Structural hierarchies in cyclodextrin-derived biocompatible frameworks: From hydrogen-bonded assemblies to metal-organic architectures.

Cyclodextrins (CDs), cyclic oligosaccharides derived from starch, possess a toroidal architecture and densely functionalized hydroxyl rims that enable directional intermolecular interactions in the solid state. Beyond their well-established host-guest chemistry, CDs have recently emerged as versatile building blocks for the construction of ordered framework materials, including hydrogen-bonded crystalline assemblies and metal-organic frameworks (CD-MOFs) formed with biocompatible metal ions. Despite growing interest, these systems are predominantly discussed from synthetic or application-driven perspectives, while a unified structural framework that connects their hierarchical organization remains lacking. This review presents a comprehensive structural and crystallographic analysis of cyclodextrin-derived biocompatible frameworks. Emphasis is placed on molecular geometry, solid-state packing motifs, hydroxyl coordination modes, symmetry characteristics, and topology evolution across hydrogen-bonded and metal-coordinated architectures. By comparatively examining dimensionality, interaction strength, and structural order, we propose a conceptual structural classification framework that relates discrete inclusion complexes (0D), hydrogen-bonded assemblies (1D/2D), and periodic metal-coordinated frameworks (3D) according to interaction hierarchy, dimensional connectivity, and structural organization. Particular attention is devoted to structure-stability relationships, including hydrolytic robustness, solvent-mediated rearrangements, and metal-dependent rigidity, which collectively govern framework integrity. Through this carbohydrate-centred crystal engineering perspective, this review delineates fundamental design principles and highlights opportunities for the rational development of next-generation cyclodextrin-based porous materials.