Bioinspired Cu/Zn-ZIF nanozyme with excellent laccase-like activity for selective colorimetric detection of phenolic pollutants.

The ingenious design of active sites in mimetic enzymes is crucial for developing enzyme-like functional materials with high activity and selectivity. Inspired by the N-ligand-rich copper centers of natural laccase, a novel laccase-like nanozyme was developed by loading copper ions into zeolite imidazolate framework-8 (Cu/Zn-ZIF). Benefiting from the precise mimicry of the catalytic center and the high dispersion of catalytic sites which were supported by the MOF backbone, Cu/Zn-ZIF manifested superior laccase-like activity. Notably, its substrate affinity and catalytic efficiency were substantially higher compared to those of natural laccase. More importantly, experimental results proved that the catalytic mechanism of Cu/Zn-ZIF was similar to that of natural laccase. In addition, Cu/Zn-ZIF nanozyme presented commendable stability under various harsh conditions compared to natural laccase. Surprisingly, limited by the pore size, Cu/Zn-ZIF exhibited the selectivity for different sizes substrates which was not found in natural laccase. As a proof of concept application, a colorimetric detection platform for 4-methoxyphenol was constructed with a broad linear range (1-150 μg/mL) and a low limit of detection (0.33 μg/mL). This study provides a novel approach for the rational design of nanozymes and serves as a feasible reference for enriching the application scenarios of laccase-like nanozymes.