Hofmann-MOF-derived CoFeNi nanoalloy@CNT as a magnetic activator for peroxymonosulfate to degrade benzophenone-1 in water

As the extensively-employed UV stabilizer, 2,4-dihydroxybenzophenone (benzophenone-1 (BP1)) has been proven an endocrine disruptor, developing of useful technologies for eliminating BP1 is highly desired. Because SO₄^•−-based oxidation technologies are promising for eliminating emerging pollutants, cobalt (Co) is an extremely useful catalyst for peroxymonosulfate (PMS) activation, and it is critical to developing an advantageous cobaltic catalyst for PMS activation. Herein, an exceptional catalyst is developed for the first time from a Hofmann-type MOF ([CoFe]pyrazine[Ni(CN)₄]), which is then pyrolyzed to afford CoFeNi alloy nanoparticles (NPs) confined in carbon nanotubes (CNTs), resulting in CoFeNi@CNT (CFNC). This CFNC would exhibit numerous promising features: (1) as Co represents the most efficient metal for activating PMS, CoFeNi alloy would offer superior activities for PMS activation; (2) the strong magnetism of CoFeNi alloy enables CFNC to be magnetically controllable; (3) CoFeNi alloy NPs confined within CNT would be guarded to increase its durability; (4) the interlaced structures of CFNC make it exhibit much more reactive surface areas for activating PMS. Thus, CFNC exhibits a significantly stronger activating capability than Co₃O₄, which is the benchmark heterogeneous catalyst for PMS. Furthermore, CFNC could also be reusable and remain highly effective, stable, and robust for multiple cycles of BP1 degradation with minimal leaching of CoFeNi alloy. Mechanisms of PMS activation and elimination path of BP1 by CFNC are also elucidated via the theoretical DFT calculation and experimental data to supply valuable information about behaviors of BP1 degraded by Hofmann MOF-derived magnetic catalysts.