Robust copper-based cationic metal-organic frameworks for efficient sequestration of perrhenate/pertechnetate.

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