The enhancement of heterobimetallic MOFs on the pyrolysis and laser ignition of FOX-7

The hydrothermal approach had been used to synthesize two new heterobimetallic Metal Organic Frameworks (MOFs), Ba4Pb4(CH3CO2)8[(CH6CO2)4Pb](CH3CO2)4 (PbBa-MOF) and Ba2Ni(CO2H)6(OH2)4 (NiBa-MOF), their structure and surface topography were then examined with XRD and SEM. By using the TG-DSC and TG-FTIR-MS methods, the pyrolytic decomposition properties of MOFs and their catalytic activities on the 1,1-diamino-2,2-dintroethene (FOX-7) pyrolysis were investigated. The PbBa-MOF has a single thermal decomposition process with a high thermal decomposition temperature, while NiBa-MOF has a three-stage thermal decomposition process initiated from a lower temperature. Furthermore, the thermolysis peak temperature of the FOX-7/PbBa-MOF and FOX-7/NiBa-MOF mixture has a great decrease by 24.2 °C and 27.4 °C compared with the FOX-7. However, the low pyrolysis peak temperature and the pyrolysis activation energy (Ea) are almost unchanged. The selective high temperature catalytic effect of the MOFs on FOX-7 results from the activation of -NH2 in the high temperature pyrolytic decomposition of FOX-7 by the metallic ions of the MOFs. This thermal catalytic property indicates that MOFs can promote the pyrolytic decomposition of FOX-7 while ensuring the safety requirements for the compatibility of energetic mixtures in the preparation of propellants. The relationship between the features of pyrolytic decomposition and laser ignition was finally covered and defined. The two MOFs decreased the minimum ignition energy and ignition delay time of the FOX-7. Novel MOFs combustion catalyst may strengthen ignition and combustion features of the high-energy and low-sensitivity solid propellants containing FOX-7.