Studying the Effect of Counter Ions on the Gas Selectivity and Volatile Organic Compounds Separation

The synthesis and characterization of three new metal chalcogenide aerogels, Chalcogels, AFe3Zn3S17 (A= Na, K, or Rb) is described. Alkali metal polychalcogenides (Na2S5, K2S5, or Rb2S5) reactwith metal acetate like Fe(OAc)2 and Zn(OAc)2in formamide solutionforming extended polymeric frameworks by gelation. Chalcogels obtained aftersupercritical drying have BET surface areas of 430, 444, and 435 m 2 /g for NaFe3Zn3S17, KFe3Zn3S17, and RbFe3Zn3S17, respectively. The effect of the counter ions (K, Na, and Rb) wasstudied by examined the adsorption capacities of the resulting chalcogels toward different gases and volatile organic compounds. The measurements showed that CO2 and toluene adsorption capacities increase with the polarizability of the surface atoms in the following order: Rb chalcogel> K chalcogel> Na chalcogel.This finding reveals a trend based on cation size and acid–base surface properties that might have a significant impact on altering adsorptive properties of chalcogels by using more polarizable counter ions.