A Covalent Organic Framework that Exceeds the DOE 2015 Volumetric Target for H_2 Uptake at 298 K

Abstract

Physisorption in porous materials is a promising approach for meeting H_2 storage requirements for the transportation industry, because it is both fully reversible and fast at mild conditions. However, most current candidates lead to H_2 binding energies that are too weak (leading to volumetric capacity at 298 K of <10 g/L compared to the DOE 2015 Target of 40 g/L). Using accurate quantum mechanical (QM) methods, we studied the H_2 binding energy to 48 compounds based on various metalated analogues of five common linkers for covalent organic frameworks (COFs). Considering the first transition row metals (Sc though Cu) plus Pd and Pt, we find that the new COF-301-PdCl_2 reaches 60 g total H_2/L at 100 bar, which is 1.5 times the DOE 2015 target of 40 g/L and close to the ultimate (2050) target of 70 g/L. The best current materials, MOF-200 and MOF-177, are predicted to store 7.6 g/L (0.54 wt % excess) and 9.6 g/L (0.87 wt % excess), respectively, at 298 K and 100 bar compared with 60 g/L (4.2 wt % excess) for COF-301-PdCl_2.