Absorbing stress via molecular crumple zones: Strain engineering flexibility into the rigid UiO-66 material

Nanostructured materials such as metal--organic frameworks and perovskites can be easily tuned towards applications ranging from sensors to photovoltaic devices. However, the key to unlock their design potential, namely causal relations between a material's atomic structure and its macroscopic function, is currently still missing. Therefore, we herein introduce strain engineering as a general approach to rationalize and design how atomic-level structural modifications induce dynamically interacting strain fields that dictate these material's macroscopic mechanical behavior. We demonstrate the potential of strain engineering by consciously designing shear instabilities in UiO-66, leading to intriguing, counterintuitive mechanical behavior. The strain-engineered structures exhibit time- and space-dependent crumple zones that instill flexibility in the otherwise rigid material and that locally focus the strain, partially preserving the porosity of the material under compression. This example demonstrates how strain engineering can be adopted to design, from the atomic level onwards, state-of-the-art materials for challenging applications.