Nanoceria-Templated Metal Organic Frameworks with Oxidase-Mimicking Activity Boosted by Hexavalent Chromium

The high toxicity and mobility of hexavalent chromium (Cr(VI)) allow it to easily spread and bioaccumulate, and its detection is a major part of environmental protection. In this work, an innovative method is developed for preparation of cerium oxide nanorod-templated metal-organic frameworks (CeO₂NRs-MOF). The in situ growth of MOF on the surface of CeO₂ nanorods (CeO₂NRs) enhances its oxidase-like activity. In the presence of a trace amount of Cr(VI), CeO₂NRs-MOF can significantly accelerate the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) due to Cr(VI)-boosted oxidation, resulting in a blue colored oxidation product. It can detect Cr(VI) over a range of 0.03-5 μM with high selectivity. Moreover, this method can be applied to the detection of Cr(VI) in different water environment samples with satisfactory recoveries, demonstrating the potential application of CeO₂NRs-MOF for the direct monitoring of Cr(VI) in environmental water systems. Thus, this work provides a facile host-templated MOF preparation method, which could possibly be extended to other fields.