Construction of a superhydrophobic microenvironment via polystyrene coating: an unexpected way to stabilize CuI against oxidation

Abstract

Cu^I-Functionalized materials show high potential in numerous applications such as adsorptive desulfurization. Nonetheless, the instability of Cu^I against oxidation limits its practical applications, and exposure of Cu^I to air can lead to the formation of Cu^II owing to the presence of oxygen and moisture. Herein, an unexpected way to stabilize Cu^I against oxidation was designed by constructing a superhydrophobic microenvironment in original hydrophilic metal–organic frameworks (MOFs) via polystyrene (PS) coating. A pre-polymerization strategy is developed to coat PS on the surface of Cu^I-functionalized MIL-101(Cr) (Cu^IM) rather than entering the pores (producing Cu^IM@PS), and the access of moisture to Cu^I is hindered, thus stabilizing Cu^I regardless of the existence of oxygen. Cu^I in Cu^IM@PS is stable in the air with a constant relative humidity of 75% for 200 days, while almost all Cu^I is converted to Cu^II in Cu^IM in only 14 days. The optimal Cu^IM@PS material after air exposure can adsorb 0.208 mmol g⁻¹ of thiophene, which is much superior to that of Cu^IM (0.024 mmol g⁻¹) despite the comparable adsorption capacity for unexposed materials. Moreover, the present Cu^IM@PS adsorbents exhibit excellent adsorption performance for water-containing model fuels.