Engineering Intersection Cobalt Sites in Silicalite-1 for Enhanced Ethane Dehydrogenation

Abstract Zeolite-supported single-atom catalysts have demonstrated notable performance in alkane dehydrogenation reactions, yet the precise location of active sites and their regulatory role in catalytic behavior remain poorly understood. Herein, the combined theoretical and experimental study aims to elucidate the location-dependent ethane dehydrogenation (EDH) performance of framework single-atom Co2+ in silicalite-1 (S1, MFI topology) zeolites. Radial distribution function and projected density of states analysis reveal that intersection Co2+ sites (exemplified by the T9-Co-S1 model) facilitate preactivation of adsorbed C2H6*, thereby lowering the activation barrier of ethane C–H bond dissociation as a rate-determining step. Metadynamics and kinetic Monte Carlo simulations further reveal that for intersection Co2+ sites, C2H5* activation proceeds along with H* coupling for simultaneous C2H4 and H2 production. This direct pathway enables the rapid recovery of the active center’s electronic state on intersection Co2+ sites, thereby facilitating subsequent catalytic cycles. This contrasts with the indirect pathway at straight and sinusoidal Co2+ sites, where additional H* coupling steps are required after C2H4* desorption. The decreased ethane activation barrier and unique direct pathway for C2H4/H2 formation enhance EDH activity on intersection Co2+ sites, which is experimentally validated across a series of Co-S1 catalysts with varying intersection Co2+ contents. The as-designed intersection-rich β-Co-S1 achieves near-equilibrium ethane conversion and promising ethylene productivity compared to state-of-the-art Co-based EDH systems. Moreover, a three-site model was established to predict catalytic activity by integrating site-specific kMC-simulated TOFs and experimentally quantified Co2+ distributions, which provides a predictive framework for location-dependent zeolite catalysis.