Synthesis of Heteroatom Rh-ReO_x Atomically Dispersed Species on Al₂O₃ and Their Tunable Catalytic Reactivity in Ethylene Hydroformylation

Atomically dispersed late-transition-metal catalysts exhibit distinct catalytic reactivity and selectivity compared to metal clusters in many reactions. Realizing the potential benefits of these catalysts requires active site uniformity and control of their local environment. Here, we propose a catalyst synthesis route for manipulating the local environment of atomically dispersed metal-active sites. This was achieved via the targeted deposition of Rh precursors near atomically dispersed ReO_x on γ-Al₂O₃ using electrostatic interactions. CO probe molecule infrared spectroscopy and aberration-corrected scanning transmission electron microscopy suggested that Rh could be preferentially located near a single ReO_x species or multiple ReO_x species by controlling ReO_x loading. Rh-ReO_x interactions promoted catalytic reactivity and selectivity for ethylene hydroformylation. Kinetic measurements suggested that ReO_x species withdrew charge from Rh, weakening Rh-CO interactions, which promoted the concentration of vacant sites under reaction conditions and in turn catalytic reactivity. This work demonstrates a general synthetic approach for creating atomically dispersed heteroatom species consisting of oxophilic and late-transition metals and the importance of regulating the local environment of atomically dispersed metals for maximizing catalytic performance.