Preparation method and application of a flexible imprint MOF catalyst capable of being recycled magnetically

Abstract

The application belongs to the field of water pollution control, and discloses a preparation method and application of a flexible imprint MOFs catalyst capable of being magnetically recycled. A core-shell structure flexible imprint catalyst is synthesized by adopting a precipitation polymerization method with a magnetic Fe-MOF as a base. The catalyst has multi-target adsorption characteristics, can simultaneously and quickly target capture various sulfonamide organic matters in water, realizes efficient targeted degradation of sulfonamide organic pollutants in water, has the characteristics of magnetic recovery, can be quickly separated from the solution by an external magnetic field to realize efficient recovery and reuse of the catalyst, conforms to the green environmental protection concept, and has a good engineering application prospect.

Description

Technical Field

[0001] This invention belongs to the field of advanced oxidation technology for treating recalcitrant organic pollutants in wastewater, specifically relating to a method for preparing and applying a magnetically recoverable flexible imprinted MOF catalyst. Background Technology

[0002] Advanced oxidation processes (AOP) are an important means of eliminating water pollution. In AOP systems, oxidants such as H₂O₂ and persulfate (PS), under the activation of a catalyst, generate reactive oxygen species (ROS), which oxidize and degrade organic pollutants in water into CO₂, H₂O, or other benign byproducts, thereby reducing water pollution. It is worth noting that existing ROS generation processes are characterized by rapid release rates, large quantities, short lifespans (generally <10 μs), and limited transport distances (generally <90 nm). The large amounts of ROS generated instantaneously are directly quenched before they can fully react with pollutants in AOP. Furthermore, wastewater contains a diverse range of organic pollutants. During AOP degradation, ROS non-selectively attack organic matter in wastewater, leading to preferential degradation of readily degradable organic pollutants in close proximity, resulting in unsatisfactory removal of specific recalcitrant organic pollutants. Therefore, achieving efficient and targeted degradation of recalcitrant organic pollutants in water is crucial for the in-depth application of AOP in water treatment technology.

[0003] In recent years, metal-organic frameworks (MOFs) have become a research hotspot in the environmental field as advanced oxidation catalysts. MOFs contain various organic ligands, including nitrogen-containing heterocyclic ligands and carboxylic acid ligands, providing a good foundation for MOF functionalization. Related studies have reported the construction of a molecularly imprinted layer on the surface of MOFs, utilizing the selective adsorption of the surface molecular imprint and the catalytic synergy of MOFs to achieve targeted degradation of specific pollutants. However, existing molecularly imprinted MOFs are all targeted at a single pollutant, and cannot quickly and effectively eliminate multiple low-concentration, recalcitrant organic pollutants in water bodies simultaneously. Furthermore, most current imprinted MOFs are in powder form, resulting in significant loss during water treatment processes, difficulty in recycling, and inability to be reused multiple times. Considering the synthesis process and cost of imprinted MOFs, this greatly limits their engineering application in water treatment processes. Summary of the Invention

[0004] To overcome the limitations of existing imprinted MOFs, such as limited selectivity and difficulty in recovery, this invention aims to provide a method for synthesizing and applying magnetically recoverable flexible imprinted MOF catalysts. First, a magnetic MOF catalytic center is synthesized, and then a molecularly imprinted layer with a flexible effect is constructed on its surface. This layer can simultaneously and selectively adsorb multiple similar or structurally similar pollutants, thereby achieving highly efficient magnetic recovery and selective degradation of multiple target pollutants using imprinted MOFs. This significantly improves the practical performance of imprinted MOFs and facilitates engineering applications.

[0005] The present invention is achieved through the following technical solution.

[0006] A method for preparing magnetically recyclable flexible imprinted MOF catalysts includes the following steps:

[0007] (1) Preparation of magnetic Fe-based MOF catalytic center donors: FeCl3·6H2O and 2-aminoterephthalic acid were added to N,N-dimethylformamide (DMF) solvent and stirred for 30-60 min. Then Fe3O4 was added and ultrasonically dispersed for 10-30 min. The prepared mixture was transferred to a polytetrafluoroethylene-lined autoclave reactor and heated at 100-150℃ for 18-22 h. The product was washed with DMF, methanol and water, purified and then vacuum dried for 24-48 h. The obtained product was the magnetic Fe-based MOF catalytic center donor.

[0008] (2) Preparation of flexible imprinted layer: First, add template molecules, functional monomers and crosslinking agents to the reaction solvent and mix evenly. Then, add magnetic Fe-based MOF catalytic center donors and disperse by ultrasonication. Let stand for 8-16 hours to allow the reaction mixture to undergo prepolymerization to obtain a prepolymer solution.

[0009] (3) Add an initiator to the prepolymer solution obtained in step (2) and purge with inert gas for more than 15 minutes to remove oxygen from the solvent. Then place it in a constant temperature shaking box at 60-65℃ for 8-12 hours to polymerize the imprinted layer. During the polymerization process, the rotation speed needs to be maintained at 220-280 r / min to ensure that the imprinted layer is uniformly loaded on the magnetic imprinted MOFs.

[0010] (4) Elution of the template molecules of the magnetically recoverable flexible imprinted MOF catalyst: The prepolymer obtained in step (3) was first separated by centrifugation at a speed of 10,000-12,000 r / min. The obtained solid product was added to a solvent prepared with ethanol and formic acid for Soxhlet extraction, wherein the volume ratio of ethanol to formic acid was 9:1. Then, the molecularly imprinted polymer was eluted with ethanol. Finally, the obtained solid product was placed in a vacuum drying oven at 60-80℃ for 24-48 h. The obtained product is a magnetically recoverable flexible imprinted MOF catalyst.

[0011] Further, the preparation of magnetic iron-based metal-organic framework materials by the hydrothermal synthesis method described in step (1) is as follows: FeCl3·6H2O and 2-aminoterephthalic acid are added to 30 mL of N,N-dimethylformamide (DMF) in a molar ratio of 2:1-5:1 (preferably 2:1). After stirring evenly, the mixture is transferred to a reaction vessel, and then a certain mass of Fe3O4 is added. The molar ratio of Fe3O4 to 2-aminoterephthalic acid is 5:3–5:9. The mixture is heated at 110 °C for 20 h, cooled, and washed three times each with DMF, methanol, and ultrapure water. The mixture is then vacuum dried to obtain magnetic Fe-MOFs.

[0012] Further, in step (2), the template molecule of the target pollutant is one or more of sulfamethoxazole, sulfapyridine, or sulfamethoxypyrimidine.

[0013] Further, in step (2), the functional monomer is one or more of methylenebisacrylamide, methacrylamide, methacrylic acid, 4-vinylpyridine, and methyl acrylate.

[0014] Further, in step (2), the crosslinking agent is one of divinylbenzene, methylene bisacrylamide, ethylene glycol dimethacrylate, or trimethylolpropane trimethacrylate.

[0015] Furthermore, in step (2), the volume of the prepolymer solution is 30-50 ml.

[0016] Furthermore, in step (2), the mass of the added magnetic Fe-MOFs is 0.2-0.5g, and the mass ratio of the functional monomer to the magnetic Fe-MOFs is 1:1-1:3.

[0017] Furthermore, in step (2), the molar ratio of the template molecule to the functional monomer is 1:3–1:5.

[0018] Furthermore, in step (2), the molar ratio of the functional monomer to the crosslinking agent is 1:1 to 1:2.

[0019] Furthermore, in step (2), the ultrasonic dispersion time is 15-30 min.

[0020] Furthermore, in step (2), the standing time in the prepolymer solution is 8-16 hours.

[0021] Furthermore, in step (3), the initiator azobisisobutyronitrile is added.

[0022] Furthermore, in step (3), the mass of the initiator added is 0.05g-0.08g.

[0023] Furthermore, in step (3), the inert gas introduced is nitrogen, and the inert gas is introduced for 15-30 minutes.

[0024] Furthermore, in step (3), the polymerization temperature is 60-65℃.

[0025] Furthermore, in step (3), the polymerization time is 8-12 hours.

[0026] Furthermore, in step (3), the rotation speed during polymerization is 220-280 r / min.

[0027] Furthermore, in step (4), the centrifuge speed is 10000-12000 r / min.

[0028] Furthermore, in step (4), the Soxhlet extraction solvent is ethanol and formic acid in a volume ratio of 9:1.

[0029] Furthermore, in step (4), the drying temperature is 60-80℃ and the drying time is 24-48h.

[0030] The present invention also provides the application of the magnetically recyclable flexible imprinted MOFs catalyst in advanced oxidation technology for the efficient removal of organic pollutants from wastewater. The flexible imprinted catalyst based on magnetic Fe-based MOFs is added to wastewater containing organic pollutants, followed by the addition of an oxidant, and then placed in a constant temperature shaking incubator for shaking reaction at a temperature of 20-40℃.

[0031] Furthermore, the organic pollutant is a sulfonamide antibiotic.

[0032] Furthermore, the sulfonamide antibiotics include sulfamethoxazole (SMX), sulfapyridine (SPD), and sulfamethoxypyrimidine (SMZ).

[0033] Furthermore, the advanced oxidation technology is a persulfate system or an H2O2 system.

[0034] Furthermore, the oxidant is persulfate or H2O2.

[0035] Furthermore, the molar ratio of the sulfonamide organic pollutants to the oxidant is 50:1-150:1, the concentration of the flexible imprinted catalyst based on magnetic MOFs in the organic wastewater is 0.1g / L-1g / L, and the concentration of organic micropollutants in the wastewater is 20mg / L-50mg / L.

[0036] This invention provides a flexible imprinted MOF of magnetic Fe-MOFs prepared by the above method. This catalyst will be used to address the problem of difficult removal of sulfonamide organic pollutants in the process of advanced wastewater treatment.

[0037] The flexible imprinted MOF catalyst based on Fe-based MOFs provided by this invention has the following advantages:

[0038] (1) This invention uses magnetic Fe-based MOFs as a catalytic substrate to achieve rapid magnetic recovery of imprinted MOFs, reduce the loss of imprinted MOFs, and lower the application cost.

[0039] (2) The imprinted layer of the present invention has certain relaxation properties and can selectively identify the same type or similar sulfonamide organic compounds, which greatly improves the application scenarios of imprinted MOFs in water treatment of organic pollutants.

[0040] (3) The method for synthesizing flexible imprinted MOFs based on magnetic Fe-MOFs proposed in this invention has simple equipment, mild reaction conditions, easy process control, no need to add toxic and harmful reagents, and facilitates the industrialization of catalysts. Attached Figure Description

[0041] Figure 1 The graph shows the adsorption performance of flexible imprinted MOFs on different sulfonamide organic pollutants.

[0042] Figure 2 This is a comparison of the selective adsorption effects of flexible imprinted MOFs on organic micropollutants with different structures.

[0043] Figure 3 STEM images of flexible imprinted MOFs.

[0044] Figure 4 XRD patterns of flexible imprinted MOFs and substrate MOFs.

[0045] Figure 5 The graph shows the hysteresis curves of the flexible imprinted MOFs and the substrate MOFs.

[0046] Figure 6 The graphs show the nitrogen adsorption and desorption of flexible imprinted MOFs and substrate MOFs.

[0047] Figure 7 The pore size distribution maps are shown for flexible imprinted MOFs and substrate MOFs. Detailed Implementation

[0048] The following examples further illustrate specific implementations of the present invention, but the implementation and protection of the present invention are not limited thereto. It should be noted that any processes not specifically described below are those that can be implemented or understood by those skilled in the art by referring to existing technology. Reagents or instruments whose manufacturers are not specified are considered to be conventional products that can be purchased commercially.

[0049] Example 1

[0050] (1) Preparation of magnetic MIL101-M: Weigh 1.35g FeCl2·6H2O and 0.45g 2-aminoterephthalic acid, add them together to 30mL DMF, stir for 30 minutes until they are mixed evenly, then add 0.72g Fe3O4, pour the mixture into a 100mL polytetrafluoroethylene-lined reaction vessel, place it in an electric thermostatic drying oven preheated to 110℃, and after 20h, take out the reaction vessel and let it cool naturally to room temperature. Filter or centrifuge to separate the solid and liquid, and wash the solid three times each with DMF, methanol and ultrapure water. Finally, dry the solid in an oven at 60℃ to obtain magnetic MIL101-M.

[0051] (2) Preparation of flexible imprinted MOFs: Weigh 0.253g of sulfamethoxazole (SMX) as template molecule, add 0.617g of functional monomer MBA to 45ml of ethanol (porogen) and stir to mix evenly, then add 0.20g of MIL101-M prepared in step (1), ultrasonically disperse for 15min and stand for 12h, add 0.754ml of ethylene glycol dimethacrylate (EGDMA), stir for 30min, introduce N2 for 30min to remove oxygen, and stand for 12h to form a prepolymer solution.

[0052] (3) Add 0.05 g of azobisisobutyronitrile (AIBN) to the prepolymer solution in step (2), purify with N2 for 30 min, and then place it in a shaker at 60 °C with stirring at 250 r / min for 8 h until the reaction is complete. Centrifuge to obtain the polymer. Elute the polymer with a Soxhlet extraction method using a mixed solvent of ethanol / formic acid (v / v = 9:1) for more than 12 h to break the bonds between the template molecules and the imprint cavity in the polymer. Wash three times each with anhydrous ethanol and ultrapure water to remove the template molecules. Centrifuge and dry the obtained material at 60 °C for 12 h to obtain the flexible imprint MIL101@MIP-E1.

[0053] (4) Prepare a 20 mg / L solution of recalcitrant organic matter for later use;

[0054] (5) A 250 mL conical flask was used as a reactor. 100 mL of sulfamethoxazole (SMX) solution was added. 0.5 g / L of MIL101@MIP-E and 0.074 g / L of PMS were added to the reactor. The reactor was placed in a shaker at 180 rpm and the degradation reaction was carried out under normal temperature and light-protected conditions.

[0055] Example 2

[0056] (1) Preparation of magnetic MIL101-M: Weigh 1.35g FeCl2·6H2O and 0.45g 2-aminoterephthalic acid, add them together to 30mL DMF, stir for 30 minutes until they are mixed evenly, then add 0.72g Fe3O4, pour the mixture into a 100mL polytetrafluoroethylene-lined reaction vessel, place it in an electric thermostatic drying oven preheated to 110℃, and after 20h, take out the reaction vessel and let it cool naturally to room temperature. Filter or centrifuge to separate the solid and liquid, and wash the solid three times each with DMF, methanol and ultrapure water. Finally, dry the solid in an oven at 60℃ to obtain magnetic MIL101-M.

[0057] (2) Preparation of flexible imprinted MOFs: Weigh 0.506g of sulfamethoxazole (SMX) as template molecule, add 0.617g of functional monomer MBA to 45ml of ethanol (porogen) and stir to mix evenly, then add 0.20g of MIL101-M prepared in step (1), ultrasonically disperse for 15min and stand for 12h, add 0.376ml of ethylene glycol dimethacrylate (EGDMA), stir for 30min, introduce N2 for 30min to remove oxygen, and stand for 12h to form prepolymer solution.

[0058] (3) Add 0.05 g of azobisisobutyronitrile (AIBN) to the prepolymer solution in step (2), purify with N2 for 30 min, and then place it in a shaker at 60 °C with stirring at 250 r / min for 8 h until the reaction is complete. Centrifuge to obtain the polymer. Elute the polymer with a Soxhlet extraction method using a mixed solvent of ethanol and formic acid (v / v = 9:1) for more than 12 h to break the bonds between the template molecules and the imprint cavity in the polymer. Wash three times each with anhydrous ethanol and ultrapure water to remove the template molecules. Centrifuge and dry the obtained material at 60 °C for 12 h to obtain the flexible imprint MIL101@MIP-E2.

[0059] Example 3

[0060] (1) Preparation of magnetic MIL101-M: Weigh 1.35g FeCl2·6H2O and 0.45g 2-aminoterephthalic acid, add them together to 30mL DMF, stir for 30 minutes until they are mixed evenly, then add 0.72g Fe3O4, pour the mixture into a 100mL polytetrafluoroethylene-lined reaction vessel, place it in an electric thermostatic drying oven preheated to 110℃, and after 20h, take out the reaction vessel and let it cool naturally to room temperature. Filter or centrifuge to separate the solid and liquid, and wash the solid three times each with DMF, methanol and ultrapure water. Finally, dry the solid in an oven at 60℃ to obtain magnetic MIL101-M.

[0061] (2) Preparation of flexible imprinted MOFs: Weigh the sulfamethoxazole template molecule and functional monomer MBA as shown in Table 1 and add them to 30 ml of ethanol (porogen) and stir to mix evenly. Then add 0.20 g of MIL101-M prepared in step (1), sonicate for 15 min and let stand for 12 h. Add the ethylene glycol dimethacrylate (EGDMA) as shown in Table 1, stir for 30 min, introduce N2 for 40 min to remove oxygen, and let stand for 12 h to form a prepolymer solution.

[0062] (3) Add 0.05 g of azobisisobutyronitrile (AIBN) to the prepolymer solution in step (2), purify with N2 for 30 min, and then place it in a shaker at 60 °C with stirring at 250 r / min for 12 h until the reaction is complete. Centrifuge to obtain the polymer, and elute the polymer with a Soxhlet extraction method using a mixed solvent of ethanol and formic acid (v / v = 9:1) for more than 12 h to break the bonds between the template molecules and the imprint cavity in the polymer. Then wash with anhydrous ethanol and ultrapure water three times each to remove the template molecules, centrifuge, and dry the obtained material at 60 °C for 12 h to obtain different flexible imprinted MOFs.

[0063] The synthesis conditions based on flexible imprinted MOFs are detailed in Table 1 below:

[0064] Table 1

[0065]

[0066] Example 4

[0067] (1) Preparation of magnetic MIL101-M: Weigh 1.35g FeCl2·6H2O and 0.45g 2-aminoterephthalic acid, add them together to 30mL DMF, stir for 30 minutes until they are mixed evenly, then add 0.72g Fe3O4, pour the mixture into a 100mL polytetrafluoroethylene-lined reaction vessel, place it in an electric thermostatic drying oven preheated to 110℃, and after 20h, take out the reaction vessel and let it cool naturally to room temperature. Filter or centrifuge to separate the solid and liquid, and wash the solid three times each with DMF, methanol and ultrapure water. Finally, dry the solid in an oven at 60℃ to obtain magnetic MIL101-M.

[0068] (2) Preparation of flexible imprinted MOFs: Weigh 0.506g of sulfamethoxazole (SMX) as template molecule, add 0.617g of functional monomer MBA to 30ml of ethanol (porogen) and stir to mix evenly, then add 0.20g of MIL101-M prepared in step (1), ultrasonically disperse for 15min and stand for 12h, add 0.376ml of ethylene glycol dimethacrylate (EGDMA), stir for 30min, introduce N2 for 30min to remove oxygen, and stand for 12h to form prepolymer solution.

[0069] (3) Add 0.1 g of azobisisobutyronitrile (AIBN) to the prepolymer solution in step (2), purify with N2 for 30 min, and then place it in an 80℃ shaker at 100 r / min for 20 h until the reaction is complete. Centrifuge to obtain the polymer. Elute the polymer with a Soxhlet extraction method using a mixed solvent of ethanol and formic acid (v / v = 9:1) for more than 12 h to break the bonds between the template molecules and the imprint cavity in the polymer. Wash three times each with anhydrous ethanol and ultrapure water to remove the template molecules. Centrifuge and dry the obtained material at 60℃ for 12 h to obtain MIL101@MIP-E2.

[0070] Comparative Example 1

[0071] (1) Preparation of magnetic MIL101-M: Weigh 1.35g FeCl2·6H2O and 0.45g 2-aminoterephthalic acid, add them together to 30mL DMF, stir for 30 minutes until they are mixed evenly, then add 0.72g Fe3O4, pour the mixture into a 100mL polytetrafluoroethylene-lined reaction vessel, place it in an electric thermostatic drying oven preheated to 110℃, and after 20h, take out the reaction vessel and let it cool naturally to room temperature. Filter or centrifuge to separate the solid and liquid, and wash the solid three times each with DMF, methanol and ultrapure water. Finally, dry the solid in an oven at 60℃ to obtain magnetic MIL101-M.

[0072] (2) Preparation of MIL101@NIP-E1: Without adding sulfamethoxazole (SMX) as a template molecule, 0.617g of functional monomer MBA was added to 45ml of ethanol and stirred until homogeneous. Then, 0.20g of MIL101-M prepared in step (1) was added, ultrasonically dispersed for 15min, and allowed to stand for 12h. 0.754ml of ethylene glycol dimethacrylate (EGDMA) was added, stirred for 30min, and N2 was introduced for 30min to remove oxygen. After standing for 12h, a prepolymer solution was formed.

[0073] (3) Add 0.05 g of azobisisobutyronitrile (AIBN) to the prepolymer solution in step (2), purify with N2 for 30 min, and then place it in a shaker at 60 °C with stirring at 250 r / min for 8 h until the reaction is complete. Centrifuge to obtain the polymer. Elute the polymer with a Soxhlet extraction method using a mixed solvent of ethanol / formic acid (v / v = 9:1) for more than 12 h to break the bonds between the template molecules and the imprint cavity in the polymer. Wash three times each with anhydrous ethanol and ultrapure water to remove the template molecules. Centrifuge and dry the obtained material at 60 °C for 12 h to obtain the flexible imprint MIL101@NIP-E1.

[0074] Application Example 1

[0075] Application Example 1 investigated the adsorption performance of Example 1 on different Sas pollutants.

[0076] Sulfamethoxazole (SMX), sulfapyridine (SPD), and sulfathiazole (SMZ) were selected as typical representatives of SA (sulfate-sensitive) pollutants, and solutions were prepared (using water as the solvent) to explore the adsorption performance of MIL101@MIP-E1 prepared in Example 1 for SMX. The concentration of each pollutant was 50 mg / L. 0.06 g of MIL101@MIP-E1 and MIL101@NIP-E1 catalysts were added to 100 mL of the above mixed solution, respectively. The reaction solution was placed in a constant temperature shaking incubator at 180 rpm and 25 °C. After adsorption equilibrium (12 h), samples were taken to detect the adsorption capacity of the catalysts for different pollutants. The adsorption capacities of the four catalysts for different pollutants are shown below. Figure 1 As shown, MIL101@MIP-E1 exhibits an adsorption capacity of 32.96 mg / g for SMX, 28.18 mg / g for SPD, and 26.13 mg / g for SMZ, indicating that MIL101@MIP-E1 demonstrates excellent adsorption performance for SA-type pollutants with similar structures. Furthermore, MIL101@MIP-E1 shows even higher adsorption capacities for MIL101@NIP-E1, suggesting a strong template effect.

[0077] Application Example 2

[0078] Application Example 2 investigated the selective adsorption performance of Example 1 in a mixed water body.

[0079] Different pollutants with varying structures, namely sulfamethoxazole (SMX), phenol (PhOH), ciprofloxacin (CIP), and tetracycline (TET), were used to prepare mixed solutions (using water as the solvent) to explore the selective adsorption performance of MIL101@MIP-E1 prepared in Example 1. The concentration of each pollutant was 20 mg / L. 0.06 g of MIL101@MIP-E1 and MIL101@NIP-E1 catalysts were added to 100 mL of the above mixed solution, respectively. The reaction solution was placed in a constant-temperature shaking incubator at 180 rpm and 25 °C. After adsorption equilibrium (12 h), samples were taken to detect the adsorption capacity of the catalysts for different pollutants. The adsorption capacities of the four catalysts for different pollutants are shown below. Figure 2 As shown, the adsorption capacity of MIL101@MIP-E1 for the target pollutant SMX can reach 21.38 mg / g, which is 1.71 times that of MIL101@NIP-E1. This indicates that the imprinted porous catalyst channel prepared in Example 1 of this invention has good template performance. In addition, the adsorption capacities of MIL101@MIP-E1 for CIP, TCH, and PhOH are 7.02 mg / g, 14.1 mg / g, and 7.8 mg / g, respectively, all of which are much lower than the adsorption capacity of SMX, indicating that it has good selective adsorption performance in mixed water bodies.

[0080] Application Example 3

[0081] Application Example 3 compared the effects of different catalyst concentrations on pollutant removal.

[0082] This application example compares the effects of the dosage of MIL101@MIP-E1 prepared in Example 1 (0.1 g / L, 0.2 g / L, 0.4 g / L, 0.6 g / L, 0.8 g / L) on the catalytic activation and degradation of SMX. Using sodium persulfate as the oxidant, four groups of simulated organic wastewater with an initial SMX concentration of 20 mg / L were prepared at a dosage of 0.188 g. Without adjusting the pH of the wastewater, conical flasks were used as reactors, and five treatment groups were set up: (1) adding 0.1 g / L of MIL101@MIP-E1; (2) adding 0.2 g / L of MIL101@MIP-E1; (3) adding 0.4 g / L of MIL101@MIP-E1; (4) adding 0.6 g / L of MIL101@MIP-E1. (5) Add 0.8 g / L of MIL101@MIP-E1 to the conical flask and add the above four reaction solutions in sequence. Stir at room temperature to make the reaction uniform. Place the conical flask in a shaker at 180 rpm and carry out the reaction at room temperature (25℃). Take samples at intervals and use high performance liquid chromatography (HPLC) to determine the residual concentration of SMX in the wastewater and convert it into the removal rate. The results are shown in Table 2.

[0083] Table 2

[0084]

[0085]

[0086] As shown in Table 2, the removal rate of SMX gradually increases with increasing catalyst concentration. When the catalyst concentration is 0.8 g / L, the maximum removal rate of SMX reaches 94.25% within 1 hour. When the catalyst concentration increases from 0.4 g / L to 0.6 g / L, the removal rate increases by 15.5%, while when the catalyst concentration increases from 0.6 g / L to 0.8 g / L, the removal rate increases by 8.9%. Considering both the reaction removal rate and the operating cost, a catalyst concentration of 0.6 g / L is optimal.

[0087] Application Example 4

[0088] Application Example 4 compared the effects of different pH values ​​on pollutant removal.

[0089] This application example compares the effect of MIL101@MIP-E1 prepared in Example 1 on the catalytic activation and degradation of SMX in different pH solutions. Using sodium persulfate as the oxidant, with an addition of 0.188 g, four groups of simulated organic wastewater with an initial SMX concentration of 20 mg / L were prepared. The pH of the solution was adjusted using 0.1 mM / L hydrochloric acid and sodium hydroxide, and a conical flask was used as the reactor. Four treatment groups were set up: (1) pH adjusted to 3; (2) pH adjusted to 5; (3) pH adjusted to 7; and (4) pH adjusted to 9. 0.6 g / L of MIL101@MIP-E1 was added sequentially to the conical flask, and the reaction was stirred at room temperature to ensure uniformity. The conical flask was placed in a shaker at 180 rpm, and the reaction was carried out at room temperature (25℃). Samples were taken at intervals, and the residual concentration of SMX in the wastewater was determined by high-performance liquid chromatography (HPLC) and converted into a removal rate. The results are shown in Table 3.

[0090] Table 3

[0091]

[0092] As shown in Table 3, MIL101@MIP-E1 exhibited the best SMX removal rate at pH 5, reaching 91.5%. Furthermore, at different pH levels, its SMX removal rate consistently exceeded 80%, indicating that it demonstrates good SMX degradation performance over a wide pH range.

[0093] Experiment and test instructions

[0094] The MIL101@MIP-E1 catalyst prepared in Example 1 was characterized, and the results are as follows: Figure 3-6 As shown. Figure 3 The STEM image of MIL101@MIP-E1 prepared in Example 1 shows that the molecular imprinted layer was successfully loaded onto the MOF substrate, forming a core-shell structure. Figure 4 The XRD patterns before and after imprinting show that the characteristic peaks after imprinting are consistent with those of the substrate MIL101-E. This indicates that the introduction of the flexible imprinted layer does not affect the crystal structure of the substrate MOFs. Figure 5 The magnetization curves of MIL101-M and MIL101@MIP-E1 prepared in Example 1 show that the hysteresis loop of MIL101-M is S-shaped, indicating that MIL101-M possesses superparamagnetism. The saturation magnetization of the imprinted MIL101@MIP-E1 decreased from 35.3 emu / g to 4.5 emu / g, indicating that the imprinted layer weakens the magnetic strength of the catalyst. However, its hysteresis loop still exhibits an S-shape, which is still sufficient to achieve rapid separation in solution. Figure 6 and Figure 7 The figures show the N2 adsorption-desorption isotherms and pore size distribution curves for MIL101-M and MIL101@MIP-E1, respectively. The results indicate that the specific surface area increased from 58.89 m² / s² after imprinting. 2 / g decreased to 23.07m 2 / g, which may be due to the decrease in the specific surface area of ​​the catalyst caused by the imprinted coating. The micropore size ranges from 0.020 cm. 3 / g increased to 0.048cm 3 / g. This facilitates the mass transfer of the oxidant. Pore size distribution results show that new micropores of 1.5 nm, mesopores of 17.02 nm, and macropores of 36.97 nm were formed after imprinting.

Claims

1. A method for preparing a magnetically recyclable flexible imprinted MOF catalyst, characterized in that, Includes the following steps: (1) Synthesis of magnetic Fe-based MOF catalytic center substrate by hydrothermal method: Ferric chloride hexahydrate and 2-aminoterephthalic acid were added to N,N-dimethylformamide solvent and stirred to dissolve. Then Fe3O4 was added and the prepared mixture was transferred to an autoclave reactor and heated. The product was washed with N,N-dimethylformamide, methanol and water respectively and dried to obtain an amino-containing magnetic Fe-based MOF catalytic center donor. The molar ratio of Fe3O4 to 2-aminoterephthalic acid was 5:3-5:

9. (2) First, add the template molecule, functional monomer, and crosslinking agent to the reaction solvent and ultrasonically disperse and mix them evenly. Then, add the amino-containing magnetic Fe-based MOF catalytic center donor obtained in step (1) and let it stand for 12-18 h to fully prepolymerize and obtain a prepolymer solution. The template molecule is one or more of sulfamethoxazole, sulfapyridine, or sulfamethoxypyrimidine. The functional monomer is one or more of methylenebisacrylamide, methacrylamide, methacrylic acid, 4-vinylpyridine, and methyl acrylate. The molar ratio of the template molecule to the functional monomer is 1:3 - 1:

5. (3) Add an initiator to the prepolymer solution, introduce nitrogen to form an inert atmosphere, and polymerize the imprinted layer in a constant temperature shaking box at 60-65℃ for 8-12 hours to form an imprinted layer on the surface of magnetic Fe-MOFs. (4) The reaction product was eluted by Soxhlet extraction using an ethanol / formic acid eluent, then washed with ethanol, centrifuged, and vacuum dried to obtain a magnetically recoverable flexible imprinted MOF catalyst.

2. The method for preparing the magnetically recyclable flexible imprinted MOF catalyst according to claim 1, characterized in that, In step (1), the hydrothermal synthesis temperature is 100-150℃ and the synthesis time is 16-24h; the molar ratio between ferric chloride hexahydrate and 2-aminoterephthalic acid is 2:1-5:

1.

3. The method for preparing the magnetically recyclable flexible imprinted MOF catalyst according to claim 1, characterized in that, In step (2), the crosslinking agent is one or more of ethylene glycol dimethacrylate, divinylbenzene, and ethylene glycol dimethacrylate; the reaction solvent is one of ethanol, methanol, and acetonitrile.

4. The method for preparing a magnetically recyclable flexible imprinted MOF catalyst according to claim 1, characterized in that, In step (2), the molar ratio of the functional monomer to the crosslinking agent is 4:3-4:7; the mass ratio of the functional monomer to the magnetic Fe-based MOF catalytic center donor is 2:3-3:4; and the volume of the reaction solvent is 30-45 ml.

5. The method for preparing a magnetically recyclable flexible imprinted MOF catalyst according to claim 1, characterized in that, In step (3), the initiator is azobisisobutyronitrile, and the molar ratio of azobisisobutyronitrile to template molecules is 1:3-1:5; the nitrogen gas is introduced for 15-20 min, and the polymerization speed is 180-300 r / min; in step (4), the volume ratio of formic acid to ethanol in the eluent is 5:1-9:1, the elution time is 16-24 h, the vacuum drying temperature is 60-80℃, and the vacuum drying time is 16-24 h.

6. A magnetically recyclable flexible imprinted MOF catalyst prepared by the preparation method according to any one of claims 1 to 5.

7. The magnetically recoverable flexible imprinted MOF catalyst of claim 6 is used in advanced oxidation technologies for the efficient removal of sulfonamide organic pollutants from water, characterized in that... The flexible imprinted catalyst was added to water containing sulfonamide antibiotics, followed by the addition of an oxidant. The reaction was carried out under constant temperature and vibration at 20-25℃.

8. The application according to claim 7, characterized in that, The advanced oxidation technology is a persulfate system; the added oxidant is sodium persulfate or potassium persulfate.

9. The application according to claim 7, characterized in that, The molar ratio of the oxidant to the recalcitrant organic pollutants is 50:1-100:1; the concentration of the flexible imprinted catalyst in the wastewater is 0.1 g / L-1.0 g / L; the concentration of organic micropollutants in the wastewater is 20 mg / L-100 mg / L; and the degradation reaction time is 30-60 min.

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