Exclusive Co-N4 Sites Confined in Two-dimensional Metal-Organic Layers Enabling Highly Selective CO2 Electroreduction at Industrial-level Current.

Abstract

Due to the rich chemistry of both metal sites and ligands, metal-organic frameworks (MOFs) possess abundant structures and tunable functionalities, which bring new opportunities for the design and fabrication of high-performance materials for catalysis and electrochemical processes. Herein, we first conduct density-functional theory (DFT) calculations and predict that Co-based porphyrin porous organic layers (Co-PPOLs) exhibit good activity for CO2-to-CO conversion because of the low *CO adsorption energy at the Co-N4 sites, which shall facilitate the *CO desorption and gaseous CO formation. Then, we rationally design and prepare novel two-dimensional (2D) Co-PPOLs through a facile surfactant-assisted bottom-up method, which have exclusive Co-N4 sites. The 2D ultrathin feature of Co-PPOLs ensures the exposure of catalytic centers. Together with the large specific surface area, high electrical conductivity and CO2 adsorption capability, the Co-PPOLs achieve outstanding activity and selectivity for electrochemical CO2 reduction to CO with FECO = 94.2% at a moderate cathodic potential (-0.9 V vs. RHE), accompanied with high chemical stability. In addition, Co-PPOLs can reach a high current above 200 mA in a membrane electrode assembly (MEA) reactor, and maintain a high FECO > 90% over 20 h, enabling industrial-level current and near-unity CO selectivity in CO2 electrolysis.