Robust Copper-based Cationic Metal-Organic Frameworks for Efficient Sequestration of Perrhenate/Pertechnetate

Abstract

Recent studies have extensively reported the use of cationic metal-organic frameworks (MOFs) for capturing perrhenate/pertechnetate (ReO4−/99TcO4−) from waste water. Despite the high sorption efficiency of some materials, their stability in strong acidic and alkaline environments remains inadequate, which hinders their further application in nuclear waste post-processing. Herein, we construct two different copper-based cationic metal-organic frameworks (ZJU-X16, ZJU-X17) with excellent resistance to strong acids and alkalis. Notably, ZJU-X16 can remove 68.6% and 68.5% of ReO4− at pH 1 and 13, respectively. And ZJU-X17 can maintain its crystalline structure even in the 15 M NaOH solution. Additionally, profiting from one-dimensional channels and exchangeable anions, ZJU-X16 could also demonstrate significant sorption ability for removing ReO4− in neutral aqueous solutions. The sorption mechanism is elucidated through scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR), and density functional theory (DFT) calculations, confirming the successful ReO4− anion-exchange within the frameworks of ZJU-X16 and ZJU-X17 and the superior ReO4− sorption selectivity of ZJU-X16. This work represents an applied instance of constructing acid and alkali-resistant MOF materials for the sequestration of perrhenate/pertechnetate.