Preparation method and application of carboxymethyl-beta-cyclodextrin modified two-dimensional chiral MXene membrane

Abstract

The invention discloses a preparation method of a two-dimensional chiral MXene membrane based on carboxymethyl-beta-cyclodextrin modification and application of the two-dimensional chiral MXene membrane in the aspect of enantiomer separation. The core of the invention lies in that the cyclodextrin is stably and orderly fixed in a two-dimensional mass transfer channel through a covalent reaction between carboxymethyl of the cyclodextrin and a functional group on the surface of MXene by utilizing the molecular recognition capability of a cyclodextrin cavity; furthermore, the highly organized cyclodextrin units are used as accurate'chiral probes' and cooperate with the high permeability of an MXene channel, so that efficient screening of enantiomers is realized, and meanwhile, excellent separation selectivity and flux are guaranteed.

Description

Technical Field

[0001] This invention relates to the field of two-dimensional membrane preparation and enantiomer separation technology, and in particular to a method for preparing a two-dimensional chiral MXene membrane based on carboxymethyl-β-cyclodextrin modification and its application in enantiomer separation. Background Technology

[0002] Chiral separation is a key technology in the fields of chemistry, pharmaceuticals, and life sciences. Many important molecules in nature, such as amino acids, sugars, and the vast majority of active pharmaceutical ingredients, are chiral, meaning they cannot be perfectly superimposed on their mirror images (enantiomers), much like the relationship between a person's left and right hands. These enantiomers have almost identical physicochemical properties in achiral environments, but in living organisms, due to their chiral environment (such as enzymes and receptors), they often exhibit drastically different physiological and pharmacological activities. One enantiomer may be an effective therapeutic drug, while the other may be ineffective or even produce serious toxic side effects.

[0003] However, due to the high similarity in physicochemical properties among enantiomers except for optical rotation, their separation (i.e., chiral separation) presents a significant scientific and technological challenge. Traditional chiral separation methods, such as chiral chromatography and crystallization resolution, generally suffer from high costs, low efficiency, and difficulty in continuous large-scale production. Therefore, developing novel chiral separation technologies that are efficient, economical, and easily scalable is of paramount practical significance and urgency for improving drug purity and safety, and promoting green manufacturing and the development of fine chemicals.

[0004] However, in the field of chiral separation science, how to efficiently and selectively identify and separate enantiomers has always been one of the core technical challenges in this research. Cyclodextrins and their derivatives, as a class of high-performance chiral selectors, occupy an important position among many chiral recognition materials due to their unique truncated conical cavity structure composed of glucose units. This structure is characterized by its internal hydrophobic and external hydrophilic properties, as well as the size selectivity provided by cavities of different sizes (such as α-, β-, and γ-cyclodextrins). More importantly, the chiral environment rich in the cavity and the edge of the cone can engage in multi-dimensional intermolecular interactions with the enantiomers of the chiral molecules to be separated. This recognition mechanism does not rely on a single interaction force, but rather uses hydrophobic forces to incorporate the hydrophobic fragments of the guest into the cavity for pre-assembly, then utilizes the steric hindrance effect of the difference between the chiral center of the cyclodextrin cone and the enantiomer substituents for preliminary screening, and finally achieves the final "lock-in" through polar interactions such as hydrogen bonds of specific orientation, strength, and quantity. This multi-faceted recognition mode, characterized by size matching, hydrophobic interaction, steric effects, and synergistic hydrogen bonding, is the fundamental reason why cyclodextrins can achieve efficient enantiomeric separation, making it one of the most widely used and most thoroughly studied chiral selection host materials.

[0005] Two-dimensional transition metal carbides / nitrides (MXenes), as an emerging nanomaterial, possess the unique advantages of both structural rigidity and tunable surface functional groups. Crucially, MXene films exhibit precise sub-nanometer interlayer spacing and the inherent rigid framework of inorganic materials, providing an excellent carrier for the highly ordered and spatially stable integration of chiral recognition groups. Through controllable intercalation and surface modification strategies, homogeneous distribution of functional groups can be achieved, thereby constructing layered separation membranes with few defects and ordered structures. This characteristic makes them an ideal material platform for overcoming the current bottlenecks in enantioselective separation technology. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a two-dimensional chiral MXene membrane modified with carboxymethyl-β-cyclodextrin and its application in enantiomeric separation. The core of this technology lies in fully utilizing the molecular recognition capability of the cyclodextrin cavity. First, through the covalent reaction between its carboxymethyl group and the functional groups on the MXene surface, the cyclodextrin is stably and orderly immobilized in the two-dimensional mass transfer channel. Then, these highly organized cyclodextrin units act as precise "chiral probes," synergistically enhancing the high permeability of the MXene channel to achieve efficient enantiomeric sieving while ensuring excellent separation selectivity and throughput.

[0007] In a first aspect, the present invention provides a method for preparing a two-dimensional chiral CD-MXene membrane modified with carboxymethyl-β-cyclodextrin, specifically comprising the following steps: S1. N-hydroxysuccinimide (NHS), 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) and carboxymethyl-β-cyclodextrin (CM-β-CD) are dissolved in deionized water to undergo a carboxyl activation reaction.

[0008] S2. The activated CD solution was added to the MXene colloidal solution, and after ultrasonic treatment and thorough mixing and reaction, the chiral CD-MXene nanosheet colloidal dispersion was obtained by centrifugation and washing. S3. A chiral CD-MXene nanosheet colloidal dispersion was formed on a substrate membrane by vacuum filtration, and after drying, a two-dimensional chiral CD-MXene membrane modified with carboxymethyl-β-cyclodextrin was formed.

[0009] Preferably, in step S1, the mass ratio of NHS:EDC·HCl:CM-β-CD is 2:5:4.

[0010] Preferably, in step S1, N-hydroxysuccinimide (NHS), 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) and carboxymethyl-β-cyclodextrin (CM-β-CD) are dissolved in deionized water and stirred to react, and the stirring time is 1~2 h.

[0011] Preferably, in step S1, the reaction is carried out at room temperature and pressure, and the reaction is carried out under a protective atmosphere throughout. Preferably, a protective atmosphere such as argon, nitrogen, or helium is used.

[0012] Preferably, in step S2, the mass ratio of CM-β-CD to MXene is 4:1.

[0013] Preferably, in step S2, the centrifugation time is 0.4~0.7 h, the rotation speed is 5000~12000 r / min, and the temperature is 20~30℃.

[0014] Preferably, in step S2, the chiral CD-MXene nanosheets have a size range of 700~1500 nm.

[0015] Preferably, in step S3, the base membrane material is one or more of polyethersulfone (PES), nylon 66, and / or polyvinylidene fluoride (PVDF), and the pore size of the base membrane is 0.18-0.25 μm.

[0016] Preferably, in step S3, the film thickness is controlled to reach a range of 400~2000 nm by controlling the mass of the chiral MXene nanosheets.

[0017] Preferably, in step S3, the drying is vacuum drying, and the vacuum drying temperature is 20~40℃, and the drying time is 2~6 h.

[0018] Secondly, the present invention also discloses a two-dimensional chiral CD-MXene membrane modified with carboxymethyl-β-cyclodextrin prepared by the preparation method of the first aspect.

[0019] Thirdly, the present invention also discloses the application of a membrane prepared by the method of the first aspect or the membrane of the second aspect.

[0020] Preferably, the enantioselective separation is applied to the selective separation of racemic solutions of different concentrations under different separation conditions.

[0021] Preferably, the racemic solution is a solution of tryptophan and its derivatives.

[0022] Preferably, the concentration of the racemic substance solution is 0.1~10 mmol / L.

[0023] Preferably, the different separation conditions are U-shaped groove permeation, dead-end filtration, or cross-flow filtration.

[0024] The present invention has the following beneficial effects: The core technical advantage of the two-dimensional chiral MXene membrane prepared in this invention stems from the synergistic effect of the carboxymethyl-β-cyclodextrin cavity and covalent bonding. On one hand, the inherent hydrophobic cavity of cyclodextrin serves as a key "molecular recognition site," enabling efficient pre-enrichment and selective inclusion of target chiral molecules through size-matching effects and van der Waals forces, thus providing a foundation for chiral separation. On the other hand, the esterification reaction covalently anchors cyclodextrin to the surface and interlayer of MXene nanosheets, constructing stable, slightly swollen two-dimensional isochiral transport channels. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the stereostructure of carboxymethyl-β-cyclodextrin used in the embodiments of the present invention; Figure 2 This is a comparison of the Fourier transform infrared spectra of the MXene and the two-dimensional chiral CD-MXene films prepared in the embodiments of the present invention (MXene is Ti3C2T). x(Taking a two-dimensional chiral CD-MXene membrane as an example); Figure 3 This is a horizontal scanning electron microscope image of the two-dimensional chiral CD-MXene film prepared in the embodiments of the present invention (MXene is Ti3C2T). x (Taking a two-dimensional chiral CD-MXene membrane as an example). Figure 4 This is a cross-sectional scanning electron microscope image of the two-dimensional chiral CD-MXene film prepared in the embodiments of the present invention (MXene is Ti3C2T). x (Taking a two-dimensional chiral CD-MXene membrane as an example). Figure 5 This is a circular dichroism chromatogram of racemic solution separated by a two-dimensional chiral MXene membrane in Example 4 of the present invention (MXene is Ti3C2T). x Taking a two-dimensional chiral CD-MXene membrane as an example, and racemic solution as an example of tryptophan racemic solution. Detailed Implementation

[0027] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0028] Specific embodiments of the present invention are as follows: A method for preparing a two-dimensional chiral CD-MXene membrane modified with carboxymethyl-β-cyclodextrin, comprising: S1. N-hydroxysuccinimide (NHS), 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) and carboxymethyl-β-cyclodextrin (CM-β-CD) are dissolved in deionized water to undergo a carboxyl activation reaction.

[0029] S2. The activated CD solution was added to the MXene colloidal solution, and after ultrasonic treatment and thorough mixing and reaction, the chiral CD-MXene nanosheet colloidal dispersion was obtained by centrifugation and washing. S3. The chiral CD-MXene nanosheet colloidal dispersion is vacuum filtered onto the substrate membrane to form a homogeneous membrane, which is then vacuum dried for later use.

[0030] This invention provides the application of the two-dimensional chiral CD-MXene membrane obtained by the preparation method described above in the separation of enantiomeric compounds, specifically preferably the application of the chiral separation membrane based on two-dimensional MXene in the separation of different racemic tryptophan and its derivative solutions under different conditions.

[0031] In embodiments of the present invention, the two-dimensional MXene material includes, but is not limited to, Ti3C2T. x For example, Mo3C2Tx Nb2CT x The different conditions include, but are not limited to, U-shaped channel permeation, such as dead-end filtration and cross-flow filtration; the different racemic amino acid solutions include, but are not limited to, racemic tryptophan and its derivative solutions, such as racemic tryptophan solutions.

[0032] The enantiomeric separation application process of this invention specifically includes: fixing the two-dimensional chiral MXene membrane in a separation device; adding a racemic tryptophan and its derivative solution to the feed side; continuously stirring with a magnetic stirrer; collecting the permeate from the permeate side after diffusion; the diffusion time can be 3-80 h. Enantiomeric separation results show that, based on the two-dimensional MXene chiral separation membrane of this invention, the enantiomeric excess value (ee) of the racemic tryptophan solution can reach 92%, achieving highly selective separation of enantiomers.

[0033] To further understand the present invention, detailed examples are provided below with reference to the embodiments. The scope of protection of the present invention is not limited to the following embodiments. In the embodiments, all original reagents and materials can be obtained commercially, and experimental methods without specific experimental conditions are conventional methods and conditions well known in the art. Example 1

[0034] A method for preparing a two-dimensional chiral CD-MXene membrane modified with carboxymethyl-β-cyclodextrin (MXene is selected from Ti3C2T). x ), the detailed steps include: Preparation of a two-dimensional CD-MXene nanosheet colloidal dispersion: 20 mg of N-hydroxysuccinimide (NHS), 50 mg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl), and 40 mg of carboxymethyl-β-cyclodextrin (CM-β-CD) solid powder were dissolved in 80 ml of deionized water and stirred for 1 hour under an argon atmosphere; 5 mg of Ti3C2T was then taken... x Nanosheets were diluted with deionized water to a final volume of 40 ml. The activated solution and the diluted Ti3C2T were then mixed. x The colloidal dispersion of nanosheets was mixed and sonicated for 30 min. Then, under argon protection, the mixture was stirred at room temperature and pressure for 24 h to obtain a blend. The blend was centrifuged at 10000 r / min for 0.5 h, the supernatant was discarded, and the precipitated nanosheets were redispersed in 50 ml of deionized water to obtain Ti3C2T. x A colloidal dispersion of two-dimensional chiral CD-MXene nanosheets with a concentration of 0.1 mg / ml.

[0035] Preparation of two-dimensional chiral CD-MXene membrane: A porous PES substrate membrane was mounted on a vacuum filtration device, and Ti3C2T was added under a negative pressure of 0.1 bar. x CD-Ti3C2T at a concentration of 0.1 mg / ml x The nanosheet colloidal dispersion was deposited on the surface of a porous PES membrane to form a two-dimensional chiral CD-MXene membrane. The membrane formation time was approximately 2 seconds by vacuum filtration.

[0036] Vacuum drying: The two-dimensional chiral CD-MXene membrane is dried in a vacuum drying oven at 40°C for 6 hours, and can then be used for subsequent separation of enantiomeric solutions. Example 2

[0037] A method for preparing a two-dimensional chiral CD-MXene membrane modified with carboxymethyl-β-cyclodextrin (MXene selected from Mo3C2T) x ), the detailed steps include: Preparation of a two-dimensional CD-MXene nanosheet colloidal dispersion: 20 mg of N-hydroxysuccinimide (NHS), 50 mg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl), and 40 mg of carboxymethyl-β-cyclodextrin (CM-β-CD) solid powder were dissolved in 80 ml of deionized water and stirred for 1 hour under an argon atmosphere; 5 mg of Mo3C2T was then taken. x Nanosheets were diluted with deionized water to a final volume of 40 ml. The activated solution and the diluted Mo3C2T were then mixed. x The colloidal dispersion of nanosheets was mixed and sonicated for 30 min. Then, under argon protection, the mixture was stirred at room temperature and pressure for 24 h to obtain a blend. The blend was centrifuged at 10000 r / min for 0.5 h, the supernatant was discarded, and the precipitated nanosheets were redispersed in 50 ml of deionized water to obtain Mo3C2T. x A colloidal dispersion of two-dimensional chiral CD-MXene nanosheets with a concentration of 0.1 mg / ml.

[0038] Preparation of two-dimensional chiral CD-MXene membrane: A porous PES substrate membrane was mounted on a vacuum filtration device, and Mo3C2T was added under a negative pressure of 0.1 bar. x CD-Mo3C2T with a content of 0.1 mg / ml x The nanosheet colloidal dispersion was deposited on the surface of a porous PES membrane to form a two-dimensional chiral CD-MXene membrane. The membrane formation time was approximately 2 seconds by vacuum filtration.

[0039] Vacuum drying: The two-dimensional chiral CD-MXene membrane is dried in a vacuum drying oven at 40°C for 6 hours, and can then be used for subsequent separation of enantiomeric solutions. Example 3

[0040] Experimental separation of racemic tryptophan and its derivatives solutions using a two-dimensional chiral CD-MXene membrane (MXene selected was Ti3C2T). x Specifically, the two-dimensional chiral CD=Mxene membrane prepared in Example 1 was used, and the separated racemic solution was tryptophan. The specific implementation method is as follows: Prepare a 1 mmol / L racemic solution of tryptophan (L-tryptophan:D-tryptophan = 1:1).

[0041] A two-dimensional chiral CD-MXene membrane was fixed in the center of a detachable U-shaped diffusion tank and sealed with a rubber gasket. 40 ml of the above-mentioned racemic aqueous solution of tryptophan was added to the feed chamber, and an equal volume of deionized water was added to the permeation chamber. The feed chamber and permeation chamber were continuously stirred using a magnetic stirrer. After diffusion for 6 hours, the permeate was collected from the permeation chamber for UV spectroscopy and circular dichroism spectroscopy analysis. The analytical results are as follows: Figure 5 .

[0042] Figure 1 A schematic diagram of the stereostructure of carboxymethyl-β-cyclodextrin is described, such as... Figure 1 As shown, carboxymethyl-β-cyclodextrin is a cyclic oligosaccharide modified with carboxymethyl, which has a "conical" cavity structure that is hydrophilic on the outside and hydrophobic on the inside.

[0043] Figure 2 The image shows a comparison of the Fourier transform infrared spectra of the MXene and the two-dimensional chiral CD-MXene films prepared in the embodiments of the present invention. It can be seen that, compared with the original MXene, CD-MXene exhibits higher wavelengths at 1050 cm⁻¹. -1 The presence of COC ether bonds proves that the chiral modification was successful.

[0044] Figure 3 and Figure 4 The images shown are scanning electron microscope (SEM) images of the horizontal plane and cross-section of the two-dimensional chiral CD-MXene film prepared in the embodiments of the present invention. The SEM images show that the film surface is smooth and free of defects such as cracks; the cross-section shows that the internal nanosheets are arranged in an ordered layered manner.

[0045] Figure 5 This is a circular dichroism chromatogram of racemic tryptophan solution separated by a two-dimensional chiral CD-MXene membrane in Example 4 of the present invention.

[0046] Chiral separation results demonstrate that the two-dimensional chiral MXene membrane exhibits excellent performance in the separation of racemic tryptophan solution. Specifically, the membrane achieves a 92% enantiomeric excess (ee) within a 6-h diffusion time, exhibits preferential selective permeation for D-tryptophan, and has a flux of 0.68 mmol / m³. -2 h -1 This efficient separation stems from the following synergistic mechanism: carboxymethyl-β-cyclodextrin acts as the core chiral selector, and its hydrophobic cavity, through host-guest interactions, specifically captures the size- and polarity-matched tryptophan enantiomers, achieving initial recognition. Subsequently, this recognition process is significantly amplified within the two-dimensional confined space constructed by MXene: on the one hand, the atomically flat channel walls, through steric hindrance and interface interactions, enhance the stereomatching effect, accurately distinguishing L / D configurations.

[0047] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing a two-dimensional chiral CD-MXene membrane modified with carboxymethyl-β-cyclodextrin, characterized in that, Includes the following steps: S1. N-hydroxysuccinimide (NHS), 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) and carboxymethyl-β-cyclodextrin (CM-β-CD) are dissolved in deionized water to undergo a carboxyl activation reaction; S2. Add the activated CD solution from step S1 to the MXene colloidal solution, disperse and mix, and separate to obtain a chiral CD-MXene nanosheet colloidal dispersion; S3. A homogeneous film was formed on a base membrane by dispersing chiral CD-MXene nanosheets colloidally, and then dried to obtain a two-dimensional chiral CD-MXene film modified with carboxymethyl-β-cyclodextrin; In step S1, the mass ratio of NHS:EDC·HCl:CM-β-CD is 2:5:

4.

2. The method for preparing a carboxymethyl-β-cyclodextrin-modified two-dimensional chiral CD-MXene membrane according to claim 1, characterized in that: In step S1, the reaction is carried out at room temperature and pressure, and under inert gas protection.

3. The method for preparing a carboxymethyl-β-cyclodextrin-modified two-dimensional chiral CD-MXene membrane according to claim 1, characterized in that: In step S2, the mass ratio of CM-β-CD to MXene is 4:

1.

4. A method for preparing a carboxymethyl-β-cyclodextrin-modified two-dimensional chiral CD-MXene membrane according to any one of claims 1-3, characterized in that, In step S2, the chiral CD-MXene nanosheet colloidal dispersion is separated by centrifugation for 0.4 to 0.7 hours, at a speed of 5000 to 12000 r / min, and at a temperature of 20 to 30°C.

5. The method for preparing a carboxymethyl-β-cyclodextrin-modified two-dimensional chiral CD-MXene membrane according to claim 4, characterized in that, In step S2, the chiral CD-MXene nanosheets have a size range of 700~1500 nm.

6. A method for preparing a carboxymethyl-β-cyclodextrin-modified two-dimensional chiral CD-MXene membrane according to any one of claims 1-3, characterized in that, In step S3, the base membrane material is one or more of polyethersulfone (PES), nylon 66, and / or polyvinylidene fluoride (PVDF), and the pore size of the base membrane is 0.18-0.25 μm.

7. A method for preparing a carboxymethyl-β-cyclodextrin-modified two-dimensional chiral CD-MXene membrane according to any one of claims 1-3, characterized in that, In step S3, the film thickness is controlled to reach a range of 400~2000 nm by controlling the mass of the chiral MXene nanosheets. Preferably, in step S3, the drying is a vacuum drying at a temperature of 20~40℃ and a drying time of 2~6 h.

8. An application, characterized in that: The material is used to separate enantiomers of tryptophan and its derivatives using a membrane prepared by any one of the preparation methods described in claims 1-7.

9. An application according to claim 8, characterized in that: The application is the selective separation of racemic solutions of different concentrations under different separation conditions, wherein the racemic solution is a solution of tryptophan and its derivatives, and the concentration of the racemic substance solution is 0.1~10 mmol / L.

10. The application according to any one of claims 8-9, characterized in that: The different separation conditions are U-shaped channel permeation, dead-end filtration, and / or cross-flow filtration.

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