Highly recyclable cysteamine-modified acid-resistant MOFs for enhancing Hg (II) removal from water

Thiol-functionalized metal-organic frameworks (MIL-101-SH and UiO-66-SH) were synthesized by a post-synthetic modification method as the proper adsorbents for Hg (II) removal from water. This facile method for the synthesis of UiO-66-SH was developed via a condensation reaction between cysteamine and carboxyl groups present in the framework of UiO-66-COOH. MIL-101 was functionalized by grafting amine group of cysteamine on coordinatively unsaturated chromium ions centres, yielding to MIL-101-SH adsorbents. These two types of thiol-functionalized MOFs samples by cysteamine-modified were characterized by XRD, XPS, FTIR and N2 adsorption–desorption isotherms respectively, which prove the successful modification of the thiol groups. The maximum adsorption capacities of mercury ions for UiO-66-SH and MIL-101-SH adsorbents were 110 and 250 mg/g at pH of 5, respectively. Moreover, the acidic medium could effectively elute Hg (II) and the adsorbents can be well reusable.