Washington, DC — A group of scientists led by the Geophysical Laboratory's Huiyang Gou and Timothy Strobel performed high-pressure experiments on linear dicyanoacetylene (C4N2) using a diamond anvil cell, in which a pressure-induced reaction process was uncovered. Discrete linear C4N2 molecules were found to polymerize into a disordered extended network without significant change to the bulk composition.
Nitrogen-bearing, carbon-rich materials are known to have multiple functionalities and diverse applications. Graphitic carbon nitride (g-C3N4) is the most common C-N phase studied, but several other phases with varying compositions and properties have been predicted. GL's Huiyang Gou and Timothy Strobel performed high-pressure experiments on linear dicyanoacetylene (C4N2) using a diamond anvil cell, in which a pressure-induced reaction process was uncovered. Discrete linear C4N2 molecules were found to polymerize into a disordered extended network without significant change to the bulk composition. The results were published in Chemistry of Materials.
C4N2 is a linear molecule with alternating triple and single bonds (N≡C-C≡C-C≡N) that can burn with a flame temperature of more than 5000 K. This high-energy state represents a novel starting point for the synthesis of new carbon nitride extended networks with an interesting C:N stoichiometry in-between typical deposition-based syntheses (nitrogen doping) and systems like graphitic C3N4.
The team found that C4N2 polymerizes into a disordered carbon/nitrogen network that can be recoverable at ambient conditions. Its local structure, composition and chemical bonding were established using a variety of optical and X-ray scattering methods. Simulations of the reaction process conducted by Li Zhu and Duck Young Kim indicate that the pressure-induced polymerization initiates between the shortest N···C distances within a single two-dimensional “sheet” of molecules within the crystal. The polymerization proceeds within individual sheets through cycloaddition reactions producing predominantly 5- and 6-membered heterocyclic rings, giving the overall structure a tendency to propagate in two dimensions.
The high-pressure behavior of C4N2 elucidates the nature of chemical bonding, reaction mechanisms, and the atomic structure of reaction products, which advances the general understanding of carbon nitride materials and provides fundamental contributions for realizing new diamond-like carbon nitride materials
Other team members included Haw-Tyng Huang, Arani Biswas, Derek Keefer, Jordan Lerach and John Badding of The Pennsylvania State University; Brian Chaloux and Albert Epshteyn of the Naval Research Laboratory; Clemens Prescher of the University of Chicago; Liuxiang Yang and Matthew Ward of Carnegie; Shengnan Wang and Artem Oganov of Stony Brook University.
