Two-dimensional cluster-assembled materials with properties beyond their individualities and bulks

Ultrathin two-dimensional (2D) cluster-assembled materials (CAMs) have emerged as a new class of 2D materials with fascinating structures and exceptional properties that differ from their individualities and bulks. Due to the covalent/non-covalent and cluster orbital interactions, 2D CAMs with molecular-level thickness and atomically precise structures exhibit unique electronic properties and exceptional applications. Moreover, the topological and electronic structures of CAMs can be regulated by the type of clusters and interactions between them. In this perspective, we summarize ultrathin 2D CAMs with well-defined structures constructed by noble metal clusters, polyhedral oligomeric silsesquioxane clusters, polyoxometalate clusters, and C60 clusters based on the interaction between clusters. The relationships between their electronic structures and catalytic properties are discussed from experimental and theoretical perspectives. Finally, we list the limitations and opportunities for developing ultrathin 2D CAMs. This viewpoint offers a fresh perspective on the in-depth understanding and design synthesis of ultrathin 2D cluster-based materials.