Imine-linked covalent organic framework with high crystallinity for constructing sensitive purine bases electrochemical sensor.

[Display omitted] • A high crystallinity, large surface area and stable imine COF was synthesized. • TADM COF grows in situ on the surface of oxide NPs to form core–shell composites. • Synergistic effect of Co 3 O 4 , TADM COF and MWCNT facilitates sensing of DNA purine bases. • The sensor is successfully used to determine G and A in thermally denatured herring sperm DNA. • In situ grown COF endows high conductivity, stability and final sensing performance. In this work, a covalent organic framework (TADM-COF) with high crystallinity and large specific surface area (2597 m2 g−1) has been successfully synthesized using 1,3,5-(4-aminophenyl) benzene (TAPB) and 2,5-dimethoxy-p-phenyldiformaldehyde (DMTP). The COF was grown in situ on oxide particles to form core–shell nanocomposites (SiO 2 @TADM COF, Fe 3 O 4 @TADM COF and Co 3 O 4 @TADM COF) to realize its function as a shell material. Among them, the Co 3 O 4 @TADM COF with the highest electrochemical response to purine bases was further cross-linked with multi-walled carbon nanotubes (MWCNT) to construct a novel electrochemical sensor (Co 3 O 4 @TADM COF/MWCNT/GCE) for detection of purine bases. In this nanocomposite, Co 3 O 4 possesses rich catalytic active sites, MWCNT ensures superior electrical conductivity and COF provides a stable environment for electrocatalytic reactions as the shell. At the same time, regular pore structure of the COFs also offers smooth channels for the transfer of analytes to the catalytic site. The synergistic effect among the three components showed remarkable sensing performance for the simultaneous detection of guanine (G) and adenine (A) with a wide linear range of 0.6–180 μM and low limits of detection (LODs) of 0.020 μM for G and 0.024 μM for A (S/N = 3), respectively. The developed sensor platform was also successfully applied in the detection of purine bases in thermally denatured herring DNA extract. The work provided a general strategy for amplifying signal of COF and its composite in the electrochemical sensing. [ABSTRACT FROM AUTHOR]