Preparation method and application of layered column three-dimensional MOF (Metal Organic Framework) enhanced mixed matrix membrane

Abstract

The invention discloses a preparation method and application of a layered column three-dimensional MOF enhanced mixed matrix membrane, and belongs to the technical field of pervaporation membrane separation. The preparation method comprises the following steps: firstly, dissolving a copper metal source and 2, 3, 6, 7, 10, 11-hexahydroxytribenzene in a solvent to obtain Cu < 2 + > and a deprotonated organic ligand, adding a pillar ligand bipyridine in situ, and co-coordinating the double ligand and Cu < 2 + > to generate a layered column three-dimensional MOF (Metal Organic Framework); and doping the layered column three-dimensional MOF into a polymer matrix to prepare a membrane casting solution, and coating the surface of a support body with the membrane casting solution to prepare the layered column three-dimensional MOF enhanced mixed matrix membrane. According to the invention, the pillar ligand dipyridyl provides a supporting effect for the three-dimensional MOF and constructs a three-dimensional pore channel at the same time; the affinity site of the three-dimensional MOF has conjugated pi-pi, hydrophobic and hydrogen bond interaction on the perfume; the three-dimensional MOF and a high-molecular polymer have excellent compatibility, and the mixed matrix membrane simultaneously has affinity of the three-dimensional MOF to 2-PE and hydrophobicity of a polymer matrix; the pervaporation membrane can be used for pervaporation membrane perfume separation.

Description

Technical Field

[0001] The present invention relates to a preparation method and application of an in-situ constructed layered pillar three-dimensional MOF-enhanced mixed matrix membrane. Specifically, the invention relates to a method of in-situ constructing a three-dimensional MOF with a layered pillar structure by utilizing a pillar coordination strategy, and doping the MOF into a polymer matrix to prepare a mixed matrix membrane. The method belongs to the field of pervaporation membrane separation technology. Background Art

[0002] Spices, as key raw materials in the food, daily chemical, and pharmaceutical industries, have complex compositions, often containing a variety of volatile and non-volatile substances. Each component varies significantly in aroma, flavor, and efficacy. Precise spice separation technology is crucial. It not only effectively removes impurities, improves spice purity, ensures product quality stability and consistency, and meets the stringent quality requirements of the high-end market, but also accurately extracts high-value active ingredients from natural spices and develops spice products with unique aromas and special functions. There are many methods for extracting natural spices, including traditional extraction methods such as steam distillation and solvent extraction, as well as emerging green extraction methods such as supercritical extraction and subcritical water extraction. The purity and quality of spices separated by different extraction methods vary. Pervaporation membrane separation technology, with its advantages of high efficiency, low energy consumption, and environmental friendliness, has shown great application potential in areas such as organic solvent dehydration, azeotropic separation, and separation of organic mixtures, and has become a research hotspot in the field of chemical separation.

[0003] Membrane materials used for pervaporation are generally classified into polymer membranes, inorganic membranes, and mixed matrix membranes. Membrane materials exploit differences in their affinity for different components to achieve selective separation. Many typical polymer materials (such as polydimethylsiloxane, polyvinyl alcohol, cellulose acetate, polyetheramide, chitosan, and polyetherester) have been studied and applied in pervaporation desalination, dehydration, and organic separation and purification. However, polymer membranes have drawbacks in organic separation, such as poor swelling resistance and mechanical strength. Industrial applications suffer from low separation efficiency and poor stability. While inorganic membranes offer advantages such as large surface area, high pore volume, tunable structure, and resistance to high temperatures and high pressures, they are difficult to prepare and expensive, hindering their commercialization. Mixed matrix membranes (MMMs), prepared by combining a polymer matrix with an inorganic filler, combine the advantages of both inorganic and organic materials and have attracted widespread attention. Tang et al. (Journal of Membrane Science 581 (2019) 93) modified graphene oxide (GO) with an ionic liquid (IL) and incorporated it into a polyether block amide (PEBA) membrane to permeate and separate aqueous butanol solutions. The experimental results showed that the incorporation of IL-GO improved membrane performance, but when the inorganic material addition exceeded 1 wt%, the poor compatibility between the polymer and IL-GO led to the formation of non-selective defects at the interface, significantly reducing the membrane's selectivity.

[0004] Metal-organic framework (MOF) materials, a class of porous crystalline materials formed by self-assembly of metal ions or clusters with organic ligands, have shown great application prospects in the field of pervaporation membrane separation due to their high specific surface area, tunable pore structure, and abundant surface functional groups. Mixed matrix membranes prepared by doping MOF materials into polymer matrices are expected to produce pervaporation membranes with excellent separation performance. Yang et al. (Journal of Environmental Chemical Engineering 11 (2023) 109390) prepared a PDMS / ZIF-8 mixed matrix membrane for the separation of aromatic compounds from lemon oil wastewater. Compared with pure PDMS, the permeation flux and selectivity of linalool, cis-citral, and trans-citral in ZIF-8 / PDMS were significantly improved. However, traditional MOF structures have poor stability in solvent environments, resulting in high membrane loss and high cost in pervaporation separation. To address these issues, a pillared three-dimensional MOF designed based on pillared ligands was constructed through a dual mechanism strategy of "interlayer support and site orientation" to achieve high separation efficiency and good stability. Yuan et al. (ACS Materials Letters 6 (2024) 3925) used 4,4′-bipyridine, 4,4′-azopyridine, 1,2-bis(4-pyridyl)ethylene, and 1,2-bis(4-pyridyl)ethynyldiyl as pillars to form a series of Zn-L three-dimensional pillared layered topological structures. The introduction of pillars greatly improved the chemical stability of the material, and they found that the introduction of unsaturated functional groups improved the C2H2 / CO2 separation performance. However, the step-by-step preparation strategy of pillared MOFs makes the MOF preparation process cumbersome and the production cost high.

[0005] Based on the above, in order to prepare a low-cost, fast mass transfer channel and good chemical stability mixed matrix membrane, the present invention designed an in situ constructed layered three-dimensional MOF reinforced mixed matrix membrane and applied it to the separation and purification of spices. Summary of the Invention

[0006] The present invention aims to provide a preparation method and application of a pillared three-dimensional MOF-enhanced mixed matrix membrane. First, a pillared three-dimensional MOF with a large number of organophilic sites and fast mass transfer channels is prepared, and then it is doped into a polymer matrix to prepare a mixed matrix membrane. The membrane can be used in the separation of the spices 2-phenylethanol, maltol and β-damascenone.

[0007] Pervaporation membrane separation technology follows a dissolution-diffusion model. The separation performance of the membrane material is directly related to the MOF filler and polymer matrix. The filler and polymer matrix adsorb the fragrance through affinity sites, and then complete mass transfer through rapid diffusion channels. This invention uses layered and pillared ligands to synthesize a three-dimensional columnar layered MOF material. Due to the unique pore size, channel and pore surface chemistry tunability and designability, it not only has excellent separation performance but also further enhances stability. The present invention adopts a pillar coordination strategy, in which the pillar ligand bipyridine bridges the layered structure of Cu3(HHTP)2 through Cu-N coordination during the formation of Cu3(HHTP)2 to in situ construct a layered three-dimensional MOF, and at the same time constructs a three-dimensional pore, providing a fast diffusion path for 2-phenylethanol, maltol and β-damascenone; the organophilicity of the three-dimensional MOF skeleton and the π-π and hydrogen bond interactions generated by the MOF structure provide more affinity sites for spices; the three-dimensional MOF is doped with a polymer material and then coated to prepare a mixed matrix membrane. The three-dimensional MOF has excellent compatibility with the high molecular polymer, and the mixed matrix membrane has both the affinity of the three-dimensional MOF for spices and the hydrophobicity of the polymer matrix, reflecting excellent spice separation performance.

[0008] The present invention provides a method for preparing a mixed matrix membrane of in-situ constructed layered three-dimensional MOF, comprising the following steps: (1) First, a pillar coordination strategy was used to in situ construct a three-dimensional MOF with a layered pillar structure: copper metal source and 2,3,6,7,10,11-hexahydroxytriphenylene were dissolved in a solvent and stirred thoroughly to obtain metal Cu 2+ and deprotonated 2,3,6,7,10,11-hexahydroxytriphenyl ligand; then bipyridine was added to the above solution as a pillar ligand, stirred and reacted, cooled to room temperature, washed and dried to obtain a three-dimensional MOF; During the formation of MOF, 2,3,6,7,10,11-hexahydroxytriphenylene undergoes deprotonation under weak acidic conditions to form local oxygen anions, Cu 2+ Coordinated with deprotonated oxygen anions to form a two-dimensional layered framework with interlayer stacking. 2+ Because the Jahn-Teller effect tends to form an octahedral coordination structure with tetragonal distortion, while maintaining the in-plane coordination bonding to form a lamellar structure, the pillar ligand bipyridine undergoes Cu-N coordination between the layers to form a three-dimensional MOF with layer pillars.

[0009] (2) The prepared layered three-dimensional MOF is doped into a polymer matrix to prepare a casting solution, and then coated on the surface of the support. The wet film thickness is controlled by a coating machine to prepare a layered three-dimensional MOF-enhanced mixed matrix membrane.

[0010] The above-mentioned pillar coordination strategy is used to prepare the layered pillar three-dimensional MOF. In the three-dimensional MOF with a layered pillar structure constructed by the pillar coordination strategy, 2,3,6,7,10,11-hexahydroxytriphenyl is used as a ligand to react with Cu 2+ Coordination is used to construct a two-dimensional layered skeleton with stacked layers; bipyridine is used as a pillar ligand to construct a three-dimensional MOF with a layered pillar structure; and the construction process of this pillar coordination strategy is carried out in situ.

[0011] The specific process is: first prepare Cu 2+ The solution was then added with 2,3,6,7,10,11-hexahydroxytriphenyl and ultrasonically dispersed; bipyridine was then added to the dispersion and stirred; finally, the obtained solution was allowed to stand and the clear liquid was removed, and the columnar three-dimensional MOF was obtained after washing, centrifugation and drying; wherein, Cu 2+ The molar ratio of Cu to 2,3,6,7,10,11-hexahydroxytriphenyl is (0.6~1.5):1; 2 + The molar ratio of bipyridine is (0.2~2):1.

[0012] The above-mentioned preparation method has the following specific steps: (1) Preparation of layered pillar three-dimensional MOF using pillar coordination strategy: The copper metal source was dissolved in solvent A and ultrasonically dispersed for 2-12 h at a temperature of 20-80 °C, an ultrasonic frequency of 20-40 kHz, and an ultrasonic power of 400-600 W to obtain a Cu-rich 2+ Solution B, in which Cu 2+ The molar concentration of Cu is 0.05~0.5 mol / L; 2,3,6,7,10,11-hexahydroxytriphenyl is added to solution B, and ultrasonic dispersion is carried out for 2~12 h using an ultrasonic disperser at a temperature of 20~80 °C, an ultrasonic frequency of 20~40 kHz, and an ultrasonic power of 400~600 W, and then magnetic stirring is carried out for 2~12 h at a temperature of 20~80 °C and a rotation speed of 100~600 r / min to obtain a dispersion C, wherein Cu 2+ The molar ratio of Cu to 2,3,6,7,10,11-hexahydroxytriphenyl is (0.6-1.5):1; finally, bipyridine is added to dispersion C, and magnetic stirring is carried out at a temperature of 20-80 °C and a rotation speed of 100-600 r / min for 2-12 h to obtain dispersion D, in which Cu 2+The molar ratio of bipyridine to dispersion D is (0.2-2):1. Dispersion D is transferred to a glass reactor and heated at 80-150°C for 12-24 hours before cooling to room temperature. The mixture is allowed to stand for 24-48 hours, then the supernatant is removed and washed 3-5 times with deionized water and methanol, respectively. The washed product E is centrifuged at 8000-12000 r / min for 3-5 minutes and dried in a vacuum oven at 60-80°C for 10-16 hours to obtain a three-dimensional pillared MOF.

[0013] The copper metal source is any one of copper sulfate, copper acetate, copper chloride or copper nitrate; and the solvent A is any one of deionized water or a mixture of N,N-dimethylformamide / water (v / v=1:1).

[0014] (2) Preparation of layered three-dimensional MOF-enhanced mixed matrix membranes: Polymer matrix F was added to solvent G and magnetically stirred at a temperature of 20-80°C and a rotation speed of 100-600 r / min for 2-12 h to obtain dispersion H. The mass ratio of polymer matrix F to solvent G was (0.1-0.8):1. A three-dimensional MOF was added to dispersion H at a mass ratio of (0.01-0.2):1 to polymer matrix F. Dispersion I was obtained after magnetic stirring at a temperature of 20-80°C and a rotation speed of 100-600 r / min for 2-12 h. Crosslinker J and catalyst K were sequentially added to dispersion I. Crosslinking was performed under magnetic stirring at a temperature of 20-80°C and a rotation speed of 100-600 r / min for 2-12 hours to obtain a casting solution L. This casting solution L was then coated onto the surface of a porous support M. The mass ratio of crosslinker J to polymer matrix F was (0.1-1):1, and the mass ratio of catalyst K to crosslinker J was (0.05-0.2):1. Finally, thermal crosslinking was performed at 40-150°C for 12-48 hours to obtain a pillared three-dimensional MOF-reinforced mixed matrix membrane.

[0015] Among them, the type of polymer matrix is mainly any one of polydimethylsiloxane and polyether block polyamide; the crosslinker J is any one of tetraethyl orthosilicate, benzyltriethoxysilane and 2-phenylethyltriethoxysilane, the catalyst K is any one of dibutyltin dilaurate, dibutyltin maleate and tetrabutyl titanate; the solvent G is any one of n-hexane, petroleum ether, isooctane and cyclohexane; the molecular weight cutoff of the support M is 5000-50000, and the material is any one of polysulfone, polyethersulfone, polyvinylidene fluoride and polytetrafluoroethylene.

[0016] Furthermore, the present invention discloses the preparation of a mixed matrix membrane of a doped layer-pillared three-dimensional MOF, wherein the wet film thickness of the prepared mixed matrix membrane is 50-250 μm.

[0017] The present invention provides the use of the above-mentioned columnar three-dimensional MOF-enhanced mixed matrix membrane in the pervaporation separation of spices. The spices include 2-phenylethanol, maltol or β-damascenone.

[0018] Furthermore, the test layer column three-dimensional MOF-enhanced mixed matrix membrane disclosed in the present invention was used to test the separation performance of the spices 2-phenylethanol, maltol and β-damascenone using a homemade pervaporation device, and the effective area of the membrane permeation was 5~100 cm 2 The liquid flow rate is 10~300 L / h, the liquid test temperature is 20~90 ℃; the permeability test uses a vacuum pump to regulate the permeability test pressure, the absolute vacuum degree of the permeability test is 50~1000 Pa, and the permeability test time is 0.5~12 h.

[0019] This invention utilizes a pillar coordination strategy to in situ synthesize a layered three-dimensional MOF. The three-dimensional MOF not only possesses organophilic, conjugated, hydrogen-bonding, and hydrophobic interaction sites, but also provides rapid mass transfer pathways for fragrance membrane separation. Combining the advantages of the three-dimensional MOF with polymers to create a mixed-matrix membrane enhances fragrance separation.

[0020] Beneficial effects of the present invention: (1) The pillared three-dimensional MOF has affinity, conjugation and hydrogen bonding interaction sites, and hydrophobic interactions for the spices 2-phenylethanol, maltol, and β-damascenone; (2) The pillar ligand bipyridine provides support for the three-dimensional MOF and constructs three-dimensional channels, providing a rapid diffusion path for the separation of spices; (3) The mixed matrix membrane doped with pillared three-dimensional MOF has both the organophilic sites and mass transfer channels of pillared three-dimensional MOF and the hydrophobicity of the polymer matrix. Due to its good compatibility, the separation performance of the membrane is further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the preparation process of layered pillar three-dimensional MOF; Figure 2 is an infrared spectrum of the pillared three-dimensional MOF prepared in Example 1; Figure 3 is the XRD pattern of the pillared three-dimensional MOF prepared in Example 1; Figure 4 This is a diagram of the interaction mechanism between the columnar three-dimensional MOF-enhanced mixed matrix membrane and the fragrance molecules (taking phenylethanol molecules as an example). DETAILED DESCRIPTION

[0022] The present invention is further illustrated by the following examples, but is not limited to the following examples.

[0023] First, three comparative examples are given, which are the methods for preparing pure PDMS membrane, Cu3(HHTP)2 / PDMS mixed matrix membrane and polyether block amide membrane in the prior art. Comparative Example 1

[0024] Polydimethylsiloxane was added to n-hexane and magnetically stirred at 30°C and 200 r / min for 4 hours to obtain a dispersion. The mass ratio of polydimethylsiloxane to n-hexane was 0.4:1. Ethyl orthosilicate (TES) as a crosslinker and dibutyltin dilaurate (DBT) as a catalyst were sequentially added to the dispersion. Crosslinking was performed at 40°C and 300 r / min for 6 hours to obtain a casting solution. This casting solution was then coated onto a porous polysulfone support with a molecular weight cutoff of 20,000. The mass ratio of TES to polydimethylsiloxane was 0.4:1, and the mass ratio of DTBT to TES was 0.1:1. Finally, a pure PDMS membrane was obtained by thermal crosslinking at 60°C for 36 hours.

[0025] The prepared pure PDMS was subjected to pervaporation performance test on 2-phenylethanol aqueous solution at a test temperature of 80 °C and a raw material concentration of 1500 ppm. The permeation flux was 630.6 g·m -2 ·h -1 , the separation factor is 12.4. Comparative Example 2

[0026] (1) Preparation of Cu3(HHTP)2 Copper acetate was dissolved in deionized water and ultrasonically dispersed for 4 h at a temperature of 50 °C, an ultrasonic frequency of 20 kHz, and an ultrasonic power of 600 W to obtain Cu-rich 2+ Solution A, in which Cu 2+ The molar concentration of Cu was 0.1 mol / L; 2,3,6,7,10,11-hexahydroxytriphenyl was added to solution A, and ultrasonic dispersion was carried out for 3 h at a temperature of 50 °C, an ultrasonic frequency of 20 kHz, and an ultrasonic power of 600 W, and then magnetic stirring was carried out for 2 h at a temperature of 50 °C and a rotation speed of 100 r / min to obtain dispersion B, in which Cu 2+ The molar ratio of HHTP to 2,3,6,7,10,11-hexahydroxytriphenyl was 0.6:1; the dispersion B was transferred to a glass reactor, heated at 100 °C for 12 h, cooled to room temperature, and allowed to stand for 24 h before removing the supernatant. The mixture was then washed 5 times with deionized water and methanol, respectively. The washed product C was centrifuged at 8000 r / min for 3 min in a high-speed centrifuge and dried in a vacuum oven at 60 °C for 10 h to obtain Cu3(HHTP)2.

[0027] (2) Preparation of Cu3(HHTP)2 / PDMS mixed matrix membrane: Polydimethylsiloxane was added to cyclohexane and magnetically stirred at 50°C and 100 r / min for 2 h to obtain Dispersion D. The mass ratio of polydimethylsiloxane to cyclohexane was 0.8:1. Cu₃(HHTP)₂ was added to Dispersion D at a mass ratio of 0.01:1 to polydimethylsiloxane. Dispersion E was obtained after magnetic stirring at 80°C and 300 r / min for 5 h. The crosslinker, benzyltriethoxysilane, and the catalyst, dibutyltin dilaurate, were sequentially added to the dispersion. Crosslinking was performed under magnetic stirring at 80°C and 300 r / min for 6 h to obtain a casting solution. This solution was then coated onto a porous polytetrafluoroethylene support with a molecular weight cutoff of 50,000. The mass ratio of benzyltriethoxysilane to polydimethylsiloxane was 0.6:1, and the mass ratio of dibutyltin dilaurate to benzyltriethoxysilane was 0.5:1. Finally, a Cu₃(HHTP)₂ / PDMS mixed matrix membrane was obtained by thermal crosslinking at 100°C for 12 h.

[0028] The prepared Cu3(HHTP)2 / PDMS mixed matrix membrane was tested for pervaporation performance of 2-phenylethanol aqueous solution at a test temperature of 80 ℃ and a raw material concentration of 1500 ppm. The permeation flux was 1046.1 g·m -2 ·h -1 , the separation factor is 23.4. Comparative Example 3

[0029] A polyether block polyamide (PEBA) was added to n-hexane and magnetically stirred at 40°C and 200 r / min for 3 hours to obtain a casting solution. The mass ratio of PEBA to n-hexane was 0.5:1. The casting solution was then coated onto a porous polytetrafluoroethylene (PTFE) support with a molecular weight cut-off of 10,000. Finally, the PBA membrane was thermally cross-linked at 100°C for 20 hours to obtain the membrane.

[0030] The prepared polyether block amide membrane was tested for the permeation vaporization performance of maltol aqueous solution at a test temperature of 60 °C and a raw material concentration of 1000 ppm. The permeation flux was 387.1 g·m -2 ·h -1 , the separation factor is 9.7. The prepared polyether block amide membrane was then used to test the permeation vaporization performance of β-damascenone aqueous solution at a test temperature of 50 °C and a raw material concentration of 300 ppm. The permeation flux was 270.0 g·m -2 ·h -1 , the separation factor is 7.3.

[0031] The following is a method for preparing a columnar three-dimensional MOF-enhanced mixed matrix membrane using the method of the present invention. Compared with the above comparative example, the use of pervaporation to separate 2-phenylethanol, maltol and β-damascenone aqueous solutions provides affinity sites and permeation mass transfer paths for the preferential permeation of organic fragrances, thereby improving the permeation flux and separation factor. Example 1

[0032] (1) Preparation of layered three-dimensional MOF: Copper sulfate was dissolved in deionized water and ultrasonically dispersed for 10 h at a temperature of 30 °C, an ultrasonic frequency of 40 kHz, and an ultrasonic power of 400 W to obtain Cu-rich 2+ Solution A, in which Cu 2+ The molar concentration of Cu was 0.05 mol / L; 2,3,6,7,10,11-hexahydroxytriphenyl was added to solution A, and ultrasonic dispersion was carried out for 2 h at a temperature of 30 °C, an ultrasonic frequency of 40 kHz, and an ultrasonic power of 400 W, and then magnetic stirring was carried out for 10 h at a temperature of 30 °C and a rotation speed of 200 r / min to obtain dispersion B, in which Cu 2+ The molar ratio of Cu to 2,3,6,7,10,11-hexahydroxytriphenyl was 1:1; finally, bipyridine was added to dispersion B, and the dispersion C was obtained after magnetic stirring at a temperature of 30 °C and a rotation speed of 300 r / min for 5 h. 2+ The molar ratio of bipyridine to dispersion C was 0.2:1. Dispersion C was transferred to a glass reactor and heated at 80°C for 24 hours before cooling to room temperature. After standing for 48 hours, the supernatant was removed and washed five times with deionized water and methanol, respectively. The washed product D was centrifuged at 10,000 r / min for 5 minutes and dried in a vacuum oven at 60°C for 16 hours to obtain a three-dimensional pillared MOF.

[0033] (2) Preparation of layered three-dimensional MOF-reinforced mixed matrix membranes: Polydimethylsiloxane was added to petroleum ether and magnetically stirred at 20°C and 100 r / min for 3 h to obtain Dispersion E. The mass ratio of polydimethylsiloxane to petroleum ether was 0.3:1. A three-dimensional MOF was added to Dispersion E at a mass ratio of 0.01:1 to polydimethylsiloxane and magnetically stirred at 20°C and 100 r / min for 6 h to obtain Dispersion F. Ethyl orthosilicate (TES) as a crosslinker and dibutyltin maleate (DBTM) as a catalyst were sequentially added to Dispersion F. Crosslinking was achieved by magnetic stirring at 20°C and 100 r / min for 5 h to obtain a casting solution. This casting solution was coated onto a porous polyethersulfone support with a molecular weight cutoff of 5000 by a coating method. The mass ratios of TES to PDMS were 0.6:1 and 0.05:1, respectively. Finally, the layered three-dimensional MOF-reinforced mixed matrix membrane was obtained by thermal cross-linking at 80 °C for 12 h.

[0034] The prepared columnar three-dimensional MOF-enhanced mixed matrix membrane was tested for pervaporation performance of 2-phenylethanol aqueous solution at a test temperature of 80 °C and a raw material concentration of 1500 ppm. The permeation flux was 1364.8 g·m -2 ·h -1 , the separation factor is 31.2. Example 2

[0035] (1) Preparation of layered three-dimensional MOF: Copper nitrate was dissolved in N, N-dimethylformamide / water (v / v=1:1) and ultrasonically dispersed for 4 h at a temperature of 60 °C, an ultrasonic frequency of 30 kHz, and an ultrasonic power of 500 W to obtain a Cu-rich 2+ Solution A, in which Cu 2 + The molar concentration of 2,3,6,7,10,11-hexahydroxytriphenyl was added to solution A, and ultrasonic dispersion was carried out for 5 h at a temperature of 60 °C, an ultrasonic frequency of 30 kHz, and an ultrasonic power of 500 W. Then, magnetic stirring was carried out for 4 h at a temperature of 60 °C and a rotation speed of 300 r / min to obtain dispersion B, in which Cu 2+ The molar ratio of Cu to 2,3,6,7,10,11-hexahydroxytriphenyl was 0.7:1. Finally, bipyridine was added to dispersion B, and magnetic stirring was carried out at a temperature of 60 °C and a rotation speed of 300 r / min for 10 h to obtain dispersion C, in which Cu 2+The molar ratio of bipyridine to dispersion C was 1:1. Dispersion C was transferred to a glass reactor and heated at 120°C for 36 hours before cooling to room temperature. After standing for 30 hours, the supernatant was removed and washed five times with deionized water and methanol, respectively. The washed product D was centrifuged at 9000 r / min for 5 minutes and dried in a vacuum oven at 70°C for 18 hours to obtain a three-dimensional pillared MOF.

[0036] (2) Preparation of layered three-dimensional MOF-reinforced mixed matrix membranes: Polyether block polyamide was added to n-hexane and magnetically stirred at 30°C and 200 r / min for 5 hours to obtain dispersion E. The mass ratio of polyether block polyamide to n-hexane was 0.5:1. A three-dimensional MOF was added to dispersion E at a mass ratio of 0.05:1 to polyether block polyamide. The mixture was magnetically stirred at 30°C and 200 r / min for 4 hours to obtain a casting solution. This casting solution was then coated onto a porous polytetrafluoroethylene support with a molecular weight cutoff of 20,000. Finally, the membrane was thermally cross-linked at 100°C for 20 hours to obtain a pillared three-dimensional MOF-reinforced mixed matrix membrane.

[0037] The prepared columnar three-dimensional MOF-enhanced mixed matrix membrane was tested for the permeation vaporization performance of maltol aqueous solution at a test temperature of 60 °C and a raw material concentration of 1000 ppm. The permeation flux was 1029.2 g·m -2 ·h -1 , the separation factor is 16.1. Example 3

[0038] (1) Preparation of layered three-dimensional MOF: Copper acetate was dissolved in deionized water and ultrasonically dispersed for 5 h at a temperature of 40 °C, an ultrasonic frequency of 20 kHz, and an ultrasonic power of 400 W to obtain Cu-rich 2+ Solution A, in which Cu 2+ The molar concentration of Cu was 0.4 mol / L; 2,3,6,7,10,11-hexahydroxytriphenyl was added to solution A, and ultrasonic dispersion was carried out for 5 h at a temperature of 40 °C, an ultrasonic frequency of 20 kHz, and an ultrasonic power of 400 W, and then magnetic stirring was carried out for 8 h at a temperature of 40 °C and a rotation speed of 150 r / min to obtain dispersion B, in which Cu 2+ The molar ratio of Cu to 2,3,6,7,10,11-hexahydroxytriphenyl was 1.2:1. Finally, bipyridine was added to dispersion B, and the dispersion C was obtained after magnetic stirring at 60 °C and 300 r / min for 10 h. 2+The molar ratio of bipyridine to dispersion C was 1.5:1. Dispersion C was transferred to a glass reactor and heated at 150°C for 48 hours before cooling to room temperature. After standing for 36 hours, the supernatant was removed and washed five times with deionized water and methanol, respectively. The washed product D was centrifuged at 13,000 r / min for 5 minutes and dried in a vacuum oven at 60°C for 20 hours to obtain a three-dimensional pillared MOF.

[0039] (2) Preparation of layered three-dimensional MOF-reinforced mixed matrix membranes: Polyether block polyamide was added to cyclohexane and magnetically stirred at 45°C and 250 r / min for 6 h to obtain dispersion E. The mass ratio of polyether block polyamide to cyclohexane was 0.8:1. A three-dimensional MOF was added to dispersion E at a mass ratio of 0.1:1 to polyether block polyamide. The mixture was magnetically stirred at 45°C and 250 r / min for 5 h to obtain a casting solution. This casting solution was then coated onto a porous polyvinylidene fluoride support with a molecular weight cutoff of 25,000. Finally, the mixture was thermally cross-linked at 150°C for 25 h to obtain a pillared three-dimensional MOF-reinforced mixed matrix membrane.

[0040] The prepared columnar three-dimensional MOF-enhanced mixed matrix membrane was subjected to pervaporation performance test on β-damascenone aqueous solution at a test temperature of 50 °C and a raw material concentration of 300 ppm. The permeation flux was 493.7 g·m -2 ·h -1 , the separation factor is 17.7. Example 4

[0041] (1) Preparation of layered three-dimensional MOF: Copper sulfate was dissolved in N, N-dimethylformamide / water (v / v=1:1) and ultrasonically dispersed for 5 h at a temperature of 25 °C, an ultrasonic frequency of 40 kHz, and an ultrasonic power of 600 W to obtain Cu-rich 2+ Solution A, in which Cu 2 + The molar concentration of 2,3,6,7,10,11-hexahydroxytriphenyl was added to solution A, and ultrasonic dispersion was carried out for 4 h at a temperature of 25 °C, an ultrasonic frequency of 40 kHz, and an ultrasonic power of 600 W. Then, magnetic stirring was carried out for 12 h at a temperature of 25 °C and a rotation speed of 200 r / min to obtain dispersion B, in which Cu 2+The molar ratio of Cu to 2,3,6,7,10,11-hexahydroxytriphenyl was 1.2:1. Finally, bipyridine was added to dispersion B, and the dispersion was stirred magnetically at 25 °C and 200 r / min for 12 h to obtain dispersion C. 2+ The molar ratio of bipyridine to dispersion C was 1.5:1. Dispersion C was transferred to a glass reactor and heated at 130°C for 24 hours before cooling to room temperature. After standing for 40 hours, the supernatant was removed and washed five times with deionized water and methanol, respectively. The washed product D was centrifuged at 10,000 r / min for 5 minutes and dried in a vacuum oven at 80°C for 15 hours to obtain a three-dimensional pillared MOF.

[0042] (2) Preparation of mixed matrix membranes of doped layer-pillared three-dimensional MOFs: Polydimethylsiloxane was added to n-hexane and magnetically stirred at 30°C and 280 r / min for 4 h to obtain Dispersion E. The mass ratio of polydimethylsiloxane to n-hexane was 0.6:1. A three-dimensional MOF was added to Dispersion E at a mass ratio of 0.15:1 to polydimethylsiloxane. Dispersion F was obtained after magnetic stirring at 30°C and 280 r / min for 6 h. The crosslinker benzyltriethoxysilane and the catalyst dibutyltin maleate were sequentially added to dispersion F. After crosslinking at 30°C and 280 r / min under magnetic stirring for 10 h, a casting solution was obtained. This casting solution was then coated onto a porous polysulfone support with a molecular weight cutoff of 50,000. The mass ratio of benzyltriethoxysilane to polydimethylsiloxane was 0.8:1, and the mass ratio of dibutyltin maleate to benzyltriethoxysilane was 0.2:1. Finally, a pillared three-dimensional MOF-reinforced mixed matrix membrane was obtained by thermal crosslinking at 80°C for 12 h.

[0043] The prepared columnar three-dimensional MOF-enhanced mixed matrix membrane was subjected to pervaporation performance test on 2-phenylethanol aqueous solution at a test temperature of 70 °C and a raw material concentration of 2500 ppm. The permeation flux was 1749.8 g·m -2 ·h -1 , the separation factor is 24.3. Example 5

[0044] (1) Preparation of layered three-dimensional MOF: Copper acetate was dissolved in N, N-dimethylformamide / water (v / v=1:1) and ultrasonically dispersed for 10 h at a temperature of 80 °C, an ultrasonic frequency of 20 kHz, and an ultrasonic power of 480 W to obtain a Cu-rich 2+ Solution A, in which Cu 2+The molar concentration of Cu was 0.5 mol / L; 2,3,6,7,10,11-hexahydroxytriphenyl was added to solution A, and ultrasonic dispersion was carried out for 10 h at a temperature of 80 °C, an ultrasonic frequency of 20 kHz, and an ultrasonic power of 480 W, and then magnetic stirring was carried out for 6 h at a temperature of 80 °C and a rotation speed of 400 r / min to obtain dispersion B, in which Cu 2+ The molar ratio of Cu to 2,3,6,7,10,11-hexahydroxytriphenyl was 1.5:1. Finally, bipyridine was added to dispersion B, and magnetic stirring was carried out at a temperature of 80 °C and a rotation speed of 400 r / min for 12 h to obtain dispersion C, in which Cu 2+ The molar ratio of bipyridine to dispersion C was 2:1. Dispersion C was transferred to a glass reactor and heated at 150°C for 24 hours before cooling to room temperature. After standing for 48 hours, the supernatant was removed and washed five times with deionized water and methanol, respectively. The washed product D was centrifuged at 12,000 r / min for 5 minutes and dried in a vacuum oven at 80°C for 15 hours to obtain a three-dimensional pillared MOF.

[0045] (2) Preparation of mixed matrix membranes of doped layer-pillared three-dimensional MOFs: Polyether block polyamide was added to n-hexane and magnetically stirred at 80°C and 200 r / min for 6 h to obtain dispersion E. The mass ratio of polyether block polyamide to cyclohexane was 0.8:1. A three-dimensional MOF was added to dispersion E at a mass ratio of 0.2:1 to polyether block polyamide. This was magnetically stirred at 80°C and 200 r / min for 6 h to obtain a casting solution. This casting solution was then coated onto a porous polysulfone support with a molecular weight cutoff of 20,000. Finally, the membrane was thermally cross-linked at 150°C for 24 h to obtain a pillared three-dimensional MOF-reinforced mixed matrix membrane.

[0046] The prepared three-dimensional MOF-enhanced mixed matrix membrane was subjected to pervaporation performance test on 2-phenylethanol aqueous solution at a test temperature of 80 °C and a raw material concentration of 1500 ppm. The permeation flux was 1633.3 g·m -2 ·h -1 , the separation factor is 34.2.

[0047] Attachment Figure 1 The figure shows the preparation process of layered pillar three-dimensional MOF: In the preparation process of three-dimensional MOF with layered pillar structure, 2,3,6,7,10,11-hexahydroxytriphenyl (HHTP) is used as a ligand, which is deprotonated under weak acidic conditions to form local oxygen anions, and Cu 2+ Coordinated with deprotonated oxygen anions to form a two-dimensional layered framework with interlayer stacking.2+ Because the Jahn-Teller effect tends to form an octahedral coordination structure with tetragonal distortion, while maintaining the in-plane coordination bonding to form a lamellar structure, the pillar ligand bipyridine (BPY) undergoes Cu-N coordination between the layers to construct a three-dimensional MOF with a layered pillar structure; and the construction process of this pillar coordination strategy is carried out in situ.

[0048] Attachment Figure 2 The infrared spectrum of the pillared three-dimensional MOF prepared in Example 1 is shown: at 568 cm -1 、 1446 cm -1 and 1641 cm -1 The absorption peaks are Cu-O (stretching vibration), C=C (aromatic ring skeleton stretching vibration), and C=O (stretching vibration) belonging to the three-dimensional MOF (line number C). The C=O absorption peak is caused by the deprotonation of the hydroxyl group of the ligand 2,3,6,7,10,11-hexahydroxytriphenyl during the coordination process. The C=N bond of bipyridine was detected at 1591 cm after coordination with the bipyridine column (line number B). -1 The diffraction peak shifted slightly to 1612 cm -1 , confirming that bipyridine and Cu 2+ The infrared spectrum of line number A is the MOF constructed without bipyridine pillar coordination, which serves as a comparison to illustrate the successful synthesis of layered pillar three-dimensional MOF.

[0049] Attachment Figure 3 The XRD pattern of the pillared three-dimensional MOF prepared in Example 1 is shown as follows: the pillared three-dimensional MOF (line number C) corresponds to the (110), (040), (220), (240), (310), (260) and (001) crystal planes at 4.77°, 9.46°, 9.54°, 12.59°, 12.85°, 16.47° and 27.77°, respectively. When the bipyridine pillars are successfully coordinated, the three-dimensional MOF generates new crystal plane peaks at 11.32°, 19.28° and 22.80°. The generated new peaks are different from the XRD pattern of bipyridine, excluding the possibility of physical blending, thus proving that the three-dimensional MOF is successfully constructed.

[0050] Attachment Figure 4 The figure shows the mechanism of interaction between the columnar three-dimensional MOF and the spice molecules (taking phenylethanol molecules as an example): the interlayer channels constructed by the columnar three-dimensional MOF can serve as a rapid mass transfer path for the spice molecules. The path channels are distributed with affinity sites with π-π interactions and hydrogen bond interactions, which can prioritize the passage of spice molecules, thereby achieving the purpose of spice separation.

[0051] In summary, the permeation flux of the pure PDMS membrane in Comparative Example 1 at a test temperature of 80 °C and a raw material concentration of 1500 ppm for 2-phenylethanol aqueous solution is 630.6 g·m -2 ·h -1 , the separation factor is 12.4; the permeation flux of 2-phenylethanol aqueous solution of Cu3(HHTP)2 / PDMS mixed matrix membrane prepared in Comparative Example 2 is 1046.1 g·m at a test temperature of 80 ℃ and a raw material concentration of 1500 ppm. -2 ·h -1 , the separation factor is 23.4. Compared with Comparative Examples 1 and 2, the separation performance of the pillared three-dimensional MOF-enhanced mixed matrix membranes prepared in Examples 1, 4 and 5 for 2-phenylethanol was significantly improved. The permeation flux of the pillared three-dimensional MOF-enhanced mixed matrix membrane prepared in Example 1 for 2-phenylethanol aqueous solution was 1364.8 g·m at a test temperature of 80°C and a raw material concentration of 1500 ppm. -2 ·h -1 , the separation factor was 31.2. Compared with Comparative Example 1, the permeation flux and separation factor increased by 116% and 152% respectively. In Example 4, the prepared three-dimensional MOF-enhanced mixed matrix membrane was subjected to a permeation vaporization performance test on a 2-phenylethanol aqueous solution at a test temperature of 70°C and a raw material concentration of 2500 ppm. The permeation flux was 1749.8 g·m -2 ·h -1 , the separation factor is 24.3. Increasing the concentration of 2-phenylethanol in the raw material solution will greatly increase the permeation flux, and the separation factor will slightly decrease. Example 5 has the greatest improvement in the separation performance of 2-phenylethanol. Under the conditions of test temperature of 80 ° C and raw material concentration of 1500 ppm, the permeation flux of 2-phenylethanol aqueous solution is 1633.3 g·m -2 ·h -1 , the separation factor was 34.2, and the permeation flux and separation factor were increased by 159% and 176% compared with Comparative Example 1. The permeation flux and separation factor of Examples 1, 4 and 5 were greatly improved compared with Comparative Example 2. The permeation flux of the polyether block amide membrane prepared in Comparative Example 3 was 387.1 g·m under the conditions of a test temperature of 60°C and a raw material concentration of 1000 ppm for the maltol aqueous solution. -2 ·h -1 , the separation factor was 9.7; the permeation flux of β-damascenone aqueous solution was 270.0 g·m at a test temperature of 50 ℃ and a raw material concentration of 300 ppm. -2 ·h -1, with a separation factor of 7.3. Compared to Comparative Example 3, the permeation flux and separation factor of maltol and β-damascenone in Examples 2 and 3 were also significantly improved. It can be seen that the columnar three-dimensional MOF-enhanced mixed matrix membrane significantly improved the permeation flux and separation factor of the spices 2-phenylethanol, maltol, and β-damascenone. The reasons are as follows: (1) Through the pillar coordination strategy, the pillar ligand bipyridine is bridged to the layered structure of Cu3(HHTP)2 through Cu-N coordination during the formation of Cu3(HHTP)2 to in situ construct a layered three-dimensional MOF, and at the same time, a three-dimensional pore is constructed to provide a fast diffusion path for 2-phenylethanol, maltol and β-damascenone; (2) The organophilicity of the three-dimensional MOF skeleton and the π-π and hydrogen bond interactions generated by the MOF structure provide more affinity sites for spices; (3) The three-dimensional MOF is doped with polymer materials and then coated to prepare a mixed matrix membrane. The three-dimensional MOF has excellent compatibility with high molecular polymers. The mixed matrix membrane has both the affinity of the three-dimensional MOF for spices and the hydrophobicity of the polymer matrix, showing excellent fragrance separation performance.

[0052] Although the present invention has been described above, the present invention is not limited to the above-mentioned specific embodiments. The above-mentioned specific embodiments are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can make many variations without departing from the purpose of the present invention. These variations are all within the protection of the present invention.

[0053] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a layered three-dimensional MOF-enhanced mixed matrix membrane, characterized in that The following steps are involved: (1) First, a pillar coordination strategy was used to in situ construct a three-dimensional MOF with a layered pillar structure: copper metal source and 2,3,6,7,10,11-hexahydroxytriphenylene were dissolved in a solvent and stirred thoroughly to obtain metal Cu 2+ and deprotonated 2,3,6,7,10,11-hexahydroxytriphenyl ligand; then bipyridine was added to the above solution as a pillar ligand, stirred and reacted, cooled to room temperature, washed and dried to obtain a layered pillar three-dimensional MOF; (2) The prepared layered three-dimensional MOF is doped into a polymer matrix to prepare a casting solution, and then coated on the surface of the support. The wet film thickness is controlled by a coating machine, and a layered three-dimensional MOF-enhanced mixed matrix membrane is prepared.

2. The method for preparing a pillared three-dimensional MOF-enhanced mixed matrix membrane according to claim 1, characterized in that: The pillar coordination strategy was used to prepare the layered three-dimensional MOF. The specific process was as follows: first, a Cu-containing 2+ The solution was then added with 2,3,6,7,10,11-hexahydroxytriphenyl and ultrasonically dispersed; bipyridine was then added to the dispersion and stirred; finally, the obtained solution was allowed to stand and the supernatant was removed, and the columnar three-dimensional MOF was obtained after washing, centrifugation and drying; wherein, Cu 2+ The molar ratio of Cu to 2,3,6,7,10,11-hexahydroxytriphenyl is (0.6~1.5):1; 2+ The molar ratio of bipyridine is (0.2~2):

1.

3. The method for preparing a pillared three-dimensional MOF-reinforced mixed matrix membrane according to claim 1, characterized in that: The wet film thickness of the prepared mixed matrix membranes ranged from 50 to 250 μm.

4. The method for preparing a pillared three-dimensional MOF-reinforced mixed matrix membrane according to claim 1, characterized in that: The specific steps are as follows: (1) Preparation of layered pillar three-dimensional MOF using pillar coordination strategy: The copper metal source was dissolved in solvent A and ultrasonically dispersed for 2-12 h at a temperature of 20-80 °C, an ultrasonic frequency of 20-40 kHz, and an ultrasonic power of 400-600 W to obtain a Cu-rich 2+ Solution B, in which Cu 2+ The molar concentration of Cu is 0.05~0.5 mol / L; 2,3,6,7,10,11-hexahydroxytriphenyl is added to solution B, and ultrasonic dispersion is carried out for 2~12 h using an ultrasonic disperser at a temperature of 20~80 °C, an ultrasonic frequency of 20~40 kHz, and an ultrasonic power of 400~600 W, and then magnetic stirring is carried out for 2~12 h at a temperature of 20~80 °C and a rotation speed of 100~600 r / min to obtain a dispersion C, wherein Cu 2+ The molar ratio of Cu to 2,3,6,7,10,11-hexahydroxytriphenyl is (0.6-1.5):1; finally, bipyridine is added to dispersion C, and magnetic stirring is carried out at a temperature of 20-80 °C and a rotation speed of 100-600 r / min for 2-12 h to obtain dispersion D, in which Cu 2+ The molar ratio of bipyridine to dispersion D is (0.2-2):1; the dispersion D is transferred to a glass reactor, heated at 80-150°C for 12-24 hours, cooled to room temperature, and allowed to stand for 24-48 hours. The supernatant is removed and washed with deionized water and methanol 3-5 times, respectively. The washed product E is centrifuged at a speed of 8000-12000 r / min for 3-5 minutes and dried in a vacuum oven at a temperature of 60-80°C for 10-16 hours to obtain a layered three-dimensional MOF. (2) Preparation of layered three-dimensional MOF-enhanced mixed matrix membranes: The polymer matrix F was added to the solvent G, and the mixture was magnetically stirred at a temperature of 20-80 °C and a rotation speed of 100-600 r / min for 2-12 h to obtain a dispersion H, wherein the mass ratio of the polymer matrix F to the solvent G was (0.1-0.8):

1. The three-dimensional MOF was added to the dispersion H at a mass ratio of (0.01-0.2):1 to the polymer matrix F, and the mixture was magnetically stirred at a temperature of 20-80 °C and a rotation speed of 100-600 r / min for 2-12 h to obtain a dispersion I. The crosslinking agent J and the catalyst K were sequentially added to the dispersion I, and the mixture was magnetically stirred at a temperature of 20-80 °C and a rotation speed of 100-600 r / min for 2-12 h to obtain a dispersion I. After h, the casting liquid L is obtained, and the casting liquid L is coated on the surface of the porous support M by a coating method, wherein the mass ratio of the crosslinker J to the polymer matrix F is (0.1~1):1, and the mass ratio of the catalyst K to the crosslinker J is (0.05~0.2):1; finally, the layered three-dimensional MOF-reinforced mixed matrix membrane is obtained by thermal crosslinking at 40~150℃ for 12~48h.

5. The method for preparing a pillared three-dimensional MOF-reinforced mixed matrix membrane according to claim 4, characterized in that: In step (1), the copper metal source is any one of copper sulfate, copper acetate, copper chloride or copper nitrate; the solvent A is any one of deionized water or N,N-dimethylformamide / water mixture; in the N,N-dimethylformamide / water mixture, the volume ratio of N,N-dimethylformamide to water is 1:

1.

6. The method for preparing a pillared three-dimensional MOF-reinforced mixed matrix membrane according to claim 4, characterized in that: In step (2), the polymer matrix is any one of polydimethylsiloxane and polyether block polyamide; the crosslinking agent J is any one of ethyl orthosilicate, benzyltriethoxysilane and 2-phenylethyltriethoxysilane; the catalyst K is any one of dibutyltin dilaurate, dibutyltin maleate and tetrabutyl titanate; the solvent G is any one of n-hexane, petroleum ether, isooctane and cyclohexane; the support M has a molecular weight cutoff of 5000-50000 and is made of any one of polysulfone, polyethersulfone, polyvinylidene fluoride and polytetrafluoroethylene.

7. Use of a pillared three-dimensional MOF-enhanced mixed matrix membrane prepared by the preparation method according to any one of claims 1 to 6 in the pervaporation separation of spices.

8. The use according to claim 7, characterized in that: The fragrance is 2-phenylethanol, maltol or beta-damascenone.

9. The use according to claim 7, characterized in that: The effective area of membrane permeation is 5~100 cm 2 The liquid flow rate is 10~300 L / h, the liquid test temperature is 20~90 ℃; the permeability test uses a vacuum pump to regulate the permeability test pressure, the absolute vacuum degree of the permeability test is 50~1000 Pa, and the permeability test time is 0.5~12 h.

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