CO₂ Dynamics in a Flexible Metal-Organic Framework with Gate-Opening Phenomenon

As a promising porous material for CO₂ adsorption and storage, elastic layer-structured metal-organic framework-11 (ELM-11) has attracted significant attention owing to its distinct gate-opening phenomenon. There is a sharp increase in CO₂ uptake once reaching the gate-opening threshold pressure. To better understand this gate-opening mechanism, we investigated its transition process from the perspective of CO₂ dynamics and its interaction with the framework via variable-temperature ¹³C solid-state nuclear magnetic resonance spectroscopy. Our findings revealed that during the gate-opening process, CO₂ is initially strongly adsorbed at one site when the gate only slightly opens, while two distinct types of CO₂ molecules exist when the gate fully opens. ¹¹B, ¹³C, and ¹⁹F magic-angle spinning NMR, in conjunction with in-situ XANES experiments, were also conducted to probe the location of adsorption sites.