Exploring cluster formation in Zr-MOF synthesis in situ using X-ray absorption spectroscopy

Area of Science:

• Materials Science
• Chemistry
• Nanotechnology

Background:

• Metal-organic frameworks (MOFs) with Zr-oxo clusters are highly stable materials with diverse applications.
• Synthesis parameters critically influence MOF properties like quality and morphology.

Purpose of the Study:

• To develop an in situ experimental setup for monitoring element-specific chemical transformations during MOF synthesis.
• To investigate the impact of reaction parameters on Zr-oxo cluster and MOF formation.

Main Methods:

• Utilized in situ X-ray absorption spectroscopy (XAS) to monitor Zr-fumarate formation in ZrCl4-DMF solutions.
• Studied the local Zr environment, reaction kinetics, and dependence on water and modulator concentrations.
• Correlated in situ findings with post-synthetic characterization of MOF products.

Main Results:

• In situ XAS provided direct evidence that increased water and modulator concentrations accelerate MOF synthesis.
• Water was confirmed as essential for Zr-oxo cluster and MOF formation in DMF-based systems.
• Anhydrous conditions prevented Zr-cluster and MOF formation, with Zr4+ ions coordinated by chlorine.

Conclusions:

• The study highlights the critical role of water in the synthesis of Zr-oxo clusters and subsequent MOF formation.
• The developed in situ method allows for detailed mechanistic understanding of MOF synthesis.
• Optimizing water and modulator concentrations is key for controlling MOF quality and properties.