A single-particle layer MOF composite film with orientation and a preparation method thereof

Abstract

The application discloses a kind of single-particle layer MOF composite membrane with orientation and preparation method, belong to membrane preparation technical field, first using modulating agent synthesis MOF crystal particle with regular appearance and uniform particle size, then it is prepared into MOF dispersion liquid;MOF dispersion liquid is coated on the surface of porous substrate using spin coating method and dried for a certain time to obtain single-particle MOF layer with orientation.Then a certain concentration of polymer solution is coated on the surface of the membrane by spin coating method to fill the gap of single-particle MOF crystal. Finally, a single-particle layer oriented MOF composite membrane is obtained by thermal crosslinking. This method can effectively construct a new type of MOF composite membrane with through-pore structure, and the obtained membrane can be used for high energy consumption, difficult separation system such as organic solvent mixture.

Description

Technical Field

[0001] This invention mainly relates to a method for preparing single-particle layer oriented MOF composite membranes using a stepwise spin-coating assembly technique, and its separation and application. It relates to membrane materials and membrane structures, and belongs to the field of membrane technology. Background Technology

[0002] The separation of organic solvent mixtures is a crucial and challenging practical problem in petrochemicals. The separation of aromatic and alkane molecules is a representative example of a high-energy-consuming and difficult-to-separate system. Systems such as benzene and cyclohexane, or toluene and n-heptane, have very similar physicochemical properties and molecular sizes; they are all nonpolar compounds and can form azeotropic systems. Therefore, traditional thermal separation methods are often difficult and energy-intensive. In recent years, the continuous development of pervaporation technology in the field of membrane separation has made efficient separation of these systems possible.

[0003] The development of novel membrane materials is considered crucial for the fabrication of high-performance separation membranes. Metal-organic frameworks (MOFs) are a class of porous crystalline materials derived from organic ligands and metal ions / clusters through coordination interactions. Due to their regular and well-defined pore structures, MOFs exhibit great potential for precise intermolecular sieving. Ideally, intact, defect-free polycrystalline MOF membranes can achieve precise molecular separation thanks to their inherent robust pores. However, polycrystalline MOF membranes still face challenges such as unavoidable non-selective defects and difficulty in precisely controlling crystal orientation. Furthermore, while mixed-matrix membranes using MOFs as fillers and polymers as the continuous phase are simple to fabricate and easy to scale up, MOFs in the polymer matrix often aggregate easily, making it difficult to effectively utilize the high permeability of MOF pores for efficient separation. This is a major reason for their low separation performance. Therefore, designing and constructing oriented MOF composite membranes with novel structures is essential for achieving high-performance intermolecular separation. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a single-particle layer oriented MOF composite film with a MOF through-hole structure. The design concept of this invention is as follows: firstly, an oriented single-particle MOF layer is constructed on the surface of a porous substrate using a layered spin-coating assembly method; then, a polymer is used to fill the gaps between the single-particle MOF crystals, ultimately obtaining a single-particle layer MOF composite film with an oriented structure.

[0005] To achieve the above objectives, the present invention employs the following steps:

[0006] (1) MOF particles with regular morphology and uniform particle size were synthesized by adding a modifier to the synthesis solution;

[0007] (2) Prepare MOF dispersion and ultrasonically stir to disperse it evenly;

[0008] (3) The MOF dispersion from step (2) is coated onto the surface of the porous substrate using a spin coating method;

[0009] (4) The substrate coated with MOF dispersion in step (3) is placed in an oven and dried to obtain a substrate with a single particle layer oriented arrangement.

[0010] (5) Prepare a polymer solution, coat the polymer solution onto the substrate with the single-particle layer orientation obtained in step (4) by spin coating, and then thermally crosslink it in an oven to obtain a single-particle layer orientation metal-organic framework film.

[0011] Preferably, in step (1), the metal salt in the synthesis solution used to prepare MOF particles is one of cobalt nitrate hexahydrate, zinc nitrate hexahydrate, copper nitrate trihydrate, and zirconium chloride; the organic ligand is one of terephthalic acid, biphenyl phthalic acid, trimesic acid, and 2-methylimidazole; the solvent is one of water, methanol, and N,N-dimethylformamide (DMF); and the modifier is one of sodium formate, acetic acid, and polyvinylpyrrolidone (PVP).

[0012] Preferably, in step (2), the solvent used to prepare the MOF dispersion is one of water, methanol, ethanol, isopropanol, and DMF, the dispersion concentration is 1 g / L to 8 g / L (preferably 2 g / L to 6 g / L), the spin coating speed is 500 to 6000 rpm (preferably 1000 to 3000 rpm), and the spin coating time is 10 to 200 s (preferably 20 to 80 s).

[0013] Preferably, in step (3), 10-100 μl (preferably 30-60 μl) is coated per square centimeter of substrate surface.

[0014] The MOF dispersion; the drying temperature is 25-120°C (preferably 40-80°C).

[0015] Preferably, in step (4), the polymer used to prepare the polymer solution is one of hyperbranched polymer HBP, polyether block amide BEBA, or polyvinyl alcohol PVA, and the solvent used is one of toluene, n-heptane, n-butanol, DMF, isopropanol, or water; the concentration of the polymer solution is 5wt%-35wt% (preferably 10wt%-25wt%).

[0016] Preferably, in step (5), the spin coating speed is 1000-8000 rpm (preferably 2000-5000 rpm), and the spin coating time is 10-100 s (preferably 20-60 s). The thermal crosslinking temperature is 40-170℃ (preferably 60-150℃).

[0017] Preferably, the porous substrate material is alumina, zirconium oxide, polyacrylonitrile, polysulfone, polytetrafluoroethylene, polyvinylidene fluoride, etc.

[0018] In the composite film obtained by this invention, MOF particles are uniformly arranged to form a single-layer structure of MOF particles; the corresponding thickness of the polymer is the same as the thickness of the single-layer structure of MOF particles.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] This invention provides a method for preparing a single-particle layer oriented MOF composite membrane. The composite membrane obtained by this method, with its MOF interconnected pore structure, effectively solves the problem of not being able to fully utilize the high permeability of MOF pores in traditional MOF-based mixed matrix membranes. Furthermore, in the separation of aromatic / alkane systems, for benzene /

[0021] In the cyclohexane system, the separation factor reached 11.3, and the permeation flux was 1246 g / m³. 2 For the toluene / n-heptane system, the separation factor reaches 10.6 and the permeation flux is 1230 g / m³. 2 h. It shows excellent application prospects in the field of separating energy-intensive and difficult-to-separate organic liquid mixtures. Attached Figure Description

[0022] Figure 1 XRD pattern of the UiO-66@HBP / PVDF composite membrane prepared in Example 1 of this invention.

[0023] Figure 2 SEM image of the UiO-66@HBP / PVDF composite membrane prepared in Example 1 of this invention.

[0024] Figure 3 The image shows a SEM image of the Cu-BTC@HBP / PVDF composite membrane prepared in Example 2 of this invention. Detailed Implementation

[0025] The technical solution of the present invention is illustrated below with specific embodiments, but the scope of protection of the present invention is not limited thereto:

[0026] Example 1

[0027] The substrate was a PVDF substrate with a pore size of 200 nm, the MOF was UiO-66, and the polymer was HBP, resulting in a UiO-66@HBP / PVDF composite film. The preparation method is as follows:

[0028] Step 1: Soak the PVDF substrate in an ethanol / water solution (volume ratio 1:1) for 24 hours, then place it in a 40℃ container.

[0029] Dry in an oven for later use.

[0030] Step 2: Acetic acid was added as a modulator to the precursor solution for MOF particle synthesis and the reaction was carried out at 120℃ for 24 h. The concentration of Zr ions, the metal ligand, in the synthesis solution was 0.008 mol / L, the concentration of terephthalic acid, the organic ligand, was 0.008 mol / L, the concentration of acetic acid was 2.4 mol / L, and the solvent used was DMF.

[0031] Step 3: Prepare a MOF dispersion with a concentration of 4 g / L, and ultrasonically stir it to ensure uniform dispersion. The solvent used is ethanol.

[0032] Step 4: Spin-coating the MOF dispersion prepared in step (3) onto the surface of the PVDF substrate. The spin-coating speed is 3000 rpm and the spin-coating time is 60 s. 40 μl of MOF dispersion is applied to each square centimeter of substrate.

[0033] Step 5: Place the substrate coated with MOF dispersion in step (4) in an oven to dry and obtain a substrate with a single particle layer orientation. The drying temperature is 40℃.

[0034] Step 6: Prepare a 15% (w / w) HBP polymer solution using toluene as the solvent. Spin-coat the polymer solution onto the substrate with the oriented monolayer obtained in step (5), then thermally crosslink it in an oven to obtain a UiO-66@HBP / PVDF composite film at 150°C.

[0035] The pervaporation performance of the UiO-66@HBP / PVDF composite membrane obtained above was tested. Test conditions:

[0036] The pressure difference was 0.1 MPa, the feed solution was a 50 wt% toluene / n-heptane mixed solution, and the feed temperature was 40℃. Test results:

[0037] The toluene / n-heptane separation factor is 10.6, and the flux is 1230 g / m³. 2 h.

[0038] Example 2

[0039] The substrate was a PVDF substrate with a pore size of 200 nm. The MOF was Cu-BTC, and the polymer was HBP, resulting in a Cu-BTC@HBP / PVDF composite film. The preparation method is as follows:

[0040] Step 1: Soak the PVDF substrate in an ethanol / water solution (volume ratio 1:1) for 24 hours, then place it in a 40℃ container.

[0041] Dry in an oven for later use.

[0042] Step 2: PVP was added as a modulator to the precursor solution for MOF particle synthesis and the reaction was carried out at 25°C for 24 h. The concentration of Cu ions (metal ligand) in the synthesis solution was 0.04 mol / L, the concentration of trimesic acid (organic ligand) was 0.04 mol / L, the concentration of PVP was 0.0045 mol / L, and the solvent used was methanol.

[0043] Step 3: Prepare a MOF dispersion with a concentration of 4 g / L, and ultrasonically stir it to ensure uniform dispersion. The solvent used is ethanol.

[0044] Step 4: Spin-coating the MOF dispersion prepared in step (3) onto the surface of the PVDF substrate. The spin-coating speed is 3000 rpm and the spin-coating time is 60 s. 40 μl of MOF dispersion is applied to each square centimeter of substrate.

[0045] Step 5: Place the substrate coated with MOF dispersion in step (4) in an oven to dry and obtain a substrate with a single particle layer orientation. The drying temperature is 40℃.

[0046] Step 6: Prepare a 15% (w / w) HBP polymer solution using toluene as the solvent. Spin-coat the polymer solution onto the substrate with the oriented monolayer obtained in step (5), then thermally crosslink it in an oven to obtain a Cu-BTC@HBP / PVDF composite film at 150°C.

[0047] The pervaporation performance of the Cu-BTC@HBP / PVDF composite membrane obtained above was tested. Test conditions:

[0048] The pressure difference was 0.1 MPa, the feed solution was a 50 wt% toluene / n-heptane mixed solution, and the feed temperature was 40℃. Test results:

[0049] The toluene / n-heptane separation factor was 6.69, and the throughput was 1548 g / m² h.

[0050] Example 3

[0051] The substrate was a PVDF substrate with a pore size of 200 nm, the MOF was UiO-67, and the polymer was HBP, resulting in a UiO-67@HBP / PVDF composite film. The preparation method is as follows:

[0052] Step 1: Soak the PVDF substrate in an ethanol / water solution (volume ratio 1:1) for 24 hours, then place it in a 40℃ container.

[0053] Dry in an oven for later use.

[0054] Step 2: Acetic acid was added as a modulator to the precursor solution for MOF particle synthesis and the reaction was carried out at 120℃ for 24 h. The concentration of Zr ions, the metal ligand, in the synthesis solution was 0.008 mol / L, the concentration of biphenyl dicarboxylic acid, the organic ligand, was 0.008 mol / L, the concentration of acetic acid was 2.4 mol / L, and the solvent used was DMF.

[0055] Step 3: Prepare a MOF dispersion with a concentration of 4 g / L, and ultrasonically stir it to ensure uniform dispersion. The solvent used is ethanol.

[0056] Step 4: Spin-coating the MOF dispersion prepared in step (3) onto the surface of the PVDF substrate. The spin-coating speed is 3000 rpm and the spin-coating time is 60 s. 40 μl of MOF dispersion is applied to each square centimeter of substrate.

[0057] Step 5: Place the substrate coated with MOF dispersion in step (4) in an oven to dry and obtain a substrate with a single particle layer orientation. The drying temperature is 40℃.

[0058] Step 6: Prepare a 15% (w / w) HBP polymer solution using toluene as the solvent. Spin-coat the polymer solution onto the substrate with the oriented monolayer obtained in step (5), then thermally crosslink it in an oven to obtain a UiO-67@HBP / PVDF composite film at 150°C.

[0059] The pervaporation performance of the UiO-67@HBP / PVDF composite membrane obtained above was tested. Test conditions:

[0060] The pressure difference was 0.1 MPa, the feed solution was a 50 wt% toluene / n-heptane mixed solution, and the feed temperature was 40℃. Test results:

[0061] The toluene / n-heptane separation factor is 6.53, and the flux is 1062 g / m³. 2 h.

[0062] Example 4

[0063] The substrate was a PVDF substrate with a pore size of 200 nm, the MOF was UiO-66, and the polymer was HBP, resulting in a UiO-66@HBP / PVDF composite film. The preparation method is as follows:

[0064] Step 1: Soak the PVDF substrate in an ethanol / water solution (volume ratio 1:1) for 24 hours, then place it in a 40℃ container.

[0065] Dry in an oven for later use.

[0066] Step 2: Acetic acid was added as a modifier to the precursor solution for MOF particle synthesis and the reaction was carried out at 120℃ for 24 h. The concentration of Zr ions in the synthesis solution was 0.008 mol / L, the concentration of organic ligands was 0.008 mol / L, the concentration of acetic acid was 2.4 mol / L, and the solvent used was DMF.

[0067] Step 3: Prepare a MOF dispersion with a concentration of 2 g / L, and ultrasonically stir it to ensure uniform dispersion. The solvent used is ethanol.

[0068] Step 4: Spin-coating the MOF dispersion prepared in step (3) onto the surface of the PVDF substrate. The spin-coating speed is 4000 rpm and the spin-coating time is 60 s. 60 μl of MOF dispersion is coated per square centimeter of substrate.

[0069] Step 5: Place the substrate coated with MOF dispersion in step (4) in an oven to dry and obtain a substrate with a single particle layer orientation. The drying temperature is 40℃.

[0070] Step 6: Prepare a 15% (w / w) HBP polymer solution using toluene as the solvent. Spin-coat the polymer solution onto the substrate with the oriented monolayer obtained in step (5), then thermally crosslink it in an oven to obtain a UiO-66@HBP / PVDF composite film at 150°C.

[0071] The pervaporation performance of the UiO-66@HBP / PVDF composite membrane obtained above was tested. Test conditions:

[0072] The pressure difference was 0.1 MPa, the feed solution was a 50 wt% toluene / n-heptane mixed solution, and the feed temperature was 40℃. Test results:

[0073] The toluene / n-heptane separation factor was 7.24, and the flux was 924 g / m² h.

[0074] Example 5

[0075] The substrate was a PVDF substrate with a pore size of 200 nm, the MOF was ZIF-67, and the polymer was HBP, resulting in a ZIF-67@HBP / PVDF composite membrane. The preparation method is as follows:

[0076] Step 1: Soak the PVDF substrate in an ethanol / water solution (volume ratio 1:1) for 24 hours, then place it in a 40℃ container.

[0077] Dry in an oven for later use.

[0078] Step 2: After adding methanol as a modifier to the precursor solution for MOF particle synthesis, the reaction was carried out at 25°C for 24 hours. The concentration of the metal ligand Co ion in the synthesis solution was 0.0075 mol / L, the concentration of the organic ligand 2-methylimidazole was 0.07 mol / L, the volume ratio of methanol to water was 1:4, and water was used as the solvent.

[0079] Step 3: Prepare a MOF dispersion with a concentration of 4 g / L, and ultrasonically stir it to ensure uniform dispersion. The solvent used is ethanol.

[0080] Step 4: Spin-coating the MOF dispersion prepared in step (3) onto the surface of the PVDF substrate. The spin-coating speed is 3000 rpm and the spin-coating time is 60 s. 40 μl of MOF dispersion is applied to each square centimeter of substrate.

[0081] Step 5: Place the substrate coated with MOF dispersion in step (4) in an oven to dry and obtain a substrate with a single particle layer orientation. The drying temperature is 40℃.

[0082] Step 6: Prepare a 15% (w / w) HBP polymer solution using toluene as the solvent. Spin-coat the polymer solution onto the substrate with the oriented monolayer obtained in step (5), then thermally crosslink it in an oven to obtain a ZIF-67@HBP / PVDF composite film at 150°C.

[0083] The pervaporation performance of the ZIF-67@HBP / PVDF composite membrane obtained above was tested. Test conditions:

[0084] The pressure difference was 0.1 MPa, the feed solution was a 50 wt% toluene / n-heptane mixed solution, and the feed temperature was 40℃. Test results:

[0085] The toluene / n-heptane separation factor is 4.07, and the flux is 207 g / m³. 2 h.

[0086] Example 6

[0087] The substrate was a PVDF substrate with a pore size of 200 nm, the MOF was UiO-66, and the polymer was HBP, resulting in a UiO-66@HBP / PVDF composite film. The preparation method is as follows:

[0088] Step 1: Soak the PVDF substrate in an ethanol / water solution (volume ratio 1:1) for 24 hours, then place it in a 40℃ container.

[0089] Dry in an oven for later use.

[0090] Step 2: Acetic acid was added as a modifier to the precursor solution for MOF particle synthesis and the reaction was carried out at 120℃ for 24 h. The concentration of Zr ions in the synthesis solution was 0.008 mol / L, the concentration of organic ligands was 0.008 mol / L, the concentration of acetic acid was 2.4 mol / L, and the solvent used was DMF.

[0091] Step 3: Prepare a MOF dispersion with a concentration of 6 g / L, and ultrasonically stir it to ensure uniform dispersion. The solvent used is ethanol.

[0092] Step 4: Spin-coating the MOF dispersion prepared in step (3) onto the surface of the PVDF substrate. The spin-coating speed is 3000 rpm and the spin-coating time is 60 s. 40 μl of MOF dispersion is applied to each square centimeter of substrate.

[0093] Step 5: Place the substrate coated with MOF dispersion in step (4) in an oven to dry and obtain a substrate with a single particle layer orientation. The drying temperature is 40℃.

[0094] Step 6: Prepare a 15% (w / w) HBP polymer solution using toluene as the solvent. Spin-coat the polymer solution onto the substrate with the oriented monolayer obtained in step (5), then thermally crosslink it in an oven to obtain a UiO-66@HBP / PVDF composite film at 150°C.

[0095] The pervaporation performance of the UiO-66@HBP / PVDF composite membrane obtained above was tested. Test conditions: pressure difference 0.1 MPa, feed solution 50 wt% benzene / cyclohexane mixed solution, feed temperature 40℃. Test results: benzene / cyclohexane separation factor 11.3, flux 1246 g / m² h.

Claims

1. A method for preparing an oriented single-particle layer MOF composite film, characterized in that, Includes the following steps: (1) MOF particles with regular morphology and uniform particle size were synthesized by adding modifier to the synthesis solution; (2) Prepare MOF dispersion and ultrasonically stir to ensure uniform dispersion; (3) The MOF dispersion from step (2) is coated onto the surface of the porous substrate using a spin coating method; (4) The substrate coated with MOF dispersion in step (3) is placed in an oven and dried to obtain a substrate with a single particle layer oriented arrangement; (5) Prepare a polymer solution, coat the polymer solution onto the substrate with the single-particle layer orientation obtained in step (4) by spin coating, and then thermally crosslink it in an oven to obtain a single-particle layer orientation metal-organic framework film. In step (1), the metal salt used in the synthesis solution for preparing MOF particles is one of cobalt nitrate hexahydrate, zinc nitrate hexahydrate, copper nitrate trihydrate, and zirconium chloride; the organic ligand is one of terephthalic acid, biphenyl phthalic acid, trimesic acid, and 2-methylimidazole; the modifier used is one of sodium formate, acetic acid, and polyvinylpyrrolidone (PVP); and the concentration of the MOF dispersion is 1 g / L to 8 g / L. In step (3), the spin coating speed is 1000~6000 rpm and the spin coating time is 10~200s; 10-100μl of MOF dispersion is coated on each square centimeter of substrate surface. In step (5), the polymer used to prepare the polymer solution is one of the following: hyperbranched polymer HBP, polyether block amide BEBA, and polyvinyl alcohol PVA; the solvent used is one of toluene, n-heptane, n-butanol, DMF, isopropanol, and water; the concentration of the polymer solution is 5wt%-35wt%. The resulting composite film has MOF particles uniformly arranged to form a monolayer structure of MOF particles; the corresponding thickness of the polymer is the same as the thickness of the monolayer structure of MOF particles.

2. The method according to claim 1, characterized in that, In step (1), the solvent used is one of water, methanol, or N,N-dimethylformamide (DMF).

3. The method according to claim 1, characterized in that, In step (2), the solvent used to prepare the MOF dispersion is one of water, methanol, ethanol, isopropanol, and DMF, and the concentration of the dispersion is 2 g / L to 6 g / L.

4. The method according to claim 1, characterized in that, In step (3), the spin coating speed is 1000~3000 rpm and the spin coating time is 20~80s; 30-60μl of MOF dispersion is applied to each square centimeter of substrate surface, and the drying temperature is 25~120℃.

5. The method according to claim 4, characterized in that, The drying temperature is 40~80℃.

6. The method according to claim 1, characterized in that, In step (5), the polymer solution concentration is 10wt%-25wt%.

7. The method according to claim 1, characterized in that, In step (5), the spin coating speed is 1000~8000 rpm, the spin coating time is 10~100s, and the thermal crosslinking temperature is 40~170℃.

8. The method according to claim 1, characterized in that, The porous substrate material is alumina, zirconium oxide, polyacrylonitrile, polysulfone, polytetrafluoroethylene, or polyvinylidene fluoride.

9. An oriented single-particle layer MOF composite membrane prepared according to any one of claims 1-8.

10. The oriented single-particle layer MOF composite membrane prepared according to any one of claims 1-8 is used as a permeation membrane for the separation of aromatic / alkane systems.

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