Aggregation of Giant Cerium-Bismuth Tungstate Clusters into a 3D Porous Framework with High Proton Conductivity

摘要

The exploration of high nuclearity molecular metal oxide clusters and their reactivity is a challenge for chemistry and materials science. Herein, we report an unprecedented giant molecular cerium-bismuth tungstate superstructure formed by self-assembly from simple metal oxide precursors in aqueous solution. The compound, {[(W14Ce6O61)-O-IV]([W3Bi6Ce3III(H2O)(3)O-14][B--BiW9O33](3))(2)}(34-) was identified by single-crystal X-ray diffraction and features 104metal centers, a relative molar mass of ca. 24000 and is ca. 3.0x2.0x1.7nm(3) in size. The cluster anion is assembled around a central {Ce-6} octahedron which is stabilized by several molecular metal oxide shells. Six trilacunary Keggin anions ([B--BiW9O33](9-)) cap the superstructure and limit its growth. In the crystal lattice, water-filled channels with diameters of ca. 0.5nm are observed, and electrochemical impedance spectroscopy shows pronounced proton conductivity even at low temperature.