WO2011089418A2 - Material for storing hydrogen - Google Patents

Material for storing hydrogen Download PDF

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WO2011089418A2
WO2011089418A2 PCT/GB2011/050070 GB2011050070W WO2011089418A2 WO 2011089418 A2 WO2011089418 A2 WO 2011089418A2 GB 2011050070 W GB2011050070 W GB 2011050070W WO 2011089418 A2 WO2011089418 A2 WO 2011089418A2
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formula
species
optionally substituted
ligand
aryl
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PCT/GB2011/050070
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WO2011089418A3 (en
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Carl Redshaw
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University Of East Anglia
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
    • C01B3/0005—Reversible uptake of hydrogen by an appropriate medium, i.e. based on physical or chemical sorption phenomena or on reversible chemical reactions, e.g. for hydrogen storage purposes ; Reversible gettering of hydrogen; Reversible uptake of hydrogen by electrodes
    • C01B3/001—Reversible uptake of hydrogen by an appropriate medium, i.e. based on physical or chemical sorption phenomena or on reversible chemical reactions, e.g. for hydrogen storage purposes ; Reversible gettering of hydrogen; Reversible uptake of hydrogen by electrodes characterised by the uptaking medium; Treatment thereof
    • C01B3/0015—Organic compounds; Solutions thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
    • B01J20/223—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material containing metals, e.g. organo-metallic compounds, coordination complexes
    • B01J20/226—Coordination polymers, e.g. metal-organic frameworks [MOF], zeolitic imidazolate frameworks [ZIF]
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C11/00—Use of gas-solvents or gas-sorbents in vessels
    • F17C11/005—Use of gas-solvents or gas-sorbents in vessels for hydrogen
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
    • Y02C20/00—Capture or disposal of greenhouse gases
    • Y02C20/40—Capture or disposal of greenhouse gases of CO2
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/32—Hydrogen storage

Abstract

In an aspect, the present invention provides a material for storing hydrogen, the material comprising a metal organic framework having a plurality of nodes, each node comprising: a plurality of metal ions, wherein at least one of the metal ions is a zinc ion; a plurality of linking ligands, wherein each ligand is coordinated to two or more of the metal ions; a plurality of monodentate ligands, wherein each of the monodentate ligands is coordinated to one of the metal ions, and at least one of the monodentate ligands is a halide or a halogenated species.

Description

Material for Storing Hydrogen Field of the Invention The present invention relates to materials for storing hydrogen. Such materials include metal organic frameworks. The present invention also provides methods for storing hydrogen using these materials.
Background
The use of hydrogen as a fuel is becoming increasingly attractive, and considerable research has been invested in improving the efficiency of the various techniques used in producing and storing the hydrogen, and then also in using the hydrogen to generate energy. One of the challenges is to provide a material that will store sufficient hydrogen for its subsequent use in a fuel cell. Much progress has been made to date, but it would be desirable to increase the hydrogen storage capacities of materials.
Many types of material have been researched as possible hydrogen storage materials. One class of material that has been studied is metal organic frameworks (MOFs). Such materials have repeated nodes, which together form a porous network. The nodes generally comprise a metal or a metal cluster, i.e. a moiety containing more than one metal. Metal organic frameworks are described in a number of publications including, for example, US 2003/0148165, WO 2004/042270, WO 2006/1 10740, US 2008/0188677 and WO 2007/1 1 1738, and Angew. C em. Int. Ed. 2007, 46, 6289- 6292, each of which is incorporated herein by reference.
One type of material that has been researched for its ability to store hydrogen is a metal organic framework material called MOF-5. It has been shown to have high hydrogen storage capacities. While this material is a promising candidate for a hydrogen storage material, it is generally very moisture and oxygen sensitive, and often requires extensive washing of its pores after synthesis. To prevent degradation, it ideally needs to be stored under vacuum.
It would be desirable to provide an alternative to the hydrogen storage materials disclosed in the prior art and ideally an improved material for storing hydrogen, for example a material with improved hydrogen storage capacity and/or a material that is less sensitive to ambient environmental conditions.
Summary of the Invention
In a first aspect, the present invention provides a material for storing hydrogen, the material comprising a metal organic framework having a plurality of nodes, each node comprising:
a plurality of metal ions, wherein at least one of the metal ions is a zinc ion;
a plurality of linking ligands, wherein each ligand is coordinated to two or more of the metal ions;
a plurality of monodentate ligands, wherein each of the monodentate ligands is coordinated to one of the metal ions, and at least one of the monodentate ligands is a halide or a halogenated species.
In a second aspect, the present invention further provides a method for storing hydrogen, the method comprising providing the material according to the first aspect, and contacting the material with hydrogen. The metal organic framework has a plurality of nodes, each node comprising a plurality of metal ions, wherein at least one of the metal ions is a zinc ion. Each node may have the features described below. Nodes are sometimes termed metal clusters in the art.
The present inventors have found that the materials of the present invention generally have acceptable hydrogen storage capacities. Additionally, it has been found that at least some embodiments of the present invention, particularly those in which the monodentate ligand is a halogenated species, for example a fluorinated aryl or an aryl group having a fluorinated alkyl substituent, have surprisingly high hydrogen storage capacities. This is exemplified for certain embodiments in the Examples below. At least some of the embodiments of the materials of the present invention also seem to be less prone to degradation than some of the materials of the prior art, e.g. MOF-5.
In a third aspect, the present invention provides a method for storing hydrogen, the method comprising providing a material comprising a metal organic framework having a plurality of zinc-containing nodes, wherein adjacent nodes are linked by an alkali metal ion, and
contacting the material with hydrogen.
In a fourth aspect, the present invention provides a material for use in the method of the third aspect, the material comprising a metal organic framework comprising a plurality of zinc-containing nodes, each zinc-containing node containing one or more species selected from O2" and OH" species, wherein an alkali metal ion links adjacent nodes.
The linkage of adjacent nodes by alkali metal ions has been found to increase the hydrogen storage capacity of the zinc-containing metal organic framework materials.
I ention provides a compound of the formula
Figure imgf000004_0001
wherein X' is a halogen selected from bromine or iodine,
-Z is a group of the formula
Figure imgf000004_0002
, wherein m is 1 to 5
Brief Description of the Figures
Figure 1 shows three embodiments of a node of the material of the present invention and an example method of its synthesis. These nodes are Zn5 type nodes, i.e. nodes containing five zinc ions. Materials E and F have nodes of this type (the nodes in Material E being represented by formula (2) of Figure 1 , and the nodes in Material F being represented by formula (1 ) of Figure 1 ). The detailed synthesis of each of these materials is given in the Examples below.
Figure 2 shows three other types of nodes of the material of the present invention of the Zn4 type, i.e. nodes containing four zinc ions. Materials formed from nodes of type IV as shown in this Figure may have the formula [(RZn)4(NMeR'-NH)4]. Material A, described further in the Examples, is of type IV as shown in Figure 2, wherein R = C6F5, R' = Ph. Material B, described further in the Examples, is of type IV as shown in Figure 2, wherein R = Et and R' = Me. Materials formed from nodes of type V as shown in this Figure may the formula [(RZn)4(OH)(NMeR'-NH)3]. Material C, described further in the Examples, is of type V as shown in Figure 2, wherein R = Et, R'= Me. Material D, described further in the Examples, is of type V as shown in Figure 2, wherein R = C6F5, R' = Ph. Materials formed from nodes of type VI as shown in this Figure may have the formula [(RZn)4(OH)2(NMeR'-NH)2].
Figure 3 shows a material having nodes linked by a lithium ion. This material is of the formula [(EtZn)(OLi)(NHNMe2)3]2- The synthesis of such a material is further described below in the Examples (Material G). Figure 4 shows, over a range of pressures, the hydrogen uptake of MOF-5, synthesised as described below in the Examples, and a selection of fluorinated and non-fluorinated MOF materials, in particular Materials A, B, C, D and G. The synthesis of these materials and the hydrogen uptake tests are further described in the Examples below.
Figure 5 shows, over a range of pressures, the hydrogen uptake of MOF-5, synthesised as described below in the Examples, and two materials containing nodes of the Zn5 type, in particular Materials E and F. The synthesis of these materials and the hydrogen uptake tests are further described in the Examples below.
Figure 6 shows the crystal structure of the diphenyl glycine complex synthesised in Example 2.
Figure 7 shows the crystal structure of the compound synthesised in Example 3. Detailed Description of the Invention
First and Second Aspects of the Invention Metal ions
The node may comprise two or more metal ions, optionally three or more metal ions, optionally four or more metal ions. The node may comprise a plurality of metal ions selected from ions of alkaline earth metals and ions of transitions metals, wherein at least one of the metal ions in the node is a zinc ion. The alkaline earth metals may be selected from beryllium and magnesium. The transition metals may be selected from Groups 3 to 12 of the periodic table, and optionally are selected from Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zi. The ion or ions of the transition metals may be M+ or M2+ ions, where M is the transition metal. Preferably, the node comprises four or five metal ions. Optionally, the node comprises at least two zinc ions, preferably, at least three zinc ions, more preferably at least four zinc ions. Preferably, the node comprises four or five zinc ions. Such nodes may be termed a Zn4 type node and a Zn5 type node, respectively. Optionally, all of the metal ions in the node are zinc ions. Linking ligands
The node has a plurality of linking ligands, wherein each linking ligand is coordinated to two or more of the metal ions. The node may comprise two or more linking ligands, optionally three or more linking ligands, optionally four or more linking ligands.
Preferably, at least one of the linking ligands in the node is a substituted hydrazide ligand or a carboxylate ligand, for example a polycarboxylate ligand. Preferably, at least one of the linking ligands is a substituted hydrazide ligand. Optionally, the node comprises four or five zinc ions and one or more of the linking ligands is a substituted hydrazide ligand. Optionally, the linking ligands in the node are selected from a substituted hydrazide ligand or carboxylate ligand, optionally, a polycarboxylate ligand. Optionally, all of the linking ligands are substituted hydrazide ligands. Optionally, all of the linking ligands are carboxylate ligands. Optionally, all of the linking ligands are polycarboxylate ligands. The substituted hydrazide ligand may be a ligand of the formula (NR1 R2-NR3), wherein R1 , R2 and R3 are each independently selected from H and an optionally substituted hydrocarbon group, and at least one of the R1 , R2 and R3 is an optionally substituted hydrocarbon group. Optionally R1 and R2 is an optionally substituted hydrocarbon group and R3 is H.
The optionally substituted hydrocarbon group may be selected from an optionally substituted alkyl, an optionally substituted alkenyl, an optionally substituted alkynyl, and optionally substituted aryl.
Optionally, R1 is alkyl or aryl, R2 is alkyl or aryl and R3 is H. Optionally, R1 is alkyl, R2 is alkyl or aryl and R3 is H. Optionally, R1 is alkyl, R2 is aryl and R3 is H. Optionally, R1 is C1 to C10 alkyl, optionally, C1 to C6 alkyl, optionally, C1 to C4 alkyl, optionally methyl or ethyl. Optionally, R2 is alkyl or aryl. Optionally, R2 is C1 to C10 alkyl, optionally C1 to C6 alkyl, optionally C1 to C4 alkyl, optionally methyl or ethyl. Optionally, R2 is phenyl or naphthyl. Optionally, R1 is Me, R2 is phenyl or C1 -6 alkyl and R3 is H.
At least one of the linking ligands in each node may be a carboxylate ligand. At least one of the linking ligands in each node may be an aryl compound having one or more carboxylate substituents on an aromatic ring thereof; the aryl compound may have one or more further substituents on an aromatic ring thereof, which, if two or more aromatic rings are present in the compound, may or may not be the same ring having a carboxylate substituent. The one or more further substituents may, for example, be selected from alkyl and halogen. At least one of the linking ligands in each node may be an optionally substituted benzoic acid species, which may be in free form or carboxylate form. The optionally substituted benzoic acid species may be selected from a substituted or unsubstituted benzoic acid species, wherein the substituents are optionally selected from halogen or alkyl. The substituted benzoic acid species may be a benzoic acid species having one or more substituents on the phenyl ring of the benzoic acid, wherein the substituents are selected from halogen and alkyl. Preferably, the substituted benzoic acid species may be a benzoic acid group having one or more halogen substituents on the phenyl ring, optionally two or more halogen substituents on the phenyl ring, optionally three or more halogen substituents on the phenyl ring. For example, the one or more linking ligands may be 2,4,6-trialkylbenzoic acid or a halobenzoic acid. For example, the one or more linking ligands may be 2,4,6- trimethylbenzoic acid or 3-chlorobenzoic acid.
At least one of the linking ligands in each node may be a polycarboxylate ligand, including, but not limited to, a di-, tri- or tetracarboxylate group. The polycarboxylate ligand may be a ligand comprising one or more phenyl groups, wherein at least two of the carboxylate groups are attached to a carbon of the one or more phenyl groups. The carboxylate groups may be attached to different carbons of the same phenyl group. If the polycarboxylate ligand comprises two or more phenyl groups, the carboxylate groups may be attached to different phenyl groups.
One or more of the linking ligands in each node may be a polycarboxylate ligand of the formulae 1 to 20 below:
Figure imgf000009_0001
Figure imgf000009_0002
Figure imgf000009_0003
Figure imgf000009_0004
Figure imgf000010_0001
Figure imgf000010_0002
Figure imgf000010_0003
Figure imgf000010_0004
Figure imgf000011_0001
Figure imgf000012_0001
Figure imgf000012_0002
Figure imgf000012_0003
Figure imgf000013_0001
Figure imgf000013_0002
Figure imgf000014_0001
Figure imgf000014_0002
Figure imgf000015_0001
Figure imgf000015_0002
©PTC) 20
wherein each X is independently selected from hydrogen, -NHR, -N(R)2, halides, C1-10 alkyl, C6-18 aryl, or C6-i 8 arylalkyl, -NH2, alkenyl, alkynyl, -Oalkyl, -NH(aryl), cycloalkyi, cycloalkenyl, cycloalkynyl, -(CO)R, -(S02)R, -(C02)R -SH, -S(alkyl), -S03H, -SO3" M+, -COOH, -COOM+, -P03H2, -Ρ03ΗΊνΓ, -P03 2 M2+, or -P03 2 M2+, -N02, -C02H, silyl derivatives; borane derivatives; ferrocenes and other metallocenes; M is a metal atom, and R is alkyl, optionally C1-10 alkyl. M may be selected from alkaline and alkaline earth metals, including, but not limited to Li, Na, K, Be, Mg and Ca.
Optionally, the carboxylate ligand is a ligand having a carboxylate group and an amine group. Preferably, the carboxylate group and the amine group each coordinate to a metal ion in the node. The amine group is preferably a primary amine group. The carboxylate group and the amine group are preferably covalently bonded to the same atom, preferably a carbon atom, in the carboxylate ligand. Optionally, the carboxylate ligand is a ligand of the formula:
Figure imgf000016_0001
wherein R4 and R5 are independently selected from H and an optionally substituted hydrocarbon group. The optionally substituted hydrocarbon group may be selected from an optionally substituted alkyl, an optionally substituted alkenyl, an optionally substituted alkynyl, and optionally substituted aryl. Optionally, R4 and R5 are independently selected from H and optionally substituted aryl. Preferably, R4 and R5 are both an optionally substituted hydrocarbon. Preferably, R4 and R5 are both an optionally substituted hydrocarbon group. Preferably, R4 and R5 are both an optionally substituted aryl group. Preferably, R4 and R5 are both an optionally substituted phenyl group. Materials in which the carboxylate ligand is a ligand having a carboxylate group and an amine group, particularly those found above, have been found to be surprisingly readily crystallised, and therefore can be purified, and produced on an industrial scale. The node may further comprise one or more polydentate ligands selected from O and OH.
Monodentate ligand
The node has a plurality of monodentate ligands, wherein each of the monodentate ligands is coordinated to one of the metal ions, and at least one of the monodentate ligands is a halide or a halogenated species. Each of the plurality of monodentate ligands may each be selected from a hydrocarbon ligand, a halide and a halogenated species, wherein each of the monodentate ligands is coordinated to one of the metal ions, and at least one of the monodentate ligands is a halide or a halogenated species. The hydrocarbon ligand may be selected from an optionally substituted alkyl, an optionally substituted alkenyl, an optionally substituted alkynyl, and optionally substituted aryl. Optionally substituted alkyl may be an optionally substituted C1 to C10 alkyl, optionally C1 to C6 alkyl, optionally C1 to C4 alkyl, optionally methyl or ethyl. Optionally substituted aryl may be phenyl or naphthyl. Optionally, every metal in the node is coordinated to a monodentate ligand, and at least one metal is coordinated to a halide or a halogenated species. Optionally, every metal in the node is coordinated to a monodentate ligand, which is a halide or a halogenated species. Optionally, every metal in the node is a zinc ion and every zinc ion is coordinated to a monodentate ligand, which is a halide or a halogenated species.
Halide may be selected from fluorine, chlorine, bromine and iodine.
The halogenated species may be a hydrocarbon group substituted with one or more halogens; the hydrocarbon group may be selected from a halogenated alkyl, a halogenated alkenyl, a halogenated alkynyl, and a halogenated aryl, and aryl having one or more halogenated hydrocarbon substituents. A halogenated group is a group substituted with one or more halogens, and, optionally, one or more further substituents. Halogen may be selected from fluorine, chlorine, bromine and iodine. The halogenated species may be a hydrocarbon group substituted with one or more halogens; the halogenated species may be selected from a halogenated alkyl, a halogenated alkenyl, a halogenated alkynyl, and a halogenated aryl, and aryl having one or more halogenated hydrocarbon substituents. A halogenated group is a group substituted with one or more halogens, and, optionally, one or more further substituents. Halogen may be selected from fluorine, chlorine, bromine and iodine.
The monodentate ligand may be an aryl group substituted with one or more halogens and/or a halogenated hydrocarbon group. The halogenated aryl may be selected from a halogenated phenyl and halogenated naphthyl. The halogenated phenyl may be a phenyl group substituted with 1 , 2, 3, 4 or 5 halogens. The halogen may be selected from chlorine or fluorine, preferably fluorine. Preferably, the halogenated phenyl is a fluorinated phenyl. Preferably, the halogenated naphthyl is fluorinated naphthyl.
The halogenated aryl, and aryl having one or more halogenated hydrocarbon substituents may be a species of any of the formulae shown below:
Figure imgf000018_0001
to 5, -Z is a group of the formula
Figure imgf000018_0002
, wherein m is 1 to 5. any of the formulae shown below:
Figure imgf000018_0003
wherein n is 1 to 5, and F3, F4i and F5 indicates, respectively, that three, four or five fluorines are attached to a ring.
In an embodiment, the aryl having one or more halogenated hydrocarbon substituents may be a species of any of the formulae shown below
Figure imgf000019_0001
wherein n is 1 to 5, -Z is a group of the formula
Figure imgf000019_0002
, wherein m is 1 to 5; optionally n is 2 or more, preferably 3 or more; optionally m is 2 to 5; optionally n is 3 and m is 5.
In an embodiment, the aryl having one or more halogenated hydrocarbon substituents is a species of the formula:
Figure imgf000019_0003
, wherein R' is C6F5.
The aryl having one or more halogenated hydrocarbon substituents may be a phenyl having one or more halogenated hydrocarbon substituents. The aryl having one or more halogenated hydrocarbon substituents may be selected from phenyl having one or more halogenated alkyl substituents. Halogenated alkyl may be C1 to C10 halogenated alkyl, optionally C1 to C4 halogenated alkyl. Halogenated alkyl may include, but is not limited to, halogenated methyl or ethyl. Halogenated alkyl may be selected from -CF3 and -CCI3.
Linker species Optionally, the material comprises a linker species that links adjacent nodes. The species may be an inorganic or an organic species.
The linker species may be an inorganic species. The linker species may be an alkali metal ion. The alkali metal ion may be selected from a lithium ion, a sodium ion and a potassium ion. The linker species may be a lithium ion. Preferably, the node contains one or more OH" or O2" ligands and the linker species is an alkali metal ion, preferably selected from a lithium ion, a sodium ion and a potassium ion. The nodes may be linked by lithium ions by providing a material of the present invention that does not include lithium ion as linkers, and contacting this material with a source of lithium, for example, 'BuLi. An example of the linkage of zinc hydrazide nodes with lithium can be found in an article authored by Redshaw et al in Chem. Commun., 2006, 523-525, entitled Synthesis and disruption of a tetrametallic zinc hydrazide, which is incorporated herein by reference. The nodes may be linked by sodium or potassium ions by providing a material of the present invention that does not include sodium or potassium ions as linkers, and contacting this material with a source of sodium or potassium, for example NaH or KH.
Optionally, the linker species may be an organic species. The linker species may be a polycarboxylate species, including, but not limited to, a di-, tri- or tetracarboxylate group. The polycarboxylate ligand may be a ligand comprising one or more phenyl groups, wherein at least two of the carboxylate groups are attached to a carbon of the one or more phenyl groups. The carboxylate groups may be attached to different carbons of the same phenyl group. If the polycarboxylate ligand comprises two or more phenyl groups, the carboxylate groups may be attached to different phenyl groups. The material may comprise one or more linker species of the formula 1 to 20 shown above, wherein each X is independently selected from hydrogen, -NHR, -N(R)2, halides, C1-10 alkyl, C6-18 aryl, or C6-ie aralkyl, -NH2, alkenyl, alkynyl, -Oalkyl, -NH(aryl), cycloalkyl, cycloalkenyl, cycloalkynyl, -(CO)R, -(S02)R, -(C02)R -SH, -S(alkyl), -S03H, - SO3" M+, -COOH, -COOM+, -Ρ03Η2, -Ρ03ΗΊνΓ, -P03 2 M2+, or -P03 2 M2+, -N02, -C02H, silyl derivatives; borane derivatives; ferrocenes and other metallocenes; M is a metal atom, and R is alkyl, optionally C1 -10 alkyl. M may be selected from alkaline and alkaline earth metals, including, but not limited to Li, Na, K, Be, Mg and Ca. The linker species may be a species having one or more carboxylate groups and one or more hydroxyl or hydroxylate groups. For example, the linker species may be a hydrocarbon moiety having one or more carboxylate substituents and one or more hydroxyl or hydroxylate groups. For example, the linker species may be an alkyl having one or more carboxylate groups and one or more hydroxyl groups or an aryl having one or more carboxylate groups and one or more hydroxyl groups. For example, the linker species may be a species of any one of formula 1 to 20, described above, wherein one of the carboxylate (-C02 ") groups has been replaced by an -OH or -O" species.
Preferred types of nodes
Preferably, the node comprises four or five metal ions, and the linking ligands are each independently selected from a substituted hydrazide ligand, a polycarboxylate ligand, and a carboxylate ligand that is a ligand having a carboxylate group and an amine group. Preferably, the node comprises four or five metal ions, and the linking ligands are each independently selected from a substituted hydrazide ligand and a polycarboxylate ligand. Preferably, the node comprises four or five zinc ions, and the linking ligands are selected from a substituted hydrazide ligand or a carboxylate ligand, optionally a polycarboxylate ligand. The node may comprise at least two linking ligands, optionally three or four linking ligands, optionally wherein each of the linking ligands are selected from a substituted hydrazide ligand and a carboxylate ligand, optionally a polycarboxylate ligand. Optionally, the node comprises or has two, three or four substituted hydrazide ligands. Optionally, all of the linking ligands in the node are substituted hydrazide ligands. Optionally, all of the linking ligands in the node are carboxylate ligands. Optionally, all of the linking ligands in the node are carboxylate ligands that are a ligands having a carboxylate group and an amine group. Optionally, all of the linking ligands in the node are polycarboxylate ligands. Optionally, the node comprises at least two zinc ions, preferably, at least three zinc ions, more preferably at least four zinc ions.
The nodes may contain ligands selected from a halide and OH" and O2". The material may comprise a plurality of nodes of the formula [(RZn)4(NR1 R2-NR3)4], [(RZn)4(OH)(NR1 R2-NR3)3], [(RZn)4(OH)2(NR1 R2-NR3)2], [(RZn)3(CIZn)(OH)(NR1 R2- NR3)3], and [(RZn4)Zn(Lc)6],
wherein R is a halogenated hydrocarbon and wherein R1 , R2 and R3 are each independently selected from H and an optionally substituted hydrocarbon group, at least one of the R1 , R2 and R3 is an optionally substituted hydrocarbon group, and Lc is optionally substituted benzoic acid, which may be in free or carboxylate form. The halogenated hydrocarbon in these formulae is preferably selected from halogenated aryl and aryl having one or more halogenated hydrocarbon substituents. Lc is an optionally substituted benzoic acid group, which may be selected from a substituted or unsubstituted benzoic acid group, the substituents optionally selected from halogen or alkyl.
The present invention provides a material having the formula [(RZn)4(NR1 R2-NR3) ], [(RZn)4(OH)(NR1 R2-NR3)3], [(RZn)4(OH)2(NR1 R2-NR3)2], [(RZn)3(CIZn)(OH)(NR1 R2- NR3)3] or [(RZn4)Zn(Lc)6],
wherein R is a halogenated hydrocarbon and wherein R1 , R2 and R3 are each independently selected from H and an optionally substituted hydrocarbon group, at least one of the R1 , R2 and R3 is an optionally substituted hydrocarbon group, and Lc is optionally substituted benzoic acid, which may be in free or carboxylate form. The halogenated hydrocarbon in these formulae is preferably selected from halogenated aryl and aryl having one or more halogenated hydrocarbon substituents. Lc is an optionally substituted benzoic acid group, which may be selected from a substituted or unsubstituted benzoic acid group, the substituents optionally selected from halogen or alkyl.
The material may comprise a plurality of nodes selected from formulae IV, V and VI below
Figure imgf000022_0001
wherein, in each of formula IV, V and VI, each R is a monodentate ligand, and at least one R is independently a halide or a halogenated species, and each R' is independently alkyl or aryl. Optionally, every R is independently in each of formula IV, V and VI is independently a halide or a halogenated species. Optionally, every R in each of formula IV, V and VI is a halogenated hydrocarbon. The halogenated hydrocarbon in these formulae is preferably selected from halogenated aryl and aryl having one or more halogenated hydrocarbon substituents. Each R' may independently be C1 -6 alkyl or phenyl.
In any of the formulae [(RZn)4(NR1 R2-NR3)4], [(RZn)4(OH)(NR1 R2-NR3)3], [(RZn)4(OH)2(NR1 R2-NR3)2], [(RZn)3(CIZn)(OH)(NR1 R2-NR3)3], [(RZn4)Zn(Lc)6], and formulae IV, V and VI, each R is preferably selected from a species of any of the formulae shown below:
Figure imgf000023_0001
wherein n is 1 to 5, -Z is a group of the formula
Figure imgf000023_0002
In any of the formulae [(RZn)4(NR1 R2-NR3)4], [(RZn)4(OH)(NR1 R2-NR3)3], [(RZn)4(OH)2(NR1 R2-NR3)2], [(RZn)3(CIZn)(OH)(NR1 R2-NR3)3], [(RZn4)Zn(Lc)6], and formulae IV, V and VI, each R is preferably selected from a species of any of the formulae shown below:
Figure imgf000024_0001
wherein n is 1 to 5, and F3, F4, and F5 indicates, respectively, that three, four or five fluorines are attached to a ring.
In any of the formulae [(RZn)4(NR1 R2-NR3)4], [(RZn)4(OH)(NR1 R2-NR3)3], [(RZn)4(OH)2(NR1 R2-NR3)2], [(RZn)3(CIZn)(OH)(NR1 R2-NR3)3], [(RZn4)Zn(Lc)6], and formulae IV, V and VI, each R is preferably selected from a species of any of the formulae shown below
p of the formula
Figure imgf000024_0002
, wherein m is 1 to 5; optionally n is 2 or more, preferably 3 or more; optionally m is 2 to 5; optionally n is 3 and m is 5.
In an embodiment, in any of the formulae [(RZn)4(NR1 R2-NR3)4], [(RZn)4(OH)(NR1 R2- NR3)3], [(RZn)4(OH)2(NR1 R2-NR3)2], [(RZn)3(CIZn)(OH)(NR1 R2-NR3)3],
[(RZn4)Zn(Lc)6], and formulae IV, V and VI, each R is species of the formula:
Figure imgf000025_0001
, wherein R' is C6F5.
In an embodiment, the material may comprise a plurality of nodes of the formula [(RZn)4(Q)4)], wherein R is a halogenated hydrocarbon and Q is a carboxylate ligand having a carboxylate group and an amine group. The halogenated hydrocarbon in this formula is preferably selected from halogenated aryl and aryl having one or more halogenated hydrocarbon substituents. The halogenated aryl and aryl having one or more halogenated hydrocarbon substituents may be selected from the halogenated aryl and aryl having one or more halogenated hydrocarbon substituents as described herein, for example in the section entitled "Monodentate ligand". Preferably, the carboxylate group and the amine group in Q each coordinate to a zinc ion in the node. The amine group is preferably a primary amine group. The carboxylate group and the amine group are preferably covalently bonded to the same atom, preferably a carbon atom, in the carboxylate ligand Q. Optionally, Q is a ligand of the formula:
Figure imgf000025_0002
wherein R4 and R5 are independently selected from H and an optionally substituted hydrocarbon group. The optionally substituted hydrocarbon group may be selected from an optionally substituted alkyl, an optionally substituted alkenyl, an optionally substituted alkynyl, and optionally substituted aryl. Optionally, R4 and R5 are independently selected from H and optionally substituted aryl. Preferably, R4 and R5 are both an optionally substituted hydrocarbon. Preferably, R4 and R5 are both an optionally substituted hydrocarbon group. Preferably, R4 and R5 are both an optionally substituted aryl group. Preferably, R4 and R5 are both an optionally substituted phenyl group. In an embodiment, the material comprises a plurality of nodes of the formula [(RZn)4(Q)4)], wherein R is selected from halogenated aryl and aryl having one or more halogenated hydrocarbon substituents and Q is a ligand of the formula:
Figure imgf000026_0001
wherein R4 and R5 are independently selected from H and an optionally substituted hydrocarbon group. Preferably, R4 and R5 are both an optionally substituted hydrocarbon group. Preferably, R4 and R5 are both an optionally substituted aryl group. Preferably, R4 and R5 are both an optionally substituted phenyl group. In the formula [(RZn)4(Q)4)], R may be selected from a species of any of the formulae shown below:
Figure imgf000026_0002
wherein n is 1 to 5, -Z is a group of the formula
Figure imgf000026_0003
In the formula [(RZn)4(Q)4)], R may be selected from a species of any of the formulae shown below:
Figure imgf000027_0001
wherein n is 1 to 5, and F3, F4, and F5 indicates, respectively, that three, four or five fluorines are attached to a ring.
In the formula [(RZn)4(Q)4)], R may be selected from a species of any of the formulae shown below:
Figure imgf000027_0002
wherein n is 1 to 5, -Z is a group of the formula
Figure imgf000027_0003
, wherein m is 1 to 5; optionally n is 2 or more, preferably 3 or more; optionally m is 2 to 5; optionally n is 3 and m is 5.
In an embodiment, R is a species of the formula
Figure imgf000028_0001
In an embodiment, the material comprises a plurality of nodes of the formula [(RZn)4(Q)4)], wherein R is aryl having one or more halogenated hydrocarbon substituents and Q is a ligand of the formula:
Figure imgf000028_0002
wherein R4 and R5 are each an optionally substituted aryl group. Preferably, R4 and R5 are each an optionally substituted phenyl group. The aryl having one or more halogenated hydrocarbon substituents may be as described herein and is preferably selected from a species any of the formulae shown below:
Figure imgf000028_0003
to 5, -Z is a group of the formula
Figure imgf000028_0004
, wherein m is 1 to 5. The present invention further provides a method for storing hydrogen, the method comprising providing the material according to the present invention, and contacting the material with hydrogen. Optionally, the hydrogen is contacted with the material at a pressure of at least 1 bar, optionally at least 5 bar, more preferably, at least 10 bar. Optionally, the hydrogen is contacted with the material at a pressure of from 1 to 15 bar. The contacting may be carried out at any suitable temperature that allows the material to store hydrogen. The temperature may be a temperature of 25 °C or below, optionally 0 °C or below, optionally, -50 °C or below, optionally, - 100 °C or below, optionally -150 °C or below, optionally -180 °C or below.
Third and Fourth Aspects of the Invention
In a third aspect, the present invention provides a method for storing hydrogen, the method comprising providing a material comprising a metal organic framework having a plurality of zinc-containing nodes, wherein adjacent nodes are linked by an alkali metal ion, and
contacting the material with hydrogen.
Optionally, the hydrogen is contacted with the material at a pressure of at least 1 bar, optionally at least 5 bar, more preferably, at least 10 bar. Optionally, the hydrogen is contacted with the material at a pressure of from 1 to 15 bar. The contacting may be carried out at any suitable temperature that allows the material to store hydrogen. The temperature may be a temperature of 25 °C or below, optionally 0 °C or below, optionally, -50 °C or below, optionally, - 100 °C or below, optionally -150 °C or below, optionally -180 °C or below.
The zinc-containing nodes each contain one or more zinc ions, optionally two or more zinc ions, preferably four or five zinc ions. The nodes may be as described herein for the first and second aspects of the invention.
The materials for use in the third aspect may, for example, be formed by providing a material having any of the formula [(RZn)4(NR1 R2-NR3)4], [(RZn)4(OH)(NR1 R2-NR3)3], [(RZn)4(OH)2(NR1 R2-NR3)2], [(RZn)3(CIZn)(OH)(NR1 R2-NR3)3] or [(RZn4)Zn(Lc)6], and contacting this material with a source of alkali metal ions, wherein R is a monodentate ligand and wherein R1 , R2 and R3 are each independently selected from H and an optionally substituted hydrocarbon group, at least one of the R1 , R2 and R3 is an optionally substituted hydrocarbon group, and Lc is optionally substituted benzoic acid, which may be in free or carboxylate form. Each of the monodentate ligands R may independently be selected from a hydrocarbon ligand, a halide and a halogenated species, wherein each of the monodentate ligands is coordinated to one of the metal ions, and, optionally, at least one of the monodentate ligands is a halide or a halogenated species. The halogenated hydrocarbon may be selected from halogenated aryl and aryl having one or more halogenated hydrocarbon substituents. Lc is an optionally substituted benzoic acid group, which may be selected from a substituted or unsubstituted benzoic acid group, the substituents optionally selected from halogen or alkyl.
The present invention further provides a material for use in the third aspect, the material being formed by providing a material having any of the formulae [(RZn)4(OH)(NR1 R2-NR3)3], [(RZn)4(OH)2(NR1 R2-NR3)2], [(RZn)3(CIZn)(OH)(NR1 R2- NR3)3] and [(RZn4)Zn(Lc)6],
and contacting this material with a source of alkali metal ions,
wherein R is a monodentate ligand and wherein R1 , R2 and R3 are each independently selected from H and an optionally substituted hydrocarbon group, at least one of the R1 , R2 and R3 is an optionally substituted hydrocarbon group, and Lc is optionally substituted benzoic acid, which may be in free or carboxylate form. Each of the monodentate ligands R may independently be selected from a hydrocarbon ligand, a halide and a halogenated species, wherein each of the monodentate ligands is coordinated to one of the metal ions, and, optionally, at least one of the monodentate ligands is a halide or a halogenated species. The halogenated hydrocarbon may be selected from halogenated aryl and aryl having one or more halogenated hydrocarbon substituents. Lc is an optionally substituted benzoic acid group, which may be selected from a substituted or unsubstituted benzoic acid group, the substituents optionally selected from halogen or alkyl.
The source of alkali metal ions is preferably selected from an alkali metal hydride and an alkali metal organometallic compound, optionally an alkyl alkali metal organometallic compound. For example, a source of lithium is 'BuLi. An example of the linkage of zinc hydrazide nodes with lithium can be found in an article authored by Redshaw et al in Chem. Commun., 2006, 523-525, entitled Synthesis and disruption of a tetra metallic zinc hydrazide, which is incorporated herein by reference. The source of sodium and potassium may, for example, comprise NaH or KH. The molar ratio of (source of alkali metal ions):(material having any of the formulae [(RZn)4(NR1 R2-NR3)4], [(RZn)4(OH)(NR1 R2-NR3)3], [(RZn)4(OH)2(NR1 R2-NR3)2], [(RZn)3(CIZn)(OH)(NR1 R2- NR3)3] or [(RZn4)Zn(Lc)6]) is preferably about 1 :2, more preferably about 1 :1.5, more preferably about 1 :1.2.
The present invention further provides a material of the formula [(ZnRa)4(NR1 R2- NR3)3(OLi)]2,
wherein Ra is a monodentate ligand, optionally selected from halide and an optionally substituted hydrocarbon,
wherein R1 , R2 and R3 are each independently selected from H and an optionally substituted hydrocarbon group, and at least one of the R1 , R2 and R3 is an optionally substituted hydrocarbon group.
R1 , R2, and R3 in the formula NR1 R2-NR3 may be as defined herein for the first and second aspect of the invention. The monodentate ligand R or Ra may be a monodentate ligand as defined herein for the first and second aspects of the invention.
New compounds for use in synthesising the materials of the present invention. ovides a compound of the formula
Figure imgf000031_0001
wherein X' is a halogen selected from bromine or iodine,
n is 2 to 5, -Z is a group of the formula
Figure imgf000032_0001
optionally n is 3 and m is 5.
In an embodiment, the compound may be of the formula:
, wherein X' is a halogen selected from bromine or iodine R'
Figure imgf000032_0002
Definitions
The term "alkyl" or "alkan" as used herein means, unless otherwise stated, a straight or branched chain or cyclic (a cycloalkyi) hydrocarbon radical, or combination thereof, which may be fully saturated and optionally may be substituted. Each alkyl may independently be a C1 -20 alkyl, optionally a C1 -10 alkyl, optionally a C1-5 alkyl, optionally C1 -3 alkyl, optionally C1-2 alkyl. Examples of saturated hydrocarbon radicals include, but are not limited to, groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, isobutyl, sec-butyl, cyclohexyl, (cyclohexyl)methyl, cyclopropylmethyl, homologs and isomers of, for example, n-pentyl, n-hexyl, n-heptyl, n-octyl, and the like. The term "alkyl," unless otherwise noted, optionally includes derivatives of alkyl.
The term "alkylene" as used herein means, unless otherwise stated, a straight or branched chain, or cyclic (a cycloalkylene) divalent hydrocarbon radical, or combination thereof, which may be fully saturated and optionally may be substituted. Unless otherwise stated, "alkylene" means optionally substituted alkylene. Each alkylene may independently be a C1 -20 alkylene, optionally a C1 -1 0 alkylene, optionally a C1 -5 alkylene, optionally C1 -3 alkylene, optionally C1 -2 alkylene. Examples of alkylene groups include, but are not limited to, groups such as methylene, ethylene, n- propylene, and isopropylene.
The term "cycloalkyl" as used herein refers to any cyclic alkyl ring. Each cycloalkyl may independently be a C3-8 cycloalkyl, optionally a C5-7 cycloalkyl, optionally a C6 cycloalkyl. Examples of cycloalkyl groups include cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl. Unless otherwise stated, "cycloalkyl" means optionally substituted cycloalkyl.
The term "acyl" as used herein refers to a group of the formula -C(=0)-R, in which R is selected from H and optionally substituted -alkyl, -alkenyl, -alkynyl. The alkyl, -alkenyl and -alkynyl may be selected from -Ci-2o alkyl, -C2-20 alkenyl and -C2-20 alkynyl; optionally -CMO alkyl, -C2-io alkenyl and -C2-10 alkynyl; optionally -C1-5 alkyl, -C2-5 alkenyl and -C2-5 alkynyl.
The term "alkenyl" as used herein as a group or part of a group refers to any linear or branched chain hydrocarbon radical containing at least one carbon-carbon double bond, which may occur at any point along the chain. Unless otherwise stated, "alkenyl" means optionally substituted alkenyl. Each alkenyl may independently be a C2-20 alkenyl, optionally a C2-1 0 alkenyl, optionally a C2-5 alkenyl, optionally C2-3 alkenyl. E- and Z-forms are both included, where applicable. Examples of alkenyl groups include vinyl, allyl, butenyl and pentenyl.
The term "alkenylene" as used herein refers to any linear or branched chain divalent hydrocarbon radical containing at least one carbon-carbon double bond, which may occur at any point along the chain. Unless otherwise stated, "alkenylene" means optionally substituted alkenylene. Each alkenylene may independently be a C2-20 alkenylene, optionally a C2-1 0 alkenylene, optionally a C2-5 alkenylene, optionally C2- 3 alkenylene. E- and Z-forms are both included, where applicable. Examples of alkenylene groups include vinylene, allylene, butenylene and pentenylene.
The term "alkynyl" as used herein as a group or part of a group refers to any linear or branched chain hydrocarbon containing at least one carbon-carbon triple bond, which may occur at any point along the chain. Unless otherwise stated, "alkynyl" means optionally substituted alkynyl. Each alkynyl may independently be a C2-20 alkynyl, optionally a C2-10 alkynyl, optionally a C2-5 alkynyl, optionally C2-3 alkynyl. Examples of suitable alkynyl groups include ethynyl, propynyl, butynyl and pentynyl.
The term "alkynylene" as used herein refers to any linear or branched chain divalent hydrocarbon radical containing at least one carbon-carbon triple bond, which may occur at any point along the chain. Unless otherwise stated, "alkynylene" means optionally substituted alkynylene. Each alkynylene may independently be a C2-20 alkynylene, optionally a C2-10 alkynylene, optionally a C2-5 alkynylene, optionally C2-3 alkynylene. Examples of suitable alkynylene groups include ethynylene, propynylene, butynylene and pentynylene.
Where a species, compound or group is described as "optionally substituted", the species, compound or group may be unsubstituted or one or more substituents may be present. Furthermore, optional substituents may be attached to the species, compounds or groups which they substitute in a variety of ways, either directly or through a connecting group, such as amine, amide, ester, ether, thioether, sulfonamide, sulfamide, sulfoxide, urea, thiourea and urethane. As appropriate, an optional substituent may itself be substituted by another substituent, either directly to the former or through a connecting group such as those exemplified above. Substituents may each independently be selected from alkyl, alkenyl, alkynyl, -O-alkyl, -O-alkanoyl, halogen, heterocyclyl, alkoxycarbonyl, hydroxy, mercapto, nitro, acyloxy, hydroxy, thiol, acyl, cycloalkyl, cycloalkenyl, substituted alkyl, substituted alkoxy, substituted alkenyl, substituted alkynyl, substituted cycloalkyl, substituted cycloalkenyl, amino, substituted amino, aminoacyl, acylamino, alkaryl, aryl, aryloxy, azido, carboxy, carboxyalkyl, cyano, halo, nitro, heteroaryl, heteroaryloxy, heterocyclic, heterocyclooxy, aminoacyloxy, oxyacylamino, thioalkoxy, substituted thioalkoxy, thioaryloxy, thioheteroaryloxy, -SO-alkyl, -SO-substituted alkyl,- SO-aryl, -SO-heteroaryl, -S02- alkyl, -S02-substituted alkyl, -S02-aryl and -S02- heteroaryl.
The term "halogen" or "halo" as used herein includes, but is not limited to, fluorine, chlorine, bromine and iodine (alternatively referred to as fluoro, chloro, bromo and iodo, respectively). The term "aryl" as used herein as a group or part of a group, includes, but is not limited to, a hydrocarbon group containing one or more aromatic rings. The term "aryl" includes heteroaryl and non-heteroaryl groups. The term "heteroaryl" as a group or part of a group includes, but is not limited to, a 5- or 6-membered aromatic ring containing one or more heteroatoms, optionally 1 , 2 or 3 heteroatoms, and the heteroatoms may be selected from N, O and S, attached through a ring carbon or nitrogen. Examples of such groups include pyrrolyl, furanyl, thienyl, pyridyl, pyrazolyl, imidazolyl, oxazolyl, isoxazolyl, thiazolyl, isothiazolyl, pyrazinyl, pyrimidinyl, pyridazinyl, triazolyl, oxadiazolyl, thiadiazolyl, triazinyl and tetrazolyl. Aryl may be selected from phenyl and naphthyl.
The term "heterocyclyl" as used herein as a group or part of a group means a 5- to 7- membered saturated or unsaturated non-aromatic ring having one or more heteroatoms, for example 1 , 2, 3 or 4 heteroatoms, optionally selected from N, O and S, attached through a ring carbon or nitrogen.
The present invention will now be further illustrated with reference to the following non- limiting Examples.
Examples Example 1 The following describes the synthesis of various types of molecular organic frameworks (MOFs), and a screening test to determine their hydrogen uptake. MOF-5 has been studied in the past for hydrogen uptake by other research groups (for example see J.L.C. Roswell, A.R. Millward, K.S. Park and O.M. Yaghi, J. Am. Chem. Soc. 2004, 126, 5666, which is incorporated herein by reference), and so was used as a comparative example in this study.
MOF-5 was synthesised using the method of Deng (for example see D. Saha, Z. Wei and S. Deng, Separation & Purific Tech. 2009, 64, 280, which is incorporated herein by reference).
Synthesis of MOF-5
0.832 g of zinc nitrate hexahydrate and 0.176 g of benzene dicarboxylic acid were dissolved in 20 ml of DEF under constant agitation at atmospheric conditions.
The resulting mixture was first degassed thrice using the freeze-pump-thaw method, and then filled up 20ml reaction vials for crystallization. The capped vials were immediately put in an oven at 85-90 °C for crystallization for about 24 h. At the end of the crystallization step clear golden crystals of MOF-5 emerged from the wall and base of the vials. The MOF-5 crystals were separated from the reaction solution, washed with DEF to remove the unreacted zinc nitrate, followed with purification in chloroform. The chloroform purification was performed by adding chloroform into 20ml vials containing the raw MOF-5 crystals. The vials were capped tightly and put back to the oven at 70 °C for another 3 days. Solvent in vials was replenished with fresh chloroform every day. After the chloroform treatment, the MOF-5 crystals changed from a golden colour to transparent.
A number of other MOFs were then synthesised, some of which were fluorinated and some of which were not: Material A (an MOF having nodes of formula IV, described above, in which each R is C6F5 and each R' is Ph), Material B (an MOF having nodes of formula IV, described above, in which each R is Et and each R' is Me), Material C (an MOF having nodes of formula V, described above, in which each R is Et and each R' is Me), Material D (an MOF having nodes of formula V, described above, in which each R is C6F5 and each R' is Ph), Material E (an MOF having nodes of the formula [(C6F5Zn)4Zn(Ar)6], in which Ar is 2,4,6-trimethylbenzoic acid), Material F (an MOF having nodes of the formula [(C6F5Zn)4Zn(Ar)6], in which Ar is 3-chlorobenzoic acid, and Material G (an MOF of formula [(EtZn)(OLi)(NHNMe2)3]2, the nodes of which are schematically shown in Figure 3 - one can see the lithium ion linkages in Figure 3). Synthesis of type IV complexes: [(ArZn)(NHNMe2)]4, wherein Ar is a fluorinated aryl group.
General synthesis methods Method a) adapted from Redshaw et al. Chem Commun. 2006, 523, which is incorporated herein by reference.
The hydrazine (either 1 ,1 -Me2NNH2 or 1 -Me,1 -PhNNH2 (1.85 mmol) and Ar2Zn. toluene (2.03 mmol) were heated at 80 °C for 2 h in toluene (30 mL). Following removal of volatiles in vacuo, the residue was extracted into acetonitrile (20 mL). The colourless solution was stored at -20 °C to afford colourless block shaped crystals.
Method b) adapted from Mitzel et al. Chem Eur. J.. 2006, 592, which is incorporated herein by reference.
Ar2Zn. toluene (2.03 mmol) was added dropwise to a hexane (20 ml) solution of the hydrazine (either 1 , 1 -Me2NNH2 or 1 -Me,1 -PhNNH2 (2.00 mmol) at 0 °C. The reaction was stirred at ambient temperature for 12 h, and following removal of volatiles in vacuo, the residue was extracted into either hexane (20 ml) or acetonitrile (20 mL). The colourless solution was stored at -20 °C to afford colourless block shaped crystals.
The fluorinated aryl group Ar can, for example, be selected from
Figure imgf000038_0001
(n = 1 to 5) (n = 1 to 5)
An example synthesis is as follows:
1 , 1 -Me2NNH2 (0.14 ml, 1 .85 mmol) and (C6F5)2Zn.toluene (1 .0 g, 2.03 mmol) were heated in toluene for 2 h. Work-up as in general synthesis method a) above (i.e. extraction into acetonitrile) afforded colourless prisms in 60 - 70 yields. 1 H NMR (CDCI3, 400 MHz) δ: 3.61 (s, 1 H, NH), 3.48 (s, 1 H, NH), 3.16 (s, 1 H, NH), 3.09 (s, 3H. HMe), 2.99 (s, 3H. HMe), 2.96 (s, 1 H, NH), 2.85 (s, 3H. HMe), 2.82 (s, 3H. HMe), 2.64 (s, 3H. NAfe), 2.53 (s, 3H. NAfe), 2.43 (s, 3H. NAfe), 2.37 (s, 3H. NAfe). 19F NMR (CDCI3, 282 MHz) δ: -1 14.28 (m, 2F, o-F), -1 15.29 (m, 2F, o-F), -1 15.72 (m, 2F, o-F), - 1 16.28 (m, 2F, o-F), -154.28 (t, 1 F, p-F), -155.15 (t, 1 F, p-F), -155.34 (t, 1 F, p-F), - 156.46 (t, 1 F, p-F), -159.88 (m, 2F, m-F), -160.17 (m, 2F, m-F), -160.49 (m, 2F, m-F), - 161 .1 1 (m, 2F, m-F). I R: 3183w (NH), 1316s, 1262m, 1243w, 1 154s, 1 100s, 1031 s, 802s, 773m, 722w, 674w, 640w. Mass Spec (El): M+ 1 166, 707 (M+ - 2C6F5 - Zn - Me2NN H).
Crystal data (½toluene solvate): Monoclinic; unit cell parameters a = 41 .8755(9), b = 10.1 152(2), c = 21 .2258(4) A; α = γ = 90, β = 108.1503(10) °. Synthesis of Material A
1 -Me, 1 -PhNNH2 (0.06 ml, 0.51 mmol) and (C6F5)2Zn.toluene (0.18 g, 0.37mmol) were heated in toluene for 2 h. Following removal of volatiles in vacuo, the residue was extracted into hexane (20 mL). The colourless solution was stored at -20 °C to afford colourless block shaped crystals in 60 % yield. C52H36F20N8Zn4 requires C 44.2, H 2.6, N 7.9; found: C 44.0, H 2.4, N 7.4; IR: 3130w, 1637m, 1602s, 1506s, 1347m, 1307s, 1 188w, 1 157w, 1 1 10s, 1051 s, 1032s, 952s, 876w, 801 m, 752s, 736m, 692s, 580w, 555w, 52ow, 502w, 494w. 1 H NMR (CDCI3, 300 MHz) delta: 6.89 - 7.55 (overlapping m, 20H, arylH), 3.80 (bs, 4H, NH), 3.14 - 3.17 (overlapping s, 12H, NHNMe).
Synthesis of Material B
1 , 1-Me2NNH2 (1.27 ml, 16.6 mmol) and Et2Zn (1 .88 ml, 18.3 mmol) were heated in toluene for 2 h. Following removal of volatiles in vacuo, the residue was extracted into acetonitrile (20 mL). The colourless solution was stored at -20 °C to afford colourless block shaped crystals in 65 % yield. 1 H NMR (CDCI3, 400 MHz) δ: 2.77 (m, 12H, N(CH3)2), 2.36 (m, 12H, N(GH3)2), 2.31 (s 1 H, N-H), 2.20 is 1 H, N-H), 2.08 (s 1 H, N- H), 2.03 (s 1 H, N-H), 1 .14 (overlapping m, 12H, Zn-CH2CH3), 20.17 (q, 2H, 2JHH 8.2 Hz, Zn-CH2), 20.22 (overlapping m,4H, 26 Zn-CH2), 20.29 (q, 2H, 2JHH 8.1 Hz, Zn- CH2). IR: v(NH):3149. Mass Spec (FAB+): 585 (M+ 2 Et).
Crystal data: Monoclinic; unit cell parameters a = 1 1 .5497(4), b = 14.6647(5), c = 16.2586(4) A; α = γ = 90, β = 101.473(2) °.
Synthesis of type V complexes. [(ArZn)4(OH)(NHNMe2)3] wherein Ar is a fluorinated aryl group, which may be selected from the formulae given above for type IV complexes.
General synthesis methods
Method a) The hydrazine (either 1 ,1 -Me2NNH2 or 1-Me, 1-PhNNH2 (1 .53 mmol), H20 (0.55 mmol) and Ar2Zn.toluene (2.03 mmol) were heated at 80 °C for 2 h in toluene (30 mL). Following removal of volatiles in vacuo, the residue was extracted into acetonitrile (20 mL). The colourless solution was stored at -20 °C to afford colourless block shaped crystals.
Method b) adapted from Mitzel et al. Chem Eur. J.. 2006, 592, which is incorporated herein by reference.
Ar2Zn. toluene (2.03 mmol) was added dropwise to a hexane (20 ml) solution of the hydrazine (either 1 , 1-Me2NNH2 or 1-Me, 1-PhNNH2 (1.50 mmol) at 0 °C. H20 (0.5 mmol) was added, and the reaction was stirred at ambient temperature for 12 h, and following removal of volatiles in vacuo, the residue was extracted into either hexane (20 ml) or acetonitrile (20 ml_). The colourless solution was stored at -20 °C to afford colourless block shaped crystals.
Synthesis of Material C
Me2NNH2 (0.12 ml, 1 .58 mmol), Et2Zn (0.21 ml, 2.05 mmol) and H20 (0.1 ml, 0.55 mmol) were heated in toluene for 2 h. Work-up as in method a) above (i.e. extraction into acetonitrile) afforded colourless prisms in 60 - 65 % yields.
1H NMR (400 MHz, CDCI3): δ = -0.26 (q, 2H; ZnCH2), 0.05 (q, 6H; ZnCH2), 1.12 (t, 3H; ZnCH2CH3), 1.16 (t, 9H; ZnCH2CH3), 2.08 (s, 3H; NH), 2.42 (s, 9H; N(CH3)2), 2.63 ppm (s, 9H; N(CH3)2). Mass spec (El): 543 (44) [M+ -C2H5]. IR: 3186 (NH), 3566 (OH).
Crystal data (from Mitzel et al): Orthorhombic; unit cell parameters a = 18.149(1 ), b = 9.409(1 ), c = 29.075(1 ) A; α = β = γ = 90 °.
Synthesis of Material D 1-Me, 1-PhNNH2 (0.18 ml, 1.53 mmol), (C6F5)2Zn.toluene (1 .0 g, 2.03 mmol) and H20 (0.1 ml, 0.55 mmol) were heated in toluene for 2 h. Work-up as in method a) above (i.e. extraction into acetonitrile) afforded colourless prisms in 70 - 75 yields. 1H NMR (CDCI3, 400 MHz) δ: 7.18 (m, 7H, arylH), 6.78 (m, 8H, arylH), 2.91 (s, 9H. HMe), 1.95 (overlapping signals, 12H, MeCN + NH). 19F NMR (acetone-d6, 282 MHz) δ: -140.47 (m, 8F, o-F), -156.35 (m, 4F, p-F), 164.28 (m, 8F, m-F). IR: 3468bw (OH), 3168w (NH), 1630w, 1599w, 1545w, 1535w, 1262s, 1096bs, 1021 bs, 871w, 801 s, 723w, 690w. [(C6F5Zn)4(OH)(NHNMe2)3].3MeCN requires C, 42.7; H, 2.6; N, 8.8 %. Found, C, 42.6, H, 2.6, N, 8.8 %.
Crystal data (1 MeCN solvate): Monoclinic; unit cell parameters a = 10.6416, b = 13.3998, c = 34.9423(4) A; α = γ = 90, β = 95.0878 °.
Crystal data (3MeCN solvate): Monoclinic; unit cell parameters a = 10.5846(4), b = 13.3665(5), c = 39.0083(4) A; α = γ = 90, β = 93.707(2) °. We also describe below the syntheses of a type VI MOF and a type V MOF in which the monodentate ligand attached to the zinc ion is a phenyl group having an o-CF3 substituent, namely [(o-CF3C6H4Zn)4(NHNMe2)4]. and [(o-
CF3C6H4Zn)4(OH)(NHNMe,Ph)3]:
[(o-CF3C6H4Zn)4(NHNMe2)4].toluene: Me2NNH2 (0.22 mL, 2.86 mmol) and (o- CF3C6H4)2Zn. toluene (1 g, 2.81 mmol) were heated under reflux in toluene (30 mL) for 4 h. Following removal of volatiles in vacuo, the residue was extracted into toluene (20 mL). Yield: 0.57 g, 70%, C37H44F12N8Zn4. C7H8 requires C 44.1 , H 4.5, N 9.6; found: C 44.0, H 4.3, N 9.3; IR: ΰ = 3178 cm"1 (N-H); 1H NMR (CDCI3, 400 MHz, 298 K): δ = 7.86 - 7.19 (m, 19 H, aryl H + aryl Ht0|Uene), 3.71 - 2.15 (overlapping m, 31 H, NCH3 + NH + tolueneCH3); 19F NMR (CDCI3, 282.4 MHz, 298 K): δ= -59.05, -60.31 (CF3).
[(o-CF3C6H4Zn)4(OH)(NHNMe,Ph)3]: Me,PhNNH2 (0.26 mL, 2.20 mmol ) was added to the toluene (20 mL) solution of (o-CF3C6H4)2Zn (1 g, 2.81 mmol) at 0°C. Water (0.018 mL, 1 mmol) was added dropwise, followed by heatd under reflux for 4 h. Following removal of volatiles in vacuo, the residue was taken up into toluene (20 mL) and stored at -20 °C to afford 4 as microcrystal. Yield: 0.30 g, 35%. C49H44Fi2N6OZn4 requires C 48.1 , H 3.6, N 6.9; found: C 48.3, H 3.5, N 6.9; IR: ΰ= 3444 (br, O-H) 3152 cm"1 (N-H); 1H NMR (CDCI3, 400 MHz, 298 K): δ = 7.47 - 6.54 (m, 31 H, aryl H + aryl HCF3), 3.04 (s, 9 H, NCH3), 2.76, 2.68 (2s, 3 H, NH); 13C{1H} NMR(CDCI3, 100.6 MHz, 298 K): δ = 138.72, 138.44, 137.41 , 136.45, 129.02, 128.55, 127.99, 126.81 , 125.17, 124.41 , 123.42, 123.37, 123.32 (aryl C + aryl CCFS), 54.28, 52.86 (NCH3), 18.77, 14.38 (CF3); 19F NMR (CDCI3, 282.4 MHz, 298 K): δ= -57.48, -59.1 1 , -59.70 (all CF3).
Synthesis of Zincpentafluorobenzene carboxylates
Synthesis of Material E (having nodes of formula (2) shown in Figure 1 ) 2,4,6-trimethylbenzoic acid (0.44 g, 2.68 mmol ) and (C6F5)2Zn.toluene (1 .1 g, 2.23 mmol) were heated at 80 °C for 12 h in toluene (30 mL). Following removal of volatiles in vacuo, the residue was extracted into hot toluene (20 mL). The colourless solution was stored at -20 °C to afford crystals of Material E. Yield: 0.72 g (75 %); C98H82F2oOi2Zn5 requires C, 54.5; H, 3.8 %. Found, C, 54.4, H, 3.8 %; 1H NMR (CDCI3, 400 MHz, 298 K): δ 7.20 - 6.49 (m, 17 H, aryl H + aryl Ht0|Uene), 2.31 (brs, 30 H, aryl Ho- Me), 2.26 (brs, 6 H, aryl Ho-Me), 1.93 (s, 6 H, aryl HMe + aryl Ht0|Uene), 1.19 (brs, 15 H, aryl HMe); 19F NMR (CDCI3, 282.4 MHz, 298 K): δ -1 16.1 (d, 3JFF = 21 .3 Hz, 8 F, o-F), - 159.6 (t, 3JFF = 19.4 Hz, 4 F, p-F,), -164.7 (m, 8 F, m-F); IR (Nujol mull): ΰ 1617 (br), 1566 (s), 1505 (vs), 1263 (s), 1 182 (s), 1 1 10 (s), 1057 (s), 954 (vs), 848 (w), 791 (w), 735 (s) cm"1.
Crystal data (2-toluene solvate): Triclinic; unit cell parameters a = 14.3253(9), b = 16.3138(10), c = 22.7460(14) A; a = 106.5017(10), β = 98.0313(10), γ = 1 10.5396(10)
0 Synthesis of Material F (having nodes of formula (1 ) shown in Figure 1 )
3-chlorobenzoic acid (0.38 g, 2.43 mmol ) and (C6F5)2Zn.toluene (1 .0 g, 2.03 mmol) were heated at 80 °C for 12 h in toluene (30 mL). Following removal of volatiles in vacuo, the residue was extracted into hot toluene (20 mL). The colourless solution was stored at -20 °C to afford colourless block shaped crystals of Material F. Yield: 0.65 g (80 %); C66H24Cl6F2oOi2Zn5 requires C, 41.1 ; H, 1.3 %. Found, C, 41 .4, H, 1 .3 %; 1H NMR (CDCI3, 400 MHz, 298 K): δ 7.98 - 7.04 (m, aryl H); 13C{1H} NMR(CDCI3, 100.6 MHz, 298 K): δ 133.2, 131 .6, 131 .4, 131.2, 130.9, 130.0, 129.5, 125.3, 125.1 (s, aryl C); 19F NMR (CDCI3, 282.4 MHz, 298 K): δ -139.9 (m, 8 F, o-F), -154.8 (triplet of triplet, 3JFF = 17.7 Hz, 4JFF = 2.5 Hz, 4 F, p-F,), -163.2 (m, 8 F, m-F); IR (Nujol mull) ΰ 1629 (vs), 1563 (s), 1506 (vs), 1265 (s), 1 158 (s), 1072 (s), 1055 (s), 954 (vs), 863 (w), 795 (w), 754 (s) cm"1.
Crystal data (1 ½ toluene solvate): Monoclinic; unit cell parameters a = 23.31 1 (2), b = 13.5883(12), c = 25.442(2) A; α = γ = 90, β = 102.7617(13) °.
A further material (not used in the screening studies below) was synthesised and characterised. This is a material having nodes of formula (3) shown in Figure 1 :
Compound 3: 3-dimethylaminobenzoic acid (0.23 g, 1.38 mmol) and (C6F5)2Zn. toluene (1.1 g, 2.23 mmol) were heated under reflux in toluene (30 mL) for 4 h. Following removal of volatiles in vacuo, the residue was extracted into toluene (20 mL). The yellowish solution as allowed to stand at -20 °C, affording crystals of a material having nodes of formula (3) of Figure 1 . Yield: 0.23 g; 1 H NMR (CDCI3, 400 MHz, 298 K): δ 7.45 - 7.08 (overlapping m, 4 H, aryl H), 2.32 (s, 6 H, N(CH3)2); 19F NMR (CDCI3, 282.4 MHz, 298 K): δ -1 19.9 (m, o-F), -139.9 (m, o-F), -154.8 (triplet of triplet, 3JFF = 20.1 Hz, 4JFF = 1.7 Hz, p-F,), -156.4 (t, 3JFF = 20.2 Hz, p-F), -162.9 (m, m-F), -163.3 (m, m-F) ); IR (Nujol mull): ΰ 1533 (s), 1509 (s), 1262 (s), 1 178 (s), 1 1 10 (w), 1095 (w), 1072 (w), 1054 (w), 1021 (w), 954 (s), 801 (s) cm"1.
Synthesis of Material G a) Inorganic linkers.
General prep. To [(RZn)4(OH)(NHNMe2)3] (0.76 mmol) in hexane at -78 °C was added ferf-butyllithium (0.77 mmol), and the system was slowly allowed to warm to ambient temperature and stirred for 6 h. Following removal of volatiles in vacuo, the residue was extracted into either hexane (20 ml). The filtered colourless solution was stored at -20 °C to afford colourless block shaped crystals.
R can be any alkyl or aryl including the previously highlighted fluorinated aryls.
Example: To [(EtZn)4(OH)(NHNMe2)3] (1 .0 g, 1.75 mmol) in hexane at -78 °C was added ferf-butyllithium ( 1.06 ml, 1 .7M, 1 .80 mmol), and the system was slowly allowed to warm to ambient temperature and stirred for 6 h. Following removal of volatiles in vacuo, the residue was extracted into either hexane (20 ml). The colourless solution was stored at -20 °C to afford colourless block shaped crystals in 40 - 45 % yield. 1H NMR (CDCIs, 400 MHz) δ: 2.79 - 2.42 (overlapping m, 21 H NMe2 + NH), 1.22 (m, 12H, ZnCH2CH3), 0.55 (m, 8H, ZnCH2CH3). IR: 3185w, 1636m, 1607w, 1532w, 1503s, 1340m, 1260s, 1 170w, 1097s, 1068s, 1050s, 1021 s, 947s, 847m, 809s, 734w, 698w. [(EtZn)4(OLi)(NHNMe2)3]2 requires C, 29.1 ; H, 7.2; N, 14.5 %. Found, C, 28.9, H, 7.0, N, 14.5 %.
Crystal data: Triclinic; unit cell parameters a = 10.1483(3), b = 10.8241 (3), c = 13.5695(5) A; a = 1 1 1.0290(18), β = 91.4522(17), γ = 1 17.6991 (19) °.
A diagram of the lithium ions acting as linking species between adjacent nodes in Material G is shown in Figure 3. b) We also describe below the synthesis for a material in which the zinc-containing nodes are linked by organic linkers, in this case, terephthalic acid:
Example: Et2Zn (8 ml_, 8 mmol; 1.0 M solution in hexanes) was added to the suspension of dried terephthalic acid (0.33 g, 2.0 mmol) in toluene (30 ml_). The reaction mixture was then refluxed for 1 h and followed by cooling to room temperature and addition of Me2NNH2 (0.61 mL, 8.0 mmol). The reaction mixture was refluxed for another 4 h. After removal of the solvent under reduced pressure, the resulting residue was filtered with warm acetonitrile (30 mL), affording small block shaped crystals at ambient temperature. IR: 3170w, 1638w, 1559m, 1261 s, 1094bs, 1048s, 1010s, 882w, 801 s, 722w, 61 Ow.
Crystal data: Monoclinic; unit cell parameters a = 10.746, b = 20.427, c = 16.763 A; a = γ = 90, β = 105.472 °. We also describe below the synthesis of two MOF materials having nodes containing Zn-CI species:
Synthesis of a material of the formula [(EtZn)3(ZnCI)(NHNMe2)4]: fBuLi (1.5 mL, 2.55 mmol; 1.7 M in solution in pentane) was added to the n-hexane (20 mL) solution of [(EtZn)4(NHNMe2)4] (1 .5 g, 2.44 mmol) at -78°C and stir for 3 h. MeAICI2 (1.275 mmol) was added slowly to this mixture and stir for overnight at ambient temperature. The volatiles were removed under vacuum and the residue was filtered using n-hexane (20 mL). The clear, colourless filtrate, when stored at -20 °C, afforded colourless crystals. Yield 40 - 45 %. C14H39CIN8Zn4 requires C 27.3, H 6.4, N 18.2; found: C 26.9, H 6.3, N 18.3; IR: 3176w, 2360w, 2341w, 1558w, 1262s, 1 160s, 1090bs, 1040s, 991 s, 951w, 870m, 819bs, 661 m, 599m, 569m, 482m, 459w.
Crystal data: Monoclinic; unit cell parameters a = 17.7876, b = 1 1.0855, c = 14.1353 A; α = γ = 90, β = 108.948 °.
Synthesis of a material of the formula [(o-CF3C6H4Zn)3(ZnCI)(OH)(NHNMe2)3]:
The same procedure was used as for the synthesis of [(EtZn)3(ZnCI)(NHNMe2) ], but using [(o-CF3C6H4Zn)4(NHNMe2)4] (1.0 g, 0.92 mmol), fBuLi (0.53 ml, !.7M, 0.90 mmol), MeAICI2 (0.53 ml, 1.7M, 0.90 mmol) and H20 (0.004 ml, 2.22 mmol) affording the product on crystallisation from acetonitrile (20 ml) at 0 °C. Yield 30 %. C32H41.5oCIF9N8.5oOZn4 (MeCN solvate) requires C, 37.3; H, 4.1 ; N, 1 1.6 %. Found: C, 37.7; H, 4.2, N, 1 1.5 %. IR: 3321 bs, 2724w, 2359w, 2342w, 2181w, 1560bs, 1323m, 1261 s, 1244s, 1 174s, 1097m, 1025m, 962m, 921w, 875w, 801 m, 722m, 668w, 618m, 521w.476m.
Crystal data (2½MeCN solvate): Triclinic; unit cell parameters a = 1 1 .9780(6), b = 1 1.9838(6), c = 16.281 1 (9) A; a = 74.2469(7), β = 81 .8956(8), γ = 68.5308(7) °.
Screening method
The isothermal adsorptions of hydrogen on porous materials were compared as a function of pressure (P). The hydrogen uptake method used for this study was as described in the reference A. Anson, M. Benham, J. Jagiello, M.A. Callejas, A.M. Benito, W.K. Maser, Z. Zuttel and M.T. Marinez, Nanotech. 2004, 15, 1503, which is incorporated herein by reference.. The hydrogen sorption was measured from 0 - 10 bar at the isothermal temperature of 85K for Material C (V (R = Et, R - Me)) and 90K for the other MOFs, using our gas soprtion analyser, IGA-003 (Hiden Isochema, Warringtion, UK). Static mode was applied for all the measurements. The bouyancy effect was corrected according to the hydrogen and sample densities calculated from the IGA software. The theoretical skeleton densities of MOFs were calculated from crystallography structures and the experimental densities of MOFs were refined from the sample mass and volume estimated from the IGA software, as shown in Table 1 .
The hydrogen adsorption isotherms of Material B (IV (R = Et, R'= Me)), Material C (V (R = Et, R'= Me)), Material G (XII), Material D (V (R = C6F5, R'= Ph)) and Material A (IV (R = C6F5, R'= Ph)) at 90K are compared to that of MOF-5 in Figure 4. The structures of these MOFs have some similarities. The subsequent results show H2 uptakes of V (R = Et, R'= Me) and IV (R = Et, R'= Me) are 0.043 wt% (1 bar) and 0.070 wt% (9bar), respectively, which is lower than that of MOF-5. XII is formed by doping Li of V (R = Et, R' = Me), and this results in increased H2 uptake, attaining 0.131 % under 9 bar, much higher than that of parent V (R = Et, R'= Me) and IV (R = Et, R'= Me) and approaching that of MOF-5. For V (R = C6F5, R'= Ph), the H2 uptake is increased to 0.384 wt% at 9 bar, whilst for IV (R = C6F5, R'= Ph) the H2 uptake is further increased to 0.968 wt% at 9 bar, the latter being the best material for hydrogen storage among the series reported herein.
The hydrogen adsorption isotherms of Material E (IX (Ar = Mesityl)) and Material F (IX (Ar = 2-CIC6H4) at 90K are compared to that of MOF-5 in Figure 5. The hydrogen adsorption experiment shows that the absorption amount for IX (Ar = 2-CIC6H4) (0.229 wt%, 9bar) is higher than that of MOF-5 (B), but the hydrogen uptake of IX (Ar = Mesityl) (0.105 wt%, 9bar) is less than that of MOF-5 (B).
The results of the above studies are given in Table I below.
Table 1 Maximum hydrogen uptakes of species in wt % at 9 bar (IGA-003, static) and
associated densities.
H2 uptake Temperature Pressure Calculated Measured
Materials
(wt%) (K) (bar) Density (g/cm3) Density (g/cm3)
MOF-5 0.140 90 9 1.92 1 .09
IV (R = C6F5,
R' = Ph) - 0.968 90 9 1.89 0.42
Material A
IV (R = Et, R' =
Me)- Material 0.070 90 9 1.53 1 .28
B
V (R = Et, R'=
Me)- Material 0.043 85 9 1.51 C6 0.80
C
V ((R = C6F5,
R' = Ph)- 0.384 90 9 1.74 0.44
Material D
IX (Ar = 2,4,6- Me3C6H2)- 0.105 90 9 1.56 1 .15
Material E
IX (Ar = 2- CIC6H4)- 0.229 90 9 1.75 0.82
Material F
XII - Material
0.131 90 9 1.60 0.80
G
Example 2
Synthesis of a diphenylqlvcine complex, [(o-CF^CfiH^Zn diphenylqlvcine^l
Figure imgf000048_0001
R = o-CF3C6H4
o-CF3C6H4)2Zn]* (2.00 g, 4.06 mmol) and 2,2 -diphenylglycine (0.68 g, 2.03 mmol) were refluxed for 12 h. Following removal of volatiles in-vacuo, the residue was extracted into acetonitrile (20 ml). Prolonged standing at 0 °C afforded colourless crystalline product in 77 % yield.
* [(o-CF3Ce 4)27.n]* prepared by the method of M.H. Chisholm et al - see Inorg. Chem. 2005, 44, 4777-4785.
IR: 3306w, 3242w, 3175w, 1661 s, 1644s, 1608s, 1493w, 1343s, 1262s, 1 195w, 1 160m, 1 131 m, 1079s, 1026s, 803s, 773w, 760w, 744w, 694s, 673m, 615w.
19F NMR (DMSO-de) δ: s, -61.09.
Crystals of the compound were grown from a saturated solution of acetonitrile on prolonged standing at 0 °C. A crystal was mounted in oil on a glass fibre and fixed in the cold stream.
Data was collected at the Department of Chemistry, Loughborough University using monochromated X-radiation (λ = 0.71073 A), and employing a Bruker Apex 2 CCD diffractometer (co rotation with narrow frames). The structure was determined by the direct methods routine in the SHELXS program, [G.M. Sheldrick, Acta Crystalogr., Sect. A: Found: Crystallogr., 2008, 64, 1 12-122] and refined by full-matrix least squares methods on F2, in SHELXL. [G.M. Sheldrick, Acta Crystalogr., Sect. A: Found: Crystallogr., 2008, 64, 1 12-122] There is merohedrally twinned via the twinlaw 010 100 00-1 , major component 54(2) %. It is also racemically twinned: Flack parameter 0.472(2). 'Detwinning' of reflection data in XPREP allow for structure refinement.
Crystal data:
Formula = C84H56F12N408Zn4
Formula weight = 1738.80
Crystal system = tetragonal
Space group = I bar 4
a = 18.401 (5)
b = 18.401 (5)
c = 1 1 .347(3)
a = 90 β = 90
γ = 90
Cell volume = 3842.1 (18)
Calculated density = 1.503 g/cm3
Absorption coefficient μ = 1.322 mm"1
Reflections collected = 16703.
Independent reflections = 3988 (Rint = 0.0642).
Final R indices [F2 > 2σ] = R1 0.0594, wR2 0.1426.
R indices (all data) = R1 0.0612, wR2 0.1447.
Goodness of fit on F2 = 1.097.
The crystal structure of this compound is shown in Figure 6.
Example 3
Synthesis of a novel compound that can be used in the synthesis of the materials of the present invention:
Figure imgf000050_0001
The new tetra-aryl fluorinated compound above was isolated in low yield from the following reaction:
Me,PhNNH2 (0.96 ml, 8.19 mmol), LiC6F5 (2.85 g, 16.38 mmol) and ZnCI2 (1.1 1 g, 8.14 mmol) were stirred in diethylether for 12 h. Following removal of volatiles in-vacuo, the residue was extracted into acetonitrile (20 ml). Prolonged standing at 0 °C afforded the product as colourless prisms in 8 % yield. Small crystals of the compound were grown from a saturated solution of acetonitrile on prolonged standing at 0 °C. A crystal was mounted in oil on a glass fibre and fixed in the cold stream. Data was collected at the Daresbury Laboratory SRS (Synchrotron Radiation Service) Station 16.2 using silicon-1 1 1-monochromated X-radiation (λ = 0.8457 A), and employing an Apex 2 CCD diffractometer (co rotation with narrow frames).
The structure was determined by the direct methods routine in the SHELXS program, [G.M. Sheldrick, Acta Crystalogr., Sect. A: Found: Crystallogr., 2008, 64, 1 12-122] and refined by full-matrix least squares methods on F2, in SHELXL. [G.M. Sheldrick, Acta Crystalogr, Sect. A: Found: Crystallogr, 2008, 64, 1 12-122] There is no disorder in the structure.
Crystal data:
Formula = C24BrF17
Formula weight = 691.5
Crystal system = triclinic
Space group = P bar 1
a = 6.1229(12)
b = 12.702(3)
c = 14.124(3)
a = 101 .991 (2)
β = 93.727(2)
γ = 90.437(2)
Cell volume = 1072.0(4)
Calculated density = 2.141 g/cm3
Absorption coefficient μ = 3.187 mm"1
Reflections collected = 7933.
Independent reflections = 4375 (Rint = 0.0410).
Final R indices [F2 > 2σ] = R1 0.0734, wR2 0.1739.
R indices (all data) = R1 0.1048, wR2 0.1958.
Goodness of fit on F2 = 1.040.
The crystal structure of this compound is shown in Figure 7. Example 4
It is proposed that the methodology employed to generate nodes of the types IV - VI, as illustrated above in Example 1 , will be readily extendable to the related nonafluorobiphenyl zinc containing clusters/nodes.
The syntheses of the required related nonafluorobiphenyl zinc are available in the literature. In particular, the 2-nonafluorobiphenyl zinc has been prepared as its toluene solvate from ethylzinc chloride and the lithium salt of 2-bromononafluorobiphenyl (see Bochmann et al, Organometallics, 2006, 25, 331 1 -3313). In the case of the 4- nonafluorobiphenyl zinc complex, this is available as the diethylether solvate via the reaction of zinc chloride and two equivalents of the Grignard reagent 4- nonafluorobiphenylmagnesium bromide (see Lancaster et al., Dalton Trans., 2009, 1593-1601 ).
Reaction of either of these nonafluorobiphenyl zinc reagents (2.03 mmol) with hydrazine (either 1 , 1-Me2NNH2 or Me,PhNNH2) (1.85 mmol) in refluxing toluene for 4 h, followed by removal of volatiles in-vacuo, and extraction of the residue into acetonitrile will afford type IV nodes upon crystallization at -20 °C. The introduction of water (0.5 mmol) at the initial stage and the use of only 1 .53 mmol of hydrazine will lead to type V nodes.
In an aspect, the present application relates to the subject matter defined in the following numbered paragraphs:
1. A material for storing hydrogen, the material comprising a metal organic framework having a plurality of nodes, each node comprising:
a plurality of metal ions, wherein at least one of the metal ions is a zinc ion;
a plurality of linking ligands, wherein each ligand is coordinated to two or more of the metal ions;
a plurality of monodentate ligands, wherein each of the monodentate ligands is coordinated to one of the metal ions, and at least one of the monodentate ligands is a halide or a halogenated species.
2. A material according to paragraph 1 , wherein the halogenated species is a hydrocarbon group substituted with one or more halogens.
3. A material according to paragraph 2, wherein the hydrocarbon group is selected from a halogenated aryl and aryl having one or more halogenated hydrocarbon substituents. 4. A material according to any one of paragraphs 1 to 3, wherein the halogenated species is selected from a species of any of the following formulae:
Figure imgf000053_0001
wherein n is 1 to 5, and F3, F4, and F5 indicates, respectively, that three, four or five fluorines are attached to a ring.
5. A material according to any one of the preceding paragraphs, wherein at least one of the linking ligands in the node is a substituted hydrazide ligand or a carboxylate ligand. 6. A material according to paragraph 5, wherein the substituted hydrazide ligand is a ligand of the formula (NR1 R2-NR3), wherein R1 , R2 and R3 are each independently selected from H and an optionally substituted hydrocarbon group, and at least one of the R1 , R2 and R3 is an optionally substituted hydrocarbon group.
7. A material according to paragraph 6, wherein R1 is alkyl or aryl, R2 is alkyl or aryl and R3 is H. 8. A material according to any one of the preceding paragraphs, wherein the node comprises four or five zinc ions.
9. A material according to any one of the preceding paragraphs, wherein a linker species links adjacent nodes.
10. A material according to any one of the preceding paragraphs, wherein the linker species is a lithium ion.
1 1. A material according to any one of paragraphs 1 to 9, wherein the linker species is a polycarboxylate.
12. A material according to any one of the preceding paragraphs, wherein the node is selected from a node of the formula: [(RZn)4(NR1 R2-NR3)4], [(RZn)4(OH)(NR1 R2- NR3)3], [(RZn)4(OH)2(NR1 R2-NR3)2], [(RZn)3(CIZn)(OH)(NR1 R2-NR3)3] and [(RZn4)Zn(Lc)6],
wherein R is a halogenated hydrocarbon
R1 , R2 and R3 are each independently selected from H and an optionally substituted hydrocarbon group, at least one of R1 , R2 and R3 is an optionally substituted hydrocarbon group, and
Lc is an optionally substituted benzoic acid group, which may be in free form or carboxylate form.
13. A material according to any of the preceding paragraphs, wherein the node is selected from the formula IV, V and VI below:
Figure imgf000055_0001
wherein each R is a monodentate ligand, and at least one R in each of formula IV, V and VI is independently a halide or a halogenated species, and each R' is independently alkyl or aryl.
14. A method for storing hydrogen, the method comprising providing the material according to any one of paragraphs 1 to 13, and contacting the material with hydrogen.
15. A method according to paragraph 14, wherein the hydrogen is contacted with the material at a pressure of at least 5 bar.
16. A method according to paragraph 15, wherein the hydrogen is contacted with the material at a pressure of at least 10 bar.
17. A method for storing hydrogen, the method comprising providing a material comprising a metal organic framework having a plurality of zinc-containing nodes, wherein adjacent nodes are linked by an alkali metal ion, and
contacting the material with hydrogen.
18. A material comprising a metal organic framework comprising a plurality of zinc- containing nodes, each zinc-containing node containing one or more species selected from O2" and OH" species, wherein an alkali metal ion links adjacent nodes.
19. A material according to paragraph 18, the material having the formula [(ZnRa)4(NR1 R2-NR3)3(OLi)]2,
wherein Ra is a monodentate ligand selected from a halide and an optionally substituted hydrocarbon, wherein R1 , R2 and R3 are each independently selected from H and an optionally substituted hydrocarbon group, and at least one of the R1 , R2 and R3 is an optionally substituted hydrocarbon group.

Claims

1. A material for storing hydrogen, the material comprising a metal organic framework having a plurality of nodes, each node comprising:
a plurality of metal ions, wherein at least one of the metal ions is a zinc ion;
a plurality of linking ligands, wherein each ligand is coordinated to two or more of the metal ions;
a plurality of monodentate ligands, wherein each of the monodentate ligands is coordinated to one of the metal ions, and at least one of the monodentate ligands is a halide or a halogenated species.
2. A material according to claim 1 , wherein the halogenated species is a hydrocarbon group substituted with one or more halogens. 3. A material according to claim 2, wherein the hydrocarbon group is selected from a halogenated aryl and aryl having one or more halogenated hydrocarbon substituents.
4. A material according to any one of claims 1 to 3, wherein the halogenated species is selected from a species of any of the following formulae:
Figure imgf000057_0001
to 5, -Z is a group of the formula
Figure imgf000057_0002
, wherein m is 1 to 5.
5. A material according to any one of claims 1 to 3, wherein the halogenated species is selected from a species of any of the following formulae:
Figure imgf000058_0001
wherein n is 1 to 5, and F3, F4, and F5 indicates, respectively, that three, four or five fluorines are attached to a ring. 6. A material according to any one of claims 1 to 3, wherein the halogenated species is selected from a species of any of the following formulae:
p of the formula
Figure imgf000058_0002
, wherein m is 1 to 5
7. A material according to any one of the preceding claims, wherein at least one of the linking ligands in the node is a substituted hydrazide ligand or a carboxylate ligand. 8. A material according to claim 7, wherein the substituted hydrazide ligand is a ligand of the formula (NR1 R2-NR3), wherein R1 , R2 and R3 are each independently selected from H and an optionally substituted hydrocarbon group, and at least one of the R1 , R2 and R3 is an optionally substituted hydrocarbon group.
9. A material according to claim 8, wherein R1 is alkyl or aryl, R2 is alkyl or aryl and R3 is H.
10. A material according to claim 7, wherein the carboxylate ligand is a ligand having a carboxylate group and an amine group.
1 1. A material according to claim 10, the carboxylate ligand is a ligand of the formula:
Figure imgf000059_0001
wherein R4 and R5 are independently selected from H and an optionally substituted hydrocarbon group.
12. A material according to claim 1 1 , wherein R4 and R5 are both an optionally substituted aryl group.
13. A material according to any one of the preceding claims, wherein the node comprises four or five zinc ions.
14. A material according to any one of the preceding claims, wherein a linker species links adjacent nodes. 15. A material according to any one of the preceding claims, wherein the linker species is a lithium ion.
16. A material according to claim 14, wherein the linker species is a polycarboxylate. 17. A material according to any one of claims 1 to 9 and 13, wherein the node is selected from a node of the formula: [(RZn)4(NR1 R2-NR3)4], [(RZn)4(OH)(NR1 R2- NR3)3], [(RZn)4(OH)2(NR1 R2-NR3)2], [(RZn)3(CIZn)(OH)(NR1 R2-NR3)3] and [(RZn4)Zn(Lc)6],
wherein R is a halogenated hydrocarbon
R1 , R2 and R3 are each independently selected from H and an optionally substituted hydrocarbon group, at least one of R1 , R2 and R3 is an optionally substituted hydrocarbon group, and Lc is an optionally substituted benzoic acid group, which may be in free form or carboxylate form.
18. A material according to any one of claims 1 to 9 and 13, wherein the node selected from the formula IV, V and VI below:
Figure imgf000060_0001
VI wherein each R is a monodentate ligand, and at least one R in each of formula IV, V and VI is independently a halide or a halogenated species, and each R' is independently alkyl or aryl.
19. A material according to claim 10 or 1 1 , wherein the node is of the formula [(RZn)4(Q)4)], wherein R is selected from halogenated aryl and aryl having one or more halogenated hydrocarbon substituents and Q is a ligand of the formula:
Figure imgf000060_0002
wherein R4 and R5 are independently selected from H and an optionally substituted hydrocarbon group.
20. A material according to claim 19, wherein R4 and R5 are both an optionally substituted aryl group. 21. A method for storing hydrogen, the method comprising providing the material according to any one of claims 1 to 20, and contacting the material with hydrogen.
22. A method according to claim 21 , wherein the hydrogen is contacted with the material at a pressure of at least 5 bar.
23. A method according to claim 22, wherein the hydrogen is contacted with the material at a pressure of at least 10 bar.
24. A method for storing hydrogen, the method comprising providing a material comprising a metal organic framework having a plurality of zinc-containing nodes, wherein adjacent nodes are linked by an alkali metal ion, and
contacting the material with hydrogen.
25. A material comprising a metal organic framework comprising a plurality of zinc- containing nodes, each zinc-containing node containing one or more species selected from O2" and OH" species, wherein an alkali metal ion links adjacent nodes.
26. A material according to claim 25, the material having the formula [(ZnRa)4(NR1 R2-NR3)3(OLi)]2,
wherein Ra is a monodentate ligand selected from a halide and an optionally substituted hydrocarbon,
wherein R1 , R2 and R3 are each independently selected from H and an optionally substituted hydrocarbon group, and at least one of the R1 , R2 and R3 is an optionally substituted hydrocarbon group.
A compound of the formula
Figure imgf000061_0001
wherein X' is a halogen selected from bromine or iodine,
-Z is a group of the formula
Figure imgf000061_0002
, wherein m is 1 to 5. A compound according to claim 27, wherein the compound is of the formula
Figure imgf000062_0001
and n is 3 or more.
29. A compound according to claim 28, wherein n is 3 and m is 5.
30. A compound according to any one of claims 27 to 29, wherein the compound is of the formula
Figure imgf000062_0002
, wherein X' is a halogen selected from bromine or iodine and R' is C6F5.
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