Hydrogen storage in molecular clathrate cages under conditions of moderate pressure and ambient temperature

Hydrogen is an ideal and predominant candidate as a clean energy for global sustainable development, while hydrogen storage is the most difficult hurdle for mobile applications. Here, molecular clathrate cages have been constructed via interfacial reaction between cyclodextrin (CD) and trimesoyl chloride (TMC). Both the inner cavities of CDs and outer cylinders of the CD/TMC clathrate architecture can restrain gas molecules in their cages. Interestingly, the gas uptake capability follows the order of α-CD/TMC > β-CD/TMC > γ-CD/TMC, which is in the opposite trend of their inner cavity sizes. All CD/TMC clathrate cages not only exhibit reversible hydrogen adsorption-desorption isothermals but also great hydrogen adsorption capabilities. The excess hydrogen uptake capability of α-CD/TMC is 2.1 wt% at 35 °C and 10 bar, which is one of the highest capacity reported to date for physisorption nanomaterials under conditions of ambient temperature and safe pressure. Comparing with previously reported materials, α-CD/TMC has the hydrogen storage capability most nearby the target set by U.S. Department of Energy (DOE).