Bottom-up synthesis of carbon materials with an exceptionally high percentage of pentagons or tertiary nitrogen by brominating precursors

Carbon materials with pentagons and graphitic nitrogen (tertiary nitrogen) have attracted much attention due to their prominent electrical and chemical properties. However, the low percentage of introduced pentagons and tertiary nitrogen as well as residual hydrogen originating from precursors have been problems. In this study, three precursors such as corannulene (Cora), indolizine (ID), and indolizino [6,5,4,3-ija]quinoline (IQ) were brominated by two different reaction methods such as heat treatment and ultrasonic treatment for preparing carbon materials with high percentages of pentagons and tertiary nitrogen. Unlike general bromination by heat treatment, ultrasonic bromination avoided the oxidation of precursors, leading to more controlled structures of carbon materials. A carbon material with exceptionally high percentages of retained pentagons (96%) and reacted edges (50%) as well as another carbon material with exceptionally high percentages of tertiary nitrogen (93%) and reacted edges (74%) were successfully synthesized by carbonizing the brominated Cora at 773 K and the brominated IQ at 873 K, respectively. Compared to non-brominated precursors such as Cora and IQ, bromination of precursors lowered the carbonization temperature and increased the percentage of reacted edges, while maintaining a high percentage of pentagons and that of tertiary nitrogen, respectively.