Novel 3D cesium(i)-based EMOFs of nitrogen-rich triazole derivatives as “green” orange-light pyrotechnics†
In this paper, an ingenious strategy based on constructing energetic metal–organic frameworks (EMOFs) with cesium salts for new green and practical pyrotechnic composition is described. In order to obtain a non-hygroscopic, chlorine-free formulation, a novel triazole nitrogen-rich energetic ligand, N-(5′-amino-1H,1′H-[3,3′-bi(1,2,4-triazol)]-5-yl)nitramine (HABTNA), was designed and synthesized, which exhibited some good properties such as insensitivity, high nitrogen content and energy, and excellent oxygen balance. More importantly, using this triazole ligand and cesium(I) salts, an energetic metal–organic framework (EMOF) structure as a pyrotechnic colorant was built by a simple and green aqueous solution crystallization method. The results of single-crystal X-ray diffraction experiments indicated that this EMOF has a compact three-dimensional structure with high density. Physical and chemical property tests revealed that this Cs(I)-based MOF has excellent moisture resistance and thermal stability, while, at the same time, it was also proved to be a high-energy insensitive energetic material with energy up to the explosive level. By a systematic pyrotechnic performance experiment, a chlorine-free pyrotechnic formulation with this flammable EMOF as the main component was developed, which was the first orange-light-emitting pyrotechnic formulation with high color purity and intensity.