Urea-Based Metal–Organic Frameworks as High and Fast Adsorbent for Hg2+ and Pb2+ Removal from Water

Water pollution by various toxic heavy-metal ions, particularly mercury and lead, has been considered as a global problem with serious threat to public health. Nowadays, a variety of adsorbents have been used extensively for the removal of heavy-metal ions from water. In this work, two Zn-based metal–organic frameworks (MOFs), named TMU-31 and TMU-32, were successfully synthesized by a solid-state method named mechanosynthesis, which can be considered as a rapid, green, convenient, solventless, and low-cost process. These two MOFs are densely decorated with urea functional groups, which results in rapid, efficient, and selective removal of diverse heavy-metal ions, such as Hg2+ and Pb2+ ions, from wastewater. The sorption capacities of 476.19 mg g–1 in less than 15 min for Hg(II) ions and 909 mg g–1 for Pb(II) metal ions in less than 5 min were obtained effectively by these two structures. In addition, adsorption isotherms of Hg2+ and Pb2+ metal ions are in good agreement with Langmuir model, and also, th...