Hydrophobic metal-organic framework-polymer composite material

Abstract

The present invention relates to a hydrophobic metal-organic framework (MOF)-polymer composite material, a method for its preparation, and its use in removing acid gases from gaseous streams. The composite comprises a core structure made of MOF and a water-insoluble polymer, coated with a hydrophobic layer, preferably a crosslinked polysiloxane layer.

Description

[0001] Hydrophobic Metal-Organic Framework-Polymer Composite Material

[0002] TECHNICAL FIELD

[0003] The present invention relates to a hydrophobic MOF-polymer composite, a method of making same, and a method for removing an acid gas from a gaseous stream using the hydrophobic MOF-polymer composite.

[0004] TECHNICAL BACKGROUND

[0005] Carbon capture, utilization and storage (CCUS) technologies are widely regarded as crucial for meeting global energy and climate goals, particularly in limiting global temperature increases to below 1.5°C. These technologies focus on capturing CO2 from various sources, including diluted gas streams such as flue gas (8 to 14 volume % CO2) and ambient atmospheric air (about 450 ppm CO2). Currently, the upfront cost for CO2 capture represents a significant portion of total CCUS costs, accounting for over 80% in most cases and nearly 99% for direct air capture (DAC).

[0006] Metal-organic frameworks (MOFs) have emerged as promising nextgeneration adsorbent materials for carbon capture and removal. These crystalline structures, formed through coordination bonds between metal cations and organic ligands, are characterized by their ultrahigh porosity, large surface area, tunable pore size and geometry, and versatile modification capabilities. Compared to traditional adsorbents like zeolites and activated carbons, MOFs offer superior performance and flexibility in design.

[0007] The typical process for CO2 capture using adsorbents like MOFs involves temperature swing adsorption (TSA) or vacuum -temperature swing adsorption (VTSA). These methods involve a cyclical process of cooling the adsorbent, adsorbing CO2, and then desorbing it through thermal means, often in combination with vacuum. The overall economics of this process are heavily influenced by the methods used for sorbent heating and regeneration.

[0008] Traditionally, externally heated TSA systems have been used, but they present significant challenges. The large thermal resistance of mesoporous adsorbents and the substantial column dimensions necessitate hours or even days for regeneration heat introduction. This results in a need for a large number of columns, significantly increasing capital costs. To address this issue, direct heating using steam has become the technology of choice for solid adsorbentbased CO2 capture technologies. Steam heating can rapidly bring the sorbent to the desorption temperature, often within seconds. However, steam utilization introduces its own set of problems. Many water-sensitive sorbents, including the majority of reported MOFs, can degrade when exposed to steam. Additionally, the condensation of steam into liquid water can cause increased pressure drop for air movement or block the pores of the sorbent, reducing its adsorption capability. To mitigate water condensation, excessive energy or high vacuum must be applied to the system, further complicating the process and increasing operational costs.

[0009] To address these limitations, researchers have developed various techniques to prepare hydrophobic MOF powders and composites. These methods include surface grafting, synthesis with hydrophobic ligands, core-shell MOF-MOF composites, hydrophobic encapsulation, and the use of porous hydrophobic matrices.

[0010] For example, WO2019207475 discloses a method to synthesize a hydrophobic composite by making a polymer grow on a MOF.

[0011] US Patent application No. 20210268476 discloses the formation of hydrophobic MOF composites by mixing a MOF powder and a hydrophobic polymer in an extruder. This method allows for the creation of hydrophobic MOF materials that can be shaped for various applications while retaining their adsorption capabilities.

[0012] L. H. M. Azmi, et al. (Chem. Eng. J., 2022, 429, 132304) reported the preparation of hydrophobic MOF composites by mixing the MOF with a polydimethylsiloxane (PDMS) solution.

[0013] W. Zhang et al. (J. Am. Chem. Soc. 2014, 136, 16978-16981 ) reported the preparation of MOFs coated with PDMS by heating the MOFs in the presence of PDMS stamp in a sealed glass container at 235 °C.

[0014] US Patent application No. 20220280918 discloses hydrophobic sorbent- polymer composites obtained using a solution-casting method with fluoropolymers, such as PVDF.

[0015] US patent applications Nos. 20230233984 and US20240139710 discloses hydrophobic sorbent polymer composites containing Teflon and solid sorbents obtained by mixing, extrusion, calendaring, and stretching.

[0016] US Patent application No. 20240207791 discloses hydrophobic MOF polymer composites utilizing an in-situ synthesis method starting with a porous Teflon article. This approach allows for the direct growth of MOFs within a hydrophobic matrix.

[0017] Y. Wan et al. (Chinese J. Chem. Eng., 2023, 61 , 82) reported a core-shell MOF@MOF composite using Mg-MOF-74 with high CO2 capture capacity as a functional core and hydrophobic zeolitic imidazolate framework-8 (ZIF-8) as a protective shell fabricated by the epitaxial growth method.

[0018] The review article by L.-H. Xie et al. (Adv. Sc / ., 2020, 7, 1901758) outlined several strategies for creating hydrophobic MOFs, including: (i) using organic linkers decorated with alkyl or fluorinated groups; (ii) post-synthetic modification of MOFs with hydrophobic groups; (iii) introduction of external surface corrugation using aromatic hydrocarbon building blocks; and (iv) creating hierarchical porous hydrophobic MOF composite.

[0019] However, the current state of hydrophobic MOF materials presents several challenges that limit their practical application in carbon capture. A significant issue is that many of these materials are primarily produced in powder form, making them difficult to handle, process, and integrate into industrial-scale systems.

[0020] Additionally, the use of polyvinylidene fluoride as a hydrophobic polymer often falls short of providing the extreme hydrophobicity required for the present applications, i.e. using water or steam for heating and regeneration of the adsorbent. Furthermore, the surface of these hydrophobic MOF materials often remains porous. This porosity, while beneficial for gas adsorption, can still allow some water molecules to penetrate the structure. These limitations become particularly evident under harsh conditions or during prolonged exposure to water or steam.

[0021] To address these challenges, there is a need for the development of new MOF-based adsorbent materials that enhance hydrophobicity while maintaining high porosity and gas adsorption capacity.

[0022] There is also a need for developing simpler and more scalable production processes of these hydrophobic MOF-based adsorbent materials.

[0023] There is also a need for designing materials in shapes compatible with various devices, such as pipes and fixed-bed reactors, without compromising adsorption performance.

[0024] SUMMARY OF THE INVENTION

[0025] It is a first object of the invention to provide a hydrophobic metal-organic framework (MOF)-polymer composite material comprising: a) a core structure comprising a MOF and a water-insoluble polymer; and b) a hydrophobic coating layer at least partially covering the surface of the core structure. Preferably, the MOF is selected from the group consisting of UiO-type MOFs; Zeolitic Imidazolate Frameworks (ZIF-type MOFs); MIL-type MOFs; PCN-type MOFs; CAU Series MOFs; zinc-based MOFs; MUF Series MOFs; MOFs containing specific anions or cations, including aluminum, magnesium, iron, or zirconium formates and fumarates; magnesium- or zinc-based amine- functionalized MOFs, and combinations thereof.

[0026] In one embodiment, the MOF is selected from zinc-based MOFs, preferably CALF-20 and / or UTSA-16(Zn).

[0027] In one embodiment, the core structure comprises from 25 to 99 % by weight of MOF, preferably from 60 to 95% by weight based on the total weight of the core structure.

[0028] Preferably, the water-insoluble polymer is selected from the group consisting of polyacrylonitrile, polyimides, polyethersulfones, polysulfones, and combinations thereof.

[0029] Preferably, the water-insoluble polymer is polyacrylonitrile, a copolymer thereof and / or a terpolymer thereof.

[0030] Preferably, the water-insoluble polymer has a weight-average molecular weight ranging from 10,000 to 2,000,000 Dalton, preferably ranging from 60,000 to 500,000 Dalton.

[0031] In one embodiment, the core structure comprises from 1 to 75 % by weight of water-insoluble polymer, preferably from 5 to 50 % by weight, based on the total weight of the core structure.

[0032] Preferably, the hydrophobic coating layer comprises a crosslinked polysiloxane polymer.

[0033] Preferably, the polysiloxane polymer is polydimethylsiloxane.

[0034] Preferably, the hydrophobic coating layer has a thickness of 0.1 to 10 pm.

[0035] Preferably, the hydrophobic coating layer covers at least 50%, preferably at least 70%, more preferably at least 90% of the surface of the core structure.

[0036] Preferably, the composite material is in a form selected from the group consisting of a fiber, a sheet, a bead, and a pellet, preferably in the form of a fiber.

[0037] It is a second object of the invention to provide a method for preparing a hydrophobic MOF-polymer composite material comprising: a) forming a dope solution containing a MOF, a water-insoluble polymer and a solvent; b) shaping said dope solution into a desired form; and c) applying a hydrophobic coating layer onto at least part of the shaped core structure. Preferably, shaping is performed by extrusion, preferably through a spinneret or die.

[0038] Preferably, the solvent in the dope solutiion is selected from the group consisting of N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N- dimethylacetamide, dimethylsulfoxide, tetrahydrofuran, and combinations thereof.

[0039] Preferably, the method further comprises passing the shaped core structure into a coagulation bath, preferably comprising water, after step (b).

[0040] Preferably, the hydrophobic coating layer is applied through dip coating or bar coating.

[0041] Preferably, the method further comprises a step of crosslinking the hydrophobic coating layer, preferably using heat and / or UV curing.

[0042] It is a second object of the invention to provide a method for removing an acid gas from an acid gas-enriched gas stream, comprising:

[0043] - a step of contacting the acid gas-enriched gas stream with the composite material described above, and

[0044] - regenerating said composite material to desorb the acid gas.

[0045] Preferably, the acid gas comprises carbon dioxide, hydrogen sulfide, or a combination thereof.

[0046] Preferably, the acid gas-enriched gas is selected from flue gas or atmospheric air.

[0047] Preferably, the regeneration step is performed by applying heat, vacuum, or steam, preferably steam.

[0048] The invention also relates to a cartridge comprising parallel or helically wound fibers made of a hydrophobic MOF-polymer composite material as defined above for use in gas adsorption systems.

[0049] The MOF-polymer composite material of the invention features a hydrophobic coating, which enhances its resistance to moisture and liquid water. This is crucial for applications where exposure to water or steam is common, as it prevents degradation of the material and ensures consistent performance in wet environments.

[0050] The MOF-polymer composite material of the invention makes it possible to enhance the water resistance of MOFs while maintaining their high CO2 adsorption capacity.

[0051] Unlike prior art adsorbents that degrade when exposed to steam, the hydrophobic nature of this composite allows for effective regeneration using steam. This enables faster desorption of captured gases like CO2, improving operational efficiency in carbon capture systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 illustrates a cross section of the hydrophobic MOF-polymer composite material according to an embodiment of the invention.

[0053] Figure 2 shows water droplets rolling on the surface of the hydrophobic MOF-polymer composite material according to the invention.

[0054] Figure 3 illustrates a setup for preparing and shaping the core structure, comprising the MOF and the water-insoluble polymer from a dope solution, via a dry-jet wet-quench process.

[0055] Figure 4 shows the difference of liquid water uptakes between a PDMS coated CALF-20 / PAN fiber and non-coated CALF-20 / PAN fiber at room temperature and 80°C respectively (Example 1 ). The X-axis represents the temperature in °C and the Y-axis represents the weight gain of the material in %.

[0056] Figure 5 shows the difference of liquid water uptakes between a PDMS coated UTSA-16Zn / PAN fiber and non-coated UTSA-16Zn / PAN fiber at room temperature and 80°C respectively (Example 5). The X-axis represents the temperature in °C and the Y-axis represents the weight gain of the material in weight %.

[0057] Figure 6 shows the difference of liquid water uptakes among coated CALF-20 / PAN fibers using different solvents and aqueous coating solutions for the coating of the fibers, along with non-coated CALF-20 / PAN fiber at room temperature (Examples 1-4). The Y-axis represents the weight gain of the material in weight %.

[0058] Figure 7 shows the difference of CO2 adsorption amounts among coated CALF-20 / PAN fibers using different solvents and an aqueous coating solution, along with non-coated CALF-20 / PAN fiber at 30°C under 1 bar CO2 pressure (Examples 1-4). The Y-axis represents the CO2 adsorption amount in weight %.

[0059] DETAILED DESCRIPTION

[0060] The invention will now be described in more detail without limitation in the following description.

[0061] According to a first aspect, the invention provides a metal-organic framework (MOF)-polymer composite material comprising a core structure and a hydrophobic coating layer.

[0062] This MOF-polymer composite material is hydrophobic, essentially due to the application of a hydrophobic coating layer on the MOF-polymer surface. Figure 2 illustrates the contact of water droplets (30) with the surface of the material, which features a hydrophobic coating layer (20) and a core structure (10). In the context of this invention, the term “hydrophobic” means that the material has a water contact angle greater than 90°, and preferably greater than 120°.

[0063] The water contact angle can be measured using an optical tensiometer, where a water droplet is placed on the material’s surface and imaged to determine the angle. Alternatively, the Sessile Drop method may be used: in this technique, a water droplet is placed on a horizontal surface of the material, and the contact angle is calculated using the formula 0 = 2 arctan (2H / D), where H represents the droplet height at the apex and D represents the base diameter of the droplet.

[0064] The hydrophobic MOF-polymer composite material of the invention exhibits excellent liquid water repelling capability and do not display sensitivity to water. The water repelling capability can be quantified by measuring the weight difference by immerging the dried material into water at room temperature or elevated temperatures.

[0065] The MOF-polymer composite material of the invention can be further characterized by analytical techniques such as nitrogen BET (Brunauer-Emmett- Teller), scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared spectrometry (FTIR). Standard methods or protocols (e.g., thermal gravity analysis, adsorption column) can be employed to assess the properties of the composite material.

[0066] The core structure composition

[0067] The core structure comprises at least a MOF and at least a waterinsoluble polymer.

[0068] This combination enhances the adsorbent material's mechanical stability and processability while enabling new functionalities, particularly increased adsorption capacity.

[0069] As used herein, the term "MOF" refers to metal-organic frameworks, which are crystalline materials composed of metal ions or clusters coordinated to organic ligands. These frameworks form porous structures that can be one-, two-, or three-dimensional and are typically characterized by high surface areas, often exceeding 5000 m2 / g.

[0070] The MOFs used in the composite material of the invention can be selected from a diverse range, including but not limited to: general MOFs such as MOF-2, MOF-3, MOF-4, MOF-5, MOF-70, MOF-73, MOF-74, MOF-75, MOF-76, MOF-177, MOF-303, MOF-505, MOF-80, and MOF-808, UiO-type MOFs including for example UiO-66, UiO-67, and UiO-68, ZIF-type MOFs (Zeolitic Imidazolate Frameworks) including for example ZIF-7, ZIF-8, ZIF-9, ZIF-10, ZIF-12, ZIF-68, ZIF-69, ZIF-70, ZIF-78, ZIF-79, ZIF-81 , ZIF-82, and ZIF-90,

[0071] MIL-type MOFs (Materials Institute Lavoisier) including for example MIL-53, MIL-88, MIL-96, MIL-101 , MIL-140L, and MIL-160, HKUST-1 , a copper-based MOF,

[0072] PCN-type MOFs (Porous Coordination Networks) including for example PCN-224 and PCN-250, zinc-based MOF such as CALF-20, CALF-15 and UTSA-16 (disclosed for example in US Patent No. 11 ,230,562), MUF Series such as for example MUF-15 and MUF-16, CAU Series such as for example CAU-10 and CAU-10-H. frameworks with specific anions or cations such as for example AI(OH) fumarate, Al-formate, Mg-formate, Zr-fumarate, Fe-BTC, MIL- 120(AI), and Mg(H2gal), and

[0073] - IISERP-MOF-2.

[0074] The MOF may consist of a single type or a mixture of two or more different MOFs.

[0075] In some embodiments, the MOF can be functionalized with suitable functional groups, including in particular amine-containing functional groups such as for example UiO-66-NH2. An amine-functionalized magnesium MOF is also described in US Patents Nos. 9,861 ,953 and 10,137,430.

[0076] The MOF (UTSA-16) with the general formula of K2(M1xM2i-x)s(Cit)2 where Cit is fully dehydrogenated citrate anion and M1 and M2 are metal cations of Zn, Co, Cu, Mg, Ni, Ca, Mn, Cr, Zr, and Fe and x is from 0 to 1 , is preferred to be manufactured by the methods disclosed in the US patent application No. 63 / 593,627. The methods utilize water as the solvent and the reactions are carried out at atmospheric pressure with temperature below 100 °C. The methods may comprise:

[0077] (a) reacting 1 molar equivalent of citric acid with / molar equivalent of a metal carbonate component and with j molar equivalent of a basic potassium compound;

[0078] (b) reacting the product of (a) with k molar equivalent of a metal salt component, wherein the method is conducted in a solvent consisting of water at ambient pressure and at a temperature no greater than 100 °C, and wherein / is from 0 to 1 .0, j is from 3.0 to 1 .0, and k is from 1 .0 to 1 .5. In one embodiment, the MOF is selected from a zinc-based MOF, such as for example CALF-20 and UTSA-16, a zeolitic imidazolate framework, such as ZIF-94, and / or an amine-functionalized magnesium MOF, such as epn- grafted Mg2(dobpdc) (epn = 1-ethylpropane-1 ,3-diamine).

[0079] In one preferred embodiment, the MOF is selected from a zinc-based MOF.

[0080] Advantageously, the amount of MOF in the core structure of the MOF- polymer composite material of the invention varies from 25 to 99 % by weight, preferably from 60 to 95% by weight, with respect to the total amount of the core structure.

[0081] For example, the amount of MOF in the core structure may vary from 25 to 35 % by weight, from 35 to 45 % by weight, from 45 to 55 % by weight, from 55 to 65 % by weight, from 65 to 75 % by weight, from 75 to 85 % by weight, from 85 to 95 % by weight, or from 95 to 99 % by weight.

[0082] The core structure further comprises a water-insoluble polymer.

[0083] As used herein, the term "water-insoluble polymer" refers to a polymer that is incapable of dissolving in water or aqueous solutions under standard conditions. Specifically, it is defined as a polymer that exhibits a solubility of less than 5 g, preferably less than 2 g, and more preferably less than 1 g per 100 g of water at 25°C. Preferably, for accurate assessment of solubility, the polymer must be thoroughly dried at 105°C for 2 hours to eliminate any residual moisture. Solubility testing may be conducted once the polymer has reached a constant dry weight.

[0084] The water-insoluble polymer can be a natural or a synthetic polymer.

[0085] Natural polymers may include but are not limited to: cellulose and its derivatives (e.g., cellulose acetate, cellulose nitrate), lignin, chitosan, starch and modified starch, alginate and its derivates and combinations thereof.

[0086] Synthetic polymers may include but are not limited to polyacrylonitrile, poly(methyl methacrylate), polystyrene, polyethylene terephthalate), aromatic polyamides, aliphatic polyamides, polyimides, polyesters, polyetherketones, polyethersulfones, polyetheresters, polysulfones, polyvinyl fluoride, polyvinyl difluoride, polyvinylchloride, polybenzimidazoles, polybenzoxazoles, polyazoaraomatics, poly(2,6-dimethylphenylene oxide), polyphenylene oxides, polyureas, polyurethanes, polyhydrazides, polyazomethines, polyacetals, polyquinoxaline, polyamideesters, polyacetylenes, polymer with intrinsic porosities (PIMs), any combinations or blends thereof and / or copolymers or terpolymers thereof. In one embodiment, the water-insoluble polymer is selected from a polyacrylonitrile (PAN), a copolymer and / or a terpolymer thereof.

[0087] PAN copolymers include for example poly(acrylonitrile-co-itaconic acid), poly(acrylonitrile-co-acrylic acid), poly(acrylonitrile-co-methacrylic acid), poly(acrylonitrile-co-methyl methyl acrylate), and poly(acrylonitrile-co-methyl acrylate).

[0088] PAN terpolymers include for example poly(acrylonitrile-methyl acrylateitaconic acid), poly(acrylonitrile-methyl methacrylate-itaconic acid) and poly(acrylonitrile-methyl acrylate-acrylic acid).

[0089] Advantageously, the water-insoluble polymer has a weight-average molecular weight (Mw) ranging from 10,000 to 2,000,000 Dalton, preferably from 60,000 to 500,000 Dalton.

[0090] Advantageously, the amount of water-insoluble polymer in the core structure of the composite material of the invention varies from 1 to 75 % by weight, preferably from 5 to 50 % by weight, based on the total weight of the core structure.

[0091] For example, the amount of polymer may vary from 1 to 5 % by weight, from 5 to 15 % by weight, from 15 to 25 % by weight, from 25 to 35 % by weight, from 35 to 45 % by weight, from 45 to 55 % by weight, from 55 to 65 % by weight or from 65 to 75 % by weight.

[0092] Advantageously, the water-insoluble polymer forms a porous matrix in which the MOF is dispersed, preferably homogeneously dispersed. This arrangement facilitates the creation of a high-surface-area material with enhanced porosity.

[0093] The term "porous matrix" refers to a solid material characterized by a network of interconnected pores or voids permeating its structure. These pores, which can vary in size, shape, and distribution, contribute to the material's high surface area and allow for the passage of gases.

[0094] Advantageously, the core structure of the composite material of the invention exhibits an open-cell or interconnected structure, where the polymer matrix encapsulates the MOF without obstructing them, promoting efficient mass transport.

[0095] The porosity of the core structure can range from 20% to 80%, preferably from 30% to 70% by volume relative to the entire volume of the core structure.

[0096] The porosity can be measured by comparing the weight difference when the material is dry and when saturated with a liquid such as water or isopropanol. The pore size of the core structure can vary and can include macroporosity, mesoporosity and / or microporosity.

[0097] As used herein, macroporosity is defined by pores having a diameter larger than about 50 nm; mesoporosity is defined by pores having a diameter within a range of from about 2 nm to about 50 nm; and microporosity is defined by pores having diameter less than about 2 nm. The type of porosity most relevant with respect to the removal of an acid gas such as carbon dioxide from a stream is macroporosity and / or mesoporosity.

[0098] The core structure of the composite material of the invention can take various forms, including fibers, sheets, beads, and pellets, with fibers being the preferred form.

[0099] MOF-polymer composite fibers, pellets, or beads can have outer diameters ranging from about 0.1 mm to 10 mm, preferably from 0.5 mm to 6 mm.

[0100] MOF-polymer composite flat sheets can have thicknesses ranging from about 0.1 mm to 10 mm, preferably from 0.5 mm to 6 mm.

[0101] The density of the core structure can range from about 0.2 g / cm3to 1 g / cm3, preferably from about 0.3 g / cm3to 0.8 g / cm3.

[0102] The hydrophobic coating layer

[0103] The MOF-polymer composite material of the invention comprises a hydrophobic coating applied to the exterior of its core structure surface.

[0104] Advantageously, the hydrophobic coating layer covers at least 50% of the total surface of the core structure, preferably at least 70%, more preferably at least 80% and most preferably at least 90%.

[0105] According to a preferred embodiment, the hydrophobic coating layer covers the totality (100%) of the surface of the core structure.

[0106] The hydrophobic coating layer serves to improve the composite material's resistance to moisture.

[0107] Advantageously, the hydrophobic coating layer comprises a crosslinked polysiloxane polymer.

[0108] In one embodiment, the hydrophobic coating layer comprises at least 50%, preferably at least 60% or at least 70%, more preferably at least 80% or at least 90%, most preferably at least 99% by weight of a crosslinked polysiloxane polymer.

[0109] In one embodiment, the hydrophobic coating layer consists essentially in a crosslinked polysiloxane polymer. In one embodiment, the crosslinked polysiloxane polymer is selected from the group consisting of siloxane elastomers, polydimethylsiloxane, methylmethoxy siloxane polymers, phenylmethoxy siloxane polymers, methyl silsesquioxane networks, phenyl silsesquioxane networks, fluorinated silicone polymers and mixtures thereof.

[0110] In a preferred embodiment, the coating layer comprises or preferably is polydimethylsiloxane.

[0111] The thickness of the hydrophobic coating layer is not particularly limited, and may be, for example, from 0.1 to 10 pm, preferably from 0.5 to 5 pm, and preferably from 1 to 2 pm.

[0112] Preparation of the MOF-polymer composite material

[0113] In a second aspect, the invention provides a method for preparing the hydrophobic MOF-polymer composite material described above.

[0114] This method advantageously involves first forming the core structure, followed by the application of the hydrophobic coating layer to its surface.

[0115] The core structure, comprising the MOF and the water-insoluble polymer, is preferably prepared from a dope solution. This dope solution is then preferably shaped into a desired form.

[0116] The hydrophobic coating layer is then formed by applying a coating solution to at least a part of the shaped core structure. Once applied, crosslinking is initiated, transforming the solution into a hydrophobic solid stable layer.

[0117] Step a): preparation of the core structure

[0118] In this step, the core structure of the hydrophobic MOF-polymer composite material is prepared by forming a dope solution that serves as the foundation for shaping the desired composite.

[0119] As used herein, “dope solution” refers to a mixture, solution, or suspension of the MOF and the polymer in a solvent, which can subsequently be processed into fibers, films, or other shapes.

[0120] The dope solution comprises a mixture of MOF, the water-insoluble polymer, and a solvent.

[0121] The MOF is preferably in powder form, with particles having a size of less than or equal to 1000 pm, typically less than or equal to 500 pm, and sometimes even less than or equal to 10 pm. Particle sizes may range from 0.01 pm to 500 pm, depending on the desired properties of the final composite material. As used herein, the term "particle size" refers to the average dimensions of a particle, as measured by methods such as scanning electron microscopy (SEM) and sieving.

[0122] The amount of MOF in the dope solution preferably ranges from 5% to 65% by weight, preferably from 15% to 55%, and more preferably from 25% to 45% based on the total weight of the dope solution. For example, the MOF content may vary in specific increments, such as from 5% to 15%, from 15% to 25%, and so on, up to 65%.

[0123] The amount of the water-insoluble polymer in the dope solution may range from 1 % to 65% by weight, preferably from 5% to 55%, and more preferably from 15% to 45%, most preferably from 25% to 35%.

[0124] The solvent used in the dope solution can be a polar protic solvent and / or a polar aprotic solvent. A single solvent or mixtures of solvents may be used.

[0125] Polar protic solvents are typically solvents that have a hydrogen atom attached to an electronegative atom, typically oxygen or nitrogen, which allows them to form hydrogen bonds.

[0126] Polar aprotic solvents are typically solvents that are polar but do not have an acidic hydrogen, meaning they lack O-H, N-H, S-H or P-H bonds. They cannot donate protons for hydrogen bonding but can accept them.

[0127] The use of polar solvents is preferred, since the polar solvent can be conveniently removed by using water, in particular during the shaping step.

[0128] In one embodiment, the solvent used in the dope solution is selected from the group consisting of N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), dimethylsufoxide (DMSO), tetrahydrofurane (THF) and combinations thereof.

[0129] In one preferred embodiment, the solvent used in the dope solution is NMP and / or DMSO.

[0130] The amount of solvent in the dope solution may vary from 20 to 80% by weight, preferably from 30% to 70%, more preferably from 40% to 60% by weight based on the total weight of the dope solution.

[0131] The dope solution may also comprise one or more additives, which can be either liquid or solid. These additives can be selected to serve various functions, including modifying viscosity, imparting porosity, and enhancing other properties of the MOF-polymer composite material.

[0132] Examples of additives that can be employed in the dope solution include but are not limited to: water, aliphatic alcohols, particularly polyhydric alcohols such as ethylene glycol, glycerine, polyethylene oxides and polypropylene oxides, polyvinylalcohol, polyvinylpyrrolidone, surfactants such as alkylaryl polyether alcohols, alkyl sulfates, alkylarylsulfates, triethylphosphate, formamide, and salts such as lithium chloride or calcium chloride, or combinations thereof.

[0133] In one embodiment, the additive is a pore-forming compound. A poreforming compound is a compound that promotes the formation of open, interconnected pores in the final product. This can be achieved through the complete or partial removal of the pore former additive during the material's processing, leaving behind a network of voids. Examples of pore-forming compounds may include polyethylene oxide), volatile solvents or 1 ,3,5- trimethylbenzene.

[0134] The amount of additive in the dope solution may vary within a range of from about 0% to about 30% by weight based on the total weight of the dope solution. The amount of additives in the dope solution may vary for example from 5 to 25 % by weight, from 10 to 20 % by weight, or from 10 to 15 % by weight.

[0135] It is to be understood that the nature and amount of the additives can be selected depending on desired material properties, process and / or equipment parameters or other factors.

[0136] In one embodiment, the dope solution comprises: from 20 to 40 % by weight of MOF particles; from 5 to 15 % by weight of polyacrylonitrile; from 50 to 70 % by weight of solvent; from 0 to 10 % by weight of additives.

[0137] In one embodiment, the dope solution is prepared by first dissolving the water-insoluble polymer in the solvent to create a polymer solution. The MOF, preferably in powder form, is then added to the polymer solution. Optional additives, such as CaCl2, LiCI, or polyethylene oxide, can be introduced either alongside the polymer or the MOF or at different stages during the preparation of the dope solution.

[0138] Step b) shaping of the core structure

[0139] The core structure is preferably shaped by extrusion of the dope solution prepared in step (a). Preferably, the core structure is extruded by way of a dryjet wet-quench spinning process as illustrated for example in Figure 3.

[0140] Prior to extrusion, the dope solution may be degassed under heat and / or vacuum to remove any trapped air or gases.

[0141] Step b) enables the creation of a core structure that is self-supporting or free-standing, eliminating the need for any external framework to maintain its shape. The resultant core structure can take various forms, including fibers, sheets, beads, or pellets, depending on the intended application.

[0142] Advantageously, the extrusion of the dope solution 1 is carried out using a die or a spinneret 2, each suited to forming different shapes. For a flat sheet, a film extrusion die can be used, while a fiber requires a spinneret. Pelletizers may follow spinneret extrusion for creating pellet-like structures. Additionally, the fiber may be either hollow or non-hollow. Hollow fibers can be produced by injecting a non-solvent or air through a specialized tube within the spinneret during the extrusion process.

[0143] In one embodiment, the extrusion of the dope solution is carried out using a spinneret to obtain a core structure in the form of a fiber, preferably a nonhollow fiber.

[0144] Advantageously, upon extrusion, the nascent MOF-polymer composite — whether in the form of fibers or sheets — enters a coagulation bath 3 preferably containing water or an alternative non-solvent. The water bath acts as a medium for phase separation and solidification. The solvent within the dope solution diffuses out while water or another non-solvent diffuses in, inducing phase separation that solidifies the material. This coagulation bath is preferably deionized water but may also include aqueous solutions or alternative nonsolvents such as methanol, ethanol, or isopropanol. In one embodiment, the coagulation bath is water.

[0145] In one embodiment, the nascent composite can be allowed to pass through an air gap before entering the water bath. This air gap serves as a cooling medium, enhancing the phase separation process.

[0146] Once solidified, the composite can be pulled from the coagulation bath onto a rotating barrel, followed by immersion in a washing medium 4, for example water or isopropanol, to remove any residual solvent or non-solvent.

[0147] The water in the water bath may be for example deionized water or an aqueous solution.

[0148] For additional washing and purification, pulling and piddling techniques (as disclosed in US Patent No. 8,753,741 ) may be applied. These steps involve directing the composite around a rotating barrel within the washing medium, ensuring comprehensive removal of residual chemicals and enhancing the structural stability of the composite.

[0149] After extrusion, the composite may remain soaked in the water bath for 1 to 72 hours, preferably from 12 hours to 48 hours, more preferably 24 hours, to allow for thorough solvent removal. For hollow fiber composites, a tube-in-orifice spinneret can be employed, with a bore fluid acting as an internal coagulant. This bore fluid may consist of water, a water-alcohol mixture, or an air stream.

[0150] The final properties and morphology of the core structure may be adjusted depending on various factors, including the spinneret design, flow rates of the dope solution and bore fluid, air gap dimensions, bath conditions, shear forces, and draw ratios.

[0151] Following extrusion, a heat treatment of the core structure can be performed using either a hot water bath or steam within a closed chamber. The heat treatment can be applied continuously, with fibers passing through the chamber on a conveyor belt, or in batch mode, by placing the fibers in a container for treatment. The heating temperature can range from 80°C to 200°C, preferably 90°C to 130°C. This treatment may include stepwise heating, maintaining a plateau temperature, and intermittent cooling and reheating periods. The heat treatment duration may range from 30 seconds to 100 minutes, preferably from 1 to 60 minutes.

[0152] After heat treatment, the core structure can be dried under ambient conditions or with heat, for example, in an oven at temperatures between 50°C and 150°C.

[0153] Step c) Application of the coating layer

[0154] The hydrophobic coating layer is advantageously formed on at least part of the surface of a shaped core structure by applying a coating solution.

[0155] Before applying the coating solution, the core structure may be completely dried to remove all water content.

[0156] Alternatively, the core structure can be partially dried, leaving some liquid water within the pores. This approach helps prevent the coating solution from entering and occluding the pores. By avoiding pore blockage, the resulting hydrophobic MOF-polymer composite material can achieve higher gas transport rates.

[0157] In one embodiment, the coating solution comprises a crosslinkable polymer precursor, a crosslinking agent and / or a catalyst, and a solvent.

[0158] Advantageously, the polymer precursor is a siloxane oligomer or mixture of siloxane oligomers.

[0159] The siloxane oligomer may be selected from octamethyltrisiloxane, polydimethyl siloxane, methylmethoxy siloxane, phenylmethoxy siloxane, methyl silsesquioxane phenyl silsesquioxane, fluorinated siloxane, partially fluorinated siloxane and mixtures thereof. These oligomers contain reactive functional groups, such as vinyl, hydroxy, or epoxy groups, that can interact with the crosslinking agent to form a dense, crosslinked hydrophobic polysiloxane layer.

[0160] The content of the functional crosslinking group may vary from 0.05 to 5 parts by weight, preferably from 0.05 to 3 parts by weight, more preferably from 0.1 to 1 part by weight, or 0.1 to 0.5 parts by weight based on 1 part by weight of the siloxane oligomer.

[0161] Advantageously, the weight ratio between the siloxane oligomers and the crosslinking agent ranges from 1 :100 to 100:1 , preferably from 1 :10 to 100:1 , more preferably from 1 :1 to 100:1 .

[0162] The organic solvent in the coating solution can be selected from methanol, acetone, isopropanol, n-butanol, pentane, hexane, heptane, octane, isoparaffin, toluene, cyclohexane, benzene, ethyl acetate, diethyl ether, ethanol, dimethyl sulfoxide, acetic acid, formic acid, propionic acid or mixtures thereof.

[0163] The polysiloxane coating solution can also be formulated as an aqueous emulsion. Examples of commercially available siloxane emulsion coating solutions are Dow SYL-OFFTM 7950, Siltech 2150, Siltech 5515, and Gelest GP50.

[0164] The application of the coating layer onto the core structure can be achieved through methods such as bar coating, spin coating, or dip coating. The coating process can be conducted either in-line, especially for continuous fibers, or in a batch process, where the core structure is immersed in the coating solution. Following application, excess coating solution is preferably removed from the surface of the material, using techniques such as an air gun or roller.

[0165] One applied, the coating solution can be crosslinked using methods like heat curing, UV curing, and / or catalytic curing.

[0166] For example, when the coating solution contains reactive vinyl groups, the siloxane oligomer can be crosslinked by a thermal reaction in the presence of a platinum catalyst, as shown in Scheme 1. An example of commercially available thermal curing siloxane system is Sylgard 184.

[0167] Scheme 1 A reactive vinyl group can be further crosslinked with a crosslinking agent containing mercapto group (-SH) in the presence of a UV light source, as shown in Scheme 3.

[0168] Scheme 2

[0169] When the coating solution contains reactive hydroxyl groups (-OH), the siloxane oligomer can be crosslinked by a condensation reaction with or without the presence of a tin catalyst, as shown in Scheme 3. Scheme 3

[0170] A reactive epoxy group can be crosslinked with amine functionalized crosslinking agent.

[0171] The crosslinking step may involve for example drying the coated composite material at temperatures from 20 to 35°C, preferably from 23 to 30°C, for 1 to 10 hours, preferably for 1 to 5 hours, followed by heat treatment at temperatures ranging from 50 to 150°C, preferably from 70 to 100°C, for a duration of 15 to 30 hours, preferably from 20 to 25 hours, ensuring complete crosslinking and formation of the hydrophobic coating layer.

[0172] In some embodiments, the coating solution may be partially crosslinked before its application on at least part of the surface of the core structure. The final crosslinking is subsequently completed using the methods outlined above.

[0173] It should be understood that the MOF-polymer composite material retains the same shape as the core structure after the application of the hydrophobic coating layer.

[0174] Applications

[0175] The hydrophobic MOF-polymer composite material described herein can be used to remove an acid gas from a fluid stream, e.g., a flue gas stream or ambient atmosphere.

[0176] The acid gas may be selected from CO2, SO2 and or H2S. In one embodiment, the acid gas is CO2.

[0177] For example, when a fluid stream containing an acid gas, in particular CO2, is brought into contact with the hydrophobic MOF-polymer composite material of the invention, the acid gas is adsorbed by the material. This process results in a fluid stream that is depleted of the acid gas and a hydrophobic MOF- polymer composite material containing the captured acid gas.

[0178] The hydrophobic MOF-polymer composite material containing the acid gas can be regenerated for reuse or for environmentally safe disposal. Various methods can be employed, using heat, vacuum, lower pressure, or any combination thereof. This process is typically called a desorption and results in a hydrophobic MOF-polymer composite material depleted from the acid gas and a captured acid gas. If the regeneration technique relies on heat, the desorption process can be a temperature swing adsorption (TSA) method, while many processes based on lowered pressures are known as pressure swing adsorptions (PSA). Another technique that can be employed to release the acid gas involves both heating and vacuum, the process being known as temperature-vacuum swing adsorption (TVSA). These regeneration techniques are well-established in the field.

[0179] The hydrophobic MOF-polymer composite material of the invention are particularly useful using steam as regeneration heat source. Steam can be directed to the hydrophobic MOF-polymer composite material directly to regenerate said material.

[0180] The acid gas, in particular the CO2, removed and captured through the method according to the invention can be utilized in various ways, including enhanced oil recovery, preparation of synthetic fuels (such as methanol, methane, or jet fuels), or for geological storage.

[0181] For these applications, the hydrophobic MOF-polymer composite described in this application can be utilized in standard equipment, such as packed beds or columns, in particular when the composite material is in the form of pellets.

[0182] When in the form of flat sheets, the composite material can be arranged in configurations such as plate-and-frame or spiral-wound devices.

[0183] When in the form of flat sheets, the composite material can be packaged into modular adsorption devices. A typical device (or "cartridge") includes two or more fibers laid parallel or wound helically around a central tube. Cartridges can be assembled into modules. In illustrative examples, modules may include multiple adsorption devices installed in series or parallel within a vessel. Operations can occur in axial or cross-flow arrangements with either shell-side or bore-side feeding.

[0184] In some implementations, a module can comprise one or more heating elements that can be used to release adsorbed acid gas, regenerating the composite material. Various cartridge and / or module configurations that can be employed are described, for example, in US patent application US No 20230008877.

[0185] The module containing the hydrophobic MOF-polymer composite may further include a liquid drainage arrangement to remove the repelled liquid water from the hydrophobic MOF-polymer composite material.

[0186] Examples

[0187] The invention is further illustrated in the following non-limiting examples. Materials:

[0188] CALF-20: Zinc-based Calgary Framework 20, [Zn2(1 ,2,4- triazolate)2(oxalate)], Synthesized in house from oxalic acdi, 1 ,2,4- triazeole, and basic zinc carbonate in 50 / 50 ethanol water solution, UTSA-16Zn: Zinc-based MOF synthesized from citric acid, potassium hydroxide and zinc oxide,

[0189] NMP: N-Methyl-2-pyrrolidone (NMP), anhydrous, 99.5%, purchased from Advanced ChemTech,

[0190] PAN: Polyacrylonitrile-acrylonitrile methyl methacrylate (MMA) copolymer, molecular weight (MW) approximately 80,000 Dalton, in powder form, purchased from Dolan Gmbh, Sylgard 184: Polydimethylsiloxane (PDMS) elastomer kit, composed of a base and curing agent, obtained from Dow Corning,

[0191] IPA: Isopropyl alcohol, anhydrous, 99.9%, purchased from Aldrich, Additional solvents, including hexane, t-butanol and acetone were purchased from Aldrich and used without further purification.

[0192] Example 1 : Sylgard 184 coated CALF-20 / PAN composite fiber

[0193] A dope solution was prepared by dispersing 21 .0 g of CALF-20 powder in 40.0 g of NMP, followed by adding 7.0 g of PAN.

[0194] After degassing, the dope solution was transferred into a fiber spinning apparatus equipped with a spinneret. The dope solution was extruded from the spinneret to form a nascent fiber and the nascent fiber was delivered into a deionized water bath.

[0195] The fiber was further soaked in water for 24 hours, to remove the NMP solvent.

[0196] The wet fiber was then placed in a hot water bath set at 95 °C for 5 min then air dried.

[0197] The resulting fiber has an outer diameter of 0.6 mm.

[0198] The nominal CALF-20 loading inside the fiber is 75 wt%, and the CALF- 20 loading based on the activated dry base is 72.5 wt%.

[0199] The fiber obtained is designated as non-coated CALF-20 / PAN fiber.

[0200] A section of the non-coated CALF-20 / PAN fiber was tested with a TGA instrument for its CO2 adsorption property. The fiber was first heated to 110 °C and held at 110 °C for 30 min to activate the fiber under nitrogen. This was followed by cooling the activated fiber to 30 °C under nitrogen. The fiber was then exposed to a dry CO2 gas stream for 30 min.

[0201] The weight gain of the fiber after the CO2 exposure was 11 .7 wt%.

[0202] A section of the non-coated CALF-20 / PAN fiber was weighed before and after immerged in water bath at room temperature for 5 min. The calculated weight gain from sorbing liquid water was 93 wt%.

[0203] A section of the non-coated CALF-20 / PAN fiber was weighed before and after immerged in water bath set at 80 °C for 5 min. The calculated weight gain from sorbing liquid water was 75 wt%.

[0204] Sections of the non-coated CALF-20 / PAN fiber were pre-dried at 90 °C for 1 hour and then dipped into a hexane solution containing 2 wt% of Sylgard 184. The dipped fibers were then air dried and heated at 90 °C for 1 hour.

[0205] A section of the Sylgard 184 coated CALF20 / PAN fiber was tested with a TGA instrument for its CO2 adsorption property. The fiber was first heated to 110 °C and held at 110 °C for 30 min to activate the fiber under nitrogen. This was followed by cooling the activated fiber to 30 °C under nitrogen. The fiber was then exposed to a dry CO2 gas stream for 30 min.

[0206] The weight gain of the fiber after the CO2 exposure was 11 .0 wt%.

[0207] A section of the Sylgard 184 coated CALF20 / PAN fiber was weighed before and after immerged in water bath at room temperature for 5 min. The calculated weight gain from sorbing liquid water was 13 wt%.

[0208] A section of the Sylgard 184 coated CALF20 / PAN fiber was weighed before and after immerged in water bath set at 80 °C for 5 min. The calculated weight gain from sorbing liquid water was 26 wt%.

[0209] The addition of a Sylgard 184 coating significantly improved the hydrophobic properties of the fiber without substantially affecting its CO2 adsorption capacity.

[0210] Example 2: Sylgard 184 coated CALF-20 / PAN composite fiber

[0211] Sections of the non-coated CALF-20 / PAN fiber as prepared in Example 1 were pre-dried at 90 °C for 1 hour and then dipped into an acetone solution containing 2 wt% of Sylgard 184. The dipped fibers were then air dried and heated at 90°C for 1 hour.

[0212] A section of the Sylgard 184 coated CALF20 / PAN fiber was tested with a TGA instrument for its CO2 adsorption property. The fiber was first heated to 110 °C and held at 110 °C for 30 min to activate the fiber under nitrogen. This was followed by cooling the activated fiber to 30 °C under nitrogen. The fiber was then exposed to a dry CO2 gas stream for 30 min. The weight gain of the fiber after the CO2 exposure was 9.7 wt%.

[0213] A section of the Sylgard 184 coated CALF20 / PAN fiber was weighed before and after immerged in water bath at room temperature for 5 min. The calculated weight gain from sorbing liquid water was 11 .5 wt%. Example 3: Sylgard 184 coated CALF-20 / PAN composite fiber

[0214] Sections of the non-coated CALF-20 / PAN fiber as prepared in Example 1 are pre-dried at 90°C for 1 hour and then dipped into a t-butanol solution containing 2 wt% of Sylgard 184. The dipped fibers were then air dried and heated at 90°C for 1 hour.

[0215] A section of the Sylgard 184 coated CALF20 / PAN fiber was tested with a TGA instrument for its CO2 adsorption property. The fiber was first heated to 110 °C and held at 110 °C for 30 min to activate the fiber under nitrogen. This was followed by cooling the activated fiber to 30 °C under nitrogen. The fiber was then exposed to a dry CO2 gas stream for 30 min. The weight gain of the fiber after the CO2 exposure was 10.8 wt%. A section of the Sylgard 184 coated CALF20 / PAN fiber was weighed before and after immerged in water bath at room temperature for 5 min. The calculated weight gain from sorbing liquid water was 7.7 wt%. Example 4: Siltech 2150 coated CALF-20 / PAN composite fiber

[0216] Sections of the non-coated CALF-20 / PAN fiber as prepared in Example 1 are pre-dried at 90 °C for 1 hour and then dipped into an aqueous solution containing 3wt% siloxane, diluted from the Siltech 2150 containing 30wt% of siloxane. The dipped fibers were then air dried and heated at 90 °C for 1 hour.

[0217] A section of the Siltech 2150 coated CALF20 / PAN fiber was tested with a TGA instrument for its CO2 adsorption property. The fiber was first heated to 110 °C and held at 110 °C for 30 min to activate the fiber under nitrogen. This was followed by cooling the activated fiber to 30 °C under nitrogen. The fiber was then exposed to a dry CO2 gas stream for 30 min. The weight gain of the fiber after the CO2 exposure was 10.7 wt%.

[0218] A section of the Siltech 2150 coated CALF20 / PAN fiber was weighed before and after immerged in water bath at room temperature for 5 min. The calculated weight gain from sorbing liquid water was 12.4 wt%. Example 5: Sylgard 184 coated UTSA-16Zn / PAN composite fiber

[0219] A dope solution was prepared first by dissolving 7.0 g of PAN in 36.0 g of NMP, followed by mixing 21 .0 g of UTSA-16(Zn) powder.

[0220] After degassing, the dope solution was transferred into a fiber spinning apparatus equipped with a spinneret. The dope solution was extruded from a spinneret to form a nascent fiber and the nascent fiber was delivered into a deionized water. The fiber was further soaked in water for 24 hours to remove the NMP solvent, then the fiber was placed in IPA for 2 hours, after which it was air dried.

[0221] The fiber obtained is designated as non-coated UTSA-16Zn / PAN fiber.

[0222] A section of the non-coated UTSA-16Zn / PAN fiber was tested with a TGA instrument for its CO2 adsorption property. The fiber was first heated to 110 °C and held at 110 °C for 30 min to activate the fiber under nitrogen. This was followed by cooling the activated fiber to 30 °C under nitrogen. The fiber was then exposed to a dry CO2 gas stream for 30 min. The weight gain of the fiber after the CO2 exposure was 10.7 wt%.

[0223] A section of the non-coated UTSA-16Zn / PAN fiber was weighed before and after immerged in water bath at room temperature for 5 min. The calculated weight gain from sorbing liquid water was 56 wt%. A section of the non-coated UTSA-16Zn / PAN fiber was weighed before and after immerged in water bath set at 80°C for 5 min. The calculated weight gain from sorbing liquid water was 43 wt%.

[0224] Sections of the non-coated UTSA-16Zn / PAN fiber were pre-dried at 90°C for 1 hour and then dipped into a hexane solution containing 2 wt% of Sylgard 184. The dipped fibers were then air dried and heated at 90°C for 1 hour.

[0225] A section of the Sylgard 184 coated UTSA-16Zn / PAN fiber was tested with a TGA instrument for its CO2 adsorption property. The fiber was first heated to 110 °C and held at 110 °C for 30 min to activate the fiber under nitrogen. This was followed by cooling the activated fiber to 30°C under nitrogen. The fiber was then exposed to a dry CO2 gas stream for 30 min. The weight gain of the fiber after the CO2 exposure was 9.6 wt%.

[0226] A section of the Sylgard 184 coated UTSA-16Zn / PAN fiber was weighed before and after immerged in water bath at room temperature for 5 min. The calculated weight gain from sorbing liquid water was 2 wt%.

[0227] A section of the Sylgard 184 coated UTSA-16Zn / PAN fiber was weighed before and after immerged in water bath set at 80°C for 5 min. The calculated weight gain from sorbing liquid water was 28 wt%.

[0228] The addition of a Sylgard 184 coating significantly improved the hydrophobic properties of the fiber without substantially affecting its CO2 adsorption capacity.

Claims

CLAIMS1. A hydrophobic metal-organic framework (MOF)-polymer composite material comprising: a) a core structure comprising a MOF and a water-insoluble polymer; and b) a hydrophobic coating layer at least partially covering the surface of the core structure.

2. The composite material of claim 1 , wherein the MOF is selected from the group consisting of UiO-type MOFs; Zeolitic Imidazolate Frameworks (ZIF-type MOFs); MIL-type MOFs; PCN-type MOFs; CAU Series MOFs; zinc-based MOFs; MUF Series MOFs; MOFs containing specific anions or cations, including aluminum, magnesium, iron, or zirconium formates and fumarates; magnesium- or zinc-based amine-functionalized MOFs, and combinations thereof.

3. The composite material of claim 2, wherein the MOF is selected from zinc-based MOFs, preferably CALF-20 and / or UTSA-16(Zn).

4. The composite material of any one of claims 1 to 3, wherein the core structure comprises from 25 to 99 % by weight of MOF, preferably from 60 to 95% by weight based on the total weight of the core structure.

5. The composite material of any one of claims 1 to 4, wherein the water-insoluble polymer is selected from the group consisting of polyacrylonitrile, polyimides, polyethersulfones, polysulfones, and combinations thereof.

6. The composite material of claim 5, wherein the water-insoluble polymer is polyacrylonitrile, a copolymer thereof and / or a terpolymer thereof.

7. The composite material of any one of the preceding claims, wherein the water-insoluble polymer has a weight-averagemolecular weight ranging from 10,000 to 2,000,000 Dalton, preferably ranging from 60,000 to 500,000 Dalton.

8. The composite material of any one of the preceding claims, wherein the core structure comprises from 1 to 75 % by weight of water-insoluble polymer, preferably from 5 to 50 % by weight, based on the total weight of the core structure.

9. The composite material of any one of the preceding claims, wherein the hydrophobic coating layer comprises a crosslinked polysiloxane polymer.

10. The MOF-polymer composite material of claim 9, wherein the polysiloxane polymer is polydimethylsiloxane.

11. The MOF-polymer composite material of any one of the preceding claims, wherein the hydrophobic coating layer has a thickness of 0.1 to 10 pm.

12. The composite material of any one of the preceding claims, wherein the hydrophobic coating layer covers at least 50%, preferably at least 70%, more preferably at least 90% of the surface of the core structure.

13. The composite material of any one of the preceding claims, in a form selected from the group consisting of a fiber, a sheet, a bead, and a pellet, preferably in the form of a fiber.

14. A method for preparing a hydrophobic MOF-polymer composite material comprising: a) forming a dope solution containing a MOF, a water-insoluble polymer and a solvent; b) shaping said dope solution into a desired form; and c) applying a hydrophobic coating layer onto at least part of the shaped core structure.

15. The method according to claim 14, wherein shaping is performed by extrusion, preferably through a spinneret or die.

16. The method of claim 14 or 15, wherein the solvent in the dope solutiion is selected from the group consisting of N-methyl-2- pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, tetrahydrofuran, and combinations thereof.

17. The method of any one of claims 14 to 16, further comprising passing the shaped core structure into a coagulation bath, preferably comprising water, after step (b).

18. The method of any one of claims 14 to 17, wherein the hydrophobic coating layer is applied through dip coating or bar coating.

19. The method according to claim 18, further comprising crosslinking the hydrophobic coating layer, preferably using heat and / or UV curing.

20. A method for removing an acid gas from an acid gas-enriched gas stream, comprising: a step of contacting the acid gas-enriched gas stream with the composite material of any one of claims 1 to 13, and regenerating said composite material to desorb the acid gas.

21. The method of claim 20, wherein the acid gas comprises carbon dioxide, hydrogen sulfide, or a combination thereof.

22. The method of claim 20 or 21 , wherein the acid gas-enriched gas is selected from flue gas or atmospheric air.

23. The method of any one of claims 20 to 22, wherein the regeneration step is performed by applying heat, vacuum, or steam, preferably steam.

24. A cartridge comprising parallel or helically wound fibers made of a hydrophobic MOF-polymer composite material as defined in any one of claims 1 to 13 for use in gas adsorption systems.

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