Synthesis and structure of anhydrous Zn2EDTA metal-organic framework

Abstract

Metal-organic frameworks (MOFs) have gained significant attention in materials science due to their unique properties such as high surface area, porosity, and tunable electrochemical characteristics. Among various MOFs, Zn-EDTA compounds have shown potential for electrochemical applications. This paper presents the accident discovery and investigation of a new anhydrous Zn2(EDTA) MOF and its electrochemical performance as an electrode material for aqueous sodium-ion batteries. The study systematically explores the influence of pH and stoichiometric ratio on the formation of Zn2(EDTA) and Zn2(EDTA)(H2O) MOFs using X-ray diffraction analysis. The single-phase anhydrous Zn2(EDTA) compound is synthesized, offering advantages over the hydrated form regarding stability and electrochemical activity. Zn2(EDTA) structure is characterized, revealing a 3D network of channels suitable for interstitial ionic mobility. Thermogravimetric analysis (TGA) is used to study the thermal behavior of Zn2(EDTA), showing two weight loss steps attributed to water and carbon dioxide elimination during decomposition. Electrochemical measurements using cyclic voltammetry in alkaline and neutral electrolytes demonstrate the electrochemical activity of Zn2(EDTA) as an anode material for aqueous sodium-ion batteries. The results suggest that the electrochemical process in both electrolytes involves the reversible stripping/deposition of zinc ions. The anhydrous Zn2(EDTA) MOF exhibits higher peak current intensities and more positive potentials than the hydrated form. The study provides valuable insights for synthesizing and controlling Zn2(EDTA) MOF formation, opening the prospects for searching for new structures in considered-to-be-studied phase regions.