Poly Tetrazole Containing Thermally Stable and Insensitive Alkali Metal-Based 3D Energetic Metal-Organic Frameworks.

Abstract

Poly tetrazole-containing thermally stable and insensitive alkali metal-based 3D energetic metal-organic frameworks (EMOFs) are promising high energy density materials to balance the sensitivity, stability, and detonation performance of explosives in defense, space, and civilian applications. Herein, the self-assembly of L3- ligand with alkali metals Na(I) and K(I) was prepared at ambient conditions, introducing two new EMOFs, [Na3(L)3(H2O)6]n (1) and [K3(L)3(H2O)3]n (2). Single crystal analysis reveals that Na-MOF (1) exhibited a 3D wave-like supramolecular structure with significant hydrogen bonding among the layers, while K-MOF (2) also featured a 3D framework. Both EMOFs were thoroughly characterized by NMR, IR, PXRD, and TGA/DSC analyses. Compounds 1 and 2 show excellent thermal decomposition Td = 344 and 337 °C, respectively, compared to the presently used benchmark explosives RDX (210 °C), HMX (279 °C), and HNS (318 °C), which is attributed to structural reinforcement induced by extensive coordination. They also show remarkable detonation performance (VOD = 8500 m s-1, 7320 m s-1, DP = 26.74 GPa, 20 GPa for 1 and 2, respectively) and insensitivity toward impact and friction (IS ≥ 40 J, FS ≥ 360 N for 1; IS ≥ 40 J, FS ≥ 360 N for 2). Their excellent synthetic feasibility and energetic performance suggest that they are the perfect blend for the replacement of present benchmark explosives such as HNS, RDX, and HMX.