Hydrophobic Promoter-Enhanced Tandem Catalysis for Alkene Epoxidation With H₂ and O₂

The efficiency of tandem catalysis is fundamentally limited by the transport of transient intermediates. In the direct epoxidation of alkenes with H₂ and O₂, in situ generated H₂O₂ rapidly decomposes during diffusion, rendering most Ti active sites kinetically inaccessible and imposing a long-standing performance ceiling. Here, we overcome this limitation by engineering hydrophobic transport channels via physical integration of a hydrophobic polymer with bifunctional Au/TS-1 catalysts. This microenvironment accelerates H₂O₂ migration away from hydroxyl-rich surfaces toward remote Ti sites while suppressing nonproductive decomposition. Molecular dynamics simulation studies show that the diffusion of H₂O₂ on hydrophobic surfaces is significantly higher than on hydrophilic surfaces, as reflected experimentally by a 25% increase in tandem H₂O₂ efficiency. Moreover, the hydrophobic channels promote rapid desorption of epoxide products, suppressing ring-opening reactions and carbonaceous accumulation, resulting in a stable ∼90% epoxide selectivity over 200 h. This strategy exhibits broad generality across Au-Ti bifunctional catalysts for alkene epoxidation using in situ generated H₂O₂, with an outstanding H₂ utilization efficiency of 73.5% achieved over the Au/TS-1-B catalyst under the identical standard reaction conditions employed throughout this work. This work establishes diffusion control of metastable surface species as a principle for breaking intrinsic transport-decomposition trade-offs in tandem catalysis.