title: Computational Characterization of Defects in Metal-Organic Frameworks: Spontaneous and Water-Induced Point Defects in ZIF-8.
abstract: Zeolitic imidazolate frameworks (ZIFs) are an important class of porous crystalline metal-organic framework (MOF) materials that have attracted widespread attention for applications ranging from gas adsorption and separation to catalysis. Although the bulk crystal structures of MOFs are typically well-characterized, comparatively little is known regarding MOF defect structures. Drawing on analogies with conventional silicon-based zeolites, we utilize computational methods to examine the structure and stability of putative point-defect structures (including vacancies, substitutions, and "dangling" linkers) within the prototypical ZIF-8 structure. Considering both postsynthetic (gas-phase) and synthetic (solution-phase) conditions, we find that several of the defect structures lie low in energy relative to the defect-free parent crystal, with barriers to defect formation that are large but surmountable under relevant temperatures. These results are consistent with prior experimental observations of ZIF stability and reactivity and suggest that defects may play an important role in influencing the long-term stability of MOFs under conditions that include exposure to water vapor and trace contaminants such as acid gases.
authors.affiliation: Theoretical Chemistry Institute and Department of Chemistry, University of Wisconsin-Madison , 1101 University Avenue, Madison, Wisconsin 53706, United States.
authors.forename: Chenyang
authors.initials: C
authors.lastname: Zhang
authors.affiliation: School of Chemistry & Biochemistry, Georgia Institute of Technology , Atlanta, Georgia 30332, United States.
authors.forename: Chu
authors.initials: C
authors.lastname: Han
authors.affiliation: School of Chemical & Biomolecular Engineering, Georgia Institute of Technology , 311 Ferst Drive NW, Atlanta, Georgia 30332-0100, United States.
authors.forename: David S
authors.initials: DS
authors.lastname: Sholl
authors.affiliation: Theoretical Chemistry Institute and Department of Chemistry, University of Wisconsin-Madison , 1101 University Avenue, Madison, Wisconsin 53706, United States.
authors.forename: J R
authors.initials: JR
authors.lastname: Schmidt
keywords: density functional theory; substitution; vacancy; zeolitic imidazolate framework