We describe an acid dissociation constant (pK(a))-based screening of chemical absorbents to treat a gas stream containing carbon dioxide (CO2) in a wide range of partial pressures (0.1-4 MPa). The solubility differences of CO2 in aqueous amine solutions at 40 and 70 degrees C plotted against pK(a) revealed volcano-shaped profiles. The availability of amines with pK(a) values suitable for capture/release cycles of CO2 with targeted partial pressures shows that the pK(a)-based screening method would be useful to develop advanced greenhouse gas control technologies.