Photochemical remediation of wastewater pollutants using metal phthalocyanine-based composites: A review

The over-accumulation of contaminants into the water bodies has been a major concern for the well-being of human life and environmental sustainability. Treating wastewater to ensure clean and safe water for the environment and humankind has become crucial. Among the popular wastewater treatment methods, photocatalysis is a simple, sustainable, swift, and efficient technique for degrading pollutants into non-toxic or less harmful byproducts using reusable photocatalysts. Metal phthalocyanines (MPcs) are highly stable, distinct π-conjugated heterocyclic complexes with special redox, photophysical, and photochemical characteristics. The complexation of metal ions is greatly facilitated by the tetra isoindole macrocycle core of MPcs, producing hybrid metal-organic molecules with high photocatalytic characteristics. MPcs extend light absorption into the visible light region since most supports are limited to the Ultraviolet absorption spectrum. The photodegradation of water pollutants from the past decade (2014–2024) using different MPc derivatives and MPc-based composites has been briefly reviewed in this work, focusing on degradation efficiency, reactive species, and reproducibility. The metal or carbon-based nanostructures and polymers incorporated with MPc photosensitizers enhance the photocatalytic activity toward pollutant remediation. The mechanism for the degradation pathway of pollutants using MPc photosensitizer has been proposed and summarized. The review also includes a table of rate constants and degradation efficiencies of various MPc-based composites.