||We investigated an approach to fabricating acetic acid-mediated cellulose-based melamine-modified carbons through hydrothermal treatment and chemical activation, where the ratios of melamine and activation conditions were tailored. The CO2 uptake properties were modified by tuning the experimental conditions. By tuning the activation condition, we obtained carbons with high specific surface area (SSA) in the range 1458–3019 m2 g−1 and an ultra-high micropore volume (0.21–1.13 cm3 g−1). The adsorbents CM1-900-2 showed an excellent CO2 adsorption capacities of 297 and 174 mg g−1 at 273 K and 298 K/1 bar. Moreover, CO2 adsorption capacities remained stable after several continuous adsorption cycles. It possessed high isosteric heats of adsorption. Furthermore, the fabricated carbons exhibited efficient CO2 selectivity over N2. Collectively, these properties indicate that the fabricated adsorbents are promising candidates for use in CO2 adsorption applications.