Versatile sulfidation of a metal-organic framework via heterolytic splitting of organo sulfides at distorted Zr-nodes

The sulfidation of metal oxides is a critical process to create catalysts for industrially relevant reactions. However, the exact sulfidation mechanism remains unclear. To investigate the sulfidation process through the heterolytic splitting of sulfur-containing molecules, we chose a structurally well-defined material, Zr-based metal-organic framework (MOF) NU-1000, as the model system. Sulfidation was achieved through thiol binding on thermally distorted Zr6 clusters. Key to the binding chemistry heterolytic S-H bond cleavage enabled by the presentation of inorganic frustrated Lewis-acid/Lewis-base pairs (FLPs) in the form of under-coordinated Zr(IV) sites and a terminal O(-II) site. In situ synchrotron based structural analysis, spectroscopic characterization, and computational studies showed that thiols bearing different functional groups interact with the distorted Zr6 nodes through dissociative adsorption, forming bridging Zr-S-Zr bonds while converting a terminal oxo to a terminal hydroxo. This study provides insights into the surface sites responsible for the sulfidation of metal oxide catalysts and offers a promising strategy for introducing S-bearing moieties to MOF scaffolds.