Extended structural materials composed of transition-metal-substituted arsenicniobates and their photocatalytic activity

Abstract

Two novel transition-metal-cluster-containing arsenicniobates, [Cu(en)₂(H₂O)][Cu(en)₂]₄{AsNb₉V₇O₄₄}·8H₂O (1) and [Cu(en)₂(H₂O)][Cu(en)₂]₄H{AsNb₈V₈O₄₄}·11H₂O (2), were designed and synthesized by reaction of K₇HNb₆O₁₉·13H₂O, Cu(Ac)₂·H₂O, Na₂VO₃, As₂O₃, and en molecules. Structural analysis revealed that compounds 1 and 2 contained the structural similar [AsNb₉V₇O₄₄]¹⁰⁻ and [AsNb₈V₈O₄₄]¹¹⁻ polyoxoanions, respectively, which are obtained by inserting a {NbV₇} or {V₈} ring into the tetravacant polyoxoniobate [AsNb₈O₃₆]²⁷⁻. Polyoxoanions in 1 and 2 could be regarded as the Keggin polyoxoniobates [AsNb₉V₃O₄₀] or [AsNb₈V₄O₄₀] capped by four VO₅ units. The high-nuclear vanadium clusters were firstly introduced into the Keggin-type arsenicniobates. Further, polyoxoanions in 1 and 2 were connected by the metal–organic linkers into the 1D chain and 2D layer-like framework, respectively. Photocatalytic studies indicated that compounds 1 and 2 are both active for photocatalytic degradation of organic dye in aqueous solution, and they are stable and easily separated from the photocatalytic system for reuse as well.