Engineering Surface Hydroxyls of Zeolites to Suppress Sintering of Confined PtSn Clusters for Stable Propane Dehydrogenation

Propane dehydrogenation (PDH) is an attractive on‐purpose route for propylene production, yet catalyst deactivation under harsh hydrogen‐free conditions remains a major challenge. Although zeolite confinement can stabilize PtSn active sites, gradual sintering during long‐term operation at high temperatures persists. Here we developed an HF‐free post‐synthetic silylation strategy using hexamethyldisilazane (HMDS) to selectively passivate surface silanols in silicalite‐1 zeolites to enhance the stability of encapsulated Pt 1 Sn 1 alloy clusters. The resulting catalyst maintains stable PDH performance during a directly measured 2160 h on‐stream test under hydrogen‐free and pure C 3 H 8 conditions at 550°C. Post‐reaction characterizations demonstrate that the enhanced stability originates from the effective suppression of PtSn sintering under reaction conditions, with the PtSn alloy clusters retaining an average size of only 1.0 ± 0.2 nm after 2160 h on stream. This remarkable sintering resistance is attributed to the passivation of external‐surface and pore‐mouth silanols, which eliminates the hydroxyl anchoring and nucleation sites that would otherwise capture outward‐migrating PtSn species and promote their nucleation and coalescence on the external zeolite surface. These findings identify post‐synthetic hydroxyl passivation as a practical strategy to reinforce zeolite confinement and stabilize sub‐nanometer bimetallic clusters for high‐temperature dehydrogenation.