Polyamide membrane having regular pore structure, and manufacturing method therefor

Abstract

Provided are a polyamide membrane that maintains a regular pore structure even in an organic solvent, has long-term stability, has excellent selectivity, and has a high separation efficiency, as well as a manufacturing method therefor. This polyamide membrane, which is formed by polymerizing an aminoporphyrin monomer and an acid chloride monomer, has a regular pore structure and a crystalline structure. The porphyrin is expanded in a horizontal direction of the membrane due to the side functional groups of the quadrilateral, and forms pore channels in a vertical direction due to the macrocycle (macrocycle compound). Additionally, the porphyrin is characterized by being protonated. Due to the porphyrin being protonated, deviation occurs in accordance with the degree of protonation of the porphyrin, the sliding distance of a stack of the aminoporphyrin monomer is adjusted, a change occurs in the vertical pore channels, and the pore size is adjusted.

Description

Polyamide film having a regular pore structure and method for producing the same

[0001] The present invention relates to a polyamide film having a regular pore structure and a method for producing the same.

[0002] Recently, achieving carbon neutrality has become a major challenge. ２ The chemical industry accounts for a large portion of total emissions, and in particular, distillation is the dominant method of chemical separation, which consumes energy and produces a lot of CO2. ２ The problem lies in the discharge of wastewater. For example, in seawater desalination, separation with less energy has been achieved using separation membranes, but in the separation of organic liquids (for example, separation of organic liquid solvents in the chemical industry or separation of valuable substances dissolved in organic liquids), energy-intensive separation methods such as distillation are still the main method used. Therefore, research is being conducted to apply separation membranes to the separation of organic liquids as well.

[0003] In the separation of organic liquids, the separation membrane must, of course, be made of a material that is resistant to organic liquids. Polyamide materials, which have been conventionally used as membrane materials, are resistant to a relatively wide range of organic liquids, including polar solvents such as alcohols. On the other hand, organic solvent nanofiltration (OSN) is expected to reduce energy costs by approximately 90% by efficiently recovering solvents in fields such as pharmaceuticals, food, and electronic component manufacturing such as semiconductor manufacturing and liquid crystal panel manufacturing. However, conventional OSN membranes have problems such as a significant decrease in separation efficiency due to issues such as swelling of the structure in organic solvents and a decrease in electrostatic interaction between the solute and the membrane surface. In addition, conventional polyamide OSN membranes have problems such as not showing sufficient selective permeability.

[0004] Polyamide materials are primarily fabricated using interfacial polymerization (IP) methods, and research in this area is progressing globally (see, for example, Non-Patent Literature 1). Non-Patent Literature 1 discloses the use of a film fabricated by interfacial polymerization on a polyketone support as an organic solvent reverse osmosis membrane for the separation of organic solvents. The main film structure is a polyamide film formed by interfacial polymerization of a diamine aqueous solution and an acid chloride organic solution, and the polyamide skin layer, which is composed of the outermost polyamide film, dominates the film's performance. The polyamide skin layer is a dense, thin layer (less than 1 μm) that exhibits reverse osmosis membrane performance (blocking ionic components, etc.), and is formed on a porous support film such as a polysulfone support film layer, functioning as a separation membrane that selectively separates water and ions. However, because polyamide films are formed by polymerization, their pore structure lacks regularity and has a pore size distribution, posing challenges to selective separation. In particular, the blocking performance due to charge repulsion is reduced in organic solvents, so there has been a desire for a polymer film that has a regular structure.

[0005] For example, it is known that OSN films of thin-film composite polyamides can be fabricated on porous polyketone supports by controlling the interfacial polymerization of m-phenylenediamine (MPD) and trimesoyl chloride (TMC) using acetone as an organic cosolvent (Non-Patent Literature 2). It has been reported that the addition of acetone broadens the reaction zone of interfacial polymerization, promotes a more vigorous exothermic reaction, accelerates the evaporation of acetone, and as a result forms a three-dimensional honeycomb structure with a high specific surface area, improving methanol solvent permeability and methyl orange (MO) rejection.

[0006] Furthermore, a film formed by assembling aluminum formate during the conversion process from amorphous to crystalline is known to have a regular structure of sub-nanometer-scale channels and possess high selectivity and permeability (Non-Patent Literature 3). This film is a metal-organic framework (MOF) film, formed by metal ions and organic ligands, and is a porous film with uniform micropores and a high specific surface area, possessing a highly regular lattice structure. However, this film has low structural stability with respect to water and cannot be used in systems containing water. Since some organic solvents, such as waste liquids, contain water, this film cannot be used in such applications.

[0007] Furthermore, as a covalent organic framework (COF) membrane, a polymer separation membrane with uniform micropores and high chemical stability is known, which is fabricated by interfacial polymerization of an azine-bonded membrane on a hydrolyzed polyacrylonitrile substrate (Non-Patent Literature 4). This membrane showed long-term stability along with resistance to organic solvents and pH, but the minimum pore size was approximately 1 nm, making it difficult to separate sub-nanometer scale molecules. Typical COF membranes are imines and imides synthesized by the condensation of aldehydes and amines, carboxylic acids and amines, boroxines synthesized by the self-condensation of boronic acids, and boronic acid esters synthesized by the condensation of boronic acids and catechols (polyamides are not included). By condensing two types of organic molecules, they are periodically linked by covalent bonds, resulting in a crystalline porous material with a two- or three-dimensional periodic structure. COF membranes are considered ideal for precise molecular separation compared to conventional polymer membranes because of their sharp pore size distribution, small molecular weight cutoff size, and robust structure.

[0008] The polyamide film of the present invention uses an aminoporphyrin monomer as one of the constituent units of the film, and Patent Document 1 is a prior art document related to this. In the thin-film composite film containing a porous layer of organic polymer disclosed in Patent Document 1, the organic polymer contains macrocycles, and the macrocycles contain porphyrins. However, there is no disclosure or suggestion regarding controlling the stacking behavior of porphyrins to adjust the pore size.

[0009] International public brochure WO2020 / 072594

[0010] C. Liu et al., “Organic Liquid Mixture Separation Using an Aliphatic Polyketone-Supported Polyamide Organic Solvent Reverse Osmosis (OSRO) Membrane”, ACS Applied Materials and Interfaces, Vol.12(6), 7586 (2020).W. Fu et al., “Polyamide composite membrane with 3D honeycomb-like structure via acetone-regulated interfacial polymerization for high-efficiency organic solvent nanofiltration”, Journal of Membrane Science 679, 121711 (2023).D. C. Shi et al., “Intercrystalline Channels at Subnanometer Scale for Precise Molecular Nanofiltration”, Journal of the American Chemical Society, 145, 15848 (2023).D. Liu et al., “Moderately Crystalline Azine-Linked Covalent Organic Framework Membrane for Ultrafast Molecular Sieving”, ACS Applied Materials and Interfaces, Vol.13(31), 37775 (2021).

[0011] As mentioned above, conventional separation membranes used on a large scale in industry are specialized for water treatment processes, and the development of membranes for organic solvent separation has not been sufficiently considered. Separation membranes suitable for membrane separation in organic solvent systems and capable of achieving high permeability are essential. However, for polyamide membranes that can be applied to harsh solvents such as organic solvents, especially nanofiltration (NF) membranes, the robustness of nanochannels and precise pore control of the membrane are important for achieving molecular separation in harsh solvents, but the reality is that separation efficiency is significantly reduced due to problems such as swelling of the structure in organic solvents and a decrease in electrostatic interaction between the solute and the membrane surface.

[0012] Furthermore, the aforementioned covalent organic framework (COF) membranes have the potential to form an ideal topological network with minimized molecular transport pathways and precisely set molecular weight cut-offs (MWCO), overcoming the trade-off between solvent permeability and selectivity in membrane separation performance. Their conjugated structure, rich in phenyl groups, provides uniform pores and stability. However, the fabrication of COF membranes involves polycrystalline growth and lamination processes, which are long-term processes for assembly from nanoparticles to dense layers, resulting in the formation of non-selective regions on the inside of the membrane. Additionally, COF is often introduced into polymer membranes for the fabrication of composite thin films, but differences in affinity create large voids at the nanoparticle-polymer interface. While this loose structure improves solvent permeability, it reduces separation performance. In short, current COF membranes have not yet established a balance between the formation of a continuous covalent network and the resulting excellent solvent permeability / selectivity.

[0013] In view of these circumstances, the present invention aims to provide a polyamide membrane that maintains a regular pore structure even in organic solvents, has long-term stability, excellent selectivity, and high separation efficiency, as well as a method for producing the same.

[0014] To solve the above problems, the polyamide membrane of the present invention is a polyamide membrane formed by polymerization of aminoporphyrin monomer and acid chloride monomer, characterized by having a regular pore structure and a crystalline structure. This reconstructs the uniform structure and pore size of the amorphous polyamide, enabling accurate molecular separation. Porphyrins are expanded horizontally in the membrane by quadrilateral side functional groups and form pore channels vertically by macrocycles (macrocyclic compounds). From another viewpoint, the polyamide membrane of the present invention is a polyamide membrane formed by polymerization of aminoporphyrin monomer and acid chloride monomer, characterized by the protonation of the porphyrins. Protonation of the porphyrins causes a shift depending on the degree of protonation, adjusting the sliding distance of the aminoporphyrin monomer stack, which in turn changes the vertical pore channels and adjusts the pore size. In other words, to reduce the pore size, steric resistance or electrostatic interaction is applied to the aminoporphyrin monomer, thereby overcoming the interlayer π-π interaction (stacking interaction), i.e., the cohesive force acting between the aromatic rings of organic compound molecules, through atomic layer sliding.

[0015] Here, the polyamide film of the present invention is a covalent organic network (CON) film in which the stacking behavior of aminoporphyrin monomers is controlled. To fabricate the CON film with an orderly structure, the adjustable stacking behavior of aminoporphyrin monomers is utilized. That is, by controlling the self-aggregation behavior of porphyrin monomers and changing the conformation of acid chloride monomers, different covalent networks are formed. By using different acid chloride monomers, the interlayer bonding between stacks of aminoporphyrin monomers in the CON film can be controlled. Furthermore, it is preferable that the sliding distance of the stacks of aminoporphyrin monomers in the polyamide film of the present invention is adjusted and the size of substances permeating the film is selected. Specifically, the pore size of the polyamide film of the present invention is preferably a molecular weight cutoff of 800 daltons or less, or preferably 2 nm or less. In this specification, the term CON film refers to a general term for crystalline porous organic polymer films that are formed solely by covalent bonds and have a two-dimensional or three-dimensional periodic structure, similar to the COF film described above.

[0016] The acid chloride monomer, which is a constituent unit of the polyamide membrane of the present invention, is preferably at least one selected from oxalyl chloride (OC), trimethoyl chloride (TMC), isophthaloyl chloride (IPC), and terephthaloyl chloride (TPC). By using different types of acid chloride monomers, the pores of the polyamide membrane of the present invention can be formed to different sizes. The polyamide membrane of the present invention is preferably interlayer-bonded with a metal selected from the group consisting of iron, aluminum, zinc, and copper. Polyamide membranes interlayer-bonded with the above metals have improved membrane stability and excellent inhibitory properties regardless of the type of solvent. Polyamide membranes interlayer-bonded with the above metals have a high inhibitory rate of 60% or more against methyl orange in dimethyl sulfoxide (DMSO), which has strong polarity. In particular, polyamide membranes interlayer-bonded with iron or aluminum exhibit a very high inhibitory rate of 80% or more against methyl orange in DMSO. Furthermore, polyamide membranes with interlayer bonding by divalent iron have a higher methyl orange rejection rate of 95% or more than those with interlayer bonding by trivalent iron. The polymer composite membrane for organic solvent membrane separation of the present invention is formed by forming the above-described polyamide membrane on a porous support membrane. The porous support membrane can be an organic polymer support membrane or an inorganic support membrane.

[0017] Next, the method for producing the polyamide membrane of the present invention will be described. The method for producing the polyamide membrane of the present invention is a method for producing a polyamide membrane having a regular pore structure formed by polymerization of an aminoporphyrin monomer and an acid chloride monomer, wherein a predetermined concentration of acid is added to a solution containing the aminoporphyrin monomer to protonate the porphyrin, and the sliding distance of the stack of aminoporphyrin monomer is adjusted according to the degree of protonation of the porphyrin. Acid-triggered protonation of porphyrin controls the stacking of porphyrin, reduces the pore size of the covalent organic network from mesopores to micropores, and enables selective molecular transport.

[0018] Specifically, the method for producing a polyamide film of the present invention comprises: 1) a step of dissolving an aminoporphyrin monomer in an aqueous solvent to obtain an aqueous phase; 2) a step of dissolving an acid chloride monomer in an organic solvent to obtain an organic phase; 3) a step of adding an acid of a predetermined concentration to the aqueous phase to protonate the porphyrin; 4) a step of polymerizing the aminoporphyrin monomer and the acid chloride monomer at the interface between the aqueous phase and the organic phase; and 5) a step of adjusting the sliding distance of the aminoporphyrin monomer stack according to the degree of protonation of the porphyrin. By encapsulating and polymerizing the amine and acid chloride monomer at the interface between the aqueous phase and the organic phase, a dense layer can be formed. In the method for producing a polyamide film of the present invention, the concentration of the acid added to the aqueous phase is 0.01 to 0.1 (mol / dm³). ３ It is preferable that the range is within the specified range. The method for producing a polyamide film of the present invention preferably further comprises the step of immersing the polyamide film in a solution containing metal ions selected from the group consisting of iron, aluminum, zinc, and copper, thereby modifying the film with metal. By immersing the polyamide film and modifying the film with metal, the surface of each layer constituting the film is modified with metal, and the layers are bonded together by the metal. The bond between the layers is a coordination bond, and the layers are bonded together by metal-oxygen-metal. Here, oxygen is oxygen from the air. Among the metal ions, the bond by divalent iron in particular provides the strongest bond between the layers.

[0019] The polyamide membrane of the present invention maintains a regular pore structure even in organic solvents, exhibiting long-term stability, excellent selectivity, and high separation efficiency. By controlling the aggregation behavior of porphyrins, it is possible to provide a CON membrane with a regular pore structure and crystalline structure not found in conventional polyamide membranes.

[0020] Schematic diagram of a polyamide film formed by polymerization of TAPP and TMC Schematic diagram of control of porphyrin stacking behavior by protonation of TAPP with acid Schematic diagram of adjustment of hydrochloric acid concentration in the aggregation behavior of TAPP Schematic diagram of how pore size changes using different acid chloride monomers Structural formulas and crystal structure images of TMC, TPC, IPC and OC Molecular structure image of a polyamide film formed by polymerization of TAPP and TMC Molecular structure image of polyamide films of TAPP and IPC, and TAPP and TPC Schematic diagram of the method for preparing APP-based CON films Flowchart of the method for preparing TAPP-based CON films SEM, AFM, and HR-TEM images of TAPP-based polyamide films XRD patterns of TAPP powder, TAPP-TMC films, and TAPP-TPC films Diagram showing the film structure, methanol permeability, and separation performance of prepared films with varying HCl concentrations Diagram explaining film thickness and surface roughness with respect to HCl concentration Diagram 1 explaining the effect of protonation on pore size Diagram 2 explaining the effect of protonation on pore size TAPP-based polyamide Diagram illustrating the membrane structure of the membrane Graph showing the separation performance of a TAPP-based polyamide membrane (1) membrane inhibition efficiency of organic dyes, (2) inhibition behavior of neutral molecules, (3) pore size distribution of the membrane Diagram illustrating the solvent stability of a TAPP-based polyamide membrane, (2) pressure stability Flowchart for the optimization of the OSN membrane Diagram showing the Fe membrane modification process and different types of interlayer bonding (covalent bond / coordinate bond) Diagram showing the solvent swelling effect, where (1) is the inhibition loss of TAPP-TMC, and (2) is the change in permeability due to solvent activation Diagram showing Fe modification of polyamide membrane Figures showing the difference in solvent permeability with and without Fe modification; Figures showing the solvent swelling effect of DMF; Figures showing XPS measurement results of different polyamide membranes before and after Fe modification; Micrographs showing morphological changes of various polyamide membranes due to activation with DMSO; Graphs showing the permeability of different polyamide membranes before and after Fe modification; Graphs showing the MO rejection rate of different polyamide membranes before and after Fe modification; Graphs showing the optimal process for modifying metal, concentration, reaction temperature, and reaction time; Graphs showing the separation performance of different metal ions; Graphs showing the difference in fractionation molecular weight before and after Fe modification.

[0021] Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. It should be noted that the scope of the present invention is not limited to the following embodiments or illustrated examples, and numerous modifications and variations are possible.

[0022] Figure 1 shows the macrocycle (macrocyclic compound) that constitutes a polyamide film formed by the polymerization of the aminoporphyrin monomer TAPP (5,10,15,20-tetrakis(4-aminophenyl)-21H,23H-porphyrin) and the acid chloride monomer TMC (Trimesoyl chloride). As shown in Figure 1, the porphyrin has amino groups (NH) in its side chains. ２ ) polymerizes with the trifunctional TMC to form a regular pore structure.

[0023] Figure 2 shows a schematic diagram of the control of porphyrin stacking behavior by acid-induced protonation of TAPP. To adjust the film structure of the polyamide film formed by polymerization of TAPP and TMC, acid-induced protonation of TAPP is manipulated to improve solubility, further relax eclipse stacking, and promote offset stacking, thereby forming a regular pore structure with smaller pore sizes. Acid-induced protonation of TAPP controls the stacking behavior of porphyrin, resulting in smaller pores. Here, when acid dissolves in water, it produces hydrogen ions (H). ＋ Any substance that produces protonation can be used, and hydrochloric acid is particularly preferred. Other substances that can be used include sulfuric acid, nitric acid, acetic acid, perchloric acid, chloric acid, phosphoric acid, and citric acid. Furthermore, the strength of the acid (degree of ionization) is related to its valency, and it is thought that the stronger the acid with a high valency, such as sulfuric acid, the more protonation will proceed at the same concentration.

[0024] Figure 3 is a schematic diagram illustrating how hydrochloric acid concentration is adjusted in the aggregation behavior of TAPP. It shows how the aggregation behavior of TAPP is controlled by adjusting the hydrochloric acid (HCl) concentration. The aggregation behavior of TAPP, which determines the membrane structure, is controlled by adjusting the HCl concentration. As the acid concentration increases, more basic interporphyrin (H) ２ TAPP ２＋) is first protonated, and subsequently the amino group (H ６ TAPP ６＋ ) is protonated. Therefore, the increase in the charge density of the TAPP monomer is related to the increase in the solubility of the aromatic ring and the slip distance of the porphyrin stack. Also, HCl is a by-product of the condensation of TAPP and TMC. When there are excessive HCl and protonated amino groups, the polymerization reaction is kinetically inhibited and the film density decreases. Therefore, in order to reflect the offset stack of porphyrin molecules in the film, it is important to accurately control the HCl concentration and the degree of protonation of the porphyrin and the amino group. Note that the protonation of the TAPP monomer can be confirmed by UV-vis spectroscopy. The higher the HCl concentration, the higher the solubility of TAPP and the color of the solution changes.

[0025] Figure 4 is a schematic diagram showing the change in pore size using different acid chloride monomers. Regarding the acid chloride monomer of the constituent unit of the TAPP-based polyamide membrane, by using different acid chloride monomers, the conformation of the acid chloride monomer is changed and the pore sizes are made different. As shown in Figure 4, when comparing the pore size of the polyamide membrane formed by the polymerization of TAPP and trifunctional TMC with the pore size of the polyamide membrane formed by the polymerization of TAPP and bifunctional TPC (Terephthaloyl chloride), the pore diameters are different. In the case of the polymerization of TAPP and TMC, the pore diameter is small, and in the case of the polymerization of TAPP and TPC, the pore diameter is large. Thus, different acid chloride monomers are applied to finely adjust the pore size, and molecular separation is achieved by the sieving effect. Here, as the acid chloride monomer constituting the polyamide membrane, TMC and TPC, which have good film blocking properties and good film permeability, are particularly preferably used. In addition, oxalyl chloride (OC: Oxalyl chloride) and isophthaloyl chloride (IPC: Isophthaloyl Chloride) are also preferably used.

[0026] Figure 5 shows the structural formulas and crystal structure images of TMC, TPC, IPC, and OC of the acid chloride monomers that can be preferably used as the constituent units of the polyamide film of the present invention. The crystal structure images are those obtained by simulating a porphyrin-based network using molecular modeling and simulation software (product name: Materials Studio), and the effective pore size can be measured. It can be seen that the pore size can be adjusted by the stack conversion from Eclipse to Offset and the adjustment of the acid chloride monomer. In the stack conversion from Eclipse to Offset, it can be used to efficiently reduce the pore size from mesopores (about 2 nm) to micropores (about 0.8 nm). On the other hand, in the adjustment of the acid chloride monomer, it can be used to finely adjust the pore size (0.7 - 0.8 nm). By using these two approaches, selective separation of smaller molecules becomes possible.

[0027] Figure 6 shows the molecular structure image of the polyamide film formed by the polymerization of TAPP and TMC. Figure 6 is an image of the molecular structures of Eclipse and Offset viewed from the X - Y direction and the Y - Z direction with the Eclipse stack direction as the Z direction. In Eclipse, the pore size is 2.05 nm, while in Offset, the pore size is 0.72 nm. Thus, it was found that the protonation of TAPP by an acid changes the stacking behavior of porphyrin and reduces the pore size. Here, the pore size of Offset is determined by measuring the distance between adjacent hydrogen atoms of two layers in the Offset stack to obtain the average pore size.

[0028] Figure 7 shows a molecular structure image of a polyamide membrane formed by the polymerization of TAPP and IPC, or TAPP and TPC. By using IPC and TPC of different acid chloride monomers respectively, it was found that the conformation of the acid chloride monomer changed, and the offset pore sizes were different, being 0.78 nm and 0.81 nm. Thus, due to the strong network connection in the horizontal direction and the designable interlayer bonding, the polyamide membrane can have stability and reversibility even when operating in harsh organic solvents.

[0029] Figure 8 shows a schematic diagram of the manufacturing method of a TAPP-based CON membrane. Figure 9 shows a flowchart (steps S01 - S05) of the manufacturing method. First, as shown in Figure 8(1), an aminoporphyrin monomer (TAPP) is dissolved in an aqueous solvent to obtain an aqueous phase (step S01). Also, as shown in Figure 8(2), an acid chloride monomer (TMC) is dissolved in an organic solvent (hexane) to obtain an organic phase (hexane phase) (step S02). Hydrochloric acid of a predetermined concentration is added to the aqueous phase to protonate the porphyrin and adjust the sliding distance of the stack of aminoporphyrin monomers according to the degree of protonation (step S03).

[0030] The two liquid phases of the aqueous phase and the hexane phase are brought into contact. Here, the aqueous solvent used for the aqueous phase that forms an interface with the organic phase is basically water. It serves as a solvent for TAPP, and the solubility of TAPP is improved by adding an acid. Also, the organic solvent used for the organic phase that forms an interface with the aqueous phase is a solvent that does not mix with water, or is difficult to mix with water, and can dissolve the acid chloride monomer, and preferably has a low solubility in water. For example, hydrocarbon solvents such as hexane, octane, cyclohexane, and isoparaffin can be preferably applied.

[0031] Next, as shown in Figure 8(3), suction filtration is performed from below the aqueous phase in a vacuum to remove the aqueous phase. It is also possible to remove the aqueous phase by methods other than suction filtration; for example, the aqueous phase can be extracted with a syringe, or the aqueous phase can be removed first while the water / hexane interface is formed, thereby firmly fixing it on the support film. In conventional interfacial polymerization methods, the support film is immersed in the aqueous phase, the water is removed, and then it is immersed in the hexane phase. However, this method can cause TAPP to aggregate or adsorb to the substrate, resulting in problems such as poor diffusion when immersed in the hexane phase. As shown in Figure 8(4), aminoporphyrin monomer (TAPP) and acid chloride monomer (TMC) undergo interfacial polymerization at the interface between the aqueous phase and the hexane phase (step S04). In vacuum-assisted interfacial polymerization between the aqueous and hexane phases, the TAPP-based layer can be completely immobilized on porous support films such as polysulfone, polyacrylonitrile, or polyketone, allowing for control of the highly conjugated conformation of TAPP and promoting the transfer of the polyamide film without mechanical damage. While vacuum filtration is used for vacuum-assisted interfacial polymerization, as mentioned above, in methods other than vacuum filtration, TAPP and TMC interfacial polymerization occurs without the need for vacuuming.

[0032] Then, the stacking behavior of porphyrins is adjusted to reduce pore size and refine the membrane structure. Protonation of TAPP is manipulated using acid as a trigger to improve the water solubility of TAPP. Eclipse stacking is further relaxed, and offset stacking is promoted to construct polyamide membranes with a more regular, smaller pore structure.

[0033] The polyamide film of the present invention will be described in more detail with reference to the following experimental examples. These examples are provided for illustrative purposes only and are not intended to limit the scope unless otherwise specified.

[0034] (Membrane fabrication method) For the porous support membrane, commercially available polyacrylonitrile (PAN; 30 kDa, manufactured by Synder Filtration, Synder, membrane type PZ), anodized aluminum oxide (AAO; WHATMAN®), and polyketones prepared using a non-solvent-induced phase separation method were used. Porphyrin monomer, specifically 5,10,15,20-tetrakis(4-aminophenyl)-21H,23H-porphyrin (TAPP; 674.79 mg / mol, 98%, BLD Pharmatech), was used as the aqueous monomer, while trimethoyl chloride (TMC; 265.48 mg / mol, Sigma-Aldrich) and terephthaloyl chloride (TPC; 203.02 mg / mol, 99.0%, Tokyo Chemical Industries) were used as acid chloride monomers. Deionized water was prepared using the Milli-Q system. Methanol, hexane, and DMF (N,N-dimethylformamide) (Fujifilm Wako Pure Chemical Industries) were used to wash the separation layer. The porphyrin aqueous solution was prepared by adding TAPP (0.6 mg / mL) to 0.05 mol / dm³. ３ The solution was prepared by dissolving it in an aqueous HCl solution. The acid chloride monomer was prepared by dissolving equimolar concentration (0.565 mmol / g) of TMC (0.15 wt%) or TPC (0.09 wt%) in hexane. A composite film containing a TAPP-based CON layer and a PAN support film was fabricated by a vacuum-assisted interfacial polymerization process. The film-forming apparatus consisted of a polytetrafluoroethylene (PTFE) frame (8 × 8 × 0.5 cm, inner diameter 6 cm) fixed substrate and a vacuum filtration system. The aqueous solution (3 mL) and hexane solution (3 mL) were slowly poured onto the PTFE frame to form a free interface on the substrate. After reacting at 20°C for 16 minutes, the aqueous solution was removed by vacuum filtration (~4 minutes). Subsequently, the hexane solution was replaced several times with fresh hexane and methanol to remove excess acid chloride monomer, and the CON layer was bonded to the support film.

[0035] (Regarding the membrane structure of the TAPP-based polyamide membrane) Figure 10 shows scanning electron microscope (SEM), atomic force microscope (AFM), and high-resolution transmission electron microscope (HR-TEM) images of the surface of a TAPP-based polyamide membrane. As described above, the TAPP-based polyamide membrane is formed by polymerization at the free interface between the aqueous phase and the hexane phase, and the TAPP-based layer is completely fixed onto a porous support membrane such as polyacrylonitrile or polyketone without causing mechanical damage by a filtration process that removes the aqueous phase. Figure 10(1) shows surface SEM image (a), AFM image (b), cross-sectional image (c), and HR-TEM image (d) of a polyamide membrane formed by polymerization of TAPP and TMC (hereinafter also referred to as a TAPP-TMC membrane), and it can be seen that a membrane with a smooth surface was successfully fabricated. Figure 10(2) shows surface SEM images (a), AFM images (b), cross-sectional images (c), and HR-TEM images (d) of a polyamide film formed by polymerization of TAPP and TPC (hereinafter also referred to as the TAPP-TPC film). Similar to the polyamide film of TAPP and TMC, it can be seen that a film with a smooth surface was successfully fabricated. Figure 10(3) shows images created from Fast Fourier Transform (FFT) patterns and their spots in regions I, II, and III of the HR-TEM image (d) in Figures 10(1) and (2). Since the sample is multilayered in the TEM image, a single layer was selected and subjected to Fast Fourier Transform processing. The TAPP-TMC film had an irregular network structure, with an interlayer spacing of approximately 0.36 nm corresponding to the c-axis direction (optical axis direction) (region I), while the TAPP-TPC film had a regular network structure, with an interlayer spacing of approximately 0.36 nm corresponding to the c-axis direction (optical axis direction) (region II). The stacking distance of the porphyrin-based film was halved, from 2.72 nm to 1.36 nm (region III). This suggests that the offset stacking of the porphyrin-based film was achieved by acid protonation. Compared to the amorphous polyamide layer, the TAPP-based CON film inherited the polycyclic aromatic monomer structure and had a regular crystalline structure, as confirmed by HR-TEM imaging.

[0036] Figure 11 shows the XRD patterns of TAPP powder, TAPP-TMC film, and TAPP-TPC film. At the molecular level, TMC functions as links between TAPPs and as knots for linking with additional amino groups, thereby forming an amorphous structure. To improve topology control of the polymer network, TPC is also used as a link between TAPPs to form a quadrilateral network. 0.05 (mol / dm ３ The XRD patterns of TAPP powder were compared with and without an HCl aqueous solution. When HCl was added to the TAPP powder, the diffraction peak generated by TAPP disappeared. This was presumed to be because the monomer aggregation process was relaxed. The TAPP-TMC polyamide film and the TAPP-TPC polyamide film generated diffraction peaks at approximately 2θ = 20–23°. This corresponds to an interlayer spacing of approximately 0.4 nm. Considering the sharp diffraction peak at 2θ = 4.9°, this suggests the formation of a regular TAPP-TPC network structure, and this peak was similar to the structure of a porphyrin-based COF film.

[0037] (Relationship between separation performance and acid concentration of TAPP-based polyamide membranes) The following describes the results of tests using a laboratory-scale cross-flow apparatus on the organic solvent nanofiltration (OSN) performance of TAPP-TMC polyamide membranes. To confirm optimal protonation for TAPP-TMC membranes, the effect of acid concentration on the OSN performance of TAPP-TMC was investigated. In order for the TAPP-TMC membranes to achieve stable performance, at each step, after operating at a pressure of 4.5 bar (1 bar = 100,000 Pa) for 12 hours, the methanol permeability and dye rejection rate in a methanol solution with a dye concentration of 50 ppm were confirmed.

[0038] In this specification, solvent permeability (L / m ２ The permeate volume (L) and inhibition rate (%) were calculated using the following formulas (1) and (2). Here, V, A, T, and P are the permeate volume (L) and effective membrane area (m²), respectively. ２ These are the permeation time (h) and the in-membrane pressure difference (bar). Also, C ｐ and C ｆThese are the solute concentrations of the permeate and feed solution, respectively.

[0039]

[0040] The molecular weight cutoff for each membrane was determined by analyzing the rejection rate of neutral molecules in water at a concentration of 1000 ppm. The concentrations of the feed solution and permeate were determined using an organic carbon analyzer (TOC-VCSH, Shimadzu Corporation). Finally, the molecular weight and Stokes diameter (d) of the neutral molecules were determined. ｐ Using the relationship (μ)(μ), the probability density function of the pore size distribution was simulated according to equations (3) and (4) below. Here, the average pore diameter (μ) of the porphyrin-based CON film is... ｐ , nm) and Stokes radius (μ ｓ The inhibition rates (nm) were calculated from the molecular weight using formula (4) with inhibition rates of 50% and 84.1%, respectively. Geometric standard deviation (σ ｐ ) is μ ｐ and μ ｓ It followed the ratio.

[0041]

[0042] Figure 12 shows the membrane structure, methanol permeability, and separation performance of TAPP-TMC membranes prepared using various HCl concentrations. Brilliant blue (BB) (828 Da; 1.79 × 2.06 nm) and methyl orange (MO) (327 Da; 0.48 × 1.49 nm) were used to confirm structural changes because their molecular sizes are close to the overlapping pore size and offset stacked pore size of the porphyrin-based membrane, respectively.

[0043] As shown in Figure 12, the HCl concentration (mol / dm ３ When LMH increased from 0.005 to 0.1, methanol permeability (LMH / bar) decreased from 4.3 to 1.7, and then increased further to 4.8 (LMH = L / m³). ２ ( / h). In contrast to the change in permeability, the rejection rate for BB increased from 88.4% to 98.3% and then slightly decreased to 96.8%, while the rejection rate for the smaller MO increased sharply from 57.6% to 97.5% and then decreased to 88.3%. HCl concentration changed from 0.005 to 0.0125 (mol / dm). ３When the concentration was increased to 0.075 (lmH / dm), the rejection rates for BB and MO increased significantly to 98.3% and 96.4%, respectively, and methanol permeability decreased from 4.3 to 2.5 (LMH / bar). It was found that TAPP had high solubility and that a high-density OSN film could be formed by offset stacking. Furthermore, at an even higher HCl concentration of 0.075 (mol / dm), ３ The protonation of the amino group by the acid in the above steps hindered the reaction between TAPP and TMC, forming interconnection defects, increasing methanol permeability, and slightly decreasing the rejection rate.

[0044] These changes in permeability and rejection rate are primarily due to the two-step protonation of TAPP. In this process, at low HCl concentrations, the protonation of interporphyrin halves the pore size through offset stacking, and the increased concentration of TAPP monomer generates a thicker selective layer. On the other hand, at high HCl concentrations, the protonation of the amino group limits the formation of a high-density layer. Furthermore, high permeability (2.9 LMH / bar) and high MO rejection rate (96.4%) are achieved at 0.05 (mol / dm³). ３ It was found that the HCl concentration in the solution was particularly favorable.

[0045] Figure 13 shows the film thickness and surface roughness of the TAPP-TMC film with respect to HCl concentration. From Figure 13, it can be seen that the SEM and AFM images of the TAPP-TMC film show similar surface morphology, and that as the HCl concentration increases, the thickness increases from 19 nm to 214 nm, and the surface roughness (Ra) increases from 1.2 nm to 29.5 nm. HCl concentration 0.1 (mol / dm ３ The AFM image of the TAPP-TMC film showed the presence of several twisted nanoribbons. This may indicate that the excess amino groups were protonated, causing the TAPP-TMC to expand one-dimensionally. Therefore, we hypothesize that in the initial stages of film formation, the protonated amino groups were unable to bind with the acid chloride monomer to form partial defects, while interfacial polymerization reactions preferentially occurred in the defect regions, resulting in the formation of a thicker, rougher layer.

[0046] The effect of protonation on pore size will be explained with reference to Figures 14 and 15. As shown in Figure 14, 5,10,15,20-tetrakis(4-hydroxyphenyl)-21H,23H-porphyrin (THPP) is dissolved in NaOH solution (0.05 M), and although it is structurally similar to TAPP, NH ２ The solubility of interporphyrin, in which the OH group was replaced, was improved without protonation. Deprotonated THPP formed a reactive phenoxide ion, which promoted the substitution reaction with TMC to form a high-density polyacrylate layer. As shown in Figure 15, the methanol permeability of the obtained THPP-TMC film was 8.3 (LMH / bar), with low rejection rates for BB (81.8%) and MO (65.6%). This result indicates that protonation of interporphyrin created an offset stack, promoting the exclusion of small MO molecules.

[0047] (Separation performance of TAPP-based polyamide membranes and types of acid chloride monomers) The separation performance of TAPP-based polyamide membranes bonded to the acid chloride monomers TMC, IPC, TPC, and OC will be explained. First, the membrane structure is shown in Figure 16. As shown in the graph on the right side of Figure 16, the TAPP-based polyamide membranes bonded to each acid chloride monomer had similar surface morphologies. However, regarding the film thickness, the membranes bonded to TMC, IPC, and TPC were approximately 100 nm thick, while the OC-bonded membrane was approximately 170 nm thick due to its twisted paraffin structure.

[0048] Figure 17 is a graph showing the separation performance of TAPP-based polyamide membranes bound to acid chloride monomers TMC, IPC, TPC, and OC, respectively. For the TMC, IPC, and TPC-bound membranes, the BB rejection rate was 97.0% or higher, with improved permeability in the high-density layer and an MO rejection level of 90% or higher. On the other hand, the OC-bound membrane, due to the shortest distance between the two acid chloride monomers and its twisted paraffin structure, exhibited high permeability and a low MO rejection rate of 86.6%.

[0049] Figure 18(1) shows the membrane blocking efficiency of organic dyes with molecular weights in the range of 250–1300 Da. Dyes with molecular weights exceeding 500 Da were significantly blocked. At a molecular weight of 320 Da, even a small size difference between MO (negative) and methylene blue (MnB, positive, 0.6 × 1.4 nm) resulted in a significant decrease in the MnB blocking rates of TMC, IPC, and TPC to 85.6%, 64.3%, and 56.5%, respectively. Assuming that electrostatic repulsion governs membrane separation, it was hypothesized that more negatively charged TAPP-TMC would promote the transport of positively charged MnB more than negatively charged MO, and thus show a much larger difference in MnB and MO blocking than TAPP-IPC, which has a similar structure. However, the opposite results were observed, suggesting that membrane separation is actually governed by the sieve size.

[0050] Figure 18(2) is a graph showing the blocking behavior of neutral molecules in water. Figure 18(3) shows a distribution graph in which the pore size distribution of the membrane was estimated using the blocking rate of neutral molecules in water. The MWCO (blocking rate = 90%) of the TMC, IPC, and TPC bound membranes were 168 Da, 229 Da, and 331 Da, respectively, and the average pore size estimated from the results was 0.48 nm, 0.56 nm, and 0.78 nm. These values ​​are consistent with the molecular size of MO, and the more highly controlled TAPP-TPC was close to the structure in which the slide distance of the porphyrin-based CON membrane is maximized.

[0051] (Solvent Stability of TAPP-Based Polyamide Films) This section describes the results of investigating the robustness of TAPP-TMC and TAPP-TPC films under harsh conditions. These films were fabricated on porous support films of polyketone, which has resistance to organic solvents. As mentioned above, there is a large difference in pore size between TAPP-TMC and TAPP-TPC films. Figure 19(1) shows the solvent stability of TAPP-TMC and TAPP-TPC films when methanol and DMF are alternately operated. In methanol, similar performance was obtained for the TAPP-TPC film (4.6 LMH / bar, MO rejection rate 92.6%) and the TAPP-TMC film (2.8 LMH / bar, MO rejection rate 99.4%). In addition, in both films, the rejection reaction was slightly improved, and permeability decreased over time due to the accumulation of dye.

[0052] Here, DMF was used as an activator to swell the polyamide membrane and remove small molecular fragments. The TAPP-TPC membrane showed significantly improved permeability to DMF (2.2 times) and methanol (1.6 times). More dye molecules were blocked with DMF (94.6%) than with methanol (72.9%), which was presumed to be due to greater clogging because of DMF's lower solubility. The TPC bond network was constructed by a weakly interconnected layered structure. Polar solvent molecules inserted between layers expanded the interlayer spacing between adjacent layers. Therefore, molecules may be transported alternately between the in-plane pores and interlayer spacing of the TAPP-TPC membrane monolayer, potentially reducing selectivity. In contrast, because the acyl chloride groups form strong interlayer covalent bonds, the TAPP-TMC membrane showed a high MO rejection rate of over 95% and low permeability to DMF (0.5 times) and methanol (0.9 times) throughout the DMF activation process.

[0053] Figure 19(2) shows the pressure stability of the TAPP-TMC membrane and the TAPP-TPC membrane under various pressures. As a result, the TAPP-TMC membrane, in particular, showed a stable molecular rejection rate of over 90% in methanol, and its performance stability was confirmed during 25 days of operation. The separation process using the TAPP-TMC membrane makes it possible to concentrate MO molecules and recycle methanol. Selective transport through in-plane pores of the offset stack of the TAPP-based polyamide membrane of the present invention can reduce the MWCO from 900 Da to approximately 320 Da, further increasing selectivity and significantly improving separation accuracy.

[0054] (Optimization of OSN film) The optimization of OSN film using a TAPP-based polyamide film will be explained. Figure 20 shows the flow chart for OSN film optimization. A TAPP-based CON film is prepared (step S11), and if the molecular weight cutoff (MWCO) is below a predetermined threshold (step S12), the stacking behavior (self-aggregation behavior) of aminoporphyrin monomers is controlled (step S13). By controlling the self-aggregation behavior, the conformation of the acid chloride monomer is changed, and different CON films are formed. Steps S12 and S13 improve the selectivity of the OSN film. Next, the film stability in the solvent is confirmed for the OSN film with improved selectivity. If the OSN film swells in a specific solvent (step S14), the interlayers are bonded with a metal (step S15) to prevent film swelling. That is, steps S14 and S15 improve the stability of the OSN film.

[0055] A specific example of bonding the interlayers of an OSN film using a TAPP-based polyamide film with iron (Fe) will be explained with reference to Figure 21. In order to improve the stability of the TAPP-based CON film, FeCl ２The CON film is immersed in a dimethyl sulfoxide (DMSO) solution containing 12.5 mg / mL of iron at 65°C for 20 hours. This modifies each layer of the CON film with iron (see Figure 21(1)). For example, Figure 21(2) shows a schematic diagram of interlayer bonding when aminoporphyrin monomer (TAPP) and isophthaloyl chloride (IPC) or trimesoyl chloride (TMC) undergo interfacial polymerization (IP) at the interface between the aqueous phase and the hexane phase. Before iron (Fe) is added to the layers, interlayer bonding occurs via covalent bonds, but after Fe modification, interlayer bonding occurs via Fe-O-Fe coordination bonds in addition to covalent bonds. Oxygen is the oxygen contained in the air. As shown in Figure 21(3), when the solvent changes from methanol to DMF to DMSO, the polymer chains forming the polyamide film swell, expanding the molecular weight cutoff and increasing the size of the solute that can permeate. If the solvent is highly polar, such as DMSO, the film will swell, degrading its performance and compromising its stability.

[0056] Figure 22 shows the solvent swelling effect, where (1) shows the decrease in the rejection rate of the polyamide membrane (TAPP-TMC), and (2) shows the change in permeability due to solvent activation. The solvent swelling effect is such that when the solvent polarity is high, such as DMSO, the degree of membrane swelling increases, resulting in increased membrane permeability and decreased membrane rejection rate. As shown in Figure 22 (1), in the TAPP-TPC membrane, the rejection rate of methyl orange in four types of solvents—methanol, N-methyl-2-pyrrolidone (NMP), DMF, and DMSO—was almost completely blocked except for DMSO, which is a highly polar solvent, while in the case of DMSO, the rejection rate was 50%. Also, as shown in Figure 22 (2), methanol permeability was highest with DMSO, twice that of methanol.

[0057] Figure 23 shows the solvent permeability of polyamide films polymerized with IPC on TAPP, with and without iron (Fe) modification (TAPP-IPC) and with Fe modification (Fe-TAPP-IPC). Here, the solvent is changed over time to methanol (0-120 mins), DMSO (120-360 mins), and methanol (360-1200 mins). This is to confirm whether the polyamide film swells and its permeability changes due to the strongly polar solvent DMSO. As shown in Figure 23, in the case of the film without Fe modification (TAPP-IPC), swelling occurs with DMSO, and the permeability with methanol after DMSO is greater than that with methanol before DMSO, indicating that the film has changed. On the other hand, in the case of the film with Fe modification (Fe-TAPP-IPC), swelling hardly occurs even with DMSO, and there is almost no change in methanol permeability before and after DMSO.

[0058] Figure 24 shows the solvent swelling effect of DMF, where (1) shows the change in MWCO in DMF and (2) shows the performance in DMF. In the figure, Dura150 is an abbreviation for the product name of a commercially available polyimide membrane, "DURAMEM® 150". As shown in Figure 24(1), the change in MWCO in DMF shows that the decrease in rejection rate due to the change to DMF is suppressed more in the TAPP-based polyamide membrane (TAPP-TMC). As shown in Figure 24(2), the performance in DMF shows that the polyamide membrane (TAPP-TMC) has a higher methyl orange rejection rate than the commercially available polyimide membrane. From this, it can be seen that the TAPP-based membrane can maintain stability in DMF and has superior separation performance compared to the commercially available membrane.

[0059] Figure 25(1) shows the measurement results of X-ray photoelectron spectroscopy (XPS) for different polyamide films (TAPP-IPC, TAPP-TMC). For the polyamide films (TAPP-IPC, TAPP-TMC), peaks originating from Fe and O were detected at 705-735 eV and 528-536 eV, respectively, in the Fe-modified films. From the O 1s peak shown in Figure 25(2), a peak originating from the -Fe-O-Fe- bond was detected in the Fe-modified film. In addition, peaks originating from Fe(II) and Fe(III) were detected in the Fe2p peak in Figure 25(3). During the modification of these films, Fe ２＋ Because Fe is used during film formation ２＋ From Fe ３＋ It can be seen that it is partially oxidized.

[0060] Figure 26 shows micrographs illustrating the morphological changes of different polyamide films upon activation with DMSO. The images show the initial state and DMSO-activated state of different TAPP-based polyamide films (TAPP-IPC, TAPP-TMC) before and after Fe modification. While there were no significant changes on the film surface, TAPP, a polycyclic aromatic porphyrin, has lower solubility in DMSO than MPD, which may hinder visible changes on the TAPP-based polyamide film surface. Micrographs of the initial state and DMSO-activated state of polyamide films on a porous polyketone support prepared by controlling the interfacial polymerization of m-phenylenediamine (MPD) and trimethoyl chloride (TMC) as disclosed in Non-Patent Literature 2 were used as controls (for comparison).

[0061] Figures 27 and 28 show the results of evaluating the structural stability of different TAPP-based polyamide membranes (TAPP-IPC, TAPP-TMC) before and after Fe modification, using a process in which methanol (first pass) was permeated for 2 hours, followed by DMSO for 4 hours, and then methanol (second pass). In other words, the results for the second methanol pass represent the results in methanol after the membrane has experienced DMSO permeation. Figure 27 shows (1) a comparison of the permeability of methanol (first pass) and DMSO, and (2) a comparison of the permeability of methanol (first pass) and (2). For control (comparison), the permeability of a conventional polyamide membrane (MPD-TMC) is shown. Figure 28 shows the MO rejection rates of different TAPP-based polyamide membranes (TAPP-IPC, TAPP-TMC) before and after Fe modification, with (1) showing the MO rejection rate in DMSO and (2) showing the MO rejection rate in methanol (second pass). Conventional polyamide membranes (MPD-TMC) swell when immersed in DMSO, resulting in membrane degradation with increased permeability and decreased blocking ability (MO blocking rate in DMSO is about 20%). Similarly, TAPP-based polyamide membranes (TAPP-TMC) swell when immersed in DMSO, just like conventional polyamide membranes (MPD-TMC), and the MO blocking rate is low, at less than 10%. Polyamide membranes (TAPP-IPC) also exhibit a low MO blocking rate of about 30%.

[0062] However, when Fe ions were introduced (modified each layer) during the post-treatment of the TAPP-based polyamide membrane (Fe-TAPP-TMC, Fe-TAPP-IPC), swelling did not occur, and permeability decreased significantly due to the viscosity of DMSO. On the other hand, as shown in Figure 28(1), while the MO rejection rate was less than 20% for the conventional polyamide membrane (MPD-TMC), a high MO rejection rate (nearly 100%) was obtained for the modified membrane. Similarly, as shown in Figure 28(2), a high MO rejection rate (nearly 100%) was also obtained for the Fe-modified membrane in methanol (second time). The reason for the high rejection rate is thought to be that when Fe is introduced into a porphyrin molecule such as TAPP, it coordinates to the central part of the porphyrin molecule, forming an Fe-O-Fe coordination bond, which improves the stability of the membrane structure. Furthermore, as shown in Figure 27(2), when Fe ions were introduced (modified each layer), there was no significant change in permeability between the first and second passes of methanol, suggesting that the flow of DMSO had no effect on the structure.

[0063] Figure 29 shows the optimal process for modification, concentration, reaction temperature, and reaction time. Figure 29(1) shows different metal ions (Cu) in the post-treatment of TAPP-based polyamide films. ２＋ Fe ２＋ Fe ３＋ This shows the permeability and blocking properties when the following is introduced. Here, FeCl showed a blocking rate of nearly 90% in the strongly polar solvent DMSO. ２ The optimal metal chloride is (see the area enclosed by the dashed line). Figure 29(2) shows the DMSO solution (FeCl) into which the TAPP-based polyamide membrane is immersed. ２ This shows the permeability and inhibitory activity of the solution at different concentrations (6.25, 12.5, and 25). Here, 12.5 mg / mL, which showed an inhibitory rate of nearly 90% for DMSO, is the optimal concentration (see the area enclosed by the dashed line). Figure 29(3) shows that 65°C was the optimal reaction temperature (see the area enclosed by the dashed line). Also, Figure 29(4) shows that 20 hours was the optimal reaction time.

[0064] Figure 30 shows the separation performance of TAPP-based polyamide membranes (TAPP-IPC) modified with different metals (Fe, Ca, Zn, Mg, Cu, Al) in each layer. Each layer was prepared by modifying it with a metal chloride in DMSO. As shown in Figure 30(1), particularly high MO rejection was obtained with divalent Fe(II) for methanol permeability. However, no significant difference was observed with metal ions other than divalent Fe. It was found that both permeability and rejection (especially permeability) were improved compared to unmodified membranes. Furthermore, as shown in Figure 30(2), significant differences were observed in DMSO permeability. The original unmodified polyamide membrane showed very low rejection (35%), but similar to methanol permeability, high rejection was obtained with Fe(II), and trivalent Al and trivalent Fe(III) showed rejection of over 80%. One possible reason for this is the metal-oxygen bonding that occurs when a metal coordinates to porphyrin. For example, when TAPP is modified with divalent Fe, the interlayers are bonded by Fe-O-Fe bonds, resulting in the structure TAPP-Fe-O-Fe-TAPP. The metal modifying each layer requires an oxygen atom to coordinate to the porphyrin, and this oxygen is thought to be from the air. According to the formation constants of the metal complex formed by the reaction of acid chlorides to -COO(H) and the metal, the formation constants for Al and Fe(III) related to inhibitory activity in DMSO are high, and the inhibitory activity is correspondingly high. However, the formation constant for Fe(II) is low, which is inconsistent with the above inhibitory activity results, but it is thought that Fe(II) was oxidized to Fe(III) due to some influence. For the reasons above, it is presumed that a bridge is formed between the metal and porphyrin, preventing interlayer swelling even in DMSO, and thus high inhibitory activity is obtained.

[0065] Figure 31 is a graph showing the difference in fractional molecular weight using polypropylene glycol in methanol and DMSO before and after divalent Fe(II) modification of TAPP-based polyamide membranes (TAPP-TMC, TAPP-IPC). (1) shows the fractional molecular weight results for the polyamide membrane (TAPP-TMC), and (2) shows the fractional molecular weight results for the polyamide membrane (TAPP-IPC). In both cases, the rejection rate of the polyamide membrane before Fe(II) modification decreased when switching from methanol to DMSO, and also decreased when switching back to methanol. In contrast, the fractional molecular weight (molecular weight at which the rejection rate is 90%) of the polyamide membrane after Fe(II) modification is 400 Da, indicating that high stability is obtained. As explained above, conventional polyamide membranes could not be used with highly polar solvents such as DMSO. However, it has been found that the TAPP-based polyamide membranes of the present invention (TAPP-TMC, TAPP-IPC) to which metals such as Fe are coordinated and interlayer-bonded exhibit excellent separation performance even in DMSO.

[0066] This invention is useful in a wide range of industrial fields, including the processing of organic liquids in the chemical and pharmaceutical industries (such as the separation, purification, and concentration of medium- and low-molecular-weight valuable substances in organic liquids). Furthermore, because it is a highly selective membrane, it can be widely applied to the purification of useful substances dissolved in aqueous systems. In particular, it has the potential to be used for pharmaceutical concentration, and since we have performed separation of antibiotics (molecular weight 400-800) in isopropanol, the polyamide membrane of this invention may be applicable.

Claims

1. A polyamide film formed by polymerization of an aminoporphyrin monomer and an acid chloride monomer, having a regular pore structure and a crystalline structure.

2. A polyamide film formed by polymerization of an aminoporphyrin monomer and an acid chloride monomer, wherein the porphyrin is protonated.

3. The polyamide film according to claim 1, wherein the stacking behavior of the aminoporphyrin monomers is controlled in a covalent organic network (CON) film.

4. The polyamide membrane according to claim 1, wherein the sliding distance of the stack of aminoporphyrin monomers is adjusted and the size of the substance permeating the membrane is selected.

5. The polyamide film according to claim 1, wherein the pore size is a molecular weight cutoff of 800 daltons or less.

6. The polyamide film according to claim 1, wherein the pore size is 2 nm or less.

7. The polyamide membrane according to claim 1, wherein the acid chloride monomer is at least one selected from oxalyl chloride (OC), trimethoyl chloride (TMC), isophthaloyl chloride (IPC), and terephthaloyl chloride (TPC).

8. The polyamide film according to claim 7, wherein different types of acid chloride monomers are used to form pores of different sizes.

9. A polyamide film according to any one of claims 1 to 8, wherein the interlayers are bonded by a metal selected from the group consisting of iron, aluminum, zinc, and copper.

10. The polyamide film according to claim 9, wherein the rejection rate of methyl orange in dimethyl sulfoxide (DMSO) is 60% or more.

11. A polymer composite membrane for organic solvent-based membrane separation, wherein a polyamide membrane according to any one of claims 1 to 8 is formed on a porous support membrane.

12. A method for producing a polyamide film having a regular pore structure formed by polymerization of an aminoporphyrin monomer and an acid chloride monomer, characterized in that an acid of a predetermined concentration is added to a solution containing the aminoporphyrin monomer to protonate the porphyrin, and the sliding distance of the stack of aminoporphyrin monomers is adjusted according to the degree of protonation of the porphyrin.

13. A method for producing a polyamide film according to claim 12, comprising the steps of: dissolving an aminoporphyrin monomer in an aqueous solvent to obtain an aqueous phase; dissolving an acid chloride monomer in an organic solvent to obtain an organic phase; adding an acid of a predetermined concentration to the aqueous phase to protonate the porphyrin; polymerizing the aminoporphyrin monomer and the acid chloride monomer at the interface between the aqueous phase and the organic phase; and adjusting the sliding distance of the stack of aminoporphyrin monomers according to the degree of protonation of the porphyrin.

14. The concentration of the acid added to the aqueous phase is 0.01 to 0.1 mol / dm³. ３ A method for producing a polyamide film according to claim 12 or 13, which is within the range of [specified range].

15. A method for producing a polyamide film according to claim 12 or 13, further comprising the step of immersing the polyamide film in a solution containing metal ions selected from the group consisting of iron, aluminum, zinc, and copper, thereby modifying the film with metal.

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