Reversible Local Coordination Relaxation of Lattice-Embedded Rh Single Sites Enables Efficient and Durable Propene Hydroformylation

Abstract

Efficient atomically dispersed Rh catalysts for propene hydroformylation require active sites that combine coordination flexibility during turnover with resistance to leaching and aggregation. Here we report Rh1@ZnO, in which Rh single sites are incorporated into cation vacancies in the ZnO lattice to couple coordination adaptability with lattice confinement. In propene hydroformylation, Rh1@ZnO affords C4 aldehydes with 100% chemoselectivity at a turnover frequency of 1.6 × 105 h–1 and reaches a cumulative turnover number of 2.2 × 105 while showing robust stability, outperforming surface-bound Rh1/ZnO and a homogeneous Rh benchmark. Kinetic analysis shows that Rh1@ZnO remains in a CO-inhibited regime but shifts the rate-controlling region toward steps involving H2. DFT calculations reveal that the embedded Rh site undergoes reversible local coordination relaxation, whereby CO coordination relaxes specific Rh–O lattice constraints and relieves local geometric strain during CO insertion, lowering the acylation barrier. Following C–C bond formation, the Rh site relaxes back to restore Rh–O lattice anchoring. These results establish lattice embedding coupled with reversible local coordination relaxation as a design principle for adaptive yet persistent Rh single sites in heterogeneous hydroformylation.