Controllable Construction of Two-Dimensional Conductive M3(HHTP)2 Nanorods for Electrochemical Sensing of Malachite Green in Fish

The conductive metal–organic framework (CMOF) is a promising application nanomaterial for the construction of electrochemical sensors. Three two-dimensional conductive M3(HHTP)2 materials with larger aspect ratios were prepared by a one-pot method using acetate-based metals (Cu, Ni, Co) and 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) with the introduction of N,N-dimethylformamide (DMF) as the limiting reagent. Compared with Ni3(HHTP)2 and Co3(HHTP)2, Cu3(HHTP)2 had a larger double capacitance, pore size, specific surface area, and smaller resistance. As a result, Cu3(HHTP)2 provided greater catalytic oxidation active surface area and charge transfer efficiency for malachite green (MG) detection. Hence, Cu3(HHTP)2 efficiently catalyzed MG oxidation and significantly improved the sensitivity of MG detection. Meanwhile, the oxidation current signal from the copper of Cu3(HHTP)2 was used as an internal reference signal to form a ratiometric electrochemical sensor with an MG oxidation current signal, which effectively reduced the external interference. The constructed electrochemical assay for MG detection displayed broad linearity (5–1000 nM) with a detection limit of 1.34 nM. In the meantime, MG residues in fish was evaluated and high reliability was obtained, confirming the feasibility of this valuable method for food safety and health evaluation of aquatic products.