CO2 Reduction with Formate Dehydrogenase mimetic compounds

Abstract

The atmospheric carbon dioxide (CO2) concentration has greatly increased in the last decades, mainly due to the excessive use of fossil fuels. The rising levels of this greenhouse effect gas are changing the climate, which will have irreversible and dramatic effects on our planet. Efficient and innovative solutions to tackle this problem are urgently needed. Several researchers around the world are developing new approaches to capture and convert CO2 into novel fuels and other chemicals with economical value. For that, different electro- and photochemical methodologies have been explored, using a variety of metal complexes as catalysts. In this work, we took inspiration from the active site of molybdenum-containing formate dehydrogenase enzymes to develop new inorganic molybdenum-based catalysts that convert CO2 into formate or other interesting added-value compounds. Our two main goals were to (i) synthesise ten molybdenum complexes and (ii) study their ability to catalyse the reduction of CO2 electrochemically. The complex ligands chosen were inspired in the dithiolene moiety of the cofactor that coordinates the molybdenum ion within the enzymes (dithiolene and derivative compounds) and also in different compounds previously described in literature (pincer-type and salen-type units). All complexes synthesised were characterised by elemental analysis and spectroscopic methodologies (NMR, FTIR and UV-vis), as well as, electrochemically (cyclic voltammetry). Controlled potential electrolysis experiments showed that four of the new compounds synthesised are selective for the CO2 reduction to formate. These promising CO2 reduction catalysts will be further studied and improved in the near future.