Enhancing bimetallic redox cycling by Olsalazine-based MOF to achieve efficient removal of ofloxacin

A bimetallic MOFs (CUMSs /Olsa (Fe, Cu)) with abundant coordinatively unsaturated metal sites was synthsized using the non-toxic organic reducing agent, olsalazine (olsa). This innovative MOFs exhibits strong capacity in degrading ofloxacin by enhancing the bimetallic redox cycle, increasing the number of unsaturated metal sites, and accelerating the mass transfer of H2O2 and olsalazine molecules in the catalytic reaction. Furthermore, the Olsa, serving as reducing organic ligands, demonstrates enhanced cycling of the Fe(III)/Fe(II) and Cu(II)/Cu(I), along with self-degradation capacity. [Display omitted] •Drug-based bimetallic MOFs are synthesize using Olsa as ligand.•Olsa accelerates the Fe(III)/Fe(II) and Cu(II)/Cu(I) redox cycling process.•The CUMSs/Olsa(Fe,Cu) MOFs demonstrate superior catalytic efficiency.•The CUMSs/Olsa(Fe,Cu) MOFs showcase the self-Degradation and reusability. The broad utilization of metal–organic frameworks (MOFs) in advanced oxidation processes (AOPs) for wastewater remediation is impeded by toxic ligands, the challenging recovery of catalysts, and the low cycling efficiency of metal redox pairs. In this study, we fabricated a highly efficient and self-degradable bimetallic catalyst with coordinatively unsaturated metal sites (CUMSs) using non-toxic Olsalazine (Olsa) as a ligand to effectively eliminate the antibiotic ofloxacin (OFL). Under optimal conditions, the OFL removal efficiency approached nearly 100 % within 100 min, with the degradation rate of bimetallic MOFs being 4 times than that of monometallic MOFs. The significant enhancement in catalytic performance of the catalyst was ascribed to its reduced charge transfer resistance (Rct), coordinatively unsaturated metal sites, and accelerated cycling of high valence metal to low valence metal, facilitated by the introduction of bimetallic and reducing non-toxic ligands. Moreover, we investigated the effects of H2O2 concentration, catalytic dose, and pH on pollutant degradation. Additionally, results from quenching experiments and electron spin resonance (ESR) tests demonstrated that the three types of free radicals generated during the catalyst activation process played a key role in pollutant degradation.