Selective surfaces: Quaternary Co(Ni)MoS-based chalcogels with divalent (Pb 2+, Cd 2+, Pd 2+) and trivalent (Cr 3+, Bi 3+) metals for gas separation

Kyriaki Polychronopoulou, Christos D. Malliakas, Jiaqing He, Mercouri G. Kanatzidis

Research output: Contribution to journalArticle

37 Citations (Scopus)

Abstract

Porous chalcogels with tunable compositions of Co xM 1-xMoS 4 and Ni xM 1-xMoS 4, where M = Pd 2+, Pb 2+, Cd 2+, Bi 3+, or Cr 3+ and x = 0.3-0.7, were synthesized by metathesis reactions between the metal ions and MoS 4 2-. Solvent exchange, counterion removal and CO 2 supercritical drying led to the formation of aerogels. All chalcogels exhibited high surface areas (170-510 m 2/g) and pore volumes in the 0.56-1.50 cm 3/g range. Electron microscopy coupled with nitrogen adsorption measurements suggest the presence of both mesoporosity (2 nm < d < 50 nm) and macroporosity (d > 50 nm, where d is the average pore size). Pyridine adsorption corroborated for the acid character of the aerogels. We present X-ray photoelectron spectroscopic and X-ray scattering evidence that the [MoS 4] 2- unit does not stay intact when bound to the metals in the chalcogel structure. The Mo 6+ species undergoes redox reactions during network assembly, giving rise to Mo 4+/5+-containing species where the Mo is bound to sulfide and polysulfide ligands. The chalcogels exhibit high adsorption selectivities for CO 2 and C 2H 6 over H 2, N 2, and CH 4 whereas specific compositions exhibited among the highest CO 2 enthalpy of adsorption reported so far for a porous material (up to 47 kJ/mol). The Co-Pb-MoS 4 and Co-Cr-MoS 4 chalcogels exhibited a 2-fold to 4-fold increase in CO 2/H 2 selectivity compared to ternary CoMoS 4 chalcogels.

Original languageEnglish
Pages (from-to)3380-3392
Number of pages13
JournalChemistry of Materials
Volume24
Issue number17
DOIs
Publication statusPublished - Sep 11 2012

Keywords

  • aerogels
  • chalcogenides
  • gas adsorption
  • porosity

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

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