Tb-MOF-based chemiluminescence for sensitive detection of Cr (Ⅲ) and Cr (Ⅵ) in environmental water

In this study, we developed a sensitive chemiluminescence (CL) method for the detection of Cr (Ⅲ) and Cr (VI), based on periodate (NaIO 4 )-hydrogen peroxide (H 2 O 2 )-terbium-based metal–organic frameworks (Tb-BTC MOF) system. Reactive oxygen species (ROSs) created from the reaction of NaIO 4 with H 2 O 2 , such as singlet oxygen ( 1 O 2 ), can effectively transfer energy to the Tb-BTC MOF, resulting in the characteristic emissions from Tb 3+ through the antenna effect. Compared to its bulk form, the nanoscale Tb-BTC MOF exhibited significantly enhanced CL intensity, which can be attributed to improved surface properties and reduced non-radiative decay. The presence of Cr (VI) led to a marked decrease in CL intensity due to energy competition with the H 3 BTC ligand. Additionally, Cr (III) was oxidized to Cr (VI) by NaIO 4 , thereby indirectly contributing to CL quenching. A linear correlation was observed between the concentrations of Cr (III)/Cr (VI) and the reduction in CL intensity, enabling quantitative analysis of both species. Following systematic optimization, the proposed method demonstrated good sensitivity, achieving detection limits of 33 nM for Cr (III) and 17 nM for Cr (VI), which are significantly lower than those obtained with fluorescence-based detection using Tb-BTC MOF. Furthermore, by employing a cation-exchange resin for pre-separation, Cr (III) and Cr (VI) could be individually quantified within mixed samples. This method was also successfully applied to real water samples, yielding satisfactory recoveries and demonstrating its practical applicability for chromium speciation analysis in environmental matrices. Overall, this work provides new insights into the design of advanced CL systems using nanostructured MOFs, offering a promising strategy for the selective and sensitive detection of metal ions in complex environmental matrices.