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

As a promising porous material for CO 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 CO uptake once reaching the gate-opening threshold pressure. To better understand this gate-opening mechanism, we investigated its transition process from the perspective of CO dynamics and its interaction with the framework via variable-temperature C solid-state nuclear magnetic resonance spectroscopy. Our findings revealed that during the gate-opening process, CO is initially strongly adsorbed at one site when the gate only slightly opens, while two distinct types of CO molecules exist when the gate fully opens. B, C, and F magic-angle spinning NMR, in conjunction with in-situ XANES experiments, were also conducted to probe the location of adsorption sites.