The assembly mechanism of hierarchical materials controlled by the choice of solvent and presence of spectator ions. In this paper, we use enhanced sampling molecular dynamics methods to investigate these effects on the configurational landscape of metal-linker interactions in the early stages of synthesis, using MIL-101(Cr) as a prototypical example. Microsecond-long well- tempered metadynamics (WTmetaD) simulations uncover a complex free energy structural landscape, with distinct crystal (C) and non-crystal (NC) like configurations and their equilibrium population. In presence of ions (Na+, F-), we observe a complex effect on the crystallinity of secondary building units (SBUs), by encouraging/suppressing salt bridges between C configurations and consequently controlling the percentage of defects. Solvent effects are assessed by introducing N, N dimethylformamide (DMF) instead of water, where SBU adducts are appreciably more stable and compact. These results shed light on how solvent and ionic strength impact the free energy of assembly phenomena that ultimately control material synthesis
Molecular Level Understanding of the Free Energy Landscape in Early Stages of MOF Nucleation
13 March 2019, Version 2
This content is a preprint and has not undergone peer review at the time of posting.
SI MIL101Cr R1 final