A catalytic membrane for removal of carbon dioxide from a gas mixture and a process of production thereof

Abstract

The application relates to a catalytic membrane for removal of carbon dioxide from a gas mixture. The catalytic membrane comprises a functional hydrophilic polymeric layer formed by plasma polymerization, having a thickness from 5 to 100 nanometres, comprising carboxylic acid functional groups and a catalytic agent. Below the functional hydrophilic polymeric layer, a tracketched layer is positioned. This track-etched layer is made of thermoplastic polymer and has cylindrical nanochannels, each with a diameter from 100 to 800 nanometres, a length from 20 to 100 micrometers, and the immobilized catalytic agent. The density of nanochannels is in a range from 10⁶ to 10⁸ nanochannels / cm² of the track-etched layer. The application also relates to a method for producing the catalytic membrane.

Description

[0001] A CATALYTIC MEMBRANE FOR REMOVAL OF CARBON DIOXIDE FROM A GAS MIXTURE AND A PROCESS OF PRODUCTION THEREOF

[0002] An invention relates to a catalytic membrane for removal of carbon dioxide from a gas mixture and a process of production thereof.

[0003] TECHNICAL FIELD

[0004] The invention belongs to the field of gas separation membranes and catalytic systems for carbon dioxide (CO2) capture and conversion from a gas mixture. More specifically, it relates to a nanostructured catalytic membrane configured for the selective removal and transformation of carbon dioxide from gas mixtures, such as ambient air, flue gas, or process gas streams. The invention is particularly suited for direct air capture (DAC) and point-source carbon capture. In general, such membranes can be used in applications where efficient and selective removal of carbon dioxide from a gas mixture is required. This includes carbon capture from atmospheric air and industrial emissions, such as in the energy sector, chemical processing, cement production, and steel manufacturing.

[0005] BACKGROUND ART

[0006] Despite the pressing global need to reduce greenhouse gas emissions and mitigate the impacts of climate change caused by carbon dioxide, existing technologies for carbon dioxide capture still face significant technical and operational limitations, particularly for large scale implementations. One of the primary challenges is the low concentration of carbon dioxide in ambient air, which demands the processing of very large volumes of gas to extract a relatively small amount of carbon dioxide it contains. This makes the whole process economically unattractive and impractical, particularly taking into account high energy demand and footprint, low efficiency, high capital and operating costs among others.

[0007] In many conventional systems, the capture of carbon dioxide relies on the use of large columns packed with liquid or solid sorbents. These systems are often complex, energy intensive and sensitive to the variations in the feed and operating conditions. Moreover, most of these systems require elevated temperatures or pressure, swings in major parameters combined with precise controls, regular regeneration of the sorbent in order to function and release the captured carbon dioxide. This regeneration process is energy intensive and contributes substantially to the overall operating cost, impacting the viability of deployment of carbon capture for large-scale and distributed sites. Furthermore, the large volumes of air or industrial flue gas needed to capture meaningful amounts of CO2 require expansive air contactor systems or large absorber columns. This significantly escalates capital expenditures and introduces logistical challenges, especially given spatial constraints at many industrial locations. These efficiency challenges, spanning both Direct Air Capture (DAC) and Carbon Capture, Utilization, and Storage (CCUS) technologies, highlight the urgent need for innovative approaches that reduce both the physical footprint and financial costs associated with effective carbon capture.

[0008] Material cost and durability further limit current technologies. Chemical solvents pose risks due to volatility, corrosiveness, and potential toxicity, leading to environmental and operational complexities. Physical sorbents often suffer from fragility and high costs, with degradation over time reducing capture efficiency.

[0009] Existing membrane systems for CO2 capture struggle with poor selectivity and low permeation of many membrane materials for carbon dioxide capture, resulting in low efficiency for this application. In particular, these materials often exhibit inadequate affinity for carbon dioxide under ambient conditions or suffer from degradation over time among others. As a result, boosting the key characteristics, performance and efficiency of existing membranes for this application remains a serious challenge.

[0010] Document US2020047132A1 discloses a catalytic membrane system intended for carbon dioxide separation, which relies on the immobilization of enzymes such as carbonic anhydrase within nanopores of a porous solid substrate. The membrane features a hydrophilic nanoporous region for retaining a liquid-phase transport medium, typically water, which acts as a solvent for CO2 and supports enzyme activity. Enzyme stabilization is achieved through physical confinement and chemical anchoring to the pore walls. The system includes both hydrophilic and hydrophobic portions, which regulate liquid retention and improve the catalytic performance of the embedded enzymes. While this approach improves selectivity and catalytic efficiency compared to conventional polymer membranes, it has several limitations that remain unaddressed. The prior art membrane struggles with performance under dry or low-humidity conditions, making it unsuitable for applications such as direct air capture. The membrane scalability and adaptability to different operational demands is limited. What is more the enzyme activity in the membrane is dependent on the presence of the moisture. Lack of moisture causes that the enzyme efficiency decreases.

[0011] Document US2021229031A1 discloses enzyme-functionalized polymer membranes for CO2 capture, where carbonic anhydrase (CA) enzymes are immobilized within or on the surface of hydrophilic or water-vapor permeable polymer layers. These membranes rely on facilitated transport in combination with solution-diffusion and include variants with CA dispersed in the polymer, covalently attached via linkers, or incorporated during copolymerization. The membranes typically consist of a single selective layer supported by a porous or dense mechanical backing. The membrane disclosed in US2021229031 Al relies on water vapor in the gas stream to keep the membrane active, which limits performance in dry environments such as direct air capture. What it is more its structure relies on single layer, which limits the degree of control over gas transport paths, reaction kinetics, and moisture regulation.

[0012] The CO2 selective membranes existing in the prior art face significant barriers to commercialization, primarily due to complex, expensive and time-consuming manufacturing processes, which render them unsuitable for large scale production. For instance, many existing methods of productions of the membranes offer limited control over the architecture of the membrane structure, namely pore distribution and size at different layers as a key factor, which impacts the selectivity of the membrane and gas transport efficiency. Furthermore, many of the membranes in the prior art struggle with degradation or loss of catalytic agents, resulting in the loss of performance or effectiveness. For example, some catalytic agents rely heavily on moisture to maintain their activity and efficiency, thus requiring a stable hydrated environment to remain functional. Existing membrane solutions that could meet the expectations for carbon capture are not suited for large-scale production due to the complexities involved in the fabrication’s steps and integration into the scalable modules. There is a particular demand for CO2 selective membrane that can sustain performance over extended durations, retain essential humidity, minimise energy consumption, and at the same be easily and flexibly applied in a large-scale across a range of industrial sectors. There is also a clear need for simplified, cost-effective method of production of such membrane. The limitations of the existing solutions highlight the need for advanced membranes for CO2 capture that could be manufactured at scale with less complexities and accurate control, can operate efficiently at major demanding industrial conditions with practical implications, while providing sufficiently large throughput, selectivity and kinetics for carbon dioxide capture and release.

[0013] SUMMARY OF THE INVENTION

[0014] The present invention improves the challenges encountered in the prior art by providing a catalytic membrane for removal of carbon dioxide from a gas mixture comprising: a functional hydrophilic polymeric layer formed by plasma polymerization, having a thickness from 5 to 100 nanometres, comprising carboxylic acid functional groups and a catalytic agent. Below the functional hydrophilic polymeric layer, a track-etched layer is positioned. This track-etched layer is made of thermoplastic polymer and has cylindrical nanochannels, each with a diameter from 100 to 800 nanometres, a length from 20 to 100 micrometers, and the immobilized catalytic agent. The density of nanochannels is in a range from 106to 108nanochannel s / cm2of the track-etched layer.

[0015] When a gas mixture comprising CO2 is brought into contact with the catalytic membrane, the CO2 molecules encounter the functional hydrophilic polymeric layer at the surface of the membrane. The gas mixture comprising CO2 may be any gas containing carbon dioxide. For example, the gas mixture comprising CO2 may be air or an emission gas with a carbon dioxide concentration from about 0.04% to about 100%, such as flue gas or raw biogas. The gas mixture comprising CO2 may further contain a promoting gas, such as ammonia, for promoting the transport of said carbon dioxide into said liquid. The functional hydrophilic polymeric layer is formed by plasma polymerization and has a thickness ranging from 5 to 100 nm, preferably from 5 to 50 nm. This range thickness for the functional hydrophilic polymeric layer keeps an optimal balance: a thickness below 5 nanometres makes it difficult to establish a uniform deposition layer with structural integrity. On the other hand, a thickness above 100 nanometres may lead to the risk of collapse of the functional hydrophilic polymeric layer during the drying or operational processes by playing resistance against the transport. More preferably the functional hydrophilic polymeric layer has thickness ranging from 5 to 50 nanometres. This layer is functionalized with carboxylic acid groups and comprises a catalytic agent. The carboxylic acid groups in the functional hydrophilic layer help condense water vapor, from the gas mixture or the environment adjacent to it, onto the functional hydrophilic layer. This results in the formation of a thin water layer on the surface of the functional hydrophilic layer, ensuring adequate hydrated environment for catalytic activity, particularly for enzymes like carbonic anhydrase acting as catalytic agent. Mentioned thin water layer within the functional hydrophilic polymeric layer acts as a distinct and important microenvironmental layer. This water layer typically has a molecular-scale thickness ranging from about 0,3 nm to 1000 nm, preferably from about 0,3 nm to 50 nm, and more preferably from about 3 nm to 50 nm. The presence of this water layer is very important for maintaining catalytic activity by providing hydration to the immobilized catalytic agents such as carbonic anhydrase. This discrete water layer forms naturally and facilitates rapid dissolution of carbon dioxide into the membrane system while reducing diffusion resistance compared to bulk water layers used in conventional membranes. The functional hydrophilic layer not only helps in humidity retention but also serves as the medium for immobilizing the catalytic agent. Both features are important for creating and establishing effective and yet selective interaction with CO2 molecules and the membrane. Further, the carboxylic acid groups ensure that the catalytic agent remains hydrated and functional. Once the CO2 molecules are captured in the water layer of the functional hydrophilic layer, they are immediately transformed into bicarbonate ions (HCO3 ) by the catalytic agents. The bicarbonate ions and remaining CO2 molecules then begin to move toward the hydrophilic layer beneath the functional hydrophilic layer. This is driven by the chemical potential gradients of components across this zone. The track-etched polymeric layer is composed of a thermoplastic polymer, characterized by a high density (in the range of 106to 108nanochannels per cm2) of cylindrical nanochannels, each having a diameter between 100 and 800 nanometres and a length ranging from 20 to 100 micrometres. The catalytic agent is immobilized inside these nanochannels. The uniform geometry of the nanochannels ensures reproducible flow dynamics, maximizes surface-to-volume ratio for catalytic conversion, minimizes diffusion resistance due to non-tortuosity and avoids possible by-pass of CO2, thus enhancing selectivity, efficiency, and stable operation of the membrane under continuous operation. The cylindrical nanochannels comprise water, especially at the entry mouth and along the nanochannels, ensuring hydration of the catalytic agent embedded inside. The catalytic agent facilitates the rapid conversion of CO2 to bicarbonate ions and vice versa. This conversion is reversible, meaning CO2 can be rapidly entered and released within the nanochannels, creating a dynamic inter-conversion of CO2 and bicarbonate throughout the channel. Finally, only CO2 molecules exit nanochannels of the hydrophilic layer forming a CCh-rich stream on the downstream side of the membrane, which can be collected or directed for further processing. The membrane of the invention allows for effective CO2 capture and ensures establishment of a stable humidity gradient, which is crucial for continuous catalytic operation. Through this integrated structure, the catalytic membrane facilitates rapid and reversible conversion of carbon dioxide, supports continuous operation, and enables scalable implementation of efficient CO2 capture and release. The invention thus provides a highly effective solution for low-energy and high-performance carbon capture, that can work continuously and with high kinetics, particularly in applications requiring compact and modular systems. Plasma polymerization enables the precise deposition of the functional hydrophilic layer with functional groups that can hold catalytic agent and humidity, while not blocking the entry points of nanochannels of the reactive layer. Plasma polymerization also allows to the reduce the thickness of the functional hydrophilic layer and therefore the whole membrane. The high nanochannel density and uniformity in ensure consistent performance. Track-etching offers several key advantages for membrane fabrication. It enables the creation of nanochannels that provide a predictable and uniform structure for gas transport. The method is industrially scalable and suitable for large-scale applications. Compared to alternative fabrication techniques, track-etching lowers membrane production costs and produces membranes with sufficient mechanical strength to withstand deployment over hundreds of meters. Other fabrication methods often struggle to maintain mechanical integrity and uniformity over such long distances. Additionally, track-etching allows precise control over nanochannels size and distribution, which is critical for optimizing catalyst loading, gas diffusion, and overall membrane performance.

[0016] Preferably, the membrane further comprises a support layer, which is hydrophobic and which is located below the track-etched layer, wherein the support layer has a network of interconnected pores, wherein each pore has a diameter and / or length larger than the corresponding diameter and / or length of the nanochannels in the track-etched layer (i.e. diameter exceeding the 100-800 nm diameter range of the nanochannels, i.e. length exceeding the 20-100 pm length of the nanochannels). The support layer provides mechanical robustness and structural integrity to the whole membrane. Its network of larger interconnected pores facilitates efficient and low- resistance transport of CO2 downstream. The hydrophobic nature of the support layer prevents unwanted water absorption, which could otherwise impair membrane performance by causing excessive water retention or flooding. The support layer is preferably made from industrially available polymers such as polypropylene, polyethylene, polyester, or polyvinylidene fluoride, materials known for their durability and chemical resistance. These material choices not only ensure long-term stability and compatibility with various operational environments but also support scalable manufacturing.

[0017] Preferably, the track-etched layer is made of polyamide, polyimide, polyacrylonitrile, polycarbonate, polyester or polysulfone. Polyamide, polyimide, polyacrylonitrile, polycarbonate, polyester and polysulfone are selected as materials for the track-etched layer due to their favourable chemical structures. An example of such thermoplastic polymer is 4,4'- bismaleimidodiphenylmethane (polyamide).

[0018] Preferably, the catalytic agent is selected from carbonic anhydrase, a metal-organic framework (MOF), an aqueous amino acid or a salt thereof, or a solid bis-iminoguanidine (BIG). Optionally, the catalytic agent may include enzyme variants or engineered strains of carbonic anhydrase to enhance stability and activity under operational conditions. Examples of MOFs include but are not limited to ZIF-8 and MOF-74, which provide high surface area and tunable catalytic sites, combining synthetic robustness with efficient catalysis. Aqueous amino acids such as histidine or glutamic acid, and their corresponding salts, may be employed due to their favorable solubility and interaction with CO2. Solid bis-iminoguanidine compounds, such as 1,1’ -(ethane- 1,2- diyl)bis(3-(trifluoromethyl)guanidine) and l,r-(methanediyl)bis(3-(trifluoromethyl)guanidine), offer strong chemical affinity for CO2 and promote hydration / dehydration reactions effectively. The selection of these catalytic agents enables highly efficient and selective conversion of carbon dioxide to bicarbonate and vice versa within the membrane structure, facilitating rapid and reversible CO2 capture and release. Carbonic anhydrase (CA), being a natural enzyme, provides biomimetic catalytic efficiency, accelerating the hydration and dehydration reactions critical for continuous CO2 capture under mild conditions. Metal-organic frameworks (MOFs) contribute high surface area and tunable catalytic sites, offering a synthetic alternative that combines stability and catalytic performance. Aqueous amino acids and their salts provide further options for catalytic activity with favorable solubility and interaction properties, while solid bis-iminoguanidine compounds offer effective CO2 binding through chemical affinity and promote hydration / dehydration reactions. Immobilizing these catalytic agents on the plasma-functionalized hydrophilic membrane surface and within its nanochannels maximizes catalyst exposure to CO2, optimizes interaction kinetics, and maintains hydration essential for catalytic function.

[0019] Preferably, the catalytic membrane is substantially flat. The substantially flat catalytic membrane has practical benefits, including ease of production and scalability. The flat configuration facilitates uniform plasma polymerization and consistent catalyst immobilization across the membrane surface, which are crucial for maintaining effective CO2 conversion and stable operation. Additionally, flat membranes allow for integration into modular systems and simplified assembly, supporting industrial-scale applications. Within the meaning of the claimed invention, the term "substantially flat" shall be understood as referring to a membrane structure that is primarily planar and uniform in its overall shape and surface profile. Minor deviations or slight surface undulations that do not materially affect the membrane’s function or integrity are also encompassed within this definition.

[0020] Preferably, nanochannels have diameter around 400 nanometres. This specific diameter offers several functional advantages. This size provides an optimal balance between nanochannels density and size, enabling efficient diffusion of carbon dioxide molecules through the membrane while maintaining a high surface area for catalyst loading. Smaller nanochannels would limit the amount of catalytic agent that can be immobilized and reduce nanochannels density, while larger nanochannels increase the risk of leaks and potentially reduce membrane stability. Channels of about 400 nm are sufficiently large to allow effective catalyst immobilization inside the nanochannels yet small enough to maintain the mechanical strength of the membrane and minimize water leakage. This nanochannel’s size supports stable hydration of the catalytic agent, which is essential for continuous operation, and contributes to improved carbon dioxide capture performance under practical operating conditions.

[0021] Preferably, nanochannels are substantially vertically aligned with respect to a surface of the catalytic membrane. Such vertical, uniform alignment of nanochannels reduces resistance to diffusion and enhances CO2 capture efficiency compared to interconnected pores, which tend to decrease stability and slow diffusion. This vertical alignment can be achieved through tracketching. The term “substantially vertically” means that the nanochannels are oriented approximately perpendicular to the membrane plane, while allowing for slight deviations or minor angular variations from an exact 90-degree angle.

[0022] The present invention provides also a method of production of the catalytic membrane comprising the following steps: providing a polymer material in a form of film (preferably thin film with a thickness ranging from about 20 micrometres to 100 micrometres) and track-etching it by irradiating using high-energy ions and chemically etching in an alkaline aqueous solution, so as to form plurality of nanochannels. The method further includes neutralizing the alkaline aqueous solution on the polymer material with an acid and drying the polymer material with multiple nanochannels. The next step of the method comprises plasma polymerizing the polymer material with multiple nanochannels under vacuum by introducing monomers of carboxylic acid in gas phase onto the polymer material to make the polymer material hydrophilic, thereby forming the track-etched layer and functional hydrophilic polymeric layer. The final step includes loading and stabilizing the catalytic agent within a surface of the functional hydrophilic polymeric layer and within the nanochannels of the track-etched layer.

[0023] Overall, the described method of production provides a catalytic membrane with highly controlled nanochannel architecture, enhanced hydrophilicity, and stable catalyst immobilization, resulting in efficient and selective carbon dioxide capture. The track-etching steps create uniform in geometry nanochannels that maximize surface area and enable predictable gas transport while maintaining mechanical robustness. Plasma polymerization imparts a thin, hydrophilic functional hydrophilic layer rich in carboxylic acid groups, which facilitates strong binding and stable immobilization of the catalytic agent both on the membrane surface and within the nanochannels. This plasma polymer layer significantly enhances membrane surface hydrophilicity by reducing the water contact angle to approximately 20-30 degrees or less, improving water and catalyst retention with less risk of evaporation or leaching. Hydrophilicity and hydrophobicity are relative properties that exist on a spectrum, which is characterized by the water contact angle. For example, polycarbonate (PC), material which can be used as a base material for the track-etched layer, initially exhibits a contact angle around 80°, which places it near the border between hydrophilic and hydrophobic. Chemical treatments and plasma polymerization reduce this angle, increasing hydrophilicity. Importantly, the plasma polymer layer penetrates into the nanochannels of track- etched layer, which may be hydrophobic or partially hydrophilic, thereby increasing the water and catalyst holding capacity of the membrane. This allows effective membrane performance regardless of the base material’s for track-etched layer initial hydrophobicity. This ensures sustained catalytic activity and hydration essential for continuous CO2 conversion ensures long- lasting catalytic activity, which improves the membrane’s durability and maintains high CO2 conversion performance over extended use.

[0024] Preferably, the method further comprises the step of rinsing the neutralized polymer material with distilled or deionized water after neutralizing. This additional step removes any residual chemicals, such as etching agents and neutralizing acids, from the polymer surface and nanochannels. This cleaning step prevents contamination or damage to the membrane structure and ensures that the subsequent drying, plasma polymerization, and catalyst loading steps occur on a clean, uncontaminated surface.

[0025] Preferably, the drying is air drying. Air drying is simple, cost-effective, and gentle drying technique that avoids the use of harsh chemicals or high temperatures, which could otherwise damage the delicate nanochannel structure.

[0026] Preferably, the alkaline aqueous solution is one of: sodium hydroxide (NaOH), potassium hydroxide (KOH), or ammonium hydroxide (NH4OH) and wherein the alkaline aqueous solution is heated to a temperature range from 40°C to 65°C, more preferably, from 50°C to 60 °C. The alkaline solution effectively develops the latent tracks created by high-energy irradiation into uniform, well-defined nanochannels by chemically etching the polymer material in a form of film. Heating the solution within this temperature range optimizes the etching rate, ensuring precise control over nanochannels size and morphology without damaging the polymer membrane. This controlled etching contributes to reproducible membrane porosity and nanochannels uniformity, which are critical for consistent CO2 transport and catalytic efficiency. Moreover, using commonly available alkaline solutions at these controlled temperatures ensures an industrially scalable, cost- effective, and reliable process, which supports large-scale membrane production with high quality and performance.

[0027] Preferably, wherein time of chemically etching the polymer material is from 1 to 15 minutes, preferably from 5 to 10 minutes. This time window allows sufficient development of the irradiated tracks into nanochannels with the desired diameter and uniformity, ensuring effective nanochannels formation. Etching for too short a time may result in incomplete or undersized nanochannels, reducing membrane performance for CO2 transport and catalytic activity. Conversely, excessively long etching can damage or weaken the polymer membrane structure, compromising mechanical strength and durability. Therefore, maintaining etching within this preferred time range balances precise nanochannels formation with preservation of membrane integrity, supporting consistent quality and reliable large-scale production as highlighted by the applicant.

[0028] Preferably, irradiating the polymer material is made using high-energy ions such as xenon, krypton, uranium or lead ions an with energy around 1-10 MeV . and a dose from 1014to 1016electrons / cm2. or. Irradiation with high-energy heavy ions such as xenon (Xe+), krypton (Kr+), uranium (U+), or lead (Pb+) at energies around 1-10 MeV per nucleon enables creation of highly uniform, straight, and well-defined latent tracks in the polymer. These tracks translate into cylindrical nanochannels with precise diameters and depths after chemical etching. It allows for partial or shallower nanochannel formation. This alternative provides flexibility to tailor nanochannel depth and characteristics to optimize membrane function. The term “high-energy" irradiation within the meaning of the claimed invention refers to ion beams with energies sufficient to penetrate the polymer film and create latent damage tracks deep enough for chemical etching.

[0029] Preferably, the plasma polymerization step lasts no longer than 5 minutes and is performed under vacuum conditions using a plasma power ranging from 5 to 10 W. This carefully controlled plasma polymerization facilitates the formation of a thin, uniform, and hydrophilic functional polymeric layer composed of carboxylic acid monomers on the membrane surface and within the nanochannels. Precise control of power and duration prevents excessive layer thickness or nanochannels blockage, ensuring the nanochannels remain open for efficient gas transport. The gas composition during plasma polymerization may be regulated, for example monomers such as formic acid and acrylic acid are employed because they enable strong bonding with the catalytic agent. Plasma can penetrate to a depth up to 50 nanometres inside nanochannels, preferably from 20 to 50 nanometres inside the nanochannels. It ensures that the functional hydrophilic layer is not only formed on the surface but also partially coats the interior walls of the nanochannels.

[0030] Preferably, loading and stabilizing the catalytic agent within a surface of the functional hydrophilic polymeric layer and nanochannels of the track-etched layer is performed by immersion in an aqueous solution comprising the catalytic agent by duration from 2 to 20 hours, preferably from 5 to 15 hours, this controlled immersion time allows effective binding of the catalytic agent to the hydrophilic plasma polymerised layer. This ensures stable immobilization of the catalyst within the nanochannels and on the surface, which improves enzyme stability and catalytic efficiency. The immobilization can be affected in any suitable manner depending on the type of catalytic agent 4 used. It may include physical adsorption and / or covalent bonding (e.g., glutaraldehyde crosslinking). For example, when the catalytic agent is carbonic anhydrase, it may be immobilized using glutaraldehyde cross-linking. To sum up, the invention offers a number of important advantages over existing carbon dioxide removal technologies, both in terms of performance and practical implementation.

[0031] This integrated design of the membrane enables selective and efficient removal of carbon dioxide from gas mixtures, even under low-concentration conditions such as those encountered in ambient air.

[0032] One significant advantage of the invention is its ability to operate continuously under mild temperature and pressure conditions. Unlike conventional systems that require thermal regeneration or cyclic switching, the membrane supports steady-state operation, thereby reducing energy input and enabling simpler system designs. The functionality of the membrane also does not require high-pressure. This makes the technology especially attractive for distributed or modular applications.

[0033] The catalytic membrane has ability to perform CO2 separation without applying pressure on the feed side, operating under natural flow conditions. This means that it can selectively capture and convert only CO2 molecules into bicarbonate within the membrane, while a slight vacuum on the downstream side enables the release and collection of pure CO2. This approach prevents other gases from passing through the membrane ensuring high selectivity and operational efficiency with reduced energy consumption.

[0034] The invention also provides enhanced catalytic performance due to uniformly structured nanochannels within the track-etched layer. These channels facilitate rapid access of large number of carbon dioxide molecules, amounting theoretically to the number of nanochannels, to the embedded catalytic agent, improving reaction kinetics and increasing conversion efficiency. The high surface area, large nanochannel density, and optimized geometry of the nanochannels maximize the reaction rates for CO2 conversion. In addition, the spatial confinement of the nanochannels improves stability and minimises leaching or degradation of catalytic agents during prolonged use while maximizing the interaction potential of CO2 molecules.

[0035] Humidity retention is another important advantage. The functional hydrophilic polymeric layer formed by plasma polymerization, is configured to promote condensation of water vapor and preserve a locally humid microenvironment around the catalytic agents embedded in the layer (due to naturally formed water layer). This is important for sustaining the catalytic reaction, especially in dry environments or when processing air with low relative humidity. Additionally, the tracketching process used for manufacturing the membrane ensures control over the nanostructure formation, leading to uniform nanochannel size and distribution, improving both performance and scalability. Plasma polymerization offers precise functionalization of the membrane’s surface, enabling the creation of a thin, uniform layer that retains humidity and ensures that the catalytic agents remain active during the CO2 conversion process. This improves the long-term stability of the membrane and ensures efficient catalytic performance under various operating conditions.

[0036] Combining plasma polymerization with catalyst immobilization offers a significant advantage by synergistically enhancing CO2 separation performance beyond what either method can achieve alone. Plasma polymerization alone provides limited improvement, and similarly, the catalyst by itself is less effective at the same membrane thickness. While very thin membranes without plasma treatment can improve capture, they often suffer from reduced mechanical strength, making them less suitable for large-scale applications. Thus, the combined process not only boosts CO2 capture but also influences membrane scalability.

[0037] These advantages result in a catalytic membrane that is compact, energy-efficient, catalytically active, and scalable. These advantages result in a process of production of the membrane, which is simplified, cost-effective and scalable.

[0038] BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Fig. 1 shows an overview of a process of carbon dioxide capture using catalytic membrane of the present invention

[0040] Fig. 2 shows an overview of a process of carbon dioxide capture using embodiment of the catalytic membrane with the support layer

[0041] Fig.3 shows schematic view for the top showing the placement of the catalytic agent on the surface of the functional hydrophilic polymeric layer

[0042] Fig. 4 shows test setup for a capture reactor incorporating the catalytic membrane of the present invention.

[0043] DETAILED DESCRIPTION OF THE INVENTION

[0044] Fig. 1 shows schematically an embodiment of the catalytic membrane 1 of the present invention and the process of carbon dioxide removal using catalytic membrane 1. The catalytic membrane 1 comprises multiple layers, each serving a specific function. The first layer is a functional hydrophilic polymeric layer 2 formed by plasma polymerization, with a thickness ranging from 5 to 100 nanometres and more preferably from 5 to 50 nanometres. This layer comprises carboxylic acid functional groups which promote the condensation of water vapor, creating a stable thin layer of water in the functional hydrophilic layer. The water layer is formed naturally with a thickness in the range of about 0.3 nm to 1000 nm, preferably from 0.3 nm to 50 nm, more preferably about 3 nm to 50 nm. This water layer is important for maintaining the hydration and activity of the catalytic agent 4, especially under low ambient humidity conditions. The functional hydrophilic layer also comprises the catalytic agent 4. Beneath the functional hydrophilic polymeric layer lies a track-etched layer 3, which is made of thermoplastic polymer. This layer comprises a high density of cylindrical nanochannels. Nanochannels can be oriented at an angle to the plane of the plane of the layer, preferably substantially perpendicularly to the plane of the layer. The nanochannels have a diameter ranging from 10 to 800 nanometres and a length from 20 to 100 micrometres. The nanochannels also comprise the catalytic agent 4, mostly on the bottom of the nanochannels and water, especially on the top of nanochannels. The catalytic agent 4 in the nanochannels facilitates the conversion of dissolved CO2 into bicarbonate ions (HCCh ) and vice versa. This conversion is reversible, meaning CO2 can be rapidly absorbed and released within the nanochannels. The density of nanochannels in the track-etched layer 3 is in the range of 106to 108nanochannel s / cm2, ensuring a high surface area for CO2 capture and conversion. The catalytic agent 4 in the track- etched layer 3 is preferably selected from carbonic anhydrase, a metal-organic framework (MOF), an aqueous amino acid or a salt thereof, or a solid bis-iminoguanidine (BIG). Preferably, the track- etched layer 3 is made of polyamide, polyimide, polyacrylonitrile, polycarbonate, polyester or polysulfone. The track-etched layer 3 can be substantially flat and preferably nanochannels span its entire thickness, meaning that track-etched layer 3 thickness is from 20 to 100 micrometres.

[0045] Figure 2 shows the embodiment of the catalytic membrane 1 with additional support layer 5 located below the track-etched layer 3. The support layer 5 also comprises a network of interconnected pores, each with dimensions larger than dimensions of nanochannels. The pores of the support layer 5 do not comprise water (the layer is hydrophobic ), so it further facilitates transport of CO2 enriched stream. The support layer the support layer 5 can be made of polypropylene, polyethylene, polyester or polyvinylidene fluoride.

[0046] Figure 3 shows schematic view for the top showing the placement of the catalytic agent 4 on the surface of the functional hydrophilic polymeric layer 2. In the catalytic membrane 1, the catalytic agent 4 is primarily located in two areas. The first area is on the surface of the functional hydrophilic polymeric layer 2, which is the outermost layer exposed to the gas mixture, but excluding the openings to the cylindrical nanochannels of the reactive polymeric layer 3. The second area where the catalytic agent 4 is present is the internal walls of the nanochannels within the track-etched layer 3. The immobilization of the catalytic agent 4 in these regions can be achieved through two main methods. First, the catalytic agent can be physically immobilized by interacting with the walls of the cylindrical nanochannels, potentially using van der Waals forces or similar physical interactions. Alternatively, chemical immobilization can occur via covalent bonding, using methods such as glutaraldehyde or polyethylenimine (PEI), which are well-known techniques in the art. The immobilization occurs both on the surface of the functional hydrophilic polymeric layer 2 and inside the nanochannels of the track-etched layer 3. As shown in Fig.3, the functionalized hydrophilic layer 2 is preferably partially covering the track-etched layer 3, meaning it does not fully cover the nanochannels.

[0047] Figure 4 provides a schematic view of the reactor 10 employing an embodiment of the catalytic membrane 1 of the present invention. As shown on Fig. 4, an ambient air enters the reactor 10 via ambient air input 7, where CO2 is selectively absorbed by the membrane. The air, with reduced CO2, exits the reactor 10 via ambient air output 8. The concentrated CO2 is collected through output 9 of the reactor 10, allowing for efficient CO2 removal and capture.

[0048] The method of production of the catalytic membrane 1 of the embodiment shown in Figure 1 includes several steps, starting with providing a polymer material in a form of a film and tracketching it. Preferably, the film is thin and has a thickness ranging from about 20 micrometres to 100 micrometres. The process of track-etching includes irradiating the polymer material by using high-energy ions and chemically etching the polymer material in an alkaline aqueous solution, so as to form plurality of nanochannels. The step of irradiating the polymer material can be made using high-energy ions such as xenon, krypton, uranium or lead ions, energy around 1-10 MeV .and a dose from 1014to 1016electrons / cm2. The irradiation with high-energy ions creates latent tracks in the polymer material. These tracks are developed into cylindrical pores by chemical etching in alkaline solution, preferably heated alkaline solution. The alkaline aqueous solution can be one of sodium hydroxide (NaOH), potassium hydroxide (KOH), or ammonium hydroxide (NH4OH) and wherein the alkaline aqueous solution is heated to a temperature range from 40°C to 65°C, more preferably, from 50°C to 60 °C. Preferably, time of chemically etching the polymer material is from 1 to 15 minutes, preferably from 5 to 10 minutes. After track-etching step the alkaline aqueous solution on the polymer material is neutralized with an acid, such as acetic acid, to stop the chemical etching. Then the polymer material is dried, preferably using air drying. The next step includes plasma polymerizing the polymer material with multiple nanochannels under vacuum by introducing monomers of carboxylic acid (e.g., formic acid, acrylic acid) in gas phase onto the polymer material to make the polymer material hydrophilic, thereby forming functional hydrophilic polymeric layer. Preferably, plasma polymerizing step lasts no longer than 5 minutes and is performed under vacuum conditions using plasma power from 5 to 10 W. Plasma can penetrate to a depths up to 50 nanometres inside nanochannels, preferably from 20 to 50 nanometres inside the nanochannels. The gas composition during plasma polymerization may also be regulated, for example monomers such as formic acid and acrylic acid are employed because. Catalytic agent 4 maybe one of the following: carbonic anhydrase (CA), metal-organic frameworks (MOFs), aqueous amino acids or salts, solid bis-iminoguanidine (BIG). The last step of the method includes loading and stabilizing the catalytic agent 4 within a surface of the functional hydrophilic polymeric layer 2 and within the nanochannels of the track-etched layer 3. This step can be performed by immersion in an aqueous solution comprising the catalytic agent by duration from 2 to 20 hours, preferably from 5 to 15 hours, more preferably for 8-15 hours, such as for about 12 hours. The catalytic agent 4 is immobilized on the surface of the functional hydrophilic polymeric layer 2 and within nanochannels of the track-etched layer 3. The immobilization can be affected in any suitable manner depending on the type of catalytic agent 4 used. It may include physical adsorption and / or covalent bonding (e.g., glutaraldehyde cross-linking). For example, when the catalytic agent 4 is carbonic anhydrase, this may be immobilized using glutaraldehyde crosslinking. The optional step of the method is additional step of rinsing the neutralized polymer material with distilled or deionized water after neutralizing. This step ensures removal of etching and neutralizing agents that could otherwise interfere with membrane function or catalyst immobilization.

Claims

CLAIMS1. A catalytic membrane (1) for removal of carbon dioxide from a gas mixture comprising: a. a functional hydrophilic polymeric layer (2) formed by plasma polymerization, having a thickness from 5 to 100 nanometres and comprising carboxylic acid functional groups and a catalytic agent (4), b. a track-etched layer (3) which is positioned below the functional hydrophilic polymeric layer (2), wherein the track-etched layer (3) is made of thermoplastic polymer and has a plurality of cylindrical nanochannels wherein each nanochannel has: i. a diameter from 100 to 800 nanometres, ii. a length from 20 to 100 micrometres, wherein the catalytic agent (4) is immobilized within the nanochannels and a density of nanochannels is in a range from 106to 108nanochannel s / cm2of the track- etched layer (3).

2. The catalytic membrane (1) according to claim 1, wherein the catalytic membrane (1) further comprises a support layer (5), which is hydrophobic and which is located below the track-etched layer (3), wherein the support layer (5) has a network of interconnected pores, wherein each pore has a diameter and / or length larger than the corresponding diameter and / or length of the nanochannels in the track-etched layer (3).

3. The catalytic membrane (1) according to claim 2, wherein the support layer (5) is made of polypropylene, polyethylene, polyester or polyvinylidene fluoride.

4. The catalytic membrane (1) according to claim 1, 2 or 3, wherein the track-etched layer (3) is made of polyamide, polyimide, polyacrylonitrile, polycarbonate, polyester or polysulfone.

5. The catalytic membrane (1) according to any of the preceding claims wherein the catalytic agent is selected from carbonic anhydrase, a metal-organic framework (MOF), an aqueous amino acid or a salt thereof, or a solid bis-iminoguanidine (BIG).

6. The catalytic membrane (1) according to any of the preceding claims wherein the catalytic membrane (1) is substantially flat.

7. The catalytic membrane (1) according to any of the preceding claims wherein nanochannels are substantially vertically aligned with respect to a surface of the catalytic membrane (1).

8. Method of production of the catalytic membrane (1) according to any of claims from 1 to 7, comprising the following steps: a. Providing a polymer material in a form of film, b. Track-etching the polymer material by i. irradiating the polymer material by using high-energy ions, ii. chemically etching the polymer material in an alkaline aqueous solution, so as to form a plurality of nanochannels, c. neutralizing the alkaline aqueous solution on the polymer material with an acid, d. drying the polymer material with multiple nanochannels, e. plasma polymerizing the polymer material with multiple nanochannels under vacuum by introducing carboxylic acid monomers in the gas phase onto the polymer material, thereby forming the layer (3) and functional hydrophilic polymeric layer (2), f. loading and stabilizing the catalytic agent (4) on a surface of the functional hydrophilic polymeric layer (2) and within the nanochannels of the track-etched layer (3).

9. The method according to claim 8, including additional step of rinsing the neutralized polymer material with distilled or deionized water after neutralizing.

10. The method according to claim 8 or 9, wherein drying is air drying.

11. The method according to any of the preceding claims, wherein the alkaline aqueous solution is one of: sodium hydroxide (NaOH), potassium hydroxide (KOH), or ammonium hydroxide (NH4OH) and wherein the alkaline aqueous solution is heated to a temperature range from 40°C to 65°C, more preferably, from 50°C to 60 °C.

12. The method according to any of the preceding claims, wherein time of chemically etching the polymer material is from 1 to 15 minutes, preferably from 5 to 10 minutes.

13. The method according to any of the preceding claims, wherein irradiating the polymer material is made by using high-energy ions such as xenon, krypton, uranium or lead ions, energy around 1-10 MeV. and a dose from 1014to 1016electrons / cm2.

14. The method according to any of the preceding claims, wherein plasma polymerizing step lasts no longer than 5 minutes and is performed under vacuum conditions using plasma power from 5 to 10 W.

15. The method according to any of the preceding claims, wherein loading and stabilizing the catalytic agent (4) within a surface of the functional hydrophilic polymeric layer (2) and nanochannels of the track-etched layer (3) is performed by immersion in an aqueoussolution comprising the catalytic agent (4) by duration from 2 to 20 hours, preferably from 5 to 15 hours.

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