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Researchers Discover Method to Transform Structure of MOFs; Potential In Applications Such as Hydrogen Storage

Scientists at the US Department of Energy’s (DOE) Argonne National Laboratory have discovered a new route to transform the structure of metal-organic framework (MOF) materials—an emerging class of porous crystalline solid—at industrially-accessible high pressures.

Karena Chapman, Gregory Halder and Peter Chupas used the Advanced Photon Source’s high-focused X-ray beams to observe the structure of ZIF-8—a commercially available metal-organic framework (MOF) with molecular-scale pores that can have valuable catalytic applications—after it withstood varying degrees of pressure. The structural transition was found to occur at relatively modest pressures—pressures that can be achieved on the larger scales needed to test how the change in structure affects the compound’s functional behavior.

Normally, these materials will spring back to their original structure after they have been compressed, almost like a spring, but above a certain pressure this material adopts a new structure. It is a related structure, but it is as if when we compressed the spring, it bounced back to a different shape.

—Karena Chapman, Argonne

Gas uptake measurements, carried out within the Materials Science Division, revealed that the material’s porosity was modified for the new structure. This could be used to optimize its performance for specific applications in areas such as hydrogen storage for fuel cells. This discovery shows that by exerting pressure on MOFs through the pelletization process, researchers can modify the compound’s structure and storage property.

While this type of structural change has been seen in traditional porous materials (e.g., zeolites) at much higher pressures, the structural changes in the MOF material occur at lower pressures and consequently, this modification can be more readily scaled up to industrial levels.

We have demonstrated that ZIF-8 is highly compressible with an irreversible pressure-induced amorphization at extremely low pressures. This has been exploited to generate a new type of noncrystalline MOF system through amorphization of an existing crystalline MOF. Although crystalline diffraction has often been used as a benchmark for MOF stability, we have shown that the pressure-treated and amorphized MOFs exhibit nanoporosity and, therefore, retain some structural order. As such, pressure can provide a new route to systematically modify the structure and properties of MOFs, a nontraditional form of postsynthetic modification. Importantly, pressure modification of MOFs is effective at lower pressures than in zeolites and, consequently, is easily scalable and industrially relevant.

—Chapman et al.

The next step is for the scientists to examine the mechanism of the structural change and how this modification process can be most effectively exploited for molecular storage and separation applications.

A paper about this discovery was recently published in the Journal of the American Chemical Society.


  • Karena W. Chapman, Gregory J. Halder and Peter J. Chupas (2009) Pressure-Induced Amorphization and Porosity Modification in a Metal-Organic Framework. J. Am. Chem. Soc., 131 (48), pp 17546–17547 doi: 10.1021/ja908415z



I think that science will come up with better ways to store hydrogen. We may see lots of hydrogen cars 20-30 years from now. We need more practical methods to reduce imported oil now, but the research should still go on. Turning the PNGV program into the all hydrogen Freedom Car was just a way to put a solution farther out into the future.


Interesting materials. ZIFs selectively capture carbon dioxide (and other gases) from several different gas mixtures at room temperature, with ZIF-100 capable of storing 28 litres per litre of material at standard temperature and pressure.

Good storage potential. And cleaning emission streams.


On this topic - I wonder where the Al anion cluster method of splitting water is these days??

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