A Water-Stable Cationic Metal-Organic Framework as a Dual Adsorbent of Oxoanion Pollutants

A three-dimensional water-stable cationic metal-organic framework (MOF) pillared by a neutral ligand and with Ni-II metal nodes has been synthesized employing a rational design approach. Owing to the ordered arrangement of the uncoordinated tetrahedral sulfate (SO42-) ions in the channels, the compound has been employed for aqueous-phase ion-exchange applications. The compound exhibits rapid and colorimetric aqueous-phase capture of environmentally toxic oxoanions (with similar geometries) in a selective manner. This system is the first example of a MOF-based system which absorbs both dichromate (Cr2O72-) and permanganate (MnO4-) ions, with the latter acting as a model for the radioactive contaminant pertechnetate (TcO4-).