Dynamics of Linkers in Metal–Organic Framework Glasses

作者：Alexander E. Khudozhitkov, Naoki Ogiwara, Masaki Donoshita, Hirokazu Kobayashi, Alexander G. Stepanov, Daniil I. Kolokolov, Hiroshi Kitagawa · 发表于：Journal of the American Chemical Society · 年份：2024 · DOI：10.1021/jacs.3c13156 · 被引用次数：29 · 研究领域：Metal-Organic Frameworks: Synthesis and Applications、Lanthanide and Transition Metal Complexes、Advanced NMR Techniques and Applications

Metal–organic framework (MOF) glasses have emerged as a new class of organic–inorganic hybrid glass materials. Considerable efforts have been devoted to unraveling the macroscopic dynamics of MOF glasses by studying their rheological behavior; however, their microscopic dynamics remain unclear. In this work, we studied the effect of vitrification on linker dynamics in ZIF-62 by solid-state 2 H nuclear magnetic resonance (NMR) spectroscopy. 2 H NMR relaxation analysis provided a detailed picture of the mobility of the ZIF-62 linkers, including local restricted librations and a large-amplitude twist; these details were verified by molecular dynamics. A comparison of ZIF-62 crystals and glasses revealed that vitrification does not drastically affect the fast individual flipping motions with large-amplitude twists, whereas it facilitates slow cooperative large-amplitude twist motions with a decrease in the activation barrier. These observations support the findings of previous studies, indicating that glassy ZIF-62 retains permanent porosity and that short-range disorder exists in the alignment of ligands because of distortion of the coordination angle.