Highly efficient solar-driven photocatalytic degradation of ciprofloxacin from aqueous solution using a novel metal–organic framework catalyst

The increasing prevalence of refractory pharmaceutical compounds in the environment and their harmful impacts on ecosystems have resulted in severe ecological challenges for living organisms worldwide. A new metal–organic framework (MOF) was designed to address this issue, comprising copper nanoparticles bonded to tryptophan amino acids. This MOF was designed to be an efficient photocatalyst for the degradation of pharmaceuticals such as ciprofloxacin, utilising environmentally sustainable and eco-friendly mater. The physicochemical properties of the MOF catalyst were confirmed through various characterization techniques, including FTIR, DRS, SEM, TEM, XPS, TGA, and BET analyses. The MOF was employed as a photocatalyst for the purification of ciprofloxacin under simulated sunlight irradiation. The degradation experiments demonstrated the complete removal of CIP under optimal conditions with a solution pH of 9, catalyst dosage of 0.5 g/L, and CIP concentration of 20 mg/L within 200 min under simulated sunlight. Furthermore, post-treatment analysis of TOC and COD revealed significant reductions of 63.11% and 76.17%, respectively, indicating extensive mineralization of the antibiotic. Additionally, HO• and h+ were identified as the primary oxidizing agents responsible for the photocatalytic degradation of CIP by the MOF catalyst. The material exhibited exceptional photocatalytic performance for CIP even after six consecutive recycling cycles. Mechanistic investigations further revealed a unique heterojunction within the MOF catalyst, where Cu nanoparticles serve as electron acceptors and co-catalysts. These nanoparticles facilitate charge separation and transfer, enhance light absorption, and reduce the recombination of photogenerated electron–hole pairs, thereby significantly improving the photocatalytic activity of the catalyst.