Fused [5,7,5] Tricyclic Energetic Scaffold with a Favorable Oxygen Balance for High-Performance Explosives

The strategic introduction of ring strain into high-energy-density materials (HEDMs) presents a powerful yet underutilized pathway to augment detonation performance and stability. However, most research focus on planar five- and six-membered structures, with few studies introducing larger rings with increased ring strain, which often require alkylene as a linkage between azoles, resulting in higher stability by sacrificing detonation properties. Here, we report a new fused [5,7,5] tricyclic energetic scaffold by the construction of robust NH-CO-NH and NH-CH₂-NH bridges and successfully incorporate a strained seven-membered ring toward tricyclic architectures. The oxygen balance was further modified by the installation of multiple nitro groups on the novel fused skeleton, which suppresses carbonaceous residue formation and contributes to its clean and efficient energy release. Notably, a hexanitro-substituted polycyclic structure was obtained, which exhibits a calculated detonation velocity of 9084 m s^-1 and a detonation pressure of 35.8 GPa with favorable sensitivity and stability, and the ignition and flame propagation experiments demonstrate that the hexanitro-substituted tricyclic energetic material exhibits a much shorter ignition delay time and brighter flame compared to HMX and RDX, indicating an enhanced ignition and combustion performance.