This paper describes the capture of CO2 by polyethylenimine (PEI) physically adsorbed on the surface of silica nanoparticles. The resulting material proved to be not only regenerable but also having the right qualities needed for a practical utilization, including absorption not only from high concentration streams like flue gases and natural gas wells but also from the air itself. Polyethyleneglycol (PEG) was used as a coadditive. The effect on CO2 capture of temperature, supports, and concentrations of polyethylenimine and polyethyleneglycol was evaluated. Based on the results, the PEI and PEG concentrations were optimized to obtain a material with optimal CO2 absorption characteristics. The obtained material demonstrated the practical possibility to capture CO2 using an inexpensive, easy-to-prepare, and regenerable absorbent.