Hydrogen Storage in Porous Cages

Over the past several years, significant advances have been made in the development of high-surface-area porous cages. Despite this, relatively little work has been done to explore their use for the storage of hydrogen and other gases. To address this knowledge gap, we explored hydrogen storage across 20 porous cages of a variety of structure types. Trends across various structure types are discussed in some detail, with adsorption sites for a subset of the materials contextualized using powder neutron diffraction data for structurally related metal–organic framework (MOF) pores. Of the studied materials, the carbazole-based octahedral cages, M₁₂(cdc)₁₂ (M = Cr²⁺, Mo²⁺; cdc^2– = carbazole-dicarboxylic acid), performed the best, with a 1 bar, 77 K hydrogen uptake of 9.26 mmol/g (13.9 g/L) for M = Cr²⁺.