Li-doped and functionalized metal-organic framework-519 for enhancing hydrogen storage: A computational study

Li-doping and functionalization are two approaches to enhance the hydrogen adsorption capacity of metal organic frameworks (MOFs). Herein, we report the simulations of modified MOF-519 implemented by Grand canonical Monte Carlo (GCMC) methodology and Density Functional Theory (DFT) to evaluate the degree of enhancement of hydrogen absorption. The adsorption mechanism and preferred adsorption sites are also investigated. The GCMC results show that Li can significantly improve hydrogen storage capacity. Besides, all functionalized MOF-519-X (X = -OH, -NO2, -Cl, -NH2, -CH3, -F) figure better adsorption performance. Compared to parent MOF-519, Li-MOF-519 has a gravimetric adsorption of 2.265 wt%, and MOF-519-OH performs the highest gravimetric adsorption among the functionalized MOFs with 2.362 wt%. Furthermore, the enhancement on hydrogen adsorption is also studied from the aspect of volumetric adsorption and isosteric heat.