Shockwave Energy Dissipation in Metal-Organic Framework MOF-5

We investigate the response of the metal organic framework MOF-5 to shock loading along various crystallographic orientations using molecular dynamics simulations with the reactive force field ReaxFF. The dynamical compressive load leads to the volumetric, collapse of the open structure of MOF-5. A two-wave structure forms with a pore-collapse wave following a leading elastic precursor that propagates at a higher speed. Interestingly, the propagating pore-collapse wave weakens the elastic precursor indicating possible applications of these materials for shockwave dissipation. Within the two-wave regime, an increase in piston velocity leads to an increase in the velocity of the pore-collapse wave, but the pressure and velocity of the elastic precursor remain unchanged. For piston velocities between 2 and 3 km/s (depending on orientation) the pore-collapse wave catches up with the elastic precursor leading to an overdriven regime. The simulation's yield insight into the molecular process of pore collapse and are used to characterize the Hugoniot equation of state for the pristine and pore-collapse materials. For piston velocities over 2 km/s we observe: significant chemical decomposition of the structure in addition to the nanopore collapse.