Visible-Light-Driven Synthesis of Benzimidazoles Using a Nickel Oxide-Doped Graphitic Carbon Nitride Photocatalyst

The sustainable synthesis of benzimidazole derivatives is critical due to their broad pharmaceutical and fine chemical significance, yet existing catalytic methods often suffer from harsh conditions, limited selectivity, and poor reusability. To overcome these challenges, we developed a nickel oxide-doped graphitic carbon nitride (NiO@g-C3N4) photocatalyst, designed for enhanced visible-light absorption and efficient charge carrier separation. Comprehensive state-of-the-art characterization techniques confirmed successful NiO doping, resulting in a narrowed band gap and an improved photocurrent response. Under mild conditions, utilizing a 12 W white LED, this catalyst efficiently promoted the coupling of benzaldehydes with o-phenylenediamine, delivering moderate to excellent yields (69–98%) across various substrates. Mechanistic studies identified a radical-mediated reaction pathway supported by photocurrent and scavenger experiments. Compared to pristine g-C3N4, NiO@g-C3N4 exhibited superior catalytic performance due to synergistic electronic and structural modifications. Importantly, the catalyst demonstrated excellent stability and recyclability over five cycles.