A Local Structure Analysis of Defects in UiO-66: Insights from Solid-State Nuclear Magnetic Resonance and X-ray...

Area of Science:

• Materials Science
• Catalysis
• Nanotechnology

Background:

• Defect engineering in metal-organic frameworks (MOFs) is a key strategy for tuning material properties.
• Zirconium-based MOFs, such as UiO-66, are promising materials for various applications.
• Controlled introduction of defects can significantly alter MOF functionality.

Purpose of the Study:

• To characterize the atomic-level local structures of defects in UiO-66 MOFs.
• To investigate the impact of engineered defects on the catalytic performance of integrated platinum nanoparticles (Pt NPs).
• To explore the potential of defective UiO-66 as a support for enhanced catalysis.

Main Methods:

• Utilized multinuclear solid-state NMR spectroscopy (SSNMR) and X-ray absorption fine structure (XAFS) for defect characterization.
• Performed in situ heating XAFS analyses at the Zr K-edge to monitor structural changes.
• Employed various multinuclear SSNMR techniques (¹H, ¹³C, ¹⁹F, ³⁵/³⁷Cl, ¹⁷O) to identify defect-associated species.

Main Results:

• In situ XAFS revealed changes in Zr local structure, including decreased Zr-O coordination and altered Zr-Zr distances upon trifluoroacetic acid (TFA) removal.
• SSNMR identified capping and defect-associated species within the MOF structure.
• Defect-engineered Pt-UiO-66 exhibited significantly enhanced hydrogen evolution reaction (HER) activity and stability compared to non-defective counterparts.

Conclusions:

• Atomic-level characterization of defects in UiO-66 is achievable using a combination of SSNMR and XAFS.
• Engineered defects in UiO-66 effectively improve the catalytic performance of integrated Pt NPs.
• Defective UiO-66 shows great promise as an advanced catalytic support material for reactions like HER.