Shock wave energy absorption via structural phase transition and bond breakage in metal-organic frameworks

Metal-organic frameworks (MOFs) are nanoporous materials with a tunable structure and high porosity, making them attractive for mechanical energy absorption applications. This study explores shock-induced structural transitions and energy absorption in ZIF-8 and SALEM-2 using ReaxFF molecular dynamics simulations and density functional theory. Results reveal a phase transition at pressures below 1 GPa, characterized by pore collapse, amorphization, and alterations in electronic and bonding structures. Thermodynamic analyses attribute the transition to enthalpy-driven mechanisms and increased entropy. SALEM-2 exhibits superior shock attenuation, attributed to greater volume reduction and extensive bond breakage, underscoring the role of linker chemistry. The ability of MOFs to absorb shock arises from dramatic volume reductions facilitated by bond bending and the sacrificial breaking of metal-linker coordination bonds, with moderate increases in internal energy compared to dense solids. This work provides molecular-level insights into MOF-based shock attenuation and guides the design of optimized MOFs for enhanced mechanical energy absorption.