Hydrogenation of Carbon Dioxide by Combining Ruthenium Hydrido Complexes with Protic Ligands and Protic Metal Oxide Sites

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Hydrogenation of CO2 to give methanol is energetically beneficial if the required dihydrogen can be generated by photovoltaics. This process will in the future be one of only a few alternatives for the maintenance of a certain standard of life and the slowdown of the coming climate change. In preliminary experiments, the group of W. R. Thiel could prove by means of quantumchemical calculations as well as catalytic reactions on model systems, that hydrido ruthenium(II) with chelating pyrazole ligands containing at least one protic NH site are promising candidates for this transformation. Due to the presence of a protic (at the ligand) as well as a hydridic (at the metal site) hydrogen atom, these systems can transfer H2 to polarized E=C double bonds.The project is split into four tasks which will be worked out in close collaboration between the groups in Kaiserslautern and Lyon.- Synthesis of novel hydridoruthenium catalysts: The organometallic chemistry of the hydridoruthenium complexes will be extended and the reactivity against small substrates involved in the CO2 reduction sequence will be investigated based on the modular generation of pyrazole containing complexes.- Evaluation of the catalytic activity: The catalytic hydrogenation of small substrates involved in the CO2 reduction will be combined with an experimental and computational investigation on the influence of the nitrogen donor ligand on the catalytic performance. - Immobilization of the catalysts: To increase the stability of the catalyst, active sites will be isolated on large surface area oxide surfaces. For this, appropriate functionalities will be introduced into the backbone of the ligands allowing a controlled grafting of complexes onto inert supports. In addition, materials with perfectly distributed functionalities will be developed to obtain a defined site isolation of surface species. - Evaluation of the catalytic performances of heterogeneous catalysts: The activity and the stability of the catalysts will be evaluated over a large range of temperature.