Cyclodextrin metal organic framework aromatic capsule for lasting fragrance retention as well as preparation method and application of cyclodextrin metal organic framework aromatic capsule

Abstract

The preparation method comprises the following steps: (1) preparation of gamma-CD-MOF: dissolving gamma-cyclodextrin and potassium hydroxide in a methanol-water mixed solvent, carrying out ultrasonic treatment, adding a morphology regulating agent, continuously carrying out ultrasonic treatment for 10 minutes, centrifuging, washing and drying to obtain gamma-CD-MOF; the nano-scale gamma-CD-MOF is obtained through a hydrothermal method; (2) hydrophobic modification of the gamma-CD-MOF: carrying out surface modification on the gamma-CD-MOF by adopting cholesterol succinic acid monoester, carrying out catalytic esterification reaction on 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and 4-dimethylaminopyridine at 60 DEG C for 24 hours, centrifuging, washing and drying to obtain hydrophobicity-enhanced MOF-CHS; and (3) packaging and slowly releasing essence, namely mixing the MOF-CHS and hemerocallis fulva flower essence in an ethanol solution, magnetically stirring, centrifuging, washing and drying to obtain the cyclodextrin metal organic framework aromatic capsule. According to the preparation method disclosed by the invention, efficient packaging and long-acting slow release of the essence are realized by accurately regulating and controlling the structure and surface functional modification of the gamma-CD-MOF.

Description

Technical Field

[0001] This invention belongs to the field of fragrance sustained-release material preparation technology, specifically relating to a cyclodextrin metal-organic framework aromatic capsule for long-lasting fragrance, its preparation method and application. Background Technology

[0002] Fragrances and flavorings have wide applications in various fields such as daily chemical products, food, and tobacco, especially in detergents, where consumers' demand for "long-lasting fragrance" is increasing. However, aromatic substances in fragrances and flavorings generally have high volatility and low stability. When exposed to environmental conditions such as air, light, and heat, they are prone to volatilization loss or deterioration, seriously affecting the retention of the product's aroma. To solve these problems, microencapsulation technology has attracted widespread attention as an effective means of fragrance encapsulation and sustained-release. By constructing physically or chemically stable wall structures, microcapsules can effectively isolate fragrances from the external environment, delaying their release and thus achieving a long-lasting fragrance effect.

[0003] In recent years, metal-organic frameworks (MOFs) have shown great potential in the fields of adsorption and sustained release due to their unique three-dimensional hollow porous structure, high specific surface area, tunable pore size, good chemical stability, and diverse functionalities. Cyclodextrin metal-organic frameworks (CD-MOFs), as green materials in the MOF family, combine the biocompatibility of natural cyclodextrins with the porosity of MOF structures, exhibiting excellent flavor loading and sustained release potential.

[0004] However, while existing cyclodextrin metal-organic frameworks (CD-MOFs) materials possess excellent fragrance loading and sustained-release potential, their synthetic routes are cumbersome and time-consuming, making it difficult to meet the efficiency requirements of actual production. Furthermore, the strong hydrophilicity of CD-MOF surfaces can easily lead to rapid fragrance release in aqueous washing environments, thereby reducing sustained-release efficiency and failing to fully realize their advantages in long-lasting fragrance retention. Summary of the Invention

[0005] To address the issues of volatile fragrances and short-lasting scent in existing detergent products, this invention aims to provide a cyclodextrin metal-organic framework aromatic capsule for long-lasting fragrance, its preparation method, and its applications. This invention achieves efficient encapsulation and long-lasting sustained release of fragrances through precise control of the structure and surface functionalization modification of γ-CD-MOF.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] In one aspect, this invention provides a method for preparing cyclodextrin-based metal-organic framework aromatic capsules for long-lasting fragrance, comprising the following steps:

[0008] (1) Preparation of γ-CD-MOF: γ-cyclodextrin and potassium hydroxide were dissolved in methanol-water mixed solvent, ultrasonically treated, and then a morphology modifier was added and ultrasonically treated for 10 min. After centrifugation, washing and drying, nano-sized γ-CD-MOF was obtained.

[0009] (2) Hydrophobic modification of γ-CD-MOF: The surface of γ-CD-MOF was modified with cholesterol succinate monoester. The esterification reaction was carried out by 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and 4-dimethylaminopyridine. The reaction was carried out at 60°C for 24 h. After centrifugation, washing and drying, MOF-CHS with enhanced hydrophobicity was obtained.

[0010] (3) Encapsulation and sustained release of fragrance: The MOF-CHS and daylily fragrance are mixed in an ethanol solution, magnetically stirred, centrifuged, washed and dried to obtain the cyclodextrin metal-organic framework aromatic capsule.

[0011] As a further aspect of the present invention: in step (1), the molar ratio of the γ-cyclodextrin to the potassium hydroxide is 1:5 to 1:10;

[0012] And / or, in step (1), the volume ratio of methanol to water is 3:5;

[0013] And / or, in step (1), the conditions for ultrasonic treatment are 28 kHz, 100 W, and 40-60 °C for 5-10 min;

[0014] And / or, in step (1), the morphology modifier is a methanol solution of PEG 20000 or hexadecyltrimethylammonium bromide at a concentration of 8 mg / mL;

[0015] And / or, in step (1), the centrifugation conditions are 8000 rpm for 30 min;

[0016] And / or, in step (1), the solvent for washing is methanol;

[0017] And / or, in step (1), the drying parameters are 50°C and 12h.

[0018] As a further aspect of the present invention: in step (2), the solvent used in the esterification reaction is N,N-dimethylformamide;

[0019] And / or, in step (2), the molar ratio of cholesterol succinate monoester, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and 4-dimethylaminopyridine is 1:1 to 2:0.5 to 1.5;

[0020] And / or, in step (2), the centrifugation conditions are 8000 rpm for 30 min;

[0021] And / or, in step (2), the solvent for washing is anhydrous ethanol;

[0022] And / or, in step (2), the drying parameters are 50°C and 12h.

[0023] As a further aspect of the present invention: in step (3), the core-to-wall ratio of the MOF-CHS to the daylily fragrance is 2:1;

[0024] And / or, in step (3), the magnetic stirring conditions are 800 rpm and 30°C for 12 h;

[0025] And / or, in step (3), the centrifugation conditions are 8000 rpm for 30 min;

[0026] And / or, in step (3), the solvent for washing is anhydrous ethanol;

[0027] And / or, in step (3), the drying operation specifically involves: pre-freezing in a refrigerator at -80°C for 24 hours, and then drying in a freeze dryer at -50°C for 48 hours.

[0028] In a second aspect, the present invention also provides a cyclodextrin metal-organic framework aromatic capsule for long-lasting fragrance, which is prepared by the above-described method for preparing a cyclodextrin metal-organic framework aromatic capsule for long-lasting fragrance.

[0029] In a third aspect, the present invention also provides the application of the above-mentioned cyclodextrin metal-organic framework aromatic capsule for long-lasting fragrance in the field of detergents.

[0030] The positive and progressive effects of this invention are as follows:

[0031] (1) The γ-CD-MOF synthesis process of the present invention is fast, the ultrasonic-assisted crystallization time is short, the process flow is simplified, and the crystallization preparation time is controlled within 30 minutes, which is superior to the long crystallization process that is common in the prior art, and is conducive to realizing large-scale continuous production.

[0032] (2) This invention constructs a MOF-CHS material with hydrophobic properties by modifying γ-CD-MOF with hydrophobic ester compounds, which can reduce the dissolution or loss of fragrance during washing and improve the efficient loading and sustained release control of daylily fragrance.

[0033] (3) When the DF@MOF-CHS fragrance capsules prepared in this invention are added to unscented laundry detergent, they can maintain a fragrance duration of ≥7 days on the surface of cotton fabric, while the unencapsulated fragrance in the control sample only lasts for about 24 hours, resulting in a fragrance retention effect that is more than 7 times better. This significantly enhances the application value and user experience of the laundry product. In addition, according to market research and third-party testing reports, mainstream fragrance-retaining laundry detergent products (such as Libai Master Fragrance Laundry Detergent and Blue Moon Lavender Scented Laundry Detergent) claim a fragrance retention time of only 48 to 72 hours. However, this invention achieves a fragrance retention effect that is significantly better than commercially available products through microencapsulation technology, reaching more than 2.3 times that of commercially available products, fully demonstrating its significant advantage in long-lasting fragrance retention. Attached Figure Description

[0034] Figure 1 This is a scanning electron microscope image of γ-CD-MOF in Embodiment 1 of the present invention;

[0035] Figure 2 These are the Fourier transform infrared (FTIR) spectra of CD-MOF, CHS, and MOF-CHS in Embodiment 1 of the present invention.

[0036] Figure 3 This is a dynamic water contact angle (WCA) diagram of CD-MOF, MOF-CHS and DF@MOF-CHS in Embodiment 1 of the present invention;

[0037] Figure 4 These are the Fourier transform infrared (FTIR) spectra of DF, MOF-CHS, and DF@MOF-CHS in Embodiment 1 of the present invention;

[0038] Figure 5 The sensory evaluation chart shows the effect of adding unencapsulated daylily fragrance essence and daylily fragrance microcapsules to unscented laundry detergent on the fragrance retention time of cotton fabric.

[0039] Figure 6 This is an electronic nose response graph showing the fragrance retention time of unencapsulated daylily fragrance essence and daylily fragrance microcapsules on cotton fabric. Detailed Implementation

[0040] The present invention will now be described in detail with reference to embodiments, providing a clear and complete description of the technical solutions to facilitate understanding of the invention by those skilled in the art. The described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Furthermore, all raw materials mentioned below, unless otherwise specified, are commercially available products; and all process steps or preparation methods not mentioned in detail are process steps or preparation methods known to those skilled in the art.

[0041] [Performance Testing]

[0042] The products prepared in the examples and comparative examples were subjected to application performance tests, and the test methods are as follows:

[0043] I. Scanning electron microscope images: The tests were conducted using an environmental scanning electron microscope, model Quattro S, manufactured by Thermo Fisher Scientific Brno Ltd.

[0044] II. Fourier Transform Infrared Spectroscopy: The Fourier Transform Infrared Spectrometer (FTIR-6501) manufactured by Tianjin Gangdong Technology Co., Ltd. was used for testing.

[0045] III. Dynamic Water Contact Angle (WCA) Diagram: The test was conducted using a droplet shape analyzer, model DSA30S, manufactured by Krüz Scientific Instruments (Shanghai) Co., Ltd.

[0046] IV. Sensory Testing: Ten professional sensory evaluators conducted daily blind tests on the experimental group (wash samples containing DF@MOF-CHS microcapsules) and the control group (wash samples containing an equal amount of free fragrance) under constant temperature conditions. A 5-point scoring system was used: 5 points for extremely strong aroma (initial concentration), 4 points for noticeable aroma (70% initial), 3 points for medium aroma (50% initial), 2 points for weak aroma (approximately 30% initial), and 1 point for very weak aroma (≤20% initial). Data were analyzed based on the average scores from the ten evaluators.

[0047] V. Electronic nose test: The electronic nose instrument, model HeraclesNEO, manufactured by Amos (Shanghai) Instruments Trading Co., Ltd., was used for testing.

[0048] Example 1

[0049] A method for preparing cyclodextrin-based metal-organic framework aromatic capsules for long-lasting fragrance includes the following steps:

[0050] (1) Preparation process of γ-CD-MOF:

[0051] 162 mg of γ-cyclodextrin and 56 mg of potassium hydroxide were accurately weighed and dissolved in a mixed solvent of 3 mL methanol and 5 mL water. The solution was placed in a constant temperature water bath at 50 °C and sonicated (28 kHz, 100 W) for 5 min. 64 mg of PEG (Mw ≈ 20000) or CTAB was dissolved in 8 mL methanol and stirred thoroughly until completely dissolved, forming a clear solution. This solution was then slowly added to the treated mixed solution, and sonication was continued for 10 min. The precipitate was collected by centrifugation (8000 rpm, 30 min). The precipitate was washed three times with methanol (8000 rpm, 10 min) to obtain preliminarily purified γ-CD-MOF. The washed CD-MOF was transferred to a vacuum drying oven at 50 °C for 12 h and dried to constant weight to obtain structurally stable and morphologically sound γ-CD-MOF.

[0052] Table 1

[0053]

[0054] Table 1 shows the comparison of the effects of different morphology modifiers. When using PEG 20000, the average particle size of the resulting γ-CD-MOF was 322.28 nm, while when using CTAB, the average particle size of the product increased to 642.91 nm. Considering both loading efficiency and sustained-release performance, this invention prefers PEG 20000 as the morphology modifier, as the nanoscale γ-CD-MOF generated by it is more conducive to the efficient loading and slow release of fragrances.

[0055] The γ-CD-MOF obtained using PEG 20000 as a morphology modifier was characterized by scanning electron microscopy, and the results are as follows: Figure 1 As shown, the size of γ-CD-MOF is approximately 269±84 nm.

[0056] (2) Hydrophobic modification steps of CD-MOF:

[0057] 1 g of CD-MOF was added to a clean and dry 200 mL beaker, followed by 30 mL of N,N-dimethylformamide (DMF) to form a dispersion. 130 mg of cholesterol succinate monoester (CHS), 76 mg of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDC), and 32 mg of 4-dimethylaminopyridine (DMAP) were added sequentially to this dispersion as catalysts. The mixture was placed at 60 °C and continuously stirred on a thermostatic magnetic stirrer for 24 hours. After the reaction, it was allowed to cool naturally to room temperature. The resulting precipitate was collected by centrifugation (8000 rpm, 30 min) and thoroughly washed with anhydrous ethanol to remove residual catalyst and unreacted CHS. The sample was then transferred to a vacuum drying oven and dried at 50 °C for 12 hours. Finally, a CHS-modified CD-MOF composite material was obtained.

[0058] To verify whether CHS was successfully immobilized on the CD-MOF surface, Fourier transform infrared spectroscopy (FTIR) was used to analyze CD-MOF, CHS, and the product MOF-CHS. The infrared spectra are shown below. Figure 2 As shown. In the modified MOF-CHS sample, in addition to retaining the characteristic peaks of the original CD-MOF, there are also peaks at 1650 cm⁻¹. -1 -1750cm -1 A distinct -C=O absorption peak was observed at this wavelength, indicating that the CHS molecule was covalently linked to the hydroxyl group in the CD-MOF via esterification. In contrast, the unmodified CD-MOF showed no significant absorption signal in this band, suggesting that the cholesterol group had been successfully introduced into the MOF structure.

[0059] Figure 3 The dynamic water contact angle diagrams for CD-MOF, MOF-CHS, and DF@MOF-CHS are shown. The initial contact angle of CD-MOF was 51.9°, while that of MOF-CHS increased to 61.5°, indicating a decrease in surface hydrophilicity. With prolonged time, the contact angle of CD-MOF rapidly decreased to 34.4° at 10 s, demonstrating rapid wetting ability; in contrast, the contact angles of MOF-CHS at 10 s and 20 s were 48.4° and 48.6°, respectively, with a significantly slower rate of decrease, indicating a marked suppression of water droplet spreading and thus reduced surface wettability and enhanced hydrophobicity. This demonstrates the successful construction of hydrophobic microcapsules of MOF-CHS.

[0060] (3) Preparation of DF@MOF-CHS inclusion complex

[0061] Weigh 1g of the prepared MOF-CHS and 0.5g of Daylily Fragrance (DF), dissolve them in 30mL of anhydrous ethanol, and mix thoroughly to form a homogeneous solution. Place the solution on a magnetic stirrer and stir at 800rpm and 30℃ for 12 hours to ensure that MOF-CHS fully adsorbs and encapsulates the Daylily Fragrance.

[0062] After stirring, the mixture was transferred to a centrifuge and centrifuged at 8000 rpm for 30 minutes to separate the MOF-CHS precipitate containing daylily fragrance. The precipitate was then washed three times with anhydrous ethanol (centrifuged at 8000 rpm for 10 minutes each time) to remove unencapsulated free fragrance and other impurities. The washed precipitate was collected and pre-frozen at -80°C for 24 hours to prepare for the subsequent freeze-drying process. The pre-frozen sample was then transferred to a freeze dryer and freeze-dried under vacuum at -50°C for 48 hours to obtain a structurally stable and homogeneous DF@CD-MOF inclusion complex.

[0063] Figure 4 The images show the FTIR spectra of MOF-CHS, DF, and DF@MOF-CHS inclusion complex in this embodiment. In the FTIR spectrum of DF@MOF-CHS, apart from retaining the characteristic absorption peaks of MOF-CHS, the typical characteristic peaks of DF itself are not clearly visible, appearing only at 1350 cm⁻¹. -1 A faint peak intensity enhancement was observed around the pores, indicating that a small amount of DF molecules are exposed on the material surface. This phenomenon can be attributed to the fact that most of the fragrance molecules are encapsulated in the internal channels of the MOF, causing their characteristic absorption peaks to be masked by the framework absorption peaks; at the same time, the high loading of DF accumulates in the pores, partially destroying the MOF structure, and only a small amount of DF generates a detectable signal at this location due to accumulation and surface exposure.

[0064] Example 2

[0065] Fragrance retention experiment of DF@MOF-CHS after washing

[0066] Add DF@MOF-CHS containing 0.015g of daylily fragrance to 1.5g of unscented laundry detergent, and mix for 15 minutes using a magnetic stirrer (500rpm) to evenly disperse the microcapsules in the laundry detergent.

[0067] Dissolve the laundry detergent containing DF@MOF-CHS in 500mL of tap water and stir until completely dissolved to simulate the concentration of a regular wash.

[0068] Immerse the standard cotton fabric completely in the washing solution and let it soak for 30 minutes to allow the fragrance to fully contact the fibers.

[0069] Take out the fabric, rub it 20 times on the front side, then rub it 20 times on the back side to simulate the hand washing process.

[0070] Rinse twice with clean water for 5 minutes each time to simulate a normal rinse and remove residual laundry detergent.

[0071] After rinsing, wring dry by hand and hang in a ventilated place to air dry naturally.

[0072] Comparative Example 1

[0073] The experimental conditions and procedures were exactly the same as in Example 2, except that the DF@MOF-CHS (containing 0.015g of daylily fragrance) in the experimental materials was replaced with 0.015g of free daylily fragrance of equal fragrance content, and all other experimental parameters remained the same.

[0074] Figure 5 The sensory evaluation diagrams show the fragrance retention time of cotton fabric in Example 2 and Comparative Example 1.

[0075] As shown in the figure, the aroma sensory value of the flavor microcapsule group was consistently higher than that of the flavor group at different storage times. The aroma intensity of the two groups was similar on day 1, but the aroma of the flavor group decreased rapidly, reaching only 1.2 on day 7, while the aroma of the microcapsule group remained at 3.2.

[0076] The results showed that aromatic microcapsules could effectively delay aroma decay and improve aroma stability, which was superior to adding unencapsulated fragrances.

[0077] Figure 6 The electronic nose response diagrams for the fragrance retention time of cotton fabric in Example 2 and Control Example 1 are shown. The diagrams show the odor profiles of the unencapsulated daylily fragrance group (A) and the daylily fragrance microcapsule group (C) at different times (1, 3, 5, and 7 days).

[0078] The signal intensity of the unencapsulated daylily fragrance group (A) showed a significant decreasing trend with the extension of days, and the odor feature profile gradually shrank, indicating that the aroma substances were volatilized or degraded relatively quickly.

[0079] The overall profile of the daylily fragrance microcapsule group (C) is more stable, with less change in signal intensity, and it exhibits good retention, especially in the high-response region.

[0080] The results showed that the daylily fragrance microcapsules had a superior aroma retention capacity and could effectively slow down the loss of aroma within 7 days, further verifying the conclusions of the sensory experiment.

[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any form or substance. It should be noted that those skilled in the art can make various improvements and additions without departing from the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention. Any modifications, alterations, and equivalent changes made by those skilled in the art based on the above-disclosed technical content without departing from the spirit and scope of the present invention are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and evolutions made to the above embodiments based on the essential technology of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing cyclodextrin-based metal-organic framework aromatic capsules for long-lasting fragrance, characterized in that, Includes the following steps: (1) Preparation of γ-CD-MOF: γ-cyclodextrin and potassium hydroxide were dissolved in methanol-water mixed solvent, ultrasonically treated, and then a morphology modifier was added and ultrasonically treated for 10 min. After centrifugation, washing and drying, nano-sized γ-CD-MOF was obtained. (2) Hydrophobic modification of γ-CD-MOF: The surface of γ-CD-MOF was modified with cholesterol succinate monoester. The esterification reaction was carried out by 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and 4-dimethylaminopyridine. The reaction was carried out at 60°C for 24 h. After centrifugation, washing and drying, MOF-CHS with enhanced hydrophobicity was obtained. (3) Encapsulation and sustained release of fragrance: The MOF-CHS and daylily fragrance are mixed in an ethanol solution, magnetically stirred, centrifuged, washed and dried to obtain the cyclodextrin metal-organic framework aromatic capsule.

2. The method for preparing cyclodextrin metal-organic framework aromatic capsules for long-lasting fragrance according to claim 1, characterized in that, In step (1), the molar ratio of the γ-cyclodextrin to the potassium hydroxide is 1:5 to 1:10; And / or, in step (1), the volume ratio of methanol to water is 3:5; And / or, in step (1), the conditions for ultrasonic treatment are 28 kHz, 100 W, and 40-60 °C for 5-10 min; And / or, in step (1), the morphology modifier is a methanol solution of PEG 20000 or hexadecyltrimethylammonium bromide at a concentration of 8 mg / mL; And / or, in step (1), the centrifugation conditions are 8000 rpm for 30 min; And / or, in step (1), the solvent for washing is methanol; And / or, in step (1), the drying parameters are 50°C and 12h.

3. The method for preparing cyclodextrin metal-organic framework aromatic capsules for long-lasting fragrance according to claim 2, characterized in that, In step (2), the solvent used in the esterification reaction is N,N-dimethylformamide; And / or, in step (2), the molar ratio of cholesterol succinate monoester, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and 4-dimethylaminopyridine is 1:1 to 2:0.5 to 1.5; And / or, in step (2), the centrifugation conditions are 8000 rpm for 30 min; And / or, in step (2), the solvent for washing is anhydrous ethanol; And / or, in step (2), the drying parameters are 50°C and 12h.

4. The method for preparing cyclodextrin metal-organic framework aromatic capsules for long-lasting fragrance according to claim 1, characterized in that, In step (3), the core-to-wall ratio of the MOF-CHS to the daylily fragrance is 2:1; And / or, in step (3), the magnetic stirring conditions are 800 rpm and 30°C for 12 h; And / or, in step (3), the centrifugation conditions are 8000 rpm for 30 min; And / or, in step (3), the solvent for washing is anhydrous ethanol; And / or, in step (3), the drying operation specifically involves: pre-freezing in a refrigerator at -80°C for 24 hours, and then drying in a freeze dryer at -50°C for 48 hours.

5. A cyclodextrin-based metal-organic framework aromatic capsule for long-lasting fragrance, characterized in that, It is prepared by the method for preparing cyclodextrin metal-organic framework aromatic capsules for long-lasting fragrance as described in any one of claims 1 to 4.

6. The application of the cyclodextrin metal-organic framework aromatic capsule for long-lasting fragrance as described in claim 5 in the field of detergents.

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