Polyoxoniobates with the long-sought feature of face-sharing octahedra stabilized by Te(IV): a synthetic analogue of natural minerals

Abstract

Polyoxometalates (POMs) are primarily constructed from {MO6} octahedra connected through corner-, edge-, and/or face-sharing modes, with the face-sharing being particularly rare. Silverton clusters, characterized by their face-sharing {MO6} octahedra, have been reported for Mo and W. However, Nb-based Silverton and polyoxoniobates (PONbs) with face-sharing octahedra remain unsynthesized, despite their occurrence in natural minerals. Herein, [(Nb13O42){Te3(B-α-TeNb9O33)}4] (1a) and its trivacant structure [(Nb10O36){Te3(B-α-TeNb9O33)}4] (2a) with the long-sought feature of face-sharing {NbO6} octahedra have been synthesized for the first time using a Te(IV) stabilizing strategy. In 1a, the central {Nb13O42}, consisting of six sets of face-sharing {Nb2O9} and a central Nb, is surrounded by 12 Te(IV) ions anchored on four {TeNb9O33}. Notably, the observed {Nb13O42} can be viewed as both a synthetic analogue of natural minerals and a topological isomer of the classic Silverton cluster. Moreover, small angle X-ray scattering data analysis confirms the formation of the targeted PONb cluster and determines the co-existed key cluster species and their proportion during the assembly or disassembly process. Further computational studies indicate that the highly charged Te(IV) ions play a key role in the stabilization of face-sharing PONbs. The photocatalytic hydrogen evolution activityof 1 has also been investigated. This work not only bridges the gap between natural and synthetic PONbs, but also deepens our understanding for the formation of face-sharing octahedra.