A Selenone-Functionalized Polyhedral Oligomeric Silsesquioxane for Selective Detection and Adsorption of Hg ²⁺ ions in Aqueous Solutions

Abstract

Developing novel functional polyhedral oligomeric silsesquioxane (POSS) for various applications is highly desirable. Herein we present the first example of a novel selenone-functionalized POSS (POSS-Se) by treating an imidazolium-containing POSS with selenium powder under mild condition. The structure of POSS-Se was characterized by FT-IR, ¹H NMR, ¹³C NMR, ²⁹Si NMR, and elemental analysis. Acid treatment of POSS-Se results in a hydrophilic red-orange colored solid, which is highly sensitive and selective for the detection of Hg ²⁺ ions in aqueous solutions by visually observing the color change to pale yellow, and to white. Interestingly, POSS-Se has no activity on this detection. This finding is due to the Se–Se formation by acid-treatment and subsequent coordination-induced cleavage upon the addition of Hg ²⁺ ions. The detection behavior can be precisely monitored by a “turn-on” fluorescence phenomenon with the limit of detection (LOD) of 8.48 ppb, comparable to or higher than many reported Hg ²⁺ sensors. Moreover, POSS-Se demonstrates a selective and efficient adsorption of Hg ²⁺ ions with a maximum capacity of 952 mg g ^–1. The value is higher than most reported adsorbents for Hg ²⁺ ions, typically thiol and/or thioether functional materials, indicating its promise as an efficient adsorbent for the selective removal of Hg ²⁺ ions from industrial wastewater. This work may open up new horizons for the exploration of selenium-containing functional POSS.