Sustainable approaches for MOF densification to enhance hydrogen storage

To enable large-scale use, hydrogen (H 2 ) requires improved storage solutions. Metal-Organic Frameworks (MOFs) provide a promising physisorption-based approach to address the low volumetric density of H₂ at standard temperature and pressure (0.09 g/L), thereby significantly improving its viability as a clean energy vector. Although MOFs have a high surface area, their use in H 2 storage is still limited because of their low packing density. In this review, we critically assess densification strategies for enhancing volumetric H 2 storage, using representative case studies on HKUST-1, ZIF-8, MOF-5, UiO-66 and MIL-101(Cr). Notably, the HKUST-1 monolith demonstrated the highest total volumetric H 2 uptake (46.7 g/L) at 100 bar and 77 K, outperforming ZIF-8 (35 g/L), MOF-5 (43 g/L), UiO-66 co-pellet (+PAN; 32 g/L) and MIL-101 (Cr) (40 g/L) under the same conditions. These values show that densification bridges the gap between adsorption properties and practical H 2 storage requirements, though the industrial viability of HKUST-1 monolith remains subject to material cost and recyclability. A semi-quantitative sustainability assessment of all the densification methods is provided; it compares solvent intensity and energy use. Among these methods, dry extrusion, spray drying and sol-gel monolith route are the most readily adaptable to large-scale production and offer proven environmental benefits.