Catalytic activity study of a laccase-like copper–gallic acid MOF and its applications in the colorimetric determination of norepinephrine and degradation of environmental pollutants†

Laccases enzymes have garnered significant research interest owing to their extensive applications in pollutant degradation, the food industry, and biosensing technologies. These green biocatalysts are distinguished by the presence of four copper active sites which are integral to their enzymatic functions. Recent advancements have led to the development of copper-based organic–inorganic nanocomposites as laccase mimetics. Hence, this study focused on the synthesis and study of the catalytic properties of a copper–gallic acid metal–organic framework (Cu–GA MOF) heterostructure as a laccase mimic. Using o-phenylenediamine (OPD) and norepinephrine as model substrates it was observed that the synthesized Cu–GA MOF exhibited a laccase-like catalytic performance. Similar to natural enzymes and other nanozymes, Cu–GA MOF demonstrated pH-dependent catalytic activity demonstrating an optimal performance under physiological conditions. It exhibited a superior Michaelis constant (K_m) of 0.06 mM, maximum reaction rate (V_max) of 4.1 × 10⁻³ mM min⁻¹ and superior recyclability compared with laccase at the same mass concentration. Remarkably, Cu–GA MOF displayed exceptional thermal tolerance maintaining substantial catalytic activity at temperatures up to 90 °C. In contrast to natural enzymes, Cu–GA MOF exhibited enhanced stability and recyclability underscoring its potential for diverse bio-applications. These findings highlight the promising role of Cu–GA MOF as a robust and versatile catalyst in biocatalytic and analytical applications.