Hydrophobic Promoter‐Enhanced Tandem Catalysis for Alkene Epoxidation With H ₂ and O ₂

ABSTRACT The efficiency of tandem catalysis is fundamentally limited by the transport of transient intermediates. In the direct epoxidation of alkenes with H 2 and O 2 , in situ generated H 2 O 2 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 H 2 O 2 migration away from hydroxyl‐rich surfaces toward remote Ti sites while suppressing nonproductive decomposition. Molecular dynamics simulation studies show that the diffusion of H 2 O 2 on hydrophobic surfaces is significantly higher than on hydrophilic surfaces, as reflected experimentally by a 25% increase in tandem H 2 O 2 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 H 2 O 2 , with an outstanding H 2 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.