Some aspects of MOF-74 (Zn2DOBDC) metal–organic framework formation using THF as the solvent†

Abstract

This study investigates the synthesis of zinc-based metal–organic frameworks (MOFs) using tetrahydrofuran (THF) as a solvent, focusing on forming distinct phases as models for potential battery applications. Contrary to expectations, the synthesis produced three unique phases: alpha, beta, and Zn-MOF-74a, instead of the anticipated Zn-MOF-74 structure. Comprehensive structural analysis using X-ray diffraction, infrared spectroscopy, and thermogravimetric analysis (TGA) revealed distinct crystallographic features for each phase, particularly the novel Zn-MOF-74a phase, which exhibits a heart-shaped pore structure and differs from the classic hexagonal MOF-74. The study also includes the first structural determination of the dry H₄DOBDC precursor, providing crucial insights for future research. The results demonstrate the significant impact of solvent choice, temperature, and pH on MOF phase formation and offer potential applications in energy storage and catalysis, especially for larger molecules. Further investigation is required to fully understand the electrochemical properties and phase stability of the newly identified Zn-MOF-74a and beta phases.