Synthesis of nitrogen-rich carbon nitride networks from an energetic molecular azide precursor

Abstract

Nitrogen-rich carbon nitrides are produced as amorphous, bulk solids from the slow thermal decomposition of 2,4,6-triazido-1,3,5-triazine [(C3N3)(N3)3]. This energetic molecular azide is thermally unstable and readily decomposes at 185 °C in a high-pressure reactor to produce carbon nitride materials, e.g., C3N4. Under applied nitrogen gas pressure, (C3N3)(N3)3 decomposes to yield a solid with one of the highest reported nitrogen-to-carbon ratios corresponding to C3N5. This azide precursor also decomposes upon rapid heating to 200 °C to form graphite nanoparticles without any retained nitrogen. Spectroscopic evidence (infrared, nuclear magnetic resonance, and ultraviolet-visible) demonstrates that thee carbon-nitrogen solids have significant sp2 carbon bonding in a conjugated doubly bonded network. Electron microscopy reveals that these powders have a glassy microstructure with large irregular pores and voids. C3N4 and C3N5 are thermally stable up to 600 °C and sublime to produce carbon nitride thin films on SiO2 and Si substrates. A discussion on possible azide decomposition pathways and carbon nitride structures is presented.