One-stone-two-birds: high-density single-site cobalt in hierarchical zeolite boosts aerobic styrene epoxidation

Abstract

The catalytic efficiency of single-component cobalt catalysts (featuring exclusively Co-based active sites) for styrene epoxidation is significantly constrained by mass-transport limitations inherent to the micropores of conventional supports. To overcome this, we devised a one-stone-two-birds strategy for synthesizing hierarchical CoSAPO-34 using a core–shell ZIF-67@SiO₂ composite as a combined Co/Si source and template. This approach simultaneously creates (i) atomically dispersed, high-loading Co(II) sites within the framework and (ii) a hierarchical pore architecture (micro/meso/macro). The introduced meso/macropores dramatically enhance reactant accessibility to the active sites. This synergistic integration yields exceptional performance in aerobic styrene epoxidation, achieving 95.8% conversion with 70.0% selectivity toward styrene oxide, corresponding to a 67.1% yield in only 4 h at 90 °C. The catalytic performance is highly prominent, placing it at a superior level among the monometallic catalysts reported to date for styrene epoxidation, especially given the significantly shorter reaction time required to achieve such high efficiency. This strategy provides a novel blueprint for designing efficient catalysts demanding maximized active-site accessibility.