A Mixed-Ligand Approach for a Gigantic and Hollow Heterometallic Cage {Ni₆₄RE₉₆} for Gas Separation and Magnetic Cooling Applications

Nanosized aggregations of metal ions shielded by organic ligands possessing both exquisite structural aesthetics and intriguing properties are fundamentally interesting. Three isostructural gigantic transition-metal–rare-earth heterometallic coordination cages are reported, abbreviated as {Ni₆₄RE₉₆} (RE=Gd, Dy, and Y) and obtained by a mixed-ligand approach, each possessing a cuboidal framework made of 160 metal ions and a nanosized spherical cavity in the center. Along with the structural novelty, these hollow cages show highly selective adsorptions for CO₂over CH₄or N₂at ambient temperatures. Moreover, the gadolinium analogue exhibits large magnetocaloric effect at ultralow temperatures.