Unravelling structure sensitivity in heterogeneous hydroformylation of aldehyde over Rh

Abstract

Delineating the geometrical and electronic structure of supported metal is significant for developing heterogeneous hydroformylation catalysts. This study modulated the configuration and charge distribution of Rh to construct highly efficient Rh@SiO2 catalysts for formaldehyde hydroformylation. The structure sensitivity of Rh species reveals that single-atom Rh can solely catalyze hydrogenation, while Rh aggregates are active for hydroformylation. Moderate Rh nanoclusters (0.98 nm) offered the highest TOF (183 h−1) and selectivity (90.8 %) of glycolaldehyde. Electronic effects demonstrate that synergy between Rh0 and Rh+ sites on the cluster is essential to enhancing the reaction. The Rh0 species function as the adsorption/activation sites for H2 and formaldehyde, and the Rh+ sites act to coordinate PPh3 and CO to form Rhδ+(CO)x(PPh3)y active species. This study provides new insights into the design of heterogeneous catalysts and guidance for understanding the structure sensitivity of active metal and hydroformylation mechanism.