Contrastive study on β-cyclodextrin polymers resulted from different cavity-modifying molecules as efficient bi-functional adsorbents
Introduction
β-Cyclodextrin (β-CD) is a unique cyclic oligosaccharide consisting of seven α-linked d-glucopyranose units [1]. The hydrophobic inner cavity of β-CD can accommodate a variety of organic substrates through host-guest inclusion [[2], [3], [4], [5]]. In addition, the hydroxyl groups lining the outer surface of β-CD are easy to be decorated by functional groups [6,7]. Therefore, the combination of these two features has allowed the preparation of a number of bi-functional β-CDs which have found a wide range of practical applications from biotherapy [8,9] to catalysis [10], especially in simultaneous removal of metal ions and organic pollutants from contaminated water [11,12]. If β-CDs are going to serve as adsorbents, a crucial factor to be considered is their capacity. However, existing β-CD-based adsorbents still suffer from the limited dimension of β-CD's inherent cavity which seriously restrains the adsorption efficiency of organic matters.
Modification by molecules with long linear chains or aromatic rings on the rim of the cavitand (a container-shaped host molecule [13]) is known to create a larger hydrophobic “pocket” for encapsulating more organic guests [[14], [15], [16]]. Inspired by this concept, lately, we constructed a bi-functional adsorbent in which the aromatic imidazole molecules were attached standing on the secondary rim of β-CD to expand the capacity of the β-CD cavity for organic dyes; meanwhile, the nitrogen atoms of the imidazole can bind heavy metal ions [17]. Besides, very few other literatures have also reported that having both the hydrophobic space of modifying group and the cavity structure of β-CD, β-CD derivatives can provide extremely rich host surroundings for loading guest molecules [18]. However, to the best of our knowledge, the role of the modifying group's structure on the inclusion property of β-CD for organic guest has not yet been discussed.
To address the foregoing knowledge gap, in this paper, the secondary rim of β-CD was alkylated by three different N-containing groups, amine with straight chain, imidazole with rigid five-membered ring and pyridine with rigid six-membered ring, to give vase-like β-CD derivatives (Scheme 1). The inclusion properties of the β-CD derivatives were compared in DMSO using Rhodamine B (RB), a typical dye contaminant with biological toxicity, as organic matter, considering its suitable molecular dimension and distinguishable characteristic absorption spectrum (Table S1). Then, the corresponding cavity-expanded adsorbents were obtained by the polymerization of vinylated β-CD and different vinyl monomers of amine, imidazole and pyridine, respectively (Scheme 2). Eventually, the removal of the resultant bi-functional adsorbents for RB and cadmium ion (Cd(II)) were investigated.
Section snippets
Materials
β-Cyclodextrin (β-CD) purchased from Aladdin Chemistry Co. Ltd. (Shanghai, China) was recrystallized three times from deionized water and dried at 70 °C for 48 h before use. tert-Butylchlorodimethylsilane (TBDMS-Cl, 97%), methacrylic anhydride (MA, 94%), 4-(dimethylamino)-pyridine (DMAP, 99%), Cysteamine (CA, 95%), allylamine hydrochloride (AA, 98%), 1-vinylimidazole (VI, 99%), 2-Vinylpyridine (VP, 97%), 2,2′-azobis (2-methylpropionitrile) (AIBN), cadmium nitrate tetrahydrate and Rhodamine B
Synthesis and characterization of β-CD derivatives
To obtain a β-CD derivative in which only the secondary rim was functionalized by N-containing groups, all the seven primary hydroxy groups in the first rim of β-CD were firstly protected by TBDMS moieties, which was confirmed by the 1H NMR spectrum of CDSi (Fig. S1). Then the CDSi was further reacted with methacrylic anhydride or acrylic anhydride to produce vinylated β-CD precursors MCD or ACD, in which 10/14 secondary hydroxy groups of β-CD were substituted by alkenyl groups according to the
Conclusions
In summary, we constructed different β-CD derivatives bearing linear or aromatic N-containing groups, made contrastive studies on their inclusion capacities as well as the adsorption properties of their corresponding polymeric adsorbents. With the help of the rigid ring expanded space, ACD-MI and ACD-PY exhibited significantly enhanced inclusion abilities toward RB as compared with MCD-CA and unmodified MCD. ACD-PY possessed the maximum cavity which can encapsulate even three guest RB
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgment
Financial support from the National Natural Science Foundation of China (Grant Nos. 51603129 and 51721091) is acknowledged.
References (43)
Review: a history of cyclodextrins
Chem. Rev.
(2014)- et al.
Synthesis of β-cyclodextrin-based electrospun nanofiber membranes for highly efficient adsorption and separation of methylene blue
ACS Appl. Mater. Inter.
(2015) - et al.
Cyclodextrin-functionalized hierarchical porous architectures for high-throughput capture and release of organic pollutants from wastewater
Chem. Mater.
(2012) - et al.
Rapid removal of organic micropollutants from water by a porous β-cyclodextrin polymer
Nature
(2015) - et al.
Selective and regenerable surface based on β-cyclodextrin for low-density lipoprotein adsorption
Langmuir
(2018) - et al.
Selective binding of bile salts by β-cyclodextrin derivatives with appended quinolyl arms
Chin. Chem. Lett.
(2013) - et al.
Highly functionalized β-cyclodextrins by solid-supported synthesis
Chem. Eur. J.
(2018) - et al.
Bifunctional conjugates comprising β-cyclodextrin, polyethylenimine, and 5-fluoro-2′-deoxyuridine for drug delivery and gene transfer
Bioconjug. Chem.
(2010) - et al.
Cyclodextrin nanoparticles bearing 8-hydroxyquinoline ligands as multifunctional biomaterials
Chem. Eur. J.
(2017) - et al.
β-Cyclodextrin-modified hybrid magnetic nanoparticles for catalysis and adsorption
J. Mater. Chem.
(2011)
Environmentally friendly β-cyclodextrin–ionic liquid polyurethane-modified magnetic sorbent for the removal of PFOA, PFOS, and Cr (VI) from water
ACS Sustain. Chem. Eng.
EDTA-cross-linked β-cyclodextrin: an environmentally friendly bifunctional adsorbent for simultaneous adsorption of metals and cationic dyes
Environ. Sci. Technol.
Cavitands: organic hosts with enforced cavities
Science
Functionalized deep-cavity cavitands
J. Org. Chem
Structure and binding properties of water-soluble cavitands and capsules
Chem. Soc. Rev.
Deep cavitand vesicles–multicompartmental hosts
Chem. Commun.
β-Cyclodextrin-crosslinked polymeric adsorbent for simultaneous removal and stepwise recovery of organic dyes and heavy metal ions: fabrication, performance and mechanisms
Chem. Eng. J.
Spectrophotometric study of selective binding behaviors of dye molecules by pyridine-and bipyridine-modified β-cyclodextrin derivatives with a functional tether in aqueous solution
J. Phys. Chem. B
Synthesis, self-assembly, and drug-loading capacity of well-defined cyclodextrin-centered drug-conjugated amphiphilic A14B7 miktoarm star copolymers based on poly(ε-caprolactone) and poly(ethylene glycol)
Biomacromolecules
Jellyfish-shaped amphiphilic dendrimers: synthesis and formation of extremely uniform aggregates
Macromolecules
Synthesis of bimodal methacrylic acid oligomers by template polymerization
Macromolecules
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