Synthesis of novel heterobimetallic MOFs and its effect on thermolysis and laser ignition of TKX-50

Two novel heterobimetallic metal-organic frameworks (MOFs), Ba4Pb4(CH3CO2)8[(CH6CO2)4Pb](CH3CO2)4 (PbBa-MOFs) and Ba2Ni(CO2H)6(OH2)4 (NiBa-MOFs), were prepared via the solvothermal method, and their structures were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques. The pyrolysis behavior of the two MOFs and their catalytic performances on the dihydroxylammonium-5,5’-bistetrazole-1,1’-diolate (TKX-50) pyrolysis were studied by thermogravimetric-differential scanning calorimetry (TG-DSC) and thermogravimetric-fourier transform infrared spectroscopy-mass spectrum (TG-FTIR-MS) methods. Compare with the pure TKX-50, the pyrolysis peak temperature and apparent activation energy (Ea) of the TKX-50/PbBa-MOFs mixture were decreased by 3.2°C and 13.47 kJ‧mol−1 respectively. The Ea of TKX-50/NiBa-MOFs was decreased by 9.35 kJ‧mol−1. And the second pyrolysis peak disappeared in the DSC curves of TKX-50 after the addition of the two MOFs, due to that the products from MOFs pyrolysis suppress the chemical reaction pathway on the production of 5,5′-bis (2-hydroxytetrazole) (ABTOX) and accelerate the direct decomposition of 1,1’-bistetrazole diol (BTO). This resulted in the percentage of H2O decreased greatly and the percentage of NO/CH2O, CO2/N2O, NH2+/O• and NH3/OH increased during the pyrolysis of TKX-50. Finally, the relation between the pyrolysis and ignition characteristics was discussed and described. The two MOFs reduced the ignition delay time of the TKX-50 at the high power density region, and the flame becomes more luminous due to the formation of metal oxides and active free radical.