Computational Screening of Metal-Catecholate-Functionalized Metal–Organic Frameworks for Room-Temperature Hydrogen Storage

Hydrogen is a promising alternative
to fossil fuels, but the storage
and transport of hydrogen for practical applications remain a significant
challenge, as high pressure and/or cryogenic temperature are required.
Adsorption-based storage utilizing nanoporous adsorbents such as metal–organic
frameworks (MOFs) can greatly reduce the storage pressure, but cryogenic
or sub-ambient temperatures are required with current adsorbents,
which limits the scope of applications. In this work, we search for
hydrogen storage adsorbents that allow room-temperature operation
by looking at MOFs functionalized with metal-catecholate groups, which
have highly unsaturated open metal sites and thus greatly enhanced
binding strength for hydrogen. We screened a data set of 2736 Zr-MOFs
that were constructed in a combinatorial fashion with wide varieties
of topologies and linkers. By counting the possible sites that can
be functionalized with metal-catecholate groups, we were able to obtain
the theoretical maximum hydrogen uptake for all of the MOFs and rank
them. For the top 100 MOFs, we built the functionalized structures
computationally and conducted grand canonical Monte Carlo simulations
to predict the hydrogen uptake at target adsorption (296 K, 100 bar)
and desorption (296 K, 5 bar) conditions. We predict up to 7 wt %
and 24 g/L deliverable capacities for some MOFs, which are very high
for room-temperature pressure-swing adsorption cycles.