Enhancing anion conductivity in a highly alkali-stable eta topologic Cu(I) framework via strong electrostatic repulsion

Abstract

Metal-organic frameworks (MOFs) based on anion exchange membranes (AEMs) have garnered considerable interest, particularly for their potential to enhance ion conductivity by pre-introducing anions into MOFs. This approach is recognized as straightforward and effective for improving ion conductivity. However, developing high-performance AEMs is limited by the inherent instability and low resistance of MOFs. This study presents a novel 1,3,5-triazine μ₃-bridged neutral Cu(I) framework, designated SXU-120 (where SXU represents Shanxi University). This framework is synthesized using melamine, a widely available industrial product, as the starting material, achieving a high space-time yield exceeding 1.1 kg m⁻³ day⁻¹. The organic ligands and metal ions in SXU-120 are 3-connected, forming a rare eta topology with the point symbol 8³. SXU-120 exhibits exceptional stability, even in a 10 M KOH solution, due to its high density of uncoordinated–NH₂ and carbonyl groups. Furthermore, the framework’s unique one-dimensional channels, characterized by their electronegativity, interact electrostatically with OH⁻ ions, thereby accelerating OH⁻ ion transfer along these channels. Consequently, the OH⁻ conductivity of this material reaches an impressive 0.49 S cm⁻¹ at 90 °C under full humidity for 100 h, representing the highest OH⁻ conductivity reported for MOF-based conductors to date. These properties make SXU-120 a promising candidate for efficient AEM materials in next generation industrial applications.