β-Cyclodextrin-based composites for wastewater treatment: Recent advances, challenges, and future perspectives

β-Cyclodextrin (β-CD) is a versatile supramolecular host whose hydrophobic cavity and chemically accessible exterior enable selective interactions with diverse contaminants. However, the limited recoverability, structural stability, and reusability of free β-CD restrict its direct application in aqueous treatment systems. Immobilization, crosslinking, and hybridization with polymers, biomass, carbonaceous materials, magnetic particles, metal-organic and covalent organic frameworks, photocatalysts, and membrane substrates improve porosity, mechanical stability, separation, and pollutant-removal performance. This review critically examines advances in β-CD-based composites for removing pharmaceuticals, dyes, pesticides, heavy metals, PFAS, and other emerging contaminants from water and wastewater reported between 2021 and 2026. Attention is given to structure-performance relationships, host-guest inclusion and complementary interfacial interactions, adsorption, photocatalytic degradation, membrane separation, regeneration, and performance in complex water matrices. Emerging computational approaches, including density functional theory, molecular dynamics, molecular docking, and artificial intelligence, are also discussed in relation to molecular-level interpretation, performance prediction, and process optimization. Finally, the review evaluates the principal barriers to practical implementation, including non-standardized testing, limited continuous-flow and real-wastewater validation, component leaching, regeneration-related waste, synthesis cost, scalability, and insufficient techno-economic and life-cycle assessment. This integrated perspective provides guides the development of more effective, durable, and practically viable β-CD-based water-treatment materials.