| The hydrogen storage properties of Isoreticular Metal-Organic Framework (IRMOF) Materials are reported. To improve our understanding of the hydrogen storage mechanism, the hydrogen binding sites in IRMOF crystals are identified, and the binding energies are calculated using high quality second-order Moller-Plesset perturbation theory. The resolution of identity approximation and the quadruple zeta QZVPP basis set are used. These calculations use terminated molecular fragments from IRMOF materials. It is found that the binding energy near Zn 4O corners is larger than that on the linker molecules. It is also found that adding amino or methyl groups on the linker molecules increases hydrogen binding energy up to 33%. The multiple hydrogen bindings on large linker molecules are studied. The linkers of IRMOF-12, IRMOF-993, and IRMOF-14 can bind two, three, and four hydrogen molecules per side, respectively.; Grand canonical Monte Carlo simulations are performed using Universal Force Field. The hydrogen uptake for IRMOF-1 is calculated at 77 Kelvin and at room temperature. The results are compared to the experiments. The Monte Carlo simulations identify a high energy binding site at the corners that quickly saturates at 78K. At room temperature, the binding near the corner is less important, and a broad range of binding sites near linker molecules are observed.; New IRMOF materials are proposed to increase the hydrogen storage capacity at room temperature. Based on the potential energy surface of hydrogen molecules on IRMOF linkers, and the interaction energy between hydrogen molecules, the saturation values of hydrogen sorption capacity at room temperature are estimated. We discuss design criteria and propose new IRMOF materials that have high gravimetric and volumetric hydrogen storage density. These new IRMOF materials may have gravimetric storage density up to 6.5 wt% and volumetric storage density up to 40 kg H2/m3 at room temperature. |
