Chiral nano composite membrane and preparation method thereof

Abstract

The invention provides a multilayer nano composite membrane with a chiral separation function and a preparation method thereof, and the preparation method comprises the following steps: preparing a middle layer with a chiral recognition function on a porous base membrane, and further preparing a skin layer with a chiral recognition function on the middle layer with the chiral recognition function through interfacial polymerization, based on the synergistic interaction effect of the middle layer and the skin layer with the chiral recognition function, the multilayer nano composite membrane with the chiral separation function is precisely constructed in a multi-layer mode, the preparation method is easy to operate, mild in condition, green and efficient, and the prepared multilayer nano composite membrane has good chiral separation stability and is suitable for large-scale production. The method has a good application prospect when being applied to separation of amino acid enantiomers.

Description

Technical Field

[0001] The present invention relates to the technical field of membrane separation, and in particular to a chiral nanocomposite membrane and a preparation method thereof. Background Art

[0002] Chiral compounds are widely present in numerous fields, including pharmaceuticals, pesticides, food additives, and fragrances. Different enantiomers of many chiral compounds exhibit significant differences in biological activity, pharmacological effects, and toxicity. For example, in the pharmaceutical field, some drugs only have specific enantiomers that exhibit therapeutic effects, while their mirror-image enantiomers may not only have no therapeutic effect but may even produce serious toxic side effects. Therefore, achieving efficient and precise chiral separations is crucial for ensuring product quality, improving production efficiency, and promoting the sustainable development of related industries.

[0003] Currently, chiral separation technologies primarily include high-performance liquid chromatography (HPLC), capillary electrophoresis (CE), and membrane separation. While HPLC and CE offer high separation efficiency, they suffer from expensive equipment, complex operation, and high separation costs, making them difficult to meet the demands of large-scale industrial production. In contrast, membrane separation, as a green and efficient separation method, has garnered significant attention in recent years due to its advantages, including low energy consumption, ease of operation, and amenability to continuous production.

[0004] Currently, researchers typically employ the strategy of introducing chiral recognition sites into the polyamide (PA) cortex of composite membranes to achieve selective separation of chiral compounds. However, this strategy faces numerous challenges in practical application. First, simply introducing chiral selectors into the PA cortex is limited in loading capacity. This is because the introduction of chiral selectors often relies on interfacial polymerization, and the steric hindrance of the PA network limits the amount of chiral molecules that can be incorporated. Furthermore, the rapid reaction rate of interfacial polymerization makes it difficult to uniformly disperse chiral molecules. Uneven interfacial polymerization results in uneven distribution of recognition sites, which in turn affects the separation selectivity of chiral compounds. Second, the PA cortex of composite membranes is susceptible to adsorption of impurities such as proteins and organic molecules during the separation process, causing membrane fouling. Over extended periods of operation, this fouling can lead to a decrease in chiral separation performance, significantly limiting the practical application of these composite membranes in industrial production. Furthermore, researchers often attempt to improve the chiral separation selectivity of composite membranes by increasing the loading of chiral selectors into the cortex, but this approach often results in reduced permeability. Therefore, in the above-mentioned traditional methods, high selectivity and high flux (permeability) are difficult to achieve simultaneously.

[0005] Therefore, there is an urgent need to develop a high-performance chiral nanocomposite membrane capable of multi-layered precision construction, excellent chiral recognition capabilities, and stability, as well as a method for preparing the membrane. This invention aims to fabricate a high-performance chiral nanocomposite membrane by forming an intermediate layer with chiral recognition capabilities on a porous base membrane, and then further forming a chiral recognition skin layer on this intermediate layer through interfacial polymerization. By leveraging the synergistic effect of these two layers, the membrane can be fabricated to meet the current demand for efficient and stable membranes in the field of chiral separation. Summary of the Invention

[0006] To solve the above problems, the first aspect of the present invention provides a method for preparing a multilayer nanocomposite separation membrane containing a chiral recognition functional intermediate layer and a skin layer, which comprises: An intermediate layer with chiral recognition function is prepared on a porous base membrane, and then a skin layer with chiral recognition function is prepared on the intermediate layer by interfacial polymerization to obtain a multilayer nanocomposite separation membrane containing the intermediate layer with chiral recognition function and the skin layer.

[0007] In some specific embodiments of the preparation method of the first aspect, the intermediate layer having a chiral recognition function is prepared on the porous base membrane, wherein a three-dimensional network structure intermediate layer is prepared on the porous base membrane, and the three-dimensional network structure intermediate layer is formed by cross-linking amino acid functionalized carbon quantum dots, cyclodextrin derivatives, sodium alginate and metal ions; The preparation method of the three-dimensional network structure intermediate layer is to use two intermediate layer coating liquids A and B to apply them on the surface of the porous base membrane respectively, and then undergo a cross-linking reaction. The A coating liquid is a mixed aqueous solution of magnesium salt and calcium salt, and the B coating liquid is a mixed aqueous solution of amino acid functionalized carbon quantum dots, cyclodextrin derivatives and sodium alginate.

[0008] In some specific embodiments of the preparation method of the first aspect, the porous base membrane includes at least one selected from polysulfone, polyethersulfone, cellulose, cellulose acetate, regenerated cellulose, polyacrylonitrile and polyvinylidene fluoride.

[0009] In some specific embodiments of the preparation method of the first aspect, the magnesium salt aqueous solution in the coating liquid A includes at least one selected from a magnesium chloride aqueous solution, a magnesium nitrate aqueous solution, and a magnesium sulfate aqueous solution.

[0010] In some specific embodiments of the preparation method of the first aspect, the mass percentage concentration of the magnesium salt in the coating liquid A is 0.01~2wt%. In some specific embodiments of the preparation method of the first aspect, the mass percentage concentration of the magnesium salt in the coating liquid A is optionally 0.1wt%, 0.3wt%, 0.6wt%, 0.9wt%, 1.2wt%, 1.5wt%, or 1.8wt%.

[0011] In some specific embodiments of the preparation method of the first aspect, the calcium salt aqueous solution in the coating liquid A includes at least one selected from a calcium chloride aqueous solution, a calcium nitrate aqueous solution, and a calcium bicarbonate aqueous solution, and the mass percentage concentration of the calcium salt in the coating liquid A is 0.01~2wt%. In some specific embodiments of the preparation method of the first aspect, the calcium salt aqueous solution in the coating liquid A includes at least one selected from a calcium chloride aqueous solution, a calcium nitrate aqueous solution, and a calcium bicarbonate aqueous solution, and the mass percentage concentration of the calcium salt in the coating liquid A is optionally 0.1wt%, 0.3wt%, 0.6wt%, 0.9wt%, 1.2wt%, 1.5wt%, and 1.8wt%.

[0012] In some specific embodiments of the preparation method of the first aspect, the amino acid functionalized carbon quantum dots include at least one selected from arginine functionalized carbon quantum dots, aspartic acid functionalized carbon quantum dots, cysteine ​​functionalized carbon quantum dots, glycine functionalized carbon quantum dots and lysine functionalized carbon quantum dots.

[0013] In some specific embodiments of the preparation method of the first aspect, the mass percentage concentration of the amino acid functionalized carbon quantum dots in the coating liquid B is 0.1~3wt%. In some specific embodiments of the preparation method of the first aspect, the mass percentage concentration of the amino acid functionalized carbon quantum dots in the coating liquid B is optionally 0.1wt%, 0.5wt%, 1.0wt%, 1.5wt%, 2.0wt%, or 2.5wt%.

[0014] In some specific embodiments of the preparation method of the first aspect, the cyclodextrin derivative includes at least one selected from carboxylated cyclodextrin, sulfonated cyclodextrin and amino cyclodextrin.

[0015] In some specific embodiments of the preparation method of the first aspect, the mass percentage concentration of the cyclodextrin derivative in the coating liquid B is 0.1~5wt%. In some specific embodiments of the preparation method of the first aspect, the mass percentage concentration of the cyclodextrin derivative in the coating liquid B is optionally 0.8wt%, 1.6wt%, 2.4wt%, 3.2wt%, 4.0wt%, or 4.8wt%.

[0016] In some specific embodiments of the preparation method of the first aspect, the molecular weight range of the sodium alginate is 5kDa~100kDa. In some specific embodiments of the preparation method of the first aspect, the molecular weight range of the sodium alginate is 5kDa, 35kDa, 55kDa, 75kDa, and 95kDa.

[0017] In some specific embodiments of the preparation method of the first aspect, the mass percentage concentration of the sodium alginate in the coating liquid B is 0.1~1wt%. In some specific embodiments of the preparation method of the first aspect, the mass percentage concentration of the sodium alginate in the coating liquid B is optionally 0.2wt%, 0.4wt%, 0.6wt%, or 0.8wt%.

[0018] In some specific embodiments of the preparation method of the first aspect, the method of preparing the cortex with chiral recognition function on the chiral recognition function intermediate layer by interfacial polymerization is: taking an immiscible aqueous phase solution and an organic phase solution to perform an interfacial polymerization reaction to obtain a cortex with chiral recognition function.

[0019] The aqueous phase solution includes polyamine reaction monomers, amino acid functionalized carbon quantum dots and cyclodextrin derivatives.

[0020] The organic phase solution includes polyacyl chloride reaction monomers and an organic solvent.

[0021] In some specific embodiments of the preparation method of the first aspect, the aqueous phase reaction monomer is at least one of piperazine and m-phenylenediamine.

[0022] In some specific embodiments of the preparation method of the first aspect, the mass percentage concentration of the polyamine reaction monomer in the aqueous solution is 0.1~3wt%. In some specific embodiments of the preparation method of the first aspect, the mass percentage concentration of the polyamine reaction monomer in the aqueous solution is optionally 0.3wt%, 0.6wt%, 0.9wt%, 1.2wt%, 1.5wt%, 1.8wt%, 2.1wt%, 2.4wt%, or 2.7wt%.

[0023] In some specific embodiments of the preparation method of the first aspect, the amino acid functionalized carbon quantum dots are at least one of arginine functionalized carbon quantum dots, aspartic acid functionalized carbon quantum dots, cysteine ​​functionalized carbon quantum dots, glycine functionalized carbon quantum dots and lysine functionalized carbon quantum dots.

[0024] In some specific embodiments of the preparation method of the first aspect, the mass percentage concentration of the amino acid functionalized carbon quantum dots in the aqueous solution is 0.1~2wt%. In some specific embodiments of the preparation method of the first aspect, the mass percentage concentration of the amino acid functionalized carbon quantum dots in the aqueous solution is optionally 0.3wt%, 0.6wt%, 0.9wt%, 1.2wt%, 1.5wt%, or 1.8wt%.

[0025] In some specific embodiments of the preparation method of the first aspect, the cyclodextrin derivative is at least one of carboxylated cyclodextrin, sulfonated cyclodextrin and amino cyclodextrin.

[0026] In some specific embodiments of the preparation method of the first aspect, the mass percentage concentration of the cyclodextrin derivative in the aqueous solution is 0.1~2wt%. In some specific embodiments of the preparation method of the first aspect, the mass percentage concentration of the cyclodextrin derivative in the aqueous solution is optionally 0.3wt%, 0.6wt%, 0.9wt%, 1.2wt%, 1.5wt%, or 1.8wt%.

[0027] In some specific embodiments of the preparation method of the first aspect, the polyvalent acyl chloride reaction monomer includes at least one selected from trimesoyl chloride, terephthaloyl chloride and isophthaloyl chloride.

[0028] In some specific embodiments of the preparation method of the first aspect, the mass volume concentration of the multi-acid chloride reaction monomer in the organic phase solution is 0.1~3w / v%. In some specific embodiments of the preparation method of the first aspect, the mass volume concentration of the multi-acid chloride reaction monomer in the organic phase solution is optionally 0.3w / v%, 0.6w / v%, 0.9w / v%, 1.2w / v%, 1.5w / v%, 1.8w / v%, 2.1w / v%, 2.4w / v%, and 2.7w / v%.

[0029] In some specific embodiments of the preparation method of the first aspect, the organic solvent is at least one of n-hexane, cyclohexane, n-heptane, and isoparaffin G.

[0030] In some specific embodiments of the preparation method of the first aspect, the amino acid functionalized carbon quantum dots are prepared by a hydrothermal method, and the precursors are citric acid and L-amino acids.

[0031] In some specific embodiments of the preparation method of the first aspect, specifically: Step 1) Preparation of an intermediate layer with chiral recognition function: The porous base membrane is contacted with a coating solution A having a total concentration of 0.02 to 4 wt% for 1 to 20 minutes, and then air-dried; the porous base membrane coated with solution A is then contacted with a coating solution B having a total concentration of 0.3 to 9 wt% for 1 to 20 minutes, and then air-dried, thereby preparing an intermediate layer with chiral recognition function on the surface of the porous base membrane; Step 2) Preparation of a cortex with chiral recognition function: Take an aqueous solution containing 0.1~2wt% amino acid functionalized carbon quantum dots, 0.1~2wt% cyclodextrin derivatives and 0.1~3wt% polyamine, calculated based on the total mass of the aqueous solution, and immerse the porous base membrane coated with an intermediate layer obtained in step 1 in the aqueous solution for 1 minute to 20 minutes, remove the excess aqueous solution, and then apply an organic phase solution containing 0.1~3w / v% polyacyl chloride on the surface, remove the excess polyacyl chloride on the surface of the obtained polyamide membrane, and dry it to form a cortex with chiral recognition function on the surface of the intermediate layer.

[0032] In some second aspects, a multilayer nanocomposite separation membrane is obtained according to any preparation method of the first aspect.

[0033] Definition of terms Unless otherwise indicated, the following terms and phrases as used herein are intended to have the following meanings: In the present invention, "MPa" means megapascals.

[0034] In the present invention, "w / v%" represents the percentage of the mass of a single component described in a solution to the total volume of the solution.

[0035] As used herein, "wt %" is defined as the weight of a single component in a composition divided by the total weight of all components of the composition and then multiplied by 100%.

[0036] In the present invention, "Da" represents the molecular weight unit, Dalton; "kDa" represents the molecular weight unit, kilodalton.

[0037] The "nanofiltration membrane" described in the present invention is a pressure-driven separation membrane between reverse osmosis and ultrafiltration, with a molecular weight cutoff of 150~2000 Da. It is a selective separation membrane that allows solvent molecules or certain low molecular weight solutes or low-valent ions to pass through.

[0038] In the foregoing text of the present invention, all numerical values ​​disclosed herein are approximate, regardless of whether the words "about" or "approximately" are used. Based on the disclosed numbers, the value of each numerical value may vary by less than ±10% or by a reasonable difference deemed by a person skilled in the art, such as ±1%, ±2%, ±3%, ±4% or ±5%.

[0039] In the present invention, "ee" stands for separation efficiency.

[0040] The drugs used in the present invention are purchased from the open legal market and have not been further purified.

[0041] In some embodiments, the room temperature is 5-45°C, in some embodiments, the room temperature is 10-40°C, in some embodiments, the room temperature is 15-35°C, in some embodiments, the room temperature is 20-30°C, and in some embodiments, the room temperature is 25°C.

[0042] Beneficial effects 1. A multi-level synergistic effect significantly improves chiral separation performance. This invention sequentially prepares an intermediate layer and a cortex layer with chiral recognition capabilities on a porous base membrane, leveraging their synergistic effect to achieve multi-level, precise construction of a high-performance, multilayer nanocomposite membrane. The intermediate layer's unique three-dimensional network structure, formed by cross-linking amino acid-functionalized carbon quantum dots, cyclodextrin derivatives, sodium alginate, and metal ions, provides abundant sites and a specialized microenvironment for chiral recognition. The cortex layer is prepared by interfacial polymerization of an aqueous solution containing amino acid-functionalized carbon quantum dots and cyclodextrin derivatives with an organic solution, further increasing the number of active sites for chiral recognition. Compared to existing chiral separation membranes with a single functional layer (cortex) structure, this multi-level chiral recognition system can accurately identify and differentiate enantiomers from multiple levels and angles, significantly improving the selectivity and efficiency of chiral separation, thereby achieving a more efficient and stable chiral separation process.

[0043] 2. Enhanced diversity of chiral recognition sites. Amino acid functionalized carbon quantum dots, cyclodextrin derivatives, etc. each play a unique role in chiral recognition. Amino acid functionalized carbon quantum dots have good hydrophilicity and biocompatibility, and the amino acid groups on their surface can form specific hydrogen bonds and mutual electrostatic interactions with chiral molecules; cyclodextrin derivatives have a unique hydrophobic cavity structure and can include chiral molecules. Different cyclodextrin derivatives can adapt to the inclusion requirements of different types of chiral molecules due to their structural differences. The combination of multiple chiral recognition components in the middle layer and the cortex makes the chiral nanocomposite membrane have a richer and more diverse chiral recognition sites than existing technologies, and can adapt to the separation of more chiral compounds.

[0044] 3. The preparation method of the intermediate layer and the skin layer with chiral recognition function of the present invention adopts the intermediate layer impregnation-crosslinking and interfacial polymerization process. This process is fully compatible with the existing industrial roll-to-roll composite film production line, suitable for large-scale production, and has good industrial application and promotion prospects. DETAILED DESCRIPTION

[0045] In order to enable those skilled in the art to better understand the technical solutions of the present invention, some non-limiting embodiments are further disclosed below to further illustrate the present invention in detail.

[0046] The reagents used in the present invention can be purchased from the market or prepared by the method described in the present invention.

[0047] Example 1: A method for preparing a multilayer nanocomposite separation membrane containing a chiral recognition functional intermediate layer and a skin layer is prepared according to the following steps: Step 1) Preparation of arginine-functionalized carbon quantum dots: 1000 g of citric acid monohydrate and 1000 g of L-arginine were added to 4.5 L of pure water, and the mixture was uniformly dissolved at a stirring speed of 1000 r / min. The mixed solution was then slowly heated from room temperature to 200°C within 20 minutes. After the reaction time of 150 minutes, the color of the solution changed from colorless to dark, and the heating was stopped. The reaction solution was further separated and purified by a combined membrane separation process of 0.2 µm microfiltration and 300 Da molecular weight cutoff nanofiltration. The purified solution was freeze-dried to obtain arginine-functionalized carbon quantum dot powder.

[0048] Step 2) Preparation of an intermediate layer with chiral recognition function: First, a coating solution A containing 0.1 wt% magnesium sulfate and 1 wt% calcium chloride is prepared.

[0049] Then, a coating solution B containing 0.05 wt% arginine-functionalized carbon quantum dots, 1 wt% carboxylated cyclodextrin, and 0.1 wt% sodium alginate was prepared.

[0050] A polyethersulfone porous base membrane with a pore size of 50 nm was placed in contact with the coating solution A for 5 minutes and then dried; The porous base membrane coated with solution A was then contacted with the coating solution B for 6 minutes and blown dry, thereby preparing an intermediate layer with chiral recognition function on the surface of the polyethersulfone porous base membrane.

[0051] Step 3) Preparation of a cortex with chiral recognition function: Take an aqueous solution containing 0.3 wt% arginine-functionalized carbon quantum dots, 1 wt% carboxylated cyclodextrin and 1 wt% piperazine, calculated based on the total mass of the aqueous solution, and immerse the porous base membrane coated with an intermediate layer obtained in step 2 in the aqueous solution for 10 minutes. Remove the excess aqueous solution, and then apply a n-hexane solution containing 0.3 w / v% trimesoyl chloride on the surface. After 5 minutes of interfacial polymerization reaction, remove the excess trimesoyl chloride on the surface, and finally dry in an oven at 60°C for 10 minutes. Dry to prepare a cortex with chiral recognition function on the surface of the intermediate layer, thereby preparing the multilayer nanocomposite separation membrane with chiral separation function, marked as Group 1.

[0052] Example 2 A method for preparing a multilayer nanocomposite separation membrane containing a chiral recognition functional intermediate layer and a skin layer is prepared by the following steps: Step 1) Preparation of aspartic acid functionalized carbon quantum dots: 1200 g of citric acid monohydrate and 1000 g of L-aspartic acid were added to 5 L of pure water, and the mixture was uniformly dissolved at a stirring speed of 1000 r / min. The mixed solution was then slowly heated from room temperature to 210°C over 25 minutes. After 160 minutes of reaction, the color of the solution changed from colorless to dark, and heating was stopped. The reaction solution was further separated and purified using a combined membrane separation process of 0.2 µm microfiltration and 300 Da molecular weight cutoff nanofiltration. The purified solution was freeze-dried to obtain aspartic acid functionalized carbon quantum dot powder.

[0053] Step 2) Preparation of an intermediate layer with chiral recognition function: First, a coating solution A containing 0.2 wt% magnesium chloride and 0.5 wt% calcium nitrate was prepared.

[0054] Then, a coating solution B containing 1 wt% aspartic acid functionalized carbon quantum dots, 1 wt% sulfonated cyclodextrin, and 0.3 wt% sodium alginate was prepared.

[0055] A polysulfone porous base membrane with a pore size of 30 nm was placed in contact with the coating solution A for 10 minutes and then dried; The porous base membrane coated with solution A was then contacted with the coating solution B for 10 minutes and blown dry, thereby preparing an intermediate layer with chiral recognition function on the surface of the polysulfone porous base membrane.

[0056] Step 3) Preparation of a cortex with chiral recognition function: Take an aqueous solution containing 0.5 wt% aspartic acid functionalized carbon quantum dots, 0.5 wt% sulfonated cyclodextrin and 2 wt% piperazine, calculated based on the total mass of the aqueous solution, and immerse the porous base membrane coated with an intermediate layer obtained in step 2 in the aqueous solution for 8 minutes. Remove the excess aqueous solution, and then apply a n-hexane solution containing 0.2 w / v% trimesoyl chloride on the surface. After interfacial polymerization reaction for 3 minutes, remove the excess trimesoyl chloride on the surface, and finally dry in an oven at 60°C for 15 minutes. Dry to prepare a cortex with chiral recognition function on the surface of the intermediate layer, thereby preparing the multilayer nanocomposite separation membrane with chiral separation function, marked as Group 2.

[0057] Example 3 A method for preparing a multilayer nanocomposite separation membrane containing a chiral recognition functional intermediate layer and a skin layer is prepared by the following steps: Step 1) Preparation of cysteine-functionalized carbon quantum dots: 1100 g of citric acid monohydrate and 1000 g of L-cysteine ​​were added to 5 L of pure water, and the mixture was uniformly dissolved at a stirring speed of 1000 r / min. The mixed solution was then slowly heated from room temperature to 205°C within 20 minutes. After 160 minutes of reaction, the color of the solution changed from colorless to dark, and heating was stopped. The reaction solution was further separated and purified using a combined membrane separation process of 0.2 µm microfiltration and 300 Da molecular weight cutoff nanofiltration. The purified solution was freeze-dried to obtain cysteine-functionalized carbon quantum dot powder.

[0058] Step 2) Preparation of an intermediate layer with chiral recognition function: First, a coating solution A containing 0.5 wt% magnesium nitrate and 0.5 wt% calcium chloride was prepared.

[0059] Then, a coating solution B containing 0.3 wt% cysteine ​​functionalized carbon quantum dots, 0.8 wt% amino cyclodextrin, and 0.6 wt% sodium alginate was prepared.

[0060] A cellulose acetate porous base membrane with a pore size of 20 nm was placed in contact with the coating solution A for 15 minutes and then dried; The porous base membrane coated with solution A was contacted with the coating solution B for 9 minutes and then blown dry, thereby preparing an intermediate layer with chiral recognition function on the surface of the porous cellulose acetate base membrane.

[0061] Step 3) Preparation of a cortex with chiral recognition function: Take an aqueous solution containing 0.7 wt% cysteine ​​functionalized carbon quantum dots, 1.5 wt% aminocyclodextrin and 1 wt% m-phenylenediamine, calculated based on the total mass of the aqueous solution, and immerse the porous base membrane coated with an intermediate layer obtained in step 2 in the aqueous solution for 10 minutes. Remove the excess aqueous solution, and then apply a n-hexane solution containing 0.5 w / v% terephthaloyl chloride on the surface. After 8 minutes of interfacial polymerization reaction, remove the excess terephthaloyl chloride on the surface, and finally dry in an oven at 60°C for 12 minutes. Dry to prepare a cortex with chiral recognition function on the surface of the intermediate layer, thereby preparing the multilayer nanocomposite separation membrane with chiral separation function, marked as Group 3.

[0062] Example 4 A method for preparing a multilayer nanocomposite separation membrane containing a chiral recognition functional intermediate layer and a skin layer is prepared by the following steps: Step 1) Preparation of glycine-functionalized carbon quantum dots: 1000 g of citric acid monohydrate and 1200 g of L-glycine were added to 5 L of pure water, and the mixture was uniformly dissolved at a stirring speed of 1000 r / min. The mixed solution was then slowly heated from room temperature to 200°C within 20 minutes. After the reaction time of 150 minutes, the color of the solution changed from colorless to dark, and the heating was stopped. The reaction solution was further separated and purified by a combined membrane separation process of 0.2 µm microfiltration and 300 Da molecular weight cutoff nanofiltration. The purified solution was freeze-dried to obtain glycine-functionalized carbon quantum dot powder.

[0063] Step 2) Preparation of an intermediate layer with chiral recognition function: First, a coating solution A containing 0.6 wt % magnesium sulfate and 0.9 wt % calcium bicarbonate was prepared.

[0064] Then, a coating solution B containing 2 wt% glycine functionalized carbon quantum dots, 0.5 wt% amino cyclodextrin, and 0.4 wt% sodium alginate was prepared.

[0065] A polyvinylidene fluoride porous base membrane with a pore size of 60 nm was placed in contact with the coating solution A for 12 minutes and then dried; The porous base membrane coated with solution A was then contacted with the coating solution B for 15 minutes and blown dry, thereby preparing an intermediate layer with chiral recognition function on the surface of the porous cellulose base membrane.

[0066] Step 3) Preparation of a cortex with chiral recognition function: Take an aqueous solution containing 2 wt% glycine-functionalized carbon quantum dots, 0.3 wt% amino-cyclodextrin and 1.5 wt% piperazine, calculated based on the total mass of the aqueous solution, and immerse the porous base membrane coated with an intermediate layer obtained in step 2 in the aqueous solution for 9 minutes. Remove the excess aqueous solution, and then apply a n-hexane solution containing 0.3 w / v% isophthaloyl chloride on the surface. After 4 minutes of interfacial polymerization reaction, remove the excess trimesoyl chloride on the surface, and finally dry in an oven at 60°C for 10 minutes. Dry to prepare a cortex with chiral recognition function on the surface of the intermediate layer, thereby preparing the multilayer nanocomposite separation membrane with chiral separation function, marked as Group 4.

[0067] Example 5 A method for preparing a multilayer nanocomposite separation membrane containing a chiral recognition functional intermediate layer and a skin layer is prepared by the following steps: Step 1) Preparation of lysine-functionalized carbon quantum dots: 1200 g of citric acid monohydrate and 1000 g of L-lysine were added to 5 L of pure water, and the mixture was uniformly dissolved at a stirring speed of 1000 r / min. The mixed solution was then slowly heated from room temperature to 210°C within 25 minutes. After 155 minutes of reaction, the color of the solution changed from colorless to dark, and heating was stopped. The reaction solution was further separated and purified using a combined membrane separation process of 0.2 µm microfiltration and 300 Da molecular weight cutoff nanofiltration. The purified solution was freeze-dried to obtain lysine-functionalized carbon quantum dot powder.

[0068] Step 2) Preparation of an intermediate layer with chiral recognition function: First, a coating solution A containing 0.3 wt% magnesium chloride and 1.2 wt% calcium nitrate was prepared.

[0069] Then, a coating solution B containing 0.8 wt% lysine functionalized carbon quantum dots, 0.9 wt% carboxylated cyclodextrin, and 0.8 wt% sodium alginate was prepared.

[0070] A polyacrylonitrile porous base membrane with a pore size of 50 nm was placed in contact with the coating solution A for 15 minutes and then dried; The porous base membrane coated with solution A was then contacted with the coating solution B for 10 minutes and blown dry, thereby preparing an intermediate layer with chiral recognition function on the surface of the porous polyacrylonitrile base membrane.

[0071] Step 3) Preparation of a cortex with chiral recognition function: Take an aqueous solution containing 1 wt% lysine-functionalized carbon quantum dots, 1 wt% carboxylated cyclodextrin and 1 wt% m-phenylenediamine, calculated based on the total mass of the aqueous solution, and immerse the porous base membrane coated with an intermediate layer obtained in step 2 in the aqueous solution for 6 minutes. Remove the excess aqueous solution, and then apply a n-hexane solution containing 0.6 w / v% trimesoyl chloride on the surface. After 6 minutes of interfacial polymerization reaction, remove the excess trimesoyl chloride on the surface, and finally dry in an oven at 60°C for 13 minutes. Dry to prepare a cortex with chiral recognition function on the surface of the intermediate layer, thereby preparing the multilayer nanocomposite separation membrane with chiral separation function, marked as Group 5.

[0072] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that the intermediate layer having chiral recognition function is not included, and the rest are the same, specifically: Step 1) Preparation of arginine-functionalized carbon quantum dots: 1000 g of citric acid monohydrate and 1000 g of L-arginine were added to 4.5 L of pure water, and the mixture was uniformly dissolved at a stirring speed of 1000 r / min. The mixed solution was then slowly heated from room temperature to 200°C within 20 minutes. After the reaction time of 150 minutes, the color of the solution changed from colorless to dark, and the heating was stopped. The reaction solution was further separated and purified by a combined membrane separation process of 0.2 µm microfiltration and 300 Da molecular weight cutoff nanofiltration. The purified solution was freeze-dried to obtain arginine-functionalized carbon quantum dot powder.

[0073] Step 2) Take an aqueous solution containing 0.3 wt% arginine-functionalized carbon quantum dots, 1 wt% carboxylated cyclodextrin and 1 wt% piperazine, calculated based on the total mass of the aqueous solution, and immerse a polyethersulfone porous base membrane with a pore size of 50 nm in the aqueous solution for 10 minutes. Remove the excess aqueous solution, and then apply a n-hexane solution containing 0.3 w / v% trimesoyl chloride on the surface. After the interfacial polymerization reaction for 5 minutes, remove the excess trimesoyl chloride on the surface, and finally dry in an oven at 60°C for 10 minutes. Dry to prepare a skin with chiral recognition function on the surface of the intermediate layer. The resulting composite membrane is marked as Group 6.

[0074] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that the chiral recognition functional cortex is not included, and the rest is the same, specifically: Step 1) Preparation of arginine-functionalized carbon quantum dots: 1000 g of citric acid monohydrate and 1000 g of L-arginine were added to 4.5 L of pure water, and the mixture was uniformly dissolved at a stirring speed of 1000 r / min. The mixed solution was then slowly heated from room temperature to 200°C within 20 minutes. After the reaction time of 150 minutes, the color of the solution changed from colorless to dark, and the heating was stopped. The reaction solution was further separated and purified by a combined membrane separation process of 0.2 µm microfiltration and 300 Da molecular weight cutoff nanofiltration. The purified solution was freeze-dried to obtain arginine-functionalized carbon quantum dot powder.

[0075] Step 2) Preparation of an intermediate layer with chiral recognition function: First, a coating solution A containing 0.1 wt% magnesium sulfate and 1 wt% calcium chloride is prepared.

[0076] Then, a coating solution B containing 0.05 wt% arginine-functionalized carbon quantum dots, 1 wt% carboxylated cyclodextrin, and 0.1 wt% sodium alginate was prepared.

[0077] A polyethersulfone porous base membrane with a pore size of 50 nm was placed in contact with the coating solution A for 5 minutes and then dried; The porous base membrane coated with solution A was contacted with the above-mentioned coating solution B for 6 minutes and blown dry to prepare an intermediate layer with chiral recognition function on the surface of the polyethersulfone porous base membrane. It was dried in an oven at 60°C for 10 minutes and dried. The resulting composite membrane was marked as Group 7.

[0078] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is step 2), and the rest is the same.

[0079] In step 2) of comparative example 3, arginine was used as feed material instead of arginine-functionalized carbon quantum dots as feed material, specifically: Step 2) First, prepare a coating solution A containing 0.1 wt% magnesium sulfate and 1 wt% calcium chloride.

[0080] Then, a coating solution B containing 0.05 wt% L-arginine, 1 wt% carboxylated cyclodextrin, and 0.1 wt% sodium alginate was prepared. A polyethersulfone porous membrane with a pore size of 50 nm was exposed to the coating solution A for 5 minutes and then air-dried. The porous membrane, coated with solution A, was then exposed to the coating solution B for 6 minutes and then air-dried.

[0081] Step 3) of Comparative Example 3 is the same as that of Example 1, and the composite membrane obtained is marked as Group 8.

[0082] Comparative Example 4: The difference between Comparative Example 4 and Example 1 is step 3), and the rest is the same.

[0083] In step 3) of comparative example 4, arginine was used as feed material instead of arginine-functionalized carbon quantum dots as feed material, specifically: Take an aqueous solution containing 0.3 wt% L-arginine, 1 wt% carboxylated cyclodextrin and 1 wt% piperazine, calculated based on the total mass of the aqueous solution, and immerse the porous base membrane coated with an intermediate layer obtained in step 2 in the aqueous solution for 10 minutes. Remove the excess aqueous solution, and then apply a n-hexane solution containing 0.3 w / v% trimesoyl chloride on the surface. After the interfacial polymerization reaction for 5 minutes, remove the excess trimesoyl chloride on the surface. Finally, dry it in an oven at 60°C for 10 minutes. The resulting composite membrane is marked as Group 9.

[0084] Comparative Example 5: The difference between Comparative Example 5 and Example 1 is that the functionalized carbon quantum dots are different. Comparative Example 5 uses tryptophan-functionalized carbon quantum dots while Example 1 uses arginine-functionalized carbon quantum dots. The rest are the same.

[0085] Step 1 of Comparative Example 5) Preparation of tryptophan-functionalized carbon quantum dots: 1000 g of citric acid monohydrate and 1000 g of L-tryptophan were added to 4.5 L of pure water, and the mixture was dissolved evenly at a stirring speed of 1000 r / min; the mixed solution was then slowly heated from room temperature to 200 ° C within 20 minutes, and the color of the solution changed from colorless to dark after 150 minutes of reaction, and the heating was stopped; the reaction solution was further separated and purified by a combined membrane separation process of 0.2 µm microfiltration and 300 Da molecular weight cutoff nanofiltration, and the purified solution was freeze-dried to obtain tryptophan-functionalized carbon quantum dot powder.

[0086] Step 2) First, prepare a coating solution A containing 0.1 wt% magnesium sulfate and 1 wt% calcium chloride.

[0087] Then, a coating solution B containing 0.05 wt% tryptophan functionalized carbon quantum dots, 1 wt% carboxylated cyclodextrin, and 0.1 wt% sodium alginate was prepared.

[0088] A polyethersulfone porous base membrane with a pore size of 50 nm was placed in contact with the coating solution A for 5 minutes and then dried; The porous base membrane coated with solution A was then placed in contact with the coating solution B for 6 minutes and then blown dry.

[0089] Step 3) Take an aqueous solution containing 0.3 wt% tryptophan functionalized carbon quantum dots, 1 wt% carboxylated cyclodextrin and 1 wt% piperazine, calculated based on the total mass of the aqueous solution, and immerse the porous base membrane coated with an intermediate layer obtained in step 2 in the aqueous solution for 10 minutes. Remove the excess aqueous solution, and then apply a n-hexane solution containing 0.3 w / v% trimesoyl chloride on the surface. After the interfacial polymerization reaction for 5 minutes, remove the excess trimesoyl chloride on the surface, and finally dry it in an oven at 60°C for 10 minutes. The resulting composite membrane is marked as Group 10.

[0090] Comparative Example 6: The difference between Comparative Example 6 and Example 1 is that carboxylated cyclodextrin is not added in steps 2-3), and the rest is the same, specifically: Step 2) First, prepare a coating solution A containing 0.1 wt% magnesium sulfate and 1 wt% calcium chloride.

[0091] Then, a coating solution B containing 0.05 wt% arginine-functionalized carbon quantum dots and 0.1 wt% sodium alginate was prepared. A polyethersulfone porous membrane with a pore size of 50 nm was exposed to the coating solution A for 5 minutes and then dried. The porous membrane coated with solution A was then exposed to the coating solution B for 6 minutes and dried to form an intermediate layer.

[0092] Step 3) Take an aqueous solution containing 0.3 wt% arginine-functionalized carbon quantum dots and 1 wt% piperazine, calculated based on the total mass of the aqueous solution, and immerse the porous base membrane coated with an intermediate layer obtained in step 2 in the aqueous solution for 10 minutes. Remove the excess aqueous solution, and then apply a n-hexane solution containing 0.3 w / v% trimesoyl chloride on the surface. After the interfacial polymerization reaction for 5 minutes, remove the excess trimesoyl chloride on the surface, and finally dry it in an oven at 60°C for 10 minutes. The prepared composite separation membrane is marked as Group 11.

[0093] Comparative Example 7: The difference between Comparative Example 7 and Example 1 is that in step 3), 1 wt% piperazine is not added to the aqueous phase solution, and the surface is coated with n-hexane instead of a 0.3 w / v% n-hexane solution of trimesoyl chloride. The remaining steps 1) and 2) are the same as in Example 1. Step 3) of Comparative Example 7 is specifically as follows: Step 3) Take an aqueous solution containing 0.3 wt% arginine-functionalized carbon quantum dots and 1 wt% carboxylated cyclodextrin, calculated based on the total mass of the aqueous solution, and immerse the porous base membrane coated with an intermediate layer obtained in step 2 in the aqueous solution for 10 minutes. Remove excess aqueous solution, and then apply n-hexane on the surface. After 5 minutes, remove excess n-hexane on the surface, and finally dry in an oven at 60°C for 10 minutes. Dry to prepare a separation membrane, which is marked as Group 12.

[0094] Example 6 The composite membranes prepared from Groups 1 to 12 were tested under the following conditions: operating temperature of 25 °C, operating pressure of 0.55 MPa, test solution of 10 mmol / L D,L-phenylalanine aqueous solution (where the ratio of D to L was 1:1), and the concentration of L-phenylalanine after membrane filtration, C L-苯丙氨酸 and D-phenylalanine concentration C D-苯丙氨酸 , calculated the membrane flux and the ee value of L-phenylalanine, and obtained Table 1.

[0095] Table 1 Chiral selectivity and permeation performance test

[0096] The membrane flux ×100%, A is the membrane area m 2 , t is time h, V is the permeate volume; Separation efficiency of L-phenylalanine ; The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a chiral nanocomposite film, comprising: An intermediate layer with chiral recognition function is prepared on a porous base membrane, and then a skin layer with chiral recognition function is prepared on the intermediate layer by interfacial polymerization to obtain a multilayer nanocomposite separation membrane containing the intermediate layer with chiral recognition function and the skin layer.

2. The preparation method according to claim 1, characterized in that The intermediate layer with chiral recognition function is specifically a three-dimensional network structure intermediate layer formed by cross-linking amino acid functionalized carbon quantum dots, cyclodextrin derivatives, sodium alginate and metal ions; and / or, the porous base membrane includes at least one selected from polysulfone, polyethersulfone, cellulose acetate, polyacrylonitrile and polyvinylidene fluoride.

3. The preparation method according to claim 1 or 2, characterized in that The intermediate layer with chiral recognition function is prepared by coating two intermediate layer coating liquids A and B on the surface of the porous base membrane respectively, and then undergoing a cross-linking reaction. The coating liquid A is a mixed aqueous solution of magnesium salt and calcium salt, and the coating liquid B is a mixed aqueous solution of amino acid functionalized carbon quantum dots, cyclodextrin derivatives and sodium alginate.

4. The preparation method according to claim 3, characterized in that The magnesium salt aqueous solution in the coating liquid A includes at least one selected from a magnesium chloride aqueous solution, a magnesium nitrate aqueous solution, and a magnesium sulfate aqueous solution; and / or, the mass percentage concentration of the magnesium salt in the coating liquid A is 0.01-2wt%; and / or, the calcium salt aqueous solution in the coating liquid A includes at least one selected from a calcium chloride aqueous solution, a calcium nitrate aqueous solution, and a calcium bicarbonate aqueous solution; and / or, the mass percentage concentration of the calcium salt in the coating liquid A is 0.01-2wt%; and / or, the amino acid functionalized carbon quantum dots include arginine functionalized carbon quantum dots, aspartic acid functionalized carbon quantum dots, cysteine ​​functionalized carbon quantum dots, and arginine functionalized carbon quantum dots. quantum dots, glycine-functionalized carbon quantum dots and lysine-functionalized carbon quantum dots; and / or, the mass percentage concentration of the amino acid-functionalized carbon quantum dots in the coating solution B is 0.1~3wt%; and / or, the cyclodextrin derivative includes at least one selected from carboxylated cyclodextrin, sulfonated cyclodextrin and amino cyclodextrin; and / or, the mass percentage concentration of the cyclodextrin derivative in the coating solution B is 0.1~5wt%; and / or, the molecular weight range of the sodium alginate is 5~100kDa; and / or, the mass percentage concentration of the sodium alginate in the coating solution B is 0.1~1wt%.

5. The preparation method according to any one of claims 1 to 4, characterized in that The preparation of the cortex with chiral recognition function includes: taking a mutually immiscible aqueous phase solution and an organic phase solution to perform an interfacial polymerization reaction to obtain a cortex with chiral recognition function, wherein the aqueous phase solution includes a polyamine reaction monomer, amino acid functionalized carbon quantum dots and a cyclodextrin derivative; and / or, the organic phase solution includes a polyacyl chloride reaction monomer and an organic solvent.

6. The preparation method according to claim 5, characterized in that The polyamine reaction monomer is at least one of piperazine and m-phenylenediamine; and / or, the mass percentage concentration of the polyamine reaction monomer in the aqueous solution is 0.1-3wt%; and / or, the amino acid functionalized carbon quantum dots are at least one of arginine functionalized carbon quantum dots, aspartic acid functionalized carbon quantum dots, cysteine ​​functionalized carbon quantum dots, glycine functionalized carbon quantum dots and lysine functionalized carbon quantum dots; and / or, the mass percentage concentration of the amino acid functionalized carbon quantum dots in the aqueous solution is 0.1-2wt%; and / or, The cyclodextrin derivative is at least one of carboxylated cyclodextrin, sulfonated cyclodextrin and amino cyclodextrin; and / or the mass percentage concentration of the cyclodextrin derivative in the aqueous solution is 0.1-2wt%; and / or the polyacyl chloride reaction monomer includes at least one selected from trimesoyl chloride, terephthaloyl chloride and isophthaloyl chloride; and / or the mass volume concentration of the polyacyl chloride reaction monomer in the organic phase solution is 0.1-3w / v; and / or the organic solvent is at least one of n-hexane, cyclohexane, n-heptane and isoparaffin G.

7. The preparation method according to any one of claims 1 to 6, characterized in that The amino acid functionalized carbon quantum preparation method comprises: mixing citric acid, L-amino acid and water, heating to a target temperature, reacting, separating and drying to obtain amino acid functionalized carbon quantum dots; The citric acid is selected from any one of monohydrated citric acid and anhydrous citric acid, or a mixture thereof; and / or the L-amino acid is selected from at least one of L-arginine, L-aspartic acid, L-cysteine, and L-glycine; and / or the feed mass ratio of the citric acid to the amino acid is (1.0-1.2):(1.0-1.2); and / or the target temperature for heating is 200-210° C.; and / or the heating time is 20-25 min.

8. A method for preparing a chiral nanocomposite film, comprising: Step 1) Preparation of an intermediate layer with chiral recognition function: contacting the porous base film with coating solution A for 1 minute to 20 minutes and then drying by air; The porous base membrane coated with solution A is then contacted with coating solution B for 1 to 20 minutes and blown dry, thereby preparing an intermediate layer with chiral recognition function on the surface of the porous base membrane; Step 2) Preparation of a cortex with chiral recognition function: Take an aqueous solution containing 0.1~2wt% amino acid functionalized carbon quantum dots, 0.1~2wt% cyclodextrin derivatives and 0.1~3wt% polyamine, calculated based on the total mass of the aqueous solution, and immerse the porous base membrane coated with an intermediate layer obtained in step 1 in the aqueous solution for 1 minute to 20 minutes, remove the excess aqueous solution, and then apply an organic phase solution containing 0.1~3w / v% polyacyl chloride on the surface, remove the excess polyacyl chloride on the surface of the obtained polyamide membrane, thereby forming a cortex with chiral recognition function on the surface of the intermediate layer, and obtaining a multilayer nanocomposite separation membrane containing a chiral recognition intermediate layer and a cortex.

9. A multilayer nanocomposite separation membrane obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the multilayer nanocomposite separation membrane according to claim 9 in separating amino acid enantiomers.

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