Utilization of CO2 as a renewable C1 building block in chemical synthesis is one of the key ingredient of the future sustainable chemical technologies. For example, formic acid (FA) generated by catalytic hydrogenation of CO2 is an attractive liquid hydrogen carrier. [1] Furthermore, the direct catalytic synthesis of FA from CO2 and H2 is an attractive alternative to the current two-step process based on the syn-gas chemistry. Recently, we have demonstrated a high potential of the homogeneous Ru-PNP pincer catalyst for the reversible hydrogenation of CO2 [2]. Despite high activities, the industrial use of homogeneous catalysis has inherent limitations. The catalyst’s ability to promote the reverse FA dehydrogenation reaction once operating pressures are lowered makes its efficient removal crucial for practical applications. Therefore, an easily separable heterogeneous catalyst is highly desired. Recent studies evidence the utility of supported Au catalysts for this reaction [3]. Here we report a comparative analysis of the kinetics and mechanism of CO2 hydrogenation by homogeneous Ru-PNP pincer complexes and heterogeneous supported Au nanoparticles . The mechanistic studies reveal a striking conceptual similarity in the chemical pathways promoted by these catalysts. In both systems, the heterolytic activation of H2 via a Lewis acid-base cooperative mechanism is proposed as one of the key elementary steps necessary for a facile conversion of CO2 to formate salts. We speculate that the resolved mechanistic understanding of the chemistry of single-site homogeneous catalysts can guide the development of their heterogenous counterparts. 1.A. Boddien, F. Gaertner, C. Federsel, P. Sponholz, D. Mellmann, R. Jackstell, H. Junge, M. Beller, Angew. Chem. Int. Ed. 50, 6411 (2011) 2.G.A. Filonenko, R. van Putten, E.N. Schulpen, E. Hensen, E.A. Pidko, ChemCatChem 6, 1526 (2014) 3.D. Preti, C. Resta, S. Squarcialupi, G. Fachinetti, Angew. Chem. Int. Ed. 50, 12551 (2011)

Mechanistic bridge between homogeneous and heterogeneous catalysis for the liquid phase CO2 hydrogenation to formates

251st National Meeting (2016)

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