Hard-and-Soft Integration Strategy for Preparation of Exceptionally Stable Zr(Hf)-UiO-66 via Thiol–Ene Click Chemistry

Abstract

UiO-66 metal-organic frameworks (MOFs) are unstable in some harsh aqueous environments, which limit their practical applications. We demonstrate a postsynthetic modification methodology to transform hydrophilic Zr(Hf)-UiO-66 into superhydrophobic Zr(Hf)-UiO-66-SH-<i>y</i> (SH = thiol, <i>y</i> = fluoroalkyl) by introducing long fluoroalkyl chains into organic linkers through a thiol-ene click reaction. Water contact angles of the four modified UiO-66 MOFs are all larger than 150°. The grafted low-surface-energy fluorine-containing groups become an effective protective shield for the MOFs, making them exhibit remarkable stability in extreme conditions such as alkaline (pH = 12), saturated HCl, and high concentration of NaCl solution (20 wt %). The Zr-UiO-66 MOFs grafted with 1<i>H</i>,1<i>H</i>,2<i>H</i>-perfluoro-1-hexene have high CO₂ adsorption contents of 1.54 and 2.88 mmol·g^-1 at 298 and 273 K, respectively. Moreover, the superhydrophobic MOFs also showed potential application in oil/water separation.