Dense pyridine nitrogen as surface decoration of interwoven Cu-MOFs for chloramphenicol-specific electrochemical sensor

The detection of chloramphenicol (CAP), a strictly prohibited antibiotic in veterinary drugs, remains challenging owing to its specific-sensing requirements. However, achieving a specific sensing strategy is crucial and requires the design of high-performance materials. In this study, a stable, double-interpenetrated dual-wall cage-in-cage metal–organic framework (MOF), SXNU-3-Cu ({[Cu2(INA)2(TATB)]·H2O}n), was designed using a mixed-linker strategy that incorporated the ligands of 4,4,4,-s-triazine-2,4,6-triyltribenzonic acid (H3TATB) and isonicotinic acid (HINA). Owing to their high connectivity and double-interpenetrated structure, the SXNU-3-Cu MOFs exhibited excellent thermal stability, as well as resistance to water and pH changes. The SXNU-3-Cu/ACET/GCE electrochemical sensor demonstrated a wide linearity range from 0.03 to 0.1 μM and 0.3–70 μM, with an impressive CAP detection limit of 9.51 nM. In particular, the interaction between –NO2 in CAP and dense pyridine nitrogen of HINA ligand enhanced the adsorption of CAP on the surface of the cage via Van der Waals forces. Subsequently, targeted oxidation–reduction catalytic reactions occurred inside accessible copper sites against nitro groups in the CAP molecules, resulting in high sensitivity and specific sensing towards CAP. Furthermore, we conducted comprehensive experimental and theoretical investigations to verify the sensing mechanism between the SXNU-3-Cu MOFs and CAP molecules. We determined that Cu-based MOFs have significant potential for drug monitoring and biochemical analyses.