Theoretical study on the reaction mechanism of carbon dioxide reduction to methanol using a homogeneous ruthenium(II) phosphine catalyst

Quantum-chemical calculations using the density functional TPSS were carried out for the catalytic reduction of carbon dioxide to methanol using a ruthenium catalyst and hydrogen gas. Preparation of the active species as well as the catalytic cycle were modeled on the quantum-chemical level with solvent effects included by means of a continuum solvation model. Outer as well as inner sphere mechanisms were considered to gain insight into the details of carbon dioxide reduction using a ruthenium(II) catalyst. The overall Gibbs free reaction energy for CO2 + 3 H-2 -> MeOH + H2O is computed to be -13.0 kJ/mol. The highest reaction barrier (112.4 kJ/mol) is found for the outer sphere hydrogen transfer from the active ruthenium species to carbon dioxide via a five-membered transition state structure. (C) 2014 Elsevier Ltd. All rights reserved.