Highly Selective and Irreversible Anion-Exchange in Two-Dimensional Bis(terpyridine)metal(II) Polymer Thin Films

Bis(terpyridine)metal(II) polymers are functional coordination polymers characterized by cationic backbones containing exchangeable anions inside. Anion-exchange with functional anions can alter or create new properties through interactions between the cationic polymer backbones and anions. Although considerable research has focused on developing functional materials, the fundamental properties of anion-exchange remain unclear. Investigation into the anions applicable for anion-exchange reactions and those selectively incorporated into the polymers is fundamental for understanding the nature of molecular interactions and developing functional anion-exchange materials for further applications, such as anion separation and wastewater remediation membranes. Here, we report the applicability of the anion-exchange reactions of two-dimensional (2D) bis(terpyridine)metal(II) polymers and their excellent selectivity for perrhenate and organic dye anions. Organic dye anions were specifically exchanged, enabling the detection of organic dyes in artificial seawater. Moreover, the anion-exchange was electrochemically irreversible, as demonstrated by the minimal leaching of organic dye anions during redox cycling. These results underscore the potential of 2D bis(terpyridine)metal(II) polymer thin films as highly selective and robust anion-exchange and anion-storage membranes.