Bottom-up Synthesis of Carbon Materials with an Exceptionally High Percentage of Pentagons and Heptagons Using Brominated Precursors

Abstract

Defect structures in carbon materials have attracted much attention in recent years since the introduction of defects such as 5- and 7-membered rings, edges, and functional groups in carbon materials improves performance in various applications. In particular, 5- and 7-membered rings are one of the most stable defects because 5- and 7-membered rings exist in the basal plane in carbon materials. However, there have been no reports of catalyst-free synthesis of carbon materials with high percentages of 5- and 7-membered rings. In this study, the catalyst-free synthesis of carbon materials with a high percentage of 5- and 7-membered rings was conducted by a simple bromination and heat treatment of azulene (Azu) composed of only 5- and 7-membered rings. Compared to the percentage of reacted edges of 31% for non-brominated Azu (873 K), that of brominated Azu was 92% at 873 K. Thus, the bromination of Azu significantly improved the reactivity of Azu, leading to the relatively low electrical resistivity. The detailed analyses of brominated and carbonized Azu using Raman, infrared spectroscopy, and full width at half maximum of C1s X-ray photoelectron spectroscopy suggest that the synthesized carbon materials contain 90% of 5- and 7-membered rings.