes, making chiral induction more stable and sustained. The absence of either layer alone leads to incomplete spatial confinement and outer layer regulation of the chiral microenvironment, resulting in a difficulty in simultaneously achieving both activity and chirality, demonstrating the synergistic gain of bilayer ionic liquids in stereoselectivity and stability.

[0116] As can be seen from the data in Example 1 and Comparative Example 3 in Table 1, the enantiomeric excess and cycling stability significantly decreased when chloride ion templating treatment was absent, while the leaching tendency of metallic ruthenium increased. The main reason for this is that chloride ion templating can pre-construct repeatable ion sites and coordination environments on the carbon support surface, allowing (S)-BINAP to accumulate and orient itself more orderly near the metallic ruthenium sites, thus forming more stable chiral recognition microregions. When templating is absent, chiral diphosphine is more prone to random adsorption or local aggregation, leading to a decrease in the uniformity of effective chiral sites and structural drift during cycling. Therefore, chloride ion templating is not simply about introducing anions, but rather amplifies the effectiveness of chiral construction through a pre-organization mechanism.

[0117] As can be seen from the data in Example 1 and Comparative Example 4 in Table 1, the activity, cycle retention rate, and ruthenium resistance to leaching of the samples significantly deteriorate when silver salt dechlorination and weak coordination anion shaping steps are lacking. Even if the enantiomeric excess value does not decrease linearly in some cases, it is difficult to obtain stable and sustainable overall performance. The main reason is that residual chloride ions may continuously occupy or interfere with the coordination environment of ruthenium, making the active sites more prone to uncontrollable reconstruction during the reaction and inducing metal species to migrate from the support / ionic liquid interface into the liquid phase. Weak coordination anion shaping can reduce the binding and poisoning of metal centers by strong coordination anions, while improving the reversibility and stability of the chiral coordination structure under cycling conditions. It can be seen that chloride ion templating + silver salt dechlorination / shaping forms a synergistic link that achieves both chiral pre-organization and stable switching of the anionic environment, showing a clear 1+1 greater than 2 effect.

[0118] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A method for preparing a ruthenium-carbon hydrogenation catalyst based on chiral diphosphine ligand modification, characterized in that, Includes the following steps: (1) Preparation of carbon supports with nitrogen defects; (2) Ruthenium is loaded onto a nitrogen-defective carbon support and reduced to form ruthenium sites, thus obtaining a ruthenium-supported nitrogen-containing carbon catalyst; (3) The ruthenium-supported nitrogen-containing carbon catalyst was pre-coated with ionic liquid A; (4) Introducing chloride ions into the pre-coated confinement system to form a templated microenvironment, wherein the chloride ions are derived from imidazolium chloride-based ionic liquids; (5) Introduce chiral diphosphine ligands into the chloride ion templated microenvironment for coordination modification to obtain a ruthenium-supported nitrogen-containing carbon intermediate modified with chiral diphosphine ligands; (6) The intermediate was treated with bis(trifluoromethanesulfonyl)imide silver to obtain ruthenium-supported nitrogen-containing carbon modified with weakly coordinated anion-shaped chiral diphosphine ligand; (7) Introducing chiral ionic liquid B to construct an outer network, resulting in a ruthenium-carbon hydrogenation catalyst modified with chiral diphosphine ligands; The ionic liquid A is 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt, the imidazolium chloride ionic liquid in step (4) is 1-butyl-3-methylimidazolium chloride, and the chiral ionic liquid B is 1-ethyl-3-methylimidazolium proline salt.

2. The method for preparing a ruthenium carbon hydro- hydrogenation catalyst based on a chiral diphosphine ligand modifier according to claim 1, characterized in that, Step (1) includes: (1-1) Acid oxidation treatment of carbon materials; (1-2) Dopamine self-polymerization coating was carried out in alkaline buffer solution; (1-3) Heat treatment under an inert atmosphere to obtain a carbon support with nitrogen defects.

3. The method for preparing the ruthenium-carbon hydrogenation catalyst based on chiral diphosphine ligand modification according to claim 1, wherein the ruthenium precursor in step (2) is ruthenium chloride hydrate, and the ruthenium loading is 4 to 6 wt% based on Ru.

4. The method for preparing the ruthenium-carbon hydrogenation catalyst based on chiral diphosphine ligand modification according to claim 1, wherein in step (3), the amount of ionic liquid A is 2% to 12% of the mass of the ruthenium-supported nitrogen-containing carbon catalyst, the pre-coating confinement treatment temperature is 20 to 30°C, and the treatment time is 1 to 3 hours.

5. The method for preparing the ruthenium-carbon hydrogenation catalyst based on chiral diphosphine ligand modification according to claim 1, wherein the amount of imidazolium chloride ionic liquid used in step (4) is 1% to 6% of the mass of the pre-coated confinement material obtained in step (3), the template treatment temperature is 20 to 30°C, and the treatment time is 0.5 to 2 h.

6. The method for preparing a ruthenium-carbon hydrogenation catalyst based on chiral diphosphine ligand modification according to claim 1, wherein the chiral diphosphine ligand in step (5) is (S)-BINAP, and the molar ratio of the chiral diphosphine ligand to ruthenium is 0.05 to 0.

30.

7. The method for preparing the ruthenium-carbon hydrogenation catalyst based on chiral diphosphine ligand modification according to claim 1, wherein the silver bis(trifluoromethanesulfonyl)imide treatment in step (6) is carried out under light-protected conditions, the treatment temperature is 2-10℃, the treatment time is 10-30 min, the treatment solvent is acetonitrile, and the amount of silver bis(trifluoromethanesulfonyl)imide is 3%-10% of the mass of the intermediate.

8. The method for preparing the ruthenium-carbon hydrogenation catalyst based on chiral diphosphine ligand modification according to claim 1, wherein the amount of chiral ionic liquid B added is 2% to 8% of the mass of the solid obtained in step (6), the treatment temperature is 20 to 30°C, and the treatment time is 0.5 to 2 h.

9. A ruthenium on carbon hydrogenation catalyst modified with a chiral diphosphine ligand, characterized in that, It is obtained by the preparation method of the ruthenium-carbon hydrogenation catalyst based on chiral diphosphine ligand modification as described in any one of claims 1-8.

10. An application of the ruthenium-carbon hydrogenation catalyst based on chiral diphosphine ligand modification according to claim 9, characterized in that, Used for hydrogenation reactions of prochiral substrates.

Images