AbstractMetal‐organic framework catalysts bring new opportunities for CO₂ electrocatalysis. Herein, we first conduct density‐functional theory calculations and predict that Co‐based porphyrin porous organic layers (Co‐PPOLs) exhibit good activity for CO₂ conversion because of the low *CO adsorption energy at Co‐N₄ sites, which facilitates *CO desorption and CO formation. Then, we prepare two‐dimensional Co‐PPOLs with exclusive Co‐N₄ sites through a facile surfactant‐assisted bottom‐up method. The ultrathin feature ensures the exposure of catalytic centers. Together with large specific area, high electrical conductivity and CO₂ adsorption capability, Co‐PPOLs achieve a peak faradaic efficiency for CO production (FE_CO=94.2 %) at a moderate potential in CO₂ electroreduction, accompanied with good stability. Moreover, Co‐PPOLs reach an industrial‐level current above 200 mA in a membrane electrode assembly reactor, and maintain near‐unity CO selectivity (FE_CO>90 %) over 20 h in CO₂ electrolysis.