Modulating Propane Dehydrogenation over Silicalite-1-Encapsulated CoO x Catalysts via Surface Silanol Engineering for Surface Barrier Control

Zeolite-encapsulated metal catalysts offer significant potential by stabilizing subnanometric metal clusters within confined micropores; however, diffusion limitations arising from structural defects often hinder accessibility to active sites and catalytic performance. This study addresses silanol-induced diffusion limitations in zeolite-encapsulated CoOx catalysts using a tetraethyl orthosilicate (TEOS)-mediated surface-silanol-healing strategy. Temperature-programmed experiments, in situ spectroscopy, and theoretical studies collectively demonstrate that TEOS treatment reduces surface silanol groups, thereby weakening van der Waals and hydrogen-bonding interactions between propane and silanol nests, while simultaneously expanding external pore entrances. These two factors mitigate propane trapping and enhance accessibility to the encapsulated cobalt sites. Additionally, X-ray absorption spectroscopy and theoretical studies reveal that the elimination of surface silanol groups leads to electron-deficient cobalt sites, which lower the activation barrier of propane C–H bond cleavage. In propane dehydrogenation (PDH) reactions, the combined diffusion and electronic enhancements enable the TEOS-modified CoOx-S1–0.3 catalyst to achieve a propylene production rate of 86.6 mmol·gcat–1·h–1 at 600 °C under a pure propane feed, representing a 1.6-fold improvement over the parent CoOx-S1 and rivaling state-of-the-art Co-based PDH catalysts. This work provides fundamental insights into silanol-mediated molecular diffusion and electronic effects in catalysis.