Improving Photogenerated Carrier Separation via Receptive Fused-Ring Acceptor Strategy for Photocatalytic Removal of U(VI)

Abstract In response to the demand for treating uranium-containing wastewater, photocatalytic U(VI) removal technology has attracted considerable attention due to its green and sustainable characteristics. Organic polymer photocatalysts offer advantages such as tunable light absorption ranges and band structures, and have been extensively studied; however, their insufficient photogenerated carrier separation efficiency severely limits photocatalytic performance. In this study, using phthalocyanine as the donor unit and anhydrides with different conjugation extents (pyromellitic dianhydride (PMDA), 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA), and biphenyltetracarboxylic dianhydride (BPDA)) as acceptor units, a series of phthalocyanine-based polyimide porous polymers were designed and synthesized via imidization reactions. The results show that the porous polymer NTDA-PC with a naphthalimide fused-ring acceptor significantly enhances intramolecular polarization, thereby improving photogenerated carrier separation efficiency. Experiments and DFT calculations indicate that NTDA-PC, containing the naphthalene fused ring, exhibits the largest dipole moment (1.954 D) and the most negative conduction band potential. Under visible light irradiation, the removal rate of U(VI) reaches 95.6%. This study reveals the intrinsic mechanism by which the fused-ring structure optimizes photocatalytic performance through enhanced intramolecular charge transfer, providing a new idea for designing efficient organic photocatalysts.