This work reports a selective chemical activation method for the controllable synthesis of porous carbons with pore sizes ranging from micropores to hierarchical micro/mesopores from date sheets. Through selectively controllable carbonization and combined activation processes, the as-prepared carbon materials exhibit a high specific surface area (3337m(2)/g) mainly derived from ultra-micropores in the range of 0.7-0.9 nm, which majorly contributes to CO2 storage at a low pressure. Among the activated carbon materials prepared, ACDS-800-4 exhibits the highest CO2 adsorption capacity (that is, 4.36 mmol/g at 25 degrees C and 1 bar, and 6.4 mmol/g at 0 degrees C and 1 bar), a good recyclability and selectivity. ACDS-800-6 exhibits a higher CO2 adsorption capacity of 22 mmol/g at 25 degrees C and a high pressure of 40 bar. This work demonstrates that the pore size is key to the CO2 storage at lower pressures while specific surface area plays an important role under high pressure adsorption process. Since these efficient microporous carbons are synthesized from biomass, this work provides a potential way to develop cost-effective adsorbents for removing CO2 at both low and high pressures and various temperatures.