Rhodium Cluster Catalysts Enable Efficient Catalytic Hydroformylation in Mild Conditions: Cluster Size Dependence

ABSTRACT The size of the reactive metal domain, termed an ‘ensemble’, in supported metal catalysts critically influences their catalytic activity. To maximize mass‐activity (MA), a deep understanding of the optimal catalytic environment is vital for the rational catalyst design concept, yet this remains challenging due to difficulties in synthesis and analysis especially in the sub‐nanometer regime. Herein, we have successfully synthesized a series of supported Rh species ranging from single‐atoms to (sub‐)nanometer clusters and nanoparticles. Their catalytic performance in the hydroformylation of styrene was evaluated. We discovered that the optimal structures are the Rh clusters, achieving a MA as high as 305.3 mol g Rh‐total −1 h −1 , a value that surpasses previously reported values for both heterogeneous catalysts and the homogeneous Wilkinson's catalyst. Kinetic and theoretical analyses reveal that nanometer‐sized clusters provide a specific reaction environment that facilitates the balanced co‐adsorption of styrene, CO, and H thereby promoting hydroformylation. Our study highlights that a profound understanding of the optimal active structure is the key to maximizing the MA and advancing beyond simplistic atom efficiency considerations.