Disclosed herein is a method and system for CO2 removal from a gas stream using a diamine solvent having a Formula I R1(R2)N-L1-NH-R3   (I) With respect to Formula I, each of R1 and R2 independently is aliphatic, cycloaliphatic, or R1 and R2 together with the nitrogen to which they are attached, form a heterocyclyl ring; L1 is aliphatic, cycloaliphatic, or L1 and R1 together with the nitrogen to which they are attached form a heterocyclyl ring; and R3 is aliphatic, cycloaliphatic, cycloalkylalkyl, or alkoxyalkyl. And/or the compound may have a viscosity of less than 75 cP at a CO2-loading of 40 mol % and at a temperature of 40° C.