Selective Host-Guest Interaction between Metal Ions and Metal-Organic Frameworks Using Dynamic Nuclear Polarization Enhanced Solid-State NMR Spectroscopy

The host-guest interaction between metal ions (Pt2+ and Cu2+) and a zirconium metal-organic framework (UiO-66-NH2) was explored using dynamic nuclear polarization-enhanced N-15{H-1} CPMAS NMR spectroscopy supported by X-ray absorption spectroscopy and density functional calculations. The combined experimental results conclude that each Pt2+ coordinates with two NH2 groups from the MOF and two Cl- from the metal precursor, whereas Cu2+ do not form chemical bonds with the NH2 groups of the MOF framework. Density functional calculations reveal that Pt2+ prefers a square-planar structure with the four ligands and resides in the octahedral cage of the MOF in either cis or trans configurations.