Pushing the Limit of Nitro Groups on a Pyrazole Ring with Energy-Stability Balance

Polynitro compounds exhibit high density and good oxygen balance, which are desirable for energetic material applications, but their syntheses are often very challenging. Now, the design and syntheses of a new three-dimensional (3D) energetic metal-organic framework (EMOF) and high-energy-density materials (HEDMs) with good thermal stabilities and detonation properties based on a polynitro pyrazole are reported. Dipotassium 3,5-bis(dinitromethyl)-4-nitro-1H-pyrazole (5) exhibits a 3D EMOF structure with good thermal stability (202 °C), a high density of 2.15 g cm-3 at 100 K (2.10 g cm-3 at 298 K) in combination with superior detonation performance (Dv = 7965 m s-1, P = 29.3 GPa). Dihydrazinium 3,5-bis(dinitromethyl)-4-nitro-1H-pyrazole (7) exhibits a good density of 1.88 g cm-3 at 100 K (1.83 g cm-3 at 298 K) and superior thermal stability (218 °C), owing to the presence of 3D hydrogen-bonding networks. Its detonation velocity (8931 m s-1) and detonation pressure (35.9 GPa) are considerably superior to those of 1,3,5-trinitro-1,3,5-triazine (RDX). The results highlight the syntheses of a 3D EMOF (5) and HEDM (7) with five nitro groups as potential energetic materials.