Important Counteranion Effect on Adsorption Efficacity of Hydrogen Sulfide by Silver(I)-Dithione Coordination...

Four new coordination polymers (CPs) have been prepared and evaluated for their efficacy in adsorbing hydrogen sulfide. The reactions of the structurally flexible assembling dithione ligand, L, with different silver(I) salts lead to four new metal-organic coordination architectures (CPs I, III, V, and VIII) exhibiting either one- or two-dimensional networks. CP I, 2D-[(Ag₂Cl₂)L], exhibits a linear series of rhomboid (S)₂Ag(μ₂-Cl)₂Ag(S)₂ secondary building units (SBUs) where S is one of the thione functions of L, altogether forming a 2D-network. CP III, 2D-[(AgI)L], is built upon parallel staircase-shaped 1D-[Ag₂(μ₃-I)₂] SBUs bridged by S atoms of L that form a 2D-grid. CP V, 2D-[(AgL)(NO₃)], presents parallel 1D-folded S-shaped [AgL]⁺ chains linked by strong argentophilic Ag···Ag interactions, forming a 2D-scaffolding. CP VIII, 1D-[(Ag₂L₃)(Cr₂O₇)], shows 1D-zigzag [{Ag(η²-μ₂,η-μ,μ-L)}₂]² chains accompanied by Cr₂O₇^2- counteranions. The adsorption isotherms of H₂S gas by these new CPs were examined and compared to those of related CPs [(Ag₂Br₂)L] (II), [(AgCN)₄L] (IV), [(Ag₂L)(CF₃SO₃)₂] (VI), and [(Ag₂L)(NO₃)(ClO₄)] (VII). Among the tested polymers, the 3D-CP IV featuring cyanide anions exhibits the highest adsorption capacity of the CPs studied in this work. In order to determine the reason for this marked difference, density functional theory (DFT) computations were used. All in all, it turns out that the electrostatic interactions (CN^-···H-SH) are significantly stronger than the O^-···H-SH ones. This investigation provides a valuable conceptual tool for other designs of CPs and MOFs having the purpose of capturing toxic gases.