Cobalt-based coordination polymers as heterogeneous catalysts for activating Oxone to degrade organic contaminants in water: A comparative study

Abstract

While Co represents the most efficient metal for activating Oxone to degrade organic contaminants, it is still highly desired to develop reusable and easy-to-recover heterogeneous Co-based catalysts. As chemistry of metal coordination compounds advances, a special class of organometallic polymers, so-called "coordination polymers" (CPs), has been developed. CPs contain repeated and cross-linked coordination entities to afford hierarchical structures with evenly-distributed Co moieties, making CPs attractive for activating Oxone. In this study, three CoCPs are particularly developed for the first time as heterogeneous catalysts to activate Oxone. Specifically, three organic ligands, including cyanuric acid (CA), trithiocyanuric acid (TTA), and pyridinedicarboxylic acid (PDA), were employed to investigate the effect of ligand on physical and chemical properties of the resulting CoCPs. More importantly, their catalytic activities for activating Oxone are compared and studied through investigating their distinct characteristics. As decolorization of Acid Red (AR) is employed as a model test for evaluating Oxone activation, these CoCPs outperform conventional Co3O4 nanoparticles (NPs) for activating Oxone. Among these CoCPs, CoCA exhibits the highest catalytic activity, followed by COTTA and CoPDA, because CoCA possesses a much higher surface area and pore volume as well as a higher fraction of Co content. These CoCPs also remain effective under weakly acidic and basic as well as saline conditions for activating Oxone to decolorize AR. CoCPs are reusable to activate Oxone over multiple cycles and maintained regeneration efficiencies > 90%. These features validate that CoCPs can be promising alterative catalysts for activating Oxone to degrade organic contaminants.