High H₂ storage of hexagonal metal-organic frameworks from first-principles-based grand canonical monte carlo simulations

Stimulated by the recent report by Yaghi and co-workers of hexagonal metal-organic frameworks (MOF) exhibiting reversible binding of up to 7.5 wt % at 77 K and 70 bar for MOF-177 (called here IRMOF-2-24), we have predicted additional trigonal organic linkers, including IRMOF-2-60, which we calculate to bind 9.7 wt % H₂ storage at 77 K and 70 bar, the highest known value for 77 K. These calculations are based on grand canonical Monte Carlo (GCMC) simulations using force fields that match accurate quantum mechanical calculations on the binding of H₂ to prototypical systems. These calculations were validated by comparison to the experimental loading curve for IRMOF-2-24 at 77K. We then used the theory to predict the effect of doping Li into the hexagonal MOFs, which leads to substantial H₂ density even at ambient temperatures. For example, IRMOF-2-96-Li leads to 6.0 wt % H ₂ storage at 273 K and 100 bar, the first material to attain the 2010 DOE target.