A highly
sensitive electrochemical sensing system is developed
via in situ integration of Cu-based metal–organic frameworks
(Cu-BTC, BTC = 1,3,5-benzenetricarboxylic acid) and high-conductivity
ball-mill-exfoliated graphene (Cu-BTC@GS) by a simple method. The
as-synthesized Cu-BTC@GS hybrids display remarkably enhanced electrochemical
activity due to the synergistic effect resulting from the integration.
Compared to those of the pristine GS, the introduction of Cu-BTC nanoparticles
leads to significant improvement in the surface area and porosity,
as revealed by the nitrogen adsorption–desorption analysis.
In addition, the oxidation behavior of nicotinamide adenine dinucleotide
studied using the rotating ring disk electrode further reveals a superior
electron-transfer rate constant (k) for the composite,
indicating higher catalytic ability. Moreover, double potential step
chronocoulometry of biomolecules (xanthine and hypoxanthine) and phenolic
pollutants (bisphenol A and p-chlorophenol) reveals
that the prepared composite possesses greatly enhanced adsorption
properties, resulting in much higher response signals and detection
sensitivity. Benefiting from the superior reactivity, a highly sensitive
electrochemical sensing platform for wide targets is successfully
fabricated. It was used in the analysis of plasma, urine, and receipt
and wastewater samples, and the results were highly consistent with
those obtained by high-performance liquid chromatography. We believe
that this study provides an effective strategy for the construction
of high-performance electrochemical sensing systems.
The properties and applications of metal‐organic frameworks (MOFs) can be tuned by their metal centers and organic ligands. To reveal experimentally and theoretically the influence of metal centers and ligands on electrochemical performance of MOFs, three MOFs with copper or zinc centers and organic ligands of 2‐methylimidazole (2MI) or 1,3,5‐benzenetricarboxylic acid (H3BTC) are synthesized and characterized in this study. 2D and porous Cu‐2MI exhibits a larger active area, faster electron transfer capability, and stronger adsorption capacity than bulk Cu‐BTC and dodecahedron Zn‐2MI. Density functional theory calculations of adsorption ability of three MOFs toward xanthine (XA), hypoxanthine (HXA), and malachite green (MG) prove that 2D Cu‐2MI has the strongest adsorption energies to three targets. Rotating disk electrode measurements reveal that 2D Cu‐2MI features the biggest intrinsic heterogeneous rate constant toward three analytes. On 2D Cu‐2MI sensitive and selective monitoring of XA, HXA, and MG is then achieved using differential pulse voltammetry. Their monitoring in real samples on 2D Cu‐2MI is accurate and comparable with that using high‐performance liquid chromatography. In summary, regulation of electrochemical sensing features of MOFs is realized through defining selected metal centers and organic ligands.
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