Novel core-shell MOFs nano composite material as well as preparation and application thereof

Abstract

The invention belongs to the field of materials, particularly relates to a novel core-shell MOFs nano composite material in the field of synthesis of nano materials and preparation and application of the novel core-shell MOFs nano composite material, and more particularly relates to an MIL-101 (Fe) coated SiO2 nano material and a preparation method and application of the MIL-101 (Fe) coated SiO2 nano material, and the novel MOFs nano material MIL-101 (Fe) coated SiO2 nano material is prepared by taking MIL-101 (Fe) as a skeleton structure and hybridizing SiO2. Experiments prove that after the nano material is sprayed on the leaf surfaces of rice in the elongation stage, the booting stage and the pustulation stage, the rice yield is remarkably increased, the Cd concentration in rice and rice shells is remarkably reduced, and the Cd stalk-grain transport coefficient is effectively reduced.

Description

Technical Field

[0001] The present invention belongs to the field of materials, particularly to the field of synthetic nanomaterials, and more specifically to novel core-shell MOFs nanocomposites and their preparation and applications. Background Art

[0002] Metal organic frameworks (MOFs) are crystalline porous materials with a periodic network structure formed by the self-assembly of inorganic metal centers (such as metal ions or metal clusters) and bridging organic ligands. MOFs combine the rigidity of inorganic materials and the flexibility of organic materials, thus showing great development potential and broad application prospects in modern materials research.

[0003] MIL-101(Fe) (Fe-MOFs) is a typical iron-based metal organic framework material, which has the advantages of flexible structure, large specific surface area, large porosity, adjustable pore size, etc. With the continuous in-depth research on MIL-101(Fe), at present, MIL-101(Fe) has made great progress in the field of catalysis, especially in the field of catalytic removal of pollutants in water bodies. Summary of the Invention

[0004] The present invention creatively applies MIL-101(Fe) to the field of liquid fertilizers, and discloses a new core-shell MOFs nanocomposite material, MIL-101(Fe)@SiO2 nanomaterial. In the MIL-101(Fe)@SiO2 nanomaterial, MIL-101(Fe) is a highly crystalline regular octahedron, and SiO2 is coated on the outer layer of MIL-101(Fe).

[0005] Furthermore, the present invention also discloses that the hydrodynamic particle size of the MIL-101(Fe)@SiO2 nanomaterial is 1762.7 nm, and the size is about 500 nm. Here, "about" means ±20%.

[0006] Meanwhile, the present invention also discloses a preparation method of the MIL-101(Fe)@SiO2 nanomaterial, which is hybridized from sodium silicate nonahydrate and MIL-101(Fe) as raw materials.

[0007] Furthermore, the preparation method of the MIL-101(Fe)@SiO2 nanomaterial includes the following steps: (1) Dissolve sodium silicate nonahydrate in water and adjust the pH value to neutral to obtain a sodium silicate solution; (2) Disperse MIL-101(Fe) in water, slowly pour the sodium silicate solution prepared in step (1), and heat and stir for reaction; (3) Centrifuge the reaction solution, remove the supernatant, and resuspend and disperse it with ethanol; (4) Centrifuge the dispersion obtained in step (3), remove the supernatant, and resuspend and disperse it with deionized water; (5) Continue to centrifuge the dispersion obtained in step (4), remove the supernatant, and resuspend and disperse it with ethanol-water; (6) Centrifuge the dispersion obtained in step (5), remove the supernatant, and resuspend and disperse it with deionized water; (7) Centrifuge the dispersion obtained in step (6), remove the supernatant, and dry to obtain the product MIL-101(Fe)@SiO2 nanomaterial.

[0008] Preferably, in step (2), heat to 60 °C and react for 3 hours.

[0009] Preferably, the centrifugation speed in steps (3), (4), (5), and (6) is 8000 rpm.

[0010] Preferably, the drying in step (6) means drying in an oven at 70 °C for 12 - 17 hours.

[0011] Preferably, in step (1), adjust the pH with 0.1 mol / L hydrochloric acid.

[0012] Meanwhile, in the present invention, the use of the MIL-101(Fe)@SiO2 nanomaterial in the preparation of foliar fertilizers is further disclosed.

[0013] The foliar fertilizer refers to a foliar fertilizer for rice.

[0014] Further preferably, the concentration of the MIL-101(Fe)@SiO2 nanomaterial in the foliar fertilizer is 200 mg / L.

[0015] In the present invention, using MIL-101(Fe) as the porous core material and silica as the shell, a core-shell nanocomposite MIL-101(Fe)@SiO2 with a stable core-shell nanostructure and highly crystalline octahedron is successfully constructed. Compared with other MOFs, MIL-101(Fe) composed of Fe3O secondary building units and 1,4-benzenedicarboxylate (BDC) has a high surface area, large pores, and non-toxic biocompatibility. At the same time, the silica shell can enhance stability, provide better water dispersibility, as well as various specific functions and high biocompatibility.

[0016] It has been experimentally confirmed that after spraying this nanomaterial on the leaves of rice at the jointing stage, booting stage, and filling stage, it can promote plant growth, significantly increase the rice yield, and the Cd concentration in rice and rice husks significantly decreases, effectively reducing the Cd stem-grain transfer coefficient. Description of the Drawings

[0017] Figure 1 It is the TEM image of MIL-101(Fe)@SiO2.

[0018] Figure 2 It is the EDS spectrum of MIL-101(Fe)@SiO2.

[0019] Figure 3 It is the EDS element proportion diagram of MIL-101(Fe)@SiO2.

[0020] Figure 4 It is the hydrodynamic diameter data diagram of SiO2, MIL-101(Fe) and MIL-101(Fe)@SiO2 nanomaterials.

[0021] Figure 5 It is the Zeta potential data diagram of SiO2, MIL-101(Fe) and MIL-101(Fe)@SiO2 nanomaterials.

[0022] Figure 6 It is the schematic diagram of grain yield after foliar spraying of SiO2, MIL-101(Fe) and MIL-101(Fe)@SiO2.

[0023] Figure 7 It is the schematic diagram of Cd accumulation in rice, grain husk, rice stem and root after foliar spraying of SiO2, MIL-101(Fe) and MIL-101(Fe)@SiO2.

[0024] Figure 8 It is the schematic diagram of bioconcentration factor after foliar spraying of SiO2, MIL-101(Fe) and MIL-101(Fe)@SiO2.

[0025] Figure 9 It is the schematic diagram of rice root-stem transfer coefficient after foliar spraying of SiO2, MIL-101(Fe) and MIL-101(Fe)@SiO2.

[0026] Figure 10 It is the schematic diagram of rice stem-rice transfer coefficient after foliar spraying of SiO2, MIL-101(Fe) and MIL-101(Fe)@SiO2. Detailed implementation mode

[0027] For a better understanding of the present invention, the present invention will be further elaborated below in combination with specific embodiments. Example 1

[0028] Dissolve 1.28 g of sodium silicate nonahydrate in 100 mL of water and stir evenly. Add 0.1 mol / L hydrochloric acid dropwise to the sodium silicate aqueous solution, and at the same time use a pH meter to detect the pH value in real time. Adjust the pH value to 7 to obtain a sodium silicate solution. Disperse 200 mg of MIL-101(Fe) (purchased from: Jiangsu Xianfeng Nano Materials Technology Co., Ltd.) in 30 ml of water, slowly pour it into the sodium silicate solution with a pH of 7, and stir in a water bath at 60 °C for 3 h.

[0029] After the reaction is completed, put the reaction solution into a 50 mL centrifuge tube. Centrifuge at a speed of 8000 rpm in a centrifuge for 8 min to separate the reaction products. Discard the supernatant and resuspend and disperse with ethanol; centrifuge at 8000 rpm for 8 min to remove the supernatant, and resuspend and disperse the precipitate with deionized water; then put the dispersion resuspended with deionized water into the centrifuge again, centrifuge at a speed of 8000 rpm for 8 min to remove the supernatant, and resuspend and disperse the precipitate with ethanol; put the dispersion resuspended with ethanol into the centrifuge again, and centrifuge again at 8000 rpm for 8 min to remove the supernatant, and resuspend and disperse with deionized water; put the obtained dispersion into the centrifuge again, and centrifuge at a speed of 8000 rpm for 8 min. After removing the supernatant, put the precipitate into an oven at 70 °C and dry overnight (16 hours), and take out the sample to obtain the product MIL-101(Fe)@SiO2. Example 2

[0030] Under an acceleration voltage of 100 - 300 kV, use a Transmission Electron Microscope (TEM) to observe the MIL-101(Fe)@SiO2 obtained in Example 1. The results are as Figure 1 shown. According to Figure 1 it can be seen that the prepared MIL-101(Fe)@SiO2 of the present invention is a highly crystalline regular octahedron, has good symmetry, and the size is about 500 nm.

[0031] Furthermore, we used EDS to analyze the element distribution and proportion of MIL-101(Fe)@SiO2. The results are as Figure 2 and Figure 3 shown.

[0032] According to Figure 2 and Figure 3 it can be seen that Si and O are distributed outside MIL-101(Fe), and SiO2 is successfully coated on the outer layer of MIL-101(Fe). Example 3

[0033] Select SiO2 nano-solution with a concentration of 200 mg / L (purchased from Shanghai Macklin Biochemical Co., Ltd.), MIL-101(Fe) nano-material (purchased from Jiangsu Xianfeng Nano Material Technology Co., Ltd.), and the MIL-101(Fe)@SiO2 nano-material solution prepared in Example 1. Use a Malvern nano particle size and Zeta potential analyzer to measure the hydrodynamic particle size and potential of the above three samples respectively.

[0034] The results are as Figure 4 and Figure 5 shown. It can be seen that the hydrodynamic particle sizes of the SiO2 nano-solution, MIL-101(Fe) nano-material, and MIL-101(Fe)@SiO2 nano-material solution are 1116.8, 1162.7, and 1762.7 nm respectively; the potentials of the SiO2 nano-solution, MIL-101(Fe) nano-material, and MIL-101(Fe)@SiO2 nano-material solution are -38.7 mV, 30.1 mV, and -6.5 mV respectively. Example 4

[0035] A pot experiment was carried out. Set to spray clear water (control group) and foliar spray the nano-SiO2 solution, MIL-101(Fe) nano-material, and MIL-101(Fe)@SiO2 nano-material in Example 3 during the jointing stage, booting stage, and filling stage of rice, with a total of 4 treatments. Each pot was filled with 15 kg of soil, the total Cd concentration in the soil was 0.18 mg / kg, the DTPA-Cd concentration was 0.10 mg / kg, and the soil pH was 5.6. Each treatment had three replicates, with a total of 12 pots, arranged in a completely random manner. After the rice seeds were disinfected and germinated, they were cultured in a seedling tray until the three-leaf and one-heart stage. Select seedlings with consistent growth and transplant them, 2 plants per pot. Spray the nano-SiO2 solution, MIL-101(Fe) nano-material, and MIL-101(Fe)@SiO2 nano-material once each during the jointing stage, booting stage, and filling stage of rice. The spraying concentration was 200 mg / L, and the application amount per pot was 50 mL. Natural light was used, and conventional water and fertilizer management was carried out.

[0036] When the rice was mature, collect the rice grains of each group and weigh them. The results are as Figure 6 shown. It can be seen that after spraying SiO2 and MIL-101(Fe)@SiO2, the rice yield increased significantly, increasing by 39.0% and 52.96% respectively compared to the control.

[0037] Detect the Cd content in the rice grains (rice), rice husks, and rice straws of each group respectively. The results are as Figure 5As shown, it can be seen that the Cd concentration in rice is significantly reduced. The Cd in rice grains (rice) sprayed with SiO2 nano-solution, MIL-101(Fe) nano-material and MIL-101(Fe)@SiO2 nano-material solution decreased by 25.7%, 25.7% and 36.2% respectively ( Figure 7 a); the Cd concentration in the rice husk also decreased significantly, by 29.3%, 33.5% and 33.2% respectively ( Figure 7 b); there was no significant effect on the Cd concentration in the rice straw ( Figure 7 c) and roots ( Figure 7 d).

[0038] Furthermore, we calculated the bioconcentration factor and translocation factor of rice after spraying foliar fertilizer.

[0039] The results are shown in Figures 8 - 10 . According to Figure 8 , it can be seen that after spraying MIL-101(Fe)@SiO2, the bioconcentration factor increased significantly, from 3.45 (Ctrl) to 4.73 (MIL-101(Fe)@SiO2). Combining Figure 9 and Figure 10 , it can be seen that spraying SiO2 nano-solution, MIL-101(Fe) nano-material and MIL-101(Fe)@SiO2 nano-material solution had no significant effect on the translocation factor of Cd from the roots to the stems of rice ( Figure 9 ), however, the translocation factor of Cd from the stems to the rice decreased by 50.9% (SiO2) and 58.4% (MIL-101(Fe)@SiO2) respectively.

[0040] Thus, it can be seen that the MIL-101(Fe)@SiO2 foliar fertilizer can significantly increase the rice yield and significantly reduce the Cd accumulation in rice grains (rice) and rice husks. At the same time, spraying MIL-101(Fe)@SiO2 can significantly increase the bioconcentration factor and reduce the stem-grain translocation factor of Cd.

[0041] The above is the specific implementation manner of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. A novel core-shell MOFs nanocomposite, characterized in that, The core-shell MOFs novel nanocomposite is MIL-101(Fe)@SiO2 nanomaterial. In the MIL-101(Fe)@SiO2 nanomaterial, MIL-101(Fe) is a highly crystalline regular octahedron, and SiO2 is coated on the outer layer of MIL-101(Fe).

2. The core-shell MOFs novel nanocomposite according to claim 1, wherein The hydrodynamic particle size of the MIL-101(Fe)@SiO2 nanomaterial is 1762.7 nm, and the TEM image shows that the size is about 500 nm.

3. The preparation method of the core-shell MOFs novel nanocomposite material according to claim 1 or 2, characterized in that, It is formed by the hybridization reaction of sodium silicate nonahydrate and MIL-101(Fe).

4. The preparation method according to claim 3, characterized in that, It includes the following steps: (1) Dissolve sodium silicate nonahydrate in water and adjust the pH value to neutral to obtain a sodium silicate solution; (2) Disperse MIL-101(Fe) in water, slowly pour it into the sodium silicate solution prepared in step (1), and heat and stir for reaction; (3) Centrifuge the reaction solution, remove the supernatant, and resuspend and disperse it with ethanol; (4) Centrifuge the dispersion obtained in step (3), remove the supernatant, and resuspend and disperse it with deionized water; (5) Continue to centrifuge the dispersion obtained in step (4), remove the supernatant, and resuspend and disperse it with ethanol; (6) Centrifuge the dispersion obtained in step (5), remove the supernatant, and resuspend and disperse it with deionized water; (7) Centrifuge the dispersion obtained in step (6), remove the supernatant, and dry to obtain the product MIL-101(Fe)@SiO2 nanomaterial.

5. The preparation method according to claim 4, characterized in that, In step (2), heat to 60 °C and react for 3 hours.

6. The preparation method according to claim 4, characterized in that, In steps (3), (4), (5), (6), and (7), the centrifugation speed is 8000 rpm.

7. The preparation method according to claim 4, characterized in that, The drying in step (6) means drying in an oven at 70 °C for 12 - 17 hours.

8. The preparation method according to claim 4, characterized in that, In step (1), adjust the pH with 0.1 mol / L hydrochloric acid.

9. Use of the MIL-101(Fe)@SiO2 nanomaterial according to claim 1 or 2 in the preparation of foliar fertilizer.

10. The use according to claim 9, characterized in that, The concentration of the MIL-101(Fe)@SiO2 nanomaterial in the foliar fertilizer is 200 mg / L.

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