Design of Metal-Organic Framework Templated Materials Using High-Throughput Computational Screening.

Momin Ahmad,Manuel Tsotsalas,Yi Luo,Alexander Schug,Christof Wöll

doi:10.3390/molecules25214875

Momin Ahmad, Manuel Tsotsalas + Show 3 more

Open Access

https://doi.org/10.3390/molecules25214875

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Abstract

The ability to crosslink Metal-Organic Frameworks (MOFs) has recently been discovered as a flexible approach towards synthesizing MOF-templated “ideal network polymers”. Crosslinking MOFs with rigid cross-linkers would allow the synthesis of crystalline Covalent-Organic Frameworks (COFs) of so far unprecedented flexibility in network topologies, far exceeding the conventional direct COF synthesis approach. However, to date only flexible cross-linkers were used in the MOF crosslinking approach, since a rigid cross-linker would require an ideal fit between the MOF structure and the cross-linker, which is experimentally extremely challenging, making in silico design mandatory. Here, we present an effective geometric method to find an ideal MOF cross-linker pair by employing a high-throughput screening approach. The algorithm considers distances, angles, and arbitrary rotations to optimally match the cross-linker inside the MOF structures. In a second, independent step, using Molecular Dynamics (MD) simulations we quantitatively confirmed all matches provided by the screening. Our approach thus provides a robust and powerful method to identify ideal MOF/Cross-linker combinations, which helped to identify several MOF-to-COF candidate structures by starting from suitable libraries. The algorithms presented here can be extended to other advanced network structures, such as mechanically interlocked materials or molecular weaving and knots.

Highlights

Network topology, i.e., the way building blocks are connected along three dimensions, critically influences key properties of natural and synthetic materials [1,2,3]
Whether a chosen cross-linker fits into a certain Metal-Organic Frameworks (MOFs) structure can be guided by (a) experience (Which often, even for experimentalists with large experience with MOFs, boils down to educated guessing), (b) experimentally testing many MOF/cross-linker combinations or (c) calculating the actual relevant sizes and manually selecting suitable leads
Automatizing the third option (c), i.e., to calculate all distances to achieve the maximum amount of matches for a given cross-linker, appears attractive to improve the probability of finding good candidates

Summary

Introduction

I.e., the way (molecular) building blocks are connected along three dimensions, critically influences key properties of natural and synthetic materials [1,2,3]. The advent of crystalline “framework” materials allowed to realize the long dreamed-of possibility to control materials on the molecular level [4]. Metal-Organic Frameworks (MOFs) [5] and Covalent-Organic Frameworks (COFs) [6] are prime examples of such “materials on demand”. MOFs and COFs share common features such as porosity and crystallinity. COFs feature attractive properties, such as extended π-conjugation and being composed of purely light weight elements [7,8]. Despite considerable progress in developing COFs [9], the structural variability of MOFs is considerable larger, as MOFs are able to leverage the vast chemical parameter space of their organic and inorganic components

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