Building internal electric fields in porous ionic polymers for fast photocatalytic degradation of tetracycline hydrochloride

Abstract

Photocatalytic degradation holds great promise for addressing the growing threat of antibiotics residues in aquatic environments. The internal electric field (IEF) can significantly enhance the photocatalytic performance by efficient separation and rapid transfer of charge. Herein, by constructing the IEF through regulating the valence state of photosensitive group, two porous imidazolium-based ionic polymers of ID-PIP and IB-PIP are obtained for photodegradation of target antibiotics of tetracycline hydrochloride (TCH). The DFT calculations demonstrate the possibility of the intramolecular charge transfer pathway from the photosensitive pole of imidazoline to the cationic imidazonium, of which the electrostatic interaction facilitates the IEF formation. More significantly, the adsorptive enrichment further enhances the photodegradation performance. As a result, the obtained ID-PIP with a shorter charge drift distance shows a higher TCH degradation efficiency of 96% within 30 min for a 20 mg L⁻¹ TCH solution under the simulated sunlight. The superoxide radicals ˙O₂⁻ and photocatalytic oxidation h⁺ are demonstrated to be the dominant active species during the photodegradation of TCH, consequently, a possible mechanism and pathway for degradation of TCH are proposed. Regulating the valence states for the IEF construction can be a feasible way for inhibiting the rapid recombination of photogenerated electrons and holes, and shows a promising application in photodegradation of antibiotics.