Oxygen‐Substituted Porous C2N Frameworks as Efficient Electrocatalysts for Carbon Dioxide Electroreduction

Abstract The electrochemical carbon dioxide reduction reaction (CO 2 RR) provides a green avenue for decarbonizing the conventional chemical industries. Here, a structure–selectivity relationship of catalysts is pivotal for the control of a highly selective and active CO 2 RR pathway. We report the fabrication of an oxygen‐substituted C 2 N as metal‐free catalyst (O─C 2 N) for electrochemical CO 2 ─to─CO conversion with tunable O microenvironment. Combined spectroscopic analysis reveals a fine tailored N─C─O moiety in O─C 2 N, where C─O─C species (e.g., ring in‐plane ether) become the dominant oxygen configurations at higher pyrolysis temperatures. Based on experimental observations, a correlation between the exocyclic O‐substituted N─C─O─C moieties and CO selectivity is established, giving clear chemical tools for active structure design. The optimized O─C 2 N electrocatalysts with the dominant appearance of C─O─C moieties exhibit an outstanding 2e − CO 2 RR performance with a CO selectivity up to 94.8%, which can be well maintained in a practical flow‐cell reactor with an adjustable syngas feature.