Fine-tuning the pore structure of metal–organic frameworks by linker substitution for enhanced hydrogen storage and gas separation

Abstract

The modification of metal–organic frameworks (MOFs) by functionalizing ligands has been investigated for improved properties. In this study, by introducing substituents to the backbone of organic linkers, isostructural dihydroxy-/dialkoxy-functionalized Zr-MOFs were delicately constructed and sophisticatedly characterized for crystallinity, morphology, porosity and structural defects. Pure-component CO₂, CH₄, N₂, and H₂ adsorption isotherms on the microporous synthesized materials were investigated under the pressure up to 10 MPa at 303 K. By the ideal adsorbed solution theory (IAST) model, enhanced adsorption selectivity towards CO₂/N₂, CO₂/CH₄, CH₄/N₂ and CO₂/H₂ binary mixtures was observed compared to the parent material, and dihydroxy functionalization endows the material with high selectivity towards CO₂/H₂. Moreover, the diethoxy-functionalized material with narrow cavities exhibits improved high pressure H₂ adsorption due to structural defects and strong overlapping potentials.