This study showed that a solid amine, composed of poly(ethylenimine) immobilized into a CARiACT G10 silica substrate, is a feasible sorbent for applications in a pressure swing adsorption (PSA) process for postcombustion CO2 capture. This deduction materialized from an extensive study of the behavior of this material over a wide range of industrially relevant conditions using thermogravimetric analysis. The temperature ranged from 40 to 100 °C, the CO2 partial pressure ranged from 1.2 to 100 vol % with the total pressure fixed at 1 atm, the relative humidity ranged from dry conditions to 2 vol %, and the number of consecutive adsorption and desorption cycles ranged from 4 to 76. The results revealed that this solid amine sorbent was very stable under the conditions investigated. Water vapor at a low relative humidity exhibited only a minor and reversible effect on both the thermodynamics and kinetics of the CO2 uptake and release. The isothermal CO2 working capacity ranged between 0.25 and 2.8 mol/kg, increased with increasing CO2 concentration, exhibited a maximum with increasing temperature, and produced a heat of adsorption/reaction of around 50.0 kJ/mol. It was also determined that the optimal operating temperature for a PSA process was around 80 °C for CO2 partial pressures >10 kPa and 60−70 °C for CO2 partial pressures <10 kPa.