Solid-state NMR Studies of Host–Guest Interaction between UiO-67 and Light Alkane at Room Temperature

Abstract

The host−guest interaction between adsorbent and adsorbate plays essential roles in the gaseous storage and chemical separation using metal−organic frameworks (MOFs). Solid-state NMR spectroscopy was employed to explore the interactions between light alkanes including methane, ethane, propane and a representative MOF, UiO-67 at room temperature. The existence of host−guest interaction between light alkanes and UiO-67 framework is clearly evidenced from twodimensional 1 H− 1 H spin diffusion homonuclear correlation and 1 H− 13 C HETCOR with spin diffusion experiments. By fitting the spin diffusion buildup curves, it is found that methane is more readily to diffuse to the UiO-67 framework compared to ethane and propane. Moreover, the spin diffusion MAS NMR results reveal that methane is mainly adsorbed neighboring the metal cluster, whereas propane and ethane are preferentially present nearby the site away from the metal cluster due to the steric hindrance effect. The results presented herein would provide a better understanding of the structure−property relationship of MOFs in the alkane storage.

Solid‐State NMR Spectroscopy: A Powerful Technique to Directly Study Small Gas Molecules Adsorbed in Metal–Organic Frameworks

“…[32] MOF-based methods have shown promising performance; [32] consequently,several SSNMR studies have been conducted to characterizeh ydrocarbon-MOF systems. [33][34][35][36][37] SSNMR spectroscopy can provide valuable insights into the adsorption mechanism of light hydrocarbonsi nM OFs. For instance,D eng andc o-workerss tudied CH 4, C 2 H 6 and C 3 H 8 adsorptioni nU iO-67 using spin diffusionS SNMR experiments.…”

“…Light hydrocarbons have many practical applications, and tremendous effort has been put into researching suitable separation and storage procedures . MOF‐based methods have shown promising performance; consequently, several SSNMR studies have been conducted to characterize hydrocarbon‐MOF systems …”

“…SSNMR spectroscopy can provide valuable insights into the adsorption mechanism of light hydrocarbons in MOFs. For instance, Deng and co‐workers studied CH 4, C 2 H 6 and C 3 H 8 adsorption in UiO‐67 using spin diffusion SSNMR experiments . CH 4 was found to be mainly adsorbed close to the metal centers, while C 2 H 6 and C 3 H 8 were found to be predominantly adsorbed further from the metal centers due to sterics.…”

“…For instance,D eng andc o-workerss tudied CH 4, C 2 H 6 and C 3 H 8 adsorptioni nU iO-67 using spin diffusionS SNMR experiments. [37] CH 4 was found to be mainly adsorbed close to the metal centers, while C 2 H 6 and C 3 H 8 were found to be predominantly adsorbed further from the metal centers due to sterics. Furthermore, studies combining SSNMR experiments with other techniques can allow for at horough understanding on gas adsorption in MOFs.…”

Exploring Host–Guest Interactions in the α-Zn3(HCOO)6 Metal-Organic Framework

“…SSNMR spectroscopy probes short-range ordering and local structure. It can provide insights into host–guest interactions 59−61 and guest dynamics. 41,62−70 Both metal– and linker–guest interactions can be directly examined using SSNMR, 39,66,67,71,72 allowing for the main adsorptive interactions to be identified.…”