Redox-active conjugated microporous polymer with favourable six-membered chelate ring for enhanced uranium extraction from highly acidic environments

Abstract

Achieving extraction of strategic nuclide uranium with robust conjugated microporous polymers (CMPs) from highly acidic radioactive wastewater holds significant promise but is extremely challenging, as it needs powerful adsorbents with high selectivity, high capacity, and excellent stability. Herein, a redox-active conjugated microporous polymer (DHBA-HAH) with favourable six-membered chelate ring is innovatively reported by integrating hexaaminobenzene trihydrochloride (HAH) and 2,5-dihydroxy-1,4-benzenedicarboxaldehyde (DHBA). The unique structure of DHBA-HAH has all the features of being well tailored as a promising adsorbent for synergistic specific ligand chelation and efficient redox mineralization, and thus exhibits high uranium extraction capacity even under highly acidic conditions (0.59 mmol g−1, pH 2.0). Both experimental results and theoretical calculations confirm that the efficient extraction of uranium onto DHBA-HAH is a synergistic process of chemisorption and reduction, and both imidazole and hydroxyl functional groups play a decisive role in seizing uranium by forming a favorable six-membered chelate ring. This work presents a promising approach for the construction of high-performance uranium adsorbents with redox activity and opens up new pathways for the application of functionalized CMPs in eliminating radioactive contamination from strongly acidic environments.