Tuning the Chemical Environment within the UiO-66-NH2 Nanocages for Charge-Dependent Contaminant Uptake and Selectivity

Ahmed H. Ibrahim, Worood A. El-Mehalmey, Rana R. Haikal, Mohamed E. A. Safy, Muhamed Amin, Hassan R. Shatla, Stavros G. Karakalos, Mohamed H. Alkordi*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

55 Citations (Scopus)
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The remarkable water stability of Zr-carboxylatebased metal-organic frameworks (MOFs) stimulated considerable interest toward their utilization in aqueous phase applications. The origin of such stability is probed here through pH titration and plc modeling. A unique feature of the Zr-6(mu 3OH)(4)(mu O-3)(4)(RCO2)(12) cluster is the Zr-bridging oxo/hydroxyl groups, demonstrating several pK(a) values that appear to provide for the water stability at a wide range of pH. Accordingly, the tunability of the cage/surface charge of the MOF can feasibly be controlled through careful adjustment of solution pH. Such high stability, and facile control over cage/surface charge, can additionally be augmented through introducing chemical functionalities lining the cages of the MOF, specifically amine groups in the UiO-66-NH2 presented herein. The variable protonation states of the Zr cluster and the pendant amino groups, their H-bond donor/acceptor characteristics, and their electrostatic interactions with guest molecules were effectively utilized in controlled experiments to demonstrate high uptake of model guest molecules (137 mg/g for Cr(VI), 1275 mg/g for methylene blue, and 909 mg/g for methyl orange). Additionally, a practical form of the silica-supported MOF, UiO-66-NH2 @SiO2, constructed in under 2 h reaction time, is described, generating a true platform microporous sorbent for practical use in demanding applications.

Original languageEnglish
Pages (from-to)15078-15087
Number of pages10
JournalInorganic Chemistry
Issue number22
Publication statusPublished - 18-Nov-2019


  • MOF
  • ZR


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