Fe–Ni metal–organic frameworks with prominent peroxidase-like activity for the colorimetric detection of Sn2+ ions

Abstract

Fe–Ni-MOFs with different amounts of Fe are synthesized through a two-step template etching method. Kinetic analysis indicates that Fe–Ni-MOF exhibits prominent intrinsic peroxidase-like activity, which could catalytically oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) to produce oxidized TMB (oxTMB) with a blue color. As a peroxidase-mimicking MOF, Fe–Ni-MOF with its efficient stable catalysis properties is demonstrated to allow a sensitive colorimetric assay for Sn²⁺ ions. The mechanism is explored, whereby Sn²⁺ ions could reduce the peroxidase-like activity of Fe–Ni-MOF based on a redox interaction, making the oxTMB color lighter and decreasing the absorbance intensity at 652 nm. The linear determination of the Sn²⁺ ion concentration using a UV-vis spectrometer ranges from 0.01 mM to 1.0 mM and from 1.0 mM to 4.0 mM. The presented Fe–Ni-MOF-based assay of Sn²⁺ ions was successfully applied to real water samples.