DNA-Functionalized Covalent Organic Framework for Colorimetric Detection and Adsorption Removal of Uranyl Ions

Inspired by the modulatable nanozymatic activity of covalent organic frameworks (COFs) by single-stranded DNA (ssDNA), herein, we developed a versatile platform for sensitive/specific colorimetric detection and efficient adsorption of UO22+ based on DNA aptamer-functionalized COFs. Three COFs with varying alkyne contents (Py-BDA, Py-BDA-BPTA, and Py-BPTA) were synthesized, followed by precisely covalent immobilization of UO22+-specific DNA aptamers via click chemistry. These COFs possess intrinsic oxidase-mimicking activity capable of catalyzing TMB oxidation to oxTMB, and the DNA aptamer covalent modification can regulate the enzymatic activity of COFs, with the most suppressing effect for Py-BDA-BPTA. The subsequent UO22+ binding can significantly restore the nanozymatic activity of Py-BDA-BPTA by charge neutralization. This "off-on" switching mechanism enabled sensitive and selective UO22+ detection with a low limit of detection (LOD) about 10 nM (3σ). Moreover, the DNA aptamer-functionalized COFs can be applied for efficient adsorption and removal of UO22+ with rapid kinetics and excellent cycling stability. This study provides novel insights into the postmodification of COFs by biomacromolecules to modulate their mimic enzymatic activity for sensing and adsorption applications.