Platinum Nanoparticle Encapsulated Metal–Organic Frameworks for Colorimetric Measurement and Facile Removal of Mercury(II)

Pt nanoparticle (Pt NP)@UiO-66-NH2 composites were synthesized and encompassed the benefits of permanent porosity, high thermal and chemical stability of metal-organic frameworks (MOFs), together with the functional behavior of isolated Pt NPs. The PVP-stabilized Pt NPs with the average diameter of 2.48 nm were well dispersed and confined within the framework of UiO-66-NH2. Pt NPs possess highly peroxidase-like activities and make the composites oxidize 3,3',5,5'-tetramethylbenzidine in the presence of H2O2. Moreover, the specific interaction between Hg2+ and Pt NPs leads to the effective suppression of the peroxidase-like activity of Pt NP@UiO-66-NH2, which endows excellent selectivity for Hg2+ measurement over the interfering metal ions. Based on the colorimetric sensing system, Hg2+ is linearly measured over the range from 0 to 10 nM with a detection limit of 0.35 nM. Moreover, the as-obtained Pt NP@UiO-66-NH2 nanocomposites exhibit high capacity and good selectivity for Hg2+ adsorption, which is successfully applied to treat Hg2+ in water with removal efficiency over 99%. With these findings, Pt NP@UiO-66-NH2 composites can be used to develop a simple and rapid colorimetric sensing system and are utilized as nanoadsorbents for facile removal of Hg2+. This work not only expands the scientific researches on MOFs but also provides practical application in environmental, biological, and relative fields.