Bio-Based Ca2+-Selective Supramolecular Metallohydrogels with Ultra-mechanical Responsiveness, Selective Dye Adsorption, and Recycling

Water pollution is one of the major problems that need to be solved in modern society, and there is a need to develop an effective adsorbent to purify the polluted water. In this article, three supramolecular metallohydrogels containing a three-dimensional network structure have been prepared from rosin derivatives. The supramolecular metallohydrogels have good thermal stability and maintain mechanical strength at high temperatures. Interestingly, the sodium N-(dehydroabiety1)maleamate/Ca2+ supramolecular metallohydrogels exhibit rare multi-stimulus responsiveness (mechanical vibration, temperature, pH, EDTA, etc.), especially to mechanical vibration with over 10 cycles, indicating ultra-mechanical response properties. More importantly, the unique three-dimensional network structure of the metallohydrogels can effectively adsorb cationic dyes in the wastewater. The adsorption amount and adsorption rate of this supramolecular metallohydrogels for rhodamine 6G after 48 h were at least 160.6 mg/g and 97%, respectively. The adsorption kinetic process of this metallohydrogel follows a quasi-secondary kinetic model, where the adsorption process is mainly electrostatic and weak π-π interactions. And the metallohydrogels can also be recovered by 0.5 mol/L hydrochloric acid solution desorption after adsorption of the dye. This is the first supramolecular metallohydrogel system prepared from the natural product rosin and applied to dye adsorption. This broadens the application of rosin in the field of supramolecular gel and dye adsorption and recycling.