北京高压科学研究中心
Center for High Pressure Science &Technology Advanced Research

Universal gas-uptake behavior in MOF - Dr. Yongjae Lee

SEPTEMBER 23, 2019  


New work led by HPSTAR scientist, Dr. Yongjae Lee, presents new results in MOF, Metal-Organic Framework materials. They performed comparative high-pressure adsorption experiments on ZIF-8 (Zeolitic Imidazolate Framework-8) using various greenhouse gases such as CO2, R22, and SF6. They find guest-independent, universal gas-uptake behavior in kilibar pressure regime, which requires only the penetration of molecules into the pores of the framework of ZIF-8. This work is published in Journal of Physical Chemistry C.



Kilobar pressures are present in many technical and geophysical processes, and the confinement of gases in microporous materials is a very active field. In this work, the team aimed to find out how the adsorption 

characteristics of nanoporous materials would be modified under pressure. They found a cross-over from a shape and size specific absorption mechanism to a universal one in kilobar pressure regime.

When an archetypal MOF framework, ZIF-8, is compressed with small greenhouse gases, such as CO2 and R22, a significantly enhanced and universal gas-uptake is observed, which requires only the penetration of molecules into the pores of ZIF-8. When the amounts of inserted gases are plotted against the applied pressures, an asymptotic logarithmic curve is derived, regardless of the type of gas molecules.

 

What is special about this study is the level of structural analyses, which had to deal with full scale Rietveld refinements on ca. 5000 Å3 unit cell structures with complex organic molecules. The team used rigid-body modeling strategy and high-resolution XRD data measured from 6D beamline at Pohang Accelerator Laboratory (PAL).

 

Pressure-induced insertion of molecules into microporous and nanoporous materials would allow a robust estimation of the behavior of ensembles of different gases independent of their particular shape and size. This work should facilitate modelling approaches to gas absorption at kilobar pressures.

 

The first author of this work is Jinhyuk Choi, a Ph.D. student at Yonsei University, and other authors include Junhyuck Im of KAERI, Kyungkyou Noh and Jaheon Kim of Soongsil University, and Thomas Vogt of University of South Carolina.