Contrastive study on β-cyclodextrin polymers resulted from different cavity-modifying molecules as efficient bi-functional adsorbents

Abstract

The adsorption capacity of existing β-CD-based adsorbents is generally restrained by the limited dimension of β-CD's inherent cavity. To find an effective way to expand the inclusion/adsorption capacity of β-CD, a series of N-containing groups, amine with straight chain, imidazole with rigid five-membered ring and pyridine with rigid six-membered ring, are firstly utilized to alkylate the secondary rim of β-CD through the thiol-Michael addition. The capsulation ability of the resultant β-CD derivatives are compared and the β-CD derivatives appended with aromatic imidazole or pyridine provide extremely rich host surroundings for loading Rhodamine B (RB), which is identified by the 1H NMR titration and UV–Vis spectroscopy. The bi-functional adsorbents correlative to those β-CD derivatives are then synthesized by the polymerization of vinylated β-CD and the corresponding vinyl N-containing monomers, and applied to remove RB and Cd (II) from the aqueous condition. Governed by multiple factors such as porosity, surface charge and binding affinity, the imidazole modified β-CD adsorbent revealed the best adsorption efficiency for organic dyes and metal ions, in both single- and bi-component solutions. Our work provides effective strategy and reliable basis for the design and fabrication of β-CD-based materials with high capacity and multi-functionality.