Metal-organic framework (MOF) thin films have potential applications in microelectronic devices. However, their mechanical stability still needs improvement to withstand traditional manufacturing processes. One approach to enhancing the mechanical stability is using polymer-based MOFs (polyMOFs), which contain a polymer as one building block of the MOF. Although polyMOFs were expected to have enhanced mechanical properties due to the polymer component, these properties had yet to be characterized.

Esther Frederick, Sandia National Laboratories, Albuquerque, NM, USA, and colleagues have developed a synthesis method for sub-5-µm polyUiO-66 thin films on gold and assessed the mechanical properties of the films. The team immersed an Au-coated silicon substrate into a reaction solution containing the polymer ligand poly-2,5-bis(pent-4-en-1-yloxy)terephthalic acid, zirconium(IV) chloride as a metal precursor, diethyl formamide, and formic acid to prepare the thin films.

An initial mechanical characterization showed that the polyUiO-66 films had lower elastic moduli (a measure of stiffness) than corresponding UiO-66 MOF films but, surprisingly, similar hardness. This shows that the impact of the polymer on the mechanical properties of the thin films is more complex than an additive performance improvement. Further investigations are needed to understand the effects of different factors on the mechanical properties of this emerging class of materials.

• Synthesis and Mechanical Properties of sub 5‐μm PolyUiO‐66 Thin Films on Gold Surfaces,
  Esther Frederick, Leah N. Appelhans, Frank W. DelRio, Kevin T. Strong, Sean Smith, Sara Dickens, Erika Vreeland,
  ChemPhysChem 2022.
  https://doi.org/10.1002/cphc.202100673