Presence vs. proximity: the role of pendant amines in the catalytic hydrolysis of a nerve agent simulant

Islamoglu, T.; Ortuño, M. A.; Proussaloglou, E.; Howarth, A. J.; Vermeulen, N. A.; Atilgan, A.; Cramer, C. J.; Farha, O. K.
Angew. Chem. Int. Ed. 2018, 57, 1949 (doi:10.1002/anie.201712645).

Amino functionalized Zr-based metal-organic frameworks have shown unprecedented catalytic activity compared to non-functionalized analogues for hydrolysis of organophosphonate-based toxic chemicals. Importantly, the effect of the amino group on the catalytic activity is significantly higher in the case of UiO-66-NH₂ where the amino groups reside in the vicinity of the node compared to UiO-67-m-NH₂ they are directed away from the node. Here, we have revealed that the proximity of the amino group is crucial to observe fast catalytic activity towards hydrolysis of organophosphonate-based nerve agents. The generality of the observed amine-proximity dictated catalytic activity has been tested on two different MOF systems which possess different topology. DFT calculations reveal that amino groups on all MOFs studied are not acting as Brønsted bases; instead they control the microsolvation environment at the Zr₆-node active site and therefore increase the overall catalytic rates.