High-Pressure Bulk Synthesis of Crystalline C6N9H3·HCl: A Novel C3N4 Graphitic Derivative

Abstract

A novel carbon nitride compound, structurally related to the proposed graphitic phase of C₃N₄, has been synthesized in a bulk well-crystallized form. The new material, with stoichiometry C₆N₉H₄Cl, was prepared through a solid-state reaction of 2,4,6-triamino-1,3,5-triazine with 2,4,6-trichloro-1,3,5-triazine at 1.0−1.5 GPa and 500−550 °C and also through a self-reaction of 2-amino-4,6-dichloro-1,3,5-triazine at similar conditions. X-ray and electron diffraction measurements on the yellowish compound indicate a hexagonal space group (P6₃/m) with cell parameters of a = 8.4379(10) Å and c = 6.4296(2) Å. This new compound possesses a two-dimensional C₆N₉H₃ framework that is structurally related to the hypothetical P6m2 graphitic phase of C₃N₄, but with an ordered arrangement of C₃N₃ voids. The large voids in the graphene sheets are occupied by chloride ions with an equivalent number of nitrogen atoms on the framework protonated for charge balance. The composition of the sample was determined by bulk chemical analysis and confirmed by electron energy loss (EELS) spectroscopy. The chemical and structural model is consistent with bulk density measurements and with the infrared and ¹³C NMR spectra. This work represents the first bulk synthesis of a well-characterized and highly crystalline material containing a continuous network of alternating carbon and nitrogen atoms.