Selective host-guest interaction between metal ions and metal-organic frameworks using dynamic nuclear polarization...

Area of Science:

• Materials Science
• Inorganic Chemistry
• Spectroscopy

Background:

• Metal-organic frameworks (MOFs) offer tunable properties for host-guest chemistry.
• Understanding metal ion interactions within MOFs is crucial for designing new materials.
• UiO-66-NH2 is a versatile zirconium-based MOF with amine functional groups.

Purpose of the Study:

• To investigate the host-guest interactions between Pt2+ and Cu2+ ions and the UiO-66-NH2 MOF.
• To elucidate the coordination behavior and structural implications of metal ion binding.
• To differentiate the binding mechanisms of Pt2+ and Cu2+ within the MOF.

Main Methods:

• Dynamic Nuclear Polarization-enhanced (15)N{(1)H} Cross-Polarization Magic Angle Spinning (CPMAS) Nuclear Magnetic Resonance (NMR) spectroscopy.
• X-ray Absorption Spectroscopy (XAS).
• Density Functional Theory (DFT) calculations.

Main Results:

• Pt2+ ions coordinate with two NH2 groups from the UiO-66-NH2 framework and two Cl- ions.
• Cu2+ ions do not form chemical bonds with the NH2 groups of the MOF.
• DFT calculations show Pt2+ adopts a square-planar geometry within the MOF's octahedral cage.

Conclusions:

• Pt2+ exhibits specific chemical bonding with the UiO-66-NH2 framework, forming stable complexes.
• Cu2+ interactions are weaker and do not involve direct chemical bonds with the amine groups.
• The study provides detailed insights into the selective binding of metal ions in functionalized MOFs.