High Proton Conduction at above 100 °c Mediated by Hydrogen Bonding in a Lanthanide Metal-Organic Framework

Qun Tang, Yiwei Liu, Shuxia Liu, Danfeng He, Jun Miao, Xingquan Wang, Guocheng Yang, Zhan Shi, Zhiping Zheng

Research output: Contribution to journalArticle

122 Scopus citations

Abstract

A lanthanide metal-organic framework (MOF) compound of the formulation [Eu2(CO3)(ox)2(H2O) 2]·4H2O (1, ox = oxalate) was prepared by hydrothermal synthesis with its structure determined crystallographically. Temperature-dependent but humidity-independent high proton conduction was observed with a maximum of 2.08 × 10-3 S cm-1 achieved at 150 °C, well above the normal boiling point of water. Results from detailed structural analyses, comparative measurements of conductivities using regular and deuterated samples, anisotropic conductivity measurements using a single-crystal sample, and variable-temperature photoluminescence studies collectively establish that the protons furnished by the Eu(III)-bound and activated aqua ligands are the charge carriers and that the transport of proton is mediated along the crystallographic a-axis by ordered hydrogen-bonded arrays involving both aqua ligands and adjacent oxalate groups in the channels of the open framework. Proton conduction was enhanced with the increase of temperature from room temperature to about 150 °C, which can be rationalized in terms of thermal activation of the aqua ligands and the facilitated transport between aqua and adjacent oxalate ligands. A complete thermal loss of the aqua ligands occurred at about 160 °C, resulting in the disintegration of the hydrogen-bonded pathway for proton transport and a precipitous drop in conductivity. However, the structural integrity of the MOF was maintained up to 350 °C, and upon rehydration, the original structure with the hydrogen-bonded arrays was restored, and so was its high proton-conduction ability.

Original languageEnglish (US)
Pages (from-to)12444-12449
Number of pages6
JournalJournal of the American Chemical Society
Volume136
Issue number35
DOIs
StatePublished - Sep 3 2014

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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