Core-shell Zn/Co MOFs derived Co3O4/CNTs as an efficient magnetic heterogeneous catalyst for persulfate activation and oxytetracycline degradation

Herein, we report a facile and straight strategy to synthesize a highly efficient and recyclable heterogeneous catalyst through a pyrolysis-oxidation of core-shell Zn/Co metal organic frameworks (MOFs). The selected Zn MOF crystals was used as a single precursor to form a nanostructured hollow framework through the evaporation of Zn at high pyrolysis temperature. Meanwhile, the numerous carbon nanotubes (CNTs) was formed on the surface of a hollow nanostructured framework under the catalytic effect of the Co nanoparticles. After subsequent acid etching to remove some large Co particles on its surface, and convert the Co/CNTs to Co3O4/CNTs after low temperature oxidation in air. The structure and surface elements distribution of as-synthesized Co3O4/CNTs catalyst were characterized using XRD, SEM, XPS, VSM and N-2 adsorption-desorption experiment. Besides, the resultant nanostructured catalyst Co3O4/CNTs had a high degradation rate of 93.6% for oxytetracycline (OTC) within 80 min and a rapid catalytic degradation rate of 0.034 min(-1) in a wide range of pH from 3.0 to 9.0. The degradation mechanism and pathway, and the effects of various parameters on degradation experiments were also studied. The material exhibited superior activity after continuously repeated use five times, and can be collected conveniently through a magnet within 2 min.