Specific K+ Binding Sites as CO2 Traps in a Porous MOF for Enhanced CO2 Selective Sorption

Na Li, Ze Chang, Hongliang Huang, Rui Feng, Wei Wei He, Ming Zhong, David G. Madden, Michael J. Zaworotko, Xian He Bu

Research output: Contribution to journalArticlepeer-review

Abstract

Metal–organic frameworks (MOFs) can be fine-tuned to boost sorbent-sorbate interactions in order to improve gas sorption and separation performance, but the design of MOFs with ideal structural features for gas separation applications remains a challenge. Herein it is reported that unsaturated alkali metal sites can be immobilized in MOFs through a tetrazole based motif and that gas affinity can thereby be boosted. In the prototypal MOF of this type-NKU-521 (NKU denotes Nankai University), K+ cations are effectively embedded in a trinuclear Co2+-tetrazole coordination motif. The embedded K+ sites are exposed to the pores of NKU-521 through water removal, and the isosteric heat (Qst) for CO2 is boosted to 41 kJ mol-1. The nature of the binding site is validated by molecular simulations and structural characterization. The K+ cations in effect serve as gas traps and boost the CO2-framework affinity, as measured by the Qst, by 24%. In addition, the impact of unsaturated alkali metal sites upon the separation of hydrocarbons is evaluated for the first time in MOFs using ideal adsorbed solution theory (IAST) calculations and column breakthrough experiments. The results reveal that the presence of exposed K+ sites benefits gas sorption and hydrocarbon separation performances of this MOF.

Original languageEnglish
Article number1900426
Pages (from-to)e1900426
JournalSmall
Volume15
Issue number22
DOIs
Publication statusPublished - 29 May 2019

Keywords

  • CO capture
  • K doping
  • metal–organic framework
  • porous materials

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