Ordered Graphane Nanoribbons Synthesized via High-Pressure Diels-Alder Polymerization of 2,2'-Bipyrazine

Graphane shares the same two-dimensional honeycomb structure of graphene, but its saturated carbon skeleton gives rise to a bandgap and therefore provides more possibilities for the development of novel carbon-based semiconductors. However, the hydrogenation of graphene usually leads to disordered and incompletely hydrogenated graphane, and the precise synthesis of graphane with a specific configuration is still very challenging. Here, we synthesized a crystalline graphane nanoribbon (GANR) via pressure-induced polymerization of 2,2'-bipyrazine (BPZ). By performing Rietveld refinement of in situ neutron diffraction data, nuclear magnetic resonance spectroscopy, infrared spectra, and theoretical calculation, we found that BPZ experienced Diels-Alder polymerization between the π···π stacked aromatic rings and formed extended boat-GANR structures with exceptional long-range order. The unreacted -C═N- groups bridge the two ends of the boat and are ready for further functionalization. The GANR has a bandgap of 2.25 eV, with booming photoelectric response (I_ON/I_OFF = 18.8). Our work highlights that high-pressure topochemical polymerization is a promising method for the precise synthesis of graphane with specific structure and desired properties.