5:15 PM - 7:15 PM
[MIS08-P05] Characterization of photo-irradiation-promoted synthesis of organic molecules from CO and CO2 using mineral catalysts.
Keywords:origin of life, chemical evolution, mineral catalysis, prebiotic chemistry, hydrothermal reaction, carbon fixation
The production of organic matter from CO and CO2 by the catalytic action of minerals is thought to have supported the supply of biomolecules necessary for the building of early life and to have driven the chemical evolutionary process. In recent years, laboratory simulations of the chemical evolution process using not only catalytically active minerals but also light-energy-supplied systems have been attracting attention as a new production process of organic matter and a way to improve the efficiency of reactions. Recently, the importance of the organic production process originating from CO generated from CO2 by UV irradiation has been recognized, and the chemical evolution scenario in an environment with sufficient UV light supply is being constructed. Previous studies have shown that photocatalytically active minerals such as ZnS and FeS catalyze CO2 reduction in the specific conditions, but the activity of other minerals is largely unknown.
In this study, in order to investigate the possible environment for the light-promoted chemical evolution in this scenario, the effects of light energy supply, temperature, pH, etc., were comprehensively investigated in the presence of mineral catalysts that promote organic matter production from inorganic carbon sources such as CO and CO2.
Hydrothermal reactions (25–100°C, 2 atm) in the presence of various mineral catalysts (FeS, NiS, CoS, ZnS, CuS, Fe3S4, and Fe sulfides doped with various transition metals) were performed with and without UV light (λ=235–265 nm) in a sealed quartz vessel filled with CO or CO2. To investigate the effects of reducing conditions, sulfide and hypophosphite were added in some reactions. When CO2 was used, H2 was also supplied as the reductant. Various sulfide minerals slightly catalyzed the production of formate without light irradiation when CO was used as a substrate. UV irradiation was found to promote the production of formate and acetate, especially when Co-doped FeS was used. In the presence of sulfide and hypophosphite with CO as substrate, the production of hydrogen, methane, formate, and acetate was promoted under UV irradiation, especially when ZnS was used. When CO2 (plus H2) was used as a substrate, a mixture of FeS and Fe3S4 catalyzed formate production at alkaline conditions (pH eight or higher), and the reaction was promoted in the presence of UV irradiation. Furthermore, the production of formate was enhanced when Fe3S4 was doped with transition metals (W, Co, Ni, and Zn at 1% each).
These results suggest that a synergistic effect exists between the photocatalytically active mineral catalysts and other mineral catalysts for organic matter synthesis. This study provides insight into the possible enhancement of mineral-catalyzed production of organic molecules in the chemical evolution scenarios on the surface of the Earth where light is available.
In this study, in order to investigate the possible environment for the light-promoted chemical evolution in this scenario, the effects of light energy supply, temperature, pH, etc., were comprehensively investigated in the presence of mineral catalysts that promote organic matter production from inorganic carbon sources such as CO and CO2.
Hydrothermal reactions (25–100°C, 2 atm) in the presence of various mineral catalysts (FeS, NiS, CoS, ZnS, CuS, Fe3S4, and Fe sulfides doped with various transition metals) were performed with and without UV light (λ=235–265 nm) in a sealed quartz vessel filled with CO or CO2. To investigate the effects of reducing conditions, sulfide and hypophosphite were added in some reactions. When CO2 was used, H2 was also supplied as the reductant. Various sulfide minerals slightly catalyzed the production of formate without light irradiation when CO was used as a substrate. UV irradiation was found to promote the production of formate and acetate, especially when Co-doped FeS was used. In the presence of sulfide and hypophosphite with CO as substrate, the production of hydrogen, methane, formate, and acetate was promoted under UV irradiation, especially when ZnS was used. When CO2 (plus H2) was used as a substrate, a mixture of FeS and Fe3S4 catalyzed formate production at alkaline conditions (pH eight or higher), and the reaction was promoted in the presence of UV irradiation. Furthermore, the production of formate was enhanced when Fe3S4 was doped with transition metals (W, Co, Ni, and Zn at 1% each).
These results suggest that a synergistic effect exists between the photocatalytically active mineral catalysts and other mineral catalysts for organic matter synthesis. This study provides insight into the possible enhancement of mineral-catalyzed production of organic molecules in the chemical evolution scenarios on the surface of the Earth where light is available.