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

Two novel transition-metal-cluster-containing arsenicniobates, [Cu(en)(2)(H2O)][Cu(en)(2)](4){AsNb9V7O44}center dot 8H(2)O (1) and [Cu(en)(2)(H2O)][Cu(en)(2)](4)H{AsNb8V8O44}center dot 11H(2)O (2), were designed and synthesized by reaction of K7HNb6O19 center dot 13H(2)O, Cu(Ac)(2)center dot 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 {V-8} 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.