Zirconium Metal-Organic Frameworks Integrating Chloride Ions for Ammonia Capture and/or Chemical Separation

Jian Liu*, Zhijie Chen, Rui Wang, Selim Alayoglu, Timur Islamoglu, Seung Joon Lee, Thomas R. Sheridan, Haoyuan Chen, Randall Q. Snurr, Omar K. Farha, Joseph T. Hupp

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

Ammonia capture by porous materials is relevant to protection of humans from chemical threats, while ammonia separation may be relevant to its isolation and use following generation by emerging electrochemical schemes. Our previous work described both reversible and irreversible interactions of ammonia with the metal-organic framework (MOF) material, NU-1000, following thermal treatment at either 120 or 300 °C. In the present work, we have examined NU-1000-Cl, a variant that features a modified node structure-at ambient temperature, Zr6(μ3-O)4(μ3-OH)4(H2O)812+ in place of Zr6(μ3-O)4(μ3-OH)4(OH)4(H2O)48+. Carboxylate termini from each of eight linkers balance the 8+ charge of the parent node, while four chloride ions, attached only by hydrogen bonding, complete the charge balance for the 12+ version. We find that both reversible and irreversible uptake of ammonia are enhanced for NU-1000-Cl, relative to the chloride-free version. Two irreversible interactions were observed via in situ diffuse-reflectance infrared Fourier-transform spectroscopy: coordination of NH3 at open Zr sites generated during thermal pretreatment and formation of NH4+ by proton transfer from node aqua ligands. The irreversibility of the latter appears to be facilitated by the presence chloride ions, as NH4+ formation occurs reversibly with chloride-free NU-1000. At room temperature, chemically reversible (and irreversible) interactions between ammonia and NU-1000-Cl result in separation of NH3 from N2 when gas mixtures are examined with breakthrough instrumentation, as evinced by a much longer breakthrough time (μ9 min) for NH3.

Original languageEnglish (US)
Pages (from-to)22485-22494
Number of pages10
JournalACS Applied Materials and Interfaces
Volume13
Issue number19
DOIs
StatePublished - May 19 2021

Keywords

  • ammonia capture
  • charge-compensating anions
  • chemical separation
  • irreversible uptake
  • metal-organic framework
  • reversible uptake

ASJC Scopus subject areas

  • Materials Science(all)

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