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

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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.

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