Chemical modification of the amino functional groups of amine-impregnated solid sorbents is an effective strategy for drastically improving the regeneration performance for CO2 capture. In this study, isopropyl groups were introduced into tetraethylenepentamine (TEPA) to obtain N-(isopropyl)-TEPA (IP-TEPA), which was impregnated in mesocellular silica foam (MSU-F). The obtained solid sorbent enabled low-temperature regeneration with a low regeneration energy. To clarify the role of the IP groups, experimental and computational methods were used to compare the IP-TEPA/MSU-F sorbent with TEPA/MSU-F in terms of CO2 working capacity, reaction product stability, self-diffusion coefficient, C-13 spin-lattice relaxation time, and CO2 capture performance in steam-aided vacuum swing adsorption.