This study evaluated the stability and reusability of amino-functionalized nanocellulose aerogels as CO2-adsorbent materials. The modified aerogels, synthesized via a controlled silylation using N-[3-(trimethoxysilyl) propyl] ethylenediamine (DAMO), demonstrated excellent thermal stability up to 250 °C (TGA) and efficient CO2 adsorption through chemisorption, which was the main adsorption mechanism. The performance of the aerogels was assessed using both adsorption isotherms and the decay pressure technique, revealing that CO2 adsorption capacity increased with higher amino group loading (4.62, 9.24, and 13.87 mmol of DAMO). At 298 K and 4 bar, CO2 adsorption capacity increased proportionally with the amino group concentration, reaching values of 3.17, 5.98, and 7.86 mmol of CO2 g−1 polymer, respectively. Furthermore, over 20 adsorption/desorption cycles, the aerogels maintained 95% CO2 desorption at ambient temperature, indicating their potential for industrial use. These findings highlight the aerogels suitability as stable, reusable materials for large scale CO2 capture and storage technologies.