Chemoselective reduction of quinoline over Rh–C60 nanocatalysts

Abstract

The design and engineering of heterogeneous nanocatalysts that are both highly active and selective for hydrogenation reactions constitute a crucial challenge. In that context, herein a series of Rh–C₆₀ nanocatalysts have been synthesized via the decomposition of an organometallic rhodium complex in the presence of fullerene C₆₀ under a H₂ atmosphere. Rhodium atomically dispersed or rhodium nanoparticles on Rh–C₆₀ spherical fulleride particles were produced by tuning the Rh/C₆₀ molar ratio. Significant charge transfer between rhodium and C₆₀ was evidenced through Raman and X-ray photoelectron spectroscopy, which indicates electron-deficient Rh species. The resulting heterostructured nanomaterials were applied successfully in the catalytic hydrogenation of quinoline, exhibiting excellent activity and producing selectively the partially hydrogenated product, 1,2,3,4-tetrahydroquinoline. Density functional theory (DFT) calculations show that the hydride coverage of the Rh NPs plays a key role in the adsorption modes of quinoline and 1,2,3,4-tetrahydroquinoline on the surface of the NPs, and that these adsorption modes are modulated by the presence of fullerene C₆₀, thus affecting the activity and selectivity obtained with this rhodium based catalyst.