Studying structural distortions of metal nodes in Zr-based MOFs during catalysis.

Zr-based metal-organic frameworks (MOFs) with well-defined Zr oxo clusters emerged as a promising class of heterogeneous catalysts. Defects on these metal-oxide clusters are central to understanding their reactivity, as they i) replace metal-ligand bonds with more labile terminal groups or ii) lower the valency of the metal sites. We have developed a rapid heat treatment that induces node distortions of the Zr oxo cluster and leads to rapid amorphization of the framework (aDUT-67). These distortions result from cluster dehydration, which creates coordinatively unsaturated Zr sites. The low-valent sites have unique Zr-O bond distances and cause distortions in the second shell Zr-Zr distances. Considering how sensitive the metal node structures are to the coordination environment of Zr, we expect to see dynamic changes in said clusters during catalytic reactions. We propose to conduct in situ total scattering experiments to study those changes.