A crown ether supramolecular host-guest complex with Keggin polyoxometalate: Synthesis, crystal structure and electrocatalytic performance for hydrogen evolution reaction

A new crown ether–polyoxometalate assembly [K(H24C12O6)]3[K(H24C12O6)(CH3CN)][SiMo12O40] (1) based on the Keggin-type polyanion [SiMo12O40]4− was successfully synthesized through one-pot strategy in acetonitrile solution. The polyanion is coordinated to two [K([18]-crown-6)]+ supramolecular cations via crown–K–O(POM) coordinate-covalent bonds, leading to the formation of a spindle-shaped discrete structure. Complex 1 exhibited good hydrogen evolution reaction (HER) activity in an acidic medium. Moreover, a small overpotential η10 of 120 mV and a Tafel slope of 112 mV dec−1 were obtained. This crown ether–polyoxometalate hybrid electrocatalyst also presented excellent HER stability even after 2000 cycles of operation.