Nanoporous organic polymers for high pressure gas storage

Abstract

The present disclosure concerns a method of producing a porous gas storage material for storing hydrogen and / or oxygen and / or nitrogen. The method comprises providing aromatic ring-containing monomers comprising at least two aromatic rings. The method also comprises subjecting the monomers to a metal-catalysed cross-coupling reaction to form a gas storage material comprising a cross-linked polymeric framework with aromatic ring containing monomeric units joined directly by covalent bonds between aromatic rings, and comprising a plurality of pores for gas sorption. Alternatively, the method comprises cross linking the monomers by a Friedel-Crafts alkylation reaction to form said gas storage material comprising a cross-linked polymeric framework with aromatic ring-containing monomeric units but joined by a cross-linking moiety between aromatic rings. This alternative material also comprises a plurality of pores for gas sorption. However, in this alternative material at least a subset of the aromatic ring-containing monomeric units comprise at least five aromatic rings. Otherwise, in this alternative material, at least a subset of the aromatic ring-containing monomeric units are selected from the group consisting of: Formula (I). The disclosure also encompasses the porous gas storage materials produced according to these methods aggregated using a binder to form one or more macroscopic objects.

Description

[0001] NANOPOROUS ORGANIC POLYMERS FOR HIGH PRESSURE GAS STORAGE

[0002] Technical Field

[0003] This invention relates to porous materials and related methods for their production as well as to methods of storing gas. More particularly, this invention relates to materials and methods for storing gas comprising, or rich of: hydrogen (H2); and / or, oxygen (O2); and / or nitrogen (N2). More particularly, this invention relates to materials and methods for storage of compressed H2, and / or of compressed O2, and / or of compressed N2.

[0004] The need for alternative fuels is greater now than ever before. With the need for alternative fuels, there may be a need for storing light gas, such as H2, at ever increasing pressures. It may also be desirable to store accessory gas, such as O2 and / or N2.

[0005] Storage of gas in highly porous materials has already been proposed and studied, but there remain limitations intrinsic with the existing materials used for this purpose. Such materials include the widely described zeolites, metal organic frameworks (MOFs), porous coordination polymers (PCPs) and, in general, metal organic compounds. In existing metalorganic compounds, positively charged metal atoms bound to organic ligands are extremely sensitive to polar substances, such as water, which may contaminate and degrade the operating material during its life-time. Water contamination is also a problem in compounds containing open metal sites, due to the easy deactivation of the porous material. Further, most metal-containing materials achieve a most effective uptake at relatively low pressures. Moreover, uptake measurements in studies are frequently limited to the range below 40 bar. Pressure ranges below 40 bar, or even below 100 bar, are likely to be insufficient, at least in connection with certain storage projects.

[0006] WO 2016 / 087471 A1 discloses a method of storing gas using a porous gas storage material comprising a cross-linked polymeric framework and a plurality of pores for gas sorption. The cross-linked polymeric framework comprises aromatic ring-containing monomeric units comprising at least two aromatic rings. The aromatic ring-containing monomeric units are linked by covalent cross-linking between aromatic rings to form a stable, rigid nanoporous material for storing the gas at pressures significantly greater than the atmospheric pressure, for example in excess of 100 bar. However, the material has been designed and tested specifically for the storage and transportation of compressed natural gas (CNG) and, potentially, CO2, given the similarities between the respective, organic molecules. WO 2016 / 087471 A1 does not address the ability of similar materials to successfully store generally much lighter gas, such as H2, or different, inorganic gas such as O2 and / or N2. Even though the storage of N2 and O2 is contemplated, H2 is of particular interest given its small size and its intrinsic storage challenges.

[0007] There is also a general desire to store, with respect to the prior art: (a) comparatively more gas per unit of available storage volume at a given pressure; and / or (b) a same quantity of gas per unit of available storage volume at a comparatively lower pressure, thereby allowing less material to be used in an associated recipient for storing and the gas, e.g. by decreasing a wall thickness of the recipient; and / or (c) a same quantity of gas at a given pressure, using less storage volume, thereby reducing an overall size of an associated recipient or of the storage system. These objectives, as it will readily be appreciated, are valid for any to-be-stored gas, including H2, O2 and / or N2. That said, H2 is of more interest both academically and practically, given its many potential industrial applications, including energy systems. Accordingly, there is a need for a porous material for high pressure storage of gas that brings forward an improved gas uptake performance, at least at relatively high pressures, compared to the porous materials for high pressure storage of gas described in the prior art. The present application aims to address one or more problems connected with the prior art, particularly for H2, but also for O2 and / or N2.

[0008] Summary of the Invention

[0009] The present invention provides materials for and methods of storing particularly H2 but also O2 and / or N2 at high pressures that overcome at least some of the restrictions connected with the materials proposed up to now for the above-mentioned purposes. This is useful for a wide-scope of applications. The invention is based on high-surface-area porous materials. This is achieved using a porous gas storage material comprising a crosslinked polymeric framework.

[0010] According to an aspect of the disclosure, there is provided a method of storing a gas comprising hydrogen and / or oxygen and / or nitrogen, the method comprising: providing a recipient for receiving said gas, the recipient being designed to sustain a nominal internal pressure P1 greater than atmospheric pressure; providing a porous gas storage material within said recipient, the gas storage material comprising: a cross-linked polymeric framework forming a plurality of pores for gas sorption, wherein the cross-linked polymeric framework comprises aromatic ringcontaining monomeric units comprising at least two aromatic rings, wherein the aromatic ring-containing monomeric units are linked by covalent cross-linking between aromatic rings; and, loading the recipient with the gas to said pressure P1. P1 may be up to 700 bar.

[0011] Said recipient may comprise or may be in the form of a pressure vessel comprising a loadbearing structural portion comprising a composite material.

[0012] The pressure vessel may comprise a metallic or polymeric liner for containing the gas.

[0013] The cross-linked polymeric framework may comprise aromatic ring-containing monomeric units comprising at least three aromatic rings, optionally at least four aromatic rings, optionally at least five aromatic rings, optionally at least six aromatic rings.

[0014] The cross-linked polymeric framework may comprise a copolymer comprising two or more structurally distinct aromatic ring-containing monomeric units.

[0015] At least a subset of the aromatic ring-containing monomeric units may comprise at least four aromatic rings.

[0016] The aromatic ring-containing monomeric units or at least a subset of the monomeric units of the copolymer, may comprise two or more aromatic rings that are fused or linked in a conjugated system.

[0017] The aromatic ring-containing monomeric units may be linked: a) by covalent bonds directly between aromatic rings; or b) by a cross-linking moiety between aromatic rings, optionally wherein the crosslinking moiety is an aliphatic group.

[0018] At least a subset of the aromatic ring-containing monomeric units may comprise two aromatic rings: a) having a centre-to-centre spatial separation from one another of at least 0.2 nm, optionally at least 0.3 nm, optionally at least 0.4 nm, optionally at least 0.5 nm, optionally at least 0.6 nm, optionally at least 0.7 nm and optionally 0.8 nm; and / or b) separated from one another by 4 or more bonds.

[0019] At least a subset of the aromatic ring-containing monomeric units may be selected from the group consisting of:

[0020] According to another aspect of the disclosure, there is provided a method of producing a porous gas storage material for storing hydrogen and / or oxygen and / or nitrogen, wherein the method comprises: providing aromatic ring-containing monomers comprising at least two aromatic rings; and subjecting the monomers to a metal-catalysed cross-coupling reaction to form a gas storage material comprising a cross-linked polymeric framework with aromatic ringcontaining monomeric units joined directly by covalent bonds between aromatic rings, and comprising a plurality of pores for gas sorption.

[0021] The cross-linked polymeric framework may be as defined hereinabove.

[0022] The method may comprise a nickel-catalysed cross-coupling reaction, optionally a Yamamoto cross-coupling.

[0023] According to another aspect of the disclosure, there is provided a method of producing a porous gas storage material for storing hydrogen and / or oxygen and / or nitrogen, wherein the method comprises: providing aromatic ring-containing monomers comprising at least two aromatic rings; and, cross-linking the monomers by a Friedel-Crafts alkylation reaction to form a gas storage material comprising a cross-linked polymeric framework with aromatic ringcontaining monomeric units joined by a cross-linking moiety between aromatic rings (optionally an aliphatic group, for example, an alkyl group), and comprising a plurality of pores for gas sorption wherein at least a subset of the aromatic ring-containing monomeric units comprises at least five aromatic rings; or wherein at least a subset of the aromatic ring-containing monomeric units are selected from the group consisting of:

[0024] The method may comprise cross-linking the monomers by a Friedel-Crafts alkylation reaction using formaldehyde dimethyl acetal and iron (III) chloride or acidic conditions as a catalyst.

[0025] According to another aspect of the disclosure, there is provided a porous gas storage material for storing hydrogen and / or oxygen and / or nitrogen comprising: a cross-linked polymeric framework; and a plurality of pores for gas sorption, wherein the cross-linked polymeric framework comprises aromatic ring-containing monomeric units comprising at least two aromatic rings and wherein the aromatic ring-containing monomeric units are linked by covalent bonds directly between aromatic rings.

[0026] According to another aspect of the disclosure, there is provided a porous gas storage material for storing hydrogen and / or oxygen and / or nitrogen comprising: a cross-linked polymeric framework; and a plurality of pores for gas sorption, wherein the cross-linked polymeric framework comprises aromatic ring-containing monomeric units comprising at least two aromatic rings and wherein the aromatic ring-containing monomeric units are linked by a cross-linking moiety (optionally an aliphatic group, for example, an alkyl group) between aromatic rings, and wherein at least a subset of the aromatic ring-containing monomeric units comprises at least five aromatic rings; or wherein at least a subset of the aromatic ring-containing monomeric units are selected from the group consisting of:

[0027] The gas storage material described herein may be an amorphous material.

[0028] The BET specific surface area of the gas storage material described herein may be greater than about 750 m2g-1, optionally greater than about 850 m2g-1, optionally greater than about 1000 m2g-1, optionally greater than about 1250 m2g-1, optionally greater than about 1500 m2g-1 , optionally greater than about 2000 m2g-1, optionally greater than about 3000 m2g-1, and optionally greater than about 4000 m2g-1.

[0029] The pores described herein may comprise micropores.

[0030] The volume of the pores of the gas storage material described herein may be greater than about 0.40 cm3g-1, optionally greater than about 0.50 cm3g-1, optionally greater than about 0.60 cm3g'1, optionally greater than about 0.90 cm3g-1, optionally greater than about 1.00 cm3g'1, optionally greater than about 0.60 cm3g-1, optionally greater than about 1.20 cm3g_1, optionally greater than about 1.40 cm3g-1, optionally greater than about 1.50 cm3g-1, optionally greater than about 2.00 cm3g-1, optionally greater than about 2.70 cm3g-1, and optionally greater than about 3.00 cm3g-1.

[0031] According to another aspect of the disclosure, there is provided a gas storage material as described herein for use in storing hydrogen and / or oxygen and / or nitrogen at a pressure higher than atmospheric pressure. According to another aspect of the disclosure, there is provided using a gas storage material as described herein for storing a gas comprising hydrogen and / or oxygen and / or nitrogen at a pressure higher than atmospheric pressure.

[0032] Brief Description of the Figures

[0033] Specific embodiments of the invention are described below by way of example only and with reference to the accompanying drawings, in which:

[0034] Figure 1 : A) Nitrogen adsorption isotherm (mmol / g) collected at 77 K of BIC-1 . BET surface area: 2062 m2 / g; Langmuir surface area: 2615 m2 / g; Pore volume: 2.00 cm3 / g; B) Nitrogen adsorption isotherm (cm3 / g, STP) collected at 77 K of BIC-1 ; C) Thermogravimetric analysis of BIC-1 , measured between 25°C and 1000°C under oxidative atmosphere (dry air, 50 mL / min).

[0035] Figure 2: A) Nitrogen adsorption isotherm (mmol / g) collected at 77 K of BIC-2. BET surface area: 3721 m2 / g; Langmuir surface area: 4244 m2 / g; Pore volume: 2.26 cm3 / g; B) Nitrogen adsorption isotherm (cm3 / g, STP) collected at 77 K of BIC-2; C) Thermogravimetric analysis of BIC-2, measured between 25°C and 1000°C under oxidative atmosphere (dry air, 50 mL / min).

[0036] Figure 3: A) Nitrogen adsorption isotherm (mmol / g) collected at 77 K of BIC-3. BET surface area: 1548 m2 / g; Langmuir surface area: 1866 m2 / g; Pore volume: 1.01 cm3 / g; B) Nitrogen adsorption isotherm (cm3 / g, STP) collected at 77 K of BIC-3; C) Thermogravimetric analysis of BIC-3, measured between 25°C and 1000°C under oxidative atmosphere (dry air, 50 mL / min).

[0037] Figure 4: A) H2 adsorption isotherm collected at 77 K of BIC-1 ; B) H2 adsorption isotherm collected at 195 K of BIC-1.

[0038] Figure 5: Reproducibility of the H2 adsorption isotherms of BIC-1 at 77 K (A) and 195 K (B).

[0039] Figure 6: A) H2 adsorption isotherm collected at 77 K of BIC-2; B) H2 adsorption isotherm collected at 195 K of BIC-2.

[0040] Figure 7: Reproducibility of the H2 adsorption isotherms of BIC-2 at 77 K (A) and 195 K (B). Figure 8: A) H2 adsorption isotherm collected at 77 K of BIC-3; B) H2 adsorption isotherm collected at 195 K of BIC-3;.

[0041] Figure 9: Reproducibility of the H2 adsorption isotherms of BIC-3; at 77 K (A) and 195 K (B).

[0042] Figure 10:13C {1H} CP MAS spectra of BIC-1 (see Figure 10A) collected at 293 K, 7.04 T, and 12.5 kHz, with a contact time of a) 2 ms and b) 0.05 ms (Figure 10B).

[0043] Figure 11 :13C {1H} CP MAS spectra of BIC-2 (Figure 11 A) collected at 293 K, 7.04 T, and 12.5 kHz, with a contact time of a) 2 ms and b) 0.05 ms (Figure 11 B).

[0044] Figure 12:13C {1H} CP MAS spectra of BIC-3 (Figure 12A) collected at 293 K, 7.04 T, and 12.5 kHz, with a contact time of a) 2 ms and b) 0.05 ms (Figure 12B).

[0045] Figure 13: A) Experimental H2 adsorption isotherm (in wt%) at 77 K for BIC-1 up to 250 bar; B) H2 adsorption isotherm (in wt%) for BIC-1 up to 700 bar. Experimental data to 100 bar and extrapolation to 250 bar and 700 bar using the dual-site Langmuir equation.

[0046] Figure 14: A) Experimental H2 adsorption isotherm (in wt%) at 195 K for BIC-1 up to 250 bar; B) H2 adsorption isotherm (in wt%) for BIC-1 up to 700 bar. Experimental data to 100 bar and extrapolation to 250 bar and 700 bar using the Langmuir Freundlich equation.

[0047] Figure 15: A) Experimental H2 adsorption isotherm (in wt%) at 77 K for BIC-2 up to 250 bar; B) H2 adsorption isotherm (in wt%) for BIC-2 up to 700 bar. Experimental data to 100 bar and extrapolation to 250 bar and 700 bar using the Langmuir Freundlich equation.

[0048] Figure 16: A) Experimental H2 adsorption isotherm (in wt%) at 195 K for BIC-2 up to 250 bar; B) H2 adsorption isotherm (in wt%) for BIC-2 up to 700 bar. Experimental data to 100 bar and extrapolation to 250 bar and 700 bar using the Langmuir Freundlich equation.

[0049] Detailed Description of the Invention

[0050] The gas storage materials of the disclosure comprise a cross-linked polymeric framework. This cross-linked polymeric framework is preferably a hypercross-linked polymeric framework. The hypercross-linked polymer arranges itself to form a highly porous, amorphous cross-linked polymeric framework. Hypercross-linked polymers have smaller pore sizes and relatively higher surface area and porosities compared with simple cross-linked polymers. The hypercross-linked polymers are prepared by extensively crosslinking aromatic ring-containing monomers with each monomer providing a monomeric unit in the polymeric framework. The monomers are linked by covalent cross-links between aromatic rings, preferably carbon-carbon bonds. This may be by direct C-C bonds between aromatic rings of respective monomeric units, which may optionally be achieved by a metal- catalysed cross coupling reaction, optionally of the Yamamoto-type, or covalent linkage through a cross-linking moiety between aromatic rings of respective monomeric units, which may optionally be achieved by a Friedel-Crafts alkylation reaction. Following either of these two linking strategies, an extensive cross-linking of monomers leads to a rigid three dimensional porous framework with a very high surface area. The higher the degree of cross-linking of the monomers in the network, the greater the specific surface area for gas adsorption is. In hypercross-linked polymers, cross-linking occurs concurrently with polymerization during synthesis by the same reaction. Accordingly, unlike simple crosslinked polymers, there may be no distinction between bonds between monomeric units in a polymer chain and the cross-links in hypercross-linked polymers. The aromatic ringcontaining monomers may possess multiple reactive sites and so form multiple cross-links with other monomers to form a lattice-like structure. This results in a highly cross-linked framework in which any monomeric unit may be bonded to two or more than two other monomeric units.

[0051] The formation of the covalent cross-links immobilizes and imparts rigidity to the aromatic ring-containing monomer units, which are consequently arranged in a poorly- packed manner. The aromatic ring-containing monomers themselves may have a high degree of structural rigidity. The aromatic ring-containing monomers may be selected on the basis of an intrinsic tendency to arrange themselves in a poorly-packed manner, i.e. irrespective of the subsequently formed cross-links between monomeric units. The multiple aromatic rings (especially six member rings, such as benzene and derivatives, or benzene- containing systems) in the monomer provide this structural stability to the porous framework. These monomers are stable and contain such an electron density that promotes interaction with methane and hydrogen molecules and positively charged carbon atoms of carbon dioxide. The multiple reaction sites on the aromatic ring-containing monomers provide further tendency for branching and spatial development of the network.

[0052] The aromatic ring-containing monomers are polymerized / cross-linked to form the cross-linked polymeric framework comprising aromatic ring-containing monomeric units, with each monomer providing a monomeric unit in the polymeric framework. The core molecular structure of the aromatic ring-containing monomers is retained within the individual aromatic ring-containing monomeric units in the cross-linked polymeric framework, irrespective of the synthetic route. A skilled person will appreciate that, depending on the method for cross-linking / polymerizing the monomers, the monomers may contain leaving groups that are no longer present in the monomeric units of the polymeric framework.

[0053] A polymer is generally formed from at least 10 monomeric units, optionally at least 20 monomeric units, optionally at least 100 monomeric units. The cross-linked polymeric framework may comprise aromatic ring-containing monomeric units, wherein the aromatic ring-containing monomeric units are all of the same structure. Alternatively, the cross-linked polymeric framework may comprise a copolymer comprising two or more subsets of structurally distinct monomeric units. Thus, a copolymer will be formed from at least two subsets of aromatic ring-containing monomeric units, each structurally distinct, or at least one subset of aromatic ring-containing monomeric units and one or more structurally distinct monomeric units. A copolymer may, for example, comprise two structurally distinct monomeric units, or comprise three structurally distinct monomeric units (in which case the copolymer may also be referred to as a terpolymer).

[0054] As used herein, the term “aromatic ring” encompasses carbocyclic aromatic rings and heteroaromatic rings. An aromatic ring may be a Ce carbocyclic aromatic ring or a 5- or 6-membered heteroaromatic ring. A heteroaromatic ring contains, in addition to carbon ring atoms, one or more ring heteroatoms selected from oxygen, nitrogen, phosphorus and sulfur, preferably nitrogen. Optionally, an aromatic ring is phenyl, pyrrolyl, imidazolyl, pyrazolyl, isoxazolyl, oxazolyl, thiazolyl, pyridinyl, pyridazinyl, pyrimidinyl or pyrazinyl preferably phenyl or pyrrolyl. An aromatic ring may optionally be fused with another aromatic ring or another cyclic organic moiety to form a bi-, tri- or poly-cyclic ring system. Preferably, a bi-, tri- or poly-cyclic ring system is a conjugated system. Accordingly, in the context herein, a bi-cyclic conjugated ring system, such as napthyl, comprises two aromatic rings. A bi-, tri- or pol-cyclic ring system is preferably napthyl, anthracyl, tetracyl, carboxazolyl, indolyl, isoindolyl, indazolyl, indolizidinyl, isoquinolyl, quinazolyl or quinolyl, preferably, antracyl, tetracyl or carboxazolyl. An aromatic ring may be optionally substituted with one or more groups selected from aliphatic (preferably alkyl), halogen (preferably fluoro), - COOR, -NR2, or -OR, wherein R is independently hydrogen or an aliphatic group (for example, alkyl).

[0055] A cross-linking moiety is a group capable of bonding to at least two other groups. According to a first cross-linking strategy, a cross-linking moiety is a group that may be introduced into the cross-linked polymeric framework in order to link aromatic ringcontaining monomeric units. A cross-linking moiety may be introduced by a Friedel-Crafts alkylation reaction, where the cross-linking moiety is the alkyl source for the alkylation (i.e. it is the electrophilic group). A cross-linking moiety may be an aliphatic group, preferably, an alkyl group.

[0056] According to a second cross-linking strategy, the aromatic ring-containing monomeric units may be cross-linked by a metal-catalysed cross-coupling reaction, optionally of the Yamamoto-type.

[0057] “Aliphatic” as used herein may be a straight or branched chain or cyclic aliphatic group which is completely saturated or contains one or more units of unsaturation. An aliphatic group may contain 1 to 6 carbon atoms, preferably 1 to 3, preferably one carbon atom. An aliphatic group is preferably an alkyl group, preferably methyl. An aliphatic group may be substituted with one or more groups selected from aliphatic (preferably alkyl) or halo (preferably fluoro) or contain one or more units of unsaturation (e.g. an alkene or alkyne moiety). The terms alkyl (or alkane) as used herein refers to a straight or branched chain alkyl group. The terms alkenyl (or alkene) as used herein refers to an alkyl chain containing at least one C=C double bond. The terms alkynyl (or alkyne) as used herein refers to an alkyl chain containing at least one C=C triple bond.

[0058] The materials described herein may be defined as nanoporous materials. Nanoporous materials generally comprise pores of 100 nm or smaller. Nanoporous materials can be subdivided into three categories: microporous materials (comprising pore sizes of less than 2 nm, generally 0.2 nm to 2 nm), mesoporous materials (comprising pore sizes of 2 to 50 nm) and macroporous materials (comprising pore sizes of more than 50 nm). The gas storage material of the invention preferably comprises micropores (preferably with pore sizes centred between about 1 nm and about 2 nm, optionally between about 1.0 nm and about 1.8 nm, optionally between about 1.2 nm and 1.8 nm). Pore size can be estimated by density functional theory (DFT) analysis or other alternative methods from the nitrogen absorption branch at 77K as shown in the examples. The pore size distribution (PSD) was calculated by non-local Density Functional Theory (DFT), applied to N2 adsorption isotherms at 77K (slit pore geometry was used). This DFT analysis is based on a library of computational results, derived by the gas adsorption on various pore sizes and specific pore morphologies. The PSD is calculated from the experimental adsorption isotherms by solving the integral adsorption equation represented as the convolution of a set of theoretical isotherms versus pore size (the DFT kernel).

[0059] The micropore volume is that portion of the total pore volume attributable to micropores (i.e. pores of less than about 2 nm). The total pore volume and the micropore volume can respectively be measured at p / p° = 0.97; and p / p° = 0.1, from the nitrogen adsorption isotherms at 77K shown, for example, in Figures 1 to 3. p° is the pressure of liquefaction of N2 at 77K, i.e. about the atmospheric pressure.

[0060] Brunauer-Emmett-Teller (BET) specific surface area (SBET) is a measure of the surface areas per unit mass of solids by physical adsorption of gas molecules. It can be calculated by the BET equation: where F / Ffi is the relative pressure, is the adsorbed gas quantity, and js the quantity of adsorbed gas as a monolayer, c is the BET constant. This can then be plotted as a BET plot, against F7 using experimental results (see the examples). The value of the slope / I and the y-intercept / of the line can be used to calculate the weight of adsorbed gas as a monolayer, and the BET constant, c, using the following equations:

[0061] The to the BET specific surface area, '"'BET, are given by: where N is the Avogadro number; s is the adsorption cross-section of the adsorbing species;

[0062] V is the molar volume of the adsorbate gas and a is the mass of the solid / adsorbent.

[0063] The Langmuir specific surface area is a measure of the surface areas of solids by physical adsorption of gas molecules. The Langmuir type isotherm is concave to the p / p° axis and the amount of adsorbed molecules to cover the surface with a monolayer of gas molecules approaches a limiting value The Langmuir adsorption isotherm equation can be described as follows: where K\_ is a constant, P is the pressure, nmis the monolayer capacity defined as the amount of adsorbate needed to cover the surface with a complete monolayer of molecules and n is the amount of adsorbed gas at a specific pressure P. The surface coverage (0) is defined as the ratio of the amount of adsorbed substance (F) to the monolayer capacity (Fmon is the maximum amount adsorbed).

[0064] The present invention derives from the desire to develop nanoporous materials for storing gas (such as hydrogen, oxygen and / or nitrogen) at high pressures, overcoming one or more restrictions connected with the nanoporous materials proposed up to now for similar purposes.

[0065] Storing gas at high pressures, for example pressures in excess of 40 bar; or in excess of 80 bar; or in excess of 100 bar; or in excess of 110 bar, and up to pressures, for example, of 180 bar; 200 bar; 250 bar; 300 bar; 500 bar or 1000 bar, allows progressively greater quantities of the gas to be confined in a given space. An effect of the materials described herein is that of increasing the amount of gas stored at a given pressure. This pressure may be a maximum pressure for an associated gas containment system. This maximum pressure can be a nominal maximum pressure.

[0066] Pressure vessels for storing the gas of interest herein may have been tested and certificated for operation up to a nominal maximum pressure of, for example, 700 bar. By using the materials described herein, it would be possible, for example, to considerably increase the amount of loaded H2 at 700 bar. Alternatively, it would be possible to store a predetermined amount of H2 at reduced pressures. For example, the same amount of H2 stored in a pressure vessel at 250 bar could be stored at a pressure well below 250 bar. This would then have a repercussion on the required pressure vessel wall thickness, which would be decreased. Assuming the pressure vessel comprises a composite structural layer that includes costly filamentous fibers (such as, for example, carbon fibers) and a thermosetting resin matrix, costs could be saved by reducing the required amount of fibers and matrix. In turn, reduction of carbon fiber supply may enable the viability of larger scale H2 storage projects.

[0067] The materials described herein have been experimentally tested under high pressure operating conditions, thereby providing confidence that the materials can deliver the intended effects. The 'deliverable' or ‘delivered’ gas amount is an important parameter in that it represents the difference between the amount of gas stored at a reference pressure and that residual gas stored at a desired delivery pressure. In the case of H2, delivery pressures can be in the range between about 1 and 10 bar. A most effective uptake at low pressure, such as that achieved by metal containing materials (for example, MOFs), could therefore prove to be less useful in view of maximizing the amount of delivered gas between the reference and delivery pressures. In the materials and methods described herein, soft gas to pore-wall interactions are provided, inducing a moderate uptake slope in the low- pressure range and maximizing the loaded-gas amount at high pressures. Gas uptake in the pressure range 80-180 bar and above is possible with at least some of the materials and methods described herein. This is of course particularly useful for H2 applications, but it will be appreciated that these materials and methods are likely to perform satisfactorily in a wide scope of further potential applications, such as for storing O2 and / or N2.

[0068] The materials described herein comprise high levels of porosity and thus high levels of surface area. These levels are achieved using a porous gas storage material comprising a cross-linked polymeric framework. Accordingly, the present disclosure provides a method of storing gas comprising: providing a recipient for receiving the gas; providing a porous gas storage material, the gas storage material comprising: a cross-linked polymeric framework; and a plurality of pores for gas sorption; wherein the cross-linked polymeric framework comprises aromatic ringcontaining monomeric units comprising at least two aromatic rings and wherein the aromatic ring-containing monomeric units are linked by covalent cross-linking between aromatic rings; the recipient being designed to sustain a nominal maximum internal pressure P1 greater than atmospheric pressure; the porous gas storage material being disposed within or inside said recipient; and loading the recipient with the gas to a pressure P2 equal to or lower than P1 .

[0069] P1 and P2 may each be significantly higher than atmospheric pressure. P2 may be equal to or exceed a value of N bar, wherein N is an integer comprised in the interval 2 to 700. The recipient can be loaded to achieve an internal pressure P2 equal to or greater than about 15 bar; 35 bar; 40 bar; 80 bar; 100 bar; 120 bar; 150 bar; or 180 bar. Thereby, the method provides for improved storage of gas at these pressures or above these pressures. P1 may be a value of up to several hundred bar, such as 700 bar.

[0070] The recipient may be a pressure vessel designed to store, or store and transport, the gases described herein.

[0071] The pressure vessel may comprise a load-bearing structural portion made of a composite material, it being optionally a filamentous composite material. The composite material may comprise a thermosetting resin, optionally a dicyclopentadiene-based (DCPD- based) resin, optionally having a purity of 92% or above. The pressure vessel may comprise a metallic or polymeric liner for containing the gas described herein.

[0072] The following discussion of the gas storage material of the disclosure applies to all aspects and embodiments of the invention as described herein, mutatis mutandis.

[0073] The cross-linked polymeric framework may comprise a copolymer comprising two or more structurally distinct aromatic ring-containing monomeric units.

[0074] The cross-linked polymeric framework may comprise aromatic ring-containing monomeric units comprising at least three aromatic rings, optionally at least four aromatic rings, optionally at least five aromatic rings, optionally at least six aromatic rings.

[0075] At least a subset of the aromatic ring-containing monomeric units may comprise at least four aromatic rings.

[0076] The aromatic ring-containing monomeric units or at least a subset of the monomeric units of the copolymer, may comprise two or more rings that are fused or linked in a conjugated system. Optionally the fused ring is a bi-, tri- or poly-cyclic ring. A bi-, tri- or polycyclic ring system is preferably napthyl, anthracyl, tetracyl, carboxazolyl, indolyl, isoindolyl, indazolyl, indolizidinyl, isoquinolyl, quinazolyl or quinolyl, preferably, antracyl, tetracyl or carboxazolyl. Optionally the rings or fused rings may be linked to form a conjugated system or a larger aromatic ring (for example an aromatic macrocycle, such as a porphyrin).

[0077] The aromatic ring-containing monomeric units may be linked: a) by covalent bonds directly between aromatic rings; or b) by a cross-linking moiety between aromatic rings, optionally wherein the crosslinking moiety is an aliphatic group, optionally an alkylene group (for example a methylene group).

[0078] The aromatic ring-containing monomeric units and / or monomers of the invention may be spatially expanded molecules with multiple aromatic rings. These aromatic rings may be separated from one another within the molecule itself. At least two of these aromatic rings may be disposed peripherally. At least two of these aromatic rings may form at least a portion of a perimeter of the monomers or monomer units. The perimeter of the monomers or monomeric units may entirely be defined by these aromatic rings. At least two of these aromatic rings may be connected to the remainder of the monomers or monomer units by a single covalent bond. These monomers are selected such that they do not exhibit a tendency to pack. These features, alone or in combination with the multiple possible reaction sites present on each aromatic ring, lead to an intrinsic predisposition, and subsequent tendency, for the monomers to branch and spatially develop into a porous cross-linked polymeric network. At least a subset of the aromatic ring-containing monomeric units may comprise two aromatic rings: a) having a spatial separation from one another (e.g. as measured from the respective centres) of at least 0.2 nm, optionally at least 0.3 nm, optionally at least 0.4 nm, optionally at least 0.5 nm or optionally at least 0.6 nm, wherein the spatial separation is measured from the centers of these aromatic rings; and / or b) separated from one another by 4 or more bonds.

[0079] With reference to any arbitrarily selected atom (for example a carbon atom, silicon atom; or nitrogen atom) comprised in the aromatic ring-containing monomers or monomer units, the aromatic ring-containing monomers or monomer units may comprise a group of aromatic rings that share said atom or are directly connected thereto. This group may comprise up to three such aromatic rings irrespective of the reference atom chosen. This group may comprise up to two such aromatic rings irrespective of the reference atom chosen.

[0080] The aromatic ring-containing monomeric units may be derived from aromatic ringcontaining monomers each comprising at least one aromatic ring that is free to rotate in relation to the rest of the monomer. This may for example be achieved when an aromatic ring is connected to the rest of the monomer or monomer unit by a single covalent bond. These freely-rotating aromatic rings serve as attachment points for cross-linking to other monomeric units within the cross-linked polymer. The fact that they are free to rotate out of the plane with respect to the rest of the monomer or monomeric unit and / or with respect to one or more other aromatic rings of the monomer or monomer unit (i.e. they may be orthogonal to the vicinal moieties) may maximize the chance that these aromatic rings may cross-link with other monomers or monomeric units.

[0081] At least a subset of the aromatic ring-containing monomeric units may be selected from the group consisting of:

[0082] Exemplary cross-linked polymeric frameworks as described herein include, without limitation: homopolymers of the above monomeric units linked by covalent bonds directly between aromatic rings; homopolymers of the above monomeric units linked by an alkylene linker (preferably a methylene linker) between aromatic rings; and copolymers of the above monomeric units, optionally linked by covalent bonds directly between aromatic rings.

[0083] In any of the aspects of the disclosure discussed herein, the aromatic ring containing monomers or monomeric units may contain an alkene group. Optionally, the aromatic ring containing monomers or monomeric units are diphenylethene, triphenylethene or tetraphenylethene.

[0084] The gas storage material may be an amorphous material. The tertiary structure of the cross-linked polymeric framework does not form a regular crystalline structure.

[0085] The BET specific surface area of the gas storage material may be greater than about 750 m2g-1, optionally greater than about 850 m2g_1 , optionally greater than about 1000 m2g_1, optionally greater than about 1250 m2g_1 , optionally greater than about 1500 m2g-1, optionally greater than about 2000 m2g-1, optionally greater than about 3000 m2g-1, and optionally greater than about 4000 m2g-1. The approximation term “about” refers to ±25 m2g_

[0086] 1 In very preferred embodiments, the pores in the gas storage material may comprise micropores. The gas storage material may comprise micropores of about 1 nm to about 2 nm, optionally about 1.0 to about 1.8 nm, optionally about 1.2 nm to about 1.8 nm.

[0087] The total pore volume of the gas storage material may be greater than about 0.40 cm3g-1, optionally greater than about 0.50 cm3g-1, optionally greater than about 0.60 cm3g_1, optionally greater than about 0.90 cm3g-1, optionally greater than about 1.00 cm3g-1, optionally greater than about 0.60 cm3g-1, optionally greater than about 1.20 cm3g-1, optionally greater than about 1.40 cm3g-1, optionally greater than about 1.50 cm3g-1, optionally greater than about 2.00 cm3g-1, optionally greater than about 2.70 cm3g-1, and optionally greater than about 3.00 cm3g-1. The approximation term “about” refers to ±5% of the relevant value.

[0088] The ratio between the volume of the micropores and the total pore volume may be greater than about 0.30 cm3g-1, optionally greater than about 0.40 cm3g-1, optionally greater than about 0.50 cm3g-1, optionally greater than about 0.60 cm3g-1, and optionally greater than about 0.70 cm3g-1. An estimate of the term “about” can be about ±8% of the relevant value.

[0089] In any of the aspects of the disclosure discussed herein, the cross-linked polymer may be a hypercross-linked polymer.

[0090] A large variety of highly absorptive materials may be produced according to gas storage material as described herein, using the methods of production given herein. These methods combine the simple use of commercially-available and sometimes cheap nonsubstituted aromatic molecules, as precursors to a facile procedure. This approach renders conceivable the industrial implementation of the reaction from a laboratory scale to larger and specifically to industrial production.

[0091] In another aspect, the disclosure provides a method of producing a porous gas storage material, wherein the method comprises: providing aromatic ring-containing monomers comprising at least two aromatic rings; and subjecting the monomers to a metal-catalysed cross-coupling reaction; to form a gas storage material comprising a cross-linked polymeric framework with aromatic ring-containing monomeric units joined directly by covalent bonds between aromatic rings, and comprising a plurality of micropores for gas sorption. The cross coupling may be carried out using nickel or palladium catalysts. The method comprises a nickel- catalysed cross-coupling reaction, optionally a Yamamoto cross-coupling. The method may be carried out as one step, where the monomers are combined with the cross-coupling reagents to directly form the cross-linked polymer.

[0092] As an alternative, the Friedel-Crafts alkylation reaction has been in use for the obtainment of industrial products since more than a century and therefore proved robust and reliable for mass production. This is a pre-requisite for interest in hydrogen, oxygen and / or nitrogen capture and storage on a large scale. In some methods, the reaction introduces short methylene (CH2) bridges between monomers. Multiple formations of bridges for each monomer unit result in the construction of the above-described porous and rigid network. These materials and methods provide a suitable wall-to-pore balance for high pressure gas storage.

[0093] Accordingly, in another aspect, the disclosure provides a method of producing a porous gas storage material, wherein the method comprises: providing aromatic ring-containing monomers comprising at least two aromatic rings; and cross-linking the monomers by a Friedel-Crafts alkylation reaction; to form a gas storage material comprising a cross-linked polymeric framework with aromatic ring-containing monomeric units joined by a cross-linking moiety between aromatic rings (optionally an aliphatic group, for example, an alkyl group), and comprising a plurality of pores for gas sorption; wherein at least a subset of the aromatic ring-containing monomeric units comprises at least five aromatic rings, optionally wherein at least a subset of the aromatic ringcontaining monomeric units comprises a carboxazolyl or porphyrin group; or wherein at least a subset of the aromatic ring-containing monomeric units are selected from the group consisting of:

[0094]

[0095] In some cases, the cross-linking moiety is a methylene group. Friedel-Crafts alkylation involves the alkylation of an aromatic ring with an alkyl source (the electrophile in the reaction, which forms the cross-linking moiety) using acidic conditions (a Lewis acid catalyst for example TiCk, BF3, SnCk, FeCh and AICI3 or a Broensted acid). The alkyl source may be an alkyl halide or an acetal, i.e. an alkyl group substituted with a leaving group). The alkyl source may preferably be de-functionalized, i.e. containing two or more leaving groups, so it may form a cross-link between two or more aromatic rings. The method may comprise cross-linking the monomers by a Friedel-Crafts alkylation reaction using formaldehyde dimethyl acetal (FDA) and optionally iron (III) chloride as a catalyst or acidic conditions. The method may be carried out as one step, where the monomers are combined with the alkylation reagents to directly form the cross-linked polymer.

[0096] In another aspect, the disclosure provides a porous gas storage material comprising: a cross-linked polymeric framework; and a plurality of pores for gas sorption; wherein the cross-linked polymeric framework comprises aromatic ring-containing monomeric units comprising at least two aromatic rings and wherein the aromatic ringcontaining monomeric units are linked by covalent bonds directly between aromatic rings.

[0097] In another aspect, the disclosure provides a porous gas storage material comprising: a cross-linked polymeric framework; and a plurality of pores for gas sorption; wherein the cross-linked polymeric framework comprises aromatic ring-containing monomeric units comprising at least two aromatic rings and wherein the aromatic ring- containing monomeric units are linked by a cross-linking moiety (optionally an aliphatic group, for example, an alkyl group) between aromatic rings and wherein at least a subset of the aromatic ring-containing monomeric units comprises at least five aromatic rings, optionally wherein at least a subset of the aromatic ringcontaining monomeric units comprises a carboxazolyl or porphyrin group; or wherein at least a subset of the aromatic ring-containing monomeric units are selected from the group consisting of:

[0098] In another aspect, the disclosure provides a gas storage material as described herein for use in storing gas at a pressure higher than atmospheric pressure. Optionally the gas storage material is for use in storing gas at pressures greater than N bar, wherein N is an integer in the interval 2 bar - 700 bar. Optionally, the gas storage material is for use in storing gas at pressures greater than about 15 bar; 35 bar; 40 bar; 80 bar; 100 bar; 120 bar; 150 bar; or 180 bar. The gas may comprise H2, O2 and / or N2.

[0099] In a seventh aspect, the disclosure provides the use of a gas storage material as described herein for storing gas at pressures higher than atmospheric pressure. Optionally the use of the gas storage material is for storing gas at a pressure greater than N bar, wherein N is an integer in the interval 2 bar - 700 bar. Optionally the gas storage material is for use in storing gas at pressures greater than about 15 bar; 35 bar; 40 bar; 80 bar; 100 bar; 120 bar; 150 bar; 180 bar, or 500 bar. The gas may comprise H2, O2 and / or N2.

[0100] Embodiments described herein in relation to any one of the aspects of the disclosure apply mutatis mutandis to the other aspects of the disclosure. Reference is now made to the following examples, which illustrate embodiments of the invention in a non-limiting fashion.

[0101] Examples described here below illustrate the synthesis of various materials comprising cross-linked polymers from the pre-synthesized aromatic ring-containing monomers. The pre-synthesized aromatic ring-containing monomers can be made by any standard organic synthesis method in the art.

[0102] Synthesis of BIC-1 via Friedel-Crafts alkylation reaction

[0103] Triptycene Spirobifluorene

[0104] In a Schlenk tube, formaldehyde dimethyl acetal (FDA) (0.8 mL, 9.042 mmol) was added to a solution of triptycene (501.6 mg, 1.972 mmol) and spirobifluorene (468.6 g, 1.481 mmol) in 1 ,2-dichloroethane (DCE) (40 mL) under inert gas atmosphere (dry nitrogen). The ratio between the two monomers was 4:3. The Schlenk tube was placed in an ice bath, cooled to 0°C, and a Bronsted acid (BA) (62.3 mmol) was added dropwise in the reaction system. The mixture was allowed to reach 25°C and it was stirred for 72 hours. After the completion of the reaction, the resulting powder was collected by filtration and then washed with EtOH, H2O, CHCh and then dried in air for one night. The solvent was removed under vacuum (p = 1*10-4bar) at 85 °C for 24 hours and under high vacuum (p = 3*10-6bar) at 120°C for 12 hours. Synthesis of BIC-2 by Yamamoto coupling

[0105] Tris(4-bromophenyl)methane-based Tetrakis(4-bromophenyl)methane

[0106] In a two-neck round-bottom flask and under dry nitrogen atmosphere 2,2 bipyridine (1.1 g) is dissolved in a solution of anhydrous DMF (175 mL) and freshly distilled THF (60 mL), in the presence of 1 ,5 cyclooctadiene (1.1 mL) and bis(1 ,5 cyclooctadiene)Ni(O) (2 g), generating a purple solution. The two monomers, tris(4-bromophenyl)methane-based monomer (X = hydrogen or alkyl groups) and tetrakis(4-bromophenyl)methane (1 :3 molar ratio) are dissolved in THF (60 mL), then added dropwise in the two-neck round-bottom flask at room temperature. The duration of the dropping process is one hour in total. The solution is stirred for 48 hours, then quenched with 30 mL of HCI, giving rise to a greenish / light blue suspension. After 4 hours, the white solid is filtered, washed with THF, water and dichloromethane and it is dried in air for one night. Finally, the product is heated up under vacuum at 150°C for 24 hours.

[0107] Synthesis of BIC-3 via Friedel-Crafts alkylation reaction

[0108] Triptycene Tetraphenylmethane In a Schlenk tube, formaldehyde dimethyl acetal (FDA) (0.8 mL, 9.042 mmol) was added to a solution of triptycene (501.2 mg, 1.971 mmol) and tetraphenylmethane (474.1 mg, 1.480 mmol) in 1 ,2-dichoroethane (DCE) (40 mL) under inert gas atmosphere (dry nitrogen). The ratio between the two monomers was 4:3. The Schlenk tube was placed in an ice bath, cooled to 0°C, and a Broensted acid (BA) (62.3 mmol) was added dropwise in the reaction system. The mixture was allowed to reach 25°C and it was stirred for 72 hours. After the completion of the reaction, the resulting powder was collected by filtration and then washed with EtOH, H2O, CHCh and then dried in air for one night. The solvent was removed under vacuum (p = 1*10'4bar) at 85 °C for 24 hours and under high vacuum (p = 3*10'6bar) at 120°C for 12 hours.

[0109] Table 1 : Elemental analysis.

[0110] Calculation of surface area and pore volume of porous gas storage materials

[0111] The surface area (m2 / g) is calculated from the nitrogen adsorption branch of the nitrogen adsorption isotherm at 77 K according to Brunauer-Emmett-Teller (BET) and Langmuir models. The total pore volume, Vtot (cm3 / g) is calculated from the nitrogen isotherms at p / p° = 0.97. The micropore volume (i.e. the fraction of the total pore volume provided by micropores) is calculated as the amount of pores with pore width below 20 A, according to IIIPAC definition. The ratio between the micropore volume and the total pore volume (which in the table below is labelled as “Micro / Total Pore Volume”) is calculated as the ratio between the micropore volume (pores with pore width below 20 A) and the total pore volume calculated at p / p° = 0.97 (pores with pore width below 500 A). The thermal stability is calculated from thermogravimetric analysis (see Figures 1 C, 2C and 3C) and the weight loss is measured at 600 °C. Table 2: Surface Area according to BET and Langmuir models (m2 / g), Total Pore Volume (cm3 / g), Micro / Total Pore Volume, Thermal stability (°C) and Weight Loss (%).

[0112] High pressure hydrogen adsorption isotherms (Figures 4, 5, 6, 7, 8 and 9)

[0113] After the experiment, a blank correction is applied to the isotherm. The blank experiment is obtained by a point-by-point method on two cycles performed with the empty jar. After the present demonstration of the high-pressure performance of the novel materials, it becomes conceivable that a large number of molecules containing benzene rings and other aromatic rings can be suitable as precursors to form effective nanoporous materials which operate for loading high pressures of hydrogen, by either the Friedel-Crafts or the Cross-Coupling Synthesis (e.g. Yamamoto-type catalysis) methods providing aromatic ring-containing monomers comprising at least two aromatic rings; and cross-linking the comonomers by either Friedel-Crafts alkylation reaction or Cross-coupling reactions to form a gas storage material comprising a crosslinked copolymeric framework with aromatic ring-containing comonomeric units joined by either a cross-linking moiety (optionally an aliphatic group, for example, an alkyl group) or direct C-C bonds between aromatic rings, and comprising a plurality of pores for gas sorption.

[0114] Before the analysis, the samples were activated overnight at 100°C under vacuum (p = 3*10'6bar), directly in the steel jar. Each experiment was performed by applying an adsorption-desorption cycle up to 100 bar at 77 K and 195 K. The temperature is controlled using the optional cryogenic kit. The ambient and analysis tree-space volumes of the empty sample tube were measured twice with helium before the hydrogen adsorption measurements and then inserted manually during experiment elaboration. After the analysis, the mass and density of the sample (measured with helium pycnometry) were used to find the sample’s physical volume. Then, the volume of the sample was subtracted from the ambient and analysis free-space values originally entered the software to correct the blank sample tube free-space values for the volume of the sample.

[0115] Hydrogen sorption measurements at high pressure are performed to test the maximum gas capacity and to determine the isotherm profile from low to high pressures. The high pressure H2 adsorption isotherms were collected using a volumetric adsorption instrument up to 100 bar. Samples were loaded in a 2 ml-steel jar. Glass beads were used to minimize the empty volume inside the sample holder.

[0116] The as-obtained isotherms are "excess" isotherms, i.e. the excess gas amount that is "adsorbed" by the sample due to their pore sites. However, at high pressures, the gas density grows over the ideal gas range, and this must be taken into account in the experiment elaboration. The "total" absorbed amount (ntot) is defined as the excess uptake plus the amount of H2 that would occupy the entirety of the gas-accessible volume of the system, Vp, in the absence of any adsorption taking place, ntot(P)=nex(P)+Vp* p(P) following the relationship, where p(P) is the density of hydrogen as a function of pressure:

[0117] The hydrogen sorption isotherms are shown below ("total" absorbed amount vs. pressure).

[0118] To avoid errors due to sample contamination between the de-gassing and the measurement stage, the sample mass was measured after the analysis.

[0119] Solid-State Nuclear Magnetic Resonance (SS NMR)

[0120] 13C CP MAS NMR spectra (Figures 10B, 11 B and 12B) demonstrated the chemical structure of the frameworks highlighting the presence of the two comonomeric units and the cross-linking moieties in the samples obtained by the Friedel Craft alkylation reactions or the formation of direct C-C bonds in the sample synthesized by the cross-coupling reaction.

[0121] Table 3:13C NMR resonance assignment of BIC-1. SP_R2

[0122] Table 4:13C NMR resonance assignment of BIC-2.

[0123] Table 5:13C NMR resonance assignment of BIC-3. Skeletal density (Helium Pycnometry)

[0124] Table 6: Skeletal density.

[0125] Materials Density i 3

[0126] V + Pore Volume= tot d(Helium Pycnometer) [cm / g]

[0127] 1 cL , = — = [gO / 3

[0128] Sample vtotLcm 1J

[0129] Table 7. Density of porous materials.

[0130] Example: H2 sorption measurements up to 100 bar

[0131] H2 sorption measurements at high pressure are performed to test the maximum gas capacity and to determine the isotherm profile from low to high pressures, i.e. in a wider range than previously achieved in the prior art. This can yield the 'deliverable gas' potential of the materials. To perform the experiments a Micromeritics HPVA II (High Pressure Volumetric Apparatus), equipped with a pressure-booster compressor was used. The booster provides to compress the gas from the gas cylinder up to 100 bar.

[0132] Samples were loaded in a 10ml-steel jar and connected to the instrument by a VCR connection with a 10 pm seal-frit gasket to avoid sample dispersion into the manifold volume.

[0133] Before the analysis, the samples were activated overnight at 130°C under vacuum, directly in the steel jar.

[0134] Each experiment was performed by applying an adsorption-desorption cycle up to 100 bar at 25°C. The temperature is controlled using a Julabo F12-ED refrigerated / heating circulator connected with the HPVA circulation Dewar. The free-space volume was measured with helium just before the first run and then inserted manually during experiment elaboration.

[0135] To avoid errors due to sample contamination between the de-gassing and the measurement stage, the sample mass was measured after the analysis.

[0136] After the experiment, a blank-correction is applied to the isotherm. The blank experiment is obtained by a point- by- point method on five cycles performed with the empty jar.

[0137] The as-obtained isotherms are “excess” isotherms, i.e. the excess gas amount that is “adsorbed” by the sample due to their active pore-surfaces. At pressures over 10 bar, the gas density grows over the ideal gas range and this must be taken into account in the experiment elaboration. To obtain the “total” absorbed amount (ntot) we must consider the total pore volume of the sample (Vp) and the ratio between the volume of the ideal gas and the volume occupied by the same amount at a certain pressure (p(P)) following the relationship: ntot(P)=nex(P)+Vp* p(P)

[0138] In this elaboration, to obtain the function p(P) H2 density values in a pressure range between 0.5 and 200 bar are fitted with a polynomial function and, then, they are calculated point by point using the pressure of each analysis point. Density values are obtained by REFPROP software of NIST database. The H2 sorption isotherms of the materials described herein are shown in Figures 4-9, respectively. The desorption branches virtually overlap with the absorption branches. The designation “wt%” of Figures indicates the percentage of adsorbed H2 mass with respect to the mass of porous material.

[0139] After the present demonstration of the high-pressure performance of the novel materials, it becomes conceivable that a large number of molecules containing benzene rings and other aromatic rings can be suitable as precursors to form effective nanoporous materials which operate for loading up to high pressures of hydrogen, oxygen and / or nitrogen, by either the Friedel-Crafts or the Cross-Coupling Synthesis (e.g. Yamamoto-type catalysis) methods. Acetylene moieties could also be inserted as structure extenders, for instance, to achieve better performances. In other examples fluorinated compounds could be used to induce a modulated uptake from high to low pressures.

[0140] In other words, the aromatic ring-containing monomers which compose the crosslinked polymeric framework were designed with a suitable shape, which hinders a favorable association to a next neighbor. This principle was applied systematically to prevent aggregation among molecular precursors during the formation of the framework: the carbon-carbon bond formation (or alkyl bridging, such as methylene groups CH2) immobilizes and imparts rigidity to the molecular building-blocks in such an ill-packed arrangement. To avoid the collapse of the structure into a more compact arrangement by conformational relaxation, aromatic ring-containing monomeric units having a suitable structural rigidity were adopted. The aromatic ring-containing monomers contain multiple aromatic rings (especially the six member rings typical of benzene and derivatives). These are endowed with exceptional stability and contain such an electron density that promotes interaction with hydrogen atoms. The multiple reaction sites on the aromatic rings provided further tendency to 3D branching and spatial development of the architecture.

[0141] Finally, Figures 13 and 16 show the expected behaviour of, taking as examples, BIC-1 and BIC-2 at 77 K and 195 K not only in the experimental storage pressure range (0-100 bar), but up to 250 bar and 700 bar using an extrapolation methodology based on the dual-site Langmuir or Langmuir Freundlich equations. Figure 13A shows the experimental hydrogen adsorption isotherm (in wt%) for BIC-1 up to 250 bar including the experimental data up to 100 bar and extrapolation data up to 250 bar using the dual-site Langmuir equation. Figure 13B represents the hydrogen adsorption isotherm (in wt%) for BIC-1 up to 700 bar, including the experimental data up to 100 bar and extrapolation data up to 700 bar using the dualsite Langmuir equation. More details are reported in the table below. Table 8. Total adsorption of BIC-1 at 77 K, experimental data up to 100 bar and extrapolation data up to 700 bar using the dual site Langmuir equation.

[0142] Figure 14 is similar to Figure 13, but it is for BIC-1 at 195 K. More details related to the fitting of the Langmuir Freundlich equation are also reported in the table below.

[0143] Table 9. Total adsorption of BIC-1 at 195 K, experimental data up to 100 bar and extrapolation data up to 700 bar using the Langmuir Freundlich equation.

[0144] Figure 15 is similar to Figure 13, but it is for BIC-2 at 77 K. More details related to the fitting of the Langmuir Freundlich equation are also reported in the table below. Table 10. Total adsorption of BIC-2 at 77 K, experimental data up to 100 bar and extrapolation data up to 700 bar using the Langmuir Freundlich equation.

[0145] Figure 16 is similar to Figure 13, but it is for BIC-2 at 195 K. More details related to the fitting of the Langmuir Freundlich equation are also reported in the table below.

[0146] Table 11. Total adsorption of BIC-2 at 195 K, experimental data up to 100 bar and extrapolation data up to 700 bar using the dual site Langmuir equation.

[0147] The particles of the cross-linked polymeric framework can be stably aggregated by a binder to produce materials which can be shaped into macroscopic objects. This process can be realized by the use of a minor quantity of binder, typically 2% to 15% by weight. The binder can be chosen among inorganic and organic materials, comprising linear polymers and copolymers of hydrophilic or hydrophobic nature, such as polyvinylalcohol and polyvinylidene fluoride. The use of the above mentioned macroscopic objects improves several material performance metrics, including loading speed of the vessels and gas diffusivity.

[0148] The methods of producing the gas storage materials described herein may comprise a metal-catalysed cross-coupling reaction to form a gas storage material using typically the preformed Ni(1 ,5-COD)2 (COD=cyclooctadiene) complex together with 2,2’-bypyridine as catalyst or, alternatively, an in situ formation of the catalyst by NiX2 with X=halide (preferentially chloride or bromide), together with a reducing metal (preferably zinc or magnesium), COD and 2,2’-bypyridine.

[0149] The storage methods described herein offer various advantages with regards to operational safety for the containment of H2 both in static containers (stationary vessels) and for transport applications, compared to compressed gas without the use of the storage materials described herein.

[0150] For the same stored or transported quantity of H2:

[0151] 1) the pressure in the containers is considerably lower, and thus the safety specifications of the containers may be lower or, in any event, they may enable broader applications and uses that respect any legislative limits;

[0152] 2) in the presence of leaks from the container, the H2 outflow times are slower due to the lower pressure and the slower diffusion through the intra- and inter-particle pores of the material.

[0153] Embodiments of the invention have been described by way of example only. It will be appreciated that variations of the described embodiments may be made which are still within the scope of the invention. In particular, applications involving gases other than hydrogen are possible in as far as the molecules of the adsorbate gas can, due to their dimensions, enter the pores of the absorbent material.

Claims

CLAIMS1. A method of producing a porous gas storage material for storing hydrogen and / or oxygen and / or nitrogen, wherein the method comprises: providing aromatic ring-containing monomers comprising at least two aromatic rings; and subjecting the monomers to a metal-catalysed cross-coupling reaction to form a gas storage material comprising a cross-linked polymeric framework with aromatic ringcontaining monomeric units joined directly by covalent bonds between aromatic rings, and comprising a plurality of pores for gas sorption.

2. The method of claim 1 , wherein the cross-linked polymeric framework: comprises aromatic ring-containing monomeric units comprising at least three aromatic rings, optionally at least four aromatic rings, optionally at least five aromatic rings, optionally at least six aromatic rings; or, comprises a copolymer comprising two or more structurally distinct aromatic ringcontaining monomeric units; or, wherein at least a subset of the aromatic ring-containing monomeric units comprises at least four aromatic rings; or, wherein the aromatic ring-containing monomeric units or at least a subset of the monomeric units of the copolymer, comprise two or more aromatic rings that are fused or linked in a conjugated system; or, wherein at least a subset of the aromatic ring-containing monomeric units comprise two aromatic rings: a) having a centre-to-centre spatial separation from one another of at least 0.2 nm, optionally at least 0.3 nm, optionally at least 0.4 nm, optionally at least 0.5 nm, optionally at least 0.6 nm, optionally at least 0.7 nm and optionally 0.8 nm; and / or c) separated from one another by 4 or more bonds; or, wherein at least a subset of the aromatic ring-containing monomeric units are selected from the group consisting of:

3. The method of claim 1 or 2, wherein the method comprises a nickel-catalysed crosscoupling reaction, optionally a Yamamoto cross-coupling.

4. The method of claim 1 , 2 or 3, wherein said metal-catalysed cross-coupling reaction uses a preformed Ni(1 ,5-cyclooctadiene)2 complex together with 2,2’-bypyridine as the catalyst.

5. The method of claim 1 , 2 or 3, wherein said metal-catalysed cross-coupling reaction comprises an in situ formation of the catalyst by NiX2, wherein X is a halide, together with a reducing metal, cyclooctadiene and 2,2’-bypyridine.

6. The method of claim 5, wherein the reducing metal is magnesium or zinc.

7. The method of claim 5 or 6, wherein X is chloride or bromide.

8. A method of producing a porous gas storage material for storing hydrogen and / or oxygen and / or nitrogen, wherein the method comprises: providing aromatic ring-containing monomers comprising at least two aromatic rings; and cross-linking the monomers by a Friedel-Crafts alkylation reaction to form a gas storage material comprising a cross-linked polymeric framework with aromatic ringcontaining monomeric units joined by a cross-linking moiety between aromatic rings (optionally an aliphatic group, for example, an alkyl group), and comprising a plurality of pores for gas sorption wherein at least a subset of the aromatic ring-containing monomericunits comprises at least five aromatic rings; or wherein at least a subset of the aromatic ring-containing monomeric units are selected from the group consisting of:9 The method of claim 8, wherein the method comprises cross-linking the monomers by a Friedel-Crafts alkylation reaction using formaldehyde dimethyl acetal (FDA) and optionally iron (III) chloride as a catalyst or acidic conditions.

10. The method of any of claims 1 to 9, wherein the gas storage material is an amorphous material.

11. The method of any of claims 1 to 10, wherein the BET specific surface area of the gas storage material is greater than about 750 m2g-1 , optionally greater than about 850 m2g-1 , optionally greater than about 1000 m2g-1 , optionally greater than about 1250 m2g- 1 , optionally greater than about 1500 m2g-1 , optionally greater than about 2000 m2g-1 , optionally greater than about 3000 m2g-1 , and optionally greater than about 4000 m2g-1 .

12. The method of any of claims 1 to 11 , wherein the pores in the gas storage material comprise micropores.

13. The method of any one of claims 1 to 12, wherein the volume of the pores of the gas storage material is greater than about 0.40 cm3g-1, optionally greater than about 0.50 cm3g_1, optionally greater than about 0.60 cm3g-1, optionally greater than about 0.90 cm3g-1, optionally greater than about 1.00 cm3g-1, optionally greater than about 0.60 cm3g-1, optionally greater than about 1.20 cm3g-1, optionally greater than about 1.40 cm3g-1,optionally greater than about 1.50 cm3g-1, optionally greater than about 2.00 cm3g-1, optionally greater than about 2.70 cm3g-1, and optionally greater than about 3.00 cm3g-1.

14. A porous gas storage material for storing hydrogen and / or oxygen and / or nitrogen comprising: a cross-linked polymeric framework; and a plurality of pores for gas sorption, wherein the cross-linked polymeric framework comprises aromatic ring-containing monomeric units comprising at least two aromatic rings and wherein the aromatic ring-containing monomeric units are linked by covalent bonds directly between aromatic rings.

15. The gas storage material of claim 14, wherein the cross-linked polymeric framework is as defined in claim 2.

16. A porous gas storage material for storing hydrogen and / or oxygen and / or nitrogen comprising: a cross-linked polymeric framework; and a plurality of pores for gas sorption, wherein the cross-linked polymeric framework comprises aromatic ring-containing monomeric units comprising at least two aromatic rings and wherein the aromatic ring-containing monomeric units are linked by a cross-linking moiety (optionally an aliphatic group, for example, an alkyl group) between aromatic rings, and wherein at least a subset of the aromatic ring-containing monomeric units comprises at least five aromatic rings; or wherein at least a subset of the aromatic ring-containing monomeric units are selected from the group consisting of:

17. The gas storage material of any of claims 14 to 16, wherein the gas storage material is an amorphous material.

18. The gas storage material of any of claims 14 to 17, wherein the BET specific surface area of the gas storage material is greater than about 750 m2g-1, optionally greater than about 850 m2g-1, optionally greater than about 1000 m2g-1, optionally greater than about 1250 m2g-1, optionally greater than about 1500 m2g-1 , optionally greater than about 2000 m2g-1, optionally greater than about 3000 m2g-1, and optionally greater than about 4000 m2g_119. The gas storage material of any of claims 14 to 18, wherein the pores comprise micropores.

20. The gas storage material of any one of claims 14 to 19, wherein the volume of the pores of the gas storage material is greater than about 0.40 cm3g-1, optionally greater than about 0.50 cm3g-1, optionally greater than about 0.60 cm3g-1, optionally greater than about 0.90 cm3g'1, optionally greater than about 1.00 cm3g-1, optionally greater than about 0.60 cm3g'1, optionally greater than about 1.20 cm3g-1, optionally greater than about 1.40 cm3g_1, optionally greater than about 1.50 cm3g-1, optionally greater than about 2.00 cm3g-1, optionally greater than about 2.70 cm3g-1, and optionally greater than about 3.00 cm3g-1.

21. The porous gas storage material of any of claims 14 to 20, further comprising a binder, wherein the porous gas storage material is formed into one or more macroscopic objects by the cross-linked polymeric framework being aggregated by said binder.

22. The porous gas storage material of claim 21 , wherein the binder is 2% to 15% by weight of the porous gas storage material.

23. The porous gas storage material of claim 21 or 22, wherein said binder comprises linear polymers or copolymers of hydrophilic or hydrophobic nature.

24. The porous gas storage material of claim 21 , 22, or 23, wherein said binder comprises polyvinylalcohol or polyvinylidene fluoride.

25. Use of the porous gas storage material of any of claims 14 to 24 for storing a gas comprising hydrogen and / or oxygen and / or nitrogen at a pressure higher than atmospheric pressure.