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.