Siderophore-inspired chelator hijacks uranium from aqueous medium

Alexander S Ivanov,John Arnold,Ilja Popovs,Sheng Dai,Vyacheslav S Bryantsev,Linfeng Rao,Briana Aguila,Zhicheng Zhang,Santa Jansone-Popova,Shengqian Ma,Richard T Mayes,Qi Sun,Bernard F Parker

doi:10.1038/s41467-019-08758-1

Abstract

Over millennia, nature has evolved an ability to selectively recognize and sequester specific metal ions by employing a wide variety of supramolecular chelators. Iron-specific molecular carriers—siderophores—are noteworthy for their structural elegance, while exhibiting some of the strongest and most selective binding towards a specific metal ion. Development of simple uranyl (UO22+) recognition motifs possessing siderophore-like selectivity, however, presents a challenge. Herein we report a comprehensive theoretical, crystallographic and spectroscopic studies on the UO22+ binding with a non-toxic siderophore-inspired chelator, 2,6-bis[hydroxy(methyl)amino]-4-morpholino-1,3,5-triazine (H2BHT). The optimal pKa values and structural preorganization endow H2BHT with one of the highest uranyl binding affinity and selectivity among molecular chelators. The results of small-molecule standards are validated by a proof-of-principle development of the H2BHT-functionalized polymeric adsorbent material that affords high uranium uptake capacity even in the presence of competing vanadium (V) ions in aqueous medium.

Highlights

Over millennia, nature has evolved an ability to selectively recognize and sequester specific metal ions by employing a wide variety of supramolecular chelators
Having established the most stable structures of the uranyl complexes in solution, we proceeded to calculate the key thermodynamic parameters, which were used in our computational protocol[34,35] for predicting stability constants. This procedure enables us to carry out in silico prediction of log β for uranyl complexes with the H2BHT ligand and compare the obtained values with those of uranyl systems with the imide-dioxime (H3IDO) functionality, which is reputedly responsible for the extraction of uranium from seawater using the current generation of amidoxime-derived sorbents[4]
With the H2BHT polymer adsorbent in hand, we investigated the uranium (VI) binding by this material using a variety of spectroscopic techniques, including X-ray photoelectron spectroscopy (XPS) and elemental distribution mapping via energydispersive X-ray (EDX) spectroscopy analysis

Summary

Introduction

Nature has evolved an ability to selectively recognize and sequester specific metal ions by employing a wide variety of supramolecular chelators. We report a comprehensive computational and experimental study on uranium binding by H2BHT in solution and in solid state, starting from small-molecule investigations and ending up with a developed polymeric adsorbent material.

Results

Conclusion