The heat of CO2 absorption is one of the important factors determining the operating cost of the CO2 absorption process when using aqueous amine solutions. Aqueous monoethanolamine (MEA) solution is a commercial absorbent, but has several drawbacks. Although piperidine (PIPD) has a high heat of absorption, it shows good CO2 absorption performance, including a high rate of CO2 absorption and a high CO2 loading capacity in comparison to MEA. PIPD derivatives were selected to identify the effect of functional groups of PIPD on the CO2 loading and heat of absorption. Introduction of a methyl group to the PIPD molecule increased the heat of absorption, whereas a hydroxyl group reduced it. The results indicate that the introduction of functional groups in particular positions could provide advantages in CO2 absorption and stripping performance.