An atomically dispersed Rh catalyst on nitrogen-doped silica for hydroformylation of sterically hindered diisobutylene

Developing ligand-free heterogeneous catalysts capable of efficient and selective hydroformylation of sterically hindered alkenes remains a challenge. In this work, we report a stable and highly efficient ligand-free heterogeneous catalyst comprising atomically dispersed Rh sites anchored on N-doped SiO 2 . The N-doped SiO 2 support was synthesized through a sol-gel method followed by high-temperature calcination under an inert atmosphere, endowing it with a large surface area, hierarchical pores, and tunable nitrogen content. This support facilitates the atomic dispersion and stabilization of Rh sites via strong Rh-N bond coordination. The morphological structure and local environment of single-Rh sites was comprehensively characterization by means of X-ray diffraction (XRD), N 2 sorption isotherm, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), high-angle angular dark field scanning transmission electron microscopy (HAADF-STEM), X-ray photoelectron spectroscopy (XPS), CO in-situ diffuse reflectance infrared Fourier transform spectroscopy (CO-DRIFTS), and X-ray absorption spectroscopy (XAS). The resulting catalyst exhibits outstanding catalytic performance and excellent selectivity in the hydroformylation of diisobutylene and also shows broad applicability to various other alkenes, including α-olefins, internal alkenes, and aromatic alkenes. Furthermore, it exhibits remarkable stability and recyclability, maintaining its catalytic performance without degradation upon successive cycles. Comparative studies further confirm the essential role of N-doping in achieving high activity and stability.