Porous carbon spheres are prepared by direct carbonization of potassium salt of resorcinol-formaldehyde resin spheres,and are investigated as CO2 adsorbents.It is found that the prepared carbon materials still maintain the typical spherical shapes after the activation,and have highly developed ultra-microporosity with uniform pore size,indicating that almost the activation takes place in the interior of the polymer spheres.The narrow-distributed ultra-micropores are attributed to the “in-situ homogeneous activation”effect produced by the mono-dispersed potassium ions as a form of-OK groups in the bulk of polymer spheres.The CS-1 sample prepared under a KOH/resins weight ratio of 1 shows a very high CO2 capture capacity of 4.83 mmol/g and good CO2/N2 selectivity of ～17-45.We believe that the presence of a welldeveloped ultra-microporosity is responsible for excellent CO2 sorption performance at room temperature and ambient pressure.