Assessing the Stability of Metal-Organic Frameworks with Local Vibrational Mode Theory

Area of Science:

• Materials Science
• Computational Chemistry
• Solid-State Chemistry

Background:

• The industrial application of metal-organic frameworks (MOFs) is limited by their stability.
• Metal-linker coordination bonds are typically the weakest points in MOF structures.
• Assessing MOF stability often relies on experimental data, which can be time-consuming.

Purpose of the Study:

• To develop a reliable quantum-mechanical method for evaluating bond strength in MOFs.
• To establish a computable metric for predicting MOF stability.
• To analyze the impact of linker functionalization on MOF bond strength.

Main Methods:

• Utilized local vibrational mode (LVM) theory to analyze bond strength.
• Calculated local mode force constants for metal-linker bonds in representative MOFs (UiO-66, MOF-5, ZIFs).
• Correlated calculated bond strengths with experimental stability data and electron density at bond critical points.

Main Results:

• Local mode force constants showed good agreement with experimental MOF stability data.
• The calculated bond strengths provided a better stability indicator than electron density at bond critical points in some cases.
• Ortho-NH2 substitutions on linkers were found to weaken adjacent coordination bonds due to intramolecular hydrogen bonding.

Conclusions:

• Local vibrational mode theory provides a robust and computable metric for assessing MOF bond strength.
• This method enables accurate evaluation and prediction of MOF stability.
• Understanding the effects of linker functionalization is key to designing more stable MOFs for industrial use.