Colorimetric Sensors Based on the Bimetal-Organic Frameworks for Highly Sensitive and Rapid Detection of Cr(VI)

The production of heavy-metal pollutants in industrialized systems contributes to a variety of hazards, including threats to both the environment and human health. Of particular concern is the release of Cr(VI) wastewater, which can be toxic and potentially carcinogenic. As a result, the capture/removal and accurate detection of Cr(VI) was extremely critical. However, there were few efficient colorimetric methods available for the detection of Cr(VI). To address this issue, we have developed a simple and convenient method utilizing the Cu bimetal-organic framework (Cu-MOF) to construct a visual colorimetric sensor specifically designed for Cr(VI) detection. The synergism effect of -SH and -NH 2 on the surface of Cu-MOF allows for the reduction of Cr(VI) to Cr(III). Meanwhile, oxidase substrate 3, 3’, 5, 5’-tetramethylbenzidine (TMB) is converted to oxTMB, rapidly turning the colorless solution into deep blue. This strategy allows for the detection of Cr(VI) with a wide linear range of 0.2–100 μM within 1 min. Additionally, the limits of detection (LOD) were determined to be 0.023 μM. This method showed excellent selectivity in against potentially interfering metal ions and anions that commonly found in wastewater. Furthermore, with its fast response time and potential for on-site screening and point-of-care testing, the Cu-MOF sensor represents a promising development in the detection of Cr(VI).