Multicomponent covalent organic frameworks: design strategies and synergistic functions.

Covalent organic frameworks (COFs) are crystalline porous polymers with modular architectures and long-range order, offering exceptional tunability in pore structure and functionality. While conventional COFs are typically constructed from one or two types of monomers, recent advances have led to the emergence of multicomponent COFs (MC-COFs), which integrate three or more distinct building blocks within a single lattice. This strategy enables the precise spatial arrangement of diverse geometries, connectivity, and functionalities, imparting synergistic complexity beyond the reach of single- or binary-component systems. In this perspective, we present a comprehensive overview of MC-COF chemistry, organised around five representative construction strategies: isostructural and heterostructural copolymerization, multicomponent topological design, multicomponent reactions, and pore partitioning strategies. We further highlight how these frameworks enable emergent functions in catalysis, alkane isomer separation, chemical sensing, and radiotherapy through rational control of both periodic backbone structure and local chemical environments. Despite these advances, challenges persist in structural characterization, expanding the scope of dynamic linkages, and achieving predictive design of emergent properties. Looking forward, the integration of dynamic covalent chemistry, topological programming, and machine learning-driven design is expected to unlock the full potential of MC-COFs as next-generation multifunctional materials.