  This work reports the hydrogen storage, and delivery capacities of Sc and Y
functionalized [1,1]paracyclophane using dispersion corrected density
functional theory calculations. The Sc and Y atoms are bind strongly with
benzene rings of [1,1]paracyclophane. Each Sc and Y atom functionalized over
[1,1]paracyclophane adsorb up to 6 H2 molecules via Kubas interaction achieving
maximum gravimetric density up to 8.22 wt% and 6.33 wt%, respectively. The
calculated average hydrogen adsorption energy (0.36 eV) is lower than the
chemisorption but higher than the physisorption process. The kinetic
stabilities are verified through the HOMO-LUMO gap and different global
reactive descriptors. ADMP molecular dynamics simulations reveal the
reversibility of adsorbed H2 molecules at sufficiently above the room
temperature and the solidity of host material at 500 K. Average Van't Hoff
desorption temperature for Sc and Y decorated system was calculated to be 439 K
and 412 K respectively at 1 atm of pressure. The estimated thermodynamically
usable hydrogen capacities are found to be 5.92 wt% and 5.87 wt% of hydrogen
which fulfil the hydrogen energy criteria (by 2025) of US-DOE. Hence, we
believe that Sc and Y functionalized [1,1]paracyclophane can be considered as a
thermodynamically viable, and potential reversible hydrogen storage materials
at ambient environment.
