Atomically Thin, Ionic–Covalent Organic Nanosheets for Stable, High‐Performance Carbon Dioxide Electroreduction

Abstract The incorporation of charged functional groups is effective to modulate the activity of molecular complexes for the CO₂ reduction reaction (CO₂RR), yet long‐term heterogeneous electrolysis is often hampered by catalyst leaching. Herein, an electrocatalyst of atomically thin, cobalt‐porphyrin‐based, ionic–covalent organic nanosheets (CoTAP‐iCONs) is synthesized via a post‐synthetic modification strategy for high‐performance CO₂‐to‐CO conversion. The cationic quaternary ammonium groups not only enable the formation of monolayer nanosheets due to steric hindrance and electrostatic repulsion, but also facilitate the formation of a *COOH intermediate, as suggested by theoretical calculations. Consequently, CoTAP‐iCONs exhibit higher CO₂RR activity than other cobalt‐porphyrin‐based structures: an 870% and 480% improvement of CO current densities compared to the monomer and neutral nanosheets, respectively. Additionally, the iCONs structure can accommodate the cationic moieties. In a flow cell, CoTAP‐iCONs attain a very small onset overpotential of 40 mV and a stable total current density of 212 mA cm^–2 with CO Faradaic efficiency of >95% at −0.6 V for 11 h. Further coupling the flow electrolyzer with commercial solar cells yields a solar‐to‐CO conversion efficiency of 13.89%. This work indicates that atom‐thin, ionic nanosheets represent a promising structure for achieving both tailored activity and high stability.