As an important greenhouse gas, CO2 attracts much attention due to its increasing emission. The adsorption and conversion of CO2 are effective ways to capture and utilize CO2, respectively. Herein, 3D graphene with surface-microporous structure, which was synthesized directly from CO2, was demonstrated as an efficient adsorbent for CO2 adsorption. The surface-microporous structure possesses advantages in the mass diffusion process and exposure of adsorption sites for CO2, achieving a high adsorption capacity of 2.28 mmol g(-1) at 298 K and 1 bar. The adsorption capacity was further increased to 3.13 mmol g(-1) by KOH activation. Such a great improvement can be attributed to the increased oxygen-functional groups.