Mechanochemical synthesis of reticular β-cyclodextrin polyurethanes for the decontamination of phenolic micropollutants

Abstract

Cyclodextrin-based porous polymers have become a kind of promising adsorbents for the remediation of wastewater by virtue of their sustainability and economic potential. The acquisition of aforementioned adsorbents commonly requires elaborate preparation procedures which involve organic solvent, catalyst, inert atmosphere, or long reaction time. Herein, a facile and scalable solid-state mechanochemical approach was developed to afford reticular β-cyclodextrin polyurethanes (CDPUs) in a short time (2 h) without any organic solvents and catalysts at ambient conditions. Various diisocyanates can be used as coupling agents to link β-CD molecules into CDPUs relying on the driving force of ball milling. CDPUs-based composites can be also successfully synthesized via a “one-pot” mechanochemical reaction. The afforded CDPUs exhibit nearly the same physiochemical characteristics as those synthesized in solvents or with the assistance of catalyst. CDPUs have numerous accessible active adsorption sites, including β-CD cavities, bridging urethane groups, dangling amino groups, and aromatic rings. Owing to the accessible porosities and abundant adsorption sites, CDPUs exhibited rapid adsorption rate and high adsorption capacity towards phenolic micropollutants. CDPUs can maintain adsorption efficiency in a wide pH range, ionic strength, and humic acid. There is no significant decrease of adsorption efficiency for more than eight regeneration cycles, indicating their suitability for practical water treatment. This solid-state mechanochemical synthesis method for reticular CD-based polymers paves a new insight into green preparation of adsorbents and their sustainable use for the practical remediation of micropollutant wastewater.