Dynamic imidazolium phosphate@titanium dioxide ionogels as environmental pollutant removers

Abstract

Phosphate-containing ionic liquids display interesting inherent properties including versatile chemical reactivity, thermal and hydrolytic stability and biological response. This contribution focuses on synthesizing diverse imidazolium dialkylphosphates through a simple method involving N-quaternization of 1-alkylimidazole with trialkylphosphate. The use of these building-blocks during sol–gel polymerization of titanium alkoxide affords novel imidazolium phosphate@TiO₂ hybrid ionogels. The highest affinity of phosphate towards titanium dioxide results in covalent functionalization of the two phases through stable P–O–Ti bridges, without compromising the molecular dynamic of the embedded ionic liquids. The cationic moiety can be fully exchanged as illustrated using Na⁺ and NH₄⁺ providing access to ionomaterials with adjustable properties. The beneficial effect of the as-prepared dynamic hybrid ionogels was clearly demonstrated by their superior efficiency in removing representative cationic dyes, pharmaceutical pollutants, and metal ions compared to unmodified, native TiO₂.