Photoassisted Carbon Dioxide Reduction and Formation of Two- and Three-Carbon Compounds
We found that aqueous carbon dioxide, in the presence of inorganic minerals with semiconducting properties, underwent photosensitized reduction by ultraviolet and visible light - the main products being formaldehyde and methanol. Effective photoactive materials included naturally occurring minerals such as nontronite, anatase, wolframite, molybdenite, minium, cinnabar and hematite. No appreciable carbon dioxide reduction was observed in the presence of bentonite. The heterogenous photoreduction of carbon dioxide by natural semiconducting minerals could be a precursor of plant photosynthesis. Photosynthetic condensation of dilute aqueous formaldehyde solutions to glyoxal and malonaldehyde was obtained by UV-irradiation in the absence of oxygen. The malonaldehyde concentration reached its maximum after several hours and then declined. The known condensation reactions of malonaldehyde with urea or guanidines to form hydroxy -or amino-pyrimidines may be a potential prebiotic route to pyrimidines.
KeywordsClay Formaldehyde Urea Cadmium Assimilation
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