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-1,2,4triazole). Structural analysis reveals that 1 displays a unique 3D inserted 3D framework, and 2 presents a rigid 2D network with strong 7C-7C packing interactions. Compounds 1 and 2 feature rarely insensitive to mechanical stimulation and exhibit excellent thermal stabilities reaching up to 371 and 366 degrees C, respectively. The calculated heats of detonation (Delta Hdet) of 2 is 5.315 kJ center dot g- 1, which is much higher than that of the traditional explosive 2,4,6trinitrotoluene (TNT, Delta Hdet = 3.72 kJ center dot g- 1). The experimental results and theoretical calculations demonstrate that the specific 3D inserted 3D 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 azidebased EMOFs.