First principle studies on triphenylene-hexathiol-based metal-organic framework for hydrogen storage application

We have studied the hydrogen storage capability of the recently synthesized triphenylene-hexathiol based metalorganic framework (MOF) with Fe and Cu metal atoms by using density functional theory and Ab Initio Molecular Dynamics (AIMD) simulations. We found that up to 12 hydrogen molecules were spontaneously adsorbed on the six Fe atoms of the MOF (FeMOF) with adsorption energy of -0.18 eV per H2 molecule, whereas only six H2 molecules were adsorbed on the six Cu atoms of the MOF (CuMOF) with an adsorption energy of -0.17 eV per H2 molecule. Hydrogen molecules were adsorbed on the Fe atom in the FeMOF surface by Kubas interaction. It is observed that the H2 storage capacity of FeMOF did not change due to the substitution of electron donating group, OCH3 on triphenylene molecules. The charge transfer from H2 molecules to the MOF through metal atoms has been confirmed through the density of states and Bader charge analysis. The gravimetric weight percentage of the FeMOF is found to be 1 wt% at room temperature and 1 atm pressure which is considerably higher than that of the studied CuMOF (0.5 wt%). Further, the AIMD results confirmed the structural stability of the studied MOFs. Therefore, the studied FeMOF surface is a suitable material for efficient and reversible hydrogen storage application.