Tuning the hydrogen storage capacity of MOF-650 by Mg2+/Ca2+ substitution and B, N co-doped atoms: Grand canonical Monte Carlo simulation and periodic density functional theory

This study used periodic density functional theory and grand canonical Monte Carlo simulations to investigate the effects of the co-doping of B and N atoms and substituting Zn2+ with Mg2+ or Ca2+ in the organic linker groups of MOF-650. The functionalization increased the polarity of the organic groups, stabilizing the interaction between the MOF and hydrogen molecules. The highest average binding energy of the adsorbed hydrogen in MOF-650 NB-C7-azulene-Mg was calculated to be -4.75 to 5.40 kcal/mol for the alpha adsorption sites. Using the substitution of NB azulene and metal cations being Mg2+ or Ca2+, The hydrogen storage capacity of functionalized MOF-650 was increased to 22 mg/g at 90 bar/298 K, implying the modification strategy of MOF-650 would strengthen the interaction between MOF frameworks and hydrogen molecules.