Flexible and Transferable ab Initio Force Field for Zeolitic Imidazolate Frameworks: ZIF-FF

Area of Science:

• Materials Science
• Computational Chemistry
• Chemical Engineering

Background:

• Zeolitic imidazolate frameworks (ZIFs) are a class of metal-organic frameworks with diverse applications.
• Accurate prediction of ZIF structural properties and stabilities is essential for their rational design and synthesis.
• Existing force fields often fail to capture the relative stability of ZIF polymorphs, hindering the understanding of nucleation and crystal growth.

Purpose of the Study:

• To develop a transferable *ab initio* intramolecular force field for ZIFs, named ZIF-FF.
• To quantitatively describe the structural properties and relative stabilities of ZIFs using the developed force field.
• To enable accurate modeling of ZIF nucleation, crystal growth, and amorphization processes.

Main Methods:

• Optimization of Zn-related force field parameters based on the General Amber Force Field (GAFF).
• Utilized dispersion-corrected density functional theory (DFT) calculations and a genetic algorithm for parameter optimization.
• Validated the ZIF-FF force field through analysis of bond/angle distributions, phonon density of states, mechanical properties, diffusion, and ZIF amorphization.

Main Results:

• The developed ZIF-FF force field accurately describes the structural properties and relative stabilities of ZIFs.
• ZIF-FF correctly predicts the relative stability of ZIF polymorphs, a significant improvement over previous models.
• The force field demonstrates transferability, accurately predicting the stability of ZIF surfaces and densities of functionalized ZIFs.

Conclusions:

• ZIF-FF is a reliable and transferable force field for *ab initio* simulations of ZIFs.
• This development facilitates accurate computational studies of ZIF nucleation, crystal growth, and material properties.
• ZIF-FF provides a valuable tool for the design and discovery of new ZIF materials with tailored functionalities.