ELECTROCHEMICAL REDUCTION OF CARBON DIOXIDE CATALYZED BY POLYOXOMETALATES

Abstract

Provided herein a polyoxometalate compound represented by formula (I): (Q).sub.n[XM.sub.aM.sub.bM.sub.c(L.sub.a)(L.sub.b)(L.sub.c)W.sub.9O.sub.37] (I) or a solvate thereof; and a method of electrocatalytic reduction of carbon dioxide (CO.sub.2) using the polyoxometalate compound.

Claims

1. A polyoxometalate compound represented by formula (I):
(Q).sub.n[XM.sub.aM.sub.bM.sub.c(L.sub.a)(L.sub.b)(L.sub.c)W.sub.9O.sub.37](I) or a solvate thereof, wherein, X is P, Si, As, Ge, Ga, B, or Al; M.sub.a, M.sub.b and M.sub.c are each independently selected from the group consisting of: Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Sn, Sb, In, Sc, Sr, Mg, Y, Yb, Ba and Ca; L.sub.a, L.sub.b and L.sub.c are each independently selected from the group consisting of: H.sub.2O, carboxylates, oxyanions, halides or pseudohalides, carbonate, bicarbonate or absent; Q is a cation such as an alkali metal cation, an alkaline earth metal cation, a lanthanide cation, a nitrogen centered cation or a phosphorous centered cation or any combination thereof; n is an integer between 4-13; and wherein at least one of M.sub.a, M.sub.b and M.sub.c is Sn, Al, Zn or Ga or M.sub.a, M.sub.b and M.sub.c are different.

2. The compound of claim 1, wherein Q is a quaternary ammonium cation.

3. The compound of claim 1, wherein M.sub.a, M.sub.b and M.sub.c are different.

4. The compound of claim 1, wherein at least one of M.sub.a, M.sub.b and M.sub.c is Sn, Al, Zn or Ga.

5. The compound of claim 1, wherein the compound is (Q).sub.n[XCu.sub.2ML.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] and M is selected from the group consisting of Sn, Zn, Al, Ga.

6. The compound of claim 1, wherein the compound is (Q).sub.n[XCu.sub.2ZnL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q).sub.n[XCu.sub.2GaL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q).sub.n[XCu.sub.2SnL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q).sub.n[XCu.sub.2AlL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q).sub.n[XCuFeZnL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q).sub.n[XCuFeNiL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q).sub.n[XCuFeAlL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q).sub.n[XCuNiZnL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q).sub.n[XCuNiAlL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q).sub.n[XCuCoZnL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q).sub.n[XCuCoAlL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q).sub.n[XCuMnZnL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or (Q).sub.n[XCuMnAlL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37].

7. The compound according to claim 1, wherein X is Si or P.

8. A method for reducing carbon dioxide to carbon monoxide, formate salt or formic acid, formaldehyde, methanol, ethane, ethylene, ethanol or any combination thereof, wherein the method comprises reacting the carbon dioxide with a polyoxometalate compound represented by formula (I):
(Q).sub.n[XM.sub.aM.sub.bM.sub.c(L.sub.a)(L.sub.b)(L.sub.c)W.sub.9O.sub.37](I) or a solvate thereof, wherein, X is P, Si, As, Ge, Ga, B, or Al; M.sub.a, M.sub.b and M.sub.c are each independently selected from the group consisting of: Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Sn, Sb, In, Sc, Sr, Mg, Y, Yb, Ba and Ca; L.sub.a, L.sub.b and L.sub.c are each independently selected from the group consisting of: H.sub.2O, carboxylates, oxyanions, halides or pseudohalides, carbonate, bicarbonate or absent; Q is a cation such as a proton, an alkali metal cation, an alkaline earth metal cation, a lanthanide cation, a nitrogen centered cation or a phosphorous centered cation or any combination thereof; n is an integer between 4-13; and wherein the reaction is conducted in an electrochemical cell comprising: a cathode, an anode, optionally a reference electrode, optionally a membrane; and the polyoxometalate compound of Formula (I) as the catalyst for the reduction of carbon dioxide.

9. The method of claim 8, wherein the applied potential is between ?3.5-0.0 V vs Fc/Fc.sup.+.

10. The method of claim 9, wherein the applied potential is ?2.5 or ?1.5 V vs Fc/Fc.sup.+.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which:

[0023] FIG. 1 depicts a mixed polyhedral and ball and stick representation of the {SiM.sub.aM.sub.bM.sub.c (H.sub.2O).sub.3W.sub.9O.sub.37}.sup.n? anion: external octahedronsW; internal tetrahedron at the middleSi; three balls at the topM.sub.a/M.sub.b/M.sub.c; small, light gray ballsO. The hydrogen atoms and counter cations are not shown.

[0024] FIGS. 2A-2B depict a presentation of an electrolyzer. FIG. 2A: Schematic design; and FIG. 2B: a photograph of the electrolyzer.

[0025] It will be appreciated that for simplicity and clarity of illustration, elements shown in the Figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the Figures to indicate corresponding or analogous elements.

DETAILED DESCRIPTION OF THE INVENTION

[0026] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that this invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure this invention.

Polyoxometalate Compound of this Invention

[0027] In some embodiments, this invention provides a polyoxometalate represented by formula (I):

##STR00003## [0028] or a solvate thereof, [0029] wherein, [0030] X is P, Si, As, Ge, Ga, B, or Al; [0031] M.sub.a, M.sub.b and M.sub.c are each independently selected from the group consisting of: Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Sn, Sb, In, Sc, Sr, Mg, Y, Yb, Ba and Ca; [0032] L.sub.a, L.sub.b and L.sub.c are each independently selected from the group consisting of: H.sub.2O, carboxylates, oxyanions, halides or pseudohalides, carbonate, bicarbonate or absent; [0033] Q is a cation such as a proton, an alkali metal cation, an alkaline earth metal cation, a lanthanide cation, a nitrogen centered cation or a phosphorous centered cation or any combination thereof; [0034] n is an integer between 4-13.

[0035] In some embodiments, this invention provides a polyoxometalate represented by formula (I):

##STR00004## [0036] or a solvate thereof, [0037] wherein, [0038] X is P, Si, As, Ge, Ga, B, or Al; [0039] M.sub.a, M.sub.b and M.sub.c are each independently selected from the group consisting of: Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Sn, Sb, In, Sc, Sr, Mg, Y, Yb, Ba and Ca; [0040] L.sub.a, L.sub.b and L.sub.c are each independently selected from the group consisting of: H.sub.2O, carboxylates, oxyanions, halides or pseudohalides, carbonate, bicarbonate or absent; [0041] Q is a cation such as a proton, an alkali metal cation, an alkaline earth metal cation, a lanthanide cation, a nitrogen centered cation or a phosphorous centered cation or any combination thereof; [0042] n is an integer between 4-13 wherein at least one of M.sub.a, M.sub.b and M.sub.c is Sn, Al, Zn or Ga.

[0043] In some embodiments, this invention provides a polyoxometalate represented by formula (I):

##STR00005## [0044] or a solvate thereof, [0045] wherein, [0046] X is P, Si, As, Ge, Ga, B, or Al; [0047] M.sub.a, M.sub.b and M.sub.c are each independently selected from the group consisting of: Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Sn, Sb, In, Sc, Sr, Mg, Y, Yb, Ba and Ca; [0048] L.sub.a, L.sub.b and L.sub.c are each independently selected from the group consisting of: H.sub.2O, carboxylates, oxyanions, halides or pseudohalides, carbonate, bicarbonate or absent; [0049] Q is a cation such as a proton, an alkali metal cation, an alkaline earth metal cation, a lanthanide cation, a nitrogen centered cation or a phosphorous centered cation or any combination thereof; [0050] n is an integer between 4-13 wherein at least two out of M.sub.a, M.sub.b and M.sub.care different.

[0051] In some embodiments, this invention provides a polyoxometalate represented by formula (I):

##STR00006## [0052] or a solvate thereof, [0053] wherein, [0054] X is P, Si, As, Ge, Ga, B, or Al; [0055] M.sub.a, M.sub.b and M.sub.c are each independently selected from the group consisting of: Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Sn, Sb, In, Sc, Sr, Mg, Y, Yb, Ba and Ca; [0056] L.sub.a, L.sub.b and L.sub.c are each independently selected from the group consisting of: H.sub.2O, carboxylates, oxyanions, halides or pseudohalides, carbonate, bicarbonate or absent; [0057] Q is a cation such as a proton, an alkali metal cation, an alkaline earth metal cation, a lanthanide cation, a nitrogen centered cation or a phosphorous centered cation or any combination thereof; [0058] n is an integer between 4-13 wherein M.sub.a, M.sub.b and M.sub.c are different (representing three different metal selected from Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Sn, Sb, In, Sc, Sr, Mg, Y, Yb, Ba and Ca).

[0059] In another embodiment, non-limiting examples of oxyanion include: borate, carbonate, nitrate, phosphate, sulphate, chlorate, perchlorate, iodate, periodate, tosylate, mesylate and triflate.

[0060] In another embodiment, the anion of the polyoxometalate is not [PW.sub.9O.sub.37{Fe.sup.III.sub.3-xNi.sub.x(L).sub.3}].sup.q? (x=1-2), [SiW.sub.9(Fe.sup.III).sub.2Ni.sup.II(L).sub.3O.sub.37].sup.n?, [SiW.sub.9(Fe.sup.III).sub.2Mn.sup.II(L).sub.3O.sub.37].sup.n?, or [SiW.sub.9(Fe.sub.III).sub.2Co.sup.II(L).sub.3O.sub.37].sup.n?.

[0061] In some embodiments Q of (Q).sub.n[XM.sub.aM.sub.bM.sub.c(L.sub.a)(L.sub.b)(L.sub.c)W.sub.9O.sub.37] is a cation selected from the group consisting of a proton, an alkali metal cation, an alkaline earth metal cation, a lanthanide cation, a nitrogen centered cation, a phosphorous centered cation and combinations thereof. In other embodiments, Q is a proton. In other embodiments, Q is an alkali metal cation. In other embodiments, Q is an alkaline earth metal cation. In other embodiments, Q is a lanthanide cation. In other embodiments, Q is a nitrogen centered cation. In other embodiments, Q is a phosphorous centered cation. In other embodiments, Q is R.sub.1R.sub.2R.sub.3R.sub.4N.sup.+ wherein [0062] R.sub.1 is H, alkyl, aryl, alkylaryl; [0063] R.sub.2 is H, alkyl, aryl, alkylaryl, or C.sub.yH.sub.2y+1 where y?8, or C.sub.zH.sub.2z+1COOH where z?7; and [0064] R.sub.3 and R.sub.4 are each independently H, alkyl, aryl, alkylaryl, or (CH.sub.2CH.sub.2O).sub.mCH.sub.2CH.sub.2R.sub.5 where m?3, wherein R.sub.5 is H, OH, alkyl, halide, pseudohalide.

[0065] In some embodiments, Q is R.sub.1R.sub.2R.sub.3R.sub.4N.sup.+ wherein R.sub.2 is C.sub.yH.sub.2y+1 where y?8. In other embodiments y is an integer between 8 and 50. In other embodiments, y is an integer between 8 and 40. In other embodiments, y is an integer between 8 and 30. In other embodiments, y is an integer between 8 and 20.

[0066] In some embodiments, Q is R.sub.1R.sub.2R.sub.3R.sub.4N.sup.+ wherein R.sub.2 is C.sub.zH.sub.2z+1COOH where y?7. In other embodiments z is an integer between 7 and 50. In other embodiments, z is an integer between 7 and 40. In other embodiments, z is an integer between 7 and 30. In other embodiments, z is an integer between 7 and 20.

[0067] In some embodiments, Q is R.sub.1R.sub.2R.sub.3R.sub.4N.sup.+ wherein R.sub.3 and R.sub.4 are the same or different. In some embodiments, R.sub.3 and R.sub.4 are each independently (CH.sub.2CH.sub.2O).sub.mCH.sub.2CH.sub.2R.sub.5 where m?3. In other embodiments. m is an integer between 3 and 50. In other embodiments, m is an integer between 3 and 40. In other embodiments, m is an integer between 3 and 30. In other embodiments. m is an integer between 3 and 20. In other embodiments. m is an integer between 3 and 15. In other embodiments. m is an integer between 3 and 10.

[0068] In some embodiments, Q is R.sub.1R.sub.2R.sub.3R.sub.4N.sup.+ wherein R.sub.1 is ethyl, R.sub.2 is C.sub.zH.sub.2z+1COOH wherein z?7 and R.sub.3 and R.sub.4 are (CH.sub.2CH.sub.2O).sub.mH where m=6-20. In other embodiments, Q is R.sub.1R.sub.2R.sub.3R.sub.4N.sup.+ wherein R.sub.1 is methyl; R.sub.2 is tetradecyl, hexadecyl or octadecyl; and R.sub.3 and R.sub.4 are (CH.sub.2CH.sub.2O).sub.mH where m=5-10.

[0069] In some embodiments, Q of the polyoxometalate of Formula (I)-(Q).sub.n[XM.sub.aM.sub.bM.sub.c(L.sub.a)(L.sub.b)(L.sub.c)W.sub.9O.sub.37] is a nitrogen centered cation, non-limiting examples thereof include quaternary ammonium, pyridinium and imidazolium cations.

[0070] In one embodiment, quaternary ammonium is selected from the group consisting of tetrahexyl ammonium, tetrabutyl ammonium, trioctylmethylammonium, cetyltrimethyl ammonium, tetraoctyl ammonium, tetraethylammonium, tetramethylammonium, benzyltrimethylammonium, and the like. Each possibility represents a separate embodiment of this invention.

[0071] In some embodiments, one example of phosphorous centered cation includes phosphonium cations, e.g. tetraphenylphosphonium.

[0072] As used herein, the term alkyl, used alone or as part of another group, refers, in one embodiment, to a C.sub.1 to C.sub.12 alkyl and denotes linear and branched, saturated or unsaturated (e.g., alkenyl, alkynyl) groups, the latter only when the number of carbon atoms in the alkyl chain is greater than or equal to two, and can contain mixed structures. Non-limiting examples are alkyl groups containing from 1 to 6 carbon atoms (C.sub.1 to C.sub.6 alkyls), or alkyl groups containing from 1 to 4 carbon atoms (C.sub.1 to C.sub.4 alkyls). Examples of saturated alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, amyl, tert-amyl and hexyl. Examples of alkenyl groups include, but are not limited to, vinyl, allyl, butenyl and the like. Examples of alkynyl groups include, but are not limited to, ethynyl, propynyl and the like. Similarly, the term C.sub.1 to C.sub.12 alkylene denotes a bivalent radical of 1 to 12 carbons.

[0073] The alkyl group can be unsubstituted, or substituted with one or more substituents selected from the group consisting of halogen, hydroxy, alkoxy, aryloxy, alkylaryloxy, heteroaryloxy, oxo, cycloalkyl, phenyl, heteroaryls, heterocycl, naphthyl, amino, alkylamino, arylamino, heteroarylamino, dialkylamino, diarylamino, alkylarylamino, alkylheteroarylamino, arylheteroarylamino, acyl, acyloxy, nitro, carboxy, carbamoyl, carboxamide, cyano, sulfonyl, sulfonylamino, sulfinyl, sulfinylamino, thiol, alkylthio, arylthio, or alkylsulfonyl groups. Any substituents can be unsubstituted or further substituted with any one of these aforementioned substituents.

[0074] The term alkylaryl used herein alone or as part of another group, refers to, in some embodiments, to an alkyl group as defined above, which is substituted by an aryl as defined herein.

[0075] The term aryl used herein alone or as part of another group denotes an aromatic ring system containing from 6-14 ring carbon atoms. The aryl ring can be a monocyclic, bicyclic, tricyclic and the like. Non-limiting examples of aryl groups are phenyl, naphthyl including 1-naphthyl and 2-naphthyl, and the like. The aryl group can be unsubstituted or substituted through available carbon atoms with one or more groups such as halogen, hydroxy, alkoxy, aryloxy, alkylaryloxy, heteroaryloxy, oxo, cycloalkyl, phenyl, heteroaryls, heterocyclyl, naphthyl, amino, alkylamino, arylamino, heteroarylamino, dialkylamino, diarylamino, alkylarylamino, alkylheteroarylamino, arylheteroarylamino, acyl, acyloxy, nitro, carboxy, carbamoyl, carboxamide, cyano, sulfonyl, sulfonylamino, sulfinyl, sulfinylamino, thiol, alkylthio, arylthio, or alkylsulfonyl groups. Any substituents can be unsubstituted or further substituted with any one of these aforementioned substituents.

[0076] In some embodiments n is an integer between 4-13. In other embodiments, n is an integer between 4-6, 4-9, 6-13, 5-10, or any ranges between integers 4, 5, 6, 7, 8, 9, 10, 11, 12 or 13.

[0077] In some embodiments, M.sub.a, M.sub.b and M.sub.c or M of the compound of Formula (I) or (Ia) are each independently selected from the group consisting of: Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Sn, Sb, In, Sc, Sr, Mg, Y, Yb, Ba and Ca. In some embodiments, M.sub.a, M.sub.b and M.sub.c are different. In some embodiments, at least two of M.sub.a, M.sub.b and M.sub.c are different. In some embodiments, at least one of M.sub.a, M.sub.b and M.sub.c is Cr. In some embodiments, at least one of M.sub.a, M.sub.b and M.sub.c is Mn. In some embodiments, at least one of M.sub.a, M.sub.b and M.sub.c is Fe. In some embodiments, at least one of M.sub.a, M.sub.b and M.sub.c is Co. In some embodiments, at least one of M.sub.a, M.sub.b and M.sub.c is Ni. In some embodiments, at least one of M.sub.a, M.sub.b and M.sub.c is Cu. In some embodiments, at least one of M.sub.a, M.sub.b and M.sub.c is Zn. In some embodiments, at least one of M.sub.a, M.sub.b and M.sub.c is Al. In some embodiments, at least one of M.sub.a, M.sub.b and M.sub.c is Ga. In some embodiments, at least one of M.sub.a, M.sub.b and M.sub.c is Sn. In some embodiments, at least one of M.sub.a, M.sub.b and M.sub.c is Sb. In some embodiments, at least one of M.sub.a, M.sub.b and M.sub.c is In. In some embodiments, at least one of M.sub.a, M.sub.b and M.sub.c is Sc. In some embodiments, at least one of M.sub.a, M.sub.b and M.sub.c is Sr. In some embodiments, at least one of M.sub.a, M.sub.b and M.sub.c is Mg. In some embodiments, at least one of M.sub.a, M.sub.b and M.sub.c is Y. In some embodiments, at least one of M.sub.a, M.sub.b and M.sub.c is Yb. In some embodiments, at least one of M.sub.a, M.sub.b and M.sub.c is Ba. In some embodiments, at least one of M.sub.a, M.sub.b and M.sub.c is Ca. In some embodiments, at least one of M.sub.a, M.sub.b and M.sub.c is Sn, Al, Zn or Ga.

[0078] In some embodiments, the polyoxometalate of Formula (I) is (Q).sub.n[XCu.sub.2ML.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], wherein M is selected from the group consisting of Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Sn, Sb, In, Sc, Sr, Mg, Y, Yb, Ba and Ca. In one embodiment, M is Fe, Ni, Al, Ga, Sn or Zn. Each possibility represents a separate embodiment of this invention.

[0079] In some embodiments, the polyoxometalate of Formula (I) is (Q).sub.n[XCuFeZn L.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q).sub.n[XCu.sub.2FeL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q) [XCuFe.sub.2L.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q).sub.n[XCu.sub.2NiL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q).sub.n[XCuNi.sub.2L.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q) [XCu.sub.2ZnL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q).sub.n[XCu.sub.2AlL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q).sub.n[XCu.sub.2GaL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q).sub.n[XCu.sub.2SnL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q).sub.n[XCu.sub.2InL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q).sub.n[XCu.sub.2SbL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q).sub.n[XCuFeNiL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q).sub.n[XCuFeAlL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q).sub.n[XCuFeGaL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q).sub.n[XCuFeSnL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q).sub.n[XCuNiZnL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q).sub.n[XCuNiAlL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q).sub.n[XCuCoZnL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q).sub.n[XCuCoAlL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37], (Q).sub.n[XCuMnZnL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or (Q).sub.n[XCuMnAlL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37]. Each possibility represents a separate embodiment of this invention.

[0080] In some embodiments, X of the polyoxometalate of Formula (I) is Si or P.

[0081] In some embodiments, L.sub.a, L.sub.b and L.sub.c of the polyoxometalate of Formula (I) or (Ia) are each independently selected from the group consisting of H.sub.2O, carboxylates, oxyanions, halides or pseudohalides, carbonate, bicarbonate or absent. In other embodiments, L.sub.a, L.sub.b and L.sub.c of the polyoxometalate of Formula (I) are each independently H.sub.2O. In other embodiments, L.sub.a, L.sub.b and L.sub.c of the polyoxometalate of Formula (I) are each independently carboxylates. In other embodiments, L.sub.a, L.sub.b and L.sub.c of the polyoxometalate of Formula (I) are each independently oxyanions. In other embodiments, L.sub.a, L.sub.b and L.sub.c of the polyoxometalate of Formula (I) are each independently halides. In other embodiments, L.sub.a, L.sub.b and L.sub.c of the polyoxometalate of Formula (I) are each independently pseudohalides. In other embodiments, L.sub.a, L.sub.b and L.sub.c of the polyoxometalate of Formula (I) are each independently carbonate. In other embodiments, L.sub.a, L.sub.b and L.sub.c of the polyoxometalate of Formula (I) are each independently bicarbonate. In other or absent.

[0082] In some embodiments, the polyoxometalate of Formula (I) is (Q).sub.9[SiCu.sub.2Fe(H.sub.2O).sub.3W.sub.9O.sub.37], (Q).sub.8[SiCuFe.sub.2(H.sub.2O).sub.3W.sub.9O.sub.37], (Q).sub.10[SiCu.sub.2Ni(H.sub.2O).sub.3W.sub.9O.sub.37], (Q).sub.10[SiCuNi.sub.2(H.sub.2O).sub.3W.sub.9O.sub.37], (Q).sub.9[SiCuFeNi(H.sub.2O).sub.3W.sub.9O.sub.37], (Q).sub.8[SiFe.sub.2Al(H.sub.2O).sub.3W.sub.9O.sub.37], (Q).sub.9[SiFeGa.sub.2(H.sub.2O).sub.3W.sub.9O.sub.37], (Q).sub.10[SiCu.sub.2Zn(H.sub.2O).sub.3W.sub.9O.sub.37], (Q).sub.9[SiCu.sub.2Al(H.sub.2O).sub.3W.sub.9O.sub.37], (Q).sub.9[SiCu.sub.2Ga(H.sub.2O).sub.3W.sub.9O.sub.37], (Q).sub.8[SiCu.sub.2Sn(H.sub.2O).sub.3W.sub.9O.sub.37], (Q).sub.9SiCuFeZn(H.sub.2O).sub.3W.sub.9O.sub.37], (Q).sub.8[SiCuFeAl(H.sub.2O).sub.3W.sub.9O.sub.37], (Q).sub.8[SiCuFeGa(H.sub.2O).sub.3W.sub.9O.sub.37], (Q).sub.7[SiCuFeSn(H.sub.2O).sub.3W.sub.9O.sub.37], (Q).sub.10[SiCuNiZn(H.sub.2O).sub.3W.sub.9O.sub.37] or (Q).sub.9[SiCuNiAl(H.sub.2O).sub.3W.sub.9O.sub.37]. Each possibility represents a separate embodiment of this invention.

Methods of Use

[0083] In one further embodiment, this invention provides a method for the reduction of carbon dioxide to carbon monoxide, formate salt or formic acid, formaldehyde, methanol, ethane, ethylene, ethanol or any combination thereof, comprising contacting the carbon dioxide with a polyoxometalate compound represented by formula (I):

##STR00007## [0084] or a solvate thereof, [0085] wherein, [0086] X is P, Si, As, Ge, Ga, B, or Al; [0087] M.sub.a, M.sub.b and M.sub.c are each independently selected from the group consisting of: Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Sn, Sb, In, Sc, Sr, Mg, Y, Yb, Ba and Ca; [0088] L.sub.a, L.sub.b and L.sub.c are each independently selected from the group consisting of: H.sub.2O, carboxylates, oxyanions, halides or pseudohalides, carbonate, bicarbonate or absent; [0089] Q is a cation such as a proton, an alkali metal cation, an alkaline earth metal cation, a lanthanide cation, a nitrogen centered cation or a phosphorous centered cation or any combination thereof; [0090] n is an integer between 4-13; [0091] and wherein the reaction is conducted in an electrochemical cell comprising: a cathode, an anode, optionally a reference electrode, optionally a membrane; and the polyoxometalate compound of Formula (I) as the catalyst for the reduction of carbon dioxide.

[0092] In some embodiments, the methods for the reduction of carbon dioxide provided herein comprises contacting the carbon dioxide with a polyoxometalate compound represented by formula (I), wherein M.sub.a, M.sub.b and M.sub.c are each independently selected from the group consisting of: Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Sn, Sb, In, Sc, Sr, Mg, Y, Yb, Ba and Ca and at least one of M.sub.a, M.sub.b and M.sub.c is Sn, Al, Zn or Ga. In other embodiments, M.sub.a, M.sub.b and M.sub.c are each independently selected from the group consisting of: Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Sn, Sb, In, Sc, Sr, Mg, Y, Yb, Ba and Ca and at least two of M.sub.a, M.sub.b and M.sub.c are different. In other embodiments, M.sub.a, M.sub.b and M.sub.c are each independently selected from the group consisting of: Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Sn, Sb, In, Sc, Sr, Mg, Y, Yb, Ba and Ca and M.sub.a, M.sub.b and M.sub.c are different.

[0093] In some embodiments, the methods for the reduction of carbon dioxide provided herein is directed to reduction of carbon dioxide to carbon monoxide. In some embodiments, the reduction of carbon dioxide provided herein is directed to reduction of carbon dioxide to formate salt or formic acid. In some embodiments, the reduction of carbon dioxide provided herein is directed to reduction of carbon dioxide to formaldehyde. In some embodiments, the reduction of carbon dioxide provided herein is directed to reduction of carbon dioxide to methanol. In some embodiments, the reduction of carbon dioxide provided herein is directed to reduction of carbon dioxide to ethane, ethylene or ethanol or any combination thereof.

[0094] In some embodiments, the electrochemical cell of this invention comprises a working (cathode), a counter (anode) and optionally a reference electrode. In one embodiment, the electrochemical cell of this invention comprises a working, a counter and a reference electrode. In one embodiment, any material and shape of an electrode known in the art can be used in this invention.

[0095] In one embodiment the electrochemical is a gas diffusion electrolyser.

[0096] In some embodiments, the electrolyte of the electrochemical cell is any electrolyte as known in the art.

[0097] In some embodiments the electrolyte is Q-Z wherein Z is and oxyanion, halide, peusdo halide, PF.sub.6.sup.? or BF.sub.4.sup.? and Q is as defined in formula (I).

[0098] In some embodiments, there is a solvent in the electrochemical cell wherein the solvent is any solvent known in the art.

[0099] In some embodiments the solvent is water at basic, neutral or acidic pH.

[0100] In some embodiments the solvent is an organic solvent or combinations of organic solvents. Non limiting examples of organic solvents include acetonitrile, glutaronitrile, adiponitrile, dimethyformamide, dimethylacetamide, dimethylsulfone, dimethylsulfoxide, tetrahydrofuran, glyme, diglyme, ethylene glycol oligomers, ethylene glycol polymers, mono alkylated ethylene glycol oligomers, mono alkylated ethylene glycol polymers, di alkylated ethylene glycol oligomers, di alkylated ethylene glycol polymers or combination thereof.

[0101] In some embodiments, the cathode of the electrochemical cell is carbon, such as a carbon disc, a carbon rod, carbon cloth or carbon paper.

[0102] In some embodiments, the cathode of the electrochemical cell is metal, such as titanium, iron or copper.

[0103] In some embodiments, the anode of the electrochemical cell is a Pt wire, carbon, iridium oxide, ruthenium oxide, iron, nickel, iron-nickel combinations, or cobalt containing compounds.

[0104] In some embodiments, the membrane of the electrochemical cell is any membrane as known in the art.

[0105] In some embodiments the membrane is anionic, in some embodiments is Nafion, in some embodiments the membrane is a ceramic material such a zirconia and alumina, in some embodiments the membrane is a porous organic polymer.

[0106] In some embodiments, the applied potential of the electrochemical cell is between ?3.5 to 0.0 V, ?3.0 to 0.0 V, ?2.5 to 0.0 V, ?2.0 to 0.0 V or ?1.5 to 0.0 V vs Fc/Fc.sup.+. In one specific embodiment, the applied potential is ?2.5 V or ?1.5 V vs Fc/Fc.sup.+.

[0107] In another embodiment, the following setup is utilized: a glassy carbon disc (d=3 mm) as a working electrode, a 15 mm Pt wire separated by a glass frit as a counter electrode and Fc/Fc.sup.+ as a reference electrode. In another embodiment, the following setup is utilized: a titanium metal working electrode, a carbon cloth counter electrode and a Nafion membrane. Each possibility represents a separate embodiment of the invention.

[0108] In one embodiment, the electrochemical cell comprises a cathode, an anode, the polyoxometalate compound (the compound of Formula (I)) and an electrolyte.

[0109] In one embodiment, the electrochemical cell comprises a cathode, an anode, the polyoxometalate compound, a reference electrode and an electrolyte.

[0110] In one embodiment, the electrocatalytic reaction is carried out in an undivided cell in an organic solvent.

[0111] In one embodiment, the electrocatalytic reaction is carried out in a divided cell configuration with a polymer membrane electrolyte separating the anode and cathode compartments.

[0112] In one embodiment, the electrocatalytic reaction is carried out in a divided cell configuration in an organic solvent, an electrolyte with a polymer membrane electrolyte separating the anode and cathode compartments.

[0113] In one embodiment, the electrocatalytic reaction is carried out in a flow cell membrane electrolyzer where the polyoxometalate is dissolved in a solvent.

[0114] In one embodiment, the electrocatalytic reaction is carried out in a gas diffusion electrolyzer.

[0115] In one embodiment, the electrochemical cell of this invention comprises a cathode and an anode, and a polyoxometalate compound (represented by formula (I)). In one embodiment, the compound is used in a solid form. In one embodiment, the compound is dissolved in a solution. In one embodiment, the solution comprises a solvent and a solute, the solute being the polyoxometalate compound of this invention and optionally an electrolyte. In one embodiment, the solvent is acetonitrile. In one embodiment, the concentration of the polyoxometalate compound ranges between 0.1 to 5 mM, 0.1 to 1 mM, 0.1 to 2 mM or 1 to 5 mM. In another embodiment, the compound's concentration is 2 mM. In one embodiment, the electrolyte concentration in the solution is between 0.01 to 1 M or 0.05-1M. In another embodiment, the electrolyte's concentration is 0.1M. Each possibility represents a separate embodiment of the invention.

[0116] In one embodiment, the electrolyte further comprises additives, stabilizers, salts, ions, or a combination thereof. In one embodiment, the pH of the electrolyte is adjusted. In one embodiment, the pH of the solution comprising water and the compound ranges between 0-14. In one embodiment, the pH value of the solution is acidic. In one embodiment, the pH of the solution is basic. In one embodiment, the solution pH ranges between 6-8, between 5-9, between 4-10, 3-11, 2-12 or 1-13. Each possibility represents a separate embodiment of the invention.

[0117] In one embodiment, the method of this invention comprises contacting the polyoxometalate compound of this invention with carbon dioxide in an electrochemical cell for a period of between 0.1-72 hours. In another embodiment, for 0.1-2 hours. In another embodiment, for 2-5 hours. In another embodiment, for 5-10 hours. In another embodiment, for 10-15 hours. In another embodiment, for 10-20 hours. In another embodiment, for 15-30 hours. In another embodiment, the step is conducted for 20-50 hours. In another embodiment, for 25-72 hours. In another embodiment, for 1 hour. In another embodiment, for 15 hours. Each possibility represents a separate embodiment of the invention.

Preparation of the Compounds of this Invention

[0118] In one embodiment, the anion of polyoxometalate of formula (I) of this invention is prepared by the following methods. In one embodiment, [XM.sub.aM.sub.bM.sub.c(L.sub.aL.sub.bL.sub.c)W.sub.9O.sub.37].sup.n? (the anion of formula (I)) is prepared by reacting a water soluble ?- or ?-[XW.sub.9O.sub.34].sup.9? anion in water with a mixture of up to three salts wherein each salt is represented by M.sub.wL.sub.y.Math.zH.sub.2O or with the compound M.sub.aM.sub.bM.sub.c(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc (Formula (Ia); see further embodiments thereof below) to yield the anion [XM.sub.aM.sub.bM.sub.c(L.sub.aL.sub.bL.sub.c)W.sub.9O.sub.37].sup.n?, where X, M.sub.a-M.sub.c, L.sub.a-L.sub.c and n are as described hereinabove, w and y are each independently an integer between 1-5, z is an integer between 0 and 10, na, nb and nc are each independently an integer between 1-5, M is Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Sc, Sr, Mg, Y, Ba or Ca and L is a carboxylate, an oxyanion, a halide or a pseudohalide, a carbonate, a bicarbonate or absent.

[0119] In one embodiment, this invention provides a method of preparing [XM.sub.aM.sub.bM.sub.c(L.sub.aL.sub.bL.sub.c)W.sub.9O.sub.37].sup.n?, comprising reacting a water soluble ?- or ?-[XW.sub.9O.sub.34].sup.9? anion in water with a mixture of up to three salts wherein each salt is represented by M.sub.wL.sub.y.Math.zH.sub.2O or with M.sub.aM.sub.bM.sub.c(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc, thereby providing [XM.sub.aM.sub.bM.sub.c(L.sub.aL.sub.bL.sub.c)W.sub.9O.sub.37].sup.n?, where X, M.sub.a-M.sub.c, L.sub.a-L.sub.c and n are as described hereinabove, w and y are each independently an integer between 1-5, z is an integer between 0 and 10, na, nb and nc are each independently an integer between 1-5, M is Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Sc, Sr, Mg, Y, Ba or Ca and L is a carboxylate, an oxyanion, a halide or a pseudohalide, a carbonate, a bicarbonate or absent.

The Following Provides Specific Methods for the Preparation of Q.sub.n[XM.sub.aM.sub.bM.sub.c(L.sub.aL.sub.bL.sub.c)W.sub.9O.sub.37]

[0120] In one embodiment, Na.sub.9[?-[SiW.sub.9O.sub.34] is reacted in water with a mixture up to three salts wherein each salt is represented by M.sub.wL.sub.y.Math.zH.sub.2O to yield Q.sub.n[SiM.sub.aM.sub.bM.sub.c(L.sub.aL.sub.bL.sub.c)W.sub.9O.sub.37] where w, y, z, M, M.sub.a-M.sub.c, L.sub.a-L.sub.c and n are as described hereinabove; Q is a cation such as a proton, an alkali metal cation, or a combination thereof and L is a carboxylate, an oxyanion, a halide or a pseudohalide, a carbonate, a bicarbonate or absent.

[0121] In one embodiment, Na.sub.9[?-[SiW.sub.9O.sub.34] is reacted in water with a mixture of up to three salts wherein each salt is represented by M.sub.wL.sub.y.Math.zH.sub.2O to yield Q.sub.n[SiM.sub.aM.sub.bM.sub.c(L.sub.aL.sub.bL.sub.c)W.sub.9O.sub.37] where w, y, z, M, M.sub.a-M.sub.c, L.sub.a-L.sub.c and n are as described hereinabove; Q is a cation such as a proton, an alkali metal cation, or a combination thereof; and L is a carboxylate, an oxyanion, a halide or a pseudohalide, a carbonate, a bicarbonate or absent.

[0122] In one embodiment, Na.sub.9[PW.sub.9O.sub.34] is reacted in water with a mixture of up to three salts wherein each salt is represented by M.sub.wL.sub.y.Math.zH.sub.2O to yield Q.sub.n[PM.sub.aM.sub.bM.sub.c(L.sub.aL.sub.bL.sub.c)W.sub.9O.sub.37] where w, y, z, M, M.sub.a-M.sub.c, L.sub.a-L.sub.c and n are as described hereinabove; Q is a cation such as a proton, an alkali metal cation, or a combination thereof; and L is a carboxylate, an oxyanion, a halide or a pseudohalide, a carbonate, a bicarbonate or absent.

[0123] In one embodiment, Na.sub.9[?-[SiW.sub.9O.sub.34] is reacted in water with the compound M.sub.aM.sub.bM.sub.c(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c)ne to yield Q.sub.n[SiM.sub.aM.sub.bM.sub.c(L.sub.aL.sub.bL.sub.c)W.sub.9O.sub.37] where y, Q, M.sub.a-M.sub.c, L.sub.a-Le and n are as described hereinabove. In another embodiment, na+nb+nc=9.

[0124] In one embodiment, Na.sub.9[?-[SiW.sub.9O.sub.34] is reacted in water with the compound M.sub.aM.sub.bM.sub.c(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc to yield Q.sub.n[SiM.sub.aM.sub.bM.sub.c(L.sub.aL.sub.bL.sub.c)W.sub.9O.sub.37] where y, Q, M.sub.a-M.sub.c, L.sub.a-L.sub.c and n are as described hereinabove. In another embodiment, na+nb+nc=9.

[0125] In one embodiment, Na.sub.9[PW.sub.9O.sub.34] is reacted in water with the compound M.sub.aM.sub.bM.sub.c(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc to yield Q.sub.n[PM.sub.aM.sub.bM.sub.c(L.sub.aL.sub.bL.sub.c)W.sub.9O.sub.37] where w, y, Q, M.sub.a-M.sub.c, L.sub.a-L.sub.c and n are as described hereinabove. In another embodiment, na+nb+nc=9.

The following provides specific methods for the preparation of XM.sub.aM.sub.bM.sub.c(L.sub.aL.sub.bL.sub.c)W.sub.9O.sub.37].sup.n?:

[0126] In one embodiment, [XM.sub.aM.sub.bM.sub.c(L.sub.aL.sub.bL.sub.c)W.sub.9O.sub.37].sup.n? is prepared by reacting a water soluble ?- or ?-[XW.sub.9O.sub.34].sup.9? anion in water with a mixture of up to three salts wherein each salt is represented by M.sub.wL.sub.y.Math.zH.sub.2O to yield the anion [XM.sub.aM.sub.bM.sub.c(L.sub.aL.sub.bL.sub.c)W.sub.9O.sub.37]n?, where w, y, z, X, M, M.sub.a-M.sub.c, L.sub.a-L.sub.c and n are as described hereinabove; and L is a carboxylate, an oxyanion, a halide or a pseudohalide, a carbonate, a bicarbonate or absent.

[0127] In one embodiment, [XM.sub.aM.sub.bM.sub.c(L.sub.aL.sub.bL.sub.c)W.sub.9O.sub.37].sup.n? is prepared by reacting a water soluble ?- or ?-[XW.sub.9O.sub.34].sup.9? anion in water with the compound M.sub.aM.sub.bM.sub.c(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc to yield the anion [XM.sub.aM.sub.bM.sub.c(L.sub.aL.sub.bL.sub.c)W.sub.9O.sub.37].sup.n? where y, X, M.sub.a-M.sub.c, L.sub.a-Le and n are as described hereinabove. In another embodiment, na+nb+nc=9.

The following provides specific methods for cation exchange from Q to Q of XM.sub.aM.sub.bM.sub.c(L.sub.aL.sub.bL.sub.c)W.sub.9O.sub.37].sup.n?

[0128] In one embodiment, (Q).sub.n[XM.sub.aM.sub.bM.sub.c(L.sub.a)(L.sub.b)(L.sub.c)W.sub.9O.sub.37], wherein Q is selected from the group consisting of: an alkaline earth metal salt, a lanthanide salt, a quaternary ammonium salt or a quaternary phosphonium salt and any combination thereof, is prepared by reacting (Q).sub.n[XM.sub.aM.sub.bM.sub.c(L.sub.a)(L.sub.b)(L.sub.c)W.sub.9O.sub.37] with an alkaline earth metal salt, a lanthanide salt, a quaternary ammonium salt or a quaternary phosphonium salt including combinations thereof, where Q, X, M.sub.a-M.sub.c, L.sub.a-L.sub.c and n are as described hereinabove.

[0129] In one embodiment, Q.sub.n[SiM.sub.aM.sub.bM.sub.c(L.sub.aL.sub.bL.sub.c)W.sub.9O.sub.37], wherein Q is selected from the group consisting of: an alkaline earth metal salt, a lanthanide salt, a quaternary ammonium salt or a quaternary phosphonium salt and any combination thereof, is prepared by reacting Q.sub.n[SiM.sub.aM.sub.bM.sub.c(L.sub.aL.sub.bL.sub.c)W.sub.9O.sub.37] with an alkaline earth metal salt, a lanthanide salt, a quaternary ammonium salt or a quaternary phosphonium salt including combinations thereof, where Q, M.sub.a-M.sub.c, L.sub.a-L.sub.c, n are as described hereinabove.

[0130] In one embodiment, Q.sub.n[PM.sub.aM.sub.bM.sub.c(L.sub.aL.sub.bL.sub.c)W.sub.9O.sub.37], wherein Q is selected from the group consisting of: an alkaline earth metal salt, a lanthanide salt, a quaternary ammonium salt or a quaternary phosphonium salt and any combination thereof, is prepared by reacting Q.sub.n[PM.sub.aM.sub.bM.sub.c(L.sub.aL.sub.bL.sub.c)W.sub.9O.sub.37] with an alkaline earth metal salt, a lanthanide salt, a quaternary ammonium salt or a quaternary phosphonium salt including combinations thereof, where Q, M.sub.a-M.sub.c, L.sub.a-L.sub.c and n are as described hereinabove.

The M.sub.aM.sub.bM.sub.c(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc Compounds

[0131] In one embodiment, this invention provides a mixed metal salt compound represented by Formula (Ia) anion:

M.sub.aM.sub.bM.sub.c(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc(Ia) [0132] wherein [0133] M.sub.a, M.sub.b and M.sub.c are each independently selected from the group consisting of: Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Sn, Sb, In, Sc, Sr, Mg, Y, Yb, Ba and Ca; [0134] L.sub.a, L.sub.b and L.sub.c are each independently selected from the group consisting of: H.sub.2O, carboxylates, oxyanions, halides or pseudohalides, carbonate, bicarbonate or absent; and [0135] na, nb and nc are each independently an integer between 1-5; [0136] wherein the cation is Q.sub.n and [0137] Q is a cation such as a proton, an alkali metal cation, an alkaline earth metal cation, a lanthanide cation, a nitrogen centered cation or a phosphorous centered cation or any combination thereof; [0138] n is an integer between 4-13.

[0139] In other embodiments, M.sub.a, M.sub.b and M.sub.c are each independently selected from the group consisting of: Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Sn, Sb, In, Sc, Sr, Mg, Y, Yb, Ba and Ca and at least one of M.sub.a, M.sub.b and M.sub.c is Sn, Al, Zn or Ga. In other embodiments, M.sub.a, M.sub.b and M.sub.c are each independently selected from the group consisting of: Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Sn, Sb, In, Sc, Sr, Mg, Y, Yb, Ba and Ca and at least two of M.sub.a, M.sub.b and M.sub.c are different. In other embodiments, M.sub.a, M.sub.b and M.sub.c are each independently selected from the group consisting of: Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Sn, Sb, In, Sc, Sr, Mg, Y, Yb, Ba and Ca and M.sub.a, M.sub.b and M.sub.c are different (representing three different metal selected from the group above).

[0140] In another embodiment, the sum of na, nb and nc (i.e. na+nb+nc) is between 3-15, 3-5, 3-10, 10-15, 12-15, 5-15, 7-12 or 8-11. In another embodiment, na+nb+nc=9.

[0141] In one embodiment, Formula (Ia) is represented by: CuFeZn(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc, Cu.sub.2Fe(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc, CuFe.sub.2(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc, Cu.sub.2Ni(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc, CuNi.sub.2(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc, Cu.sub.2Zn(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc, Cu.sub.2Ga(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc, Cu.sub.2Al(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc, Cu.sub.2SC(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc, Cu.sub.2Mg(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc, Fe.sub.2Ni(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc, FeNi.sub.2(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc, CuFeNi(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc, CuFeAl(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc, CuNiZn(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc, CUNiAl(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc, CuCoZn(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.ncCuCoAl(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.ncCuMnZn(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc, or CuMnAl(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc.

[0142] In one embodiment, Formula (Ia) is represented by: [Cu.sub.2Fe(MeCOO).sub.6(H.sub.2O).sub.3], [Cu.sub.2Ni(MeCOO).sub.6(H.sub.2O).sub.3], [Cu.sub.2Zn(MeCOO).sub.6(H.sub.2O).sub.3], [Cu.sub.2Ga(MeCOO).sub.6(H.sub.2O).sub.3], [Cu.sub.2Al(MeCOO).sub.6(H.sub.2O).sub.3], [Cu.sub.2Sc(MeCOO).sub.6(H.sub.2O).sub.3], [Cu.sub.2Mg(MeCOO).sub.6(H.sub.2O).sub.3], [CuFeNi(MeCOO).sub.6(H.sub.2O).sub.3], [CuFeZn(MeCOO).sub.6(H.sub.2O).sub.3], [CuFeAl(MeCOO).sub.6(H.sub.2O).sub.3], [CuNiZn(MeCOO).sub.6(H.sub.2O).sub.3] or [CuNiAl(MeCOO).sub.6(H.sub.2O).sub.3]. Each possibility represents a separate embodiment of the invention.

[0143] In one embodiment, M.sub.aM.sub.bM.sub.c(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc (Ia) is prepared by reacting up to three salts such as M.sub.wL.sub.y.Math.zH.sub.2O, and isolating the obtained salt as M.sub.aM.sub.bM.sub.c(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc (Ia), wherein w and y are each independently an integer between 1-5, z is an integer between 0 and 10, L.sub.a, L.sub.b, L.sub.c is each independently a carboxylate, an oxyanion, a halide or a pseudohalide, a carbonate, a bicarbonate or absent and M.sub.a, M.sub.b, M.sub.c is each independently Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Sn, Sb, In, Sc, Sr, Mg, Y, Yb, Ba or Ca.

[0144] In one embodiment, this invention provides a method of preparing M.sub.aM.sub.bM.sub.c(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc (Ia), comprising mixing a solution(s) of up to three salts wherein each salt is represented by M.sub.wL.sub.y.Math.zH.sub.2O, and isolating the obtained salt as M.sub.aM.sub.bM.sub.c(L.sub.a).sub.na(L.sub.b).sub.nb(L.sub.c).sub.nc (Ia), wherein w, y, z, L.sub.a, L.sub.b, L.sub.c and M.sub.a, M.sub.b, M.sub.c are described hereinabove.

[0145] In another embodiment, the solutions are aqueous or any other as known in the art. In another embodiment, the solutions of the salts are filtered prior to the mixing thereof. In other embodiments, the isolation of M.sub.aM.sub.bM.sub.c(L.sub.a).sub.na(Lo).sub.nb(L.sub.c).sub.nc (Ia) comprises any isolation step as known in the art (non-limiting examples include evaporation, precipitation/crystallization, extraction, sublimation etc.). In another embodiment, the isolation comprises vacuum evaporation of the mixture obtained by mixing the M.sub.wL.sub.y.Math.zH.sub.2O salts. Each possibility represents a separate embodiment of the invention.

SPECIFIC EMBODIMENTS

[0146] In one embodiment, this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[XCu.sub.2ML.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell and where M is Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Sn, Sb, In, Sc, Sr, Mg, Y, Yb, Ba and Ca.

[0147] In one embodiment, this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[SiCu.sub.2ML.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0148] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[PCu.sub.2ML.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0149] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[XCuFeZnL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0150] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[SiCuFeZnL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0151] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[PCuFeZnL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0152] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[XCuFeAlL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0153] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[SiCuFeAlL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0154] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[PCuFeAlL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0155] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[XCuFeGaL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0156] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[SiCuFeGaL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0157] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[PCuFeGaL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0158] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[XCuFeSnL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0159] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[SiCuFeSnL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0160] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[PCuFeSnL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0161] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[XCuNiZnL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0162] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[SiCuNiZnL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0163] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[PCuNiZnL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0164] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[XCuNiAlL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0165] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[SiCuNiAlL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0166] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[PCuNiAlL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0167] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[XCuNiGaL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0168] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[SiCuNiGaL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0169] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[PCuNiGaL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0170] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[XCuCoZnL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0171] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[SiCuCoZnL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0172] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[PCuCoZnL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0173] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[XCuCoAlL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0174] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[SiCuCoAlL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0175] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[PCuCoAlL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0176] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[XCuMnZnL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0177] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[SiCuMnZnL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction conducted in an electrochemical cell.

[0178] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[PCuMnZnL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0179] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[XCuMnAlL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0180] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[SiCuMnAlL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0181] In one embodiment this invention provides a method of reducing carbon dioxide to carbon monoxide by reacting polyoxometalate compound (Q).sub.n[PCuMnAlL.sub.aL.sub.bL.sub.cW.sub.9O.sub.37] or solvates thereof with carbon dioxide, wherein the reaction is conducted in an electrochemical cell.

[0182] In some embodiments, within the above specific embodiments, X, Q, L.sub.a-L.sub.c and n are as described hereinabove for the compound of formula (I).

EXAMPLES

Example 1

[0183] Synthesis of {SiW.sub.9O.sub.37[Cu.sub.2Ga(L)].sub.3}.sup.9? as a cesium salt, where L=H.sub.2O or OAc.sup.?:

[0184] A solution of sodium acetate trihydrate (0.32 mol) in water (70 mL) was added to a filtered, stirred solution of copper(II) nitrate trihydrate (0.02 mol) and gallium(III) nitrate hydrate (0.01 mol) in water (70 mL). This resulted in a blue solution, which was evaporated and dried under vacuum to yield [Cu.sub.2Ga(MeCOO).sub.6(H.sub.2O).sub.3]. To a solution of [Cu.sub.2Ga(MeCOO).sub.6(H.sub.2O).sub.3] (1.75 mmol) in water (15 mL), Na.sub.9[?-SiW.sub.9O.sub.34H].Math.23H.sub.2O (1.75 mmol, prepared according to: G. Herve and A. Teze, Study of alpha-and. beta.-enneatungstosilicates and-germanates Inorg. Chem., 1977, 16, 2115-2117) dissolved in NaOAc/HOAc solution (pH 6) was added in small amounts with vigorous stirring, and was heated to 50? C. for 1 hour. After adding CsCl (0.33 g/ml) solution at room temperature, this produced a light green precipitate of Cs.sub.9[SiW.sub.9O.sub.37{Cu.sub.2Ga(L).sub.3}]. The compound was characterized by Infra-red and High Resolution Mass Spectroscopy, Yield48%.

Example 2

[0185] Synthesis of {SiW.sub.9O.sub.37[Cu.sub.2Zn(L)].sub.3}.sup.10 as a cesium salt, where L=H.sub.2O or OAc.sup.?:

[0186] A solution of sodium acetate trihydrate (0.32 mol) in water (70 mL) was added to a filtered, stirred solution of copper(II) nitrate trihydrate (0.02 mol) and zinc(II) nitrate hexahydrate (0.01 mol) in water (70 mL). This resulted in a blue solution, which was evaporated and dried under vacuum to yield [Cu.sub.2Zn(MeCOO).sub.6(H.sub.2O).sub.3]. To a solution of [Cu.sub.2Zn(MeCOO).sub.6(H.sub.2O).sub.3] (1.75 mmol) in water (15 mL), Na.sub.9[?-SiW.sub.9O.sub.34H].Math.23H.sub.2O (1.75 mmol, prepared according to: G. Herve and A. Teze, Study of alpha-and. beta.-enneatungstosilicates and-germanates Inorg. Chem., 1977, 16, 2115-2117) dissolved in NaOAc/HOAc solution (pH 6) was added in small amounts with vigorous stirring, and was heated to 50? C. for 1 hour. After adding CsCl (0.33 g/ml) solution at room temperature, this produced a light green precipitate of Cs.sub.10[SiW.sub.9O.sub.37{Cu.sub.2Zn(L).sub.3}]. The compound was characterized by Infra-red and High Resolution Mass Spectroscopy, Yield57%.

Example 3

[0187] Synthesis of {SiW.sub.9O.sub.37[Cu.sub.2Sn(L)].sub.3}.sup.8? as a cesium salt, where L=H.sub.2O or OAc:

[0188] A solution of sodium acetate trihydrate (0.32 mol) in water (70 mL) was added to a filtered, stirred solution of copper(II) nitrate trihydrate (0.02 mol) and tin(IV) acetate (0.01 mol) in water (70 mL). This resulted in a blue solution, which was evaporated and dried under vacuum to yield [Cu.sub.2Zn(MeCOO).sub.6(H.sub.2O).sub.3]. To a solution of [Cu.sub.2Sn(MeCOO).sub.6(H.sub.2O).sub.3] (1.75 mmol) in water (15 mL), Na.sub.9[?-SiW.sub.9O.sub.34H].Math.23H.sub.2O (1.75 mmol, prepared according to: G. Herve and A. Teze, Study of alpha-and. beta.-enneatungstosilicates and-germanates Inorg. Chem., 1977, 16, 2115-2117) dissolved in NaOAc/HOAc solution (pH 6) was added in small amounts with vigorous stirring, and was heated to 50? C. for 1 hour. After adding CsCl (0.33 g/ml) solution at room temperature, this produced a light green precipitate of Cs.sub.8[SiW.sub.9O.sub.37{Cu.sub.2Sn(L).sub.3}]. The compound was characterized by Infra-red and High Resolution Mass Spectroscopy, Yield49%.

Example 4

[0189] Synthesis of {SiW.sub.9O.sub.37[Cu.sub.2Al(L)].sub.3}.sup.9? as a cesium salt, where L=H.sub.2O or OAc.sup.?:

[0190] A solution of sodium acetate trihydrate (0.32 mol) in water (70 mL) was added to a filtered, stirred solution of copper(II) nitrate trihydrate (0.02 mol) and aluminium(III) nitrate nonahydrate (0.01 mol) in water (70 mL). This resulted in a blue solution, which was evaporated and dried under vacuum to yield [Cu.sub.2Al(MeCOO).sub.6(H.sub.2O).sub.3] To a solution of [Cu.sub.2Al(MeCOO).sub.6(H.sub.2O).sub.3] (1.75 mmol) in water (15 mL), Na.sub.9[?-SiW.sub.9O.sub.3H].Math.23H.sub.2O (1.75 mmol, prepared according to: G. Herve and A. Teze, Study of alpha-and. beta.-enneatungstosilicates and-germanates Inorg. Chem., 1977, 16, 2115-2117) dissolved in NaOAc/HOAc solution (pH 6) was added in small amounts with vigorous stirring, and was heated to 50? C. for 1 hour. After adding CsCl (0.33 g/ml) solution at room temperature, this produced a light green precipitate of Cs.sub.9[SiW.sub.9O.sub.37{Cu.sub.2Al(L).sub.3}]. The compound was characterized by Infra-red and High Resolution Mass Spectroscopy, Yield51%.

Example 5

[0191] Synthesis of {SiW.sub.9O.sub.37[Cu.sub.2Sc(L)].sub.3}.sup.9? as a cesium salt, where L=H.sub.2O or OAc.sup.?:

[0192] A solution of sodium acetate trihydrate (0.32 mol) in water (70 mL) was added to a filtered, stirred solution of copper(II) nitrate trihydrate (0.02 mol) and scadium(III) nitrate hexahydrate (0.01 mol) in water (70 mL). This resulted in a blue solution, which was evaporated and dried under vacuum to yield [Cu.sub.2Sc(MeCOO).sub.6(H.sub.2O).sub.3] To a solution of [Cu.sub.2Sc(MeCOO).sub.6(H.sub.2O).sub.3] (1.75 mmol) in water (15 mL), Na.sub.9[?-SiW.sub.9O.sub.34H].Math.23H.sub.2O (1.75 mmol, prepared according to: G. Herve and A. Teze, Study of alpha-and. beta.-enneatungstosilicates and-germanates Inorg. Chem., 1977, 16, 2115-2117) dissolved in NaOAc/HOAc solution (pH 6) was added in small amounts with vigorous stirring, and was heated to 50? C. for 1 hour. After adding CsCl (0.33 g/ml) solution at room temperature, this produced a light green precipitate of Cs.sub.9[SiW.sub.9O.sub.37{Cu.sub.2Sc(L).sub.3}]. The compound was characterized by Infra-red and High Resolution Mass Spectroscopy, Yield36%.

Example 6

[0193] Synthesis of {SiW.sub.9O.sub.37[Cu.sub.2Mg(L)].sub.3}.sup.10? as a cesium salt, where L=H.sub.2O or OAc.sup.?:

[0194] A solution of sodium acetate trihydrate (0.32 mol) in water (70 mL) was added to a filtered, stirred solution of copper(II) nitrate trihydrate (0.02 mol) and magnesium (II) nitrate hexahydrate (0.01 mol) in water (70 mL). This resulted in a lightblue solution, which was evaporated and dried under vacuum to yield [Cu.sub.2Mg(MeCOO).sub.6(H.sub.2O).sub.3]. To a solution of [Cu.sub.2Mg(MeCOO).sub.6(H.sub.2O).sub.3] (1.75 mmol) in water (15 mL), Na.sub.9[?-SiW.sub.9O.sub.34H].Math.23H.sub.2O (1.75 mmol, prepared according to: G. Herve and A. Teze, Study of alpha-and. beta.-enneatungstosilicates and-germanates Inorg. Chem., 1977, 16, 2115-2117) dissolved in NaOAc/HOAc solution (pH 6) was added in small amounts with vigorous stirring, and was heated to 50? C. for 1 hour. After adding CsCl (0.33 g/ml) solution at room temperature, this produced a light green precipitate of Cs.sub.10[SiW.sub.9O.sub.37{Cu.sub.2Mg(L).sub.3}]. The compound was characterized by Infra-red and High Resolution Mass Spectroscopy, Yield35%.

Example 7

[0195] Synthesis of {SiW.sub.9O.sub.37[CuFeNi(L)].sub.3}.sup.9? as a cesium salt, where L=H.sub.2O or OAc.sup.?:

[0196] A solution of sodium acetate trihydrate (0.32 mol) in water (70 mL) was added to a filtered, stirred solution of copper(II) nitrate trihydrate (0.01 mol), iron(III) nitrate nonahydrate (0.01 mol) and nickel(II) nitrate hexahydrate (0.01 mol) in water (70 mL). This resulted in a yellow-green solution, which was evaporated and dried under vacuum to yield [CuFeNi(MeCOO).sub.6(H.sub.2O).sub.3]. To a solution of [CuFeNi(MeCOO).sub.6(H.sub.2O).sub.3] (1.75 mmol) in water (15 mL), Na.sub.9[?-SiW.sub.9O.sub.34H].Math.23H.sub.2O (1.75 mmol, prepared according to: G. Herve and A. Teze, Study of alpha-and. beta.-enneatungstosilicates and-germanates Inorg. Chem., 1977, 16, 2115-2117) dissolved in NaOAc/HOAc solution (pH 6) was added in small amounts with vigorous stirring, and was heated to 50? C. for 1 hour. After adding CsCl (0.33 g/mL) solution at room temperature, this produced a light yellow-green precipitate of Cs.sub.9[SiW.sub.9O.sub.37{CuFeNi(L).sub.3}]. The compound was characterized by Infra-red and High Resolution Mass Spectroscopy, Yield47%.

Example 8

[0197] Synthesis of {SiW.sub.9O.sub.37[CuFeZn(L)].sub.3}.sup.9? as a cesium salt, where L=H.sub.2O or OAc.sup.?:

[0198] A solution of sodium acetate trihydrate (0.32 mol) in water (70 mL) was added to a filtered, stirred solution of copper(II) nitrate trihydrate (0.01 mol), iron(III) nitrate nonahydrate (0.01 mol) and zinc(II) nitrate hexahydrate (0.01 mol) in water (70 ml). This resulted in a brown solution, which was evaporated and dried under vacuum to yield [CuFeZn(MeCOO).sub.6(H.sub.2O).sub.3].

[0199] To a solution of [CuFeZn(MeCOO).sub.6(H.sub.2O).sub.3] (1.75 mmol) in water (15 mL), Na.sub.9[?-SiW.sub.9O.sub.34H].Math.23H.sub.2O (1.75 mmol, prepared according to: G. Herve and A. Teze, Study of alpha-and. beta.-enneatungstosilicates and-germanates Inorg. Chem., 1977, 16, 2115-2117) dissolved in NaOAc/HOAc solution (pH 6) was added in small amounts with vigorous stirring, and was heated to 50? C. for 1 hour. After adding CsCl (0.33 g/mL) solution at room temperature, this produced a light yellow-green precipitate of Cs.sub.9[SiW.sub.9O.sub.37{CuFeZn(L).sub.3}]. The compound was characterized by Infra-red and High Resolution Mass Spectroscopy, Yield37%.

Example 9

[0200] Synthesis of {SiW.sub.9O.sub.37[CuFeAl(L)].sub.3}.sup.8? as cesium salt, where L=H.sub.2O or OAc.sup.?:

[0201] A solution of sodium acetate trihydrate (0.32 mol) in water (70 mL) was added to a filtered, stirred solution of copper(II) nitrate trihydrate (0.01 mol), iron(III) nitrate nonahydrate (0.01 mol) and aluminium(III) nitrate nonahydrate (0.01 mol) in water (70 mL). This resulted in a green-brown solution, which was evaporated and dried under vacuum to yield [CuFeAl(MeCOO).sub.6(H.sub.2O).sub.3]. To a solution of [CuFeAl(MeCOO).sub.6(H.sub.2O).sub.3] (1.75 mmol) in water (15 mL), Na.sub.9[?-SiW.sub.9O.sub.34H].Math.23H.sub.2O (1.75 mmol, prepared according to: G. Herve and A. Teze, Study of alpha-and. beta.-enneatungstosilicates and-germanates Inorg. Chem., 1977, 16, 2115-2117) dissolved in NaOAc/HOAc solution (pH 6) was added in small amounts with vigorous stirring, and was heated to 50? C. for 1 hour. After adding CsCl (0.33 g/mL) solution at room temperature, this produced a yellow-green precipitate of Cs.sub.8[SiW.sub.9O.sub.37{CuFeAl(L).sub.3}]. The compound was characterized by Infra-red and High Resolution Mass Spectroscopy, Yield54%.

Example 10

[0202] Synthesis of {SiW.sub.9O.sub.37[CuNiZn(L)].sub.3}.sup.?10 as cesium salts, where L=H.sub.2O or OAc.sup.?:

[0203] A solution of sodium acetate trihydrate (0.32 mol) in water (70 mL) was added to a filtered, stirred solution of copper(II) nitrate trihydrate (0.01 mol), nickel(II) nitrate hexahydrate (0.01 mol) and zinc(II) nitrate hexahydrate (0.01 mol) in water (70 ml). This resulted in a blue solution, which was evaporated and dried under vacuum to yield [CuNiZn(MeCOO).sub.6(H.sub.2O).sub.3].

[0204] To a solution of [CuNiZn(MeCOO).sub.6(H.sub.2O).sub.3] (1.75 mmol) in water (15 mL), Na.sub.9[?-SiW.sub.9O.sub.34H].Math.23H.sub.2O (1.75 mmol, prepared according to: G. Herve and A. Teze, Study of alpha-and. beta.-enneatungstosilicates and-germanates Inorg. Chem., 1977, 16, 2115-2117) dissolved in NaOAc/HOAc solution (pH 6) was added in small amounts with vigorous stirring, and was heated to 50? C. for 1 hour. After adding CsCl (0.33 g/mL) solution at room temperature, this produced a light green precipitate of Cs.sub.10[SiW.sub.9O.sub.37{CuNiZn(L).sub.3}]. The compound was characterized by Infra-red and High Resolution Mass Spectroscopy, Yield52%.

Example 11

[0205] Synthesis of {SiW.sub.9O.sub.37[CuNiAl(L)].sub.3}.sup.?9 as cesium salts, where L=H.sub.2O or OAc.sup.?:

[0206] A solution of sodium acetate trihydrate (0.32 mol) in water (70 mL) was added to a filtered, stirred solution of copper(II) nitrate trihydrate (0.01 mol), nickel(II) nitrate hexahydrate (0.01 mol) and aluminium(III) nitrate nonahydrate (0.01 mol) in water (70 ml). This resulted in a blue solution, which was evaporated and dried under vacuum [CuNiAl(MeCOO).sub.6(H.sub.2O).sub.3]. To a solution of r [CuNiAl(MeCOO).sub.6(H.sub.2O).sub.3] (1.75 mmol) in water (15 mL), Na.sub.9[?-SiW.sub.9O.sub.34H].Math.23H.sub.2O (1.75 mmol, prepared according to: G. Herve and A. Teze, Study of alpha-and. beta.-enneatungstosilicates and-germanates Inorg. Chem., 1977, 16, 2115-2117) dissolved in NaOAc/HOAc solution (pH 6) was added in small amounts with vigorous stirring, and was heated to 50? C. for 1 hour. After adding CsCl (0.33 g/mL) solution at room temperature, this produced a light green precipitate of Cs.sub.9[SiW.sub.9O.sub.37{CuNiAl(L).sub.3}]. The compound was characterized by Infra-red and High Resolution Mass Spectroscopy, Yield49%.

Example 12

[0207] Synthesis of {SiW.sub.9O.sub.37[CuFeGa(L)].sub.3}.sup.8? as a cesium salt, where L=H.sub.2O or OAc.sup.?:

[0208] A solution of sodium acetate trihydrate (0.32 mol) in water (70 mL) was added to a filtered, stirred solution of copper(II) nitrate trihydrate (0.01 mol), iron(III) nitrate nonahydrate (0.01 mol) and gallium(II) nitrate (0.01 mol) in water (70 ml). This solution was evaporated and dried under vacuum to yield [CuFeGa(MeCOO).sub.6(H.sub.2O).sub.3].

[0209] To a solution of [CuFeGa(MeCOO).sub.6(H.sub.2O).sub.3] (1.75 mmol) in water (15 mL), Na.sub.9[?-SiW.sub.9O.sub.34H].Math.23H.sub.2O (1.75 mmol, prepared according to: G. Herve and A. Teze, Study of alpha-and. beta.-enneatungstosilicates and-germanates Inorg. Chem., 1977, 16, 2115-2117) dissolved in NaOAc/HOAc solution (pH 6) was added in small amounts with vigorous stirring, and was heated to 50? C. for 1 hour. After adding CsCl (0.33 g/mL) solution at room temperature, this produced a light yellow-green precipitate of Cs.sub.8[SiW.sub.9O.sub.37{CuFeGa(L).sub.3}]. The compound was characterized by Infra-red and High Resolution Mass Spectroscopy, Yield47%.

Example 13

[0210] Synthesis of {SiW.sub.9O.sub.37[CuFeSn(L)].sub.3}.sup.7? as a cesium salt, where L=H.sub.2O or OAc.sup.?:

[0211] A solution of sodium acetate trihydrate (0.32 mol) in water (70 mL) was added to a filtered, stirred solution of copper(II) nitrate trihydrate (0.01 mol), iron(III) nitrate nonahydrate (0.01 mol) and tin(IV)acetate (0.01 mol) in water (70 ml). This solution was evaporated and dried under vacuum to yield [CuFeGa(MeCOO).sub.6(H.sub.2O).sub.3].

[0212] To a solution of [CuFeSn(MeCOO).sub.6(H.sub.2O).sub.3] (1.75 mmol) in water (15 mL), Na.sub.9[?-SiW.sub.9O.sub.34H].Math.23H.sub.2O (1.75 mmol, prepared according to: G. Herve and A. Teze, Study of alpha-and. beta.-enneatungstosilicates and-germanates Inorg. Chem., 1977, 16, 2115-2117) dissolved in NaOAc/HOAc solution (pH 6) was added in small amounts with vigorous stirring, and was heated to 50? C. for 1 hour. After adding CsCl (0.33 g/mL) solution at room temperature, this produced a light yellow-green precipitate of Cs.sub.7[SiW.sub.9O.sub.37{CuFeSn(L).sub.3}]. The compound was characterized by Infra-red and High Resolution Mass Spectroscopy, Yield36%.

Example 14

[0213] Representative Exchange of Alkali Metal Cation with Quaternary Ammonium Cation:

[0214] Cs.sub.10[SiCu.sub.3(H.sub.2O).sub.3W.sub.9O.sub.37] (300 mg) was dissolved in a beaker containing 50 mL of deionized water. Tetrahexyl ammonium bromide (3.6 g) was dissolved in 100 mL dichloromethane with sonication for 15 min. After mixing the two solutions, two separate phases were formed: the upper phase was the water phase and the lower phase was the oily phase containing [(n-hexyl).sub.4N].sub.10[SiCu.sub.3(H.sub.2O).sub.3W.sub.9O.sub.37] which was extracted and washed several times with deionized water. The clear solution was then evaporated to dryness.

Example 15

Reduction CO.SUB.2 .in an Undivided Cell:

[0215] Constant potential electrolysis was carried out for 1 h at room temperature in an electrolyzer (FIG. 2) containing 2 mM of [(n-hexyl).sub.4N].sub.n[SiM.sub.aM.sub.bM.sub.c(L.sub.aL.sub.bL.sub.c)W.sub.9O.sub.37] (prepared as detailed in Example 14) and 0.1 M (n-butyl).sub.4NPF.sub.6 as supporting electrolyte in acetonitrile, a titanium metal working electrode, a carbon cloth counter electrode and a Nafion membrane. The results, amounts of CO and faradaic efficiency (FE) for formation of CO for six [SiM.sub.aM.sub.bM.sub.c(H.sub.2O).sub.3W.sub.9O.sub.37].sup.n? anions at various are presented in the Table below.

TABLE-US-00001 [SiW.sub.9CuFeGaO.sub.37].sup.8? Potential, V ?2.8 ?2.5 ?2.2 ?2.0 ?1.8 ?1.5 ?1.4 Yield, ?mol 83 71 2 0 4 16 0 Faradaic Efficiency 84 96 4 0 28 86 0

TABLE-US-00002 [SiW.sub.9Cu.sub.2GaO.sub.37].sup.9? Potential, V ?2.8 ?2.5 ?2.2 ?2.0 ?1.8 ?1.5 ?1.4 Yield, ?mol 31 11 7 0 0.1 10 0 Faradaic Efficiency 21 56 12 0 0.4 67 0

TABLE-US-00003 [SiW.sub.9CuFeZnO.sub.37].sup.9? Potential, V ?2.8 ?2.5 ?2.2 ?2.0 ?1.8 ?1.5 ?1.4 Yield, ?mol 191 79 2 0 3 10 0 Faradaic Efficiency 44 32 7 0 9 23 0

TABLE-US-00004 [SiW.sub.9Cu.sub.2ZnO.sub.37].sup.10? Potential, V ?2.8 ?2.5 ?2.2 ?2.0 ?1.8 ?1.5 ?1.4 Yield, ?mol 94 73 4 0 3 7 0 Faradaic Efficiency 53 42 52 0 8 21 0

TABLE-US-00005 [SiW.sub.9CuFeSnO.sub.37].sup.7? Potential, V ?2.8 ?2.5 ?2.2 ?2.0 ?1.8 ?1.5 ?1.4 Yield, ?mol 22 32 2 1 3 7 2 Faradaic Efficiency 26 60 2 5 6 17 8

TABLE-US-00006 [SiW.sub.9Cu.sub.2SnO.sub.37].sup.8? Potential, V ?2.8 ?2.5 ?2.2 ?2.0 ?1.8 ?1.5 ?1.4 Yield, ?mol 36 16 7 0 0 7 4 Faradaic Efficiency 67 45 21 0 0 19 9

[0216] While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those of ordinary skill in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.