Recent Advances in Hierarchical Porous Organic Cages: From Discrete Structure to Integrated Assemblies

In nature, functional complexity often arises from multiscale assembly across hierarchical levels. Inspired by this principle, porous organic cages (POCs), featuring well-defined intrinsic cavities, solution processability, and high chemical tunability, have emerged as versatile molecular platforms for multiscale materials engineering. This concept highlights representative examples in which POCs act as modular, shape-persistent building blocks within hierarchical assemblies, and elucidates how their confined cavities, solubility, and structural modularity enable the rational construction of sophisticated materials systems. At the molecular level, POCs function as enzyme-mimetic hosts that encapsulate and stabilize metal clusters (MCs) within discrete cavities. Benefiting from their structural tunability, POCs can also serve as bulky building blocks for integration into extended frameworks (e.g., COFs, MOFs, and supramolecular frameworks), as well as for the construction of nested host-in-host architectures and well-ordered multiscale crystalline materials. Such hierarchical assembly integrates structural advantages across length scales by preserving intrinsic porosity while introducing efficient mass and electron transport pathways, thereby enabling enhanced separation and catalytic performance. By translating bioinspired design principles into synthetic materials, these systems offer a programmable route towards multifunctional platforms.