Adsorption of anionic dyes from water by thermostable supramolecular hydrogel

Abstract

A supramolecular hydrogel was successfully constructed by the noncovalent association of cucurbit[8]uril (CB[8]) with a tetraphenylethylene (TPE) derivative bearing four monocharged viologens (TPE-4Q). Due to the attractive photophysical behaviours of TPE and its rigid complexation with CB[8], the obtained hydrogel emits bright orange fluorescence and is highly thermostable even at 200 °C. Rheological analyses and microscopic investigations jointly confirm that the supramolecular hydrogel possesses good rheological properties and well-organised lamellar structures. Significantly, the assembly/disassembly process of this supramolecular hydrogel can be efficiently modulated by several external stimuli, including pH, mechanical force and competitive guests. Moreover, as investigated by UV/Vis and fluorescence titrations, this two-dimensional self-assembly can specifically adsorb π-conjugated anionic dyes in water with high adsorption efficiency, mainly through the π-stacking interaction with TPE backbones and the electrostatic interaction with monocharged viologen sites.

Keywords:

• Supramolecular hydrogel
• stimuli-responsiveness
• cucurbituril
• tetraphenylethylene