Construction of Covalent Organic Framework-Loaded Gold-Silver Composites with the Catalysis Enhanced by Mercury: A Turn-On Colorimetric Detection and Removal Strategy for Mercury

Abstract

In this article, gold (Au) and silver (Ag) nanoparticles (NPs) were synergistically grown into flower-like covalent organic frameworks (COFs) through a chemical reduction method. It was discovered that COF-Au could present the obvious oxidase-like catalysis, which could decrease after adding silver elements to yield COF-Au-Ag. To our surprise, the catalytic activities of COF-Au-Ag were obviously enhanced with mercury (II) (Hg2+) by forming Au-Ag-Hg alloys, which was 7.0 and 2.5-folds higher than those of COF-Ag and COF-Au separately with Hg2+, respectively. A COF-Au-Ag catalysis-based colorimetric method was then developed for the turn-on detection of Hg2+ ions in fish muscle samples, providing a linear detection range from 0.0010-2.0 mg/kg. Moreover, the as-fabricated COF-Au-Ag could selectively absorb Hg2+ ions through forming stable coordination complexes. Importantly, it could facilitate Hg2+ ions to be eliminated from the aquaculture tailwater with the removing efficiency up to 99.61% and adsorption capacity of 200.59 mg/g, which is significantly higher than that of COF, highlighting the superior adsorption efficiency of COF-Au-Ag. Such a COF-Au-Ag-based colorimetric detection and removal method for Hg2+ ions may promise extensive applications in the Hg2+-toxic disease diagnosis, environmental monitoring and aquaculture food safety fields.

Keywords: Covalent organic framework, Gold-silver nanocomposite, Nanozyme catalysis, colorimetric assay, Adsorption-based removal, Hg2+ ions