Chemical engineering of adamantane by lithium functionalization: A first-principles density functional theory study

Using first-principles density functional theory, we investigated the hydrogen storage capacity of Li-functionalized adamantane. We showed that if one of the acidic hydrogen atoms of adamantane is replaced by Li/Li⁺, the resulting complex is activated and ready to adsorb hydrogen molecules at a high gravimetric weight percent of around $~7.0%$. Due to polarization of hydrogen molecules under the induced electric field generated by positively charged Li/Li⁺, they are adsorbed on ADM.Li/Li⁺ complexes with an average binding energy of $~$${-}0.15$ eV/H${}₂$, desirable for hydrogen storage applications. We also examined the possibility of the replacement of a larger number of acidic hydrogen atoms of adamantane by Li/Li${}⁺$ and the possibility of aggregations of formed complexes in experiments. The stability of the proposed structures was investigated by calculating vibrational spectra and doing MD simulations.