1 research outputs found
High-Pressure Chemistry of a Zeolitic Imidazolate Framework Compound in the Presence of Different Fluids
Pressure-dependent structural and
chemical changes of the zeolitic
imidazolate framework compound ZIF-8 have been investigated
using different pressure transmitting media (PTM) up to 4 GPa. The
unit cell of ZIF-8 expands and contracts under hydrostatic pressure
depending on the solvent molecules used as PTM. When pressurized in
water up to 2.2(1) GPa, the unit cell of ZIF-8 reveals a gradual contraction.
In contrast, when alcohols are used as PTM, the ZIF-8 unit cell volume
initially expands by 1.2% up to 0.3(1) GPa in methanol, and by 1.7%
up to 0.6(1) GPa in ethanol. Further pressure increase then leads
to a discontinuous second volume expansion by 1.9% at 1.4(1) GPa in
methanol and by 0.3% at 2.3(1) GPa in ethanol. The continuous uptake
of molecules under pressure, modeled by the residual electron density
derived from Rietveld refinements of X-ray powder diffraction, reveals
a saturation pressure near 2 GPa. In non-penetrating PTM (silicone
oil), ZIF-8 becomes amorphous at 0.9(1) GPa. The structural changes
observed in the ZIF-8-PTM system under pressure point to distinct
molecular interactions within the pores