The targeted design of dual-functional metal-organic frameworks (DF-MOFs) as highly efficient adsorbents for Hg2+ ions: synthesis for purpose.

Abstract

Designing adsorbents with accessible chelating sites and achieving high contaminant purification efficiency are still important to overcome environmental remediation challenges. As one of the significant global concerns, the presence of heavy metal ions in the environment has attracted increasing attention due to their toxicity, carcinogenicity, and bioaccumulation in the food chain. Herein, we performed a targeted design of a new dual-functionalized metal-organic framework (DF-MOF) by incorporating different percentages of the N1,N3-di(pyridine-4-yl) malonamide ligand (S) into urea-containing MOF (TMU-32); the produced material was labeled as TMU-32S (with 33%, 65%, and 100% incorporation percentages). Designing DF-MOF is our "design-for-purpose" approach for the decoration of MOF walls by suitable functional groups, resulting in high removal capacity of heavy metal ions. Among the TMU-32S series having different concentrations of the S ligand, TMU-32S-65% demonstrated exceptional Hg2+ ion selectively. To the best of our knowledge, this is the first report of mixed urea-malonamide-based MOF, which provides a proper coordination site to strongly coordinate with Hg2+ ions, along with 1428 mg g-1 maximum adsorption capacity. Generally, we attributed the impressive implementation of TMU-32S-65% to the synergistic effects of both hydrophilic chelating urea and the malonamide functional group. Hence, the results reported in this work indicate the exceptional potential of DF-MOFs for the high accomplishment of environmental remediation.