Tuning Extrinsic Stability of Rhodium Catalysts in Heterogeneous Hydroformylation

Understanding and mitigating metal leaching in heterogeneous catalysis are crucial for maintaining the stability and efficiency in liquid-phase hydroformylation. Here, we investigated the leaching mechanism of Rh using an ideal model catalyst, Rh1/ZnO(100), by combining density functional theory (DFT) calculations with experimental validation. Our findings reveal that Rh leaching is governed by two distinct molecular species, HRh(CO)n* and Rh(CO)n*, and exhibits pronounced temperature dependence. A volcano-shaped leaching trend was observed, peaking at 393 K, beyond which leaching decreased with increasing temperature. This behavior was also observed in other Rh-based catalysts, including Rh and Rh2P. Multiple other environmental factors, including CO and H2 partial pressures and olefin concentration, modulated Rh leaching by altering the thermodynamic and kinetic stability of these species. Through such environmental modulation, Rh leaching was effectively controlled over a wide range, from 89.8% to a negligible level. These insights provide a molecular-level understanding of Rh leaching in hydroformylation and establish a foundation for improving catalyst durability without altering the intrinsic structure, thereby achieving extrinsic stability.