Additive free, room temperature direct homogeneous catalytic carbon dioxide hydrogenation in aqueous solution using an iron(II) phosphine catalyst

Abstract The negative consequences of the global warming require an important reduction of CO 2 emission; and the valorization of the carbon dioxide, its transformation into useful chemicals is essential. We present here our studies on the direct CO 2 hydrogenation reaction, yielding formic acid. In water, for the first time, an Fe(II) catalyst using meta-trisulfonated-tris[2-(diphenyl-phosphino)-ethyl]phosphine (PP 3 TS) ligand, has been found active in CO 2 reduction. In homogeneous catalytic reactions, without any additives, at room temperature, under hydrogen and carbon dioxide gas pressures up to 0.5 M of formic acid is obtained, in acidic aqueous solutions. The same catalyst is active also in the reverse reaction, under different reaction conditions, i.e. at low pressure and high temperature. The CO 2 reduction and formic acid dehydrogenation catalytic cycle has been repeated several times; without deactivation of the catalyst, it is not sensitive to oxygen/air. The Fe(II)-PP 3 TS complex could be a suitable catalyst in a chemical hydrogen storage/delivery system.