"Frozen" π- π stacking on perylene diimide molecules induces oxygen vacancies synergistic activation of persulfate towards degradation of tetracycline

Oxygen vacancy-rich self-assembled perylene diimide (OV-SA-PDI) supramolecules were prepared via freezedrying, which froze the molecular backbone by retaining n-n stacking to induce additional OVs. The OVs content on OV-SA-PDI (1.956 x 10(13) spins center dot mm(-3)) was 1.9 times that of SA-PDI (1.029 x 10(13) spins center dot mm(-3)) with vacuum drying. The photocatalytic performance of OV-SA-PDI was demonstrated to be excellent in activating persulfate (PS) to degrade tetracycline (TC), achieving a remarkable degradation efficiency of 94.6% in 60 min under visible light (Vis). Mechanistic studies revealed a synergistic interaction among OV-SA-PDI, PS, and Vis to produce an abundance of active species. Vis activated a small portion of PS to produce center dot OH and SO4 center dot-, whereas the photogenerated electrons generated by OV-SA-PDI directly cleaved the O-O bond to produce abundant SO4 center dot-. Furthermore, the OVs acted as an electron trap to promote carrier separation and produced 10.0 mu M O-1(2) within 12 min. The active species were determined to decompose TC into low-toxicity products with lower molecular weights (m/z = 352, 340, and 227). This study presented a novel approach to the introduction of OVs into organic semiconductors and offered a mechanistic analysis of the synergistic relationship between defective organic semiconductors and sulfate radical-based advanced oxidation processes for wastewater treatment.