Construction of Guanidinium-Functionalized Covalent Organic Frameworks via Phototriggered Click Reaction as a Dual-Mode Accurate Sensor for Malondialdehyde

Malondialdehyde (MDA) serves as a pivotal indicator to estimate the lipid peroxidation status and as a biomarker for the assessment of oxidative stress and screening of disease by people excretion. However, most of the existing analytical methods for MDA suffer from complicated derivation, leading to poor accuracy and inconvenience. In this work, the guanidinium-functionalized covalent organic framework (COF) was delicacy-designed and used to tune the modular structure by the building blocks with condensation, phototriggered click reaction, and further guanidylation process. A methoxy-group-containing linker in the skeleton was adopted to form lone-pair delocalized oxygen atoms, trigger the resonance effect, attenuate the polarization of the C═N bond linkages, and weaken the interlayer repulsion, supporting the stability of the guest gating COF. The available guanidino groups grew from the ordered pore walls of the COF and served as the customized talon with an enhanced interaction site density to rapidly grab the target guest by charge-assisted strong hydrogen bonds and electrostatic attraction forces. This distinctive feature significantly bolstered sensitive signal transduction, enabling rapid MDA sensing (within 120 s) without derivation treatment, and achieved a calculated limit of detection (LOD) as low as 0.08 μM. With the accessible image-data transmission process, the portable dual-channel sensing platform achieved sensitive and accurate MDA monitoring.