A magnetic metal-organic framework sponge for microplastic removal and a preparation method thereof
By constructing a three-dimensional sponge structure filled with fiber skeleton and MOF, the problems of limited adsorption capacity and inconvenient separation in the removal of microplastics from food liquids were solved, achieving efficient, safe and sustainable microplastic removal.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JILIN INST OF CHEM TECH
- Filing Date
- 2026-03-19
- Publication Date
- 2026-06-16
AI Technical Summary
Existing technologies are insufficient for efficiently removing microplastics from liquid food, and traditional methods suffer from problems such as limited adsorption capacity, inconvenient separation, and insufficient structural stability, making it particularly difficult to achieve high-throughput processing in complex food matrices.
A three-dimensional sponge structure with fiber skeleton-MOF filling was constructed by anchoring Bi2L3-MOF material on bamboo fiber/PEI electrospun membrane loaded with Fe3O4 to form multi-level channels. Combined with the rapid separation characteristics of magnetic components, a composite material with high adsorption capacity, fast mass transfer kinetics and excellent mechanical stability was constructed.
It achieves efficient, safe and sustainable removal of microplastics in food and beverages, with an adsorption capacity of up to 392.3 mg/g and a removal rate of up to 99%. The material can be easily recovered by an external magnetic field, avoiding secondary pollution.
Smart Images
Figure CN122209359A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of functional materials technology, specifically relating to a magnetic metal-organic framework sponge for microplastic removal and its preparation method. Background Technology
[0002] Microplastics (MPs) generally refer to plastic particles, fibers, or fragments with a diameter of less than 5 millimeters. In recent years, their widespread detection in global water environments and even food systems has raised serious public health and ecological safety concerns. In the food sector, particularly in bottled water, beverages, and tea drinks, microplastics may originate from aging packaging materials, contamination during processing, or the water source itself. The potential health risks of these microplastics after ingestion (such as inflammatory responses, cytotoxicity, and the release of chemical additives) are becoming urgent scientific issues that need to be addressed.
[0003] Currently, the mainstream technologies for removing microplastics from liquid foods mainly include: Membrane filtration technology: It can effectively trap larger particles by using the sieving effect of pore size, but it has problems such as easy clogging of membrane pores, high operating pressure, need for frequent cleaning or replacement, and a sharp decline in the removal efficiency of submicron particles.
[0004] Centrifugation and flocculation technology relies on the density difference between microplastics and the medium, or on the addition of chemical flocculants to cause them to agglomerate and settle. This method is prone to introducing new chemical substances, which may affect food quality, and has limited effectiveness in removing nanoscale microplastics. Subsequent solid-liquid separation steps are also cumbersome.
[0005] Adsorption technology: This technology utilizes the surface physicochemical interactions of porous materials (such as activated carbon and porous resins) to capture microplastics. Although traditional adsorption materials are relatively inexpensive, they generally suffer from drawbacks such as limited adsorption capacity, poor selectivity for microplastics, slow adsorption kinetics, and difficulty in regenerating materials after adsorption saturation.
[0006] To overcome these shortcomings, researchers have begun exploring novel removal strategies based on advanced functional materials. Among them, metal-organic frameworks (MOFs) have shown great potential in adsorption and separation due to their ultra-high specific surface area, highly tunable pore structure, and abundant surface active sites. However, directly using MOF powders for liquid processing faces engineering bottlenecks such as difficulty in recycling, susceptibility to secondary pollution, and large pressure drop in dynamic fluids. To solve the recycling problem, introducing magnetic components (such as Fe3O4 and γ-Fe2O3) to construct magnetic MOF composites and achieving rapid separation with the aid of an external magnetic field has become an important research direction. However, existing magnetic MOF materials are mostly prepared by in-situ growth or physical blending methods, and their structures usually exhibit loosely aggregated core-shell or heterogeneous structures, resulting in insufficient mechanical stability and recyclability, and they are easily disturbed in complex food matrices.
[0007] On the other hand, electrospinning technology can prepare three-dimensional nanofiber membranes with high porosity, large specific surface area, and good flexibility, making them ideal flexible substrates for carrying functional nanoparticles (such as magnetic particles). Encapsulating magnetic nanoparticles inside the fibers can effectively prevent their detachment and impart overall magnetism to the material. However, due to the limitations of its two-dimensional layered structure, single electrospun fiber membranes have low flux when processing large volumes of liquids, high internal mass transfer resistance, and their adsorption capacity for target analytes mainly depends on the limited functional groups on the fiber surface, making it difficult to meet the requirements for efficient removal.
[0008] Therefore, how to organically combine the high adsorption performance of MOFs, the convenient separation characteristics of magnetic particles, and the flexible skeleton structure of electrospun fibers to construct a composite material with high adsorption capacity, rapid mass transfer kinetics, excellent mechanical stability, and green and easily recyclable features has become a key technical challenge in this field. Especially for food applications, the material itself must also meet the basic requirements of safety, non-toxicity, and no introduction of additional pollution.
[0009] Existing technological solutions have failed to effectively address the aforementioned comprehensive needs: they either prioritize adsorption performance at the expense of ease of separation (e.g., powdered MOFs), prioritize ease of separation but have limited adsorption capacity (e.g., ordinary magnetic particles), or struggle to achieve high-throughput processing while ensuring structural stability (e.g., dense fiber membranes). Furthermore, a large amount of research relies on synthetic polymers as fiber substrates, which have shortcomings in terms of sustainability and biocompatibility.
[0010] Against this backdrop, this invention proposes an innovative three-dimensional sponge structure design of "fiber skeleton-MOF filling". By self-assembling a bamboo fiber / PEI electrospun membrane loaded with Fe3O4 with Bi2L3-MOF in solution, the high-density adsorption sites of MOF are successfully anchored in interconnected hierarchical channels. At the same time, it inherits the rapid separation advantage of magnetic components and the porous characteristics of bamboo fiber sponge, providing a brand-new solution for the efficient, safe and sustainable removal of microplastics from food and beverages. Summary of the Invention
[0011] In view of this, the purpose of this invention is to provide a magnetic metal-organic framework sponge for microplastic removal. This material is suitable for the efficient removal of microplastics in various liquid food systems such as bottled water, beverages, and tea, and has good matrix adaptability.
[0012] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing a magnetic metal-organic framework sponge for microplastic removal, comprising the following steps: S1. Bismuth nitrate and 2,5-bis(4-carboxyphenyl)-1,3,4-oxadiazole were dissolved together in a mixed solvent and reacted at an isothermal temperature to obtain Bi2L3MOF material; S2. Bamboo fiber, polyethyleneimine, solvent, and Fe3O4 nanoparticles are mixed and dispersed evenly to obtain an electrospinning precursor solution; S3. Electrospin the electrospinning precursor solution to form a Fe3O4 nanoparticle flexible film. S4. Fe3O4 nanoparticle flexible membrane fragments, Bi2L3MOF material, and water are mixed and stirred to form a uniform suspension. After filtration and vacuum drying, a magnetic metal-organic framework sponge is obtained.
[0013] Preferably, the mass-to-volume ratio of bismuth nitrate, 2,5-bis(4-carboxyphenyl)-1,3,4-oxadiazole, and the mixed solvent in S1 is (90~100) mg: (90~100) mg: 4.5 mL.
[0014] Preferably, the mixed solvent is a mixture of N,N-dimethylformamide and ethylene glycol in a volume ratio of 2:1.
[0015] Preferably, the isothermal reaction temperature in S1 is 93~97℃ and the time is 1~3h.
[0016] Preferably, the specific surface area of the Bi₂L₃MOF material in S1 is not less than 1000 m². 2 / g.
[0017] Preferably, the mass ratio of bamboo fiber, polyethyleneimine, solvent, and Fe3O4 nanoparticles in S2 is 1:(0.5~2):(20~30):(0.075~0.6).
[0018] Preferably, the electrospinning voltage in S3 is 10~25 kV and the receiving distance is 10~20 cm.
[0019] Preferably, the mass ratio of Fe3O4 nanoparticle flexible membrane fragments to Bi2L3MOF material in S4 is 1:(1~5).
[0020] Preferably, the stirring time in step S4 is 2 to 4 hours.
[0021] Preferably, the filtration time in step S4 is 20-30 min.
[0022] The present invention also provides a magnetic metal-organic framework sponge for microplastic removal, which is prepared by the above method.
[0023] It contains at least the following beneficial technical effects: This invention constructs a three-dimensional sponge structure with a fiber skeleton and MOF filling. By anchoring high specific surface area Bi2L3 MOF onto a bamboo fiber / PEI electrospun skeleton loaded with Fe3O4, the defects of easy agglomeration and difficult recovery of MOF powder are overcome, and the problem of limited adsorption capacity of single electrospun membranes is solved. This structure achieves a synergistic effect among the high-efficiency adsorption performance of MOF, the convenient magnetic separation characteristics of Fe3O4, and the porous skeleton support of bamboo fiber sponge.
[0024] Thanks to the ultra-high specific surface area and abundant adsorption sites of Bi₂L₃MOF, as well as the rapid mass transfer channels provided by the three-dimensional porous structure of the sponge material, the material of this invention exhibits extremely fast adsorption kinetics and extremely high adsorption capacity for microplastics. Example data show that adsorption equilibrium is reached within 15 minutes, with a maximum adsorption capacity of up to 392.3 mg / g for polystyrene (PS) microplastics and a removal rate of up to 99%.
[0025] By encapsulating Fe3O4 nanoparticles within electrospun fibers, the shedding of magnetic particles is effectively prevented, and the material is endowed with excellent overall magnetic response properties. After processing, the adsorbent material can be quickly and easily separated from liquid food using an external magnetic field, avoiding secondary pollution and facilitating material recycling and reuse.
[0026] This material is suitable for the efficient removal of microplastics from various liquid food systems, including bottled water, beverages, and tea, and exhibits excellent matrix adaptability. Furthermore, the bamboo fiber used is derived from natural biomass, demonstrating good biocompatibility and sustainability, meeting the safety requirements for food contact materials, and showcasing its enormous application potential in the field of food safety. Attached Figure Description
[0027] Figure 1 Diagram of the coordination environment of Bi2L3; Figure 2 The three-dimensional structure diagram of Bi2L3 is shown below. Figure 3 The graph shows the specific surface area of Bi2L3. Figure 4 The magnetic characterization diagram of the magnetic Bi2L3 sponge; Figure 5 Scanning electron microscope image of a magnetic Bi₂L₃ sponge; Figure 6 The graph shows the adsorption performance of magnetic Bi2L3 sponge on polystyrene microplastics. Detailed Implementation
[0028] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.
[0029] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.
[0030] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.
[0031] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.
[0032] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.
[0033] Unless otherwise specified, "room temperature" and "normal temperature" in this invention refer to 25±2℃.
[0034] Unless otherwise specified, all raw materials or instruments used in the following embodiments of the present invention are commercially available.
[0035] Example 1: Preparation of Magnetic MOF Sponge (1) Synthesis of Bi2L3MOF material: In a 25 mL reactor, 97 mg of bismuth nitrate and 93 mg of 2,5-bis(4-carboxyphenyl)-1,3,4-oxadiazole were mixed, and 4.5 mL of N,N-dimethylformamide and ethylene glycol in a volume ratio of 2:1 were added. The mixture was stirred evenly, sealed, and kept at a constant temperature of 95°C for 2 days. After naturally cooling to room temperature, Bi2L3MOF powder was prepared with a yield of 72%. The powder was thoroughly ground for later use.
[0036] Single-crystal X-ray diffraction analysis showed that the coordination environment of the prepared Bi₂L₃ was as follows: Figure 1 As shown, it belongs to the monoclinic crystal system. P2(1) / n Space group, cell parameters a = 17.3002 Å, b = 16.8938 Å, c = 29.2971 Å, α = 90°, β = 92.294°, γ = 90°. Each unit cell contains two Bi ions, three divalent ligands 2,5-bis(4-carboxyphenyl)-1,3,4-oxadiazole, one coordinated N,N-dimethylformamide, and one water molecule.
[0037] Figure 2 The figure shows the three-dimensional structure of the prepared Bi2L3. As can be seen from the figure, the compound has a large number of pores. The porosity of the MOF material was calculated to be 53.5% by oLex software.
[0038] The adsorption of nitrogen at 77 K on Bi₂L₃ was measured using a BSD-PM₂ physical adsorption analyzer. The results are shown in [Figure number missing]. Figure 3 As shown in the figure, the nitrogen adsorption capacity reaches 337.8 cm⁻¹ at 77 K. 3 g -1 Its specific surface area is 1350.6 cm². 2 g -1 This indicates that the prepared compound has a high specific surface area and is suitable for use as an adsorbent material.
[0039] (2) Preparation of electrospinning precursor solution loaded with Fe3O4 nanoparticles: In a 20 mL glass bottle, 1 g of bamboo fiber and 0.5 g of polyethyleneimine (PEI) were dissolved in 20 mL of N,N-dimethylformamide, and 150 mg of Fe3O4 nanoparticles were added. The mixture was stirred for 6 hours until it was evenly dispersed. (3) Electrospinning to prepare magnetic nanofiber membrane: The above solution is drawn into a syringe for electrospinning at a voltage of 20 kV and a receiving distance of 15 cm to form a flexible membrane in which Fe3O4 nanoparticles are wrapped in fibers. (4) Preparation of magnetic Bi2L3 sponge The 50 mg magnetic nanofiber membrane obtained in step (3) was cut into pieces and mixed with the 50 mg Bi2L3MOF powder obtained in step (1) in water. The mixture was stirred for 2 hours to form a uniform suspension. The suspension was then filtered under reduced pressure for 20 minutes using a sand core funnel and dried under vacuum to remove moisture, resulting in a three-dimensional porous sponge-like material.
[0040] The vibration magnetic properties of the prepared magnetic MOF sponge material were tested, and the results are shown in the figure. Figure 4 The magnetic strength reaches 17.7 emu / g, indicating that it possesses strong magnetism. The morphology of the magnetic Bi₂L₃ sponge is as follows: Figure 5 As shown, this indicates that the sponge material was successfully composited.
[0041] Example 2: Preparation of Magnetic MOF Sponge (1) Synthesis of Bi2L3MOF material: In a 25 mL reaction vessel, 90 mg of bismuth nitrate and 100 mg of 2,5-bis(4-carboxyphenyl)-1,3,4-oxadiazole were mixed, and 4.5 mL of N,N-dimethylformamide and ethylene glycol in a volume ratio of 2:1 were added. The mixture was stirred evenly, sealed, and kept at a constant temperature of 93°C for 1 day. After naturally cooling to room temperature, Bi2L3MOF powder was prepared with a yield of 70%. The powder was thoroughly ground for later use.
[0042] (2) Preparation of electrospinning precursor solution loaded with Fe3O4 nanoparticles: In a 20 mL glass bottle, 1 g of bamboo fiber and 1 g of polyethyleneimine (PEI) were dissolved in 25 mL of N,N-dimethylformamide, and 300 mg of Fe3O4 nanoparticles were added. The mixture was stirred for 6 hours until it was evenly dispersed. (3) Electrospinning to prepare magnetic nanofiber membrane: The above solution is drawn into a syringe for electrospinning at a voltage of 10 kV and a receiving distance of 10 cm to form a flexible membrane in which Fe3O4 nanoparticles are wrapped in fibers. (4) Preparation of magnetic Bi2L3 sponge The 50 mg magnetic nanofiber membrane obtained in step (3) was cut into pieces and mixed with the 150 mg Bi2L3MOF powder obtained in step (1) in water. The mixture was stirred for 3 hours to form a uniform suspension. The suspension was then filtered under reduced pressure for 20 minutes using a sand core funnel and dried under vacuum to remove moisture, resulting in a three-dimensional porous sponge-like material.
[0043] The prepared magnetic MOF sponge material was subjected to vibration magnetic tests, and the magnetic strength reached 18.0 emu / g, indicating that it has strong magnetism.
[0044] Example 3: Preparation of Magnetic MOF Sponge (1) Synthesis of Bi2L3MOF material: In a 25 mL reaction vessel, 100 mg of bismuth nitrate and 90 mg of 2,5-bis(4-carboxyphenyl)-1,3,4-oxadiazole were mixed, and 4.5 mL of N,N-dimethylformamide and ethylene glycol in a volume ratio of 2:1 were added. The mixture was stirred evenly, sealed, and kept at a constant temperature of 97°C for 3 days. After naturally cooling to room temperature, Bi2L3MOF powder was prepared with a yield of 74%. The powder was thoroughly ground for later use.
[0045] (2) Preparation of electrospinning precursor solution loaded with Fe3O4 nanoparticles: In a 20 mL glass bottle, 1 g of bamboo fiber and 2 g of polyethyleneimine (PEI) were dissolved in 30 mL of N,N-dimethylformamide, and 450 mg of Fe3O4 nanoparticles were added. The mixture was stirred for 6 hours until it was evenly dispersed. (3) Electrospinning to prepare magnetic nanofiber membrane: The above solution is drawn into a syringe for electrospinning at a voltage of 25 kV and a receiving distance of 20 cm to form a flexible membrane in which Fe3O4 nanoparticles are wrapped in fibers. (4) Preparation of magnetic Bi2L3 sponge The 50 mg magnetic nanofiber membrane obtained in step (3) was cut into pieces and mixed with the 250 mg Bi2L3MOF powder obtained in step (1) in water. The mixture was stirred for 4 hours to form a uniform suspension. The suspension was then filtered under reduced pressure for 30 minutes using a sand core funnel and dried under vacuum to remove moisture, resulting in a three-dimensional porous sponge-like material.
[0046] The prepared magnetic MOF sponge material was subjected to vibration magnetic tests, and the magnetic strength reached 17.9 emu / g, indicating that it has strong magnetism.
[0047] Comparative Example 1 The preparation method of this comparative example is the same as that of Example 1, except that it does not contain Bi2L3MOF.
[0048] Experimental Example 1 Microplastic removal detection 1. Using polystyrene (PS), a typical substance in microplastics, as the adsorbate, the adsorption performance of the magnetic Bi2L3 sponge material prepared in Example 1 above on microplastics was measured when the PS concentration was 200 ppm.
[0049] The test steps are as follows: 10 mg of magnetic Bi2L3 sponge material was placed in 20 mL of PS microplastic solution with a concentration of 200 ppm and shaken at room temperature. The changes in the solution before and after adsorption were observed. 2 mL of the above supernatant was taken at intervals (5, 10, 20, 30, 60, 120, 180 minutes) in groups, and the concentration after adsorption was obtained using a UV-Vis spectrometer. The adsorption efficiency (ηe) and adsorption capacity (qc) of the magnetic Bi2L3 sponge material were calculated using formulas (1) and (2).
[0050] (1) (2) Where C0 (mg / L) and C1 (mg / L) are the initial and post-adsorption concentrations of the PS microplastics, respectively. V (mL) is the volume of the solution, and m (mg) is the mass of the magnetic MOF sponge.
[0051] The results are as follows Figure 6 As shown, the magnetic Bi2L3 sponge exhibits excellent adsorption performance for PS microplastics, reaching a maximum adsorption capacity of 392.3 mg / g at 15 minutes, with a removal rate of up to 99%. Figure 6The illustrations show that the magnetic Bi2L3 sponge removes microplastics from liquid foods (bottled water, beverages, tea) at a rate close to 99%.
[0052] 2. The materials prepared in Comparative Example 1 were tested using the same method, as shown in Table 1.
[0053] Table 1. Comparison of PS microplastic removal between magnetic sponge and magnetic Bi2L3 sponge. The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing a magnetic metal-organic framework sponge for microplastic removal, characterized in that, Includes the following steps: S1. Bismuth nitrate and 2,5-bis(4-carboxyphenyl)-1,3,4-oxadiazole were dissolved together in a mixed solvent and reacted at an isothermal temperature to obtain Bi2L3MOF material; S2. Bamboo fiber, polyethyleneimine, solvent, and Fe3O4 nanoparticles are mixed and dispersed evenly to obtain an electrospinning precursor solution; S3. Electrospin the electrospinning precursor solution to form a Fe3O4 nanoparticle flexible film. S4. Fe3O4 nanoparticle flexible membrane fragments, Bi2L3MOF material, and water are mixed and stirred to form a uniform suspension. After filtration and vacuum drying, a magnetic metal-organic framework sponge is obtained.
2. The preparation method according to claim 1, characterized in that, The mass-to-volume ratio of bismuth nitrate, 2,5-bis(4-carboxyphenyl)-1,3,4-oxadiazole, and the mixed solvent in S1 is (90~100) mg: (90~100) mg: 4.5 mL.
3. The preparation method according to claim 2, characterized in that, The mixed solvent is a mixture of N,N-dimethylformamide and ethylene glycol in a volume ratio of 2:
1.
4. The preparation method according to claim 1, characterized in that, The isothermal reaction in S1 is at a temperature of 93~97℃ for 1~3 hours.
5. The preparation method according to claim 1, characterized in that, The specific surface area of the Bi2L3MOF material in S1 is not less than 1000 m². 2 / g.
6. The preparation method according to claim 1, characterized in that, The mass ratio of bamboo fiber, polyethyleneimine, solvent, and Fe3O4 nanoparticles in S2 is 1:(0.5~2):(20~30):(0.075~0.6).
7. The preparation method according to claim 1, characterized in that, In S3, the electrospinning voltage is 10~25kV and the receiving distance is 10~20 cm.
8. The preparation method according to claim 1, characterized in that, The mass ratio of Fe3O4 nanoparticle flexible membrane fragments to Bi2L3MOF material in S4 is 1:(1~5).
9. The preparation method according to claim 1, characterized in that, The stirring time in S4 is 2-4 hours.
10. A magnetic metal-organic framework sponge for microplastic removal, characterized in that, Prepared by the method described in any one of claims 1-9.