Preferential adsorption of volatile hydrocarbons on high surface area chalcogels KMBiTe₃ (M = Cr, Zn, Fe)

Three chalcogels KCrBiTe₃, KZnBiTe₃, and KFeBiTe₃ were synthesized by the sol–gel metathesis route. K⁺ and the transition metal cations Cr²⁺, Zn²⁺ or Fe²⁺ connect [BiTe₃]³⁻ anions to form amorphous black compounds. Supercritical drying of the black gels produced porous materials with BET surface areas of 230 m²/g (KCrBiTe₃), 450 m²/g (KZnBiTe₃) and 514 m²/g (KFeBiTe₃). The adsorption properties of the resulting chalcogenide aerogels or chalcogels have been studied using volatile organic hydrocarbons (VOCs) and gases as adsorptives. The results show preferential adsorption of toluene vapor over cyclohexane vapor. The adsorption capacity toward toluene is 5.02 mmol/g for KCrBiTe₃, 5.58 mmol/g for KZnBiTe₃ and 7.89 mmol/g for KFeBiTe₃. Preferential adsorption of CO₂ over CH₄ or H₂ was observed for the chalcogels: KCrBiTe₃ (CO₂/H₂: 175, CO₂/CH₄: 50), KZnBiTe₃ (CO₂/H₂: 180 and CO₂/CH₄: 60) and KFeBiTe₃ (CO₂/H₂: 225 and CO₂/CH₄: 65).