Green Photooxidation of 1-Naphthol Using a Zinc Phthalocyanine-Loaded MCM-41 Heterogeneous Catalyst

Developing sustainable methods for organic synthesis is a key goal in modern chemistry. Herein, a novel heterogeneous photocatalyst, Pc-1@MCM-41, is synthesized by immobilizing a zinc(II) phthalocyanine photosensitizer onto mesoporous silica (MCM-41) through a simple mixing process. The material is thoroughly characterized by fourier-transform infrared spectroscopy, solid-state UV-vis, thermogravimetric analysis, scanning electron microscopy-energy dispersive X-ray spectroscopy, X-ray diffraction, trasmission electron microscopy, and N₂ sorption analyses, confirming the successful incorporation of Pc-1 without compromising the structural features of the support. The photocatalytic efficiency of Pc-1@MCM-41 is evaluated in the selective oxidation of 1-naphthol to 1,4-naphthoquinone under visible light, using a custom-built, low-cost 3D-printed photoreactor with red LEDs. Under ambient conditions and air as the oxidant, the catalyst achieves 89% conversion and >99% selectivity in just 15 min. Control experiments confirm the essential roles of light, oxygen, and the phthalocyanine moiety. The catalyst shows high stability and reusability over multiple cycles and performs well in various solvents, with acetonitrile being the most effective. The use of MCM-41 as a support effectively minimizes aggregation issues and enhances catalyst dispersion, thereby increasing the photocatalytic efficiency. This work highlights the potential of low-cost heterogeneous systems combined with custom photoreactors as practical and scalable solutions for green chemical synthesis.