{Nb288O768(OH)48(CO3)12}: A Macromolecular Polyoxometalate with Close to 300 Niobium Atoms

A protein-sized (ca. 4.2x4.2x3.6nm(3)) non-biologically derived molecule {Nb288O768(OH)(48)(CO3)(12)} (Nb-288) containing up to 288 niobium atoms has been obtained, which is by far the largest and the highest nuclearity polyoxoniobate (PONb). Particularly, in terms of metal nuclearity number, Nb-288 is the second largest cluster so far reported in classic polyoxometalate chemistry (V, Mo, W, Nb, and Ta). Nb-288 can be described as a giant windmill-like cluster aggregate of six nanoscale high-nuclearity PONb units {Nb47O128(OH)(6)(CO3)(2)} (Nb-47) joined together by six additional Nb ions. Interestingly, the 47-nuclearity Nb-47 units generated insitu can be isolated and bridged by copper complexes to form an inorganic-organic hybrid three-dimensional PONb framework, which exhibits effective catalytic activity for hydrolyzing nerve agent simulant of dimethyl methylphosphonate. The unique Nb-47 cluster also provides a new type of topology to very limited family of Nb-O clusters.