Lowering the Kinetic Barrier via the Synergistic Catalysis of N-CNTs Supported RhP Subnanoclusters and Confined Co Nanoparticles for Olefins Hydroformylation

Abstract

Developing synergistic sites for a multistep elementary reaction is important, but challenging. Herein, the coexistence of Co nanoparticles confined inside the carbon nanotubes and RhP subnanoclusters loaded on the outside of carbon nanotube (Co@N-CNTs|RhP) is synthesized by a defect-assisted impregnation strategy. Notably, Co nanoparticles and RhP subnanoclusters have a synergistic engineering distance of 0.66 nm. The turnover frequency over Co@N-CNTs|RhP catalyst could reach 82603 h^–1 during the diisobutylene hydroformylation, 15 times higher than that of the commercial Rh homogeneous catalysts. More importantly, the obtained Co@N-CNTs|RhP achieved 25 catalytic cycles. Kinetic experiments show that the synergistic engineering of confined Co nanoparticles and RhP subnanoclusters is the key to promote the hydroformylation of diisobutylene, which reduces the activation energy to 64.6 kJ/mol. Further in situ DRIFT spectra and theoretical calculations reveal the confined Co nanoparticles modified by RhP subnanoclusters are conducive to the adsorption of H₂, CO, and diisobutylene, while the RhP subnanoclusters are responsible for the formation of aldehydes. This work provides profound insight for the construction of efficient multisite heterogeneous catalyst for long-chain olefin conversion reactions.