The study investigates a magnesium borohydride framework, γ-Mg(BH₄)₂, with small pores and a partially negatively charged non-flat interior, for hydrogen and nitrogen uptake. Using neutron powder diffraction, volumetric gas adsorption, inelastic neutron scattering, and first-principles calculations, the researchers found that hydrogen and nitrogen occupy distinct adsorption sites in the pores, with hydrogen packing extremely densely, achieving a density of about 144 g H₂ per liter of pore volume, twice that of liquid hydrogen. The hydrogen molecules form a penta-dihydrogen cluster where one molecule has rotational freedom, while the others have a well-defined orientation and a directional interaction with the framework. This study demonstrates that densely packed hydrogen can be stabilized in small-pore materials at ambient pressures, offering potential for high-density hydrogen storage.The study investigates a magnesium borohydride framework, γ-Mg(BH₄)₂, with small pores and a partially negatively charged non-flat interior, for hydrogen and nitrogen uptake. Using neutron powder diffraction, volumetric gas adsorption, inelastic neutron scattering, and first-principles calculations, the researchers found that hydrogen and nitrogen occupy distinct adsorption sites in the pores, with hydrogen packing extremely densely, achieving a density of about 144 g H₂ per liter of pore volume, twice that of liquid hydrogen. The hydrogen molecules form a penta-dihydrogen cluster where one molecule has rotational freedom, while the others have a well-defined orientation and a directional interaction with the framework. This study demonstrates that densely packed hydrogen can be stabilized in small-pore materials at ambient pressures, offering potential for high-density hydrogen storage.