Design and synthesis of Zn(ii)/Cd(ii)-based energetic metal coordination polymers with the bis(tetrazole)methane (H2btm) ligand: a comparative assessment of heat resistance and catalytic effects on the thermal decomposition of ammonium perchlorate

Abstract

We report two energetic metal coordination polymers (CPs), [Zn(Hbtm)₂]_n (1) and [Cd₃(btm)₂Br₂(H₂O)₂]_n·4H₂O (2), based on the bis(tetrazole)methane (H₂btm) ligand. SCXRD analysis shows that 1 forms a 2D layered structure extending into a 3D supramolecular network via hydrogen bonding, while 2 features a 3D framework. Thermal analysis indicates that 1 is stable up to 330 °C, while 2 remains stable up to 395 °C after losing water molecules at 126 °C. Complex 1 exhibits a detonation velocity of 7.46 km s⁻¹ and a detonation pressure of 26.16 GPa, whereas 2 exhibits values of 6.02 km s⁻¹ and 12.50 GPa, respectively. Both complexes are insensitive to impact (>40 J) and friction (>360 N). The kinetic parameters were determined using the Kissinger and Ozawa methods, and the results are in good agreement with those obtained from the ASTM-E698 method. Additionally, both complexes catalyze the thermal decomposition of ammonium perchlorate (AP). Owing to its high thermal stability, comparable to that of TATB and other H₂btm-based complexes, 1 is a promising candidate as a heat-resistant explosive, while both complexes show potential for application in advanced energetic formulations.