A method for preparing MOF-808 film assisted by zirconium-oxygen cluster and application thereof

Abstract

The application discloses a method for preparing MOF-808 film with the assistance of zirconium oxygen clusters and application thereof. The specific steps comprise the following steps: firstly, zirconium oxygen cluster powder is prepared as a metal zirconium source; then, the zirconium oxygen cluster powder and trimesic acid are added into a reaction solution, and MOF-808 crystal seeds are obtained through reaction; finally, the MOF-808 film is prepared under different reaction conditions by using an epitaxial growth method. The prepared molecular sieve film has good mechanical, chemical and thermal stability. In the application, the zirconium oxygen cluster powder is used as the metal zirconium source, and the composition of the raw material solution is regulated, so that the reaction kinetics is significantly reduced, and the number of ligand defects in the MOF-808 skeleton structure is precisely regulated. The film material exhibits excellent interception and selective separation performance in dye desalination and seawater uranium extraction and the like, thereby providing a guidance scheme for efficient separation of solution phase guest molecules.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of membrane separation technology, and particularly relates to a method for preparing MOF-808 membrane assisted by zirconium oxygen clusters and application thereof. TECHNICAL BACKGROUND

[0002] As a clean energy, nuclear energy is gradually replacing the traditional energy structure. Compared with land, the content of uranium (usually in the form of UO2 2+ ) in seawater is extremely rich (about 4.5×10 9 tons), which is more than 1000 times of that of land uranium mine [3-5]. So far, scientists have developed various seawater uranium extraction technologies such as chemical precipitation method, biological treatment method, superconducting magnetic separation method, solvent extraction method, ion exchange method and adsorption method. However, due to the low content of uranium in seawater (~3.3mg / t) and the high concentration of interfering ions such as Na + , K + , Ca 2+ , Mg 2+ , Fe 3+ , the above technologies generally have problems such as complicated operation process, serious secondary pollution and high pre-investment cost.

[0003] Membrane separation is a new technology that uses the difference in mass transfer rate of different guest molecules or components in membrane materials to realize selective separation driven by pressure difference. Since membrane separation is not limited by phase change and thermodynamic equilibrium, it has the advantages of low energy consumption, high separation efficiency, small land occupation and simple operation. Among them, metal organic framework (MOF) can accurately identify molecules or ions with small structural differences due to its uniform pore size, flexible adjustable framework structure and chemical composition. For the preparation of MOF-808 polycrystalline membrane, the rate-determining step of growth is the formation of Zr6O x (OH) y secondary structure unit in the bulk solution. This process needs to rely on external input of sufficient energy to overcome the activation energy required for growth. Higher reaction temperature often leads to unnecessary intergranular defects in the membrane preparation process, forming a large number of non-selective diffusion paths, resulting in attenuation of separation performance. By tailoring the preparation of specific MOF-808 membrane, it is expected to have great application prospects in the fields of organic matter purification, seawater desalination, ion sieving and seawater uranium extraction. SUMMARY

[0004] Zirconium-oxygen cluster is an important member of the tetravalent transition metal clusters. The good coordination between the cluster core and the charge compensation anion makes the zirconium-oxygen cluster a promising metal source for the synthesis of MOF-808 membrane. The zirconium-oxygen cluster powder can pre-form the cluster core in the MOF-808 skeleton, significantly reduce the activation energy required for the formation of the MOF-808 skeleton, and realize the preparation of the MOF-808 membrane with good intergrowth under mild reaction conditions. Meanwhile, the number of missing ligands in the MOF-808 can be precisely controlled by changing the composition of the raw material solution or the reaction temperature, so as to realize the great breakthrough of the MOF-808 membrane in the separation performance.

[0005] The application provides a method for preparing MOF-808 membrane assisted by zirconium-oxygen cluster. The zirconium-oxygen cluster powder is prepared as a metal zirconium source, and the trimesic acid is added to the reaction solution. The polycrystalline membrane with good intergrowth is obtained on the porous carrier by using the epitaxial growth method at-20-120 DEG C. The MOF-808 membrane can rapidly permeate the small-size interfering metal ions, effectively intercept the large-size uranyl ions, and has inherent skeleton stability in the water environment. The size screening effect can be used to realize the desalination of salt-containing dye wastewater and the efficient and selective separation of uranyl ions.

[0006] The technical scheme of the application is:

[0007] A method for preparing MOF-808 membrane assisted by zirconium-oxygen cluster, comprising the following steps:

[0008] (1) dissolving the metal zirconium salt in the mixed solution of acid I and organic solvent, carrying out reaction, after the reaction is completed, washing and drying to obtain the zirconium-oxygen cluster powder; the organic solvent comprises one or more of methanol, ethanol, propanol, isopropanol, water and acetonitrile; the acid I comprises one or more of formic acid, acetic acid, propionic acid and benzoic acid;

[0009] (2) dissolving the trimesic acid and the zirconium-oxygen cluster powder in the mixed solution of acid II and reaction solvent, loading into a reaction kettle to carry out reaction, then washing and drying to obtain the MOF-808 crystal seed;

[0010] (3) uniformly coating or dipping the MOF-808 crystal seed liquid on the surface of the porous carrier, and drying for standby use;

[0011] (4) dissolving the trimesic acid and the zirconium-oxygen cluster powder in the mixed solution of acid II and reaction solvent to obtain a membrane preparation precursor solution;

[0012] (5) sealing the crystal seed modified carrier at both ends, and placing it in the membrane preparation precursor solution in the above (4), and loading into a reaction kettle to carry out reaction;

[0013] (6) after the reaction is completed, washing and drying can obtain the MOF-808 molecular sieve membrane with good intergrowth;

[0014] The reaction solvent includes at least one or several of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylformamide, methanol, chloroform, dichloroethane, methanol, ethanol, propanol, isopropanol, water and acetonitrile; the acid II includes one or several of formic acid, acetic acid, propionic acid, sulfuric acid, hydrochloric acid, nitric acid and benzoic acid.

[0015] Preferably, the metal zirconium salt in step (1) includes one or several of zirconium tetrachloride, zirconium n-propylate, zirconium disulfide, zirconium oxychloride, zirconium acetate, zirconium sulfate, zirconium nitrate and organic zirconium salt.

[0016] Preferably, the mass ratio of the zirconium salt, the organic solvent and the acid I in step (1) is 1:1-10:1-5.

[0017] Preferably, the reaction temperature in step (1) is 60-180℃, and the reaction period is 10 min-24 h.

[0018] Preferably, the mass ratio of the reaction solvent, the acid II, the zirconium oxygen cluster powder and the trimesic acid in step (2) and step (4) is 1-100:1-80:1-100:1, and more preferably, the mass ratio of the reaction solvent, the acid II, the zirconium oxygen cluster powder and the trimesic acid is 1-20:1-5:1-20:1.

[0019] Preferably, the reaction temperature in step (2) and step (5) is -20-120℃, and the reaction time is 1-720 h. More preferably, the reaction temperature in step (2) and step (5) is 25-50℃.

[0020] Preferably, the concentration of the seed crystal liquid in step (3) is 0.1-0.5 wt.%, and the coating method includes dip coating, spin coating, spray coating, rubbing coating or interfacial self-assembly.

[0021] Preferably, the porous carrier in step (3) includes one or several of porous metal oxide, porous non-metal oxide, porous metal, carbide and porous polymer; and the structure of the porous carrier includes flat plate structure, tube structure, hollow fiber structure or roll structure.

[0022] Preferably, the reaction solvent in step (2) and step (4) includes at least one of methanol, ethanol, propanol, isopropanol, water and acetonitrile.

[0023] Preferably, the heating method in step (5) is convection heating or microwave heating (single-mode or multi-mode heating).

[0024] The application also provides the application of the MOF-808 film in desalination of salt-containing dye wastewater.

[0025] The application also provides the application of the MOF-808 film in uranium ion interception and uranium extraction from seawater.

[0026] Examples of metals mainly contained in natural seawater are K + / Na + / Mg 2+ / Ca 2+ / Fe 3+ / UO2 2+ .

[0027] MOF-808 is a typical representative of zirconium-based metal organic frameworks, which has a sieve empty window. Based on the micro-sized size difference, the MOF-808 membrane accurately identifies the uranyl ion (molecular dynamics diameter: UO2 2+ : K + : Na + : Ca 2+ : Mg 2+ : and Fe 3+ : ) in real seawater, so that the uranyl ion or large-sized dye molecule can be accurately separated from many metal ions by size sieving, and the MOF-808 membrane material can realize specific recognition of the uranyl ion and the large-sized dye molecule.

[0028] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0029] The present application uses a synthesized zirconium oxygen cluster powder as a zirconium source, which can significantly reduce the activation energy required for the growth of MOF-808; and a seed epitaxial growth method is used to prepare a MOF-808 membrane with excellent intergrowth and good compactness on a porous carrier. Using the zirconium oxygen cluster as a metal source, on the one hand, the preparation of the MOF-808 membrane at a lower reaction temperature is realized, and the defects of the MOF-808 membrane at the mesoscopic level are reduced as much as possible; on the other hand, the number of ligand defects in the MOF-808 membrane skeleton can be accurately controlled at the microscopic level, which has a positive effect on the separation performance, ensures the effective permeation of small-sized hydrated metal ions, and efficiently retains large-sized dye molecules and uranyl ions, which highlights a huge application prospect in pervaporation dehydration, nanofiltration, uranyl ion retention and seawater uranium extraction. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 (a) SEM image and (b) XRD image of the zirconium oxygen cluster powder prepared in Example 1.

[0031] Figure 2 (a) XRD image and (b) SEM image of the MOF-808 seed prepared in Example 1.

[0032] Figure 3 (a) XRD pattern of MOF-808 membrane prepared for Example 2.

[0033] Figure 4 (a) SEM image and (b) SEM cross-section image of MOF-808 membrane prepared for Example 2.

[0034] Figure 5 SEM image of MOF-808 membrane prepared for Example 3.

[0035] Figure 6 SEM image of MOF-808 membrane prepared for Example 4.

[0036] Figure 7 (a) XRD pattern and (b) SEM image of MOF-808 seed prepared for Example 5.

[0037] Figure 8 (a) SEM planar image and (b) SEM cross-section image of MOF-808 membrane prepared for Example 6.

[0038] Figure 9 Separation performance of MOF-808 membrane prepared for Example 2 for uranyl ion in seawater.

[0039] Figures 10-11 Separation stability test of MOF-808 membrane prepared for Example 2.

[0040] Figure 12 MOF-808 membrane prepared for Comparative Example 1 directly in-situ on original support.

[0041] Figure 13 MOF-808 membrane prepared for Comparative Example 2 at room temperature using zirconium chloride as zirconium source.

[0042] Figure 14 MOF-808 membrane prepared for Comparative Example 2 at room temperature using zirconium oxychloride as zirconium source.

[0043] Figure 15 MOF-808 membrane prepared for Comparative Example 2 at room temperature using zirconium n-propoxide as zirconium source.

[0044] Figures 16-18 MOF-808 membrane prepared for Comparative Example 3 at room temperature with single controlled reaction time.

[0045] Figure 19 MOF-808 membrane prepared for Comparative Example 4 at room temperature using liquid phase metal cluster.

[0046] Figure 20 (a) XRD pattern and (b) SEM image of MOF-808 seed prepared for Comparative Example 5.

[0047] Figure 21 (a) XRD pattern and (b) SEM image of the MOF-808 film prepared for Comparative Example 6.

[0048] Figure 22 SEM cross-section image of the MOF-808 film prepared for Comparative Example 6. DETAILED DESCRIPTION

[0049] The application will be further described in conjunction with specific examples. The following examples are intended to help the researchers and technical personnel in the field to further understand the application. Once the concept of the application is known, the following examples can be changed, modified or even improved by the skilled in the art. Therefore, all of these should belong to the protection scope of the application.

[0050] Example 1: Preparation of MOF-808 seed crystals by hydrothermal method at room temperature (25°C)

[0051] (1) 10 g of zirconium oxy-cluster was added into a mixed solution of 15 mL of acetic acid and 25 mL of isopropanol, and heated at 120°C for 1 h under stirring. After washing and drying, zirconium oxy-cluster powder was obtained.

[0052] (2) 1.201 g of zirconium oxy-cluster and 0.301 g of trimesic acid were added into a mixed solution of 12 mL of formic acid and 20 mL of deionized water, and the solution was stirred to obtain a reaction precursor solution.

[0053] (3) The reaction precursor was left at room temperature for 3 d.

[0054] (4) After the reaction, the product was washed and centrifuged with a large amount of deionized water and methanol, and finally dried in an oven at 80°C to obtain MOF-808 seed crystals.

[0055] The SEM (1a) image showed that the size of the zirconium oxy-cluster powder was about 1-2 μm, and the XRD (1b) diffraction peak indicated that the obtained powder was pure-phase zirconium oxy-cluster; the XRD (2a) diffraction peak indicated that the obtained powder was pure-phase MOF-808, and the SEM (2b) image showed that the MOF-808 seed crystals had good dispersibility and uniform size of about 300 nm. The number of ligand missing was 0.95.

[0056] Example 2: Preparation of MOF-808 film by hydrothermal method at room temperature (25°C)

[0057] (1) 0.375 g of zirconium oxy-cluster powder prepared in Example 1 and 0.095 g of trimesic acid were dissolved in a mixed solution of 12 mL of formic acid and 25 mL of deionized water to obtain a film preparation precursor solution.

[0058] (2) The MOF-808 seed crystals prepared in Example 1 were uniformly coated onto the surface of the alumina carrier and dried thoroughly in an oven at 80°C.

[0059] (3) The alumina carrier coated with the seed crystals was sealed at both ends and placed in a liner, and then the film-forming precursor solution was added. The stainless steel reactor was sealed and reacted at room temperature for 7 days.

[0060] (4) After the reaction was completed, the tube membrane was removed and washed with deionized water and methanol, and then naturally air-dried.

[0061] XRD( Figure 3 ) diffraction peaks indicated that the prepared product was a pure-phase MOF-808 membrane; SEM( Figure 4 a) Figure shows that the MOF-808 membrane is continuous and dense with no obvious defects; the film thickness is ~ 1.9 μm( Figure 4 b).

[0062] Example 3: Preparation of MOF-808 membrane on a sheet carrier by hydrothermal synthesis at room temperature

[0063] The difference from Example 2 is that in step (3), the tube carrier is replaced with a sheet carrier, and the remaining steps are the same as in Example 4.

[0064] SEM( Figure 5 ) Figure shows that the prepared MOF-808 membrane is continuous and dense with no obvious defects.

[0065] Example 4: Preparation of MOF-808 membrane by hydrothermal synthesis at 50°C

[0066] (1) 0.131 g of the zirconium-oxygen cluster powder prepared in Example 1 and 0.069 g of trimesic acid were dissolved in a mixture of 10 mL of formic acid and 26 mL of deionized water, and stirred uniformly to obtain a film-forming precursor solution.

[0067] (2) The MOF-808 seed crystals prepared in Example 1 were uniformly coated onto the surface of the alumina carrier and dried thoroughly in an oven at 50°C.

[0068] (3) The alumina carrier coated with the seed crystals was sealed at both ends and placed in a liner, and then the film-forming precursor solution was added. The stainless steel reactor was sealed and reacted at 50°C for 3 days.

[0069] (4) After the reaction was completed, the tube membrane was removed and washed with deionized water and methanol, and then naturally air-dried.

[0070] SEM( Figure 6 ) Figure shows that the MOF-808 membrane is continuous and dense with no obvious defects.

[0071] Example 5: Preparation of MOF-808 seed crystals by hydrothermal synthesis at 80°C

[0072] (1) 0.101 g of the zirconium oxo-cluster prepared in Example 1 and 0.051 g of trimesic acid were added into a mixed solution of 12 mL of formic acid and 21 mL of deionized water, and the solution was stirred to obtain a reaction precursor solution.

[0073] (2) The above reaction precursor was placed in an 80 °C oven for 18 h.

[0074] (3) After the reaction was completed, the product was washed with a large amount of deionized water and methanol, centrifuged, and finally dried in an 80 °C oven to obtain MOF-808 seed crystals.

[0075] XRD Figure 7 a) The diffraction peaks indicated that the obtained powder was pure-phase MOF-808, and the SEM (7b) image showed that the MOF-808 seed crystals had good dispersibility and uniform size, about 360 nm. The number of ligand vacancies was 0.65.

[0076] Example 6: Hydrothermal preparation of MOF-808 membrane at 70 °C

[0077] (1) 0.100 g of the zirconium oxo-cluster and 0.050 g of trimesic acid were dissolved in a mixed solution of 12 mL of formic acid and 20 mL of deionized water, and the solution was stirred to obtain a membrane preparation precursor solution.

[0078] (2) The MOF-808 seed crystals prepared in Example 5 were uniformly coated onto the surface of the alumina carrier and dried in an 80 °C oven.

[0079] (3) The alumina carrier coated with the seed crystals was sealed at both ends and placed in a liner, and then the membrane preparation precursor solution was added. After the stainless steel reactor was sealed, the reaction was carried out at 70 °C for 2 d.

[0080] (4) After the reaction was completed, the membrane was cooled to room temperature, washed with deionized water and methanol, and naturally air-dried.

[0081] SEM Figure 8 a) The SEM image showed that the prepared MOF-808 membrane was continuous and dense, with no obvious defects, and the thickness of the membrane layer was about 2.1 μm Figure 8 b).

[0082] Example 7: Test of dye desalination performance of MOF-808 membrane

[0083] The MOF-808 membrane prepared in Example 2 was subjected to dye desalination test, and the test conditions were as follows: the transmembrane pressure difference was 1 bar, the salt concentration was 2 g / L, the dye concentration was 0.1 g / L, and the cross-flow separation test was carried out.

[0084] The ion separation performance of the MOF-808 membrane is shown in Table 1. The epitaxially grown membrane layer shows selective separation for the NaCl / dye mixed system (intercepting macromolecular dyes and permeating smaller-sized water and Na + The ion separation performance of the MOF-808 membrane is shown in Table 1. The epitaxially grown membrane layer shows selective separation for the NaCl / dye mixed system (intercepting macromolecular dyes and permeating smaller-sized water and Na + The ion separation performance of the MOF-808 membrane is shown in Table 1. The epitaxially grown membrane layer shows selective separation for the NaCl / dye mixed system (intercepting macromolecular dyes and permeating smaller-sized water and Na -2 h - 1 bar -1 The ion separation performance of the MOF-808 membrane is shown in Table 1. The epitaxially grown membrane layer shows selective separation for the NaCl / dye mixed system (intercepting macromolecular dyes and permeating smaller-sized water and Na + / CR can reach 429.5. The above results show that the MOF-808 membrane prepared by using the cluster room temperature exhibits excellent separation performance for dye desalination.

[0085] Table 1 Dye desalination performance test of MOF-808 membrane

[0086]

[0087]

[0088] Example 8: Test of metal interception performance of MOF-808 membrane

[0089] The MOF-808 membrane prepared in Example 2 was subjected to uranium ion interception test, and the test conditions were as follows: the transmembrane pressure difference was 1 bar, the K + , Na + , Ca 2+ , Mg 2+ , Fe 3+ ion concentration was 1 mM, and the uranium ion concentration was 0.1 mM. The cross-flow separation test was performed. The results are shown in Table 2. The prepared membrane shows low interception rate (7.9-98.6%) for metal ions (K + , Na + , Ca 2+ , Mg 2+ , Fe 3+ ) with small hydrated ions, and the permeation flux is 4.982 L m -2 h -1 bar -1 to 6.473 L m -2 h -1 bar -1 ; and shows 99.99% interception rate for uranium ions. The above results show that the MOF-808 membrane prepared by using zirconium oxygen cluster has high interception performance for uranium ions and high permeation flux.

[0090] Table 2 Ion interception performance test of MOF-808 membrane

[0091] The ion separation performance of the MOF-808 membrane is shown in Table 1. The epitaxially grown membrane layer shows selective separation for the NaCl / dye mixed system (intercepting macromolecular dyes and permeating smaller-sized water and Na

[0092] Example 9: Performance test of MOF-808 membrane for uranium extraction from seawater

[0093] The MOF-808 membrane prepared in Example 2 was used to test the uranium extraction performance of seawater. The seawater mainly contains K + (~357ppm),Na + (~9336ppm),Mg 2+ (~873ppm),Ca 2+ (~357ppm), Fe 3+ (0.0041ppm), UO2 2+ (0.0030ppm) plasma, MOF-808 membrane still shows excellent selectivity for uranyl ions in real seawater (such as Figure 9 ), the highest K + / UO2 2+ The separation selectivity reached 315.0.

[0094] Example 10: MOF-808 membrane stability test

[0095] The MOF-808 membrane prepared in Example 2 was subjected to continuous testing for uranium extraction from seawater (e.g. Figures 10-11 ), after 12 h, the flux remained relatively stable, and the separation selectivity still reached 301.6, indicating that the MOF-808 membrane prepared with the assistance of zirconium oxide has excellent operational stability.

[0096] Comparative Example 1: Direct in-situ preparation of MOF-808 membrane using original support

[0097] The specific implementation steps are the same as those in Example 2, except that the alumina support used in step (3) is replaced with an alumina support that is not coated with MOF-808 seeds.

[0098] SEM( Figure 12 ) showed that only sporadic grains were scattered on the surface of the support and most of the support was still exposed, proving that the original support was not easy to form a dense MOF-808 film.

[0099] Comparative Example 2: Preparation of MOF-808 membrane at room temperature by changing the type of metal source

[0100] The specific implementation steps are the same as those in Example 2, except that the zirconium oxycluster metal source used in step (1) is replaced with common zirconium chloride, zirconium oxychloride and zirconium n-propoxide.

[0101] SEM( Figures 13-15) shows that the seed layer on the surface of the carrier has no signs of conjoining, which proves that the use of zirconium oxygen clusters can greatly reduce the activation energy required to form MOF-808. Therefore, by investigating different metal sources, under the optimal formula and reaction conditions, selecting the best metal source (zirconium oxygen cluster powder) is an effective means to prepare MOF-808 membranes with excellent performance.

[0102] Comparative Example 3: Preparation of MOF-808 membrane at room temperature by single control of reaction time

[0103] The specific implementation steps are the same as those of Example 2, except that the reaction time in step (3) is changed to 24 h, 72 h, and 120 h.

[0104] SEM( Figures 16-18 ) shows that as the reaction time gradually increases, the seed layer on the surface of the carrier and the cross section gradually show signs of conjoining, which shows that under the optimal formula and reaction conditions, controlling the reaction time is one of the effective ways to prepare MOF-808 membranes with excellent performance.

[0105] Comparative Example 4: Preparation of MOF-808 membrane at 50°C by liquid metal cluster

[0106] (1) 42 mL of N,N-dimethylformamide and 20 mL of formic acid were mixed, then 0.15 g of zirconium oxychloride was added, and ultrasonic treatment was performed for 10 min to obtain a homogeneous solution. Then the above raw material solution was heated at 150°C for 3 h, and cooled to room temperature to form a liquid cluster as a metal source for preparing a membrane layer.

[0107] (2) 0.180 g of trimesic acid was added to the above solution (1), and ultrasonic treatment was performed for 30 min to obtain a precursor solution.

[0108] (3) MOF-808 seeds were prepared according to Example 1 and coated on the surface of the carrier, and then dried in a 70°C oven overnight.

[0109] (4) The carrier coated with MOF-808 seeds was placed in a liner, and the above precursor solution was poured in, and then reacted at 50°C for 7 d.

[0110] SEM( Figure 19 ) shows that even if the reaction time is extended to one week, the seed layer on the surface of the carrier still does not show signs of conjoining, and the seed layer shows signs of falling off, which shows that liquid zirconium oxygen clusters cannot realize the preparation of MOF-808 membranes with good conjoining at room temperature.

[0111] Comparative Example 5: Preparation of MOF-808 seeds by hot solvent method

[0112] (1) MOF-808 seeds were prepared by solvothermal method.

[0113] (1) 0.965 g of zirconium oxychloride and 0.210 g of trimesic acid were dissolved in 25 mL of formic acid and 45 mL of N,N-dimethylformamide to obtain a precursor solution.

[0114] (2) The precursor solution was reacted at 120°C for 24 h.

[0115] (3) After the reaction, the product was washed with a large amount of N,N-dimethylformamide and methanol, and then dried in an oven at 80°C.

[0116] XRD Figure 20 a) The diffraction peaks indicated that the prepared powder was pure MOF-808; SEM Figure 20 b) The figure showed that the MOF-808 seed crystals were well dispersed and uniform in size, about 360 nm. The number of ligand vacancies was 0.08.

[0117] Comparative Example 6: Solvothermal epitaxial growth of MOF-808 film

[0118] (1) 0.121 g of zirconium oxychloride and 0.086 g of trimesic acid were dissolved in 20 mL of formic acid and 20 mL of N,N-dimethylformamide to obtain a precursor solution for film preparation.

[0119] (2) The MOF-808 seed crystals prepared in Comparative Example 5 were uniformly coated on the surface of the alumina carrier and dried in an oven at 80°C.

[0120] (3) The alumina carrier coated with the seed crystals was sealed at both ends and placed in a liner, and then the precursor solution for film preparation was added. After sealing with a stainless steel reactor, the reaction was carried out at 120°C for 36 h.

[0121] (4) After the reaction, the product was cooled to room temperature, removed from the tube, and washed with N,N-dimethylformamide and methanol, and then naturally air-dried.

[0122] XRD Figure 21 a) The diffraction peaks indicated that the prepared product was pure MOF-808 film; SEM Figure 21 b) The figure showed that the MOF-808 film was continuous and dense, with no obvious defects, and the thickness was about 2.3 μm Figure 22 ).

[0123] Although the preferred embodiments of the present application have been described, those skilled in the art, once aware of the basic inventive concept, can make additional changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0124] Obviously, many modifications and variations of the present application are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims and their equivalents, the application can be practiced otherwise than as specifically described.

Claims

1. A method for preparing MOF-808 membranes assisted by zirconium oxo clusters for uranyl ion retention and uranium extraction from seawater, characterized by: The steps include: (1) dissolving a metal zirconium salt in a mixture of an acid I and an organic solvent, reacting the mixture, and washing and drying the mixture to obtain zirconium oxide cluster powder; the organic solvent comprises one or more of methanol, ethanol, propanol, isopropanol, water, and acetonitrile; and the acid I comprises one or more of formic acid, acetic acid, propionic acid, and benzoic acid; (2) dissolving trimesic acid and zirconium oxide powder in a mixture of acid II and a reaction solvent, placing the mixture into a reactor for reaction, and then washing and drying to obtain MOF-808 seed crystals; (3) uniformly coating or dipping the MOF-808 seed solution on the surface of the porous support and drying it for later use; (4) dissolving trimesic acid and zirconium oxide cluster powder in a mixed solution of acid II and a reaction solvent to obtain a film precursor solution; (5) Seal both ends of the carrier modified with the seed crystals in (3), place it in the film precursor solution, and place it in a reactor for reaction; (6) After the reaction is completed, washing and drying can obtain a MOF-808 molecular sieve membrane with good intergrowth properties; The reaction solvent includes N,N -dimethylformamide, N,N -dimethylacetamide, N- At least one or more of methylformamide, methanol, chloroform, dichloroethane, methanol, ethanol, propanol, isopropanol, water and acetonitrile; the acid II includes one or more of formic acid, acetic acid, propionic acid, sulfuric acid, hydrochloric acid, nitric acid and benzoic acid.

2. The method for preparing MOF-808 membrane with the aid of zirconium oxo clusters according to claim 1, characterized in that: In step (1), the mass ratio of the zirconium salt, the organic solvent and the acid I is 1:1-10:1-5.

3. The method for preparing MOF-808 membrane with the assistance of zirconium oxo clusters according to claim 1, characterized in that: In step (1), the reaction temperature is 60-180°C, and the reaction period is 10 min-24 h.

4. The method for preparing MOF-808 membrane with the assistance of zirconium oxo clusters according to claim 1, characterized in that: In step (2) and step (4), the mass ratio of the reaction solvent, acid II, zirconium oxide cluster powder and trimesic acid is 1-100:1-80:1-100:

1.

5. The method for preparing MOF-808 membrane with the assistance of zirconium oxo clusters according to claim 1, characterized in that: The reaction temperature of step (2) and step (5) is -20~120°C; the reaction time is 1-720 h.

6. The method for preparing MOF-808 membrane with the assistance of zirconium oxo clusters according to claim 5, characterized in that: The reaction temperature in step (2) and step (5) is 25-50°C.

7. The method for preparing MOF-808 membrane with the assistance of zirconium oxo clusters according to claim 1, characterized in that: The concentration of the seed solution in step (3) is 0.1-0.5 wt.%; Coating methods include: dip coating, spin coating, spray coating, wipe coating or interface self-assembly.

8. The method for preparing MOF-808 membrane with the assistance of zirconium oxo clusters according to claim 1, characterized in that: The porous carrier described in step (3) includes: 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 coiled structure.

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