Atomistic Models of Amorphous Metal–Organic Frameworks

Abstract

There is an increasing interest in the amorphous states of metal−organic frameworks (MOFs) and porous coordination polymers, which can be produced by pressureinduced amorphization, temperature-induced amorphization, melt−quenching, ball milling, irradiation, etc. They can exhibit useful physical and chemical properties, distinct from those achievable in the crystalline states, along with greater ease of processing, and intrinsic advantages over crystals and powders, such as high transparency and mechanical robustness. However, these amorphous states are particularly challenging to characterize, and the determination of their framework structure at the microscopic scale is difficult, with only indirect structural information available from diffraction experiments. In this Perspective, we review and compare the existing methodologies available for the determination of microscopic models of amorphous MOFs, based on both experimental data and simulation methods. In particular, we present the atomistic models that can be obtained using Reverse Monte Carlo (RMC) methods, Continuous Random Networks (CRN), classical and ab initio molecular dynamics, reactive force fields, and simulated assembly/polymerization algorithms.

CrystalNets.jl: Identification of Crystal Topologies

“…For many graphs, this search space remains rather large compared to the set of all possible triplets of edges. Our goal in this project was for our software to be able to tackle very big structures very efficiently, for two different types of applications: high-throughput screening of hypothetical materials, where the topological detection is performed on hundreds of thousands (and sometimes several millions) of structures [44], and application to very large periodic structures, such as models of amorphous framework materials [45]. Therefore, reducing this search space is crucial for performance since it directly tackles one of the bottlenecks in the original implementation of Systre.…”

Investigating the chemical sensitivity of melting in zeolitic imidazolate frameworks

“…The field of metal-organic frameworks (MOFs) has expanded to encompass defective, disordered, and amorphous materials, with many studies demonstrating that structural disorder can be utilised to enhance chemical and physical properties. [1][2][3][4][5][6] For example, amorphous MOFs have already gained interest as potential candidates for trapping iodine and encapsulating bioactive molecules. [7][8][9] These amorphous MOFs retain the short range order of their parent crystalline frameworks, whilst lacking long range periodicity.…”

Modelling the effect of defects and disorder in amorphous metal−organic frameworks

“…38 The absence of a unique crystallographic unit cell makes modelling amorphous materials more challenging, and limits the predictive capabilities of computational researchers in the field of aMOFs. 39 To overcome such challenges, previous works on modelling aMOFs have used reverse mapping approaches, where models of simpler amorphous inorganic materials are transformed to possess the correct chemistry of a MOF, and then in some cases refined against experimental data (e.g., using reverse Monte Carlo modelling). 20,[40][41][42] Alternatively, direct simulations of the amorphization procedure from a crystalline structure can be performed using molecular dynamics (MD).…”