52 results about "Ion selectivity" patented technology

This invention discloses a method and system for selective separation of monovalent and divalent ions in an alginate fiber coagulation bath based on electrodialysis, belonging to the field of fiber production and membrane separation technology. The method and system integrate a selective electrodialysis device into a traditional coagulation bath circulation system. Utilizing an ion exchange membrane with monovalent and divalent cation selectivity, sodium ions accumulated in the coagulation bath are selectively migrated and removed under the action of an electric field, while divalent metal ions are efficiently retained, thereby maintaining a stable molar ratio of divalent ions to sodium ions in the coagulation bath within the required process range. Compared to traditional methods, this invention eliminates the need for large-scale replenishment of divalent metal salts or full replacement solution, significantly reducing production costs and resource waste. It achieves online regeneration and continuous circulation of the coagulation bath, significantly improving production stability, fiber quality, and resource utilization efficiency, and is suitable for the green and efficient production of various alginate fibers.

This invention discloses an interlayer confined piezoelectric composite film of graphene oxide, its electric field-driven preparation method, and its application. The preparation method includes: preparing a graphene oxide dispersion using the Hummers method and filtering it to form a graphene oxide film; placing the graphene oxide film in an electric-driven device, introducing different precursor solutions on both sides of the film, and driving the precursor components to migrate into the interlayer confined space of the graphene oxide under the action of an applied electric field; under the synergistic effect of electric field driving and interlayer confinement, the precursors entering the interlayer react and crystallize in situ to form a piezoelectric functional phase. The prepared composite film can generate piezoelectric polarization under mechanical stimulation conditions and can be used for ion selective adsorption / separation, especially suitable for the selective adsorption / separation of uranium and vanadium ions in high-salt water systems. This invention achieves a synergistic improvement in interfacial charge regulation and ion selectivity regulation by constructing a piezoelectric functional phase in situ within the interlayer confined space of graphene oxide.

This invention provides a covalent organic framework hybrid matrix membrane, its in-situ growth method, and its application in ion separation. The method includes: dissolving cellulose derivatives, aldehyde monomers of covalent organic frameworks, and amine monomers of covalent organic frameworks in an organic solvent to obtain a first solution, a second solution, and a third solution; mixing acetic acid solution with the first, second, and third solutions to obtain a homogeneous casting solution; and drop-coating the homogeneous casting solution for in-situ growth. This invention constructs a CD@COF hybrid matrix membrane based on a cellulose derivative matrix and a low-loading covalent organic framework filler using an in-situ growth method. The prepared hybrid matrix membrane exhibits good interfacial compatibility between the matrix and the filler. The above-mentioned hybrid matrix membrane preparation process is simple, possesses good mechanical strength and high scalability, and demonstrates high ion flux and excellent ion selectivity for separating monovalent and divalent ions. It has broad application prospects in wastewater resource treatment, lithium extraction from salt lakes, and energy storage.

This invention discloses a bipyridine derivative for the separation of lanthanum and actinide and its preparation method, belonging to the field of organic synthesis technology. The method first dissolves bipyridine OSU in DMSO, then adds it to a reaction solution, and stirs at room temperature to obtain a homogeneous solution. Next, a crystallization solvent is slowly added to the mixed solution, and the precipitated crystals are sequentially filtered, washed, and dried to obtain the bipyridine derivative. The bipyridine derivative is 6,6'-bis(N-hydroxyethylformyl)-2,2'-bipyridine or 6,6'-bis(N-hydroxybutylformyl)-2,2'-bipyridine. The target product synthesized by this method has good solubility in water, effectively improving the product's dispersibility. After complete dissolution, the product exhibits significant actinide ion selectivity due to the presence of a soft coordinating atom N in the ligand molecule, which allows it to complex with trivalent actinide ions more strongly than trivalent lanthanide ions.

This invention relates to the field of ion-conducting membrane technology, and particularly to a wedge-shaped amphiphilic molecule, a biomimetic ion-conducting membrane, and its preparation method. The biomimetic ion-conducting membrane utilizes the self-assembly behavior of the wedge-shaped amphiphilic molecule to form a columnar mesocrystalline phase containing transport channels. This columnar structure is fixed within a membrane framework composed of methacrylate polymers using ultraviolet graft copolymerization to form an ion-transfer membrane. This membrane exhibits strong ion selectivity and conductivity, and its mechanism of action is similar to that of biological cell membranes. It can be used for the transport and separation of microparticle materials such as ions, small molecules, and micro-electronic conductors, showing broad application prospects in fields such as biology, medicine, and environmental analysis. Furthermore, its ion conductivity and chemical stability also demonstrate its potential application in proton exchange membrane fuel cells.

This invention provides a multi-channel structure for a rapid, highly selective water-voltaic ion sensor, its fabrication method, and its applications. The sensor comprises a multi-channel sandwich-structured fiber membrane, a gradient polarization interface, and an electrode assembly. The multi-channel sandwich-structured fiber membrane includes a first macroporous layer, an intermediate microporous layer, and a second macroporous layer stacked sequentially, dividing the membrane into multiple independent sensing channels on a plane. The gradient polarization interface exhibits different degrees of interface polarization in different sensing channels. The electrode assembly connects to both ends of each sensing channel. The rapid, highly selective water-voltaic ion sensor provided by this invention utilizes a sandwich structure to form ion transport channels with rapid transport at both ends and precise sieving in the middle. This allows for the synergistic enhancement of both rapid ion transport and high-sensitivity response. Furthermore, by constructing differentiated sensing channels with "identical structures but different interfaces," the sensor synergistically amplifies and identifies differences in the intrinsic properties of ions, significantly improving ion selectivity.

Provided is a bipolar electrodialysis apparatus for producing lithium hydroxide, including, in sequence, an anode, a first bipolar membrane, an anion-selective ion exchange membrane, a cation-selective ion exchange membrane, a second bipolar membrane, and a cathode, the apparatus comprising: an acidic solution compartment which is formed between the first bipolar membrane and the anion-selective ion exchange membrane and in which an acidic solution is generated; a basic solution compartment which is formed between the second bipolar membrane and the cation-selective ion exchange membrane and in which a basic solution is generated; and a salt solution compartment which is formed between the anion-selective ion exchange membrane and the cation-selective ion exchange membrane, wherein a lithium salt aqueous solution is introduced into the salt solution compartment, water is introduced into each of the acidic solution compartment and the basic solution compartment, an electrode solution is introduced between the anode and the first bipolar membrane and between the cathode and the second bipolar membrane, and the electrode solution includes a redox compound.

This invention belongs to the field of biomedical nanomaterials and radiation damage drugs, specifically relating to a magnesium-ethylene glycol tetraacetic acid (EGTA) nanomedicine, its preparation method, and its applications. This study proposes using magnesium-EGTA nanomedicine to treat radiation dermatitis. EGTA's chelating ability for calcium ions is significantly higher than that of magnesium ions and other metal ions. Its unique ion selectivity provides an important theoretical basis and application potential for targeting and inhibiting mitochondrial calcium overload in the pathological process of radiation dermatitis. Magnesium ions are cofactors of many enzymes and have anti-inflammatory, collagen synthesis-promoting, and angiogenesis-enhancing effects. This study constructs a Mg-EGTA-based nanomedicine system, utilizing EGTA's stronger chelating ability for calcium ions, thereby achieving targeted regulation of mitochondrial calcium homeostasis through a calcium-magnesium ion intelligent replacement mechanism in response to calcium overload, providing new ideas and methods for the prevention and treatment of radiation dermatitis.

The present invention relates to a bipolar electrodialysis apparatus for producing lithium hydroxide and sulfuric acid from a lithium sulfate solution. A bipolar electrodialysis apparatus (100) for producing lithium hydroxide and sulfuric acid from lithium sulfate comprises: a positive electrode (20) and a negative electrode (30) that face each other; a first bipolar film (40), an anion-selective dialysis film (60), a cation-selective dialysis film (70), and a second bipolar film (50) that are disposed between the positive electrode (20) and the negative electrode (30); and a porous first nickel foam (80) disposed on the plane of the positive electrode (20) to be in close contact with each other and a porous second nickel foam (90) disposed on the plane of the negative electrode (30) to be in close contact with each other, wherein the nickel foams (80, 90) have a porosity of 50-90%.

The application relates to the field of liquid flow batteries and fuel cells, and particularly relates to a method for preparing a PBI ion exchange membrane through acid solution induced phase separation in one step. After a film-forming resin is made into a resin solution, the resin solution is scraped onto a clean glass plate by using a film coater, and then the glass plate is immersed in an acid solution with different concentrations to induce phase separation, so that the PBI ion exchange membrane is prepared in one step. The PBI ion exchange membrane prepared through the acid solution induced phase separation technology in one step has good ion selectivity and high proton conductivity. In the performance test of the liquid flow battery, the energy efficiency of nearly 82% can be achieved under a current density of 300 mA cm ‑2 , and the long-term battery performance is good; meanwhile, the concentrated resin solution is used as the film-forming liquid, the use of organic solvents can be greatly reduced, and the pollution to the environment is reduced.

The application discloses a battery separator, a preparation method and a battery. The preparation method of the battery separator comprises the following steps: coating a coating liquid on the surface of a base film, then immersing the base film coated with the coating liquid into a coagulation bath, and then performing drying to obtain the battery separator. According to the application, the coating liquid comprises 3-5% of a polymer lithium salt, 9-15% of a binder and 80-88% of a solvent in terms of mass fraction. According to the preparation method of the battery separator, a porous polymer film with an ion selective transmission function can be constructed in situ on the premise of maintaining the mechanical properties of the PE base film, and the high lithium ion migration number and the high ion conductivity can be synergistically improved.

The application discloses a membrane capacitive deionization anode and a preparation method thereof and a membrane capacitive deionization system, relates to the technical field of wastewater treatment and resource utilization, and discloses a membrane capacitive deionization anode preparation method, which comprises the following steps: providing oxidized carbon, wherein the surface of the oxidized carbon contains carboxyl groups; dispersing the oxidized carbon in water, adding nitrate, a first metal salt containing divalent metal ions and a second metal salt containing trivalent metal ions for pre-adsorption; adjusting the pH value and performing crystallization to make the divalent metal ions and the trivalent metal ions form a layered double hydroxide (LDH), so as to obtain an LDH / oxidized carbon composite anode material; and preparing a slurry of the LDH / oxidized carbon composite anode material and loading the slurry on a current collector to obtain the membrane capacitive deionization anode. The embodiment of the application prepares a membrane capacitive deionization anode with high capacity, low energy consumption and excellent ion selectivity, and can efficiently recover phosphates from wastewater.

The present application relates to the field of plant factory water culture, and specifically discloses a kind of plant factory three-dimensional cultivation automatic liquid supply equipment and hierarchical compensation control method, including independent liquid supply unit, comprising: a pneumatic sensing assembly, with a closed flexible sensing capsule inside encapsulating low-boiling working medium, the sensing capsule is configured to respond to the microenvironment humidity change caused by crop transpiration in the cultivation layer. The plant factory three-dimensional cultivation automatic liquid supply equipment and hierarchical compensation control method, through the mechanical combination of transpiration-condensation sensing capsule and nonlinear cam differential proportional valve, realizes the passive, real-time, independent compensation of the different water and fertilizer requirements of each layer of three-dimensional cultivation, and gets rid of the dependence on expensive and frequently maintained online ion selective electrode.

Provided is a method for producing lithium hydroxide, comprising the steps of: introducing a lithium salt solution into a salt solution compartment, and introducing water into an acidic solution compartment and a basic solution compartment; discharging, from the acidic solution compartment, a sulfuric acid solution including sulfuric acid ions separated from the lithium salt solution by an anion-selective ion exchange membrane and hydrogen ions generated by decomposing water through electrodialysis in a first bipolar membrane; discharging, from the basic solution compartment, a lithium hydroxide solution including lithium ions separated from the lithium salt solution by a cation-selective ion exchange membrane and hydroxide ions generated by decomposing water through electrolysis in a second bipolar membrane; and adding an additive to the lithium hydroxide solution discharged from the basic solution compartment to precipitate impurities and remove same.

The application belongs to the technical field of fluorescent analysis and detection, and particularly relates to a tridentate Schiff base compound and a preparation method and application thereof. 2 The formylhydrazine Schiff base compound is widely applied in coordination chemistry, and a parent structure thereof can be used to better study the transformation of a complex under light stimulation, and the imino group also has good photoisomerization performance, at this time, the light stimulation can catalyze the ligand to produce more rich coordination modes, so the isomerization phenomenon of the compound under the action of ultraviolet light is tested, and the application of the compound in a colorimetric chemical sensor is studied. Further research is conducted on whether the compound has different ion selectivity after the conversion configuration under the action of ultraviolet light and the change of the coordination mode, and finally, the complex of the ligand Ni 2+ , Cu 2+ metal is synthesized.

This invention discloses a composite electrodialysis membrane material, comprising a porous support base fabric, an ion exchange layer, and a surface-selective permeation layer. The porous support base fabric is impregnated in the ion exchange layer as a skeleton reinforcement material. The ion exchange layer is formed by mixing and curing ion exchange resin powder, a polymer binder, and a pore-forming agent. The surface-selective permeation layer is coated on at least one surface of the ion exchange layer and comprises nanosheet materials with charged groups and a crosslinking agent. The advantages of this invention compared to existing technologies are: it provides a composite electrodialysis membrane material, its preparation method, and its application, which achieve synergistic improvement in mechanical strength, conductivity, and ion selectivity through a multi-layer structure design.

This invention discloses a method for separating zinc and magnesium from the frozen crystallization product of waste electrolyte in hydrometallurgical processes, belonging to the field of hydrometallurgical technology. The frozen crystallization product of the waste electrolyte in hydrometallurgical processes is heated to 950-1050℃ and held for 2-4 hours, causing zinc sulfate heptahydrate to decompose into zinc oxide and magnesium sulfate heptahydrate to dehydrate into anhydrous magnesium sulfate. Both are transferred as pyrolysis solid products to the next process. Then, the pyrolysis solid products are added to an aqueous leaching solution at a liquid-to-solid ratio of 2-10:1, maintaining the temperature at 20-60℃, and leaching with stirring for 10-60 minutes. Solid-liquid separation yields magnesium-rich solution and zinc-rich slag, achieving zinc-magnesium separation. This method, through thermodynamic transformation, converts ion-selective separation into a solid-liquid leaching separation process based on the differences in the physical properties of the phases, resulting in more efficient, thorough, and cleaner separation. The process flow is shorter, and energy consumption is lower, improving resource utilization while reducing processing costs.

An example sensor includes a conductive electrode and an ion-selective membrane over the conductive electrode. The ion-selective membrane includes an ionophore that is selective for ionized magnesium (iMg) and at least two types of anionic lipophilic salts. The at least two types of anionic lipophilic salts may include one or more fluorinated borate salts and one or more chlorinated borate salts.

This invention discloses a continuous electrochemical lithium extraction device and process from salt lakes, belonging to the field of lithium extraction technology. The device employs a two-chamber structure, separated into a brine chamber and a recovery chamber by a membrane electrode assembly (MEA). By applying voltage to both the brine chamber and the recovery chamber on either side of the MEA, lithium ions are inserted into the MEA in the brine chamber and extracted from the MEA in the recovery chamber. Simultaneously, an oxygen evolution reaction occurs at the electrode in the brine chamber, and a hydrogen evolution reaction occurs at the electrode in the recovery chamber. The MEA, the two-chamber structure, and the liquid path remain fixed throughout the process, eliminating the need to move electrodes, switch chambers, or change liquid paths, thus achieving continuous operation. Furthermore, OH- is generated at the hydrogen evolution electrode in the recovery chamber. ‑ Li released from the membrane electrode + This combination forms a high-value-added lithium hydroxide solution. The device of this invention has a simple structure, is easy to operate, has a recyclable membrane electrode, high lithium-ion selectivity, no acid or alkali consumption, and is environmentally friendly. It is suitable for lithium extraction from high magnesium-to-lithium ratio salt lake brines.

The application is suitable for the field of new energy energy storage flow battery, and provides a polyaryl ion conductive film containing double electron-withdrawing side chain structure and a preparation method thereof.The application is characterized by comprising the following steps: (1) preparing a polyaryl main chain polymer through an ultrastrong acid mediated polycondensation reaction, wherein the polyaryl main chain contains double electron-withdrawing side chain structure; (2) performing a sulfonation reaction on the polyaryl main chain polymer to graft a sulfonic acid group capable of conducting protons on the main chain benzene ring; and (3) preparing a homogeneous and dense ion conductive film from the sulfonated polyaryl polymer through a solution casting method.The polyaryl ion conductive film containing double electron-withdrawing functional side chains prepared by the application can redistribute the electron cloud density of the main chain through the electron-withdrawing effect of the side chain, promote the dissociation of the sulfonic acid group and repel vanadium ions, so that the hydrogen vanadium ion selectivity and cycle stability of the energy storage all-vanadium redox flow battery are significantly improved.

This invention discloses an ion-electronic device, its fabrication method, and its applications. The ion-electronic device comprises a polymer hydrogel matrix and an organic framework material embedded therein, including anion-selective framework materials and cation-selective framework materials. The ion-electronic device of this invention constructs a microstructure with a periodic electrostatic potential field, overcoming the problem of complex ion transport paths and reduced efficiency caused by the disordered microstructures of traditional ion conductors. The organic framework material simulates the function of the lattice potential field in a semiconductor within an organic molecular system. Through the spatial confinement effect of the ordered periodic structure and the synergistic effect of the electrostatic field, it can achieve highly selective transport of specific charged ions, thereby significantly improving the efficiency and selectivity of ion transport.

This invention relates to a monovalent selective anion exchange membrane, its preparation method, and its application. The preparation method includes the following steps: placing the anion exchange base membrane in an electrodeposition solution for electrodeposition; the electrodeposition solution includes a negatively charged polymer and a neutral salt; then placing it in an oxidant solution for a chelation reaction; and finally placing it in a polymer monomer solution for polymerization to obtain the monovalent selective anion exchange membrane. This invention, through sequential electrodeposition, chelation, and polymerization reactions, utilizes the active sites formed by the chelation reaction between the negatively charged layer and the oxidant to regulate the directional polymerization of the polymer, forming a dense polymer-modified layer. This avoids polymer clogging of the anion exchange base membrane pores, achieving high ion selectivity, effectively weakening the trade-off effect between flux and selectivity of the monovalent selective anion exchange membrane, and exhibiting good antifouling performance.

Embodiments herein generally disclose systems and methods of producing a product using electrochemical reduction. The method comprises introducing a gas, the gas comprising carbon dioxide, into a base solution, thereby producing a catholyte solution; feeding the catholyte solution into a cathode chamber and an anolyte solution into an anode chamber of an electrolytic cell, the electrolytic cell comprising: the cathode chamber comprising a cathode; and the anode chamber comprising an anode; applying a first electric potential across the anode and the cathode for a first period of time; applying a second electric potential across the anode and the cathode for a second period of time, wherein the second electric potential is substantially reduced in comparison to the first electric potential; and extracting the product from the cathode chamber. In various embodiments, the membrane comprises a non-ion-selective layer comprising a non-ion-selective material, a first ion-selective layer comprising a first ion-selective material, and a second ion-selective layer comprising a second ion-selective material.

A seawater desalination method based on the photon effect belongs to the field of seawater desalination technology. This invention employs a seawater desalination device, including a base, a seawater power generation chamber, a cooling device, a water vapor separation device, and a shell device; the water vapor separation device includes primary, secondary, and tertiary separation mechanisms. The method steps are as follows: external seawater flows into the inlet tank of the primary separation mechanism through an inlet; under illumination, the seawater flows and evaporates under centrifugal force, and the water vapor is separated by a water vapor separation membrane; the unevaporated seawater is circulated through the secondary and tertiary separation mechanisms; the water vapor is reheated at the hot end of a semiconductor thermoelectric plate and then collected by a gas collecting fan to the cold end for condensation into fresh water; high-concentration seawater and normal seawater generate current under the action of an ion-selective membrane, providing power to the system. This invention utilizes osmotic pressure to generate electricity through the seawater power generation chamber, reducing dependence on external energy; multi-stage water vapor separation and efficient cooling improve desalination efficiency and water quality; an intelligent control system monitors operating parameters in real time to ensure stable operation; and the modular design facilitates maintenance and upgrades, reducing equipment costs and maintenance difficulty.

The utility model discloses an intelligent bioreactor integrated with a multi-parameter biochemical analysis function. The intelligent bioreactor comprises an optical detection module, an electrochemical sensor module and an overflow pool biochemical detection module, the optical detection module adopts a transmission-type optical measurement principle and is used for measuring the optical density of the culture solution; the electrochemical sensor module adopts an electrochemical principle and is used for detecting the concentration of at least 10 metabolites in the culture solution; the overflow pool biochemical detection module adopts an ion selective electrode principle and is used for simultaneously detecting the concentrations and pH values of NH4 < + >, K < + >, Na < + > and Ca < 2 + > ions in the culture solution; the three modules are sequentially connected through fluid channels to form a complete detection flow path.

This invention discloses a method for preparing a high-efficiency uranium extraction hydrogel from seawater, comprising the following steps: Step I: Hydroxylamine hydrochloride is completely dissolved in dimethylformamide (DMF), then Na2CO3 and NaOH are added and stirred rapidly; Step II: Polyacrylonitrile (PAN) is added to the above mixture for reaction, and the resulting reaction mixture is filtered twice through a 0.22 μm filter membrane to obtain poly(aminoamine)oxime (PAO); Step III: A precursor solution containing Zn(NO3)2·6H2O and Cu(NO3)2·3H2O is added in batches to an aqueous solution of Na2CO3, and NaOH solution is gradually added dropwise to adjust the pH; Step IV: The suspension is continuously stirred in a water bath, filtered, thoroughly washed with acetone, and dried to obtain Zn-Cu layered hydroxide (ZnCu-LDH); Step V: The PAO solution and ZnCu-LDH are mixed in a certain proportion to rapidly form a hydrogel. Practical verification shows that the PAO-ZnCu-LDH hydrogel has an adsorption capacity of up to 282 mg / g for uranium. This invention features a simple, quick, and reliable preparation process with high adsorption performance, making it a promising candidate for application in the field of ion selective recovery.

This invention discloses an in-situ small-molecule encapsulated COF composite membrane for ion-selective separation, its preparation method, and its application. The preparation method includes: immersing a porous membrane in an organic phase containing trialdehyde compounds, then removing it and contacting it with an aqueous phase containing COF monomers and functional small molecules to undergo an interfacial reaction; or, immersing the porous membrane in an organic phase containing trialdehyde compounds and COF monomers, then removing it and contacting it with an aqueous phase containing functional small molecules to undergo an interfacial reaction, thereby obtaining the in-situ small-molecule encapsulated COF composite membrane for ion-selective separation. This invention proposes a "one-step in-situ interfacial polymerization + functional small molecule encapsulation" strategy for constructing COF composite membranes. This technical solution utilizes the pore formation window during the COF film formation process to achieve in-situ simultaneous encapsulation of ion-affinity functional small molecules, controlling ion migration paths, thereby achieving a balance between high selectivity and high throughput in ion separation.

This invention relates to the field of water pollution detection technology, specifically to a method for constructing an electrode membrane for resisting EPS contamination in electrochemical water quality sensors. The electrode membrane comprises a solid contact layer, an ion-selective membrane layer, an antifouling substrate, and an enzyme layer sequentially disposed on the conductive substrate surface of the electrochemical water quality sensor. The construction method includes the following steps: S1, preparing the solid contact layer; S2, preparing the ion-selective membrane layer; S3, preparing the antifouling substrate; S4, preparing the enzyme layer; thereby constructing the electrode membrane. This invention constructs an antifouling electrode membrane on an electrochemical water quality sensor. Its main function is to reduce the formation of biofilm on the electrode surface by inhibiting EPS secretion and weakening the EPS bridging structure. Through the synergistic effect of quorum sensing quenching enzymes and complexing functional materials, this invention can significantly improve the antifouling ability of the electrochemical water quality sensor in complex water environments and maintain the long-term stable operation of the electrochemical water quality sensor.

This invention provides a method for constructing an ultrathin polyarylene ether sulfone (PAES-COOH) membrane containing aligned cyclodextrins within an interface confinement, belonging to the field of polyarylene ether sulfone membrane preparation technology. The method involves subjecting PAES-COOH containing carboxyphenyl side groups to an acylation reaction to obtain an acylated PAES-COOH solution. β-cyclodextrin is then added dropwise to the aforementioned acylated PAES-COOH solution to react and obtain PAES-CD powder. The PAES-CD powder is dissolved in a good solvent and then diluted with a low surface tension solvent to prepare a membrane-forming solution. The membrane-forming solution is then dropped onto a water surface, where the droplets spontaneously spread, inducing the β-CD molecules on the PAES-CD side chains to align parallel along the liquid-liquid interface, forming an ultrathin polymer membrane with controllable thickness. This method can obtain ultrathin polymer membranes with uniform angstrom-level pores and excellent ion selectivity.