Preparation Of Noble Metal Covalent Organic Framework Composite Catalytic Materials And Their Application In Mercury Ion Analysi

Covalent organic frameworks（COFs）materials have been widely applied in gas storage and separation,catalysis,analytical assays,and drug delivery because of their advantages of large specific surface area,high porosity,adjustable pore size,and good stability.In this work,two kinds of COFs-based composite nanozyme-catalyzed materials have been developed by using 1,3,5-Tris（4-aminophenyl）benzene（TPB）and 2,5-divinylterephthalaldehyde（DVA）as monomers to synthesize COFs materials,and then combining with silver nanoparticles（Ag NPs）and platinum nanoparticles（Pt NPs）with enzyme-like catalytic activity and magnetic materials（Fe₃O₄ NPs）,respectively.Thus,two nanozyme-catalyzed colorimetric detection technology platforms have been established to achieve specific and highly sensitive colorimetric analysis of mercury ions.The main contents include:（1）A colorimetric method has been constructed based on COFs-loaded Ag NPs（COF-Ag）as a mimetic oxidase for the high-efficiency detection of Hg²⁺（Chapter 2）.The COF-Ag nanozymes have been fabricated by firstly synthesizing COFs with hierarchical flower-like hollow structures using TPB and DVA as monomers,and then growing Ag NPs in situ on COFs by chemical reduction method.It was found that the COFs with high specific surface area could effectively achieve size control and uniform dispersion by covalently bonding Ag NPs due to their nitrogen-rich groups,while the resulting COF-Ag nanozymes showed extremely high stability but low catalytic activity.However,the oxidase-like catalytic activity of COF-Ag nanozymes could be significantly enhanced once Hg²⁺was introduced to form COF-Ag-Hg alloys.A COF-Ag catalysis-based colorimetric assay for Hg²⁺was thereby constructed,with a linear concentration range of 0.050-10.0μM and a detection limit of 3.7 n M.In addition,the colorimetric strategy has been successfully applied for detecting Hg²⁺in human blood with favorable detection recoveries,promising a wide range of applications in biomedical analysis,environmental monitoring,and food safety fields.（2）To further improve the catalytic performance of COF-based nanozymes,a magnetic nanocomposite catalytic material of Fe₃O₄@COF-Pt has been fabricated by combining COFs with Pt NPs and Fe₃O₄ NPs,and a highly sensitive colorimetric analysis method has been developed based on its enzyme-like catalytic activity（Chapter 3）.It was shown that the obtained Fe₃O₄@COF-Pt nanozymes had dramatically enhanced peroxidase-like activity compared to conventional Pt NPs,where the introduction of COFs not only endowed the highly ordered porous structure of Fe₃O₄@COF,but also its nitrogen-containing groups effectively achieved size control and improved dispersion of Pt NPs,thus remarkably enhancing the enzyme-like catalytic activity of products.Especially,the catalytic activity of Fe₃O₄@COF-Pt nanozymes could be selectively inhibited in the presence of Hg²⁺,showing a regular decrease of catalytic activity related to the Hg²⁺concentration.Therefore,a colorimetric detection strategy for Hg²⁺with a detection limit as low as 0.23 n M has been developed and successfully used for the highly sensitive and selective detection of Hg²⁺in blood.Besides,Fe₃O₄@COF-Pt nanozymes exhibited excellent magnetic separation performance and storage stability,which is conducive to its recycling.