Mo₈O₂₆⁴⁻ based organic polyoxomolybdate salts of general formula [Hmim]₄Mo₈O₂₆ (Hmim = 1-hexyl-3-methylimidazolium), [Dhmim]₄Mo₈O₂₆ (Dhmim = 1,2-dimethyl-3-hexylimidazolium) and [Hpy]₄Mo₈O₂₆·H₂O (Hpy = 1-hexylpyridinium) have been prepared and characterized. These compounds were applied as catalysts for olefin epoxidation using hydrogen peroxide (H₂O₂) as oxidant in CH₃CN. The polyoxomolybdate salts exhibit excellent catalytic performance and are also self-separating, a great advantage for catalyst recycling. The catalysts can be reused for at least 10 runs without significant loss of activity.