Green synthesis of MOF for GAZ capture

Abstract

The present invention relates to a Metal-Organic Framework (MOF) that exhibits superior CO2 adsorption efficiency, notably in some humid environments, and an advanced method for fabricating said MOF, the method complying with environment constraints, and a CO2 capture process using the MOF of the present invention.

Description

DescriptionGREEN SYNTHESIS OF MOF FOR GAZ CAPTURE

[0001] The present invention relates to a Metal-Organic Framework (MOF) that exhibits superior CO2 adsorption efficiency, notably in some humid environments, and an advanced method for fabricating said MOF, the method complying with environment constraints, and a CO2 capture process using the MOF of the present invention.Technical Field

[0002] This disclosure pertains to the field of CO2 capture and more specifically to the use of Metal- Organic Framework (MOF) for CO2 capture and method for producing them.Background Art

[0003] The field of CO2 capture has been identified as critically significant for the forthcoming decades as part of the global effort to combat climate change. A variety of methods have been developed with the aim of capturing CO2, either directly from the atmosphere or from industrial exhaust gases. Among these, one particularly promising technique involves the utilization of Metal- Organic Frameworks (MOFs) for the effective adsorption of CO2.

[0004] MOFs are a class of porous materials composed of inorganic entities, such as clusters, coordinated to organic linkers to form one-, two-, or three-dimensional structures. They are known for their high and modulable specific surface area, tunable porosity, and the ability to be designed with specific functional properties, which makes them useful in a variety of applications. MOFs are beneficially used because they can effectively capture CO2 by adsorption.

[0005] It is, for instance, established in the field of CO2 capture to utilize MOFs known as MIL-n, an acronym for Matériaux de l'institut Lavoisier, such as, for example, aluminum terephthalate MIL-53, aluminum naphthalate MIL-69, aluminum trimsates MIL-96 as well as MIL-100 or MIL-110, and aluminum pyromellitate MIL-120 which are recognized for their CO2 adsorption capabilities. This adsorption property can typically be evidenced by a characteristic S-shaped isotherm.

[0006] Nevertheless, the adsorption capability of these MOFs may be significantly compromised due to the presence of humidity in the gas to be treated. Furthermore, the production process of some of these MOFs necessitates the utilization of reagents that are recognized as being detrimental to environmental sustainability, such as dimethylformamide (DMF).

[0007] Consequently, there exists a requirement to develop MOFs that demonstrate enhanced carbon dioxide adsorption capacity, even in environments laden with humidity. There is also a need to develop methods for the synthesis of these MOFs that better comply with the environmental constraints of our time.Summary

[0008] According to a first aspect of the present invention, it is provided a metal-organic framework(MOF) comprising inorganic entities and organic linkers connecting the inorganic entities,wherein each of the inorganic entities has one of the following formulae MO4(OH)(2-n)Ynor MO2(OH)<3- P)ZP(H2O) or MO2(OH)(4-q)Xqwherein n is an integer from 1 to 2, p is an integer from 1 to 3, and q is an integer from 1 to 4, and wherein M is a metallic cation, wherein Y, Z, and X are, independently from each other, an ionic group that is less hydrophilic than OH- or a mixture of different ionic groups that are less hydrophilic than OH-.

[0009] The MOF described in the present invention demonstrates superior CO2 adsorption capabilities, even in humid environments.

[0010] A humid environment can be characterized by its relative humidity (RH) which measures the amount of water vapor present in the air relative to the maximum amount of water vapor the air can hold at a given temperature, expressed as a percentage. It is typically measured using hygrometers or humidity sensors.

[0011] In the present invention, the humid environment may be characterized by a relative humidity from 5 to 90%RH at 25°C, particularly from 10 to 80 %RH at 25°C, even more particularly from 10 to 50%RH at 25°C, and even more particularly from 10 to 15%RH at 25°C.

[0012] According to another aspect, the present invention is directed to a process for producing a MOF according to the present invention, comprising the following steps: a) mixing, in a liquid solvent, an organic linker and a metallic salt to obtain a reactive mixture, b) heating the reactive mixture to synthesize the MOF, characterized in that the liquid solvent is an aqueous solvent, and the metallic salt is MY, MZ, MX or a mixture thereof, wherein M is a metallic cation, and wherein Y, Z, and X are, independently from each other, an ionic group that is less hydrophile than OH- or a mixture of different ionic groups that are less hydrophilic than OH-.

[0013] This method induces the formation of a Metal-Organic Framework (MOF) having a modified chemical composition, leading to elevating its hydrophobic properties. Additionally, this method allows for the MOF synthesis to be conducted at ambient pressure and reduced temperature, which contributes to a lower energy expenditure during the manufacturing process. Importantly, this method eliminates the need for utilizing toxic reagents as the Dimethylformamide (DMF).

[0014] According to another aspect, the present invention is directed to a process for purifying a gas containing CO2, comprising the step of contacting the gas containing CO2 with the MOF of the invention or produced by the process of the invention, to obtain a gas depleted in CO2.

[0015] The CO2 capture process of the present invention enables the purification of substantial volumes of gas, such as atmospheric air or industrial exhaust gases, even when these gases are subject to varying humidity levels.Brief Description of Drawings

[0016] [Fig. 1] shows the uptake of CO2 at 298 Kelvin (25°C), with respect to absolute pressure (mbar), by a MOF of the invention and a comparative MIL-96(AI) MOF.Fig. 2

[0017] [Fig. 2] shows the uptake of H2O at 298 Kelvin (25°C), with respect to the relative pressure (P / PO), by a MOF of the invention and a comparative MIL-96(AI) MOF.Fig. 3

[0018] [Fig. 3] is the same as figure 2, focusing on the region between 0 and 0.2 relative pressure.Fig. 4

[0019] [Fig. 4] (A) shows a comparative PXRD (ÀCu(Ka)~1 .5406 Â) plot of calculated pattern of the comparative MIL-96(AI) versus MOF according of the invention, showing the phase purity of the MOF according of the invention. (B) shows FTIR spectra of MIL-96(AI), an organic linker and a MOF according to the invention (C) shows TGA curve (under O2 atmosphere, scan rate = 5°C / min) of a MOF of the invention suggesting no free organic linker in the MOF pores.Description of Embodiments

[0020] The invention is generally directed to defective-MOFs, which are Metal-Organic Frameworks intentionally designed with structural defects, such as missing linkers or metal nodes. These defects create additional active sites and increase the material's surface area, enhancing its overall adsorption properties. Defective-MOFs can be engineered to allow ionic groups that are less hydrophilic than OFT, preferably sulfates, to bind. This strategic incorporation of less hydrophilic ionic groups can reduce the framework's affinity for water, thereby improving its performance in humid environments and enhancing its CO2 adsorption capacity.

[0021] Inorganic entities of known MOFs can be represented by the formulae: MO4(OH)2 or MO2(OH)3(H2O) or MO2(OH)4, where M is a metallic cation. These structures typically include several OH groups. The absence of some OH groups can create defects, resulting in what are known as defective MOFs.

[0022] The inorganic entities in the present invention has one of the following formulae: MO4(OH)(2- njYn Or MO2(OH)(3-p)ZP(H2O) or MO2(OH)(4.q)Xqwherein n is an integer from 1 to 2, p is an integer from 1 to 3 and q is an integer from 1 to 4, and wherein M is a metallic cation, it indicates that at least one OH group in the MOF's known formulation has been replaced by a group Y, Z, or X wherein Y, Z, and X are, independently from each other, an ionic group that is less hydrophilic than OH- or a mixture of different ionic groups that are less hydrophilic than OH-.

[0023] While not willing to be bound by any specific theory, the inventors believe that substituting parts of the hydrophilic groups of conventional MOFs with less hydrophilic groups could enhance their performances in humid environments. This modification reduces, in humid conditions, the extent to which the MOF's pores are occupied by water molecules, thereby preserving relatively more pore space for CO2 adsorption.

[0024] An "ionic group that is less hydrophilic than OH " refers to an ion or ionic moiety that exhibits lower affinity for water compared to the hydroxide ion (OH ). These groups are less likely to form strong hydrogen bonds with water molecules than hydroxyl groups, resulting in reduced solubility or interaction with water.

[0025] The ionic group that is less hydrophile than OH- may be chosen from the list consisting of a phosphonate, a phosphate, a sulfonate, a sulfate, a sulfide, their protonated versions, and mixtures thereof, preferably the ionic group that is less hydrophile than OH- is chosen from the list consisting of a phosphonate, a phosphate, a sulfonate, a sulfate, a sulfide or a mixture thereof.

[0026] In a preferred embodiment, the ionic group that is less hydrophile than OH- may be chosen from among the list consisting of a sulfate and its protonated version, even more preferably a sulfate.

[0027] The MOF of the invention may have the structure of the MIL-96, MIL-1 10, Ml P-213, MOF-801 , MOF-808, MIP-177 LT, in particular the MIL-96, MIL-110, or a combination thereof and more particularly MIL-96.

[0028] These structures of MOF are well known by the skilled person and are described for instance in Devic et al. Chem. Soc. Rev., 2014,43, 6097-6115.

[0029] Metal-organic framework (MOF)

[0030] According to the present disclosure, inorganic entities in the context of Metal-Organic Frameworks (MOFs) refer to the metal centers, which are metal ions or metal clusters (at least two metallic atoms chemically linked together by a ligand) that serve as the structural nodes or vertices within the framework.

[0031] In the MOF’s formulae of the invention, M is a metallic cation. A metallic cation can be characterized by its oxidation degree. A trivalent metal, for instance, is a metal element that forms ions with a +3 charge by losing three electrons. This metal has an oxidation degree of +3, meaning it can form three bonds with other atoms or ions in chemical compounds.

[0032] The metal of the metallic cation M of the invention can be selected among the list consisting of Vanadium (V), Ruthenium (Ru), Cerium (Ce), Aluminum (Al), Iron (Fe), Cobalt (Co), Nickel (Ni), Chromium (Cr), Manganese (Mn), Titanium (Ti), Zirconium (Zr), Indium (In), and Gallium (Ga), preferably Aluminum (Al), Iron (Fe), Cobalt (Co), Nickel (Ni), Chromium (Cr), Manganese (Mn), Titanium (Ti), Zirconium (Zr), Indium (In), eve more preferably Chromium (Cr) or Aluminum (Al), even more preferably Aluminum (Al).

[0033] In the Metal-Organic Frameworks (MOFs) formula, the organic linkers are organic molecules that connect the inorganic entities (metal ions or clusters) forming the MOF’s network structure.

[0034] An organic linker typically consists of a core and at least two coordinating groups. A coordinating group can coordinate to one or multiple metal centers and can typically be selected from the list consisting of, but not limited to, carboxylates, phosphonates, sulfonates, and coordinating group comprising at least one coordinating nitrogen atom.

[0035] For instance, a coordinating group comprising a coordinating nitrogen atom can be selected from the list consisting of a coordinating nitrogen atom, an azolate such as triazolate, imidazolate, 2- Methylimidazolate, lmidazolate-2-carboxyaldehyde, or 5-Methyltetrazolate.

[0036] The core of an organic linker comprising at least two coordinating groups wherein at least one is a carboxylate, may be aliphatic or aromatic.

[0037] The organic linker can typically consist of an aliphatic core and at least one, preferably at least two carboxylates.

[0038] In a preferred embodiment, the organic linker that consists of an aliphatic core and at least two carboxylates, is selected from the list consisting of fumarate, 1 ,3-adamantanedicarboxylate, trans-1 ,4-cyclohexanedicarboxylate, and isophthalate.

[0039] The organic linker can typically consist of an aromatic or heteroaromatic core and at least one, preferably at least two carboxylates.

[0040] In a preferred embodiment, the organic linker that consists of an aromatic or heteroaromatic core and at least two carboxylates, is selected from the list consisting of benzene-1 ,3,5-tricarboxylate, 2-aminoterephthalate, 1 ,3,5-benzenetrisbenzoate, 4,4'-benzophenonedicarboxylate, 4, 4', 4"- [benzene-1 ,3,5-triyl-tris(oxy)]tribenzoate, meso-tetrakis(4-carboxylatephenyl)porphyrin, 4,4',4"-s- triazine-2,4,6-triyl-tribenzoate, 3,3",5,5"-tetrakis(4-carboxyphenyl)-p-terphenyl, 4',4",4'",4""-(ethene- 1 ,1 ,2,2-tetrayl)tetrabiphenyl-4-carboxylate, 4',4",4'",4""-methanetetrayltetrabiphenyl-4-carboxylate, 4,4',4",4'"-methanetetrayltetrabenzoate, 4,4'-((1 E , 1 'E)-(2,5-bis((4-carboxylatephenyl)ethynyl)-1 ,4- phenylene)bis(ethene-2,1 -diyl))dibenzoate, terephthalate, naphthalene-2,6-dicarboxylate, 1 ,2,4,5- benzenetetracarboxylate, 1 ,4,5,8-naphthalenetetracarboxylate, biphenyl-4,4'-dicarboxylate, biphenyl-3,3',5,5'-tetracarboxylate, 4,4'-azobenzenedicarboxylate, 2,5-thiophenedicarboxylate, and 1 H-Pyrazole-3,5-dicarboxylate, preferably the organic linker that consists of an aromatic or heteroaromatic core and at least two carboxylates is benzene-1 ,3,5-tricarboxylate.

[0041] In a preferred embodiment, the organic linker comprising at least one coordinating nitrogen atom, is selected from the list consisting of 2-Methylimidazolate, lmidazolate-2-carboxyaldehyde, 5- Methyltetrazolate, 1 H-Pyrazole-3,5-dicarboxylate, 1 ,3,5-Tris((1 H-pyrazol-4-yl)phenyl)benzene, 1 ,3,5-Tris(1 H-pyrazol-4-yl)benzene, 1 ,4-Benzenedi(4'-pyrazolyl), 1 ,3-Benzenedi(4'-pyrazolyl), 10,15,20-Tetra(1 H-pyrazol-4-yl)-porphyrin, Benzimidazolate, 2-Nitroimidazolate, 5- Chlorobenzimidazolate, and 2-Methylbenzimidazolate.

[0042] According to a preferred embodiment of the invention, the organic linker is the benzen-1 ,3,5- tricarboxylate or one of its protonated forms.

[0043] According to preferred embodiment of the invention, the MOF comprises inorganic entities and organic linkers connecting the inorganic entities, wherein each of the inorganic entities has one of the following formulae MO4(OH)(2-n)Yn Or MO2(OH)(3-p)ZP(H2O) or MO2(OH)(4-q)Xqwherein n is an integer from 1 to 2, p is an integer from 1 to 3 and q is an integer from 1 to 4, and wherein the metal of the metallic cation M is Al,wherein Y, Z and X are sulfates or their protonated versions, even more preferably SCk2-group, and the MOF has the structure of the MIL-96(AI).

[0044] This specific configuration has demonstrated an enhanced ability to adsorb CO2 even in humid environments. Without wishing to be bound by any theory, the inventors believe that this improved CO2 adsorption capacity is attributed to the presence of sulfate groups, which reduce the hydrophilicity of the framework. This reduction in hydrophilicity helps maintain high CO2 adsorption capacity and stability in the presence of water.

[0045] SynthesisAccording to another aspect, the invention is directed to a process for producing the MOF of the invention, the method comprises the following steps: a) mixing, in a liquid solvent, an organic linker and a metallic salt to obtain a reactive mixture, b) heating the reactive mixture to synthesize the MOF, characterized in that the liquid solvent is an aqueous solvent, and the metallic salt is MY, MZ, MX or a mixture thereof, wherein M is a metallic cation as defined above, and wherein Y, Z and X are, independently from each other, an ionic group or mixture of different ionic groups as defined above, that is less hydrophile than OFF.

[0046] The ionic group that is less hydrophile than OH- may be chosen from the list consisting of a phosphonate, a phosphate, a sulfonate, a sulfate, a sulfide, their protonated versions, and mixtures thereof, preferably the ionic group that is less hydrophile than OH- is chosen from the list consisting of a phosphonate, a phosphate, a sulfonate, a sulfate, a sulfide or a mixture thereof.

[0047] In a preferred embodiment, the ionic group that is less hydrophile than OH- may be chosen from among the list consisting of a sulfate and its protonated version, even more preferably a sulfate.

[0048] The metal of the metallic cation M is selected among the list consisting of Vanadium (V), Ruthenium (Ru), Cerium (Ce), Aluminum (Al), Iron (Fe), Cobalt (Co), Nickel (Ni), Chromium (Cr), Manganese (Mn), Titanium (Ti), Zirconium (Zr), Indium (In), and Gallium (Ga), ùpre preferably Aluminum (Al), Iron (Fe), Cobalt (Co), Nickel (Ni), Chromium (Cr), Manganese (Mn), Titanium (Ti), Zirconium (Zr), Indium (In), and Gallium (Ga), even more preferably Chromium (Cr) or Aluminum (Al), even more preferably Aluminum (Al).

[0049] In a particular embodiment, the metallic salt MY, MZ, MX are chosen among the list consisting of AIPO4, AI(NO3)3, Al2(SO4)3, NaAIO2, AICIs, or a mixture thereof, more particularly the metallic salt is Al2(SO4)3, NaAIO2,or a mixture thereof, even more preferably the metallic salt is Al2(SO4)3

[0050] Dimethylformamide (DMF) is preferably not used in the synthesis of the invention.

[0051] This synthesis method results in a MOF ensuring satisfactory CO2 adsorption capacity even in the presence of a certain amount of water. Specifically, this synthesis route enhances the hydrophobic character of the MOF, which can be evidenced by a more pronounced S-shaped water adsorption isotherm and an increased CO2 adsorption capacity.

[0052] Also, this synthesis uses a solvent which is not dangerous and does not require excessively high-pressure conditions.

[0053] The aqueous solvent is preferably a mixture of water and acetic acid or water and alcohol such as ethanol, propanol, butanol, benzyl alcohol or a mixture thereof, in particular ethanol. The aqueous solvent is preferably water and alcohol such as ethanol, propanol, butanol, benzyl alcohol or a mixture thereof, in particular ethanol.

[0054] Benzyl alcohol can be avoided if a greener synthesis approach is desired.

[0055] The mass ratio water:alcohol in the liquid solvent may be from 1 .00:0.25 to 1.00:1.00, in particular from 1 .00:0.30 to 1 .00:0.75, more particularly from 1 .00:0.40 to 1 .00:0.60.

[0056] If the metallic salt is NaAIC , the aqueous solvent is preferably a mixture of water and acetic acid.

[0057] If the metallic salt is Ah(SO4)3, the aqueous solvent is preferably a mixture of water and alcohol.

[0058] The organic linker may be chosen among the organic linkers defined above or their protonated forms. Preferably, the organic linker is the benzen-1 ,3,5-tricarboxylate or one of its protonated forms, even more preferably the organic linker is the protonated form of benzen-1 ,3,5- tricarboxylate, even more preferably benzene-1 ,3,5-tricarboxylic acid.

[0059] At the beginning of step a) of the process of the invention, the molar ratio of organic linker: metallic salt may be from 1 .00:0.50 to 1 .00:2.00, in particular from 1 .00:0.75 to 1 .00:1 .50, for instance 2.00:3.00 or 1.33:1.00.

[0060] At the beginning of step a) of the process of the invention, the mass ratio of metallic salt:organic linker may be from 1.00:0.25, in particular from 1.00:0.40, more particularly from 1.00:0.42 to 1.00:0.60.

[0061] During step b) of the process of the invention, the reactive mixture may be heated at a temperature ranging from 70°C to 120°C, in particular from 80°C to 100°C, more particularly the reactive mixture is refluxed.

[0062] The temperatures involved in the process of the invention are relatively low, making it energyefficient and contributing to its classification as a green synthesis.

[0063] Step b) of the invention may last from 36 hours to 96 hours, in particular from 40 hours to 72 hours, more particularly from 45 hours to 50 hours.

[0064] This duration allows for a reduction in the working temperature and pressure required for the reaction, while still achieving a good yield.

[0065] According to a preferred embodiment, the invention is directed to a process for producing a MOF, the method comprises the following steps:a) mixing, in a liquid solvent, an organic linker and a metallic salt, preferably the molar ratio organic linker metallic salt is from 1 .00:1 .00 to 1 .00:3.00, for instance 2.00:3.00, to obtain a reactive mixture, b) heating the reactive mixture to synthesize the MOF, preferably at a temperature over 40°C, even more preferably at a temperature from 80°C to 100°C, characterized in that the liquid solvent is a mixture of water and acetic acid, the metallic salt is NaAIC and the organic linker is the benzen-1 ,3,5-tricarboxylic acid, having the formula CeH3(COOH)3, where Dimethylformamide (DMF) is not used in the synthesis of the invention.

[0066] According to another preferred embodiment, the invention is directed to a process for producing a MOF, the method comprises the following steps: a) mixing, in a liquid solvent, an organic linker and a metallic salt, preferably the molar ratio organic linker:metallic salt is from 1.10:1.00 to 1 .50:1.00, for instance 1.33:1 , to obtain a reactive mixture, b) heating the reactive mixture to synthesize the MOF, preferably at a temperature over 40°C, even more preferably at a temperature from 80°C to 100°C, characterized in that the liquid solvent is a mixture of water and alcohol, the metallic salt is Ah(SO4)3, and the organic linker is the benzen-1 ,3,5-tricarboxylic acid and its salt, having the formula CeHs (COOH)3, where Dimethylformamide (DMF) is not used in the synthesis of the invention.

[0067] The process of the invention may further comprise a step of washing the MOF synthesized in step b) to obtain a purified MOF. Alternatively, the process of the invention may further comprise a step of drying and washing the MOF synthesized in step b) to obtain a purified MOF.

[0068] In a preferred embodiment, the process of the invention may further comprise the following steps: c) filtering the MOF synthesized in step b) to obtain a filtered MOF, d) drying the filtered MOF to obtain a dried MOF, and e) washing and further drying the dried MOF obtained in step d) to produce a purified MOF.

[0069] The MOF synthesized in step b) can be filtered (step c) by passing the reaction mixture through a suitable filtration medium, such as a filter paper or a membrane, to separate the solid MOF from the liquid components. This process involves pouring the mixture into a filtration apparatus, allowing the liquid to pass through while retaining the solid MOF on the filter. The filtered MOF is then collected and can be further washed and dried in a step e) if needed to obtain a purified MOF.

[0070] During step d), the filtered MOF may be dried by air.

[0071] The washing and drying of the process of the invention may be operated at a temperature ranging from 60°C to 100°C, in particular from 70°C to 90°C, more particularly from 75°C to 85°C.

[0072] Such temperatures are energy-efficient and minimize the environmental impact of the process.

[0073] Washing of the MOF may be performed with a solvent being water, isopropyl alcohol, methanol or a mixture thereof, in particular water.

[0074] Using water may be preferred because it minimizes the environmental impact and promotes a more sustainable process.

[0075] Alternatively, the MOF synthesized in step b) can be centrifuged to obtain a centrifuged MOF, the centrifuged MOF is washed and dry or alternatively just washed to obtain a purified MOF.

[0076] CO2capture process

[0077] According to another aspect, the invention is directed to a process for purifying a gas containing CO2, comprising contacting the gas containing CO2 with the MOF of the invention or produced by the process of the invention to obtain a gas depleted in CO2.

[0078] This process results in enhanced CO2 adsorption capacity, even in humid environments.

[0079] The step of contacting the gas containing CO2 with the MOF can be achieved through various methods. These include passing the gas through membranes embedded with the MOF of the invention, using contactors with surfaces coated with the MOF, employing a packed bed filled with the MOF, or utilizing an adsorption column packed with the MOF material." In the case where an adsorption column is used, the gas can be introduced at one end of the column, and fans or blowers can be used to ensure a consistent flow rate and uniform contact between the gas and the MOF adsorbent.

[0080] Alternatively, the gas can be bubbled through a slurry of the MOF in a suitable solvent, allowing the CO2 to be adsorbed by the MOF particles suspended in the liquid. After sufficient contact time, the gas depleted in CO2 can be collected from the top of the column or vessel. This method ensures efficient CO2 capture and can be easily integrated into existing gas purification systems.

[0081] The gas may be pretreated before contacting with the MOF of the invention or produced by the process of the invention. For example, the concentration of CO2 within the gas may be increased.

[0082] The gas containing CO2 may be from the atmosphere or from industrial exhaust gases.

[0083] The CO2 partial pression in the gas containing CO2 may be greater than 500 Pascal (5mbar) at 25°C. This ensures a sufficient driving force for the adsorption process. This higher partial pressure enhances the efficiency of CO2 capture by the MOF, leading to more effective purification of the gas.

[0084] The gas containing CO2 in the present invention further comprises H2O, wherein the concentration of H2O corresponds to a relative humidity from 5 to 90%RH at 25°C, particularly from 10 to 80 %RH at 25°C, even more particularly from 10 to 50%RH at 25°C, and even more particularly from 10 to 15%RH at 25°C.

[0085] In the context of the present invention, the gas containing CC may also include water vapor, so that its relative humidity is from 5 to 90%RH at 25°C, particularly from 10 to 80 %RH at 25°C, even more particularly from 10 to 50%RH at 25°C, and even more particularly from 10 to 15%RH at 25°C.

[0086] This level of humidity can impact the adsorption process, as water molecules can compete with CO2 for adsorption sites on the MOF. However, the MOF of the present invention is designed to maintain important CO2 adsorption capacity even in the presence of humidity, ensuring efficient CO2 capture under these conditions.

[0087] This robustness against humidity makes the MOF particularly effective for real-world applications where gases often contain significant levels of water vapor.Examples

[0088] The following synthesis, in accordance with the invention, has been made. Ah(SO4)3 and benzene-1 ,3,5-tricarboxylate (BTC) were mixed at a mass ratio of 2.38:1.00 in a water and ethanol mixture at a mass ratio of 2.00:1 .00 and refluxed for 48 hours. The solid was filtered and dried in air. Further, the synthesized MOF was washed with water at 80°C overnight to obtain the pure MOF.

[0089] The metal-organic framework (MOF) obtained through the synthesis of the invention comprises inorganic entities and organic linkers connecting the inorganic entities, wherein each of the inorganic entities has one of the following formulae MO4(OH)(2-n)Ynor MO2(OH)(3- P)ZP(H2O) or MO2(OH)(4-q)Xqwherein n is an integer from 1 to 2, p is an integer from 1 to 3 and q is an integer from 1 to 4, and wherein M is Aluminum, wherein Y, Z and X are, independently from each other, SO42-group, protonated versions thereof, or a mixture thereof.

[0090] The MOF was characterized using PXRD, FTIR and TGA and results are shown in figure 4.

[0091] Powder X-ray Diffraction (PXRD) is a technique that provides detailed information about the crystalline structure of a material. PXRD involves directing X-rays at a powdered sample and measuring the intensity and angles of the diffracted beams. The resulting diffraction pattern is used to determine the lattice parameters, phase purity, and crystallinity of a MOF.

[0092] It is now made reference to Figure 4. A that shows a comparative PXRD (ÀCu(Ka)~1 .5406 Â) plot of simulated MOF versus MOF according of the invention. It can be seen in figure 4. A that the MOF obtained through the synthesis according to the invention is very pure even if it cannot be exactly equivalent as the MIL-96(AI) simulated because it does not comprise strictly the same chemical composition of MIL-96(AI), OH group have been replaced by SO42-group or protonated versions thereof.

[0093] Fourier Transform Infrared Spectroscopy (FTIR) measures the absorption of infrared radiation by a sample as a function of wavelength, providing information about the molecular vibrations and chemical bonds within the material. By analyzing the FTIR spectrum, functional groups can be identified to confirm the presence of specific organic linkers and metal-ligand interactions in the MOF.

[0094] It is now made reference to figure 4.B that shows FTIR spectra of MIL-96(AI), an organic linker and a MOF according to the invention. It can be seen in figure 4.B that the MOF according to the invention comprises the organic linker.

[0095] Thermogravimetric Analysis (TGA) involves heating a sample at a controlled rate while measuring the weight loss as a function of temperature. This technique provides insights into the thermal decomposition behavior, humidity content, and the presence of volatile components in the MOF.

[0096] It is now made reference to figure 4.C that shows TGA curve (under O2 atmosphere, scan rate = 5°C / min) of a MOF of the invention. It can be seen in fig. 4.C that the MOF obtained through the method according to the invention suggests no free organic linkers stay in the MOF pores.

[0097] Comparative examples

[0098] [Table 1]

[0099] Ex. 1 is a MIL-96(AI) synthesized by the synthesis according to the invention using NaAIO2 as a metallic salt, and BTC as organic linker.

[0100] Ex. 2 is a MOF according to the invention. Ex. 2 is metal-organic framework (MOF) comprising inorganic entities and organic linkers connecting the inorganic entities, wherein each of the inorganic entities has one of the following formulae MO4(OH)(2-n)Ynor MO2(OH)(3-P)Zp(H2O) or MO2(OH)(4-q)Xqwherein n is an integer from 1 to 2, p is an integer from 1 to 3 and q is an integer from 1 to 4, and wherein M is Aluminum, wherein Y, Z and X are SO42-groups. The MOF has the structure of the MIL-96(AI).

[0101] Ex. 3, not from the invention, is the CALF-20 MOF.

[0102] Table 1 shows the CO2 capacity at 5000 Pa (0.05 bar) (mmol / g) for Ex. 1 , Ex. 2, and Ex. 3. It can be seen that CALF-20 exhibits excellent performance, adsorbing 2.1 mmol / g of CO2, which is higher than both Ex. 1 and Ex. 2. Specifically, Ex. 2, which is part of the invention, demonstrates nearly twice the performance of Ex. 1 , adsorbing 0.94 mmol / g of CO2 compared to Ex. Ts 0.45 mmol / g. This highlights the significant improvement achieved in Ex. 2 over Ex. 1 at 5000 Pa (0.05 bar).

[0103] Table 1 shows the CO2 capacity at 15000 Pa (0.15 bar) (mmol / g) for Ex. 1 , Ex. 2, and Ex. 3. It can be seen that CALF-20 exhibits good performance, adsorbing 2.75 mmol / g of CO2, which is higher than both Ex. 1 and Ex. 2. Specifically, Ex. 2, which is part of the invention, demonstratesbetter performance of Ex. 1 , adsorbing 1 .67 mmol / g of CO2 compared to Ex. l 's 1 .08 mmol / g. This highlights the significant improvement achieved in Ex. 2 over Ex. 1 at 15000 Pa (0.15 bar).

[0104] Table 1 finally shows the water uptake at 5% RH (mmol / g) for Ex. 1 , Ex. 2, and Ex. 3. It can be seen that CALF-20 exhibits good performance, adsorbing only 0.85 mmol / g of water, which is higher than both Ex. 1 and Ex. 2. Specifically, Ex. 2, which is part of the invention, demonstrates better performance of Ex. 1 , adsorbing almost half 3.95 mmol / g of water compared to Ex. l 's 6.00 mmol / g. This highlights the better water adsorption capacity achieved in Ex. 2 over Ex. 1 at 5%RH.

[0105] Reference is now made to Figure 1 , which illustrates the uptake of CO2 expressed in mmol / g at 298 Kelvin (25°C) with respect to pressure. The figure compares a MOF synthesized by a known method with a MOF according to the invention. It can be observed that the CO2 uptake is very similar for both MOFs, demonstrating that the synthesis method of the invention does not reduce the CO2 adsorption capacity across the entire pressure range analyzed, from 0 to 100000 Pa (0 to 1000 mBar).

[0106] Reference is now made to Figure 2, which illustrates the uptake of H2O expressed in mmol / g, at 298 Kelvin (25°C) with respect to relative pressure (P / P0). The figure clearly shows that a MOF in accordance with the invention, exhibits equivalent water uptake capacity across the upper ranges, from 0.5 to 1 and better water uptake capacity below 0.5 compared with a MOF synthesized by known method. Figure 3, which is equivalent to Figure 2, focused on the region of partial pression between 0 and 0.2 shows the S-Shaped of Ex. 2 and it shows that MOF of the invention acts better in these ranges of relative pressure.

Claims

Claims

1. A metal-organic framework (MOF) comprising inorganic entities and organic linkers connecting the inorganic entities, wherein each of the inorganic entities has one of the following formulae MO4(OH)(2-n)Ynor MO2(OH)(3- P)ZP(H2O) or MO2(OH)(4-q)Xqwherein n is an integer from 1 to 2, p is an integer from 1 to 3, q is an integer from 1 to 4, and wherein M is a metallic cation, wherein Y, Z, and X, are, independently from each other, an ionic group that is less hydrophile than OH- or a mixture of different ionic groups that are less hydrophile than OH-.

2. The MOF according to claim 1 , wherein the ionic group that is less hydrophile than OH- is selected from the list consisting of a phosphonate, a phosphate, a sulfonate, a sulfate, a sulfide, their protonated versions, and mixtures thereof.

3. The MOF according to claim 1 or claim 2, wherein the metal of the metallic cation M is selected among the list consisting of Vanadium (V), Ruthenium (Ru), Cerium (Ce), Aluminum (Al), Iron (Fe), Cobalt (Co), Nickel (Ni), Chromium (Cr), Manganese (Mn), Titanium (Ti), Zirconium (Zr), Indium (In), and Gallium (Ga).

4. The MOF according to any of claims 1 to 3, wherein the organic linker consists of a core and at least two coordinating groups, wherein the coordinating groups can be selected among the list consisting of carboxylates, phosphonates, sulfonates, and coordinating group comprising at least one coordinating nitrogen atom.

5. The MOF according to any of claims 1 to 4, wherein the organic linkers is benzen-1 ,3,5- tricarboxylate.

6. The MOF according to any of claims 1 to 5 which has a structure of the MIL-96, MIL-110, MIP-213, MOF-801 , MOF-808, MIP-177_LT.

7. A process for producing a MOF as defined in any one of claim 1 to 6 comprising the following steps: a) mixing, in a liquid solvent, an organic linker and a metallic salt to obtain a reactive mixture, b) heating the reactive mixture to synthesize the MOF, characterized in that the liquid solvent is an aqueous solvent, and the metallic salt is MY, MZ, MX or a mixture thereof, wherein the metal M of the metallic salt MY, MZ, MX is according to claim 3 and wherein Y, Z and X are, independently from each other, an ionic group or a mixture of different ionic groups according to claim 2 that is less hydrophile than OH-.

8. The process according to claim 7, wherein the metallic salt MY, MZ, MX are chosen from the list consisting of AIPO4, AI(NOs)3 Al2(SO4)3, NaAIO2, AlCb, or a mixture thereof.

9. The process of claims 7 or 8 wherein the aqueous solvent is a mixture of water and alcohol such as ethanol, propanol, butanol, benzenalcool or a mixture thereof, in particular ethanol, or a mixture of water and acetic acid.

10. The process according to claim 9, wherein the mass ratio water:alcohol in the liquid solvent is from 1 .00:0.25 to 1 .00:1 .00.

11. The process according to any one of claims 7 to 10, wherein the organic linker is the protonated of the organic linker according to claim 4.

12. The process according to any one of claims 7 to 10, wherein the organic linker is the benzen-1 ,3,5-tricarboxylic acid.

13. The process according to any one of claims 7 to 12, wherein, at the beginning of step a), the mass ratio metallic salt:organic linker is from 1 .00: 0.25.

14. The process according to any one of claims 7 to 13, wherein, during step b), the reactive mixture is heated at a temperature ranging from 70°C to 120°C.

15. The process according to any one of claims 7 to 14, wherein step b) is performed from 36 hours to 96 hours.

16. The process according to any one of claims 7 to 15, further comprising the following step of washing the synthesized MOF obtained in step b) to produce a purified MOF.

17. The process according to claim 16, wherein the washing is performed with a solvent being water, isopropyl alcohol, methanol or a mixture thereof.

18. The process according to any one of claims 7 to 15, further comprising the following step of drying and washing the MOF synthesized in step b) to produce a purified MOF

19. The process according to claim 18, wherein the step of drying is operated at a temperature ranging from 60°C to 100°C.

20. A process for purifying a gas containing CO2 comprising the step of contacting the gas containing CO2with a MOF as defined in any one of claim 1 to 6 or produced by the process according to any one of claim 7 to 19 to obtain a gas depleted in CO2.

21. The process according to claim 20, wherein the gas containing CO2 is from the atmosphere or from industrial exhaust gases.

22. The process according to any one of claims 20 to 21 , wherein the gas containing CO2 further comprises H2O, wherein the concentration of H2O is from 10%RH to 80%RH at 25°C.

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