Exploring Hydrogen-Bonded 3D MOFs: High-Performance, Thermally Stable Self-Assembled Iodine-Encapsulated Frameworks
Manojkumar Jujam1, Richa Rajak1, Navaneet Kumar1
1Energetic Materials Laboratory, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh, 208016, India.
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Modern high-performing insensitive energetic materials are becoming more and more in demand to meet the growing needs of civilians and military applications. Here, the self-assembly of azole-based energetic molecules was described to construct potassium- and sodium-based energetic metal-organic frameworks (E-MOFs) using polyazole-based energetic 5,5'-(2-((1H-tetrazol-5-yl)methyl)-2H-1,2,3-triazole-4,5-diyl)bis(1H-tetrazole) (TBTT) linker. The X-ray analysis authenticates K-MOF (1) and Na-MOF (2), introducing hydrogen-bonded 3D frameworks. Both compounds were extensively studied by thermogravimetric analysis-differential scanning calorimetry (TGA-DSC), elemental analysis (EA), infrared spectroscopy (IR), Scanning Electron Microscopy (SEM), dynamic light scattering (DLS), and powder X-ray diffraction analyses (PXRD). Further, mechanical sensitivity, detonation properties, and Hirshfeld surface analyses were examined. As expected, both E-MOFs showed excellent thermal decomposition temperature (Td = 333-387 °C), which exceeds benchmark explosives like hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) (210 °C), 2,4,6-trinitrotoluene (TNT), hexanitrostilbene (HNS) (318 °C), and 2,4,6-triamino-1,3,5-trinitrobenzene (TATB) (315 °C). They also have shown high positive heat of formation (HOF = 366-525 kJ/mol) and superior detonation performance (VOD = 6857-8903 m/s; DP = 17.41-28.23 GPa). Additionally, the two E-MOFs exhibited low sensitivity toward impact sensitivity (IS > 60 J) and friction sensitivity (FS > 360 N), which may be attributed to strong structural reinforcement and multiple hydrogen bonding interactions, which is also proven by Hirshfeld surface analyses. Moreover, the high covalent bonds are beneficial in strengthening the E-MOF structures, which require high energy to collapse, thereby sustaining excellent thermal stability. E-MOFs 1 and 2 exhibit high iodine encapsulation and recyclability, maintaining effectiveness over six cycles, making them ideal for water remediation. Thus, compounds 1 and 2 can serve as promising next-generation highly thermally stable energetic materials, which can be a perfect replacement for currently used conventional explosives RDX, HNS, and TATB.
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