Recovery of dimethyl sulfoxide from aqueous solutions by highly selective adsorption in hydrophobic metal-organic frameworks

Abstract

Metal-organic frameworks (MOFs) have emerged as a new family of nanoporous materials. While gas separation in MOFs has been extensively investigated, liquid separation is scarcely examined and lacks a microscopic understanding. A molecular simulation study is reported here for the recovery of dimethyl sulfoxide (DMSO) from aqueous solutions in three hydrophobic MOFs, namely, Zn 4O(bdc)(bpz) 2, Zn(bdc)(ted) 0.5, and ZIF-71. Type I adsorption isotherms are observed for DMSO, while H 2O exhibits type V adsorption isotherms with hysteresis. The saturation capacities of both DMSO and H 2O decrease following the order of Zn 4O(bdc) (bpz) 2 > Zn(bdc)(ted) 0.5 > ZIF-71, in accordance with the variation of free volume and porosity in the three MOFs. As attributed to hydrophobic frameworks, the three MOFs are highly selective toward DMSO adsorption from DMSO/H 2O mixtures. The highest selectivity is predicted up to 1700 in ZIF-71. This simulation study provides molecular insight into the separation mechanism of DMSO/H 2O liquid mixtures and suggests that hydrophobic MOFs are superior candidates for DMSO recovery. © 2012 American Chemical Society.