Unraveling the Structural Sensitivity of Metal Catalysts in Ethylene Hydroformylation: Insights from Theory and Experiments

In this study, we combined experimental and theoretical methods to investigate the structural sensitivity of metal catalysts in the ethylene hydroformylation reaction. Among Rh, Pt, Ir, Ni, Au, Ag, Pd, and Cu catalysts studied using experimental and theoretical methods, Rh showed the highest selectivity toward the C–C coupling product from CO and C2H5 (i.e., C2H5CHO). The results from DFT and microkinetic simulations revealed that the activation energy barrier for C–C coupling is lowest on the Rh nanocluster, which explains the experimentally observed highest C2H5CHO selectivity on the Rh catalyst. Furthermore, DFT results demonstrated that the sites located on the flat surfaces of nanoparticles primarily promote the hydrogenation reaction, leading to the formation of undesired C2H6. In contrast, undercoordinated edge and corner sites of the nanocluster promote the C–C coupling reaction. Thus, our results illustrate that the selectivity toward C3 oxygenates in ethylene hydroformylation reaction can be steered by tuning the size of Rh nanoparticles (the best-performing catalyst) to optimize the active (edge and corner) sites that preferentially promote the C–C coupling reaction.