Energetic metal–organic frameworks achieved from furazan and triazole ligands: synthesis, crystal structure, thermal stability and energetic performance†
Abstract
Energetic metal–organic frameworks (EMOFs) have witnessed increasing development and been proved as promising candidates for new high energy density materials (HEDMs). Here, three metal energetic complexes based on 3,4-diaminofurazan (DAF) and 3-amino-1H-1,2,4-triazole (Hatz) ligands have been synthesized via a routine method and fully characterized by IR, 1H NMR, 13C NMR spectroscopy, X-ray single-crystal diffraction and DSC-TG techniques. The standard heats of combustion were obtained by an oxygen bomb calorimeter, and the detonation performance was calculated using the EXPLO5 program. Crystal structure determinations reveal that 1 shows a one-dimensional zigzag chain structure consisting of Zn(II) and bidentate DAF, ultimately producing a 2D MOF through extensive hydrogen bond interactions. The crystal densities of these complexes are up to 1.9 g cm−3 at 298 K. The thermal analyses from the DSC-TG test show that most of them have good thermal stability with the highest decomposition temperature of 241 °C. The as-synthesized compounds possess highly positive heats of formation with values for 2 and 3 of 2329.30 kJ mol−1 and 3261.57 kJ mol−1, respectively, and high heats of detonation with value for 2 of 10231 kJ kg−1, superior to that of HMX and RDX, which are most powerful organic explosives in use today. Expectedly, they exhibit excellent detonation performance, of which 2 has the best detonation velocity (9405 m s−1) and detonation pressure (46.64 GPa), and thus shows a great promise for potential applications as a high-energy density material. In addition, DFT calculations were performed in order to investigate the electronic properties based on the structures. This study highlights the great potential of nitrogen-rich group containing EMOFs (or complexes) for new eco-friendly energetic materials.