Metal–Organic Cages with {SiW9Ni4} Polyoxotungstate Nodes

A tritopic, Ni-substituted Keggin cluster, {SiW9 Ni4 }, assembles with rigid dicarboxylate linkers to give rise to a set of discrete, POM2n L3n -type structures (POM={SiW9 Ni4 }) with defined interior voids. The outcome of coordination-driven self-assemblies of these polyhedral cages-from fused dimers to trigonal prisms-was found to be sensitive to bend angles of the ditopic ligands, which vary from 122° to 180°. These polyoxotungstate-based metal-organic polyhedra, when coupled with [Ru(bpy)3 ]Cl2 as a photosensitizer and triethanolamine as the electron donor, serve as highly effective catalysts for CO2 reduction, with turnover numbers up to 328 and CO selectivity as high as 96.2 %. The inner cavities of such cage structures, if functionalized or of sufficient size to encapsulate targeted guest molecules, could present a new strategy towards functional materials for potential applications.