Cluster-based materials: design and applications

Nanoclusters constitute an interdisciplinary field bridging chemistry, physics, biology, medicine, and materials science. Its broad appeal is fueled not only by the expectation that one can gain a fundamental understanding of how the structure and properties of matter evolve one atom at a time, but also, how they could be designed, with specific size and composition, to mimic the chemistry of atoms in the periodic table. Referred to as superatoms, these clusters can function as modular building units for a new generation of cluster-assembled materials, provided they retain their structural identity upon integration into extended architectures. C₆₀ fullerene is an example of such a cluster. Clusters, protected by ligands or supported on a substrate, can also form cluster-assembled materials with unique properties. In contrast, atoms in an existing crystal can be replaced by corresponding superatoms to form "cluster-based materials". While several perspectives and review articles have been published to highlight the unique structure- and composition-specific properties of isolated clusters and cluster-assembled materials, it is during the past few years that attention has been focused on cluster-based materials. This review focuses on the recent developments in the design, synthesis, and applications of clusters with uncommon properties and highlights their potential as building blocks of cluster-based materials. The topics include isolated clusters enabling unusual reactions, their role in the design and synthesis of materials such as super-electrides, solid state electrolytes with fast ionic conductivity and stable interfaces, moisture resistant hybrid perovskite solar cells, thermoelectric materials with high figure of merit, and a new class of single-superatom catalysts. Also outlined are the challenges and opportunities going forward.