Hydrogenation of CO₂ at Room Temperature and Low Pressure with a Cobalt Tetraphosphine Catalyst

Large-scale implementation of carbon neutral energy sources such as solar and wind will require the development of energy storage mechanisms. The hydrogenation of CO₂ into formic acid or methanol could function as a means to store energy in a chemical bond. The catalyst reported here operates under low pressure, at room temperature, and in the presence of a base much milder (7 pK_a units lower) than the previously reported CO₂ hydrogenation catalyst, Co(dmpe)₂H. The Co(I) tetraphosphine complex, [Co(L3)(CH₃CN)]BF₄, where L3 = 1,5-diphenyl-3,7-bis(diphenylphosphino)propyl-1,5-diaza-3,7-diphosphacyclooctane (0.31 mM), catalyzes CO₂ hydrogenation with an initial turnover frequency of 150(20) h^-1 at 25 °C, 1.7 atm of a 1:1 mixture of H₂ and CO₂, and 0.6 M 2-tert-butyl-1,1,3,3-tetramethylguanidine.