This study fabricated a low-cost activated carbon (AC) adsorbent from readily available bamboo trees to control indoor CO₂ levels and reduce energy costs associated with sustaining clean indoor air. Bamboo is naturally high in potassium content and has narrow fibrous channels that could enhance selective CO₂ adsorption. The prepared bamboo-based activated carbon (BAC) exhibits predominantly micropores with an average pore size of 0.17 nm and a specific surface area of 984 m²/g. Upon amination, amine functionalities, such as pyridine, pyrrole, and quaternary N, were formed on its surface, enhancing its CO₂ adsorption capacity of 0.98 and 1.80 mmol/g for low-level (3000 ppm) and pure CO₂ flows at the ambient condition, respectively. In addition, the 0.3% CO₂/N₂ selectivity (α_s,g) of the prepared sorbents revealed a superior affinity of CO₂ by BAC (8.60) over coconut shell-based adsorbents (1.16–1.38). Furthermore, amination enhanced BAC’s CO₂α_s,g to 13.4. These results exhibit this sustainable approach’s potential capabilities to ensure the control of indoor CO₂ levels, thereby reducing the cost associated with mechanical ventilation systems. Further research should test the new sorbent’s adsorption properties (isotherm, kinetics, and thermodynamics) for real-life applicability.