Intrinsic catalase-mimicking MOFzyme for sensitive detection of hydrogen peroxide and ferric ions

Lanthanide metal-organic frameworks (Ln-MOFs) exhibit outstanding properties, including high chemical and thermal stability, as well as their promising enzyme-mimic activity (MOFzyme). A new cerium MOFs (Ce-MOF) was synthesized via a solvothermal method using organic linker 4,4′,4″-nitrilotribenzoic acid (H3NTB). The crystallinity of the prepared material was confirmed using X-ray diffraction (XRD). The coordination between Ce and H3NTB was approved using Fourier transforms infrared (FT-IR). The chemical and oxidation state of Ce-MOF was characterized using X-ray photoelectron spectroscopy (XPS). The analysis of XPS data suggested the presence of two oxidation states of cerium, i.e., Ce(III) and Ce(IV). According to the imaging using a scanning electron microscope (SEM) and transmission electron microscope (TEM), Ce-MOF exhibits hexagonal rods’ morphology. Ce-MOF offered thermal stability up to 350 °C. It showed a fluorescence emission signal at wavelength 550 nm with a Stock’s shift of 200 nm. Ce-MOF’s application as a probe for sensing hydrogen peroxide (H2O2) and ferric ions (Fe3+) was reported. Ce-MOF exhibited peroxidase MOFzyme activity. Thus, it offered a turn-on emission upon interaction with different concentrations of H2O2. It detects Fe3+ ions with a limit of detection (LOD) and a linear range of 0.016 µM and 0.016–0.133 µM, respectively. The study also investigated the mechanisms of sensing for H2O2 and Fe3+ ions. The changes in the emission signals were due to the intrinsic catalase activity of Ce-MOF. Ce-MOF offered MOFzyme properties providing a promising feature for biocatalysis and biosensing applications.