Tunable amine-functionalized silsesquioxane-based hybrid networks for efficient removal of heavy metal ions and selective adsorption of anionic dyes

Abstract

By changing the acid scavenger from NEt3 to NaHCO3, two novel kinds of amine-functionalized silsesquioxane (SQ)-based hybrid networks (PCS-N1, PCS-N2) with different molar ratios of –NH2/NH– and NH3+ were successfully prepared via nucleophilic substitution of octa(3-chloropropyl) silsesquioxane (SQ-Cl8) with triaminoethylamine, respectively. Both networks were fully characterized by FTIR, SEM, TEM, XPS, BET, TGA, WCA and solid-state 13C and 29Si NMR spectra. No porosity was observed for these two hybrid networks; however, they exhibited good thermal stability and hydrophilicity. To our surprise, they strongly adsorb heavy metal ions due to ion exchange and coordination. The adsorption capacities for Ag+ and Hg2+ are as high as 358 ± 6 and 721 ± 5 mg g−1, respectively. More interestingly, PCS-N1 can selectively adsorb the anionic dye methyl orange with a capacity as high as 731 ± 13 mg g−1. Furthermore, they regenerate easily and offer potential for water purification. This work provides a new approach to prepare and tune amine-functionalized SQ-based networks for multipurpose.