Metal-organic frameworks-derived CoFeN-NC materials with the enhanced catalytic activity and selectivity for the degradation of organic dyes via adsorption and heterogeneous photo-Fenton

Possible schematic illustration of photocatalytic degradation of organic dyes under visible light. • MOFs derived cobalt iron bimetallic catalysts (Co x Fe 1- x N-NCs) were fabricated via self-assembly and annealing treatment. • Co 0.8 Fe 0.2 N-NC exhibited excellent adsorption and photo-Fenton synergistic effect in the degradation of organic dyes. • Co 0.8 Fe 0.2 N-NC had obvious selective degradation toward non-azo dyes. • Co 0.8 Fe 0.2 N-NC displayed favorable stability characteristics. • The active species were determined and a possible photo-Fenton degradation mechanism was proposed. Nanoscale iron-based materials are widely used as photocatalytic materials for catalytic oxidative degradation of organic dyes in water. Here, a series of MOFs derived nitrogen doped cobalt iron bimetallic carbon composite nanomaterials (Co x Fe 1- x N-NCs) were prepared by self-assembly and annealing treatment, and their application in the removal of organic dyes in water was investigated by the synergistic effect of adsorption and photo-Fenton. The study found that the Co 0.8 Fe 0.2 N-NC exhibit superior catalytic performance for different types of organic dyes. For example, when the concentration of MB was 40 mg L -1 , the degradation rate constant was 3.88 × 10 -2 min −1 , which were 2.9 and 25.2 times the corresponding values of the Fenton-like and photocatalytic system, respectively. Meanwhile, compared with azo dyes Methyl Orange and Congo Red (MO and CR), Co 0.8 Fe 0.2 N-NC has obvious selective catalysis for non-azo dyes Methylene Blue, Malachite Green, Rhodamine B and Neutral Red (MB, MG, RhB and NR). Moreover, the reaction of cobalt iron active centers with hydrogen peroxide (H 2 O 2 ) further promotes the generation of active substances (·OH, ·O 2 – and h + ), speeding up the degradation of organic dyes. These results suggest that the synergistic effect of adsorption and photo-Fenton may provide new clues for the treatment of organic pollutants in wastewater.