Encapsulating Co⁰ Sites in Hollow Silicalite-1 for Highly Efficient and Stable Propane Dehydrogenation

Abstract

Cobalt-based catalysts have recently emerged as a promising frontier in propane dehydrogenation (PDH) research. Despite their potential, achieving selective suppression of nonselective metallic cobalt (Co 0 ) species remains a critical challenge. In this work, we report a hollow zeolite architecture (Co@S-1-Hol) that effectively addresses this dilemma through spatial confinement engineering. Through depth-profiling XPS analysis complemented by H 2 -TPR and UV–vis spectroscopy characterization, we demonstrate a unique cobalt valence distribution where metallic Co 0 species are preferentially encapsulated within hollow cavities, while Co 2+ ions remain atomically dispersed in the zeolite shell matrix. DFT calculations coupled with kinetic studies reveal that the cavity-confined Co 0 clusters serve as the predominant active centers for C–H bond activation. Notably, STEM-EDS mapping and TGA uncover a self-regulating mechanism: the hierarchical hollow structure facilitates rapid and selective coking on nonselective surface sites during initial reaction phases, effectively passivating undesirable side reactions while preserving intrinsic catalytic activity. This spatial engineering strategy endows the Co@S-1-Hol catalyst with superior PDH performance compared to the conventional impregnated Co/S-1 catalyst, exhibiting an enhanced C 3 H 6 formation rate (21.6 mmol g cat –1 h –1, equivalent to 1330 mmol g Co –1 h –1 ) coupled with a significantly reduced deactivation rate. Under optimized conditions at 550 °C, the catalyst achieves 35% propane conversion with 95% propylene selectivity, representing state-of-the-art performance among reported cobalt-based PDH catalysts. This work not only provides fundamental insights into cobalt active site engineering but also establishes a paradigm for designing spatially modulated zeolite catalysts in alkane dehydrogenation applications.