Hydrogen Storage Capacities in Nanoporous M2(m-dobdc) Metal–Organic Frameworks at Near Ambient Temperatures

Abstract

Green hydrogen presents a cleaner alternative to petroleum-based energy, with onboard storage challenges addressed by metal–organic frameworks (MOFs). This study evaluates M₂(m-dobdc) MOFs (M = Mn, Fe, Co, and Ni) for H₂-storage using Grand Canonical Monte Carlo simulations (GCMC) at five distinct temperatures (77, 160, 198, 233, and 298 K) and pressures of 1–100 bar. The Fe₂(m-dobdc) MOF achieves a promising volumetric H₂ storage capacity of 51.2 g/L under cryogenic conditions, meeting the target of the Department of Energy, United States of America (USDOE), while the calculated value of the gravimetric uptake is 4.2 wt %, which approaches the USDOE 2025 target of 5.5 wt %. M₂(m-dobdc) MOF series reflect exceptional volumetric uptake capacities at room temperature, ranging from 11.0 to 12.3 g/L, while gravimetric capacities are moderate, indicating key challenges in physisorption-based nanoporous materials when operating at ambient conditions. Density functional theory (DFT) calculations reveal the heat of H₂ adsorption (Q_st) ranging from −15 to −18 kJ/mol in this M₂(m-dobdc) MOF series, confirming the reversible physisorption phenomenon. Our results highlight the potential of M₂(m-dobdc) MOFs for mobile H₂-storage applications, with deliverable volumetric capacities ranging from 36.3 to 40.8 g/L and gravimetric uptake ranging from 2.7 to 3.4 wt % under a temperature–pressure swing range (77 K/100 bar to 160 K/5 bar). The present investigation indicates that the M₂(m-dobdc) MOFs have shown advances of the USDOE target and promise to meet the practical onboard hydrogen-storage requirements in automobile applications. Their balanced gravimetric-volumetric capacities make them promising candidates for near-future implementation in green energy systems.