Computational Study of ZIF-8 and ZIF-67 Performance for Separation of Gas Mixtures

Panagiotis Krokidas, Marcelo Castier, Ioannis Economou

Research output: Contribution to journalArticle

25 Citations (Scopus)

Abstract

ZIF-67, a modification of ZIF-8 framework through Zn substitution with Co, is tested for the first time for the separation of ethylene/ethane mixture using molecular simulations. The framework consists of cages connected with narrow apertures, which exhibit flexibility through a swelling motion, allowing for relatively large penetrants to diffuse. ZIF-67 demonstrates an enhanced separation for the specific mixture. Various computational techniques are employed (conventional molecular dynamics and Monte Carlo simulations, umbrella sampling, and Widom particle insertion), and the separation mechanism is investigated in terms of sorption and diffusion, for both ZIF-8 and ZIF-67. The stiffer bonding of Co with the adjacent N atoms results in a tighter structure and an aperture with smaller size and lower swelling amplitude than ZIF-8. The diffusion results show a clear dependency of the kinetic-driven separation on the aperture flexibility of the different frameworks. The diffusivities of different sized molecules (from He to n-butane) are simulated in both ZIF-8 and ZIF-67 frameworks, and the molecular size is correlated with the aperture's response variations. A generalized method based on these results is developed which helps the understanding of the sieving mechanism as a function of the penetrant size and of the aperture size and flexibility. This approach provides an efficient screening of modifiable frameworks toward more efficient separations.

Original languageEnglish
Pages (from-to)17999-18011
Number of pages13
JournalJournal of Physical Chemistry C
Volume121
Issue number33
DOIs
Publication statusPublished - 24 Aug 2017

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ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Surfaces, Coatings and Films
  • Physical and Theoretical Chemistry

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