Hierarchical porous material, method for preparing the same and use thereof
By preparing hierarchical porous materials of micropores and mesopores under hydrolysis conditions, the problems of insufficient adsorption and thermal stability of MOFs in macromolecules are solved, realizing the efficient and environmentally friendly preparation of materials and excellent adsorption performance, which are suitable for industrial production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-05-31
- Publication Date
- 2026-03-31
AI Technical Summary
Existing metal-organic frameworks (MOFs) have shortcomings in terms of macromolecular adsorption and thermal stability, and traditional preparation methods use strong acids and bases, which limits their applications.
Metal-organic framework precursors were prepared by hydrolysis of ytterbium salt and pyromellitic acid. The resulting microporous and mesoporous hierarchical porous material was formed by etching with an aqueous solution at pH 7, thus avoiding the use of strong acids and bases and maintaining the thermal stability and adsorption performance of the material.
The prepared hierarchical porous material has good thermal stability and macromolecular adsorption. The preparation method is green, mild, and low in cost, making it suitable for industrial production.
Smart Images
Figure CN116693925B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of porous materials technology, and specifically relates to a hierarchical porous material, its preparation method, and its application. Background Technology
[0002] Metal-organic frameworks (MOFs) are a class of novel porous crystalline materials that self-assemble from metal ions / clusters and organic ligands. Due to their periodicity, well-defined structure, high specific surface area, structural diversity, and functionalizability, they show potential applications in many fields, such as gas adsorption / separation, catalysis, and sensing. However, most MOFs exhibit microporous characteristics (less than 2 nm), which hinders the adsorption of macromolecules, thus greatly limiting their application in certain situations. Therefore, hierarchical porous MOFs (HP-MOFs), which incorporate both micropores and mesopores, have attracted increasing attention. Micropores can provide high specific surface area, while mesopores can provide the adsorption required for rapid diffusion of macromolecules; the structural characteristics of hierarchical porous materials broaden their applications.
[0003] In recent years, two main methods have been employed to construct HP-MOFs. One method involves extending the length of the organic ligands. While this strategy produces MOFs with periodic nanostructures, most HP-MOFs exhibit pore sizes <5 nm. Furthermore, longer connectors typically lead to reduced thermal stability. The second method involves introducing crystalline "defects" into microporous MOFs. Chemical etching and template methods are commonly used to construct defect-containing HP-MOFs, but these methods often employ strong acids and bases during etching, limiting their further application. Developing green and mild methods to construct HP-MOFs with high stability and high adsorption capacity is of great significance for the practical application of porous crystalline materials.
[0004] Therefore, there is an urgent need to provide a hierarchical porous material that has good thermal stability and adsorption properties, and whose preparation method is simple, green, mild, and has a high yield. Summary of the Invention
[0005] This invention aims to solve one or more technical problems existing in the prior art, and at least provide a beneficial alternative or create conditions. This invention provides a hierarchical porous material with good thermal stability and adsorption properties, and its preparation method is simple, environmentally friendly, mild, and yields high costs.
[0006] The inventive concept of this invention: The XRD patterns of the hierarchical porous material of this invention show diffraction peaks at 2θ of 4.1, 5.8, 7.3, 8.2, and 12.4 ± 0.2°. This crystal structure gives the material specific structural characteristics. The hierarchical porous material includes micropores and mesopores, and the pore sizes of the micropores and mesopores have specific dimensions. The micropores provide a large specific surface area, while the mesopores provide the adsorption required for the rapid diffusion of macromolecules. The combination of the different specific sizes of the micropores and mesopores gives the hierarchical porous material good thermal stability and adsorption performance.
[0007] Therefore, a first aspect of the present invention provides a hierarchical porous material.
[0008] Specifically, a hierarchical porous material has XRD patterns with diffraction peaks at 2θ of 4.1, 5.8, 7.3, 8.2, and 12.4 ± 0.2°.
[0009] Preferably, the XRD pattern also has diffraction peaks at 2θ of 11.8, 13.3, 16.5, 17.12, 17.7, 18.9, 24.96, 26.0, 31.58, and 33.46 ± 0.2°.
[0010] Preferably, the hierarchical porous material includes micropores and mesopores; the pore size of the micropores is greater than or equal to 0.35 nm and less than 2.0 nm; the pore size of the mesopores is 2-12 nm.
[0011] Preferably, the specific surface area of the hierarchical porous material is 330-440 m². 2 / g.
[0012] More preferably, the specific surface area of the hierarchical porous material is 300-400 m². 2 / g.
[0013] Preferably, the pore volume of the hierarchical porous material is 0.25-0.45 cm³. 3 / g.
[0014] More preferably, the pore volume of the hierarchical porous material is 0.3-0.4 cm³. 3 / g.
[0015] Preferably, the nitrogen adsorption capacity of the hierarchical porous material is 180-330 cm³. 3 / g.
[0016] More preferably, the nitrogen adsorption capacity of the hierarchical porous material is 200-300 cm³. 3 / g.
[0017] A second aspect of the present invention provides a method for preparing the hierarchical porous material described in the first aspect of the present invention.
[0018] Specifically, the method for preparing the hierarchical porous material includes the following steps:
[0019] (1) Ytterbium salt, pyromellitic acid (H3TTCA), N,N-dimethylacetamide (DMA) and acid solution were mixed and reacted to prepare metal-organic framework precursors (MOFs);
[0020] (2) The metal-organic framework precursor obtained in step (1) is placed in an etching solution and left to stand to obtain the hierarchical porous material (HP-MOFs).
[0021] Preferably, in step (1), the molar ratio of the ytterbium salt to the pyromellitic acid is (0.8-2.2):1.
[0022] More preferably, in step (1), the molar ratio of the ytterbium salt to the pyromellitic acid is (1-2):1.
[0023] Preferably, the ytterbium salt is Yb(NO3)3·5H2O.
[0024] Preferably, in step (1), the acid solution is selected from either hydrochloric acid or nitric acid.
[0025] Preferably, in step (1), the reaction temperature is 90-160℃ and the reaction time is 33-75h.
[0026] More preferably, in step (1), the reaction temperature is 100-150℃ and the reaction time is 36-72h.
[0027] Specifically, in step (1), the obtained metal-organic framework precursor is a bulk crystal with micropores, and its chemical formula is: (Me2NH2)3{[Yb4(NO3)]3(TTCA)8(H2O) 12 ]·23DMA}. Among them, Yb(II) ions are separated by TTCA 3- The four O atoms, one O atom in water, and one disordered NO3. - Yb4(TTCA4-NO3) is formed, along with 8 TTCA molecules. 3- It forms sodalite cages with 6 Yb4(TTCA4-NO3).
[0028] Preferably, the pore size of the micropores in the metal-organic framework precursor is greater than or equal to 0.35 nm and less than 2.0 nm.
[0029] Preferably, in step (2), the etching solution is an aqueous solution with pH=7.
[0030] Preferably, in step (2), the ratio of the amount of the metal-organic framework precursor to the amount of the etching solution added is 0.02-1.25g: 35-110mL.
[0031] More preferably, in step (2), the ratio of the amount of the metal-organic framework precursor to the amount of the etching solution added is 0.03-1.15g: 40-100mL.
[0032] Preferably, in step (2), the settling time is 11-26 hours.
[0033] More preferably, the settling time is 12-24 hours.
[0034] Preferably, in step (2), the settling process further includes filtration and drying; the filtered solid is then dried.
[0035] Preferably, the drying is carried out by air drying.
[0036] Specifically, the drying method includes, but is not limited to, air drying, as long as it can dry the prepared hierarchical porous material.
[0037] A third aspect of the present invention provides an application of the hierarchical porous material described in the first aspect of the present invention in the fields of dye adsorption, catalysis, and sensing.
[0038] Compared with the prior art, the beneficial effects of the technical solution provided by the present invention are as follows:
[0039] (1) The hierarchical porous material of the present invention includes micropores and mesopores, and the pore sizes of micropores and mesopores have specific dimensions. Micropores provide a large specific surface area, and mesopores provide the adsorption required for the rapid diffusion of macromolecules. The combination of different specific sizes of micropores and mesopores makes the hierarchical porous material have a large specific surface area and pore volume, thereby making the hierarchical porous material have good thermal stability and adsorption performance.
[0040] (2) This invention uses blocky MOFs with micropores as precursors. Since metal ions are easy to combine with water molecules, the partial coordination bonds between the metal and the organic ligands are broken through substitution or hydrolysis, and finally a hierarchical porous material with micropores and mesopores is formed. In addition, this invention does not use strong acids or strong bases for etching when preparing hierarchical porous materials, but uses an aqueous solution with pH=7 for etching, making the preparation process green and mild. The preparation process is simple, easy to operate, low in cost, and high in yield, which facilitates large-scale industrial production. Attached Figure Description
[0041] Figure 1 This is a schematic diagram of the preparation process of the hierarchical porous material of the present invention;
[0042] Figure 2 The adsorption-desorption curves of MOFs and HP-MOFs prepared in Example 1 of this invention are shown.
[0043] Figure 3 The images show the morphological changes of MOFs and HP-MOFs prepared in Example 1 of this invention.
[0044] Figure 4 X-ray powder diffraction patterns of MOFs and HP-MOFs prepared in Example 1 of this invention;
[0045] Figure 5 Thermogravimetric analysis curves of MOFs and HP-MOFs prepared in Example 1 of this invention;
[0046] Figure 6 Color change diagram of MOFs and HP-MOFs prepared in Example 1 of this invention before and after adsorption of macromolecular dyes;
[0047] Figure 7 The graph shows the changes in dye concentration before and after the adsorption of macromolecular dyes by the MOFs and HP-MOFs prepared in Example 1 of this invention. Detailed Implementation
[0048] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.
[0049] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.
[0050] A schematic diagram of the preparation process of the hierarchical porous material of the present invention is shown below. Figure 1 As shown, under the action of aqueous solution, MOF precursors are hydrolyzed to obtain HP-MOFs.
[0051] Example 1
[0052] A method for preparing a hierarchical porous material includes the following steps:
[0053] (1) Mix 0.045g Yb(NO3)3·5H2O, 0.018g H3TTCA, 8.0mL DMA and 12μL hydrochloric acid, place in a reaction vessel, react at 100℃ for 36h, filter, and obtain yellow blocky MOFs((Me2NH2)3{[Yb4(NO3)]3(TTCA)8(H2O)) 12 ]·23DMA});
[0054] (2) Take 0.03g of the MOFs obtained in step (1) and place it in a stoppered glass bottle containing 40mL of aqueous solution with pH=7. Let it stand for 12h, filter, take the solid and air dry to prepare fractional porous materials (HP-MOFs) with a yield of 60%.
[0055] Example 2
[0056] A method for preparing a hierarchical porous material includes the following steps:
[0057] (1) Mix 0.0225g Yb(NO3)3·5H2O, 0.018g H3TTCA, 10.0mL DMA and 16μL hydrochloric acid, place them in a reaction vessel, and react at 150℃ for 72h to obtain yellow blocky MOFs((Me2NH2)3{[Yb4(NO3)]3(TTCA)8(H2O) 12 ]·23DMA});
[0058] (2) Take 1.15g of MOFs obtained in step (1) and place it in a stoppered glass bottle containing 100mL of aqueous solution with pH=7. Let it stand for 24h, filter, take the solid and air dry to prepare fractional porous materials (HP-MOFs).
[0059] Performance testing:
[0060] 1. Nitrogen adsorption-desorption test
[0061] The MOFs and HP-MOFs obtained in Example 1 were subjected to nitrogen adsorption-desorption tests. The nitrogen adsorption-desorption curves of Example 1 are shown below. Figure 2 As shown. Among them. Figure 2 (a) is a graph of nitrogen adsorption-desorption. Figure 2 In (a), the horizontal axis represents the relative pressure and the vertical axis represents the amount of nitrogen adsorbed. Figure 2 (b) is a diagram showing the aperture distribution, with the horizontal axis representing aperture and the vertical axis representing aperture volume; Figure 2 (c) is the aperture distribution diagram. Figure 2 In (c), the horizontal axis represents the aperture and the vertical axis represents the aperture volume.
[0062] Depend on Figure 2 (b)(c) It can be seen that the hierarchical porous material prepared in Example 1 contains micropores and mesopores.
[0063] The micropore and mesopore diameters of the hierarchical porous material in Example 1 are 0.67-1.7 nm and 2-10 nm, respectively, and the specific surface area is 350 m². 2 / g, pore volume 0.3cm 3 / g, nitrogen adsorption capacity is 210cm³ 3 / g.
[0064] Similarly, nitrogen adsorption-desorption tests were performed on the MOFs and HP-MOFs obtained in Example 2. The hierarchical porous material of Example 2 also contains micropores and mesopores, wherein the pore sizes of the micropores and mesopores are 0.73-1.2 nm and 2-12 nm, respectively, and the specific surface area is 356 m². 2 / g, pore volume 0.35m 3 / g, nitrogen adsorption capacity is 220cm³ 3 / g.
[0065] 2. Observation of crystal morphology before and after etching
[0066] The crystal morphology of the MOFs obtained in step (1) and the HP-MOFs obtained in step (2) of Example 1 was observed. The crystal morphology images before and after etching are shown below. Figure 3 As shown. Among them, Figure 3 (a) shows the morphology of the precursor MOF crystal. Figure 3 (b) shows the morphological features of HP-MOFs. Figure 3 It can be seen that the crystal morphology did not change significantly before and after etching with aqueous solution; both remained as blocky, yellow crystals.
[0067] 3. X-ray powder diffraction
[0068] X-ray powder diffraction analysis was performed on the MOFs and HP-MOFs prepared in Example 1, and the X-ray powder diffraction patterns are shown below. Figure 4 As shown. The horizontal axis 2Theta represents the diffraction angle 2θ, deg represents the unit (°), and the vertical axis intensity represents the diffraction intensity, with au representing any unit. From Figure 4 It can be seen that the powder diffraction patterns of HP-MOFs are basically consistent with those of MOFs, indicating that the crystal structure of HP-MOFs is similar to that of MOFs.
[0069] 4. Thermogravimetric analysis
[0070] Thermogravimetric analysis was performed on the MOFs and HP-MOFs prepared in Example 1, and the thermogravimetric test results are as follows: Figure 5 As shown in the figure. The horizontal axis, Temperature, represents temperature in °C, and the vertical axis, Weight (%), represents weight percentage (%). Figure 5 It can be seen that the decomposition temperature of MOFs and HP-MOFs remained basically unchanged before and after etching with an aqueous solution at pH 7, still remaining at 500℃, indicating that the HP-MOFs prepared in this invention have good thermal stability.
[0071] 5. Adsorption test
[0072] (1) The MOFs and HP-MOFs prepared in Example 1 were subjected to adsorption tests, and the changes in appearance and color of MOFs and HP-MOFs before and after adsorption were observed.
[0073] The test method is as follows: Take two portions of MOFs prepared in Example 1, 30 mg each, and place them in DMF solutions containing the macromolecular organic dye Alczynblue (5 mL) and methyl green (5 mL), respectively; take two portions of HP-MOFs prepared in Example 1, 30 mg each, and place them in DMF solutions containing the macromolecular organic dye Alczynblue (5 mL) and methyl green (5 mL), respectively, to obtain the sample solutions required for the adsorption test; let the above sample solutions stand for 48 h, filter, take the solid, and obtain the appearance and color changes of the adsorbed MOFs and adsorbed HP-MOFs, as shown in the figure. Figure 6 As shown. Among them, Figure 6 (a) is an optical photograph of MOFs before adsorption. Figure 6 (b) is an optical photograph of the adsorption of alpha-1,4-cyanine by MOFs. Figure 6 (c) is an optical photograph of methyl green adsorbed by MOFs. Figure 6 (d) is an optical photograph of HP-MOFs before adsorption. Figure 6 (e) is an optical photograph of the adsorption of alcinolan by HP-MOFs. Figure 6 (f) is an optical photograph of HP-MOFs after adsorption of methyl green.
[0074] from Figure 6 As can be seen from (a)-(c), the color of the MOF crystals did not change significantly before and after adsorption, and the MOFs showed almost no adsorption of Alcian Blue and Methyl Green; from Figure 6 As can be seen from (d)-(f), HP-MOFs have a significant adsorption effect on Alcian Blue and Methyl Green, and the color of HP-MOFs changed significantly before and after adsorption.
[0075] (2) The dye concentration in the sample solution before and after adsorption of MOFs and HP-MOFs was detected by ultraviolet spectroscopy. The dye concentration change graph is shown in the figure below. Figure 7 As shown. Among them, Figure 7 (a) shows the UV-Vis spectrum of MOFs for Alcin Blue. Figure 7 (b) shows the UV-Vis spectrum of MOFs for methyl green. Figure 7 (c) shows the UV-Vis spectrum of HP-MOFs for Alcin Blue. Figure 7 (d) shows the UV-Vis spectrum of HP-MOFs for methyl green. Figure 7(e) Optical graphs showing the color change of Alcin Blue solution after 0 h and 48 h after the addition of HP-MOFs. Figure 7 (f) Optical graphs showing the color change of methyl green solution after 0 h and 48 h after the addition of HP-MOFs. Figure 7 In (a), (b), (c) and (d), the horizontal axis represents wavenumber and the vertical axis represents absorbance.
[0076] The testing procedure is as follows: Two MOFs, 30 mg each, were placed in 5 mL of DMF solution containing the macromolecular organic dye Alczynblue and 5 mL of DMF solution containing the macromolecular organic dye Methyl Green, respectively. The DMF solutions containing Alczynblue and Methyl Green with added MOFs were allowed to stand for 0 h and 24 h, respectively. The supernatant was then used to test the dye concentration using a UV spectrometer. After each test, the supernatant was poured back into the sample solution. The test results are as follows: Figure 7 As shown in (a) and 7(b). From Figure 7 As can be seen from (a) and 7(b), the dye concentration curves after standing for 0 h and 24 h are basically unchanged, indicating that MOFs hardly adsorb Alcian Blue and Methyl Green.
[0077] Two 30 mg portions of HP-MOFs were taken and placed in 5 mL of DMF solution containing the macromolecular organic dye Alczynblue and 5 mL of DMF solution containing the macromolecular organic dye methyl green, respectively, to obtain the test sample solutions. The above-mentioned DMF solutions containing Alczynblue with added HP-MOFs were allowed to stand for 0 h, 24 h, and 48 h, respectively. The dye concentration of the supernatant was measured using a UV spectrometer. After each test, the supernatant solution used for the test was poured back into the test sample solutions. The test results are as follows: Figure 7 As shown in (c). Figure 7 (c) It can be seen that the concentration of the organic dye Alczynblue in the test solution gradually decreases with the extension of the standing time, indicating that HP-MOFs have a good adsorption effect on the macromolecular organic dye Alczynblue. The optical diagrams of the color change of the DMF solution containing Alczynblue after adding HP-MOFs and standing for 0 h and 48 h are shown below. Figure 7 As shown in (e), by Figure 7 (e) It can be seen that the color of the solution gradually fades and becomes lighter after the addition of HP-MOFs. This is because HP-MOFs adsorb Alcian Blue, which reduces the concentration of Alcian Blue in the solution.
[0078] The DMF solution containing the macromolecular organic dye methyl green, with added HP-MOFs, was allowed to stand for 0 h, 2 h, 5 h, 8 h, 12 h, and 24 h, respectively. The supernatant was then used for dye concentration testing using a UV spectrometer. After each test, the supernatant was poured back into the sample solution. The test results are as follows: Figure 7 As shown in (d). Figure 7 (d) It can be seen that the concentration of the organic dye methyl green in the test solution gradually decreases with the extension of the standing time, and after 24 hours, the concentration of methyl green is almost undetectable. This indicates that HP-MOFs have a good adsorption effect on the macromolecular organic dye methyl green. The optical graphs showing the color changes of the DMF solution containing methyl green after adding HP-MOFs for 0 hours and 48 hours (after UV-Vis spectroscopy testing, the solution was allowed to stand for another 48 hours) are shown below. Figure 7 As shown in (e), by Figure 7 (e) It can be seen that the color of the solution gradually fades and becomes lighter after the addition of HP-MOFs. This is because HP-MOFs have a good adsorption effect on methyl green, which reduces the concentration of methyl green in the solution through adsorption.
[0079] In summary, compared with MOF precursors, HP-MOFs exhibit superior adsorption performance for organic macromolecular dyes.
[0080] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.
Claims
1. A method for producing a hierarchically porous material, characterized in that, The preparation method comprises the following steps: (1) mixing ytterbium salt, triphenylene tricarboxylic acid, N,N-dimethylacetamide and acid solution, and reacting to obtain a metal organic framework precursor; (2) placing the metal organic framework precursor obtained in step (1) in an etching solution, and standing to obtain the hierarchical porous material; In step (1), the micropores of the metal organic framework precursor have a pore size of greater than or equal to 0.35 nm and less than 2.0 nm; In step (2), the etching solution is an aqueous solution with pH=7; In step (2), the standing time is 12 h; The XRD pattern of the hierarchical porous material has diffraction peaks at 2θ of 4.1, 5.8, 7.3, 8.2 and 12.4±0.2°; The hierarchical porous material comprises micropores and mesopores; the micropores have a pore size of greater than or equal to 0.35 nm and less than 2.0 nm; and the mesopores have a pore size of 2-12 nm.
2. The production method according to claim 1, characterized by, The XRD pattern also has diffraction peaks at 2θ of 11.8, 13.3, 16.5, 17.12, 17.7, 18.9, 24.96, 26.0, 31.58 and 33.46±0.2°.
3. The preparation method according to claim 1, characterized in that, The specific surface area of the hierarchical porous material is 330-440 m 2 / g; the pore volume is 0.25-0.45 cm 3 / g; the nitrogen adsorption amount is 180-330 cm 3 / g.
4. The method of claim 1, wherein, In step (1), the molar ratio of the ytterbium salt to the triphenylene tricarboxylic acid is (0.8-2.2):
1.
5. The preparation method according to claim 1, characterized in that, In step (1), the reaction temperature is 90-160 ℃, and the reaction time is 33-75 h.
6. The method of claim 1, wherein, In step (1), the metal organic framework precursor has the chemical formula (Me2NH2)3{[Yb4(NO3)]3(TTCA)8(H2O) 12 ]·23DMA}.
7. The preparation method according to claim 1, characterized in that, In step (2), the etching solution is an aqueous solution with pH=7; and the ratio of the addition amount of the metal organic framework precursor to the etching solution is 0.02-1.25 g:35-110 mL.
8. Application of the hierarchical porous material prepared by the preparation method of any one of claims 1-7 in the fields of dye adsorption, catalysis and sensing.