Engineered synthesis of hierarchical porous organic polymers for visible light and natural sunlight induced rapid degradation of azo, thiazine and fluorescein based dyes in a unique mechanistic pathway

Abstract

We report the synthesis of two hierarchical organic polymeric networks for extremely efficient visible light and natural sunlight induced degradation of versatile wastewater organic contaminants under different simulated physical conditions following two distinct mechanistic protocols concomitantly. Tailored synthesis of the polymers by effective utilization of high-dilution-technique leads to extremely low density and hence high dispersibility of the networks featuring impressive surface area and gas adsorption abilities. UV–vis absorption spectra of both composites showed a significant coverage of the natural solar irradiance spectrum. A synthetic control over energy-state potentials allowed the materials to demonstrate an unprecedented dye pollutant degradation capability following two mechanisms, the conventional catalyst sensitized pathway, and a substrate-sensitized secondary pathway, simultaneously. Furthermore, the catalyst exhibited a unique time-dependent, sequential, in-situ alteration in substrate selectivity when subjected to a mixed-component pollutant probe. The photocatalytic ability retained essentially unaltered at outdoor condition under natural sunlight illumination as well as after five successive iterations. This work provides an experimental proof of the concept that strategic synthesis can be employed to control the physical and chemical properties of polymeric networks including their energy-states to achieve novel photo-responsive behaviour, and utilize them as green, sustainable environmentally benign and industrially viable heterogeneous catalysts.