Over the past decade, metal-organic frameworks (MOFs) have attracted increasing attention as a new class of porous materials. They have extraordinarily high surface areas, well defined crystalline structures and controllable surface functionalities. They have been considered as promising materials in many application areas such as gas storage, gas separation, sensing and heterogeneous catalysis. Because many of these applications involve exposing MOFs to high pressures and high temperatures, it is fundamentally important to understand the structural stability of MOFs under extreme conditions. However, relatively few studies on this topic have been reported to date, most of which are performed by nanoindentaion or diamond anvil cell methods.  We report the first in situ high pressure study of the behavior of the metal organic framework Zn4O(1,4-benzenedicarboxylate)3�xH2O (IRMOF-1) up to 7.43 GPa, using a synchrotron radiation source and a diamond anvil cell.  Even at pressures as low as 0.21 GPA, IRMOF-1 begins to convert to a new material and this process is essentially complete at 5.17 GPa. Some amorphization occurs along with the formation of the new phase.  The new phase is the result of pressure-induced hydrolysis, in which water molecules that are present in the MOF react with the framework, presumably by attacking the bonds between the zinc cations and the 1,4-benzenedicarboxylate groups.  At higher pressures, this new material is further compressed, and it reexpands (but not fully elastically) upon decompression.  The hydrolysis product persists even upon return to ambient pressure, with no reversion to the original IRMOF-1 structure.

Mechanical properties of metal-organic frameworks

243rd National Meeting (2012)

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