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DFT Study on the H2 Storage Properties of Sc-Decorated Covalent Organic Frameworks Based on Adamantane Units
journal contribution
posted on 2018-06-28, 00:00 authored by Amol Deshmukh, Thong Nguyen Minh Le, Cheng-chau Chiu, Jer-Lai KuoWe follow the idea
of using metal-decorated polyhydroxy adamantane
structures as H2 adsorption sites and develop it further
by integrating such structures into porous framework structures. We
use density functional theory calculations to investigate the hydrogen
adsorption in five Sc-decorated, porous, covalent organic frameworks.
Each of them consists of polyhydroxy adamantane units connected by
molecular linkers. A polyhydroxy adamantane unit acting as an anchor
site for four Sc atoms, in return, can bind up to four H2 molecules per Sc site. At full coverage, the average H2 adsorption energy is between −0.17 and −0.19 eV/H2. We use a simplified thermodynamic model to estimate the
gravimetric and volumetric hydrogen uptake as a function of temperature
and H2 pressure. The most promising framework found here
is a structure with benzene units as linkers, which is predicted to
achieve 3.04 wt % or 27.28 g/L H2 uptake at 233 K and 100
bar H2 pressure. We also show that the relatively weak
framework–H2 interaction leads to the circumstance
that at typical operating conditions, the hydrogen uptake deviates
significantly from the full coverage, illustrating the necessity to
account for the temperature and pressure dependency of the H2 uptake.
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Keywords
hydrogen uptakeH 2 uptakepolyhydroxy adamantane unitpolyhydroxy adamantane unitsframeworkH 2 pressureH 2 moleculesSc-Decorated Covalent Organic FrameworksDFTH 2 adsorption energymetal-decorated polyhydroxy adamantane structureslinkerH 2 adsorption sitesH 2 Storage Propertiescoverage100 bar H 2 pressure