Porous composite and use thereof for gas storage

Abstract

The present application relates to the storage of gases, using a porous composite based on a porous matrix and an organic compound confined in solid form within pores of the matrix with a diameter of less than 10 nm.

Description

[0001] Porous composite and its use for gas storage

[0002] The present invention relates to the field of energy storage and in particular the storage of gases, such as dihydrogen (H2).

[0003] Hydrogen is at the heart of tomorrow's ecological transition and is seen as one of the fuels of the future. Public policies and major energy players are positioning themselves strongly in this area. The means of storing H2 in the hydrogen energy chain is a major obstacle to large-scale deployment.

[0004] There are different types of hydrogen storage, such as conventional tanks (in gaseous or liquid form) and solid form (in adsorbed, absorbed or trapped form). None of these techniques is, to date, completely satisfactory for stationary and mobile storage, whether for reasons of insufficient performance, safety, social acceptability, or profitability.

[0005] Solid storage is currently carried out either by adsorption in porous matrices, but the storage capacities are only interesting at very low temperatures, in particular at cryogenic temperatures (77K), or by absorption in metal or complex hydrides. Even if some of them have an interesting storage volume density (higher than that of liquid hydrogen) and even if the pressures involved are moderate, the use of this type of material encounters two major drawbacks: the kinetics of hydride formation and dehydration are slow and the dehydration temperatures are high (above 300°C and 480°C for MgH2 and LiBH4 respectively).

[0006] FR 3000907 describes a reactive medium comprising a porous support on which is deposited in solid form an organic compound capable of forming gas clathrates, such that the porous support comprises pores with a size between 10 nm and 150 nm, preferably between 30 nm and 120 nm. After impregnation carried out in a liquid manner, the organic compound in solid form is deposited on the surface and / or within the pores of the support. The gas can be captured by the organic compound in the form of clathrates.

[0007] This technique has the disadvantage of using solvents, requiring dissolution, filtration and drying steps. It therefore remains to provide a dihydrogen storage technique with interesting storage capacities and allowing storage and release of the gas under easy conditions.

[0008] These aims are notably achieved by the present invention.

[0009] Thus, the present invention relates to a porous composite for gas storage comprising:

[0010] - a porous matrix comprising pores with a diameter of less than 10 nm, and

[0011] - an organic compound, said porous composite being characterized in that said organic compound is present within said pores with a diameter of less than 10 nm.

[0012] For the purposes of the present invention, the term "composite" denotes the system consisting of at least two materials, namely a porous matrix and an organic compound.

[0013] The term "porous matrix" means a solid material comprising pores within which an organic compound can be deposited.

[0014] The porous matrices suitable within the framework of the invention can in particular be used in industrial processes, in particular for the storage and use of stored gases, and in particular, do not degrade under the temperature and / or pressure conditions implemented within these processes.

[0015] Advantageously, the porous matrix is ​​chosen from organic or mineral micro- and / or mesoporous supports, in particular those capable of forming inclusion compounds, and more particularly silica, carbon, alumina, aluminosilicates, activated carbons, molecular sieves, zeolites, organo-metallic framework materials (Metal Organic Frameworks, MOFs), Hofmann clathrates and polymers.

[0016] An inclusion compound is a supramolecular structure in which one of the components (host molecule) forms a cavity in which the molecular entity(ies) of a second chemical species (guest molecule) are stabilized. The concept extends to solids (crystalline or amorphous) whose network has interstices (in the form of tunnels, channels of various shapes) that can contain an included species. The stabilization of guest molecules within the network formed by the host molecules is generally ensured by non-covalent bonds, such as van der Waals forces. If the interstices formed in the host network are surrounded on all sides so that the included species is "trapped" as in a cage, the inclusion compound can be called a "clathrate" or "cage compound".The concept of inclusion compound as defined also includes "inclusion complex" type structures, in which the interactions involved to stabilize the guest molecules in the host network may be stronger than van der Waals bonds (hydrogen bonds, for example).

[0017] Preferably, the porous matrix may be selected from mesoporous silicas MCM-41 and SBA-15, aluminosilicates, carbon xerogels, activated carbons and porous polymers.

[0018] According to IUPAC nomenclature, "mesoporous" refers to pores with diameters between 2 and 50 nm and "microporous" refers to pores with diameters less than 2 nm.

[0019] Pore ​​size can be measured by gas porosimetry using nitrogen or argon as the probe molecule. This technique involves measuring the adsorption isotherm of the probe molecule at cryogenic temperatures (77K for nitrogen and 87K for argon generally) for pressures ranging from 10' 7 bar to 1 bar. Thermodynamic models, preferably Density Functional Theory (DFT), are then used to deduce the pore volume and pore size distribution of the porous matrices from these isotherms.

[0020] According to one embodiment, the matrix comprises a micro- or mesoporous volume, i.e. a volume defined by micropores and mesopores.

[0021] Thus, according to one embodiment, the pores of the porous matrix with a diameter of less than 10 nm represent at least 30%, preferably at least 50%, of the micro- / mesoporous volume of the porous matrix. This percentage is determined experimentally by a combination of analyses carried out by gas porosimetry (which makes it possible to characterize pores with a diameter of less than 30 nm), by mercury porosimetry (which makes it possible to characterize pores with a diameter of between 30 nm and several hundred micrometers), and by pycnometry (which makes it possible to evaluate the total pore volume).

[0022] Typically, porous matrix particles are used, such as beads, grains, pellets or fabrics for example, in particular silica beads or pellets, or grains, pellets or fabrics of activated carbon. Small porous particles will preferably be chosen, whose characteristic dimension (the diameter for a spherical particle, the height of the cylinder for a pellet) varies, for example, between 30 μm and 10 mm.

[0023] According to one embodiment, the porous matrix has a high specific surface area, in particular between 200 m 2 / g and 3000 m 2 / g.

[0024] The organic compound is chosen from compounds capable of forming hydrogen bonds.

[0025] According to one embodiment, said bonds can be described as "intermolecular" in that they are formed between a molecule of organic compound and another molecule, typically between at least two molecules of the organic compound, or between a molecule of the organic compound and a molecule of the stored gas (for example hydrogen).

[0026] Thus, suitable organic compounds have one or more electronegative atoms carrying at least one lone pair, such as oxygen O, nitrogen N, fluorine F, chlorine Cl, bromine Br, iodine I.

[0027] According to one embodiment, the organic compound may be chosen in particular from polyphenols, polythiols, ureas, thioureas and calixarenes. In particular, said organic compound may be chosen from the group consisting of hydroquinone, resorcinol, fluorohydroquinone, 2-5 dihydroxyl-pyridine, catechol, urea, thiourea, calix[4]arene and mixtures thereof.

[0028] Preferably, the organic compound is hydroquinone, urea, calix[4]arene.

[0029] According to one embodiment, said organic compound is present in condensed form within the pores. According to one embodiment, said organic compound may be present in crystalline, semi-crystalline and / or amorphous form within the pores of the porous matrix.

[0030] According to the invention, the organic compound can be deposited within small pores, in particular those with a diameter of less than 10 nm.

[0031] Preferably, said organic compound occupies a large portion of the pores of the porous matrix, and in particular of the micropores and mesopores of the porous matrix. Thus, according to one embodiment, said organic compound occupies at least 25%, preferably at least 40% of the micro- and mesoporous volume of the porous matrix.

[0032] According to one embodiment, the organic compound may occupy up to the entire pore volume of the porous matrix. The volume percentage of pores occupied by said organic compound may be determined by gas porosimetry.

[0033] According to another object, the present invention also relates to a process for the dry preparation of a porous composite according to the invention, said process comprising the diffusion of organic vapors into the porosity of said porous matrix, followed by the adsorption / condensation of said organic compound within the pores of said porous matrix.

[0034] The process according to the invention is carried out “dry”, i.e. without solvent.

[0035] The term "adsorption / condensation" refers to the change in state of the organic compound during the process.

[0036] Without wishing to be bound by theory, the physical mechanism of incorporation of the organic compound within the pores of the matrix is ​​based on adsorption, in particular by physisorption, or even chemisorption, involving in particular the formation of hydrogen or van der Waals type bonds, and the simultaneous condensation of the gas phase, hereinafter referred to as adsorption / condensation.

[0037] According to one embodiment, the condensation of the organic product takes place within the pores of the porous matrix.

[0038] More specifically, the organic compound in gaseous form condenses during adsorption within the pores of the matrix.

[0039] Within the composite of the invention, the organic compound confined within the pores is therefore present in condensed form.

[0040] The organic compound can be described here indifferently as an “impregnated”, “condensed” or “confined” compound and designates a homogeneous or inhomogeneous state, solid and / or liquid.

[0041] According to one embodiment, the organic compound in gaseous form can be obtained from its solid form by sublimation.

[0042] According to one embodiment, said method may therefore also comprise the prior step of sublimation of said organic compound from the solid phase to the gas phase. This sublimation step may typically be carried out at reduced pressure, under heating, for example under vacuum and at a temperature between 50 and 250°C. According to one embodiment, the confinement of the hydroquinone may be carried out by placing it under vacuum in order to sublimate it, in particular at a temperature between 80 and 170°C, followed by a return to room temperature.

[0043] Thus, the sublimed organic compound, in the gaseous state, penetrates into the pores of the porous matrix where it condenses / adsorbs in condensed form.

[0044] The said organic compound can thus be confined in the pores, after condensation, without decomposition or degradation.

[0045] The present invention also relates to a porous composite capable of being obtained by the method described above.

[0046] According to the invention, the composite thus obtained has the particularity of comprising a condensed organic compound confined within pores with a diameter of less than 10 nm of a porous matrix.

[0047] The porous composite described above makes it possible to store gases. According to another object, the present invention also relates to a method for storing gas, said method comprising: bringing the porous composite according to the invention into contact with the gas to be stored or a mixture comprising said gas;

[0048] - submission to one or more successive temperature cycles.

[0049] Typically, storage is achieved by the capture of gas by the organic compound confined within the meso- or micropores of the matrix. The capture and then retention of the gas are generally achieved by means of weak bonds, for example of the van der Waals type, established between the atoms of said organic compound and the hydrogen atoms of the gas.

[0050] The expression "temperature cycle" used here is understood as the successive passage from a temperature T1 to a temperature T2, such that T1 <T2.

[0051] According to one embodiment, T1 can be chosen from temperatures greater than or equal to 77 K, in particular 0°C.

[0052] According to one embodiment, T2 can be chosen from temperatures lower than the desorption temperature of the condensed organic compound, in particular approximately 100°C. The pressure used during these cycles can be, for example, between 1 and 200 bar, preferably between 5 and 150 bar, advantageously between 20 and 120 bar.

[0053] One or more cycles may be applied successively. The number of cycles may vary depending on the nature of the matrix and the organic compound. Generally, a sufficient number of cycles is applied when the amount of organic compound incorporated reaches a plateau. This amount can be determined by measurements of adsorbed gas quantities carried out, for example, using gravimetric or volumetric techniques.

[0054] Advantageously, the composite according to the invention makes it possible to store dihydrogen.

[0055] According to another object, the invention also relates to the system consisting of the composite incorporating the stored gas capable of being obtained by the method according to the invention.

[0056] The invention therefore also relates to a gas storage device comprising the porous composite according to the invention and a gas, said gas being stored within the pores comprising the organic material.

[0057] Advantageously, storage is stable under normal temperature and pressure conditions, for example at 25°C / 1 bar or at 0°C / 1 bar (CNTP).

[0058] According to another object, the present invention also relates to the use of this device, comprising the release of said gas at ambient pressure and at a temperature below 150°C.

[0059] Destocking is carried out by releasing the gas. This step is carried out at a temperature depending on the nature of the organic compound. Typically, destocking is carried out at a temperature lower than the desorption temperature of the condensed organic compound.

[0060] Advantageously, in the case of hydrogen, the destocking of dihydrogen can be carried out at ambient pressure and at a temperature less than or equal to 150°C, in particular less than 100°C. The present invention also relates to the use of the porous composite according to the invention for the storage of gas, in particular dihydrogen.

[0061] The gas storage in the porous composite according to the invention has the advantage of being reversible. Indeed, if the destocking is carried out, the organic compound remains confined within the pores and can again capture gas, in a manner identical to the previous capture reaction. In particular, the dihydrogen capture reaction is reproducible in terms of the quantity of gas captured. The composite according to the invention is therefore reusable once the gas has been desorbed.

[0062] According to another of its objects, the invention also relates to the use of the storage device according to the invention for the purpose of using the gas stored therein. According to the invention, the use therefore comprises the step of destocking said gas. Typically, the destocking can be carried out at a temperature lower than the temperature T2 mentioned above. In the case of hydroquinone, the destocking can be carried out at a temperature lower than 150°C, in particular lower than 100°C.

[0063] The invention will be better understood by reading the following description, given solely by way of example, and made with reference to the appended drawings, in which:

[0064] Figures:

[0065] Figure 1 illustrates a schematic of the impregnation device.

[0066] Figure 2 shows results obtained after impregnation of different porous matrices with hydroquinone (HQ). (A) Influence of impregnation time on the mass content of impregnated HQ (in %) for 3 carbon matrices (1 fibrous matrix called "fabric" and 2 activated carbons), 3 mesoporous matrices based on silica and a porous polymer. (B): TGA / DSC analysis showing that HQ is in the pores of MCM-41 silica (peak shift compared to solid HQ). (C) Analysis of the pore volume by argon porosimetry at 87 K before (grey curve) and after HQ impregnation (impregnation time: 8h) (black curve): 80% of the pore volume is occupied by HQ. (D) Pore size distribution by argon porosimetry at 87 K before (grey curve) and after HQ impregnation (black curve).Figure 3 represents the evolution of the mass percentage of H2 captured (per total mass of material) as a function of temperature cycles varying between 0 and 100°C for MCM-41 impregnated with HQ (case of an impregnation duration of 8 h) (P=20 bars).

[0067] Figure 4 represents the mass percentage of H2 captured (per total mass of material) as a function of temperature cycles varying between 0 and 100°C for porous polymer beads (case of an impregnation duration of 14 h) impregnated with HQ (P=20 bars).

[0068] Figure 5 represents the comparison of the variation of the quantity of hydrogen stored per mass of total sample (matrix+HQ) as a function of the number of cycles at 0°C, for the MCM41 support and the comparative support SF300A.

[0069] Figure 6 represents the comparison of the variation in the quantity of stored hydrogen, reduced by mass of HQ impregnated in the matrices, for the MCM41 support and the comparative SF300A support.

[0070] Figure 7 represents the curve obtained by ATG of the variation of the mass of the porous support alone (MCM41) and of the support after impregnation with calix[4]arene.

[0071] Figure 8 represents the cumulative volume curves obtained by argon porosimetry at 87 K (IQ-Quantachrome-Anton Paar) for the matrix (PSP) before impregnation with urea and after impregnation (mass impregnation rate of 13%).

[0072] Figure 9 illustrates the H2 storage capacity of PSP impregnated with 13% urea during temperature cycles 0-100°C per gram of composite.

[0073] Figure 10 illustrates the H2 storage capacity of MCM41 impregnated with 18% calix[4]arene during temperature cycles, compared to the MCM41 +HQ composite.

[0074] Examples:

[0075] Preparation of the porous composite

[0076] The protocol is illustrated in Figure 1: 1 - Between 1 and 5 g of solid organic compound (hydroquinone, HQ) is introduced into a crucible above which is placed another crucible containing the porous matrix to be impregnated (between 200 and 1000 mg) and previously purified under primary vacuum at a suitable temperature (200°C for carbons, 300°C for silicas and 120°C for the polymer) depending on the material.

[0077] 2- The two crucibles are separated by a Durapore filter with a porosity of 0.45 prn.

[0078] 3- The assembly is placed in a vacuum oven at 120°C for a period of between 1 and 64 hours in order to sublimate the HQ and for it to adsorb inside the pores of the matrix placed above, in crystalline, semi-crystalline and / or amorphous form. The influence of the impregnation time was analyzed.

[0079] 4- The system is then cooled (controlled temperature ramp) and returned to atmospheric pressure.

[0080] Impregnation results:

[0081] The protocol was tested on micro / mesoporous adsorbents based on carbon and silica:

[0082] 1: Fabric

[0083] 2: G- Bac

[0084] 3: F400

[0085] 4: Porous polymer

[0086] 5: MCM-41

[0087] 6: SBA-15

[0088] 7: If-AI

[0089] Fabric (PICA woven activated carbon from PICY Company, Levallois, FRANCE), G-bac (from Kureha®) and F400 (Filtrasorb®400 from Calgon Carbon Corporation) are carbon matrices.

[0090] MCM-41, SBA-15 and Si-AI are silica-based matrices referenced under these names. The porous polymer is Dow Chemicals' Optipore, newly referenced at Dupont.

[0091] The organic product used is hydroquinone (purity > 99.5%, from the supplier Acros Organics). Maximum impregnation rates are reached after a few hours and are between 12 and 38% by mass depending on the support. Figure 2A illustrates the results obtained for the different matrices 1-7 identified above.

[0092] SEM, ATG / DSC analyses and gas porosimetry characterizations showed that the HQ was well impregnated within the porosity (see Fig. 2).

[0093] H2 capture tests

[0094] • H2 capture tests were carried out by gravimetric technique using a magnetic suspension balance (Rubotherm).

[0095] • The influence of temperature and pressure was analyzed. A comprehensive study of the MCM-41 / HQ hybrid material showed the following results:

[0096] - an initial temperature rise is necessary to “activate” the system, 80°C for the MCM-41,

[0097] - successive temperature cycles (from 0°C as minimum temperature to 100°C as maximum temperature for the example given in Figure 3, i.e. MCM-41 / HQ) allow on the one hand to capture / release the H2 and on the other hand to reach a maximum capture rate after around ten cycles;

[0098] - the compound remains stable at ambient pressure for at least 48 hours;

[0099] - for the MCM-41 / HQ system, the mass percentage of H2 obtained at atmospheric pressure and at 25°C (Figure 3) is approximately 1.2% by total mass of impregnated material or 5.7% by mass of HQ.

[0100] • Capture tests on a very different porous matrix (polystyrene-based porous polymer, Optipore from Dow Chemicals) gave similar results (Figure 4), which seems to show that the variability of nanoporous matrices (in terms of chemical nature and pore sizes) that can be used is large.

[0101] Comparison with existing solid H2 storage:

[0102] The H2 capture rate per mass of composite (1.2%) or per mass of HQ (5.7%) thus obtained is in the average of existing processes, with reference to the classification made for different existing solid storages by Gupta et al., Energy Storage Materials, vol. 41, p. 69-107, Oct. 2021. Nevertheless, the system according to the invention has the considerable advantage of operating at ambient pressure and for moderate temperatures (1 bar, 25°C), with a lower cost and superior stability compared to hydrides in particular.

[0103] Comparative test

[0104] Tests were also carried out on porous particles of SiliaFlash SF300A silica (supplier Silicycle) with a diameter between 200 and 500 microns (particles identical to those used in the article Coupan et al. (Chemical Engineering Journal 2017, 325, 35-48).

[0105] - Drying of SF300A (particle purification) for 24 hours at 110°C. Cooling in a desiccator and placing in an oven in a closed container at 35°C.

[0106] - Hydroquinone / ethanol impregnation solution: 7 g of hydroquinone are introduced into an Erlenmeyer flask. The total mass is adjusted to 20 g with absolute ethanol. The Erlenmeyer flask is closed, stirred magnetically, then placed in an oven at 35°C until the crystals are completely dissolved in the solvent (clear solution).

[0107] - 3 grams of SF300A silica particles (maintained at 35°C) are introduced into a glass bottle, and are covered with a sufficient quantity of HQ / ethanol impregnation solution (at 35°) until all the particles are completely immersed. The bottle containing the silica particles and the impregnation solution is shaken manually, sealed, and left in the oven at 35°C for 24 hours.

[0108] - after 24 hours of contact between the silica particles and the impregnation solution, the liquid-impregnated particles are filtered with a Bushner filter connected to a vacuum flask, collected in a crystallizer, then dried in an oven at 35°C for 24 hours.

[0109] The SF300A / HQ composites thus manufactured appear in the form of a uniform white powder (no black or gray particles, no clumps, no plates) which is perfectly dry.

[0110] The impregnation rate of these composites measured by TGA is equal to 32% by mass of HQ. After drying, the composite particles were packaged in a glass bottle with a hermetic cap, under air and at room temperature. They were stored in this bottle until they were tested on the magnetic suspension balance.

[0111] The composite was then tested for hydrogen storage. We followed the same capture protocol, namely temperature cycles between 0°C and 100°C, for a pressure of 20 bar of hydrogen.

[0112] The results are illustrated in Figures 5 and 6, where the H2 capture cycles are compared with MCM41 +HQ which has an average pore size of 3 nm but a surface chemistry comparable to that of SF300A.

[0113] According to Figure 5, the amount of hydrogen stored per total sample mass (matrix+HQ) is plotted against the number of cycles at 0°C (the amounts stored at 100°C are zero for SF300A+HQ).

[0114] The stored quantities of H2 for the MCM41 +HQ sample are ten times greater than those in the SF300A after about ten cycles.

[0115] According to Figure 6, the stored quantities are reduced by mass of HQ impregnated in the matrices. They are 7 times greater in MCM41 +HQ.

[0116] These results demonstrate that when HQ is impregnated into small pore sizes (less than 10 nm), the stored quantities are significantly greater due to the confinement effect in pores of this size.

[0117] Impregnation and capture with calixarene

[0118] Impregnation was also carried out with calix[4]arene (CX4) in the porous support MCM41, by sublimation of CX4 at 300°C under secondary vacuum for 72 h.

[0119] A mass impregnation percentage of 16% was obtained.

[0120] The TGA results shown in Figure 7 confirm the presence of CX4 in the nanoporosity. Indeed, pure (unconfined) CX4 has a melting point around 310-315°C (verified by TGA) while the main mass loss occurs after 420°C. This shift towards higher temperatures indicates that CX4 is present in the nanoporosity as shown for HQ in Figure 2 (B). The hydrogen capture test was performed with the porous support of MCM41 impregnated with calix4aren at 18% by mass.

[0121] The hydrogen capture results for the first 3 cycles are shown in Figure 10.

[0122] In this figure, the captured hydrogen mass for the MCM41 +HQ and MCM41 +Calix4aren composites were compared.

[0123] Abilities are scaled by crystal mass. For the first 3 cycles, the progression is indeed similar to that of HQ, namely growth based on the cycles.

[0124] Impregnation and capture with urea

[0125] Impregnation and occupancy tests of pores with diameters less than 10 nm were also carried out with urea, following the protocol above for HQ (Figure 1) on a PSP matrix.

[0126] An impregnation rate of 13% was obtained.

[0127] The results are illustrated in Figure 8, in which the % boxed in the figure corresponds to the percentage of pore volume smaller than 10 nm in the initial matrix that was lost following impregnation, i.e. that was filled by urea (20% here).

[0128] Hydrogen capture tests were also carried out with the composite thus formed: The results are illustrated in Figure 9.

Claims

DEMANDS 1. Porous composite for gas storage comprising: - a porous matrix comprising pores with a diameter of less than 10 nm, and - an organic compound, said porous composite being characterized in that said organic compound is present within said pores of diameter less than 10 nm.

2. Porous composite according to claim 1 such that the pores of the porous matrix with a diameter of less than 10 nm represent at least 30%, preferably at least 50% of the micro- / mesoporous volume of the porous matrix.

3. Porous composite according to claim 1 or 2 such that the organic compound is selected from compounds capable of forming intermolecular hydrogen bonds.

4. Porous composite according to any one of the preceding claims, wherein said organic compound is selected from the following compounds: polyphenols, polythiols, ureas, thioureas and calixarenes.

5. Porous composite according to any one of the preceding claims, wherein said organic compound is selected from hydroquinone, resorcinol, fluorohydroquinone, 2-5 dihydroxyl-pyridine, catechol, urea, thiourea, calix[4]arene.

6. Porous composite according to any one of the preceding claims, wherein said organic compound is present in crystalline, semi-crystalline and / or amorphous form within the pores.

7. Porous composite according to any one of the preceding claims wherein the porous matrix is ​​selected from micro- and / or mesoporous organic or mineral supports, such as silica, carbon, alumina, aluminosilicates, activated carbons, molecular sieves, zeolites, Metal Organic Frameworks (MOFs), Hofmann clathrates and polymers.

8. Porous composite according to any one of the preceding claims wherein the porous matrix is ​​selected from mesoporous silicas MCM-41 and SBA-15, aluminosilicates, carbon xerogels, activated carbons and porous polymers.

9. Porous composite according to any one of the preceding claims such that the organic compound occupies at least 25%, preferably at least 40% of the micro- and mesoporous volume of the porous matrix.

10. A dry process for preparing a porous composite according to any one of the preceding claims comprising the adsorption / condensation of said organic compound in the gas phase within the pores of said porous matrix.

11. A process according to claim 10 comprising the preliminary step of sublimating said organic compound from the solid phase to the gaseous phase.

12. Gas storage method comprising: bringing the porous composite according to any one of claims 1 to 9 into contact with the gas to be stored or a mixture comprising said gas; - subjection to one or more successive temperature cycles.

13. A method according to claim 12 wherein the gas is dihydrogen.

14. Gas storage device comprising the porous composite according to any one of claims 1 to 9, and further comprising a gas, said gas being stored within the pores comprising the organic material.

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