Rare Earth Chalcogels Na<i>Ln</i>SnS₄ (<i>Ln</i> = Y, Gd, Tb) for Selective Adsorption of Volatile Hydrocarbons and Gases

Abstract

The synthesis and characterization of the rare earth chalcogenide aerogels NaYSnS 4 , NaGdSnS 4 , and NaTbSnS 4 is reported. Rare earth metal ions like Y 3+ , Gd 3+ , and Tb 3+ react with the chalcogenide clusters [SnS 4 ] 4– in aqueous formamide solution forming extended polymeric networks by gelation. Aerogels obtained after supercritical drying have BET surface areas of 649 m 2 · g –1 (NaYSnS 4 ), 479 m 2 · g –1 (NaGdSnS 4 ), and 354 m 2 · g –1 (NaTbSnS 4 ). Electron microscopy and physisorption studies reveal that the new materials have pores in the macro (above 50 nm) and meso (2–50 nm) regions. These aerogels show higher adsorption of toluene vapor over cyclohexane vapor and CO 2 over CH 4 or H 2 . The notable adsorption capacity for toluene (NaYSnS 4 : 1108 mg · g –1 ; NaGdSnS 4 : 921 mg · g –1 ; and NaTbSnS4: 645 mg · g –1 ) and high selectivity for gases (CO 2 /H 2 : 172 and CO 2 /CH 4 : 50 for NaYSnS 4 , CO 2 /H 2 : 155 and CO 2 /CH 4 : 37 for NaGdSnS 4 , and CO 2 /H 2 : 75 and CO 2 /CH 4 : 28 for NaTbSnS 4 ) indicate potential future use of chalcogels in adsorption‐based gas or hydrocarbon separation processes.