  Novel MOF-based polymer nanocomposite films were successfully prepared using
Zr-based UiO-67 as a metal-organic framework (MOF) and polyurethane (PU) as a
polymeric matrix. Synchrotron X-ray powder diffraction (SXRPD) analysis
confirms the improved stability of the UiO-67 embedded nanocrystals and
scanning electron microscopy images confirm their homogeneous distribution
(average crystal size ~100-200 nm) within the 50-um thick film. Accessibility
to the inner porous structure of the embedded MOFs was completely suppressed
for N2 at cryogenic temperatures. However, ethylene adsorption measurements at
25{\deg}C confirm that at least 45% of the MOF crystals are fully accessible
for gas phase adsorption of non-polar molecules. Although this partial blockage
limits the adsorption performance of the embedded MOFs for ocular drugs (e.g.,
brimonidine tartrate) compared to the pure MOF, an almost 60-fold improvement
in the adsorption capacity was observed for PU matrix after incorporation of
the UiO-67 nanocrystals. UiO-67@PU nanocomposite exhibits a prolonged release
of brimonidine (up to 14 days were quantified). Finally, the combined use of
SXRPD, thermogravimetric analysis (TGA) and FTIR analysis confirmed the
presence of the drug in the nanocomposite film, the stability of the MOF
framework and the drug upon loading, and the presence of brimonidine in an
amorphous phase once adsorbed. These results open the gate towards the
application of these polymeric nanocomposite films for drug delivery in optical
therapeutics, either as a component of contact lens, in the composition of
lacrimal stoppers (e.g., punctal plugs) or in sub-tenon inserts.
