A chiral composite membrane and its preparation method and application

Abstract

The present application relates to the field of membrane separation technology, in particular to a kind of synergic assembly chiral composite membrane and its preparation method and application.The method comprises: providing graphene oxide and acyl chloride single-walled carbon nanotube as carrier;With thiol-containing chiral compound as chiral ligand, respectively by click chemistry and amidation reaction modification on the surface of graphene oxide and single-walled carbon nanotube oxide, functionalized modification chiral material is prepared;In the presence of reducing agent, make two through self-assembly composite, form the two-component chiral composite material with intercalation structure, then through purification, film forming chiral composite membrane is obtained.The composite membrane is driven by concentration difference, through the synergistic effect of specific adsorption and size sieving, the efficient selective separation of target enantiomer is realized, the trade-off between selectivity and flux in traditional chiral separation membrane is effectively overcome, and the chiral separation efficiency is significantly improved.

Description

Technical Field

[0001] This invention relates to the field of membrane separation technology, specifically to a co-assembled chiral composite membrane, its preparation method, and its application. Background Technology

[0002] Chiral compounds are the basis of most active pharmaceutical ingredients, and their different enantiomers can exhibit significantly different or even completely opposite pharmacological activities. L-amino acids, as key building blocks of living systems, have their chiral purity directly affecting the structure and function of biomolecules. Therefore, developing efficient and precise chiral separation techniques for chiral amino acids and other chiral drug molecules is crucial. Currently, obtaining single enantiomers mainly relies on techniques such as chromatography, crystallization resolution, and liquid-liquid extraction. However, these methods typically face challenges such as complex processes, high costs, and difficulty in continuous large-scale production. In contrast, chiral membrane separation technology, with its outstanding advantages of low energy consumption, simple operation, and ease of continuous and large-scale integration, shows great application potential in the field of chiral purification.

[0003] Among numerous chiral membrane materials, carbon-based nanomaterials, especially two-dimensional graphene oxide, have attracted much attention for chiral membrane separation due to their single-atom-layer thickness, abundant surface functional groups, and ability to form uniform nanochannels. Furthermore, one-dimensional carbon nanotubes, with their unique hollow nanotube structure, high aspect ratio and mechanical strength, as well as their ability to precisely construct chiral sites through inner / outer wall modification, have also become important candidate materials for building high-performance chiral membranes.

[0004] However, the selective nanochannels constructed from these carbon materials are limited by their inherent tendency to aggregate and interfacial compatibility with the matrix, hindering enantiomeric permeation and separation. Furthermore, single-material systems often struggle to simultaneously integrate high-density specific chiral recognition sites and efficient mass transport channels. Therefore, there is an urgent need to develop novel material systems capable of synergistically regulating the mass transfer channel structure and the surface chiral microenvironment to overcome the limitations of enantiomeric permeability and selectivity, achieving a synergistic improvement in both high throughput and high selectivity. Summary of the Invention

[0005] In view of this, the present invention proposes a co-assembled chiral composite film, its preparation method, and its application. The present invention uses graphene oxide and single-walled carbon nanotubes as substrates, respectively, and performs chiral functionalization modifications on them. Through co-assembly, a chiral composite film with precise control over interlayer spacing and mass transfer channels is successfully prepared. The technical solution of the present invention is achieved as follows: In a first aspect, the present invention proposes a method for preparing a co-assembled chiral composite film, comprising the following steps: S1 provides graphene oxide and acyl chloride single-walled carbon nanotubes as carriers; S2. The chiral compounds containing thiol groups are modified onto graphene oxide and acyl chloride single-walled carbon nanotubes respectively by thermocatalytic thiol-alkene click chemistry reaction and amidation reaction to obtain graphene oxide and single-walled carbon nanotubes functionalized with thiol chiral compounds. S3. The graphene oxide functionalized with thiol chiral compounds in S2 is combined with single-walled carbon nanotubes functionalized with thiol chiral compounds to obtain the co-assembled chiral composite film.

[0006] Preferably, step S1 includes: S1-1. Graphite and potassium permanganate are placed in a mixed acid, and after reaction, termination, washing and drying, the graphene oxide is obtained. S1-2. Single-walled carbon nanotubes are placed in a mixed acid and sonicated to carry out a carboxylation reaction. After washing, purification, and drying, carboxylated single-walled carbon nanotubes are obtained. S1-3. The carboxylated single-walled carbon nanotubes are placed in a mixture of thionyl chloride and N,N-dimethylformamide and reacted under reflux. After washing and purification, the acyl chloride single-walled carbon nanotubes are obtained.

[0007] More preferably, in step S1-1, the mass ratio of graphite to potassium permanganate is 1:(20-30); the mixed acid is phosphoric acid and sulfuric acid, with a volume ratio of 1:9; and the reaction time is 6-12 hours.

[0008] More preferably, in steps S1-2, the ratio of the amount of single-walled carbon nanotubes, thionyl chloride, and N,N-dimethylformamide is (15-25) mg; (12-18) ml; and (0.5-3) ml; the mixed acid is nitric acid and sulfuric acid in a volume ratio of 1:3; the ultrasonic time is 4-8 h; and the reflux temperature is 50-70 °C.

[0009] Preferably, step S2 includes: S2-1. Graphene oxide is ultrasonically dispersed in an organic solvent; a thiol-chiral compound and azobisisobutyronitrile are added; under inert gas protection, a thermocatalytic thiol-alkene click chemical reaction is carried out by heating; after the reaction is completed, the graphene oxide functionalized with the thiol-chiral compound is obtained by washing, purification and drying (GO-MC). S2-2. The thiol-chiral compound and acyl chloride single-walled carbon nanotubes are ultrasonically dispersed in an organic solvent and heated under reflux for amidation reaction. After the reaction is completed, the single-walled carbon nanotubes (SWCNTs-MC) functionalized with the thiol-chiral compound are obtained after washing and drying.

[0010] Preferably, the thiol chiral compound described in steps S2-1 and S2-2 includes at least one of cysteine, penicillamine, thiol-β-cyclodextrin, ergothioneine, or a chiral protein containing a thiol group.

[0011] Preferably, in step S2-1, the mass ratio of graphene oxide, mercapto chiral compound, and azobisisobutyronitrile is 1:(0.01~10):(0.1~5); the reaction temperature is 50~180℃; and the inert gas includes nitrogen.

[0012] Preferably, in step S2-2, the mass ratio of the acyl chloride single-walled carbon nanotubes to the thiol chiral compound is 1:(2~5); and the reflux temperature is 50~80℃.

[0013] Preferably, step S3 includes: Graphene oxide functionalized with thiol chiral compounds and single-walled carbon nanotubes functionalized with thiol chiral compounds were intercalated and self-assembled in ethanol in the presence of a reducing agent by ultrasound and stirring. After washing, drying and film formation, a chiral composite film cofunctionalized with thiol chiral compounds was obtained.

[0014] Preferably, the mass ratio of the thiol-chiral compound-functionalized graphene oxide to the thiol-chiral compound-functionalized single-walled carbon nanotubes is 1:(0.5~4); the reducing agent includes hydrazine hydrate; and the self-assembly time is 12~16h.

[0015] In a second aspect, the present invention provides a chiral composite membrane prepared by the method described in the first aspect.

[0016] Preferably, the chiral composite membrane is composed of graphene oxide functionalized with thiol chiral compounds, single-walled carbon nanotubes functionalized with thiol chiral compounds, and a support membrane, wherein the sum of the masses of the graphene oxide functionalized with thiol chiral compounds and the single-walled carbon nanotubes functionalized with thiol chiral compounds accounts for 1% to 12% of the mass of the support membrane; more preferably, it is 6%.

[0017] Thirdly, the present invention provides an application of the chiral composite membrane as described in the second aspect in chiral separation.

[0018] Preferably, the chiral composite membrane is used for the enantiomeric transformation of chiral compounds, and more preferably for amino acids and their derivatives, wherein the amino acids and their derivatives are selected from at least one of phenylalanine, tyrosine, tryptophan, histidine, threonine, methionine, alanine, glutamic acid, arginine, aspartic acid, serine, levodopa, propranolol, or ibuprofen.

[0019] Compared with the prior art, the advantages of the present invention are as follows: (1) This invention successfully embeds SWCNTs-MC as nanospacer pillars into the interlayer of GO-MC to construct a stable intercalation structure. This design not only effectively suppresses the re-stacking of graphene sheets and constructs a uniform and regular two-dimensional nanomass transfer channel, but also forms a high density of cooperative chiral recognition sites on the inner wall of the channel through covalent chiral modification of the surfaces of the two materials.

[0020] (2) Thanks to the stable intercalation structure and abundant chiral sites mentioned above, the rGO-MC / SWCNTs-MC composite membrane prepared by the present invention achieves a synergistic improvement in mass transfer efficiency and chiral selectivity, and simultaneously achieves high throughput and high enantioselectivity.

[0021] (3) The chiral composite membrane prepared by the present invention exhibits good separation effect on a variety of amino acid enantiomers, overcoming the limitations of many existing chiral membranes that have a single separation target and narrow applicability, and providing a more universal material platform for the design and large-scale application of chiral separation membranes. Attached Figure Description

[0022] 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 of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the co-assembled chiral composite membrane and its chiral separation principle according to the present invention; Figure 2 The Fourier transform infrared (FT-IR) spectrum of L-Cys covalently modified with GO and SWCNTs prepared in Example 1 of this invention is shown. Figure 3 The X-ray diffraction (XRD) spectra of the rGO-Cys / SWCNTs-Cys chiral composite material and GO-Cys prepared in Example 1 of this invention are shown. Figure 4 The images show the morphology of the rGO-Cys / SWCNTs-Cys chiral composite film prepared in Example 1 of this invention. A is a photograph of rGO-Cys / SWCNTs-Cys on a CA substrate film; B is a scanning electron microscope (SEM) image of rGO-Cys / SWCNTs-Cys. Figure 5 Typical high-performance liquid chromatography (HPLC) chromatograms before and after permeation of the prepared rGO-Cys / SWCNTs-Cys chiral composite membrane for separating racemic D,L-phenylalanine. Detailed Implementation

[0024] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0025] It should be noted that the following embodiments detail a preferred embodiment of constructing a chiral composite membrane by using L-cysteine ​​(L-Cys) as a model chiral ligand, covalently modifying graphene oxide and single-walled carbon nanotube supports through thermocatalytic thiol-olefin click chemistry and amidation reactions, respectively, and then synergistically self-assembling. The present invention selects chiral compounds containing thiol groups (-SH) as key functional molecules based on the unique reactivity of their functional groups, which is closely related to the core modification strategy of the present invention: (1) Modification with GO: The thiol group can undergo a highly efficient and selective "thiol-alkene" click chemical reaction with the carbon-carbon double bond (C=C) on the GO sheet, achieving high-density covalent grafting on the GO surface, while better preserving other oxygen-containing functional groups of GO.

[0026] (2) Modification of SWCNTs: Through pre-carboxylation and acyl chloride treatment, highly reactive acyl chloride groups (-COCl) can be introduced into the surface of SWCNTs; the amino group (-NH2) in the thiol-containing chiral compound (such as L-Cys containing amino group) can undergo amidation reaction to form a stable amide bond (-CONH-), thereby anchoring the chiral molecule firmly to the surface of SWCNTs, and the thiol group at the end can still participate in chiral recognition.

[0027] Therefore, the selection of "thiol-containing chiral compounds" is the chemical basis for achieving the core technical path of "covalent modification through click chemistry and amidation reaction, respectively." Based on this verified path, any thiol-containing compound with a suitable structure and chiral recognition potential can theoretically serve as the chiral ligand (MC) of this invention. This includes, but is not limited to, other chiral amino acids (such as D-penicillamine), chiral thiol catalysts, chiral peptides or proteins containing active cysteine ​​residues, etc. Those skilled in the art can select or design suitable MCs based on this chemical basis according to the characteristics of the target isolate, thereby customizing the chiral recognition microenvironment of the composite membrane. The core concept of "separate modification and synergistic assembly" verified by this invention, and the resulting synergistic improvement in mass transfer and recognition performance, have been fully and strongly confirmed through the above-mentioned preferred scheme represented by L-cysteine.

[0028] All materials used in this invention were purchased commercially. Specifically, graphite powder and SWCNTs were purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.; potassium permanganate was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; azobisisobutyronitrile and L-cysteine ​​hydrochloride were purchased from Shanghai Adamas Reagent Co., Ltd.; and hydrazine hydrate was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0029] Example 1

[0030] This embodiment provides a method for preparing a co-assembled chiral composite membrane, including the following steps: S1. Preparation of graphene oxide: At room temperature, 27 mL of 98 wt% concentrated sulfuric acid and 3 mL of 85 wt% concentrated phosphoric acid were mixed and stirred. 0.225 g of graphite powder and 1.32 g of potassium permanganate were slowly added, and the mixture was reacted at room temperature for 6 h until the system turned dark green. The reaction was terminated by adding 0.675 mL of 30 wt% hydrogen peroxide solution dropwise under ice bath, and stirring was continued for 10 min. Then, 10 mL of 37 wt% hydrochloric acid and 30 mL of deionized water were added, and the supernatant was discarded after centrifugation. The obtained solid product was washed twice with deionized water, 5 wt% hydrochloric acid and ethanol, and finally dried under vacuum at 60 °C to obtain blocky GO. S2. Preparation of acyl chloride single-walled carbon nanotubes: 20 mg of SWCNTs were dispersed in 26 mL of a mixed acid solution of 98 wt% sulfuric acid and 68 wt% nitric acid (3:1, v / v), magnetically stirred for 15 min, and then sonicated at 30 °C for 6 h. After the reaction was completed, the solution was filtered through a 0.22 μm PTFE membrane, washed with water until the filtrate was neutral, and vacuum dried at 60 °C overnight to obtain SWCNTs-COOH. Subsequently, SWCNTs-COOH was added to a mixed solvent consisting of 15 mL of thionyl chloride and 1 mL of N,N-dimethylformamide, ultrasonically dispersed for 15 min, and refluxed at 60 °C for 48 h. After the reaction was completed, excess thionyl chloride was removed by distillation, and the resulting solid was washed three times with tetrahydrofuran / ethanol (1:1, v / v), filtered, and vacuum dried to obtain SWCNTs-COCl. S3. Preparation of L-cysteine-functionalized graphene oxide: 200 mg of GO was ultrasonically dispersed in 60 mL of anhydrous N,N-dimethylformamide. Separately, 100 mg of azobisisobutyronitrile and 100 mg of L-cysteine ​​hydrochloride were dissolved in 5 mL of N,N-dimethylformamide. Under a N2 atmosphere, the mixture was slowly added dropwise to the GO suspension, and the reaction was stirred in an oil bath at 70 °C for 12 h. After the reaction was completed, the product was collected by centrifugation, washed three times with ethanol and water, and finally dried under vacuum at 60 °C overnight to obtain GO-Cys. S4. Preparation of L-cysteine-functionalized single-walled carbon nanotubes: 15 mg of L-cysteine ​​hydrochloride and 5 mg of SWCNTs-COCl were added to a mixture of ethanol and water in a ratio of 30:10 (v / v) and ultrasonicated for 15 min; then stirred continuously under reflux at 80 °C for 8 h; after the reaction, the mixture was further washed with water and ethanol solution; finally, it was vacuum dried at 60 °C to obtain SWCNTs-Cys. S5. Preparation of rGO-Cys / SWCNTs-Cys chiral composite membrane: 5 mg of GO-Cys was ultrasonically dispersed in 20 mL of ethanol for 2 h; then 10 mg of SWCNTs-Cys and 10 μL of hydrazine hydrate (80 wt%) were added, and ultrasonication was continued for 1 h to promote assembly; after stirring the mixture at room temperature for 14 h, it was washed multiple times with deionized water, and the resulting composite material was designated as rGO-Cys / SWCNTs-Cys. It was then ultrasonically dispersed again in 20 mL of deionized water, and the composite material was uniformly deposited on the surface of the CA membrane using a cellulose acetate membrane with a diameter of 47 mm and an average pore size of about 0.22 μm as the supporting matrix by vacuum filtration, forming a continuous functional layer; after air drying at room temperature for 24 h, the rGO-Cys / SWCNTs-Cys chiral composite membrane was obtained; in this embodiment, the active layer loading of the membrane (the percentage of the dry weight of the composite material to the dry weight of the supporting membrane) was about 6%; this membrane was designated as membrane S1 and used for subsequent performance testing.

[0031] To confirm the successful preparation and structural characteristics of each intermediate product and the final composite membrane, the following characterization was performed: FT-IR analysis was performed on the product in Example 1, such as... Figure 2 As shown, GO-Cys is at 665 cm. -1 and 1320 cm -1 Characteristic absorption peaks of CS and -CH2-S appear at 1620 cm⁻¹. -1 The weakening of the C=C peak confirms that L-cysteine ​​is grafted via a thiol-alkene click reaction. An amide bond C=O peak (1630 cm⁻¹) was observed in the SWCNTs-Cys spectrum. -1 Characteristic peaks such as NH and NH confirm the success of the amidation reaction.

[0032] XRD analysis was performed on the chiral functionalized vector in Example 1, such as... Figure 3 As shown, compared with pure GO-Cys, the (001) diffraction peak of the composite material shifts to a smaller angle, corresponding to an increase in interlayer spacing from 0.81 nm to 0.88 nm. These two results corroborate each other, directly proving that SWCNTs-Cys was successfully intercalated and acted as a nanospacer, which is key evidence for constructing a three-dimensional mass transfer network.

[0033] Figure 4 The original photograph of the membrane shows a smooth, defect-free surface morphology. The SEM image clearly shows that the fibrous SWCNTs-Cys are uniformly embedded and dispersed between the folded layers of GO-Cys, forming a stable intercalation structure.

[0034] Comparative Example 1 An unmodified cellulose acetate (CA) ultrafiltration membrane with the exact same specifications as in Example 1 was used directly as a control sample. This membrane served only as a support layer and was not loaded with any functional materials; it was labeled as membrane C1.

[0035] Comparative Example 2 Unchiral modified GO (prepared as in Example 1 S1) and unchiral modified SWCNTs-COCl (as in Example 1 S2) were weighed at a mass ratio of 1:2 (e.g., 5 mg GO, 10 mg SWCNTs-COCl) and ultrasonically dispersed. This physical mixture was dispersed in 20 mL of water using the same method as in Example 1 S5, and deposited onto a CA-supported membrane by vacuum filtration, then dried at room temperature to form a membrane. This membrane, without any chiral modification, is labeled as membrane C2.

[0036] Comparative Example 3 Weigh 15 mg of GO-Cys prepared in step S3 of Example 1, disperse it in 20 mL of deionized water, and sonicate for 2 h to form a uniform dispersion. Then, directly following the same vacuum filtration method as in step S5 of Example 1, load the dispersion onto a CA support membrane of the same specifications and dry it at room temperature to form a membrane. This membrane consists of only the single active component GO-Cys and is labeled as membrane C3.

[0037] Comparative Example 4 Weigh 30 mg of SWCNTs-Cys prepared in step S4 of Example 1, disperse it in 20 mL of deionized water, and sonicate for 2 h. Then, using the same vacuum filtration method as in step S5 of Example 1, load the dispersion onto a CA support membrane of the same specifications and dry at room temperature. This membrane consists of only the single active component SWCNTs-Cys and is labeled as membrane C4.

[0038] Example 2

[0039] Following the preparation method of Example 1, only the mass ratio of GO-Cys to SWCNTs-Cys in step S5 was changed to prepare membranes with mass ratios of 1:0.5 (GO-Cys 10 mg, SWCNTs-Cys 5 mg), 1:1 (GO-Cys 7.5 mg, SWCNTs-Cys 7.5 mg), and 1:4 (GO-Cys 3 mg, SWCNTs-Cys 12 mg). All other preparation and film-forming conditions remained consistent with those of Example 1 and were designated as S2, S3, and S4, respectively.

[0040] Example 3

[0041] With the mass ratio of GO-Cys to SWCNTs-Cys fixed at 1:2 (optimal ratio), and referring to the preparation method of Example 1, a series of composite membranes with different active layer loadings were prepared by changing the total amount of composite material in step S5 while keeping the dispersion volume (20 mL water) and film area constant: samples with total feed amounts of 2.5 mg (loading of about 1%), 7.5 mg (loading of about 3%), 15 mg (loading of about 6%, i.e. membrane S1 of Example 1), 25 mg (loading of about 10%) and 30 mg (loading of about 12%), which were labeled as membranes L1, L2, L4 and L5, respectively.

[0042] Example 4

[0043] The difference between this embodiment and Embodiment 1 is that: In step S3, the mass ratio of graphene oxide, thiol chiral compound, and azobisisobutyronitrile was 1:0.2:0.2 (200 mg GO, 40 mg azobisisobutyronitrile, 40 mg L-cysteine ​​hydrochloride); the reaction temperature was 60℃. In step S4, the mass ratio of acyl chloride single-walled carbon nanotubes to thiol chiral compound is 1:2 (5 mg SWCNTs-COCl, 10 mg L-cysteine ​​hydrochloride); the reflux temperature is 50 °C. In step S5, sonication is performed for 1 hour, followed by stirring for 11 hours.

[0044] Everything else is the same as in Example 1, and is referred to as membrane S5.

[0045] Example 5

[0046] The difference between this embodiment and Embodiment 1 is that: In step S3, the mass ratio of graphene oxide, thiol chiral compound, and azobisisobutyronitrile is 1:1:1 (200 mg GO, 200 mg azobisisobutyronitrile, 200 mg L-cysteine ​​hydrochloride); the reaction temperature is 150℃. In step S4, the mass ratio of acyl chloride single-walled carbon nanotubes to thiol chiral compound is 1:5 (5 mg SWCNTs-COCl, 25 mg L-cysteine ​​hydrochloride); the reflux temperature is 80 °C. In step S5, sonicate for 1 hour and stir for 15 hours.

[0047] Everything else is the same as in Example 1, and is referred to as membrane S6.

[0048] Experimental Example 1 Chiral separation performance was tested using an isobaric osmosis apparatus with an effective membrane area of ​​9.6 cm². 2 (Diameter 3.5 cm), operating temperature 25℃. Using membrane S1 (the composite membrane of this invention), membrane C1 (pure CA membrane), and membrane C2 (physically mixed membrane) as test samples, under concentration gradient drive, 1.0 mmol·L⁻¹... -1 The D,L-phenylalanine racemic aqueous solution was subjected to osmotic separation, and the permeate was collected periodically.

[0049] The concentrations of D- and L-enantiomers in the permeate were analyzed by high-performance liquid chromatography (HPLC) using an FLMChiral AAOA chiral column (3 µm, 4.6 × 100 mm), a mobile phase of 2 mM copper sulfate aqueous solution and isopropanol (95:5, v / v), and a detection wavelength of 254 nm. To ensure data reliability, all experiments were repeated in triplicate, and the average results were used for subsequent calculations and analyses. The chiral separation selectivity and permeation performance of the membrane were further evaluated using enantiomeric excess (ee, Equation 1) and enantiomeric flux (J, Equation 2).

[0050] The enantiomeric excess ee (%) is calculated using the following formula:

[0051] Among them, C P(L) (mmol L) -1 ) and C P(D) (mmol L) -1 ( ) represent the concentrations of L-enantiomer and D-enantiomer in the permeate, respectively.

[0052] Enantiomer osmotic flux J (mmol m -2 h -1 Calculate using the following formula:

[0053] Where, n P(i) (mmol) is the amount of osmotic enantiomer, A(m 2 t(h) and t(h) are the effective permeation area and permeation time of the membrane, respectively.

[0054] Table 1. Comparison of the separation performance of the composite membrane of the present invention and the control membrane for D,L-phenylalanine.

[0055] The enantioselectivity (ee) of membrane S1 reached 97.27%, and the flux of L-phenylalanine was greater than that of D-type. Figure 5 The difference in high-performance liquid chromatography (HPLC) spectra before and after permeation demonstrates excellent chiral separation capabilities. In contrast, the pure CA membrane (C1) showed almost no selectivity (ee≈0%), and the physically mixed membrane (C2) exhibited very low selectivity (ee=2.53%), indicating that the chiral separation function mainly originates from the covalent modification and ordered assembly of the material surface. This confirms that "covalent chiral functionalization" constructs stable recognition sites, while the intercalation structure formed by "co-assembly" optimizes the mass transfer channels. The two work synergistically to achieve high selectivity at high throughput, reflecting the unity of "chemical recognition" and "structural sieving" at the nanoscale.

[0056] Experimental Example 2 When the feed solution is 1.0 mmol·L -1 Under the same conditions and methods as in Experimental Example 1, the separation performance of membranes S2, S3, S1 and S4 was tested for D,L-phenylalanine.

[0057] Table 2. Effect of Composite Material Ratio on Chiral Separation Performance of Chiral Composite Membranes

[0058] The results show that the mass ratio significantly affects separation performance. At a ratio of 1:2, both the ee value and flux reach their maximum values, indicating that at this ratio, the intercalation of SWCNTs-Cys can most effectively construct stable mass transfer channels and achieve optimal chiral site density, realizing the best synergistic effect. Ratios that are too high or too low lead to performance degradation.

[0059] Experimental Example 3 When the feed solution is 1.0 mmol·L -1 Under the same conditions and methods as in Experiment 1, the separation performance of membranes L1, L2, S1 (6% loading), L3 and L4 was tested for D,L-phenylalanine.

[0060] Table 3. Effect of composite material content on the chiral separation performance of chiral composite membranes

[0061] The results showed that as the loading increased, the ee value first increased and then decreased, reaching a peak at 6%; while the permeation flux decreased monotonically. This indicates that a moderate loading (6%) can achieve the best balance between selectivity (ee value) and permeability (flux) by forming sufficient chiral recognition sites while avoiding channel blockage caused by excessive material accumulation.

[0062] Test Example 4 Under the same conditions and methods as in Experiment 1, with a fixed temperature of 25℃, the feed concentrations of 1.0, 2.0, 5.0, 8.0, and 10.0 mmol·L⁻¹ were tested. -1 The membrane S1 separation performance in D,L-phenylalanine solution.

[0063] Table 4 Effect of feed concentration on the chiral separation performance of chiral composite membranes

[0064] The separation performance of the composite membrane of this invention is significantly affected by the feed concentration. At lower concentrations, the membrane achieves the highest enantiomeric excess value due to sufficient chiral recognition sites, allowing enantiomeric molecules to bind fully and specifically. As the concentration increases, the recognition sites tend to saturate, intensifying intermolecular competitive adsorption and leading to a decrease in selectivity. Simultaneously, the permeate flux increases approximately linearly with increasing concentration, indicating that the membrane maintains good separation efficiency even at higher concentrations, demonstrating excellent process adaptability.

[0065] Experimental Example 5 Under the same conditions and methods as in Experiment 1, with a constant temperature of 25℃, the test was conducted at 1.0 mmol·L⁻¹. -1 The chiral separation performance of membrane S1 for different amino acid enantiomers was evaluated using solutions of D,L-tyrosine, D,L-tryptophan, D,L-histidine, D,L-threonine, D,L-methionine, D,L-alanine, D,L-glutamic acid, and D,L-arginine as feed solutions.

[0066] Table 5. Study on the chiral separation performance of chiral composite membranes for different amino acid enantiomers

[0067] The rGO-Cys / SWCNTs-Cys composite membrane (membrane S1) prepared in this invention exhibits excellent and stable chiral separation capabilities for various amino acid enantiomers with different structures. The separation effect is particularly outstanding for phenylalanine (ee = 97.27%) and tyrosine (ee = 92.40%), which contain aromatic rings. This is attributed to the enhanced chiral recognition through the π-π interaction between the aromatic ring and the membrane material. Furthermore, although the permeate flux varies among different amino acids, the flux for L-enantiomers is consistently significantly higher than that for D-enantiomers, confirming the universality and reliability of its chiral recognition function.

[0068] In summary, this composite membrane not only exhibits high efficiency in separating the model molecule phenylalanine, but also broadly recognizes the chiral centers of various amino acids, overcoming the limitation of traditional chiral membranes that can only separate a single target. This is mainly attributed to the chiral microenvironment constructed by the synergistic assembly of GO and SWCNTs, which combines size sieving with multiple molecular interactions. These results demonstrate the broad application potential of this membrane in the separation of complex chiral compounds.

[0069] The embodiments described above are some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing a co-assembled chiral composite membrane, characterized in that, Includes the following steps: S1 provides graphene oxide and acyl chloride single-walled carbon nanotubes as carriers; S2. The chiral compounds containing thiol groups are modified onto graphene oxide and acyl chloride single-walled carbon nanotubes respectively by thermocatalytic thiol-alkene click chemistry reaction and amidation reaction to obtain graphene oxide and single-walled carbon nanotubes functionalized with thiol chiral compounds. S3. The graphene oxide functionalized with thiol chiral compounds in S2 is combined with single-walled carbon nanotubes functionalized with thiol chiral compounds to obtain the co-assembled chiral composite film.

2. The preparation method according to claim 1, characterized in that, Step S1 includes: S1-1. Graphite and potassium permanganate are placed in a mixed acid, and after reaction, termination, washing and drying, the graphene oxide is obtained. S1-2. Single-walled carbon nanotubes are placed in a mixed acid and sonicated to carry out a carboxylation reaction. After washing, purification, and drying, carboxylated single-walled carbon nanotubes are obtained. S1-3. The carboxylated single-walled carbon nanotubes are placed in a mixture of thionyl chloride and N,N-dimethylformamide and reacted under reflux. After washing and purification, the acyl chloride single-walled carbon nanotubes are obtained.

3. The preparation method according to claim 1, characterized in that, Step S2 includes: S2-1. Graphene oxide is ultrasonically dispersed in an organic solvent; a thiol chiral compound and azobisisobutyronitrile are added; under inert gas protection, a thermocatalytic thiol-alkene click chemical reaction is carried out by heating; after the reaction is completed, graphene oxide functionalized with the thiol chiral compound is obtained by washing, purification and drying. S2-2. The thiol-chiral compound and acyl chloride single-walled carbon nanotubes are ultrasonically dispersed in an organic solvent and heated under reflux to carry out an amidation reaction. After the reaction is completed, the single-walled carbon nanotubes functionalized with the thiol-chiral compound are obtained after washing and drying.

4. The preparation method according to claim 3, characterized in that, The thiol chiral compounds described in steps S2-1 and S2-2 include at least one of cysteine, penicillamine, thiol-β-cyclodextrin, ergothioneine, or a chiral protein containing a thiol group.

5. The preparation method according to claim 3, characterized in that, In step S2-1, the mass ratio of graphene oxide, mercapto chiral compound, and azobisisobutyronitrile is 1:(0.2~1):(0.2~1); the reaction temperature is 60~150℃; and the inert gas includes nitrogen.

6. The preparation method according to claim 3, characterized in that, In step S2-2, the mass ratio of the acyl chloride single-walled carbon nanotubes to the thiol chiral compound is 1:(2~5); the reflux temperature is 50~80℃.

7. The preparation method according to claim 1, characterized in that, Step S3 includes: Graphene oxide functionalized with thiol chiral compounds and single-walled carbon nanotubes functionalized with thiol chiral compounds were intercalated and self-assembled in ethanol in the presence of a reducing agent by ultrasound and stirring. After washing, drying and film formation, a chiral composite film cofunctionalized with thiol chiral compounds was obtained.

8. The preparation method according to claim 7, characterized in that, The mass ratio of thiol-chiral compound-functionalized graphene oxide to thiol-chiral compound-functionalized single-walled carbon nanotubes is 1:(0.5~4); the reducing agent includes hydrazine hydrate; the self-assembly time is 12~16h.

9. A chiral composite membrane prepared by the method as described in claims 1 to 8.

10. The application of the chiral composite membrane as described in claim 9 in chiral separation.

Images