P1-C7N4O8: Improved Stability and Energy Density via a Covalent Framework with Uniform Single Bonds

Abstract

Energy can be stored in the chemical bonds of CNO energetic materials. However, non-uniform chemical bonds hinder the trade-off between structural stability and energy density: strong chemical bonds reduce energy density, whereas weak bonds lower the decomposition barrier. In this work, we propose a 3D close-packed structure of P1-C7N4O8 with uniform chemical single bonds using first-principles crystal structure search method, the results show that the P1-C7N4O8 becomes thermodynamically favorable via the reaction of C3N4 and dry ice (CO2) at a pressure of 31 GPa. The calculated results show that the P1-C7N4O8 exhibits excellent structural stability under high pressure, and can be retained to ambient condition. In addition, the C−N and C−O single bonds are elongated during decompression, which can further increase the energy density. As a result, P1-C7N4O8 shows remarkably outstanding mass density (3.08 g/cm3), volumetric energy density (18.12 kJ/cm3), outperforming the known CHON and CxNyOz energetic materials. This work indicates that 3D covalent structure with uniform chemical single bonds is crucial to balancing the stability and performance for energetic materials.