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.