Predesigned covalent organic framework with sulfur coordination: Anchoring Au nanoparticles for sensitive colorimetric detection of Hg(II)

Targeted construction of new covalent organic frameworks (COFs) with specific purposes and rationalities to build colorimetric assay platform for environmental pollutant monitoring have attracted increasing interest. However, it is still challenging due to lack of available coordination sites inside COFs pores and only a slight bonding ability for anchoring metal. In this work, a two-dimensional (2D) COFs (termed as Tz-COF) with high crystallinity, excellent chemical stability, and abundant sulfur coordination in its skeletons was synthesized and used for the confined growth of Au NPs. It was found that the Au NPs showed significant dispersibility for the support of Tz-COF. The proposed Tz-COF@Au NPs possessed outstanding Hg2+-activated peroxidase-like activity benefited from physicochemical properties of gold amalgam and synergistic effect between COFs and Au NPs to oxidize chromogenic substrate. Based on highly efficient activity and distinctive color evolution, the strategy for detecting Hg2+ was developed and successfully applied to determine the content of Hg2+ in real environmental samples. This work manifests that a potential strategy to establish a colorimetric assay platform for environmental pollutant monitoring based on the targeted manufacturing of novel COFs with specific functions.