Covalent organic framework-inspired chromogenic system for visual colorimetric detection of carcinogenic 3, 3′-diaminobenzidine

The colorimetric assay is considered to be a simple and reliable analytical approach for visual detection of various analytes. However, the low sensitivity of traditional colorimetric methods greatly restricts their further applications. Herein, inspired by the large π-conjugated system of imine-linked covalent organic frameworks (COFs), we propose a new colorimetric detection methodology by enhancing the extinction coefficient via introduction of large π-conjugated system to effectively improve the sensitivity. As a proof-of-concept demonstration, the classical imine condensation reaction is selected as the model reaction. Terephthalaldehyde (TPA) is employed as the colorimetric probe for detection of mutagenic and carcinogenic 3, 3′-diaminobenzidine (DAB), realizing the sensitive and selective detection of DAB down to 900 nM level. Moreover, this colorimetric assay can detect DAB at as low as 5 μM with the naked eye and achieve satisfactory recoveries in real water samples.