(513ev) Tuning Surface Characteristics of Graphene Aerogel to Control Catalytic Properties of Atomically Dispersed Iridium Complexes

The catalytic performance of the active sites located on the supported metal nanoparticles can be influenced by their electronic interactions with the support. Elucidation of these interactions and their consequences on the catalytic performance is one of the main challenges in the field. Such information is crucial for tuning the electronic environment over the active sites to control the catalytic properties. Therefore, graphene aerogel (GA), becomes a proper support material to investigate this issue because of having controllable surface characteristics.

The influence of annealing conditions on the surface characteristics of graphene-based materials for their tunability on the electronic structure of the atomically dispersed supported iridium complexes anchored on these reduced GA supports and on partial hydrogenation of 1-3 butadiene reaction was investigated.

Reduced GA-supported Ir(CO)₂ complexes were synthesized by the reaction of Ir(CO)₂(acac) with GA samples at an Ir loading of 10 wt.%. Detailed characterization was done to understand ligand-support interactions as well as catalytic activity.

To probe the consequences of these changes on the electronic environment of atomically dispersed supported metal complexes, Ir(CO)₂ complexes were anchored on these supports, and investigated the variation of the partial hydrogenation selectivity with the corresponding ν(CO) band positions of carbonyl ligands on the iridium complexes. Data presented a decreasing trend between partial selectivity of 1-3 butadiene hydrogenation and ν(CO) band positions (image), indicating that more electron rich iridium sites became more selective as the annealing temperature decreases. This comparison illustrated a strong correlation between the partial hydrogenation activity of the supported complexes with the corresponding ν(CO) band positions probing the electron density on iridium. Results present a broad potential for tuning the catalytic properties of atomically dispersed supported metal complexes. GA but also provides opportunities for tuning the selectivity of partial hydrogenation reaction in a wide range.