Carbon dioxide to formate

The mechanism of carbon dioxide reduction in aqueous and nonaqueous solutions was investigated by several authors. It is now generally accepted that the reduction of carbon dioxide to formate ions is a multistep reaction with the intermediate formation of free radicals CO2 and HCO2 either in the solution or adsorbed on the electrode ... 

A little later, Russell et al.19 tried to obtain methanol from carbon dioxide by electrolysis. Reduction of carbon dioxide to formate ion took place in a neutral electrolyte at a mercury electrode. On the other hand, formic acid was reduced to methanol either in a perchloric acid solution at a lead electrode or in a buffered formic acid solution at a tin electrode. The largest faradaic efficiency for methanol formation from formic acid was ca. 12%, with poor reproducibility, after passing 1900 C in the perchloric acid solution at Pb in a very narrow potential region (-0.9 to -1.0 V versus SCE). In the buffered formic acid solution (0.25 M HCOOH + 0.1 M... 

Scheme 107 Cathodic reduction of carbon dioxide to formate.

Khan MMT, Rao NN, Chatterjee D. A novel photosynthetic mimic reaction catalysed by K[Ru(H-EDTA)C1]-2H20 reduction of carbon dioxide to formate and formaldehyde in the presence of an aqueous suspension of Pt-CdS-Ru02. / Photochem Photobiol A Chem 1991 60 311-18. 

Biocatalytic synthetic reactions also include carbon dioxide fixation with the production of methanol in artificial multi-enzyme systems [188]. Formate dehydrogenase (FDH, EC 1.2.1.2) can catalyze the reduction of carbon dioxide to formate, and methanol dehydrogenase (MDH, EC 1.1.99.8) can catalyze the reduction of formate to methanol. Both of these enzymes require NAD+-NADE1 cofactor, and in the presence of the reduced dimethyl viologen mediator (MV+), they can drive a sequence of enzymatic reactions. The cascade of biocatalytic reactions results in the reduction of CO2 to formate catalyzed by FDEI followed by the reduction of formate to methanol catalyzed by MDH. A more complex system composed of immobilized cells of Parococcus denitrificans has been demonstrated for the reduction of nitrate and nitrite [189]. 

The reduction of carbon dioxide to formate in the presence of FDH represents a photochemical C02-fixation process. In addition to MV+, the enzyme recognizes other electron carriers such as 2,2 -bipyridinium radical cations [184]. Reduction of nitrate (N03 ) to nitrite (NO2 ) and subsequently the reduction of nitrite to ammonia in the presence of NitraR and NitriR, respectively, allows the sequential 8e ... 

The application of such systems to the multi-electron reduction of carbon dioxide to formate, methanol or methane is now under active investigation in our laboratory. 

The challenging photochemical reduction of carbon dioxide to formate is catalyzed by Ru" [111] (cf. Section 3.3.4). For example, with the 2,2 -bipyridine-ruthenium(II) complex the active species is formed by photolabilization. Water renders the system more efficient with quantum yields up to 15%. Methanol is the photoproduct when CO2 is reduced with Ti02 in propene carbonate/2-propanol... 

A) Some long range goals of the work are to develop an understanding of the essential synthetic and mechanistic chemistry leading to reduction of carbon dioxide to formate, formaldehyde, methanol and oxalate and to use the results to develop new transition metal... 

Selective photosensitized reduction of carbon dioxide to formate was accomplished in a photosystem composed of Ru(bpy)3 as photosensitizer, TEOA as electron donor, and dicarbonyl Ru(II)-bis(bipyridine), Ru(bpy)2-(CO)2, as homogeneous catalyst [143]. Formate, HCOJ, is generated in this photosystem with a quantum efficiency of — 0.14. A possible mechan-... 

Agarwal AS, Zliai YM, Hill D, Sridhar N (2011) The electrochemical reduction of carbon dioxide to formate/formic acid enginetring and economic feasibility. Chem Sus Chem 4 1301-1310... 

Reduction of Carbon Dioxide to Formates and Carbon Monoxide... 

Direct addition of CO2 across a Zr-Ir bond leading to stoichiometric reduction of carbon dioxide to formate was shown by Bergman and co-workers.[Gp2Zr(/t-NBu )IrCp ] 766 reacts rapidly with CO2 and heterocumulenes. Insertion of CO2 into an M-H bond, leading to a unique heterobimetallic formato complex and stoichiometric conversion of the formato complex to 766 and Li formate by addition of base, was also demonstrated. Different reactions gave the products listed in Scheme 109 and a possible mechanism for their formation was suggested. 

Catalytic Hydrogenatirai of Carbon Dioxide to Formate Salts.79... 

Scheme 11 Hydrogenation of carbon dioxide to formats by iridium(ni) trihydride PNP pincer complex 32...

Nozaki et al. applied the metal-ligand cooperation of Ir(III) PNP pincer complexes for the highly efficient catalytic hydrogenaticm of carbon dioxide to formats [83]. The chloroiriditim(ni) dihydride PNP complex 31 was synthesized by the reaction of [Ir(coe)2Cl]2 (coe = cyclooctene) with PNP ligand under hydrogen pressure. Reaction of complex 31 with excess of NaH resulted in the formation of stable Ir(III) trihydride PNP pincer complex 32 (Scheme 10). 

S.R. Narayanan, B. Haines, J. Soler, T.l. Valdez, Electrochemical conversion of carbon dioxide to formate in alkaline polymer electrolyte membrane cells, J. Electrochem. Soc., 158 (2011)A167-A173. 

Trialkylborane additives promote the reduction of carbon dioxide to formate, via bis(diphosphine) Ni(II) and Rh(III) hydride complexes. Late transition metal hydrides, which can be formed by the reaction with molecular H2, transfer hydride to CO2 to yield a formate-borane adduct. In order to drive this process, the borane must be of appropriate Lewis acidity hence, weaker... 

M. Jitaru and M. Toma, Electroreduction of carbon dioxide to formate on bronze electrodes, Studia Univ. Babes-Bolyai. Chemia 53,2008,135-142. 

K. Subramanian, K. Asokan, D. Jeevarathinam and M. Chandrasekaran, Electrochemical membrane reactor for the reduction of carbon dioxide to formate, /. Appl. Electrochem. 37,2007, 255-260. 

A.S. Agaiwal, Y.M. Zhai, D. Hill and N. Sridhar. The electrochemical reduction of carbon dioxide to formate/ formic add Engineering and economic feasibility, ChemSusChem 4,2011,1301-1310. 

K. Subramanian, G. Gomathi and K. Asokan, Reduction of carbon dioxide to formate in an electrochemical membrane reactor in KHCO3 buffer solutions. In N.R. Neelameggham and R.G. Reddy (eds.). Carbon Dioxide Reduction Metallurgy, Publication of The Minerals, Metals Materials Society (TMS), Warrendale,... 

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