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

The sulfidation of metal oxides is critical to the creation of catalyst active sites for industrially-relevant reactions, but occurs at high temperatures for refractory oxides like zirconia. Here, we investigate sulfidation of the structurally-well-defined, Zr-based metal-organic framework (MOF) NU-1000 as a model system. Sulfidation with H2S and alkane thiols occurred readily at room temperature after thermal distortion of the Zr6 clusters in NU-1000. The sulfidation occurred via heterolytic S-H bond cleavage over frustrated Lewis-acid/Lewis-base pairs in the form of under-coordinated Zr(IV) sites and a terminal O(-II) site formed during the thermal distortion. In situ synchrotron based structural analysis, spectroscopic characterization, and computational studies provide evidence that thiols react with distorted Zr6 nodes to form stable bridging Zr-S-Zr bonds and a terminal hydroxo. This study provides insight into the surface structures responsible for the sulfidation of high-valent metal oxides and also suggests a promising strategy for introducing S-bearing moieties to otherwise sulfur-resistant MOF nodes.