Ultrasonic-assisted synthesis of highly efficient and robust metal oxide QDs immobilized-MOF-5/Ni-Co-LDH photocatalyst for sunlight-mediated degradation of multiple toxic dyes

Concerns regarding the supply of clean and safe water are key issues that demand a suitable solution for improved wastewater treatment. Developing an efficient photocatalytic material for environmental applications is a growing research area in the present day. The present work emphasizes the natural sunlight-mediated photodegradation of toxic thiazine, xanthene, and triarylmethane dyes, employing a heterogenous advanced oxidation process. A novel heterogenous MOF-5/Ni-Co-LDH composite loaded with metal-oxide quantum dots (ZNCQD) was synthesized via ultrasonication. The polyhedral-shaped MOF-5 composite exhibited excellent photo-activity in a sunlight-driven, H2O2-assisted advanced oxidation process towards the degradation of Methylene Blue (MB), Rose Bengal (RB), and Malachite Green (MG). The experimental results indicated maximum degradation of Malachite Green. The maximum percentage degradation of MB, RB, and MG was 96.2, 95.8, and 99.6%, respectively. In addition, the photocatalyst demonstrated good stability for up to six consecutive cycles. The photodegradation was governed by a pseudo-first-order reaction kinetics, with MG having the highest rate constant (0.105 min-1) of all the dyes. The increased photocatalytic effectiveness could be attributed to the improved light absorption capacity by the metal quantum dots deposited on the composite surface. A detailed degradation mechanism and pathways have been proposed using various analysis techniques. Such an efficient photocatalyst with excellent activity towards both cationic and anionic dyes from aqueous medium unveils opportunities to employ MOF/LDH composites for efficient wastewater treatment and environmental remediation.