Functionalized Porous Aromatic Framework for Efficient Uranium Adsorption from Aqueous Solutions.

We demonstrate the successful functionalization of a porous aromatic framework for uranium extraction from water as exemplified by grafting PAF-1 with the uranyl chelating amidoxime group. The resultant amidoxime-functionalized PAF-1 (PAF-1-CH2AO) exhibits a high uranium uptake capacity of over 300 mg g-1 and effectively reduces the uranyl concentration from 4.1 ppm to less than 1.0 ppb in aqueous solutions within 90 min, well below the acceptable limit of 30 ppb set by the US Environmental Protection Agency. The local coordination environment of uranium in PAF-1-CH2AO is revealed by X-ray absorption fine structure spectroscopic studies, which suggest the cooperative binding between UO22+ and adjacent amidoxime species.