A series of hierarchical porous carbons (HPCs) with different morphologies and well-developed porosity have been successfully synthesized via a facile and flexible template-free method using hierarchical assembly of polyimide as carbon precursor. Amongst, cornflower-like hierarchical porous carbon (FC4) displays the best CO2 capture property with an adsorption capacity up to 4.05 and 2.87 mmol g(-1) at 273 and 298 K, respectively. The excellent CO2 capture capability of FC4 can be owing to the cooperative effect of moderate meso-/macropore channels and abundant framework micropores, which are conducive to diffusion and capture of CO2 adsorbate. Moreover, FC4 shows superior stability and recyclability and CO2 trapping selectivity with CO2/N-2 initial and final adsorption ratios of 24 and 6.4, respectively. It can be anticipated that the FC4 is a promising adsorbent in the adsorption and separation of carbon dioxide under actual conditions.