Novel Ni-IRMOF-74 Postsynthetically Functionalized for H₂ Storage Applications

Abstract

Herein, the synthesis of the porous-expanded material Ni-IRMOF-74, structurally analogous to the widely studied microporous Ni-MOF-74 but with a larger pore size resulting from the extended length of the linker, is reported. Next, the organometallic complex LiCrw, formed by the complexation of lithium cation with the hydrophobic 18Crown6 species, has been included into the pores of the Ni-IRMOF-74 structure. This postsynthetic modification significantly increases the volumetric hydrogen adsorption capacity at room temperature of the material as well as the H2–metal-organic framework (MOF) interaction, reaching an adsorption enthalpy value around −15 kJ mol–1, which makes this new structure a promising candidate for hydrogen storage at moderate conditions of temperature and pressure. Density function theory (DFT) calculations allow proposing a location for Crw and Li+ cation within the Ni-IRMOF-74 channels, with the Li+ cation offering a favorable adsorption site for H2 molecules. Therefore, this work contributes with important discoveries in the materials’ knowledge as well as in the hydrogen storage application since: a new large microporous MOF material was developed; a postsynthesis modification of the Ni-IRMOF-74 was conducted by incorporating the organometallic complex LiCrw into its pores; the location for Crw and Li+ cation within the Ni-IRMOF-74 channels was proposed by means of DFT calculations; an optimal hydrogen interaction with the MOF structure was achieved; and there was better hydrogen adsorption excess capacity at room temperature, which is one of the main targets in this field.