Effective photocatalytic and bifunctional electrocatalytic materials based on Keggin arsenomolybdates and different transition metal capped assemblies

Abstract

Three novel Keggin arsenomolybdates with transition metal modifying caps, (Hbimb)(H₂bimb)[AsMo^VI₈V^V₄Co₂O₄₀] (1), (Hbimb)₂(H₂bimb)_0.5[AsMo^VI₈V^V₄Cu₂O₄₀]·1.5H₂O (2), and [Cu^I(imi)₂][{Cu^I(imi)₂}₄{AsMo^V₆V^VI₆O₄₀(V^IV₂O₂)}] (3) (bimb = 1,4-bis(imidazol-l-yl)butane; imi = imidazole), were obtained via altering the solution pH and the organic ligands in the reaction system, and were characterized via routine techniques. Compounds 1 and 2 are tetra-vanadium substituted {AsMo^VI₈V^V₄O₄₀} clusters capped by two Co²⁺ or Cu²⁺ cations at two symmetrical pit positions of two opposite {Mo₄O₁₈} tetramers, and these represent the first tetra-vanadium substituted bi-cobalt(II)/copper(II) capped assemblies. The basic unit of compound 3 is one hexa-electron-reduced Keggin polyoxoanion {AsMo^V₆Mo^VI₆O₄₀} capped by two {VO₅} units at the same positions. The adjacent basic units were bonded together via the square binuclear linker {Cu₂(imi)₄O₂} to yield an infinite 1D cap-to-cap chain, which was further aggregated together in A–B–A–B mode via a pair of {Cu(1)(imi)₂} linkers, forming an unique 2D layer. Compounds 1–3 show bifunctional electrocatalytic character and effective photocatalytic performance toward the degradation of typical dyes under UV irradiation.