Structure and Synthesizability of Iron–Sulfur Metal–Organic Frameworks

Sulfur-based metal–organic frameworks (MOFs) and
coordination
polymers (CPs) are an emerging class of hybrid materials that have
received growing attention due to their magnetic, conductive, and
catalytic properties with potential applications in electrocatalysis
and energy storage. In this work, we report a high-throughput virtual
screening protocol to predict the synthesizability of candidate metal–sulfur
MOFs/CPs by computing the thermodynamically stable structures resulting
from a particular combination of metal cluster, linker, cation, and
synthetic conditions. Free energies are computed by using all-atom
classical mechanical thermodynamic integration. Low-free-energy structures
are refined using ab initio density functional theory,
and pair distribution functions and powder X-ray diffraction patterns
are calculated to complement and guide experimental structure determination.
We validate the computational approach by retrospective predictions
of the stable structure produced by experimental syntheses, and a
subsequent screen predicts Fe4S4-BDT–TPP
as a new thermodynamically stable one-dimensional (1D) CP comprising
a redox-active Fe4S4 cluster, a 1,4-benzenedithiolate
(BDT) linker, and a tetraphenylphosphonium (TPP) countercation. This
material is experimentally synthesized, and the 1D chain structure
of the crystal is confirmed using microcrystal electron diffraction.
The computational screening pipeline is generically transferable to
neutral and ionic MOFs/CPs comprising arbitrary metal clusters, linkers,
cations, and synthetic conditions, and we make it freely available
as an open source tool to guide and accelerate the discovery and engineering
of novel porous materials.