Recent advances in polyoxometalate-covalent organic framework composites: rational design, structural modulation, and application perspectives.

Polyoxometalates (POMs) are structurally well-defined and physicochemically tunable anionic metal-oxygen clusters with broad potential in catalysis, energy, and biomedicine. However, their practical application is often limited by aggregation, poor solubility, and insufficient stability. To address these issues, a confinement strategy has been developed, using covalent organic frameworks (COFs) as ideal host matrices due to their high specific surface area, ordered pores, and structural designability. By encapsulating, covalently linking, or dynamically assembling POMs within COFs, the resulting composites effectively inhibit POMs' migration and aggregation, improve stability and dispersibility, and leverage synergistic effects in catalysis, energy storage, and environmental remediation. This review outlines the interaction mechanisms in POM-COF composites, followed by a systematic summary of their structural characterization, design principles, and synthesis strategies. It subsequently summarizes application progress in relevant fields as well as current challenges and future prospects, thereby providing guidance for the rational design and practical application of these catalysts.