In Situ Confining Single-Atom Rh Species on Oxygen-Vacancy-Enriched ZnO Polyhedron Frames for Enhanced Hydroformylation

The structural design and regulation of a single-atom catalyst for enhancing the hydroformylation of olefins is extremely important but still challenging. Herein, we propose an “adsorption–oxidation” strategy to achieve controllable synthesis of ZnO polyhedron frames with abundant oxygen vacancy defects (O_v) anchored single-atom Rh catalyst (Rh/ZnO-O_v) derived in situ from ZIF-8. The as-constructed Rh/ZnO-O_v catalyst exhibits high catalytic activity, with 1-hexene conversion up to 99%, heptanal selectivity of 97.2%, and heptanal space time yield of 26270 μmol·g_cat^–1·h^–1, which is the highest value reported up to now. It also exhibits good cyclic stability and wide substrate generality for at least 18 substrate olefins. In situ diffuse reflectance infrared Fourier transform spectroscopy, X-ray absorption spectroscopy, and theoretical calculations further discover a synergistic hydroformylation mechanism that 1-hexene is coadsorbed and activated at Rh–Zn dual sites, the induction of oxygen vacancy results in enriching electrons at single-atom Rh sites, not only greatly promotes the dissociation and activation of H₂ but also reduces the space steric hindrance and rate-determining energy barrier of CO insertion process. This work reveals a design concept by regulating support vacancy defects of a single-atom Rh catalyst for the enhancement of olefin hydroformylation.