Multivariate metal-organic frameworks

Abstract

Disclosed is a multivariate metal organic framework (MOF) comprising metal cations and organic linkers, wherein the organic linkers comprise 5-aminoisophthalic acid or an anion thereof (AIP) and one or more non-AIP organic linkers. Also disclosed is a method of enhancing the adsorptive properties of a MOF by utilising a multivariate MOF strategy. Also disclosed is a method and a system for separating carbon dioxide from a mixture of gases, comprising contacting the mixture of gases with a sorbent comprising the multivariate MOF. The multivariate MOF may be a component of a composite such as polymeric materials, resins, biomolecules, clays, ceramics, carbon, inorganic oxides or a support material.

Description

[0001] MULTIVARIATE METAL-ORGANIC FRAMEWORKS

[0002] FIELD

[0003] This invention relates to multivariate metal organic frameworks, and more specifically to multivariate metal organic frameworks for adsorbing carbon dioxide.

[0004] BACKGROUND

[0005] Metal-organic frameworks (MOFs) composed of metal ions or clusters and organic linkers are an important class of porous materials. MOFs may have regular repeating extended structures, which can be understood as being made up of notional secondary building unit (SBU) subunits. SBUs can be discrete metal-ligand clusters or can be repeating metalligand chains (sometimes referred to as infinite SBUs or SBU rods).

[0006] Small molecules can occupy the pores of MOFs. Thus, MOFs can be used to capture, store, separate and deliver small molecules.

[0007] One important feature of MOFs is that their structures can be systematically tuned by the use of particular metal ions or particular organic linkers. Unlike traditional porous materials (such as zeolites, silica, and activated carbons), the designer is able to have fine control over the structures, pore size, and functionalities of MOFs. Suitable porous materials for separations are those with judiciously designed pore sizes and geometries which are able to adsorb specific types of molecules while completely excluding others. In addition to pore geometry, MOFs may be designed to selectively adsorb particular gases based on other characteristics, such as functional groups and particular electrostatic characteristics (e.g. polarizability, polarity and dipole) within the pore.

[0008] The selective adsorption of gases by MOFs makes them an exciting prospect for addressing the causes of the greenhouse effect and climate change. The amount of carbon dioxide in the atmosphere continues to rise, which underlies the greenhouse gas effect, global atmospheric and oceanic temperature increases, and ocean acidification. Reducing the amount of carbon dioxide released to the environment by industry, or capturing and storing carbon dioxide directly from the environment, is a way to at least partially address these problems,

[0009] Reducing carbon dioxide is also important in industrial processes. For example, reducing levels of carbon dioxide in natural gas improves its ability to be transported and lessens the corrosion of equipment and pipelines. Also, carbon dioxide may need to be removed from syngas before it can be used as feedstock. Further, carbon dioxide often needs to be scrubbed from flue gases before they are released to the atmosphere. Most MOFs comprise just one kind of organic linker and one kind of metal ion. Mixed component MOFs are also known. These MOFs comprise more than one type of organic linker or more than one type of metal ion. If the multiple components are arranged in order and each component occupies a specific position in the framework then long-range periodicity is maintained. Alternatively, the multiple components can alternate randomly in the framework and there is no long-range periodicity. As used herein, and unless the context clearly requires otherwise, the term 'multivariate MOFs' encompasses mixed component MOFs both with long range periodicity and without long range periodicity.

[0010] In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally to provide a context for discussing features of the invention. Unless specifically stated otherwise, reference to such external documents or sources of information is not to be construed as an admission that such documents or such sources of information, in any jurisdiction, are prior art or form part of the common general knowledge in the art.

[0011] SUMMARY OF THE INVENTION

[0012] This invention may be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more said parts, elements or features. Where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually described.

[0013] The term 'comprising' as used in this specification and claims means 'consisting at least in part of'. When interpreting statements in this specification and claims that include the term 'comprising', other features besides those prefaced by this term can also be present. Related terms such as 'comprise' and 'comprised' are to be interpreted in a similar manner.

[0014] As used herein, "hydrogen" is intended to encompass isotopes of hydrogen, including deuterium. "Hydrocarbon" means a saturated or unsaturated organic compound comprising a linear, branched or cyclic carbon structure, which may be functionalised or non-functionalised.

[0015] The term "alkyl" means any saturated non-functionalised hydrocarbon radical and is intended to include both straight-chain and branched-chain alkyl groups. Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, / so-propyl, n-butyl, isobutyl, sec-butyl, t-butyl, n-pentyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 2,2- dimethylpropyl, 1-ethylpropyl, 2-ethylpropyl, n-hexyl, and l-methyl-2-ethylpropyl. The term "alkenyl" means any non-functionalised hydrocarbon radical having at least one double bond, and is intended to include both straight- and branched-chain alkenyl groups. Examples of alkenyl groups include, but are not limited to, ethenyl, n-propenyl, isopropenyl, n-butenyl, / so-butenyl, sec-butenyl, t-butenyl, n-pentenyl, 1,1- dimethylpropenyl, 1,2-dimethylpropenyl, 2,2-dimethylpropenyl, 1-ethylpropenyl, 2- ethylpropenyl, n-hexenyl, and l-methyl-2-ethylpropenyl.

[0016] The term "alkynyl" means any non-functionalised hydrocarbon radical having at least one triple bond, and is intended to include both straight- and branched-chain alkynyl groups. Examples of alkynyl groups include, but are not limited to, ethynyl, n-propynyl, iso- propynyl, n-butynyl, / so-butynyl, sec-butynyl, t-butynyl, n-pentynyl, 1,1- dimethylpropynyl, 1,2-dimethylpropynyl, 2,2-dimethylpropynyl, 1-ethylpropynyl, 2- ethylpropynyl, n-hexynyl, and l-methyl-2-ethylpropynyl.

[0017] The term "alkylene" means a diradical corresponding to an alkyl group. Examples of alkylene groups include, but are not limited to, methylene and ethylene.

[0018] The term "cycloalkyl" means a saturated or partially saturated non-aromatic carbocyclic group, having preferably from 3 to 8 ring carbon atoms. Examples of cycloalkyl groups include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl.

[0019] The term "heterocycloalkyl" means a cycloalkyl group where one or more of the ring carbon atoms is replaced with one or more heteroatoms, e.g. nitrogen, oxygen or sulfur. Examples of heterocycloalkyl groups include, but are not limited to, pyrrolidinyl, pyrrolinyl, pyrazolidinyl, aziridinyl, thiiranyl, 1,2-dithietanyl, morpholinyl, furanyl, pyranyl, thiophenyl, isoxazolyl, furazanyl, tetrahydrofuranyl, thietanyl, piperidinyl, azetidinyl, oxiranyl, epoxide, and thia cyclo hexyl.

[0020] The term "alkoxy" means an alkyl group singular bonded to an oxygen atom. Examples of alkoxy groups include, but are not limited to, methoxy, ethoxy, propoxy, n-butoxy, isobutoxy, sec- butoxy, and t- butoxy,

[0021] The term "aryl" means an aromatic radical. Examples include monocyclic groups as well as fused groups such as bicyclic groups and tricyclic groups. Examples include, but are not limited to, phenyl, indenyl, 1-naphthyl, 2-naphthyl, azulenyl, heptalenyl, biphenyl, indacenyl, acenaphthyl, fluorenyl, phenalenyl, phenanthrenyl, anthracenyl, cyclopentacyclooctenyl, and benzocyclooctenyl.

[0022] The term "heteroaryl" means a heterocyclic aromatic (heteroaromatic) radical. Examples include monocyclic groups as well as fused groups such as bicyclic groups and tricyclic groups. Examples include, but are not limited to, pyridyl, pyrrolyl, pyridazinyl, pyrimidinyl, pyrazinyl, triazolyl, tetrazolyl, benzotriazolyl, pyrazolyl, imidazolyl, benzimidazolyl, indolyl, isoindolyl, indolizinyl, purinyl, indazolyl, furyl, pyranyl, benzofuryl, isobenzofuryl, thienyl, thiazolyl, isothiazolyl, benzothiazolyl, oxazolyl, and isoxazolyl.

[0023] The term "aralkyl" means an aryl group which is attached to an alkylene moiety, where aryl and alkylene are as defined above. Examples include benzyl group.

[0024] It is intended that reference to a range of numbers disclosed herein (for example, 1 to 10) also incorporates reference to all rational numbers within that range and any range of rational numbers within that range (for example, 1 to 6, 1.5 to 5.5 and 3.1 to 10). Therefore, all sub-ranges of all ranges expressly disclosed herein are hereby expressly disclosed.

[0025] As used herein the term '(s)' following a noun means the plural and / or singular form of that noun. As used herein the term 'and / or' means 'and' or 'or', or where the context allows, both.

[0026] In one aspect, there is provided a multivariate metal organic framework (MOF) comprising metal cations and organic linkers, wherein the organic linkers comprise 5-aminoisophthalic acid or an anion thereof (AIP) and one or more non-AIP organic linkers.

[0027] The multivariate MOF may be isoreticular or isostructural with MUF-16.

[0028] The one or more non-AIP organic linkers may comprise a core portion connected to a first coordinating moiety and to a second coordinating moiety. The first coordinating moiety and the second coordinating moiety may each be selected from a carboxylate group and an amino group. The core portion may be a phenyl ring. For example, the one or more non-AIP organic linkers may comprise a structure of of formula 1, or an anion thereof: wherein Ri, R3 and R4 are hydrogen, and 2 is selected from hydrogen, hydroxyl, halogen, haloalkyl, haloalkoxy, amino, amido, borono, seleno, phosphino, silyl, nitro, cyano, cyanato, thiocyanato, nitrosyl, imino, aminoalkyl, dialkylamino, aminoalkenyl, alkyloxy, alkenyloxy, alkyl, alkenyl, alkynyl, aryl, aralkyl, cycloalkyl, heteroaryl, heterocycloalkyl, cycloalkyl, carboxyl, carboxyalkyl, carboxyalkenyl, thiol, alkylthio, arylthio, aralkylthio, sulfato, sulfonato, sulfono, sulfoxo , each of which may be optionally further substituted. In an embodiment, R2 may be selected from H, OH, F, Cl, Br, I, HS, H2N, NO2, NH2, CH3, CF3, B(OH)2, CO2H, C2H5. In a specific embodiment, the non-AIP organic linker may be selected from 3-aminobenzoic acid (aba), 3,5-diaminobenzoic acid (daba), 3-amino-5- methylbenzoic acid (amba), 3-amino-5-carboxybenzeneboronic acid (acbba), 3-amino-5- bromobenzoic acid (abba) and anions thereof.

[0029] The proportion of non-AIP organic linker may be greater than or equal to 1% by mole, relative to AIP.

[0030] The metal cations may be selected from any metal, preferably having an octahedral coordination geometry. In a specific embodiment, the metal cation may be selected from cations of manganese, cobalt and a combination thereof.

[0031] In another aspect, there is provided a multivariate MOF comprising: a plurality of secondary building units (SBUs) comprising metal ions connected to each other via organic linkers; a plurality of layers of SBUs, each layer comprising adjacent SBUs connected to each other by coordination of the organic linker in one SBU to metal cations in adjacent SBUs; and adjacent layers connected to each other via bonding interactions between an organic linker in one layer and an organic linker in an adjacent layer; wherein the organic linkers comprise 5-aminoisophthalic acid or an anion thereof (AIP) and one or more non-AIP organic linkers.

[0032] Each SBU may comprise a repeating unit of one metal cation connected to another metal cation via a first coordinating moiety of the organic linkers. The first coordinating moiety may comprise a carboxylate group. A second coordinating moiety of an organic linker in a first SBU may be connected to a metal cation of an adjacent SBU, for example to form a layer of connected SBUs. The second coordinating moiety may comprise an amino group.

[0033] The multivariate MOF may comprise hydrogen bonding interactions between an organic linker in one layer and an organic linker in an adjacent layer. The hydrogen bonding interactions may comprise carboxyl -carboxyl hydrogen bonds.

[0034] In another aspect, there is provided a method for separating carbon dioxide from a mixture of gases, comprising contacting the mixture of gases with a sorbent comprising the multivariate MOF described herein.

[0035] In another aspect, there is provided a composite comprising the multivariate MOF as described herein and one or more of polymeric materials, resins, biomolecules, clays, ceramics, carbon, inorganic oxides or a support material. Support materials may include materials that retain or hold the multivariate MOF, and may include a substrate such as paper, a solid filter medium or a ceramic.

[0036] In another aspect, there is provided a system for separating carbon dioxide from a mixture of species comprising: one or more chambers, each of the one or more chambers having an inlet adapted to receive the mixture; and a sorbent comprising the multivariate MOF as described herein positioned within the one or more chambers and configured to contact the mixture.

[0037] In another aspect, there is provided a method of enhancing the adsorptive properties of a metal organic framework, comprising preparing a multivariate metal organic framework (MOF) comprising metal cations and organic linkers, wherein the organic linkers comprise 5-aminoisophthalic acid or an anion thereof (AIP) and one or more non-AIP organic linkers. The non-AIP organic linker may be selected such that the MOF affinity for a selected species of gas molecules is changed. The amount of non-AIP organic linker may also be selected such that the MOF affinity for a selected species of gas molecules is changed. In an example, the method is for enhancing the carbon dioxide adsorptive properties, and comprises selecting a non-AIP linker such that the affinity of carbon dioxide is increased at low gas pressure.

[0038] BRIEF DESCRIPTION OF THE FIGURES

[0039] The present invention will now be described by way of example only and with reference to the accompanying drawings in which:

[0040] Figure 1 shows a molecular model of part of the 1-dimensional SBU of MUF-16. Metal cations (octahedra) are connected by 1 2-bridging carboxylate groups of the organic linkers, and nitrogen donor atoms from organic linkers of adjacent SBUs coordinate at axial positions.

[0041] Figure 2 shows a molecular model of a part of a layer of four connected SBUs of MUF-16.

[0042] Figure 3 shows a molecular model of the inter-layer hydrogen bonding in MUF-16.

[0043] Figure 4 shows a molecular model of the structure of MUF-16, including a view down the 1-dimensional SBUs, pores and interlayer hydrogen bonding between the layers.

[0044] Figure 5 shows theXH NMR spectrum of [Co(Haip)i.4o(aba)o.6o] digested in in 0.6 mL D2O / NaOD.

[0045] Figure 6 shows theXH NMR spectrum of [Co(Haip)i.52(daba)o.4s] digested in 0.6 mL D2O / NaOD. Figure 7 shows theXH NMR spectrum of [Co(Haip)i.44(amba)o.56] digested in 0.6 mL D2O /

[0046] NaOD.

[0047] Figure 8 shows theXH NMR spectrum of [Co(Haip)i.69(acbba)o.3i] digested in 0.6 mL D2O / NaOD.

[0048] Figure 9 shows theXH NMR spectrum of [Mn(Haip)i.57(aba)o.43] digested in 0.6 mL D2O / NaOD.

[0049] Figure 10 shows theXH NMR spectrum of [Co(Haip)i.3i(aba)o.2o(daba)o.49] digested in 0.6 mL D2O / NaOD.

[0050] Figure 11 shows theXH NMR spectrum of [Co(Haip)i.si(aba)o.26(abba)o.23] digested in 0.6 mL D2O / NaOD.

[0051] Figure 12 shows theXH NMR spectrum of [Coo.79Mno.2i(Haip)i.7s(acbba)o.22] digested in 0.6 mL D2O / NaOD.

[0052] Figure 13 shows an EDX spectrum of [Coo.79Mno.2i(Haip)i.7s(acbba)o.22].

[0053] Figure 14 shows PXRD patterns of a simulation of MUF-16 and [Co(Haip)i.4o(aba)o.6o] as synthesised, after isotherm measurements, after immersion in water for 1 day, after exposure to an air for at least 1 year, after breakthrough measurements and after incorporation into a PVDF pellet.

[0054] Figure 15 shows PXRD patterns of a simulation of MUF-16 and [Co(Haip)i.52(daba)o.4s] as synthesised, after isotherm measurements, after immersion in water for 1 day, after exposure to an air for at least 1 year, and after breakthrough measurements.

[0055] Figure 16 shows PXRD patterns of a simulation of MUF-16 and [Co(Haip)i.44(amba)o.56] as synthesised, after isotherm measurements, after immersion in water for 1 week, after exposure to an air for at least 1 year.

[0056] Figure 17 shows PXRD patterns of a simulation of MUF-16 and [Co(Haip)i.69(acbba)o.3i] as synthesised and after isotherm measurements.

[0057] Figure 18 shows PXRD patterns of a simulation of MUF-16 and [Mn(Haip)i.57(aba)o.43] as synthesised and after isotherm measurements.

[0058] Figure 19 shows PXRD patterns of a simulation of MUF-16 and

[0059] [Co(Haip)i.3i(aba)o.2o(daba)o.49] as synthesised and after isotherm measurements.

[0060] Figure 20 shows PXRD patterns of a simulation of MUF-16 and

[0061] [Co(Haip)i.5i(aba)o.26(abba)o.23] as synthesised and after isotherm measurements. Figure 21 shows PXRD patterns of a simulation of MUF-16 and [Coo.79Mno.2i(Haip)i.7s(acbba)o.22] as synthesised and after isotherm measurements.

[0062] Figure 22 shows a thermogravimetric curve of activated [Co(Haip)i.4o(aba)o.6o].

[0063] Figure 23 shows a thermogravimetric curve of activated [Co(Haip)i.52(daba)o.4s].

[0064] Figure 24 shows a thermogravimetric curve of activated [Co(Haip)i.44(amba)o.56].

[0065] Figure 25 shows a thermogravimetric curve of activated [Co(Haip)i.69(acbba)o.3i].

[0066] Figure 26 shows a thermogravimetric curve of activated [Mn(Haip)i.5?(aba)o.43].

[0067] Figure 27 shows a thermogravimetric curve of activated [Co(Haip)i.3i(aba)o.2o(daba)o.49].

[0068] Figure 28 shows a thermogravimetric curve of activated [Co(Haip) i.5i(aba)o.26(abba)o.23] .

[0069] Figure 29 shows a thermogravimetric curve of activated [Coo.79Mno.2i(Haip)i.7s(acbba)o.22].

[0070] Figure 30 shows the experimental N2 adsorption isotherm at 77 K and BET surface area plots for [Co(Haip)i.4o(aba)o.6o].

[0071] Figure 31 shows the experimental N2 adsorption isotherm at 77 K and BET surface area plots for [Co(Haip)i.52(daba)o.4s].

[0072] Figure 32 shows the experimental N2 adsorption isotherm at 77 K and BET surface area plots for [Co(Haip)i.44(amba)o.56].

[0073] Figure 33 shows the experimental carbon dioxide, CH4, and N2adsorption isotherms of [Co(Haip)i.4o(aba)o.6o] at 293 K.

[0074] Figure 34 shows the experimental carbon dioxide, CH4, and N2adsorption isotherms of [Co(Haip)i.4o(aba)o.6o] at 273 K.

[0075] Figure 35 shows the experimental carbon dioxide, CH4, and N2adsorption isotherms [Co(Haip)i.52(daba)o.4s] at 293 K.

[0076] Figure 36 shows the experimental CO2, CH4, and N2 adsorption isotherms of [Co(Haip)i.52(daba)o.4s] at 273 K.

[0077] Figure 37 shows the experimental carbon dioxide, CF , and N2 adsorption isotherms [Co(Haip)i.44(amba)o.56] at 293 K.

[0078] Figure 38 shows the experimental CO2, CH4, and N2 adsorption isotherms of [Co(Haip)i.69(acbba)o.3i] at 293 K.

[0079] Figure 39 shows the experimental CO2, CH4, and N2 adsorption isotherms [Mn(Haip)i.57(aba)o.43] at 293 K. Figure 40 shows the experimental CO2, CH4, and N2adsorption isotherms of [Co(Haip)i.3i(aba)o.2o(daba)o.49] at 293 K.

[0080] Figure 41 shows the experimental CO2, CH4, and N2adsorption isotherms of [Co(Haip)i.5i(aba)o.26(abba)o.23] at 293 K.

[0081] Figure 42 shows the experimental CO2, CH4, and N2adsorption isotherms of [Coo.79Mno.2i(Haip)i.7s(acbba)o.22] at 293 K.

[0082] Figure 43 shows the experimental water vapor adsorption isotherms of

[0083] [Co(Haip)i.4o(aba)o.6o] and MUF-16 at 293 K.

[0084] Figure 44 shows the experimental water vapor adsorption isotherms of [Co(Haip)i.44(amba)o.56] and MUF-16 at 293 K.

[0085] Figure 45 shows a breakthrough apparatus described in Example 12 and used to measure the gas separation performance of multivariate MOFs under dynamic conditions.

[0086] Figure 46 shows experimental breakthrough curves for a mixture of 15 / 85 CO2 / N2at 1 bar and 298 K over 10 cycles in a column packed with [Co(Haip)i.4o(aba)o.eo].

[0087] Figure 47 shows experimental breakthrough curves for a mixture of 10 / 90 CO2 / CH4at 1 bar and 298 K over 2 cycles in a column packed with [Co(Haip)i.4o(aba)o.eo].

[0088] Figure 48 shows experimental breakthrough curves for a mixture of 5 / 95 CO2 / CH4at 1 bar and 298 K in a column packed with [Co(Haip)i.4o(aba)o.eo].

[0089] Figure 49 shows experimental breakthrough curves for a mixture of 15 / 85 CO2 / N2at 1 bar and 298 K over 10 cycles in a column packed with [Co(Haip)i.52(daba)o.4s].

[0090] Figure 50 shows experimental breakthrough curves for a mixture of 10 / 90 and 5 / 95 CO2 / CI- at 1 bar and 298 K in a column packed with [Co(Haip)i.52(daba)o.4s].

[0091] Figure 51 shows a photograph of [Co(Haip)i.4o(aba)o.eo] / PVDF pellets.

[0092] Figure 52 shows experimental CO2, N2, CH4adsorption isotherms of [Co(Haip)i.4o(aba)o.eo] and [Co(Haip)i.4o(aba)o.6o] / PVDF pellets at 293 K.

[0093] DETAILED DESCRIPTION

[0094] While the present invention may be embodied in many different forms, for the purpose of promoting an understanding of the principles of the present invention, reference will now be made to the figures and Examples, which relate to exemplary embodiments of the invention. The multivariate MOFs described herein comprise metal cations and organic linkers, wherein the organic linkers comprise 5-aminoisophthalic acid or an anion thereof (AIP), and one or more non-AIP organic linkers.

[0095] Organic linker

[0096] 5-aminoisophthalic acid comprises a phenyl ring comprising a 1,3,5 substitution of two carboxyl groups and an amino group. It has the structure:

[0097] Throughout this specification, AIP may be alternatively termed H2AIP or HAIP to denote the protonation or deprotonation of the carboxyl groups. Unless the context clearly requires otherwise, references to AIP should be understood to encompass H2AIP or HAIP'. When AIP is incorporated into the multivariate MOF, it may be in its anionic form HAIP' (see Examples 1-8), comprising a carboxyl group and a deprotonated carboxylate group.

[0098] AIP and the non-AIP organic linker both comprise a first coordinating moiety and a second coordinating moiety. The first coordinating moiety coordinates to two metal ions. The second coordinating moiety coordinates to another metal ion.

[0099] In AIP, the first coordinating moiety comprises a carboxylate group which bridges two adjacent metal ions to form an SBU, and the second coordinating moiety comprises an amino group which coordinates to another metal ion in an adjacent SBU to form a plane of SBUs. AIP further comprises a third moiety for forming linker-to-linker bonding interactions which connects adjacent planes of SBUs. In AIP, the third moiety comprises a carboxyl group.

[0100] The non-AIP organic linker may comprise a core portion connected to a first coordinating moiety and to a second coordinating moiety. The first coordinating moiety and the second coordinating moiety may each be selected from a carboxylate group and an amino group. The first coordinating moiety of each non-AIP organic linker may comprise a carboxylate group. The second coordinating moiety of each non-AIP organic linker may comprise an amino group. The first and second coordinating moieties of the non-AIP organic linkers have the same bonding roles as those of AIP. The non-AIP organic linker may comprise a core portion connected to each of the first and second coordinating moieties. The core portion may comprise an aryl or heteroaryl group, such as phenyl, pyridyl, pyrazyl, pyrimidyl, biphenyl, naphthyl, bipyridyl and quinolinyl groups. A preferred core portion comprises a six-membered aryl ring group or heteroaryl ring group. A specific example of the core portion is a phenyl ring group. The first and second coordinating moieties may be connected in a 1,3-substitution arrangement (i.e., a meta arrangement) on the six membered aromatic ring. In the exemplified multivariate MOFs, the first moiety is a carboxylate group, the second moiety is an amino group and the core portion comprises a phenyl ring. The non-AIP organic linker may be further substituted. In particular, the non-AIP organic linker may be substituted at the 5-position (relative to the 1,3- arrangement described above).

[0101] The non-AIP organic linkers may further comprise a third moiety connected to the core portion. The first coordinating moiety, second coordinating moiety and third moiety may be connected in a trigonal arrangement around the core. For example, where the core is a six-membered aryl or heteroaryl group, the first coordinating moiety, second coordinating moiety and third moiety have a 1,3,5 or 2,4,6 substitution pattern on the core. The third moiety may be configured to form bonding interactions with other third moieties or with a carboxylate group. The bonding interactions may be hydrogen bonding interactions.

[0102] Each non-AIP organic linker may independently have the structure of formula 1 : where Ri, R2, R3, R4, are independently selected from hydrogen, hydroxyl, halogen, haloalkyl, haloalkoxy, amino, amido, borono, seleno, phosphino, silyl, nitro, cyano, cyanato, thiocyanato, nitrosyl, imino, aminoalkyl, dialkylamino, aminoalkenyl, alkyloxy, alkenyloxy, alkyl, alkenyl, alkynyl, aryl, aralkyl, cycloalkyl, heteroaryl, heterocycloalkyl, cycloalkyl, carboxyl, carboxyalkyl, carboxyalkenyl, thiol, alkylthio, arylthio, aralkylthio, sulfato, sulfonato, sulfono, sulfoxo , each of which may be optionally further substituted .

[0103] In an example, Ri, R2, R3, R4 can be any functional group such as H, OH, F, Cl, Br, I, HS, H2N, NO2, NH2, CH3, CF3, B(OH)2, CO2H, C2H5 connected to a benzene ring or heteroaromatic ring.

[0104] In an example, Ri, R3 and R4 are hydrogen, and R2 is a functional group. R2 may be selected from hydrogen, hydroxyl, halogen, haloalkyl, haloalkoxy, amino, amido, borono, seleno, phosphino, silyl, nitro, cyano, cyanato, thiocyanato, nitrosyl, imino, aminoalkyl, dialkylamino, aminoalkenyl, alkyloxy, alkenyloxy, alkyl, alkenyl, alkynyl, aryl, aralkyl, cycloalkyl, heteroaryl, heterocycloalkyl, cycloalkyl, carboxyl, carboxyalkyl, carboxyalkenyl, thiol, alkylthio, arylthio, aralkylthio, sulfato, sulfonato, sulfono, sulfoxo , each of which may be optionally further substituted. More preferably, R2 is selected from H, OH, F, Cl, Br, I, HS, H2N, NO2, NH2, CH3, CF3, B(OH)2, CO2H, C2H5 connected to a benzene ring or heteroaromatic ring.

[0105] In Examples 1-8, the multivariate MOFs comprise non-AIP organic linkers selected from 3-aminobenzoic acid (aba), 3,5-diaminobenzoic acid (daba), 3-amino-5-methylbenzoic acid (amba), 3-amino-5-carboxybenzeneboronic acid (acbba), 3-amino-5-bromobenzoic acid (abba) and anions thereof. Aba, daba, amba, acbba and abba may be alternatively termed Haba, Hdaba, Hamba, Hacbba, and Habba, respectively, denote the protonation of the carboxyl groups. Unless the context clearly requires otherwise, references to aba, daba, amba, acbba and abba should be understood to encompass the corresponding protonated compounds. When aba, daba, amba, acbba and abba are incorporated into the multivariate MOF, they may be in its anionic form (see Examples 1-8), in which a carboxyl group is a deprotonated carboxylate group.

[0106] The proportion of AIP to non-AIP organic linkers in the multivariate MOFs may vary. Preferably, the proportion of non-AIP organic linker relative to AIP is greater than a trace or trivial amount. For example, the proportion of non-AIP organic linker is preferably greater than or equal to 1% by mole, relative to AIP. The Examples show the multivariate MOFs having proportions of AIP of at least 65%, and proportions of non-AIP of up to 35% by mole (see, for example, [Co(Haip)i.3i(aba)o.2o(daba)o.49], in Example 6).

[0107] Alternatively, where the multivariate MOF is considered by the formula [M(AIP)2-x(L)x], where M is one or more metal cations, and L is the one or more non-AIP organic linkers, x is less than 2, and preferably less than or equal to 0.7.

[0108] Metal cation

[0109] The multivariate MOF may comprise a single metal cation or a combination of different metal cations. Preferably, where the multivariate MOF comprises a combination of metal cations, each have the same charge.

[0110] In Examples 1 to 8, multivariate MOFs have been synthesised with metal cations selected from Co2+and Mn2+and combinations thereof. Structural characterization of the exemplary multivariate MOFs shows that the structure is preserved where the metal cations are fully or partially substituted with other metals. Further, the multivariate MOFs are shown to adsorb carbon dioxide and be selective for carbon dioxide in a mixture of species. Based on this finding, the identity of the metal cation is not considered essential to the framework's selectivity for carbon dioxide. Accordingly, the multivariate MOF may include a metal cation selected from: M1+(e.g., Na, K, Li, Ag, etc.); M2+(e.g., Mg, Cu, Zn, Co, Mn, Mo, Cr, Fe, Ca, Ba, Cs, Pb, Pt, Pd, Ru, Rh, Cd, etc.); M3+(e.g. In, Fe, Y, Ln (Yb, Tb, etc.)); M4+(e.g., Zr, Ti, V, etc.); or other higher oxidative state metals such as +4, + 5, +6, +7, and +8. In an example, the metal cations have a substantially octahedral coordination geometry.

[0111] Structure

[0112] Multivariate MOFs of the present invention are preferably isostructural to, or isoreticular with, MUF-16. MUF-16 is described in W02020 / 130856A1, the contents of which are incorporated herein by reference. Further, the multivariate MOFs are comparable with MUF-16 in their adsorption capacity and selectivity for carbon dioxide in the presence of a mixture of species.

[0113] 1-dimensional chain

[0114] The multivariate MOF comprises a plurality of secondary building units (SBUs) comprising metal ions connected to each other via organic linkers. As used herein and described below with reference to Figure 1, for the purposes of the multivariate MOFs described herein the term 'SBU' refers to the repeating metal-organic linker chain (i.e., an infinite SBU or an SBU rod).

[0115] In an SBU, metal ions are connected to each other via the first coordinating moiety of the organic linkers. The metal ions in each SBU are preferably connected to each other by carboxylate functional groups of the organic linkers. The carboxylate group comprises two donor atoms that coordinates to adjacent metal ions in a j .2-bridging mode. Each metal ion is connected to an adjacent metal ion by a 1 2-bridging carboxylate group of two organic linkers.

[0116] Figure 1 shows an SBU of MUF-16, which as noted above is isostructural or isoreticular with the multivariate MOFs described herein. The SBU comprises a plurality of metal ions in octahedral geometry. A metal ion is connected to an adjacent metal ion by the first coordinating moiety of two organic linkers. The first coordinating moiety may be a carboxylate group, wherein the carboxylate group of each the two organic linkers bridges two adjacent metal ions. The SBU has a repeating unit of -[M J2(OCRO)2M J2(OCRO)2]-. where M symbolises the metal, OCRO symbolises the organic linker, R symbolises the remainder of the organic linker, and where the identity of the R group of one organic linker may vary independently of the R group of another organic linker.

[0117] 2-dimensional layer

[0118] The multivariate MOFs described herein comprise a plurality of layers of SBUs, each layer comprising adjacent SBUs connected to each other by coordination of the organic linker in one SBU to metal cations in adjacent SBUs. Each organic linker in a first SBU may comprise a second coordinating moiety comprising a donor atom that coordinates to a metal cation in an adjacent SBU. Coordination of the donor atom to the adjacent SBU forms a two-dimensional layer of SBUs. The second coordinating moiety may be an amino group.

[0119] Figures 1 and 2 show a donor atom from the second coordinating moiety of the organic linker in one SBU coordinating to a metal ion in an adjacent SBU.

[0120] 3-dimensional framework

[0121] The multivariate MOFs described herein comprise adjacent layers of SBUs connected to each other via bonding interactions between an organic linker in one layer and an organic linker in an adjacent layer.

[0122] The three-dimensional framework of the multivariate MOFs is preferably isostructural or isoreticular with MUF-16. With reference to the visualisation of MUF-16 in Figures 3 and 4, the multivariate MOF structure can be similarly described as comprising a plurality of 1- dimensional SBUs of organic linker bridged metal ions; a plurality of 2-dimensional layers comprising adjacent SBUs connected together by coordination of organic linkers in one SBU to metal ions in adjacent SBUs; and a three dimensional framework comprising a stack of a plurality of 2-dimensional layers connected by linker-to-linker bonding interactions between organic linkers in adjacent layers. Thus, each organic linker in the multivariate MOF coordinates to three metal ions.

[0123] Pores are formed between adjacent 2-dimensional layers. The pores are co-axial with the SBU.

[0124] A third moiety of an organic linker may form a linker-to-linker bonding interaction with a third moiety of another organic linker in an adjacent layer to connect the adjacent layers in the stack. The third moiety of AIP comprises a carboxyl group, which may form hydrogen bonding interactions with the third moiety of organic linkers in adjacent layers. These Flbonding interactions link the two-dimensional layers into three-dimensional frameworks.

[0125] The non-AIP organic linkers may or may not form linker to linker bonding interactions. More specifically, at least some of the organic linkers will not form carboxyl -carboxyl hydrogen bonds between layers of SBUs. For example, the multivariate MOFs described in the Examples comprise aba, daba, amba, acbba, and / or abba as non-AIP organic linkers, in which the third moiety respectively comprises hydrogen, amino, methyl, borono and bromo groups at the 5-position on the phenyl ring. These non-AIP organic linkers are thus unable to form carboxyl -carboxyl bonding interactions between layers of SBUs. Yet, the multivariate MOFs are isostructural or isoreticular with MUF-16 and have similar stability, adsorption and selectivity for carbon dioxide. Method of preparation

[0126] The multivariate MOF of the present invention may be prepared by combining the AIP and non-AIP organic linkers with the metal ion(s) in a solvent. Preferably, the multivariate MOF is prepared under conditions which allow the self-assembly of the framework.

[0127] Examples 1 to 8 describe the preparation of exemplary multivariate MOFs, in which AIP, one or more non-AIP organic linkers and metal ion(s) are dissolved, combined and heated to form a multivariate MOF which forms as a precipitate. The method may comprise forming the multivariate MOF at above atmospheric pressures. For example, the multivariate MOF may be prepared at autogenous pressure in a sealed reaction vessel.

[0128] One method for forming the multivariate MOF comprises the combination of metal ion and organic linker precursors in a solvent. In an example, the solvent is a protic solvent. The protic solvent can be selected from water, alcohols (e.g. methanol, ethanol, propanol) or a combination thereof. For example, the solvent can be a combination of methanol and water. The solvent is heated and then cooled to yield a solid multivariate MOF product. Preferably, the reaction conditions comprise a reaction time of less than 5 hours, more preferably less than 4 hours, more preferably less than 3 hours. The multivariate MOF may be prepared in solvothermal conditions. The solvothermal conditions may comprise a closed reaction vessel and autogenous pressure. The solvothermal conditions may include temperatures of less than 150 °C, more preferably less than 130 °C, more preferably less than 110 °C, more preferably less than 100 °C, more preferably less than 90 °C. The multivariate MOF can be used in the form it is retrieved from its reaction vessel, such as in a solid powder form as obtained from the solvothermal reaction, or can be further modified, for example, by washing, sonication, solvent exchange, activation, or mechanical grinding of the reaction product. The multivariate MOF can be used in any particle size.

[0129] Alternative methods of preparation envisioned by the inventors include mechanochemical methods of synthesis, melt synthesis and synthesis in a flow reactor.

[0130] In their as-synthesized form the pores of the multivariate MOF may contain occluded solvent (often water). Occluded solvents can be removed from the pores of the multivariate MOF by heating, or in vacuo, or by purging with a flow of dry air, or a combination of two or more of the aforementioned methods.

[0131] Adsorption and selectivity

[0132] The multivariate MOFs of the present invention preferentially adsorb carbon dioxide from a mixture of species. The Examples show that multivariate MOFs effectively separate carbon dioxide from carbon dioxide / N2 and carbon dioxide / CFU mixtures. They take up a significant amount of carbon dioxide but lesser amounts of other gases. The introduction of certain linkers into the multivariate MOF may cause its affinity for gas molecules to change. Analysis of the adsorption and breakthrough testing of the multivariate MOF, described in Examples 11 and 12, shows a strong binding toward carbon dioxide. For example, the isosteric heat of adsorption (Qst) of carbon dioxide for [Co(Haip)i.4o(aba)o.6o], [Co(Haip)i.52(daba)o.4s], and [Co(Haip)i.44(amba)o.56] was calculated to be about -37 kJ / mol, -36 kJ / mol, and -34 KJ / mol, respectively, at low loadings. Further, gas adsorption studies indicate that the multivariate MOFs exhibit high carbon dioxide / N2 uptake ratios and carbon dioxide / CFU uptake ratios. Analysis of the experimental water vapor adsorption isotherm of [Co(Haip)i.44(amba)o.56] in Example 11 shows the uptake of water vapour at low partial pressures is reduced compared to MUF- 16.

[0133] While the selectivity for carbon dioxide of the multivariate MOF has been exemplified herein for mixtures comprising CF and N2, it is a reasonable extrapolation for the multivariate MOF to have similar selectivity for carbon dioxide in the presence of species with similar properties to CF and N2 and / or similar dissimilarities with carbon dioxide. Accordingly, it is reasonable to extrapolate the selectivity towards carbon dioxide of the multivariate MOFs described in the Examples of selectivity towards carbon dioxide in mixtures further comprising hydrogen (H2), oxygen (O2), nitrogen (N2), methane (CH ), helium, neon, argon, krypton, xenon, radon, ozone (O3), carbon monoxide (CO), and nitric oxide (NO). The introduction of certain linkers into the multivariate MOF may cause its selectivity for CO2 over another gas, or combinations of other gases, to change.

[0134] The multivariate MOF may thus be used to adsorb carbon dioxide from industrial, crude, unrefined or partially refined sources of hydrocarbons, such as natural gas, liquefied petroleum gas, biogas, syngas, coal seam gas, acetylene, methane, ethane and combinations thereof. The multivariate MOF may be used to adsorb carbon dioxide from carbon dioxide containing flue gases. Examples of flue gases include those generated by combustion of carbon-containing organic matter (such as fossil fuels, hydrocarbons and carbohydrates) and by calcination reactions of carbonates such as in the manufacture of cement. The multivariate MOF may be used to adsorb carbon dioxide from exhaled air in rebreather devices. The multivariate MOF may be used to adsorb carbon dioxide in closed or partially closed anaesthesia systems or respiratory devices, and / or to enhance the recovery of anaesthetic gases (e.g. isoflurane, sevoflurane, desflurane, cyclopropane and xenon). The multivariate MOF may be deployed in the ambient environment to adsorb carbon dioxide from the atmosphere. The multivariate MOF may deployed in closed or sealed systems such as on board submarines, spacecraft or military bunkers as a carbon dioxide scrubber or scavenger. The multivariate MOF may be selective for carbon dioxide in the presence of humidified gases; that is, the multivariate MOF may be selective for carbon dioxide in the presence of water vapour. The introduction of certain linkers into the multivariate MOF may cause its selectivity for CO2 over water vapour to change. The multivariate MOF may retain its selectivity towards carbon dioxide for a commercially and industrially useful amount time when heated. The multivariate MOF is preferably stable under a nitrogen atmosphere at temperatures of up to 200 °C, more preferably up to 250 °C, more preferably up to 300 °C. In use, and / or in ambient conditions, the multivariate MOF is selective for carbon dioxide at a range of temperatures. For example, the multivariate MOF can be selective for carbon dioxide at temperatures over 50 °C or over 80 °C.

[0135] The multivariate MOF is preferably selective for adsorbing carbon dioxide from a mixture of species even where the concentration (or partial pressure) of carbon dioxide in the mixture is low. Preferably, the multivariate MOF may be selective for adsorbing carbon dioxide from a mixture where the carbon dioxide is 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, 5% or less, 1% or less, 0.1% or less, 0.01% or less, 0.001% or less, 0.0001% or less, 1000 ppm or less, 100 ppm or less, 10 ppm or less, or 1 ppm or less. The multivariate MOF may retain a stable structure and remains selective at low and high gas pressures. For example, the MOF may have a stable structure and preferably remains selective at a near-vacuum, and preferably at gas pressures of up to about 50 bar, 100 bar, 150 bar, 200 bar, 250 bar, 300 bar, 350 bar, 400 bar, 450 bar, 500 bar.

[0136] The multivariate MOF preferably retains its adsorption activity and selectivity towards carbon dioxide in the presence of air and / or water for a commercially and industrially useful amount of time. Preferably, the multivariate MOF is stable in humid air at room temperature (70% humidity at approx. 20 °C) for more than 1 week, more preferably more than 2 weeks, more preferably more than 1 month, more preferably more than 2 months, more preferably more than 3 months, more preferably more than 4 months, more preferably more than 5 months, more preferably more than 6 months, more preferably more than 7 months, more preferably more than 8 months, more preferably more than 9 months, more preferably more than 10 months, more preferably more than 11 months, and more preferably more than 12 months.

[0137] The multivariate MOF preferably retains its selectivity towards carbon dioxide, in the presence of toxic and / or corrosive gases such as (but not limited to) ammonia, hydrogen sulfide, sulfur dioxide, carbon monoxide, nitrogen dioxide, and nitric oxide.

[0138] The multivariate MOF may be used to selectively adsorb carbon dioxide from a fluid, a fluid flow, a liquid, a liquid flow, a gas and a gas flow. The multivariate MOF may be used in continuous streams of fluid, for example in a filter or bed through or across which the fluid flows, or can be added to batches of fluid.

[0139] The multivariate MOF may be activated by heating and / or under reduced pressure, and due to its selectivity towards carbon dioxide over gases in the ambient environment it can be stored under ambient conditions (but preferably excluding ambient carbon dioxide) until required. The multivariate MOF can thus be used and regenerated using temperature and / or pressure swings.

[0140] Regeneration

[0141] After use in the presence of carbon dioxide, the multivariate MOF may be regenerated by desorbing carbon dioxide under vacuum and / or heating and / or purging with gas for reuse. The multivariate MOF is preferably able to completely desorb the adsorbed guest species by the reduction of pressure and / or the increase in temperature (optionally in the presence of another gas). In one example, the multivariate MOF may desorb carbon dioxide by heating to between about 30°C and about 130°C. Once the multivariate MOF is free of guest species it may be used for further carbon dioxide adsorption.

[0142] During breakthrough testing, complete carbon dioxide desorption of the multivariate MOFs was achieved by placing them under reduced pressure for 20-30 mins (see Example 12). Alternatively, or in addition, the multivariate MOFs may be regenerated by purging with a flow of carbon dioxide-free gas at elevated temperatures, such as an inert gas at temperatures at or above 70 °C.

[0143] The multivariate MOF is preferably able to perform multiple adsorption / desorption cycles. Preferably, the multivariate MOF may maintain its carbon dioxide uptake and complete desorption over at least 5 cycles, preferably more than 10 cycles, preferably more than 50 cycles and preferably more than 100, 200, 300, 400, or 500 cycles.

[0144] Stability

[0145] The multivariate MOFs of the present invention are stable in the presence of water and high temperatures. For example, Figures 22 to 29 and Table 5 in Example 10 show that the multivariate MOFs are stable up to at least 300 °C. PXRD data shows the structure of the multivariate MOFs is retained after: (i) gas adsorption isotherm measurements, (ii) gas breakthrough experiments, (iii) exposure to an air with relative humidity of >70% for at least one year, and (iv) after soaking in water for 1 day.

[0146] Incorporation into other materials

[0147] The multivariate MOF may be deployed in combination with other compounds. For example, the multivariate MOF can be combined with a polymer or other binding agent to form pellets, beads, granules or other aggregates or composites. Thus, there is provided a composite material comprising the multivariate MOF and a further component which may be selected from polymeric materials, resins, biomolecules, clays, ceramics, carbon, inorganic oxides or support materials. Examples of support materials are materials that retain or hold the multivariate MOF, and may include a substrate such as paper, a solid filter medium or a ceramic.

[0148] Incorporation of the multivariate MOFs into a composite material improves their handling and widens the potential uses for their gas capture properties. The composite material may take the form, for example, of a pellet, membrane (such as a gas separation membrane), sheet, or monolith. For example, the multivariate MOFs may be combined with further components to form a gas separation membrane.

[0149] Example 13 describes the preparation of a composite comprising the multivariate MOF and a binder (polyvinylidene fluoride (PVDF)), to make composite pellets. Figure 14 shows that the crystalline structure of the composite is substantially the same as the as-synthesised multivariate MOF. Figure 52 shows that the composite has the same adsorption profile as the as-synthesised multivariate MOF and that the gas adsorption characteristics are unchanged.

[0150] System

[0151] A system is provided for removing carbon dioxide from a fluid comprising a mixture of species. The system comprises the multivariate MOF positioned in contact with the fluid or in a flow path of the fluid. The system may comprise one or more chambers for receiving the multivariate MOF, and an inlet for the fluid or its flow path. The system may further comprise one or more: fluid sources, fluid lines, fluid inlets for directing the fluid mixture to the chamber, valves for controlling the flow of fluid through the system, treated fluid outlets for directing the treated fluid (scrubbed of carbon dioxide) from the chamber, pumping components for moving the fluid mixture within the system, and heating or fluid purging components for regenerating the multivariate MOF. The fluid preferably exits the system comprising a lower level of carbon dioxide compared to the fluid that entered the system. A temperature and / or pressure swing can be included, comprising a temperature controller configured to control the temperature of the multivariate MOF and / or a pressure controller configured to control the pressure of the fluid in which the multivariate MOF is located.

[0152] The breakthrough apparatus shown in Figure 45 and described in Example 12 is one embodiment of a system for removing carbon dioxide from a fluid.

[0153] EXAMPLES

[0154] All starting reactants and solvents were obtained from commercial sources and used without further purification unless otherwise noted. Example 1: [Co(Haip)i.4(aba)o.6]

[0155] CO(OAC)2-4H2O (0.1 mmol), a mixture of H2aip and Haba (0.4 mmol total, ligand ratio 1: 1), methanol (3.2 mL), and water (0.2 mL) was sonicated for 5 min in a 20 mL vial, which was then heated in a pre-heated oven at 85 °C for 3 h under autogenous pressure. The resulting powder was isolated by decanting off the mother liquor, washed with methanol several times, and then dried under vacuum at 130 °C overnight. This delivered a product with the formula [Co(Haip)i.4(aba)o.e] with a yield of 38.5 mg and a reaction yield of 98% based on cobalt. Figure 5 shows theXH NMR spectrum of the product digested in 0.6 mL D2O / NaOD, revealing a 2.4: 1 ratio between Haip and aba.

[0156] The method was repeated with different input ratios of l- aip and Haba. The ratio of the organic linkers in the multivariate MOFs thus produced are shown in Table 1.

[0157] Table 1

[0158] Input organic linker ratio NMR ratio (Haip / aba) Multivariate MOF formula

[0159] CO(OAC)2-4H2O (0.1 mmol), a mixture of H2aip and Hdaba (0.4 mmol total, ligand ratio 2: 1), methanol (3.2 mL), and water (0.2 mL) was sonicated for 5 min in a 20 mL vial, which was then heated in a pre-heated oven at 85 °C overnight under autogenous pressure. The resulting powder was isolated by decanting off the mother liquor, washed with methanol several times, and then dried under vacuum at 130 °C overnight. This delivered a product with the formula [Co(Haip)i.52(daba)o.4s] with a yield of 38.6 mg and a reaction yield of 95% based on cobalt. Figure 6 shows theXH NMR spectrum of the product digested in 0.6 mL D2O / NaOD, revealing a 3.1 : 1 ratio between Haip and daba.

[0160] The method was repeated with different input ratios of Hzaip and Hdaba. The ratio of the organic linkers in the multivariate MOFs thus produced are shown in Table 2.

[0161] Table 2

[0162] Input organic NMR ratio Multivariate MOF linker ratio (Haip / daba) formula

[0163] CO(OAC)2-4H2O (0.15 mmol), a mixture of H2aip and Hamba (0.6 mmol total, ligand ratio 1: 1) where Hamba is 3-amino-5-methylbenzoic acid, methanol (5 mL), and water (0.31 mL) was sonicated for 5 min in a 20 mL vial, which was then heated in a pre-heated oven at 85 °C for 4 h under autogenous pressure. The resulting powder was isolated by decanting off the mother liquor, washed with methanol several times, and then dried under vacuum at 130 °C overnight. This delivered a product with the formula [Co(Haip)i.44(amba)o.56] with a yield of 50.8 mg and a reaction yield of 84% based on cobalt. Figure 7 shows theXH NMR spectrum of the product digested in 0.6 mL D2O / NaOD, revealing a 2.57: 1 ratio between Haip and amba. Example 4: [Co(Haip)i.69(acbba)o.3i]

[0164] CO(OAC)2-4H2O (0.6 mmol), a mixture of H2aip and Hacbba (1.2 mmol total, ligand ratio 4: 1) where Hacbba is 3-amino-5-carboxybenzeneboronic acid, was refluxed stirring in ethanol (10 ml) in a 100 mL round bottom flask at 90 °C overnight. A pink precipitate was filtered off while the solution was hot, successively washed with ethanol several times, and then dried under vacuum at 130 °C. This delivered a product with the formula [Co(Haip)i.69(acbba)o.3i] with a yield of 210.4 mg and a reaction yield of 84% based on cobalt. Figure 8 shows theXH NMR spectrum of the product digested in 0.6 mL D2O / NaOD, revealing a 5.6: 1 ratio between Haip and acbba, corresponding to [Co(Haip)i.69(acbba)o.3i].

[0165] The method was repeated with different input ratios of H2aip and Hacbba. The ratio of the organic linkers in the multivariate MOFs thus produced are shown in Table 3.

[0166] Table 3

[0167] Input organic linker ratio NMR ratio (Haip / acbba) Multivariate MOF formula

[0168] Example 5: [Mn(Haip) i.57(aba)o.43] 2a p

[0169] Mn(NO3).6H2O (3.5 mmol), a mixture of H2aip and Haba (7 mmol total, ligand ratio 1: 1), was refluxed stirring in ethanol (37.5 ml) in a 250 mL round bottom flask at 90 °C for 3 h. A precipitate was filtered off while the solution was hot, successively washed with ethanol several times, and then dried under vacuum at 130 °C. This delivered a product with the formula [Mn(Haip)i.5?(aba)o.43] with a yield of 237.5 mg and a reaction yield of 17.1% based on manganese. Figure 9 shows theXH NMR spectrum of the product digested in 0.6 mL D2O / NaOD, revealing a 3.6: 1 ratio between Haip and aba, corresponding to [Mn(Haip)i.5?(aba)o.43].

[0170] Example 6: [Co(Haip)i.3i(aba)o.2o(daba)o.49]

[0171] CO(OAC)2-4H2O (0.1 mmol), a mixture of H2aip, Haba and Hdaba (0.4 mmol total, ligand ratio 2: 1: 1), methanol (3.2 mL), and water (0.2 mL) was sonicated for 5 min in a 20 mL vial, which was then heated in a pre-heated oven at 85 °C for 4 h under autogenous pressure. The resulting powder was isolated by decanting off the mother liquor, washed with methanol several times, and then dried under vacuum at 130 °C overnight. This delivered a product with the formula [Co(Haip)i.3i(aba)o.2o(daba)o.49] with a yield of 35.8 mg and a reaction yield of 90.4% based on cobalt. Figure 10 shows theXH NMR spectrum of the product digested in 0.6 mL D2O / NaOD, revealing a 6.5: 1:2.4 ratio between Haip, aba and daba, respectively, corresponding to [Co(Haip)i.3i(aba)o.2o(daba)o.49].

[0172] Example 7: [Co(Haip) i.5i(aba)o.26(abba)o.23]

[0173] CO(OAC)2-4H2O (0.1 mmol), a mixture of H2aip, Haba and Habba (0.4 mmol total, ligand ratio 2: 1: 1), methanol (3.2 mL), and water (0.2 mL) was sonicated for 5 min in a 20 mL vial, which was then heated in a pre-heated oven at 85 °C for 4 h under autogenous pressure. The resulting powder was isolated by decanting off the mother liquor, washed with methanol several times, and then dried under vacuum at 130 °C overnight. This delivered a product with the formula [Co(Haip)i.si(aba)o.26(abba)o.23]. It yields 36.3 mg with a reaction yield of 87.3% based on cobalt. Figure 11 shows theXH NMR spectrum of the product digested in 0.6 mL D2O / NaOD, revealing a 6.4: 1.1 : 1 ratio between Haip, aba and abba, respectively, corresponding to [Co(Haip)i.si(aba)o.26(abba)o.23]. Example 8: [Coo.79Mno.2i(Haip)i.7s(acbba)o.22]

[0174] CO(OAC)2-4H2O and Mn(NOs).6H2O (1 mmol total, input Co / Mn ratio: 70 / 30) were added to a mixture of 1: 1 water and methanol (8 mL) in a conical flask and heated slowly to ~50 °C with stirring. In another conical flask, H2aip and Hacbba (2 mmol total, input ratio 4: 1) was added to methanol (12 mL) and heated to boiling with stirring. The metal solution was then added dropwise to the boiling ligand solution using a pipette. The resulting precipitate was collected by vacuum filtration using a sinter funnel, washed with methanol several times, then dried at 130 °C overnight. This delivered a product with the formula [Coo.79Mno.2i(Haip)i.7s(acbba)o.22]. It yields 255.3 mg with a reaction yield of 61.2%. Figure 12 shows theXH NMR spectrum of the product digested in 0.6 mL D2O / NaOD, revealing a 8: 1 ratio between Haip and acbba, respectively. Figure 13, showing EDX analysis of the product, showed a 15.3:3.8 weight % ratio for Co:Mn (see Table 4, below). ^NMR and EDX analysis indicates the product has the formula [Coo.79Mno.2i(Haip)i.7s(acbba)o.22].

[0175] Table 4 - EDX data

[0176] Element Wt% At% Input ratio: 70 / 30 Co / Mn

[0177] Co 15.3 4.41 Calculated EDX ratio: 79 / 21 Co / Mn

[0178] Example 9: Structure

[0179] For PXRD measurements, unless otherwise noted, samples were kept damp with solvent prior to and during measurements. The two-dimensional images of the Debye rings were integrated to give 20 vs I diffractograms.

[0180] The as-synthesized multivariate MOFs show that they are isostructural to MUF-16, [Co(Haip)2]. For example, PXRD diffractograms of the multivariate MOFs described in Examples 1 to 8 are shown in Figures 14 to 21. They match a simulated PXRD diffractogram of MUF-16. Example 10: Stability

[0181] Thermogravimetric analysis measurements were performed as follows: Freshly prepared MOF samples were washed with methanol then activated at 130 °C under vacuum for 10 hours. Measurements were performed on a TA Instruments Q50 instrument. Measurements were made on approximately 3 mg of activated sample under a N2 flow with a heating rate of 5 °C / min. Results of thermogravimetric analysis for the multivariate MOFs of Examples 1 to 7 are shown in Table 5 below.

[0182] Table 5

[0183] Example # MOF Degradation Figure # onset temperature (TGA), °C

[0184] 8 [Coo.79Mno.2i(Haip)i.78(acbba)o.22] 375 29

[0185] PXRD analysis of the multivariate MOF before and after breakthrough testing (described at Example 12) indicated good stability. The multivariate MOF materials remained unchanged after: (i) gas adsorption isotherm measurements, (ii) gas breakthrough experiments, (iii) exposure to an air with relative humidity of >70% for at least one year, and (iv) after soaking in water for 24 hr.

[0186] Further, PXRD analysis of samples of [Co(Haip)i.4o(aba)o.6o] showed it to be stable in a laboratory atmosphere (>70% humidity, ambient temperature) for at least one year (see Figure 14). Similarly, PXRD analysis of [Co(Haip)i.52(daba)o.4s] showed it to be stable in a laboratory atmosphere (approximately 70% humidity, ambient temperature) for at least one year and in water for at least 24 hr (see Figure 15).

[0187] Example 11: Adsorption

[0188] The N2 adsorption isotherms at 77 K of [Co(Haip)i.4o(aba)o.6o], [Co(Haip)i.52(daba)o.4s], and [Co(Haip)i.44(amba)o.56] gave a BET surface area of 287, 199 and 309 m2 / g, respectively (see Figures 30-32). Uptake capacity of CO2 and low-pressure CO2, CF , and N2 sorption data at different temperatures for the multivariate MOFs of Examples 1-8 and MUF-16 (for comparison) are shown in Tables 6 and7.

[0189] Table 6- Uptake capacity of carbon dioxide at 293 K and 1 bar.

[0190] Example # MOF Uptake (wt%)

[0191] The water adsorption isotherms of [Co(Haip)i.4o(aba)o.6o] and [Co(Haip)i.44(amba)o.56] are shown in Figures 43 and 44. The uptake of water vapour at low partial pressures is reduced in these multivariate MOFs compared to MUF-16.

[0192] To evaluate the binding strength between the adsorbent and the adsorbate, the isosteric heat of adsorption (Qst) of carbon dioxide was calculated using the Clausius- Clapeyron equation. The obtained Qst value at zero-coverage was about -37, -36 and -34 kJ / mol for [Co(Haip)i.4o(aba)o.6o], [Co(Haip)i.52(daba)o.4s], and [Co(Haip)i.44(amba)o.56], respectively. Example 12: Breakthrough testing

[0193] The feasibility of CO2 / N2 and CO2 / CH4 hydrocarbon separations under dynamic conditions was investigated through experimental breakthrough tests for a mixture of 15 / 85 of CO2 / N2, CO2 / CH4(5 / 95), and CO2 / CH4 (10 / 90) at 298 K and 1 bar. Each separation process was carried out at 298 K and Ibar. The multivariate MOF was regenerated by being kept under vacuum for 20-30 min.

[0194] A breakthrough apparatus shown in Figure 45 was used to measure the gas separation performance of the multivariate MOFs under dynamic conditions.

[0195] Each activated sample (around 0.5 g) was placed in an adsorption column (6.4 mm in diameter x 11 cm in length) to form a fixed bed. The adsorbent was activated at 120 °C under high vacuum for 1 hour and then the column was left under vacuum while being cooled to 20 °C. The column was then purged under a 10 ml_N / min flow of He gas for 10 min at 1 bar prior to the breakthrough experiment. A gas mixture containing gas pairs selected from CO2, N2, and CH4 was introduced to the column at 1 bar and 25 °C. A feed flowrate of 6 mLw / min was set for all experiments. The operating pressure was controlled at 1 bar with a back-pressure regulator. The outlet composition was continuously monitored by the mass spectrometer until complete breakthrough was observed. The adsorbent was regenerated under vacuum for 20-30 minutes between each cycle.

[0196] Figures 46 to 50 show the dimensionless concentration of CO2 / N2(15 / 85), C02 / CH4(10 / 90), and CO2 / CH4(5 / 95) exiting the column packed with the multivariate MOF as a function of the time at 1 bar. A summary of inlet gas feed streams and associate data for the breakthrough tests is shown in Table 8. Complete separation was realized by all multivariate MOFs for all gas mixtures.

[0197] Table 8

[0198] Breakthrough tests revealed that samples maintained its CO2 uptake and complete removal of CO2 over 10 cycles (Figures 46 and 49), illustrating the recyclability of these samples in the separation of CO2 / N2 or CO2 / CH4 mixture. The frameworks can be fully regenerated between cycles by placing them under vacuum for around 20-30 mins or by purging with an inert gas at 70 °C.

[0199] Example 13: Incorporation into other materials

[0200] The multivariate MOF [Co(Haip)i.4o(aba)o.6o] was formed into pellets with a binder, polyvinylidene difluoride (PVDF), according to the following method:

[0201] 1. The multivariate MOF (~0.47 g, 95 % w / w) was gently ground using mortar and pestle.

[0202] 2. PVDF (25 mg, 5% w / w) was placed in a 20 mL vial and completely dissolved in DMF (0.5 mL) 3. The ground sample was then added to the vial and mixed thoroughly.

[0203] 4. The paste was transferred into a plastic syringe using a spatula and pressed it out in thin noodles onto an aluminium foil.

[0204] 5. The noodles were dried in vacuum oven at 130 °C overnight.

[0205] PXRD patterns (Figure 14) and adsorption isotherms of carbon dioxide (Figure 52), comparing the pelletised and non-pelletised materials, show that the pelletisation of the materials leave the extended structure of the multivariate MOF substantially unchanged, and its adsorption capacity is retained.

Claims

CLAIMS1. A multivariate metal organic framework (MOF) comprising metal cations and organic linkers, wherein the organic linkers comprise 5-aminoisophthalic acid or an anion thereof (AIP) and one or more non-AIP organic linkers.

2. The multivariate MOF of claim 1, wherein the one or more non-AIP organic linkers comprise a core portion connected to a first coordinating moiety and to a second coordinating moiety.

3. The multivariate MOF of claim 2, wherein the first coordinating moiety and the second coordinating moiety are each selected from a carboxylate group and an amino group.

4. The multivariate MOF of claim 2 or 3, wherein the core portion is a phenyl ring.

5. The multivariate MOF of any one of claims 1 to 4, wherein the one or more non- AIP organic linkers comprise a structure of of formula 1, or an anion thereof:wherein Ri, R3 and R4 are hydrogen, and R2 is selected from hydrogen, hydroxyl, halogen, haloalkyl, haloalkoxy, amino, amido, borono, seleno, phosphino, silyl, nitro, cyano, cyanato, thiocyanato, nitrosyl, imino, aminoalkyl, dialkylamino, aminoalkenyl, alkyloxy, alkenyloxy, alkyl, alkenyl, alkynyl, aryl, aralkyl, cycloalkyl, heteroaryl, heterocycloalkyl, cycloalkyl, carboxyl, carboxyalkyl, carboxyalkenyl, thiol, alkylthio, arylthio, aralkylthio, sulfato, sulfonato, sulfono, sulfoxo , each of which may be optionally further substituted, provided that when R2 is carboxyl, Ri, R3 and R4 are not hydrogen.

6. The multivariate MOF of claim 5, wherein R2 is selected from H, OH, F, Cl, Br, I, HS, H2N, NO2, NH2, CH3, CF3, B(OH)2, CO2H, C2H5, provided that when R2is CO2H, Ri, R3 and R4 are not hydrogen.

7. The multivariate MOF of any one of the preceding claims, wherein the non-AIP organic linker is independently selected from 3-aminobenzoic acid (aba), 3- amino-5-methylbenzoic acid (amba), 3,5-diaminobenzoic acid (daba), 3-amino-5- carboxybenzeneboronic acid (acbba), 3-amino-5-bromobenzoic acid (abba) and anions thereof.

8. The multivariate MOF of any one of the preceding claims, wherein the metal cations are selected from manganese and cobalt and a combination thereof.

9. The multivariate MOF of any one of the preceding claims, comprising a proportion of non-AIP organic linker that is greater than or equal to 1% by mole, relative to AIP.

10. The multivariate MOF of any one of the preceding claims, that is isoreticular or isostructural with MUF-16.

11. A multivariate MOF comprising: a plurality of secondary building units (SBUs) comprising metal ions connected to each other via organic linkers; a plurality of layers of SBUs, each layer comprising adjacent SBUs connected to each other by coordination of the organic linker in one SBU to metal cations in adjacent SBUs; and adjacent layers connected to each other via bonding interactions between an organic linker in one layer and an organic linker in an adjacent layer; wherein the organic linkers comprise 5-aminoisophthalic acid or an anion thereof (AIP) and one or more non-AIP organic linkers.

12. A method of enhancing the adsorptive properties of a metal organic framework, comprising preparing a multivariate metal organic framework (MOF) comprising metal cations and organic linkers, wherein the organic linkers comprise 5- aminoisophthalic acid or an anion thereof (AIP) and one or more non-AIP organic linkers.

13. A method for separating carbon dioxide from a mixture of gases, comprising contacting the mixture of gases with a sorbent comprising the multivariate MOF of any one of claims 1 to Error! Reference source not found..

14. A composite comprising the multivariate MOF of any of claims 1 to 11 and one or more of polymeric materials, resins, biomolecules, clays, ceramics, carbon, inorganic oxides or a support material.

15. A system for separating carbon dioxide from a mixture of species comprising: one or more chambers, each of the one or more chambers having an inlet adaptedeceive the mixture; and a sorbent comprising the multivariate MOF of any one of claims 1 to 11 positioned within the one or more chambers and configured to contact the mixture.

Images