Insensitive energetic azide-based metal-organic frameworks: highly stable frameworks constructed by nitrogen-rich and rigid ligands

The design and development of azide-based energetic metal–organic frameworks (EMOFs) with high energy and reliable stabilities for energetic materials still remains significant challenges. Herein, we utilized two rigid triazole-based polydentate ligands to design and synthesize two stable azide-based EMOFs [Cd(N3)(TRZ)]n 1 (HTRZ = 1,2,4-triazole) and [Cd(N3)(ATRT)(H2O)]n 2 (HATRT = 5-amino-3-(4H-1,2,4-triazol-4-yl)-1H-1,2,4-triazole). Structural analysis reveals that 1 displays a unique 3D inserted 3D framework, and 2 presents a rigid 2D network with strong π-π packing interactions. Compounds 1 and 2 feature rarely insensitive to mechanical stimulation and exhibit excellent thermal stabilities reaching up to 371 and 366 °C, respectively. The calculated heats of detonation (ΔHdet) of 2 is 5.315 kJ·g−1, which is much higher than that of the traditional explosive 2,4,6-trinitrotoluene (TNT, ΔHdet = 3.72 kJ·g−1). The experimental results and theoretical calculations demonstrate that the specific structure of 1 and the rigid 2D network of 2 produce high mechanical strength. This study not only provides two azide-based EMOFs with reliable stabilities as potential replacements for traditional energetic materials, but also illustrates a new insight into building stable structural models of azide-based EMOFs.