Photocatalytic Reduction of Carbon Dioxide to CO and HCO₂H Using fac-Mn(CN)(bpy)(CO)₃

Abstract

Studies are reported regarding the use of Mn(CN)(bpy)(CO)3 (1) as a catalyst for CO2 reduction employing [Ru(dmb)3](2+) as a photosensitizer in mixtures of dry N,N-dimethylformamide-triethanolamine (N,N-DMF-TEOA) or acetonitrile-TEOA (MeCN-TEOA) with 1-benzyl-1,4-dihydronicotinamide as a sacrificial reductant. Irradiation with 470 nm light for up to 15 h yields both CO and HCO2H with maximum turnover numbers (TONs) as high as 21 and 127, respectively, with product preference dependent on the solvent. Further data suggests that upon single electron reduction this catalyst avoids the formation of a Mn-Mn dimer and instead undergoes a disproportionation reaction, which requires 2 equiv of [Mn(CN)(bpy)(CO)3](•-) to generate 1 equiv each of the active catalyst [Mn(bpy)(CO)3](-) and the starting compound 1. Additional characterization by cyclic voltammetry (CV) and infrared spectroelectrochemistry (IR-SEC) indicates that the stability of the singly reduced [Mn(CN)(bpy)(CO)3](•-) differs slightly in the N,N-DMF-TEOA solvent system compared to the MeCN-TEOA system. This contributes to the observed selectivities for HCO2H vs CO production.

CoIICryptates Convert CO2into CO and CH4under Visible Light

“…Even though human society is slowly movingt oa lternative ways of generating energy,8 5% of the total energyc onsumed still hasits origins in fossil fuels, resulting in an uncontrolled increase of CO 2 in the atmosphere.T his has not only been connected to climate change and its dramatic irreversiblee ffects, but has also been seen by scientists as an opportunity to develop new materials and alternative methods to capturea nd/ or convert CO 2 into other chemicals with economic value. [1,2] One of the mosta ppealing of these new methods is the use of visible light to convert or recycle this greenhouse gas, which has been chosen by many groups who have reported the applicationo fs everalt ypes of metal complexes as catalystst o photoreduceC O 2 .C yclams and their derivatives, [3][4][5][6][7][8][9][10][11] porphyrins [12][13][14][15][16][17] and polypyridyl [18][19][20][21][22][23][24][25] are among the moste xplored ligands.…”

The concept of photochemical enzyme models – State of the art

“…Similar to the enzymatic substrate activation process described above, in many of the investigated systems the formation of an inner-sphere CO 2 adduct is part of the proposed reaction mechanisms [161][162][163][164][165][166][167]. Only a few photocatalysts are able to reach a certain degree of selectivity for the type of CO 2 reduction products.…”

Photocatalytic Conversion of CO2 to CO by a Copper(II) Quaterpyridine Complex

“…Regarding molecular‐based catalytic systems, 3d complexes have been widely studied as viable catalysts for solar fuel production by the splitting of water and the reduction of CO 2 . A number of CO 2 reduction catalysts based on Mn, Fe, Co, and Ni have been reported . On the other hand, there are only very few reports on the use of molecular Cu complexes for the electrocatalytic reduction of CO 2 , although electrocatalytic, and more recently also photocatalytic, CO 2 reduction by Cu heterogeneous materials has been well documented .…”