It is notably challenging to fabricate controllable heteroatom-doped porous carbons for both highly effective mixed-gas separation and supercapacitor electrodes. In this work, novel algae-derived nitrogen-containing porous carbons were prepared as bifunctional materials. The pore structure of obtained carbons could be easily tailored by altering activation temperature or porogen/biomass ratio. The as-prepared porous carbon has a very high specific surface area of 1538.7 m(2) g(-1) and a large pore volume of 0.99 cm(3) g(-1) with a high N content of 2.77 wt%. As a solid-state adsorbent, the algae-derived carbon has an excellent CO2 adsorption capacity of 5.7 and 3.9 mmol g(-1) at 273 and 298 K, respectively. The extraordinarily high CO2/N-2, CO2/CH4, and CH4/N-2 selectivity are demonstrated by the ideal adsorption solution theory (IAST) calculation and dynamic adsorption breakthrough experiments. As an electroactive material, the porous carbon exhibits outstanding capacitive performance in 6M KOH aqueous electrolyte, with the specific capacitance of 287.7 and 190.0 F g(-1) at 0.2 A g(-1) in a three-and two-electrode system, respectively. Furthermore, the obtained carbon shows outstanding rate capability of 79.3% at 10 A g(-1) and unprecedented cycling stability with 98% capacitance retention at 10 A g(-1)