Two Birds with One Stone Strategy: Selective Uranium Extraction and Detection by a Fluorescent Covalent Organic Framework with High-Affinity Binding Sites

Abstract

Uranium as a crucial ingredient for nuclear reaction, has provided a risk to the environment and human safety due to its chemical toxicity and radioactivity. Monitoring and management of uranium contamination are of great significance for the rational utilization of uranium resources and the maintenance of the environment. Herein, we fabricated a novel fluorescent covalent organic framework (COF-AO) with multifunctional groups via facile Schiff base condensation and amidoximation reactions for selective uranium detection and extraction simultaneously. COF-AO featured a short adsorption equilibrium time of 45 min and a high saturated adsorption capacity of 229.9 mg/g, leading to a fast adsorption rate (5.1 mg g-1 min-1). Meanwhile, COF-AO demonstrated excellent uranium selectivity and an ultra-low fluorescence detection limit (14.6 nM). Furthermore, COF-AO displayed exceptional adsorption capacities in different natural water samples. Notably, the uranium extraction capacity of COF-AO from natural seawater was 16.0 mg/g in 28 days, indicating a high utilization rate of the COF-AO active sites in low-concentration solutions. Our work provides an effective strategy for designing fluorescent COF materials aimed at uranium detection and capture, which may be expanded to the detection and extraction of other pollutants through the rational design of specific ligands.

Keywords: covalent organic framework, amidoxime groups, uranium extraction, fluorescent detection, adsorption