Metal Oxocluster-Based Organic-Inorganic Hybrid Materials: From Design Principles to Applications

The structural, compositional, and morphological versatility of organic-inorganic hybrid materials, deriving from the virtually infinite combinations of both organic and inorganic building blocks, their mutual molar ratios, and kinds of interactions (e.g., covalent bonds and van der Waals interactions), makes this wide class of materials particularly appealing for many application fields. Among hybrid materials, particularly relevant are those involving metal oxocluster-reinforced polymers, where polynuclear metal oxoclusters based on M-O-M bonds are used to cross-link macromolecular backbones, endowing them with unusual structural and functional properties. In this Review, we provide an updated and critical overview of the most recent literature dealing with the synthesis and applications of metal oxocluster-based organic-inorganic hybrid materials. Starting from a concise survey of organically modified metal oxoclusters and their structural variability, we also shortly survey their use as inorganic building blocks for metal-organic frameworks (MOFs) as well as vitrimers. In a further section, we discuss the main routes to embed them into a macromolecular matrix, organized by taking into account the polymerization mechanism (i.e., thermo- or photoactivated, in bulk/in solvent, in miniemulsion droplets). Eventually, an updated overview of the main applications of metal oxocluster-reinforced polymers, with a specific focus on catalytic applications, is provided.