A strategy developed from the observed energetic–energetic cocrystals of BTF: cocrystallizing and stabilizing energetic hydrogen-free molecules with hydrogenous energetic coformer molecules

Abstract

Energetic–energetic cocrystals (EECCs) are promising alternatives to high-energy and low-sensitivity explosives, the development of which is still a challenge in the field of energetic materials due to their intrinsic energy-sensitivity contradiction (high energy usually accompanies high sensitivity). We propose a strategy to combine highly energetic but unstable hydrogen-free molecules with hydrogenous energetic molecules to form stable EECCs and maintain their high energy, developed by analyzing the crystal packing of all observed BTF-based EECCs. That is, in contrast to the pure BTF crystal, which is very sensitive to mechanics and shock, the increased intermolecular hydrogen bonding consolidates the EECCs, leading to largely enhanced cohesive energy densities. Furthermore, hydrogen bonds are formed regardless of coformer molecular geometry, suggesting a large number of potential coformer molecules and EECCs. The thermodynamics driving the EECC formation is discussed, and the increased lattice energy and increased entropy are thought to be the driving force for EECC formation. This strategy for consolidating crystals to stabilize unstable molecules by increasing intermolecular hydrogen bonding will renew the interest in some highly energetic compounds that have been overlooked for a long time due to their poor environmental compatibility.