Large‐Scale Synthesis of a New Polymeric Carbon Nitride—C3N3 with Good Photoelectrochemical Performance

Abstract Polymeric carbon nitride (PCN) has been extensively researched in recent years. This research has mainly focussed on C 3 N 4 because types of PCN are quite limited and other types are not easily synthesized. Therefore developing new types of easily‐synthesized PCN beyond C 3 N 4 offers new opportunities. C 3 N 3 has been predicted but it has not been successfully synthesized before. Herein it is prepared in large scale from cheap cyanuric chloride on a copper surface under nonvacuum conditions. The C 3 N 3 has a good photoelectrochemical (PEC) activity for water splitting and can be exfoliated to 2D polymeric films. This breakthrough work not only enlarges the family of PCN, but also opens the door for large‐scale synthesis of other similar C–C bonded 2D conjugated polymers based on Ullmann polymerization. Similar to graphene and C 3 N 4 , follow‐up research related to this C 3 N 3 in different fields may emerge in the near future.