Role of MOF surface defects on the microscopic structure of MOF/polymer interfaces: A computational study of the ZIF-8/PIMs systems

Overview & Synopsis

The influence of defects at the metal-organic framework (MOF) surface on the microscopic structure of a MOF/polymer composite has been studied by a computational methodology that combines density functional theory calculations with force field-based molecular dynamics simulations. This has been applied to composites formed by ZIF-8 and two different polymers of intrinsic microporosity: PIM-1 and PIM-EA-TB. Analysis of the MOF/polymer interactions, surface coverage, polymer conformation/stiffness and a full characterization of the interfacial voids are provided. We found that, although the nature of the MOF/polymer interactions changes in the presence of defects, the coverage and conformation of the polymer, as well as the morphology of the "interfacial microvoids" remain practically unchanged from a microscopic point of view. These results suggest that there is no microscopic evidence that defective MOF surfaces drastically change the geometry of the MOF/polymer interface and the strength of the physisorption-type interactions in play. (C) 2017 Elsevier Inc. All rights reserved.