In this work, highly efficient nitrogen-doped porous carbonaceous CO2 sorbents were synthesized by sodium amide activation of petroleum coke at a temperature range of 400-500 degrees C. The as-obtained sorbents exhibit an excellent CO(2 )uptake of 3.84 mmol/g (25 degrees C) and 5.93 mmol/g (0 degrees C) under atmospheric pressure. It is found that in addition to the two well-accepted factors, i.e., narrow micropore volume and nitrogen content, the pore size and pore size distribution also exhibit important effects on CO2 uptake under ambient condition for these adsorbents. Furthermore, these petroleum-coke-derived nitrogen-enriched carbonaceous sorbents also exhibit other merits such as high selectivity of CO2 over N-2, excellent recyclability, fast adsorption kinetics, suitable heat of adsorption, and excellent dynamic CO2 uptake. This paper offers additional insight and useful information in preparing highly efficient nitrogen-doped porous carbonaceous CO2 adsorbents.