How adsorption geometry of reactants on catalytic surfaces directs their chemical reactivity

The adsorption geometry of molecules on catalytic surfaces has a critical influence on their reactivity. However, direct proof for such a correlation between adsorption geometry and chemical reactivity cannot be easily achieved. Herein, by using addressable self-assembled carbenes as probe molecules, we demonstrate that high proximity between functional groups and catalytic surfaces is essential for chemical transformation. By tuning the anchoring geometry of NO₂-functionalized surface anchored carbenes, it was identified that the reducibility of the nitro groups is enhanced once the distance between the nitro group to the catalytic surface is minimized. IR nanospectroscopy measurements on various sites on the surface of single nanoparticles identified that the proximity effect is more influential than the specific adsorption site on which the molecule is adsorbed in directing the surface-induced reactivity. The high spatial resolution and ensemble-based spectroscopy measurements specified the proximity of the functional group to the catalytic surface as the dominant factor that directs the reactivity.