# Identifying phase transitions in zeolitic imidazolate frameworks: microscopic insight from molecular simulations

## TL;DR

This paper introduces a new method to study the structure of metal-organic frameworks, helping identify different phases and transitions using molecular simulations.

## Contribution

The novel contribution is a computational methodology for characterizing middle-range order in MOFs applicable to both crystalline and amorphous phases.

## Key findings

- A new method for structural characterization of MOFs was developed using supramolecular ring analysis.
- The method identifies phases and phase transitions by analyzing ring statistics and geometrical properties.
- The approach is applicable to both ordered and disordered MOF phases.

## Abstract

Metal–organic frameworks (MOFs) feature a rich structural diversity, including crystalline, amorphous, and liquid phases of varying topologies. Their structural characterization is often performed either at the local scale (through pair distribution functions, bond angle distributions, etc.) or, for crystalline phases, through topology analysis of the periodic framework—leaving out disordered and amorphous phases. In this work, we develop a computational methodology for the structural characterization of middle-range order in MOFs that is applicable to both crystalline and amorphous phases. We base our method on the statistical analysis of the geometry of the supramolecular framework at the microscopic level, and its evolution during molecular simulation. We analyze the statistics of metal–organic rings, their distribution in size, as well as their geometrical characteristics through mathematical tools derived from polymer physics: radius of gyration, asphericity, and writhe. We show that this advanced characterization can be leveraged for the identification of phases and the detection and analysis of phase transitions.

We present a computational methodology for the structural characterization of middle-range order in metal–organic frameworks (MOFs), based on analysis of their supramolecular rings and applicable to both crystalline and amorphous phases.