Diverse Polyoxometalate-Based Cobalt Complexes for Catalyzing Olefin Epoxidation at Room Temperature: Regulation of Active Sites by Polyoxometalate Templates

• • Co-P2W18 achieved 99% yield of 1,2-epoxycyclooctane within 3 h at room temperature using O2 as oxidant, outperforming most reported catalysts and enabling energy-efficient industrial epoxidation. • • The catalyst maintained 99% yield after 5 catalytic cycles, with FT-IR, PXRD, and XPS confirming unchanged structure and Co(II) oxidation state, indicating high stability and recyclability for continuous processes. • • The use of different POM templates (PMo12, PW12, SiW12, P2W18) allowed systematic regulation of Co(II) coordination unsaturation, directly influencing active site accessibility and catalytic performance. • • The Mukaiyama epoxidation approach with O2 and isobutyraldehyde as sacrificial reductant enables mild conditions, reducing harmful byproducts compared to traditional haloalcohol methods, aligning with green chemistry principles.