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(H 24 C 12 O 6 )] 3 [K(H 24 C 12 O 6 )(CH 3 CN)][SiMo 12 O 40 ] ( 1) based on the Keggin-type polyanion [SiMo 12 O 40 ] 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 η 10 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. A supramolecular assembly built from Keggin-type polyoxometalate and [18]crown-6 ether building block exhibit a spindle-like supramolecular host-guest structure with high HER activity. • A supramolecular complex contains Keggin-type polyanion and [18]crown-6 units. • This complex is an efficient electrocatalyst for the hydrogen evolution reaction. • The high structural integrity is also maintained after 2000 cycles.