Characterizing the decomposition of CL-20 catalyzed by hydrophobic porphyrin MOFs

Abstract

Porphyrin metal–organic frameworks (PMOFs) with intrinsic characteristics have been extensively applied but still hold great potential as catalysts for energetic materials. Three analogous PMOFs with rod-like single-crystal structures, namely, [C₄₈H₂₈N₄O₈Cu]₂·C₂NH₆ (PCN-74), C₄₈H₂₈N₄O₈Cu (PCN-68) and [C₄₈H₂₈N₄O₈Cu]₃·C₂NH₆ (PCN-52), were successfully synthesized by a simple hydrothermal approach. These samples were hydrophobic with a contact angle of 141.2°. The catalytic performance of the PMOFs in promoting hexanitrohexaazaisowurtzitane (CL-20) decomposition was studied by differential scanning calorimetry (DSC). The thermal decomposition gases produced from CL-20 were further studied by thermogravimetric/Fourier-transform infrared spectroscopy/mass spectrometry (TG/FTIR/MS) with or without PMOFs. The results showed that the introduction of the catalysts decreased the thermal decomposition temperature by about 1.4 °C and reduced the activation energy of CL-20 by about 13.5 kJ mol⁻¹. In addition, real-time detection of decomposition product fragments demonstrated that MOFs influence the decomposition pathway. These effects were evidenced by the reduced laser ignition time and changes in combustion flame images.