Theoretical hydrogen cryostorage in doped MIL-101(Cr) metal-organic frameworks

The cryoadsorption (77 K) of H ₂ in the MIL-101(Cr) [MIL: Materials from the Institute Lavoisier] metal-organic framework (MOF) material and its Li ⁺, Mg ²⁺, Mn ²⁺, and Co ²⁺-doped analogues was explored by grand canonical Monte Carlo simulations (GCMC). The optimal hydrogen uptake in this highly porous material is still experimentally unknown considering the experimental difficulty to fully activate this sample. Indeed, a H ₂ adsorption isotherm has only been measured for a mildly activated version (MIL-101b(Cr)). Moreover, the recent adsorption of CO ₂ in better activated form (MIL-101c(Cr)) shows an increase up to 30% of the saturation capacity in comparison to MIL-101b(Cr). From GCMC simulations, we provide the optimal uptake and delivery of H ₂ at 77 K in the MIL-101(Cr) and its doped analogues at 77 K. For the Li-doped material we predict a hydrogen uptake of 10 wt % and a delivery of 6 wt %, which achieve the mass storage and delivery density target established by the U.S. Department of Energy for 2015.