Lithium-Induced Covalent Organic Frameworks with Enhanced Sorption Heat for Efficient Hydrogen Storage

Covalent organic frameworks (COFs) possess high surface areas and tunable pore structures and are promising candidates for H2 physisorption materials. However, their interaction with H2 molecules is too weak to take advantage of the high porosity of the COFs. Here, we report the first example of metal-doped enhanced H2-physisorption COF. By leveraging the superior stability of TPB-DMTP-COF, we can well preserve the porosity of the COF after lithium (Li) doping, yielding a surface area of 1350 m2/g. Due to the Li-doping-enhanced H2 isosteric heat, the material's total H2 uptake increased from 4.98 to 6.91 wt % at 77 K and 80 bar. The Li-doping-induced enhancement effect does not involve chemisorption, and the material shows excellent cycling performance: 10 cycles at 30 bar with a capacity retention of 99%. Our results reveal that tuning H2 adsorption heat by postmodification is a promising strategy to exploit the potential of porous materials for efficient H2 storage.