Cu-Based Metal–Organic Framework Nanoparticles for Sensing Cr(VI) Ions

A nanoscale MOF-199 was synthesized in a simple and fast way by mixing btc triethylammonium and copper nitrate solution at room temperature and characterized by scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction. The mimicking enzyme activity and the steady-state kinetics of the nanozyme were investigated. The prepared MOF-199 was a uniformly nanosized octahedron, and it exhibited excellent Cr(VI)-activated oxidoreductase catalytic properties. MOF-199 was employed as a catalyst; in 5 min, 3,3′,5,5′-tetramethylbenzidine (TMB) was oxidized by Cr(VI) into a bluish and oxidized TMB, which was recorded by UV–vis spectroscopy, and the mechanism was discussed. It facilitated the sensing of Cr(VI), and a linear range of 0.1–30 μM was obtained with a limit of detection of 20 nM. The selectivity of the present method for Cr(VI) was excellent, and its application to environmental water samples was accomplished.