A MOF / rGO composite aerogel, a preparation method and use thereof

Abstract

The application discloses a kind of MOF / rGO composite aerogel and its preparation method and use, the preparation method includes the following steps: middle-four (4-carboxyl phenyl) porphyrin and zirconium oxychloride are dissolved in N,N-dimethylformamide to form solution A, then add difluoroacetic acid to solution A to form solution B, solution B is transferred to reaction kettle to carry out solvothermal reaction, after natural cooling, obtain uniform suspension, centrifugal cleaning obtains PCN-222;Graphene oxide is dispersed in water to form suspension C;PCN-222 powder is obtained and a certain amount of suspension C is mixed evenly, then a certain amount of ascorbic acid is added, and after dissolving, suspension D is formed;Suspension D is placed in water bath kettle for constant temperature treatment for a certain time, to obtain MOF / rGO composite hydrogel;After washing hydrogel, freeze-drying and low-temperature annealing obtain MOF / rGO composite aerogel.The MOF / rGO composite aerogel prepared by the method is mainly applied to glyoxylic acid decolorizing material.

Description

Technical Field

[0001] This invention relates to the field of micro / nano composite material synthesis technology, specifically to a MOF / rGO composite aerogel, its preparation method, and its applications. Background Technology

[0002] In recent years, metal-organic frameworks (MOFs) and reduced graphene oxide (rGO) have been widely used in the preparation of adsorbent materials due to their advantages such as high specific surface area, good stability, and tunability. MOFs possess advantages such as large pore size, high specific surface area, and tunable structure, but their applications are limited by factors such as their crystal properties and stability. rGO exhibits excellent conductivity and chemical stability, but its irregular structure results in a relatively small specific surface area and limited adsorption performance. Combining MOFs and rGOs can fully leverage the advantages of both materials, improving adsorption performance and stability. Aerogels are nanoscale porous solid materials formed through the sol-gel method, where gas replaces the liquid phase in the gel using a specific drying process. Aerogels are the least dense solids in the world.

[0003] During long-term storage, glyoxylic acid undergoes oxidation reactions due to exposure to light, oxygen, and heat, producing colored substances that cause it to exhibit different colors. This not only affects the quality and purity of glyoxylic acid but also its effectiveness in certain applications. To address the issue of colored substances forming after long-term storage, various chemical and physical methods can be used for decolorization to improve the quality and purity of glyoxylic acid, ensuring its effectiveness and safety in applications. However, currently, there is no optimal method for efficiently removing these colored substances from glyoxylic acid. Summary of the Invention

[0004] The purpose of this invention is to provide a MOF / rGO composite aerogel, its preparation method and uses, which can improve the adsorption and separation performance of materials and be used as a glyoxylic acid decolorizing material.

[0005] In one aspect of the present invention, a method for preparing MOF / rGO composite aerogel is provided. According to an embodiment of the present invention, the method includes the following steps:

[0006] (1) Dissolve 4-tetra(4-carboxyphenyl)porphyrin and zirconium oxychloride in N,N-dimethylformamide to form solution A, and stir thoroughly;

[0007] (2) Add difluoroacetic acid to solution A to form solution B;

[0008] (3) Transfer solution B to a reaction vessel for solvothermal reaction. After natural cooling, centrifuge, wash and dry to obtain PCN-222 powder.

[0009] (4) Graphene oxide is dispersed in water to form a suspension C;

[0010] (5) Disperse PCN-222 powder in suspension C, and then add ascorbic acid to form a mixed suspension D;

[0011] (6) The mixed suspension D was placed in a water bath and kept at a constant temperature for a certain period of time to obtain MOF / rGO composite hydrogel.

[0012] (7) The MOF / rGO composite hydrogel was washed and then freeze-dried, followed by low-temperature annealing to obtain the MOF / rGO composite aerogel.

[0013] In addition, the method for preparing MOF / rGO composite aerogel according to the above embodiments of the present invention may also have the following additional technical features:

[0014] In some embodiments of the present invention, in step (1), the concentration of methyl-tetra(4-carboxyphenyl)porphyrin in solution A is 0.5-2 mol / L, the concentration of zirconium oxychloride is 5-10 mol / L, and the volume of N,N-dimethylformamide is 10-50 mL.

[0015] In some embodiments of the present invention, in step (2), the volume of difluoroacetic acid is 0.2-1 mL.

[0016] In some embodiments of the present invention, in step (3), the temperature of the solvothermal reaction is 100-160°C, the solvothermal reaction time is 24-36h, the cleaning is performed by alternating washing with N,N-dimethylformamide and ethanol 2-4 times, and the drying temperature is 75-85°C.

[0017] In some embodiments of the present invention, in step (4), the concentration of suspension C is 4-10 mg / mL.

[0018] In some embodiments of the present invention, in step (5), the mass of PCN-222 powder is 12-20 mg, the volume of suspension C is 3-5 mL, and the mass of ascorbic acid is 10-20 mg.

[0019] In some embodiments of the present invention, in step (6), the water bath temperature is 80-100°C and the reaction time is 10-30 min.

[0020] In some embodiments of the present invention, in step (7), the mixture of ethanol and water with a volume ratio of 1:3 is used to wash 3-5 times, the freeze-drying time is 48-72h, the freezing temperature is -40℃ to -120℃, and the low-temperature annealing temperature is 200-300℃.

[0021] In another aspect of the present invention, the present invention provides a MOF / rGO composite aerogel prepared according to the preparation method of the MOF / rGO composite aerogel.

[0022] In another aspect of the invention, a glyoxylic acid decolorizing material is provided. According to an embodiment of the invention, the decolorizing material is the aforementioned MOF / rGO composite aerogel.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] 1) The MOF / rGO composite aerogel prepared in this invention achieves the reduction and self-assembly of graphene under low-temperature conditions, utilizing the self-assembled graphene to physically bind PCN-222, thus fully leveraging the high specific surface area, high porosity, and modifiability of MOF. Furthermore, the aerogel structure formed by the organic combination of graphene and MOF effectively avoids secondary contamination of samples caused by MOF dissolution in liquids during separation processes using MOF.

[0025] 2) MOFs are not easily stable in highly oxidizing or highly reducing environments. When highly reducing ascorbic acid is added, GO and MOF are thoroughly mixed first. Due to the defects on the surface of MOF, the positive charge of the metal on the surface attracts the GO nanosheets to tightly wrap the MOF. Furthermore, GO is reduced on the surface first, consuming the ascorbic acid, which effectively avoids the destruction of MOF. Thus, it has a significant effect on the stabilization of MOF / rGO composite aerogels.

[0026] 3) The MOF / rGO composite aerogel exhibits excellent decolorization ability for glyoxylic acid, primarily due to the dual synergistic effect of MOF and rGO aerogel. Firstly, glyoxylic acid aqueous solution is inherently acidic, and MOF, being a crystalline carboxylate, generally cannot exist effectively in acidic solutions; even highly acid-resistant MOFs will slowly decompose in acidic environments. Secondly, rGO aerogel has poor water affinity, resulting in extremely slow decolorization of glyoxylic acid. Finally, the MOF / rGO composite aerogel fully utilizes the high specific surface area of ​​MOF, leading to excellent adsorption performance, while the water-repellent properties of the rGO nanosheets encapsulating MOF effectively prevent MOF from being corroded and decomposed by acidic solutions.

[0027] 4) The preparation method of the present invention is simple and easy to operate, safe and pollution-free, and low in cost. Attached Figure Description

[0028] Figure 1 Low-magnification (a) and high-magnification (b) FESEM images of the PCN-222 nanorods prepared in Example 1 of this invention;

[0029] Figure 2 Low-magnification (a) and high-magnification (b) FESEM images of the microstructure of the reduced graphene oxide aerogel prepared in Example 2 of this invention;

[0030] Figure 3 Low-magnification (a) and high-magnification (b) FESEM images of the microstructure of the MOF / rGO composite aerogel prepared in Example 3 of this invention;

[0031] Figure 4 Optical photographs of the rGO aerogel (a) prepared in Example 2 and the MOF / rGO composite aerogel (b) prepared in Example 3 of the present invention;

[0032] Figure 5 XRD diffraction patterns of PCN-222 nanorods prepared in Example 1 and MOF / rGO composite aerogels prepared in Example 3 of this invention;

[0033] Figure 6 The glyoxylic acid decolorization performance of PCN-222 nanorods prepared in Example 1, rGO aerogel prepared in Example 2, and MOF / rGO composite aerogel prepared in Example 3 are shown in the figure. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0035] Example 1

[0036] The preparation method of PCN-222 nanorod powder includes the following steps:

[0037] (1) Dissolve 6.8 mg of zirconium oxychloride and 37.7 mg of 4-tetra(4-carboxyphenyl)porphyrin in 16 mL of N,N-dimethylformamide to form solution A, and stir thoroughly in a magnetic stirrer.

[0038] (2) Add 0.226 mL of difluoroacetic acid to solution A to form solution B;

[0039] (3) Transfer solution B to a reaction vessel for a solvothermal reaction at a temperature of 120°C for 24 hours.

[0040] (4) After natural cooling, the product was centrifuged and washed with N,N-dimethylformamide and ethanol alternately. Then it was dried in an oven at 80°C to obtain PCN-222 nanorod powder.

[0041] Figure 1 The image shows an FESEM image of the PCN-222 nanorods prepared in this embodiment. The nanorods are approximately 500 nanometers long and 100 nanometers in diameter.

[0042] Example 2

[0043] The preparation method of rGO aerogel includes the following steps:

[0044] (1) Place 16 mg of graphene oxide in 4 mL of deionized water and sonicate at a constant temperature for 4 h to form a 4 mg / mL graphene oxide suspension C.

[0045] (2) Place the suspension C in a water bath at 90°C and let it stand for 15 minutes. After completion, remove it immediately and cool it quickly to obtain reduced graphene oxide hydrogel.

[0046] (3) The rGO aerogel was washed with a 1:3 mixture of water and ethanol, followed by freeze-drying and thermal reduction at 200°C.

[0047] Figure 2 The image shown is a FESEM image of the rGO aerogel prepared in this embodiment. Its microstructure indicates that the rGO nanosheets cross-link to form a porous three-dimensional structure.

[0048] Example 3

[0049] The preparation method of MOF / rGO composite aerogel includes the following steps:

[0050] (1) 12 mg of graphene oxide was placed in 3 mL of deionized water and sonicated at a constant temperature for 4 h to form a 4 mg / mL graphene oxide suspension C. Then, 12 mg of PCN-222 prepared in Example 1 was added to the suspension C, and 24 mg of ascorbic acid was added. The suspension was then sonicated and dispersed to form a uniform suspension D.

[0051] (2) The suspension D was quickly placed in a water bath at 90°C and kept at a constant temperature for 15 minutes. After completion, it was immediately taken out and cooled rapidly to obtain MOF / rGO composite hydrogel.

[0052] (3) The MOF / rGO composite hydrogel was cleaned with a water and ethanol mixture with a volume ratio of 1:3, and then freeze-dried for 60 h at a freezing temperature of -60 °C. The MOF / rGO composite aerogel was then annealed at 200 °C to obtain the MOF / rGO composite aerogel.

[0053] Figure 3The image shown is an FESEM image of the MOF / rGO aerogel prepared in Example 3. Its microstructure shows that the rGO nanosheets cross-link to form a porous three-dimensional structure, and PCN-222 is dispersed on the rGO nanosheets and coated by the rGO nanosheets, forming a PCN-222 dispersed three-dimensional porous aerogel structure.

[0054] Figure 4 (a) and (b) are optical photographs of the samples prepared in Example 2 and Example 3, respectively. Morphologically, both aerogels are in a fluffy state, but the MOF / rGO composite aerogel containing PCN-222 is rougher than the rGO aerogel.

[0055] Figure 5 The XRD diffraction patterns of the samples prepared in Examples 1 and 3 show that PCN-222 in the MOF / rGO composite aerogel can be dispersed in the rGO aerogel, and the phase structure of MOF is not destroyed during the preparation process.

[0056] Example 4

[0057] The glyoxylic acid decolorization performance verification tests of the PCN-222 nanorod powder prepared in Example 1, the rGO aerogel prepared in Example 2, and the MOF / rGO composite aerogel prepared in Example 3 included the following steps:

[0058] (1) Prepare a 50% glyoxylic acid aqueous solution by mass, and then heat it at 80°C for 4 hours to obtain a glyoxylic acid aqueous solution with a certain degree of color development.

[0059] (2) The materials prepared in Examples 1-3 were directly immersed in the color-developing glyoxylic acid aqueous solution and adsorbed for 2 hours. The mass ratio of the materials prepared in Examples 1-3 to the volume ratio of 50% glyoxylic acid aqueous solution was 1:2.

[0060] Figure 6 The graphs show the decolorization performance of glyoxylic acid by the PCN-222 nanorod powder prepared in Example 1, the rGO aerogel prepared in Example 2, and the MOF / rGO composite aerogel prepared in Example 3. It can be seen that the MOF / rGO composite aerogel exhibits the best glyoxylic acid decolorization performance.

[0061] The above embodiments are typical examples of the present invention and are not intended to limit the invention in any way. For example, the reaction concentration, reaction time, water bath temperature, annealing temperature, etc., can be further adjusted. Therefore, based on the overall concept of the present invention, any adjustments or modifications to the process parameters described by those skilled in the art, as long as they do not deviate from the inventive concept or exceed the scope defined in the claims, should fall within the protection scope of the present invention.

Claims

1. A method for preparing a MOF / rGO composite aerogel, characterized in that, Includes the following steps: (1) Dissolve 4-tetra(4-carboxyphenyl)porphyrin and zirconium oxychloride in N,N-dimethylformamide to form solution A, and stir thoroughly; (2) Add difluoroacetic acid to solution A to form solution B; (3) Transfer solution B to a reaction vessel for solvothermal reaction. After natural cooling, centrifuge, wash and dry to obtain PCN-222 powder; (4) Graphene oxide is dispersed in water to form a suspension C; (5) Disperse PCN-222 powder in suspension C, and then add ascorbic acid to form a mixed suspension D; (6) The mixed suspension D is placed in a water bath and kept at a constant temperature for a certain time to obtain MOF / rGO composite hydrogel, wherein the water bath temperature is 80-100 ℃ and the reaction time is 10-30 min; (7) The MOF / rGO composite hydrogel is washed and then freeze-dried, followed by low-temperature annealing at a temperature of 200-300℃ to obtain MOF / rGO composite aerogel, which is used as a glyoxylic acid decolorizing material.

2. The preparation method of the MOF / rGO composite aerogel according to claim 1, characterized in that: In step (1), the concentration of methyl-tetra(4-carboxyphenyl)porphyrin in solution A is 0.5-2 mol / L, the concentration of zirconium oxychloride is 5-10 mol / L, and the volume of N,N-dimethylformamide is 10-50 mL.

3. The method for preparing a MOF / rGO composite aerogel according to claim 2, characterized in that: In step (2), the volume of difluoroacetic acid is 0.2-1 mL.

4. The method for preparing a MOF / rGO composite aerogel according to claim 1, characterized in that: In step (3), the temperature of the solvothermal reaction is 100-160℃, the reaction time is 24-36 h, the cleaning is performed by alternating washing with N,N-dimethylformamide and ethanol 2-4 times, and the drying temperature is 75-85℃.

5. The method for preparing a MOF / rGO composite aerogel according to claim 1, characterized in that: In step (4), the concentration of suspension C is 4-10 mg / mL.

6. The method for preparing a MOF / rGO composite aerogel according to claim 1, characterized in that: In step (5), the mass of PCN-222 powder is 12-20 mg, the volume of suspension C is 3-5 mL, and the mass of ascorbic acid is 10-20 mg.

7. The method for preparing a MOF / rGO composite aerogel according to claim 1, characterized in that: In step (7), the mixture of ethanol and water with a volume ratio of 1:3 is used to wash 3-5 times, the freeze-drying time is 48-72 h, and the freezing temperature is -40℃ to -120℃.

8. A MOF / rGO composite aerogel prepared by the method according to any one of claims 1-7.

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