A bimetallic Co/Mn metal–organic-framework with a synergistic catalytic effect as peroxidase for the colorimetric detection of H2O2
Metal–organic frameworks (MOFs) with a metal coordination structure mimicking that of enzymes have been widely applied in the sensing field for bioassays, and most of the reports focus on single-metal MOFs. However, bimetallic MOFs have fascinating catalytic capabilities due to their bimetallic coordination. Herein, a two-dimensional sheet-like bimetallic Co/Mn-based MOF (Co/Mn-MOF) with peroxidase-like activity was synthesized through a one-step hydrothermal method to accelerate the decomposition of H2O2 with the generation of ˙OH, which further oxidized the classic chromogenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB) into oxTMB. The Michaelis–Menten constants (Km) and maximum initial velocities (Vmax) of the catalyst were found to be 0.27 mM and 1.64 × 10−7 M s−1 for TMB and 0.24 mM and 5.80 × 10−7 M s−1 for H2O2, respectively. Accordingly, we successfully utilized Co/Mn-MOF-1-1-150 to establish a colorimetric detection platform for the detection of H2O2. A linear absorbance response ranging from 1 to 100 μM with the limit of detection of 0.85 μM (S/N = 3) was obtained under the optimized conditions. The LOD of our catalyst is comparable to that of other MOF-based enzyme mimics for colorimetric detection; this can be ascribed to the synergistic catalytic effect between its two metals, its two-dimensional structure with a small diffusion barrier for the substrate molecules, and large exposed surface area. More importantly, using the proposed sensing method, the determination of H2O2 released by living cells and in spiked water samples was achieved. This revealed that the as-prepared bimetallic Co/Mn-MOF could be a promising candidate as a catalytic material due to its peroxidase activity.
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