Method for preparing Zr-MOF film with assistance of vapor phase

Abstract

The invention belongs to the technical field of metal organic framework membranes, and discloses a method for preparing a Zr-MOF membrane with the assistance of a vapor phase. The preparation method comprises the following steps: dissolving a metal salt and an organic ligand in a solvent containing a regulator to form a precursor solution, loading the precursor solution on the surface of a porous carrier through a pulling method, and inducing Zr-MOF crystals to rapidly and epitaxially grow at 90-150 DEG C for 2-6 hours by using a vapor phase, thereby obtaining the compact and continuous Zr-MOF film. The preparation method obviously reduces the use amount of the organic solvent, is short in reaction time, and has the characteristics of environmental protection, low cost and simple preparation. The obtained Zr-MOF membrane shows excellent interception performance in dye wastewater treatment.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal organic framework membranes and relates to a method for preparing Zr-MOF membranes with vapor phase assistance, which is particularly suitable for the green and efficient synthesis of molecular sieve membranes. Background Art

[0002] Membrane separation technology, due to its advantages such as high efficiency, low energy consumption, and ease of operation, has been widely used in the chemical, environmental, and energy sectors. However, conventional polymer and ceramic membranes are limited in their efficient use due to their swellability and small, irregular pores. Therefore, the development of new membrane materials that combine high separation accuracy, excellent stability, and low cost has become an urgent need in the industry.

[0003] Metal-organic framework (MOF) materials are self-assembled from metal nodes and organic ligands. They have ultra-high specific surface area, adjustable pore size, and rich surface functional groups. They can achieve precise separation at the molecular level through size screening, electrostatic interaction, and chemical adsorption, making them ideal membrane separation materials. In recent years, MOF membranes have shown great application potential in carbon dioxide capture, hydrocarbon separation, desalination, and dye wastewater treatment. Among them, zirconium-based metal-organic frameworks (Zr-MOF) have excellent chemical, thermal, and mechanical stability and are not easily destroyed by environmental factors such as acid, alkali, or high temperature. However, the existing Zr-MOF membrane preparation mainly relies on solvothermal methods, which have problems such as high solvent consumption, long reaction cycle, and high membrane thickness. Therefore, there is an urgent need to develop a green and efficient method for synthesizing Zr-MOF ultrathin films. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology, the present invention provides a method for vapor-phase assisted preparation of Zr-MOF membranes. This preparation method uses a small amount of organic solvent, has low cost and low pollution, meets the requirements of green chemistry, and has a fast reaction and high production efficiency, making it suitable for industrial continuous production.

[0005] The above-mentioned object of the present invention is achieved through the following technical solutions:

[0006] A method for vapor-assisted preparation of a Zr-MOF membrane comprises the following steps:

[0007] S1. Pre-modification: Pre-modify the surface of the porous carrier;

[0008] S2. Preparing a precursor solution; dissolving a metal zirconium salt and an organic ligand in a mixed solution of a modifier and a solvent to obtain a precursor solution;

[0009] S3. Pulling; forming a uniform liquid film on the support pre-modified in step S1 by pulling the precursor solution;

[0010] S4 film formation; the carrier after step S3 is pulled into the reactor containing the bottom liquid heated steam-assisted film growth;

[0011] S5. After drying, a Zr-MOF film is obtained.

[0012] Furthermore, in step S1, the porous carrier is any one or more of porous metal oxides, porous non-metallic oxides, porous metals, carbides and porous polymers; the structure of the porous carrier includes a flat plate structure, a tubular structure, a hollow fiber structure or a rolled structure.

[0013] Furthermore, in step S1, the porous support is pre-modified with a seed layer, zirconium oxide, and PVP. The pre-modification conditions are: a dispersion concentration of 0.05-0.5 wt%, a loading number of 1-3 times, and coating methods including dip coating, spin coating, and wipe coating.

[0014] Furthermore, in step S2, the metal zirconium salt is any one or more of zirconium tetrachloride, zirconium n-propoxide, zirconium disulfide, zirconium oxychloride, zirconium acetate, zirconium nitrate and organic zirconium salts; and the organic ligand is any one of terephthalic acid, 2-aminoterephthalic acid or fumaric acid.

[0015] Furthermore, in step S2, the molar ratio of the metal zirconium salt to the organic ligand is 4:1-1:3.

[0016] Furthermore, in step S2, the regulator is one of acetic acid, formic acid, and benzoic acid.

[0017] Furthermore, in step S2, the solvent is N,N-dimethylformamide.

[0018] Furthermore, in step S2, the molar ratio of the solvent to the regulator is 2:1-1:2.

[0019] Furthermore, in step S2, the metal zirconium salt and the organic ligand are dissolved by ultrasound or stirring.

[0020] Furthermore, in step S3, the pulling time is 10s-30s, and the pulling is repeated 1-3 times.

[0021] Furthermore, in step S4, the bottom liquid of the kettle includes a solvent and a regulator. The molar ratio of the solvent to the regulator is 5:1-2:1. The regulator is one of acetic acid, formic acid, and benzoic acid. The solvent is N,N-dimethylformamide.

[0022] Furthermore, in step S4, the reaction temperature is 90-150° C. and the reaction time is 2-12 h. Furthermore, the reaction time is preferably 2-6 h.

[0023] Furthermore, in step S5, the drying condition is vacuum drying, the drying temperature is 20-50° C., and the drying time is 24 hours.

[0024] The present invention also seeks to protect the application of the Zr-MOF membrane prepared by the above method in dye wastewater treatment.

[0025] The beneficial effects of the present invention compared with the prior art are:

[0026] The present invention provides a method for preparing a Zr-MOF film with steam assistance. The reaction time of the traditional solvent thermal method for preparing the Zr-MOF film is usually 12-72 hours, while the method provided by the present invention only takes 2-6 hours, which significantly shortens the reaction time and significantly improves production efficiency. At the same time, the film forming process of the present invention is limited to the surface of the carrier, reducing the homogeneous nucleation rate and improving the utilization rate of the precursor solution. Compared with the traditional solvent thermal method for preparing the Zr-MOF film, the total amount of solvent used is reduced by more than 80%, with low cost and low pollution, and the preparation process is simple, easy to control, and can be formed into a large area. In addition, the preparation process has good universality and scalability. It is not only suitable for the preparation of UiO-66 films, but also can achieve precise and controllable preparation for various Zr-MOF films such as UiO-66-NH2 and MOF-801. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a scanning electron microscope (SEM) image of the UiO-66 seed layer prepared in Example 1; Figure a is a surface image, and Figure b is a cross-sectional image;

[0028] Figure 2 The scanning electron microscope (SEM) image of the UiO-66 film prepared in Example 1; Figure a is a surface image and Figure b is a cross-sectional image;

[0029] Figure 3 X-ray diffraction (XRD) pattern of the UiO-66 film prepared in Example 1;

[0030] Figure 4 This is a scanning electron microscope (SEM) image of the MOF-801 membrane prepared in Example 3; Figure a is a surface image, and Figure b is a cross-sectional image;

[0031] Figure 5 X-ray diffraction (XRD) pattern of the MOF-801 film prepared in Example 3;

[0032] Figure 6 This is a scanning electron microscope (SEM) image of the UiO-66-NH2 film prepared in Example 4; Figure a is a surface image and Figure b is a cross-sectional image;

[0033] Figure 7X-ray diffraction (XRD) pattern of the UiO-66-NH2 film prepared in Example 4;

[0034] Figure 8 The scanning electron microscope (SEM) image of the UiO-66 film prepared in Comparative Example 1 is shown in FIG. 1 , wherein FIG. a is a surface view and FIG. b is a cross-sectional view.

[0035] Figure 9 This is a scanning electron microscope (SEM) image of the UiO-66 film prepared in Comparative Example 2, wherein Figure a is a surface image and Figure b is a cross-sectional image. DETAILED DESCRIPTION

[0036] The present invention is described in detail below by specific examples, but the scope of protection of the present invention is not limited. Unless otherwise specified, the experimental methods adopted in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels.

[0037] The present invention dissolves a metal salt and an organic ligand in a solvent containing a modifier to form a precursor solution. This precursor solution is then loaded onto the surface of a porous support via a Czochralski method. Subsequently, vapor-phase induced Zr-MOF crystals undergo rapid epitaxial growth at 90-150°C for 2-6 hours to produce a dense, continuous Zr-MOF membrane. This preparation method significantly reduces the amount of organic solvent used, shortens the reaction time, and is environmentally friendly, low-cost, and simple to prepare. The resulting Zr-MOF membrane exhibits excellent retention properties in dye wastewater treatment, making it suitable for industrial production.

[0038] Example 1

[0039] Preparation of UiO-66 membrane by vapor-assisted method

[0040] (1) 0.1 g zirconium chloride and 0.3 g terephthalic acid were dissolved in a mixed solution of 60 mL N,N-dimethylformamide and 1.0 mL acetic acid, and reacted at 120 ° C for 24 h to obtain UiO-66 seed crystals, which were prepared into a 0.1 wt% seed solution and pulled onto a porous alumina support;

[0041] (2) 0.32 g zirconium n-propoxide and 0.06 g terephthalic acid were dissolved in a mixed solution of 10 mL acetic acid and 20 mL DMF, and ultrasonicated for 30 minutes to prepare a precursor solution;

[0042] (3) Dipping the alumina support after seed deposition in the precursor solution for 10-30 seconds;

[0043] (4) Add 5 mL of DMF / acetic acid (volume ratio 5:1) solution to the bottom of the reactor;

[0044] (5) Suspend the liquid membrane-loaded carrier in a kettle, seal it, and react at 120°C for 3 hours;

[0045] (6) The support was removed and dried at room temperature overnight to obtain a UiO-66 membrane.

[0046] SEM images of the UiO-66 seed layer are shown in Figure 1 As shown, the seed layer is uniform and flat, and the UiO-66 film is as shown in FIG. Figure 2 As shown, the surface is continuous and dense, the film thickness is 1 μm, and the corresponding XRD pattern ( Figure 3 ) diffraction peaks indicate that the prepared film is pure phase UiO-66.

[0047] Example 2

[0048] Preparation of UiO-66 membrane by vapor-assisted method

[0049] (1) A seed layer is introduced onto the alumina ceramic tube by means of pulling and impregnation. The seed layer preparation process is the same as step (1) of Example 1.

[0050] (2) 0.22 g ZrOCl2·8H2O and 0.06 g terephthalic acid were dissolved in a mixed solution of 10 mL acetic acid and 20 mL DMF and ultrasonicated for 30 min to prepare a precursor solution;

[0051] (3) Pull and immerse the alumina ceramic tube after seed deposition in the precursor solution for 30 seconds;

[0052] (4) Add 5 mL of DMF / acetic acid (volume ratio 5:1) solution to the bottom of the reactor;

[0053] (5) Suspend the liquid membrane-loaded carrier in a kettle, seal it, and react at 120°C for 3 hours;

[0054] (6) The support was removed and dried at room temperature overnight to obtain a UiO-66 membrane.

[0055] Example 3

[0056] Preparation of MOF-801 membrane by vapor-assisted method

[0057] (1) 0.21 g ZrOCl2·8H2O and 0.4 g fumaric acid were dissolved in a mixed solution of 40 mL N,N-dimethylformamide and 5 mL formic acid, and reacted at 120°C for 24 h to obtain MOF-801 seeds, which were then prepared into a 0.1 wt% seed solution and pulled onto a porous alumina support;

[0058] (2) 0.32 g zirconium n-propoxide and 0.13 g fumaric acid were dissolved in a mixed solution of 10 mL formic acid and 20 mL DMF, and ultrasonicated for 30 minutes to prepare a precursor solution;

[0059] (3) Pull and immerse the alumina ceramic tube after seed deposition in the precursor solution for 30 seconds;

[0060] (4) Add 5 mL of DMF / formic acid (volume ratio 5:1) solution to the bottom of the reactor;

[0061] (5) Suspend the liquid membrane-loaded carrier in a kettle, seal it, and react at 120°C for 3 hours;

[0062] (6) The support was removed and dried at room temperature overnight to obtain a MOF-801 membrane.

[0063] SEM images of MOF-801 membrane Figure 4 As shown, the surface is continuous and dense, and the corresponding XRD pattern ( Figure 5 ) diffraction peaks indicate that the prepared MOF-801 membrane is a pure phase.

[0064] Example 4

[0065] Preparation of UiO-66-NH2 membrane by vapor-assisted method

[0066] (1) A layer of zirconia gel was pulled onto an alumina ceramic tube. 8 g of ZrOCl2·8H2O was dissolved in 40 mL of ethanol and stirred at room temperature for 24 h to obtain a uniform zirconia gel. The gel was then calcined in a muffle furnace at 400°C for 4 h to obtain a highly stable and active zirconia modified layer.

[0067] (2) 0.32 g zirconium n-propoxide and 0.06 g 2-aminoterephthalic acid were dissolved in a mixed solution of 10 mL acetic acid and 20 mL DMF, and ultrasonicated for 30 minutes to prepare a precursor solution;

[0068] (3) Pull and immerse the alumina ceramic tube after seed deposition in the precursor solution for 30 seconds;

[0069] (4) Add 5 mL of DMF / acetic acid (volume ratio 5:1) solution to the bottom of the reactor;

[0070] (5) Suspend the liquid membrane-loaded carrier in a kettle, seal it, and react at 120°C for 3 hours;

[0071] (6) The support was removed and dried at room temperature overnight to obtain a UiO-66-NH2 membrane.

[0072] SEM image of UiO-66-NH2 membrane Figure 6 As shown, the surface is continuous and dense, and the corresponding XRD pattern ( Figure 7 ) diffraction peaks indicate that the prepared film is a pure phase UiO-66-NH2 film.

[0073] Example 5

[0074] Separation performance of Zr-MOF membrane

[0075] The dye separation performance of the Zr-MOF membrane prepared in the embodiment of the present invention was tested, and the Congo red retention performance is shown in Table 1 below. The results show that the Zr-MOF membrane prepared by vapor phase assistance has excellent dye separation performance.

[0076] Table 1 Congo red rejection performance of Zr-MOF membrane

[0077]

[0078]

[0079] Comparative Example 1

[0080] Vapor-assisted preparation of UiO-66 membranes without modification layer

[0081] (1) 0.32 g zirconium n-propoxide and 0.06 g terephthalic acid were dissolved in a mixed solution of 10 mL acetic acid and 20 mL DMF, and ultrasonicated for 30 minutes to prepare a precursor solution;

[0082] (2) Dipping the alumina support after seed deposition in the precursor solution for 10-30 seconds;

[0083] (3) Add 5 mL of DMF / acetic acid (volume ratio 5:1) solution to the bottom of the reactor;

[0084] (4) Suspend the liquid membrane-loaded carrier in a kettle, seal it, and react at 120°C for 3 hours;

[0085] (5) The support was removed and dried at room temperature overnight to obtain a UiO-66 membrane.

[0086] Figure 8 This is an SEM image of a vapor-assisted film prepared without any support modification. It can be observed that only scattered grains are present on the support surface, with no crosslinking occurring. Therefore, compared to the results of Example 1, pre-modification of the support is necessary to increase the density of heterogeneous nucleation on the support surface and ensure the formation of a continuous, dense film under vapor-assisted preparation conditions.

[0087] Comparative Example 2

[0088] Vapor-phase assisted preparation of UiO-66 membranes with PVP pre-modified supports

[0089] (1) Introducing a PVP modification layer on the surface of an alumina ceramic tube. Dissolve 0.24 g of PVP in 40 mL of ethanol solution, pull the PVP onto the surface of the alumina ceramic tube, and dry it at 100°C for 5 h.

[0090] (2) 0.32 g zirconium n-propoxide and 0.06 g terephthalic acid were dissolved in a mixed solution of 10 mL acetic acid and 20 mL DMF, and ultrasonicated for 30 minutes to prepare a precursor solution;

[0091] (3) Dipping the alumina support after seed deposition in the precursor solution for 10-30 seconds;

[0092] (4) Add 5 mL of DMF / acetic acid (volume ratio 5:1) solution to the bottom of the reactor;

[0093] (5) Suspend the liquid membrane-loaded carrier in a kettle, seal it, and react at 120°C for 3 hours;

[0094] (6) The support was removed and dried at room temperature overnight to obtain a UiO-66 membrane.

[0095] Figure 9 This is an SEM image of a film layer prepared by steam-assisted preparation after pre-modification of the carrier with PVP. It can be observed that only a few uneven grains are scattered on the carrier surface, but no film layer has formed. Therefore, compared with the results of Example 1, pre-modification of the carrier with a seed layer is the only way to ensure the formation of a continuous, dense film layer under steam-assisted preparation conditions.

[0096] Comparative Example 3

[0097] The specific implementation steps are the same as those in Example 1, except that no regulating agent acetic acid is used in the preparation of the precursor solution in step (2).

[0098] The results showed that there were obvious cracks in the membrane layer, no dense membrane layer was formed, and no separation performance.

[0099] Comparative Example 4

[0100] The specific implementation steps are the same as those in Example 1, except that only steps (1)(2)(3)(5)(6) are performed without the use of a bottom solution, and the UiO-66 membrane is directly prepared. The results show that the membrane layer has obvious defects and the cross-linking between the grains on the carrier surface is poor.

[0101] The above-described embodiments are only preferred embodiments of the present invention, and are not intended to be all feasible embodiments of the present invention. Any obvious modifications made by a person skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a Zr-MOF membrane by vapor phase assistance, characterized in that: The following steps are involved: S1. Pre-modification: Pre-modify the surface of the porous support; S2. Preparing a precursor solution; dissolving a metal zirconium salt and an organic ligand in a mixed solution of a modifier and a solvent to obtain a precursor solution; S3. Pulling; forming a uniform liquid film on the support pre-modified in step S1 by pulling the precursor solution; S4 film formation; the carrier after step S3 is pulled into the reactor containing the bottom liquid heated steam-assisted film growth; S5. After drying, a Zr-MOF film is obtained.

2. The method for preparing a Zr-MOF film by vapor phase assistance according to claim 1, wherein: In step S1, the porous carrier is any one or more of porous metal oxide, porous non-metal oxide, porous metal, carbide and porous polymer; the structure of the porous carrier includes a flat plate structure, a tubular structure, a hollow fiber structure or a coiled structure.

3. The method for preparing a Zr-MOF film by vapor phase assistance according to claim 1, wherein: In step S1, the porous support is pre-modified with a seed layer, zirconium oxide, and PVP; The pre-modification conditions are: dispersion concentration of 0.05-0.5 wt %, loading times of 1-3 times; The coating methods include: dip coating, spin coating, and wiping coating.

4. The method for preparing a Zr-MOF film by vapor phase assistance according to claim 1, wherein: In step S2, the metal zirconium salt is any one or more of zirconium tetrachloride, zirconium n-propoxide, zirconium disulfide, zirconium oxychloride, zirconium acetate, zirconium nitrate and organic zirconium salts; the organic ligand is any one of terephthalic acid, 2-aminoterephthalic acid or fumaric acid.

5. The method for preparing a Zr-MOF film by vapor phase assistance according to claim 1, characterized in that: In step S2, the molar ratio of the metal zirconium salt to the organic ligand is 4:1-1:

3.

6. The method for preparing a Zr-MOF film by vapor phase assistance according to claim 1, wherein: In step S2, the molar ratio of the solvent to the regulator is 2:1-1:

2.

7. The method for preparing a Zr-MOF film by vapor phase assistance according to claim 1, wherein: In step S3, the pulling time is 10s-30s, and the pulling is repeated 1-3 times.

8. The method for preparing a Zr-MOF film by vapor phase assistance according to claim 1, wherein: In step S4, the reaction temperature is 90-150° C. and the reaction time is 2-6 hours.

9. The method for preparing a Zr-MOF film by vapor phase assistance according to claim 1, wherein: In step S5, the drying condition is vacuum drying, the drying temperature is 20-50° C., and the drying time is 24 h.

10. Use of the Zr-MOF membrane prepared by the method according to any one of claims 1 to 9 in dye wastewater treatment.

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