We report the synthesis of ion-exchangeable molybdenum sulfide chalcogel through an oxidative coupling process, using (NH₄)₂MoS₄ and iodine. After supercritical drying, the MoS_x amorphous aerogel shows a large surface area up to 370 m²/g with a broad range of pore sizes. X-ray photoelectron spectroscopic and pair distribution function analyses reveal that Mo⁶⁺ species undergo reduction during network assembly to produce Mo⁴⁺-containing species where the chalcogel network consists of [Mo₃S₁₃] building blocks comprising triangular Mo metal clusters and S₂^2- units. The optical band gap of the brown-black chalcogel is ∼1.36 eV. The ammonium sites present in the molybdenum sulfide chalcogel network are ion-exchangeable with K⁺ and Cs⁺ ions. The molybdenum sulfide aerogel exhibits high adsorption selectivities for CO₂ and C₂H₆ over H₂ and CH₄. The aerogel also possesses high affinity for iodine and mercury.

From: Kota S. Subrahmanyam, Christos D. Malliakas, Debajit Sarma, Gerasimos S. Armatas, Jinsong Wu, and Mercouri G. Kanatzidis,
‘Ion-Exchangeable Molybdenum Sulfide Porous Chalcogel: Gas Adsorption and Capture of Iodine and Mercury‘,
J. Am. Chem. Soc.,
137(43), 13943-13948 (2015).