A redox-active perylene-anthraquinone donor-acceptor conjugated microporous polymer with an unusual electron delocalization channel for photocatalytic reduction of uranium (VI) in strongly acidic solution

Abstract

Achieving photoreduction uranium with D-A type conjugated microporous polymers in strongly acidic radioactive wastewater holds great promise but is extremely challenging, as it requires proper electron transport channels. Herein, a redox-active perylene-anthraquinone D−A conjugated microporous polymer photocatalyst (ECUT-AQ) which electron-rich perylene unit as donor and electron-deficient anthraquinone (AQ) as acceptor is innovatively reported. The results clearly demonstrates that AQ with dual characteristics of electron deficiency and redox activity plays a key role in photocatalytic reduction of UO22+ to UO2. On one hand, the constructed D-A structure induces the formation of a huge built-in electric field, which enhances the intramolecular charge transfer, thus significantly broadening visible light absorption range and improving electron-hole pairs separation efficiency. On the other hand, and very significantly, the redox-active AQ acts as a matched electron transfer channel, which further accelerates the photogenerated electrons transfer from the photocatalyst to the UO22+. Consequently, the ECUT-AQ achieves 86% photoreduction UO22+ removal within two hours irradiation and obtains an impressive reduction rate constant (k = 0.015 min-1, pH=1 and T = 293.15 K). Encouragingly, the current work can enlighten a whole new direction for the subsequent cultivation of more practical metal-free photocatalysts for purification radioactive wastewater.