Construction of Unsaturated Coordinated Cu-Metal–Organic Frameworks for Iodine Adsorption

Radioactive iodine from nuclear energy poses serious risks to aquatic environments, driving the need for efficient adsorbents for nuclear wastewater treatment. Metal-organic frameworks (MOFs) have shown promise in iodine capture due to their tunable pores and functional surfaces. In this work, three copper-triazolate-based MOFs with unsaturated coordination (CuCl₂(TRZ) for <b>1</b>, Cu₄OCl₃(TRZ)₃ for <b>2</b>, Cu₃HOCl₂(TRZ)₃·2.4H₂O for <b>3</b>; TRZ = 1,2,4-triazole) were synthesized and characterized. Compound <b>1</b> exhibits a one-dimensional chain structure, compound <b>2</b> exhibits a two-dimensional layer, and compound <b>3</b> exhibits a three-dimensional cage architecture featuring a 10 Å molecular cage with two kinds of window sizes at 5 and 7.8 Å, respectively. In the evaluation of iodine adsorption in aqueous solution, compound <b>3</b> demonstrated outstanding iodine adsorption, removing 95% of iodine from aqueous solution within 200 min and maintaining high efficiency and structural stability over four adsorption-desorption cycles. This study offers a new strategy for designing radioactive iodine adsorbents and enhances the understanding of interactions between unsaturated metal sites and iodine species.