Transition metal coordination frameworks as artificial nanozymes for dopamine detection via peroxidase-like activity

Abstract

Enzyme-like metal–organic frameworks are currently one type of star material in the fields of artificial enzymes and analytical sensing. However, there has been little progress in making use of MOF structures based on a catalytically active metal center. Herein, transition metal coordination frameworks (Cu–HMT and Ni–HMT) are used as artificial nanozymes for the visual detection of a Parkinson's disease biomarker (dopamine, DA) through peroxidase-like catalytic activity. We prepared hexamine and transition metal coordination frameworks (Cu–HMT and Ni–HMT) through a trouble-free green synthetic route and characterized them in detail. Comparative studies of peroxidase mimic activity were conducted in the presence of the as-prepared Cu–HMT and Ni–HMT. Impressively, Cu–HMT possesses formidable peroxidase mimic activity, which allows UV-vis spectra and naked-eye detection of DA. Furthermore, Ni–HMT has its own limitations, including lower water stability and poorer activity compared to Cu–HMT. However, the peroxidase-like activity of Cu–HMT was strongly inhibited in the presence of DA. Notably, the proposed sensing system was proven to show an enhanced inhibition effect, including visual detection, high selectivity, specificity and low detection limits of 0.7 and 4.2 mM for H₂O₂ and DA, respectively. Based on this phenomenon, the as-synthesized Cu–HMT could be used as a kind of nanozyme to enhance the performance of colorimetric sensors.