Early-Stage Formation of the SIFSIX-3-Zn Metal–Organic Framework: An Automated Computational Study

Abstract

Metal−organic frameworks (MOFs) have attracted significant attention over the past 2 decades due to their wide applicability as functional materials. However, targeted synthesis of novel MOFs remains problematic as their formation mechanisms are poorly understood, which forces us to rely on serendipity in the synthesis of novel MOFs. Here, we demonstrate a workflow employing the artificial force induced reaction (AFIR) method to investigate the self-assembly process of the node of the SIFSIX-3-Zn MOF, [Zn(pyz) 4 (SiF 6 ) 2 ] 2− (pyz = pyrazine), in an automated manner. The workflow encompassing AFIR calculations, generation of extensive reaction path networks, propagation simulations of intermediates, and further refinements of identified formation pathways showed that the nodal structure can form through multiple competing pathways involving interconvertible intermediates. This finding provides a plausible rationale for the stochastic multistage processes believed to be key in MOF formation. Furthermore, this work represents the first application of an automated reaction mechanism discovery method to a MOF system using a general workflow that is applicable to study the formation of other MOF motifs as well.

Understanding and controlling the nucleation and growth of metal–organic frameworks

“…This model is supported by a study of the MIL- n MOF family by Fe K-edge extended X-ray absorption fine structure (EXAFS), which revealed that SBUs are present during both the nucleation and growth of MOFs, retaining their connectivity and structure throughout. 44 The formation of the SBUs themselves has been studied in systems including Mg-carboxylate MOFs, 45 ZIF-8, 46 MIL-101, 47 UiO-66, 48 In-MIL-68, 49 ZIF-67, 50 MOF-2/MOF-5, 51 and SIFSIX-3-Zn 52 using a variety of techniques from electrospray ionization-mass spectrometry (ESI-MS) and UV-visible spectroscopy to pair distribution function analysis and single molecule electron microscopy. These studies have shown that SBUs can assemble through a variety of mechanisms, such as ligand exchange and elimination at a single metal node, 50 chain growth from a single metal node and linker, 49 or organic linker coordination to inorganic metal clusters.…”