Ce-based UiO-66 metal-organic frameworks as a new redox catalyst for atomic spectrometric determination of Se(VI) and colorimetric sensing of Hg(II).

The cerium (Ce)-based UiO-66 metal-organic frameworks were employed for the first time as an effective catalyst for both oxidation and reduction. On one hand, selenium (Se)(VI) was efficiently photo-reduced to volatile species derived from the low lying of Ce 4f orbital and efficient generation of photo-electrons through the frameworks of UiO-66(Ce); on the other hand, the chromogenic substrate, 3, 3′, 5, 5′-tetramethylbenzydine (TMB), was oxidized based on the oxidase-like behavior of UiO-66(Ce) derived from the Ce4+/Ce3+ spontaneous redox couple. The photo-reduced Se(VI) was determined by atomic fluorescence spectrometry, with a linear range of 5.0–200.0 μg/L−1, correlation coefficient of 0.998, and detection limit of 1.5 ng/mL−1 obtained. The colorimetric sensing of mercury (Hg)(II) was accomplished based on the inhibition of TMB oxidation via Hg (II)-TMB interaction, with two linear ranges of 0.1–2.0 μM and 2.25–4.1 μM obtained, and a correlation coefficient of 0.993 and 0.995 obtained, respectively. The catalytic activity of UiO-66(Ce) was demonstrated to be satisfactory for both oxidation and reduction, which further explored the application of UiO-66(Ce) in the field of catalysis. • UiO-66(Ce) was first used as a single catalyst for both oxidation and reduction; • The Se(VI) reduction was derived from the low lying Ce 4f orbital in UiO-66(Ce); • UiO-66(Ce) and TMB was first used for colorimetric sensing of Hg(II); • This work explored limited applications of Ce-based MOFs in catalysis. [ABSTRACT FROM AUTHOR]