Ordered graphane nanoribbons synthesized via HP Diels−Alder polymerization - Drs. Kuo Li and Haiyan Zheng

New research from a team of scientists led by Drs. Kuo Li and Haiyan Zheng from Center for High Pressure Science and Technology Advanced Research (HPSTAR) reported the formation of extended boat-Graphane Nanoribbons (boat-GANRs) structures with long-range order from 2,2'-bipyrazine, through [4+2] Diels-Alder reactions under high pressure. The crystalline GANRs has a bandgap of 2.25 eV, with booming photoelectric response (I_ON/I_OFF =18.8). This work is published in the Journal of the American Chemical Society (DOI: 10.1021/jacs.5c03116).

Graphane shares the same two-dimensional honeycomb structure of graphene, but its saturated carbon skeletal gives rise to a band gap, and therefore provides more possibilities for the development of novel carbon-based semiconductors. However, the hydrogenation of graphene usually leads the unsatisfied crystallinity and selectivity of product, as it is hard to control the direction of hydrogen’s attacking. Thus, the precise synthesis of highly-ordered structure-specific graphane is required urgently.

The team demonstrated the pressure-induced topochemical polymerization of 2,2'-Bipyrazine, and found [4+2] Diels-Alder reactions of two rings each molecule above 20 GPa. The atom-level ordered crystalline GANRs with uniform boat-configuration was obtained, showing an obvious contrast to the previously reports of GANRs. The remained -C=N- groups modified the bandgap of the GANR, which shows an evident photocurrent response resulting from the free charge carrier due to the electron transfer from -C=N- to graphane framework.

This work shows that the PIP of polyaromatics is a robust method to synthesize well-defined and functionalized graphane materials with specific configurations. Based on this proof-of-concept work, more functional groups can be incorporated to modify the electronic structure of graphane and its electronic and photonic properties.