Isosteric heats of adsorption for CO2 in a series of amine-functionalized mesoporous MSU-H silicas were calculated from the adsorption isotherms by using the Clausius-Clapeyron equation. In the results, it was found that the amine-functionalization by using N-(2-aminoethyl)-3-aminopropyltriethoxysilane (AEAPS) or (3-trimethoxysilylpropyl)diethylenetriamine (TA) provided effective weak adsorption sites for CO2, contributing to the decrease in the heats of adsorption. Particularly, in the case of CO2 adsorption under the like condition of postcombustion CO2 capture, AEAPS-functionalized MSU-H silica containing primary and secondary amino groups in the ratio of 1:1 exhibited lower integrated isosteric heat of adsorption during the adsorption-desorption cycles (corresponding to the energy required to regenerate the sorbent) than the other functionalized MSU-H silicas. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.