Dipyrromethanes grafting on a poly (vinyl alcohol) nanofibrous mat as naked-eye sensor/receptor for detection and removal of ionic pollutants from water

A user-friendly and reusable molecular sensor for detection and removal of ionic pollutants from water through the grafting of dipyrromethanes on poly (vinyl alcohol) (PVA) nanofibrous mats has been developed. The synthesis of dipyrrolylperezone was driven from pyrrole via condensation of dipyrromethanes and perezone, while the grafting to the PVA nanofibers surface was achieved using boronic ester bond formation under friendly reaction conditions, namely without the use of catalysts, under no inert atmosphere, at room temperature and preserving the nanofibers 3D structure. UV/Vis analysis demonstrates the efficient recognition of different anions, with predilection towards fluoride by chemisorption without thermal activation, the use of calcium or aluminum oxides, or pH modification of water samples. Grafted nanofibers exhibit an evident color change from indigo to gray after fluoride ions exposition, demonstrating the potential use of this composite as a naked-eye sensor for fluoride ions with a maximum adsorption capacity of 50 mg/g, amount considerably superior to previous reports using different adsorbent materials. After 50 h of adsorption, the grafted PVA nanofibers exhibits gradual desorption, which can lead to the use of this material in several adsorption-desorption cycles.