Effects of Missing Linker Defects on the Elastic Properties and Mechanical Stability of the Metal–Organic Framework HKUST-1

Abstract

The defects can naturally exist or be artificially designed in metal–organic frameworks (MOFs), which could significantly affect their mechanical properties. In this paper, the elastic properties of HKUST-1 with randomly distributed missing linker defects are investigated by reactive molecular dynamics simulations together with the strain-fluctuation method. Although all elastic constants of HKUST-1 are found to reduce due to the linker missing, the cubic symmetry is retained in the defective HKUST-1, indicating that the simplified Born stability criterion is still applicable in determining its mechanical stability. On the basis of the simplified Born stability criterion together with direct compression simulations, the critical pressure of instability of HKUST-1 with randomly distributed defects is found to almost linearly decrease as the defect concentration grows. The mechanical instability is similarly attributed to the compression mode in both pristine and defective HKUST-1. Moreover, the direct compression simulations indicate an obvious intermediate transition process existing during the structural collapse of the defective HKUST-1, which is absent in its pristine counterpart. Overall, this work is expected to provide a more precise understanding of the mechanical properties of realistic MOFs.