Hydrogen storage in 3D covalent organic frameworks. A multiscale theoretical investigation

A multiscale theoretical approach is used for the investigation of hydrogen storage in three-dimensional covalent organic frameworks (3D-COFs). First, ab initio calculations were performed at the density functional level of theory, accompanied with more accurate MP2 calculations to obtain the hydrogen binding sites in these recently synthesized ultralight materials with large surface areas. Second, classical grand canonical Monte-Carlo simulations were carried out to obtain the hydrogen uptake of these frameworks under different thermodynamic conditions. Our results demonstrate that the gravimetric uptake of COFs is in some cases 2 times larger than that of the best known metal-organic frameworks while the volumetric remains comparable. Especially for COF-108, the gravimetric uptake has reached the value of 21 wt% in 77 K and 100 bar conditions and the very promising value of 4.5 wt% at room temperature and 100 bar conditions.