Presence versus Proximity: The Role of Pendant Amines in the Catalytic Hydrolysis of a Nerve Agent Simulant

Amino-functionalized zirconium-based metal-organic frameworks (MOFs) 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 near the node, compared to UiO-67-m-NH2, where they are directed away from the node. Herein, we show that the proximity of the amino group is crucial for 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 have different topology. DFT calculations reveal that amino groups on all the MOFs studied are not acting as Bronsted bases; instead they control the microsolvation environment at the Zr-6-node active site and therefore increase the overall catalytic rates.