TY - JOUR
T1 - Selective surfaces
T2 - Quaternary Co(Ni)MoS-based chalcogels with divalent (Pb 2+, Cd 2+, Pd 2+) and trivalent (Cr 3+, Bi 3+) metals for gas separation
AU - Polychronopoulou, Kyriaki
AU - Malliakas, Christos D.
AU - He, Jiaqing
AU - Kanatzidis, Mercouri G.
PY - 2012/9/11
Y1 - 2012/9/11
N2 - 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.
AB - 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.
KW - aerogels
KW - chalcogenides
KW - gas adsorption
KW - porosity
UR - http://www.scopus.com/inward/record.url?scp=84866124135&partnerID=8YFLogxK
U2 - 10.1021/cm301444p
DO - 10.1021/cm301444p
M3 - Article
AN - SCOPUS:84866124135
SN - 0897-4756
VL - 24
SP - 3380
EP - 3392
JO - Chemistry of Materials
JF - Chemistry of Materials
IS - 17
ER -