Synthesis of a novel highly active single-atom nanozyme Cu-N-C with high surface area as a laccase-mimicking catalyst for the efficient catalytic aerobic oxidative synthesis of pyridines and quinazolinones at room temperature

Nanozymes currently face challenges regarding their structure and efficiency compared to natural enzymes. Single-atom nanozymes (SAzymes) enable the optimal utilization of metal atoms and the capability to surpass intrinsic limitations. Herein, we synthesized a novel laccase-mimicking nanozyme based on copper single atoms anchored on N-doped carbon (Cu-N-C) using a precursor mixture of 2-methylimidazole, zinc nitrate, and copper(II) nitrate. The synthesized SAzyme was subjected to various characterization techniques, including Fourier transform infrared spectroscopy (FT-IR), High-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), Inductively coupled plasma optical emission spectroscopy (ICP-OES), Scanning electron microscopy (SEM), and Energy-dispersive X-ray spectroscopy (EDX). Additionally, the Cu-N-C SAzyme, featuring spherical particles, exhibited a mesoporous structure with a high surface area of 321.14 m²/g as measured by BET, an average pore size of 1.29 nm, and a pore volume of 1.25 cm³/g. Cu-N-C combines the benefits of heterogeneous catalysts, such as easy separation and reusability, with those of homogeneous catalysts, including high activity and reproducibility. We report the first application of a Cu-N-C/DDQ/O₂ cooperative catalytic system for the efficient oxidation of 1,4-dihydropyridines to pyridines (85–96 % yield) and 2,3-dihydroquinazolinones to quinazolinones (83–96 % yield) in water/acetonitrile as a solvent at room temperature.