Cucurbit[6]uril-heteropoly acids self-assemblies for adsorption and photocatalytic synergistic removal of diquat and paraquat in water

The synergistic removal of organic pollutants by adsorption and photocatalysis can be achieved by adsorption of enriched pollutants, followed by photocatalytic degradation to decompose the pollutants into non-toxic substances. In this work, a category of adsorption-photocatalytic bifunctional composite materials Q[6]-HPAs have been developed through the self-assembly of cucurbit[6]uril (Q[6]) and heteropoly acids (HPAs) like phosphomolybdic acid (PMA), phosphotungstic acid (PTA) and silicotungstic acid (STA). These composites exhibit enhanced surface area, structural stability, and extended light absorption into the visible range. Notably, Q[6]-HPAs have surface charge properties that attract cations and an energy band structure suitable for the generation of reactive oxygen species, thus possessing the potential for efficient adsorption and photodegradation of cationic pesticides. Among which, Q[6]-PMA and Q[6]-PTA removed over 95 % of diquat and paraquat through sequential adsorption and photodegradation. Electrostatic attraction drives the adsorption process, and ·O 2 − and ·OH radicals detected via Electron Spin Resonance (ESR) are the key to photodegradation. Ultimately, Liquid Chromatography-Mass Spectrometer (LC-MS) analysis revealed potential degradation intermediates and products, and toxicity analysis was performed.