A zif-derived defective material, methods of making and using the same

Abstract

The application discloses a ZIF-derived defective material, a preparation method and application thereof, and relates to the technical field of MOF materials. Defect etching regulation of three-dimensional Zn-Co-ZIF material by nickel ions or tannic acid can provide surface support for ZIFs, effectively improve the mechanical strength of ZIFs, change the three-dimensional pore structure of ZIFs, expose active sites, increase the mass transfer speed, improve the rapid separation characteristics and stability in practical application, and enhance the adsorption performance and rapid separation characteristics of ZIFs on the polystyrene nano plastic residues in environmental water samples and fruit and vegetable samples. The application also studies the recognition and adsorption performance of the ZIF-derived defective material on polystyrene nano plastic, proves that the material has good application prospect in the enrichment and separation of the new hazard factor nano plastic, and has important practical significance for improving the quantitative accuracy and detection efficiency of nano plastic residues.

Description

Technical Field

[0001] This invention relates to the field of MOF materials technology, and more specifically, to a ZIF-derived defect material, its preparation method, and its application. Background Technology

[0002] Plastic film mulching, as a traditional agricultural planting technique, allows fruits and vegetables to fully utilize resources such as light, heat, water, and soil nutrients during growth, improving yield and economic value. However, the widespread use of agricultural plastic film has also led to pollution of agricultural land by plastic residues. Due to their non-degradability, these residues gradually decompose into microplastics (MPs) or nanoplastics (NPs) over time, eventually migrating and accumulating in fruits and vegetables, posing a potential risk to human health. For example, an early study by Lian et al. (2021) found that applying polystyrene nanoparticles (PS-NPs) to lettuce leaves had adverse effects on their development and nutritional composition. Researchers also found that PS-NPs could migrate from leaves through stomata and downwards into the plant roots. Subsequently, Jiang et al. (2022) observed PS-NPs migrating from the roots of peanuts and rice into the grains during the ripening stage. This migration adversely affected the nutritional quality of the grains, including a reduction in mineral elements, amino acids, and unsaturated fatty acids. When strawberry seedlings are contaminated with PS-NPs, Zhang et al. (2023) found that NPs can migrate upwards from the roots to the stems and leaves, affecting photosynthesis and growth. Therefore, there is an urgent need to develop control technologies / nanomaterials to adsorb and remove MPs / NPs from fruits and vegetables, which is of great significance for ensuring the quality and safety of agricultural products in my country.

[0003] Highly efficient adsorbents can effectively concentrate trace amounts of harmful substances from large quantities of fruit and vegetable samples, improving detection sensitivity while eliminating interference from the fruit and vegetable matrix. Selecting suitable porous materials is key to improving adsorption and removal performance. Currently, different types of porous materials have been reported for adsorbing and removing MPs / NPs in aqueous solutions, such as magnetic biochar, magnetic sepiolite, cellulose benzoate adsorbents, magnetic sponge carbon, plant-based nanocellulose networks, magnetic zeolite adsorbents, layered double oxides, and Zn / Al layered double hydroxides. However, the synthesis processes of these materials are complex, requiring high temperature and pressure, and are time-consuming and labor-intensive.

[0004] Three-dimensional (3D) MOFs possess significant potential for environmental pollutant removal and adsorption due to their advantages such as large specific surface area / porosity, excellent chemical stability, remarkable tunability of functional groups, and direct synthesis. However, 3D MOFs also face some challenges in pollutant removal processes, including deeply buried active sites, slow mass transfer rates, and low efficiency.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a ZIF-derived defect material, its preparation method and application, with the aim of preparing MOF materials with good adsorption performance and rapid separation characteristics.

[0007] This invention is implemented as follows:

[0008] In a first aspect, the present invention provides a method for preparing ZIF-derived defective materials, which prepares three-dimensional Zn-Co-ZIF materials using imidazole organic ligands, zinc sources and cobalt sources as raw materials, and reacts the three-dimensional Zn-Co-ZIF materials with a modification solution.

[0009] The modified solution contains at least one of nickel ions and tannic acid.

[0010] In an optional embodiment, the preparation process of the three-dimensional Zn-Co-ZIF material includes: mixing and dissolving a zinc source, a cobalt source, and a first solvent to obtain a mixed salt solution, and then mixing and reacting the mixed salt solution with an imidazole organic ligand.

[0011] Preferably, the reaction temperature of the mixed salt solution and the imidazole organic ligand is 15℃-30℃, and the reaction time is 20h-30h.

[0012] In an optional embodiment, the molar ratio of zinc, cobalt, and imidazole organic ligands is adjusted to (1.5-3.5):(4-5):(240-480) by controlling the amount of zinc source, cobalt source, and imidazole organic ligands.

[0013] Preferably, the imidazole organic ligand is selected from at least one of 2-methylimidazole and 1-methylimidazole;

[0014] Preferably, the imidazole organic ligands include 2-methylimidazole and 1-methylimidazole, and the molar ratio of 2-methylimidazole to 1-methylimidazole is 1:(0.5-1.5).

[0015] In an optional embodiment, the first solvent is selected from at least one of water, methanol, and ethanol; preferably, the first solvent is water and methanol; or, the first solvent is water and ethanol; or the first solvent is methanol and ethanol.

[0016] Preferably, both the zinc source and the cobalt source are nitrates or sulfates.

[0017] In an optional embodiment, after the reaction between the mixed salt solution and the imidazole organic ligand is completed, solid-liquid separation is performed, and the resulting solid material is washed and dried.

[0018] Preferably, solid-liquid separation is performed by centrifugation, with the rotation speed controlled at 8000 r / min-10000 r / min and the centrifugation time at 10 min-15 min;

[0019] Preferably, the washing process involves multiple washes using anhydrous ethanol or deionized water.

[0020] In an optional embodiment, the modification solution is a solution containing nickel ions, and the three-dimensional Zn-Co-ZIF material is mixed with a nickel source and a second solvent to react, with the reaction temperature controlled at 15℃-30℃ and the reaction time at 15min-60min.

[0021] Preferably, the molar ratio of zinc, cobalt and nickel is (2-5):(4-5):(1-10) by controlling the amount of nickel source used; more preferably, the nickel source is nitrate.

[0022] Preferably, the second solvent is selected from at least one of water, methanol, and ethanol; more preferably, the second solvent is water and methanol; or, the second solvent is water and ethanol; or the second solvent is methanol and ethanol.

[0023] Preferably, after the three-dimensional Zn-Co-ZIF material is mixed and reacted with the nickel source and the second solvent, solid-liquid separation is performed, and the resulting solid material is washed and dried.

[0024] In an optional embodiment, the modification solution is a solution containing tannic acid, and the three-dimensional Zn-Co-ZIF material is mixed with tannic acid and a third solvent to react, with the reaction temperature controlled at 15℃-30℃ and the reaction time at 15min-60min.

[0025] Preferably, by controlling the amount of tannic acid used, the molar ratio of zinc, cobalt and tannic acid is (2-5):(4-5):(1-5);

[0026] Preferably, the third solvent is selected from at least one of water, methanol, and ethanol; more preferably, the third solvent is water and methanol; or, the third solvent is water and ethanol; or the third solvent is methanol and ethanol.

[0027] Preferably, after the three-dimensional Zn-Co-ZIF material is mixed and reacted with tannic acid and a third solvent, solid-liquid separation is performed, and the resulting solid material is washed and dried.

[0028] Secondly, the present invention provides a ZIF-derived defect material, which is prepared by any of the preparation methods described in the foregoing embodiments.

[0029] Thirdly, the present invention provides the application of ZIF-derived defect materials prepared by any of the preparation methods in the foregoing embodiments in water treatment or fruit and vegetable treatment.

[0030] In an optional implementation, ZIF-derived defect materials are used to adsorb polystyrene nanoplastic residues.

[0031] The present invention has the following beneficial effects: by using nickel ions or tannic acid to perform defect etching control on three-dimensional Zn-Co-ZIF materials, it can provide surface support for ZIFs, effectively improve the mechanical strength of ZIFs, change the three-dimensional pore structure of ZIFs, and increase the exposure of active sites, which can accelerate the mass transfer rate, improve its rapid separation characteristics and stability in practical applications, and enhance the adsorption performance and rapid separation characteristics of ZIFs for polystyrene nanoplastic residues in environmental water samples and fruit and vegetable samples. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 The apparent morphology of ZIFs prepared in different embodiments is shown below; (a) represents Zn-Co-ZIF, (b) represents Zn-Co-Ni (10 mg)-ZIF, (c) represents Zn-Co-Ni (20 mg)-ZIF, (d) represents Zn-Co-Ni (60 mg)-ZIF, (e) represents Zn-Co-Ni (100 mg)-ZIF, (f) represents Zn-Co-TA (4 mg)-ZIF, (g) represents Zn-Co-TA (6 mg)-ZIF, (h) represents Zn-Co-TA (10 mg)-ZIF, and (i) represents Zn-Co-TA (20 mg).

[0034] Figure 2 SEM images of Zn-Co-Ni-ZIF and Zn-Co-TA-ZIF nanoframework samples;

[0035] Figure 3 The N2 adsorption-desorption isotherms and corresponding pore size distributions are shown below; (a) represents the N2 adsorption-desorption isotherm of Zn-Co-Ni-ZIF; (b) represents the pore size distribution of Zn-Co-Ni-ZIF; (c) represents the N2 adsorption-desorption isotherm of Zn-Co-TA-ZIF; (d) represents the pore size distribution of Zn-Co-TA-ZIF.

[0036] Figure 4 A standard curve for fluorescence determination of polystyrene microplastics;

[0037] Figure 5 The adsorption efficiency of Zn-Co-Ni (60 mg)-ZIF on PS-NPs in irrigation water, watermelon, strawberry and carrot. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0039] The inventors creatively regulated the defect functional groups of 3D-MOFs materials and endowed the materials with a wider range of application properties by adding specific functional modifiers (nickel ions or tannic acid). This significantly improved the material's stability and adsorption efficiency, increased the surface roughness of the material, and endowed it with a porous and wrinkled structure, thereby further improving its adsorption capacity for nanoplastics in environmental water samples and fruit and vegetable samples.

[0040] This invention provides a method for preparing ZIF-derived defect materials, comprising the following steps:

[0041] S1. Preparation of three-dimensional Zn-Co-ZIF materials

[0042] Using imidazole organic ligands, zinc source, and cobalt source as raw materials, a three-dimensional Zn-Co-ZIF material is formed after reaction, with imidazole organic ligands as support and zinc and cobalt metal ions as connection points.

[0043] In some embodiments, the preparation process of the three-dimensional Zn-Co-ZIF material includes: mixing and dissolving a zinc source, a cobalt source, and a first solvent to obtain a mixed salt solution; mixing the mixed salt solution with an imidazole organic ligand and reacting the solution; controlling the reaction temperature at 15℃-30℃ and the reaction time at 20h-30h. The reaction can be carried out at room temperature, and the long reaction time allows the reaction to proceed fully. Specifically, the reaction temperature can be 15℃, 20℃, 25℃, 30℃, etc., and the reaction time can be 20h, 22h, 25h, 28h, 30h, etc.

[0044] Furthermore, the types of zinc and cobalt sources are not limited; they can be nitrates or sulfates, but are not limited to these. For example, the zinc source can be Zn(NO3)2·6H2O, and the cobalt source can be Co(NO3)2·6H2O, etc. The zinc source can also be zinc sulfate monohydrate or zinc sulfate heptahydrate, and the cobalt source can be cobalt sulfate dihydrate or cobalt sulfate dihydrate, etc.

[0045] Furthermore, the imidazole organic ligand is selected from at least one of 2-methylimidazole and 1-methylimidazole, and can be any one or more of them. In a preferred embodiment, the imidazole organic ligand includes 2-methylimidazole and 1-methylimidazole, and the molar ratio of 2-methylimidazole to 1-methylimidazole is 1:(0.5-1.5), such as 1:0.5, 1:1.0, 1:1.5, etc. By optimizing the type of imidazole organic ligand, the adsorption performance of the product can be further improved.

[0046] Furthermore, by adjusting the amounts of zinc source, cobalt source, and imidazole organic ligands, the molar ratio of zinc, cobalt, and imidazole organic ligands can be (1.5-3.5):(4-5):(240-480). By adjusting the molar ratio of zinc, cobalt, and imidazole organic ligands, values ​​such as 1.5:4:240, 1.8:4.2:300, 2.0:4.5:350, 3.0:4.8:400, and 3.5:5.0:480 can be made, or any value between the above adjacent values.

[0047] In some embodiments, the first solvent is selected from at least one of water, methanol, and ethanol, and can be any one or more of the above. Preferably, the first solvent is water and methanol (volume ratio can be 1:1); or, the first solvent is water and ethanol (volume ratio can be 1:1); or the first solvent is methanol and ethanol (volume ratio can be 1:1). All three combinations are suitable for the preparation method provided in the embodiments of the present invention. Reacting in a mixed solvent system can make the prepared product more stable and prevent agglomeration. The amount of the first solvent is not limited, as long as it can effectively solvent the reactants. For example, the amount of Zn(NO3)2.H2O can be 0.5g-1.0g, the amount of Co(NO3)2.6H2O can be 1.2g-1.5g, the amount of 2-methylimidazole can be 10g-20g, and the amount of 1-methylimidazole can be 10g-20g. Methanol can be added in two steps (part of the methanol is used to dissolve 2-methylimidazole first), and the total amount of methanol can be 300mL-400mL.

[0048] Furthermore, after the reaction of the mixed salt solution and the imidazole organic ligands is completed, solid-liquid separation is performed. The obtained solid material is washed and dried. Unreacted metals and organic ligands are removed by washing, and surface solvent is removed after drying to obtain the intermediate product, three-dimensional Zn-Co-ZIF material.

[0049] In some embodiments, centrifugation can be used for solid-liquid separation, with the rotation speed controlled at 8000 r / min-10000 r / min and the centrifugation time at 10 min-15 min. Centrifugation can better separate solid materials. Specifically, during the centrifugation process, the rotation speed can be controlled at 8000 r / min, 8500 r / min, 9000 r / min, 9500 r / min, 10000 r / min, etc., and the centrifugation time can be 10 min, 13 min, 15 min, etc.

[0050] In some embodiments, washing may be performed multiple times with anhydrous ethanol or deionized water, such as three times, using 10 mL to 20 mL each time, to fully remove unreacted ions.

[0051] In some embodiments, freeze drying can be used for drying, and the drying time can be 20-30 hours.

[0052] S2, Defect Modification

[0053] A three-dimensional Zn-Co-ZIF material was reacted with a modification solution containing at least one of nickel ions and tannic acid. Nickel ions and tannic acid were used as etching modifiers to modify the three-dimensional Zn-Co-ZIF material. The etching modifiers were then used to hybridize and control defects in the ZIF material, thereby altering its properties. The inventors investigated the modified material's recognition and adsorption properties for polystyrene nanoplastics. This material shows great promise for the enrichment and separation of novel risk factor microplastics and nanoplastics, and has significant practical implications for improving the accuracy, stability, and detection efficiency of nanoplastic residue quantification.

[0054] It should be noted that introducing nickel ions or tannic acid can significantly improve the adsorption performance and rapid separation characteristics of polystyrene nanoplastic residues in environmental water samples and fruit and vegetable samples. The inventors hypothesize that defective etching can provide surface support for ZIFs, effectively improving their mechanical strength, altering their three-dimensional pore structure, increasing the exposure of active sites, accelerating mass transfer, and enhancing their rapid separation characteristics and stability in practical applications. Depending on the modification solution, the following two cases apply:

[0055] Case (1):

[0056] The modification solution is a solution containing nickel ions. The three-dimensional Zn-Co-ZIF material is mixed with a nickel source and a second solvent and reacted. The reaction temperature is controlled at 15℃-30℃ and the reaction time is 15min-60min. The reaction can be completed in a short time at room temperature. In an acidic environment, nickel ions have a stronger binding ability with ligands. Nickel ions partially replace zinc and cobalt ions, increasing the binding and adsorption capacity of the material with microplastics.

[0057] In some embodiments, by controlling the amount of nickel source, the molar ratio of zinc, cobalt, and nickel is (2-5):(4-5):(1-10), and the amount of nickel source is preferably within this range, in order to further improve the adsorption performance of the final ZIF-derived defect material. Specifically, the molar ratio of zinc, cobalt, and nickel can be 2.0:4.0:1.0, 2.5:4.2:2.0, 3.0:4.4:4.0, 3.5:4.6:6.0, 4.0:4.8:8.0, 4.5:5.9:9.0, 5.0:5.0:10.0, etc.

[0058] In some embodiments, the second solvent is selected from at least one of water, methanol, and ethanol, and can be any one or more of the above. Preferably, the second solvent is water and methanol; or, the second solvent is water and ethanol; or the second solvent is methanol and ethanol. Reactions in a mixed solvent system are more likely to form ZIF-derived defect materials with better stability and adsorption performance. The amount of the second solvent is not limited; for example, the amount of Zn-Co-ZIF material can be 20mg-50mg; the nickel source can be Ni(NO3)2·6H2O, and the amount can be 10mg-100mg; the ethanol can be anhydrous ethanol, and the amount can be 20mL-50mL.

[0059] Furthermore, after the three-dimensional Zn-Co-ZIF material is mixed and reacted with the nickel source and the second solvent, solid-liquid separation is performed, and the resulting solid material is washed and dried. Unreacted metal ions are removed by washing, and the surface solvent is removed after drying to obtain the ZIF-derived defect material.

[0060] In some embodiments, centrifugation can be used for solid-liquid separation, with the rotation speed controlled at 8000 r / min-10000 r / min and the centrifugation time at 10 min-15 min. Centrifugation can better separate solid materials. Specifically, during the centrifugation process, the rotation speed can be controlled at 8000 r / min, 8500 r / min, 9000 r / min, 9500 r / min, 10000 r / min, etc., and the centrifugation time can be 10 min, 13 min, 15 min, etc.

[0061] In some embodiments, washing may be performed multiple times with anhydrous ethanol, such as three times, using 10 mL to 20 mL each time, to fully remove unreacted ions.

[0062] In some embodiments, freeze drying can be used for drying, and the drying time can be 20-30 hours.

[0063] Case (2):

[0064] The modification solution was a solution containing tannic acid. The three-dimensional Zn-Co-ZIF material was mixed with tannic acid and a third solvent for reaction. The reaction temperature was controlled at 15℃-30℃, and the reaction time was 15min-60min. The reaction was complete in a short time at room temperature. Under acidic conditions, tannic acid gradually disrupted the binding energy between metal ions and 2-methylimidazole, modulated the internal porosity of the material, destroyed the internal framework structure, and introduced hydroxyl groups, which then interacted electrostatically with the target analyte, thereby improving the adsorption capacity.

[0065] Furthermore, by controlling the amount of tannic acid used, the molar ratio of zinc, cobalt, and tannic acid can be (2-5):(4-5):(1-5). Maintaining the amount of tannic acid within this range is preferable to further improve the adsorption performance of the final ZIF-derived defect material. Specifically, the molar ratio of zinc, cobalt, and tannic acid can be 2:4.0:1, 3:4.2:2, 4:4.5:3, 4.5:4.7:4, 5:5.0:5, etc.

[0066] In some embodiments, the third solvent is selected from at least one of water, methanol, and ethanol, and can be any one or more of the above. Preferably, the third solvent is water and methanol; or, the third solvent is water and ethanol; or the third solvent is methanol and ethanol. Reactions in a mixed solvent system are more likely to form ZIF-derived defect materials with better stability and adsorption performance. The amount of the third solvent is not limited; for example, the amount of Zn-Co-ZIF material can be 20mg-50mg; the amount of tannic acid can be 4mg-20mg; and the amount of methanol can be 20mL-50mL.

[0067] Furthermore, after the three-dimensional Zn-Co-ZIF material is mixed and reacted with tannic acid and a third solvent, solid-liquid separation is performed, and the resulting solid material is washed and dried. Unreacted metal ions are removed by washing, and the surface solvent is removed after drying to obtain the ZIF-derived defect material.

[0068] In some embodiments, solid-liquid separation can be performed by centrifugation, washing can be performed multiple times with anhydrous ethanol, and drying can be performed by freeze drying. The specific operating parameters are similar to those in case (1), and will not be repeated here.

[0069] This invention provides a ZIF-derived defect material prepared by the above-described method. By introducing nickel ions or tannic acid, it can significantly improve the adsorption performance and rapid separation characteristics of polystyrene nanoplastic residues in environmental water samples and fruit and vegetable samples.

[0070] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0071] Example 1

[0072] This embodiment provides a method for preparing ZIF-derived defect materials, including the following steps:

[0073] (1) Preparation of three-dimensional Zn-Co-ZIF materials

[0074] 0.5 g Zn(NO3)2·6H2O, 1.2 g Co(NO3)2·6H2O, and 150 mL methanol were mixed in a 500 mL Erlenmeyer flask and sonicated at room temperature for 5 min to ensure complete dissolution and uniform dispersion of the materials, resulting in a mixed salt solution. Then, 10 g 2-methylimidazole and 150 mL methanol were sonicated and mixed thoroughly before being added to the mixed salt solution, followed by 10 mL 1-methylimidazole. The mixture was magnetically stirred at room temperature (approximately 25°C) for 24 h. After the reaction was complete, the mixture was centrifuged at 8000 r / min for 10 min to obtain a solid material. The solid material was washed three times repeatedly with anhydrous ethanol and deionized water, using 10 mL of anhydrous ethanol or 10 mL of deionized water each time. After washing, the solid material was freeze-dried in a freeze dryer for 24 h.

[0075] (2) Preparation of Zn-Co-Ni-ZIF derived defect materials

[0076] Dissolve 20 mg Zn-Co-ZIF and 10 mg Ni(NO3)2·6H2O in 20 mL of anhydrous ethanol and stir magnetically for 30 min at room temperature. Then, centrifuge at 8000 r / min for 10 min to obtain a solid material. Wash the solid material three times with 10 mL of anhydrous ethanol each time. After washing, freeze dry in a freeze dryer for 24 h.

[0077] Examples 2-5

[0078] The only difference between Examples 2-5 and Example 1 is that the amount of Ni(NO3)2.6H2O used in step (2) is 20mg, 60mg, and 100mg respectively.

[0079] Example 6

[0080] This embodiment provides a method for preparing ZIF-derived defect materials, including the following steps:

[0081] (1) Preparation of three-dimensional Zn-Co-ZIF materials

[0082] Refer to step (1) of Example 1.

[0083] (2) Preparation of Zn-Co-TA-ZIF derived defect materials

[0084] 20 mg Zn-Co-ZIF and 4 mg tannic acid (TA) were dissolved in 20 mL of methanol and magnetically stirred at room temperature for 30 min. The mixture was then centrifuged at 8000 r / min for 10 min to obtain a solid material. The solid material was washed three times with 10 mL of anhydrous ethanol each time. After washing, the mixture was freeze-dried for 24 h.

[0085] Examples 7-9

[0086] The only difference between Examples 7-9 and Example 6 is that the amount of tannic acid (TA) used in step (2) is 6 mg, 10 mg, and 20 mg respectively.

[0087] Experimental Example 1

[0088] The appearance morphology of the products prepared in Examples 1-9 was tested and compared with that of Zn-Co-ZIF. The results are as follows: Figure 1 As shown. From Figure 1 As can be seen, Zn-Co-ZIF is a dark purple powder. As the nickel nitrate etching concentration increases, the color gradually turns to light purple, while as the tannic acid etching concentration increases, the color gradually changes from dark purple to dark brown.

[0089] SEM images of the products prepared in Examples 1-9 were tested, and the results are as follows: Figure 2 As shown. From Figure 2It can be seen that the synthesized Zn-Co-Ni-ZIF particles are positively correlated with the Ni(NO3)2 content. The particle size of the Zn-Co-ZIF, Zn-Co-Ni (10 mg)-ZIF, Zn-Co-Ni (20 mg)-ZIF, Zn-Co-Ni (60 mg)-ZIF, and Zn-Co-Ni (100 mg)-ZIF samples varies between 104 nm and 120 nm. By sequentially controlling the addition of Ni(NO3)2, the crystallization kinetics are enhanced. Therefore, the generation of smaller particle sizes does not show obvious aggregation, indicating great potential in adsorption. For Zn-Co-TA-ZIF, although the particle size gradually increases with the increase of TA content (from 110 nm to 136 nm), the particle surface of Zn-Co-TA (6-20 mg)-ZIF is coarser than that of Zn-Co-TA (4 mg)-ZIF. After introducing TA (6mg-20mg) into Zn-Co-ZIF, the morphology became much larger (119-136nm) and obvious aggregation occurred, indicating poor adsorption performance.

[0090] Experimental Example 2

[0091] The N2 adsorption-desorption isotherms and corresponding pore size distributions of the products prepared in the test examples are shown in the following figures. Figure 3 As shown. Figure 3 In the figure, (a) represents the N2 adsorption-desorption isotherm of Zn-Co-Ni-ZIF; (b) represents the pore size distribution of Zn-Co-Ni-ZIF; (c) represents the N2 adsorption-desorption isotherm of Zn-Co-TA-ZIF; and (d) represents the pore size distribution of Zn-Co-TA-ZIF.

[0092] from Figure 3 As can be seen, the effects of etching on the pore size and BET surface area of ​​ZIF-derived nanoframeworks were investigated using the N2 adsorption-desorption isotherm and the corresponding pore size distribution diagram. Figure 3 (a) and Figure 3 As shown in (c), the original Zn-Co-ZIF exhibits a type IV isotherm, a typical characteristic of the H3 hysteresis loop mesoporous structure. With increasing Ni(NO3)2 and TA etching, the amplitude of the H3 hysteresis loop gradually increases, indicating an increase in the mesoporous proportion, similar to PV. meso / PV micro The results were consistent.

[0093] In addition, from Figure 3 It can also be seen that Zn-Co-Ni (60mg)-ZIF and Zn-Co-TA (4mg)-ZIF have the best adsorption effects.

[0094] Experimental Example 3

[0095] The products prepared in each embodiment were used to conduct nanoplastic adsorption and removal experiments. The experimental steps are as follows:

[0096] Add 8 mL of 20 mg / L green fluorescent labeled polystyrene (PS) nanoplastic solution to a 10 mL centrifuge tube, add 2 mg of ZIF-derived material, sonicate to fully disperse the material evenly, then shake at 300 rpm for a certain period of time, then centrifuge at 8000 r / min for 5 min, collect the supernatant for fluorescence intensity measurement, the excitation wavelength is 495 nm and the emission wavelength is 515 nm.

[0097] The adsorption capacity of ZIF-derived nanoframework materials for PS-NPs was calculated using the following equation:

[0098]

[0099] In the formula, Q e To balance the adsorption capacity (mg / L), C0 and C e The initial and equilibrium concentrations of PS-NPs are given by m and V, respectively (mg / L), where m is the adsorbent mass (g) and V is the PS-NPs solution volume (L).

[0100] The standard curve for fluorescence determination of polystyrene microplastics is as follows: Figure 4 As shown, the linear equation is Y = 20.25104X + 0.44191, and the linear correlation coefficient is 0.99958.

[0101] Figure 5 The adsorption efficiency of Zn-Co-Ni (60 mg)-ZIF on PS-NPs in irrigation water, watermelon, strawberry, and carrot is shown. Figure 5 As shown, the adsorption efficiencies of Zn-Co-Ni(60mg)-ZIF for polystyrene nanoplastics in irrigation water, watermelon, strawberry and carrot were >87.8%, >89.49%, >90.36% and >92.72%, respectively, indicating that it has a superior ability to remove polystyrene nanoplastics.

[0102] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. Application of ZIF-derived defect materials in water treatment or fruit and vegetable treatment; The ZIF-derived defect material was used to adsorb polystyrene nanoplastic residues. The method for preparing the ZIF-derived defect material includes: preparing a three-dimensional Zn-Co-ZIF material using imidazole organic ligands, zinc source and cobalt source as raw materials, and reacting the three-dimensional Zn-Co-ZIF material with a modification solution; The modified solution contains at least one of nickel ions and tannic acid.

2. The application according to claim 1, characterized in that, The preparation process of the three-dimensional Zn-Co-ZIF material includes: mixing and dissolving the zinc source, the cobalt source and the first solvent to obtain a mixed salt solution, and then mixing and reacting the mixed salt solution with the imidazole organic ligand.

3. The application according to claim 2, characterized in that, The reaction temperature of the mixed salt solution and the imidazole organic ligand is 15℃-30℃, and the reaction time is 20h-30h.

4. The application according to claim 2, characterized in that, By adjusting the amounts of the zinc source, the cobalt source, and the imidazole organic ligand, the molar ratio of zinc, cobalt, and the imidazole organic ligand is made to be (1.5-3.5):(4-5):(240-480).

5. The application according to claim 4, characterized in that, The imidazole organic ligand is selected from at least one of 2-methylimidazole and 1-methylimidazole.

6. The application according to claim 5, characterized in that, The imidazole organic ligands include 2-methylimidazole and 1-methylimidazole, and the molar ratio of 2-methylimidazole to 1-methylimidazole is 1:(0.5-1.5).

7. The application according to claim 2, characterized in that, The first solvent is selected from at least one of water, methanol, and ethanol.

8. The application according to claim 7, characterized in that, The first solvent is water and methanol; or, the first solvent is water and ethanol; or the first solvent is methanol and ethanol.

9. The application according to claim 2, characterized in that, Both the zinc source and the cobalt source are nitrates or sulfates.

10. The application according to claim 2, characterized in that, After the reaction between the mixed salt solution and the imidazole organic ligand is complete, solid-liquid separation is performed, and the resulting solid material is washed and dried.

11. The application according to claim 10, characterized in that, Solid-liquid separation was performed by centrifugation, with the rotation speed controlled at 8000 r / min-10000 r / min and the centrifugation time at 10 min-15 min.

12. The application according to claim 10, characterized in that, The washing process involves multiple washes using anhydrous ethanol and deionized water.

13. The application according to claim 1, characterized in that, The modification solution is a solution containing nickel ions. The three-dimensional Zn-Co-ZIF material is mixed with a nickel source and a second solvent and reacted. The reaction temperature is controlled at 15℃-30℃ and the reaction time is 15min-60min.

14. The application according to claim 13, characterized in that, By controlling the amount of nickel source used, the molar ratio of zinc, cobalt and nickel is (2-5):(4-5):(1-10); the nickel source is nitrate.

15. The application according to claim 13, characterized in that, The second solvent is selected from at least one of water, methanol, and ethanol.

16. The application according to claim 15, characterized in that, The second solvent is water and methanol; or, the second solvent is water and ethanol; or the second solvent is methanol and ethanol.

17. The application according to claim 16, characterized in that, After the three-dimensional Zn-Co-ZIF material is mixed and reacted with the nickel source and the second solvent, solid-liquid separation is performed, and the resulting solid material is washed and dried.

18. The application according to claim 1, characterized in that, The modification solution is a solution containing tannic acid. The three-dimensional Zn-Co-ZIF material is mixed with tannic acid and a third solvent and reacted. The reaction temperature is controlled at 15℃-30℃ and the reaction time is 15min-60min.

19. The application according to claim 18, characterized in that, By controlling the amount of tannic acid used, the molar ratio of zinc, cobalt and tannic acid is (2-5):(4-5):(1-5).

20. The application according to claim 18, characterized in that, The third solvent is selected from at least one of water, methanol, and ethanol.

21. The application according to claim 20, characterized in that, The third solvent is water and methanol; or, the third solvent is water and ethanol; or the third solvent is methanol and ethanol.

22. The application according to claim 18, characterized in that, After the three-dimensional Zn-Co-ZIF material is mixed and reacted with the tannic acid and the third solvent, solid-liquid separation is performed, and the resulting solid material is washed and dried.

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