Activation of persulfate with metal-organic framework-derived nitrogen-doped porous Co@C nanoboxes for highly efficient p-Chloroaniline removal

Cobalt-based nanostructures have shown a great potential for radical production by activating persulfate (PS). Here, we report a facile strategy to synthesize nitrogen-doped porous Co@C nanoboxes (Co@NC) by pyrolysis of zeolitic imidazolate frameworks (ZIF-67), followed by partially etching away the metallic cobalt. With a nitrogen-enriched hollow porous carbon nanobox and embedded Co nanoparticles, the Co@NC shows high efficiency in PS activation for p-Chloroaniline (PCA) removal. The degradation study shows that a complete removal of high concentration PCA is done within two minutes, which is superior to most of the reported PCA removals with PS-based advanced oxidation processes (A0Ps). More importantly, the Co@NC exhibits high catalytic activities in a wide range of pH from 5 to 9. The Co@NC also shows very limited Co2+ release with a dissolution proportion of 0.28%, much lower than previously reported Co-based catalysts, and remains high efficiency after five successive reaction cycles. A heterogeneous activation mechanism though surface reaction is proposed, in which PCA firstly absorbs on the carbon nanobox surface, then being oxidized by generated radicals and nonradical species. The unique structure and outstanding performance of Co@NC catalysts present new insights in catalyst design for PS-based advanced oxidation for organic pollutants removal in waste water.