Metal–Organic Cages with {SiW₉Ni₄} Polyoxotungstate Nodes

A tritopic, Ni-substituted Keggin cluster, {SiW₉Ni₄}, assembles with rigid dicarboxylate linkers to give rise to a set of discrete, POM_2nL_3n-type structures (POM={SiW₉Ni₄}) 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.