Ammoniating Covalent Organic Framework (COF) for High‐Performance and Selective Extraction of Toxic and Radioactive Uranium Ions

An ideal porous adsorbent toward uranium with not only large adsorption capacity and high selectivity but also broad applicability even under rigorous conditions is highly desirable but still extremely scarce. In this work, a porous adsorbent, namely [NH₄]⁺[COF-SO₃ ^-], prepared by ammoniating a SO₃H-decorated covalent organic framework (COF) enables remarkable performance for uranium extraction. Relative to the pristine SO₃H-decorated COF (COF-SO₃H) with uranium adsorption capacity of 360 mg g^-1, the ammoniated counterpart of [NH₄]⁺[COF-SO₃ ^-] affords ultrahigh uranium uptake up to 851 mg g^-1, creating a 2.4-fold enhancement. Such a value is the highest among all reported porous adsorbents for uranium. Most importantly, a large distribution coefficient, K _d ^U, up to 9.8 × 10⁶ mL g^-1 is observed, implying extremely strong affinity toward uranium. Consequently, [NH₄]⁺[COF-SO₃ ^-] affords highly selective adsorption of uranium over a broad range of metal ions such as S_U/Cs = 821, S_U/Na = 277, and S_U/Sr = 124, making it as effective uranium adsorbent from seawater, resulting in amazing uranium adsorption capacity of 17.8 mg g^-1. Moreover, its excellent chemostability also make it an effective uranium adsorbent even under rigorous conditions (pH = 1, 8, and 3 m acidity).