First-principles prediction of high-energy-density C–O–N polymers and nitrogen-substitution approach in carbon oxide frameworks

By combining first-principles calculations with crystal structure searching, we predict three new high-energy-density C x O y N z polymers: C 4 O 4 N 8 - C 2/ m (6.58 kJ/g), C 6 O 2 N 2 - Imm 2 (5.24 kJ/g), and C 6 O 6 N 4 - Imm 2 (6.65 kJ/g). Among them, C 4 O 4 N 8 - C 2/ m adopts a one-dimensional tubular structure, whereas C 6 O 2 N 2 - Imm 2 and C 6 O 6 N 4 - Imm 2 are structurally analogous to the known C 6 O 4 - I -4 m 2 and C 4 O 4 - Cmcm phases, respectively, and may be regarded as site-specific nitrogen-substituted derivatives. Substitution-enthalpy calculations suggest that these nitrogen-substituted derivatives are high-enthalpy metastable phases relative to their parent polymeric carbon oxides. All three compounds exhibit high energy densities and favorable detonation performance. C 4 O 4 N 8 - C 2/ m and C 6 O 2 N 2 - Imm 2 also show comparatively favorable mechanical and dynamical stability and therefore warrant further experimental evaluation. In contrast, C 6 O 6 N 4 - Imm 2 remains dynamically stable only up to approximately 100 K even at 40 GPa, severely limiting its practical applicability despite its high energy density. These findings deepen the understanding of structure–property relationships in C–O–N energetic materials and provide theoretical guidance for the design and optimization of new high-energy-density energetic materials.