PROCESS FOR PRODUCING FUNCTIONALIZED ORGANIC MOLECULES AND USES THEREOF

Abstract

A process for producing functionalized organic molecules having 1 to 3 carbon atoms. The method includes the step of contacting carbon dioxide as the only gas, or a gas mixture that includes carbon dioxide and methane, in the presence of water, with a catalyst that includes permanently polarized hydroxyapatite.

Claims

1.-16. (canceled)

17. A process for producing functionalized organic molecules having 1 to 3 carbon atoms, the process comprising the step of: contacting carbon dioxide as the only gas or a gas mixture comprising or consisting of carbon dioxide and methane in a presence of water with a catalyst comprising or consisting of permanently polarized hydroxyapatite.

18. The process according to claim 17, wherein the permanently polarized hydroxyapatite has: a crystallinity >65% and/or a proportion of amorphous calcium phosphate <18% by weight, based on the total weight of the permanently polarized hydroxyapatite, and/or a proportion of β-tricalcium phosphate <36% by weight, based on the total weight of the permanently polarized hydroxyapatite, and/or a bulk resistance from 10.sup.7Ω cm.sup.2 to 10.sup.5Ω cm.sup.2, wherein the bulk resistance increases by only 4% to 73% after 3 months, and/or a surface capacitance decreasing less than 8% after 3 months.

19. The process according to claim 17, wherein the permanently polarized hydroxyapatite is obtained by a process comprising the steps of: (a) preparing samples of hydroxyapatite, (b) sintering the samples prepared in step (a) at a temperature between 700° C. and 1200° C., (c) applying a constant or variable DC voltage between 250 V and 2500 V to the samples obtained in step (b) or to shaped bodies thereof or applying an equivalent electric field between 1.49 kV/cm and 15 kV/cm to the samples obtained in step (b) or to shaped bodies thereof or applying an electrostatic discharge between 2500 V and 1500000 V to the samples obtained in step (b) or to shaped bodies thereof or applying an equivalent electric field between 148.9 kV/cm and 8928 kV/cm to the samples obtained in step (b) or to shaped bodies thereof and (d) cooling the samples obtained in step (c) maintaining the DC voltage or the equivalent electric field or cooling the samples obtained in step (c) maintaining or without maintaining the electrostatic discharge or the equivalent electric field.

20. The process according to claim 17, wherein the permanently polarized hydroxyapatite is obtained by a process comprising the steps of: (a) preparing samples of hydroxyapatite, (b) sintering the samples prepared in step (a) at a temperature between 700° C. and 1200° C., (c) applying a constant or variable DC voltage between 250 V and 2500 V for at least 1 minute at a temperature between 900° C. and 1200° C. to the samples obtained in step (b) or to shaped bodies thereof or applying an equivalent electric field between 1.49 kV/cm and 15 kV/cm for at least 1 minute at a temperature between 900° C. and 1200° C. to the samples obtained in step (b) or to shaped bodies thereof or applying an electrostatic discharge between 2500 V and 1500000 V for less than 10 minutes at a temperature between 900° C. and 1200° C. to the samples obtained in step (b) or to shaped bodies thereof or applying an equivalent electric field between 148.9 kV/cm and 8928 kV/cm for less than 10 minutes at a temperature between 900° C. and 1200° C. to the samples obtained in step (b) or to shaped bodies thereof and (d) cooling the samples obtained in step (c) maintaining the DC voltage or the equivalent electric field or cooling the samples obtained in step (c) maintaining or without maintaining the electrostatic discharge or the equivalent electric field.

21. The process according to claim 17, wherein the permanently polarized hydroxyapatite is obtained by a process comprising the steps of: (a) preparing samples of hydroxyapatite, (b) sintering the samples prepared in step (a) at a temperature of 1000° C., (c) applying an equivalent electric field of 3 kV/cm at a temperature of 1000° C. to the samples obtained in step (b) or to shaped bodies thereof and (d) cooling the samples obtained in step (c) maintaining the equivalent electric field.

22. The process according to claim 17, wherein the permanently polarized hydroxyapatite is obtained by a process comprising the steps of: (a) preparing samples of hydroxyapatite, (b) sintering the samples prepared in step (a) at a temperature of 1000° C. for 2 h, (c) applying an equivalent electric field of 3 kV/cm at a temperature of 1000° C. for 1 h to the samples obtained in step (b) or to shaped bodies thereof and (d) cooling the samples obtained in step (c) maintaining the equivalent electric field for 30 minutes.

23. The process according to claim 17, wherein the contacting step is carried out in the presence of liquid water.

24. The process according to claim 17, wherein the contacting step is carried out with a volumetric ratio of the permanently polarized hydroxyapatite to water of 1000:1 to 0.01:1.

25. The process according to claim 17, wherein the contacting step is carried out with a volumetric ratio of carbon dioxide to methane of 200:1.

26. The process according to claim 17, wherein the contacting step is carried out under a total pressure of 0.1 bar to 100 bar.

27. The process according to claim 17, wherein the contacting step is carried out under a pressure of carbon dioxide of 0.035 bar to 100 bar.

28. The process according to claim 17, wherein the contacting step is carried out under a partial pressure of carbon dioxide of 0.035 bar to 90 bar.

29. The process according to claim 17, wherein the contacting step is carried out with a molar ratio of carbon dioxide to permanently polarized hydroxyapatite of 0.1 to 0.5 and/or with a molar ratio of methane to permanently polarized hydroxyapatite of 0.1 to 0.5.

30. The process according to claim 17, wherein the contacting step is carried out under UV irradiation or UV-Vis irradiation having a wavelength from 200 nm to 850 nm.

31. The process according to claim 17, wherein the contacting step is carried out under UV irradiation and or Visible light irradiation having a irradiance from 0.1 W/m.sup.2 to 200 W/m.sup.2.

32. The process according to claim 17, wherein the contacting step is carried out at a temperature of 25° C. to 250° C.

33. The process according to claim 17, wherein the functionalized organic molecules are selected from a group consisting of: ethanol, methanol, formic acid, acetic acid, malonic acid, acetone and a mixture of at least two of the afore-said functionalized organic molecules.

34. The process according to claim 17, wherein the process is used for producing ethanol or a mixture comprising or consisting of ethanol and at least one further functionalized organic molecule selected from a group consisting of methanol, formic acid, acetic acid, malonic acid and acetone, or a mixture comprising or consisting of ethanol, methanol, formic acid, acetic acid and acetone or a mixture comprising or consisting of ethanol, methanol, acetic acid, malonic acid and acetone.

35. The process according to claim 17, wherein the process is used for removing carbon dioxide from the atmosphere.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0129] For a better understanding of what has been disclosed, some figures are attached which schematically or graphically and solely by way of non-limiting example show a practical case of embodiment of the present invention.

[0130] FIG. 1 graphically shows a .sup.31P-NMR spectrum of the permanently polarized hydroxyapatite (p-HAp) according to the present invention.

[0131] FIG. 2(a) schematically depicts the Raman spectra of hydroxyapatite (HAp) samples with the deconvolution of the v.sub.1 peak in the 930-990 cm.sup.−1 interval.

[0132] FIG. 2(b) schematically depicts the Raman spectra of permanently polarized hydroxyapatite (p-HAp) samples with the deconvolution of the v.sub.1 peak in the 930-990 cm.sup.−1 interval.

[0133] FIG. 3(a) shows a scanning electron microscopy micrograph of the permanently polarized hydroxyapatite.

[0134] FIG. 3(b) graphically shows the .sup.1H-NMR spectrum of a solution obtained after extraction of the reaction products of a reaction that was conducted for 72 h using CO.sub.2 (3 bar), CH.sub.4 (3 bar), H.sub.2O (1 mL) in the presence of conventional (i.e. non-polarized) hydroxyapatite as a catalyst, at 95° C. under UV radiation.

[0135] FIG. 3(c) graphically shows the .sup.1H-NMR spectrum of a solution obtained after extraction of the reaction products of a reaction that was conducted for 72 h using CO.sub.2 (3 bar), CH.sub.4 (3 bar), H.sub.2O (1 mL) using (uncoated) permanently polarized hydroxyapatite as catalyst, at 95° C. under UV radiation.

[0136] FIG. 3(d) graphically shows the .sup.1H-NMR spectrum of a solution obtained after extraction of the reaction products of a reaction that was conducted for 72 h using CO.sub.2 (3 bar), CH.sub.4 (3 bar), H.sub.2O (1 mL) in the presence of coated p-HAp. The p-HAp was coated with aminotris(methylenephosphonic acid), hereafter denoted as ATMP, and zirconium oxychloride (ZrOCl.sub.2), hereafter denoted as ZC, at 95° C. under UV radiation.

[0137] FIG. 4(a) graphically shows a further .sup.1H-NMR spectrum of a solution obtained after extraction of the reaction products achieved after 72 h from CO.sub.2 (3 bar), CH.sub.4 (3 bar) and H.sub.2O (1 mL) using (uncoated) permanently polarized hydroxyapatite as catalyst and 95° C. and UV radiation as reaction conditions.

[0138] FIG. 4(b) graphically shows the .sup.1H-NMR spectrum of a solution obtained after extraction of the reaction products achieved after 72 h from CO.sub.2 (3 bar), CH.sub.4 (3 bar) and H.sub.2O (1 mL) using (uncoated) permanently polarized hydroxyapatite as catalyst and 95° C. without UV radiation as reaction conditions.

[0139] FIG. 4(c) graphically shows the .sup.1-NMR spectrum of a solution obtained after extraction of the reaction products achieved after 72 h from CO.sub.2 (3 bar), CH.sub.4 (3 bar) and H.sub.2O (1 mL) using permanently polarized hydroxyapatite as catalyst and 140° C. without UV radiation as reaction conditions.

[0140] FIG. 4(d) graphically shows a further .sup.1H-NMR spectrum of the liquid water after reaction for 72 h from CO.sub.2 (3 bar), CH.sub.4 (3 bar) and H.sub.2O (1 mL) using (uncoated) permanently polarized hydroxyapatite as catalyst and 95° C. and UV radiation as reaction conditions. Spectra were cut to avoid the very intense peak of water at 4.7 ppm.

[0141] FIG. 4(e) graphically shows a further .sup.1H-NMR spectrum of a solution obtained after extraction of the reaction products achieved after 72 h from CO.sub.2 (3 bar), CH.sub.4 (3 bar) and H.sub.2O (1 mL) using (uncoated) permanently polarized hydroxyapatite as catalyst and 95° C. and UV radiation as reaction conditions.

[0142] FIG. 5 graphically shows representation of three protonated forms of CO.sub.2 adsorbed molecules on the OH.sup.− vacancy of permanently polarized hydroxyapatite.

[0143] FIG. 6 graphically shows a further .sup.1H-NMR spectrum of a solution obtained after extraction of the reaction products achieved after 72 h from CO.sub.2 (3 bar), CH.sub.4 (3 bar) and H.sub.2O (1 mL) in the presence of permanently polarized hydroxyapatite coated with aminotris(methylenephosphonic acid) and zirconium oxychloride, at 95° C. under UV radiation.

[0144] FIG. 7 graphically shows the .sup.1H-NMR spectrum of the liquid water after 72 h from CO.sub.2 (3 bar), CH.sub.4 (3 bar) and H.sub.2O (1 mL) at 95° C. using UV radiation (control 1) and without using UV radiation (control 2).

[0145] FIG. 8(a) shows a further .sup.1H-NMR spectrum of the reaction products achieved after 72 h from CO.sub.2 (3 bar), CH.sub.4 (3 bar) and H.sub.2O (1 mL) at 95° C. using UV radiation and (uncoated) permanently polarized hydroxyapatite as catalyst, wherein the analysis of the solution obtained after extraction of the products was performed by dissolving the catalyst with 100 mM HCl and 50 mM NaCl.

[0146] FIG. 8(b) graphically shows the .sup.1H-NMR spectra of the reaction products achieved after 72 h from CO.sub.2 (3 bar), CH.sub.4 (3 bar) and H.sub.2O (1 mL) at 95° C. using UV radiation and using (uncoated) permanently polarized hydroxyapatite as catalyst, wherein liquid water, which has been incorporated to the reaction chamber, has been analyzed.

[0147] FIG. 9(a) graphically shows the .sup.1H-NMR spectrum of the reaction products achieved after 72 h from CO.sub.2 (3 bar) and CH.sub.4 (3 bar) at 95° C. using UV radiation and (uncoated) permanently polarized hydroxyapatite as catalyst in absence of water.

[0148] FIG. 9(b) graphically shows the .sup.1H-NMR spectrum of the reaction products achieved after 72 h from CO.sub.2 (3 bar) and CH.sub.4 (3 bar) at 95° C. using UV radiation and (uncoated) permanently polarized hydroxyapatite as catalyst with an excess of water.

[0149] FIG. 10 graphically shows the .sup.1H-NMR spectrum of the solution obtained after extraction of the reaction products achieved after 72 h from polluted air (atmospheric pressure) and H.sub.2O (1 mL) at 95° C. using (uncoated) permanently polarized hydroxyapatite as catalyst at 95° C. and under UV radiation.

[0150] FIG. 11(a) graphically shows a further .sup.1H-NMR spectrum of the liquid water after reaction for 48 h from CO.sub.2 (6 bar) and H.sub.2O (1 mL) using (uncoated) permanently polarized hydroxyapatite as catalyst and 140° C. as reaction conditions (without UV radiation).

[0151] FIG. 11(b) graphically shows a further .sup.1H-NMR spectrum of a solution obtained after extraction of the reaction products achieved after 48 h from CO.sub.2 (6 bar) and H.sub.2O (1 mL) using (uncoated) permanently polarized hydroxyapatite as catalyst and 140° C. as reaction conditions (without UV radiation).

[0152] FIG. 12(a) graphically shows the variation of the yield (expressed as μmol of product/g of catalyst) of ethanol (EtOH), acetic acid (AcOH), methanol (MeOH), formic acid (HCOOH) and acetone (Ace) against the CO.sub.2 pressure (in bars) as determined by .sup.1H NMR spectroscopy from the solution obtained after extraction of the reaction products achieved after 48 h using CO.sub.2 (1, 2, 4 or 6 bars) and H.sub.2O (1 mL) at 140° C. (without UV radiation).

[0153] FIG. 12(b) graphically shows the variation of the yield (expressed as μmol of product/g of catalyst) of ethanol (EtOH), acetic acid (AcOH), methanol (MeOH), formic acid (HCOOH) and acetone (Ace) against the CO.sub.2 pressure (in bars) as determined by .sup.1H NMR spectroscopy from the liquid water using (uncoated) permanently polarized hydroxyapatite as catalyst.

[0154] FIG. 12(c) graphically shows the variation of the sum of the yields (expressed as μmol of product/g of catalyst) achieved from the solution obtained after extraction of the reaction products from the catalyst (FIG. 12a) and the supernatant (FIG. 12b) for ethanol (EtOH), acetic acid (AcOH), methanol (MeOH), formic acid (HCOOH) and acetone (Ace) against the CO.sub.2 pressure (in bars).

[0155] FIG. 12(d) graphically shows the variation of the sum of the yields (expressed as μmol of product/g of catalyst) achieved from the solution obtained after extraction of the reaction products from the catalyst (FIG. 12a) and supernatant (FIG. 12b) for C1 (methanol and formic acid; MeOH+HCOOH), C2 (ethanol and acetic acid; EtOH+AcOH) and C3 (acetone; Ace) against the CO.sub.2 pressure (in bars).

[0156] FIG. 13(a) graphically shows the variation of the yield (expressed as μmol of product/g of catalyst) of ethanol (EtOH), acetic acid (AcOH), methanol (MeOH), formic acid (HCOOH) and acetone (Ace) against the temperature (in ° C.) as determined by .sup.1H NMR spectroscopy from the solution obtained after extraction of the reaction products achieved after 48 h using CO.sub.2 (6 bars) and H.sub.2O (1 mL) at 95, 120 or 140° C. (without UV radiation).

[0157] FIG. 13(b) graphically shows the variation of the yield (expressed as μmol of product/g of catalyst) of ethanol (EtOH), acetic acid (AcOH), methanol (MeOH), formic acid (HCOOH) and acetone (Ace) against the temperature (in ° C.) as determined by .sup.1H NMR spectroscopy from the liquid water using (uncoated) permanently polarized hydroxyapatite as catalyst.

[0158] FIG. 13(c) graphically shows the variation of the sum of the yields (expressed as μmol of product/g of catalyst) achieved from the solution obtained after extraction of the reaction products from the catalyst (FIG. 13a) and the supernatant (FIG. 13b) for ethanol (EtOH), acetic acid (AcOH), methanol (MeOH), formic acid (HCOOH) and acetone (Ace) against the temperature (in ° C.).

[0159] FIG. 13(d) graphically shows the variation of the sum of the yields (expressed as μmol of product/g of catalyst) achieved from the solution obtained after extraction of the reaction products from the catalyst (FIG. 13a) and supernatant (FIG. 13b) for C1 (methanol and formic acid; MeOH+HCOOH), C2 (ethanol and acetic acid; EtOH+AcOH) and C3 (acetone; Ace) against the temperature (in ° C.). In all cases the reaction was conducted for 48 h using CO.sub.2 (6 bars) and H.sub.2O (1 mL) at 95, 120 or 140° C. (without UV radiation).

[0160] FIG. 14(a) graphically shows the variation of the yield (expressed as μmol of product/g of catalyst) of ethanol (EtOH), acetic acid (AcOH), methanol (MeOH), formic acid (HCOOH) and acetone (Ace) against the reaction time (in hours) as determined by .sup.1H NMR spectroscopy from the solution obtained after extraction of the reaction products achieved after 24, 48 and 72 h using CO.sub.2 (6 bars) and H.sub.2O (1 mL) at 140° C. (without UV radiation).

[0161] FIG. 14(b) graphically shows the variation of the yield (expressed as μmol of product/g of catalyst) of ethanol (EtOH), acetic acid (AcOH), methanol (MeOH), formic acid (HCOOH) and acetone (Ace) against the time (in hours) as determined by .sup.1H NMR spectroscopy from the liquid water using (uncoated) permanently polarized hydroxyapatite as catalyst.

[0162] FIG. 14(c) graphically shows the variation of the sum of the yields (expressed as mol of product/g of catalyst) achieved from the solution obtained after extraction of the reaction products from the catalyst (FIG. 14a) and the supernatant (FIG. 14b) for ethanol (EtOH), acetic acid (AcOH), methanol (MeOH), formic acid (HCOOH) and acetone (Ace) against the time (in hours).

[0163] FIG. 14(d) graphically shows the variation of the sum of the yields (expressed as mol of product/g of catalyst) achieved from the solution obtained after extraction of the reaction products from the catalyst (FIG. 14a) and supernatant (FIG. 14b) for C1 (methanol and formic acid; MeOH+HCOOH), C2 (ethanol and acetic acid; EtOH+AcOH) and C3 (acetone; Ace) against the time (in hours).

[0164] FIG. 15 graphically shows the .sup.1H-NMR spectrum of the solution obtained after extraction of the reaction products achieved after 72 h from polluted air (atmospheric pressure) and H.sub.2O (1 mL) at 95° C. using (uncoated) permanently polarized hydroxyapatite as catalyst at 95° C. and under UV radiation.

DETAILED DESCRIPTION

[0165] FIG. 1 graphically shows a .sup.31P-NMR spectrum of the permanently polarized hydroxyapatite (p-HAp) according to the present invention.

[0166] FIG. 2(a) schematically depicts the Raman spectra of hydroxyapatite (HAp) samples with the deconvolution of the v.sub.1 peak in the 930-990 cm.sup.−1 interval. Counts (A.U.) are plotted on the ordinate. Raman shift (cm.sup.−1) is plotted on the abscissa.

[0167] FIG. 2(b) schematically depicts the Raman spectra of permanently polarized hydroxyapatite (p-HAp) samples with the deconvolution of the v.sub.1 peak in the 930-990 cm.sup.−1 interval. Counts (A.U.) are plotted on the ordinate. Raman shift (cm.sup.−1) is plotted on the abscissa.

[0168] FIGS. 2(a) and 2(b), which compare the Raman v.sub.1 peak in the 930-990 cm.sup.−1 interval before and after polarization of Hap, prove the success of the polarization process.

[0169] The area of HAp, amorphous calcium phosphate (ACP) and β-tricalcium phosphate (β-TCP) indicates the content of each phase. The content of co-existing phases experiences a reduction in polarized samples (i.e. 4.3% and 9.8% for ACP and β-TCP, respectively) that is accompanied by a decrease of the full width at half maximum (FWHM) from 9 cm.sup.−1 in HAp to 5 cm.sup.−1 in p-HAp. This result indicates an increase of the HAp phase by means of a reduction of crystal imperfections, such as PO.sub.4.sup.3− tetrahedrons distortions.

[0170] FIG. 3(a) shows a scanning electron microscopy micrograph of the permanently polarized hydroxyapatite. Accordingly, the permanently polarized hydroxyapatite can be described as particles of (approximately) 100 nm to 300 nm that aggregate forming agglomerates of up to 1 μm in size.

[0171] FIG. 3(b) graphically shows the .sup.1H-NMR spectrum of a solution obtained after extraction of the reaction products of a reaction that was conducted for 72 h using CO.sub.2 (3 bar), CH.sub.4 (3 bar), H.sub.2O (1 mL) in the presence of conventional (i.e. non-polarized) hydroxyapatite as a catalyst, at 95° C. under UV radiation. The reacted catalyst was dissolved in an aqueous solution with 100 mM HCl and 50 mM NaCl.

[0172] FIG. 3(c) graphically shows the .sup.1H-NMR spectrum of a solution obtained after extraction of the reaction products of a reaction that was conducted for 72 h using CO.sub.2 (3 bar), CH.sub.4 (3 bar), H.sub.2O (1 mL) using (uncoated) permanently polarized hydroxyapatite as catalyst, at 95° C. under UV radiation. The reacted catalyst was dissolved in an aqueous solution with 100 mM HCl and 50 mM NaCl.

[0173] FIG. 3(d) graphically shows the .sup.1H-NMR spectrum of a solution obtained after extraction of the reaction products of a reaction that was conducted for 72 h using CO.sub.2 (3 bar), CH.sub.4 (3 bar), H.sub.2O (1 mL) in the presence of coated p-HAp. The p-HAp was coated with aminotris(methylenephosphonic acid), hereafter denoted as ATMP, and zirconium oxychloride (ZrOCl.sub.2), hereafter denoted as ZC, at 95° C. under UV radiation. The reacted catalyst was dissolved in an aqueous solution with 100 mM HCl and 50 mM NaCl.

[0174] As is shown in FIGS. 3(b)-(d), chemical shifts observed after the dissolution of the coated p-HAp are slightly deshielded with respect to the peaks of products derived from non-coated catalysts. This effect has been attributed to the aminotris(methylenephosphonic acid) (ATMP), which increases the acidity of the medium, causing downfield shifts that are not detected for p-HAp and HAp, independently of the conditions. On the other hand, FIGS. 3(b) and 3(c) indicate that the elimination of the coating from the catalyst not only increases the conversion into ethanol by 20%, but also maximizes the selective synthesis of ethanol as the major reaction product.

[0175] FIG. 4(a) graphically shows a further .sup.1H-NMR spectrum of a solution obtained after extraction of the reaction products achieved after 72 h from CO.sub.2 (3 bar), CH.sub.4 (3 bar) and H.sub.2O (1 mL) using (uncoated) permanently polarized hydroxyapatite as catalyst and 95° C. and UV radiation as reaction conditions. The catalyst was dissolved in an aqueous solution with 100 mM HCl and 50 mM NaCl.

[0176] FIG. 4(b) graphically shows the .sup.1H-NMR spectrum of a solution obtained after extraction of the reaction products achieved after 72 h from CO.sub.2 (3 bar), CH.sub.4 (3 bar) and H.sub.2O (1 mL) using (uncoated) permanently polarized hydroxyapatite as catalyst and 95° C. without UV radiation as reaction conditions. The catalyst was dissolved in an aqueous solution with 100 mM HCl and 50 mM NaCl.

[0177] FIG. 4(c) graphically shows the .sup.1H-NMR spectrum of a solution obtained after extraction of the reaction products achieved after 72 h from CO.sub.2 (3 bar), CH.sub.4 (3 bar) and H.sub.2O (1 mL) using permanently polarized hydroxyapatite as catalyst and 140° C. without UV radiation as reaction conditions. The catalyst was dissolved in an aqueous solution with 100 mM HCl and 50 mM NaCl.

[0178] FIG. 4(d) graphically shows a further .sup.1H-NMR spectrum of the liquid water after reaction for 72 h from CO.sub.2 (3 bar), CH.sub.4 (3 bar) and H.sub.2O (1 mL) using (uncoated) permanently polarized hydroxyapatite as catalyst and 95° C. and UV radiation as reaction conditions. Spectra were cut to avoid the very intense peak of water at 4.7 ppm.

[0179] FIG. 4(e) graphically shows a further .sup.1H-NMR spectrum of a solution obtained after extraction of the reaction products achieved after 72 h from CO.sub.2 (3 bar), CH.sub.4 (3 bar) and H.sub.2O (1 mL) using (uncoated) permanently polarized hydroxyapatite as catalyst and 95° C. and UV radiation as reaction conditions. The catalyst was dissolved in an aqueous solution with 100 mM HCl and 50 mM NaCl. Spectra were cut to avoid the very intense peak of water at 4.7 ppm.

[0180] The spectra reveal the apparition of methanol and formic acid as reaction products in the liquid water used for the reaction. Ethanol and acetic acid appears in both the catalyst and the liquid water, while acetone is only detected in the former.

[0181] FIG. 5 graphically shows representation of three protonated forms of CO.sub.2 adsorbed molecules on the OH.sup.− vacancy of permanently polarized hydroxyapatite. The numeric values (in eV) stand for the calculated adsorption energies.

[0182] In order to support the p-HAp fixation mechanism based on the formation of carboxylates, DFT calculations were performed at the PBE-D3 level. Calculations were performed considering the (0001) facet, which is the most stable HAp surface, and considering an isodesmic model in which H.sub.2 is used as a source of protons. The adsorption energies of three different protonation products of CO.sub.2 were calculated by inserting the molecules in the hydroxyl vacancy of the mineral. Results proved that the protonation of CO.sub.2 to formic acid is exothermic in the gas phase by −3.1 kcal/mol, but it is more exothermic when adsorbed on p-HAp substrate, by −32.7 kcal/mol. Yet, all protonated species display endothermic adsorption energies, the one for the protonated formic acid is very small (0.2 kcal/mol) while the one for the CO.sub.2 is 5.1 kcal/mol (other sites were checked on the p-HAp displaying higher energies, as shown for some representative cases in FIG. 5), thus making this pathway unfeasible to be followed completely and shifting the catalysis location elsewhere close to.

[0183] FIG. 6 graphically shows a further .sup.1H-NMR spectrum of a solution obtained after extraction of the reaction products achieved after 72 h from CO.sub.2 (3 bar), CH.sub.4 (3 bar) and H.sub.2O (1 mL) in the presence of permanently polarized hydroxyapatite coated with aminotris(methylenephosphonic acid) and zirconium oxychloride, at 95° C. under UV radiation. The reacted catalyst was dissolved in an aqueous solution with 100 mM HCl and 50 mM NaCl. The spectrum includes the OH band at 4.65 ppm.

[0184] FIG. 7 graphically shows the .sup.1H-NMIR spectrum of the liquid water after 72 h from CO.sub.2 (3 bar), CH.sub.4 (3 bar) and H.sub.2O (1 mL) at 95° C. using UV radiation (control 1) and without using UV radiation (control 2). No catalyst was used for this reaction.

[0185] FIG. 8(a) shows a further .sup.1H-NMR spectrum of the reaction products achieved after 72 h from CO.sub.2 (3 bar), CH.sub.4 (3 bar) and H.sub.2O (1 mL) at 95° C. using UV radiation and (uncoated) permanently polarized hydroxyapatite as catalyst, wherein the analysis of the solution obtained after extraction of the products was performed by dissolving the catalyst with 100 mM HCl and 50 mM NaCl.

[0186] FIG. 8(b) graphically shows the .sup.1H-NMR spectra of the reaction products achieved after 72 h from CO.sub.2 (3 bar), CH.sub.4 (3 bar) and H.sub.2O (1 mL) at 95° C. using UV radiation and using (uncoated) permanently polarized hydroxyapatite as catalyst, wherein liquid water, which has been incorporated to the reaction chamber, has been analyzed.

[0187] FIG. 9(a) graphically shows the .sup.1H-NMR spectrum of the reaction products achieved after 72 h from CO.sub.2 (3 bar) and CH.sub.4 (3 bar) at 95° C. using UV radiation and (uncoated) permanently polarized hydroxyapatite as catalyst in absence of water.

[0188] FIG. 9(b) graphically shows the .sup.1H-NMR spectrum of the reaction products achieved after 72 h from CO.sub.2 (3 bar) and CH.sub.4 (3 bar) at 95° C. using UV radiation and (uncoated) permanently polarized hydroxyapatite as catalyst with an excess of water.

[0189] FIG. 10 graphically shows the .sup.1H-NMR spectrum of the solution obtained after extraction of the reaction products achieved after 72 h from polluted air (atmospheric pressure) and H.sub.2O (1 mL) at 95° C. using (uncoated) permanently polarized hydroxyapatite as catalyst at 95° C. and under UV radiation. The reacted catalyst was dissolved in an aqueous solution with 100 mM HCl and 50 mM NaCl.

[0190] FIG. 11(a) graphically shows a further .sup.1H-NMR spectrum of the liquid water after reaction for 48 h from CO.sub.2 (6 bar) and H.sub.2O (1 mL) using (uncoated) permanently polarized hydroxyapatite as catalyst and 140° C. as reaction conditions (without UV radiation). Spectra were cut to avoid the very intense peak of water at 4.7 ppm.

[0191] FIG. 11(b) graphically shows a further .sup.1H-NMR spectrum of a solution obtained after extraction of the reaction products achieved after 48 h from CO.sub.2 (6 bar) and H.sub.2O (1 mL) using (uncoated) permanently polarized hydroxyapatite as catalyst and 140° C. as reaction conditions (without UV radiation). The catalyst was dissolved in an aqueous solution with 100 mM HCl and 50 mM NaCl. Spectra were cut to avoid the very intense peak of water at 4.7 ppm.

[0192] The spectra reveal the apparition of methanol, formic acid, ethanol, acetic acid and acetone as reaction products in both the liquid water and the catalyst and the liquid water. The yields (μmol/g of catalyst) in the liquid water were: 0.21±0.07 (methanol), 2.44±0.97 (formic acid), 4.50±0.91 (ethanol), 2.22±0.88 (acetic acid) and 0.74±0.15 (acetone). The yields (μmol/g of catalyst) in the catalyst were: 0.56±0.19 (methanol), 3.22±0.54 (formic acid), 6.60±2.32 (ethanol), 0.49±0.12 (acetic acid) and 0.62±0.27 (acetone).

[0193] FIG. 12(a) graphically shows the variation of the yield (expressed as μmol of product/g of catalyst) of ethanol (EtOH), acetic acid (AcOH), methanol (MeOH), formic acid (HCOOH) and acetone (Ace) against the CO.sub.2 pressure (in bars) as determined by .sup.1H NMR spectroscopy from the solution obtained after extraction of the reaction products achieved after 48 h using CO.sub.2 (1, 2, 4 or 6 bars) and H.sub.2O (1 mL) at 140° C. (without UV radiation). The catalyst was dissolved in an aqueous solution with 100 mM HCl and 50 mM NaCl.

[0194] FIG. 12(b) graphically shows the variation of the yield (expressed as μmol of product/g of catalyst) of ethanol (EtOH), acetic acid (AcOH), methanol (MeOH), formic acid (HCOOH) and acetone (Ace) against the CO.sub.2 pressure (in bars) as determined by .sup.1H NMR spectroscopy from the liquid water using (uncoated) permanently polarized hydroxyapatite as catalyst. In all cases the reaction was conducted for 48 h using CO.sub.2 (1, 2, 4 or 6 bars) and H.sub.2O (1 mL) at 140° C. (without UV radiation).

[0195] FIG. 12(c) graphically shows the variation of the sum of the yields (expressed as μmol of product/g of catalyst) achieved from the solution obtained after extraction of the reaction products from the catalyst (FIG. 12a) and the supernatant (FIG. 12b) for ethanol (EtOH), acetic acid (AcOH), methanol (MeOH), formic acid (HCOOH) and acetone (Ace) against the CO.sub.2 pressure (in bars). In all cases the reaction was conducted for 48 h using CO.sub.2 (1, 2, 4 or 6 bars) and H.sub.2O (1 mL) at 140° C. (without UV radiation).

[0196] FIG. 12(d) graphically shows the variation of the sum of the yields (expressed as μmol of product/g of catalyst) achieved from the solution obtained after extraction of the reaction products from the catalyst (FIG. 12a) and supernatant (FIG. 12b) for C1 (methanol and formic acid; MeO0H+HCOOH), C2 (ethanol and acetic acid; EtOH+AcOH) and C3 (acetone; Ace) against the CO.sub.2 pressure (in bars). In all cases the reaction was conducted for 48 h using CO.sub.2 (1, 2, 4 or 6 bars) and H.sub.2O (1 mL) at 140° C. (without UV radiation).

[0197] FIG. 13(a) graphically shows the variation of the yield (expressed as μmol of product/g of catalyst) of ethanol (EtOH), acetic acid (AcOH), methanol (MeOH), formic acid (HCOOH) and acetone (Ace) against the temperature (in ° C.) as determined by .sup.1H NMR spectroscopy from the solution obtained after extraction of the reaction products achieved after 48 h using CO.sub.2 (6 bars) and H.sub.2O (1 mL) at 95, 120 or 140° C. (without UV radiation). The catalyst was dissolved in an aqueous solution with 100 mM HCl and 50 mM NaCl.

[0198] FIG. 13(b) graphically shows the variation of the yield (expressed as μmol of product/g of catalyst) of ethanol (EtOH), acetic acid (AcOH), methanol (MeOH), formic acid (HCOOH) and acetone (Ace) against the temperature (in ° C.) as determined by .sup.1H NMR spectroscopy from the liquid water using (uncoated) permanently polarized hydroxyapatite as catalyst. In all cases the reaction was conducted for 48 h using CO.sub.2 (6 bars) and H.sub.2O (1 mL) at 95, 120 or 140° C. (without UV radiation).

[0199] FIG. 13(c) graphically shows the variation of the sum of the yields (expressed as μmol of product/g of catalyst) achieved from the solution obtained after extraction of the reaction products from the catalyst (FIG. 13a) and the supernatant (FIG. 13b) for ethanol (EtOH), acetic acid (AcOH), methanol (MeOH), formic acid (HCOOH) and acetone (Ace) against the temperature (in ° C.). In all cases the reaction was conducted for 48 h using CO.sub.2 (6 bars) and H.sub.2O (1 mL) at 95, 120 or 140° C. (without UV radiation).

[0200] FIG. 13(d) graphically shows the variation of the sum of the yields (expressed as μmol of product/g of catalyst) achieved from the solution obtained after extraction of the reaction products from the catalyst (FIG. 13a) and supernatant (FIG. 13b) for C1 (methanol and formic acid; MeOH+HCOOH), C2 (ethanol and acetic acid; EtOH+AcOH) and C3 (acetone; Ace) against the temperature (in ° C.). In all cases the reaction was conducted for 48 h using CO.sub.2 (6 bars) and H.sub.2O (1 mL) at 95, 120 or 140° C. (without UV radiation).

[0201] FIG. 14(a) graphically shows the variation of the yield (expressed as μmol of product/g of catalyst) of ethanol (EtOH), acetic acid (AcOH), methanol (MeOH), formic acid (HCOOH) and acetone (Ace) against the reaction time (in hours) as determined by .sup.1H NMR spectroscopy from the solution obtained after extraction of the reaction products achieved after 24, 48 and 72 h using CO.sub.2 (6 bars) and H.sub.2O (1 mL) at 140° C. (without UV radiation). The catalyst was dissolved in an aqueous solution with 100 mM HCl and 50 mM NaCl.

[0202] FIG. 14(b) graphically shows the variation of the yield (expressed as μmol of product/g of catalyst) of ethanol (EtOH), acetic acid (AcOH), methanol (MeOH), formic acid (HCOOH) and acetone (Ace) against the time (in hours) as determined by .sup.1H NMR spectroscopy from the liquid water using (uncoated) permanently polarized hydroxyapatite as catalyst. In all cases the reaction was conducted for 24, 48 or 72 h using CO.sub.2 (6 bars) and H.sub.2O (1 mL) at 140° C. (without UV radiation).

[0203] FIG. 14(c) graphically shows the variation of the sum of the yields (expressed as μmol of product/g of catalyst) achieved from the solution obtained after extraction of the reaction products from the catalyst (FIG. 14a) and the supernatant (FIG. 14b) for ethanol (EtOH), acetic acid (AcOH), methanol (MeOH), formic acid (HCOOH) and acetone (Ace) against the time (in hours). In all cases the reaction was conducted for 24, 48 or 72 h using CO.sub.2 (6 bars) and H.sub.2O (1 mL) at 140° C. (without UV radiation).

[0204] FIG. 14(d) graphically shows the variation of the sum of the yields (expressed as μmol of product/g of catalyst) achieved from the solution obtained after extraction of the reaction products from the catalyst (FIG. 14a) and supernatant (FIG. 14b) for C1 (methanol and formic acid; MeOH+HCOOH), C2 (ethanol and acetic acid; EtOH+AcOH) and C3 (acetone; Ace) against the time (in hours). In all cases the reaction was conducted for 24, 48 or 72 h using CO.sub.2 (6 bars) and H.sub.2O (1 mL) at 140° C. (without UV radiation).

[0205] FIG. 15 graphically shows the .sup.1H-NMR spectrum of the solution obtained after extraction of the reaction products achieved after 72 h from polluted air (atmospheric pressure) and H.sub.2O (1 mL) at 95° C. using (uncoated) permanently polarized hydroxyapatite as catalyst at 95° C. and under UV radiation. The reacted catalyst was dissolved in an aqueous solution with 100 mM HCl and 50 mM NaCl.

EXPERIMENTAL SECTION

1. Materials

[0206] Calcium nitrate (Ca(NO.sub.3).sub.2), diammonium hydrogen phosphate ((NH.sub.4).sub.2HPO.sub.4; purity >99.0%) and ammonium hydroxide solution 30% (NH4OH; purity: 28-30% w/w) were purchased from Sigma Aldrich. Ethanol (purity >99.5%) was purchased from Scharlab. All experiments were performed with milli-Q water.

2. Hydrothermal Synthesis of Hydroxyapatite (HAp)

[0207] 15 mL of 0.5 M of NH.sub.4).sub.2HPO.sub.4 in de-ionized water were added at a rate of 2 mL min.sup.−1 to 25 mL of 0.5 M of Ca(NO.sub.3).sub.2 in ethanol (with pH previously adjusted to 10.5 using ammonium hydroxide solution) and left aging for 1 h. The whole process was performed under gentle agitation (150 rpm) and at room temperature. Hydrothermal treatment at 150° C. was applied using an autoclave Digestec DAB-2 for 24 h. The autoclave was allowed to cool down before opening. The precipitates were separated by centrifugation and washed with water and a 60/40 v/v mixture of ethanol-water (twice). After freeze-drying it for three days, the white powder obtained was sintered for 2 h at 1000° C. in air using the Carbolite ELF11/6W/301 furnace.

3. Thermally Stimulated Polarization Process (TSP)

[0208] Mechanical consistent discs of around 1.5 mm of thickness were obtained by pressing 150 mg of previously sintered HAp powder at 620 MPa for 10 min. Thermal polarization was done placing the HAp discs between two stainless steel (AISI 304) and applying 3 kV/cm at 1000° C. for 1 h with a GAMMA power supply at 1000° C. using the same laboratory furnace as mentioned above. The discs were allowed to cool down maintaining the applied electric potential for 30 minutes, and finally, all the system was powered off and left to cool overnight.

4. Characterization

[0209] Vibrational spectra for a structural fingerprint were obtained by a confocal Raman microscope available from Renishaw under the trademarks INVIA™ QONTOR®, equipped with a detector available from Renishaw under the trademark CENTRUS™, model 2957T2 and a 785 nm laser.

[0210] SEM images were obtained using a microscope available from Zeiss NEON 40™ equipped with a SEM column available from Zeiss under the trademark GEMINI™. HRTEM was performed in a microscope model 2010F available from Japan Electron Optics Laboratory equipped with a field emission electron source and operated at an accelerating voltage of 200 kV. The point-to-point resolution was 0.19 nm, and the resolution between lines was 0.14 nm. Samples were dispersed in an alcohol suspension in an ultrasonic bath, and a drop of the suspension was placed over a grid with holey-carbon film. Images were not filtered or treated by means of digital processing and they correspond to raw data. All .sup.1H-NMR spectra were acquired with a spectrometer available from Bruker under the trademark AVANCE III™ model 400 operating at 400.1 MHz and accumulating sixty-four scans. The chemical shift calibration was carried out using tetramethylsilane as internal standard. The samples were dissolved in milli-Q water containing 100 mM of HCl and 50 mM NaCl with the final addition of deuterated water.

5. Computational Details

[0211] The 2×1×2 HAp supercell was chosen to build the (0001) facet for p-HAp. The latter was built by removing an OH.sup.− orthonormal to the surface from the HAp supercell, which was previously optimized at the chosen DFT level. Consequently, a +1 global charge was applied for all calculations except for those involving formate, unpaired spin being considered when necessary. The initial coordinates of HAp were optimized following the computational details provided below to unwind surface tensions. The plane waves approach implemented in the Quantum Espresso 4.6 suite of Open-Source computer codes was used. Calculations were performed at the PBE level of theory corrected with the Grimme three body dispersion potentials (PBE-D3), applying the default C.sub.6 software coefficients. A kinetic energy cutoff for the wave functions of 40 Ry was employed. A k-point mesh of 3×3×1 was automatically generated. Instead, a Gamma-center 1×1×1 k-mesh was used for calculations of discrete molecules and a 7×7×7 k-mesh for the bulk HAp calculations. Geometry optimizations were performed using the conjugated gradient algorithm until both the energy and force variation between consecutive steps was below 10.sup.−3 a.u and 10.sup.−4 a.u, respectively. The energy at each step was optimized until the deviation from self-consistency was below 10.sup.−5 Ry. Adsorption energies were calculated according to the following process: A+S.fwdarw.AS*, where A is the adsorbate; S the surface and AS* the adsorbed state. The adsorption energy (E.sub.ads) was expressed as E.sub.ads=E.sub.AS*−(E.sub.A+E.sub.s).

6. Reaction Chamber

[0212] A high pressure stainless steel reactor, which was designed ad hoc, was used to perform all the reactions. In brief, the reactor was dotted with a manometer, an electric heater with a thermocouple and an external temperature controller. The reactor was also characterized by an inert reaction chamber coated with a perfluorinated polymer (Teflon, 120 mL), where both the catalyst and water were incorporated. The reactor was equipped with three independent inlet valves for the incorporation of gases and an outlet valve to recover the gaseous reaction products. A UV lamp (GPH265T5L/4, 253.7 nm) was also placed in the middle of the reactor to irradiate the catalyst directly, the lamp being protected by a UV transparent quartz tube. All surfaces were coated with a thin film of perfluorinated polymer (Teflon) in order to avoid any contact between the reaction medium and the reactor surfaces, in this way discarding other catalyst effects.

7. Synthesis of Coated p-HAp

[0213] Three-layered systems consisting of the successive deposition of aminotris(methylenephosphonic acid) (ATMP) and zirconium oxychloride (ZC) onto p-HAp were obtained by immersion in the corresponding aqueous solutions at room temperature for 5 h. In order to deposit a first ATMP layer, p-HAp was immersed into a 5 mM ATMP solution for 5 h. Subsequently, ZC was deposited onto the ATMP layered p-HAp by immersing the latter into a 5 mM ZrOCl.sub.2 solution for 5 h. Finally, a second layer of ATMP was deposited on the ZC and ATMP layered p-HAp by immersing the latter into a 1.25 mM ATMP solution for 5 h.

8. Synthesis of Functionalized Organic Molecules having 1 to 3 Carbon Atoms Using Uncoated p-HAp as Catalyst

[0214] Functionalized organic molecules having 1 to 3 carbon atoms were synthesized from CO.sub.2 gas alone (1, 2, 4 or 6 bars) as well as from CO.sub.2 and CH.sub.4 gas mixture (3 bar each) in the presence of uncoated p-HAp as catalyst and in the presence of liquid H.sub.2O (1 mL). The reaction was carried out for 24, 48 or 72 h at 95, 120 or 140° C. and under irradiation of an UV lamp (GPH265T5L/4, 253.7 nm) illuminating directly the uncoated p-HAp or without UV radiation.

[0215] As representative examples of reactions, the following yields (expressed as μmol of product per gram of catalyst) were obtained: [0216] Reaction conducted for 72 h using CO.sub.2 (3 bar), CH.sub.4 (3 bar) and H.sub.2O (1 mL) at 95° C. under UV radiation.

[0217] Yields obtained from the solution obtained after extraction by dissolving the catalyst: ethanol (19.4±3.8 μmol/g), acetone (0.9±0.1 μmol/g) and acetic acid (0.6±0.1 μmol/g). Methanol and formic acid were not detected.

[0218] Yields obtained from the liquid water (supernatant): ethanol (0.7±0.14 μmol/g), acetic acid (2.0±0.5 μmol/g), methanol (1.5±0.3 μmol/g) and formic acid (1.9±0.6 μmol/g). Acetone was not detected. [0219] Reaction conducted for 48 h using CO.sub.2 (6 bar) and H.sub.2O (1 mL) at 140° C. without UV radiation.

[0220] Yields obtained from the solution obtained after extraction by dissolving the catalyst: ethanol (6.6±2.3 μmol/g), formic acid (3.2±0.5 μmol/g), acetone (0.6±0.3 μmol/g), methanol (0.6±0.2 μmol/g) and acetic acid (0.5±0.1 μmol/g).

[0221] Yields obtained from the liquid water (supernatant): ethanol (4.5±0.9 μmol/g), formic acid (2.4±1.0 μmol/g), acetic acid (2.2±0.9 μmol/g), acetone (0.7±0.1 μmol/g) and methanol (0.2±0.1 μmol/g). [0222] Reaction conducted for 48 h using CO.sub.2 (1 bar) and H.sub.2O (1 mL) at 140° C. without UV radiation.

[0223] Yields obtained from the solution obtained after extraction by dissolving the catalyst: acetone (1.6±0.6 μmol/g), formic acid (1.1±0.3 μmol/g), ethanol (0.8±0.2 μmol/g), acetic acid (0.8±0.2 μmol/g) and methanol (0.5±0.2 μmol/g).

[0224] Yields obtained from the liquid water (supernatant): acid acetic (2.4±1.0 μmol/g), formic acid (1.3±0.3 μmol/g), acid formic (1.1±0.3 μmol/g), acetone (0.8±0.3 μmol/g), ethanol (0.8±0.1 μmol/g) and methanol (0.1±0.03 μmol/g). [0225] Reaction conducted for 48 h using CO.sub.2 (6 bar) and H.sub.2O (1 mL) at 95° C. without UV radiation.

[0226] Yields obtained from the solution obtained after extraction by dissolving the catalyst: formic acid (1.1±0.3 μmol/g), ethanol (0.7±0.3 μmol/g), acetone (0.6±0.2 μmol/g), acetic acid (0.5±0.1 μmol/g) and methanol (0.3±0.1 μmol/g).

[0227] Yields obtained from the liquid water (supernatant): acid acetic (4.6±0.6 μmol/g), acetone (2.3±0.3 μmol/g), formic acid (1.1±0.1 μmol/g), and ethanol (0.4±0.1 μmol/g). Methanol was not detected. [0228] Reaction conducted for 72 h using CO.sub.2 (6 bar) and H.sub.2O (1 mL) at 140° C. without UV radiation.

[0229] Yields obtained from the solution obtained after extraction by dissolving the catalyst: ethanol (10.2±3.0 μmol/g), formic acid (2.4±0.5 μmol/g), acetone (0.9±0.2 μmol/g), acetic acid (0.7±0.2 μmol/g) and methanol (0.6±0.2 μmol/g).

[0230] Yields obtained from the liquid water (supernatant): ethanol (7.0±1.1 μmol/g), acetic acid (3.0±1.2 μmol/g), formic acid (1.9±0.8 μmol/g), acetone (1.1±0.4 μmol/g) and methanol (0.2±0.1 μmol/g).

9. Synthesis of Functionalized Organic Molecules having 1 to 3 Carbon Atoms Using Coated p-HAp as Catalyst

[0231] Functionalized organic molecules having 1 to 3 carbon atoms were synthesized from CO.sub.2 and CH.sub.4 gas mixture (3 bar each) in the presence of coated p-HAp as catalyst and in the presence of liquid H.sub.2O (1 mL). The reaction was carried out for 72 h at 95° C. and under irradiation of an UV lamp (GPH265T5L/4, 253.7 nm) illuminating directly the coated p-HAp. The p-HA was coated with two layers of aminotris(methylenephosphonic acid) and a layer of zirconium oxychloride (ZrOCl.sub.2), wherein the layer of zirconium oxychloride was arranged or sandwiched between the two layers of aminotris(methylenephosphonic acid). The yields (expressed as μmol of product per gram of coated p-HAp) obtained from the solution obtained after extraction by dissolving the catalyst were: ethanol (16.1±3.2 μmol/g), methanol (4.9±1.0 μmol/g), acetone (0.8±0.2 μmol/g) and acetic acid (0.6±0.1 μmol/g).

10. Synthesis of Ethanol Using Coated p-HAp as Catalyst

[0232] Ethanol was synthesized from CO.sub.2 and CH.sub.4 gas mixture (3 bar each) in the presence of coated p-HAp as catalyst and in the presence of liquid H.sub.2O (1 mL). The reaction was carried out for 72 h at 95° C. and under irradiation of an UV lamp (GPH265T5L/4, 253.7 nm) illuminating directly the coated p-HAp. The p-HA was coated with two layers of aminotris(methylenephosphonic acid) and a layer of zirconium oxychloride (ZrOCl.sub.2), wherein the layer of zirconium oxychloride was arranged or sandwiched between the two layers of aminotris(methylenephosphonic acid). The reaction resulted in the following yields (expressed as μmol of product per gram of coated p-HAp): ethanol (16.1±3.2 μmol/g), methanol (4.9±1.0 μmol/g), malonic acid (1.6±0.2 μmol/g), acetone (0.8±0.2 μmol/g) and acetic acid (0.6±0.1 μmol/g). The predominant product, ethanol, was identified by means of .sup.1H-NMR spectroscopy not only by the quartet (CH.sub.2) and the triplet (CH.sub.3) at 3.53 ppm and 1.06 ppm, respectively, but also by the intense OH peak at 4.65 ppm.

11. Synthesis of Ethanol Using (Uncoated) HAp as Catalyst

[0233] Ethanol was synthesized from CO.sub.2 and CH.sub.4 gas mixture (3 bar each) in the presence of (uncoated) HAp as catalyst and in the presence of liquid H.sub.2O (1 mL). The reaction was carried out for 72 h at 95° C. and under irradiation of an UV lamp (GPH265T5L/4, 253.7 nm) illuminating directly the p-HAp. The reaction resulted in a very poor yield of ethanol (1.9±0.5 μmol/g catalyst). Further, the yield of acetone and acetic acid was <0.1 μmol/g catalyst.

12. Synthesis of Ethanol without a Solid Support Acting as Catalyst

[0234] Ethanol was synthesized from CO.sub.2 and CH.sub.4 gas mixture (3 bar each) in the presence of (uncoated) HAp as catalyst and in the presence of liquid H.sub.2O (1 mL). The reaction was carried out for 72 h at 95° C. and under irradiation of an UV lamp (GPH265T5L/4, 253.7 nm). In absence of any solid support acting as catalyst (see FIG. 7(a)), the yield of ethanol is practically 0 (0.1±0.05 μmol/g). Such a small amount, which has been attributed to eventual photo-induced CO.sub.2 reduction and water splitting, completely disappears in absence of UV radiation (see 7(b)).

13. Synthesis of Functionalized Organic Molecules having 1 To 3 Carbon Atoms, in Particular Ethanol, Using Traffic Contaminated Air

[0235] As a proof of concept the reaction for synthesizing ethanol was conducted at atmospheric pressure using contaminated air taken from the surrounding area of the UPC (Universitat Politècnica de Catalunya) east campus in Barcelona, an area heavily contaminated by car traffic, since it is in front of one of the main roads of the city. The contaminated air by combustion of fossil carburant contains significantly higher CO.sub.2 and CH.sub.4 than the average of the ambient air. The reaction was conducted using p-HAp as catalyst, in presence of 1 mL of water and at 95° C. with UV radiation. Analysis of the reaction products after 72 h showed ethanol among other products, some of them non-identified in previous reactions with controlled gas mixtures. Despite the fact that the amount of ethanol (1.1±0.2 μmol/g), acetic acid (0.03±0.01 μmol/g), acetone (0.09±0.02 μmol/g), formic acid (0.13±0.05 μmol/g) and methanol (0.16±0.04 μmol/g) were very small, it was found the formation of high-value chemical products confirming the potential applicability of p-HAp as catalyst to regenerate contaminated air while obtaining functionalized organic molecules having 1 to 3 carbon atoms as valuable products.

14. Further Investigations in Terms of the Mechanism Pathway

[0236] The formation of functionalized organic molecules having 1 to 3 carbon atoms might be associated to the pressure of the feeding gas, the temperature and the reaction time. In order to explore the role of the reaction conditions, the process without UV illumination at was repeated using CO.sub.2 gas and uncoated p-HAp as catalyst. As shown in FIGS. 12(a)-(d), the yield of functionalized organic molecules having 1 to 3 carbon atoms increases with pressure. The total yield (sum of the yields obtained for each product by dissolving the catalyst+sum of the yields obtained for each product from the supernatant) increased from 11.9±1.6 to 23.1±2.3 μmol/g when the pressure increases from 1 to 6 bars.

[0237] In summary, it could be confirmed the catalytic activity of permanently polarized hydroxyapatite to convert gaseous CO.sub.2 in high-value organic chemicals, namely functionalized organic molecules having 1 to 3 carbon atoms, following an electro-reduction mechanism. Experiments under different reaction conditions reflect the formation of functionalized organic molecules having 1 to 3 carbon atoms, which are formed through the permanently polarized hydroxyapatite induced electro-reduction of CO.sub.2. As a proof of concept, the proposed reaction has been successful in obtaining high-value chemical products from road traffic contaminated air, opening an exciting new avenue to transform greenhouse gas emissions into valuable chemical products using a simple catalyst based on an earth-abundant mineral.