Molecular engineering of biomimetic donor-acceptor conjugated microporous polymers with full-spectrum response and an unusual electronic shuttle for enhanced uranium(VI) photoreduction

Abstract

Realizing an efficient photochemical uranium reduction process using metal-free conjugated polymers is highly desirable, but is extremely challenging, as it requires a broad photo-response range and efficient electron transmission channels. Herein, three novel full-spectrum (200 ≤ λ ≤ 800 nm) responsive biomimetic donor–acceptor conjugated microporous polymers (CMPs) were successfully constructed to photoreduce uranium through a molecular engineering strategy. The optical band gap and built-in electric field of the CMPs were conveniently optimized via various quinone-containing acceptors. Furthermore, the quinone-containing block exhibited outstanding redox activity, which could serve as an unique electron shuttle to rapidly transfer electrons. Consequently, ECUT-TQ with 2,6-dibromobenzo[1,2-b:4,5-b']dithiophene-4,8-dione block exhibits a narrow band gap as low as 1.70 eV, a stronger built-in electric field and more efficient charge separation, achieving 97.4% photocatalytic U(VI) reduction efficiency with a photoreaction rate constant of 0.057 min−1. The exhaustive mechanism analysis illustrates that the dominant active species in the photocatalytic process where U(VI) is reduced to UO2 are photoelectrons and •O2– radicals. This work provides a novel approach for designing high-performance green biomimetic photocatalysts for removing radioactive pollution.