Guanidinium-based ionic porous organic polymer as a propitious material for inordinate uptake of permanganate ions from water

Abstract

Metal-based oxo anions are major contributors towards freshwater contamination. Bioaccumulation and biomagnification through food chains pose threats to the sustainability of the environment. We introduced a novel guanidinium-based cationic porous organic polymer (POP) designed for the rapid and efficient removal of permanganate via electrostatic interaction between a cationic polymer and the anionic pollutant permanganate. The polymer had exceptionally high uptake of 9.4 g g⁻¹ for permanganate ions. This is far superior than that reported in the literature. The material exhibited rapid sorption kinetics and a removal efficiency of 100%. Moreover, selectivity, pH and recyclability experiments were evaluated to confirm the practical applicability of the material. In addition, we employed two distinct strategies for the synthesis of a guanidinium-based cationic POP: solvothermal and mechanochemical. Both polymers were characterized using CPMAS ¹³C NMR, FT-IR, powder-XRD, N₂ sorption analysis, TGA and FE-SEM. The physicochemical properties of both polymers were compared. The polymers showed 100% removal efficiency for permanganate from aqueous solution. The mechanochemical method did not involve energy consumption, long-time duration or involvement of toxic organic solvents, so the process was environmentally benign and economically viable. The solvothermal method consumed more energy and time. Hence, the mechanochemical method was found to be more efficient, cost-effective and environmentally sustainable for the fabrication of a highly efficient guanidinium-based polymeric adsorbent material for permanganate removal from aqueous solutions.