Exclusive Co-N Sites Confined in Two-dimensional Metal-Organic Layers Enabling Highly Selective CO Electroreduction at Industrial-Level Current.

Metal-organic framework catalysts bring new opportunities for CO electrocatalysis. Herein, we first conduct density-functional theory calculations and predict that Co-based porphyrin porous organic layers (Co-PPOLs) exhibit good activity for CO conversion because of the low *CO adsorption energy at Co-N sites, which facilitates *CO desorption and CO formation. Then, we prepare two-dimensional Co-PPOLs with exclusive Co-N 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 CO adsorption capability, Co-PPOLs achieve a peak faradaic efficiency for CO production (FE =94.2 %) at a moderate potential in CO 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 >90 %) over 20 h in CO electrolysis.