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

Abstract

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.