Palladium(II) Modulation Enhances the Water Stability and Aqueous <sup>99</sup>TcO<sub>4</sub><sup>–</sup>/ReO<sub>4</sub><sup>–</sup> Removal Performance of Metal–Organic Frameworks
Xinyue Zhang, Xinyi Yang, Yinghui Xie, Xiaolu Liu, Mengjie Hao, Hui Yang, Geoffrey I. N. Waterhouse, Shengqian Ma, Xiangke Wang
Abstract
Improving the water stability of metal–organic frameworks (MOFs) is essential for their use in water pollution treatment and environmental remediation, though it remains technically challenging. Herein, we report a novel cationic MOF constructed with [Th 6 O 4 (OH) 4 (COO) 12 ] units and [CoN 4 ·Cl 2 ] units possessing a ftw-type topology (denoted as 1–Th-Co ). 1–Th-Co itself exhibited poor water stability but excellent stability following a palladium(II) modulation strategy. Experimental studies reveal that Co(II) ions in 1–Th-Co were replaced by Pd(II) ions through cation exchange in N,N-diethylformamide (yielding 1–Th-Pd ). The planar PdN 4 units in 1–Th-Pd were responsible for improving the water stability of the framework. As a result, 1–Th-Pd offered excellent stability, fast adsorption kinetics, and high removal ratios for 99 TcO 4 – and ReO 4 – (as a 99 TcO 4 – surrogate) in contaminated water. When used in packed columns, 1–Th-Pd can dynamically capture ReO 4 – from groundwater. This work provides a new avenue for improving the water stability of MOFs, offering new vistas for the decontamination of aqueous solutions containing 99 TcO 4 – and ReO 4 – .