High-enthalpy hydrogen adsorption in cation-exchanged variants of the microporous metal-organic framework Mn3[(Mn4Cl)3(BTT)8(CH3OH)10]2

Exchange of the guest Mn2+ ions in Mn-3[(Mn4Cl)(3)(BTT)(8)(CH3OH)(10)](2) (1-Mn2+; BTT = 1,3,5-benzenetristetrazolate) with selected cations results in the formation of isostructural framework compounds 1-M (M = Li+, Cu+, Fe (2+), CO2+, Ni2+, CU2+, Zn2+). Similar to the parent compound, the new microporous materials are stable to desolvation and exhibit a high H-2 storage capacity, ranging from 2.00 to 2.29 wt % at 77 K and 900 torr. Measurements of the isosteric heat of adsorption at zero coverage reveal a difference of 2 kJ/mol between the weakest and strongest H-2-binding materials, which is attributed to variations in the strength of interaction between H-2 molecules and unsaturated metal centers within each framework. The Co2+-exchanged compound-CO2+, exhibits an initial enthalpy of adsorption of 10.5 kJ/mol, the highest yet observed for a microporous metal-organic framework.