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

ABSTRACT

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.