Multifunctional copper–nitrogen/carbon laccase-mimicking nanozyme for colorimetric sensing of phenolic compounds and degradation of organic pollutants

Abstract

In this study, a novel nitrogen-doped carbon-based copper nanozyme (Cu–N/C) was constructed via an in situ derivatization of designed copper complexes, which shows excellent laccase-like catalytic activity. In it, a copper complex was synthesized using copper chloride dihydrate and 1,10-phenanthroline as the precursors, and then a controlled pyrolysis strategy was conducted to obtain the nitrogen-doped carbon-based composites with atomically dispersed copper active sites. These isolated copper sites are anchored within the nitrogen-doped carbon framework, providing an effective catalytic center that mimics natural laccase. In the catalytic process, the Cu–N/C nanozyme exhibits better substrate affinity and faster catalytic rates in comparison with other laccase mimics. The catalytic mechanism studies demonstrate that the Cu–N/C nanozyme directly drives the substrate oxidation by using activating oxygen molecules, and the reaction path is similar to that of natural laccase. These Cu–N/C nanozymes maintain satisfactory catalytic activity at high temperatures and across a wide pH range, and can also be used in high-salt environments, thereby overcoming the operation limitations of biological laccase. Based on that, we have developed a smartphone-assisted portable colorimetric sensing platform to achieve a rapid visual detection of phenolic contaminants in the water. More interestingly, these Cu–N/C nanozymes can also efficiently degrade dye contaminants, with a decolorization rate of more than 75% within 40 min. The work highlights a ‘coordination–pyrolysis’ strategy as an effective way to design a biomimetic nanozyme with tunable active sites, and its stable catalytic performance provides a feasible solution to environmental detection and pollutant degradation.