Mechanical Tunability via Hydrogen Bonding in Metal–Organic Frameworks with the Perovskite Architecture

Two analogous metal–organic frameworks (MOFs) with the perovskite architecture, [C­(NH<sub>2</sub>)<sub>3</sub>]­[Mn­(HCOO)<sub>3</sub>] (<b>1</b>) and [(CH<sub>2</sub>)<sub>3</sub>NH<sub>2</sub>]­[Mn­(HCOO)<sub>3</sub>] (<b>2</b>), exhibit significantly different mechanical properties. The marked difference is attributed to their distinct modes of hydrogen bonding between the A-site amine cation and the anionic framework. The stronger cross-linking hydrogen bonding in <b>1</b> gives rise to Young’s moduli and hardnesses that are up to twice those in <b>2</b>, while the thermal expansion is substantially smaller. This study presents clear evidence that the mechanical properties of MOF materials can be substantially tuned via hydrogen-bonding interactions.