Tuning Metal-Organic Framework Nanocrystal Shape through Facet-Dependent Coordination.

Liu, Xiao-Yuan; Lo, Wei-Shang; Wu, Chunhui; Williams, Benjamin P; Luo, Lianshun; Li, Yang; Chou, Lien-Yang; Lee, Yongjin et al. · Nano Lett · 2020

basic_science · Level V

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Abstract

We studied coordination-dependent surfactant binding on shaped MOF nanocrystals. Cetyltrimethylammonium bromide (CTAB) on the surface of ZIF-8 was used as a model system. Infrared spectroscopic analysis and molecular dynamics simulations reveal different coordination environments for Zn nodes on {100} and {110} facets, resulting in different CTAB adsorption. We found that we are able to fine-tune the ratio of {100} and {110} facets in the nanocrystals. We also observed that once the MOF nanocrystals are enclosed by pure {110} facets growth along the {100} facets is terminated because the MOF nanocrystal has no surface area for CTAB adsorption. Growth can then be reinitiated through the etching of these rhombic dodecahedral nanocrystals to form a small amount of undercoordinated sites. This work represents the first systematic study of the design principles underpinning the synthesis of shaped MOF nanocrystals.