Metal-binding compounds and metal complexes, methods of their preparation, and uses in the complexing of metal ions

Abstract

The present invention provides a metal-binding compound according to compound 1: Ch-O-(CH2)n-O-C(O)-C(R)-(CH2)m-B Compound 1 wherein Ch is selected from any neutral chelating ligand, n is 1 to 12, m is 0 to 3, R is selected from amine, amide, carbamide and carbamate optionally substituted with C1 to C6 linear or branched alkyl (eg –NHC(O)OH, –NHC(O)OCH3, –NHC(O)OCH2CH3, – NHC(O)Otertbutyl), and B is phenyl group substituted by one to five optionally protected hydroxyl groups.

Description

Metal-binding compounds and metal complexes, methods of their preparation, and uses in the complexing of metal ions Field of the invention

[0001] The present invention relates to ligands for chelating metal ions, preferably reversible chelation. The ligands are optionally bound to a substrate. The present invention further relates to methods of preparing the ligands and substrate bound ligands, and methods of using the ligands to bind and / or unbind metal ions. Background of the invention

[0002] The removal of metal ions from water is important in various industries.

[0003] Cleaning the surface water in urban areas is particularly difficult, as the surface water is usually rainwater runoff from sealed surfaces. These sealed surfaces can be road surfaces, parking lots, airports, or other areas that are frequented by any vehicles. A variety of pollutants are taken from these sealed surfaces in the rainwater including solids, light liquids and dissolved pollutants. The dissolved pollutants are often polyaromatic hydrocarbons and metals from automotive brake and tyre wear. In addition, roofs (especially metal roofs) are surfaces leading to the pollution of metal in surface water as rainwater absorbs the metals ions.

[0004] Due to various regulations, water contaminated with metals may not be permitted to infiltrate into the subsoil without prior cleaning, nor may contaminated water be re-used.

[0005] The removal of metals from water has been based on technologies such as chemical precipitation, adsorption, ion exchange, and electrochemical processes. These conventional methods, however, have exhibited a series of shortcomings, including one or more of the production of toxic by-products, high-energy consumption, biofouling and high cost.

[0006] Therefore, there is a need to develop alternative technologies that reduce one of more of the above shortcomings.

[0007] Reference to any prior art in the specification is not an acknowledgment or suggestion that this prior art forms part of the common general knowledge in anyjurisdiction or that this prior art could reasonably be expected to be understood, regarded as relevant, and / or combined with other pieces of prior art by a skilled person in the art. Summary of the invention

[0008] The inventors of the present invention have developed an alternative technology for removal of metal ions from liquids using complexation. Strong metal adhesions is beneficial for applications where there the complexed ligand is subject to strong forces. For example, the turbulence of waste water processing. This technology can be used to remove high concentrations of metals.

[0009] The materials for binding the metal ions preferably are capable of releasing the metal ions post-complexation so that the materials can be regenerated for further use.

[0010] For a potential water treatment application however, the ability of the materials system to adhere to a surface while providing active treatment properties is also preferable because this allows for easy removal of the materials and metal ions from the liquid. A strong adhesion also provides advantages in being able to withstand more vigorous aqueous conditions. Metal-binding compound

[0011] The present invention provides a metal-binding compound according to one or more of compound 1, 1A, and 1B: Ch-A1-(CH2)n-A2-C(O)-C(R1)-(CH2)m-B Compound 1 Ch-A1-L-A2-C(O)-C(R1)-(CH2)m-B Compound 1A Ch-A1-(CH2)n-A2-C(O)-LDOPA Compound 1B wherein:Ch is selected from any neutral chelating ligand A1and A2are each independently selected from a covalent bond, -C(R2)2-, -NR2-, -O- and –S-, preferably -O- and –NR2-, more preferably -O-, n is 1 to 12, preferably 4 to 8, more preferably 6 m is 0 to 3, preferably 1 to 2, more preferably 1 L is selected from C1-C12 alkyl, alkenyl or alkynyl optionally substituted with C1 to C4 linear or branched alkyl, alkenyl or alkynyl. R1is selected from amine, amide, carbamide and carbamate optionally substituted with C1 to C6 linear or branched alkyl (eg –NHC(O)OH, –NHC(O)OCH3, –NHC(O)OCH2CH3, –NHC(O)Otertbutyl) R2is independently selected from hydrogen, C1-C6 alkyl, alkenyl or alkynyl optionally substituted with C1 to C4 linear or branched alkyl, alkenyl or alkynyl, hydroxyl, C1-C6 alkoxy and halo, preferably R2is independently selected from hydrogen, C1-C6 alkyl, hydroxyl, C1-C6 alkoxy and halo, more preferably R2is independently selected from hydrogen or C1-C6 alkyl B is phenyl substituted by one to five hydroxyl groups, optionally the hydroxyl groups are protected (for example, with a silyl ether group).

[0012] The present invention provides a metal-binding compound according to compound 1: Ch-A1-(CH2)n-A2-C(O)-C(R1)-(CH2)m-B Compound 1 wherein: Ch is selected from any neutral chelating ligand A1and A2are each independently selected from a covalent bond, -C(R2)2-, -NR2-, -O- and –S-., preferably -O- and –NR2-, preferably -O-, n is 1 to 12, preferably 4 to 8, more preferably 6m is 0 to 3, preferably 1 to 2, more preferably 1 R1is selected from amine, amide, carbamide and carbamate optionally substituted with C1 to C6 linear or branched alkyl (eg –NHC(O)OH, –NHC(O)OCH3, –NHC(O)OCH2CH3, –NHC(O)Otertbutyl) R2is independently selected from hydrogen, C1-C6 alkyl, alkenyl or alkynyl optionally substituted with C1 to C4 linear or branched alkyl, alkenyl or alkynyl, hydroxyl, C1-C6 alkoxy and halo, preferably R2is independently selected from hydrogen, C1-C6 alkyl, hydroxyl, C1-C6 alkoxy and halo, more preferably R2is independently selected from hydrogen or C1-C6 alkyl B is phenyl substituted by one to five hydroxyl groups, optionally the hydroxyl groups are protected (for example, with a silyl ether group).

[0013] The present invention provides a metal-binding compound according to compound 1A: Ch-A1-L-A2-C(O)-C(R1)-(CH2)m-B Compound 1A wherein: Ch is selected from any neutral chelating ligand A1and A2are each independently selected from a covalent bond, -C(R2)2-, -NR2-, -O- and –S-., preferably -O- and –NR2-, preferably -O-, m is 0 to 3, preferably 1 to 2, more preferably 1 L is selected from C1-C12 alkyl, alkenyl or alkynyl optionally substituted with C1 to C4 linear or branched alkyl, alkenyl or alkynyl. R1is selected from amine, amide, carbamide and carbamate optionally substituted with C1 to C6 linear or branched alkyl (eg –NHC(O)OH, –NHC(O)OCH3, –NHC(O)OCH2CH3, –NHC(O)Otertbutyl) R2is independently selected from hydrogen, C1-C6 alkyl, alkenyl or alkynyl optionally substituted with C1 to C4 linear or branched alkyl, alkenyl or alkynyl, hydroxyl, C1-C6alkoxy and halo, preferably R2is independently selected from hydrogen, C1-C6 alkyl, hydroxyl, C1-C6 alkoxy and halo, more preferably R2is independently selected from hydrogen or C1-C6 alkyl B is phenyl substituted by one to five hydroxyl groups, optionally the hydroxyl groups are protected (for example, with a silyl ether group).

[0014] The present invention provides a metal-binding compound according to compound 1B: Ch-A1-(CH2)n-A2-C(O)-LDOPA Compound 1B wherein: Ch is selected from any neutral chelating ligand A1and A2are each independently selected from a covalent bond, -C(R2)2-, -NR2-, -O- and –S-., preferably -O- and –NR2-, preferably -O-, n is 1 to 12, preferably 4 to 8, more preferably 6 R2is independently selected from hydrogen, C1-C6 alkyl, alkenyl or alkynyl optionally substituted with C1 to C4 linear or branched alkyl, alkenyl or alkynyl, hydroxyl, C1-C6 alkoxy and halo, preferably R2is independently selected from hydrogen, C1-C6 alkyl, hydroxyl, C1-C6 alkoxy and halo, more preferably R2is independently selected from hydrogen or C1-C6 alkyl.

[0015] Optionally, Ch is bipyridine (Bpy), terpyridine (Terpy or Tpy), ethylenediamine (En), tris(2-aminoethyl)amine (Tren), Diethylenediamine (dien), porphyrins, crown ethers, or cryptands. Preferably, Ch is terpyridine or diethylenediamine.

[0016] The terpyridine can be connected to the metal-binding compound via any of the pyridine rings in the terpyridine. Preferably, the terpyridine is connected via the central pyridine ring. The connection to the metal-binding compound can be via any carbon in the terpyridine. Preferably, the connection to the metal-binding compound is via the carbon para to the nitrogen in the central pyridine ring in the terpyridine.

[0017] The diethylenediamine can be connected to the metal-binding compound via any of the carbon or nitrogen atoms in the diethylenediamine. Preferably, the diethylenediamine is connected via the central nitrogen atom.

[0018] Optionally, L is C5 to C7 alkyl. Preferably, L is C6 alkyl.

[0019] Where B has one or two hydroxyl groups, optionally they are at position 3 and / or 4 on the phenyl ring. Where B has three or four hydroxyl groups, optionally they are at positions 2 to 5 on the phenyl ring. Optionally the hydroxyl groups on B are protected by a protecting group, preferably a silyl ether group.

[0020] Alternatively, the metal-binding compound is L-DOPA connected to a neutral metal ion chelator via a linker. Optionally, the linker is O-(CH2)nOC(O)- where n is 1 to 12, or -(O-CH2-CH2)m-OC(O)-, where m is 1 to 4. Preferably, the chelating ligand is terpyridine.

[0021] The present invention provides a metal-binding compound selected from: ,,, and .Substrate bound metal-binding compound

[0022] Optionally, one or more metal-binding compound of the invention is bound to a substrate. Preferably, the substrate is bound to a plurality of metal-binding compounds. In some embodiments, at least a portion of the substrate is coated in metal-binding compounds. By coated, it is meant that one or more portions of the surface area of the substrate are covered or saturated with metal-binding compound.

[0023] Optionally, the substrate is a silicone, silicone coated substance, fibrous material or combination thereof (for example, a silicone coated fibrous material). The fibrous substance is selected from mineral wool (preferably stone wool or silicon wool), slag wool, glass wool or ceramic fibres. More preferably, the fibrous material is silicon wool or a silicon wafer or stone wool.

[0024] Optionally, when the substrate is a mineral wool (preferably stone wool or silicon wool), substrate further comprises a binder.

[0025] Optionally, the binder is selected from one or more inorganic binders, or organic binders. Preferably, the binder is selected from phenol formaldehyde binder, urea formaldehyde binder, phenol urea formaldehyde binder, melamine formaldehyde binder, condensation resins, acrylates and other latex compositions, epoxy polymers, silane binder, sodium silicate, hotmelts of polyurethane, polyethylene, polypropylene, and polytetrafluoroethylene polymers.

[0026] Optionally, the binder is coated onto to the substrate. In some embodiments, the substrate is coated with binder and then coated with metal-binding compound.

[0027] The one or more metal-binding compound attaches to the substrate via the binding group B. Optionally, the attachment is by one or more covalent bond, preferably by oxidative polymerisation. The attachment is optionally directly to the substrate or to the binder portion of a substrate. Optionally, binding group B is a phenol, catechol, pyrogallol, hydroxyquinol or 1,2,3,4-benzenetetrol group. Preferably, binding group B is a catechol group.

[0028] The binding group B may include groups such as L-DOPA, dopamine, tyrosine, tyramine, synephrine, epinephrine, norepinephrine or 3-methoxytyramine. The binding group B may include groups such as DOPA, dopamine, tyrosine, tyramine, synephrine, epinephrine, norepinephrine or 3-methoxytyramine. Preferably, the binding group B comprises DOPA (3,4-dihydroxyphenylalanine), optionally L-DOPA or D-DOPA. In some embodiments, the binding group comprises L-DOPA. Metal-complex

[0029] The present invention further provides a metal-complex comprising the metal- binding compound of the invention complexed with one or more metal ion, preferably positively charged metal ion. Optionally, the metal ion has a 1+ charge, optionally the metal ion has a 2+ charge, optionally, the metal ion has a 3+ charge, optionally the metal ion has a 4+ charge, optionally the metal ion has a 5+ charge, optionally the metal ion has a 6+ charge. Preferably the metal ion has a 1+, 2+, or 3+ charge. Optionally, the metal-binding compound is complexed with more than one type of metal ion.

[0030] Preferred metal ions are lead (Pb2+) zinc (Zn2+), nickel (Ni2+), mercury (Hg2+), cadmium (Cd2+), copper (Cu2+), chromium (Cr3+or Cr6+), arsenic (As3+or As5+), silver (Ag+), iron (Fe2+or Fe3+), manganese (Mn2+), molybdenum (Mo6+), calcium (Ca2+), antimony (Sb5+), cobalt (Co2+) and combinations thereof. Other metal ions are contemplated.

[0031] The number of different ions for complexation is not limited. The binding of metal ions to the ligands of the metal-binding compound would be able to be determined through the different stability constants.Substrate bound metal-complex

[0032] Optionally, one or more metal-complex of the invention is bound to a substrate. Preferably, the substrate is bound to a plurality of metal-complexes. The options for the substrate are the same as described for the substrate bound metal-binding compound. Options for the metal-complex are also as described above.

[0033] The substrate usually includes a plurality of metal-complexes.

[0034] In another aspect, the present invention provides a substrate bound to one or more metal-binding compound, the metal-binding compound having a structure according to compound 1, 1A or 1B: Ch-O-(CH2)n-O-C(O)-C(R)-(CH2)m-B Compound 1 or Ch-O-L-O-C(O)-C(R)-(CH2)m-B Compound 1A or Ch-O-(CH2)n-O-C(O)-LDOPA Compound 1B wherein: Ch is selected from any neutral chelating ligand, n is 1 to 12, preferably 4 to 8, more preferably 6, m is 0 to 3, preferably 1 to 2, more preferably 1, L is selected from C1-C12 alkyl, alkenyl or alkynyl optionally substituted with C1 to C4 linear or branched alkyl, alkenyl or alkynyl,R is selected from amine, amide, carbamide and carbamate optionally substituted with C1 to C6 linear or branched alkyl (eg –NHC(O)OH, –NHC(O)OCH3, –NHC(O)OCH2CH3, –NHC(O)Otertbutyl), B is phenyl group substituted by one to five hydroxyl groups, optionally the hydroxyl groups are protected, wherein the one or more metal-binding compound is bound to the substrate via B, and the substrate is selected from silicone, silicone coated substance, fibrous material, or combinations thereof. Preferably, the fibrous material is selected from mineral wool, slag wool, glass wool, ceramic fibres and combinations thereof. More preferably, the mineral wool is stone wool.

[0035] Optionally, Ch is bipyridine (Bpy), terpyridine (Terpy or Tpy), ethylenediamine (En), tris(2-aminoethyl)amine (Tren), Diethylenediamine (dien), porphyrins, crown ethers, or cryptands. Preferably, Ch is terpyridine or diethylenediamine.

[0036] Optionally, L is C5 to C7 alkyl. Preferably, L is C6 alkyl.

[0037] Optionally, binding group B is a phenol, catechol, pyrogallol, hydroxyquinol or 1,2,3,4-benzenetetrol group. Preferably, binding group B is a catechol group.

[0038] Alternatively, the one or more metal-binding compound is bound to the substrate via B, D-DOPA or L-DOPA. Preferably, L-DOPA. Alternatively, the metal- binding compound is L-DOPA connected to a neutral metal ion chelator via a linker. Optionally, the linker is O-(CH2)nOC(O)- where n is 1 to 12, or -(O-CH2-CH2)m-OC(O)-, where m is 1 to 4. Preferably, the chelating ligand is terpyridine.

[0039] Optionally, the metal-complex comprising the substrate bound metal-binding compound is complexed with one or more metal ions. Preferably, the metal ions are lead (Pb2+) zinc (Zn2+), nickel (Ni2+), mercury (Hg2+), cadmium (Cd2+), copper (Cu2+), chromium (Cr3+or Cr6+), arsenic (As3+or As5+), silver (Ag+), iron (Fe2+or Fe3+), manganese (Mn2+), molybdenum (Mo6+), calcium (Ca2+), antimony (Sb5+), cobalt (Co2+) and combinations thereof. Other metal ions are contemplated.Method of preparing metal-binding compound

[0040] The present invention further provides a method of preparing a metal-binding compound, the method comprising reacting a compound according to formula 2A: Formula 2A wherein, Ch is selected from any neutral chelating ligand; A1is selected from a covalent bond, -C(R2)2-, -NR2-, -O- and –S-; R2is independently selected from hydrogen, C1-C6 alkyl, alkenyl or alkynyl optionally substituted with C1 to C4 linear or branched alkyl, alkenyl or alkynyl, hydroxyl, C1-C6 alkoxy and halo, preferably R2is selected from hydrogen, C1-C6 alkyl, hydroxyl, C1-C6 alkoxy and halo; n is 1 to 12, preferably 4 to 8, more preferably 6; and Z is selected from -N(R2)H, -OH, -SH and halo, with a compound according to formula 2B:wherein, m is 0 to 3, preferably 1 to 2, more preferably 1; X is selected from hydroxyl, -N(R2)H2, chloride, bromide, or iodide, preferably hydroxyl or chloride, more preferably hydroxyl; R1is selected from amine, amide, carbamide and carbamate optionally substituted with C1 to C6 linear or branched alkyl (eg –NHC(O)OH, –NHC(O)OCH3, –NHC(O)OCH2CH3, –NHC(O)Otertbutyl); R2is selected from the options as recited above; andB is phenyl substituted by one to five hydroxyl groups, to produce a metal-binding compound according to Compound 1:

[0041] The skilled person is able to adjust this method for the preparation of any of the metal-binding compounds of the invention.

[0042] In another aspect, the invention provides a further method of preparing a metal- binding compound, the method comprising contacting a compound according to formula 2C:wherein, Ch is selected from any neutral chelating ligand; A1is selected from a covalent bond, -C(R2)2-, -NR2-, -O- and –S-; R2is independently selected from hydrogen, C1-C6 alkyl, alkenyl or alkynyl optionally substituted with C1 to C4 linear or branched alkyl, alkenyl or alkynyl, hydroxyl, C1-C6 alkoxy and halo, preferably R2is selected from hydrogen, C1-C6 alkyl, hydroxyl, C1-C6 alkoxy and halo; Z is selected from -N(R2)H, -OH, -SH and halo; and L is selected from C1-C12 alkyl, alkenyl or alkynyl optionally substituted with C1 to C4 linear or branched alkyl, alkenyl or alkynyl, with a compound according to formula 2B:Formula 2B wherein, m is 0 to 3, preferably 1 to 2, more preferably 1; X is selected from hydroxyl, - N(R2)H2, chloride, bromide, or iodide, preferably hydroxyl or chloride, more preferably hydroxyl; R1is selected from amine, amide, carbamide and carbamate optionally substituted with C1 to C6 linear or branched alkyl (eg –NHC(O)OH, –NHC(O)OCH3, –NHC(O)OCH2CH3, –NHC(O)Otertbutyl); R2is selected from the options as recited above; and B is phenyl substituted by one to five hydroxyl groups, to produce a metal-binding compound according to Compound 1A:Compound 1A.

[0043] Optionally, the hydroxyl groups in B are protected by silyl ether groups. When the hydroxyl groups in B are protected by silyl ether groups, the method further comprises the step of removing the protecting groups after forming Compound 1 or Compound 1A.

[0044] Optionally, the protecting groups are removed via fluoride-mediated cleavage or via acid-mediated cleavage. Preferably, the protecting groups are removed via fluoride- mediated cleavage.

[0045] Optionally, the methods of preparing the metal-binding compound further comprise a preliminary step of protecting the hydroxyl groups in B with a suitable protecting group (such as silyl ether groups).

[0046] Optionally, contacting the compounds comprises dissolving the compounds in an organic solvent. Preferably, the organic solvent is a halogenated solvent. More preferably, the halogenated solvent is dichloromethane.

[0047] The skilled person is able to adjust this method for the preparation of any of the metal-binding compounds of the invention.

[0048] Optionally, the methods of preparing the metal-binding compound further comprise a step of deprotecting the hydroxyl groups in B to remove the suitable protecting group (such as silyl ether groups). Method of preparing substrate bound metal-binding compound

[0049] The present invention provides a method comprising: - selecting a metal-binding compound according to the invention - removing any protecting groups from the binding group B - contacting the metal-binding compound of the invention (with an unprotected binding group B) with the substrate in the presence of an oxidising agent - oxidative polymerisation of the metal-binding compound with the substrate to prepare a substrate bound metal-binding compound.

[0050] Optionally, the oxidising agent is acid, optionally HCl such as Tris-HCl.

[0051] Optionally, the binding group B of the metal-binding compound includes one or more hydroxyl group. The one or more hydroxyl group is optionally protected by tert- butyldimethylsilyl (TBDMS) groups, trimethylsilyl (TMS) groups, tri-iso- propylsilyloxymethyl (TOM) groups, or triisopropylsilyl (TIPS) groups. Optionally, the protecting groups are removed via fluoride-mediated cleavage or via acid-mediated cleavage following preparation of the substrate bound metal-binding compound.

[0052] Optionally, the contacting of the metal-binding compound with the substrate occurs in a liquid, preferably water comprising the oxidising agent. In some embodiments, the contacting is by at least partially submerging the substrate in a liquid comprising the oxidising agent and metal-binding compound (ie dipping). Preferably, the concentration of metal-binding compound is sufficient to result in substrate with at leasta portion coated in metal-binding compound. In some embodiments, the contacting is by spraying the substrate with a liquid comprising the metal-binding compound and a liquid comprising the oxidising agent. In some embodiments, the substrate is sprayed with the oxidising agent and the metal-binding compound separately.

[0053] The present invention provides a method of producing a substrate bound to one or more metal-binding compound comprising: - selecting a metal-binding compound according to the invention - removing any protecting groups from the binding group B - contacting the metal-binding compound of the invention (with an unprotected binding group B) with a substrate in the presence of an oxidising agent - oxidative polymerisation of the metal-binding compound with the substrate to prepare the substrate bound metal-binding compound according to the invention.

[0054] Optionally, the oxidising agent is acid, optionally HCl such as Tris-HCl.

[0055] Optionally, the binding group B of the metal-binding compound includes one or more hydroxyl group. The one or more hydroxyl group is optionally protected by tert- butyldimethylsilyl (TBDMS) groups, trimethylsilyl (TMS) groups, tri-iso- propylsilyloxymethyl (TOM) groups, or triisopropylsilyl (TIPS) groups. Optionally, the protecting groups are removed via fluoride-mediated cleavage or via acid-mediated cleavage following preparation of the substrate bound metal-binding compound.

[0056] Optionally, the contacting of the metal-binding compound with the substrate occurs in a liquid, preferably water comprising the oxidising agent. In some embodiments, the contacting is by at least partially submerging the substrate in a liquid comprising the oxidising agent and metal-binding compound (ie dipping). Preferably, the concentration of metal-binding compound is sufficient to result in substrate with at least a portion coated in metal-binding compound. In some embodiments, the contacting is by spraying the substrate with a liquid comprising the metal-binding compound and a liquid comprising the oxidising agent. In some embodiments, the substrate is sprayed with the oxidising agent and the metal-binding compound separately.Method of complexing metal ions

[0057] The present invention further provides a method of preparing a metal-binding compound complexed to metal ions comprising: - contacting a metal-binding compound according to the invention or a substrate bound metal-binding compound according to the invention with a liquid comprising metal ions; - resulting in complexation of the metal ions with the metal-binding compound to form a metal-complex.

[0058] Optionally, the liquid is water. Optionally, the water is wastewater, surface water, rainwater, urban water or storm water.

[0059] When there is a plurality of metal-binding compound attached to a substrate, optionally, following complexing the ratio of metal ion to metal-binding compound is 0.5 to 0.9, 0.6 to 0.9, 0.7 to 0.8, or about 0.75.

[0060] Optionally, contacting of the metal ions with the metal-binding compound is for at least 1 second. The contacting of the metal ions with the metal-binding compound may be between 1 second and 1 week, 30 seconds and 1 week, 1 hour and 3 days, or 1 hour and 1 day. Optionally binding is between 15 to 45 minutes, 20 to 40 minutes, or about 30 minutes.

[0061] Optionally, the concentration of the metal ions are between about 0.01 mg / L and about 1 g / L, preferably between about 1 mg / L and about 0.1 g / L, preferably between about 1 mg / L and about 50 mg / L, more preferably between about 1 mg / L and about 10 mg / L.

[0062] Optionally, contact with the liquid comprising metal ions is via flow of the liquid via the metal-binding compound. Alternatively, the liquid is stagnant.

[0063] Optionally, the method results in a liquid having a reduced metal ion content. Method of reversing complexation of the metal ions

[0064] The present invention further provides a method of reversing the complexation of metal ions from a metal-complex comprising:- selecting a metal-complex of the invention (ie a metal-binding compound of the invention that is complexed to metal ions) - contacting the metal-complex of the invention with a competitive chelator that favourably binds the metal ions when compared to the metal-complex resulting in metal ions bound to the competitive chelator and metal-binding compound uncomplexed from metal ions.

[0065] Optionally, the competitive chelator is EDTA, DOTA, NOTA, TETA, DOTAM, TCMC, DTPA or HEDTA. Preferably, the competitive chelator is EDTA.

[0066] Optionally, the contacting is by inclusions of the metal-complex and the competitive chelator in the same liquid. Preferably, the liquid is water.

[0067] Optionally, the metal-complex is contacted with the competitive chelator for at least 1 second, at least 30 seconds, or 1 second to 1 week, 30 seconds to 1 week. Optionally, 30 seconds to 24 hours,

[0068] Optionally, the contact of the metal-complex with the competitive chelator results in removal of 50 to 100%, 55 to 95%, 60 to 90%, 65 to 85%, 70 to 80% or about 75% of the complexed metal ions.

[0069] The concentration of the competitive chelator and metal binding-compound is dependent on the application. The amount of chelator will depend on the amount of metal-complex formed, the concentration of metal ions targeted, the quantity of substrate and the surface area covered by the metal-binding compound attached to the substrate. Optionally, the competitive chelator is used at a 1 to 3 mmol concentration, preferably 2 mmol. Method of treating water

[0070] In another aspect, the present invention includes a method of treating water comprising metal ions including: - contacting a metal-binding compound of the invention and / or a substrate bound metal-binding compound with wastewater comprising metal ions;- complexing the metal ions with the metal-binding compound / substrate bound metal-binding compound to form a metal-complex / substrate bound metal- complex.

[0071] In an alternative aspect, a method of treating water comprising metal ions including: - contacting a substrate bound metal-binding compound with wastewater comprising metal ions; - complexing the metal ions with the substrate bound metal-binding compound to form a substrate bound metal-complex.

[0072] Optionally, the method further comprises, contacting the metal- complex / substrate bound metal-complex with a competitive chelator that favourably complexes the metal ions to produce metal-binding compound of the invention and / or a substrate bound metal-binding compound uncomplexed from metal ions. Optionally, the method further comprises contacting the uncomplexed metal-binding compound of the invention and / or a substrate bound metal-binding compound with water comprising metal ions again.

[0073] Optionally, the method reduces the concentration of metal ions in a liquid.

[0074] In another aspect, the present invention includes a water filter comprising: a body comprising a filter material, the body having an upstream end for receiving liquid to be filtered and a downstream end for releasing filtered liquid from the body following contact of the liquid with the filter material, wherein the filter material comprises one or more metal-binding compound and / or substrate bound metal-binding compound of the present invention.

[0075] In an alternative aspect, the present invention includes a water filter comprising: a body comprising a filter material, the body having an upstream end for receiving liquid to be filtered and a downstream end for releasing filtered liquid from the body following contact of the liquid with the filter material,wherein the filter material comprises one or more substrate bound metal-binding compound of the present invention.

[0076] The body is suitable to facilitate contact between a liquid containing metal ions (preferably water) passed through the upstream end and into the body and the filter material and such that the metal ions bind with the one or more metal-binding compound and / or substrate bound metal-binding compound of the present invention to form metal-complex or substrate bound metal-complex of the invention.

[0077] Optionally, the upstream end may further comprise an inlet.

[0078] Optionally, the downstream end may further comprise an outlet.

[0079] Optionally, the filter material is a fibrous material preferably, mineral wool, coated with one or more metal-binding compound of the present invention.

[0080] Optionally, the liquid is water. Optionally, the water is wastewater, surface water, rainwater, urban water or storm water.

[0081] Optionally, the filter material is installed as part of a wastewater, rainwater or underground water system.

[0082] Preferably, the substrate for the substrate bound metal-binding compound in the filter is stone wool. Specific aspect of interest

[0083] In one aspect, the present invention provides substrate covalently bound to one or more metal-binding compound according to compound 1: Ch-O-(CH2)n-O-C(O)-C(R)-(CH2)m-B Compound 1 wherein: Ch is selected from any neutral chelating ligand, n is 4 to 8, preferably 6, m is 1 to 2, more preferably 1,R is selected from amine, amide, carbamide and carbamate optionally substituted with C1 to C6 linear or branched alkyl (eg –NHC(O)OH, –NHC(O)OCH3, –NHC(O)OCH2CH3, –NHC(O)Otertbutyl), and B is phenyl group substituted by one to five hydroxyl groups, optionally the hydroxyl groups are protected, wherein the substrate is a fibrous material, preferably stone wool.

[0084] Optionally, the substrate is covalently bound to the one or more metal-binding compound by oxidative polymerisation.

[0085] Optionally, the one or more metal-binding compound is a coating of metal- binding compounds over at least a portion of the substrate.

[0086] Further limitations for the substrate and metal-binding compound are as described elsewhere in the specification. Methods of making the metal-binding compound and substrate bound metal-binding compound, and metal complexed versions of these are as described elsewhere in the specification. Methods of using the metal-binding compound and substrate bound metal-binding compound to bind metal ions and reverse the metal binding are also described elsewhere in the specification. The method of treating water and water filter of the invention are also contemplated to include this substrate covalently bound to one or more metal-binding compound.

[0087] As used herein, except where the context requires otherwise, the term "comprise" and variations of the term, such as "comprising", "comprises" and "comprised", are not intended to exclude further additives, components, integers or steps.

[0088] Further aspects of the present invention and further embodiments of the aspects described in the preceding paragraphs will become apparent from the following description, given by way of example and with reference to the accompanying drawings. Brief description of the drawings

[0089] Figure 1. Synthetic pathway of exemplified modified L-DOPA containing a bromine (compounds 3 and 4) or terpyridine (compounds 6 and 7) moiety – denoted as the split hemisphere referring to the bromine or terpyridine respectively.

[0090] Figure 2. (A) Wide scan XPS spectra of silicon surfaces coated with Br- modified L-DOPA and the corresponding C 1s (B) and Br 3d (C) high resolution spectra.

[0091] Figure 3. ToF-SIMS spectra of an exemplary silicon surface coated with Br- modified L-DOPA.

[0092] Figure 4. UV-Vis spectra of the protected DOPA, DOPA containing the ligand, its complexes with Zn(tf)2 and NiCl2, and Zn(tf)2 and NiCl2 in CHCl3, concentration 2.6 × 10-5mol / L.

[0093] Figure 5. (A) 600 MHz1H-NMR spectrum in DMSO-d6of the terpyridine carrying L-DOPA entity (7) as well as (B) the associated high-resolution ESI-MS spectrum.

[0094] Figure 6. (A) XPS wide scan spectra of Si-surfaces coated surface with terpyridine carrying L DOPA, exposed to Zn2+(B) corresponding XPS wide scan spectra of Si-surfaces coated with ligand-free L-DOPA control analysis (highlights from left to right indicate Zn 2p, O 1s, N 1s and C 1s respectively) and (C) XPS wide scan spectra of Si-surfaces coated with terpyridine carrying L-DOPA, exposed to Ni2+analysis and (D) corresponding Si-surfaces coated ligand-free control surface (highlights from left to right indicate Ni 2p, O 1s, N 1s and C 1s respectively).

[0095] Figure 7. (A) XPS High resolution Zn 2p spectra of Si-surfaces coated surface with terpyridine carrying L DOPA, exposed to Zn2+(B) corresponding XPS High resolution Zn 2p spectra of Si-surfaces coated with ligand-free L-DOPA control analysis and (C) XPS high resolution Ni 2p spectra of Si-surfaces coated with terpyridine carrying L-DOPA, exposed to Ni2+analysis and (D) corresponding Si-surfaces coated ligand-free control surface.

[0096] Figure 8. Time-dependent evolution of the amount of surface bound Zn2+on the surface of terpyridine containing L-DOPA coated Si-wafers exposed to EDTA solution, evidencing the removal of the metal ions from the surface, followed by XPS of the Zn 2p signal.

[0097] Figure 9. Time-dependent evolution of the amount of surface bound Zn2+on the surface of terpyridine carrying L DOPA coated Si-wafers exposed to EDTA solution, evidencing the removal of the metal ions from the surface. High resolution XPS spectraof Zn 2p (A) Zn2+coordinated to terpyridine containing L-DOPA coated Si surface, (B) Zn2+coordinated surface exposed to EDTA for 1 min. (C) Zn2+coordinated surface exposed to EDTA for 10 min and (D) Zn2+coordinated surface exposed to EDTA for 30 min.

[0098] Figure 10. XPS wide scan spectra of control experiments to determine the effect of pH on the efficacy of metal removal. (A) shows the Zn2+coordinated terpyridine carrying L-DOPA substrate exposed to pH =10 solution for 10 min (highlights from left to right indicate Zn 2p, O 1s, N 1s and C 1s respectively). (B) shows the Ni2+coordinated terpyridine carrying L-DOPA substrate placed in a pH =10 solution for 10 min (highlights from left to right indicate Ni 2p, O 1s, N 1s and C 1s respectively). After 10 min, the metal ion is still coordinated to the ligand, evidencing that pH has no effect on the ability of EDTA to remove the metal from the surface.

[0099] Figure 11. Wide scan XPS spectra of (A) a fiber coated with Br-modified L--DOPA, and (B) pristine fiber and inset showing the ToF-SIMS image of a single fiber. The white colour of the image represents the Br- fragment.

[0100] Figure 12. (A) XPS wide scan spectra of fibers coated with terpyridine carrying L-DOPA (7), exposed to Zn2+solution (B) corresponding XPS wide scan spectra of pristine fibers exposed to Zn2+solution (highlights from left to right indicate Zn 2p, O 1s, N 1s and C 1s respectively) and C) and D) shows the TOF-SIMS image results of Zn2+element. Images clearly show the presence of coordinated metal on fibers. Intensity variation seen on the fibers are due to the non-uniform size of the fibers.

[0101] Figure 13. Comparison XPS wide spectra of (A) fibers coated with terpyridine carrying L-DOPA (7), exposed to Zn2+solution; (B) fibers coated with ligand free L- DOPA exposed to Zn2+solution, and (C) pristine fibers exposed to Zn2+solution.

[0102] Figure 14. XPS wide scan spectra of metal mixtures coordinated to the ligand- modified L-DOPA on Si surfaces; (A) Zn and Pb; (B) Zn and Fe; (C) Zn and Cu; (D) Zn and Ni; and (E) Fe and Pb.

[0103] Figure 15. XPS spectra of (A) Zn2+coordinated to ligand-modified L-DOPA coated fibers, (B) Zn2+coordinated fibers exposed to EDTA for 10 minutes, and (C) re- coordination of Zn2+to the ligand-modified L-DOPA coated fibers, after exposing toEDTA for 10 minutes (highlights from left to right indicate Zn 2p, O 1s, N 1s and C 1s respectively). Detailed description of the embodiments

[0104] The invention discloses a general principal of removing metals from a solution by way of binding the metals to a compound bearing a chelating ligand (Ch) and subsequently removing said metals from the compound by the addition of a preferred chelator ligand, thus providing the metal-free binding compound for further use. The one or more metal-binding compound may be chemically bound to a substrate support by a binding group that is linked to the chelating ligand to provide a more durable and more stable metal binding system. The choice of ligand and binding group can be varied depending on the targeted metal, the substrate, or the application.

[0105] It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention. Definitions

[0106] For purposes of interpreting this specification, terms used in the singular will also include the plural and vice versa.

[0107] As used herein, except where the context requires otherwise, the term "comprise" and variations of the term, such as "comprising", "comprises" and "comprised", are not intended to exclude further additives, components, integers or steps.

[0108] "About" as used herein when referring to a measurable value such as an amount, a temporal duration, and the like, is meant to encompass variations of ±20% or ±10%, in some instances ±5%, in some instances ±1%, and in some instances ±0.1% from the specified value, as such variations are appropriate to perform the disclosed methods.

[0109] Ranges: throughout this disclosure, various aspects of the disclosure can be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as aninflexible limitation on the scope of the disclosure. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 2.7, 3, 4, 5, 5.3, and 6. This applies regardless of the breadth of the range.

[0110] All of the patents and publications referred to herein are incorporated by reference in their entirety.

[0111] Unless otherwise herein defined, the following terms will be understood to have the general meanings which follow.

[0112] The term “C1-C12 alkyl” refers to optionally substituted straight chain or branched chain hydrocarbon groups having from 1 to 12 carbon atoms. Examples include methyl (Me), ethyl (Et), propyl (Pr), isopropyl (i-Pr), butyl (Bu), isobutyl (i-Bu), sec-butyl (s-Bu), tert-butyl (t-Bu), pentyl, neopentyl, hexyl and the like.

[0113] The term “alkenyl” refers to an alkyl group containing at least one carbon- carbon double bond. Examples of alkenyl groups include ethenyl, propenyl, butadienyl (including 1,2-butadienyl and 1,3-butadienyl).

[0114] The term “alkynyl” refers to an alkyl group containing at least one carbon- carbon triple bond. The term “alkynyl” also includes those groups having one triple bond and one double bond.

[0115] The term “hydroxy” or “hydroxyl” refers to the group -OH.

[0116] The term “optionally substituted” in reference to a particular moiety of the compounds of the present invention (eg, an optionally substituted alkyl group) refers to a moiety wherein all substituents are hydrogen or wherein one or more of the hydrogens of the moiety may be replaced by the listed substituents.

[0117] The term “catechol group” as used herein includes groups such as catechol and other catecholamines. For example, L-DOPA, D-DOPA, dopamine, tyrosine, tyramine, synephrine, epinephrine, norepinephrine and 3-methoxytyramine.Substrate

[0118] A substrate as defined herein is a material that provides a surface upon which a metal-binding compound can be coated, deposited, bound or attached.

[0119] Optionally, the substrate is a soft and / or flexible material.

[0120] The substrate may be in the form of a wafer, a wool, or a thread. Other potential forms for a substrate are contemplated.

[0121] The substrate may be made from silicon or have silicon coated on another material, eg a silicon wafer, or a mineral wool, eg stonewool fibers. Other suitable substrates known in the art are contemplated and the person skilled in the art would be able to determine whether a substrate is suitable for a particular application.

[0122] Preferably, the substrate would be able to retain the solution comprising the metals and gradually release it, allowing adequate time for the metal-binding compound on the substrate to capture the metal. Therefore, removing the metal from the solution.

[0123] Optionally, the substrate is able to chemically bind to the metal-binding compound through a separate binding group to the chelating ligand. For example, the OH groups in a substrate such as mineral wool would bind to catechol as a binding group through the hydroxyl groups via two hydrogen-bonds, or a hydrogen-bond and direct coordination with one catechol hydroxyl group, or direct coordination with both catechol hydroxyl groups. Other binding modes and binding groups known in the art are contemplated and the skilled person would be able to determine whether a particular combination of substrates and binding groups would allow favourable binding.

[0124] Optionally, one or more metal-binding compound of the invention is coated onto the substrate. The coating may be applied by dip coating or spray-coating the substrate. Mineral wool / stone wool fibres

[0125] Mineral fibres / stone fibres used in the present invention can have any suitable oxide composition. Stone fibres such as stone wool fibres commonly comprise the following oxides, in percent by weight: SiO2: 30 to 51Al2O3: 12 to 25 CaO: 8 to 30 MgO: 2 to 25 FeO (including Fe2O3): 2 to 15 Na2O+K2O: not more than 10 CaO+MgO: 10 to 30.

[0126] Preferably, the fibres have the following levels of elements, calculated as oxides in wt%: SiO2: at least 30, 32, 35 or 37; not more than 51, 48, 45 or 43 Al2O3: at least 12, 16 or 17; not more than 30, 27 or 25 CaO: at least 8 or 10; not more than 30, 25 or 20 MgO: at least 2 or 5; not more than 25, 20 or 15 FeO (including Fe2O3): at least 4 or 5; not more than 15, 12 or 10 FeO+MgO: at least 10, 12 or 15; not more than 30, 25 or 20 Na2O+K2O: zero or at least 1; not more than 10 CaO+MgO: at least 10 or 15; not more than 30 or 25 TiO2: zero or at least 1; not more than 6, 4 or 2 TiO2+FeO: at least 4 or 6; not more than 18 or 12 B2O3: zero or at least 1; not more than 5 or 3 P2O5: zero or at least 1; not more than 8 or 5 Others: zero or at least 1; not more than 8 or 5.

[0127] More preferably, the fibres used in the invention have the composition in wt%:SiO2 35 to 50 Al2O3 12 to 30 TiO2 up to 2 Fe2O33 to 12 CaO 5 to 30 MgO up to 15 Na2O 0 to 15 K2O 0 to 15 P2O5 up to 3 MnO up to 3 B2O3 up to 3.

[0128] Another preferred composition for the fibres is as follows in wt%: SiO239-55% preferably 39-52% Al2O316-27% preferably 16-26% CaO 6-20% preferably 8-18% MgO 1-5% preferably 1-4.9% Na2O 0-15% preferably 2-12% K2O 0-15% preferably 2-12% R2O (Na2O + K2O) 10-14.7% preferably 10-13.5% P2O50-3% preferably 0-2% Fe2O3 (iron total) 3-15% preferably 3.2-8% B2O30-2% preferably 0-1%TiO20-2% preferably 0.4-1% Others 0-2.0%. Methods of producing mineral wool / stone fibres

[0129] The raw materials used as the mineral material for mineral wool / stone wool fibres can be selected from a variety of sources as is known. These include basalt, diabase, nepheline syenite, glass cullet, bauxite, quartz sand, limestone, rasorite, sodium tetraborate, dolomite, soda, olivine sands, phonolite, K-feldspar, garnet sand and potash.

[0130] Fibres can be made from a mineral melt. A mineral melt is provided in a conventional manner by providing mineral materials and melting them in a furnace. This furnace can be any of the types of furnace known for production of mineral melts, for instance a shaft furnace such as a cupola furnace, a tank furnace, or a cyclone furnace.

[0131] Any suitable method may be employed to form fibres from the mineral melt by fiberisation. The fiberisation can be by a spinning cup process in which the melt is centrifugally extruded through orifices in the walls of a rotating cup (spinning cup, also known as internal centrifugation). Alternatively, the fiberisation can be by centrifugal fiberisation by projecting the melt onto and spinning off the outer surface of one fiberising rotor, or off a cascade of a plurality of fiberising rotors, which rotate about a substantially horizontal axis (cascade spinner).

[0132] The melt is thus formed into a cloud of fibres entrained in air and the fibres are collected as a web on a conveyor and carried away from the fiberising apparatus. The web of fibres is then consolidated, which can involve cross-lapping and / or longitudinal compression and / or vertical compression and / or winding around a mandrel to produce a cylindrical product. Other consolidation processes may also be performed.

[0133] A binder composition may be applied to the fibres preferably when they are cloud entrained in air. Alternatively it can be applied after collection on the conveyor but this is less preferred.

[0134] Conventional types of binder known for use with mineral wool fibres may be used. For example, the binder may be an inorganic binder, or an organic binder.Preferably the binder is an organic binder such as phenol formaldehyde binder, urea formaldehyde binder, phenol urea formaldehyde binder, melamine formaldehyde binder, condensation resins, acrylates and other latex compositions, epoxy polymers, silane binder, sodium silicate and hotmelts of polyurethane, polyethylene, polypropylene, and polytetrafluoroethylene polymers.

[0135] Conventionally-used phenol-formaldehyde or phenol-urea-formaldehyde (PUF) based resol binders optionally contain a sugar component. For these binders, without sugar component, reference is for example made to EP 0148050 and EP 0996653. For these binders, with sugar component, reference is made to WO 2012 / 076462. Another group of binders that can be used are based on alkanolamine-polycarboxylic acid anhydride reaction products. A cured thermoset binder, the non-cured binder comprising (1) a water-soluble binder component obtainable by reacting at least one alkanolamine with at least one polycarboxylic acid or anhydride and, optionally, treating the reaction product with a base; (2) a sugar component; and optionally (3) urea. For these binders, reference is for example made to WO 2012 / 010694 and WO 2013 / 014076.

[0136] After consolidation, the consolidated web of fibres is passed into a curing device to cure the binder. Spray-coated mineral fibre webs are generally cured in a curing oven by means of a hot air stream. The hot air stream may be introduced into the mineral fibre web from below, or above or from alternating directions in distinctive zones in the length direction of the curing oven.

[0137] If desired, the mineral wool web may be subjected to a shaping process before curing. The bonded mineral fibre product emerging from the curing oven may be cut to a desired format e.g., in the form of a batt.

[0138] In one embodiment, the curing is carried out at temperatures from 100 to 300°C, such as 170 to 270°C, such as 180 to 250°C, such as 190 to 230°C.

[0139] Preferably, the curing takes place in a conventional curing oven for mineral wool production, preferably operating at a temperature of from 150 to 300°C, such as 170 to 270°C, such as 180 to 250°C, such as 190 to 230°C.

[0140] The curing takes place for a time of 30 seconds to 20 minutes, such as 1 to 15 minutes, such as 2 to 10 minutes.

[0141] In a typical process, curing takes place at a temperature of 150 to 250 °C for a time of 30 seconds to 20 minutes.

[0142] The curing process may commence immediately after application of the binder to the fibres. The curing is defined as a process whereby the binder composition undergoes a physical and / or chemical reaction that in case of a chemical reaction usually increases the molecular weight of the compounds in the binder composition and thereby increases the viscosity of the binder composition, usually until the binder composition reaches a solid state. The cured binder composition binds the fibres to form a structurally coherent matrix of fibres.

[0143] The curing of the binder in contact with the mineral fibres may take place in a heat press.

[0144] The curing of a binder in contact with the mineral fibres in a heat press has the particular advantage that it enables the production of high-density products.

[0145] The curing process may comprise drying by pressure. The pressure may be applied by blowing air or gas through / over the mixture of mineral fibres and binder.

[0146] Conventional fibres have a median diameter of 2 to 5µm and a median length of 1800 to 3000 µm. The ratio of the fibre length to fibre diameter for conventional mineral wool fibres is generally in the range of 600 to 800. The median diameter of the fibres can be obtained automatically using a scanning electron microscope (SEM) to measure the diameter of the fibres and counting the number of fibres in the sample. The ratio of the median fibre length to median fibre diameter is in the range 25 to 500, preferably in the range 100 to 300.

[0147] When mineral / stone wool is placed in water, water flows into the mineral wool until the wool is saturated. The water is then retained. After about one hour, about 80% v / v of the water retained by the wool is released back into solution. It may take about 24 hours or more for all water retained by the mineral wool to exchange with water in the solution.

[0148] When a substrate comprising mineral / stone wool bound to one or more metal- binding compound of the invention has been contacted with a liquid containing metal ions it may be left in the liquid indefinitely, to constantly retain and exchange water withthe solution. The metal ions complexed with the metal-binding compound to form metal- complex of the invention will remain as metal complex until the substrate is removed from the liquid for contact with a competing chelator.

[0149] As little as a few seconds contact with the liquid could result in binding of metal ions and improving the metal ion concentration in the liquid. On the other hand, the metal-binding compound or substrate bound metal-binding compound can remain in the liquid as long as desired. Chelating ligands

[0150] A ligand herein defined is an ion or molecule containing a chemical functional group that binds to a central metal atom to form a coordination complex. Binding with the metal generally involves the formal donation of one or more of the ligand’s electron pairs and the nature of the donation can range from covalent to ionic.

[0151] Chelating ligands are ligands containing two or more separate coordinating bonds to a single central metal atom. Chelating ligands may also be referred to as chelants, chelators, chelating agents, or sequestering agents.

[0152] The denticity of a chelating ligand refers to the number of groups that bind to the metal centre. Chelating ligands may be bidentate (two groups), tridentate (three groups), tetradentate (four groups) or polydentate (many groups). Examples of chelating ligands and their denticity would be known to the person skilled in the art and the selection of chelating ligands for preferentially coordinating different metals is contemplated.

[0153] Non-limiting examples of chelating ligands are bipyridine (Bpy), terpyridine (Terpy or Tpy), ethylenediamine (En), tris(2-aminoethyl)amine (Tren), diethylenediamine (dien), porphyrins, crown ethers, or cryptands. Other examples of chelating ligands known in the art are contemplated.

[0154] Chelating ligands have a greater affinity of binding to metal ions to that of similar monodentate ligands (ligands with a single electron pair donor). This is known as the chelate effect. The binding of a chelating ligand is likely to be thermodynamically favourable compared to aqueous metals ions in solution (eg metal complexes of the form [E(OH2)n]m+]) as the change in entropy (∆S) when displacing the water ligand willincrease due to an increased number of discrete molecules produced in the reaction. For example, one bidentate ligand will displace two water molecules from a metal ion. This leads to a favourable (negative) Gibbs energy (∆G) for the reaction.

[0155] This can be shown by the following simplified equation: ∆G = ∆H - T∆S wherein ∆H is the enthalpy and T is the temperature. The larger the value of T∆S, the more likely ∆G will be negative, and therefore mean a favourable reaction / binding.

[0156] Binding of a metal to a chelating ligand of the present invention may be reversible by providing the metal-complex compound with a more favourable chelator, thus releasing the metal from the metal-complex. For example, when the chelating ligand is a tridentate ligand, a competing chelator with a higher denticity such as ethylenediaminetetraacetic acid (EDTA), can be added to the solution containing the metal-complex. Metal binding to the chelator would be more favoured due to the higher denticity and therefore remove the metal from the metal-complex. This then removes the bound metal coordinated to EDTA and regenerates the metal free metal-binding compound for further metal complexation. General principle of synthesis

[0157] The person skilled in the art would be aware of the various methods that are available to synthesise the compounds of the present invention. In particular, the person skilled in the art would know various ways by which the chelating ligand and the linker group may be chemical bound. For example, the skilled person may use the non-limiting examples of nucleophilic aromatic substitution, Fischer ester synthesis, Fischer amide synthesis, Steglich esterification chemistry or cross-coupling chemistry to bind the chelating ligand, linker and binding group. Other methods known in the art are contemplated.

[0158] Non-limiting examples of cross-coupling reactions include Kumada, Heck, Sonogashira, Negishi, Stille, Suzuki, Murahashi, Hiyama, Fukuyama, Ullmann, Chan- Lam and Buchwald-Hartwig. Other methods known in the art are contemplated.

[0159] The person skilled in the art would be aware of Fischer ester synthesis or Fischer amide synthesis, wherein a carbonyl acid halide (-C(O)X, wherein X is ahalogen) is directly bonded with a compound containing an alcohol or an amine to produce an ester or amide from the carbonyl acid halide and the alcohol or amine. The person skilled in the art would be aware of the various conditions and reagents used in such reactions and could adapt the conditions to synthesise compounds disclosed by the present invention. Certain embodiments

[0160] Embodiment 1: A metal-binding compound according to compound 1, 1A or 1B: Ch-O-(CH2)n-O-C(O)-C(R)-(CH2)m-B Compound 1 or Ch-O-L-O-C(O)-C(R)-(CH2)m-B Compound 1A or Ch-O-(CH2)n-O-C(O)-LDOPA Compound 1B wherein: Ch is selected from any neutral chelating ligand, n is 1 to 12, preferably 4 to 8, more preferably 6, m is 0 to 3, preferably 1 to 2, more preferably 1, L is selected from C1-C12 alkyl, alkenyl or alkynyl optionally substituted with C1 to C4 linear or branched alkyl, alkenyl or alkynyl, R is selected from amine, amide, carbamide and carbamate optionally substituted with C1 to C6 linear or branched alkyl (eg –NHC(O)OH, –NHC(O)OCH3, –NHC(O)OCH2CH3, –NHC(O)Otertbutyl), andB is phenyl group substituted by one to five hydroxyl groups, optionally the hydroxyl groups are protected.

[0161] Embodiment 2: The metal-binding compound according to embodiment 1, wherein Ch is bipyridine (Bpy), terpyridine (Terpy or Tpy), ethylenediamine (En), tris(2- aminoethyl)amine (Tren), Diethylenediamine (dien), porphyrins, crown ethers, cryptands, 1,2-bis(dimethylphosphino) ethane (dmpe) or 1,2-bis(diphenylphosphino) ethane (dppe).

[0162] Embodiment 3: The metal-binding compound according to embodiment 1, wherein Ch is terpyridine or diethylenediamine.

[0163] Embodiment 4: The metal-binding compound according to any one of embodiments 1 to 3, wherein L is C5 to C7 alkyl.

[0164] Embodiment 5: The metal-binding compound according to any one of embodiments 1 to 4, wherein B is phenol, catechol, pyrogallol, hydroxyquinol, or 1,2,3,4-benzenetetrol group.

[0165] Embodiment 6: A metal-binding compound comprising L-DOPA connected to a neutral metal ion chelator via a linker.

[0166] Embodiment 7: The metal-binding compound according to embodiment 6, wherein the linker is O-(CH2)nOC(O)-, where n is 1 to 12, or -(O-CH2-CH2)m-OC(O)-, where m is 1 to 4.

[0167] Embodiment 8: A substrate bound to one or more metal-binding compounds according to any one of embodiments 1 to 7, preferably the one or more metal-binding compound is bound to the substrate via B or L-DOPA.

[0168] Embodiment 9: The substrate bound metal-binding compound according to embodiment 8, wherein the substrate is selected from silicone, silicone coated substance, fibrous material or combinations thereof, preferably the fibrous material is selected from mineral wool (preferably stone wool), slag wool, glass wool, ceramic fibres and combinations thereof.

[0169] Embodiment 10: A metal-complex comprising a metal-binding compound according to any one of embodiments 1 to 7 or substrate bound metal-bindingcompound according to embodiment 8 or 9, wherein the metal-binding compound is complexed with one or more metal ions.

[0170] Embodiment 11: The metal-complex according to embodiment 10, wherein the metal ions are selected from lead (Pb2+) zinc (Zn2+), nickel (Ni2+), mercury (Hg2+), cadmium (Cd2+), copper (Cu2+), chromium (Cr3+or Cr6+), arsenic (As3+or As5+), silver (Ag+), iron (Fe2+or Fe3+), manganese (Mn2+), molybdenum (Mo6+), calcium (Ca2+), antimony (Sb5+), cobalt (Co2+) and combinations thereof.

[0171] Embodiment 12: A method of preparing a metal-binding compound according to any one of embodiments 1 to 7, the method comprising reacting a compound according to formula 2A with a compound according to Formula 2B to produce the metal-binding compound according to Compound 1: Formula 2A wherein, Ch is selected from any neutral chelating ligand; A1is selected from a covalent bond, -C(R2)2-, -NR2-, -O- and –S-; R2is independently selected from hydrogen, C1-C6 alkyl, alkenyl or alkynyl optionally substituted with C1 to C4 linear or branched alkyl, alkenyl or alkynyl, hydroxyl, C1-C6 alkoxy and halo. Preferably R2is selected from hydrogen, C1-C6 alkyl, hydroxyl, C1-C6 alkoxy and halo; n is 1 to 12, preferably 4 to 8, more preferably 6; and Z is selected from -N(R2)H, -OH, -SH and halo, with a compound according to formula 2B:Formula 2B wherein, m is 0 to 3, preferably 1 to 2, more preferably 1;X is selected from hydroxyl, -N(R2)H2, chloride, bromide, or iodide, preferably hydroxyl or chloride, more preferably hydroxyl; R1is selected from amine, amide, carbamide and carbamate optionally substituted with C1 to C6 linear or branched alkyl (eg –NHC(O)OH, –NHC(O)OCH3, –NHC(O)OCH2CH3, –NHC(O)Otertbutyl); R2is selected from the options as recited above; and B is phenyl substituted by one to five hydroxyl groups, to produce a metal-binding compound according to Compound 1:Compound 1.

[0172] Embodiment 13: A method comprising: - selecting one or more metal-binding compound according to any one of embodiments 1 to 7; - optionally removing protecting groups from the binding group B; - contacting the metal-binding compound with the substrate in the presence of an oxidising agent; and - oxidative polymerisation of the one or more metal-binding compound with the substrate to prepare a substrate bound metal-binding compound according to embodiment 8 or embodiment 9.

[0173] Embodiment 14: The method according to embodiment 13, wherein the contacting is by (i) at least partially submerging the substrate in a liquid comprising the oxidising agent and metal-binding compound (ie dipping) or (ii) by spraying the substrate (in either order or concurrently) with a liquid comprising the metal-binding compound and a liquid comprising the oxidising agent, preferably the concentration ofmetal-binding compound is sufficient to result in substrate with at least a portion coated in metal-binding compound.

[0174] Embodiment 15: A method of preparing a metal-complex according to embodiment 10 or 11 comprising: - contacting a metal-binding compound according to any one of embodiments 1 to 7 or a substrate bound metal-binding compound according to embodiment 8 or embodiment 9 with a liquid comprising metal ions; - resulting in complexation of the metal ions with the metal-binding compound.

[0175] Embodiment 16: A method of reversing the complexation of metal ions from a metal-complex comprising: - selecting a metal-complex according to embodiment 10 or 11; - contacting the metal-complex with a competitive chelator that favourably binds the metal ions when compared to the metal-complex resulting in metal ions bound to the competitive chelator and metal-binding compound uncomplexed from metal ions.

[0176] Embodiment 17: A method of treating water comprising metal ions including: - contacting a metal-binding compound of any one of embodiments 1 to 7 and / or a substrate bound metal-binding compound according to embodiment 8 or 9 with water comprising metal ions; - complexing the metal ions with the metal-binding compound / substrate bound metal-binding compound to form a metal-complex or substrate bound metal- complex according to embodiment 10 or 11.

[0177] Embodiment 18: The method of embodiment 15 or embodiment 17, wherein the method reduces the concentration of metal ions in the water.

[0178] Embodiment 19: The method of any one of embodiments 15, 17 and 18, wherein the liquid is still or the contact with the liquid comprising metal ions is via flow of the liquid via the metal-binding complex.

[0179] Embodiment 20: A water filter comprising: a body comprising a filter material, the body having an upstream end for receiving liquid to be filtered and a downstream end for releasing filtered liquid from the body following contact of the liquid with the filter material, wherein the filter material comprises one or more metal-binding compound according to any one of embodiments 1 to 7 and / or substrate bound metal- binding compound according to any one of embodiments 8 or 9. Examples

[0180] The invention will be further described by way of non-limiting examples. It will be understood by the person skilled in the art of the invention that modifications may be made without departing from the spirit and scope of the invention. Example 1 – Materials and methods Materials

[0181] All chemicals and solvents listed were used as received from the relevant supplier without further purification, unless stated otherwise: Acetonitrile (Chemsupply), tetrahydrofuran (Thermo Fisher), ethyl acetate (Thermo Fisher), dichloromethane (Chemsupply), methanol (Thermo Fisher), dimethyl sulfoxide (Thermo Fisher), ethanol (Thermo Fisher), water (Milli-Q, Merck), 3,4-Dihydroxy-L-phenylalanine (Sigma-Aldrich), tert-butyldimethylsilyl chloride (95%, Sigma-Aldrich), 1,8-diazabicyclo[5.4.0]undec-7-ene (99%, Sigma-Aldrich), sodium bicarbonate (Sigma-Aldrich), di-tert-butyl dicarbonate (Sigma-Aldrich), hydrochloric acid (32% solution, Thermo Fisher), magnesium sulfate (Merck), N-Ethyl-N′-(3-dimethylaminopropyl)carbodiimide (98%, Thermo Fisher), 11- bromo-1-undecanol (Thermo Fisher), 4-Dimethylaminopyridine (Merck), sodium chloride (Thermo Fisher), tetra-n-butylammonium fluoride in tetrahydrofuran (1.0 M) (Sigma- Aldrich), acetic acid (glacial, Thermo Fisher), potassium hydroxide (Thermo Fisher), 1,6- hexanediol (99%, Sigma-Aldrich), 4′-chloro-2,2′:6′,2′′-terpyridine (99%, Sigma-Aldrich), tris(hydroxymethyl)aminomethane (Merck), ethylenediaminetetraacetic acid (Thermo Fisher), zinc trifluoromethanesulfonate (98%, Sigma-Aldrich), nickel(II) chloride (98%, Sigma-Aldrich), Sodium hydroxide (Thermo Fisher). Rock wool was obtained from Lapinus.

[0182] Methanol-d4(99.8%, Sigma-Aldrich), chloroform-d1(CDCl3, 99.8%, Sigma- Aldrich), and dimethyl sulfoxide-d6 (DMSO-d6, 99.9%, Sigma-Aldrich) were used as the solvents for NMR measurements. Methods Flash Chromatography

[0183] Flash column chromatography was performed on an Interchim XS420+ flash chromatography system consisting of a SP-in-line filter 20-μm, an UV-VIS detector (200-800 nm) and a SofTA Model 400 ELSD (55 °C dift tube temperature, 25 °C spray chamber temperature, filter 5, EDR gain mode) connected via a flow splitter (Interchim Split ELSD F04590). The separations were performed using an Interchim dry load column (dryload on celite 565) and an Interchim Puriflash Silica HP 30 μm column. Nuclear Magnetic Resonance (NMR) Spectroscopy

[0184] 1H- and13C NMR-spectra were recorded on a Bruker System 600 Ascend LH, equipped with a BBO-Probe (5 mm) with z-gradient (1H 600.13 MHz,13C 150.90 MHz) at 298 K. Resonances are reported in parts per million (ppm) relative to tetramethylsilane (TMS). UV-visible Spectroscopy

[0185] UV / vis spectra were recorded on a Shimadzu UV-2700 spectrophotometer equipped with a CPS-100 electronic temperature control cell positioner. Samples were prepared in chloroform and measured in Hellma Analytics quartz high precision cells with a path length of 10 mm at 20 °C. The spectra were recorded in a range of 250 to 700 nm. Liquid Chromatography-Mass Spectrometry (LC-MS)

[0186] LC-MS measurements were performed on an UltiMate 3000 UHPLC System (Dionex, Sunnyvale, CA, USA) consisting of a pump (LPG 3400SZ), autosampler (WPS 3000TSL) and a temperature-controlled column compartment (TCC 3000). Separation was performed on a C18 HPLC column (Phenomenex Luna 5μm, 100 Å, 250 × 2.0 mm) operating at 40 °C. Water (containing 5 mmol L-1ammonium acetate) and acetonitrile were used as eluents. A gradient of acetonitrile: H2O, 5:95 to 100:0 (v / v) in 7 min at aflow rate of 0.40 mL·min-1was applied. The flow was split in a 9:1 ratio, where 90% of the eluent was directed through a DAD UV-detector (VWD 3400, Dionex) and 10% was infused into the electrospray source. Spectra were recorded on an LTQ Orbitrap Elite mass spectrometer (Thermo Fisher Scientific, San Jose, CA, USA) equipped with a HESI II probe. The instrument was calibrated in the m / z range 74-1822 using premixed calibration solutions (Thermo Scientific). A constant spray voltage of 3.5 kV, a dimensionless sheath gas, and a dimensionless auxiliary gas flow rate of 5 and 2 were applied, respectively. The capillary temperature was set to 300 °C, the S-lens RF level was set to 68, and the aux gas heater temperature was set to 100 °C. X-ray Photoelectron Spectroscopy (XPS)

[0187] XPS spectra were collected using a Kratos Axis Supra system operating with a monochromatic Al Kα source (1486.7 eV). Survey spectra and high-resolution core-level spectra were collected with pass energies of 160 and 20 eV respectively and a step size of 0.1 eV. All XPS data were processed with CasaXPS. All spectra were calibrated by setting the C 1s peak to 285.00 eV. Time of Flight – Secondary Ion Mass Spectroscopy (ToF-SIMS)

[0188] Data were acquired using an IONTOF M6 ToF-SIMS instrument (IONTOF GmbH, Germany) with a reflectron time-of-flight analyser and 30 keV Bi / Mn primary-ion source. Bi3+ cluster ions were selected from the pulsed primary-ion beam for the analysis and “bunched” for optimal mass resolution. Surface charging was compensated by flooding the sample with low-energy (20 eV) electrons between primary-ion pulses. The pressure in the analysis chamber was at below 1 × 10–9mbar. Data were acquired in both positive and negative polarities, and the mass scales calibrated using spectral peaks attributed to either C+, CH+, CH2+,and CH3+, or C–, CH2–, C3–,and C4–, respectively. (Recalibrate the positive-ion data using peaks covering a similar mass range to that used in negative polarity). All data were processed with the built-in module of the SurfaceLab 7.2 software (IONTOF GmbH).Example 2 – Synthesis of metal binding ligand 2-amino-3-(3,4-bis((tert-butyldimethylsilyl)oxy)phenyl)propanoic acid (1)

[0189] 3,4-Dihydroxy-L-phenylalanine (1.60 g, 8.0 mmol) and tert-butyldimethylsilyl chloride (3.60 g, 24.0 mmol) were dissolved in 18 mL dry acetonitrile. The reaction mixture was cooled to 0 °C. Afterwards, 1,8-diazabicyclo[5.4.0]undec-7-ene (3.6 mL, 24.0 mmol) was added dropwise and the reaction mixture was stirred at room temperature for 24 hours. The addition of cold acetonitrile (20 mL) resulted in the precipitation of a white solid. The precipitate was filtered and dried under vacuum. Yield: 1.80 g (53%).1H NMR (600 MHz, d4 - MeOD): δ = 0.22 (d, 12H, Si-CH3), 1.00 (d, 18H, C(CH3), 2.84 (m, 1H, CH2), 3.20 (m, 1H, CH2), 3.67 (m, 1H, CH), 6.75 – 6.85 (3H, H-aromatic) ppm.13C NMR (150 MHz, d4 - MeOD): δ = -3.5, 19.6, 26.8, 37.9, 58.0, 122.7, 123.7, 130.9, 148.2, 174.1 ppm. LC-MS: calculated: m / z = 426.2490 [M+H]+; found: m / z = 426.2494 [M+H]+. 3-(3,4-bis((tert-butyldimethylsilyl)oxy)phenyl)-2-((tert-butoxycarbonyl)amino) propanoic acid (2)

[0190] Sodium bicarbonate (0.32 g, 3.77 mmol) and 2-amino-3-(3,4-bis((tert- butyldimethylsilyl)oxy)phenyl)propanoic acid (1.5 g, 3.52 mmol) were dissolved in 20 mL water. Di-tert-butyl dicarbonate (0.87 g, 4.00 mmol) dissolved in 20 mL tetrahydrofuran was added and the reaction mixture was stirred for 24 h at room temperature.tetrahydrofuran was evaporated and 10 mL of water was added to the residue. The solution was acidified with dilute HCl to pH 5. The aqueous phase was extracted with ethyl acetate (3 x 30 mL). The combined organic phases were dried over magnesium sulphate and the solvent was evaporated. Yield: 1.55 g (58%).1H NMR (600 MHz, d4- MeOD): δ = 0.19 (d, 12H, Si-CH3), 0.99 (d, 18H, C(CH3), 1.39 (s, 9H, O-C(CH3)3), 2.78 (m, 1H, CH2), 3.03 (m, 1H, CH2), 4.24 (m, 1H, CH), 6.69 – 6.76 (3H, H-aromatic) ppm.13C NMR (150 MHz, d4- MeOD): δ = -4.1, 19.0, 26.4, 28.5, 38.0, 56.7, 80.1, 121.7, 123.1, 132.1, 146.5, 147.4, 157.4, 171.3 ppm. LC-MS: calculated: m / z = 524.2858 [M- H]-; found: m / z = 524.2863 [M-H]-. 11-bromoundecyl 3-(3,4-bis((tert-butyldimethylsilyl)oxy)phenyl)-2-((tert- butoxycarbonyl)amino)propanoate (3)

[0191] EDC·HCl (1.97 g, 10.30 mmol) and 3-(3,4-bis((tert- butyldimethylsilyl)oxy)phenyl)-2-((tert-butoxycarbonyl)amino) propanoic acid (1.80 g, 3.42 mmol) were dissolved in 100 mL dry dichloromethane and the reaction mixture was stirred for 30 minutes at room temperature. Afterwards 11-bromo-1-undecanol (1.04 g, 4.12 mmol) and DMAP (0.42 g, 3.45 mmol) were added to the reaction mixture and the reaction mixture was stirred for 20 h at room temperature.50 mL dichloromethane was added to the reaction mixture and the organic phase was extracted with brine (4 x 50 mL) and water (4 x 50 mL). The organic phase was dried over magnesium sulphate and purified via column chromatography (dichloromethane : methanol = 1 : 0.1). Yield: 0.99 g (38%).1H NMR (600 MHz, CDCl3): δ = 0.18 (d, 12H, Si-CH3), 0.98 (d, 18H, C(CH3), 1.27 (m, 14H, CH2), 1.42 (s, 9H, O-C(CH3)3), 1.59 (m, 2H, CH2), 1.85 (m, 2H CH2), 2.95 (m, 2H, CH2), 3.40 (t, 2H, CH2), 4.07 (m, 2H, CH2), 4.50 (m, 1H, CH), 6.55 – 6.72 (3H, H-aromatic) ppm.13C NMR (150 MHz, CDCl3): δ = -4.1, 18.4, 25.8-29.6, 32.8, 34.0, 37.5, 54.3.65.4, 79.7, 120.9, 128.9, 146.6, 171.9, 188.0 ppm. LC-MS: calculated: m / z = 780.3661 [M+Na]+; found: m / z = 780.3652 [M+Na]+.11-bromoundecyl 2-((tert-butoxycarbonyl)amino)-3-(3,4-dihydroxyphenyl)propanoate (4)

[0192] 11-bromoundecyl 3-(3,4-bis((tert-butyldimethylsilyl)oxy)phenyl)-2-((tert- butoxycarbonyl)amino)propanoate (0.25 g, 0.33 mmol) was dissolved in 1 mL tetrahydrofuran. Tetra-n-butylammonium fluoride (TBAF) (0.65 mL, 0.65 mmol) in THF (1.0 M) was added and the reaction mixture was stirred for 30 min at room temperature. The solvent was evaporated, and the residue was dissolved in dichloromethane. The organic phase was extracted with water (2 x 15 mL), diluted Hac (0.05 M) (2 x 15 mL), brine (2 x 15 mL) and water (2 x 15 mL). The organic phase was dried over magnesium sulphate and the solvent was removed. The product was applied for the surface reactions immediately. Yield: 0.12 g (71%). LC-MS: calculated: m / z = 552.1931 [M+Na]+; found: m / z = 552.1930 [M+Na]+. 6-([2,2':6',2''-terpyridin]-4'-yloxy)hexan-1-ol (5)

[0193] Potassium hydroxide (0.51 g, 9.15 mmol) was suspended in 13 mL DMSO and stirred at 40 °C for 15 min. Subsequently, 1,6-hexanediol (2.22 g, 18.79 mmol) was added and stirred for 30 min at 40 °C. Afterwards, 4′-chloro-2,2′:6′,2′′-terpyridine (0.50 g, 1.87 mmol) was added and stirred at 40 °C for 4 h. The reaction mixture was poured into water (300 mL) and after 15 h the white precipitate was filtered off and washed three times with water. After drying at 40 °C under vacuum a colorless solid was obtained. Yield: 0.28 g (43%).1H NMR (600 MHz, CDCl3): δ = 1.43 – 1.84 (m, 8H,CH2), 3.61 (m, 2H, -CH2-OH), 4.27 (m, 2H, -CH2-O-), 7.38 (m, 2H, H-Tpy5,5´´), 7.91 (m, H- Tpy4, 4´´), 8.08 (s, 2H, H-Tpy3´,5´), 8.64 (m, 2H, H-Tpy6,6´´), 8.70 (m, 2H, H-Tpy3,3´´)ppm.13C NMR (150 MHz, CDCl3): δ = 25.4, 25.7, 28.9, 32.6, 62.8, 68.0, 107.4, 121.3, 123.7, 136.8, 149.0, 156.1, 157.0, 167.3 ppm. LC-MS: calculated: m / z = 350.1861 [M+H]+; found: m / z = 350.1863 [M+H]+. 6-([2,2':6',2''-terpyridin]-4'-yloxy)hexyl 3-(3,4-bis((tert-butyldimethylsilyl)oxy)phenyl)-2- ((tert-butoxycarbonyl)amino)propanoate (6)

[0194] EDC·HCl (0.83 g, 4.30 mmol) and 6-([2,2':6',2''-terpyridin]-4'-yloxy)hexan-1-ol (0.50 g, 1.43 mmol) were dissolved in 100 mL dry dichloromethane and the reaction mixture was stirred for 30 minutes at room temperature.3-(3,4-bis((tert- butyldimethylsilyl)oxy)phenyl)-2-((tert-butoxycarbonyl)amino)propanoic acid (1.00 g, 1.90 mmol) and DMAP (0.18 g, 1.43 mmol) were added to the reaction mixture. The reaction mixture was stirred for 20 h at room temperature.20 mL dichloromethane was added, and the organic phase was extracted with brine (4 x 50 mL) and water (4 x 50 mL). The organic phase was dried over magnesium sulphate and purified via column chromatography (dichloromethane : methanol = 1 : 0.1). Yield: 1.027 g (84%).1H NMR (600 MHz, CDCl3): δ = 0.18 (m, 12H, Si-CH3), 0.97 (m, 18H, C(CH3), 1.39 (s, 9H, O- C(CH3)3), 1.45 (m, 2H, CH2), 1.54 (m, 2H, CH2), 1.66 (m, 2H, CH2), 1.87 (m, 2H, CH2), 2.95 (m, 2H, CH2(DOPA)), 4.10-4.28 (m, 4H, -CH2-O-, -CH2-OH), 4.50 (m, 1H, CH), 6.55 – 6.73 (3H, H-aromatic), 7.39 (m, 2H, H-Tpy5,5´´), 7.92 (m, H-Tpy4, 4´´), 8.09 (s, 2H, H-Tpy3´,5´), 8.67 (m, 2H, H-Tpy6,6´´), 8.73 (m, 2H, H-Tpy3,3´´) ppm.13C NMR (150 MHz, CDCl3): δ = -4.2, 18.4, 25.6, 25.7, 25.9, 28.3, 28.4, 28.9, 37.4, 54.3, 65.2, 67.9, 79.7, 107.3, 120.9, 121.3, 122.2, 123.7, 128.9, 136.7, 145.8, 146.6, 149.0, 155.0, 156.1,157.0, 167.2, 171.9 ppm. LC-MS: calculated: m / z = 857.4699 [M+H]+; found: m / z = 857.4681 [M+H]+. 6-([2,2':6',2''-terpyridin]-4'-yloxy)hexyl 2-((tert-butoxycarbonyl)amino)-3-(3,4- dihydroxyphenyl)propanoate (7)

[0195] 6-([2,2':6',2''-terpyridin]-4'-yloxy)hexyl 3-(3,4-bis((tert- butyldimethylsilyl)oxy)phenyl)-2-((tert-butoxycarbonyl)amino)propanoate (0.28 g, 0.33 mmol) was dissolved in 1 mL tetrahydrofuran. Tetra-n-butylammonium fluoride (TBAF) (0.65 mL, 0.65 mmol) in THF (1.0 M) was added and the reaction mixture was stirred for 30 min at room temperature. The solvent was evaporated, and the residue was dissolved in dichloromethane. The organic phase was extracted with water (2 x 15 mL), diluted Hac (0.05 M) (2 x 15 mL), brine (2 x 15 mL) and water (2 x 15 mL). The organic phase was dried over magnesium sulphate and the solvent was removed. The product was applied for the surface reactions immediately. Yield: 0.18 g (88%).1H NMR (600 MHz, DMSO): δ = 1.33 (s, 9H, O-C(CH3)3), 1.36 (m, 2H, CH2), 1.47 (m, 2H, CH2), 1.55 (m, 2H, CH2), 1.80 (m, 2H, CH2), 2.73 (m, 2H, CH2 (DOPA)), 4.02 (m, 3H, - CH2-O-, CH), 4.26 (m, 2H, -CH2-O-), 6.45 (m, 1H, H-aromatic), 6.60 (m, 2H, H-aromatic), 7.16 (m, 1H, NH), 7.54 (m, 2H, H-Tpy5,5´´), 8.00 (s, H-Tpy4, 4´´), 8.05 (m, 2H, H-Tpy3´,5´), 8.64 (m, 2H, H-Tpy6,6´´), 8.73 (m, 2H, H-Tpy3,3´´) ppm.13C NMR (150 MHz, DMSO): δ = 25.3, 28.3, 28.6, 36.3, 56.1, 64.5, 68.3, 78.5, 107.4, 115.6, 116.7, 120.0, 121.4, 125.0, 128.5, 138.2, 144.1, 145.2, 149.2, 154.6, 156.4, 167.2 ppm. LC- MS: calculated: m / z = 629.2970 [M+H]+; found: m / z = 629.2967 [M+H]+. Example 3 - Synthesis and characterisation of ligand coated surfaces

[0196] To explore the metal binding ligands of Example 2 as a universally adherent coating for metal adsorption, the inventors employed a systematic stepwise strategy. Specifically, the catechol and the amine functionalities are protected by employing tert- butyldimethylsilyl (TBDMS) ether and tert-butyloxycarbonyl (Boc), respectively. The carboxylic acid subsequently provides a handle to ligate various moieties, as exemplified herein with a Steglich esterification. Before surface coating, the TBDMS groups are removed via fluoride-mediated cleavage. Subsequently, the oxidative polymerization is performed in a Tris-HCl buffer solution as the oxidizing agent (Figure 1)

[0197] Initially, the ligand was functionalised with a bromine moiety that is readily traceable via analytical techniques (e.g., XPS, ToF-SIMS) on surfaces, enabling the investigation of the ligands surface adhesion abilities on various substrates. The Br- modified-ligand was synthesized as described in Example 2 via Steglich esterification of 11-bromo-1-undecanol and 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) as a coupling agent, proceeded by protecting the catechol and the amine functionalities with TBDMS and Boc protective groups, respectively.

[0198] The surfaces were placed into a petri dish, and 60 μL of tris buffer solution (0.3 M) was added. Subsequently, DOPA-containing moieties (2.7 mg dissolved in 60 μL EtOH) were added. The surfaces were then left overnight, washed with Milli-Q water, and subsequently dried using a stream of N2. Followed by analysis using XPS and TOF- SIMS.

[0199] Subsequently, coated surfaces (silicon wafers) with the Br-modified L-DOPA (4) were investigated via XPS and TOF-SIMS. Wide scan XPS spectra unambiguously evidence the presence of Br on the Si surfaces with peaks at 181 eV and 69 eV, corresponding to Br 3p and Br 3d, respectively (Figure 2A). In-depth analysis of C 1sreveals three main components associated with C-C / C-H at 285.0 eV, C-O and C-N at 286.3 eV, O=C-O at 288.3 eV and C-Br at 289.2 eV. The doublet peaks in the corresponding Br 3d high resolution spectrum (Figure 2C) further confirms the presence of Br- modified L-DOPA (4) on Si surface.

[0200] In addition, the Br-modified surfaces were analyzed via TOF-SIMS, further confirming the surface functionalization with Br (Br isotopes peaks at 79 and 81 m / z) (Figure 3). Example 4 – Metal chelating ability of ligand coated surfaces

[0201] Before moving to explore the ability of the ligand-containing L-DOPA’s ability to bind metal ions on planar surfaces post-coating, the ability of the binding system to coordinate metal ions via UV / Vis spectroscopy in solution was assessed. Specifically, the protected version of the ligand-modified L-DOPA (7) was dissolved in chloroform and NiCl2 and Zn(tf)2 were added (concentration 2.6 × 10-5mol / L).

[0202] The obtained UV / Vis spectra (Figure 4) unambiguously demonstrates that upon addition of a metal ion, binding to the terpyridine ligand occurs. Which is indicated by a second absorption band arising at around with a maximum at 311 nm, demonstrating successful coordination of the metal.

[0203] Once the successful surface modification with Br-modified L-DOPA (4) on silicon wafer was confirmed, the ability of a metal-chelating ligand carrying L-DOPA to bind metal ions once coated onto a silicon wafer was examined. A terpyridine ligand was selected, due to its high propensity of bind specific metal ions. The synthesis was carried out in a similar fashion to the bromine marker synthesis described in Example 2, where a Steglich esterification was employed to couple the ligand onto the protected L- DOPA (Figure 1). Figure 5 shows the1H-NMR spectrum and the associated electrospray ionization (ESI) mass spectrum of the terpyridine carrying L-DOPA.

[0204] The Si-surface coating procedure was identical to that followed for the Br- modified L-DOPA (4) system. After Si-surface coating with the DOPA modified Ligand, it was placed in the metal solution (Zn2+and Ni2+, M= 0.01) for 30 minutes. Following this, the Si surfaces were thoroughly washed using Milli-Q water and subsequently dried using a stream of N2. Followed by analysis using XPS. Critically, control experiments were conducted with blank Si-wafers and Si-wafers that had been coated with non-ligand containing L-DOPA. All planar surfaces were subsequently analyzed via XPS and ToF-SIMS.

[0205] XPS wide scan spectra of terpyridine functional surface exposed to Zn2+and exposed to ligand-free L-DOPA are depicted in Figure 6A and 6B, respectively. The presence of Zn is confirmed by the doublet peaks at 1021 eV. The absence of the same peak at 1021 eV in the L-DOPA-only coated control surface suggests that the L-DOPA surfaces are unable to coordinate with Zn2+(Figure 6B). Similarly, XPS wide scan spectra of Si-surfaces coated with ligand carrying L-DOPA (7) and ligand-free L-DOPA exposed to Ni2+ions are displayed in Figure 6C and 6D, respectively. The presence of Ni on the coated surface is confirmed by the peak at 860 eV. In comparison, the absence of the same peak at 860 eV in the L-DOPA-only coated control surface confirms that the terpyridine moiety is necessary to coordinate with Ni2+. High-resolution XPS spectra are depicted in Figure 7. Example 5 – Reversible metal binding of ligand coated surfaces

[0206] In a subsequent step, the ability of the terpyridine L-DOPA (7) coated Si surfaces to shed the bound metal ions using ethylenediamine tetra acetic acid (EDTA) as an extracting ligand in free-solution was explored.

[0207] After Silicon surfaces were metal coordinated according to Example 4, the surfaces were immersed into an EDTA solution (2 mmol, pH= 10) for 1 min, 10 min and 30 min, respectively. Subsequently, the surfaces were thoroughly washed using Milli-Q water, subsequently dried using a stream of N2, and followed by XPS analysis. The time dependent removal of the metal ions from the surface is depicted in Figure 8 and XPS spectra are depicted in Figure 9.

[0208] Since these experiments were carried out independently to each other, the Zn 2p atomic ratio to Si 2p atomic ratio was normalized by calculating the ratio of Zn2+to Si after each varying exposure times to EDTA, by comparing the area under the curve of the Zn 2p and Si 2p peaks, thus determining the relative amounts of Zn present on the surface (Table 1).

[0209] Table 1. Analysis by XPS region to determine the Zn to Si ratio

[0210] After a 1-minute exposure to EDTA, a decrease in the Zn content on the Si surface is observed. After 10 minutes exposure to EDTA, the metal content reaches a plateau. However, EDTA was not able to remove all the metal from the Si surface. Control experiments were carried out to elucidate a variation to high pH (pH~10) does not affect the removal of the metals (Figure 10) Example 6 – 3D surfaces / Stonewool fibers

[0211] Given the success for reversible metal binding in the surface systems, functional coating of 3D surfaces such as stonewool fibers was conducted. Stonewool is recognized for its ability to retain water over extended periods and gradually release it back into the environment. The feasibility of utilizing ligand modified L-DOPA (7) to coat fibers for the purpose of removing metals salts, focusing on Zn2+was assessed.

[0212] A Lapinus rock wool fiber cube measuring 0.5×0.5×0.5 cm³ was dipped-coated in a solution containing a 1:1 ratio of tris buffer and DOPA-containing moieties for an overnight period. Following this, the fiber cubes were thoroughly washed using Milli-Q water and subjected to analysis using XPS and ToF-SIMS.

[0213] The fibers were coated and subsequently exposed to metal salts in a similar fashion to the Si surfaces and analyzed. Similarly, the Br-modified L-DOPA (4) molecule was used to evidence that the approach is able to coat the fibers. Figure 11 displays both XPS and ToF-SIMS data, evidencing the presence of the Br- modification on the fibers as indicated by the presence of a peak at 289.2 eV. Further, the uniform coating was confirmed by ToF-SIMS imaging a single fiber using the Br-ion signals.

[0214] After the fibers coated with the terpyridine carrying L DOPA were placed in the metal solution (M= 0.01) for 30 minutes. Subsequently, the fiber cubes were thoroughly washed using Milli-Q water and subjected to analysis using XPS and ToF-SIMS.

[0215] The XPS wide scan spectra of fibers coated with terpyridine carrying L-DOPA exposed to Zn2+as well as the corresponding pristine fibers exposed to Zn2+are presented in Figure 12A and 12B, respectively. The identification of Zn presence is supported by the observation of doublet peaks at 1021 eV. Notably, the absence of this peak at 1021 eV in the pristine fibers indicates that the pristine fibers alone do not possess the ability to coordinate with Zn2+(Figure 12B).

[0216] Furthermore, Figure 12C and 12D depict the ToF-SIMS images of fibers coated with terpyridine carrying L-DOPA coordinating to Zn2+, thus providing additional confirmation of the presence of Zn on the fiber surfaces. The images reveal that Zn coordination occurs uniformly across the fiber surfaces. However, variations in intensity are attributed to the non-uniform size and shape of the fibers. A control experiment was carried out to confirm that the ligand free L-DOPA coated fibers are unable to coordinate Zn2+(Figure 13). Example 7 – investigations on mixed metal solutions

[0217] The affinity of different metals in mixed metal solutions was investigated. Similar to the XPS measurements that were conducted with a single metal solution, Si surfaces were coated with a ligand-modified L-DOPA according to the present disclosure. The coated surfaces were then immersed in metal solutions containing zinc and another metal for 30 minutes and subsequently analysed by XPS. The preparation of the metal solutions (Zn2+, Ni2+, Pb2+, Fe3+, and Cu2+) and the immersion procedure were conducted as described in Example 4.

[0218] Figure 14 depicts the XPS-wide scan of the different combinations of the two metal solutions tested on the Si surfaces coated with ligand-modified L-DOPA. Quantitative XPS analysis was conducted to assess the ratio of metal ion coordination to ligand-modified L-DOPA on the silicon surface. Figure 14A revealed that in a mixture of Zn and Pb metal ions a ratio of 0.5:1.0 (Zn: Pb) is present. A ratio of 0.1:0.3 (Zn: Fe) was found for the Zn / Fe mixture (Figure 14B). The experiment featured in Figure 14C revealed no presence of Zn ions ion the surface in a Zn / Cu mixed solution. Similarly,Figure 14D showed no presence of Ni on the surface in a Zn / Ni mixed solution. Finally, Figure 14E indicates that when combining Pb and Fe there is no detection of Pb on the surface, solely Fe.

[0219] In summary the results indicate that that the metal coordination affinity progresses from Fe3+> Pb2+> Cu2+> Zn2+>Ni2+. Example 8 – Reversible metal binding of ligand coated fibers

[0220] To investigate the reversibility of the metal coordination on the fibers, a complexing agent – specifically EDTA – was utilized to remove Zn2+ions coordinated to ligand coated fibers. The wide scan XPS spectra revealed the initial coordination (Figure 15A), as indicated with a doublet arising at 1021 eV. After immersion of the Zn2+coordinated fibers in the EDTA solution for 10 minutes, the XPS spectrum (Figure 15B) reveals the near absence of the Zn doublet at 1021 eV, thus demonstrating the successful removal of the Zn2+metal ions from the fibers.

[0221] The fibers were re-immersed in the Zn2+solution to explore their reversibility. Figure 15C depicts the XPS wide scan spectrum of the re-coordination experiment. The re-arising peak at 1021 eV indicates the successful re-coordination of the Zn2+metal ions on the fibers, proving the reversibility of the metal ion binding, and demonstrating the applicability of the coating on the 3D surfaces for the same applications as shown for the Si wafers (2D surfaces).

Claims

CLAIMS 1. A substrate bound to one or more metal-binding compound, the metal-binding compound having a structure according to compound 1, 1A or 1B: Ch-O-(CH2)n-O-C(O)-C(R)-(CH2)m-B Compound 1 or Ch-O-L-O-C(O)-C(R)-(CH2)m-B Compound 1A or Ch-O-(CH2)n-O-C(O)-LDOPA Compound 1B wherein: Ch is selected from any neutral chelating ligand, n is 1 to 12, preferably 4 to 8, more preferably 6, m is 0 to 3, preferably 1 to 2, more preferably 1, L is selected from C1-C12 alkyl, alkenyl or alkynyl optionally substituted with C1 to C4 linear or branched alkyl, alkenyl or alkynyl, R is selected from amine, amide, carbamide and carbamate optionally substituted with C1 to C6 linear or branched alkyl (eg –NHC(O)OH, –NHC(O)OCH3, –NHC(O)OCH2CH3, –NHC(O)Otertbutyl), B is phenyl group substituted by one to five hydroxyl groups, optionally the hydroxyl groups are protected, wherein the one or more metal-binding compound is bound to the substrate via B,and the substrate is selected from silicone, silicone coated substance, fibrous material, or combinations thereof.

2. The substrate of claim 1, wherein Ch is bipyridine (Bpy), terpyridine (Terpy or Tpy), ethylenediamine (En), tris(2-aminoethyl)amine (Tren), Diethylenediamine (dien), porphyrins, crown ethers, cryptands, 1,2-bis(dimethylphosphino) ethane (dmpe) or 1,2- bis(diphenylphosphino) ethane (dppe).

3. The substrate of claim 1 or claim 2, wherein Ch is terpyridine or diethylenediamine.

4. The substrate of any one of claims 1 to 3, wherein L is C5 to C7 alkyl.

5. The substrate of any one of claims 1 to 4, wherein B is phenol, catechol, pyrogallol, hydroxyquinol or 1,2,3,4-benzenetetrol group.

6. A substrate bound to one or more metal-binding compound comprising L-DOPA or D-DOPA connected to a neutral metal ion chelator via a linker.

7. The substrate of claim 6, wherein the linker is O-(CH2)nOC(O)-, where n is 1 to 12, or -(O-CH2-CH2)m-OC(O)-, where m is 1 to 4.

8. The substrate of any one of claims 1 to 7, wherein the one or more metal-binding compound is bound to the substrate via B, D-DOPA or L-DOPA.

9. The substrate of any one of claims 1 to 8, wherein the fibrous material is selected from mineral wool (preferably stone wool), slag wool, glass wool, ceramic fibres and combinations thereof.

10. A metal-complex comprising the substrate bound metal-binding compound according to any one of claims 1 to 9, wherein the metal-binding compound is complexed with one or more metal ions.

11. The metal-complex of claim 10, wherein the metal ions are selected from lead (Pb2+) zinc (Zn2+), nickel (Ni2+), mercury (Hg2+), cadmium (Cd2+), copper (Cu2+), chromium (Cr3+or Cr6+), arsenic (As3+or As5+), silver (Ag+), iron (Fe2+or Fe3+), manganese (Mn2+), molybdenum (Mo6+), calcium (Ca2+), antimony (Sb5+), cobalt (Co2+) and combinations thereof.

12. A method of preparing a metal-binding compound, the method comprising reacting a compound according to formula 2A with a compound according to Formula 2B to produce the metal-binding compound according to Compound 1: Formula 2A wherein, Ch is selected from any neutral chelating ligand; A1is selected from a covalent bond, -C(R2)2-, -NR2-, -O- and –S-; R2is independently selected from hydrogen, C1-C6 alkyl, alkenyl or alkynyl optionally substituted with C1 to C4 linear or branched alkyl, alkenyl or alkynyl, hydroxyl, C1-C6 alkoxy and halo. Preferably R2is selected from hydrogen, C1-C6 alkyl, hydroxyl, C1-C6 alkoxy and halo; n is 1 to 12, preferably 4 to 8, more preferably 6; and Z is selected from -N(R2)H, -OH, -SH and halo, with a compound according to formula 2B:Formula 2B wherein, m is 0 to 3, preferably 1 to 2, more preferably 1; X is selected from hydroxyl, -N(R2)H2, chloride, bromide, or iodide, preferably hydroxyl or chloride, more preferably hydroxyl; R1is selected from amine, amide, carbamide and carbamate optionally substituted with C1 to C6 linear or branched alkyl (eg –NHC(O)OH, –NHC(O)OCH3, –NHC(O)OCH2CH3, –NHC(O)Otertbutyl); R2is selected from the options as recited above; and B is phenyl substituted by one to five hydroxyl groups,to produce a metal-binding compound according to Compound 1:Compound 1.

13. A method of producing a substrate bound to one or more metal-binding compound comprising: - selecting one or more metal-binding compound in accordance with any one of claims 1 to 8; - optionally removing protecting groups from the binding group B; - contacting the metal-binding compound with a substrate in the presence of an oxidising agent; and - oxidative polymerisation of the one or more metal-binding compound with the substrate to prepare the substrate bound metal-binding compound according to any one of claims 1 to 9.

14. The method of claim 13, wherein the contacting is by (i) at least partially submerging the substrate in a liquid comprising the oxidising agent and metal-binding compound (ie dipping) or (ii) by spraying the substrate (in either order or concurrently) with a liquid comprising the metal-binding compound and a liquid comprising the oxidising agent, preferably the concentration of metal-binding compound is sufficient to result in substrate with at least a portion coated in metal-binding compound.

15. A method of preparing a metal-complex according to claim 10 or 11 comprising: - contacting a substrate bound metal-binding compound according to any one of claims 1 to 9 with a liquid comprising metal ions; - resulting in complexation of the metal ions with the metal-binding compound.

16. A method of reversing the complexation of metal ions from a metal-complex comprising: - selecting a metal-complex according to claim 10 or 11; - contacting the metal-complex with a competitive chelator that favourably binds the metal ions when compared to the metal-complex resulting in metal ions bound to the competitive chelator and metal-binding compound uncomplexed from metal ions.

17. A method of treating water comprising metal ions including: - contacting a substrate bound metal-binding compound according to any one of claims 1 to 9 with water comprising metal ions; - complexing the metal ions with the metal-binding compound / substrate bound metal-binding compound to form a metal-complex or substrate bound metal- complex according to claim 10 or 11.

18. The method of claim 15 or claim 17, wherein the method reduces the concentration of metal ions in the water.

19. The method of any one of claims 15, 17 and 18, wherein the liquid is still or the contact with the liquid comprising metal ions is via flow of the liquid via the metal- binding complex.

20. A water filter comprising: a body comprising a filter material, the body having an upstream end for receiving liquid to be filtered and a downstream end for releasing filtered liquid from the body following contact of the liquid with the filter material, wherein the filter material comprises one or more substrate bound metal-binding compound according to any one of claims 1 to 9.

21. A compound selected from:

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