Multiscale study on hydrogen storage based on covalent organic frameworks

Abstract

In this paper, we performed a multiscale study on the hydrogen storage capacity of Li–Sc doped and Li-C60 injected covalent organic frameworks (COFs)-based phthalocyanine, porphyrin and TBPS COFs. We combined the first-principles studies of hydrogen adsorption and grand canonical Monte Carlo (GCMC) simulations of hydrogen adsorption in nine designed COFs. The first-principles calculations revealed that the Li atoms can be doped on the surface of the Sc-doped COFs with binding energy from −83.9 to −160.2 kJ/mol. Each Li atom can bind three H2 molecules with the adsorption energy between −16.8 and −20.0 kJ/mol. The GCMC simulations have predicted that all the nine designed COFs can reach the Department of Energy’s 2015 target (5.5 wt% and 40 g/L) at T = 77 K and P = 100 bar. The optimum conditions of hydrogen storage for Li-C60@Li–Sc-PR-TBPS2, the promising materials, are T = 193 K (−80 °C) and P = 100 bar with a gravimetric H2 density of 8.19 wt% and volumetric H2 uptake of 42.6 g/L. Finally, we further convinced the importance of Sc in improving H2 uptake in doped COFs.