Laccase-like nanozyme fabricated by Cu²⁺-doped ZIF8 for dopamine determination and catalytic degradation of phenolic pollutants

Designing new nanozyme systems as a simple substitute of natural enzymes with higher catalytically active sites and stability has attracted growing research interests for widespread applications especially in environmental remediation. Laccases belong to a group of multicopper-containing enzymes that show significant potential in diverse biotechnological and bioremediation applications. In this paper, a facile strategy is reported for the preparation of an efficient laccase mimic inspired by structural features and electron transfer mechanism of natural laccase, via Cu²⁺ ions doping in ZIF8 framework (denoted as Cu-ZIF8). Cu-ZIF8 nanozyme showed laccase-like activity and significant catalytic performance in the oxidation of a wide range of phenolic pollutants such as 2,4-dichlorophenol, phenol, catechol, hydroquinone, and o-nitrophenol. Kinetic studies were carried out to estimate the kinetic parameters of the as-prepared Cu-ZIF8 nanozyme including apparent Michaelis–Menten constant (K_m) and maximum velocity (V_max). The K_m and V_max were calculated to be 0.28 mM and 0.017 mM min⁻¹, respectively. In addition, Cu-ZIF8 nanozyme was robust over a wide range of temperature (30–90 °C), at extreme pH and high salt concentration. In addition, Cu-ZIF8 nanozyme can catalyze the oxidation of dopamine to a brown product, where an absorption band at 290 nm was observed. Accordingly, a simple colorimetric assay has been established for detection of dopamine in the linear range of 0.01–0.44 mM with a detection limit of 1.1 × 10⁻³ mM (S/N = 3). The developed colorimetric method showed good selectivity and high sensitivity in measuring dopamine among potential interfering components.