Pyrene-based covalent organic framework material and preparation method and application thereof

Abstract

The application provides a pyrene-based covalent organic framework material and a preparation method and application thereof. The pyrene-based covalent organic framework material is constructed by subjecting a polyamine-based pyrene monomer and a chiral pyrrole monomer to Schiff base reaction; wherein the chiral pyrrole monomer comprises a compound shown in formula I and / or a compound shown in formula II. The pyrene-based covalent organic framework material has high crystallinity and high specific surface area, is applied to catalyze asymmetric aldol condensation reaction, has high yield and good stereoselectivity, and is easy to recycle and reuse.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic asymmetric catalysis and organic porous materials, and particularly relates to a covalent organic framework material containing a pyrene functional group, a preparation method thereof, and an application thereof in catalyzing an asymmetric aldol condensation reaction. Background Art

[0002] Chiral organic synthesis is an indispensable tool for obtaining highly stereoselective chemicals, enabling the controlled and selective preparation of a wide range of chiral compounds and substances, playing an irreplaceable role in fields such as biochemistry and medicine. Chiral catalysts, which can directly control product chirality and determine their optical purity, are crucial components of chiral organic synthesis. The design and synthesis of efficient asymmetric catalysts has become a research hotspot. In 2000, Benjamin List discovered that the organic chiral small molecule proline can act as a natural chiral catalyst for the direct asymmetric aldol condensation reaction between acetone and various aldehydes, attracting widespread attention (DOI: 10.1021 / ja994280y). However, as homogeneous catalysts, the high loading and difficulty of separation of organic small molecule catalysts often limit their large-scale practical application. Compared to homogeneous catalysts, heterogeneous catalysts offer greater potential for industrial application due to their ease of recovery and rapid reuse.

[0003] Covalent organic frameworks (COFs) are a class of polymers with high crystallinity and high porosity, a well-defined pore structure, and easily designed functional groups. In recent years, COFs have been widely used in fields such as gas adsorption and separation, energy conversion, and storage. Particularly noteworthy is their insolubility in organic solvents, rich active catalytic sites, and well-developed pore structure, which give them a unique advantage in heterogeneous catalysis. However, there are few reports on the use of COFs in asymmetric catalysis. Fixing small organic molecule catalysts to the skeleton of a rigid COF can promote product separation and catalyst reuse, and it is foreseeable that this will greatly expand the application of organic frameworks in the field of chiral catalysis.

[0004] CN105622579B discloses a method for synthesizing a chiral covalent organic framework and its asymmetric catalytic application. The method comprises the following steps: synthesizing a chiral precursor, condensing the chiral precursor with trimesicaldehyde to obtain a crystallized product, washing and drying the product to obtain CCOF-LZU22-Boc, and then removing the tert-butyloxycarbonyl group of CCOF-LZU22-Boc at high temperature to obtain the final product, CCOF-LZU72. The chiral covalent organic framework CCOF-LZU72 is applied to the aldol reaction of acetone and p-nitrobenzaldehyde, achieving a product yield of 90% and an enantioselectivity of 45%. However, this method has many synthetic steps, resulting in high catalyst preparation costs.

[0005] CN111138283B discloses a method for asymmetric photocatalytic preparation of chiral aldehyde compounds using a benzoxazole-linked covalent organic framework. This method uses the benzoxazole covalent organic framework LZU90 as a photocatalyst, aldehydes and alkyl bromides as reaction substrates, and the addition of an imidazolinone chiral catalyst, solvent, and base. Under visible light illumination in an inert gas atmosphere, the target chiral aldehyde compound can be synthesized with a high enantiomeric excess (EE) of 53%-58%, with an EEE of 80%-87%. However, the catalyst prepared by this method is not suitable for catalyzing asymmetric aldol condensation reactions. Furthermore, this method relies on the addition of an additional imidazolinone chiral small molecule catalyst, resulting in a homogeneous reaction during the reaction process, making the catalyst difficult to recover and reuse.

[0006] CN114805832B discloses a chiral covalent organic framework photocatalyst containing a transition metal and a method for preparing the same. This method, under solvothermal conditions, uses polyaldehyde- and polyamine-based monomers in the presence of a chiral modifier to prepare a chiral covalent organic framework material with excellent crystallinity and porosity. Transition metal atoms can be loaded onto the framework using an impregnation method to produce a chiral covalent organic framework material containing transition metal atoms. This chiral covalent organic framework material can be used as a photocatalyst for visible light-induced water decomposition to produce hydrogen, significantly improving hydrogen production efficiency. However, the catalyst prepared by this method is not suitable for catalyzing asymmetric aldol condensation reactions.

[0007] "Stable, crystalline, porous, covalent organic frameworks as a platform for chiral organocatalysts, Nature Chemistry, 2015, 7(11): 905-912" reports a synthesis method for a series of mesoporous chiral organic framework materials. This method successfully integrates chiral pyrrolidine units into mesoporous imine covalent organic frameworks by utilizing a click reaction between acetylene and azide compounds. By adjusting the addition ratio of chiral pyrrole, the content of chiral centers in the covalent organic framework can be finely controlled. The resulting [(S)-Py]x-TPB-DMTP-COFs catalyst can be used in Michael addition reactions to obtain highly stereoselective products. However, the catalyst prepared by this method is not suitable for catalyzing asymmetric aldol condensation reactions.

[0008] “Multivariate Chiral Covalent Organic Frameworks with Controlled Crystallinity and Stability for Asymmetric Catalysis, Journal of the American Chemical Society, 2017, 139(24), 8277-8285” reports a multivariate strategy for preparing chiral covalent organic frameworks (CCOFs) with controllable crystallinity and stability. A series of CCOFs were prepared by crystallizing a mixture of triamine monomers, chiral organic catalysts and dialdehyde monomers. The organic catalyst is periodically attached to the channel wall, and its content can be systematically adjusted. The ternary CCOF exhibits relatively high crystallinity and stability. Under harsh conditions, ternary CCOFs can be used as efficient heterogeneous catalysts to catalyze a variety of chiral reactions; the catalysts prepared by this method are not suitable for catalyzing asymmetric aldol condensation reactions. Summary of the Invention

[0009] In order to solve the above problems, the purpose of the present invention is to provide a pyrene-based covalent organic framework material and its preparation method and application. The pyrene-based covalent organic framework material has high crystallinity and high specific surface area, is used to catalyze asymmetric aldol condensation reactions, has high yield, good stereoselectivity, and is easy to recycle and reuse.

[0010] In order to achieve the above-mentioned object, the present invention provides a pyrene-based covalent organic framework material, which is constructed by reacting polyaminopyrene monomers with chiral pyrrole monomers through a Schiff base reaction; wherein the chiral pyrrole monomers include the compound shown in Formula I and / or the compound shown in Formula II,

[0011]

[0012] According to a specific embodiment of the present invention, preferably, the chiral pyrrole monomer includes a compound represented by formula IV and / or a compound represented by formula V,

[0013]

[0014] According to a specific embodiment of the present invention, preferably, the polyaminopyrene monomer has a structure shown in Formula III,

[0015]

[0016] According to a specific embodiment of the present invention, preferably, the pyrene-based covalent organic framework material is selected from

[0017]

[0018] ( represents omitted repeating structural units).

[0019] The present invention also provides a method for preparing the above-mentioned pyrene-based covalent organic framework material, which comprises the following steps:

[0020] (1) preparing chiral pyrrole monomers with protecting groups;

[0021] (2) Solvothermal crystallization: Solvothermal crystallization of polyaminopyrene monomers and chiral pyrrole monomers with protective groups in the presence of acid catalysts;

[0022] (3) Preparing a pyrene-based covalent organic framework material: subjecting the product obtained in step (2) to a deprotection treatment to obtain the pyrene-based covalent organic framework material.

[0023] According to a specific embodiment of the present invention, preferably, step (1) comprises the following steps: condensing N-protected proline (e.g., R-proline) with 2,5-dibromoaniline or condensing tert-butyl 2-(aminomethyl)-1-pyrrolidinecarboxylate with 2,5-dibromobenzenesulfonyl chloride, and then reacting with 4-formylphenylboronic acid through Suzuki coupling reaction to obtain a chiral pyrrole monomer with a protective group.

[0024] According to a specific embodiment of the present invention, preferably, in step (2), the temperature of the solvent thermal crystallization is 60 to 150° C., and the time is 12-120 h.

[0025] According to a specific embodiment of the present invention, preferably, in step (2), the molar ratio of the acid catalyst to the chiral pyrrole monomer with a protecting group is 0.05-3.

[0026] According to a specific embodiment of the present invention, preferably, in step (2), the acid catalyst includes an inorganic acid and / or an organic acid, more preferably includes one or a combination of two or more of scandium trifluoromethanesulfonate, formic acid, acetic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, and p-toluenesulfonic acid.

[0027] According to a specific embodiment of the present invention, preferably, in step (2), the molar ratio of the polyaminopyrene monomer to the chiral pyrrole monomer with a protecting group is 1:(1-4), more preferably 1:(1.5-2.5).

[0028] According to a specific embodiment of the present invention, preferably, the solvent used for solvothermal crystallization includes one or a combination of two or more of 1,4-dioxane, n-butanol, benzyl alcohol, o-dichlorobenzene, mesitylene, N,N-dimethylformamide, tetrahydrofuran, and dimethyl sulfoxide, more preferably one or a combination of two or more of 1,4-dioxane, n-butanol, benzyl alcohol, o-dichlorobenzene, and mesitylene, for example, a mixed solvent of 1,4-dioxane + mesitylene, a mixed solvent of o-dichlorobenzene + n-butanol, or a mixed solvent of mesitylene + benzyl alcohol.

[0029] According to a specific embodiment of the present invention, the above preparation method comprises the following specific steps:

[0030] (1) Preparation of chiral pyrrole monomer with protecting group:

[0031] N-protected R-proline is condensed with 2,5-dibromoaniline and then reacted with 4-formylphenylboronic acid via Suzuki coupling to obtain a chiral pyrrole monomer with a protected group. The conditions for the first condensation reaction are: temperature of -20 to 30°C, time of 6 to 24 hours; the conditions for the second coupling reaction are: temperature of 60 to 120°C, time of 12 to 72 hours. The product is extracted, concentrated, purified, and dried for later use.

[0032] (2) Solvothermal crystallization:

[0033] Polyaminopyrene monomers and chiral pyrrole monomers with protective groups are subjected to solvothermal crystallization in the presence of an acid catalyst. The solvothermal crystallization conditions are: temperature of 60 to 150°C, time of 12-120 hours, and a molar ratio of acid catalyst to chiral pyrrole monomer with protective groups of 0.05-3. The product is centrifuged, washed, and dried to obtain a highly crystalline pyrene-based covalent framework material, but the covalent framework material at this stage lacks catalytic activity. The reaction temperature and time of this step vary depending on the amount of raw materials, monomers, catalyst, and solvent added.

[0034] (3) Preparation of pyrene-based covalent organic framework materials:

[0035] The pyrene-based covalent organic framework material obtained in step (2) is treated with acid under the following reaction conditions: acid concentration of 0.1-1 g / mL, temperature of -20 to 60° C., and time of 2-24 hours. The product is filtered, washed, and dried to obtain a catalytically active pyrene-based covalent organic framework material. More preferably, the acid used in the acid treatment process can be an inorganic acid and / or an organic acid, such as one or a combination of two or more of hydrochloric acid, sulfuric acid, hydrofluoric acid, trifluoroacetic acid, and trifluoromethanesulfonic acid.

[0036] The present invention also provides a method for catalyzing an asymmetric aldol condensation reaction, which uses the pyrene-based covalent organic framework material as a catalyst.

[0037] According to a specific embodiment of the present invention, preferably, the method for catalyzing the asymmetric aldol condensation reaction comprises the following steps: mixing an aromatic aldehyde, a ketone compound, an acid catalyst, a solvent and the pyrene-based covalent organic framework material, and reacting at -20 to 30° C. for 4-72 hours.

[0038] According to a specific embodiment of the present invention, preferably, after the reaction is completed, the pyrene-based covalent organic framework material is recovered.

[0039] According to a specific embodiment of the present invention, preferably, the aromatic aldehyde includes one or a combination of two or more of p-nitrobenzaldehyde, p-bromobenzaldehyde, p-trifluoromethylbenzaldehyde, and p-cyanobenzaldehyde; and the ketone compound includes one or a combination of two or more of acetone, cyclopentanone, and cyclohexanone.

[0040] According to a specific embodiment of the present invention, preferably, in the method for catalyzing an asymmetric aldol condensation reaction, the acid catalyst is one or a combination of two or more of p-nitrobenzoic acid, benzoic acid, o-nitrobenzoic acid, and trifluoroacetic acid.

[0041] According to a specific embodiment of the present invention, preferably, in the method of catalyzing the asymmetric aldol condensation reaction, the addition amount of the pyrene-based covalent organic framework material is 5%-50% of the mass of the aldehyde-based substrate (aromatic aldehyde), more preferably 10%-30%.

[0042] According to a specific embodiment of the present invention, the method for catalyzing an asymmetric aldol condensation reaction comprises the following specific steps:

[0043] (1) An aromatic aldehyde, a ketone compound, an acid catalyst, a solvent, and the prepared pyrene-based covalent organic framework material are mixed and stirred in a certain proportion. The reaction conditions are: a temperature of -20 to 30° C., and a time of 4 to 72 hours. After the reaction, the mixture is centrifuged and washed to recover the solid pyrene-based covalent organic framework material. The solution is concentrated and purified to obtain the target product.

[0044] (2) The purified target product is weighed and the yield is calculated based on the amount of aromatic aldehyde fed. The target product is tested by high performance liquid chromatography (HPLC) to obtain the enantiomeric excess value of the product.

[0045] The present invention has the following beneficial effects:

[0046] 1. The pyrene-based covalent organic framework material of the present invention has high crystallinity and high specific surface area. Its skeleton contains abundant periodically arranged chiral pyrrole groups, which can serve as active sites for the Aldol condensation reaction of ketones and aldehydes. The catalyst is easily recyclable and can produce aldol condensation products with high yield and good stereoselectivity. As a heterogeneous catalyst, it has very broad application prospects in the field of chiral molecule synthesis.

[0047] 2. The prepared chiral covalent organic framework material has a periodic diamond-shaped pore structure and a uniform pore size distribution. It is an ideal chiral organic porous material with high product stereoselectivity and is expected to be used in biology, medicine and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 Schematic diagram of the structure of pyrene-based covalent organic framework materials COF-PRI1-Boc and COF-PRI1;

[0049] Figure 2 Schematic diagram of the structure of pyrene-based covalent organic framework materials COF-PRI2-Boc and COF-PRI2;

[0050] Figure 3 X-ray diffraction spectra of pyrene-based covalent organic framework materials COF-PRI1-Boc (a) and COF-PRI1 (b);

[0051] Figure 4 X-ray diffraction spectra of pyrene-based covalent organic framework materials COF-PRI2-Boc (a) and COF-PRI2 (b);

[0052] Figure 5 Nitrogen adsorption and desorption curves of pyrene-based covalent organic framework materials COF-PRI1-Boc (a) and COF-PRI1 (b);

[0053] Figure 6 These are the nitrogen adsorption and desorption curves of pyrene-based covalent organic framework materials COF-PRI2-Boc (a) and COF-PRI2 (b). DETAILED DESCRIPTION

[0054] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be understood as limiting the scope of implementation of the present invention.

[0055] The raw materials used in the embodiment are:

[0056] Organic raw materials: N-tert-Butyloxycarbonyl-R-proline (purity 98%), isobutyl chloroformate (purity 99%), 2,5-dibromoaniline (purity 98%), tetrakis(triphenylphosphine)palladium(0) (purity 99%), 4-formylphenylboronic acid purity (98%), tert-butyl 2-(aminomethyl)-1-pyrrolidinecarboxylate (purity 98%), 2,5-dibromobenzenesulfonyl chloride (purity 98%), 1,3,6,8-tetrakis(4-aminophenyl)pyrene (purity 97%), p-nitrobenzaldehyde (purity 99%), o-nitrobenzoic acid (purity 99%).

[0057] Inorganic salts: sodium chloride (purity 99%), sodium carbonate (99%), anhydrous magnesium sulfate (99%).

[0058] Solvent: dichloromethane (purity 99%), triethylamine (purity 98%), tetrahydrofuran (purity 99%), o-dichlorobenzene (purity 99%), n-butanol (purity 99%), 1,4-dioxane (purity 99%), acetone (purity 99%), ethyl acetate (purity 99%), acetic acid (purity 98%), trifluoroacetic acid (purity 99%), n-hexane (purity 99%), and deionized water.

[0059] Preparation Example 1

[0060] This preparation example provides a pyrene-based covalent organic framework material COF-PRI1, which is prepared by the following steps:

[0061] 1. Synthesis of chiral monomer 1, as shown in the following reaction formula:

[0062]

[0063] (1) Synthesis of compound 4: N-tert-Butyloxycarbonyl-R-proline (2.50 g, 11.6 mmol) was placed in a round-bottom flask and added with 40 mL of dichloromethane, followed by the addition of isobutyl chloroformate (1.67 mL, 12.8 mmol) and triethylamine (1.80 mL, 12.8 mmol). After stirring at 0°C for 20 minutes, 2,5-dibromoaniline (3.21 g, 12.8 mmol) was added, and the reaction was heated to room temperature and stirred overnight. The reactants were washed with 1 M aqueous potassium sulfate, saturated aqueous sodium bicarbonate, and saturated aqueous sodium chloride in sequence. The organic layer was dried over anhydrous sodium sulfate and concentrated to obtain a light brown solid. The crude solid was ultrasonically dispersed in hexane, cooled to 0°C, and filtered to obtain a light yellow solid. The solid was separated by column chromatography using petroleum ether / EtOAc (v / v = 10:1) to obtain a white powder with a yield of 87%.

[0064] (2) Synthesis of chiral monomer 1: Compound 4 (0.82 mmol, 0.37 g), 4-formylphenylboronic acid (2.46 mmol, 0.37 g), sodium carbonate (6.2 mmol, 1.1 g), tetrakis(triphenylphosphine)palladium(0) (0.06 mmol, 0.12 g) and tetrahydrofuran / water (50 mL, v / v = 4 / 1) were placed in a Schlenk tube under a nitrogen atmosphere, and then heated under reflux for 24 hours; after cooling to room temperature, the mixture was filtered using diatomaceous earth, and the filtrate was poured into water. After filtration, a white solid powder was obtained. The crude product was purified by silica gel column chromatography using dichloromethane as an eluent to obtain a white powder with a yield of 90%. 1H NMR(400MHz, CDCl3)δ=10.10(2H),7.96–8.02(4H),7.75–7.85(3H),7.60(2H),7.55( 1H),7.39(1H),4.35(1H),3.10–3.29(3H),1.65–1.98(4H),1.35(9H).HRMS(ESI),m / z calcd for[C 30 H 30 N2O5+H] + 499.2228, found 499.2223.

[0065] 2. Synthesis of pyrene-based covalent organic framework material COF-PRI1, as shown in the following reaction formula:

[0066]

[0067] (1) Synthesis of pyrene-based covalent organic framework material COF-PRI1-Boc: 28.3 mg of 1,3,6,8-tetrakis(4-aminophenyl)pyrene, 50 mg of chiral monomer 1, and 3 mL of o-dichlorobenzene / n-butanol (2:1) mixed solution were added to a 10 mL pressure tube in sequence. After ultrasonic treatment for 5 min to obtain a uniform suspension, 0.2 mL of 6 M acetic acid aqueous solution was added and ultrasonicated for 5 min. After three freeze-thaw cycles, the pressure tube was sealed and heated at 120°C for 3 days. After the reaction, the solid product was centrifuged and washed with 1,4-dioxane, tetrahydrofuran, and n-hexane respectively. The obtained solid was placed in a vacuum oven at 120°C and dried for 12 hours to obtain 67 mg of yellow powder, named COF-PRI1-Boc.

[0068] (2) Synthesis of pyrene-based covalent organic framework material COF-PRI1: 50 mg of COF-PRI1-Boc powder was ultrasonically dispersed in a beaker containing 20 mL of anhydrous dichloromethane, and then 0.2 mL of trifluoroacetic acid was added. The reaction was stirred at room temperature for 12 h. The suspension after the reaction was filtered, and the filter cake was washed with tetrahydrofuran and n-hexane. The obtained solid was placed in a vacuum oven at 120°C and dried for 12 h to obtain 45 mg of yellow powder, named COF-PRI1.

[0069] Preparation Example 2

[0070] This preparation example provides a pyrene-based covalent organic framework material COF-PRI2, which is prepared by the following steps:

[0071] 1. Synthesis of chiral monomer 2, as shown in the following reaction formula:

[0072]

[0073] (1) Synthesis of compound 6: 2-(aminomethyl)-1-pyrrolidinecarboxylic acid tert-butyl ester (2 g, 10 mmol) and triethylamine (2.1 mL, 15 mmol) were added to a round-bottom flask containing 50 mL of dichloromethane, and then 2,5-dibromobenzenesulfonyl chloride (3.7 g, 11 mmol) was added. The resulting mixture was stirred at room temperature for 3 hours, then diluted with ethyl acetate and washed sequentially with 1 M aqueous hydrochloric acid solution, deionized water, and saturated aqueous sodium chloride solution. The organic extract was dried over anhydrous magnesium sulfate and concentrated under reduced pressure. The residue was purified by column chromatography (petroleum ether / ethyl acetate = 10:1, v / v) to obtain a white powder solid with a yield of 88%;

[0074] (2) Synthesis of chiral monomer 2: Compound 6 (0.82 mmol, 0.41 g), 4-formylphenylboronic acid (2.46 mmol, 0.37 g), sodium carbonate (6.2 mmol, 1.1 g), tetrakis(triphenylphosphine)palladium(0) (0.06 mmol, 0.12 g) and tetrahydrofuran / water (50 mL, v / v = 4 / 1) were placed in a Schlenk tube under a nitrogen atmosphere, and then heated under reflux for 24 hours; after cooling to room temperature, the mixture was filtered using diatomaceous earth, and the filtrate was poured into water. After filtration, a white solid powder was obtained. The crude product was purified by silica gel column chromatography using dichloromethane as an eluent to obtain a white powder with a yield of 84%. 1 H NMR(400MHz, CDCl3)δ=10.18(2H),8.02–8.10(4H),7.80–7.92(4H),7.68(2H),7.43(1H) ,3.75(1H),3.12–3.20(3H),2.85–3.10(2H),1.55–1.73(4H),1.42(9H).HRMS(ESI),m / z calcdfor[C 30 H 32 N2O6S+H] + 549.2054,found 549.2045.

[0075] 2. Synthesis of pyrene-based covalent organic framework material COF-PRI2, as shown in the following reaction formula:

[0076]

[0077] (1) Synthesis of pyrene-based covalent organic framework material COF-PRI2-Boc: 28.3 mg of 1,3,6,8-tetrakis(4-aminophenyl)pyrene, 55 mg of chiral monomer 2, and 3 mL of o-dichlorobenzene / n-butanol (2:1) mixed solution were added to a 10 mL pressure tube in sequence. After ultrasonic treatment for 5 min to obtain a uniform suspension, 0.2 mL of 6 M acetic acid aqueous solution was added and ultrasonicated for 5 min. After three freeze-thaw cycles, the pressure tube was sealed and heated at 120°C for 3 days. After the reaction, the solid product was washed by centrifugation with 1,4-dioxane, tetrahydrofuran, and n-hexane, and the obtained solid was placed in a vacuum oven at 120°C and dried for 12 hours to obtain 72 mg of yellow powder, named COF-PRI2-Boc.

[0078] (2) Synthesis of pyrene-based covalent organic framework material COF-PRI2: 50 mg of COF-PRI2-Boc powder was ultrasonically dispersed in a beaker containing 20 mL of anhydrous dichloromethane, and then 0.2 mL of trifluoroacetic acid was added. The reaction was stirred at room temperature for 12 h. The suspension after the reaction was filtered, and the filter cake was washed with tetrahydrofuran and n-hexane. The obtained solid was placed in a vacuum oven at 120°C and dried for 12 h to obtain 44 mg of yellow powder, named COF-PRI2.

[0079] The chiral pyrene-based covalent organic framework materials obtained in Preparation Example 1 and Preparation Example 2 were characterized accordingly. Figure 1 Schematic diagram of the structure of pyrene-based covalent organic framework materials COF-PRI1-Boc and COF-PRI1, Figure 2 Schematic diagram of the structure of pyrene-based covalent organic framework materials COF-PRI2-Boc and COF-PRI2, both of which have regular diamond-shaped pore structures. Figure 3 and Figure 4 is the X-ray diffraction pattern, where Figure 3 (a) corresponds to COF-PRI1-Boc, Figure 3 (b) corresponds to COF-PRI1, Figure 4 (a) corresponds to COF-PRI2-Boc, Figure 4 (b) corresponds to COF-PRI2, both of which have high crystallinity, which can be confirmed that the present invention has successfully synthesized two new pyrene-based covalent organic framework materials. Figure 5 and Figure 6 is the nitrogen isothermal adsorption-desorption curve, where Figure 5 (a) corresponds to COF-PRI1-Boc, Figure 5 (b) corresponds to COF-PRI1, Figure 6 (a) corresponds to COF-PRI2-Boc, Figure 6 Middle (b) corresponds to COF-PRI2, both of which have a higher specific surface area.

[0080] Asymmetric catalytic properties of pyrene-based covalent organic frameworks

[0081] The aldol reaction of p-nitrobenzaldehyde with acetone was used as a model reaction to investigate the asymmetric catalytic activity of two pyrene-based covalent organic frameworks, COF-PRI1 and COF-PRI2. The purified target product was weighed, and the yield was calculated based on the amount of aromatic aldehyde added. The target product was then analyzed by Agilent 1260 HPLC (equipped with a Daicel OD-H chiral column, a detection wavelength of 240 nm, a mobile phase of 9:1 hexane / isopropanol, and a flow rate of 1 mL / min) to determine its enantiomeric excess (ee) (also referred to as "enantioselectivity"). The ee value was calculated as follows:

[0082]

[0083] Where t is the retention time and S is the peak area of ​​the compound at the retention time.

[0084] Example 1

[0085] 30.2 mg of p-nitrobenzaldehyde, 3.3 mg of o-nitrobenzoic acid, and 5 mg of COF-PRI1 were added to a reaction flask. 3 mL of acetone was then added and sonicated for 5 minutes. The reaction was stirred at room temperature for 12 hours. After completion of the reaction, the solid catalyst (COF-PRI1) was recovered by centrifugation. The collected liquid was then freed of solvent using a rotary evaporator, and the residual solid was purified by silica gel column chromatography (petroleum ether / ethyl acetate = 5 / 1, v / v) to obtain the desired product in 89% yield with 58% enantioselectivity. The results are shown in Table 1.

[0086] Example 2

[0087] 30.2 mg of p-nitrobenzaldehyde, 3.3 mg of o-nitrobenzoic acid, and 5 mg of COF-PRI2 were added to a reaction flask. 3 mL of acetone was then added and sonicated for 5 minutes. The reaction was stirred at room temperature for 12 hours. After completion of the reaction, the solid catalyst (COF-PRI2) was recovered by centrifugation. The solvent was removed from the collected liquid using a rotary evaporator, and the residual solid was purified by silica gel column chromatography (petroleum ether / ethyl acetate = 5 / 1, v / v) to obtain the desired product in 92% yield with 66% enantioselectivity. The results are shown in Table 1.

[0088] Example 3

[0089] 30.2 mg of p-nitrobenzaldehyde, 3.3 mg of o-nitrobenzoic acid, and 2.5 mg of COF-PRI1 were added to a reaction flask. 3 mL of acetone was then added and sonicated for 5 minutes. The reaction was stirred at room temperature for 12 hours. After completion of the reaction, the solid catalyst (COF-PRI1) was recovered by centrifugation. The collected liquid was then freed of solvent using a rotary evaporator, and the residual solid was purified by silica gel column chromatography (petroleum ether / ethyl acetate = 5 / 1, v / v) to obtain the desired product in 82% yield with 57% enantioselectivity. The results are shown in Table 1.

[0090] Example 4

[0091] 30.2 mg of p-nitrobenzaldehyde, 3.3 mg of o-nitrobenzoic acid, and 2.5 mg of COF-PRI2 were added to a reaction flask. 3 mL of acetone was then added and sonicated for 5 minutes. The reaction was stirred at room temperature for 12 hours. After completion of the reaction, the solid catalyst (COF-PRI2) was recovered by centrifugation. The solvent was removed from the collected liquid using a rotary evaporator, and the residual solid was purified by silica gel column chromatography (petroleum ether / ethyl acetate = 5 / 1, v / v) to obtain the desired product in 85% yield with 65% enantioselectivity. The results are shown in Table 1.

[0092] Comparative Example 1

[0093] CCOF-LZU72 (13.2 mg, disclosed in CN105622579A), o-nitrobenzoic acid (5.0 mg), and acetone (1.0 mL) were added to a reaction tube and stirred at room temperature for 5 minutes. Then, p-nitrobenzaldehyde (45.3 mg) was added, and the reaction was stirred at room temperature for 4 hours. After the reaction, the liquid was collected by centrifugation or filtration and washing. The solvent was removed under reduced pressure, and the residue was purified by column chromatography (petroleum ether:ethyl acetate = 3:1, v / v) to obtain the desired product with a yield of 90% and an enantioselectivity of 45%. The results are shown in Table 1.

[0094] Table 1

[0095]

[0096] As shown in Table 1, the pyrene-based covalent organic framework material of the present invention is applied to catalyze asymmetric aldol condensation reaction with high yield and good stereoselectivity.

[0097] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make several modifications and improvements to the form and details based on the present invention, but these corresponding changes and modifications should fall within the scope of protection of the present invention.

Claims

1. A pyrene-based covalent organic framework material, which is constructed by reacting a polyaminopyrene monomer with a chiral pyrrole monomer with a protective group via a Schiff base reaction; in, The chiral pyrrole monomer with a protecting group includes the compound represented by Formula I and / or the compound represented by Formula II, wherein the N atom on the tetrahydropyrrole ring in Formula I and Formula II carries a protecting group. Formula I; Formula II; The polyaminopyrene monomer has a structure shown in formula III, Formula III.

2. The pyrene-based covalent organic framework material according to claim 1, wherein The pyrene-based covalent organic framework material is selected from and / or .

3. The method for preparing the pyrene-based covalent organic framework material according to claim 1 or 2, comprising the following steps: (1) Preparation of chiral pyrrole monomers with protecting groups; (2) Solvothermal crystallization: Solvothermal crystallization of polyaminopyrene monomers and chiral pyrrole monomers with protective groups in the presence of acid catalysts; (3) Preparing a pyrene-based covalent organic framework material: The product obtained in step (2) is subjected to a deprotection treatment to obtain the pyrene-based covalent organic framework material.

4. The preparation method according to claim 3, wherein Step (1) includes the following steps: N-protected proline is condensed with 2,5-dibromoaniline or tert-butyl 2-(aminomethyl)-1-pyrrolidinecarboxylate is condensed with 2,5-dibromobenzenesulfonyl chloride, and then reacted with 4-formylphenylboronic acid through Suzuki coupling reaction to obtain a chiral pyrrole monomer with a protective group.

5. The preparation method according to claim 3, wherein In step (2), the temperature of the solvent thermal crystallization is 60 to 150°C and the time is 12-120 h.

6. The preparation method according to claim 3, wherein In step (2), the molar ratio of the acid catalyst to the chiral pyrrole monomer with a protecting group is 0.05-3.

7. The preparation method according to claim 3, wherein In step (2), the acid catalyst includes an inorganic acid and / or an organic acid.

8. The preparation method according to claim 7, wherein The acid catalyst includes one or a combination of two or more of scandium trifluoromethanesulfonate, formic acid, acetic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, and p-toluenesulfonic acid.

9. The preparation method according to claim 3, wherein In step (2), the molar ratio of the polyaminopyrene monomer to the chiral pyrrole monomer with a protecting group is 1:(1-4).

10. The preparation method according to claim 3, wherein In step (2), the molar ratio of the polyaminopyrene monomer to the chiral pyrrole monomer with a protecting group is 1:(1.5-2.5).

11. The preparation method according to claim 3, wherein In step (2), the solvent used for solvent thermal crystallization includes one or a combination of two or more of 1,4-dioxane, n-butanol, benzyl alcohol, o-dichlorobenzene, mesitylene, N,N-dimethylformamide, tetrahydrofuran, and dimethyl sulfoxide.

12. The preparation method according to claim 3, wherein In step (2), the solvent used for solvent thermal crystallization is one or a combination of two or more of 1,4-dioxane, n-butanol, benzyl alcohol, o-dichlorobenzene, and mesitylene.

13. A method for catalyzing an asymmetric aldol condensation reaction, which uses the pyrene-based covalent organic framework material according to claim 1 or 2 as a catalyst.

14. The method according to claim 13, wherein The method for catalyzing an asymmetric aldol condensation reaction comprises the following steps: The aromatic aldehyde, the ketone compound, the acid catalyst, the solvent and the pyrene-based covalent organic framework material are mixed and reacted at -20 to 30° C. for 4 to 72 hours.

15. The method according to claim 14, wherein After the reaction is completed, the pyrene-based covalent organic framework material is recovered.

16. The method according to claim 14, wherein The aromatic aldehyde includes one or a combination of two or more of p-nitrobenzaldehyde, p-bromobenzaldehyde, p-trifluoromethylbenzaldehyde, and p-cyanobenzaldehyde; the ketone compound includes one or a combination of two or more of acetone, cyclopentanone, and cyclohexanone.

17. The method according to claim 14, wherein: The acid catalyst is one or a combination of two or more of p-nitrobenzoic acid, benzoic acid, o-nitrobenzoic acid, and trifluoroacetic acid.

18. The method according to claim 14, wherein The added amount of the pyrene-based covalent organic framework material is 5%-50% of the weight of the aldehyde-based substrate.

19. The method according to claim 14, wherein The added amount of the pyrene-based covalent organic framework material is 10%-30% of the weight of the aldehyde-based substrate.

Images