Preparation and application of organic acid and polyethylene glycol modified sodium-based beta-cyclodextrin metal organic framework

Abstract

The invention discloses a preparation method and application of an organic acid and polyethylene glycol modified sodium-based beta-cyclodextrin metal organic framework, and belongs to the technical field of metal organic framework materials (MOF). The method comprises the following steps: firstly, preparing a Na-beta-CD-MOF (Na-beta-CD-MOF) by utilizing a methanol steam diffusion method or an ultrasonic-assisted synthesis method, and then carrying out crosslinking modification on the Na-beta-CD-MOF, organic acid (such as dibasic acid or tribasic acid as citric acid and malic acid) and polyethylene glycol (the molecular weight is 200-50000); the water stability, the pore structure and the adsorption performance on antibiotics and dye pollutants are obviously improved. The prepared organic acid and polyethylene glycol modified sodium-based beta-cyclodextrin metal organic framework has good biocompatibility and chemical stability, more adsorption sites are introduced, and pollutants such as ciprofloxacin hydrochloride, tetracycline hydrochloride and Congo red in wastewater can be efficiently removed. The method is green, environment-friendly, low in cost and simple and convenient to operate, and has a wide industrial application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the fields of environment, chemical industry, medicine and food, and in particular to the preparation and application of organic acid and polyethylene glycol modified sodium-based β-cyclodextrin metal-organic frameworks. BACKGROUND

[0002] Due to the continuous discharge of untreated pollutants into water by the pharmaceutical, dye and other industries, great harm has been caused to human health and the ecological environment. Congo red (CR) is a kind of aromatic azo dye with biphenylamine as base material, which is widely used in the industries of printing and dyeing, leather making, etc. This dye has high toxicity and has teratogenic and carcinogenic properties even at low concentrations. Tetracycline hydrochloride (TCH) and ciprofloxacin hydrochloride (CIP) are two common antibiotic pollutants, which are widely produced and used due to their low cost and strong antibacterial effect. However, only a small part of the ingested TCH or CIP is metabolized by humans or animals, and about 40-90% is excreted outside the body and discharged into the environment, causing the evolution of antibiotic resistance genes of microorganisms, which may lead to uncontrollable public health challenges. Therefore, there is an urgent need for effective methods and strategies to remove CR, TCH and CIP from water environment.

[0003] The methods for removing CR, TCH and CIP from water include nanofiltration technology, electrochemical removal, catalytic oxidation and adsorption removal, etc. Among them, adsorption removal is widely used due to its simple operation, high efficiency and low equipment requirement. The selection of adsorbent is often carbon-based compounds, natural polymer materials and metal-organic frameworks (MOFs), etc. Among them, MOFs have attracted wide attention in the field of adsorption due to their simple preparation and large specific surface area.

[0004] Metal-organic frameworks (MOFs) are coordination polymers based on the theory of coordination polymerization, which are self-assembled from multidentate organic ligands containing oxygen, nitrogen, etc. and metal ions. Due to the controllable structure of pores and large specific surface area, MOFs have more extensive application prospects than other porous materials, such as adsorption separation, catalysts, magnetic materials, energy storage materials and optical materials, etc., and have become one of the popular research materials. However, metal-organic frameworks often contain some heavy metal ions, which may have the risk of leaching during use, and the problems of less surface active sites and poor stability also limit their practical application.

[0005] β-cyclodextrin (β-CD) is usually obtained from corn, potato, wheat and other crops. Under the action of cyclodextrin glucose transposase (CGTase), it is converted into low viscosity starch, and then further converted into cyclodextrin at 62-65℃ and a certain pH value, which contains α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin and other components. Because the solubility of β-cyclodextrin in water is small, it is easy to crystallize and precipitate, so β-cyclodextrin can be obtained by concentration, crystallization, decolorization, recrystallization and other processes. β-CD has excellent chemical stability, is non-toxic, non-irritating and biodegradable. Under common acid-base environment and heating conditions, its structure can still remain relatively stable. In addition, β-CD has a permanent hydrophobic cavity and abundant hydroxyl functional groups, which lays a theoretical foundation for the construction of β-cyclodextrin metal organic framework material (β-CD-MOF). However, the existing CD-MOF generally has the shortcomings of poor water stability and long preparation time, which limits its industrial production and practical application in wastewater treatment.

[0006] Therefore, in order to solve the above problems, it is necessary to design a synthetic fast, green, efficient and stable adsorption material, which is the key to breakthrough in the field of antibiotic and dye wastewater treatment.

[0007] The relevant literature is as follows:

[0008] 1、GOU C L, WENG Z Q, DAI X S, et al. Water-stable PEG2000-modified citric acid crosslinked β-CD MOF for efficient removal of tetracycline hydrochloride: synthesis, adsorption behavior, and mechanism [J]. Carbohydr Res, 2025, 557: 15. SUMMARY

[0009] The purpose of the present application is to solve the above technical problems, and provide an organic acid and polyethylene glycol modified sodium based β-cyclodextrin metal organic framework (PEG-OA-Na-β-CD MOF) and its preparation method and application. The organic acid and polyethylene glycol modified sodium based β-cyclodextrin metal organic framework water treatment agent can solve the problems of long synthesis time, low adsorption efficiency, poor adsorption process stability and adsorption process accompanied by dangerous ion leaching of the existing cyclodextrin metal organic framework.

[0010] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows.

[0011] The organic acid (OA) and polyethylene glycol (PEG) modified sodium-based β-cyclodextrin metal organic framework is composed of a sodium-based β-cyclodextrin metal organic framework, an organic acid and a polyethylene glycol in a molar ratio of 1:1-10:1-10.

[0012] The sodium-based β-cyclodextrin metal organic framework is formed by β-cyclodextrin (β-CD) and sodium hydroxide or sodium salt as a sodium-based metal node coordination.

[0013] Further, the sodium-based metal node can be selected from any one or a combination of sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium oxalate and the like, preferably sodium hydroxide and sodium carbonate.

[0014] Further, the preparation method of the sodium-based β-cyclodextrin metal organic framework is methanol steam method and ultrasonic assisted method, preferably ultrasonic assisted method.

[0015] Further, the organic acid is selected from one or a combination of malic acid (MA), citric acid (CA), tartaric acid (TA), fumaric acid (FA), maleic acid (MLA), malonic acid (MNA), succinic acid (SA), phthalic acid (PA), terephthalic acid (TPA), trimesic acid (TMA) and the like, preferably malic acid and citric acid.

[0016] Further, the polyethylene glycol (PEG) has a molecular weight of 200-50000, preferably PEG-400, PEG-2000, PEG-5000, PEG-10000 and PEG-20000.

[0017] The sodium-based metal node in the present application can be selected from any one or a combination of sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium oxalate and the like, but is not limited thereto.

[0018] The organic acid in the present application is selected from any one or a combination of malic acid, citric acid, tartaric acid, fumaric acid, maleic acid, malonic acid, succinic acid, phthalic acid, terephthalic acid, trimesic acid and the like, but is not limited thereto.

[0019] The polyethylene glycol (PEG) in the present application has a molecular weight of 200-50000, and can be any one or a combination of PEGs with different molecular weights, but is not limited thereto.

[0020] The present application also provides a preparation method of the organic acid and polyethylene glycol modified sodium-based β-cyclodextrin metal organic framework (PEG-OA-Na-β-CD MOF), comprising the following steps:

[0021] (1) Ultrasonic-assisted preparation of sodium-based beta-cyclodextrin metal organic framework: a certain molar ratio of beta-cyclodextrin and sodium carbonate is dissolved in a test tube containing an appropriate amount of water, and the mixed solution is subjected to ultrasonic work using an ultrasonic cell crusher, and the mother liquor after ultrasonic treatment is incubated to obtain a cubic sodium-based beta-cyclodextrin metal organic framework (Na-β-CD MOF), and it is washed and dried;

[0022] Further step (1) the certain molar ratio of beta-cyclodextrin and sodium carbonate dissolved in a test tube containing an appropriate amount of water refers to the molar ratio of beta-cyclodextrin and sodium carbonate is 1:0.1~5; preferably 1:0.3~1.

[0023] (2) Organic acid and polyethylene glycol modified sodium-based beta-cyclodextrin metal organic framework: a certain amount of sodium-based beta-cyclodextrin metal organic framework, organic acid and polyethylene glycol are dissolved in water, and under the catalysis of a certain amount of sodium dihydrogen phosphate, crosslinking is heated. Get insoluble organic acid and polyethylene glycol modified sodium-based beta-cyclodextrin metal organic framework, and it is washed and dried;

[0024] Further step (2) the certain amount of sodium-based beta-cyclodextrin metal organic framework (Na-β-CD MOF), organic acid and polyethylene glycol are dissolved in water. It refers to the molar ratio of sodium-based cyclodextrin metal organic framework, organic acid, PEG and sodium dihydrogen phosphate is 1:1~10:1~10:1, preferably 1:3~5:1~3:1.

[0025] Advantages of the application:

[0026] The application provides a preparation method and application of an organic acid and polyethylene glycol modified sodium-based beta-cyclodextrin metal organic framework, and the main advantages are as follows:

[0027] 1. Beta-cyclodextrin as an organic ligand is dissolved in an aqueous solution with sodium ions provided by sodium hydroxide / sodium salt, and sodium-based beta-cyclodextrin metal organic framework is generated by using ultrasonic-assisted coordination ultrafast reaction, which has excellent industrialization potential.

[0028] 2. Sodium, which is green and safe, is used as the metal node of the metal organic framework, which avoids secondary pollution caused by heavy metal ion leakage. Compared with potassium-based beta-cyclodextrin metal organic framework, sodium-based beta-cyclodextrin metal organic framework has a more regular three-dimensional network. The smaller ionic radius of sodium makes it more structurally superior, which helps to form stable coordination geometry, thereby realizing the ordered stacking of beta-cyclodextrin and further laying a foundation for subsequent modification work.

[0029] 3、The organic acid modified sodium-based beta-cyclodextrin metal organic framework improves the water stability of the sodium-based beta-cyclodextrin metal organic framework, and the free carboxyl functional groups on the organic acid host introduce additional adsorption sites after cross-linking, thereby improving the adsorption performance.

[0030] 4、The organic acid and polyethylene glycol modified sodium-based beta-cyclodextrin metal organic framework of the present application further uses PEG modification on the basis of the organic acid cross-linked sodium-based beta-cyclodextrin metal organic framework, thereby improving the water stability and the ability to adsorb pollutants in wastewater.

[0031] 5、The organic acid and polyethylene glycol modified sodium-based beta-cyclodextrin metal organic framework prepared by the present application has simple preparation process, short reaction time, mild reaction conditions, is easy to implement, easy to batch prepare and conducive to subsequent recycling. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 SEM images of sample 1d, sample 2b, sample 11a and sample 16a.

[0033] Figure 2 XRD images of sample 1d, sample 2b, sample 11a and sample 16a.

[0034] Figure 3 FTIR images of sample 1d, sample 2b, sample 11a and sample 16a.

[0035] Figure 4 Water stability of sample 1d, sample 2b, sample 3b, sample 4b, sample 11a and sample 16a.

[0036] Figure 5 CIP concentration vs. absorbance standard curve at 277 nm.

[0037] Figure 6 TCH concentration vs. absorbance standard curve at 357 nm.

[0038] Figure 7 CR concentration vs. absorbance standard curve at 488 nm. DETAILED DESCRIPTION

[0039] The following detailed description of various example embodiments of the application will not be considered limiting of the application, but rather as a description of certain aspects, features, and embodiments of the application. It is to be understood that the terminology used herein is for the purpose of describing particular embodiments of the application only and is not intended to limit the application. Additionally, the use of "including", "comprising", "having", "containing", "involving", and variations thereof, are meant to encompass the items listed thereafter and any subsequent items. The use of "consisting of" is meant to encompass only the items listed thereafter. The use of "consisting essentially of" is meant to encompass the items listed thereafter and any additional items that do not materially change the basic and novel characteristics of the application.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, the preferred methods and materials are described. All publications mentioned herein are incorporated by reference to disclose and describe the methods and / or materials in connection with which the publications are cited. The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present application is not entitled to antedate such publication by virtue of prior application.

[0041] Various modifications and variations of the described embodiments of the application will be apparent to those skilled in the art from the foregoing detailed description of the application. Other embodiments of the application will be apparent from the foregoing detailed description of the application and from the examples described herein. The embodiments of the application described herein are examples only and are not intended to limit the scope of the application. Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein.

[0042] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" or variants thereof are open-ended, and include one or more steps, integers, compositions or elements listed thereafter, but not to the exclusion of any additions thereof.

[0043] The application will be further described by way of specific examples, but the scope of the application is not limited thereto.

[0044] Example 1

[0045] Preparation of sodium-based β-cyclodextrin metal organic framework by methanol vapor method:

[0046] A certain amount of β-cyclodextrin (β-CD) and sodium hydroxide were completely dissolved in a small beaker with 10 ml of water, 60 ml of methanol was poured into a large beaker for standby, the small beaker was put into the large beaker and the large beaker was sealed, the large beaker was put into an oven, the incubation temperature was set to 50°C, and the heating incubation was carried out. The solid was separated and washed with methanol for 3 times, and dried in an oven at a temperature of 50°C for 24 hours.

[0047] The concentration of sodium ions in the solution was determined using an AVIO 500 inductively coupled plasma spectrometer (PerkinElmer, USA), and the reaction was considered complete when the concentration of sodium ions did not change over 3 hours.

[0048] Table 1 Preparation of sodium-based β-cyclodextrin metal-organic frameworks (Na-β-CD MOFs) by the methanol vapor method and comparison of their preparation times

[0049] Sample β-CD (mmol) Sodium hydroxide (mmol) Preparation time (days) 1a 0.1 0.2 12 1b 0.1 0.4 11 1c 0.1 0.6 6 1d 0.1 0.8 3 1e 0.1 1.0 3

[0050] As can be seen from Table 1, the fastest preparation time is obtained when the molar ratio of β-cyclodextrin to sodium hydroxide is 1:8 or higher. This is probably because as the concentration of sodium hydroxide increases, the alkalinity of the solution increases, making it easier for β-cyclodextrin to dissolve in the solution, and more sodium ions are provided by the sodium hydroxide for coordination with β-cyclodextrin. Therefore, the molar ratio of β-cyclodextrin to sodium hydroxide is preferably 1:8.

[0051] Example 2

[0052] Preparation of sodium-based β-cyclodextrin metal-organic frameworks (Na-β-CD MOFs) by the ultrasonic-assisted method:

[0053] A certain amount of β-cyclodextrin and sodium carbonate was completely dissolved in a test tube containing 10 ml of water, heated in a 60°C water bath for 20 minutes until completely dissolved. Intermittent ultrasonic treatment was performed at a power of 200 watts for 10 minutes, with an intermittent time of 0.1 second. After the ultrasonic treatment, the sample was incubated for 2 hours, the solid was separated, washed with methanol for 3 times, and dried in an oven at a temperature of 50°C for 24 hours.

[0054] Table 2 Preparation of sodium-based β-cyclodextrin metal-organic frameworks (Na-β-CD MOFs) by the ultrasonic-assisted method and comparison of their preparation times

[0055] Sample β-CD (mmol) Sodium carbonate (mmol) Preparation time (hours) 2a 0.1 0.1 24 2b 0.1 0.3 2 2c 0.1 1 2 2d 0.1 2 1.5 2e 0.1 5 1

[0056] As can be seen from Table 2, the fastest preparation time is obtained when the molar ratio of β-cyclodextrin to sodium carbonate is 1:0.3 or higher. This is probably because as the concentration of sodium carbonate increases, the alkalinity of the solution increases, making it easier for β-cyclodextrin to dissolve in the solution, and more sodium ions are provided by the sodium carbonate for coordination with β-cyclodextrin. When the molar ratio of β-cyclodextrin to sodium carbonate exceeds 1:0.3, the incubation time does not increase much, so the molar ratio of β-cyclodextrin to sodium carbonate is preferably 1:0.3 to 1.

[0057] From Table 1 and Table 2, compared with the traditional method of methanol steam method, the time of using ultrasonic assisted method to prepare sodium based β-cyclodextrin metal organic framework (Na-β-CD MOF) is faster, and the molar ratio of β-cyclodextrin to sodium carbonate is 1:0.3~1, and the preparation time is the shortest. Therefore, the next sample 2b formula is used to prepare sodium based β-cyclodextrin metal organic framework (Na-β-CD MOF) and the next step of crosslinking modification is carried out.

[0058] Example 3

[0059] Preparation of sodium based β-cyclodextrin metal organic framework (Na-β-CD MOF) crosslinked with citric acid by hydrothermal polymerization method:

[0060] A certain amount of sodium based β-cyclodextrin metal organic framework (Na-β-CD MOF) and different molar ratios of citric acid are completely dissolved in a test tube containing 8ml of water, and 0.1mol of catalyst sodium dihydrogen phosphate is added, heated at 150℃ for 5 hours, soaked in water for 10 hours, and the solid not dissolved in water is separated and washed with water for 5 times, and then dried at 50℃.

[0061] Table 3 Formulas of sodium based β-cyclodextrin metal organic framework (Na-β-CD MOF) crosslinked with different molar ratios of citric acid

[0062] Sample Na-β-CD MOF (mmol) Citric acid (mmol) 3a 0.1 0.1 3b 0.1 0.3 3c 0.1 0.5 3d 0.1 0.7 3e 0.1 0.9

[0063] Example 4

[0064] Preparation of sodium based β-cyclodextrin metal organic framework (Na-β-CD MOF) crosslinked with malic acid / maleic acid / trimesic acid by hydrothermal polymerization method:

[0065] Compared with Example 3, the difference is that the organic acid is replaced by malic acid (sample 4) or maleic acid (sample 5) or trimesic acid (sample 6).

[0066] Table 4 Formulas of sodium based β-cyclodextrin metal organic framework (Na-β-CD MOF) crosslinked with different molar ratios of malic acid / maleic acid / trimesic acid

[0067] Sample Na-β-CD MOF (mmol) Malic acid / Maleic acid / Trimesic acid (mmol) 4a 5a 6a 0.1 0.1 4b 5b 6b 0.1 0.3 4c 5c 6c 0.1 0.5 4d 5d 6d 0.1 0.7 4e 5e 6e 0.1 0.9

[0068] Example 5

[0069] Preparation of sodium based β-cyclodextrin metal organic framework (Na-β-CD MOF) crosslinked with PEG-400 / 2000 / 5000 / 10000 / 20000 and citric acid by hydrothermal polymerization method:

[0070] Further improvement based on Example 3, i.e. adding a certain amount of PEG-400 (sample 7) or PEG-2000 (sample 8) or PEG-5000 (sample 9) or PEG-10000 (sample 10) or PEG-20000 (sample 11) in the process of dissolution, and then cross-linking by heating.

[0071] Table 5 Formulation of PEG-400 / 2000 / 5000 / 10000 / 20000 and citric acid cross-linked sodium-based β-cyclodextrin metal-organic frameworks (Na-β-CD MOF) with different molar ratios

[0072] Sample Na-β-CD MOF (mmol) Citric acid (mmol) PEG-400 / 2000 / 5000 / 10000 / 20000 (mmol) 7a 8a 9a 10a 11a 0.1 0.3 0.1 7b 8b 9b 10b 11b 0.1 0.3 0.3 7c 8c 9c 10c 11c 0.1 0.3 0.5 7d 8d 9d 10d 11d 0.1 0.3 0.7 7e 8e 9e 10e 11e 0.1 0.3 0.9

[0073] Example 6

[0074] Preparation of PEG-400 / 2000 / 5000 / 10000 / 20000 and malic acid cross-linked sodium-based β-cyclodextrin metal-organic frameworks by hydrothermal polymerization method:

[0075] Further improvement based on Example 4, using malic acid as the acid acceptor and adding a certain amount of PEG-400 (sample 12) or PEG-2000 (sample 13) or PEG-5000 (sample 14) or PEG-10000 (sample 15) or PEG-20000 (sample 16), and then cross-linking by heating.

[0076] Table 6 Formulation of PEG-400 / 2000 / 5000 / 10000 / 20000 and malic acid cross-linked sodium-based β-cyclodextrin metal-organic frameworks (Na-β-CD MOF) with different molar ratios

[0077] Sample Na-β-CD MOF (mmol) Malic acid (mmol) PEG-400 / 2000 / 5000 / 10000 / 20000 (mmol) 12a 13a 14a 15a 16a 0.1 0.3 0.1 12b 13b 14b 15b 16b 0.1 0.3 0.3 12c 13c 14c 15c 16c 0.1 0.3 0.5 12d 13d 14d 15e 16e 0.1 0.3 0.7 12e 13e 14e 15e 16e 0.1 0.3 0.9

[0078] Example 7

[0079] Preparation of PEG-400 / 2000 / 5000 / 10000 / 20000 and maleic acid cross-linked sodium-based β-cyclodextrin metal-organic frameworks by hydrothermal polymerization method:

[0080] Further improvement based on Example 4, using maleic acid as the acid acceptor and adding a certain amount of PEG-400 (sample 17) or PEG-2000 (sample 18) or PEG-5000 (sample 19) or PEG-10000 (sample 20) or PEG-20000 (sample 21), and then cross-linking by heating.

[0081] Table 7 Formulation of PEG-400 / 2000 / 5000 / 10000 / 20000 and maleic acid cross-linked sodium-based β-cyclodextrin metal-organic frameworks (Na-β-CD MOF) with different molar ratios

[0082] Sample Na-β-CD MOF (mmol) Maleic acid (mmol) PEG-400 / 2000 / 5000 / 10000 / 20000 (mmol) 17a 18a 19a 20a 21a 0.1 0.3 0.1 17b 18b 19b 20b 21b 0.1 0.3 0.3 17c 18c 19c 20c 21c 0.1 0.3 0.5 17d 18d 19d 20d 21d 0.1 0.3 0.7 17e 18e 19e 20e 21e 0.1 0.3 0.9

[0083] Example 8

[0084] Preparation of PEG-400 / 2000 / 5000 / 10000 / 20000 and trimesic acid cross-linked sodium-based β-cyclodextrin metal-organic frameworks by hydrothermal polymerization:

[0085] Further improvement based on Example 4, using trimesic acid as the acid acceptor and adding a certain amount of PEG-400 (Sample 22) or PEG-2000 (Sample 23) or PEG-5000 (Sample 24) or PEG-10000 (Sample 25) or PEG-20000 (Sample 26), and then heating and cross-linking.

[0086] Table 8 Formulation of PEG-400 / 2000 / 5000 / 10000 / 20000 and trimesic acid cross-linked sodium-based β-cyclodextrin metal-organic frameworks (Na-β-CD MOF) with different molar ratios

[0087] Sample Na-β-CD MOF (mmol) Trimesic acid (mmol) PEG-400 / 2000 / 5000 / 10000 / 20000 (mmol) 22a 23a 24a 25a 26a 0.1 0.3 0.1 22b 23b 24b 25b 26b 0.1 0.3 0.3 22c 23c 24c 25c 26c 0.1 0.3 0.5 22d 23d 24d 25d 26d 0.1 0.3 0.7 22e 23e 24e 25e 26e 0.1 0.3 0.9

[0088] Comparative Example

[0089] Since the preparation method of potassium-based β-cyclodextrin metal-organic framework (K-β-CD MOF) and citric acid and polyethylene glycol modified potassium-based β-cyclodextrin metal-organic framework (PEG-CA-K-β-CD MOF) has been published in a journal [1], we use its method to prepare citric acid and polyethylene glycol modified potassium-based β-cyclodextrin metal-organic framework (PEG-CA-K-β-CD MOF) as a comparative example. The preparation method is as follows:

[0090] Dissolve 1 mmol of β-cyclodextrin and 8 mmol of potassium hydroxide completely in a small beaker containing 10 ml of water, pour 60 ml of methanol into a large beaker, put the small beaker into the large beaker and seal the large beaker, put the large beaker into an oven, set the incubation temperature to 50°C, and incubate for 3 days. Separate the solid and wash it with methanol 3 times, and dry it in an oven at a temperature of 50°C for 24 hours. Potassium-based β-cyclodextrin metal-organic framework is prepared, 0.1 mmol of potassium-based β-cyclodextrin metal-organic framework, 0.4 mmol of citric acid and 0.1 mmol of sodium dihydrogen phosphate are completely dissolved in a test tube containing 8 ml of water, 0.1 mol of potassium dihydrogen phosphate is used as catalyst, heated at 150°C for 5 hours, soaked in water for 10 hours, separated the insoluble and washed with water 5 times, and dried at 50°C.

[0091] Example 9

[0092] Scanning electron microscopy (SEM) characterization:

[0093] The surface morphology of sample 1d (Na-β-CD MOF prepared by methanol vapor method), sample 2b (Na-β-CD MOF prepared by ultrasonic assisted method), sample 11a (PEG-20000 and citric acid modified Na-β-CD MOF) and sample 16a (PEG-20000 and malic acid modified Na-β-CD MOF) was observed under 10.0 kV voltage by Phenom ProX scanning electron microscope (Phenom-World (Shanghai) Co., Ltd.) (Fig. 1). Figure 1 It can be seen that sample 1d is rod-shaped crystal structure, sample 2b is cubic crystal structure, and the surface morphology of sample 11a and sample 16a has changed significantly compared with sample 1d and sample 2b, showing a porous structure, which proves the successful preparation of citric acid / malic acid and polyethylene glycol modified sodium-based β-cyclodextrin metal organic framework.

[0094] Example 10

[0095] X-ray diffraction (XRD) characterization:

[0096] The XRD spectra of sample 1d (Na-β-CD MOF prepared by methanol vapor method), sample 2b (Na-β-CD MOF prepared by ultrasonic assisted method), sample 11a (PEG-20000 and citric acid modified Na-β-CD MOF) and sample 16a (PEG-20000 and malic acid modified Na-β-CD MOF) were obtained by DX-2700BH diffractometer (Dandong Haoyuan Instrument Co., Ltd.) at 30 MA, voltage 40 kV (Fig. 2). Figure 2 The peak value of sample 1d and sample 2b at about 9° indicates the formation of a left-handed spiral channel structure, in which sodium ions are connected to the primary and secondary faces of the β-CD ring. The prominent peaks observed at about 12° and at about 17° in sample 1d and sample 2b indicate the formation of a crystalline cage structure, indicating the successful preparation of sodium-based β-cyclodextrin metal organic framework. Sample 11a and sample 16a are both amorphous, which is consistent with the characteristics of crosslinked polymers, which indicates the successful preparation of citric acid / malic acid and polyethylene glycol modified sodium-based β-cyclodextrin metal organic framework.

[0097] Example 11

[0098] Fourier infrared spectroscopy (FTIR) characterization:

[0099] The infrared spectrum of the sample was analyzed by CARY630 (Agilent Technologies). The resolution is 2 cm -1 in the range of 4000~400 cm -1Infrared spectra of sample 1d (Na-β-CD MOF prepared by methanol steam method), sample 2b (Na-β-CD MOF prepared by ultrasonic assisted method), sample 11a (PEG-20000 and citric acid modified Na-β-CD MOF) and sample 16a (PEG-20000 and malic acid modified Na-β-CD MOF) were determined (Figure 1). Figure 3 ). Sample 1d and sample 2b exhibited characteristic broad absorption peaks at 3374 cm −1 around, corresponding to the stretching and asymmetric vibration of -OH group. The absorption peak at 2922 cm −1 around corresponds to the C-H stretching vibration. In addition, the absorption peak attributed to the bending vibration of -OH group was observed at 1350 cm −1 around. The absorption peaks in the range of 1030-1160 cm −1 are related to the C-O-C stretching vibration of pyranose ring and the glycosidic bond in glucose unit. Sample 11a and sample 16a retained most of the peaks of the above functional groups, but both appeared the stretching vibration absorption peak of ester bond C=O at 1730 cm −1 around, which indicated the successful preparation of citric acid / malic acid and polyethylene glycol modified sodium β-cyclodextrin metal organic framework.

[0100] Example 12

[0101] Water stability test:

[0102] Sample 1d (Na-β-CD MOF prepared by methanol steam method), sample 2b (Na-β-CD MOF prepared by ultrasonic assisted method), sample 3b (citric acid modified Na-β-CD MOF), sample 4b (malic acid modified Na-β-CD MOF), sample 11a (PEG-20000 and citric acid modified Na-β-CD MOF) and sample 16a (PEG-20000 and malic acid modified Na-β-CD MOF) were respectively taken 20 mg and placed in 10 ml water for three days, and the water stability of the above samples was observed (Figure 2). Figure 4 It can be seen that sample 1d and sample 2b were completely dissolved after three days, while sample 3b, sample 4b, sample 11a and sample 16a were still well preserved, indicating that the water stability of sodium β-cyclodextrin metal organic framework can be effectively improved after cross-linking with organic acid or organic acid / polyethylene glycol.

[0103] Example 13

[0104] Adsorption test:

[0105] For each test, 20 mg of sample was added to 10 mL of CIP or TCH or CR solution, and an adsorption experiment was performed to evaluate the adsorption capacity. The mixture was then shaken in a shaker at a rotation speed of 150 rpm. The absorbance of CIP, TCH and CR was measured at wavelengths of 277 nm, 357 nm and 488 nm, respectively, using a UV-5800 ultraviolet-visible spectrophotometer (Shanghai Yuanzhi Instrument Co., Ltd.), and the absorbance was converted into concentration using a standard curve, which was brought into a standard adsorption equation to calculate the adsorption amount q of the adsorbent for CIP, TCH and CR e .

[0106]

[0107] The equilibrium adsorption capacity of the sample for CIP, TCH and CR was represented by the value of q e (mg / g) in the formula, where the initial pollutant concentration was represented by C0(mg / L), and the equilibrium pollutant concentration was represented by C e (mg / L). In addition, V(L) represented the volume of the solution, and m(g) represented the mass of the adsorbent used.

[0108] The sample adsorbed with CIP, TCH and CR was desorbed with hydrochloric acid and ethanol, and after desorption was completed, the adsorption capacity was continuously measured. The adsorption-desorption process was stopped when the adsorption capacity decreased by more than 10%, and the maximum cycle number was tested

[0109] Table 9 Maximum adsorption capacity and maximum cycle number of different samples for CIP, TCH and CR

[0110] Sample Maximum adsorption capacity for CIP Maximum adsorption capacity for TCH Maximum adsorption capacity for CR Maximum number of cycles mg / g mg / g mg / g times 3a 287 316 295 5 3b 318 347 326 5 3c 339 368 354 5 3d 311 342 323 5 3e 279 305 288 5 4a 307 336 318 5 4b 338 362 347 6 4c 359 388 376 6 4d 331 362 345 6 4e 299 328 303 5 5a 267 296 278 5 5b 298 329 315 5 5c 319 348 335 5 5d 291 326 302 5 5e 259 288 261 5 6a 237 263 248 4 6b 268 297 272 5 6c 289 318 296 5 6d 261 292 265 3 6e 229 258 242 4 7a 376 397 425 5 7b 382 403 431 6 7c 362 388 417 6 7d 357 379 406 6 7e 347 366 395 5 8a 427 416 478 5 8b 432 421 483 6 8c 417 406 463 6 8d 407 398 456 6 8e 392 386 447 5 9a 477 435 528 6 9b 482 446 533 6 9c 467 428 516 6 9d 453 412 505 6 9e 447 408 496 6 10a 527 455 578 6 10b 536 462 583 6 10c 513 446 567 6 10d 505 438 557 6 10e 498 423 546 6 11a 574 467 648 6 11b 582 476 653 7 11c 563 458 637 7 11d 557 445 628 7 11e 547 438 616 6 12a 397 416 448 6 12b 402 421 453 6 12c 386 403 437 6 12d 372 398 427 6 12e 367 386 416 6 13a 445 436 497 6 13b 456 442 503 6 13c 437 428 485 6 13d 422 417 478 6 13e 417 403 465 6 14a 496 457 548 6 14b 505 462 553 6 14c 487 443 538 7 14d 475 438 527 7 14e 462 427 516 6 15a 547 466 598 6 15b 556 472 603 6 15c 535 458 587 7 15d 522 447 578 7 15e 515 438 566 6 16a 605 476 684 6 16b 609 478 687 7 16c 595 466 673 7 16d 587 453 664 7 16e 575 443 652 6 17a 297 316 348 7 17b 302 326 353 7 17c 288 303 335 7 17d 272 298 327 7 17e 264 287 316 7 18a 347 336 398 5 18b 352 341 403 5 18c 336 328 383 5 18d 325 319 378 5 18e 313 307 366 5 19a 396 356 448 5 19b 403 364 453 5 19c 386 347 432 6 19d 377 338 423 6 19e 366 327 416 5 20a 447 372 498 5 20b 451 385 503 6 20c 432 361 487 6 20d 425 359 478 6 20e 413 347 466 5 21a 495 396 548 5 21b 502 408 553 6 21c 487 383 538 6 21d 477 379 528 6 21e 467 364 516 5 22a 247 266 298 6 22b 253 272 300 6 22c 235 253 287 6 22d 222 249 278 6 22e 217 232 266 6 23a 297 286 348 6 23b 305 292 353 6 23c 286 277 334 6 23d 276 269 328 6 23e 267 252 316 6 24a 347 306 398 5 24b 355 312 403 5 24c 336 297 385 5 24d 327 289 378 5 24e 313 277 366 5 25a 395 326 448 5 25b 406 332 453 5 25c 387 318 436 5 25d 375 309 428 5 25e 367 296 416 5 26a 447 342 498 5 26b 455 352 503 6 26c 433 334 487 6 26d 425 329 478 6 26e 413 317 466 5 Comparative Example 188 222 176 4

[0111] According to the data in Table 9, compared with the sample containing potassium-based β-cyclodextrin metal organic framework (comparative example), the sample containing sodium-based β-cyclodextrin metal organic framework (example) had better maximum adsorption capacity and cycle stability for CIP, TCH and CR. This was because the sodium-based β-cyclodextrin metal organic framework was more likely to form a regular and ordered three-dimensional network structure, which benefited from the smaller radius of sodium ions, which helped to form a stable coordination geometry and promote the ordered stacking (such as vertical arrangement) of β-cyclodextrin, thereby improving the structural stability of the material. Therefore, the sodium-based β-cyclodextrin metal organic framework could form a more uniform and stable structure, thereby improving the adsorption performance and cycle life.

[0112] As shown in Table 9, samples 3a-3e are CA-Na-β-CD MOFs prepared by mixing sodium-based β-cyclodextrin metal-organic frameworks with citric acid in different molar ratios. When the molar ratio of sodium-based β-cyclodextrin metal-organic framework to citric acid is 1:3–5, the material exhibits the best adsorption capacity and cycling performance for CIP, TCH, and CR. Other organic acid-modified sodium-based β-cyclodextrin metal-organic frameworks show similar trends. Insufficient organic acid content leads to inadequate cross-linking, affecting the material's water stability and adsorption capacity; excessive organic acid content easily causes over-stabilization and hyperbranching. Therefore, organic acid modification is recommended within a molar ratio range of 1:3–5.

[0113] Under the same conditions, comparing the adsorption performance of samples 3b (citric acid modified), 4b (malic acid modified), 5b (maleic acid modified), and 6b (pyromellitic acid modified) for CIP, TCH, and CR, it was found that the adsorption capacity and cycling stability of 3b, 4b, and 5b were all superior to those of 6b. This is mainly because malic acid, citric acid, and maleic acid have high solubility in water, which is conducive to the full progress of the cross-linking reaction, thereby improving the water stability of the material and introducing more adsorption sites. Further comparison revealed that samples 4b and 3b performed better than 5b. This is attributed to the fact that malic acid and citric acid are hydroxycarboxylic acids, which can undergo self-dehydration condensation during the cross-linking process to form a polyester structure, constructing a more developed three-dimensional cross-linked network, and retaining some hydroxyl / carboxyl groups to form stable hydrogen bonds, making the material's pores more open, the structure more flexible, and the hydrolysis resistance better. Among them, the performance of sample 4b was slightly better than that of 3b, possibly because malic acid is a dihydroxycarboxylic acid with a smaller molecular weight and fewer carboxyl groups, further alleviating the problems of polymer dense packing and hyperbranching. Therefore, it is recommended to use malic acid or citric acid to modify sodium-based β-cyclodextrin metal-organic frameworks.

[0114] According to Table 9, under the same conditions, samples 7a-11e (PEG of different molecular weights co-modified with citric acid) exhibited higher adsorption capacity and cyclic stability for CIP, TCH and CR than samples 3a-3e (modified only with citric acid). The co-modification system of PEG of different molecular weights and other organic acids also showed similar rules, indicating that PEG might play a buffering role between the metal organic framework of β-cyclodextrin and the organic acid, reducing the dense packing and hyperbranched problem of the polymer. Samples 7a-7e were PEG-20000-CA-Na-β-CDMOF prepared by different molar ratios of sodium-based metal organic framework of β-cyclodextrin, PEG-20000 and citric acid. When the molar ratio of sodium-based metal organic framework of β-cyclodextrin and PEG-20000 was 1:1-3, the adsorption performance of the material was best, and the test results of sodium-based metal organic framework of β-cyclodextrin modified by PEG of other molecular weights and citric acid were also consistent, and the co-modification system of PEG of different molecular weights and other organic acids also showed similar rules. Too much PEG would cause the organic acid to preferentially react with PEG rather than effectively crosslink with the sodium-based metal organic framework of β-cyclodextrin, affecting the structure of the sample, and the excessive unreacted PEG might cover the surface and pores of the material, affecting the exposure of the adsorption sites, resulting in a decrease in the adsorption capacity. Therefore, it is recommended to control the molar ratio of sodium-based metal organic framework of β-cyclodextrin and PEG-20000 within the range of 1:1-3 for preparation.

[0115] Under the same conditions, the test results of samples 7a (PEG-400 co-modified with citric acid), 8a (PEG-2000 co-modified with citric acid), 9a (PEG-5000 co-modified with citric acid), 10a (PEG-10000 co-modified with citric acid) and 11a (PEG-20000 co-modified with citric acid) showed that the sample co-modified with PEG-20000 and citric acid exhibited the best adsorption capacity and cyclic stability, and the co-modification system of PEG of different molecular weights and other organic acids also showed similar rules. This is due to the long molecular chain of high molecular weight PEG-20000, which can act as a flexible spacer to produce more suitable steric hindrance in the crosslinked framework constructed by citric acid, thereby synergistically widening the pore of the material and promoting the diffusion of pollutant molecules; at the same time, PEG-20000 can further optimize the network structure formed by the crosslinking of citric acid, avoid the pore blockage caused by too high crosslinking density, and alleviate the excessive packing phenomenon that easily occurs when using organic acid alone; in addition, the abundant ether oxygen atoms in the long chain of PEG can also synergistically act with the carboxyl / hydroxyl groups of citric acid to enhance the hydrogen bond adsorption. The synergistic effect of the above factors together realizes the significant improvement of the adsorption performance of the material.

[0116] Those skilled in the art should understand that the above discussion of any embodiment is only intended to be exemplary in nature and is not intended to suggest that the present application is limited to these examples; under the concept of the present application, the above embodiments or technical features among different embodiments can be combined, steps can be implemented in any order, and there are many other variations of different aspects of the present application as described above, which are not provided in details for the sake of brevity.

Claims

1. An organic acid and polyethylene glycol modified sodium based β-cyclodextrin metal organic framework (PEG-OA-Na-β-CD MOF) characterized in that, The metal organic framework comprises the following components: (1) sodium-based β-cyclodextrin metal organic framework (Na-β-CD MOF); (2) organic acid (OA) crosslinked to the sodium-based β-cyclodextrin metal organic framework (OA-Na-β-CD MOF); (3) polyethylene glycol (PEG) connected to the crosslinked sodium-based β-cyclodextrin metal organic framework; The organic acid and polyethylene glycol modified sodium-based β-cyclodextrin metal organic framework (PEG-OA-Na-β-CD MOF) is prepared by the following method: (A1) β-cyclodextrin (β-CD) is coordinated with sodium hydroxide or sodium salt to form a sodium-based β-cyclodextrin metal organic framework (Na-β-CD MOF); (A2) The sodium-based β-cyclodextrin metal organic framework (Na-β-CD MOF) obtained in step A1 is crosslinked with the carboxyl group of the organic acid, and then covalently modified with PEG.

2. The MOF material of claim 1, wherein, The sodium-based metal node can be selected from any one or combination of sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium oxalate and the like, and preferably sodium hydroxide and sodium carbonate.

3. The MOF material of claim 1, wherein, The organic acid can be selected from any one or combination of malic acid (MA), citric acid (CA), tartaric acid (TA), fumaric acid (FA), maleic acid (MLA), malonic acid (MNA), succinic acid (SA), phthalic acid (PA), terephthalic acid (TPA), trimesic acid (TMA) and the like, and preferably malic acid and citric acid.

4. The MOF material of claim 1, wherein, The molecular weight of the polyethylene glycol (PEG) is selected to be 200-50000, and can be any one or combination of PEGs with different molecular weights, and preferably PEG-400, PEG-2000, PEG-5000, PEG-10000 and PEG-20000.

5. The MOF material of claim 1, wherein, In the crosslinked sodium-based β-cyclodextrin metal organic framework, the molar ratio of the sodium-based β-cyclodextrin metal organic framework to the organic acid is 1:1-10, and preferably 1:3-5; and the molar ratio of the crosslinked sodium-based β-cyclodextrin metal organic framework to the polyethylene glycol PEG is 1:0.5-10, and preferably 1:1-3.

6. A method of preparing the metal organic framework of claim 1, characterized in that, The preparation method of the Na-β-CD MOF is a methanol steam method and an ultrasonic-assisted method, and the ultrasonic-assisted method is preferred.

7. The ultrasonic-assisted method of claim 6, comprising the following steps: (1) dissolving β-cyclodextrin and sodium hydroxide / sodium salt in water according to a certain molar ratio; (2) ultrasonically treating the mixture of β-cyclodextrin and sodium hydroxide / sodium salt with an ultrasonic cell disruptor; (3) incubating the mother liquor after ultrasonic treatment to obtain a sodium-based β-cyclodextrin metal organic framework (Na-β-CD MOF), and separating and drying; The molar ratio of the β-cyclodextrin and sodium hydroxide / sodium salt in step 1 is 1:0.1-5, and preferably 1:0.3-1.

8. The production method according to claim 1, wherein The organic acid and polyethylene glycol modified sodium-based β-cyclodextrin metal organic framework (PEG-OA-Na-β-CD MOF) is prepared by a hydrothermal polymerization method, comprising the following steps: (1) dissolving sodium-based β-cyclodextrin metal organic framework (Na-β-CD MOF) prepared by ultrasonic-assisted method, organic acid and PEG in water, and adding catalyst sodium dihydrogen phosphate; (2) heating and crosslinking under high temperature for a certain time; (3) separating and washing the product and drying; The molar ratio of sodium-based β-cyclodextrin metal organic framework (Na-β-CD MOF), organic acid, PEG and sodium dihydrogen phosphate in step (1) is 1:1-10:1-10:1, preferably 1:3-5:1-3:1; the crosslinking time in step (2) is 1-8 hours, preferably 5 hours.

9. The sodium-based β-cyclodextrin metal organic framework modified by organic acid and polyethylene glycol obtained by the method, is mainly used in the field of wastewater treatment, preferably for the treatment of antibiotics and dyes in pharmaceutical wastewater or industrial wastewater.

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