Tailoring MIL-101 for enhanced hydrogen storage via functional group introduction and Li+ doping

Metal-organic frameworks (MOFs) are advantageous for hydrogen storage owing to their tunable porosity. Two independent series were constructed: (i) MIL-101(Cr) functionalized with –NH 2 or –OH, and (ii) Li + -doped MIL-101 at controlled loadings. All samples retained their framework integrity. Textural analysis reveals a concentration-dependent, non-monotonic effect of Li + : at 0.015 wt%, Li + acts as an entrance unblocking (window reopening) effect, markedly increasing S BET and V total and strengthening the 1–2 nm window population; at 0.036 wt%, an optimal balance between reopened windows and accessible microporosity yields a peak H 2 uptake of 3.00 wt% (77 K, 100 kPa), surpassing both the parent framework and the –NH 2 derivative (2.37 wt%); at 0.296 wt%, partial occupation of cages/windows reduces accessibility. GCMC density maps and isosteric-heat data further corroborate that –NH 2 enhances polarity and strengthens host-guest interactions, whereas –OH blocks ultramicropores; moderate Li + simultaneously improves pore accessibility and introduces polarized adsorption sites. Overall, H 2 storage correlates more strongly with the coupling between accessible microporosity and pore-surface polarity than with S BET alone, highlighting dopant concentration as a key lever for optimizing MOF-based hydrogen storage.