This work presents an unprecedented capacitive performance of porous carbons synthesized from carbon dioxide (CO2). CO2 is specifically converted to boron-doped porous carbons (BPCs) by reaction with sodium borohydride (NaBH4) at 1 atm and temperatures around 500 C. The pristine BPCs subsequently undergo treatment steps of salt removal and potassium hydroxide (KOH) activation. The activated BPCs provide specific capacitance of 130-140 F/g in a neutral solution of 1 M Na2SO4 after several thousand cycles. Main contributing factors to the high capacitance of the activated BPCs are their large surface area and well-defined micropores induced by the KOH activation. The observations have been elucidated by various spectroscopic and microscopic analyses.