Metal-organic framework-magnetic fiber composite material and in-situ preparation method thereof

Abstract

The present application relates to a kind of metal organic framework-ferroferric oxide magnetic fiber composite material and its in-situ preparation method, the precursor fiber is prepared by electrospinning technology in the present application, it is heated to a certain temperature under nitrogen atmosphere and obtains ferroferric oxide fiber, and then through solvent thermal method, ferroferric oxide on the surface of fiber is in-situ converted into MOFs nanoparticles.The present application uses ferroferric oxide electrospinning fiber as base material, the obtained composite material can keep the self-supporting performance of fiber, effectively prevent MOFs aggregation, while retaining the characteristics of magnetic separation, more easily recycled and used.Compared with commonly used organic base material, ferroferric oxide fiber does not need to carry out complex surface treatment, can be directly used as iron source and ligand reaction and is converted into MOFs structure, the obtained composite material is evenly dispersed in MOFs particle on the surface of fiber, is closely combined, can keep stable in water for a long time, is not easy to fall off, provides a new product for the preparation and application of MOFs composite material.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of metal organic framework-ferroferric oxide magnetic fiber composite material and its in-situ preparation method, belong to composite material technical field. BACKGROUND

[0002] Pharmaceutical and personal care products (PPCPs) include antibiotics, tranquilizers, shampoos, insect repellents, preservatives, etc., and are widely used in people's daily life. Once the PPCPs are discharged into the environment, they are difficult to be naturally degraded, and their biological toxicity and bacterial drug resistance characteristics pose a serious threat to the ecological environment, so it is urgent to find an effective treatment method. Fenton and Fenton-like catalysis as a representative of advanced oxidation technology has been widely used in the degradation of organic pollutants due to its high efficiency, complete treatment, good reproducibility and easy operation.

[0003] In recent years, it has been found that metal organic framework (MOFs) materials have attracted widespread attention from researchers in the fields of adsorption and catalysis due to their high specific surface area and porosity. Among them, MIL series of materials have excellent stability and adjustable pore structure, and show excellent photocatalytic performance. MIL-53, MIL-88, MIL-100, MIL-101, etc. can be used as efficient heterogeneous Fenton-like catalysts. The metal cluster in the material contains a large number of iron ion sites and unsaturated coordination iron ion sites, which can accept electrons from the reactants and further promote the catalytic reaction to proceed in the positive direction. On the other hand, the metal sites and ligands in MOFs can adsorb pollutants on the surface, making them more easily contact and react with the catalytic sites. However, the morphology of MOFs materials is mostly nano-powder, which inevitably causes agglomeration during use, affecting the catalytic efficiency, and is difficult to separate from the liquid phase, causing waste and secondary pollution.

[0004] Iron-based MOFs materials represented by MILs series have the characteristics of large specific surface area, moderate pore size and rich active metal sites, which are ideal heterogeneous Fenton-like catalysts. Combining them with suitable substrates can uniformly disperse the MOF particles that are prone to agglomeration under normal circumstances, and further improve their catalytic efficiency and recycling performance. Currently, the substrates used for MOFs composites are mostly organic fibers such as polyacrylonitrile (PAN), cellulose acetate (CA), polyamide (PA), polyimide (PI), polyacrylamide (PAM), or inorganic ceramic plates such as alumina and zinc oxide, and the composites are prepared by grafting, coating, hot pressing, seed growth, blending, etc. However, the obtained MOFs material is easy to fall off, the loading is not firm, and the loading amount is small.

[0005] Chinese patent document CN115873264A discloses a one-step formed MOFs adsorbent material and a preparation method thereof, which requires the use of a large amount of adhesive and thickening agent as additives in the reaction solution, and cannot effectively solve the problems of easy falling off, easy agglomeration and low utilization rate of MOFs. Chinese patent document CN115753929A discloses a MOFs@ nanofiber carbon aerogel and a preparation method thereof and an electrochemical detection of heavy metal ion sensing, which adds MOFs to the electrospinning precursor solution, and uses a blending spinning method to prepare a composite fiber, solving the problems of MOFs load stability and easy agglomeration of MOFs, but the load is small, the adsorption and catalytic activity is low, and the application effect is not ideal.

[0006] How to obtain MOFs with high load and strong adsorption and catalytic activity is a problem to be solved at present. SUMMARY

[0007] In view of the shortcomings of the prior art, the present application provides a kind of metal organic framework-ferroferric oxide magnetic fiber composite material and its in-situ preparation method.

[0008] The ferroferric oxide fiber is first prepared, the ferroferric oxide electrospinning nanofiber is used as a carrier and a metal source, the in-situ growth method is used to convert the ferroferric oxide on the surface of the nanofiber into an iron-based MOF, and a series of MOF-magnetic fiber composite materials are prepared. The MOF nanoparticles on the surface of the obtained composite fiber are uniformly dispersed, the MOF grains on the surface of the fiber present a continuous distribution, have a large load, a uniform distribution, a firm combination, will not fall off during the adsorption and catalytic reaction, compared with the MOF powder, the MOF particles on the surface of the composite fiber exhibit higher adsorption and catalytic activity, and can remain stable in water for a long time, have good recycling, and the composite fiber also retains the magnetism of the ferroferric oxide fiber, and can be quickly separated by using a magnet.

[0009] The in-situ method is used in the present application, the operation is simple, the raw material consumption is small, and the present application is easy to implement, which may have an expanding significance for the preparation of the iron-based MOF composite material and the application of the iron-based MOF composite material in the adsorption and catalytic degradation of organic pollutants.

[0010] The technical scheme of the present application is as follows:

[0011] The metal organic framework-ferroferric oxide magnetic fiber composite material has a micro-morphology that a layer of uniform and dense MOF grain layer is distributed on the surface of the ferroferric oxide magnetic fiber, the grain size is 100-200 nm, and the fiber has an irregular granular shape, and the diameter of the fiber is 900-1300 nm.

[0012] The in-situ preparation method of the metal organic framework-ferroferric oxide magnetic fiber composite material comprises the following steps:

[0013] (1) Dissolve the iron hydroxide and the carboxylic acid in deionized water under stirring to obtain a clear solution; concentrate under reduced pressure to obtain a viscous glue; dilute the glue with a solvent, and add a spinning aid, and fully dissolve under stirring to obtain a precursor spinning sol;

[0014] (2) electrospin the precursor spinning sol obtained in step (1) to obtain a precursor fiber;

[0015] (3) heat treat the precursor fiber prepared in step (2) to remove the organic matter in the precursor fiber to obtain a ferroferric oxide fiber;

[0016] (4) add the ferroferric oxide fiber into a MOFs precursor solution, transfer to a polytetrafluoroethylene reaction kettle, and perform a solvothermal reaction by heating, washing, and drying to obtain a fibrous metal organic framework-ferroferric oxide magnetic fiber composite material.

[0017] According to the application, preferably, in step (1), the molar ratio of the iron hydroxide to the carboxylic acid is 1:1-3.

[0018] Most preferably, in step (1), the molar ratio of the iron hydroxide to the carboxylic acid is 1:1-1.5.

[0019] Further preferably, the iron hydroxide is a freshly prepared iron hydroxide precipitate, which is prepared by the following method: dropwise add an alkaline solution to an iron salt solution until the iron ions are completely precipitated, centrifuge and wash multiple times to obtain the freshly prepared iron hydroxide precipitate.

[0020] Further preferably, the iron salt is one or more than two combinations of ferric nitrate nonahydrate, ferric chloride hexahydrate, and ferric sulfate nonahydrate.

[0021] Further preferably, the alkaline solution is one or more than two combinations of sodium hydroxide, potassium hydroxide, ethylenediamine, triethylamine, and aqueous ammonia solution.

[0022] According to the application, preferably, in step (1), the mass-to-volume ratio of the iron hydroxide to the deionized water is 1:30-120, in g / mL.

[0023] According to the application, preferably, in step (1), the carboxylic acid is one or more than two combinations of monohydrate citric acid, anhydrous citric acid, formic acid, acetic acid, propionic acid, oxalic acid, and tartaric acid.

[0024] According to the application, preferably, in step (1), the concentration temperature under reduced pressure is 40-60℃.

[0025] According to the present application, preferably, in step (1), the solvent is one or more than two combinations of deionized water, methanol, ethanol, isopropanol.

[0026] Further preferably, in step (1), the solvent is a mixed solvent of water and ethanol, and the volume ratio of water to ethanol is 1:0.5-2.

[0027] According to the present application, preferably, in step (1), the mass ratio of the solvent to the auxiliary spinning agent is (8-24):(0.01-0.1).

[0028] According to the present application, preferably, in step (1), the auxiliary spinning agent is one or more than two combinations of polyvinylpyrrolidone (PVP), polyethylene oxide (PEO), and polyvinyl alcohol (PVA).

[0029] According to the present application, preferably, in step (1), the mass ratio of the auxiliary spinning agent to the precursor spinning sol is 1:400-1000.

[0030] According to the present application, preferably, in step (2), the electrospinning conditions are as follows: a stainless steel needle with an inner diameter of 0.21-0.62 mm is used for spinning, the pushing speed is 0.6-2.0 mL / h, the spinning temperature is 15-45℃, the spinning humidity is 20-70%, the spinning voltage is 8-20 kV, and the receiving distance is 15-25 cm.

[0031] Further preferably, in step (2), the electrospinning conditions are as follows: the pushing speed is 1.0-1.7 mL / h, the spinning temperature is 20-35℃, the spinning humidity is 20-45%, and the spinning voltage is 10-14 kV.

[0032] According to the present application, preferably, in step (3), the heat treatment is performed in a nitrogen atmosphere, the heat treatment temperature is 450-600℃, the treatment time is 0.5-5 h, and the heating rate is 1-5℃ / min.

[0033] According to the present application, preferably, in step (4), the MOFs precursor solution comprises a ligand and a solvent, and the molar ratio of the ligand to the solvent is 1:(400-1000).

[0034] According to the present application, preferably, in step (4), the ligand is one or more than two combinations of terephthalic acid, amino terephthalic acid, trimesic acid, 4,4’-diphenyldicarboxylic acid, fumaric acid, glutaric acid, and succinic acid; and the solvent is one or more than two combinations of deionized water, methanol, ethanol, DMF, N,N-dimethylacetamide (DMA), N-methylformamide (NMF), and N-methylacetamide (NMA).

[0035] Further preferably, in step (4), the solvent is deionized water or a mixed solvent of deionized water and DMF, and the volume ratio of deionized water to DMF in the mixed solvent is (0.1-0.2):(18-25).

[0036] According to the application, preferably, in step (4), the mass ratio of the ligand to the ferriferrous oxide fiber is (1-10):1.

[0037] According to the application, preferably, in step (4), the solvent thermal reaction is carried out at a temperature of 80-150 DEG C for 12-36 h.

[0038] According to the application, preferably, the obtained metal organic framework-ferriferrous oxide magnetic fiber composite material MOFs is MIL-88A, MIL-88B or MIL-100. The fiber diameter is 0.8-2 microns, the high aspect ratio and magnetism of the fiber are retained, and the fiber can be quickly separated by a magnet. The MOFs particles obtained by in-situ growth on the fiber surface present a continuous distribution morphology, the grain size is 30-300 nm, the grains are closely connected without gaps, and the advantages of high loading, uniform distribution and firm combination are achieved. The application is prepared by an in-situ method, and has the advantages of simple operation, saving of raw materials and easy repetition. The composite material can remain stable in water for a long time and can be repeatedly used, and is suitable for application in the adsorption and catalytic treatment of various pollutants, especially PPCPs pollutants in water.

[0039] The application of the above metal organic framework-ferriferrous oxide magnetic fiber composite material is used for adsorbing or Fenton-like degrading dye pollutants norfloxacin in water.

[0040] Compared with the prior art, the application has the advantages of:

[0041] 1. The ferriferrous oxide fiber is prepared by electrospinning, the ferriferrous oxide electrospinning nanofiber is used as a carrier and a metal source, the ferriferrous oxide on the surface of the nanofiber is converted into an iron-based MOF by a solvothermal reaction by using an in-situ growth method, and a series of MOF-magnetic fiber composite materials are prepared. The MOF nanometer particles on the surface of the obtained composite fiber are uniformly dispersed and firmly combined, and will not fall off during the adsorption and catalytic reaction process. The ferriferrous oxide fiber serves as a substrate and a metal source, the MOF is directly converted on the surface of the fiber, the process is simple and easy to repeat, the structural stability of the composite material is ensured to the greatest extent, the composite material can be used in water for a long time, almost no iron ions are leached out, and excellent cycle stability is achieved.

[0042] 2. The precursor sol used in this invention effectively improves the spinnability of the spinning sol. The precursor spinning sol requires very little additive, resulting in continuous and flexible fibers, making it a suitable structural material for loading MOF particles. The iron oxide fibers obtained by electrospinning exhibit good flexibility and chemical stability, are safe and non-toxic, and possess the unique advantage of magnetic separability.

[0043] 3. This invention uses electrospun iron oxide fibers as the substrate, which are lightweight, have a large aspect ratio, are resistant to organic solvents, and exhibit good stability. After hydrothermal reaction, they retain their original fiber shape and excellent self-supporting properties, effectively solving the problem of MOFs' easy agglomeration. Simultaneously, the iron oxide fibers also serve as a functional material, giving the composite fibers the advantage of rapid magnetic separation, making them easier to recycle and avoiding secondary pollution.

[0044] 4. This invention employs an in-situ growth method, which is simple and easy to operate. During the preparation process, iron oxide fibers, in addition to serving as structural and functional materials, also act as a metal source for MOF preparation. Through the reaction, the surface is directly transformed into a MOF structure. The resulting composite material exhibits a tight and strong bond between the MOFs and fibers, with no voids between the MOF grains, making it less prone to detachment during use and giving the composite material excellent reusability. The composite material also demonstrates good water stability and low iron ion leaching after the catalytic reaction, making it adaptable to various application environments.

[0045] 5. Due to the self-supporting properties of the composite material of this invention, MOF powder agglomeration can be effectively avoided, resulting in better adsorption and catalytic performance than pure MOF powder. For 20 and 50 mg / L norfloxacin solutions, the adsorption capacities of the MIL-88B-Fe3O4 magnetic fiber composite material can reach 72.5 and 124.3 mg / g, respectively, which is 2.8 times higher than that of an equal mass of MOF powder prepared under the same conditions. For a 20 mg / L norfloxacin solution, the MOF-magnetic fiber composite material can achieve a degradation efficiency of over 98% within 30 minutes. In contrast, the degradation efficiency of the same mass of MOF powder within 30 minutes is only 83%. Attached Figure Description

[0046] Figure 1 This is a SEM image of the iron oxide fibers prepared in step (3) of Example 1 of the present invention.

[0047] Figure 2 SEM image of the MIL-88B-Fe3O4 magnetic fiber composite material prepared in Example 1 of this invention.

[0048] Figure 3XRD pattern of the MIL-88B-Fe3O4 magnetic fiber composite material prepared in Example 1 of the present application.

[0049] Figure 4 Magnetization curve of the MIL-88B-Fe3O4 magnetic fiber composite material prepared in Example 1 of the present application.

[0050] Figure 5 SEM image of the MIL-100-Fe3O4 magnetic fiber composite material prepared in Example 10 of the present application.

[0051] Figure 6 SEM image of the MIL-88A-Fe3O4 magnetic fiber composite material prepared in Example 11 of the present application.

[0052] Figure 7 SEM image of the Fe3O4@MIL-88B composite fiber prepared in Comparative Example 4 of the present application.

[0053] Figure 8 SEM image of the MIL-88B-Fe3O4 magnetic fiber composite material prepared in Comparative Example 6 by adding excess ligand.

[0054] Figure 9 Adsorption isotherm and second-order nonlinear fitting results of the MIL-88B powder and the MIL-88B-Fe3O4 magnetic fiber composite material in Experimental Example 1 of the present application.

[0055] Figure 10 Cycle performance curve of the MIL-88B-Fe3O4 magnetic fiber composite material in Experimental Example 1 of the present application.

[0056] Figure 11 Degradation curve of the Fe3O4 fiber, the MIL-88B powder and the MIL-88B-Fe3O4 magnetic fiber composite material in Experimental Example 2 of the present application. DETAILED DESCRIPTION

[0057] The present application is further described below by way of examples and with reference to the accompanying drawings, but the scope of the present application is not limited thereto.

[0058] The raw materials used in the examples are all conventional raw materials, and the equipment used is all conventional equipment, and the commercially available products.

[0059] Example 1:

[0060] The preparation method of the MIL-88B-Fe3O4 magnetic fiber composite material is as follows:

[0061] (1) Take 10 mmol (4.04 g) of iron nitrate nonahydrate, dissolve in 40 mL of deionized water, dropwise add ammonia water under stirring until the iron ions are completely precipitated, centrifugal wash, and obtain the freshly prepared iron hydroxide precipitate;

[0062] Take 1 g of the freshly prepared iron hydroxide precipitate and add 50 mL of deionized water and 15 mmol (3.15 g) of citric acid monohydrate, stir at room temperature until completely dissolved; the obtained clear solution is distilled under reduced pressure at 46°C until viscous, after the viscous sol cooled, add 8 g of water and ethanol mixed solvent (volume ratio of water to ethanol is 1:1) and 0.03 g of PEO, fully mix under stirring condition to obtain a clear precursor spinning sol;

[0063] (2) The precursor spinning sol obtained in step (1) is added to a syringe, a stainless steel needle with an inner diameter of 0.33 mm (model 23G) is used, the pushing speed is 1.5 mL / h, electrospinning is carried out under the conditions of spinning temperature of 20°C, spinning humidity of 20%, and spinning voltage of 10 kV, the receiving distance is 20 cm, and the precursor fiber is collected;

[0064] (3) The precursor fiber obtained in step (2) is placed in a porcelain boat, heated to 450°C at a heating rate of 2°C / min under nitrogen atmosphere, and kept for 1 h, and the fiber is taken out after completely cooled, to obtain the ferriferrous oxide fiber;

[0065] The SEM photo of the prepared ferriferrous oxide fiber is shown in Figure 1 , the diameter of the fiber is between 500-800 nm;

[0066] (4) 5 mmol (0.831 g) of terephthalic acid is completely dissolved in 19.8 mL of DMF, 0.2 mL of deionized water is added dropwise, then 0.2 g of the ferriferrous oxide fiber prepared in step (3) is added to the reaction solution, and ultrasonic treatment is carried out for 15 minutes. The mixture is transferred to a 50 mL volume stainless steel autoclave with a polytetrafluoroethylene liner, reacted in a 120°C oven for 24 h, and the product is naturally cooled, washed with DMF and methanol alternately for three times, and the solvent is completely evaporated in an 80°C oven to obtain the MIL-88B-ferriferrous oxide magnetic fiber composite material.

[0067] The SEM photo of the MIL-88B-ferriferrous oxide magnetic fiber composite material prepared in this example is shown in Figure 2 , the diameter of the fiber is increased to 900-1300 nm. A uniform and dense MOFs crystal layer is distributed on the surface of the fiber, the crystal size is between 100-200 nm, and it presents irregular granular shape. The XRD pattern of the MIL-88B-ferriferrous oxide magnetic fiber composite material is shown in Figure 3As shown, after the reaction, the characteristic peaks of MIL-88B appeared in the composite material, indicating that the MOFs crystal grains have been successfully prepared. The magnetization curves of the ferroferric oxide fiber and the MIL-88B-ferroferric oxide magnetic fiber composite material are as shown in the following figure: Figure 4 As shown, the saturation magnetization value of the ferroferric oxide fiber is about 30 emug -1 The saturation magnetization value of the MIL-88B-ferroferric oxide magnetic fiber composite material is reduced to about 20 emug -1 Although the saturation magnetization value is reduced, it does not affect the rapid separation of the magnet.

[0068] Example 2:

[0069] The preparation method of the MIL-88B-ferroferric oxide magnetic fiber composite material is the same as described in Example 1, except that in step (1), the iron salt used is replaced by 10 mmol (2.7 g) of iron chloride hexahydrate.

[0070] Example 3:

[0071] The preparation method of the MIL-88B-ferroferric oxide magnetic fiber composite material is the same as described in Example 1, except that in step (1), after the viscous sol is cooled, the solvent used is replaced by ethanol.

[0072] Example 4:

[0073] The preparation method of the MIL-88B-ferroferric oxide magnetic fiber composite material is the same as described in Example 1, except that:

[0074] In step (1), after the viscous sol is cooled, 8 g of water and ethanol mixed solvent (the volume ratio of water to ethanol is 1:1) and 0.03 g of PEO are added, and the mixture is fully mixed and uniform under stirring conditions to obtain a clear precursor spinning sol.

[0075] Example 5:

[0076] The preparation method of the MIL-88B-ferroferric oxide magnetic fiber composite material is the same as described in Example 1, except that in step (3), the temperature is raised to 400°C at a heating rate of 2°C / min under a nitrogen atmosphere, and the temperature is maintained for 1 h.

[0077] Example 6:

[0078] The preparation method of the MIL-88B-ferroferric oxide magnetic fiber composite material is the same as described in Example 1, except that the temperature is raised to 500°C at a heating rate of 2°C / min under a nitrogen atmosphere, and the temperature is maintained for 1 h.

[0079] Example 7:

[0080] The preparation method of the MIL-88B-Fe3O4 magnetic fiber composite material is the same as described in Example 1, except that in step (3), the temperature is raised to 600°C at a temperature raising rate of 2°C / min under a nitrogen atmosphere, and the temperature is kept for 1 h.

[0081] Comparative Example 1:

[0082] The preparation method of the MIL-88B-Fe3O4 magnetic fiber composite material is the same as described in Example 1, except that in step (3), the temperature is raised to 700°C at a temperature raising rate of 2°C / min under a nitrogen atmosphere, and the temperature is kept for 1 h.

[0083] Comparative Example 2:

[0084] The preparation method of the MIL-88B-Fe3O4 magnetic fiber composite material is the same as described in Example 1, except that in step (3), the temperature is raised to 800°C at a temperature raising rate of 2°C / min under a nitrogen atmosphere, and the temperature is kept for 1 h.

[0085] With the increase of the heat treatment temperature, the saturation magnetization of the composite fiber gradually increases, and the magnetism is further enhanced. The SEM photos of the composite materials prepared from the fibers obtained at different heat treatment temperatures do not show obvious differences in the MOFs morphology and distribution. However, the strength of the fibers obtained by heat treatment at a temperature higher than 600°C gradually decreases, and part of the fibers will be broken in the later hydrothermal reaction.

[0086] Example 8:

[0087] The preparation method of the MIL-100-Fe3O4 magnetic fiber composite material is the same as described in Example 1, except that:

[0088] In step (4), 5 mmol (1.051 g) of trimesic acid is added to 20 mL of deionized water, and stirred for 6 h. After uniform dispersion, 0.2 g of the Fe3O4 fiber prepared in step (3) is added to the reaction solution, and ultrasonic treatment is performed for 15 min. The mixture is transferred to a 50 mL volume stainless steel autoclave with a polytetrafluoroethylene liner, and reacted in a 160°C oven for 12 h. After natural cooling, the product is washed with water and methanol alternately for three times, and the solvent is completely evaporated in an 80°C oven to obtain the MIL-100-Fe3O4 magnetic fiber composite material.

[0089] The SEM photo of the prepared MIL-100-Fe3O4 magnetic fiber composite material is as shown in FIG. 6. Figure 5As shown, the average diameter of the fiber is between 800-1200 nm, and the surface of the composite is covered with evenly distributed MIL-100 nanocrystals, which are irregularly granular, with a size of 50-150 nm.

[0090] Example 9:

[0091] The preparation method of the MIL-88A-ferroferric oxide magnetic fiber composite is as described in Example 1, except that:

[0092] In step (4), 4 mmol (0.464 g) of fumaric acid is completely dissolved in 20 mL of DMF, and then 0.2 g of the ferroferric oxide fiber prepared in step (3) is added to the reaction solution, which is ultrasonically treated for 15 minutes. The mixture is transferred to a 50 mL volume stainless steel autoclave with a polytetrafluoroethylene liner, and is reacted in a 90°C oven for 10 h. After the product is naturally cooled, it is washed three times with DMF and methanol alternately, and the solvent is completely evaporated in an 80°C oven to obtain the MIL-88A-ferroferric oxide magnetic fiber composite.

[0093] The SEM photograph of the prepared MIL-88A-ferroferric oxide magnetic fiber composite is as shown in FIG. 2. Figure 6 As shown, the average diameter of the fiber is between 700-1100 nm, and the surface of the composite is covered with evenly distributed MIL-88A nanocrystals, which are irregularly granular, with a size of tens of nanometers. At the same time, a small amount of MOFs crystals with a size of 300-500 nm is observed to be generated on the surface of the fiber.

[0094] Comparative Example 3:

[0095] The preparation method of the MOFs-ferroferric oxide magnetic fiber composite is as described in Example 1, except that in step (4), deionized water is not added to the reaction solution.

[0096] Comparing the SEM photographs of the composite obtained in Example 1 and Comparative Example 1, it can be seen that the surface of the composite obtained according to the scheme of Example 1 is evenly and densely covered with MOFs, and there are no gaps between the MOFs crystals, while the surface of the composite obtained in Comparative Example 1 is only covered with small unformed crystals.

[0097] The reason is that water participates in the construction of the metal cluster structure unit Fe3O(BDC)3(OH2)3 of MIL-88B, which can promote the hydrolysis of DMF into formic acid and formamide. The former can act as a regulator for the nucleation and growth of MOFs, and the latter is believed to promote the hydrolysis of the carboxyl group in the terephthalic acid ligand, so that it is easier to coordinate with iron ions, and a layer of evenly and densely distributed MOFs crystals is obtained on the surface of the fiber. In Comparative Example 3, water is not involved, and only a small amount of fine crystals can be obtained.

[0098] Comparative Example 4:

[0099] The preparation method of the MOFs-Fe3O4 magnetic fiber composite material was carried out according to Example 1, except that:

[0100] In step (4), 2.5 mmol (0.675 g) of FeCl3·6H2O and 5 mmol (0.831 g) of terephthalic acid were dissolved in 19.8 mL of DMF under ultrasonic oscillation assistance, and 0.2 mL of deionized water was added. Then, 0.2 g of the Fe3O4 fiber prepared in step (3) was added to the reaction solution, and ultrasonic treatment was performed for 15 minutes. The mixture was transferred to a 50 mL volume stainless steel autoclave with a polytetrafluoroethylene liner, and reacted in a 120°C oven for 24 h. After the product was naturally cooled, it was washed with DMF and methanol alternately for three times, and the solvent was completely evaporated in an 80°C oven to obtain the Fe3O4@MIL-88B composite fiber.

[0101] The SEM image of the Fe3O4@MIL-88B composite fiber is shown in Figure 7 As compared with the SEM image of the composite material obtained in Example 1, the morphology has obvious difference. In Comparative Example 4, a new iron source is introduced, and only a small amount of MIL-88B is nucleated on the surface of the fiber, forming larger crystal grains, and the morphology presents a spindle shape consistent with the MIL-88B powder.

[0102] Comparative Example 5:

[0103] The preparation method of the MOFs-Fe3O4 magnetic fiber composite material was carried out according to Example 1, except that:

[0104] In step (3), the temperature was increased to 350°C at a rate of 2°C / min under an air atmosphere, and held for 1 h to obtain the Fe3O4 fiber. The other steps were carried out according to Example 1, and finally the MOFs-Fe3O4 fiber composite material was obtained.

[0105] Comparing the MOFs-Fe3O4 fiber composite material obtained in Comparative Example 5 with the SEM image of the composite material obtained in Example 1, it can be seen that only a layer of fine MOFs crystal grains is covered on the surface of the Fe3O4 fiber, and the growth effect is significantly poorer than that of the MOFs-Fe3O4 magnetic fiber composite material.

[0106] Comparative Example 6:

[0107] The preparation method of the MIL-88B-Fe3O4 magnetic fiber composite material was carried out according to Example 1, except that:

[0108] Step (4), 3 g of terephthalic acid was completely dissolved in 19.8 mL of DMF, 0.2 mL of deionized water was added dropwise, and then 0.2 g of the prepared Fe3O4 fiber in step (3) was added to the reaction solution, and ultrasonic treatment was performed for 15 minutes. The rest was carried out according to Example 1. The SEM image of the prepared MIL-88B-Fe3O4 magnetic fiber composite material is shown in Figure 8 As shown in Figure 8 It can be seen that the product obtained by adding excess ligand will appear spindle-shaped free MIL-88B crystal grains, and larger and irregular crystal grains, which may be caused by the crushing of the precipitated terephthalic acid ligand or Fe3O4 fiber.

[0109] Experimental Example 1:

[0110] The preparation method of the MIL-88B powder comprises the following steps:

[0111] 2.5 mmol (0.675 g) of FeCl3·6H2O and 5 mmol (0.831 g) of terephthalic acid were dissolved in 15 mL of DMF under ultrasonic oscillation assistance, and then the obtained mixed solution was transferred to a 50 mL stainless steel autoclave with a polytetrafluoroethylene liner, sealed and incubated in a 120°C oven for 24 hours. The obtained sample was washed with DMF and methanol alternately for three times, and then vacuum dried in an 80°C oven for 8 hours to obtain orange MIL-88B powder.

[0112] The thermogravimetric curves of the Fe3O4 fiber of step (3) of Example 1, the MIL-88B powder and the MIL-88B-Fe3O4 magnetic fiber composite material prepared in Example 1 were tested respectively, and according to the weight loss percentage, the loading amount of MIL-88B in the composite material of Example 1 was calculated to be about 30% of the total mass of the composite material.

[0113] Subsequently, the adsorption performance test was carried out, and the steps were as follows:

[0114] 10 mg of the MIL-88B-Fe3O4 magnetic fiber composite material prepared in Example 1 and 10 mg of the MIL-88B powder were respectively placed in 30 mL of norfloxacin solutions with different concentrations, and oscillated at a temperature of 25°C through a constant temperature orbital shaker, with a shaking frequency of 120 rpm and a shaking time of 6 hours. After the adsorption was completed, the concentration after adsorption was determined by a UV-Vis spectrophotometer (UV-Vis), the adsorption amount of the adsorbent corresponding to different initial concentrations of pollutants was calculated, and the relationship between the two was made into an adsorption isotherm, and the curve was fitted by a second-order nonlinearity, and the results are shown in Figure 9 As shown in the fitting results, the adsorption isotherms of the two adsorbents for norfloxacin are more consistent with the Langmiur model.

[0115] By comparing the data, the MIL-88B-Fe3O4 magnetic fiber composite material maintains the high adsorption performance of the MIL-88B powder. For 20 and 50 mg / L norfloxacin solutions, the adsorption capacity of the MIL-88B-Fe3O4 magnetic fiber composite material can reach 72.5 and 124.3 mg / g, respectively. Considering the actual content of MIL-88B (wt% ≈ 30%) in the composite material and the fact that the Fe3O4 fiber hardly adsorbs norfloxacin, compared with the MIL-88B powder prepared under the same conditions, the adsorption capacity of the MIL-88B contained in the composite material is increased by 2.8 times. This proves that the compounding with the fiber material effectively solves the problem of easy agglomeration of the MOFs powder, and the adsorption performance is improved.

[0116] Cyclic stability test: after the adsorption catalytic reaction is completed, the MIL-88B-Fe3O4 magnetic fiber composite material is separated using a magnet, and then washed with water and ethanol alternately three times. The washed MIL-88B-Fe3O4 magnetic fiber composite material is dried in an oven for the next catalytic performance test. After four cycles, the degradation rate of norfloxacin within 1 h decreases from 98% to 86%, and the cyclic performance curve is shown in Figure 10 .

[0117] Iron ion leaching amount: take 5 mL of the solution after the catalytic reaction, dilute and digest, and then use ICP-MS to detect the content of iron ions in the solution. According to the dilution factor, the actual content of iron ions in the solution is calculated to be 0.231 mg / L.

[0118] Experimental Example 2:

[0119] Fenton-like catalytic performance test, the steps are as follows:

[0120] Considering the actual loading amount of MIL-88B (wt% ≈ 30%) in the composite material, 20 mg of Fe3O4 fiber, MIL-88B-Fe3O4 magnetic fiber composite material prepared in Example 1 and 6 mg of MIL-88B powder are weighed, respectively, and put into 40 mL of 20 mg / L norfloxacin solution. After adjusting the pH value to 4.0 using 0.1 M NaOH or HNO3 solution, the beaker is placed in a constant temperature shaker, 45 μL of 30 wt% H2O2 solution is added in a dark environment, and the degradation is carried out at a vibration frequency of 120 rpm and a room temperature of 25°C. Samples are collected at a certain time, 2 mL of the solution is taken out and centrifuged, the upper solution is collected, and the concentration after degradation is determined by UV-Vis, and then the degradation rate corresponding to different reaction times is calculated, and the results are shown in Figure 11 .

[0121] By comparing the data, MIL-88B-Fe3O4 magnetic fiber composite material can achieve more than 98% degradation efficiency in 30 min. While the powder sample containing the same mass of MOFs, the degradation efficiency in 30 min is 83%. As a comparison, the unmodified Fe3O4 fiber has a degradation efficiency of only 7% in 30 min. It can be seen that the MIL-88B-Fe3O4 magnetic fiber composite material has more excellent catalytic performance.

Claims

1. A kind of metal organic framework-ferroferric oxide magnetic fiber composite material, the micro-morphology of the composite material is that a layer of uniform and dense MOFs crystal grain layer is distributed on the surface of ferroferric oxide magnetic fiber, the crystal grain size is 100-200 nm, and it presents irregular granular shape, and the diameter of the fiber is 900-1300 nm; A method for in-situ preparation of metal organic framework-ferroferric oxide magnetic fiber composite material, comprising the following steps: (1) Dissolve iron hydroxide and carboxylic acid in deionized water under stirring to obtain a clear solution, concentrate under reduced pressure to obtain a viscous gel, dilute the gel with a solvent, and fully dissolve under stirring to obtain a precursor spinning sol; (2) Electrospinning the precursor spinning sol obtained in step (1) to obtain a precursor fiber; (3) Heat-treat the precursor fiber prepared in step (2) to remove the organic matter in the precursor fiber to obtain a ferroferric oxide fiber; (4) Add the ferroferric oxide fiber into a MOFs precursor solution, transfer to a polytetrafluoroethylene reaction kettle, and perform a solvothermal reaction at elevated temperature, then wash and dry to obtain a fibrous metal organic framework-ferroferric oxide magnetic fiber composite material; The MOFs precursor solution comprises a ligand and a solvent, and the molar ratio of the ligand to the solvent is 1:(400-1000), the ligand is one or more than two combinations of terephthalic acid, amino terephthalic acid, trimesic acid, 4,4'-diphenyldicarboxylic acid, fumaric acid, glutaric acid, and succinic acid, the solvent is one or more than two combinations of deionized water, methanol, ethanol, DMF, N,N-dimethylacetamide (DMA), N-methylformamide (NMF), and N-methylacetamide (NMA), the mass ratio of the ligand to the ferroferric oxide fiber is (1-10):1, the solvothermal reaction is performed at a temperature of 80-150℃ for 12-36 h, the solvent is deionized water or a mixed solvent of deionized water and DMF, and the volume ratio of deionized water to DMF in the mixed solvent is (0.1-0.2):(18-25). 2.The metal organic framework-ferroferric oxide magnetic fiber composite material according to claim 1, wherein in step (1), the molar ratio of iron hydroxide to carboxylic acid is 1:1-3, the iron hydroxide is a freshly prepared iron hydroxide precipitate, which is prepared by the following method: adding an alkaline solution dropwise into a ferric salt solution until the ferric ions are completely precipitated, centrifuging and washing multiple times to obtain the freshly prepared iron hydroxide precipitate, and the ferric salt is one or more than two combinations of ferric nitrate nonahydrate, ferric chloride hexahydrate, and ferric sulfate nonahydrate, and the alkaline solution is one or more than two combinations of sodium hydroxide, potassium hydroxide, ethylenediamine, triethylamine, and aqueous ammonia solution. 3.The metal organic framework-ferroferric oxide magnetic fiber composite material according to claim 1, wherein ​ In step (1), the mass-volume ratio of iron hydroxide to deionized water is 1:30-120, unit g / mL, the carboxylic acid is one of monohydrate citric acid, anhydrous citric acid, formic acid, acetic acid, propionic acid, oxalic acid, tartaric acid or two or more combinations, the reduced pressure concentration temperature is 40-60℃, and the solvent is one of deionized water, methanol, ethanol, isopropanol or two or more combinations.

4. The metal organic framework-ferroferric oxide magnetic fiber composite material according to claim 1, characterized in that, In step (1), the mass ratio of solvent to spinning aid is (8-24):(0.01-0.1), the spinning aid is one of polyvinylpyrrolidone (PVP), polyethylene oxide (PEO), and polyvinyl alcohol (PVA) or two or more combinations, and the mass ratio of the spinning aid to the precursor spinning sol is 1:400-1000.

5. The metal organic framework-ferroferric oxide magnetic fiber composite material according to claim 1, characterized in that, In step (2), the electrospinning conditions are as follows: a stainless steel needle with an inner diameter of 0.21-0.62 mm is used for spinning, the push speed is 0.6-2.0 mL / h, the spinning temperature is 15-45℃, the spinning humidity is 20-70%, the spinning voltage is 8-20 kV, and the receiving distance is 15-25 cm.

6. The metal organic framework-ferroferric oxide magnetic fiber composite material according to claim 1, characterized in that, In step (3), the heat treatment is carried out in a nitrogen atmosphere, the heat treatment temperature is 450-600℃, the treatment time is 0.5-5 h, and the heating rate is 1-5℃ / min.

7. Use of the metal organic framework-ferroferric oxide magnetic fiber composite material according to claim 1 for adsorbing or Fenton-like degrading dye pollutants norfloxacin in water.

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