Guest-dependent mechanical anisotropy in pillared-layered soft porous crystals - a nanoindentation study

Soft porous crystals (SPCs) of the type [Zn-2(L)(2)(dabco)](n) (L _ linear dicarboxylate linker, dabco _ 1,4-diazabicyclo[2.2.2]octane) show exceptional mechanical anisotropy. Single-crystal nanoindentation experiments reveal very large changes of the elastic modulus and hardness triggered by exchange of the guests adsorbed in the porous metal-organic framework. The substantial variations of the mechanical properties as a function of the guest molecules can be explained by the responsive nature of these SPCs. Based on non-specific guest-framework interactions, crucial changes of the network geometry induce a complex and dynamical mechanical behaviour.