Gas Adsorption Snapshots in Metal–Organic Frameworks Unveil the Impact of Pore Geometry on Hydrogen Storage

Metal–organic frameworks (MOFs) are promising candidates for hydrogen (H₂) storage. However, effective H₂ storage in MOFs is challenging, because of weak adsorbent–adsorbate interactions. Optimizing the pore volume, size, and functionality in porous MOFs is crucial, but it is still unclear how to maximize H₂ storage capacity while minimizing loading pressure. Herein, we investigate Al-TBAPy (H₄TBAPy: 1,3,6,8-tetrakis(p-benzoic acid)pyrene), a low-density MOF, for H₂ storage. Al-TBAPy features three interconnected pores (A–C), possesses a pore volume of 0.51 cm³/g, and demonstrates a H₂ uptake of 22.5 mmol/g at 77 K and 100 bar. In situ deuterium (D₂) gas loading neutron diffraction experiments reveal molecular-level insights into pore filling. Pores B and C exhibit high H₂ affinity, while pore A, with a larger volume, takes up more H₂ molecules. The collective properties of all pores and their interconnection result in a high deliverable gravimetric H₂ capacity of 4.3 wt % under combined temperature and pressure swing conditions.