Rigid crosslink improves the surface area and porosity of β-cyclodextrin beads for enhanced adsorption of flavonoids

Many reported β-cyclodextrin (β-CD) polymers have poor flavonoid adsorption performance due to their low surface area and porosity resulting from the compact stack of the β-CD molecules crosslinked by flexible crosslinkers. Here, we propose a rigid crosslink strategy that uses phytic acid (PA) having rigid cyclic group as crosslinkers, achieving a high-surface-area (61.42-140.23 m²/g) and porous β-CD beads. The improved surface area and porosity are attributed to the rigid cyclic groups in PA, which expand the network structure of β-CD polymers. Benefitting from the advantages, the optimized PA-crosslinked β-CD (PA-β-CD) beads have an over tenfold increased adsorption amount and an threefold increased diffusivity for rutin compared with traditional non-porous β-CD beads crosslinked by epichlorohydrin. Moreover, dynamic adsorption experiments reveal that PA-β-CD beads are able to treat about 1100 mL of rutin solution (0.05 mg/mL), over 5 times higher than that of the non-porous β-CD beads (200 mL). These results demonstrate the promise of PA-β-CD beads for rapid and high-capacity adsorption of rutin.