Gel clathrates for the removal of aromatic amino acids by adsorption and methods for their preparation

Abstract

The application discloses a gel inclusion compound for aromatic amino acid adsorption removal and a preparation method thereof. The method comprises the following steps: firstly, preparing a functionalized cyclodextrin through a substitution reaction; then, dissolving the functionalized cyclodextrin and a ligand compound in a benign solvent; and finally, preparing the gel inclusion compound through a solvent replacement self-assembly method. Specifically, the ligand compound ions are self-assembled with the functionalized cyclodextrin through coordination bonds to form a compound with a specific structure. After the addition of an inclusion compound molecule and a crosslinking agent, the crosslinking agent molecules replace the ligand compound ions in the original compound molecules, change the weak coordination bonds between the functionalized cyclodextrin molecules into stable covalent bonds while keeping the original specific structure, include the inclusion compound molecules, and finally form the gel inclusion compound. The gel inclusion compound prepared by the application has a porous three-dimensional network structure which can accommodate and fix guest molecules, and has adjustable mechanical properties and responsiveness to external environment, and can be used for the adsorption removal of aromatic amino acids.

Description

Technical Field

[0001] This invention belongs to the field of chemical preparation and application technology, specifically relating to a gel inclusion complex for the adsorption and removal of aromatic amino acids and its preparation method. Background Technology

[0002] Cyclodextrins are a class of cyclic oligosaccharides formed by multiple glucose units linked by α-1,4-glycosidic bonds. Based on the number of glucose units, cyclodextrins can be classified into α-cyclodextrins (6 glucose units), β-cyclodextrins (7 glucose units), and γ-cyclodextrins (8 glucose units). The unique structure of cyclodextrins gives them a hollow, cylindrical structure, which allows them to form inclusion complexes with various organic molecules through hydrophobic interactions. However, due to their hydrophilic nature and good solubility in water, cyclodextrins are unsuitable for direct use as adsorbents. Therefore, strategies such as immobilization, derivatization, and supramolecular assembly must be employed to expand their applications.

[0003] The hydroxyl groups in cyclodextrin molecules facilitate chemical modification, allowing the introduction of different functional groups through various chemical reactions to obtain modified cyclodextrin derivatives with different properties and functions. For example, etherification can introduce alkyl or other alkoxy groups onto the hydroxyl groups of cyclodextrin, thereby altering its hydrophilicity or hydrophobicity; grafting can fix polymer chains onto cyclodextrin, thus preparing polymeric materials with specific properties. Liu et al. utilized the hydrogen bonding between the small-terminal hydroxyl group of cyclodextrin and biothiols to covalently modify cyclodextrin with coumarin derivatives possessing Michael addition sites, achieving highly sensitive detection of biothiols. This demonstrates that the hydroxyl groups of cyclodextrin can not only be modified, but these modifications can also be used to construct supramolecular assemblies with specific functions. However, some modification reactions may be difficult to occur or require harsh reaction conditions, such as high temperature, strong acid, strong base, or organic solvents. These conditions may affect the structural stability of cyclodextrin or even lead to its degradation.

[0004] Solvent-displacement self-assembly is a method that induces the self-assembly of materials into ordered structures through a solvent displacement process. Its basic principle utilizes the interaction between two or more solvents, where one solvent has good solubility for the target polymer or material (called a "good solvent"), while the other solvent has poor solubility (called a "bad solvent"). By gradually increasing the proportion of the bad solvent or by directly replacing it, the material can be induced to transform from a dissolved state to a cohesive state, thereby forming a self-assembled structure with a specific morphology and structure. By adjusting the solvent ratio and addition rate, the morphology and size of the self-assembled structure can be precisely controlled. However, the solvent-displacement self-assembly process places high demands on solvent selection, ratio adjustment, and displacement rate control. The resulting self-assembled structure may not be stable enough after solvent removal, potentially requiring additional curing steps to improve its stability.

[0005] Diatomaceous earth and montmorillonite are commonly used natural adsorbent materials, characterized by high specific surface area, good adsorption performance, chemical stability, and low cost. However, they also have drawbacks, such as limited adsorption capacity requiring frequent replacement, and difficulty or high regeneration costs after adsorption saturation. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a gel inclusion complex for the adsorption and removal of aromatic amino acids and its preparation method, so as to solve the problems of the solubility of cyclodextrin in aqueous solution and the limited adsorption capacity and regeneration difficulty of natural adsorbent materials in the prior art.

[0007] To achieve the above and other related objectives, the present invention provides a method for preparing a gel inclusion complex for the adsorption and removal of aromatic amino acids, the method comprising the following steps:

[0008] Step 1: Preparation of functionalized cyclodextrin:

[0009] (A) Substitution reaction: Cyclodextrin, haloalkanes and catalyst are placed in the first reaction solvent. The hydroxyl groups of cyclodextrin and haloalkanes undergo a substitution reaction under the action of the catalyst to prepare functionalized cyclodextrin intermediates.

[0010] (B) Deprotection of protecting group: The functionalized cyclodextrin intermediate is dissolved in a deprotection reagent solution, and the protecting group is removed by reaction to prepare functionalized cyclodextrin;

[0011] Step 2, Preparation of gel inclusion complex:

[0012] (1) Dissolve the functionalized cyclodextrin and ligand compounds in a benign solvent;

[0013] (2) Solvent replacement is performed by poor solvent vapor diffusion to obtain the reaction solution;

[0014] (3) Add the target inclusion complex to the reaction solution, stir, and perform self-assembly;

[0015] (4) Add a crosslinking agent, adjust the pH of the solution to alkaline, and prepare a gel inclusion complex;

[0016] The gel inclusion complex is used for the adsorption and removal of aromatic amino acids in aqueous solution.

[0017] Optionally, in one embodiment of the present invention, the functionalized cyclodextrin has the structural formula shown in formula (Ⅰ):

[0018]

[0019] In the formula, n = 6, 7, and 8 represent α, β, and γ-cyclodextrin, respectively.

[0020] Optionally, in one embodiment of the present invention, in step (A), the cyclodextrin is one of α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin.

[0021] Optionally, in one embodiment of the present invention, in step (A), the halocarbon reagent is one or more of N-[4-(bromomethyl)phenyl]carbamate tert-butyl, N-[3-(bromomethyl)phenyl]carbamate tert-butyl, N-[2-(bromomethyl)phenyl]carbamate tert-butyl, N-[4-(chloromethyl)phenyl]carbamate tert-butyl, N-[3-(chloromethyl)phenyl]carbamate tert-butyl, and N-[2-(chloromethyl)phenyl]carbamate tert-butyl.

[0022] Optionally, in one embodiment of the present invention, in step (A), the first reaction solvent is one of tetrahydrofuran, diethyl ether, dichloromethane, N,N-dimethylformamide, and dimethyl sulfoxide.

[0023] Optionally, in one embodiment of the present invention, in step (A), the amount of the first reaction solvent is 100-200 mL / g cyclodextrin.

[0024] Optionally, in one embodiment of the present invention, in step (A), the catalyst is one or more of triethylamine, N,N-diisopropylethylamine, sodium hydride, and potassium hydride.

[0025] Optionally, in one embodiment of the present invention, in step (A), the molar mass ratio of the cyclodextrin to the haloalkane is 1:6 to 1:8.

[0026] Optionally, in one embodiment of the present invention, in step (A), the molar mass ratio of the cyclodextrin to the catalyst is 1:6 to 1:8.

[0027] Optionally, in one embodiment of the present invention, in step (A), the reaction conditions are room temperature; the reaction time is not less than 24 hours.

[0028] Optionally, in one embodiment of the present invention, in step (A), the reaction is carried out in the following order: cyclodextrin, catalyst, and haloalkane reagent are dissolved in the reaction solvent in sequence.

[0029] Optionally, in one embodiment of the present invention, in step (A), the post-processing of the reaction is to remove the reaction solvent from the reaction solution under vacuum conditions using a rotary evaporator, add acetone solution, stir and filter, and then vacuum dry the obtained functionalized cyclodextrin intermediate product at 40-45°C for no less than 24 hours.

[0030] Optionally, in one embodiment of the present invention, in step (B), the deprotection reagent solution is formed by dissolving the deprotection reagent in a second reaction solvent, wherein the deprotection reagent is a strong acid, including one or more of trifluoroacetic acid and hydrochloric acid.

[0031] Optionally, in one embodiment of the present invention, in step (B), the second reaction solvent is one or more of dichloromethane, tetrahydrofuran, dioxane, and pure water.

[0032] Optionally, in one embodiment of the present invention, in step (B), the amount of the second reaction solvent is 100-200 mL / g of the cyclopaste intermediate.

[0033] Optionally, in one embodiment of the present invention, in step (B), the molar mass ratio of the functionalized cyclodextrin intermediate to the deprotecting agent is 1:20 to 1:50.

[0034] Optionally, in one embodiment of the present invention, in step (B), the reaction conditions are 40°C and the reaction time is 24 hours.

[0035] Optionally, in one embodiment of the present invention, in step (B), the post-processing of the reaction is to remove the reaction solvent from the reaction solution under vacuum conditions using a rotary evaporator, add acetone solution, stir and filter, and then vacuum dry the obtained functionalized cyclodextrin at 40-45°C.

[0036] On the other hand, the present invention also provides a method for preparing a gel inclusion complex, the method comprising the following steps:

[0037] (1) The functionalized cyclodextrin and ligand compound are dissolved in a benign solvent, wherein the functionalized cyclodextrin is any of the functionalized cyclodextrins described above and has the structural formula shown in formula (Ⅰ):

[0038]

[0039] In the formula, n = 6, 7, and 8 represent α, β, and γ-cyclodextrin, respectively;

[0040] (2) Solvent replacement is performed by poor solvent vapor diffusion to obtain the reaction solution;

[0041] (3) Add the target inclusion complex to the reaction solution, stir, and perform self-packing. The target inclusion complex includes one or more of diatomaceous earth, Florisil, and montmorillonite.

[0042] (4) Add a crosslinking agent and adjust the pH of the solution to alkaline to prepare a gel inclusion complex.

[0043] Optionally, in one embodiment of the present invention, in step (1), the benign solvent is pure water or a buffer salt solution.

[0044] Optionally, in one embodiment of the present invention, in step (1), the ligand compound is one or more of manganese nitrate, manganese acetate, manganese sulfate, and manganese chloride.

[0045] Optionally, in one embodiment of the present invention, in step (1), the molar mass ratio of the functionalized cyclodextrin to the ligand compound is 1:6 to 1:8.

[0046] Optionally, in one embodiment of the present invention, in step (1), the solution dissolved in a benign solvent is filtered using a 0.22 μm filter membrane.

[0047] Optionally, in one embodiment of the present invention, in step (2), the undesirable solvent is one or more of methanol, ethanol, and N,N-dimethylformamide.

[0048] Optionally, in one embodiment of the present invention, the specific operation of the diffusion of the undesirable solvent vapor in step (2) includes placing a small container containing a good solvent into another large container containing an undesirable solvent, with the solution level in the small container being lower than the solution level in the large container, and then taking out the sealed large container after water bathing at 40-60°C for 6 hours and then letting it stand overnight at room temperature.

[0049] Optionally, in one embodiment of the present invention, in step (3), the target inclusion compound is one or more of diatomaceous earth, Florisil, and montmorillonite.

[0050] Optionally, in one embodiment of the present invention, in step (3), the mass ratio of the functionalized cyclodextrin to the target inclusion complex is 1:0.05 to 1:0.1.

[0051] Optionally, in one embodiment of the present invention, in step (3), the stirring rate is 500-600 rpm; the stirring time is not less than 2 hours.

[0052] Optionally, in one embodiment of the present invention, in step (4), the crosslinking agent is polyethylene glycol-modified bis(sulfosuccinimino) octanoate.

[0053] Optionally, in one embodiment of the present invention, in step (4), the amount of PEG in the polyethylene glycol-modified bis(sulfosuccinimino) octanoate is 3, 5, or 9.

[0054] Further optionally, in one embodiment of the present invention, in step (4), the amount of PEG in the polyethylene glycol-modified bis(sulfosuccinimino) octanoate is 3.

[0055] Further optionally, in one embodiment of the present invention, in step (4), the amount of PEG in the polyethylene glycol-modified bis(sulfosuccinimino) octanoate is 5.

[0056] Further optionally, in one embodiment of the present invention, in step (4), the amount of PEG in the polyethylene glycol-modified bis(sulfosuccinimino) octanoate is 9.

[0057] Optionally, in one embodiment of the present invention, in step (4), the molar mass ratio of the functionalized cyclodextrin to the crosslinking agent is 1:6 to 1:8.

[0058] Optionally, in one embodiment of the present invention, in step (4), the pH value of the solution is 7 to 8.5.

[0059] Optionally, in one embodiment of the present invention, in step (4), the reaction time is not less than 8 hours.

[0060] Optionally, in one embodiment of the present invention, in step (4), the post-processing of the reaction is to centrifuge and filter the reaction solution after the reaction is completed, add 20% ethanol solution to the obtained gel inclusion complex, stir and filter, and freeze-dry the obtained gel inclusion complex.

[0061] On the other hand, the present invention also provides a gel inclusion complex prepared by any of the methods described above.

[0062] Optionally, in one embodiment of the present invention, the gel inclusion complex is formed by a cross-linked functionalized cyclodextrin polymer containing the target inclusion complex, wherein the cross-linked functionalized cyclodextrin polymer is the cross-linked functionalized cyclodextrin polymer described above.

[0063] Optionally, in one embodiment of the present invention, the crosslinked cyclodextrin polymer is formed by crosslinking polymerization of functionalized cyclodextrin, wherein the functionalized cyclodextrin is any of the functionalized cyclodextrins described above or functionalized cyclodextrins prepared by any of the methods described above, and the crosslinked functionalized cyclodextrin polymer has the structural formula shown in formula (II) below:

[0064]

[0065] In the formula, n is 6, 7, or 8.

[0066] Optionally, in one embodiment of the present invention, the target inclusion compound includes one or more of diatomaceous earth, Florisil, and montmorillonite.

[0067] On the other hand, the present invention provides an application of a gel inclusion complex, wherein the gel inclusion complex is as described above, or a gel inclusion complex prepared by any of the methods described above, the application comprising using the gel inclusion complex for the adsorption and removal of aromatic amino acids in aqueous solution.

[0068] Optionally, in one embodiment of the present invention, the aromatic amino acid is one or a combination of phenylalanine, tyrosine, and tryptophan.

[0069] Optionally, in one embodiment of the present invention, the aqueous solution of the aromatic amino acid has an acidic pH, more preferably a weakly acidic pH.

[0070] As described above, the gel inclusion complex of the present invention for the adsorption and removal of aromatic amino acids has the following beneficial effects:

[0071] This method prepares functionalized cyclodextrins through substitution reactions. The reaction conditions are mild and do not damage the structure of the cyclodextrin itself. The functional groups provide the cyclodextrins with higher reactivity, physicochemical properties, and application range. The gel inclusion complexes prepared by solvent displacement self-assembly exhibit good stability in aqueous solutions and have a porous three-dimensional network structure that can accommodate and immobilize guest molecules. They also have tunable mechanical properties and responsiveness to the external environment, which improves the adsorption capacity. They can be rapidly regenerated and reused and can be used for the adsorption and removal of aromatic amino acids. Attached Figure Description

[0072] Figure 1 This is a schematic diagram of the molecular structures of α, β, and γ-cyclodextrins.

[0073] Figure 2 A schematic diagram of the reaction equation for the preparation of functionalized cyclodextrins.

[0074] Figure 3 This is a schematic diagram of the reaction equation for cross-linked functionalized cyclodextrin.

[0075] Figure 4 This is a schematic diagram of the synthesis process of gel inclusion compounds.

[0076] Figure 5 This is an electron micrograph of the gel inclusion complex. Detailed Implementation

[0077] Given that cyclodextrins are hydrophilic and have good solubility in water, they are unsuitable for direct use as adsorbents. Therefore, strategies such as immobilization, derivatization, and supramolecular assembly must be employed to expand their applications. This invention provides a method for preparing gel inclusion compounds, such as... Figure 4 As shown, gel inclusion complexes are prepared via solvent displacement self-assembly. First, functionalized cyclodextrins are prepared via a substitution reaction. Then, the functionalized cyclodextrins and ligand compounds are dissolved in a benign solvent, and solvent displacement occurs via diffusion of unfavorable solvent vapors. The ligand compound ions autonomously assemble with the functionalized cyclodextrins through coordination bonds to form compounds with specific structures. Upon addition of inclusion complex molecules and a cross-linking agent, the cross-linking agent molecules replace the ligand compound ions in the original compound molecules, transforming the weak coordination bonds between the functionalized cyclodextrin molecules into stable covalent bonds while maintaining the original specific structure, thus encapsulating the inclusion complex molecules and ultimately forming a gel inclusion complex.

[0078] The method includes the following steps:

[0079] (a) Preparation of functionalized cyclodextrins, such as Figure 2 As shown

[0080] S1. Functionalized cyclodextrin intermediates were prepared by reacting the alcohol hydroxyl groups of cyclodextrin with haloalkanes under the action of a catalyst.

[0081] S2. Functionalized cyclodextrin intermediates are deprotected under certain conditions to prepare functionalized cyclodextrins.

[0082] (II) Preparation of gel inclusion complexes formed by cross-linked functionalized cyclodextrins, such as Figure 3 , 4 As shown

[0083] S3. By using a solvent displacement self-assembly method, a suitable benign solvent is selected to fully dissolve the functionalized cyclodextrin and ligand compounds, and to ensure that there are no undissolved solid particles in the solution.

[0084] S4. Select a suitable unsuitable solvent, heat it to diffuse the unsuitable solvent vapor, slowly immerse it in a good solvent, and let it stand overnight.

[0085] S5. Add the target inclusion complex and stir at a constant speed to ensure that it is evenly distributed in the solution. The compounds in the solution will begin to self-assemble around the target inclusion complex.

[0086] S6. Add a cross-linking agent to the above solution, adjust the pH value of the solution, and prepare a gel inclusion complex.

[0087] (III) Gel inclusion complexes are used for the adsorption and removal of aromatic amino acids in aqueous solutions.

[0088] Optionally, in one embodiment, in step S1, the cyclodextrin is one or more of α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin, and the structural formula of the cyclodextrin is as follows: Figure 1 As shown.

[0089] Optionally, in one embodiment, in step S1, the halocarbon reagent is one or more of N-[4-(bromomethyl)phenyl]carbamate tert-butyl, N-[3-(bromomethyl)phenyl]carbamate tert-butyl, N-[2-(bromomethyl)phenyl]carbamate tert-butyl, N-[4-(chloromethyl)phenyl]carbamate tert-butyl, N-[3-(chloromethyl)phenyl]carbamate tert-butyl, and N-[2-(chloromethyl)phenyl]carbamate tert-butyl.

[0090] Optionally, in one embodiment, in step S1, the reaction is carried out in a first reaction solvent, which is one or more of tetrahydrofuran, diethyl ether, dichloromethane, N,N-dimethylformamide, and dimethyl sulfoxide.

[0091] Optionally, in one embodiment of the present invention, in step (A), the amount of the first reaction solvent is 100-200 mL / g cyclodextrin.

[0092] Optionally, in one embodiment, in step S1, the catalyst is one or more of triethylamine, N,N-diisopropylethylamine, sodium hydride, and potassium hydride.

[0093] Optionally, in one embodiment, in step S1, the molar mass ratio of the cyclodextrin to the haloalkane reagent is 1:6 to 1:8.

[0094] Optionally, in one embodiment, in step S1, the molar mass ratio of the cyclodextrin catalyst is 1:6 to 1:8.

[0095] Optionally, in one embodiment, in step S1, the reaction feed order is that cyclodextrin, catalyst, and haloalkane reagent are dissolved in the first reaction solvent in sequence.

[0096] Optionally, in one embodiment, the reaction condition in step S1 is room temperature.

[0097] Optionally, in one embodiment, the reaction time in step S1 is not less than 24 hours.

[0098] Optionally, in one embodiment, in step S1, the post-processing process involves removing the reaction solvent from the reaction solution under vacuum using a rotary evaporator after the reaction is completed, adding acetone solution, stirring and filtering, and then vacuum drying the obtained functionalized cyclodextrin intermediate at 40-45°C for no less than 24 hours.

[0099] Optionally, in one embodiment, in step S2, the deprotecting reagent solution is formed by dissolving the deprotecting reagent in a second reaction solvent.

[0100] Optionally, in one embodiment, in step S2, the deprotecting agent is a strong acid, including one or more of trifluoroacetic acid and hydrochloric acid.

[0101] Optionally, in one embodiment, in step S2, the second reaction solvent is one or more of dichloromethane, tetrahydrofuran, dioxane, and pure water.

[0102] Optionally, in one embodiment of the present invention, in step S2, the amount of the second reaction solvent is 100-200 mL / g of the cyclopaste intermediate.

[0103] Optionally, in one embodiment, in step S2, the molar mass ratio of the functionalized cyclodextrin intermediate to the deprotecting agent is 1:20 to 1:50.

[0104] Optionally, in one embodiment, the reaction condition in step S2 is 40°C.

[0105] Optionally, in one embodiment, the reaction time in step S2 is 24 hours.

[0106] Optionally, in one embodiment, in step S2, the post-processing of the reaction involves removing the reaction solvent from the reaction solution under vacuum using a rotary evaporator, adding acetone solution, stirring, and filtering, and then vacuum drying the obtained functionalized cyclodextrin at 40-45°C.

[0107] Optionally, in one embodiment, in step S3, the benign solvent is pure water or a buffer salt solution; the ligand compound is one or more of manganese nitrate, manganese acetate, manganese sulfate, and manganese chloride.

[0108] Optionally, in one embodiment, in step S3, the molar mass ratio of the functionalized cyclodextrin to the ligand compound is 1:6 to 1:8.

[0109] Optionally, in one embodiment, in step S3, the solution dissolved in a benign solvent is filtered using a 0.22 μm filter membrane.

[0110] Optionally, in one embodiment, in step S4, the undesirable solvent is one or more of methanol, ethanol, and N,N-dimethylformamide.

[0111] Optionally, in one embodiment, in step S4, the diffusion of the undesirable solvent vapor is specifically operated by placing a small container containing a good solvent into another large container containing an undesirable solvent, wherein the solution level in the small container is lower than the solution level in the large container, the sealed large container is placed in a water bath at 40-60°C for 6 hours, then removed and left to stand overnight at room temperature.

[0112] Optionally, in one embodiment, in step S5, the substance to be encapsulated is one or more of diatomaceous earth, Florisil, and montmorillonite.

[0113] Optionally, in one embodiment, in step S5, the mass ratio of the functionalized cyclodextrin to the target inclusion complex is 1:0.05 to 1:0.1.

[0114] Optionally, in one embodiment, in step S5, the stirring speed is 500-600 rpm and the stirring time is not less than 2 hours.

[0115] Optionally, in one embodiment, in step S6, the crosslinking agent is polyethylene glycol-modified bis(sulfosuccinimino) octanoate. The number of PEG molecules in the crosslinking agent can vary, all of which are within the scope of protection of this invention. In some examples of this invention, the number of PEG molecules is 3, 5, or 9.

[0116] Optionally, in one embodiment, in step S6, the molar mass ratio of the functionalized cyclodextrin to the crosslinking agent is 1:6 to 1:8.

[0117] Optionally, in one embodiment, in step S6, the solution pH is 7 to 8.5.

[0118] Optionally, in one implementation, the reaction time in step S6 is not less than 8 hours.

[0119] Optionally, in one embodiment, in step S6, the post-processing of the reaction involves centrifuging and filtering the reaction solution after the reaction is completed, adding 20% ​​ethanol solution to the obtained gel inclusion complex, stirring and filtering, repeating this process three times, and then freeze-drying the obtained gel inclusion complex.

[0120] The present invention will be further described below with reference to the accompanying drawings and embodiments. The present invention can be better understood from the following embodiments. However, those skilled in the art will readily understand that the specific material ratios, process conditions, and results described in the embodiments are for illustrative purposes only and should not, and will not, limit the present invention as described in detail in the claims.

[0121] Example 1: Preparation of gel inclusion complex

[0122] (1) Accurately weigh 1.0 g (0.77 mmol) of γ-cyclodextrin and place it in a round-bottom flask containing 150 mL of N,N-dimethylformamide. Add 1.49 g (6.17 mmol) of N-[4-(chloromethyl)phenyl]carbamate tert-butyl ester and 1.07 mL (6.17 mmol) of N,N-diisopropylethylamine sequentially and stir until completely dissolved. React at room temperature for 24 hours. Remove the solvent from the solution under vacuum, add 200 mL of acetone to the flask, stir, and filter. Repeat this process three times. Dry the obtained functionalized cyclodextrin intermediate in a vacuum drying oven at 45 °C for 24 hours.

[0123] (2) Place all the dried functionalized cyclodextrin intermediates into a round-bottom flask containing 50 mL of dioxane, add 5 mL (38.5 mmol) of trifluoroacetic acid, stir and heat the solution to 40 °C. After reacting for 24 hours, add 50 mL of acetone to the flask, stir and filter. Repeat three times. The obtained functionalized cyclodextrin is dried in a vacuum drying oven at 45 °C for 24 hours.

[0124] (3) Accurately weigh 1.0 g (0.77 mmol) of functionalized cyclodextrin and 1.07 g (6.17 mmol) of manganese acetate, dissolve them in 100 mL of pure water, and filter them into a clean 250 mL beaker using a 0.22 μm needle filter; place the beaker in another large beaker containing about 100-200 mL of methanol, seal it, and place it in a water bath at 50 °C for 6 hours. Then remove it and let it stand overnight at room temperature.

[0125] (4) Take out the small beaker and add 0.05 g of diatomaceous earth. Stir at 500 rpm for 2 hours, then add 3.28 g (6.17 mmol) of polyethylene glycol-modified bis(sulfosuccinimino) octanoate. Adjust the pH of the solution to between 7.5 using dilute sodium hydroxide solution and stir at room temperature for 8 hours. Centrifuge and filter the solution after the reaction is complete. Add 20% ethanol solution to the collected gel inclusion complex, stir and filter. Repeat this process three times. After freeze-drying, the gel inclusion complex is obtained.

[0126] The electron microscopy images of the obtained gel inclusion complex are as follows: Figure 5As shown in the figure, this method prepares functionalized cyclodextrins through substitution reactions. The reaction conditions are mild and do not damage the structure of the cyclodextrin itself. The functional groups provide the cyclodextrin with higher reactivity, physicochemical properties, and application range. The gel inclusion complex prepared by solvent displacement self-assembly has good stability in aqueous solution and has a porous three-dimensional network structure that can accommodate and immobilize guest molecules. It also has adjustable mechanical properties and responsiveness to the external environment, which improves the adsorption capacity. It can be rapidly regenerated and reused and can be used for the adsorption and removal of aromatic amino acids.

[0127] The adjustable mechanical properties refer to the different structural properties of gel polymers formed after using different crosslinking agents (with varying amounts of PEG); the response to the external environment refers to the ability to change its adsorption effect and capacity for amino acids by adjusting the pH value. Specifically, the present invention is described in detail using the following Examples 2, 3, and 4.

[0128] Example 2: The effect of different crosslinking agents on the regulation of mechanical properties

[0129] Experimental Methods: Following the same preparation method as in Example 1, gel inclusion complexes were prepared using γ-cyclodextrin with different amounts of PEG-crosslinking agent bis(sulfosuccinimino) octanoate (n = 3, 5, 9), and named CDGI-3, CDGI-5, and CDGI-9, respectively. The samples were immersed in a 25°C constant temperature water bath until swelling equilibrium was reached, and then the surface moisture was blotted dry with filter paper. The test sample was a cylinder approximately 30 mm in diameter and 50 mm in height, subjected to vertical compression at a rate of 2 mm / min, and the measurement was repeated three times.

[0130] Experimental Results and Analysis: All three groups of samples (CDGI-3, CDGI-5, and CDGI-9) underwent 80% strain compression before fracture, exhibiting high compressibility and elasticity. The fracture stresses of CDGI-3, CDGI-5, and CDGI-9 were 71 kPa, 59 kPa, and 50 kPa, respectively. The elastic moduli of CDGI-3, CDGI-5, and CDGI-9 were 85 kPa, 67 kPa, and 61 kPa, respectively. This indicates that the amount of PEG affects the mechanical properties of the gel inclusion complex. Different amounts of PEG can be selected as crosslinking agents to adjust the mechanical properties of the gel inclusion complex as needed.

[0131] Example 3: Gel inclusion complex for the adsorption and removal of aromatic amino acids

[0132] Three aromatic amino acids were selected: phenylalanine (Phe), tyrosine (Tyr), and tryptophan (Trp). Under conditions of 25°C, the amounts of the gel inclusion complex obtained in Example 1 were 5 mg / mL, 10 mg / mL, and 20 mg / mL, respectively. The concentrations of Phe, Tyr, and Trp solutions were 2 mg / mL, 0.2 mg / mL, and 0.2 mg / mL, respectively (Tyr and Trp had relatively high responses on the instrument, so their concentrations were reduced to prevent instrument overload). With the instant of adsorbent addition as 0, the UV absorbance of the solutions before and after adsorption was measured at 30 s, 1 min, 2 min, 5 min, 10 min, and 30 min, respectively, and the removal rate was calculated.

[0133] Table 1. Investigation of Phe removal rate

[0134]

[0135] Table 2. Investigation of Tyr Removal Rate

[0136]

[0137]

[0138] Table 3. Investigation of Trp removal rate

[0139]

[0140] The results showed that the gel inclusion complex had a very rapid adsorption rate for the three aromatic amino acids, and the higher the concentration of the gel inclusion complex, the higher the removal rate. As the adsorption time of the gel inclusion complex increased, the adsorption gradually reached an equilibrium state.

[0141] Example 4: Comparative analysis of the maximum adsorption capacity, pH response, and cyclic adsorption experiments of gel inclusion complexes and other adsorbents for aromatic amino acids.

[0142] (1) Maximum adsorption capacity

[0143] Three aromatic amino acids were selected: phenylalanine (Phe), tyrosine (Tyr), and tryptophan (Trp). Solutions of various concentrations were prepared (Phe, Tyr, and Trp solutions had concentrations of 2 mg / mL, 0.2 mg / mL, and 0.2 mg / mL, respectively). At 25 °C, the gel inclusion complex and other adsorbents were kept at a fixed dosage of 20 mg / mL, and the adsorption time was fixed at 30 min. The UV absorbance of the solutions before and after adsorption was measured, and the maximum adsorption capacity was calculated.

[0144] Table 4. Analysis and Comparison of Maximum Adsorption Capacity

[0145]

[0146] Note: γ-cyclodextrin and functionalized cyclodextrin are soluble in water, so they cannot adsorb aromatic amino acids in aqueous solutions; in addition, non-functionalized cyclodextrin cannot construct gels through the same reaction.

[0147] The results showed that the gel inclusion complex had a significantly higher adsorption capacity for the three aromatic amino acids in aqueous solution than other adsorbents.

[0148] (3) Adsorption response under different pH conditions

[0149] Three aromatic amino acids were selected: phenylalanine (Phe), tyrosine (Tyr), and tryptophan (Trp). Solutions of various concentrations were prepared (Phe, Tyr, and Trp solutions had concentrations of 2 mg / mL, 0.2 mg / mL, and 0.2 mg / mL, respectively), with initial pH values ​​of 5.8, 5.2, and 6.0. The pH values ​​were adjusted to 9 and 10 with dilute sodium hydroxide solution, and then adjusted back to the initial pH value with dilute hydrochloric acid solution. Under conditions of 25℃, the amount of gel inclusion complex was kept constant at 20 mg / mL, and the adsorption time was fixed at 30 min. The UV absorbance of the solutions before and after adsorption was measured, and the adsorption capacity of the gel inclusion complex for aromatic amino acids in solutions with unadjusted pH, pH values ​​of 9 and 10, and pH values ​​adjusted back to the initial pH value was compared.

[0150] Table 5 Adsorption response under different pH conditions

[0151]

[0152] The results showed that after adjusting the pH of the amino acid solution to 9 and 10, the gel inclusion complex had almost no adsorption capacity for the three aromatic amino acids in the aqueous solution. However, when the pH was adjusted back to the initial value with dilute hydrochloric acid solution, the gel inclusion complex exhibited excellent adsorption capacity for the three aromatic amino acids in the aqueous solution. Therefore, it can be considered that the gel inclusion complex has a significant adsorption response to changes in the pH of the solution environment and has excellent adsorption capacity in non-alkaline acidic environments, especially under weakly acidic conditions.

[0153] (3) Cyclic Adsorption Experiment

[0154] A 0.2 mg / mL tryptophan standard solution was used. At 25℃, the gel inclusion complex was applied at a concentration of 20 mg / mL. After adsorption for 30 min, the solution was centrifuged, and the UV absorbance before and after adsorption was measured. The gel inclusion complex containing tryptophan was washed three times with 5% ethanol solution, dried at 80℃, and the adsorption experiment was repeated. The removal rate of the gel inclusion complex after multiple cycles of adsorption and desorption was compared. The same method was used to determine the removal rates of diatomaceous earth and gels without diatomaceous earth inclusion.

[0155] Table 6 Cyclic Adsorption Experiments of Gel Inclusion Compounds

[0156]

[0157] The results showed that the gel inclusion complex could be rapidly eluted by 5% ethanol solution after adsorbing tryptophan, and the removal rate of tryptophan did not decrease significantly after five repeated adsorption-desorption cycles. The removal rate of tryptophan from the gel without diatomaceous earth inclusion was significantly lower than that from the gel inclusion complex. When diatomaceous earth was used directly for tryptophan adsorption, the removal rate decreased significantly after repeated use. Therefore, it is believed that the gel inclusion complex can be repeatedly used for the adsorption of aromatic amino acids.

[0158] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a gel inclusion complex for the adsorption and removal of aromatic amino acids, characterized in that, The method includes the following steps: Step 1: Preparation of functionalized cyclodextrin: (A) Substitution reaction: Cyclodextrin, haloalkanes and catalysts are placed in the first reaction solvent. The hydroxyl groups of cyclodextrin react with haloalkanes under the action of catalysts to prepare functionalized cyclodextrin intermediates. (B) Deprotection of protecting group: The functionalized cyclodextrin intermediate is dissolved in a deprotection reagent solution, and the protecting group is removed by reaction to prepare functionalized cyclodextrin; Step 2, Preparation of gel inclusion complex: (1) Dissolve the functionalized cyclodextrin and ligand compound in a benign solvent; The benign solvent is pure water or a buffer salt solution; The ligand compound is one or more of manganese nitrate, manganese acetate, manganese sulfate, and manganese chloride; (2) Solvent replacement is performed by diffusion of poor solvent vapor to obtain the reaction solution; The undesirable solvent is one or more of methanol, ethanol, and N,N-dimethylformamide; (3) Add the target inclusion compound to the reaction solution, stir, and perform self-assembly; The target inclusion compound is one or more of diatomite, Florisil, and montmorillonite. (4) Add a cross-linking agent and adjust the pH of the solution to alkaline to prepare a gel inclusion complex; The gel inclusion complex is used for the adsorption and removal of aromatic amino acids in aqueous solution.

2. The method according to claim 1, characterized in that, The functionalized cyclodextrin has the following structural formula (Ⅰ): Equation (I) In the formula, n=6, 7, 8 represent α, β, and γ-cyclodextrin, respectively.

3. The method according to claim 1, characterized in that, In step (A), the cyclodextrin is one of α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin; and / or The halocarbon reagent is one or more of the following: N-[4-(bromomethyl)phenyl]carbamate, N-[3-(bromomethyl)phenyl]carbamate, N-[2-(bromomethyl)phenyl]carbamate, N-[4-(chloromethyl)phenyl]carbamate, N-[3-(chloromethyl)phenyl]carbamate, and N-[2-(chloromethyl)phenyl]carbamate; and / or The first reaction solvent is one of tetrahydrofuran, diethyl ether, dichloromethane, N,N-dimethylformamide, and dimethyl sulfoxide.

4. The method according to claim 1, characterized in that, In step (A), the amount of the first reaction solvent used is 100-200 mL / g cyclodextrin; The catalyst is one or more of triethylamine, N,N-diisopropylethylamine, sodium hydride, and potassium hydride; and / or The molar ratio of the cyclodextrin to the haloalkane reagent is 1:6 to 1:8; and / or The molar mass ratio of the cyclodextrin to the catalyst is 1:6 to 1:8; and / or The reaction conditions are room temperature; the reaction time is not less than 24 hours; and / or The order of reaction is as follows: cyclodextrin, catalyst, and haloalkane reagent are dissolved sequentially in the first reaction solvent; and / or The post-reaction process involves removing the reaction solvent from the reaction solution under vacuum using a rotary evaporator, adding acetone solution, stirring, and filtering. The resulting functionalized cyclodextrin intermediate is then vacuum dried at 40-45°C for at least 24 hours.

5. The method according to claim 1, characterized in that, In step (B), the deprotecting reagent solution is formed by dissolving the deprotecting reagent in a second reaction solvent, wherein the deprotecting reagent is a strong acid, including one or more of trifluoroacetic acid and hydrochloric acid; and / or The second reaction solvent is one or more of dichloromethane, tetrahydrofuran, dioxane, and pure water; and / or The amount of the second reaction solvent used is 100-200 mL / g mL / g cyclic paste intermediate; and / or The molar ratio of the functionalized cyclodextrin intermediate to the deprotecting agent is 1:20 to 1:50; and / or The reaction conditions are 40°C; the reaction time is 24 hours; and / or The post-reaction process involves removing the reaction solvent from the reaction solution under vacuum using a rotary evaporator, adding acetone solution, stirring, and filtering. The resulting functionalized cyclodextrin is then vacuum dried at 40-45°C.

6. The method according to claim 1, characterized in that, In step (1), the molar mass ratio of the functionalized cyclodextrin to the ligand compound is 1:6 to 1:8; and / or The solution dissolved in a benign solvent was filtered through a 0.22 μm filter membrane. In step (2), the specific operation of the diffusion of the undesirable solvent vapor includes placing a small container containing a good solvent into another large container containing an undesirable solvent, with the liquid level in the small container being lower than the liquid level in the large container, and then taking out the sealed large container after water bathing at 40~60℃ for 6 hours and then letting it stand overnight at room temperature.

7. The method according to claim 1, characterized in that, In step (3), the mass ratio of the functionalized cyclodextrin to the target inclusion complex is 1:0.05 to 1:0.1; and / or The stirring rate is 500-600 rpm; the stirring time is not less than 2 hours.

8. The method according to claim 1, characterized in that, In step (4), the crosslinking agent is polyethylene glycol-modified bis(sulfosuccinimino) octanoate; and / or The number of PEGs in the polyethylene glycol-modified bis(sulfosuccinimide) octanoate is 3, 5, or 9; and / or The molar ratio of the functionalized cyclodextrin to the crosslinking agent is 1:6 to 1:8; and / or The solution has a pH of 7-8.5; and / or The reaction time is not less than 8 hours; and / or The post-processing of the reaction involves centrifuging and filtering the reaction solution after the reaction is completed, adding 20% ​​ethanol solution to the obtained gel inclusion complex, stirring and filtering, and then freeze-drying the obtained gel inclusion complex.

9. A gel inclusion complex for the adsorption and removal of aromatic amino acids prepared by the method according to any one of claims 1-8.

10. An application of a gel inclusion complex, characterized in that, The gel inclusion complex is the gel inclusion complex as described in claim 9, and the gel inclusion complex is used for the adsorption and removal of aromatic amino acids in aqueous solution; The aromatic amino acid is one or a combination of phenylalanine, tyrosine, and tryptophan; and / or the aqueous solution of the aromatic amino acid has an acidic pH.

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