Pressure-Driven Loading of Large Guests in Metal–Organic Frameworks

Confining guest molecules within metal–organic
frameworks
(MOFs) allows their physical and chemical properties to be harnessed
in their heterogenized form. However, apart from the loading of small
molecules that can freely diffuse into and out of MOF pores, there
is not yet a general and efficient strategy for loading and confining
bulky organic molecules into MOFs with small apertures. In this work,
we demonstrated that pressure can be employed to facilitate the diffusion
of guest molecules into the cavities of UiO-66 and UiO-66-NH2, even when the aperture sizes are smaller than the guests. This
approach enables rapid and high-capacity loading of liquids or meltable
solids that otherwise cannot be incorporated under atmospheric pressure.
By studying the loading mechanism, we found that applying pressure
can activate local geometric rearrangements of the MOF cavities and
guests, enabling physical confinement of the guests within MOFs.
As a result, a wide range of guest molecules can be readily encapsulated
using our strategy, allowing for broad potential applications, including
heterogeneous catalysis, postsynthetic modifications, and drug release.