Immobilization of Alkali Metal Ions in a 3D Lanthanide-Organic Framework: Selective Sorption and H2 Storage Characteristics

A lanthanide-alkali (Ho-III-K-I) bimetallic alpha-Po type 3D framework {KHo(C2O4)(2)(H2O)(4)}(n) (I) (C2O42- = oxalate dianion) has been synthesized and structurally characterized. Its dehydrated framework 1, after removal of the K-bound water molecules, is found to exhibit permanent porosity with a clear size selective vapor sorption properties and H-2 storage capability. High heat of H-2 sorption (approximately -10 kJ/mol) observed in experiment is shown to arise from the preferential interaction of H-2 With unsaturated K-I sites decorated on the pore surfaces, using first-principles density functional theory-based calculations of energetics as well as the detailed structure. Our work shows that a material with better hydrogen storage and release properties can be developed through immobilization of unsaturated reactive alkali metal ions at the pore surfaces in a metal-organic framework.